# Numerical Investigation of Thermal Efficiency of a Solar Cell
## 1 Introduction  
The burning of fossil fuels has degraded the quality of the environment to a great extent. The need for production of cleaner energy to save the environment has led researchers to increase the efficiency of non-conventional methods of energy production, as their efficiencies are quite low. Because of the rapid growth in a share of non-conventional electrical energy production, there is a need for efficient technology to ensure the operation of renewable energy sources at the highest possible efficiency. Since the photovoltaic (PV) costs per 1 kW are decreasing every year, the PVs attract attention of the potential end users. However, the nominal efficiency of PV panels is low (maximum 26.7% for mono-crystalline laboratory set and maximum 24.4% for multi-crystalline silicon wafers) [1] and it is decreasing (0.5% per 1 \({}^{\circ}\)C if temperature is higher than 25 \({}^{\circ}\)C) with the PV surface temperature. Therefore, even during a day with high solar irradiation, the electrical energy production from PV is lower than expected. Therefore, to maintain the high electrical energy conversion efficiency, there is a need to propose an efficient method for the cooling of PV panels. Multiple studies had been carried out in the past, suggesting various techniques for improving PV cell efficiencies. We carried out a brief review of the existing literature. [PERSON] et al. [2] noted that a part of the incoming sunlight converts to energy on the solar cell's surface, whereas the remaining sunlight absorbs within the cell. As a result, its surface temperature increases. The greater the surface temperature, the worse the transformation efficiency (the proportion of solar energy received by a PV device that is transformed into useful power), and the weaker the long-term durability. [PERSON] et al. [3] observed that the solar cells have a low electrical efficiency (in most cases around 12-15%). Although sunshine was necessary for generating power, the rate of warming at the underside of the cell had a negative impact on the efficiency. They related the increase intemperature to the conversion of sunlight's energy into heat, and it may have a detrimental impact on the electrical parameters and the cell's life span. Using cooling measures would reduce the amount of heat generated and lower the overall temperature of the cell. We can cool solar cells using a variety of approaches, including forced air/water flow, hybrid PV/thermal systems, and phase change material-based PV applications [4]. According to the results of some studies on passive and active cooling strategies, [PERSON] [5] concluded that the flow rate in the water cooling method had a direct relationship with the reduction in temperature and rise in cell efficiency. We mention the effect of cooling techniques on the cell efficiencies in the literature highlighting the benefits of cooling PV modules. [PERSON] and [PERSON] [6] used a unique reflector for this purpose and installed a heat pipe for the cooling of PV modules to maximize the power output. [PERSON] et al. [7] used a heat pipe for cooling the concentration PV (CPV) module. They used a natural convection through a heat pipe with aluminum fins that rejected a heat flux of 40 W/cm\({}^{2}\) to the atmosphere. This helped in maintaining the rise in cell temperature by only 40 \({}^{\circ}\)C compared with the ambient temperature. [PERSON] and [PERSON] [8] sprayed water on the front surface of the PV cell to improve the effectiveness of the water pumping system. The results proved that spraying water could enhance PV cell efficiency by 3.26% and total system efficiency by 1.35% at 16 m pumping head. [PERSON] [9] used a thin film of water on the PV array to cool the surface and increase electrical efficiency. He reported two vital parameters of this method, i.e., array of nominal power and system head, and concluded that a decrease in nominal power and increase in system head generates more power.