Excessive heat undermines the performance of solar panels, particularly in areas subject to high ambient temperatures and solar radiation levels. The potential use of shallow geothermal energy to help solar energy systems keep cool in such environments was tested in Iraq, where ambient temperatures in summer often exceed 113° F.

Researchers from University of Baghdad, Mustansiriyah University, the Iraq Ministry of Education and the Iraq Ministry of Electricity assembled a closed-loop geothermal system, which uses a heat transfer solution to Closed-loop (a) and open-loop (b) cooling systems. Source: Ahmed F. Atwan et al.Closed-loop (a) and open-loop (b) cooling systems. Source: Ahmed F. Atwan et al.continuously circulate heat through buried or submerged plastic pipes. A rectangular jacket made of a thin layer of galvanized iron, measuring 2 mm in thickness, served as a container for the heat transfer fluid. The jacket was placed on the back of a solar module connected to a spiral ground heat exchanger immersed in a well at 9 m depth. A pump circulated distilled water and transferred heat from the panel to the heat exchanger. An open-cycle cooling system designed to circulate well water around the solar panel was also evaluated.

The two geothermal cooling options were field tested with 175 W photovoltaic (PV) modules during summer, when irradiance levels can be as high as 972 W/m2 and the operating temperature of the panels is in the 161° F to 197° F range. Input water temperature in the closed-loop system was 80° F while in the open-cycle system it was 73° F.

The power yield loss for panels operating without the cooling systems was around 30% and was reduced to 6% with the closed-loop system and to 4.1% with open-loop cooling. Despite higher initial costs, the open-cycle technique is deemed economically feasible for utility-scale PV application.

A paper on this research was published in AIP Conference Proceedings.

To contact the author of this article, email shimmelstein@globalspec.com