Solar Cooling Used for SolarAir Conditioning - A CleanSolution for a Big ProblemStefan BaderEditorWerner LangAurora McClaincsdCenter for Sustainable Development

II-Strategies Technology2

2.10 Solar Cooling for Solar Air ConditioningSolar Cooling Used for SolarAir Conditioning - A CleanSolution for a Big ProblemStefan BaderBased on a presentation by Dr. Jan CremersFigure 1: Vacuum Tube CollectorsIntroduction“The global mission, these days, is anextensive reduction in the consumption offossil energy without any loss in comfort orliving standards. An important method toachieve this is the intelligent use of current andfuture solar technologies. With this in mind, weare developing and optimizing systems forarchitecture and industry to meet the highindividual demands.” Philosophy of SolarNextAG, Germany.1When sustainability is discussed, one of thefirst techniques mentioned is the use of solarenergy. There are many ways to utilize theenergy of the sun when designing a building.The primary and most efficient use of solarenergy is daylighting. In order to use naturallight effectively, the architect has to designsensibly, allowing the light to enter the buildingwhile avoiding excessive heat gain. Keepingthis balance is the difficult part.In addition to providing natural daylight, solarenergy can also be used through solar thermalcollectors or photovoltaic panels. Using eitherof these two devices requires a certain amountof technical equipment. Solar thermalcollectors gather solar energy and transfer it toa medium, normally water, that can then beused to heat a certain space. While solarthermal collectors transfer the solar energydirectly from one medium to another, photovol-taics convert the heat produced by solarenergy into electrical power. This power can beused to run a variety of devices which forexample produce heat for domestic hot water,lighting or indoor temperature control.Photovoltaics produce electricity, which can beused to power other devices, such ascompression chillers for cooling buildings.While using the heat of the sun to coolbuildings seems counter intuitive, a closer lookinto solar cooling systems reveals that it mightbe an efficient way to use the energy receivedfrom the sun. On the one hand, during the timethat heat is needed the most - during thewinter months - there is a lack of solar energy.However, during the summer, when cooling isneeded, there is a great surplus of solarenergy. The best conclusion to draw fromthese facts is that an efficient way might be toutilize solar energy to additionally generatecooling energy.In the following pages, the advantages of solarcooling will be explained by comparing solarcooling with existing compression coolingtechnology, while analyzing the efficiency andapplicability of each system.3

II-Strategies TechnologySolar cooling overviewHistorical reviewFigure 2: World Exhibition 1878 in Paris - A. Mouchotproduced the first manufactured ice block using solar energySolar cooling technology is actually not arecent invention. It had already been used inthe late 19th century when a solar collectorwas used to produce ice blocks at the 1878World Exhibition in Paris by A. Mouchot - thefirst solar cooling device (Figure 2). In 1892, asolar hot water heater was advertised in theUnited States of America. Several years later,in 1910, one of the first private home solarthermal applications was seen in PomonaValley, USA, where solar collectors wereinstalled on the roof of a private house (Figure3). MIT took a closer look into solar thermalcollectors while building the MIT Solar Housein 1939, a research building with an integratedsolar collector roof (Figure 4). Absorptionchillers are not a new invention either. The firstapplications were developed in the early 20thcentury for ships and there are some machinesthat are still running after more than 70 years.Figure 3: Private home with Solar Thermal application SolarNext AG / Hightex Group - Solar Air-Conditioning - Jan Cremers, September 24th, 2008A similar situation can be found when lookingat cogeneration processes which also benefiteconomically from running continuously.Therefore, it is interesting to combine standardcogeneration with thermal cooling: In summer,the heat produced can be converted to colddirectly and thereby prolong the running timeof the engines (Figure 6). The same applies ona larger scale to district heating. Here again, insummer it is hard to sell the heat directly, butwith the addition of a thermal cooling processthe heat can be used all year.Conventional air conditioningUp to now, solar thermal energy has generallybeen used only for domestic hot water andheating support. Because of the variationthrough the