The accumulation of dust on solar panels or mirrors is already a major problem, it can reduce the production of photovoltaic panels by up to 30%, so regular cleaning is essential for these installations.
It is estimated that cleaning solar panels consumes around 35,000 million liters of water per year, enough to provide drinking water to two million people.
Attempts to clean without water are labor intensive and tend to cause irreversible scratches on surfaces, which also reduce effectiveness.
Now, a team of MIT researchers has developed a way to automatically clean solar panels, or the mirrors of solar thermal power plants, in a waterless, contactless system that could significantly reduce the dust problem.
The new system uses electrostatic repulsion to cause dust particles to detach and virtually jump off the surface of the panel, without the need for water or brushes.
To activate the system, a simple electrode passes just above the surface of the solar panel, imparting an electrical charge to the dust particles, which are then repelled by a charge applied to the panel itself.
The system can operate automatically with a simple electric motor and guide rails located on the side of the panel.
Despite great efforts to develop ever more efficient solar panels, a trivial problem like dust can render all these efforts in vain.
Lab tests have shown that the drop in panel energy production occurs very early in the dust accumulation process and can easily reach a 30% reduction after just one month without cleaning. They calculated that even a 1% reduction in power, on a 150 megawatt solar installation, could mean a loss of $200,000 in annual revenue. The researchers say that globally, a 3-4% reduction in electricity generation from solar power plants would mean a loss of between $3.3 billion and $5.5 billion.
Many of the largest solar energy installations in the world, such as those in China, India, the United Arab Emirates and the United States, are located in desert regions. The water used to clean these solar panels with pressurized water jets must be brought from far away by truck, and it must be very pure so as not to leave deposits on the surfaces. Dry cleaning is sometimes used, but is less effective at cleaning surfaces and can cause permanent scratches which also reduce light transmission.
Water purification accounts for around 10% of the operating costs of solar installations. According to the researchers, the new system could reduce these costs and improve overall energy production by allowing more frequent automatic cleaning.
The new system they have developed only requires an electrode, which can be a simple metal bar, to pass over the panel, producing an electric field that imparts a charge to the dust particles as they pass. An opposing charge applied to a transparent conductive layer a few nanometers thick deposited on the glass cover of the solar panel then repels the particles, and by calculating the right voltage to apply, the researchers were able to find a voltage range sufficient to overcome the attraction of the solar panel. forces of gravity and adhesion, and cause dust to rise.
In practice, at scale, each solar panel could have guardrails on either side, with an electrode running through the panel. A small electric motor, perhaps using a small part of the output from the panel itself, would drive a system of belts to move the electrode from one end of the panel to the other, causing all the dust to come loose. The whole process can be automated or controlled remotely. Alternatively, thin strips of conductive transparent material could be permanently attached to the panel, eliminating the need for moving parts.
By eliminating reliance on trucked water, eliminating dust buildup that may contain corrosive compounds, and reducing overall operating costs, these systems have the potential to significantly improve overall efficiency and reliability. solar installations.
More information: www.science.org (English text).