A review of solar thermo-mechanical refrigeration and cooling methods

Use of solar energy to produce refrigeration and air conditioning can be a viable option to replace conventional cooling systems. Research and development activities on solar cooling systems started in the 1970s because of the energy crisis and has picked up again in the past few years due to greater awareness of the necessity to reduce emission of greenhouse and Ozone depletion gases. Although, most of the attention in the past has been on using solar heat to run absorption refrigeration systems, solar thermo-mechanical cooling systems have received a renewed attention in recent years due to the advantages such as, ability to produce low refrigeration temperatures (<0°C) by using appropriate working fluids, ability to produce electricity when cooling is not needed by coupling the prime mover with an electric generator, maintaining high performance at off-design conditions and utilization of a wide range of temperatures from solar collectors. In a solar thermo-mechanical cooling system, the heat gained from the solar collector is converted into mechanical work, which is used to compress the working fluid in a vapor compression cycle directly (i.e. ejector cooling cycle) or indirectly (i.e. coupled with an organic Rankine cycle). Hybrid solar thermo-mechanical cooling with conventional cooling systems also offers a great potential for energy demand reduction for buildings.