seasons and the opposite demandfor cooling in Europe, it appears that it is notideal to use solar energy for heating alone.The cooling loads of buildings display aparallel energy curve compared to the solarenergy curve throughout the year. It seemsideal to benefit from solar input while combining solar cooling with a standard solar heatingtechnology. When solar collectors are used forsolar heating, large installations are necessary.clean energy for youBecause of the large size of the collectorSolar cooling has a big potential to restrict theenormous amounts of electrical energycurrently consumed for conventional compression cooling. Electrically driven split-units havetheir peak loads at the same time during theday, when a lot of other electrical consumersreach their maximum capacity as well. In manycountries energy providers have a hard timeproviding enough energy for these kinds ofair-conditioning machines during their peaktimes. In addition to electricity demands whichare predominantly met by burning fossil fuels,these units use ozone-damaging gases andhave a leaking range up to 5 - 15 % per yearwhich leads to an additional severe globalwarming potential (Figure 7). However, theoption to power these units with solarphotovoltaic panels could as an alternative toG[W]P[W]Solar thermal cooling as a valuable add-onfeature to conventional applicationsPrivate(aroundHome withSolar PomonaThermal Application(around 1910), Pamona Valley, USA1910),Valley, USAfields, some part of the gained energy needsto be used for re-cooling the large system andmost of it will not be necessary in summer(and then might even lead to stagnationproblems), which seems counterproductive.Instead, when it is used for cooling, the energycollected in the summer will produce cold atthe time when it is most needed (Figure 5).P[W]132Jan1 Global Radiation3 Heating LoadFigure arHouse,ResearchBuildingwith IntegratedSolar withCollectorRoof (1939),FigureUSAsolar collector roof (1939), USA SolarNext AG / Hightex Group - Solar Air-Conditioning - Jan Cremers, September 24th, 20084Dez2 Cooling LoadSolar Surplus Supplyin Summer5: Relationship between Solar Radiation and Coolingclean energy for youDemand0delta t8760 [h]Thermal Heat Energy DemandHeat Energy Demand for CoolingFigure 6: Combined Heat, Cold and Power: Extension ofOperation Time

2.10 Solar Cooling for Solar Air Conditioningsolar thermal cooing help to reduce theirenvironmental impact.Competitive advantage of solar thermalcooling against conventional compressioncoolingComparing solar cooling with traditionallypowered compression cooling reveals somesignificant differences between the twosystems, as can be seen in Figures 8 and 9.Solar cooling produces much lower CO2emissions than compression cooling due to itsuse of the sun as a CO2-free renewable energysources. Although the Coefficient of Performance (COP), which is defined as the ratio ofthe cooling output to the driving heat required,is lower in the case of solar cooling, the overallCO2 emissions (primary energy related) aresignificantly lower as it is not the standardnational energy mix which has to be taken intoaccount but nearly only the sun: 80% of theprimary energy used for solar cooling comesfrom the sun rather than from external sourcessuch as fossil fuels, unlike compressioncooling, which primarily uses these sources.The higher re-cooling capacities for the solarcooling process are due to the lower COP andthe additional heat energy from the collectorsthat is brought into the process. The casedescribed in Figures 8 and 9 compare smallcapacity applications ( 10kWh).EuropeUSA 17.08.1China 21.5MiddleEast 3.7Central/SouthAmerica3.9India 2.4Japan 8.4East Asia 7.1Africa 1.3Australia 0.9Figure 7: Market Situation of Conventional Air-Conditioning Worldwide in 2007Lost Heat: 1.67 kWhthCO2 Emission:369 g/kWhStatus on installed solar cooling systemsIn Europe there are about 200 systems running, which is about 2/3 of all built systems.The reality that the combined capacity ofthese units is about 15 MW for which theyneed a surface of only 30,000 m2 (322,917 ft2)proves the existence of a still small market.The following cooling technologies were used(Figures 15 and 16): 60 %100 %Primary Energy1.91 kWh29 %0.67 kWhelLost Energy:1.24 kWhth1 kWhth Cooling11 %Figure 8: Standard Compression Chiller ( 10 kwth cooling)60 % absorption cooling11 % adsorption cooling25 % DEC systems4 % liquid sorptionProcess of solar coolingLost Heat: 2.67 kWhthThe solar thermal driven cooling technologiescan be divided into four principal technologies: CompressionChillerCOP: 1.5absorption chillersadsorption chillersopen sorption cooling systems (DEC)compression chillers ( when driven byPVs these are another option for “solarcooling”. However, this is not a thermallydriven process.)In principle, there are three different tech-CO2 Emission:83 g/kWh80 %20 %100 %Primary Energy2.1 kWh1.67 kWhthchillii - TechnologyCOP: 0.61 kWhth Cooling0.15 kWhelLost Energy:0.28 kWhthFigure 9: Solar Cooling Absorption Chiller ( 10 kwth cooling)5

