Heat Source Contribution Analysis of Dual-Source Pv/T Modules for Direct-Expansion Solar Heat Pump

Abstract

This study introduces a novel uninsulated microchannel photovoltaic / thermal (PV/T) module integrated with a solar direct-expansion heat pump system. During dynamic operation, the system effectively regulates evaporation / collector temperature to a couple of solar and air heat sources. A dedicated experimental platform was established to evaluate performance by investigating the impacts of solar irradiance, ambient temperature, wind speed, expansion valve opening, and compressor speed on the contribution ratios of the two heat sources. Results reveal that a 484.6 W/m2 reduction in solar irradiance decreases the solar contribution ratio by 37.09% and lowers the PV/T evaporator’s heat transfer and performance coefficient (COPpvt) by 40.82% and 53.79%, respectively. Ambient temperature and wind speed have minor effects; a 2°C rise increases the air contribution ratio by 5.83%. Meanwhile, a 2.8 m/s increase in wind speed raises the air contribution ratio by 2.99%. Under low solar irradiance, reducing the expansion valve opening boosts the air contribution ratio by 25.65%, and raises the evaporator’s heat transfer rate and heat pump performance coefficient (COPhp) by 9.07% and 4.62%. Conversely, under high solar irradiance, increasing compressor speed further enhances the solar contribution ratio by 7.06%, increases the evaporator’s heat transfer by 69.07%, reduces photovoltaic module temperature, and improves overall system efficiency by 18.31%. This study provides experimental evidence and theoretical support for optimizing heat source regulation and efficiency in direct-expansion dual heat source microchannel PV/T heat pump systems.

Keywords: Dual-source PV/T modules, heat pump, coefficient of performance, Solar Energy, Photovoltaic