ESTIMATION OF ENERGY PAY-BACK TIME AND AIR POLLUTION MITIGATION POTENTIAL OF A 25-KWP GRID CONNECTED ROOFTOP SOLAR PHOTOVOLTAIC SYSTEM

Transcription

1 International Journal of Electrical Engineering & Technology (IJEET) Volume 8, Issue 6, Nov-Dec 2017, pp. 1 8, Article ID: IJEET_08_06_001 Available online at ISSN Print: and ISSN Online: Journal Impact Factor (2016): (Calculated by GISI) IAEME Publication ESTIMATION OF ENERGY PAY-BACK TIME AND AIR POLLUTION MITIGATION POTENTIAL OF A 25-KWP GRID CONNECTED ROOFTOP SOLAR PHOTOVOLTAIC SYSTEM Sheeraz Kirmani Assistant Professor, Department of EE, Jamia Millia Islamia (A Central University) New Delhi, India Mohammad Kalimullah Research Scholar, Department of EE, Jamia Millia Islamia (A Central University) New Delhi, India ABSTRACT Rooftop solar photovoltaic (SPV) system has been analyzed for energy payback time (EPBT) and air pollution mitigation potential. A 25 kw solar photovoltaic power plant has been installed on a rooftop of a school building in New Delhi. Actual power generated by the system over a period has been monitored and used for calculating EPBT. Air pollution mitigation potentials of SPV Power Systems are discussed. The analysis shows that EPBT is lower than the lifetime of the plant and there are significant environmental advantages after EPBT period is over. Studies indicate that significant amount of air pollutants like Nitrogen Oxides, Carbon monoxide, Hydro Carbons and particulate materials emitted from diesel generator sets can be mitigated. Key words: Carbon Monoxide, Energy Payback Time, Mitigation, Nitrogen Oxides, Particulate Materials. Cite this Article: Sheeraz Kirmani and Mohammad Kalimullah, Estimation of Energy Pay-Back Time and Air Pollution Mitigation Potential of A 25-KWP Grid Connected Rooftop Solar Photovoltaic System. International Journal of Electrical Engineering & Technology, 8(4), 2017, pp INTRODUCTION Nowadays, the buildings are designed for utmost convenience and comfort. The construction of buildings are growing up with a fast pace and nearly 30-40% of total global resources are using in constructing houses. The energy generated by fossil fuel is mostly used by industry than agriculture and then by residential/commercial buildings. The European commission has started Asia-Link program to assist and unfold the knowledge on construction of building with zero energy approach. In this program, it has been spread and promoted to integrate the 1 editor@iaeme.com

2 Estimation of Energy Pay-Back Time and Air Pollution Mitigation Potential of A 25-KWP Grid Connected Rooftop Solar Photovoltaic System renewable energy resources for several applications such as water heating, heating/cooling, and electricity generation [1]. According to central Electricity Authority of India, 22% of total electric energy consumption of India is by residential and commercial buildings only. India s domestic energy consumption has increased from 80 TWh in 2000 to 186 TWh in Figure 1 shows the growth of electricity consumption in India, according to Central Electricity Authority (CEA), It has been expected by Dr.Satish Kumar, formerly chief of party, United States agency for International Development (USAID) ECO-III project, 2011 that the floor area will increase by 400% and 20 billion m 2 of new building area will add by Furthermore, since the comfort of the consumer is continuously increasing then the purchasing of the electricity will increase sharply in coming decades. With the current trend of electricity business, it is expected that the energy consumption will increase by eight times more by 2050, so it is very important to evolve energy efficient strategies especially for residential buildings to limit the huge demand of fossil fuel power which is escalating the climate. As on 30 th June 2017, the total installed capacity of SPV generation in India is MW, the share of the capital city Delhi in renewable energy resources generation is MW only. According to Delhi Electricity regulation Commission, the maximum installed capacity of SPVPP should not be more than 80% of the sanctioned load. The photovoltaic-based power systems have distinct advantages like pollution-free operations; do not produce any ecological imbalances. As compared to fossil fuel-based power systems, the photovoltaic-based power systems do not cause green house effect, i.e., emission of gases (CO2, NO2, etc), acid gases (SO2, NO2, etc) and harmful particles during their operational lifetime. However, it is only at first glance, if one goes deeper it turns out that all the components of photovoltaic-based power system require high energy during its manufacturing stage. Thus as pointed out by Alsema [4] E. Nieuwlaar [5,6] any new energy technology which is promoted as being renewable or sustainable should be subject to an analysis of energy balance in order to assess its energy viability and to calculate the net energy gain. Similarly one should assess the net emissions (pollutants) saving potential of new technology taking into account the emissions during the manufacturing stage. Figure 1 The growth of Electricity Consumption in India, Source: CEA, 2012 [2]. Thus consideration of (1) the net energy gain and (2) net pollutant saving potential of new technology will give us a more accurate assessment of any new renewable technology. In the following chapter, we have developed a methodology to assign the new technology and a case study has been presented for 25 kwp grid connected SPVPP. In this study the payback time and air pollution mitigation potential of 25 kwp solar photovoltaic power plant installed on a school building have been studied. 2 editor@iaeme.com