II-Strategies Technologyniques used for thermal cooling. Absorptionand Adsorption chillers use heat produced bysolar thermal collectors or other heat sourcesto run the process, with a minimum amount ofadditional electrical energy needed for solutionpumps, controller, etc. The thermal collectorprovides water heated to between 70 C(158 F) and 120 C (248 F), which is guidedinto a storage system. This hot water will beused to drive the chiller, which will thenproduce cold water that is kept in anotherstorage system from which it can be distributed to different cooling devices.Open sorption and desiccant cooling systemsuse heat gathered from solar collectors to dryout a desiccant that is then used to absorbmoisture from hot air so that it can be cooledusing evaporation.Compression chillers use photovoltaicelements to drive an electrical device thatproduces cold by using a compressionprocess. This process is not as attractive asthe use of systems powered by solar thermalcollectors, due to the currently still high cost ofinstalling the volume of photovoltaic elementsneeded for producing enough electricity topower the compression system.Most solar cooling systems use absorptionchillers (60% in Europe, Source: IEA SHC Task38, Solar Air-conditioning and Refrigeration).Driving heat sources for thermal coolingsystem not only has to get rid of the CoolingCapacity QO (heat inside the room) but also ofthe heat running the system (Heating CapacityQH) which leads to a higher Re-Cooling Capacity QC. These chillers use the hot watergenerated by solar collectors or other heatsources to provide cold water at temperaturesbetween 6 C (42.8 F) and 18 C (64.4 F). Theycan therefore be used for central air conditioners as well as cooling systems with decentralised air treatment, such as fan coils, coolingceilings, or concrete slabs.Thermal cooling systems can utilize differentheat sources for driving cooling and heatingsystems, for example: solar energy harvested by a solarcollector like a vacuum tube, flat plate collector or even concentrating systems. district heating energy (a central systemproducing heat). waste heat from power stations (normally,energy is used to get rid of this heat; withthis technology the heat coming frompower stations or centralized solar powerplants can actually be used for cooling insummer). heat from cogeneration processes(Cogeneration Heat and Power orCHP-Units use both heat and energyproduced by an engine to reach a highlevel of efficiency.Instead of using electricity, the Absorption andAdsorption Chillers are driven by heat sources.This system has a lower efficiency, whichleads to a higher need for driving energy.When using heat as a driving energy, theBy using a CHP-Unit in an office building heatcan either be used for producing heat and hotwater or it can be converted into cold. Smallerunits can even be used in residential buildings.Figure 14: Application of Solar Cooling in a BuildingFigure 13: Fresnel Collectors6Figure 10: Vacuum Tube CollectorsFigure 11: Parabolic CollectorsFigure 12: Flat Plate Collectors

2.10 Solar Cooling for Solar Air ConditioningIf solar thermal collectors are used as the heat6011source for the solar cooling system they could25also be used to provide hot water during the4year (kitchen, shower etc.) and to support theheating system in winter time.1 Using there-cooling capacities for heating a pool isespecially appealing if the swimming pool ispartially or even completely shaded. In order tohave agreeable temperatures in the pool, theheat extracted out of the indoor environmentwill be guided directly into the pool. In the bestcase scenario, solar collectors can be used tosupply four different kinds of systems: Solar CoolingSolar HeatingSolar Domestic Hot Water (DHW)Solar Pool Heating (by using 1%60%28%Absorption CoolingDEC SystemsGermanyAdsorption CoolingLiquid SorptionFigure 15: Solar Cooling Systems, Different Systems, 2007SpainGreeceRest of EuropeFigure 16: Solar Cooling Systems, Main Countries, 2007Solar thermal collector technologies Vacuum Tube Collector: very wellinsulated absorber - suited to climateswith very low temperatures (Figure 10) Parabolic Collector: focuses sunlight onabsorber in the middle - a spot is heatedup to temperatures of 300 C by using aspecial oil (Figure 11) Flat Plate Collector: dark metal and glasscovered absorbing