Enhancing the Performance of Photovoltaic Solar Modules by Active Thermal Management

Abstract

The electrical efficiency and reliability of photovoltaic (PV) modules are severely limited by elevated cell operating temperature in high solar irradiation and ambient air temperature environments, such as in the Middle East. In this study the potential of water-cooling to improve the electrical performance of stationary south facing and sun-tracked flat-type PV modules is experimentally investigated for application at oil and gas facilities in the Persian Gulf. The cooling design is based on gravity-assisted water trickling over the module active surface. In parallel with measurements of PV module electrical characteristics, global solar irradiation, ambient air and cooling water temperatures are also recorded. From the results obtained, the following initial guidelines are derived for the operation of PV modules in late winter to early spring conditions (G ≈ 485–900 W/m2, T∞ ≈ 26–40°C) in the United Arab Emirates (24.43°N, 54.45°E), which would correspond to summer at for example mid European latitudes: i) vertical single-axis sun tracking improves module peak electrical power output by 6% to 10% compared to operation in stationary, geographical south facing orientation, for both passively- or water-cooled modules; ii) for cooling water temperatures ranging from 26 to 33°C, water-cooling enhances the power output of stationary south facing and sun-tracked modules for a significant portion of the day, up to 19.8 W (21%) at solar noon; iii) the integration of water-cooling and sun-tracking increases power output by 22 W (26%) at for example 10:30 a.m. relative to a stationary, passively-cooled module. For the latitude and seasonal conditions considered, water-cooling a stationary PV module is 9 to 15% more effective than sun-tracking a passively-cooled module in terms of peak power output. Higher performance improvements could be obtained using either chilled or underground water at a temperature below ambient air temperature, particularly in Middle East summer conditions.