Researchers had placed a cotton sheet on the back of a PV module, which was then made wet and cooled. At the front, water was pumped from a pipe in a way that kept the panel both cool and clean. Their experimental setup showed superior results compared to reference cooling technologies.
A group, led by scientists from Al-Azhar University in Egypt, has proposed a new double use system for solar PV (SPV), so that they are cooled from both sides and at the same time cleans birds at the front. By developing an experimental attitude of the system, the group has also tested it under the circumstances in Cairo.
“It is estimated that 17% of the incident solar radiation is absorbed for power during the operation, while the remaining part is wasted as heat. In addition, the heat in the surrounding air relegates the efficiency and power of solar panels by increasing the temperature of their cells, “the researchers explained. “Bird droppings also contain digestive fluids that cannot clean heavy rainfall. Bird Guano gathered on the SPV modules that reduce the performance of solar panels by reducing the transmission of the glass cover on the PV panels. “
The team used water to solve both efficiency problems, that of high temperature and those of Dalen. The team takes a solar panel with 360 W and has attached a wooden surface to the back. A 1 mm thick cotton fabric plate was placed between the back of the model and the wood, while a 6 mm thick acrylic plate was attached to the outside of the wood. A central water pipe dropped water through holes on the cotton, on which fans pushed air.
“The air is saturated with moisture, so the temperature of the air between the dust and the surface of the solar panel decreases,” they explained.
At the front of the panel, the academics placed a pipe with holes, allowing water to flow on the panel for both cleaning and cooling. A submersible pump moved water from a 50 l water reservoir to the pipe, while a water collector was installed on the bottom of the module. “To make up for the water shortage, water is added periodically to the tank,” they emphasized.
Image: Al-Azhar University, Scientific Reports, CC by 4.0
That system was then tested against a operating system of a cleaned 360 W panel without cooling, and against an untriled 360 W with four excrement of birds. Back and temperatures for the front, module output flow, module voltage, sunlight intensity, ambient temperature and relative humidity were measured for the three modules from 10 a.m. to 5 p.m. on 10 August 2023. All panels were oriented to the south and had a tilt of 30 °.
“The structure of bird droppings on photovoltaic solar modules creates ‘hotspots’ on the panel surfaces, which increases their temperature by 5% compared to clean modules,” the researchers said. This temperature rise reduces the power output by 36-38% when there are four droppings or more. “
The cooled PV module, according to the results, showed an output current increase of 8% and 9% compared to the contaminated and controlled modules respectively; While the output voltage rose by 7% and 9% respectively.
A power increase of 12%–33%and 7%–12%respectively, compared to bird droppings and control modules was reported. The average efficiency of the cooled module was 20%, while the control panel was 18%and the uncooled module with bird collection fell to 15%. The level of energy costs (LCOE) were $ 0.11/kWh for both cooled and controlled systems, while it rose to $ 0.13/kWh in the system with birds.
“As a result of the current study, the cleaning system must be operated if the number of birds that drops is larger than four drops. That is because the power reduction was high in the case of the presence of four excrement of birds on the PV panels (33% lower than cooled PV panel), which significantly reduced the module efficiency, ”concluded the researchers. “The cooling system must also work based on the temperature of the PV modules during the day. In the operation we adjust the system to work when the temperature exceeds 35 ° C during the day. “
The results were presented in “Improving the PV performance of solar energy under bird dropping conditions with a double cooling approach“Published in Scientific reports. Scientists from Al-Azhar University in Egypt and Chinese Huazhong University of Science and Technology have conducted the study.
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