plate which getsheated by solar radiation (Figure 12) Fresnel Collector: flat mirrors focusing ona specific and central absorber area(Figure 13)Heating Capacity QH(Solar Collector)Electrical Input PelRe-Cooling Capacity QC(Cooling Tower)Re-Cooling Capacity QC(Cooling Tower)Electrically driven compression chillerThe conventional cooling process - compression technology - needs an electrical input torun the process (Figure 17). For this processsplit units are commonly used - a condenserand a separated evaporator which produce thecold energy (Figure 19). This system uses anelectrically powered pump to pressurize thegas. When the pressure is released, the gasbecomes very cold, similar to a campingcartridge, which gets cold while the gas isreleased.Cooling Capacity QO(fan coils / cold ceilings)Figure 17: Schematic Cooling Processes - Electrically DrivenCompression ChillerCooling Capacity QO(fan coils / cold ceilings)Figure 18: Schematic Cooling Processes - Thermally DrivenAbsorption or Adsorption ChillerCondenserCondenserThermally driven absorption chillerThe thermal process replaces the compressorby two other components - the generator andthe absorber. These two components enablethe use of heat to drive the cooling process,rather than electricity (Figures 18 and 20).What follows is a sample description of thetechnology of a small scale Absorption Chiller(here for an Ammonia-Water chiller, 12 kW).High pressure level PHThrottleLow pressure level PLGeneratorHigh pressure level PHSolution HeatExchangerElectricitySolution PumpThrottleCompressorEvaporatorFigure 19: Scheme of a Electrically Driven Compression ChillerThrottleLow pressure level PLEvaporatorAbsorberFigure 20: Scheme of a Thermally Driven Absorption Chiller7

II-Strategies TechnologyThe process of a typical small scale absorptionchiller contains four major components: GeneratorCondenserammonia vapor 12 bar,i.e. depending on point of operation:approx. 70 - 110 C (158 - 230 F)The GeneratorThe CondenserThe EvaporatorThe Absorbere.g. 12 bar,30 C (86 F)85 C (185 F)29 C (84 F)78 C (172 F)24 C (75 F)GeneratorTo run the generator, temperatures of about85 C (185 F) are needed. This could comefrom the sun, or any other appropriate heatsource. The heat expels ammonia out of a“rich” ammonia water solution to generate ammonia vapor. The left over solution becomesa “weak solution”, which means that it hasless ammonia in the water. At a pressure of 12bars, the heat causes the ammonia to evaporate out of the solution. The ammonia vapor isled to the condenser. To be able to work withthe ammonia vapor the pressure has to beadjusted depending on the point of operation(Figures 21 and 22).ammonia water solutionammonia vapor6 C (43 F)12 C (54 F)e.g. 4 bar,5 C (41 F) 4 bar,i.e. depending on point of operation:approx. 28 - 39 C (82 - 102 F)CondenserThe re-cooling device causes the ammoniavapor to condense at a temperature of around24 C (75 F) in the condenser (Figure 23). PureAmmonia is created.AbsorberEvaporatorFigure 21: Small Scale Absorption Chiller (Ammonia-Water, 12 kW)EvaporatorThe liquid ammonia is guided through a throttlein order to release the pressure. After thatstep, the actual cold is produced through heatsupply by the external cold water circuit. Whenthe pressure is reduced the ammonia is notonly turned back from the liquid phase intovapor but also cooled down to the desiredtemperature (5 C or 41 F) (Figure 24).AbsorberThe ammonia vapor reaches the absorber5 kWwhere it reacts with water and becomes theFigure22:Principle:The Generatorrich ammonia water solution again, which isPrinciple:TheGeneratorthen used for the first step of the wholeprocess by reducing the pressure and the hightemperatures that are received by the coolingprocess. The rich ammonia water solutiongoes back to the condenser and the heat islost in the re-cooling process, closing the loop(Figure 25). SolarNext AG / Hightex Group - Solar Air-Conditioning - Jan Cremers, September 24th, 20085 kWFigure 23: Principle: The CondenserPrinciple: The Condenser SolarNext AG / Hightex Group - Solar Air-Conditioning - Jan Cremers, September 24th, 2008clean energy for youclean energy for youRe-coolingThere are several options for rejecting the heatproduced by the system. One option is to usea recooler. There are three types of appropriate re-cooling processes: the “wet coolingtower” exposes the water directly to the air sothat it can be cooled through evaporation,5 kWFigure 24: Principle: The EvaporatorPrinciple: The Evaporator SolarNext AG / Hightex Group - Solar Air-Conditioning - Jan Cremers, September 24th, 20085 kWFigure 25: Principle: The Absorbercleanenergy for youPrinciple: TheAbsorber SolarNext AG / Hightex Group - Solar Air-Conditioning - Jan Cremers, September 24th, 20088clean energy for you

