Thermally activated refrigeration technologies

Abstract

The current energy generation and utilization patterns can directly lead to considerable wasted energy either at medium or high availabilities. For example, power plants utilize the high-grade portion of fossil-derived energy and reject a large amount of medium-grade thermal energy. Meanwhile, these fossil fuels are also used more ubiquitously in residential water heaters, in which almost all of the highgrade thermal availability is wasted, with the water being heated to a relatively low 60 °C. With energy consumption having been accordingly increased, energy conservation becomes increasingly essential. Vapor compression refrigeration technology has dominated in refrigeration field because of its simple in structure and satisfactory performance, while vapor compression refrigeration consumes power and its working fluids (CFCs, HCFC, HFC) usually have high ODP or GWP. Compared to compression refrigeration, thermally activated refrigeration technologies can utilize low-grade heat, such as solar energy heat and waste heat from the production process. Furthermore, it can use natural refrigerants, such as H 2 O and NH 3 . As an important way of energy conservation, thermally activated refrigeration technologies have attracted more attention in recent years. A detailed analysis is made on the thermally activated refrigeration technologies in this chapter, including vapor absorption refrigeration, adsorption refrigeration, and vapor ejector expansion refrigeration. Specifically, the working principles of various refrigeration cycles, the development and classification, research interests as well as the advantages and disadvantages of these refrigeration cycles in recycling low-grade heat are talked about.