Comprehensive performance assessment of photovoltaic/thermal system using MWCNT/water nanofluid and novel finned multi-block nano-enhanced phase change material-based thermal collector: Energy, exergy, economic, and environmental (4E) perspectives

An innovative multi-block finned nano-enhanced phase change material (NePCM)-based photovoltaic/thermal (PV/T) system with thermal regulations through deionized water (DIW) and nanofluid at 0.25, 0.5, and 0.75 wt% is designed, fabricated, and tested in this study. The main goals are to achieve consistent heat transfer distribution, mitigate temperature stratification within each thermal energy storage block, and prevent material shrinkage at the bottom. The energy and exergy performance of the proposed PV/T-NePCM is investigated using indices such as power output, efficiency, exergy destruction, entropy generation, and sustainability index. Furthermore, environmental metrics such as CO2 emission, carbon credit gained, and net CO2 mitigation, as well as economic performance parameters such as energy payback time and energy cost are analyzed. The proposed system uses nanofluid as the heat transfer fluid at 1.5 l/min and 0.75 wt% NePCM, resulting in 9.26 % and 2.93 % higher energy and exergy efficiency than the DIW-based system. The economic evaluation shows that the PV/T-NePCM system has a cost of energy of 5.24 INR/kWh (0.063 USD/kWh), while the conventional PV module costs 5.64 INR/kWh (0.069 USD/kWh) with an 8 % interest rate and a 20-year lifespan. For environmental sustainability, the nanofluid-cooled PV/T-NePCM system has 637.28 kWh of embodied energy.