TEWI Assessment of Conventional and Solar Powered Cooling Systems

Abstract

Conventional cooling and refrigeration systems already evolved to efficient design, have higher COP and compact size. However, the compressor section of such system consumes a tremendous amount of electricity and contribute indirectly to global warming. The working fluids of these systems are typically HFC or HFC blends which possess very high global warming potential. A significant percentage of working fluid is leaked from the high-pressure side of the system and directly contribute to global warming. The summation of indirect and direct warming impact, namely, total equivalent warming impact (TEWI) of the vapour compression cooling systems are significantly high. Adsorption cooling system (ACS) can resolve this critical issue. In ACS, the mechanical compressor of the traditional cooling system is replaced by a thermal compressor, namely, a pair of adsorption beds. Highly porous adsorbent material (silica gel, activated carbon, zeolite and so forth) is the key component of an adsorption bed. These materials have the capability to capture and hold certain types of fluid. This phenomenon is known as adsorption. Upon heating, the adsorbed fluid is liberated from the pores (desorption process) and gets thermally compressed. Solar thermal energy is the most prospective option for the desorption process to occur. Since there is no mechanical compressor, electricity consumption is deficient, which significantly minimizes the indirect warming impact. Moreover, natural or alternative refrigerants are used as the working fluid, which has zero/negligible GWP. Hence, the direct warming impact is also shallow. In this chapter, the working principle and governing equations of a solar energy driven adsorption cooling system will be elaborated. Besides, TEWI assessment procedure will be explained and compared for both vapour compression and adsorption cooling systems.