SIMULATION OF A DOUBLE EFFECT H2O-LIBR ABSORPTION CHILLER DRIVEN BY SOLAR CONCENTRATING PARABOLIC TROUGH COLLECTORS

摘要

Nowadays, the increasing electrical energy consumption in most industrialized countries, in which electrical energy demand for air conditioning is a key piece, is leading to a growing interest in solar cooling technology. Employing the energy of the sun in refrigeration systems can substantially reduce electricity peaks during the summer months and at the same time reduce CO_2 emissions. Furthermore, refrigeration via solar energy application is particularly attractive because of its non-dependence on conventional power and the near coincidence of peak cooling loads with the solar energy availability. In particular, the high levels of solar radiation in southern European regions make the use of solar assisted air-conditioning systems very suitable. In the light of the previous considerations, the main goal of this research it to model and simulate a double effect water-lithium bromide absorption cooling system, aimed at air conditioning, where the solar energy is absorbed by parabolic concentrating solar trough collectors. To enhance the performances of the plant and to increase the fraction of solar energy exploited, the integration of a cold storage tank was studied. Each individual component of the system is modelled in its fundamental equations in Engineering Equation Solver (EES) environment and a validation is carried out using manufacturer data. Summer simulation results in the city of Madrid showed that the solar cooling plant performances evaluation parameters, such as the solar cooling ratio (SCR) or the hours of operation ratio increase about linearly with the increasing storage tank size. The best results over the summer simulations were obtained for the storage volume of 50 m~3, reaching a seasonal energy conversion efficiency, from solar energy input to cooling energy output (SCR), equal to 55%, with an auxiliary chiller utilization factor of about the 52%.