The Japan Refrigeration and Air ConditioningIndustry Association (JRAIA) have estimatedworldwide sales of 94.5 million units in 20111.Conventional split-units have a high-energyconsumption using non-environmentallyfriendly refrigerants. The refrigerants that arecurrently used in the split-units no longer havean Ozone Depletion Potential (ODP), but theyhave a considerable global warming potential(GWP). Solar cooling and especially sorptionchillers use environmentally friendly refrigerants(water or ammonia) and have only very lowelectricity demand. Therefore the operatingcosts of these chillers are very low and the CO2

balance compared to compressor chillers isconsiderably better. In case of solar cooling, themain advantage is the link between solarirradiation and cooling demand, whichcomplements the sunny and hot climates allover the world.

A definition Before presenting the solar cooling tech-nology status, it is important to define thetechnology currently on the market and underdevelop ment2. Solar energy can be convertedinto cooling using two main principles (see Figure 1):! Electricity generated with photovoltaic

modules can be converted into coolingusing common technologies that are mainly based on vapour compression cycles (PV Cooling).

! Heat generated with solar thermalcollectors can be converted into coolingusing thermally driven refrigeration or air-conditioning technologies (Solar thermalCooling). Most of these systems employ thephysical phenomena of sorption in either anopen or closed thermodynamic cycle. Othertechnologies, such as steam jet cycles orother cycles use a conversion of heat tomechanical energy. Mechanical energy to cooling is less significant.

The first principle – solar electricity drivencooling (PV Cooling) – is not commercially

widespread and mainly used now for solardriven refrigerators for cooling medicine inremote, sunny regions. The second principle –solar thermally driven cooling – is mainlyapplied for comfort cooling and air-conditioningin buildings and first pilot installations that havebeen realised for large capacity refrigerationapplications. The first principle installed inbuildings is normally not considered a ‘solarcooling system’ today, since most photovoltaicplants are connected to the electric grid and areoperated completely independent from theHVAC installations used in buildings, or the refrigeration machines used in industrialapplications. This may change in the future, forinstance, when the price of electricity producedwith photovoltaic systems will be lower than theprice that has to be paid for electricity from the grid. Nevertheless, this article focuses on thedominating technology using the secondprinciple; heat driven air-conditioning and

International Sustainable Energy ReviewVolume 6, Issue 1, 2012

Worldwide, the energy consumption required for cold and air conditioning isrising rapidly. Usual electrically driven compressor chillers (split units) havemaximum energy consumption in peak-load periods during the summer. In thelast few years in Southern Europe this has regularly led to grids working tomaximum capacity and blackouts. In recent years, the sales figures of split unitswith a cooling capacity range of up to 5KW have risen rapidly.

Keeping cool with the sun

SOLAR COOLING28Daniel MugnierManager of the Solar Cooling Department ofTECSOL Solar Heating and Operating Agent at theInternational Energy Agency

Dr Uli JakobGeneral Manager of Solem Consultingin Europe and internationally renownedsolar cooling expert

Figure 1: Principles for solar driven cooling (Source: Fraunhofer ISE)

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Hybrid systems (dry/wet) seem to be apromising solution.

! High efficient auxiliary components likepumps, careful hydraulic design andadvanced control systems. This isparticularly important as solar coolingsystems need more hydraulic loops thanstandard solutions.

! Integration of all components into a com -plete system. Packaging efforts for small aswell as for large solar cooling systems6.

Standardisation and quality procedure As mentioned previously, there is a significantpotential for further improvement of solarcooling energy and cost performance,particularly at the system level. Solar coolingtechnology is a complex technology andrequires much more standardisation for the coupling of key components and thedevelopment of robust, standardised solutionsin the future. Therefore, R&D on systemoptimisation and accompanying measures(development of tools for planners) has beenrecently addressed by decision makers in energyR&D. Also the industry and installation sector isstarting to contribute here to provide turn-keysolar cooling installations with guarantee on theperformance. Besides work on the system level,R&D on the component level will enhanceoverall performance in terms of energy and cost.These topics are beginning to be covered innational (such as in France8 and in Germany) andinternational R&D programmes.

A particular focus is starting to be put into quality procedures for designing,commissioning, monitoring, operating andmaintaining solar heating and cooling systems.This is an extremely important step2 forovercoming most of the barriers that standagainst the development of a mature market inthe sector. Such a quality procedure has to fix the steps towards uniform and consistentplanning, providing information, recommenda -tions, and minimum requirements for each of itssteps. This, in consequence, will contribute to anincrease in awareness and acceptance of thetechnology and positively impact the number ofapplications since it would strengthen thestakeholders’ trust and thus enhance the marketpotential of solar heating and cooling systems.Moreover, the introduction of concepts, such asa guarantee of solar results or minimum energyconsumption, will stimulate the interest ofinvestors and create the boundary conditions

of a correct financial risk assessment, crucial forcontracting energy service activities. This qualityprocedure will also work as a support tool for thepolicy implementation of the nationalrenewable energy targets and begin the base forsubsidy mechanisms.

