Analytical and Comparative Study for Solar Thermal Cooling and Photovoltaic Solar Cooling in the MENA Region

Transcription

1 Analytical and Comparative Study for Solar Thermal Cooling and Photovoltaic Solar Cooling in the MENA Region By Younis Yousef Abidrabbu Badran A Thesis Submitted to the Faculty of Engineering at Cairo University and Faculty of Electrical Engineering and Computer Science at Kassel University in Partial Fulfillment of the Requirements for the Degree of Master of Science in Renewable Energy and Energy Efficiency Faculty of Engineering Cairo University Giza, Egypt Kassel University Kassel, Germany March, 2012

2 Analytical and Comparative Study for Solar Thermal Cooling and Photovoltaic Solar Cooling in the MENA Region By Younis Yousef Abidrabbu Badran A Thesis Submitted to the Faculty of Engineering at Cairo University and Faculty of Electrical Engineering and Computer Science at Kassel University in Partial Fulfillment of the Requirements for the Degree of Master of Science in Renewable Energy and Energy Efficiency Reviewers Prof. Dr. Adel Khalil Member Mechanical Power Engineering Department Faculty of Engineering, Cairo University Prof. Dr. Albert Claudi Member Faculty of Engineering and Computer Science Kassel University Supervisors Dr.-Ing. Norbert Henze Systems Engineering and Grid Integration Department Head of group. Engineering and Measuring Technology Fraunhofer Institute IWES, Kassel, Germany Dipl.-Ing. Siwanand Misara Member Group of Engineering and Measuring Technology Fraunhofer Institute IWES, Kassel, Germany March, 2012

3 Analytical and Comparative Study for Solar Thermal Cooling and Photovoltaic Solar Cooling in the MENA Region By Younis Yousef Abidrabbu Badran A Thesis Submitted to the Faculty of Engineering at Cairo University and Faculty of Electrical Engineering and Computer Science at Kassel University in Partial Fulfillment of the Requirements for the Degree of Master of Science in Renewable Energy and Energy Efficiency Approved by the Examining Committee: Prof.Dr. Adel Khalil, Thesis main Advisor Prof. Dr. Albert Claudi, Thesis main Advisor Dr. Sayed Kaseb, Member Faculty of Engineering Cairo University Giza, Egypt Kassel University Kassel, Germany March, 2012

4 Acknowledgements First and foremost I would like to thank God. This work could not have been possible without the help of many people who supported my work. I would like to show my gratitude to my family in Palestine for their continued love, encouragement over the years of my education. This thesis is dedicated to them. I am heartily thankful to my supervisor Dipl.-Ing. Siwanand Misara from Fraunhofer Institute for Wind Energy and Energy System Technology (IWES) in Kassel, who has guided and supported me in every phase of this thesis from the initial to the final level and enlightened the work with his vast knowledge on the subject. Deepest gratitude to my supervisor from Cairo university, Professor. Dr. Adel Khalil for his support and giving me the chance to carry out this research. It has been a pleasure to work with this professor who has a high scientific competence and professionalism. In addition I would like to thank my supervisor from Kassel university, Prof. Dr.-Ing. Albert Claudi for his available advice in this study. Thanks to Dr.-Ing Michael Krause from Fraunhofer Institute of Building Physics - Kassel(IBP), who has guided and supported me especially in the TRNSYS simulation and the thermal air-conditioning cooling design in this study. I am grateful to Mr. Salah Azzam and Mr. Firas Alawneh from The Higher Council for Science and Technology National Center (NERC) in Jordan, who supported me in getting the meteorological measurement data for Aqaba city. Thanks to the German Academic Exchange Service (DAAD) for their financial assistance which made it possible for me to pursue the REMENA master program and this study. Thanks to my teachers, friends and staff of the REMENA master program and IWES Fraunhofer Institute in Kassel for encouraging me during my work. IV

5 Abstract In this thesis, a comparison and analyses of solar thermal and solar photovoltaic (PV) air-conditioning technologies for a Typical Single Family House (TSFH) in two different MENA climates, Aswan-Egypt and Aqaba-Jordan, are performed. The building cooling demand is firstly obtained from annual building simulation in TRNSYS software. Based on these simulation results, three scenarios are designed in order to compensate the TSFH s annual cooling demand in each selected climate. These scenarios are solar thermal air-conditioning with storage (absorption chiller), PV air-conditioning without storage and PV air-conditioning with storage. The cooling compensation is simulated by Matlab-Simulink for each scenario. TRNSYS simulations for Aswan-TSFH and Aqaba-TSFH respectively demonstrate that the maximum cooling load demand during summer season are: 13.9 kw and 15.3 kw; the annual cooling energy demands are: 44,330 kwh/year and 43,490 kwh/year which represents 97.5 % and 96.3 % of the total annual energy consumption (heating and cooling). On the other hand, Matlab-Simulink demonstrates that the total annual percentage of cooling energy compensation (direct plus storage) difference between the PV and thermal with storage scenarios does not exceed 1 % in both cases. However, differences exist between the two scenarios. The performance of daily direct cooling compensation by the PV air-conditioning scenarios is more efficient than in the thermal air-conditioning scenario. The direct cooling compensation percentage for the Aswan- TSFH and the Aqaba-TSFH respectively are 39.3 % and 35.8 % for the PV airconditioning scenarios and 30.8 % and 30.9 % for the thermal air-conditioning scenario. The compensation by the storage are 10.7 % and 7.3 %, by the PV air-conditioning with storage scenario and 20.1 % and 11.9 %, by thermal air-conditioning with storage scenario for the two cases respectively. The PV air-conditioning scenario with storage behaves and compensates the cooling demand better than the solar thermal air-conditioning with storage scenario and needs less storage to cover the same amount of cooling load demand. However, the storage system in the PV air-conditioning scenario is minor and the direct compensation is major. That is vice versa in the thermal air-conditioning scenario. This research can be extended to compare and analyze the scenarios in terms of primary energy, economic analysis and different buildings. Moreover, the future cost reduction by learning curves of both technologies can influence the economic feasibility. V

6 Contents Acknowledgements... iv Abstract... v List of Figures... ix List of Tables... xii List of Symbols... xiii List of Abbreviations... xvi 1. Introduction Background Objectives and Boundary Conditions Thesis Structure Determination of the Reference Building in MENA Regions Reference Location Climates Meteorological Data for Reference Locations Reference Building Architecture Design Facade Stricter Wall Construction Windows Internal Gain Air Change Condition Cooling and Heating Set Points Reference Building Thermal Cooling and Heating Load Simulation TRNSYS Software Simulation Environments Description of the Simulation Type 56 Mathematical Description TSFH Modeling with Type56 and TRNBuild TSFH Modeling with Type56 and TRNStudio Thermal Cooling Load Simulation Results and Analysis of Results VI

7 3.3.1 The Annual Energy Consumption The Performance of Cooling Load Solar Air-Conditioning Technologies Solar Photovoltaic Air-Conditioning Technology Solar Thermal Air-conditioning Technology Solar Air-Conditioning Scenarios Design and Simulation Matlab-Simulink Simulation Environments Solar PV Air -Conditioning Scenarios System Components and Design Systems Simulation and Methodology PV air-conditioning Without Storage Scenario PV Air-conditioning with Storage Scenario Solar Thermal Air-conditioning Scenario(absorption chiller) System Components and Design Solar Thermal Heating System Absorption Chiller System Simulation and Methodology Simulation Results and Analysis for Solar Air-Conditioning Scenarios Solar Photovoltaic (PV) Air-conditioning Scenarios The Influence of a Direct Cooling production Excess of Cooling Production and External Back-up Cooling for a Battery Design Annual Cooling Energy Compensation Analysis PV Air-conditioning Without Storage Scenario PV Air-conditioning With Storage Scenario Results and Analysis for Solar Thermal Air-conditioning Scenario The Influence of Cooling Production Annual Cooling Energy Compensation Analysis VII

8 Excess Cooling Production and External Back-up Cooling Loads Annual Cooling Energy Compensation Solar Fraction Thermal Air-conditioning Scenario Versus PV Air-conditioning Scenarios The Direct Cooling Production Load Performance Annual Cooling Compensation Energy Percentage Conclusions and Future Research conclusions Future Research References Appendices Appendix A: Schematic vapour compression cycle Appendix B: Solar Photovoltaic module data sheet Appendix C : Inverter data sheet, [45] Appendix D:Description of Wet Cooling Tower, [37] Declaration VIII

9 List of Figures Figure 2.1: Annual distribution of horizontal global solar radiation for Aswan and Aqaba cities, [16], [17]...6 Figure 2.2 Annual distribution of ambient air temperatures for Aqaba and Aswan cities, [16], [17]....6 Figure 2.3:Annual distribution of ambient air relative humidity in Aswan and Aqaba cities, [16], [17]...7 Figure 2.4: sketch of Typical Single Family House(TSFH) in MENA regions plan, [20]...9 Figure 3.1: Zones of TSFH model in TRNBuild Figure 3.2: Aswan-TSFH model (Type 56) with all the required components and connections in TRNStudio Figure 3.3: Aqaba-TSFH model (Type 56) with all required components and connections in TRNStudio Figure 3.4: Yearly cooling and heating energy demand for the Aswan-TSFH and Aqaba- TSFH Figure 3.5: Monthly cooling and heating energy demand in (kwh) for the Aswan-TSFH and Aqaba-TSFH Figure 3.6: Yearly Cooling and heating demands distribution(kw) for the Aswan-TSFH Figure 3.7:Yearly Cooling and heating demands distribution in (kw) for the Aqaba- TSFH Figure 3.8: Weakly Cooling load demand distribution in (kw) for the Aqaba-TSFH and Aswan-TSFH Figure 4.1 :Basic structure of PV air-conditioning systems, [2] Figure 4.2 :Basic structure of heat driven and desiccant air-conditioning systems, [2].. 27 Figure 5.1: Schematic flow diagram for solar PV air-conditioning without storage Figure 5.2: Schematic flow diagram for solar PV air-conditioning with storage Figure 5.3: The dimensions of a typical single family house (TSFH) - roof area (1) for PVarray installation IX

10 Figure 5.4: Solar thermal air-conditioning system scenario, coupling of an absorption chiller with a solar heating system Figure 5.5: Schematic diagram for an absorption chiller for chilled water production, [37] Figure 6.1: PV air-conditioning cooling production along the year for Aswan-TSFH Figure 6.2: PV air-conditioning cooling production along the year for Aqaba-TSFH Figure 6.3: Solar-PV air-conditioning cooling production in Summer week for Aswan- TSFH Figure 6.4: Solar-PV air-conditioning cooling production in Summer week for Aqaba- TSFH Figure 6.5: Solar PV air-conditioning cooling production in winter week for Aswan- TSFH Figure 6.6: Solar PV air-conditioning cooling production in winter week for Aqaba- TSFH Figure 6.7: PV air-conditioning without storage scenario, Excess cooling production and external back-up cooling loads for Aswan-TSFH Figure 6.8: PV air-conditioning without storage scenario, Excess cooling production and external back-up cooling loads for Aqaba-TSFH Figure 6.9: yearly cooling energy compensation by the solar PV air-conditioning system with and without storage scenarios for the Aswan-TSFH and Aqaba-TSFH Figure 6.10: Monthly cooling energy compensation by solar PV air-conditioning system with and without storage scenarios for Aswan-TSFH and Aqaba-TSFH Figure 6.11: Solar thermal air-conditioning cooling production along the year for Aswan-TSFH Figure 6.12: Solar thermal air-conditioning cooling production along the year for Aqaba- TSFH Figure 6.13: Solar thermal air-conditioning cooling production in summer week for Aswan-TSFH Figure 6.14: Solar thermal air-conditioning cooling production in summer week for Aqaba-TSFH X

11 Figure 6.15: Solar thermal air-conditioning cooling production in winter week for Aswan-TSFH Figure 6.16: Solar thermal air-conditioning cooling production in Winter week for Aqaba-TSFH Figure 6.17: Solar thermal air-conditioning excess cooling production and external back-up cooling loads for Aswan-TSFH Figure 6.18: Solar thermal air-conditioning excess cooling production and external back-up cooling loads for Aswan-TSFH Figure 6.19: The cooling energy compensation by the solar thermal air-conditioning system scenario for Aqaba-TSFH and Aswan-TSFH Figure 6.20: Monthly cooling energy compensation by the solar thermal air-conditioning system scenario for Aswan-TSFH and Aqaba-TSFH Figure 6.21: Annual solar fraction for the solar thermal air-conditioning system scenario in Aswan-TSFH and Aqaba-TSFH Figure 6.22: Monthly solar fraction for the solar thermal air-conditioning system scenario in Aswan-TSFH and Aqaba-TSFH Figure 6.23: PV air-conditioning versus solar thermal air-conditioning, cooling production performance in Summer Week for Aswan-TSFH Figure 6.24: PV air-conditioning versus solar thermal air-conditioning, cooling production performance in Summer Week for Aqaba-TSFH Figure 6.25:PV air-conditioning versus solar thermal air-conditioning, cooling production performance in Summer day for Aswan-TSFH Figure 6.26: PV air-conditioning versus solar thermal air-conditioning, cooling production performance IN Summer day for Aqaba-TSFH Figure 6.27: Percentage of cooling Energy compensation by the three scenarios for Aswan-TSFH Figure 6.28: percentage of cooling Energy compensation by the three scenarios for Aqaba-TSFH Figure A: Schematic vapour compression cycle, [2] Figure D: Schematic drawing of an open type wet cooling tower, [37] XI

12 List of Tables Table2.1 :Constructional components of the reference building (TSFH), [21], [20] Table2.2 : Thermal properties of the Single glass window for the reference TSFH in Aswan and Aqaba, TRNSYS library and [13] Table2.3 :Air change(ventilation and infiltration) rate for Aswan-TSFH and Aqaba-TSFH Table 5.1 : Parameters of the flat plate collector, [52] Table5.2: Lithium Bromide-water (WEGRACAL SE 15ACS15) absorption chiller parameters, compiled from [56] and [10] Table5.3: Technical parameters of the back-up heater, storage and cooling tower, Table6.1: Yearly cooling energy compensation by the solar PV air-conditioning system with and without storage scenarios for Aswan-TSFH and Aqaba-TSFH XII

13 List of Symbols Variables Units Description m 2 PV-array area AF - Autonomy factor Acoll,Spec m 2 Specific collector area As m 2 Storage surface area Cnom,Batt Ah Nominal capacity of battery C1 W/m 2 K linear heat transfer coefficient C2 W/m 2 K 2 Quadratic heat transfer coefficient COPideal COPABCH Ideal coefficient of performance Coefficient of performance for absorption chiller Cw kj/kg.k Specific heat capacity of water Wh The average daily electric DC of the excess energy Wh The back-up cooling energy Gtilt W/m 2 Global solar radiation on a tilted surface G W/m 2 Global radiation on horizontal surface W Output electric power of PV-array W Output electric power of Inverter W Output cooling power of Compressed chiller W W W W W Excess cooling power Back-up cooling power Demand Cooling power Electric power charged in the battery Cooling power produced by the battery P habch h W Heat power required by the absorption chiller W Heat power production by the absorption chiller Pcoll h W Heat power production from the collector PST;loss h W Heat power losses of the storage tank PhABH h W Heat power losses from the storage by the demand of cooling system W Direct heating power W Back-up cooling power XIII

14 W Compensated cooling power by the storage W Direct cooling power Wh Back-up cooling energy Wh Cooling energy compensation by the storage Wh Direct compensation of cooling energy K, C Module s operation temperature TNOCT K, C Operation cell temperature K Ambient temperature K Inlet temperature of the generator K Outlet temperature of evaporator K Inlet temperature of condenser TmaxSTH K Maximum temperature of the storage tank T coll K Average fluid temperature in the collector TS K The temperature difference of the storage tank U W/m 2 K Storage heat losses coefficient V storage m 3 Volume of the storage w kg/m 3 Density of water - Collector efficiency - Optical efficiency - Photovoltaic module efficiency - Battery efficiency - PV module efficiency at the standard test condition - Temperature coefficient of the PV module XIV

15 XV Subscripts Subscript Description ABCH Absorption chiller Amb Ambient temperature BAH Back-up Batt Battery C Cooling Coll Collector Chrge Charging Cond Condenser Combined Convection D Diffuse Electric Evap Evaporator Equivalent Gen Generator Inverter I Internal Ir Infrared radiation Loss Losses Max Maximum Nom Nominal o External P Peak R Radiative S surface T Time W Water

16 List of Abbreviations TSFH MENA PV STC NOCT SRE TRNSYS NERC IWES IBP EPW DNI DOS ETMY IWEC DOD SF HCB TFM DC AC LiBr H2O Typical Single Family House Middle East and North Africa Photovoltaic Standard Test Conditions Operation Cell Temperature Standard Reference Environment TRaNsient SYstem Simulation program National Energy Research Center Institute for Wind Energy and Energy System Technology Institute of Building Physics Energy Plus weather Direct Normal Irradiance Department Of Statistic Egyptian Typical Meteorological Year International Weather for Energy Calculations Depth Of Discharge Solar Fraction Hollow Concrete Block Transfer Function Method Direct current Alternating Current Lithium Bromide Water XVI

