Design and Analysis of a Continuous Operating Solar Absorption Cooling System

Abstract

It has been estimated that approximately 15% of electricity produced in the whole world is utilized for refrigeration and air-conditioning applications. Increased use of air conditioning and related appliances during hot summer days leads to high electricity demands in metropolitan areas, which have to be met, in part, by generations from expensive and polluting peaking units. Thus solar cooling has great potential in reducing peaking electricity demands and the overall energy demands. We first compared the overall efficiencies of two solar cooling systems, i.e., vapor compression powered by electricity generated from photovoltaics, and vapor absorption using solar heating. Both systems matched evenly when the coefficients of performance (COP) were compared. But the payback time for vapor compression was five times longer than that for vapor absorption. Then we designed a novel solar cooling system by combining vapor absorption refrigeration (NH3-H2O absorption cycle), concentrated solar and thermal storage. The system is capable of operating autonomously at nights or two days without adequate sunlight. Heating oil is heated by a parabolic trough collector and is then stored in an insulated tank. The oil is then used to heat the refrigerants (i.e., NH3). Oil flows in two loops, one from parabolic collector to tank using thermo-syphon action and other from the tank to refrigerator using a small pump. Next, we created a model to calculate the volume of storage tank, area of solar collector for a given longitude and latitude and application. A micro-processor controlled program can be then be developed in future to control mass flow of oil in the second loop to control the output temperature.