Performance comparison and risk assessment of BIPVT-based trigeneration systems using vapor compression and absorption chillers

Abstract

A building integrated photovoltaic-thermal (BIPVT) system, which generates both electrical and thermal energy, is an encouraging technique to significantly reduce building energy consumption. This paper compares the thermoelectric performance of two BIPVT-based trigeneration systems using vapor compression and absorption chillers for supplying the cooling load of the building. Dynamic simulation of the system performance using TRNSYS shows that the annual electrical solar fraction of the system is on average 6% higher using an absorption chiller in comparison with using a vapor compression chiller; whereas, the annual thermal solar fraction of the system is 27% lower using absorption chiller than that using vapor compression chiller. It is also found that although the electrical energy generation by the two systems is slightly different, the thermal energy generation of the system using a vapor compression chiller is about 5.5% less than that using an absorption chiller, due to the consumption of more thermal energy of the absorption chiller and thus, better cooling of the photovoltaic panels. The deterministic economic analysis indicates that despite the higher coefficient of performance of the vapor compression chiller, the payback time of the system with the absorption chiller is 4 years lower than that with the vapor compression chiller, in which the hot water generated by the system in warm months is useless. The stochastic economic analysis based on the Monte Carlo algorithm shows that the probability of the net present value of the system with an absorption chiller and a vapor compression chiller is 98.42% and 70.83%, respectively. The probability of the internal rate of return of the system with an absorption chiller and with vapor compression is also 24% and 20%, respectively. All indicators show that using the absorption chiller in the proposed trigeneration system is far less risky than using a vapor compression chiller.