British scientists have developed an experimental compressed air system for the simultaneous cleaning and cooling of PV modules. The system was built with a compressed air unit consisting of a compressor, an air tank, an air flow control valve and a series of nozzles. The technique was tested on a PV system located in northwest India.
British researchers have proposed using the airflow generated by compressed air for the simultaneous cleaning and cooling of solar modules.
They used a mathematical model to analyze how the adhesion of dust on the surface of the photovoltaic panels is removed by the airflow and how the air also has a positive impact on the operating temperature of the panel. These findings were used to build a pilot cleaning and cooling system based on a compressed air unit consisting of a compressor, an air tank, an air flow control valve and a a series of nozzles with a thickness of 5 mm. All components, according to the research team, are low-cost, standardized products.
“The compressor is directly powered by the photovoltaic panels and the release of compressed air from the reservoir is regulated by the valve to meet the cleaning and cooling mass flow requirements,” the scientists explained. “The air released from the nozzles installed at the edge of the panels overlaps and forms a snowflake-shaped airflow, then discharges dust and heat from the surface of the panel.” Air can be transmitted over the panels through a set of pipes which can be moved through a facility to clean and cool its parts when most needed.
The British team tested the system on a photovoltaic system based on monocrystalline photovoltaic panels operating in an unspecified area of north-west India. “The average size of the dust deposited on the surface of the panel was 20µm and nearly 90% of the particles had diameters less than 30µm”, he specifies. “The tilt angle of the panel has been set at 30 degrees and the average surface temperature can reach up to 333 Kelvin.”
After two weeks of testing, the surface of the panel was covered with 5.3g of dust, which reduced its power output from 42.5W to 37.5W at 303 Kelvin. After the implementation of the cleaning operations thanks to the air flow injected by two nozzles, the power of the module returned to an average of 41.82 W. The experiment also showed that at a temperature of 333 Kelvin, module efficiency drops to 28.24 W while after 130 seconds of airflow, the temperature has dropped to 315 Kelvin and the output power has increased to 32.42 W.
The blowing time was then set at 10, 15 and 20 seconds and the output power of the tested PV systems increased, from 567.4 W, by 30.7%, 33.6% and 36.1% , respectively. The cooling effect, however, can only be achieved for short periods of time during cleaning operations, since the costs of producing the airflow are higher than the benefits obtained from long cooling operations. “Therefore, the specific blowing time and particle size for removals must be determined, taking into account the optimal balance between the energy consumption in air compression and the energy gain from improved PV performance, for the studied application scenario,” the academics asserted.
In further research, they want to investigate nozzle configuration, frequency and duration of cleaning operations, and how to integrate maximum power point tracking (MPPT) under different dust deposition rates and module temperatures. PV.
Full details of the system, which is described as an ideal solution for arid climates, can be found in the article Study on the cleaning and cooling of photovoltaic solar panels by compressed air flowPosted in Solar energy. All researchers come from University of Warwick, UK.
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