PV thermal regulation and water harvesting hybrid system using evaporative cooling of silica gel layer

Abstract

A proposed system for a passive cooling technique of photovoltaic (PV) via desorption cooling and water harvesting using a silica gel layer is investigated numerically. The harvested water is discussed, and the performance of the desorption-cooled PV is compared with the naturally cooled PV cell. The silica gel layer provides the water needed for evaporative cooling, so the proposed system can be used where water does not exist. The system model is presented, solved using MATLAB, and validated. The impact of the ambient conditions (ambient temperature and relative humidity), solar intensity, and silica gel layer thickness on the PV performance and silica gel uptake are presented for constant conditions and transient input weather conditions. The findings show a considerable reduction in the cell temperature and an enhancement in the cell efficiency. Also, The harvested water quantities are obtained at different operating conditions and layer thicknesses. At constant input conditions, a maximum reduction in the average PV cell temperature of 16.18 °C and an efficiency enhancement of 8.76% are achieved using a silica gel layer of 1 cm thickness. In addition, the maximum harvested water is reported as 1.238 kg/m2 for 2 cm layer thickness. For transient input weather conditions, the same performance enhancement with a reduced daily average cell temperature of 7 °C and an efficiency enhancement of 4.8% is achieved at the different silica gel layer thicknesses during 13 hr of simulation. Also, the maximum harvested water is reported as 2.35 kg/m2 for 3 cm thickness. Increasing the silica gel layer thickness influences the cell performance adversely under constant operating conditions, while this effect vanishes for actual transient input weather conditions. In contrast, increasing the thickness layer can increase the harvested water, which depends on the incident flux.