17 1. Introduction 1.1 Background Worldwide, the growing demand for traditional air-conditioning has caused a significant increase in demand for primary energy resources. This results in a significant increase in peak electric power demand in summer reaching, in many cases, the capacity limits of the network and causing the risk of blackouts [1]. That due to, increasing living standards, comfort expectations and global warming. In many countries of Middle East and North Africa (MENA), air-conditioning is one of the main consumers of electrical energy today. For example in Egypt, at least 32 % of the electrical energy used by the domestic sector is for air-conditioning: [2], [3]. However, there is a higher solar radiation in the MENA regions, with a potential that is larger than the total electricity demand worldwide. The average daily sunlight exceeds 8.8 hours, with an average DNI 1 of 2,334 kwh/m 2 /year [4]. Solar air-conditioning is one of the technologies which allows to obtain important energy savings compared to traditional air-conditioning plants, by using the renewable solar source. This is definitely the case for the hot and sunny regions in the MENA. In addition, the growing demand for airconditioning in typical single family houses (TSFH) and small office buildings is opening new sectors for this technology in the MENA regions. Today, there are two main solar air-conditioning technology options: solar thermal airconditioning, where the solar absorption cooling is the first type of this option and it is still practical for remote building in places where there is an excess of heat energy available. Another option is the solar photovoltaic air-conditioning, by using electricity from renewable sources to power the conventional cooling equipment. On the other hand, the market introduction of photovoltaic systems is much more aggressive than that of solar thermal power plants; cost reductions can be expected to be faster for photovoltaic systems. But even if there is a 50% cost reduction in photovoltaic systems and no cost reduction at all in solar thermal power plants, electricity production with solar thermal power plants in southern Europe and North Africa remains more costeffective than with photovoltaic systems [5]. 1 Direct Normal Irradiance 1

18 A lot of papers have been published that describe the performance of thermal airconditioning technology under different climate conditions in the world: [6], [7], [8] and [9]. In addition, there are also a number of publications available that cover the performance of solar photovoltaic air-conditioning technology or different performance between the two technologies such as [10]. However, there are very few research on the solar air-conditioning technology under the MENA region climate conditions, for its importance in this region. Therefore, there are areas in which one or the other of the two technologies should be preferred for technical reasons under the MENA regions climates. 1.2 Objectives and Boundary Conditions The performance of solar air-conditioning technology is strongly dependent on the ambient climate conditions, the building standards and the users behaviour. The main objective of this thesis is to analyze and compare the solar thermal air-conditioning technology and the photovoltaic air-conditioning technology under different thermal load profiles and under the MENA region climate conditions. Additionally, to evaluate the cooling compensation by employing this technology to the cooling load demand of the selected building (TSFH) in two different climate locations: Aswan-Egypt, Aqaba- Jordan. In order to achieve the aforementioned objectives, the study focuses on the: Determination of TSFH as a reference building for the two selected locations in this study : Aswan city in Egypt and Aqaba City in Jordan. Determination of the TSFH cooling load demand for the two selected locations carried out by the TRNSYS Software. Design and simulation of three solar air-conditioning scenarios to cover the cooling load demand of a TSFH for the two respective locations where the simulation is carried out by MATLAB-Simulink. The considered scenarios are as following: Solar photovoltaic air-conditioning without storage Solar photovoltaic air-conditioning with storage Solar thermal air-conditioning with storage (absorption chiller) 2

19 1.3 Thesis Structure The climate of the selected location and a detailed description of the reference building are given in chapter 2. The description of the reference building includes its architectural design, orientation, wall construction, window type, indoor climate, air change rate, internal gain, cooling and heating set points. The thermal cooling and heating load demands for the reference building (TSFH) are simulated by TRNSYS software for the two selected locations. A description of the simulation environments, the models as well as the simulation results and their analysis are given in Chapter 3. Chapter 4 includes a general description of available solar airconditioning technologies and its state-of-the-art. In Chapter 5, three solar air-conditioning scenarios have been designed and simulated for each TSFH in the selected locations. This chapter discusses three parts: simulation environments, solar radiation on a tilted surface by TRNSYS software and then each of the scenario components and design followed by the scenario simulations and methodology. Chapter 6 includes the simulation results and the analysis for each scenario. Then, the comparison between the solar thermal air-conditioning with storage scenario and the two solar PV- air-conditioning scenarios with and without storage is done. The conclusions of this study are summarized in chapter 7. Moreover, an outlook for further work that could be done is given. 3

20 2. Determination of the Reference Building in MENA Regions To investigate the above objective two cities in two countries were selected from MENA regions, Aqaba city in Jordan from Middle East(ME) and Aswan in Egypt from North Africa(NA). The reference building model in this study was selected for the two locations, namely typical single family house (TSFH). The aim of this chapter is to determine the reference building TSFH, for various climate conditions of the selected locations in MENA regions. For the locations climate conditions, solar radiation, ambient air temperature and relative humidity. For the building, the construction (i.e. wall U- values, type of window glazing), internal heat gains air exchange rate etc... were defined. That in order to simulate the TSFH thermal load demand by using TRNSYS software. The Simulation in more details will be further explained in next chapter. 2.1 Reference Location Climates The building cooling and heating demands are strongly influenced by the outdoor ambient air temperature and global solar radiation around it. In this study, the TSFH cooling demand calculations depends on the selected locations climates Aqaba city in Jordan and Aswan city in Egypt. Jordan is located in Middle East (ME) regions its area is 9 X 10 4 km 2, 80% of its area is desert. The climate of Jordan may be divided into three main categories depending on the altitude: low-, medium- and high-mean temperature regions [11]. Aqaba city is located south of Jordan at latitude 29 31'N and longitude 35 E on the Aqaba Gulf of the Red Sea. The meteorological station is 51 meters above sea level. It is located in the high mean temperature regions. This city is characterized by very hot and dusty weather in summer; summer temperatures rise above 45 C. Winter is mild therefore there is little need for heating with extremely little amount of precipitation. The mean annual daily average temperature is estimated at around 24.1 C [12], [13]. 4

21 Egypt is located in North Africa (NA) regions its area 1,001,450 km 2 and it is mostly desert. Aswan city is the 3rd biggest city in Egypt today and the biggest one in upper Egypt located at latitude 23 54'N and longitude 32 E [14]. Aswan enjoys a relatively high temperatures, dry weather and arid climate; Summers in Aswan grow unbearably hot with the average temperature ranging from 31.6 C to 33 C and in July sear up to almost 34 C. In Winter the average temperature ranging from C and rainfall almost non-existent and no need for heating [15] Meteorological Data for Reference Locations The meteorological data for the two reference locations (Aswan, Aqaba) had been selected, these data sets were used to perform the calculations and generate the results presented in this study. The meteorological data file of Aqaba city contains measurement data in 15 minute intervals for the year It is includes, the horizontal solar radiation (beam, diffuse and global), ambient air temperature and relative humidity. The file was received in Excel-format from the National Energy Research Centre (NERC) in Jordan. The meteorological data of Aswan city, in Egyptian Typical Meteorological Year (ETMY) format and in Energy Plus Weather (EPW) format Were received. This formats was developed as a standard development for energy simulation by Joe Huang with data provided by the U. S. National Climatic Data Center which for periods of record from 12 to 21 years, all ending in This file was hourly data included the horizontal solar radiation (beam, diffuse and global), ambient air temperature and relative humidity [16]. Figures 2.1 to 2.3 represent the horizontal global irradiation, ambient air temperature and relative humidity data for each location Aqaba and Aswan. 5

22 Figure 2.1: Annual distribution of horizontal global solar radiation for Aswan and Aqaba cities, [16], [17]. Figure 2.1 shows, distribution of the global horizontal solar radiation for Aswan city and Aqaba city, in Aswan city has higher peak daily of global horizontal solar radiation than Aqaba city along the year; in summer season reaches near to 1000 W/m 2,1050 W/m 2 and in winter 600 W/m 2, 700 W/m 2 for Aqaba and Aswan respectively. In addition the radiation difference between the two cities, in winter higher than in summer seasons. Figure 2.2 Annual distribution of ambient air temperatures for Aqaba and Aswan cities, [16], [17]. 6

23 Figure2.2 illustrates, the annual distribution of ambient temperatures in Aqaba city and Aswan. Approximately in both cities; in summer season the daily maximum peak temperatures reaches to 40 o c and in sometimes to 45 o c, in winter changes between 25 o C to 30 o C. Aqaba city daily temperatures are fluctuated along the year higher than Aswan, this means Aswan night temperatures higher than Aqaba night temperatures. This leads to higher night cooling consumption by the buildings in Aswan city than in Aqaba city. Figure 2.3:Annual distribution of ambient air relative humidity in Aswan and Aqaba cities, [16], [17]. As shown in Figure2.3,the relative humidity distribute along the year for both cites Aqaba and Aswan. Generally Aqaba city has higher ambient air relative humidity along the year than Aswan, especially in July, August and September. Additionally, it is fluctuated in Aqaba more than in Aswan. The high relative humidity of location, leads to increase building cooling consumption. 7

24 2.2 Reference Building The reference building which has been selected in this study is a typical single family house (TSFH) relates to the MENA locations, Aswan city in Egypt and Aqaba city in Jordan. This section defines the TSFH and the definition include architecture design and orientation, constriction building elements descriptions (walls, roof, floor and windows), internal heat gain, the heating and cooling set points and the air change conditions. This building data must be determined in order to simulate the thermal cooling and heating demands for the building by using TRNSYS software. More details about the thermal consumption simulation by TRNSYS software for TSFH will be further explained in next chapter. According to department of statistic (DOS), type of building (TSFH) called Dar in Jordan represents about 72 % of the total residential building in Jordan [18], [19]. As mentioned by [11], 54.6 % of the dwellings in Jordan are detached as TSFH. In addition the average useful living floor area per capita is about 20m 2 and 6 persons residents per dwelling. Hollow cement-blocks are most widely used for constructing walls: nearly two-thirds of the total housing being built with such cheap blocks, followed by reinforced concrete and white-stone. Nearly 95% of flat roofs, in Jordan are constructed using reinforced concrete, and the remaining fraction employed roof tiling, asbestos and/or corrugated steel-sheets. Most of TSFH in MENA regions specially in Jordan and Egypt, has same building architecture design, it has a flat roof, it consists Gust room, living room, kitchen, two or three bedrooms and the bathrooms. However a simplification was made in this study, the typical Single family house in Jordan same that s in Egypt. In order to simplify the comparison of solar thermal airconditioning scenarios and solar photovoltaic air-conditioning scenarios, which as the major objective in this study, Figure 2.4 shows the TSFH sketch and It can be described as follows [20], [13]: 8

25 2.2.1 Architecture Design The reference object (of TSFH) was taken from [20], [13] (see Figure 2.4). The floor area is about 224 m 2, perimeter is m and ceiling internal height is 2.86 m. It is rectangular shape and consists of three bedrooms, living room, guest room and Kitchen. Number of occupants is 6 persons. The sketch of TSFH in Figure 2.4 shows the building orientation where the Gust room and the living room are facing to south. The zones dimensions were provided by Eng. Tawfiq Al- Khamayseh (Architecture engineer works for Al-Bayader Company for construction and engineering in Ramallah, Palestine). This architecture design of the TSFH was considered for the two climate locations, Aswan and Aqaba cites. Figure 2.4: Sketch of Typical Single Family House(TSFH) in MENA regions plan, [20]. 9

26 2.2.2 Facade Stricter Wall Construction The construction consists of typical stone walls(external walls), it consists of stone, concrete, concrete blocks and plaster. The various material of the building envelope, layers the thicknesses and energy performance data describing the reference building (TSFH) listed in Table 2.1 [21], [20]. Table2.1 : Constructional components of the reference building (TSFH), [21], [20]. Assembly Layer Thickness Density Thermal Specific U-Value of [m] [kg/m3] Conductivity heat component [kj/h m K] capacity [W/m2K] [kj/kg K] External Cement plaster wall H.C.B for wall Reinforced concrete Stone Internal Cement plaster wall H.C.B for wall Cement plaster Roof Cement plaster 0.01 H.C.B for roof Reinforced concrete Bitumen Ground Tile floor Cement tile Sand Reinforced concrete Under floor

27 Windows A single glazed window with U-value of 5.68 W/m 2 O k was selected for the reference building TSFH. This considered as one of the most popular windows type in the selected locations. The U-value indicates the rate of heat flow due to conduction, convection, and radiation through a window as a result of a temperature difference between the inside and outside in (W/m 2.K) [13]. The windows parameter are summarized in Table 2.2. This parameters According to TRNSYS library and [13]. According to [13], the optimum window area for the TSFH in Aqaba city, on the east and on west facades amounts to 20% of the wall surface area. On the North facade, windows area is 10% whereas 30% for the west facade. Same for Aswan-TSFH was assumed. The TSFH windows were considered without any internal or external shading. Table2.2 : Thermal properties of the Single glass window for the reference TSFH in Aswan and Aqaba, TRNSYS library and [13]. Single glaze window Value Unit U-Value 5.68 [W/m2 o K] g-value [ - ] Frame U-value [W/m 2 O K] Frame fraction 0.15 [ - ] Solar reflectance Of outer surface [ - ] Visible transmittance [ - ] Internal Gain Internal gain is thermal (sensible or latent) heat which dissipates from persons, lighting, or electric equipments (computer, wash machine,..etc.). This heat gains contributes in the building cooling and heating load demands. The rate of internal heat gain is 150 W from occupants and electric equipment. It is considered based on ISO 7730 standard where the number of occupants is 6 persons in TSFH. The heat gain 120 W/person (Seated, very light writing) was considered constant, which represents an average activity could be done daily by the occupants in addition the heat gain from appliance defined also as a constant (300 W/day) during the year that according to ISO 7730 standard in TRNSYS data library. 11

28 2.2.4 Air Change Condition The air tightness of Middle East and South East Asia buildings is less than European standard, which leads to higher infiltration rate. According to the United Arab Emirates UAE building regulations, the ventilation rate should be 0.4/h. In this study, the TSFH for both locations Aswan and Aqaba have the same ventilation and infiltration rates. Natural ventilation was considered for this building according to MASDAR energy design guide line [22]as it regarded a proper code for efficient building design where the natural ventilation is constant during the day and throughout the year. The value of infiltration rate has been defined according to ASHRAE 90.1 standard [23]. The Iinfiltration and ventilation rats for TSFH are given in Table2.3. Table2.3 : Air change (ventilation and infiltration) rate for Aswan-TSFH and Aqaba- TSFH. Parameter Unit Aswan-TSFH Aqaba-TSFH Infiltration 1/h Ventilation rate 1/h 1 1 Total air change 1/h Cooling and Heating Set Points The initial step in the cooling and heating load consumption calculation is defending indoor and outdoor conditions of TSFH. Indoor conditions depends on building use, number and type of occupancy, and/or code requirements. In this study, the TSFH indoor design conditions, the set-point temperature and relative humidity for cooling and heating are set according to ASHRAE, Handbook Fundamental (2005) [24], [20]. For cooling, it is 24 C dry bulb and a maximum of 50 65% relative humidity. For heating, it is 20 C dry bulb and 30% relative humidity. 12

29 3. Reference Building Thermal Cooling and Heating Load Simulation The major objective for this chapter is to calculate the thermal cooling and heating loads for the two cases: Aswan-TSFH and Aqaba-TSFH cases. That is in order to investigate the main objective of this study: to compare and to analyze the solar thermal airconditioning technology and PV air-conditioning technology in the MENA regions. This chapter has two parts. The first part discusses and describes the thermal cooling and heating loads simulation by using TRANSYS Software. The second part includes the thermal cooling load simulation results and analysis of the results. 3.1 TRNSYS Software Simulation Environments TRANSYS is a transient system simulation program. It is a well known software diffusely adopted for both commercial and academic purposes. The software includes a large library of built-in components, often validated by experimental data [8], [25]. It is a component-based simulation engine. Components (or types) are individual engineering systems such as a boiler, thermal storage tank, PV panels, or a pipe that are defined by a discrete set of inputs, outputs, parameters, and the mathematical functions which govern their operation. It is dynamic, transient building energy and energy supply systems modelling tool which offers distinct advantages as well as disadvantages over its alternatives (e.g. energy plus) [26]. It is a complete and extensible simulation environment for the transient simulation of systems, including multi-zone buildings [20]. The program allows the users to create and design complex energy engineering systems by adding and dropping components from the software library to a simulation map and connects this components inputs and outputs together [26]. This makes TRANSYS a very capable tool to simulate the building cooling and heating loads. For the sake of the aforesaid reasons, the TRANSYS software is selected in this study to simulate TSFH cooling and heating loads for each case: Aswan-TSFH and Aqaba-TSFH. TRNSYS consists of suitable of programs. In this study, only two of these programs have been deployed: TRNSYS simulation studio and Multi-zone building (TRNBuild) [27]. 13

30 3.2 Description of the Simulation The first step before starting this simulation, which is done in Chapter 2, includes: the selecting TSFH-indoor design conditions ( such as, number of occupancy, internal gains, air change conditions,heating and cooling set points etc. ), selecting TSFH-envelope data ( e.g. architectural design, facade stricter data etc..) and selecting TSFH-outdoor climatic data (solar radiation, ambient temperature, relative humidity). TYPE 56 (Multi-zone building model) in TRNSYS is chosen to simulate the heat conduction through opaque surfaces of the TSFH-envelop. In order to use this type, two separate processing program must be carried out. The first process, TRNBuild program reads in and processes a file containing the TSFH description and generate two files (described later). The second process occurred in the TRNStudio program, the two generated files will be used by the TYPE 56 component during a TRNSYS simulation Type 56 Mathematical Description The TRNSYS mathematical model calculations are influenced by the outdoor climatic conditions, the indoor design conditions and the TSFH envelop structure. The heat balance method is used by TRNSYS as a base for all calculations. For conductive heat gain at the surface on each wall, TRNSYS use Transfer Function Method (TFM) as a simplification of the arduous heat balance method [28], [29]: (3.1) -...(3.2) Where the surface temperatures and heat fluxes are evaluated at equal time intervals. The k refers to the term in the time series, and it specified by the user within the TRNBUILD description. within the TRNBUILD program the coefficients of the time 14

31 series (a's, b's, c's, and d's) are determined by the z-transfer function routines of literature [30]. The Heat gain by radiation and convection is calculated using [28]: (3.3)...(3.4) q comb,s,i/o is the combined convective and long wave radiation of the inside/outside surface [28]:.....(3.5) (3.6)...(3.7)...(3.8) In these equations the Ss,i, is the radiative heat flux absorbed at the inside surface, the inside surface area, is the view factor to the sky, artificial temperature is node, is referred to the resistance. The Latent heat gain by the ventilation or infiltration is calculated by using [28], [31], [32]:.....(3.9) For more details about the mathematical model which are used by TRNSYS simulation, see TRNSYS16 manual [33]. 15

