Design and dynamic simulation of a photovoltaic thermal-organic Rankine cycle considering heat transfer between components

Abstract

Photovoltaic thermal systems concept is very attractive for two reasons; Firstly, using the coolant fluids decreases the temperature of the photovoltaic modules. Secondly, the heat, gathered from photovoltaic modules, can be employed in a thermal or energy conversion system. Hence, the efficiency of a photovoltaic is enhanced from both sides. In this study, a combination of an organic Rankine cycle with photovoltaic modules is proposed. Despite previous works, which considered such schemes for a limited environmental conditions, dynamic model of heat transfer for varying radiation and temperature throughout a typical year is employed. A detailed model of the heat transfer between the photovoltaic-thermal components is utilized to investigate the combination's thermal behavior. Also, for the first time, the optimum photovoltaic array area is calculated based on the heat transfer between photovoltaic modules and the Rankine cycle working fluid. Considering design conditions, 80 m2 area of photovoltaic arrays are needed to preheat the working fluid before entering the evaporator. The round trip efficiency of the system is equal to 22.62%, using HFO-1234yf as the working fluid. Besides, the effect of changing pressure of evaporator and condenser along with using different coolants is investigated. Four pure refrigerant and two fluid mixture are used to find the effect of working fluid on the performance of the system. The parametric analysis shows that using isobutane results in the highest achievable round trip efficiency (22.81%), among the selected fluids. Cost analysis showed that the levelized cost of electricity is 0.05 $/kW h, which is slightly higher than the electricity price for the same installed capacity of PV without cooling.