Performance of a-Si thin film PV modules with and without water flow: An experimental validation

•Thermal modelling for module efficiency of a-Si thin film PV modules is presented.•Module efficiency (ηm) is observed to increase with decrease in module temperature.•A model is developed for ηm when module heat is driven away by water, flown over it.•Performance of PV modules is calculated for different environmental/test conditions.•The calculated results for different conditions have been validated experimentally. Analytical expressions have been developed to calculate the temperature dependent electrical efficiency (ηm) and the effect of water flow on the performance of a-Si thin film photovoltaic (PV) modules. The calculated results have been validated by experimental investigations on commercially available a-Si thin film PV modules. With water flow on the PV module, ηm is observed to increase, which has been attributed to the dissipation of thermal energy associated with the PV modules due to water flow on it. The effects of mass flow rates of water (m.w) on module to water heat transfer coefficient (hm,w) and ηm have also been calculated. Increment in m.w, increases both the hm,w and ηm. For low m.w of 0.001kg/s, the hm,w and ηm were calculated to be 14.2W/m2K and 7% respectively, whereas for high m.w of 0.85kg/s, the hm,w and ηm were calculated to be 413W/m2K and 7.45% respectively. Daily average electrical efficiencies of a-Si PV module with and without water flow have been found to be 7.36% and 6.85% respectively. Overall thermal efficiency and overall exergy of PV module with water flow have been found to be 22% and 7.33% respectively.