1 Héctor Rubio Plana Gas Natural, SDG S.A. 18th. June 2009
Table of contents 1. Introduction 2. How does it work? 3. Experiences 4. Conclusions and future scenario 5. Future previsions 2
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Solar Cooling Introduction Fitting demand to solar energy Daily evolution of solar radiation and cooling demand Solar Radiation Cooling Demand Radiation [W/m 2 ] 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Hour 1200 1000 800 Annual Evolution of solar radiation and cooling/heating demand Average solar radiation Cooling demand Heating demand Coincidence between maximal irradiation periods and maximal cooling demand periods 600 400 200 0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Source: TECSOL-SOLAIR Month 4
Solar Cooling Introduction First approach Challenges High electrical demand peaks in summer due to the increasing number of cooling systems Overload of electrical grids Generation mix still based on fossil fuels Oportunities Lack of technologies to take advantage of high irradiation levels in summer Gas distribution grid underemployed in summer Need to reduce the greenhouse gas emissions. 5
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Solar Cooling How does it work? Components and diagram Solar primary circuit Chilled water Solar field: solar collectors transform energy from the Sun into thermal energy, transferring it to a working fluid. Absorption chilling machine: Based on a similar principle to the compression cycle, but powered by a head source and using a pair absorbent-refrigerant (LiBr-Water or Water-Amonia) Cooling system: cooling tower, air cooler, collected water (lake, river, well), borehole thermal dissipation Thermal storage system: excess of energy from the solar field is stored to use it during low irradiation periods. Natural gas burner 13 bar / 165º C Linear Fresnel Collector Overheated water 13 bar/ 180º C Thermal storage PCM Circuito de Agua refrigeración Hydraulic system: carries different thermal fluids through the equipment (chilled water, hot water, primary solar water ) Control system: it manages the different inputs from solar field, probes, absorption chiller, flow meters, etc. and controls the elements to optimise the system performance. Absorption chiller Guadalquivir river 7
8 Solar Cooling How does it work? Absorption technology Absorption chillers should be considered the most ecological alternative to compression chillers for air conditioning and cooling Advantages regarding compression systems No CFC o HCFC emissions Feeding flexibility: steam, hot water or direct fired Complementary to high-efficiency systems such as cogeneration or renewable heat production Primary energy can be used directly (gas or solar) Reduction of power term in electrical invoice Stable efficiency at partial loads Noiseless. Solution and refrigerant pumps are the only mobile parts Low maintenance, but specialised
Steam 9 Solar Cooling How does it work? Double stage absorption cycle. Simplified diagram Hot 165 C solar water 180 C 3. GENERATOR HT LiBr + Water Generation stage at higher temperature Double stage absorption cycle Higher efficiency. COP greater than 1.3 (single stage absorption only reaches 0.7). Heat Exch. HT 4. GENERATOR LT LiBr + Water Steam 5. CONDENSER A heat source between 170 C and 180 C is needed to power the cycle (80 y 90 C in case of single stage). Heat Exch. LT Water Liquid water Concentrated solution Steam 2. ABSORBER 1. EVAPORATOR These temperatures are only reachable using concentrated solar energy (flat collectors are enough for single stage). Cooling water LiBr + Water Diluted solution Water 7 C Chilled water. 12 C Solution pump Refrigerant pump
Solar Concentration Technologies 10 Solar Cooling How does it work? Solar thermal collectors Parabolic Trough Collectors Evacuated tube collectors www.sopogy.com Linear Fresnel Collectors Flat collectors Mirroxx Linear Fresnel Viessmann collectors
Solar Cooling How does it work Linear Fresnel Collector Parabolic Trough Advantages Low wind charge and good weight-spread High ground usage factor (m 2 /kw) Primary mirrors made of flat glass Stationary receiver No North-South alignment necessary Mirrors are driven to stow position when it rains or in case of overheating Easy Cleaning procedure Linear Fresnel Working Principle
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Solar Cooling Experiences Two projects in Andalusia Single Stage Abs. + Evacuated tube collector Project: Solar cooling system based on a single stage absorption chiller Location: Gas Natural Building in Pineda, Seville Started: 2006 Deadline: 2007 Aim: preliminary analysis of single stage Solar Cooling technology using high efficiency flat collectors and natural gas boiler support. Project : Refrigeración solar por Absorción en el Sector Terciario Double Stage Absorption + Linear Fresnel Collector Location: Engineering School University of Seville Started: January 2007 Deadline: March 2009 Cost: The total cost of the installation has been 594.000, promoted by Gas Natural SDG and financed partially by Corporación Tecnológica de Andalucía and Agencia IDEA (Junta de Andalucía) Research Groups: AICIA Termotecnia, AICIA Automática from the Engineering School. 13
Solar Cooling Experiences Double stage absorption chiller + Linear Fresnel Collector 14 Aim The main purpose is to promote solar cooling installations in tertiary sector with maximal efficiency criteria and lay down design basis by putting together different existing technologies, as well as improving or developing new ones in order to use solar energy for cooling. Specific goals Building a solar cooling plant to lay dawn technical, economical and environmental design criteria for similar installations by means of suitable control and monitoring. Promote Solar Cooling by developing a software friendly application for design and simulation of these installations Encourage the combined use of absorption chillers powered by solar energy and natural gas as a complement to compression cycles in order to reduce greenhouse gases emissions Diversification of energetic resources: Reduction of electrical demand. Reduction of fossil fuel consumption for electrical generation Reduction of external energy dependence. Extend CALENER capabilities including absorption technology. CALENER is the Spanish software for building energetic qualification.