3 Sheeraz Kirmani and Mohammad Kalimullah 2. ENERGY PAY-BACK TIME AND AIR POLLUTION MITIGATION POTENTIAL ANALYSIS In this section, a comprehensive account of all energy inputs and outputs involved in the Solar Photovoltaic Power System is given. We will calculate the following: 1. Total power generated by Solar Photovoltaic Power system. 2. Total energy consumed by each component of Solar Photovoltaic Power system. 3. Total pollutants generated by Solar Photovoltaic Power system during manufacturing. 4. Total pollutants prevented by Solar Photovoltaic Power system during its lifetime. Total Power /Energy generated by Solar Photovoltaic Power System during its Lifetime The energy generated by Solar Photovoltaic array during its Lifetime is given by Rtηtdt = Rtηt 1 Where, R (t) = Radiation falling on 1m 2 of solar panel. η (t) =overall conversion efficiency of the system. N= life time of solar photovoltaic power system in years. The energy generated by SPVPP = n Rtηt 2 Where, n=number of modules in the solar photovoltaic power system. The energy consumed during its manufacturing = C E 3 Where, Ci = i th component, Ei = corresponding energy consumed, break-even time for recovery of energy consumed during its manufacturing is given by, $ n Rtηt = C E 4 Where, N is the energy payback period in years. The different components of Solar Photovoltaic Power System are processed by conventional sources. The major energy component is electricity, which is generated by a coalbased power plant. One can always estimate the pollutants emitted for getting a unit Watt/joule of electricity by burning coal. The major pollutants are particulates and SO2. Table 6 shows a number of major pollutants (CO2, NO2, SO2 and particulate) for various coal-based energy conversion technologies during operational period given by Mudgal [7]. Based on the values of Table 1, the amount of energy required for fabrication during the processing of different components of Solar Photovoltaic Power System can be calculated. 3 editor@iaeme.com

