Energy, exergy and economic analysis of a novel solar driven CCHP system powered by organic Rankine cycle and photovoltaic thermal collector

Combing solar energy systems and polygeneration units is an optimal way of producing useful outputs by utilizing a renewable energy source. Most of the polygeneration systems studied in the literature utilize only one solar collector whereas the studies on multiple solar source polygeneration systems are limited. On the other hand, multiple source polygeneration systems are of great interest in zero energy buildings. Hence, this study proposes a novel polygeneration system powered by two solar sources. Photovoltaic thermal and parabolic trough collectors are used in a series configuration with water as working fluid for this purpose. The proposed system is equipped with an ejector - compression refrigeration cycle (VCRC) with two different temperature levels (above zero and sub-zero) and an organic Rankine cycle (ORC) to provide cooling, heating, and power. The water out coming from the photovoltaic thermal (PVT) unit is used to cool the VCRC condenser, and hence it is preheated before entering the parabolic trough collector (PTC) resulting in reduced sizing and the cost of the PTC unit. In this study, the impact of parameters such as water flow rate in PVT-PTC circuit, the effect of working fluid in the ORC cycle, and solar irradiation are investigated using the first and second laws of thermodynamic and economic analysis. The results show that in the same conditions, R123, R600, R245fa, R600a refrigerants have higher energy efficiency, respectively, so that the highest energy efficiency of 70.78% and exergy efficiency of 10.70% were calculated for R123 refrigerant. Furthermore, it is shown that the highest energy and exergy efficiency cannot be achieved together. Also, the results showed a payback period of 6.4 years for the proposed system.