Hybrid PV cooling system boosts electrical efficiency by 26%, provides building ventilation

An international research team has developed a hybrid PV-evaporative cooling system that can simultaneously improve PV electrical efficiency and provide precooled ventilation air. The system combines rear-side evaporative cooling using water-soaked cellulose pads with intermittent water spraying on the front surface of the PV module.

“The core novelty of this research lies in introducing an advanced, highly integrated dual-effect cooling framework specifically tailored to overcome the severe thermal-electrical degradation in hyper-arid desert climates like Iraq,” corresponding author Deyaa M.N. Mahmood told pv magazine. “Beyond recovering the electrical power yield, the system cleverly harnesses the conditioned exhaust airflow—optimized in temperature and humidity to provide effective secondary building ventilation, thereby directly reducing indoor cooling loads.”

The system uses a water-soaked cellulose pad installed behind a PV module in combination with intermittent front-side spraying. A pump recirculates water through the pad, while a 35 W fan draws air through it, cooling the module and producing cooler, humidified ventilation air. Front-side spraying is activated when the module temperature exceeds 45 C, with water applied in bursts lasting approximately 10 to 20 seconds.

The researchers compared two identical 150 W PV modules, one cooled and one uncooled, on a rooftop in Baghdad, Iraq. Testing was conducted on clear days from July 1 to Sept. 15, 2023, between 09:00 and 15:00.

In the first scenario, the researchers tested rear-side cooling using cellulose pads with thicknesses of 50 mm, 100 mm, and 150 mm and water flow rates ranging from 1 L/min to 3 L/min. In the second scenario, they added front-side spraying, using a 50 mm pad at 2 L/min and a 100 mm pad at 3 L/min. At a fixed air velocity of 3 m/s, the researchers measured module temperature, electrical output, efficiency, and outlet-air temperature and humidity.

“The most striking and impactful finding was the exceptional thermal regulation stability achieved under peak solar irradiation,” Mahmood said. “The synergistic integration of the front-side intermittent water spraying and backside evaporative cooling demonstrated a profound, rapid reduction in operating cell temperatures. This translated into a massive, sustained recovery of electrical efficiency compared to unmanaged reference panels, proving that hyper-efficient thermal management can be successfully engineered using sustainable, low-energy processes even under extreme desert constraints.”

The results showed that rear-side evaporative cooling in the first scenario reduced PV module temperature by approximately 20 C compared with the uncooled module. The cooled air supplied to the space had an average temperature of around 35 C. In the second scenario, the addition of intermittent front-side spraying resulted in a maximum module temperature reduction of 29.7 C.

“In scenario 1, the maximum efficiency enhancements were 13.3%, 9.3%, and 14.2% for the 50 mm, 100 mm, and 150 mm pads, respectively,” the researchers said. “For the 100 mm pad, the average PV panel temperature reduction increased from 15.0 C without front-side spraying to 29.7 C with front-side spraying, while the average power output difference increased from 8.3 W to 16.7 W, respectively. Across both scenarios, the highest maximum efficiency enhancements were 14.2% for the 150 mm pad in scenario 1 and 26% for the 100 mm pad in scenario 2.”

The second configuration also reduced the supply-air temperature to approximately 30 C to 33 C at around 62% relative humidity. The researchers said this could support the system’s use for passive precooling and ventilation rather than as a stand-alone thermal comfort solution.

“Building directly upon the success of this framework, our ongoing and upcoming research is shifting toward next-generation intelligent optimization. We are currently integrating AI and the Internet of Things (IoT) technologies to execute real-time, multi-objective control algorithms,” Mahmood said. “The primary objective of this next phase is to dynamically regulate water spraying and airflow rates to achieve the absolute lowest possible water consumption while maintaining peak electrical and thermal performance for large-scale commercial deployments.”

The article “Performance enhancement of a hybrid photovoltaic-evaporative cooling system for hot arid regions” appeared in Results in Engineering.

The research group included scientists from Iraq’s Middle Technical University, the University of Baghdad, and the University of Fallujah, as well as Sweden’s University of Gävle, Qatar’s University of Doha for Science and Technology, Sudan’s Nile Valley University and Sudan University of Science and Technology, Serbia’s MB University Belgrade, and China University of Petroleum-Beijing.

The post appeared first on pv magazine Global.