2.10 Solar Cooling for Solar Air Conditioningwhile the “dry recooler” uses a heat exchangerto transfer heat through an intervening mediumso that the water does not come into contactwith the air. A “hybrid recooler” combines thetwo processes, passing hot water throughtubes that are sprayed with a fluid thatevaporates to cool them and the water within.The excess heat can also be rejected into abody of water, such as a swimming pool, lake,or groundwater. Each of these options hasbenefits and drawbacks, the most important ofwhich are the hazards of excess humidityproduced by “wet” cooling towers and thedanger of altering the ecosystem in a body ofwater by substantially altering the temperature.High outdoor temperatures ( 100 C or 212 F) might require additional sources oflower temperatures like geothermal orevaporative cooling, depending on the climateconditions, or alternative re-cooling options.Back-up heat sourcesOne can imagine situations in which coolingwould be needed but the levels of solarradiation needed to produce temperatures thatcould power the chiller might not be available,e.g. a hot but cloudy day or generally hotnights. In this cases the energy from the heatstorage system will be taken but in cases thisis not enough or the storage’s dimensions arenot sufficient the chiller can be driven by aback-up heat source such as a burner toproduce the temperatures that it needs tooperate. Ideally, the back-up burner is also runby renewable energy sources (e.g. biomass).ControllerThe controller is essential to the stability andefficiency of the system. It manages andcoordinates the function of the chiller, heatsource, pumps, fans, storage(s), back-up,re-cooling and heat and cold distributionsystems. It can be set to preferentially userenewable energy sources and to respondquickly and efficiently to cooling demands. Thecontroller manages the flow of energy throughthese complex systems in order to ensure thatno energy will be wasted and that the systemruns in an economical way which is a verycomplex task. A well designed controller isnecessary to maximize the potential of thecooling system.vapor into liquid.COP: Coefficient of Performance. The COP isdefined as the ratio of the energy output (e.g.cold) and the driving energy (e.g. solar thermalenergy) required for this.Evaporator: A solution containing the desiredproduct is fed into the evaporator and passesa heat source. The applied heat converts theConclusionUsing solar thermal energy to produce coldseems to be a complicated process requiringnumerous steps. It is certainly true that usingvery high temperatures to produce lowtemperatures requires the integration of manydiverse components, which need to functiontogether perfectly in order to be efficient andsustainable. However, every new technologyseems complicated before it becomes widelyused, and solar cooling systems build ontechnologies and components that have beenin use for decades. With the use of electroniccontrol systems, all of the different processescan be coordinated to create a very efficientsystem with multiple llerMechanicalSolution MixerSolution HeatExchangerGeneratorGlossaryChiller: A machine that removes heat froma liquid via a vapor-compression or ad-/orabsorption refrigeration cycle.Solution PumpCompressor: Mechanical device that compresses a gas (e.g. air or natural gas).Condenser: Device or unit used to condenseFigure 27: Example of a small scale absorption ammoniawater-Sorbentlithium bromidelithium bromidewatersilicia gelsilicia gel orlithium chlorideCooling Mediumwaterwaterwater glycolwaterairCooling Temperature6 - 20 C(42 -70 F)6 - 20 C(42 -70 F)-20 - 20 C(-4 - 70 F)6 - 20 C(42 -70 F)16 - 20 C(61 - 70 F)Heating Temperature75 - 100 C(167 - 212 F)130 - 160 C(266 - 320 F)80 - 160 C(176 - 320 F)55 - 100 C(130 - 212 F)55 - 100 C(130 - 212 F)Cooling Water Temperature30 - 50 C(86 - 122 F)30 - 50 C(86 - 122 F)30 - 50 C(86 - 122 F)25 - 35 C(77 - 95 F)not requiredCooling Capacity Range (per Unit)5 - 20,500 kW170 - 23,300 kW5 - 1,000 kW5 - 350 kW6 - 300 kWCoefficient of Performance (COP)0.6 - 0.71.1 - 1.40.5 - 0.60.6 - 0.70.5 - 1.0Figure 26: Overview of Thermal Driven Cooling and Air Conditioning Applications9

