Energyand Buildings 43 (2011) 3161–3172 Contentslists availableat ScienceDirect Energy and Buildings j o u r n a l h o me p a g e : w w w . e l s e v i e r . c o m / l o c a t e / e n b u i l d Exergy efficiency analysis in buildings climatized with LiCl–H 2 O solar cooling systemsthat use swimming pools as heat sinks D. Borge,A. Colmenar ∗ , M. Castro,S. Martín, E. Sancristobal Departamento deIngeniería Eléctrica, Electrónica y deControl, UNED,Juan del Rosal, 12,CiudadUniversitaria, 28040Madrid, Spain a r t i c l e i n f o Articlehistory: Received30 May 2011 Receivedin revisedform 4 August 2011 Accepted8 August 2011 Keywords: Renewableenergy Exergyanalysis Solar cooling Absorption chillers Solar thermal energy a b s t r a c t Solar cooling is emergingas one of the most interestingapplicationsin the harnessingof solar energyfor alternativeuses.Current devicescan effectivelycontrol the climatesof small buildings while addressing the issuesassociated with the excessive thermal energycapturedduring the summer months.This article presentsan exergyanalysisof buildings with solar thermal systemsusedfor DomesticHot Water (DHW) production and heatingand cooling support.The cooling systemanalyzedis a LiCl–H 2 O thermally driven heat pump with integral energystoragethat uses outdoor swimming pools as heat sink. All subsystems were integratedinto the model and consideredas a single energy system,and data from installations in three different locations were used. The influencesof the heatingand cooling demand ratios and the dead stateand house temperatureswere analyzed.Further, the use of dissipatedenergywas analyzed, demonstratingthat the proposed method facilitates the realistic study of these systems and provides useful analytical tools for improving the overall exergyperformance. The energydelivered for heating, cooling and DHW production strongly influences global performance,suggestingthat the appropriate sizing of eachsystemis a priority. ©2011 ElsevierB.V. All rights reserved. 1. Introduction Exergyis defined as the maximum work obtainablein a system interacting with the environment until it reachesthe steady state [1,2]. Although exergy analyseshave been widely applied to ana- lyze the efficiency of power plants [3–6], the amount of literature on the use of this method to analyze energy efficiency in build- ings is limited. A significant percentageof energy is consumed in industrialized countries in Heating,Ventilating, and Air Condition- ing (HVAC) systemsand DomesticHot Water (DHW) production for buildings,and more attentionshould bepaid to strategies for reduc- ing CO 2 emissionsand identifying the most rational usesof energy. Exergy analysis is a useful and advancedtool, the results of which are more detailed than those of a simple energy analysis because this method considers energyuse, loss factors and efficiency. Renewable energy devices are emerging as one of the best options for reducing CO 2 emissions. A renewable energy source is defined as any process for which the rate of energy source and raw material consumption does not exceed the rate of regener- ation. Solar energy meets this strict definition, and any strategy that enhancesand diversifies its use implies substantial benefits. Solar energyis often used to heat water for various uses; however, ∗ Correspondingauthor. Tel.: +34913 987 788; fax: +34913 986 028. E-mail address: acolmenar@ieec.uned.es (A. Colmenar). absorption systems powered by solar thermal energy can cleanly and efficiently climatize a home and therebyreduceelectricenergy consumption.In Spain,recenteffortshavebeenfocusedon optimiz- ing systemsbasedon photovoltaic applications [7,8]. Photovoltaic energycould be usedto provide renewableelectricity for compres- sion cooling machines. Comparedwith the exergylevels of the energyassociatedwith conventional systems, which typically yield low overall exergy efficiencies, the exergylevel associated with the incident solar radi- ation in a solar collector is generally low. Several studies [9–11] have used exergy analysis to investigatesingle- or multiple-effect LiBr–H 2 O absorption systemsand auxiliary devices. The main nov- elty of the studyis analyzingthe behaviorof a triple stateabsorption machine using LiCl–H 2 O as the working pair. This technology was patentedin 2000 [12] and provides a hugepotential in cooling sys- temsbecause of the internal energystoragecapacityof the machine so that cooling can be provided in lack of solar radiation. The exergy performancesof different renewable-energy-based HVAC and distribution systems have been studied [10]. However, to the authors’ knowledge, no studies of the behavior of the instal- lations and facilities described in this article have been published [13–17]. A heat sink is required because of the nature of the absorptionsystem, which exchanges energybetweenthe high tem- perature focus, the generator,and the low temperaturefocus, the location where useful effectsare obtained.A third focus servesas a heat sink. For safety and aestheticreasons,cooling towers are not 0378-7788/$– seefront matter ©2011ElsevierB.V. All rights reserved. doi:10.1016/j.enbuild.2011.08.014