32 3.2.2 TSFH Modeling with Type56 and TRNBuild TRNBuild is used to enter the TSFH input data and to create the TSFH description file (*.bui). This file includes all the information required to simulate the building where (*.bui) file used to generate three new files: the (*.bld) 2, (*trn) 3 files which are used by TYPE 56 during the simulation process in TRNStudio program and information file(*.inf) 4 ) As shown in Figure 3.1, TRNBuild allows the users to specify all the building structure in details that is needed to simulate the thermal behaviour of the TSFH such as geometry data, wall construction data, windows data, etc. Furthermore, it needs SCHEDUALE information which define the internal heat gain from the equipment and occupants during the day in the TSFH. Figure 3.1: Zones of TSFH model in TRNBuild. 2 The file containing the Geometric information about the building. 3 The file containing the wall transfer function coefficients. 4 An informational file. 16

33 This section includes a brief description of steps for the TSFH modelling with TYPE 56 and TRNBuild which are followed in this study. As shown in Figure 3.1, the TRNBuild manager defines the project details: TSFH orientation, iconic properties which define the parameter value for software calculation such as air density, specific heat of air etc. Inputs icon which is used to add the required INPUTS to TYPE 56 (such as, control strategies etc.) whereas the outputs icon describe the OUPUTS of TYPE 56 such as sensible energy demand of zone etc. where this is the last step of the building description. The TSFH zones thermal definition step include the adding zone walls and windows in addition to its thermal description (see Tables 2.1 and 2.2): defining the materials that will make up the layers of the wall (from internal zone to external) in addition to the wall area, geography (external and internal), thermal conductivity etc., defining the materials that will make up the layers of the window and adding (its thermal properties, area and orientations etc.). After the TSFH zones definition step, inserting the TSFH zones required regime, data step has been followed which includes: infiltration and ventilation data, heating and cooling set points, internal gain setting data, comfort and Humidity. In this study,chapter 2 includes all of the required data for the second step where the infiltration and ventilation data listed in Table2.3, the internal gain is considered based on ISO 7730 standard. Cooling set point is 24 0 C dry bulb and a maximum of % relative humidity. The Heating set point is 20 0 C dry bulb and 30 % relative humidity. Defining the outputs needed from TYPE 56, in this step the output can be selected from the list such as, sensible energy demand (cooling and heating) of building, air temperature of zone, etc. In this study, the sensible energy demand of three bedrooms, living room, guest room and kitchen is defined as outputs for TYPE 56. The final step in the running model is to generate the TYPE 56 files: (*.bui) file used to generate three new files: the (*.bld) 5, (*trn) 6 files which are used by TYPE 56 during the simulation process in TRNStudio program and information file (*.inf) 7. 5 The file containing the Geometric information about the building 6 The file containing the wall transfer function coefficients 17

34 3.2.3 TSFH Modeling with Type56 and TRNStudio After the TSFH Model in TRNBuild is created and the TSFH description file (*.bui) is generated, the TSFH modelling with Type56 and TRNStudio started to complete the simulation of the TSFH thermal cooling and heating loads demands. The brief description of the simulation steps which are followed in this software (TRNStudio) are as described as follows: The first step, creating a new Multizone building project and all its necessary parameters have been entered (such as drawing TSFH plan, setting zone properties, setting window,...etc). Once the created project has been finished the simulation studio will create a multi zone building description (stored in a.bui file), translate the TSFH description file (*.bui) file to the internal files necessary for simulation (*.bld 8, *trn 9 files) from TRNBuild program, create a simulation project (stored in a.tmf file) and open it in the simulation studio [33]. So a simulation with the important components and links for the first run are automatically generated. Figure 3.2: Aswan-TSFH model (Type 56) with all the required components and connections in TRNStudio. 7 An informational file 8 The file containing the Geometric information about the building 9 The file containing the wall transfer function coefficients 18

35 Figure 3.3: Aqaba-TSFH model (Type 56) with all required components and connections in TRNStudio. Figure 3.2 and Figure 3.3 show that the TSFH model (Type 56) with all required components and connections in simulation studio for Aswan and Aqaba respectively. The studio simulation has been started to specify the values for the variables in the components of the TSFH model then determines how data flows from one component to another (such as solar radiation data flows from TYPE 16e to TYPE 56 ). This data flow is indicated by a link between two components in the Assembly Panel window. Assembly Panel window includes the simulation components as shown in the right hand side in Figure 3.2 and Figure 3.3. However, the link shown on the assembly panel is purely informational. So it must specify the details of the link between two components to actually flow data from one component to another [33]. As known in Chapter 2, the meteorological data of Aswan city in TMY and EPW format and its hourly horizontal solar radiation data. In addition, regarding the TSFH geometry, the direct and diffuse radiation of every hour should be determined. Then it must be converted into hourly tilted radiations depending on the sun position in the sky and on the TSFH surface s slope from the horizontal plan. So TYPE 15-3, weather data reading and processing have been chosen for the Aswan-TSFH model in order to read the Aswan 19

36 meteorological data file and to calculate the hourly solar radiation (direct plus diffuse) regarding to the TSFH surface s slope and on the sun position in the sky. After that data has been processed, it will be provided from TYPE 15-3 to TYPE 56 in order to simulate the TSFH cooling and heating demands. In the simulation case of Aqaba-TSFH, there is a difference because the metrological data file has been in Excel format. So the TYPE 9e has been chosen in order to call and read the excel data file which provides this data through the link to TYPE 16e. The TYPE 16e completes the data processing before delivering it to TYPE 56 as in Aswan-TSFH case. In this step, the Reindl model has been chosen in TYPE 15-3 and TYPE 16e in order to calculate the tilted solar radiation. For more details about Reindl mathematical model, see the TRNSYS16 module [33]. As shown in the above figures, TYPE 33e has been chosen for both cases. This component takes as input the dry bulb temperature and relative humidity of moist air from the processing data component and calls the TRNSYS Psychrometrics routine, returning the following corresponding moist air properties: dry bulb temperature, dew point temperature, wet bulb temperature, relative humidity, absolute humidity ratio, and enthalpy [33]. This data is transferred to TYPE 56 to use it in the cooling and heating demand calculations. TYPE 69b is selected for each model in order to determine the effective sky temperature, which is used by TYPE 56 to calculate the long-wave radiation exchange between an arbitrary external surface of the TSFH and the atmosphere. TYPE 65 is online graphics component which is used to display selected system variables while the simulation is progressing [33]. Final step in the TRNStudio simulation is the running step, where the cooling load is calculated in 15 minutes time step by TRNSYS software for the two case studies. Then the cooling and heating load demand simulation results for the TSFH has been provided for both cases. 20

37 Energy [kwh] 3.3 Thermal Cooling Load Simulation Results and Analysis of Results As mentioned before, the major objective of this simulation is to determine the cooling load of a typical single family house in two different climate locations in the MENA regions: Aswan city in Egypt and Aqaba city in Jordan. The discussion and analysis on simulation results concentrate mainly on sensible cooling load demand of TSFH (three bedrooms, living room, guest room and Kitchen). The simulation results and the analysis of the results are documented in subsequent subsections The Annual Energy Consumption This section discusses the annual cooling load consumption for both cases, Aswan-TSFH and Aqaba-TSFH. Figure 3.4 and Figure 3.5 below diagram the total annual and monthly cooling and heating energy consumptions for the aforementioned cases respectively Heating demand Cooling demand Aswan-TSFH Aqaba-TSFH Figure 3.4: Yearly cooling and heating energy demand for the Aswan-TSFH and Aqaba-TSFH. The simulation result in Figure 3.4 shows the annual energy consumption where the total cooling load energy are : 44,330 kwh/year and 43,490 kwh/year; the total heating load energy are: 1114 kwh/year and 1635 kwh/year for the Aswan-TSFH and the Aqaba-TSFH cases respectively. On the other hand, 97.5 % and 96.3 % of the annual energy consumption are cooling load for the two cases respectively. 21

38 Energy demand [KWh] JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Aqaba-TSFH Heating demand Aqaba-TSFH Cooling demand Aswan-TSFH Heating demand Figure 3.5 shows the cooling energy required during a long period throughout the year which is ten months, from February to the end of November, while the heating energy period is very short, three months (January, February and December) for both cases. The previous results and discussion show the extent of a need and importance of cooling compared to heating for both cases in the aforementioned locations. The monthly cooling energy demand in Aswan-TSFH is higher than Aqaba TSFH s throughout the year except for the months of June, July and August. Whereas, in Aqaba- TSFH, there is a higher cooling energy consumption due to a higher humidity in Aqaba city than in Aswan city as shown in Figure 2.3 for the reason that the ventilation increases the inside building s humidity and hence it causes the mentioned difference. Aswan- TSFHCooling demand Figure 3.5: Monthly cooling and heating energy demand in (kwh) for the Aswan- TSFH and Aqaba-TSFH. 22

39 3.3.2 The Performance of Cooling Load Now this section is dealing with the TSFH cooling power demand(real-time power kw), not energy yields (kwh). Because this study going to compensate the power production from the solar air-conditioning systems, not energy Production. However, Figure 3.6 and Figure 3.7 display the cooling load demand distribution throughout the year, for Aswan-TSFH and Aqaba-TSFH cases. These loads follow the solar radiation load which was shown in Figure 2.1. In addition, it follows the outdoor ambient air temperature distribution throughout the year. Furthermore it follows the outdoor ambient air relative humidity, where high relative humidity leads to increasing the cooling demands. So it will be worth to compensate the solar irradiation to this cooling consumption. The maximum cooling load for Aswan-TSFH is 13.9 kw as viewed in Figure 3.6. As shown in the Figure, the peak load takes place during the months of June and August. On the other hand, the smallest cooling load occurs during January, February and December. For Aqaba-TSFH, the simulation result diagrammed in Figure 3.7 shows that the maximum cooling load is in the range kw and this load occurs during the periods of June and August. Besides, the smallest cooling load happens during January and December. Figure 3.6: Yearly Cooling and heating demands distribution(kw) for the Aswan- TSFH. 23

40 Figure 3.7: Yearly Cooling and heating demands distribution in (kw) for the Aqaba- TSFH. The cooling demand generally follows the outside ambient air temperature. Normally, higher temperature leads to higher cooling load due to a heat transition through the building s envelope from hotter outside to a cooler inside of the building. In Aqaba city, the outside average monthly ambient temperature varies from around 15 0 C in January to almost 35 0 C in August. In addition, there are bigger daily ambient temperature fluctuations compared with Aswan s ambient air temperature (see Figure 2.2) which in turn leads to a variation in cooling load throughout the year. In Aqaba-TSFH, as shown in Figure 3.7, the highest cooling load occurs between June and August, which matches the highest outside ambient temperature. In comparison with Aqaba city, the ambient temperature in Aswan city does not vary a lot throughout the year. The minimum monthly ambient temperature is 20 0 C in January and the maximum is 35 0 C in August. In addition, it has low daily fluctuations (see Figure 2.2). A small variation in ambient temperature leads to a minor variation in the cooling load demand in Aswan-TSFH (see Figure 3.6). The lower cooling load fluctuation of Aswan-TSFH means higher night cooling load demand, compared with Aqaba-TSFH. According to Figure 3.5; during the months of June, July and August; the cooling energy consumption in Aqaba-TSFH is higher than Aswan-TSFH s. Hence, identical results are 24

41 shown in Figure 3.6 and Figure 3.7. However, the solar radiation and the ambient air temperature in Aswan city are higher than in Aqaba city because of the presence of a higher ambient relative humidity in Aqaba-TSFH than in Aswan-TSFH (See Figure 2.3). This in turn means, the ventilation during these months increases the inside building s cooling demand due to a prominent ambient air humidity which has entered the building. Figure 3.8: Weakly Cooling load demand distribution in (kw) for the Aqaba-TSFH and Aswan-TSFH. The High cooling load demand shows a less daily fluctuation and is dominated by the external temperature conditions. The Performance of the cooling load during the day of the week in July for both cases (see Figure 3.8), the maximum daily cooling demand occurs at noon and the minimum occurs in the morning of the daytime. Additionally, this Figure shows the extent needed for cooling in huge amounts (approximately 8 to10 kw) during the night as well as in the daytime in addition the night cooling load in Aswan-TSFH higher than Aqaba-TSFH. 25

42 4. Solar Air-Conditioning Technologies The aim of this chapter is to give a brief description of the available solar airconditioning technology. Solar air-conditioning systems can be divided into two groups of systems: solar autonomous systems and solar-assisted systems. In a solar autonomous system all energy used by the air-conditioning system is solar energy. In a solar assisted system the solar energy covers a certain fraction of the energy used by the air-conditioning system and the rest of the energy is provided through an auxiliary or backup system [2]. Only the solar-assisted systems are considered in this study. Solar air-conditioning technologies are any air-conditioning system that use solar radiation as source of power to drive the cooling process in order to produce cold air for buildings. This can be achieved through solar thermal conversion or solar photovoltaic (PV) conversion. In PV air-conditioning systems, PV cells arranged in modules convert solar radiation to electric power which then drives a traditional compression chiller. Solar thermal air-conditioning technology converts solar radiation to heat power (through thermal collector) which is fed into a thermal cooling process or into a direct air-conditioning system. 4.1 Solar Photovoltaic Air-Conditioning Technology Figure 4.1 :Basic structure of PV air-conditioning systems, [2]. 26

43 Figure 4.1 shows the main components of PV air-conditioning systems available. This system consists of three main parts: solar energy collection (includes PV cells) which converts solar radiation into electric power in order to drive the electric machine heat pump. This machine is any electric traditional air-conditioning system which converts the electric power to cooling power. The cooling power is distributed for space cooling either directly in a decentralized system or by a cooling coil and sometimes by a hidronic system [2]. The PV air-conditioning system can include a storage system (battery system) or it can be without a battery system. 4.2 Solar Thermal Air-conditioning Technology Figure 4.2 :Basic structure of heat driven and desiccant air-conditioning systems, [2]. Figure 4.2 shows the basic components and structure of a thermal air-conditioning systems available. This technology can be divided in two groups [2]: a solar heat driven air-conditioning system which consists of a solar thermal collectors (high temperature or medium temperature hot water) where typically flat plate collectors, evacuated tube collectors or concentrated parabolic collectors are used. This converts the solar 27

44 radiation to heat power. Then this power is provided to drive another system in order to produce cooling power for buildings. This system can be either an electrical air-conditioning (such as traditional airconditioning) or thermal air-conditioning (such as absorption/adsorption chillers) or both. The other type is a desiccant cooling system which uses water as refrigerant in direct contact with air and the desiccant dehumidification is combined with an additional cooling system which may be a conventional cooling coil or evaporative cooling. Most thermally driven cooling systems and solar assisted air-conditioning systems installed today are based on absorption chillers [34], [35]. According to [34], [36], [35], [2], [37] and [9], the most commonly used thermal air-conditioning system with the cooling power capacity below 30 kw is a single effect Lithium Bromide-water (LiBr- H2O) absorption chiller with flat-plate collectors. Under normal operation conditions such machines need a typical temperature of the driving heat of 80 o C 100 o C and achieve a COP of about 0.7. In addition, this system is the most economical option since it requires a comparatively lower temperature heat input than a double effect chiller because the additional evacuated tube collectors providing high temperature heat is very costly. This system will be explained in detail later in Chapter 6. 28

45 5. Solar Air-Conditioning Scenarios Design and Simulation The main objective of this thesis is to analyse and compare the performance of solar thermal air-conditioning technology and solar photovoltaic (PV) air-conditioning technology under the MENA region s climate conditions and cooling load profiles. Additionally, to compensate the cooling power production by these technology to TSFH load demands for each case (Aswan-TSFH, Aqaba-TSFH). In order to investigate the above stated objective, the following three scenarios are designed and simulated for each building: Aswan-TSFH and Aqaba-TSFH, as: Solar photovoltaic air-conditioning without storage Solar photovoltaic air-conditioning with storage Solar thermal air-conditioning with storage (absorption chiller) In this chapter the design procedure, simulation and methodology for each scenario are explained. Where the simulation of cooling production by each scenario is carried out by Matlab-Simulink, where the solar radiation on tilted surface has been calculated by using TRNSYS software. That based on the TSFH cooling demand profile which simulated by TRNSYS software for each case as in chapter Matlab-Simulink Simulation Environments Simulations are powerful tools for process design, for study of new processes, and for understanding how existing systems function and might be improved [36]. Numerical simulation offers the possibility to virtually study physical solar air-conditioning systems. Simulation is then the most adapted method to investigate the performance of the cooling profile of the system s output. There are different dynamic simulation software s available for simulating the air-conditioning system and calculating it s cooling products. To mention, SPARK, Energy Plus, EES, Easy Cool, TRNSYS and INSE, MATLAB [38]. 29

