Solar Ejector Cooling Technologies

Using low-grade thermal energy instead of electricity to operate a refrigeration system can have important environmental benefits, especially when it is powered by a renewable energy source. Ejector refrigeration is one of the most promising technologies because of its relative simplicity and low capital cost when compared to an absorption refrigerator. An ejector heat pump is a heat-operated cycle capable of utilizing solar energy, waste energy, natural gas or hybrid sources (e.g. solar/gas). An ejector system basically consists of a generator, evaporator, condenser, ejector, expansion valve, and a pump. The ejector system has very few moving parts and so is simple in design. In addition, it has the potential of long life and, unlike vapour-compression systems, produces no noise or vibration. The system could be manufactured at relatively low cost, since inexpensive construction materials may be used. Although they have a relatively low coefficient of performance compared to air-conditioning systems using mechanical compressors, the ejector cooling technologies have attracted extensive attentions with ever-increasing awareness and pressures for protecting the environment and have achieved significant improvement in coefficient of performance as compared to other systems. The continuous developments in solar collector technology open the way to the effective utilization of solar energy to power the ejector systems and utilization of environmental friendly refrigerants is also the major concern. This chapter introduces the principle of the ejector, basic ejector cycle, solar-driven ejector system and its operating. The refrigerants, solar collectors, and PCM heat storage for solar ejector system applications are also introduced. A complete solar ejector air-conditioning system used in a building is presented in this chapter.