The solar energy segment faces a number of challenges – from dependence on sunlight, through the storage of the electricity produced and the relatively low efficiency of the panels, to the clogging of photovoltaic power plants with dust. The unpleasant fact is that solar panels lose up to 30% of their power after a month without cleaning.
Researchers at the Massachusetts Institute of Technology (MIT) have developed a method that uses static electricity to keep the solar panels free of dust. Its main advantage is the elimination of the need for constant water cleaning.
Clean and without water
By 2030, the share of solar energy in global electricity production is expected to reach 10%, with much of it likely to be generated in desert areas where there is plenty of sunlight. However, the accumulation of dust on the surface of solar panels is already a significant problem, due to which it is necessary to clean them regularly.
It is estimated that about 38 billion liters of water are needed annually to clean solar panels, which would be enough to cover the needs of up to two million people. Waterless cleaning attempts are labor intensive and tend to cause irreversible scratching of the surface, which also reduces efficiency.
The MIT research team has designed a method for automatically cleaning solar panels or mirrors of solar thermal power plants with a contactless system, which they say could significantly reduce the problem of dust clogging.
The system uses electrostatic repulsion, which causes the dust particles to literally peel off and practically jump out of the panel surface without the need for water or brushes. The system is activated by passing a simple electrode just above the surface of the solar panel, which gives the dust particles an electric charge. These are then repelled by the charge supplied to the panel.
Just add a simple mechanism
To operate the system, simply add a simple electric motor and guide rails along the panels. The details were published in the journal Science Advances in an article by doctoral student Sreedath Panat and professor of mechanical engineering Kripa Varanasi.
According to Varanasi, global efforts to develop more efficient solar panels can “Seriously jeopardize an everyday problem like dust”. Laboratory tests carried out by Panat and Varanasi have shown that the energy performance of the panels decreases sharply at the very beginning of the dust accumulation process and after one month without cleaning it can easily reach up to a third reduction.
The researchers calculated that even a reduction in output of just one percent could result in a loss of $ 200,000 (approximately 4.5 million crowns) for a 150-megawatt solar installation. They state that a worldwide reduction in the output of solar power plants by 3 to 4 percent would mean a loss of 3.3 to 5.5 billion dollars (approximately 75 to 124 billion crowns).
“Solar materials are being worked on very intensively,” says Varanasi. “Boundaries are pushing and they’re trying to get a few percent here and there to improve efficiency, and here’s something that can erase everything right away.”
Water cleaning is unnecessarily complicated
Many of the largest solar power plants in the world, including those in China, India, the United Arab Emirates and the United States, are located in desert areas. Water used to clean solar panels it must be imported from a great distance and must be very cleanso as not to leave deposits on the surface. Sometimes a dry path is used, but it is less effective when cleaning surfaces and can cause permanent scratches.
Water treatment accounts for about 10% of the operating costs of operating solar systems. The new system could potentially reduce these costs while improving overall performance by enabling more frequent automatic cleaning, scientists say.
“The water footprint of the solar industry is staggering,” says Varanasi, saying it will increase as these installations expand worldwide. “The industry must therefore be very careful and think about how to make it a sustainable solution.”
In the past, scientists have tried to develop solutions based on electrostatics, where they relied on a layer called an electrodynamic sieve that used interconnected electrodes. However, these screens could have defects that let moisture through and cause them to fail. In a place like Mars, where humidity is not a problem, they can be useful, but in a desert environment on Earth, it can be a serious problem.
The new system only requires passage of the electrode through the panel, which can be a simple metal rod generating an electric field that transfers charge to dust particles. The opposite charge on the transparent conductive layer with a thickness of only a few nanometers deposited on the glass cover of the solar panel then repels the dust particles.
Experiments using specially prepared laboratory dust samples with different particle sizes have shown that this process works effectively. Tests have shown that the humidity creates a thin layer of water on the particles, which has proven to be crucial for this effect to work.
“We performed experiments at different air humidity from 5% to 95%,” says Panat. “If the ambient humidity is higher than 30%, almost all particles can be removed from the surfacebut with decreasing humidity it is more difficult. “
According to Varanasi, the system has the ability to effectively prevent the accumulation of dust that may contain corrosive compounds by eliminating dependence on imported water. It can also reduce overall operating costs and significantly improve the overall efficiency and reliability of solar systems.