46 In this study, for the Matlab-Simulink simulation in order to calculate the cooling production by each scenario for each case (Aswan-TSFH and Aqaba-TSFH). Two time series of data with 15 minute time steps are required as input data, in almost every simulation of cooling production for each scenario: the first type of the time series contains the global solar radiation on a tilted surface and the outside ambient air temperature. The second type of the time series contains the cooling load demand of a TSFH which is obtained from the TRNSYS simulation results of Chapter3. However, the Aswan and Aqaba weather data files which received in this study include the solar radiation data on horizontal surface. Additionally, Aswan data file is in TMYE format which is unreadable by this program. Thus the solar radiation on tilted surface has been calculated by using TRNSYS 16 before starting with the cooling production simulation in Matlab-Simulink. Where the tilt angle is considered to be equal to the latitude of the location (23 54'N for Aswan-TSFH and 29 31'N for Aqaba-TSFH). 5.2 Solar PV Air -Conditioning Scenarios As per the objective of this study, two scenarios of the PV air-conditioning systems have been investigated: PV air-conditioning without storage (see Figure 5.1) and PV airconditioning with storage (see Figure 5.2). These scenarios are designed for each case, Aswan-TSFH and Aqaba-TSFH. This section discusses the system components and designs followed by the system simulations and methodology System Components and Design Figure 5.1 and Figure 5.2 show the two scenarios based on a PV-driven compressed chiller. The PV air-conditioning without a storage scenario consists of a PV module, inverter, a compressed chiller and a system distribution. The system set up of a PV airconditioning with storage is similar to the first scenario, but it additionally has a storage (battery) system and a charge controller. The PV module converts solar radiation into electric power as direct current (DC ). The solar charge controller regulates the voltage and the current which comes from the PV module into the battery. This prevents from the overcharging of the battery and increases the battery life. 30

47 The inverter converts DC into alternating current (AC ) which is needed to drive the compressed chiller. The battery stores the excess energy for supplying the compressed chiller when there is no enough solar radiation to cover the cooling demand. The compressed chiller converts the AC power to the cold air. The compressed chiller is supplied as a back-up with an electric AC power from the grid, when there is not enough DC power from the PV-array and the battery bank, especially at night, evening and morning of the day when there is no enough solar radiation to drive the compressed chiller. PV Module Back-up From grid Inverter Compressed chiller cold air Figure 5.1: Schematic flow diagram for solar PV air-conditioning without storage. PV Module Back-up from grid Charge controller Inverter Compressed chiller Battery system cold air Figure 5.2: Schematic flow diagram for solar PV air-conditioning with storage. 31

48 Compressed Chiller Design The vapour compression system is the dominant system today for cooling and refrigeration and is being used in almost all kind of applications [2]. It is available for a wide range of sizes from 50 W up to 50 MW [2], [39]. Because of its dominance especially in MENA regions and due to its simplicity it was selected for the design of these PV air-conditioning scenarios. A schematic flow diagram of the vapour compressor system and its components are listed in Appendix A. For more details about the system, the process cycles and concepts, see the detail in [2]. A useful parameter to compare the performance of air-conditioning is the coefficient of performance (COP), which is defined as the useful cooling capacity per input power [2]:...(5.1) The COP value of a vapour compression systems for an air-conditioning seems to be around 3 for a smaller to medium size units and up to 4-5 for larger systems [2], [40], [41], [42]. The COP value of the system in this study is assumed to be equal to 3. The cold air is distributed throughout the building by a ductwork. PV array Sizing and Design The first step in designing a solar PV air-conditioning system is to find out the cooling power and energy consumption that need to be supplied by the PV-array. As discussed in chapter 3, the maximum cooling power demands were 13.9 kw in Aswan-TSFH and 15 kw in Aqaba-TSFH.In this study, the maximum cooling power demands were 15 kw assumed for both Aswan-TSFH and Aqaba-TSFH in order to simplify the comparison between the two cases. This means the cooling peak of 15 kw must be delivered by the solar air-conditioning scenarios in this study. Given the coefficient of the performance as 3 for the selected compressed chiller (see Section ), the AC peak power is required to reach up to 5 kw (calculated by employing equation 5.1). 32

49 To compensate the power losses in the inverter and the battery system 20 % of power is added to this value. Thus, the required peak DC power equals:...(5.2) Different sizes of PV modules produce different amounts of power. The power produced depends on the size of the PV system and the radiation at the site. The polycrystalline solar module (SCHOTT PERFORM TM POLY) 225 watt peak (Wp), is produced by SCHOTT solar company in Germany where the Module s efficiency is 13.4 %.It was selected for all PV air-conditioning scenarios. The data sheet of the PV module is attached in Appendix B. The number of PV modules required is calculated by Equation 5.3. The airconditioning system should be powered by at least 27 PV-modules with 225 Wp each:...(5.3) The total PV array s area required is calculated by using equation 5.4 where the PV module area equals m 2 as stated in Appendix B:...(5.4) The modules in a PV-array must be connected in combined connection, i.e 14 modules in parallel and two in series, in order to deliver an output voltage of 44 V-64 V which is the DC input voltage range for the inverter and battery system. 33

50 8.7 m 6.05 m 5.05 m As shown in Figure 5.3, the TSFH roof is flat with an area of 224 m 2. The area is large enough for the installment of 27 PV modules with ( )and additional, other applications. This is one of the building advantages in the MENA region. The PV-array was installed on the surface area (1) on the TSFH-roof which covers the three rooms(see Figure 5.3). The area equals 81 m 2 which is enough by assuming that there are no shading effects on the collectors and enough free space for maintenance. The optimum PV-array orientation will depend on the latitude of the site, prevailing weather conditions and the load to be met. As a rule of thumb, for low latitudes (as in MENA-regions) the maximum annual power output is obtained when the array tilt angle roughly equals the latitude and the array faces due south (in the northern hemisphere) or due north (in the southern hemisphere) [43]. The PV-array orientation for the two PV air-conditioning scenarios is designed facing south. The tilt angle equals the latitude which is 23 54' N and 29 31'N, for each case study: Aswan-TSFH and Aqaba-TSFH respectively m m Aria (1) = m 2 Area (2) 13.9 m Figure 5.3: The dimensions of a typical single family house (TSFH) - roof area (1) for PV-array installation. 34

51 Inverter Sizing and Design An inverter is used in the system where AC power output is needed. The input rating of the inverter should never be lower than the total watt of appliances. The inverter must have the same nominal voltage as the battery. The inverter size should be % bigger than the total power of appliances [44]. The maximum DC power demand is calculated and equals 6 kw in Section Stand-alone inverters are used to convert (DC )current from PV-array and battery to (AC) in order to run the compressed chiller. For the suggested PV system, in this study the required inverter should supply 230 V AC, 50 Hz, 6 kw. The chosen inverter is the Outback Inverter XW , 6 kw,( 44-64) V DC, 230 V AC/50 Hz with a peak efficiency of 95.4 %. This inverter is produced by the Xantrex Technology Inc. Company and the data sheet is attached in Appendix (c) [45]. Storage (battery) System Design Energy produced by the PV array is accumulated and stored in batteries for use on demand. The battery system is designed for a PV air-conditioning with storage. In this scenario, when the electric DC power is higher than the electric power needed by the compression chiller. The battery accumulated and stored the excess DC power as electric energy. The battery s capacity for storing energy is rated in amp-hours. The battery capacity is listed in amp-hours at a given voltage. Batteries are sensitive to climate, charge/discharge cycle history, temperature and age [46]. The battery system should be sized to be able to store excess power for 2 days. The following calculations can be performed to select the suitable size of batteries for PV airconditioning with storage: The excess energy is calculated based on simulation results of a PV air-conditioning without storage scenario. This calculation is discussed later in more details in Chapter 6.2.2, where the results of this scenario: in April and October, the excess cooling production is almost equal to the External back-up cooling load for both cases. Thus ten days of an excess cooling power in April is taken. Then the average daily excess cooling 35

52 energy in Aswan-TSFH is calculated which is equal to kwh/ day. The average daily electric DC excess energy is 6.4 kwh/day which should be stored. This value is close to the value which is calculated in Aqaba-TSFH. The battery system size is thus, the same for both cases. Given the compressed chiller COP of 3, the inverter efficiency of 95.4% and the daily excess cooling energy of kwh, the resulting DC energy is 6.4 kwh (see Equation 5.5): (5.5) The required nominal battery capacity (Cnom,Batt) in amp-hour for the daily power is calculated by using Equation5.6 [47]. The required output voltage (VBtt) is 48 V. The required autonomy factor (AF) for the scenario locations which are close to the equator is 2. It is defined as the duration of time during which the nominal battery capacity,starting from full charging conditions, can cover the energy demand of the consumer. The minimum allowable depth of discharging (DOD) is %. Deep-cycle batteries are capable of many repeated deep cycles and are best suited for PV power systems [46]. In the case study, the battery safety requires that the discharge of batteries should not exceed 80 % of its capacity. The battery efficiency is 85 %. :...(5.6) According to the above calculations, the battery system which is required for this scenario needs to produce about 392 Ah. Thus 8 batteries of 12 V each are required and each 4 batteries are connected in series. Sun extender batteries PVX2120L are selected for this scenario [46]. 36

53 Controller The solar charge controller regulates the voltage and the current which comes from the PV module into battery. According to the previous calculations 27 PV modules are required; each module producing 29.8 V and 225Wp (7.55 A). PV panels are connected in parallel to supply 106 A. A controller is needed to hold at least A. A controller that carries a current of A, 48 V DC has been chosen for the PV air-conditioning with storage scenario. Back-up System When there is no enough electric power coming from the PV-array and the battery system to cover the cooling power demands, the back-up system is designed to deliver the remaining needed AC power. The back-up system is assumed to have a direct connection to the electricity grid and to the compressed chillers. This connection is considered and designed for both PV air-conditioning scenarios without and with storage Systems Simulation and Methodology There are different simulation tools which are available to estimate the cooling production of the PV air-conditioning system. A model based on Matlab-Simulink has been carried out to perform the cooling power gain and its influence to cover the cooling demands. The simulation process is conducted for one year with a time step of 15 min using the two time of series as an input data in Matlab-Simulink: the first data set is the time series of meteorological data, solar radiation on a tilted surface and the ambient temperature. As discussed in Section 5.1, the solar radiation on a tilted surface Gtilt in W/m 2 and is calculated by using TRNSYS software. The second time series contains the cooling load demand. The cooling load demand is simulated by using TRNSYS program in Chapter 3. 37

54 PV air-conditioning Without Storage Scenario PV-array Electric Power Output The DC power production of a PV-array is calculated by using Equations (5.7, 5.8,5.9) where the selected PV module efficiency is 14.3 % (See Appendix B), the PV-array area is m 2 as discussed before: (5.7) Module s operation temperature is a parameter that has a great influence on the behaviour of a PV system as it influences its system efficiency and energy output. It depends on the module encapsulating material, its thermal dissipation and absorption properties, the working point of the module, the atmospheric parameters such as irradiance level, ambient temperature and wind speed [48]. There are many empirical relations expressing Tc, the PV cell temperature, as a function of weather variables such as the ambient temperature Tamb, and the local wind speed, as well as the solar radiation, Gtilt [49]. In this study, the scenario simulations take the PVmodule operating temperature and associated effects on the power output into account. Equation 5.8 represents the traditional linear expression for the PV electric efficiency [49]. The module efficiency at the standard test condition (STC) is 14.3 % and module s temperature coefficient is 47.2 o C (both are given by the PV manufacturer and listed in Appendix B)....(5.8) The Operation cell temperature TNOCT is employed in Equation 5.9. It is common to use it as an indicator of module temperature, in fact, manufacturers usually include this parameter in their module data sheets. It is defined as a mean solar cell junction temperature within an open-rack mounted module in a standard reference environment (SRE): tilt angle at a normal incidence to the direct solar beam at local solar noon; total irradiance of 800 W/m 2 ; ambient temperature of 20 0 C; wind speed of 38

55 1 m/s and nil electrical load. It is an important parameter in module characterisation since it is a reference of how the module will work when operating in real conditions. Furthermore, in PV system design and simulation programs, many calculations are based on the determination of module temperature from ambient temperature and NOCT [48]....(5.9) Inverter Electric Power Output After designing the PV-array, the DC power output is calculated. The inverter converts the DC power to AC power by Equation The inverter s efficiency is 95.4 % (see the data sheet in Appendix C): (5.10) Compressed Chiller Cooling Power Output The compressed chiller converts the AC power into cooling power. This calculation is the final step in each scenarios simulation and is represented by Equation 5.11 (where COP is 3): P c coolling OP P In electric...(5.11) Excess and Back-up Cooling Power The excess and back-up cooling power are calculated by subtracting the output cooling power of the PV air-conditioning system from the cooling power demand (Equation 5.12). If the value is positive, then the excess cooling power P E cess1 is available. If it is negative, back-up cooling power P ack up cooling1 is necessary. The latter is compensated by the back-up system connected to the grid: P E cess1 ack up cooling1 P c coolling P demand...(5.12) 39

56 PV Air-conditioning with Storage Scenario In this scenario, the direct cooling power produced from the system is calculated. The same calculation procedure as in the first scenario (without storage) is followed (Equation 5.7 to Equation 5.12).Then the excess produced cooling power is converted to DC by Equations 5.11 and The electric power charged in the battery system is calculated by Equation 5.13 where the battery efficiency is assumed to be 85 %. It is taken into account that the battery capacity is limited (see Equation 5.13), where the maximum battery capacity of the system is 6.4kWh as discussed before:...(5.13) Then, the cooling power produced by the contribution of the battery system discharging is calculated by using Equation 5.14, where the DOD is considered to be 80% and the chiller COP 3: (5.14) There is a balance between excess power and the required back-up power. Excess energy is usually available at noon while back-up power is needed during the morning, evening and night. The back-up cooling energy which should be provided by the grid E ack up cooling is calculated by Equation 5.15 : t E ack up cooling P 0 ack up cooling1 dt t P 0 att cooling dt (5.15) 40

57 5.3 Solar Thermal Air-conditioning Scenario (absorption chiller) The thermally driven air-conditioning process is the heart of every solar cooling system. Thermally driven air-conditioning systems are available on the market which commonly utilize sorption processes. For air-conditioning applications, mainly absorption chillers using the sorption pair Lithium bromide-water (LiBr-H2O) are applied [9] since they require a comparatively low temperature as heat input. Most of the thermally driven cooling system and solar assisted air-conditioning systems installed today are based on absorption chillers [34], [35]. A Lithium bromide-water (LiBr-H2O)absorption chiller is selected for the two cases, Aswan-TSFH and Aqaba-TSFH, in order to compensate the cooling demands for each building. This section discusses the system components, design and; thereafter the system simulation and methodology System Components and Design As shown in Figure 5.4, an absorption chiller coupled with a solar heating system and an auxiliary energy supply as back-up electric heater is analyzed. In the assumed case, the collector converts the solar radiation into heat and then the pump delivers it to the storage tank. The storage tank then supplies the absorption chiller with thermal energy to produce cold water. The coil and the fan system transfer the cooling power from cold water to the inside air of the building. A duct system distributes it in the building. If solar heat is insufficient e.g. at night or during cloudy days, the conventional back-up electric heater is connected directly with the storage tank can provide heat. The system components and design can be described as follows: 41

58 ABCH absorption chillers A absorber C condenser E evaporator G generator SC ABCH CT B FC SC HST thermal backup Fan coil solar collector hot storage tank B HST G C CT cooling tower FC A E Solar heating system Absorption chiller Figure 5.4: Solar thermal air-conditioning system scenario, coupling of an absorption chiller with a solar heating system Solar Thermal Heating System The basic elements in the solar thermal heating system (see Figure 5.4) includes a collector, a stratified hot water storage tank, and a back-up electric heater. All components are described in the following. Solar Collector A solar collector is a special kind of heat exchanger converting the solar radiation into thermal heat which is carried by a working fluid, e.g. water which is flowing through the collector. There are three types of solar collectors which are typically used in a solar thermal air-conditioning systems: flat plate collectors, evacuated tube collectors and concentrated parabolic collector. In the solar thermal air-conditioning system, the temperature level that should be supplied by the solar thermal collector depends on the cooling technology used. Flat plate collectors can be designed for applications requiring energy delivery at moderate temperatures, up to perhaps C above the ambient temperature. The operation of absorption air-conditioning with energy from flat plate collectors and storage systems is the most common approach to solar cooling [36]. 42

59 The solar flat plate collector industry is available in the MENA regions especially in Jordan and Egypt which are the selected locations in this study. To model this scenario, a high quality flat plate collector from Schüco company is used. The collector parameters are summarized in Table 5.1. According to [50], a very simple assessment (rule of thumb) of the collector dimensions in a solar-assisted air conditioning system 10 can be made using a single design point. The specific collector area, defined as the collector area per nominal cooling capacity can be roughly chosen according to the following Equation 5.16 [35]:...(5.16) Where : G: is the global radiation [w/m 2 ] : is the collector s efficiency in design condition coll OP : coefficient of performance For our case, G=800 W/m 2 resulted is Acoll,Spec =3.5 m 2 for a 1kW of cooling capacity. =50%, OP=0.7 and the specific design collector s area coll According to this rule of thumb, the solar collector area for the solar thermal airconditioning scenario is designed. The solar radiation for the two locations, Aqaba city and Aswan city is approximately G=1000 W/m 2 in summer (see Figure 2.1). This means a specific collector s area is Acoll,Spec = 3.5 m 2 for 1kW cooling capacity which is needed for this scenario. As discussed in chapter 3, the maximum cooling load demand is 13.9 kw and 15.3 kw for Aswan TSFH and Aqaba-TSFH respectively. The assumption is made for both cases that the maximum cooling load demand is 15 kw in each case. So, the area of the collector needed for the system is 42 m A solar air-conditioning system can be either a standalone autonomous system where all energy input is from solar or a solar-assisted air-conditioning system where partial energy input is supplied from solar. 43

60 In order to simplify the comparison between the PV air-conditioning scenarios and thermal air-conditioning scenarios which is a major objective of this study, the solar flat plate collector is designed for 45m 2 which is equal to the PV-array area in the PV airconditioning scenarios. Flat plate collectors are fixed and there is no tracking system. The collectors should be oriented directly towards the equator. The collector s location in the northern hemisphere should be facing the south and vice-versa in order to maximize the amount of daily and seasonal solar energy received by the collector. The optimal tilt angle of the collector is an angle equal to latitude of its location [51]. However, in summer the tilt angle should be smaller than the latitude to receive more solar radiation. Table 5.1 : Parameters of the flat plate collector, [52]. Parameter Flat plate collector Unit 78.4 [%] C [W/m 2 K] C [W/m 2 K 2 ] Surface area 2.69 [m 2 ] 44

