A comparative performance evaluation and sensitivity analysis of a photovoltaic-thermal system with radiative cooling

Radiative cooling (RC) of solar cells has received growing attention in recent years primarily due to its passive nature as compared to the other active cooling techniques. By using novel high emittance materials, the RC technique can also be integrated with a photovoltaic-thermal (PVT) system, to eventually improve the system's total efficiency (electrical and thermal output) during the day and provide additional cooling power at night. To quantify the effect of enhanced RC in a PVT system, this study investigated the performance of a regular glass encapsulated PVT module, and a spectrally modified module by using a polydimethylsiloxane coating on top of the glass layer to simulate enhanced RC. An experimentally validated simulation model was developed for performance comparison. Furthermore, a sensitivity analysis was conducted to investigate the influence of varying input parameters on system output performance. Results show that during the day, solar cell operating temperature reduced by most 1.7 degrees C, and electrical efficiency and total exergy efficiency increased by 0.76% and 0.5%, respectively. As for nighttime, an additional 4-7 W/m(2) cooling power can be obtained. Although some improvements, the potential gains achieved by integrating enhanced RC in PVT systems are not substantially large as compared to the regular glass encapsulation in commercial PVT modules, since glass naturally has a fairly high emittance in the atmospheric window.