4 Estimation of Energy Pay-Back Time and Air Pollution Mitigation Potential of A 25-KWP Grid Connected Rooftop Solar Photovoltaic System Table 1 Break up of energy requirement for balance of system component BOS component Energy required PV module 9900 MJ/m 2 Module frame 500MJ/m 2 Array support field 1900 MJ/m 2 Power Conditioning Unit (PCU) 1 MJ/kW 2.1. SYSTEM DESCRIPTION The design, fabrication, and layout of rooftop solar photovoltaic system installed on the roof of a school building are done by Tesla engineering enterprises, New Delhi. This grid interactive SPV power plant comprises of the following main components: PV array, PCU, Cables, Junction Boxes, and Distribution Board. There are 80 numbers of PV modules for 25-kWp systems each of 315 Wp. These modules are arranged in five arrays, each separate array contains 14, 18, 12, 17 and 19 arrays. These panels are oriented east-west facing south tilted at an angle of The PV modules have a conversion efficiency of % under standard test condition (STC) and the system operating voltage at maximum power is 36.75V. The modules are fixed on a steel frame with clamp and screw without shading any other module. There is provision for islanding protection, which means that the system would be shutdown automatically and separated when the grid fails [6]. Figure 2 shows the SPV array installed on the roof of the school building. 4-core cable of diameter 25 mm 2 has been used to limit the voltage drop to 2%.Table 2 shows the panel parameters under STC of 1000 W/m 2 irradiance, air mass 1.5 spectrums and 25 0 C cell temperature. Figure 2 Polycrystalline solar module installed on the rooftop. Table 2 Electrical characteristics of the solar panel model (WS-315). Nominal maximum power 315W Open circuit voltage 45.25V Short circuit current 9.29 Voltage at maximum power 36.75V Current at maximum power 8.58A Maximum system voltage 1000V Module efficiency Maximum series fuse current 15A Limiting reverse current 15A 4 editor@iaeme.com

5 Sheeraz Kirmani and Mohammad Kalimullah 2.3. OPERATION OF THE SPVPP This SPVPP is connected to the micro grid through a net metering system. The plant generates power satisfactorily from 9 am to 6 pm for 9 hours. The power generation is first utilized by the school loads. If the power generation is less than the power required by load then it gets from the micro grid and when the generation is more than the consumption then the power fed to the grid.net-metering allows consumers who generate some or all of their own electricity to use that electricity anytime, instead of when it is generated. This is particularly important with wind and solar, which is non-dispatchable. Monthly net metering allows consumers to use solar power generated during the day at night, or wind from a windy day later in the month. Annual net metering rolls over a net kilowatt credit to the following month, allowing the solar power that was generated in July to be used in December. Unlike a feed-in tariff (FIT), which requires two meters, net metering uses a single, bi-directional meter and can measure a current flowing in two directions BALANCE-OF-SYSTEM COMPONENTS Table 3 Inverter input data Maximum input current 44.2 A Maximum array short-circuit current 71.6A Minimum input voltage 580V Feed-in start voltage 650V Nominal input voltage 580V Maximum input voltage 1000V Maximum power point voltage range V Number of maximum power point trackers 1 Number of DC connection 6 Maximum PV generator output 35.7 kwp Table 4 Inverter output Data AC nominal output 25000W Maximum output power 25000VA AC output current 36.1A Grid connection 3-NPE 380V/220V or 400V/230V The SPVPP consists of Polycrystalline Silicon module (Po-Si), module frames, array support, and inverter. Balance-of-system component energy analysis has been carried out. The energy requirement for present day polycrystalline silicon modules vary considerably, between MJ/m 2. A nominal value of 9900MJ/m 2 has been taken in the present analysis. Energy requirements in near future for the module production in India can be reduced, by making frame fewer modules. The energy requirement for an aluminum frame for the modules has been taken as 500 MJ/m 2 assuming that per m 2 module area 2.5 Kg of aluminum is used. The energy requirement for steel frames array support field has been taken as 1900 MJ/m 2. Batteries constitute an important part in stand-alone mode for the PV system. It is assumed that within the next ten years there shall be no significant improvement in battery technology or battery energy requirement Kato et al. [8] and Jackson [9]. Using Table 1, total energy consumed for fabricating solar photovoltaic power system including po-si SPV module can be calculated using Equation 3, which comes out MJ in terms of primary energy and kwh in terms of electrical energy. Throughout this paper, energy data have been presented as equivalent primary energy requirement, which is the amount of primary energy necessary to produce the component in mega joules (MJ). Module efficiency is 16.23% and the 5 editor@iaeme.com