61 Storage Tank The solar photovoltaic air-conditioning system stores the excess DC in batteries. Similarly, It is necessary to use a thermal energy storage tank, either heat or cold storage in thermal air-conditioning system. According to [36], the thermal energy from the collector can be stored to be used when needed by the air-conditioning (heat storage). Alternatively, the cooling product by the air-conditioning can be stored in a low temperature (below ambient) thermal storage unit (cold storage). That s to provide cold energy for a few hours in the afternoon when solar radiation already decreases but internal cooling load demand is still high. These two alternatives are not equivalent in capacity, costs or effect on the overall system design and performance. The required capacity of a cold storage tank is less than that required of a heat storage tank because the heat storage has a higher conversion efficiency than the cold storage tank [36]. In addition, heat storage tanks can be used for other applications for example domestic hot water or space heating. There are two technologies for hot water storage tanks which can be used. Either with thermal stratification or without. Stratification means moving the thermal heat from layers of cold water at the bottom of the tank to the hot water at the top of the tank. That will increase the performance efficiency of the system. According to [6], in order to achieve a solar fraction of 80 % for the given cooling load profile, a collector aperture area of 48.5 m 2 and a storage tank volume of 2 m 3 is required if the generator is always operated at an inlet temperature of 85 0 C. This study analyzes a solar thermal air-conditioning system (Lithum-Bromide water absorption chiller with a COP of 0.7 and a nominal cooling capacity of 15 kw ) in Madrid. Madrid has a Mediterranean climate similar to the selected locations in this study,where the solar radiation reaches 1000 W/m 2 in summer. In this study the stratification of a hot water storage tank volume is 2m 3. The tank is produced by KWB company in Germany (see Table 5.3) [53]. The tank parameters are listed in Table 5.3. According to [50]and [35], high temperature differences between the inlet and outlet of a collector are not recommended in a solar air-conditioning systems. The basic reason is 45

62 that thermally driven chillers in general work at comparatively low temperature differences between inlet and outlet, e.g C. Therefore, in this study 20 0 C temperature difference in the storage tank is assumed.the storage tank has 20 0 C temperature nodes to simulate stratification with minimum temperature equal to the chiller outlet hot water temperature of 75 0 C and the maximum temperature of 95 0 C. Back-up System When there is no enough solar radiation (e.g. at evening, night or on cloudy days), it will be a necessary to have a back-up system for the cold production or to allow the solar air-conditioning system to continue. Two different back-up approaches can be used to achieve this objective, either back-up heating or cooling systems. The back-up heating system usually uses burners (oil, gas or pellet) or electric heater connected directly to the heat storage tank. The back-up cooling system usually uses conventional vapour pressure cooling devices. In this study, a back-up electric heater supplies the storage tank with heat whenever the storage tank temperature drops below the set point temperature required for driving the sorption chiller (85 0 C). This gives stability for the cooling production of the chiller especially in the afternoon(see Table 5.3).This choice (back-up heater)and not back-up cooling system has been built based on two arguments. Firstly compared with back-up cooling system, the back-up heater support the absorption chiller to going on even if the hot water which delivered by the collectors is lower than the minimum operation temperature of the absorption chiller, this leads to increase the absorption chiller operation time during the presence of solar radiation. which means higher solar gain and benefit. The second argument the price of back-up heater system is much less than the back-up cooling system. 46

63 Absorption Chiller Most of the thermally driven cooling system and solar assisted air-conditioning systems installed today are based on absorption chillers [34], [35]. The absorption chillers are used to produce chilled (cold) water which can be used for any type of air-conditioning equipment to cover the cooling load demand in the building. Physical Description Heating rejection (cooling tower ) Driving heat (e.g. Solar collector ) Condenser Generator Throttle valve solution heat exchanger Throttle valve Pressure Evaporator pump Absorber Useful cold (Qcooling) Heat rejection (cooling tower) Temperature Figure 5.5: Schematic diagram for an absorption chiller for chilled water production, [37]. Figure 5.5 depicts the schematic diagram for the working principle of absorption chiller systems. They are similar to a mechanical compression cooling system with respect to the system components evaporator and condenser. In a mechanical compression cooling system, a mechanical compressor is employed in order to produce the pressure differences and to circulate the refrigerant. Whereas the absorption chiller uses a heat source. The absorption chiller consists of an absorber, a pump, a heat exchanger, a generator and a throttle valve instead of a mechanical compressor.the steps description of the absorption cycle as following [37]: 47

64 In the evaporator: the refrigerant (water) converts from liquid to vapour by extracting heat from a low temperature heat source like building to be cold. The results from this process is a useful cold. The refrigerant vapour moves to the absorber: where a concentrated hygroscopic solution (Lithium-Bromide) absorbs the refrigerant vapour. This process generates latent heat which should be removed to keep the process going usually by using a cooling tower. The mixture of the two fluids is pumped to the generator which is connected to the driving heat source, e.g. the solar collector. In the generator, the mixture is separated again by increasing temperature and partial pressure by the heat supply. The refrigerant vapour is released at high pressure and moves to the condenser and the concentrated hygroscopic solution flows back to the absorber. In the condenser: the refrigerant vapour is condensed, heat is rejected to a heat sink and usually removed by using a cooling tower. In this step, the pressure of the refrigerant condensate is reduced by streaming through an expansion valve, afterwards it flows back to the evaporator. Coefficient Of Performance (COP) The efficiency of a thermal absorption chillers is determined by the coefficient of performance COP. Looking to the absorption chiller as shown in Figure 5.5, the position of the components represents the pressure and temperature levels. The COP depends on three external temperature levels: hot water inlet temperature (heating) which comes from the collectors, the required temperature of the chilled water (chilled) which needs to cover the cooling demand in the building and the temperature of the re-cooled water(re-cooling) which circulates through the cooling tower. According to the first and the second laws of thermodynamics, the ideal coefficient of performance, COPideal, can be expressed as follows [55], [35]: 48

65 ......(5.17) Where : : inlet temperature of the generator (heating ), [ 0 K] : outlet temperature of evaporator (chilled), [ 0 K ] : inlet temperature of condenser (re-cooling), [ 0 K] Equation 5.17 shows how the COP is affected by the three temperature levels depending on the external technical operational side: for heating (flat plate or evacuated tube collectors, waste heat source), re-cooling (cooling tower) and cooling application (sensible and /or dehumidification, fan coils etc). Finally, when making the choice of the product, the boundary conditions should be taken into consideration as done in this study. Absorption Chiller Selection and Design Absorption chillers are available on the market in a wide range of capacities and design for different application. For air-conditioning applications, mainly absorption chillers using the sorption pair Lithium Bromide-water (LiBr-H2O) are applied [9]. There are two types of absorption chiller technologies. Single-effect or double-effect absorption chillers. The term single-effect refers to the fact that the supplied heat is used once by a single generator. A double-effect absorption chiller can be viewed as two single-effect cycles stacked on top of each other. The top cycle requires heat at a higher temperature level compared to a single-effect machine. Double-effect cycles have a higher COP than single-effect cycles [37]. For solar-assisted air-conditioning systems with common solar collectors, single-effect LiBr absorption chillers are the most commonly used systems since they require a comparatively low temperature heat input [37]. 49

66 According to the simulation results of the thermal cooling load demands for the Aswan- TSFH and Aqaba-TSFH, the maximum cooling load demand are 13.9 kw and 15.3 kw respectively. Based on this results the absorption chiller has been selected in this study. WEGRACAL SE 15ACS15 is a water /Lithium Bromide single effect absorption chiller 11 with a nominal capacity of 15 kw and a COP of This absorption chiller is selected for the solar thermal air-conditioning scenario as shown in Figure 5.4. In this study, the system is designed to work under the device parameters from the manufacturer in all cases (see Table 5.2). Table5.2: Lithium Bromide-water (WEGRACAL SE 15ACS15) absorption chiller parameters, compiled from [56[, [37] and [10]. Parameter Absorption chiller LiBr-Water Unit Manufacturer EAW [-] Designation Wegracal SE 15ACS15 [-] Technology Absorption [-] Sorbent refrigerant LiBr/H2O [-] Cooling capacity 15 [kw] COP 0.71 [-] Heating temperature 90/80 [ 0 C] Re cooling temperature 30/35 [ 0 C] Cold water temperature 17/11 [ 0 C] Electricity demand 30 [W] Hot water 2 [m3/h] Cold water 5 [m3/h] 11 It is designed by the company EAW, Westenfeld and the Institute of Air Conditioning and Refrigeration in Dresden (ILK-Dresden) [35]. 50

67 Cooling Tower A cooling tower is a special heat exchanger where re-cooling water is brought into contact with ambient air to transfer rejected heat from the coolant. Heat rejection greatly affects the performance and efficiency of the chiller. In most systems the waste heat is released into the environment by dry coolers or wet cooling towers. The wet cooling tower is suitable for moderate climate zones that only occasionally have high outside temperatures (>30 C) [56]. However, the dry cooling tower generally shows less efficient operation, increased electricity consumption due to larger fans and at least double the investment costs in comparison to wet cooling towers [37]. In this study, a wet cooling tower is assumed 12 (see Table 5.3) Cold distribution System The type of cold distribution system in the building is assumed to be fan coils with a working temperature of 11 o C / 17 C. The chilled water circuit consists of a pump and a water/air heat exchanger (fan coil) which refrigerates the building zones through a duct system. The fan coil is located inside the building. Table5.3: Technical parameters of the back-up heater, storage and cooling tower, [37]and [10]. Parameter Back-up heater Cooling tower Storage tank Unit 0.95 [-] K hllosses 0.8 [W/(m 2 K)] T maxsth 98 [ C] Volume 2 [m 3 ] Electricity Consumption 6-10 [W/kWof cooling power] 12 For more details about the wet cooling tower system see the schematic diagram and the description of this system in according to [37] in Appendix D. 51

68 5.3.3 System Simulation and Methodology The simulation provides useful information about the long-term performance of a solar thermal air-conditioning system. This section describes the simulation steps for the solar thermal air-conditioning scenario by the using Matlab-Simulink for both cases of Aswan-TSFH and Aqaba-TSFH. Simplifications are made by keeping the coefficient of performance of the absorption chiller (COPABCH) constant at 0.71, by assuming a constant heating water temperature of 85 o C re-cooling water temperature (30 o C) and a cold water temperature (11 o C) as indicated by the manufacturer (see Table 5.2). The simulation process is done step by step for each case, starting with the loads that have to be compensated by the chiller depending on the cooling load demands. In the first step, the hot water and the power consumption of the chiller together with the cooling tower is calculated by assuming the cooling power demands Pcool- load c and the coefficient of performance for the absorption chiller COPABCH. The heat power supply required by the absorption chiller P habch h is calculated by using the following equation (5.18) [36] :...(5.18) In the second step, the heat power production Pcoll h from the collector is calculated by using Equation (5.19). The collector s efficiency is calculated by Equation (5.20) [57]. The collector s efficiency is defined as the ratio of the usable thermal energy and the received solar energy. It could also be obtained for each time step if the optical and the thermal loss coefficients of the collector, C1 and C2, are known. The optical efficiency indicates the percentage of the solar rays penetrating the transparent cover of the collector (transmission) and the percentages being absorbed. Basically, it is the product of the rate of transmission of the cover and the absorption rate of the absorber [58]. For more details about the collector parameters see Table

69 ....(5.19)...(5.20) Where : : Collector optical efficiency; [-] C1 : linear heat transfer coefficient; [W/m 2 K] C2: quadratic heat transfer coefficient; [W/m 2 K 2 ] T coll: average fluid temperature in the collector; [K] G tilt : solar radiation on a tilted surface; [W/m 2 ] At the storage tank, based on the first and second steps, the heat power product by the solar collector Pcoll h and the heat losses from the storage PhABH h by the demand of cooling system are known. In addition to that, the heat losses PST;loss h to the surrounding from the surface of the storage tank due to non-ideal insulation is determined by Equation The temperature of the storage differs from one time step to the next due to the heat consumption by the adsorption chiller from the storage tank, heat losses and the heat supply by the collector to the storage tank. The temperature difference ( TS) of the storage between the two time steps is calculated by using Equations (5.21) [36]:...(5.21) Where: w : density of water; [kg/m 3 ] 53

70 V storage: Volume of the storage; [m 3 ] Cw : specific heat capacity of water; [4.2kJ/kg.K] : storage temperature deference; [k]...(5.22) Where : U : storage heat losses coefficient in [W/m 2 K] As: storage surface area [m 2 ] For the heat losses of the storage tank due to non-ideal insulation, it was assumed that the temperature difference between the storage Tstorage and its surrounding is constant throughout the year for all location with 65 o K (Tstorage =85 o C and the room temperature 20 o C). The fourth step refers to Equation If the Ts (TSTHset TSTHnew) is negative, the heating power from the back-up heater is required. The heat which has to be supplied by the back-up heater and is calculated by Equation 5.23 where the back-up heater efficiency is 0.95 (see Table 5.3) [10] as:...(5.23) From Equation (5. 1), if the value for the Ts (TSTHset TSTHnew) is positive, there is excess heat available from the collector which is not required according to the cooling load demands. So the amount of heat power which has to be stored PS h in the tank as a thermal energy is calculated by using Equation 5.24 [36]:...(5.24) 54

71 The daily heat capacity limit for the storage tank is taken into account by using Equation The maximum daily heat capacity in (kwh) of the storage water is calculated for the given storage size of 2 m 3 by using Equation 5.25 as:...(5.25) where the is the storage tank difference in (K). As discussed before the maximum was 20 k in this study. The direct heat power(under assumption: the system without storage) which is driving the chiller to produce the direct cooling power was calculated by using Equation 5.26 :...(5.26) The powers are converted from heat power to the cooling powers: and, where the is as in the subsequent Equations:...(5.27)...(5.28)...(5.29) 55

72 ...(5.30) A simplification is made in this study by neglecting the power consumption of the pumps. For the technical parameters of the back-up heater and storage tank see Table 5.3. The back-up cooling power is calculated by using Equation 5.29 without subtracting the cooling power which is compensated by the storage since there is a mismatching between the charging heat power in storage tank and the back-up heat power needed; where the charging heat power happened at noon of the day while the back-up heat power is needed in the morning, evening and night. So in this scenario, the back-up cooling energy which should be covered by the grid using Equation 5.31 as: is calculated by =...(5.31) where the cooling energy which is compensated by the storage and the direct cooling energy compensation is calculated by using Equation 5.32 and Equation 5.33 respectively. The total cooling energy demand is calculated by employing Equation 5.34 :...(5.32)...(5.33)..... (5.34) 56

73 Solar Fraction The solar fraction is the fraction of the total load which is covered by the solar energy which is usually expressed as percentage [50]. The solar fraction of a particular system depends on many factors such as the collector and storage size, the operation and the weather. Therefore, it is a key indicator for sizing the solar thermal system [35]. The annual solar cooling fraction (SF) is calculated by employing Equation 5.35:...(5.35) where the is the annual back-up heat energy for driving the chiller process which is calculated by using Equation 5.36 :...(5.36). Where t=35041 is the number of time steps (15 min) per year and the annual required heat energy for driving the chiller process which is calculated by using Equation 5.37: (5.37) 57

74 6. Simulation Results and Analysis for Solar Air-Conditioning Scenarios This chapter includes the simulation system scenarios results. The results are analysed for each scenario. Then, the comparison between the solar thermal air-conditioning with storage scenario and a solar PV- air-conditioning scenarios with and without storage scenarios is done. Eventually, conclusions and the further work are delineated. So in this study the e pressions, Cooling production energy/power means the cooling energy/power which is produced by any air-conditioning system scenario as without storage. Direct cooling compensation energy/power means the cooling energy/power which compensate part from the cooling demand by the air-conditioning system scenario as without storage. Storage compensation means the cooling energy which compensates part from the cooling demand by the contribution of the storage system in the air-conditioning system scenario. External back-up cooling energy/power means the cooling energy/power which produced by the contribution of the backup system of the solar air-conditioning system from the grid electricity in each scenario, in order compensate the residual cooling demand, (the electric back-up heater in thermal airconditioning scenario, direct grid connection with the compressed chiller in PV airconditioning scenarios). 6.1 Solar Photovoltaic (PV) Air-conditioning Scenarios The simulation results and analysis of the results for the two PV air-conditioning system scenarios, without and with storage (battery) has been discussed for the Aswan-TSFH and Aqaba-TSFH cases. The battery was designed to compensate the cooling load demands. Firstly, the influence of the cooling production load by the solar PV airconditioning system without (battery) scenario is diagrammed. Then it is followed by the excess of cooling production and the external back-up cooling load results analysis, in order to explain the storage which is designed for the solar air-conditioning system with battery scenario. Finally, analysis of the results is made for annual cooling energy products to compensate the cooling energy demands of the two cases, Aqaba-TSFH and Aswan-TSFH. That s for each scenario, PV solar air-conditioning system without battery and PV solar air- conditioning with battery. 58

75 6.1.1The Influence of a Direct Cooling production Yearly Analysis: Figure 6.1: PV air-conditioning cooling production along the year for Aswan-TSFH. Figure 6.2: PV air-conditioning cooling production along the year for Aqaba-TSFH. The cooling production covers almost entirely the maximum peak of the cooling load demand for Aswan-TSFH especially in the summer. On the contrary, for the case of Aqaba-TSFH, the cooling production is lower than the maximum peak of the cooling load consumption by 3 to 4 kw for the reason that there is a higher solar radiation in Aswan than in Aqaba. Besides, Aqaba-TSFH has higher peak load demand in summer than Aswan. 59

