Exergy analysis of a weir‐type cascade solar still connected to PV/T collectors

Abstract

In this study, the exergy analysis of a weir-type cascade solar still connected to photovoltaic thermal (PV/T) collectors is provided. By formulating the energy balance for different components of solar still system, the governing equations were obtained as a set of non-linear ordinary differential equations. A perfect exergy analysis is used to obtain irreversibility rates, exergy fractions and exergy efficiency. To find various temperatures and freshwater productivity, the governing equations are solved numerically. Moreover, through experimental data of previous studies, the numerical results were validated. In this study, the effect of the mass flow rate of brackish water and the number of PV/T collectors on the hourly variation of exergy efficiency, irreversibility rates and exergy fractions were investigated. Results showed that by connecting two PV/T collectors to the cascade solar still, the exergy efficiency can be improved twice. Moreover, the connection of two PV/T collectors and use of their output electrical power for heating brackish water can increment the fresh water production rate by 56.8%. The absorber plate and PV/T collectors include maximum 55.8 and 36.8% of system total irreversibility, respectively. The maximum exergy fraction is obtained in evaporating with a value of 0.85.