Experiences Solar Cooling Double stage + Fresnel collector (Seville) Engineering School University of Seville Fuente: Google Earth 15
Experiences Solar Cooling double stage + Fresnel, ubicación: Sevilla Perfect location: High irradiation level: ~2.000 kwh/m 2 Large available surface Orientation: ~South (deviation 12 ) Close to Guadalquivir river A number of research groups involved in renewable energy and energy efficiency N Fuente: Google Earth 16
Solar Cooling Experiences Double stage (Linear Fresnel Collector) 17 Manufacturer: PSE AG (Mirroxx) Technical details Technology: linear Fresnel collector Peak power: 180 kw Used surface: 512 m 2 Mirror surface: 352 m 2 Length: 64 m (16 modules) Total mirrors number: 176 (11 rows) Remote control via LAN Every row of mirrors rotates following the sun path and reflecting sunrays to the absorber tube
Solar Cooling Experiences Double stage (absorption chiller) 18 Supplier: BROAD Modelo: BZH 15 IX Features and technical details Technology: Double stage, LiBr / water cycle Cooling power: 174 kw Heating power: 135 kw Cooling COP : 1,34 Heating COP: 0,925 Inlet heat water temperature: 165 C/180 C Hybrid operation overheated water or gas direct fired Water cooling circuit from Guadalquivir (EXPO 92)
19 Refrigeración Solar Experiencias Double stage absorption + Linear Fresnel 2.00E+05 1.80E+05 1.60E+05 Final Energía cooling final energy producida produced (kwh) [kwh] Results Total cooling demand during summer 2008: 822.788 kwh Cooling fraction covered by the absorption chiller: 41.86 % (solar 11.31 %) Total Power of the compression system: 1.233,2 kw 1.40E+05 1.20E+05 1.00E+05 8.00E+04 6.00E+04 4.00E+04 2.00E+04 0.00E+00 M Jn Jl A S O Solar Gas Electricity Solar Gas Electricidad 1/3 of the total cooling power has been supplied during peak irradiation periods during summer 2008. Some minor incidences took place in solar collector related with thermal expansion and also related with water leaks in the hydraulic circuit Need to use direct firing in the absorption machine due to high thermal inertia and the lack of a storage system
Solar Cooling Experiences Software for design and simulation of Solar Cooling Installations (SICAR) Is a design and simulation software for calculating and evaluating energetic performance of Solar Cooling Installations based on absorption units. Features It has been validated according to the empiric results of the real installation at the Engineering School of Seville. This application will be upgraded with a dynamic model of thermal storage systems using Phase Change Materials (PCM). SICAR will be presented as a recognized document to the Comisión Asesora para la Certificación Energética in order to be accepted as an additional capability to CALENER VYP and CALENER GT SICAR is the result of the co-operation agreement between Gas Natural and the Group of Thermodynamics of AICIA (Asociación de Investigación y Cooperación Industrial de Andalucía) in the framework of a R&D project financed by Corporación Tecnológica de Andalucía (CTA) 20
Solar Cooling Experiences Software for design and simulation of Solar Cooling Installations (SICAR) Módule for energy demand calculation (heating, air conditioning and hot water) Starting from general building data, like: surface, location, needed temperatures for heating and cooling, thermal transmittance of roof and floor y hot water consumption. Buildings are divided in modules, which are defined by: orientation, surface, shape and other parameters. For the time being only available for Spanish climate 21
Solar Cooling Experiences Software for design and simulation of Solar Cooling Installations (SICAR) Cooling System Definition and Results Cmponent Definition : Heating system, solar or conventional Heat and cool storage Heating and cooling distribution Absorption and compression systems Basic control parameters Results: Demand results of cooling and heating Hourly results of the selected variables Monthly cumulated results and comparison to conventional CO 2 emissions calculation Complete report SICAR includes a database of components and calculates an economical and sensibility study 22
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Solar Cooling Conclusions and future scenario 24 We have proved the feasibility of that solution, by covering 1/3 of the cooling power required in the ESI and we evidenced that solar cooling solutions with good efficiency are possible thanks to double stage absorption technology There are many pilot and demonstration experiences of solar cooling systems, but there is a long way to go for manufacturers to increase range of products, improve cost efficiency as well as develop better control strategies. Before installing a solar cooling system a complete analysis and optimization of energetic needs is required, as well as a study of solar radiation availability Heat storage is entirely necessary in the solar circuit in order to take maximal advantage of solar resource and control differences between cooling/heating demand and solar radiation availability. Gas Natural is making a huge effort promoting good maintenance of solar thermal installations and giving training to technicians and contractors
Thank you for your attention 25
26 This presentation is a Gas Natural Group property. Either thematic content and graphic design are only for use of his own staff. Copyright Gas Natural SDG, S.A.