76 For both cases, the cooling production in winter is higher than in summer. This in turn means, operation module is more efficient in winter than in summer. That s due to the PV module s operation temperature being lowered in winter than in summer. As a result, it leads to enhancing the PV module efficiency and increasing the electric power outputs from the PV array. On the other hand, the ambient air temperature in winter is lower than in summer for both cases (see Figure 2.2 ). This reduces the thermal effect on the PV module by improving the heat transfer rate from the PV module to the ambient air with the help of the temperature difference between the module and the air which is higher in winter than in summer. This leads to increase the module efficiency and electric power output. In winter, the cooling production reaches 17 kw and 15 kw in Aqaba-TSFH and Aswan- TSFH respectively, due to a lower thermal effect on the module as discussed before. In addition, there could be a higher diffused solar radiation and a higher reflected radiation by the ground in Aqaba than in Aswan where the PV module is tilted at angle of 29 31' in Aqaba and is higher than Aswan s 23 54'. Weekly Analysis: Figure 6.3 to Figure 6.6 illustrates the weekly distribution of cooling production in summer and in winter for the two cases by PV air-conditioning system without storage. Figure 6.3: Solar-PV air-conditioning cooling production in Summer week for Aswan-TSFH. 60

77 Figure 6.4: Solar-PV air-conditioning cooling production in Summer week for Aqaba-TSFH. Figure 6.5: Solar PV air-conditioning cooling production in winter week for Aswan- TSFH. Figure 6.6: Solar PV air-conditioning cooling production in winter week for Aqaba- TSFH. 61

78 In summer (see Figure 6.3 and Figure 6.4), in general, Aswan-TSFH has excess cooling production than the cooling demands compared with the case of Aqaba-TSFH by which there is a little of excess cooling production. This due to a bigger solar radiation in Aswan city than in Aqaba city and vice versa of cooling demand. There is a bigger cooling demand in Aqaba than in Aswan especially in summer; June,July and August; as discussed before. As shown in Figure 6.3 and Figure 6.4, most of the external back-up cooling load is needed during the evening, the night and in the morning due to a high cooling load demand in these periods of the day. The shape of the daily cooling production curves are diagrammed in Figure 6.3 and Figure 6.4. As can be seen in the figures, there are several differences between the two cases. In Aqaba-TSFH case, the curve starts increasing in the morning with a high slope and reaches its peak at noon and in turn it decreases to reach zero in the evening, compared with the Aswan-TSFH case. The reason is the increment in the solar radiation which is higher than Aqaba during the day time and this increases the thermal heat effect on the PV module s efficiency and reduces the module electric power output. In addition, the presence of a higher ground solar reflection and diffusion in Aqaba city than in Aswan city could lead to an increment in power output from the PV module. In winter as shown in Figure 6.5 and Figure 6.6, there is an excess cooling production than cooling load demands due to a low cooling consumption in winter. This in turn means a high wastage of power during this season. In addition, the percentage of the daily cooling demand which is covered by the production reaches approximately 50 % to 70 %.The wastage power in winter, it can be a benefit power if it has been stored in the grid network. This leads increase the aver all efficiency of PV air-conditioning system, so it is one of the PV air conditioning technology advantages compared with the solar thermal air-conditioning technology. 62

79 6.1.2 Excess of Cooling Production and External Back-up Cooling for a Battery Design After the discussion of the cooling production load by the solar PV air-conditioning without battery, we deducted the direct cooling compensation by this scenario which covers apart from the cooling load demand. This section discusses and analyses the excess cooling production and the residual cooling load demands which should be covered by external back-up system. The external back-up system as discussed in Chapter 5 is designed to have a direct connection of electric compressed chiller in the solar PV-air-conditioning system with the grid electricity and hence it covers the residual cooling load demand. As shown in Figure 6.7 and Figure 6.8 there are excess cooling production and external back-up cooling power from the first scenario, without battery. So to increase the solar power gain as cooling compensation and to reduce the external back-up cooling power. Hence, that is the main reason for the selection of the second scenario: solar PV airconditioning with battery for both cases. The storage battery is designed for the second scenario, based on the results of the first scenario as illustrated in Figure 6.7 and Figure 6.8. Figure 6.7: PV air-conditioning without storage scenario, Excess cooling production and external back-up cooling loads for Aswan-TSFH. 63

80 Figure 6.8: PV air-conditioning without storage scenario, Excess cooling production and external back-up cooling loads for Aqaba-TSFH. As shown in Figure 6.7 and 6.8, Aswan-TSFH has an excess of cooling production along the year but in Aqaba TSFH case, there is a little excess of cooling production in summer season especially in June, July and August. That s due to a higher solar radiation in Aswan and a higher cooling demand in Aqaba-TSFH in these periods as discussed in section Aswan-TSFH has a higher external back-up cooling than Aqaba-TSFH. Approximately there is no external back-up cooling load needed in January,February and December and there is a significant excess cooling production load. In April and October, the excess cooling production is almost equal to the external back-up cooling load for both cases. So based on the design optimization and by taking into account the battery, it benefits as much as possible for both cases. Ten days in April having excess cooling production load is selected to calculate the nominal battery capacity in order to design the battery system in the second scenario. The calculation results show as discussed in chapter 5, The battery system should participate in compensating the cooling demands with a maximum cooling capacity equals to18.32 kwh/ day, as cooling energy in Aswan-TSFH. This value is close to the value which was calculated in Aqaba- TSFH. This value equals to 6.4 kwh/ day as DC electric energy. According to the batteries system design, which was done in chapter 5, the battery system which is required for the solar PV air-conditioning with storage scenario is designed to produce about 392 Ah. Eight batteries of 12 V each are required and each of 4 batteries are connected in series. 64

81 Cooling Energy Annual Cooling Energy Compensation Analysis This section discusses the annual cooling energy compensation using two scenarios: solar PV air-conditioning without battery and Solar PV air-conditioning with battery. Figure 6.9 and Figure 6.10 show the total yearly and monthly cooling energy compensation for each scenario, where the direct cooling compensation in each figure means the cooling that is covered by the first scenario (PV air -conditioning without storage scenario) without storage and the remaining quantity means the external backup cooling of the first scenario which is covered by the grid electricity. The direct cooling compensation plus the storage compensation means the total cooling compensation by the second scenario: solar PV-air-conditioning system with battery.the back-up cooling in the figures means the external back-up cooling energy needed for this scenario Aswan Aqaba Direct compensation Compensation by storage Back-up cooling energy Figure 6.9: yearly cooling energy compensation by the solar PV air-conditioning system with and without storage scenarios for the Aswan-TSFH and Aqaba-TSFH. 65

82 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Cooling Energy [KWh] Table6.1: Yearly cooling energy compensation by the solar PV air-conditioning system with and without storage scenarios for Aswan-TSFH and Aqaba-TSFH. Compensation [kwh] PV air-conditioning Without storage PV air-conditioning With storage Aswan-TSFH Direct cooling compensation Cooling compensation by storage External back-up Cooling energy Total compensation Aqaba-TSFH Direct cooling compensation Cooling compensation by storage External back-up Cooling energy Total compensation Aswan Aqaba Back-up cooling energy Cooling compensation by storage Direct cooling compensation Figure 6.10: Monthly cooling energy compensation by solar PV air-conditioning system with and without storage scenarios for Aswan-TSFH and Aqaba-TSFH PV Air-conditioning Without Storage Scenario Figure 6.9 shows the yearly cooling energy production to compensate the cooling demand in each case: PV air-conditioning with and without storage. The yearly direct cooling energy compensated in Aswan-TSFH case is higher than the Aqaba-TSFH case by 1876 kwh due to a higher solar radiation in Aswan city than in Aqaba city and due to a lower yearly cooling energy demand in Aqaba-TSFH than in Aswan-TSFH.The yearly external back-up cooling energy which is covered by the grid electricity, it is higher in Aswan-TSFH than Aqaba-TSFH in by 1038 kwh. This leads to a conclusion that the PV air-conditioning without storage scenario in Aswan-TSFH is more efficient than Aqaba- TSFH. 66

83 Figure 6.9 displays the direct cooling energy in May, June, July, August, October and November in Aswan-TSFH is higher than in Aqaba-TSFH. This in turn means the yearly direct cooling energy compensation difference between the two cases comes from these months of the year for the presence of a higher solar radiation in Aswan than in Aqaba (see Figure 2.1). In addition, the tilted PV modules angle is designed at 9.31 o and 23 o for the Aswan and Aqaba cases respectively. Consequently, in summer the solar radiation declination angle is more normal to the horizontal surface. This in turn means a higher tilted angle PV will result in a lower efficiency PV Air-conditioning With Storage Scenario Figure 6.9 shows that the Aswan case has a higher total cooling compensation (direct cooling compensation energy plus cooling compensation by the storage) than the Aqaba-TSFH case by 3428 kwh in one year as shown in Table 6.1. Figure 6.10 shows that the Aswan-TSFH case has a higher monthly cooling energy compensation (direct cooling compensation energy plus cooling compensation by the storage) which is produced by the Solar PV air-conditioning with batteries scenario than the Aqaba-TSFH in each month. The reason for this is, the Aswan-TSFH case has a higher monthly direct cooling energy compensation than the Aqaba-TSFH case. Furthermore, there is a compensation by the storage in Aswan-TSFH, where there is no cooling energy compensation by storage in June, July and somehow in August in Aqaba- TSFH case. That s due to the presence of a higher solar radiation in Aswan city. Figure 6.10 and Figure 6.9 could help in taking a technical decision for the Solar PV airconditioning with storage scenario for both cases. The storage system is more efficient in Aswan case than in Aqaba case because of a higher excess solar radiation in Aswan especially in summer season. For both cases, in January, in February and in December, the battery system has a small contribution to the compensation of a cooling energy demand which is useless in December and January due to a lower cooling energy consumption in these months. This in turn means the stored energy by the battery system will be a waste energy. 67

84 Full cooling demand is covered in November for both cases. This means the battery system contributes for the compensation with the best efficiency by reducing the mismatch between the excess energy and the external back-up cooling energy which is needed at night. In February, the battery system in Aqaba-TSFH is more efficient than in Aswan-TSFH,due to a higher cooling energy demand in Aqaba especially at night. As shown in Figure 6.9, the contribution of the battery system in the Aswan-TSFH case for the cooling energy compensation almost doubles the contribution of the battery system in Aqaba-TSFH. In Figure 6.10, the monthly battery system contribution with full capacity is distributed along 9 months in one year in Aswan-TSFH case. On the other hand, in Aqaba-TSFH case it was only 6 months long. That s due to a higher solar radiation in Aswan city than in Aqaba city especially in these months. This leads to a technical decision that the design of a battery system is more efficient for Aswan-TSFH case than for Aqaba-TSFH case. To design a battery system for the PV-air-conditioning with storage system, it should be based on the influence of the excess cooling power curve and a external back-up cooling power curve along the year as it is done in this study. Besides, it is also based on the total energy consumption of a cooling energy demand. 68

85 6.2 Results and Analysis for Solar Thermal Air-conditioning Scenario The solar thermal air-conditioning system (absorption chiller) cannot be realized without a storage tank. But in the first part of this section, the system assumed as without storage, for the sake of several reasons. Namely, in order to understand and investigate the influence of the cooling production under assumption as the system without storage, to understand and investigate the storage contribution in the cooling compensation, to make a comparison between the two case studies for the solar thermal air-conditioning system simulation results and to clarify the results of the a whole system with storage. So the e pression cooling production means the cooling load which is produced by any air-conditioning system scenario as without storage. This section is divided in to two parts. The first part discusses the influence of cooling production. This includes a yearly and a weekly cooling production where the system as without storage. The second one discusses the annual compensation cooling energy analysis for the howl of system with storage The Influence of Cooling Production Yearly Analysis: Figure 6.11: Solar thermal air-conditioning cooling production along the year for Aswan-TSFH. 69

86 Figure 6.12: Solar thermal air-conditioning cooling production along the year for Aqaba-TSFH. Figure 6.11 and Figure 6.12 give an overview of the cooling production throughout the year by the solar thermal air-conditioning systems as without storage for Aswan-TSFH and Aqaba-TSFH respectively. These graphs show that in Aswan-TSFH case, there is a higher cooling production along the year than the cooling load demand in Aqaba-TSFH. In addition to that, it is beyond the maximum peak cooling demand in summer season. In the case of Aqaba, the situation is different in the summer season. The cooling production rises up to near the maximum peak cooling load demand. In other words, there is a little excess of cooling production. Both cases have a high overloaded cooling production in winter season as a waste of energy especially in January and December because there is no cooling demand. Generally, the results due to the summer solar radiation in Aswan city is higher than in Aqaba city(see Figure 2.1). And the change in the solar inclination angle during the year leads to a lower solar gain from the tilted collectors in summer season. That especially when the collector is tilted by an angle o C in Aqaba case which is higher than in Aswan case which is designed at 23 o C. In addition, as discussed in chapter 3, in June, July and August, the cooling demands of Aqaba-TSFH is higher than Aswan-TSFH s. Furthermore, Aqaba has a higher solar thermal losses from the flat plate collector to the ambient air (see Figure 2.2) which shows the summer daily ambient air temperature in Aqaba is lower than in Aswan city and a more daily fluctuation. This specially during July and August. 70

87 The solar thermal air-conditioning system is designed to give the nominal capacity equal to 15 kw as a peak cooling load. This amount is based on the simulation results of the thermal cooling load demand for Aqaba-TSFH and Aswan-TSFH, where 45 m 2 of a flat-plate collectors area was installed. As discussed in hapter 5, the collectors tilt angle is designed so as to be equal to the location latitude based on the rule of thumb [51]. However, Figure 6.11 and Figure 6.12 help in taking a technical decision and the design is correct for both cases. But in the case of Aqaba, to optimize the performance of the compensation cooling load in the summer, the collector should be tilted at 15 greater than the latitude. Weekly Analysis : This section includes a weekly result samples in summer and winter in order to zoom in, analyse and evaluate the performance of the cooling production by the solar thermal air-conditioning as without storage. Figure 6.13: Solar thermal air-conditioning cooling production in summer week for Aswan-TSFH. 71

88 Figure 6.14: Solar thermal air-conditioning cooling production in summer week for Aqaba-TSFH. Figure 6.15: Solar thermal air-conditioning cooling production in winter week for Aswan-TSFH. Figure 6.16: Solar thermal air-conditioning cooling production in Winter week for Aqaba-TSFH. 72

89 In each plot, generally the cooling production load of the thermal air-conditioning system starts to grow late in the morning and reaches the maximum peak compensation cooling load around noon time at 12. And then, it begins to decline until it reaches zero at the beginning of the evening due to the movement of the sun during the day. In summer season, Figure 6.13 and Figure 6.14 in Aswan case display that there are excess of cooling production than the cooling demand. On the contrary, for Aqaba-TSFH case, there is a little excess of cooling production. In addition, it has a higher mismatching with cooling load demand due to higher solar radiation in Aswan city than Aqaba city. And it has a higher heat losses from the solar collector to the ambient air. Most of the external back-up cooling needed for compensation is during evening and night due to a bigger cooling load demand in both Aswan-TSFH and Aqaba-TSFH. This shows the importance of a daily storage for a system in summer especially for Aswan- TSFH case since it has a higher excess cooling production and night cooling demands compared with Aqaba-TSFH, as discussed in chapter 3. In winter Figure 6.15 and Figure 6.16 show, for both cases, that the cooling production reaches approximately 40% or 50% of the daily cooling demand which in turn means higher matching between the cooling load demands and the cooling production than in the summer. Furthermore, in winter it has a huge excess cooling production than demand where in some days for instance on Friday, there is no cooling load demand for both cases. This leads to a generalization that all of the excess cooling production will be a waste of power. In addition, less daily external back-up cooling is needed in winter than in summer due to the lower cooling demands in this season. The excess of heat power gain from the thermal collector in winter, it can be used for other applications such as space heating or domestic hot water which leads to increase the aver all system efficiency. This is one of the solar thermal air-conditioning technology compared with PV air conditioning technology. 73

90 6.2.2 Annual Cooling Energy Compensation Analysis Now this section dealing with cooling production of the air-conditioning scenario as with storage.the hot water storage tank is one of the main components in the solar thermal air-conditioning system which combines the solar heat source (solar collector) and the absorption chiller. Hence, the solar thermal air-conditioning system cannot work in the absence of the storage tank. As discussed in Chapter 5, the solar thermal air-conditioning system scenario for each case includes the solar thermal heating system (45 m 2 of solar flat plat collector, 2m 3 hot water storage tank and the external back-up system) integrated with the absorption Lithium Bromide/water chiller where the external back-up system is electric boiler. This section discusses the annual cooling energy compensation by the solar thermal cooling system with storage scenario for both cases. In addition,it explains how the contribution of the storage to reduce the external back-up cooling by the compensation from the excess power for each case study Excess Cooling Production and External Back-up Cooling Loads Figure 6.17: Solar thermal air-conditioning excess cooling production and external back-up cooling loads for Aswan-TSFH. 74

91 Figure 6.18: Solar thermal air-conditioning excess cooling production and external back-up cooling loads for Aswan-TSFH. The Figure 6.17 and Figure 6.18 shows the excess of cooling production load and the external back-up cooling load after deducting the direct cooling which covered part from cooling demand. As shown by the weekly results analysis earlier, most of the external back-up cooling is at night due to a higher cooling demand for both cases. As can be seen in the above figures, for the Aswan-TSFH case there is a surplus in the cooling production along year. On the contrary, there is no surplus in the summer months, especially in June, July and August for the Aqaba-TSFH case. The Aswan-TSFH case has a higher external back-up cooling than Aqaba-TSFH. There is implies a mismatching between the excess of cooling production and the external backup cooling due to a huge night cooling demand. 75

