Building integration of concentrating systems for solar cooling applications

The high energy consumption in buildings in Mediterranean countries, especially in the spring and summer months due to the extensive use of air conditioning, requires immediate actions to minimise energy costs and environmental impact given the current energy crisis. Solar cooling systems offer an attractive solution, but the main drawbacks of this type of systems are the low efficiency of the currently used single-effect absorption chillers and the large areas of thermal collectors needed to produce the thermal energy. These large solar installations make difficult their building integration. A way to overcome these difficulties is the use of high efficient integrated solar concentrator systems able to achieve temperatures around 150 °C that could be used to activate the more energy efficient double-effect absorption chillers. In the frame of this concept, in the present work a comparison between two cooling systems for a specific three-floor building, with and without solar concentration, is performed. The first is a conventional system which consists of evacuated tube collectors feeding a single-effect absorption chiller. On the other hand, a Fresnel reflective solar concentrating system, integrated on the building façade, is coupled to a double-effect absorption chiller. The results show an important reduction of the solar collectors absorber area in the concentrating system compared with the standard solar thermal installation. However, the solar concentrating system requires a large aperture area. In addition, the rejected heat in the double-effect chiller is lower, implying that the investment and operation costs of the solar concentrating cooling system can be reduced significantly.