Possibilities of combining radiant wall cooling with ejector cooling cycle powered by Fresnel solar collectors

Abstract

Solar ejector cooling presents an alternative to the commonly used compressor vapour machines. It is a potentially feasible technology for space cooling providing that the temperature of the cooling water is high enough to assure reasonable efficiency of the chiller. This could be achieved by increasing the evaporation temperature of the cooling cycle through its combination with a high-temperature radiant cooling system. We explore the possibilities and benefits of combining a high-temperature radiant wall system with a solar ejector cycle for space cooling of buildings. The lowest water temperature in the wall to prevent condensation was 18°C for the wall with pipes underneath the surface whereas it was 14°C for the wall with pipes embedded in the thermal core. Thus, the evaporation temperature was substantially higher for the radiant systems than for fancoils. For the conventional vapour compressor cooling, this increased the system efficiency (COP) by 30 to 50%. The COP of the ejector cooling cycle was about half of that for the compressor vapour cycle when R1234ze was used as the refrigerant, however, the primary energy was lower for ejector cooling. Using thermally active building systems (TABS) provided a reasonable cool storage capacity for as much as five hours which allows turning the cooling machines off for several hours during peaks in energy demand.