New IEA SHC Task 48: Quality assuranceand support measures for solar cooling So as to deal with this important need of qualityprocedures and support measures, the IEA SolarHeating and Cooling (SHC) programme expertson solar cooling have initiated a new Task inearly 2011. Called Task 489 started in October2011 for a 3.5 year duration that will stronglyaddress these topics. It is divided into four

subtasks (quality procedure on componentlevel, quality procedure on system level, marketsupport measures and dissemination and policyadvice). More than 30 international experts(from Australia, Austria, Canada, Belgium,France, Germany, Italy, Singapore, South Africa,Spain and USA) from the industry and R&D sideare putting together their experience to work onthese topics. First results are expected at the end of 2012.

ConclusionSolar cooling technology is at a critical stage butfacing a very exciting challenge. Mature com -ponents are available and many installationshave been realised worldwide. The technologyhas shown that significant energy savings arepossible, and it has reached a level of earlymarket deployment. However, the financial riskfor parties involved in solar cooling business isstill not clear. This is because:! There is no complete assurance on the

quality of the system the user cannot besure about the level of energy savings andrelated cost savings.

! Most planners and installers have littleexperience with solar cooling tech-nology and thus the effort and related costto install those systems is higher thanstandard systems.

! There are unstable and small markets,manufacturers cannot be sure about salerates and thus cannot bear the risk tosignificantly increase their production scale.

Therefore, technical developments are ongoingbut strong measures to support a sustainablemarket development are necessary as well.Establishment of quality procedures planned byR&D collaborative IEA SHC Task 48 is going in theright direction. This will cover all phases of aproject and will satisfy the expectations of allinvolved stakeholders. Overall renewableenergies will play an increasingly important rolein future energy systems due to the strong needto limit CO2 emissions originating fromconventional energy sources. Solar coolingtechnology is one of the important solutionsapplicable to reducing these figures.

References1. JARN, World Air Conditioner Market: The 2010 Overview,

JARN, Serial No. 508-S, pp. 49-62, 2011

2. Henning, H.M., Solar cooling position Paper, IEA SHCTask 38 Solar Air-Conditioning and Refrigeration,Freiburg, Germany, August 2011

3. Mugnier, D., Solar Thermal Energy for cooling andrefrigeration : status and perspectives, Proceedings ofthe First Saudi Renewable Energy Conference &Exhibition – SAREC & E 2012, Dahran, South Arabia,20.02.2012

4. SolarNext, chilli® Prices 2011, price list SolarNext, April 2011

5. Jakob, U., Solar Cooling in Europe, Proceedings of theausSCIG Conference 2009, CSIRO, Newcastle, Australia,19 May 2009

6. Mugnier, D., Latest and future developments of solarcooling, Proceedings of the Second Annual Conferenceof the European Technology Platform on RenewableHeating and cooling – RHC conference, Budapest,Hungary, 05.05.2011

7. Jakob, U., Sorption Cooling – a technology review, IEAHeat Pump Center Newsletter, Volume 29, No. 4, pp. 38-41, 2011

8. Le Denn, A., Siré, R., First results of MeGaPICS project(performance guarantee method for Solar Heating andCooling installations), Proceedings of the 4thInternational Conference on Solar Air conditioning –OTTI 2011 SAC – Larnaca, Cyprus, 14.10.2011

9. IEA SHC Task 48 website: http://www.iea-shc.org/task48/

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SOLAR COOLING30

Dr Uli Jakob is the GeneralManager of Solem Consulting inEurope and an internationallyrenowned solar cooling expert. Hehas over 10 years of professionalexperience with solar thermal andsolar cooling systems, especiallywith the product development andcommercialisation of solar/thermalcooling kits.

BIOGRAPHY

Daniel Mugnier is Manager of theSolar Cooling Department ofTECSOL. He is Operating Agent of the IEA SHC Task 48 on QualityAssurance and support Measure forSolar Cooling and is involved innumerous R&D projects on solarcooling. He has professionalexperience in engineering solar

thermal systems for large DHW applications and solar heating and cooling systems.

BIOGRAPHY

Solar cooling technology is at a critical stage but facing a very

exciting challenge

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