6 Estimation of Energy Pay-Back Time and Air Pollution Mitigation Potential of A 25-KWP Grid Connected Rooftop Solar Photovoltaic System inverter efficiency is 98%.1 MJ of primary energy can supply kwh of electrical energy with an assumed conversion efficiency of 15.6% ENERGY PAY-BACK TIME OF SPVPP The energy payback time for the SPVPP installed on the school building has been calculated. The energy generated and supplied to the utility grid during the day has been taken into account. There is no storage facility available in this system. Total energy generated is consumed by the load and the excess amount of energy generation is fed to the utility grid. The energy payback time for the SPVPP is given below. The energy payback time has been calculated using Equation 4 and the total energy generated by this SPVPP are calculated using Equation 2. The monitored data have been validated with calculations based on design specification and then extrapolated for the total life span of the SPVPP. The total energy output generated by this SPVPP in one year is given in MJ by: Power generated per unit time x Total number of hours operated per day x Number of sunny days in a year x Different factors (de-rating of module output due to aging and dust, mismatch losses, cable losses and inverter efficiency etc). The energy generated by the SPVPP per m 2 is obtained by taking into consideration the total area of the modules. The EPBT have been calculated using Equation 4 and the results have been tabulated and presented in Table 5. We have taken two cases for EPBT calculation, the first one deals with the actual generated output of the working SPVPP and its interpolation for life time and the second one deals with the designed (estimated) value based on the available solar radiation of that particular region. Table 5 also shows the total energy output from the SPVPP after the EPBT is over, assuming a life span of 25 years. Table 5. Energy payback time in years and energy output for the SPVPP. Energy requirement Actual generated output for the SPVPP Designed output of SPVPP Energy requirement kwh kwh Energy output after EPBT kwh kWh EPBT in years 9.4 years 8.5 years 2.6. SAVING POTENTIAL OF POLLUTANTS FROM THE SPVPP DURING ITS LIFE CYCLE Once the Energy Pay Back Time (EPBT) is over, Solar Photovoltaic Power System will provide pollution-free energy during its lifetime of 25 years. Solar Photovoltaic Power system is supposed to be one of the cleanest energy conversion systems, as it does not emit any pollutants during its operating lifetime. The energy produced is clean and all the emissions that would have been emitted for getting equivalent electrical energy (coal or diesel generated) can be avoided. S. No Technology Table 6 amount of pollutants produced by power plant CO 2 emission in (kg) at 930 (g/kwh) NO 2 emission in (kg) at 9.6 (g/kwh) SO 2 emission in (kg) at 7.4 (g/kwh) PM emission in (kg) at 205 (g/kwh) 1 Coal-based plant SPV system Nil Nil Nil Nil The energy payback period as shown in the previous chapter varies between 6-8 years on an expected generation and 8-9 years on actual values. The life of the system is estimated to vary between years. All the energy generated by the PV System after EPBT during its lifetime will be pollution free. There shall be neither carbon dioxide emissions, nor emission of acid gas or particulates. The advantages of using PV systems become apparent if one compares 6 editor@iaeme.com

