Solar panels just got more eco-friendly

By Stephen Beech via SWNS

A green way of cleaning solar panels without using water has been devised.

Dust accumulating on the panels is a major problem, but washing them normally involves huge amounts of water.

Now engineers have developed a water-free cleaning method to remove dust and dirt from solar installations.

Solar energy is expected to reach 10 percent of global power generation by the year 2030, and much of that is likely to be located in desert areas.

But the accumulation of dust on solar panels or mirrors is already a significant issue as it can reduce output by as much as 30 percent in just one month, so regular cleaning is essential.

However, cleaning solar panels is currently estimated to use about 10 billion gallons of water per year - enough to supply drinking water for up to two million people.

Scientists say that previous attempts at waterless cleaning were labor-intensive and tended to cause irreversible scratching of the surfaces, which also reduces efficiency.

Now, a team of researchers at the Massachusetts Institute of Technology (MIT) in the United States has devised a way of automatically cleaning solar panels, or the mirrors of solar thermal plants, in a waterless, no-contact system.

They say it could "significantly reduce" the dust problem.

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Professor Kripa Varanasi said: "The new system uses electrostatic repulsion to cause dust particles to detach and virtually leap off the panel’s surface, without the need for water or brushes.

"To activate the system, a simple electrode passes just above the solar panel’s surface, imparting an electrical charge to the dust particles, which are then repelled by a charge applied to the panel itself.

"The system can be operated automatically using a simple electric motor and guide rails along the side of the panel."

Despite major efforts worldwide to develop ever more efficient solar panels, Prof Varanasi said: "A mundane problem like dust can actually put a serious dent in the whole thing.”

Lab tests conducted by MIT graduate student Sreedath Panat and Prof Varanasi showed that the drop-off of energy output from the panels happens steeply at the very beginning of the process of dust accumulation and can easily reach 30 percent reduction after just one month without cleaning.

The researchers say that globally, a three to four percent reduction in power output from solar plants would amount to a loss of between $3.3 billion and $5.5 billion.

Prof Varanas said: “There is so much work going on in solar materials.

“They’re pushing the boundaries, trying to gain a few percent here and there in improving the efficiency, and here you have something that can obliterate all of that right away.”

Many of the largest solar power installations in the world, including ones in China, India, and the US, are located in desert regions.

The water used for cleaning these solar panels using pressurized jets has to be trucked in from a distance, and it has to be very pure to avoid leaving behind deposits on the surfaces.

Dry scrubbing is sometimes used but is less effective at cleaning the surfaces and can cause permanent scratching that also reduces light transmission.

Water cleaning makes up about 10 percent of the operating costs of solar installations. But the researchers say that the new system could potentially reduce these costs while improving the overall power output by allowing for more frequent automated cleanings.

Prof Varanasi said: “The water footprint of the solar industry is mind-boggling, and it will be increasing as these installations continue to expand worldwide. So, the industry has to be very careful and thoughtful about how to make this a sustainable solution.”

He explained that the new system they 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 it goes.

Using specially prepared lab samples of dust with a range of particle sizes, experiments showed that the process works effectively on a laboratory-scale test installation,

Doctoral candidate Mr. Panat said: "The tests showed that humidity in the air provided a thin coating of water on the particles, which turned out to be crucial to making the effect work."

He added: “We performed experiments at varying humidities from five percent to 95 percent.

“As long as the ambient humidity is greater than 30 percent, you can remove almost all of the particles from the surface, but as humidity decreases, it becomes harder.”

Mr. Panat added: “Moreover, unlike some of the prior work on electrodynamic screens, which actually do not work at high or even moderate humidity, our system can work at humidity even as high as 95 percent, indefinitely."

Prof Varanasi says that by eliminating the dependency on trucked-in water, by eliminating the build-up of dust that can contain corrosive compounds, and by lowering the overall operational costs, such systems have the potential to "significantly improve" the overall efficiency and reliability of solar installations.

The findings were published in the journal Science Advances.