Feasibility of air-cooled solar air-conditioning in hot arid climate regions

Abstract

In air-cooled lithium bromide absorption chillers, the working conditions in the absorber and condenser are shifted to higher temperatures and salt concentrations, thereby increasing the risk of crystallisation in the solution heat exchanger. In this paper, we present the results of numerical investigations performed in order to find out the appropriate operating conditions to avoid salt crystallisation by ensuring an acceptable coefficient of performance. It is shown that, to this purpose, the lowest and highest temperatures in the machine must be modified (evaporation at 11 °C, generator at 90 °C). Based on these results, we evaluated the potential of an integrated solar air-conditioning system for a middle-class house (150 m2) under the climatic conditions of Tunis city. The chiller generator is supplied with heat via an external pressurised water loop from an insulated tank storing solar heat from an evacuated tube collector field and maintained at a maximum temperature of 110 °C with make-up energy from fossil fuel combustion. It is shown that the collector surface is unlikely to exceed 32 m2.