Photovoltaic Heat Research Articles

Numerical and experimental investigation of a two-stage thermochemical water-splitting reactor based on a cerium oxide reduction–oxidation cycle

Climate change has made clear the need to decarbonize the global energy matrix, and green hydrogen has emerged as a promising alternative fuel. In this framework, this work investigates the green hydrogen production by means of a two-stage thermochemical water-splitting reactor heated by both a parabolic dish receiver and a photovoltaic heater. A mathematical model is proposed to simulate reduction–oxidation process for the solar-powered reactor composed of a porous cerium oxide medium. Experimental and numerical thermal profiles show good agreement, with a high temperature in the reduction stage (>1100 K) and a lower temperature in the oxidation stage (860–715 K). Green hydrogen productions show maximum values close to 100 ppm and 2000 μmolH2O/gCeO2, for experimental and numerical tests, respectively. It is concluded that the photovoltaic heater is more relevant than the solar concentration heater, and that green hydrogen production could be improved by allowing longer residence times for the reduction–oxidation stages.

The Effect of Radiation Intensity on the Performance of Direct-Expansion Solar PVT Heat Pump Systems

The objective of this study was to investigate the impact of solar radiation intensity on the performance of direct-expansion solar PVT heat pump systems. To this end, an experimental setup was constructed for direct-expansion photovoltaic (PVT) solar heat pump water heating systems and photovoltaic (PV) power generation systems. The system performance and main parameters were analyzed and discussed under different solar radiation intensities. The winter experiments in southern China revealed that the exhaust temperature of the heat pump unit varied considerably under clear conditions, while the back temperature remained stable, fluctuating between approximately −13.5 °C and 24 °C. In contrast, the power generation of PVT panels increased with the increase in radiation intensity, from 78.33 W to 122.68 W, for an increase of 56.6%. Furthermore, the total electricity generation of the PVT panels was higher than that of PV panels, with an increase of 8.7–8.3%. Nevertheless, discrepancies between experimental and theoretical data were observed, particularly under overcast conditions, where the back panel temperature error was pronounced. Additionally, the system exhibited enhanced stability at elevated temperatures in comparable environments, accompanied by an improvement in the system’s coefficient of performance (COP) by 5.67%.

Purwarupa dan Kinerja Pengering Gabah Hybrid Solar Heating dan Photovoltaic Heater dengan Sistem Monitoring Suhu

Grain drying is a process to reduce grain moisture content to certain conditions, so the grain can last longer in storage. The grain dryer model used in this research was Indirect Type Solar Dryer (ITSD). In order to make this dryer can work at night, heating element that used electrical energy from solar panels was added. This energy is a renewable and environmentally friendly energy. This dryer was equipped with a temperature monitoring system and control of the photovoltaic heater. The results of temperature monitoring and voltage sensors to controlling photovoltaic heaters based on validation are categorized as work measurement tools, because they have an error of 0.5% – 2%. Whereas the relay works when the battery voltage is 11 - 10.9 V. This dryer can dry grain to reach a moisture content of 14.90% from initial moisture content of 48.46%. The drying process lasts for 11 hours, which is 7 hours using solar energy and 4 hours using photovoltaic heaters. The average temperature produced by dryer system during the drying process is 35.28 °C with a drying efficiency of 60.14%.