A review on passive cooling techniques applied to PV modules conducted by an Indian-Malaysian group of scientists has found that two systems, based on coir pith and plants, provide the strongest improvement in terms of power yield.
The research entailed a test of five techniques on a 50 W polycrystalline module with a tilt angle of 15 degrees located in Kumbakonam, Tamil Nadu. Broadly, the five techniques included placing domestic plants around the panels at around 10cm, using a greenhouse net placed on top of the panels to prevent overexposure to sunlight, a combination of plants and the greenhouse net, placing water-soaked coir pith underneath the panels, and using phase change materials. An infrared thermometer was used to take measurements from 9 am to 4 pm. The performance was compared against a reference panel without cooling.
Coir pith and plant cooling techniques provided better temperature regulation along with considerable power enhancement, compared to the uncooled PV module. The strongest improvement for the module power yield was 11.34 per cent, which was achieved with coir cooling, followed by 7.34 per cent using plant cooling. The coir cooling technique provided maximum power improvement along with the optimum temperature reduction. The highest reduction in the module operational temperature was 14 degrees Celsius, achieved by the combination of plants with a greenhouse net. The panel without cooling had an average voltage of 17.8 V. With cooling, this value ranged from 18.1 V to 20.3 V. The highest value was achieved by coir pith due to its moisture-retaining property, followed by the plant and greenhouse net combination.