92 Cooling Energy [kw h] Annual Cooling Energy Compensation Figure 6.19 and Figure 6.20 show how the yearly and monthly distribution of the cooling energy compensation through the solar thermal air-conditioning system scenario in order to fulfill the cooling energy demand for both cases, Aswan-TSFH and Aqaba-TSFH. That are a direct cooling compensation, the cooling compensation by the storage in addition to the external back-up cooling energy which is covered from the grid electricity Aqaba Aswan Back-up cooling Energy compensation by storage Direct compensation Figure 6.19: The cooling energy compensation by the solar thermal air-conditioning system scenario for Aqaba-TSFH and Aswan-TSFH. Figure 6.19 shows the highest annual cooling energy compensation by the system via (direct plus storage) which occurs in Aswan-TSFH. The lowest compensation occurs in Aqaba-TSFH.In Aswan-TSFH case,the total annual cooling energy compensation by the (direct plus storage) is higher than the Aqaba-TSFH case by 4348 kwh. The other point seen from identical figure is, the cooling energy compensation by the storage and by the direct cooling energy separately, in Aswan-TSFH case is higher than in Aqaba-TSFH case. In addition, the external back-up cooling in Aqaba-TSFH is higher than in Aswan-TSFH for a twofold reason. Firstly, there is a higher solar radiation in Aswan city than in Aqaba city. Secondly, the Aswan-TSFH case has a higher cooling energy demand than Aqaba-TSFH as discussed in Section

93 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Cooling Energy The contribution of the storage tank in the cooling energy compensation is to overcome the cooling energy demand. In this regard, the Aswan-TSFH case almost doubles that of the Aqaba-TSFH case per year due to the contribution of the storage tank which improves the performance of the device. This in turn means a better solar gain stored and it overcomes the cooling night demands, because there are higher solar radiation and night cooling demand in Aswan-TSFH Aqaba Aswan Direct compensation compensation by storage Back-up cooling Energy Figure 6.20: Monthly cooling energy compensation by the solar thermal airconditioning system scenario for Aswan-TSFH and Aqaba-TSFH. Figure 6.20 shows the storage contribution in the cooling compensation which extends over all months of the year in Aswan-TSFH case. On the other hand, the Aqaba-TSFH case shows that there is no compensation by the storage during the summer months. In the summer season, especially in June, July and August for the case of Aswan-TSFH, the total compensation (direct plus storage ) of the cooling energy is higher than the Aqaba-TSFH case as shown in Figure This is due to the contribution of the hot water storage tank in the cooling compensation. This leads to the main reason as shown in Figure 6.17 and Figure 6.18, where there is no excess of cooling energy produced in the summer season in the case of Aqaba-TSFH contrary to Aswan-TSFH. This due to a higher of solar radiation in Aswan than in Aqaba. In addition, there is a lower cooling demand in Aswan-TSFH. Furthermore, a higher heat losses from the solar 77

94 collector to the ambient air in Aqaba than in Aswan, where the collector temperature is designed to work at 85 o C and the outside air temperature in the Aqaba is lower than in Aswan during the summer and a more fluctuation (see Figure 2.2 ). In winter for both cases the cooling energy demand is fully covered especially in November, December, February and October. This in turn means the cooling demand at the evening and at night happens by the storage participation without requiring a external back-up cooling. That is due to the cooling demand in winter being less than the summer s. The month of March fulfil cooling demands where the compensation by the storage is higher than the direct. This in turn means a better overcoming of night demand in both cases is obtained in this month of the year. Generally, the Aswan-TSFH case has a higher external back-up cooling in April and October than the Aqaba-TSFH case due to a higher night cooling demand in these months. In Aqaba-TSFH case, the month of October has a higher contribution by the storage to compensate the cooling energy demand than in Aswan-TSFH case. This is because of a higher night cooling in Aqaba-TSFH than in Aswan-TSFH. On the other hand, the storage in this month reduces the mismatching between the cooling production and the demand more efficiently in Aqaba-TSFH case. 78

95 Solar fraction [%] Solar fraction [%] Solar Fraction As discussed in Chapter 5, solar fraction (SF) is a key factor in sizing the solar thermal system which works as the source of energy to drive the absorption chiller. It is dependent on many factors such as the load demand, the collector, the storage size,the operation,and the climate and hence SF is calculated for the two cases Aqaba Aswan Figure 6.21: Annual solar fraction for the solar thermal air-conditioning system scenario in Aswan-TSFH and Aqaba-TSFH Aqaba Aswan JAN MAR MAY JUL SEP NOV FEB APR JUN AUG OCT DEC Figure 6.22: Monthly solar fraction for the solar thermal air-conditioning system scenario in Aswan-TSFH and Aqaba-TSFH. 79

96 Figure 6.21 and Figure 6.22, give an overview of the monthly and yearly solar fraction that can be obtained for the solar thermal system under a solar thermal air-conditioning system with a storage scenario designed for both locations under the same storage size of 2 m 3 and a collector area of 45 m 2. The graphs are valid for a TSFH in the two selected locations, Aqaba and Aswan, and for the flat plate collector under the system design boundary conditions of this study. As shown in Figure 6.21, the yearly SF is 50% and 41% for Aswan and Aqaba cases respectively. While comparing those SF values by which the Aswan case is higher than Aqaba case. This is due to the high solar radiation. As a result, much of the heat produced by the collector can be stored. Therefore, better overcoming of the solar gain and load mismatching is obtained. In addition, we can achieve a better overcoming of a night demand in Aswan-TSFH case. Further more in Aqaba-TSFH case has higher heat losses from the collector and the storage tank than Aswan-TSFH, this due to low ambient air temperature in Aqaba city. In summer(see Figure 22), the higher SF is obtained in Aswan than in Aqaba case. As already discussed, it is because the Aswan-TSFH case has higher solar gain and it means better to overcome the night demand which is obtained by the contribution of the storage (see Figure 6.20). The graph could help in taking a technical decision. The storage tank size for the solar thermal air-conditioning system scenario in Aswan-TSFH could play for the compensation of a cooling load better than in Aqaba-TSFH system scenario. In winter for both cases(see Figure 22), the solar fraction reaches 100% which in turn means the cooling load demand has been covered fully 100% by the solar thermal airconditioning system without the need to external back-up cooling. This due to a low cooling demand and a high solar energy gain by the collector in this period (see Figure 6.20 ). But it should be clear that the Cooling energy consumption is very little or negligible in some months, such as November, January and February. As a result, most of the heat produced from the collectors will be a waste energy. 80

97 6.3 Thermal Air-conditioning Scenario Versus PV Air-conditioning Scenarios The Direct Cooling Production Load Performance This section discusses and analyzes the solar thermal air-conditioning scenario versus solar PV air-conditioning scenarios based on the performance of the cooling production on the weekly and daily bases(as the systems without storage). Weekly Performance: Figure 6.23 and Figure 6.24 illustrate the weekly cooling production load for the solar PV air-conditioning scenarios versus thermal air-conditioning scenario where the systems as without storage. Generally, these samples represent the weekly cooling compensation especially in the summer where there are high cooling demands. Figure 6.23: PV air-conditioning versus solar thermal air-conditioning, cooling production performance in Summer Week for Aswan-TSFH. 81

98 Figure 6.24: PV air-conditioning versus solar thermal air-conditioning, cooling production performance in Summer Week for Aqaba-TSFH. Figure 6.23 and Figure 6.24 generally show the following for each day in the week for both cases: Aswan-TSFH and Aqaba-TSFH. The daily cooling production along the week by the thermal air-conditioning scenarios has a higher peak curve than the PV air-conditioning scenarios. In addition, the excess cooling production which is above the cooling load demand curve of the solar thermal air-conditioning scenario is higher than the curve for the solar PV air-conditioning scenario. That could lead us to say that the storage system for the thermal airconditioning scenario is more important and efficient than the PV scenarios especially in summer for Aswan-TSFH. The daily cooling production curve which is produced by the solar PV air- conditioning starts in the morning before the curve of the solar thermal air-conditioning system scenario and ends at the evening and vice versa. This leads to a conclusion that the daily direct cooling compensation by the PV air-conditioning scenario is more efficient than the thermal scenario. In another way, the daily direct cooling energy compensation which is the area under the cooling production curve, under the cooling demand curve in PV air-conditioning scenarios is higher than in the thermal air-conditioning scenario. 82

99 In addition, the daily external back-up cooling energy needed is the remaining area under the cooling demand curve after deducted the area of direct cooling compensation energy. This external back-up cooling energy is higher than the direct compensation energy for both scenarios. That s due to a higher night cooling demand. Furthermore, the external back-up cooling needed for the PV-system is lower than for the thermal system. which leads to say that the thermal system as without storage has a higher mismatching with the cooling load demand than in the PV-system without storage. Daily Performance: After the weekly discussion and analysis, this Section discusses and analyzes the daily performance of the cooling production in order to link the results with the main technical and physical reasons. And this leads to clarify the weekly results in the whole scenarios results. Figure 6.25:PV air-conditioning versus solar thermal air-conditioning, cooling production performance in Summer day for Aswan-TSFH. 83

100 Figure 6.26: PV air-conditioning versus solar thermal air-conditioning, cooling production performance IN Summer day for Aqaba-TSFH. Figure 6.23 to Figure 6.26, diagram that the PV air-conditioning scenarios have higher direct cooling compensation than the one by the solar thermal air-conditioning scenario, the cooling production curve by the PV air-conditioning scenario starts earlier in the morning than the thermal air-conditioning scenario. Furthermore, at the evening the curve of the PV air-conditioning scenarios ended at a zero value and late compared with the curve of thermal air-conditioning scenario. In addition approximately, in morning and at evening, the cooling compensation curve of the PV air-conditioning scenario is higher than that of the thermal air-conditioning scenario in this period. The reasons are summarized below. The reasons are, firstly the thermal collector has higher efficient compared to PV module where the solar collector efficiency is around 50% and PV module is around 14%. But not too much due to the COP of compressed chiller and Absorption chiller is completely different. Where the COP is nearly 3 for the compressed chiller in the PV airconditioning scenario and it is around 0.7 for the absorption chiller in the thermal airconditioning scenario, this lead to say in the direct cooling compensation, the overall system efficiency of PV air-conditioning scenarios is higher than the one by the solar thermal air-conditioning scenario. 84

101 The second reason, the high thermal losses from the flat plate collector in thermal airconditioning scenario to the sounding outside air, where its temperature is lower in the morning and at the evening compared with the noon. In addition, the thermal losses from the hot water storage tank. As discussed in Chapter 5, where the solar thermal collector is designed to work at a temperature as high as 85 0 C in order to drive the adsorption chiller. That leads the solar flat collector to start working late in the morning and ended earlier in the evening especially when the thermal losses are higher than the solar gain from the collector as designed in this study. The third reason, in the morning and at the evening, the ambient air temperature is lower than the noon s. The PV module works with a high efficiency where the operation temperature of the module is low due to a high thermal heat transferred to the ambient air. And hence a low thermal effect on the PV module efficiency. In addition, in the morning and at the evening there is a high reflection and diffused radiation compared with a noon and in turn a higher electric power gain from the PV module. On the contrary, the diffused and reflected radiation are not so sufficient to produce heat by flat plate collector. At noon of the day, the solar thermal air-conditioning scenario is more efficient to produce a cooling load than the PV air-conditioning scenario. But most of the cooling compensation by thermal air-conditioning scenario in this period exceeds the cooling demand. As discussed before, the storage system is more important for thermal airconditioning scenario than the PV air-conditioning scenario. The reason for this result is the flat plate collector works at noon with the highest efficiency because of a higher solar radiation which increases the solar gain as hot water in addition to a small thermal heat losses from the collector at this period, where the ambient air temperature is higher compared with the morning and the evening. In addition the peak cooling demand occurs at noon. On the contrary at noon, the PV module efficiency reduces and stops due to the thermal effect, where the module operation temperature is high by time the ambient temperature is high. This low driving temperature reduces the heat transfer from the module to the ambient air. 85

102 Comparison Between Aqaba-TSFH Case and Aswan-TSFH Case: As shown from Figure 6.23 to Figure 6.26, there are generally two major differences in the performance of the cooling production by the thermal and PV scenarios as without storage, for both the Aswan-TSFH case and Aqaba-TSFH case. These differences are elaborated below. The first difference in all scenarios, the Aswan TSFH case has a higher extra cooling production compared with Aqaba-TSFH due to a higher solar radiation in Aswan especially in the summer season ( see Figure 2.1). Secondly in all scenarios, the direct cooling production curve behaviour for the Aswan- TSFH is more thin during the day than the Aqaba-TSFH. Besides, the Aswan-TSFH case is mismatching a lot between the cooling compensation and the cooling load demand than the Aqaba-TSFH case. That s due to the behaviour of the solar radiation in each city. In addition, a higher diffusion and reflected solar radiation is observed in Aqaba city than in Aswan city especially for this boundary condition of this study. Where an immense reflected solar radiation in Aqaba city comes from the collector tilted angle, designed in this study, 29 31' which is higher than 23 54' for Aswan case. That in turn means a higher ground reflected radiation which is collected by the collectors in Aqaba. In addition, the Aqaba city is near the Red Sea and therefore has a higher air humidity compared with Aswan (see Figure 2.3 ). This then leads to an increase in the diffused radiation in Aqaba city. 86

103 6.3.2 Annual Cooling Compensation Energy Percentage Figure 6.27 and Figure 6.28 illustrate the yearly percentage of the direct cooling energy compensation, the compensation of the cooling energy by storage and the external back-up cooling energy which is covered by the grid for each scenario. This percentage is calculated based on daily energy yield compensation in order to calculate the yearly cooling energy compensation for each case study, Aswan-TSFH and Aqaba-TSFH. SO as to make a comparison between the scenarios. 20.1% Compensation by storage 30.8% Direct copensation 50.1% Backup compensation Solar Thermal air-conditioning system with storage 39.3% Direct copensati on 10.7% Compens ation by storage 50% Backup compens ation 39.3% Direct copensat ion 60.7% Backupc ompens ation Solar PV air conditioning system with storage Solar PV air conditioning System without storage Figure 6.27: Percentage of cooling Energy compensation by the three scenarios for Aswan-TSFH. 87

104 30.9% Direct copensation 11.9% Compensation by storage 57.2% Backup compensation Solar thermal air-conditioning system with storage 35.8% Direct copensat ion 7.3% Compen sation by storage 56.9% Backupc ompensa tion 35.8% Direct copensat ion 64.2% Backup compens ation Solar PVair-conditioning system with storage Solar PV air-conditioning System without storage Figure 6.28: percentage of cooling Energy compensation by the three scenarios for Aqaba-TSFH. From Figure 6.27 and Figure 6.28, several observations are made below. The yearly direct cooling compensation percentage of the PV air-conditioning scenarios is 39.3% and 35.8% for the Aswan-TSFH and for the Aqaba-TSFH cases respectively. The above mentioned percentages are higher than the direct cooling compensation percentage by the thermal air-conditioning scenario, 30.8 % and 30.9 % for the Aswan- TSFH and for the Aqaba-TSFH cases respectively. This in turn means a higher mismatching between the direct cooling compensation and the cooling demand in the thermal air-conditioning scenario. 88

105 As discussed before, the main reason is a higher daily direct cooling compensation in the morning and at the evening by the PV air-conditioning scenarios than the thermal air-conditioning scenario. That s due to the COP of compressed chiller and Absorption chiller is completely different where the COP of the compressed chiller is around 3 and it is around 0.7 for the absorption chiller. That leads to enhanced the overall system efficiency of the PV-air conditioning scenarios comparatively with thermal airconditioning scenario. In addition at the evening and in the morning, low ambient air temperature makes the thermal losses be higher than the solar gain from the flat plate collector in addition to the thermal losses storage tank. In addition, PV module works early with a higher efficiency at low solar radiation in the morning and the evening time. Yearly, the total percentage cooling energy compensation by direct and storage in solar thermal air-conditioning system with storage scenario is 50.9 % and 42.8 % for Aswan- TSFH case and for the Aqaba-TSFH case respectively. The total compensation by PV airconditioning with storage scenario, 50 % and 43.1 % are respectively for Aswan-TSFH and for Aqaba-TSFH cases. From these results, the percentage difference between the two scenarios does not exceed 1 % in both cases(aswan-tsfh and Aqaba-TSFH)and in turn there is no big difference between the two scenarios based on the cooling demand and the boundary condition of this study. that due the same reason which mentioned above, the COP effects on the overall system efficiency. The percentage of the cooling energy compensation by the storage in the thermal airconditioning scenario is 20.1 % and 11.9 % for Aswan-TSFH and for Aqaba-TSFH respectively. The aforementioned percentages are higher than the percentage compensation by the storage in PV air-conditioning with storage scenario, 10.7 % and 7.3 % for Aswan-TSFH and Aqaba-TSFH respectively. That s because of significantly excess output power, from the thermal air-conditioning system with storage scenario compared with the PV air-conditioning system with storage scenario, where the contribution power which is produced by the flat plate collector is higher than the output power of the PV module at noon. This contribute to compensate the night cooling demand throughout the storage. This helps to make a technical decision based on the study boundary condition. We can deduct that the storage technology for thermal air-conditioning scenario is more efficient to improve the whole system s efficiency than a PV air-conditioning scenario. 89

106 7. Conclusions and Future Research 7.1 Conclusions The traditional air-conditioning is one of the main consumers of electrical energy today in the MENA region. However, this region has a huge solar energy potential with an average DNI 13 of 2,334 kwh/m 2 /year and with average daily sunlight exceeding 8.8 hours [4]. Solar air-conditioning technology is definitely a solution to cover the cooling demand for this hot and sunny region. The present study analyzes and compares the solar thermal air-conditioning technology and the photovoltaic air-conditioning technology under two different locations in the MENA region (Aswan, Egypt and Aqaba, Jordan). That is based on the cooling demand for the reference building (TSFH ) in these regions. Cooling load demands: The thermal load demands for the reference building (TSFH) in each location were determined by TRNSYS software. The following points can be concluded: The maximum cooling load demand during the summer season are: 13.9 kw and 15.3 kw for Aswan-TSFH and Aqaba-TSFH respectively. For both cases, the cooling demand occurs for ten months while the heating demand is only required in two months. The annual cooling energy demands are: 44,330 kwh/year and 43,490 kwh/year for the Aswan-TSFH and the Aqaba-TSFH respectively which represents 97.5 % and 96.3 % of the total annual energy consumption (heating and cooling). That shows the importance of cooling compared to heating in these locations. The performance of the cooling load during a summer day shows a huge cooling demand (approximately 8 to 10 kw) during the night. Therefore, it is necessary to cover the night cooling demand as well as the day time in these regions. 13 Direct Normal Irradiance 90

