A research team from Iran's Semnan University has tested the use of a solar module cooling technique that is based on a pulsating water spray system. The team claims that the system uses a minimal amount of water.
The system relies on a 140-cm iron pipe with a diameter of 1.5 cm and nine nozzles. The pipe is shaped to avoid shading and the distance between each nozzle is 12 cm. The cooling structure works through different angles of spray by using locking clamps.
“Another specific feature was the ability to set the system on five different distances from the PV panel surface,” the academics said. “The distance between the panel upper edge and the set of nozzles was adjustable from 10 to 50 cm in five different modes (10, 20, 30, 40 and 50 cm).”
The system is also based on a solenoid valve and a timer to provide a pulsating water spray, which are both aimed at reducing water consumption.
They tested the technique on an 85 W monocrystalline module with an effective surface of 0.59 m2, at a laboratory in Semnan. July temperatures ranged from 32 C to 37 C, with negligible wind. The water temperature was around 16.5 C. The module surface temperature was measured in both cooling and non-cooling modes for 10 and 20 minutes, respectively.
The scientists tested three different on-off time periods to to identify the optimal amount of needed time to cool the PV panel surface. The pipe was provided with an average water pressure of 4.8 bars, which equals that of the water system of Semnan.
Via an infrared thermometer, the scientists found that the highest module temperature of 64 C was reached by a non-cooled panel. A drop of 40 C occurred with cooling, with the minimum panel temperature reaching 24 C.
“The minimum PV panel temperatures were observed for the lowest nozzles to PV panel distance and the smallest angle 15 degrees,” they explained.
They recorded the lowest increase in yield when the pipe was placed at the highest distance from the PV panel.
They analyzed the system in three modes, with nine, five, and three nozzles. With the first configuration, power yield grew by 19.8%, and with the second and the third setups, it rose by 11.59% and 8.73%. The academics found that a water-spraying frequency of 0.2 Hz offered the best balance between water consumption and PV module performance.
“The maximum increase in PV panel electrical efficiency is 25.86% compared to non-cooled mode, and it occurred at steady water spray cooling with H/L = 0.83 and the spray angle = 15 degrees which they are the lowest nozzles to PV panel distance and spray angle respectively,” the group said.
They said that the main goal of the research project was to investigate the spray angle effect and the distance of nozzles from the PV module.
“It will be important that future research provides the economic approach of this water spraying system,” they concluded.
They presented their findings in “Experimental investigations of spray flow rate and angle in enhancing the performance of PV panels by steady and pulsating water spray system,” which was recently published in Springer Nature.
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