Simulation study on the performance of solar/natural gas absorption cooling chillers

Abstract

Solar radiation is a clean form of energy and solar cooling systems is one of the technologies which allow obtaining an important energy saving. Natural gas is a cheaper fuel than oil. It also burns cleaner than oil. Natural gas and renewable energy are complementary and in the future, the alignment of natural gas and renewable energy may be the most effective way to service the demand for clean energy. This paper presents a numerical study of solar/natural gas single effect lithium bromide absorption chillers. The development of this system is based on hot water chiller. As auxiliary power, fire from the natural gas burners is used to heat the hot water on its way to the generator. The overall performance of the absorption chiller system is analysed and discussed. For an evaporator temperature of 5°C and when the condenser temperature is varied from 28°C to 36°C and generator temperatures is varied from 54 to 83°C the maximum COP is 0.82 and the maximum exergetic efficiency is about 30%. For a given condenser temperature there is an optimum generator temperature for which the number of flat plate collectors is minimum. This optimum generator temperature corresponds to the generator temperature giving the maximum COP and exergy efficiency of the absorption cooling system. The solar/natural gas single effect lithium bromide absorption chillers, using solar energy as the energy source with only limited amount of gas as auxiliary power, not only reduces greatly the cost for electricity and operates in regions where there are abundant solar energy and cheap natural gas resources, but also compensates the peak-valley load difference and reduce CO2 gas emissions. For a refrigeration capacity of 10kW, the quantity of natural gas used to provide auxiliary load is very small and consequently the CO2 gas emissions is very small (the maximum mass flow rate of CO2 is less than 3kgh−1).