107 Solar Thermal Air-conditioning Scenario and PV Air-conditioning Scenarios : The cooling production and compensation of each scenario is determined by Matlab- Simulink for three scenarios: Solar thermal air-conditioning with storage scenario includes a single water/lithium- Bromide absorption chiller with 15 kw nominal capacity and requires 85 o C driving temperature, 45 m 2 flat plate collectors, a stratified storage tank with 2 m 3 volume and an electric heater as back-up system. Two PV air-conditioning systems with and without storage scenarios were designed with a 45 m 2 of PV-array, a compressed chiller and the grid as a back-up system. The PV air-conditioning system with storage includes additionally 8 batteries. Form the analysis and comparison between the thermal and the PV scenarios the following points can be concluded: The total annual percentage of cooling energy compensation (direct 14 plus storage 15 ) by the solar thermal air-conditioning system with storage scenario is 50.9 % and 42.8 % for Aswan-TSFH and for Aqaba-TSFH respectively. The compensation by the PV airconditioning with storage scenario which is 50 % and 43.1 % respectively for Aswan- TSFH and for Aqaba-TSFH. The percentage difference between the two scenarios does not exceed 1 % in both cases. However, there are differences in the direct cooling compensation and the compensation by the storage: 1. The yearly direct cooling compensation percentage of the PV air-conditioning scenarios is 39.3 % and 35.8 % for the Aswan-TSFH and for the Aqaba-TSFH respectively. The aforesaid percentages are higher than the direct cooling compensation percentages by the thermal air-conditioning scenario, 30.8 % and 30.9 % for the Aswan- TSFH and for the Aqaba-TSFH cases respectively. 2. The performance of the daily direct cooling compensation by the PV air-conditioning scenarios is more efficient than in the thermal scenario although the flat plate collector efficiency is around 50 % and the PV module is around 14 %, due to three reasons. 14 The cooling energy which covers the cooling demand when the air-conditioning system as without storage. 15 The cooling energy which covers the cooling demand only by the contribution of the storage in the airconditioning system. 91

108 The first and the main reason, the COP of the compressed chiller and the absorption chiller are completely different. It is nearly 3 for the compressed chiller in the PV airconditioning scenario and it is around 0.7 for the absorption chiller in the thermal airconditioning scenario. The second reason, the solar flat plate collector starting to work late in the morning and ended earlier in the evening. That is due to a low ambient air temperature in the evening and in the morning times and the collector works at a high temperature as 85 0 C in order to drive the adsorption chiller. This makes the thermal losses be higher than the solar gain from the flat plate collector which leads to shutdown the device in these duration. The third reason, in the morning and at the evening, there is electric power gain from the PV modules due to a high share of diffused radiation and the ambient air temperature is lower than the noon s. Hence a low thermal effect on the PV module efficiency in these duration. 3. The percentage of the cooling energy compensation by the storage in the thermal airconditioning scenario is 20.1 % and 11.9 % for the Aswan-TSFH and for the Aqaba- TSFH cases respectively. These are higher compared to those of PV air-conditioning with storage scenario, 10.7 % and 7.3 % for Aswan-TSFH and Aqaba-TSFH respectively. That s because of the contribution of the e cess power which is produced by the flat plate collector is higher than the excess output power of the PV module at noon. It can be concluded that the PV air-conditioning with storage scenario needs less storage to cover the same amount of cooling load demand compared to solar thermally airconditioning with storage scenario. In addition, the storage system in PV airconditioning scenario is minor and the direct compensation is major. That is vice versa in the thermal air-conditioning scenario. 4. In winter season, the excess solar power gain is more useful in the PV airconditioning scenarios than the thermal air-conditioning scenario due to, the electric power is more universal conversion compared with the thermal power conversion. The excess electric power can be used for many other electric applications such as building lighting or space heating etc.. The excess of the thermal heat power can be used only for space heating or domestic hot water. In addition the excess electric power gain can be fed to the grid if there is a feed-in-tariff in this region. 92

109 Comparison Between Aqaba-TSFH and Aswan-TSFH The cooling demand follows the outside solar radiation and ambient air temperature along the year due to solar gain through the building s envelope. The monthly cooling demand in Aswan-TSFH is higher than Aqaba TSFH s throughout the year e cept in June, July and August although the solar radiation and the ambient air temperature in Aswan city are higher than in the Aqaba city. Therefore, it is due to a higher ambient relative humidity in Aqaba than in Aswan. This means ventilation increases the humidity inside the building and results in a higher cooling demand in Aqaba-TSFH. The contribution of the storage system (storage tank or battery system) to the cooling energy compensation in each technology is more efficient in Aswan-TSFH case than in Aqaba-TSFH case and it is almost double, because there is a higher solar radiation in Aswan especially in summer season. This in turn means a better solar gain is stored which can cover the night cooling demands. The direct cooling compensation curve behaviour during the day of the PV airconditioning scenarios for the Aqaba-TSFH is better than the Aswan-TSFH. That s due to a higher diffusion and a reflected solar radiation which is observed in Aqaba city than in Aswan city. In the summer season, the cooling production by all scenarios in Aswan-TSFH case has an excess of cooling production power at noon. But in the case of Aqaba-TSFH, the situation is different: the cooling production rises up close to the maximum peak cooling load demand. It can be concluded that the performance of the compensation cooling load in the summer is optimized if the collector is tilted at 15 greater than the latitude in each scenario in Aqaba-TSFH case. Then, more energy can be stored and used at night. 93

110 7.2 Future Research In terms of energy efficiency in buildings and the feed-in-tariff law in Germany and in Europe of self-consumption which becomes more important in these days, the calculations of the TSFH cooling demand calculation and the cooling compensation of each scenario based on the meteorological data with less than one hour or a 15 minute time interval is necessary. In addition, it should be based on the real-time compensation especially for the storage contribution. One of the main objectives of the solar air-conditioning systems is to save primary energy consumption, therefore the study can be extended to analyse and compare the solar thermal air-conditioning scenario and the solar PV air-conditioning scenarios under MENA regions climates in terms of primary energy and economic analysis. Moreover, the future cost reduction by learning curves of both technologies can influence the economic feasibility. Further work should compare and analyse between the two technological scenarios in the case of heat pump system in order to compensate the heating demand as well as the cooling demand. Also, a comparison between these two technologies is necessary if there is feed-in-tariff in the MENA region and the PV air-conditioning scenarios can use the grid as storage. The determination of the reference building (TSFH) in this study for the two locations (Aswan, Aqaba) was based on the Jordanian TSFH envelope construction for both cases under the assumption that there is no big difference between the Jordanian TSFH and the Egyptian TSFH. Therefore, the Egyptian TSFH s envelop constructions should also be considered. In addition, this research can be extended to include different building types such as office buildings. 94

111 References [1] Umberto Desideri, Stefania Proietti, Paolo Sdringol, Solar-powered cooling systems: Technical and economic analysis on industrial refrigeration and air-conditioning applications, Available online 20 February 2009, contents lists available at Science Direct Website, [2] Nathan Rona, Solar Air-Conditioning Systems, Focus on components and their working principles, Building Services Engineering, Department of Building Technology, CHALMERS UNIVERSITY OF TECHNOLOGY, Göteborg, Sweden 5765/2004. [3] Elsafty A, Al-Daini A.J, Economical comparison between a solar-powered vapour absorption air-conditioning system and a vapour compression system in the Middle East Renewable Energy, Vol. 25 No. 4 pp ISSN: , 2002, contents lists available at Science Direct Website, [4] Unlocking the Potential of Alternative Energy in MENA, Al Masah Capital Management Limite, Dubai International Financial Centre, Dubai-UA, Jan-11. [5] Dr. Volker Quaschning, Dr. Manuel Blanco Murie, Photovoltaics or Solar Thermal Power Plants?, DLR, Plataforma Solar de Almería, Spain, CIEMAT, Plataforma Solar de Almería, Spain, VGB Congress Power Plants 2001 Brussels October 10 to 12, 2001, the contents available at : [6] Ursula Eicker, Dirk Pietruschka, Design and performance of solar powered absorption cooling systems in office buildings, University of Applied Sciences Stuttgart, Schelling strasse, 28 July 2008, 24, D Stuttgart, Germany, contents lists available at Science Direct Website, [7] A. González-Gil, M. Izquierdo, J.D. Marcos, E. Palacios, Experimental evaluation of a direct air-cooled lithium bromide-water absorption prototype for solar air-conditioning, 95

112 Applied Thermal Engineering, Volume 31, Pages , Issue 16, November 2011, contents lists available at Science Direct Website, [8] Francesco Calise 2011, High temperature solar heating and cooling systems for different Mediterranean climates: Dynamic simulation and economic assessment, DETEC, University of Naples Federico II, P.le Tecchio 80, Naples, Italy, contents lists available at Science Direct Website, [9] Hans-Martin Henning, Solar assisted air-conditioning of building-an Overview, Applied Thermal Engineering, 27 (2007) , contents lists available at Science Direct Website, [10] N. Hartmann, C. Glueck b, F.P. Schmidt, Solar cooling for small office buildings: Comparison of solar thermal and photovoltaic options for two different European climates, a University of Stuttgart, Institute of Energy Economics and the Rational Use of Energy (IER), Renewable Energy 36 (2011) 1329e1338, 8 December 2010, contents lists available at Science Direct Website, [11] Jamal O. Jaber, Prospects of energy savings in residential space heating, Energy and Buildings 34 (2002) , Department of Mechanical Engineering, Hashemite University, Zarqa, Jordan, 13 August 2001, contents lists available at Science Direct Website, [12] Doppelintegral GmbH, in: INSEL Users Manual (2009), 8th ed., MS Windows, Stuttgart, Germany, [13] Samar Jaber, Salman Ajib, Thermal and economic windows design for different climate zones, Energy and Buildings 43 (2011) , 16 August 2011, Technical University of Ilmenau, Department of Thermodynamics and Fluid Mechanics, Ilmenau, Germany, contents lists available at Science Direct Website, [14] Egypt, mission, Country-Profiles, This paper is available at this link, 96

113 [15] Aswan, Egypt, Aswan overview, Aswan Weather, Asia rooms Website, last visit , [16] Weather data for Egypt, Africa, Building Technologies Program, Energy Plus Energy Simulation Software, Energy efficiency & renewable Energy, U.S. Department of Energy website, [17] Mr. Salah Azzam and Mr. Firas Alawneh, Meteorological measurement data for Aqaba city, The Higher Council for Science and Technology National Center (NERC), Amman, Jordan. [18] Population and Housing Census, Department of Statistic DOS, Jordan, [19] Samar Jaber, Salman Ajib, Optimum design of Trombe wall system in Mediterranean region, Ilmenau University of Technology, Department of Thermo and Fluid Dynamics, P.O Box , Ilmenau, Germany,25 April 2011, contents lists available at Science Direct Website, [20] Samar Jaber, Salman Ajib, Optimum, technical and energy efficiency design of residential building in Mediterranean region, Ilmenau University of Technology, Department of Thermo and Fluid Dynamics, P.O Box , Ilmenau, Germany, 22March 2011, contents lists available at Science Direct Website, [21] Thermal insulation code (2009), Ministry of Public Work and Housing, Amman, Jordan. [22] MASDAR ENERGY DESIGN GUIDELINES (MEDG) VERSION 2.0 Office & Residential (2010), MASDAR (Abu Dhabi Future Energy Company) Page. 66.,

114 [23] ASHRAE 90.1 standard (2007), American society of Heating Refrigerating and Airconditioning Engineers, Page [24] ASHRAE, Handbook Fundamental (2005), American Society of Heating, Refrigerating and Air-conditioning Engineers, [25] S.A. Klein, et al.,, TRNSYS. A Transient System Simulation Program, Solar Energy Laboratory, University of Wisconsin, Madison, [26] Energy modelling and building physics resource base, Software, TRNSYS, University of Cambridge, [27] TRNSYS 16: A TRaNsient System Simulation program Volume 1 Getting Started. Solar Energy Laboratory, University of Wisconsin-Madison, [28] Petrus Tri Bhaskoro and Syed Ihstham Ul Haq Gilani,Transient Cooling Load Characteristic of an Academic Building, using TRNSYS, SCENCE ALERT, An open ACESS Publisher, February 23, Contents lists available at : [29] TRNSYS Group, TRNSYS 16 manual, 2003, [30] Mitalas, Arseneault, FORTRAN IV Program to Calculate z-transfer Functions for the Calculation of Transient Heat Transfer Through Walls and Roofs, Division of National Research Council of Canada, Ottawa. [31] Wang, S.K., Handbook of Air-conditioning and Refrigeration. 2nd Edn., McGraw- Hill, New York, ISBN-13: , [32] Cengel and Boles, Thermodynamics: An Engineering Approach. 5th Edn., McGraw- Hill, New York,

115 [33] TRNSYS 16 manual, a TRaNsient SYstem Simulation program, Volume 1 to volume 9,Using the Simulation Studio. [34] Eicker, Ursula, Solar Tehchnology for Buildings, JohnWiely& Sons Ltd, USA, [35] Nada Mekki, Application of absorption solar air-conditioning Technology depending on climate and building standard, Energy and semiconductor Research Laboratory, Department of physics, Faculty of Mathematics &Science,Carl Von Ossietzky University,Oldenburg/F.R. Germany, [36] Duffie, John A.and William A Beckman, Solar Enginnering of Thermal processes, 3 d edition, Published by John Wiely &Sons Inc., Hobokev, New Jersey, [37] Marc Delorme,Reinhard Six, Sabrine Berthaud, PROMOTING SOLAR AIR CONDITIONIN, Technical overview of active technique, ALTENER Project Number /Z/02-121/200. [38] Paul Bourdoukan, Task 38 Solar Air Conditioning and Refrigeration, Description of simulation tools used in solar cooling, New developments in simulation tools and models and, their validation Solid desiccant cooling, Absorption chiller, A technical report of subtask C, Deliverable C2-A,Date: November 9, [39] Lindholm T. (2003a) Inneklimat Komfortkyla Evaporativ och sorptiv kylning Göteborg: Department of building services engineering, Chalmers, [40] Gordon J.,Choon Ng (2000) High-efficiency solar cooling Solar energy Vol. 68 No. 1,pp ISSN: x, [41] Filipe Mendes L., Collares-Pereira M. Ziefler F., Supply of cooling and heating with solar assisted absorption heat pumps: an energetic approach. International Journal of Refrigeration Vol. 21, No. 2, pp ISSN: , 1998, contents lists available at Science Direct Website, 99

116 [42] ASHRAE, 2000, HVAC Systems and Equipment (SI edition) Atlanta: American Society of Heating. Refrigerating an Air-conditioning Engineers, Inc (2000 ASHRAE,HANDBOOK),2000. [43] NICOLAM. PEARSALL and ROBERT HILL, PHOTOVOLTIC MODULES SYSTEMS AND APPLICATIONS, 25/04/01, Northumbria Photovoltaic Applications Center, University Of Northumbria at Newcastle. [44] Leonics Company, home page,support, How to Design Solar PV System, last visited homepage, 11/ [45] Inverter data sheet Characteristic, jul6, 2011, last visit in 26/01/ cs.pdf. [46] Al-Salaymeh, Al-Hamamre, Sharaf, Abdelkader, a Technical and economical assessment of the utilization of photovoltaic systems in residential buildings: The case of Jordan, December 2009, contents lists available at Science Direct Website, [47] Prod. Dr.-Ing.Mohamed Ibrahem, Estimation the battery capacity (Ah), module photovoltaic II, REMENA master program, Kassel university, Germany, [48] M.. Alonso Garcı a-,j.l. Balenzategui, Technical note, Estimation of photovoltaic module yearly temperature and performance based on Nominal Operation Cell Temperature calculations, Renewable Energy 29 (2004) , 23 March 2004, contents lists available at Science Direct Website, [49] E. Skoplaki, J.A. Palyvos,On the temperature dependence of photovoltaic module electrical performance: A review of efficiency/power correlations, 4 November 2008, contents lists available at Science Direct Website, 100

117 [50] Hining,H.-M(Ed): Solar-Assisted Air Conditioning in Building A Handbook for planners.springer-verlag/wien, [51] U.S. Department of Energy, Sitting Your Solar Water Heating System's Collector, U.S Energy efficiency & renewable, last visit [52] Schüco Premium V Flat plate Solar collector, Solar flat plate technical data sheet,schüco Company USA L.P, [53] KWB Germany,hot water storage tank, KWB Deutschland Kraft und Wärme aus Biomasse GmbH, Branch office, South Königsberger Straße 46, D Mertingen, [54]ASHRAE, in: Ventilation and Acceptable Air Quality in Low-rise Residential Buildings Standard, American Society of Heating, Refrigerating and Air-conditioning Engineers, [55] Agrawal,Shyam K.,2002, Applied Thermo sciences Principles &Applications, Viva Books Private Limited, New Delhi. [56] Solar-assisted heating and cooling of buildings: technology, markets and perspectives by Björn Nienborg, , solar magazine, [57] Duffie, John A.and Beckman, William A.,1991, Solar Engineering of Thermal processes, 2 nd edition, John Wiely &Sons Inc.,USA, [58] Solar collector :Different type and fields of application, Knowledge Solar Collectors- Solar Server forum for solar energy webpage, last visit , 101

118 Appendices Appendix A: Schematic vapour compression cycle Figure A: Schematic vapour compression cycle, [2]. Appendix B: Solar Photovoltaic module data sheet Taken from SCHOTT solar COMPANY in Germany 102