Performance enhancement of photovoltaic systems by semi-passive water cooling

We report here an approach for improving the efficiency of photovoltaic panels by taking advantage of overnight cooling of the coolant (water) and the influence of gravitational free flow of the water to cut down or coolant circulation energy requirements. By cooling the PV panels using a heat exchanger installed at the back of the panel, the influence of cooling of the back surface on the electrical power generated and hence efficiency has been investigated. This technique is cheap, conserves water and also present an efficient approach for managing the energy required for circulating the cold water in the heat exchanger. The water is pumped only once in the morning and stored in a thermally insulated and elevated tank using a low energy DC pump. This was made possible by maintaining a small pumping height of 1.7 m. During the cooling process, no electrical energy was required for the coolant circulation as the water was made to circulate naturally by gravity. Furthermore, the water cools down naturally in the lower tank (thermally conducting) to an average temperatures of about 23 0C. The cooling system was able to maintain the PV panel temperature at an average of 35.2 0C throughout the day compared to an average of 44.6 0C as shown by the PV panel without cooling system. The study revealed that the pumping system consumed less than 0.8 % of the daily energy production. Two identical PV panels were simultaneously tested under outdoor conditions; with and without cooling and their performances compared. The results show a maximum improvement in the electrical power generated with the cooled PV panel of about 19.3%, leading to an increased efficiency from 8.2 % without cooling to 9.4% for the PV panel with the cooling system installed. This study has applications for enhancing PV panels used in hot environments where hot season temperatures can have significant adverse effect on the PV panel performance as well as its effective life. Therefore, the system proposed in this paper presents a concrete realization of an aspect of, Sustainable Development Goal Number 7 (SDG7) to provide affordable and clean energy, by improving the output efficiencies of ready-made PV panels (that provides a clean and renewable form of energy).