Configuration based modeling and performance analysis of single effect solar absorption cooling system in TRNSYS

Solar based cooling systems may assume various configurations depending upon the manner in which the individual system components are inter-connected and the adopted control scheme. In this study, simulation based performance analysis of a solar assisted single effect absorption cooling system is done for two system configurations in TRNSYS. The analysis is carried out to meet a peak cooling demand of 298 kW for an educational building located in Islamabad (33.71 degrees N, 73.06 degrees E). In configuration-1 (C-1), the working fluid returning from the generator of the absorption chiller always flows towards the hot storage tank which acts as a common element between the solar collector and the absorption chiller. In configuration-2 (C-2), the working fluid returning from the absorption chiller may become isolated from the collector-storage tank loop if the fluid temperature in the storage tank is less than the required temperature (i.e. 110 degrees C) and is directly fed to the auxiliary boiler. Both system configurations are fully modelled in TRNSYS and dynamic simulations are run for the entire summer season. Various performance factors such as solar fraction, collector efficiency and primary energy savings are evaluated to optimize the key system design variables which include collector tilt, storage volume, type and size of the solar collector. Simulation results demonstrate that for the whole summer season, C-2 with flat plate or evacuated tube solar collectors always results in higher primary energy savings than C-1. However, on the basis of solar fraction and monthly collector efficiency, difference between C-1 and C-2 is estimated to be marginal. Overall, C-2 in conjunction with evacuated tube collectors (ETC) results in minimum collector area per kilowatt of cooling demand and higher monthly collector efficiency than C-1.