Impact of graphene nanofluid and phase change material on hybrid photovoltaic thermal system: Exergy analysis

Ambient temperature rise has an inadequate effect on the performance of photovoltaic cells. To reduce PV surface temperature, different methodologies have been suggested. In this study, an effective approach is demonstrated to simultaneously utilize active and passive cooling mediums in one system. This paper revolves around the fabrication, experimentation and exergy analysis of hybrid photovoltaic thermal system using both RT-35HC PCM and graphene nanofluid simultaneously as coolants. Exergy analysis is performed to determine actual energy available which can be utilized for useful purposes. It also interprets the losses and sustainability of the system. Results are compared with PV integrated with PCM module and Conventional PV module. Heat loss in the system is minimized to enhance the stability. Working fluids are distilled water and graphene nanofluid with 0.05%-0.15% volume concentrations. Experiments are also performed at different flow rates ranging from 20 to 40 L per minute in outdoor with clear sky. Highest electrical and thermal exergy efficiencies achieved are 13.02% at 40 L per minute and 1.78% at 20 L per minute with 0.1% volume concentration by hybrid photovoltaic thermal system. Maximum overall exergy efficiency is 14.62% attained by same system at 0.1% volume concentration and 40 L per minute. Overall exergy efficiency displays increasing trends with the rise in flow rates of working fluids. It is depicted that thermal exergy impact on overall exergy efficiency is very low compared to electrical exergy. Maximum sustainability index of 1.17 is shown at optimum conditions. Further, exergy losses, exergy destruction, entropy generation and improvement potential have been discussed with graphs to ameliorate and revamp hybrid photovoltaic thermal system sustainability in future work. (C) 2020 Elsevier Ltd. All rights reserved.