II-Strategies Technologywater in the solution into vapor. The vapor isremoved from the rest of the solution and iscondensed while the now concentrated solution is either fed into a second evaporator or isremoved.Flat Plate Collector: Consists of a thinabsorber sheet (of thermally stable polymers,aluminum, steel or copper, to which a black orselective coating is applied) backed by a gridor coil of fluid tubing and placed in an insulatedcasing with a glass or polycarbonate cover.Fresnel Collector: Uses a series of long,narrow, shallow-curvature (or even flat) mirrorsto focus light onto one or more linear receivers positioned above the mirrors. On top ofthe receiver a small parabolic mirror can beattached for focusing the light further. Thesesystems aim to offer lower overall costs bysharing a receiver between several mirrors(as compared with trough and dish concepts),while still using the simple line-focus geometrywith one axis for tracking.Parabolic Collector: Functions due to thegeometric properties of the paraboloid shape:if the angle of incidence to the inner surfaceof the collector equals the angle of reflection,then any incoming ray that is parallel to theaxis of the dish will be reflected to a centralpoint, or “focus”. Because many types ofenergy can be reflected in this way, parabolicreflectors can be used to collect and concentrate energy entering the reflector at aparticular angle.Primary Energy: Energy that has not beensubjected to any conversion or transformationprocess. It is contained in raw fuels and anyother forms of energy received by a system asinput to the system.Notes1 - 2 pdfFiguresFigure 1: 3029.jpgFigures 2-4: Hegger, Manfred. Energy ManualSustainable Architecture. Munich: Birkhäuser,2008. p. 111/112Figures 5-6: SolarNext AG, Rimsting, Germany. Modified by Stefan BaderFigures 7-9: Jarn / SolarNext AG, Rimsting,Germany.Further ReadingHenning, Hans-Martin. Solar Assisted AirConditioning in Buildings - A Handbook forPlanners. New York: Springer Verlag, 2004.Hegger, Manfred. Energy Manual - Sustainable Architecture. Munich: Birkhäuser, 2008.Jakob, Uli. Cool climate from the scorchingsun. Sun & Wind Energy. No. 2, pp 64-72.ISSN 1861-2741, 2008.Zimmermann, Mark. Case Studies of LowEnergy Cooling Technologies. Coventry: BritishCrown, 1998.Figures 8-9: SolarNext AG, Rimsting, Germany.Figure 10: nlage%2BNr.%2B1.jpg&imgrefurl eder-waermetechnik-gmbh/boxid-150226.Figure 11: e/galerie/parabolrinnen.jpgFigure 12: Flachkollektor Indachmontage.jpgFigure 13: news/newsarchiv2007/fresnel.JPGThermal Collector: Takes up the heat ofthe solar radiation through a medium (water antifreeze). This is heated and circulatesbetween the collector and the storage tank. Ahigh degree of efficiency is achieved by usingblack absorbers or, even better, through selective coating.Figure 14: SolarNext AG, Rimsting, Germany.Vacuum Tube Collector: Made of a seriesof modular tubes, mounted in parallel, whosenumber can be added to or reduced as hotwater delivery needs to be changed. This typeof collector consists of rows of parallel transparent glass tubes, each of which contains anabsorber tube (in place of the absorber plateto which metal tubes are attached in a flatplate collector). The tubes are covered with aspecial light-modulating coating. In an evacuated tube collector, sunlight passing throughan outer glass tube heats the absorber tubecontained within it.Figure 27: Werner Pink / SolarNext10Technology. München: Birkhäuser, 2005.Hausladen, Gerhard. Climateskin - BuildingSkin Concepts that Can Do More with LessEnergy. München: Birkhäuser, 2006.Figures 15 - 16: Source IEA - SHC Task 38 Solar Air-Conditioning and Refrigeration, 2007Figures 17 - 26: SolarNext AG, eng/home/home mlHausladen, Gerhard. ClimateDesign - Solutions for Buildings that Can Do More with LessBiographyJan Cremers is the Director of EnvelopeTechnology ofat Solarnext AG / and HightexGroup, Rimsting (Germany).He studied at the University of Karlsruhe from1991-1999, at which time he received the 1stprize in the building network competition forthe Diploma of the Year. He has also studiedArchitecture and management at WestminsterUniversity, London, UK.In 2006 he received awards for his outstanding doctoral thesis: “Applications of VacuumInsulation Systems in the Building Envelope”from both the Alliance of Friends of the Technical University in Munich and the MarshallFoundation.Jan Cremers has lectured frequently at theTechnical University of Munich School ofArchitecture on topics concerning membranesand facade construction. He is a regularreviewer for the referenced internationalmagazine Solar Energy, official journal of theInternational Solar Energy Society. Since 2008he is a full professor of Building Technologyand Integrated Architecture at the Universityof Applied Sciences Hochschule für Technik inStuttgart, Germany.

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Air Conditioning - A Clean Solution for a Big Problem Stefan Bader Editor Werner Lang . of technical equipment. Solar thermal collectors gather solar energy and transfer it to a medium, normally water, that ca