7 Sheeraz Kirmani and Mohammad Kalimullah lifecycle emissions of pollutants from SPVPP to those of the pollutants emitted by Diesel Set (DG) generating systems in the region. In India, as also in rest of the world, power generation is through pulverized coal combustion boilers mostly. Therefore for comparison, conventional pulverized coal boilers (PC Boilers) are considered: Pollutants saving potential of SPVPP are enormous when compared to those of PC Boilers power plants as is apparent from Table 6 during the operational phase. The life cycle analysis of SPVPP system for emission saving potential has been carried out. The net emission saving will be obtained by deducting the energy payback period of the system from span life of 30 years. Table 6 shows the calculated amount of pollutants generated by the different coal-based power generating systems, which will be saved by the SPVPP after its payback period of ( 1 ) 9.4 years for actual electricity generated value and, (2) 8.5 years for designed (expected) electricity generated values. It may be observed from Table 6 that replacing coal-based power systems with 25-kWp SPVPP will save the following pollutants: (i) kg CO2 (ii) 10800kg NO2 (iii) 10800kg SO2 (iv) kg of PM. Calculations have also been done for SPVPP, based on the savings in terms of emissions coming out from the DG set electricity generation. We have calculated the actual amount of pollutants saved by using grid interactive PV system in place of DG set considering that the limit set by the Central Pollution Control Board (CPCB) is adhered to. The calculations are based on the assumptions that The DG set emits 9.2 g/ kwh of NO2, 1.3 of g/kwh HC, 3.5 g/kwh of CO and 0.3 g/kwh of PM [10]. The pollutants such as Nitrogen Oxides (NO2), Hydrocarbons (HC), Carbon Monoxides (CO) and Particulate Material (PM) coming out from the emission of DG sets are not only harmful to flora and fauna but also to the human beings living in the region. The emissions of CO2 are important for the green house effect. Table 6 shows that, by replacing DG set with a 25-kW, SPVPP there will be saving of 1913 kg of CO, kg of NO2,710.7 kg of HC and 164 kg of PM. This is enormous air pollution mitigation potential could be achieved through the 25kWp SPVPP. 3. CONCLUSIONS The following conclusions have been deduced from 25kWp SPVPP installed on the roof of a school building. The life time of the SPVPP is expected to be 25 years and the actual EPBT of the plant is 9.4 years. There are several environmental advantages by installing the solar modules as compared to PC boiler or DG set for the same amount of power generation. Green house gases and the particulate materials saved due to SPV power generation has been discussed in previous sections. ACKNOWLEDGEMENT Authors gratefully acknowledge Tesla Engineering Enterprises; New Delhi based company to provide the information of a grid connected rooftop SPV system. 7 editor@iaeme.com

8 Estimation of Energy Pay-Back Time and Air Pollution Mitigation Potential of A 25-KWP Grid Connected Rooftop Solar Photovoltaic System REFERENCES [1] Arvind Chel, Geetanjali Kaushik, Renewable energy technologies for sustainable development of energy efficient building, Alexandria Engineering Journal, [2] Technical report on Residential buildings in India: energy use projections and savings potentials, Global building performance network (GBPN), September [3] Imtiaz Ashraf, A. Chandra, Energy pay-back time and air pollution mitigation of a 100- kwp Grid-connected SPV power plant for Lakshadweep Island, 39 th IEEE Power Engineering Conference, Bristol, UK, [4] Alsema E, Nieuwlaar E, Energy viability of photovoltaic systems, Energy policy, vol. 28. pp , [5] Alsema. E A, Energy Payback Time and CO! Emissions of PV Systems, Progress in Photovoltaics: Research and Applications, Volume 8, pp , [6] Alsema. E A., Energy Requirement and CO2 mitigation potential of PV Systems, BNL/NREL Workshop: PV and the Environment 1998, Keystone, CO, [7] Mudgal, S., Thermal Issues in Thermal power generation, Proceedings of the International Workshop on Energy for and sustainability, Indian National Academy of Engineering, New Delhi, India, pp , [8] Kazuhiko Kato, Akinobu Murata, Koichi Sakuta., Energy Pay-back Time and Life Cycle CO 2 Emission of Residential PV Power Systems with Silicon PV Module, Progress in Photovoltaic: Research and Applications, Volume 6, pp , [9] Tim Jackson and Mark Oliver, The viability of solar photovoltaic, Energy policy, Volume 28, pp , [10] Challen E, Baranescu, R., Diesel Engine Reference Book, Second Edition, and Butterworth -Heinemann: Oxford; pp , [11] Babu.Uppalapati, Design and Anlysis of Modified Hybrid Solar System Using Nano Fluids. International Journal of Design and Manufacturing Technology 6(2), 2015, pp [12] Swapnil Shende, Sankalp Pund, Pratik Suryawanshi, Shubhankar Potdar, Analysis of PI Controller s Manual Tuning Technique for Residential Loads Powered by Solar Photovoltaic Arrays. International Journal of Electrical Engineering & Technology, 7(6), 2016, pp [13] Nishanur Rahman, Sanjana Kumari, Anukul Prakash Anurag and Ajeet Kumar Rai, Design of Photovoltaic System for School Library: A Case Study. International Journal of Advanced Research in Engineering and Technology, 7(5), 2016, pp editor@iaeme.com