Although solar panels might appear bright and shiny, in desert environments, where they are most frequently installed, layers of dust and other particles can quickly coat their surface. These coatings can affect the panels’ ability to absorb sunlight and drastically reduce the conversion of the sun’s rays into energy, making it necessary to periodically wash the panels with water. But often, in areas like Nevada, water resources are scarce.

Consequently, NEXUS scientists have turned their attention toward developing technologies for waterless cleaning. NASA has already been using such techniques to wash panels in the lunar and Mars missions, but their developed methodologies prove too expensive for widespread public application. NEXUS scientist Biswajit Das of UNLV and his team are aiming to develop a water-free cleaning technology that will be cost-effective for large-scale photovoltaic generation, whereby they look to nanotechnology, rather than water, to clean the panels.

“Our mission is to develop a waterless, or at least a less-water cleaning technique to address the effect of dust on solar panels,” Das says. “Once developed, this method will significantly reduce water use for the future PV generation.”

A Microscopic, and Dry, Solution

The Das team project relies on tiny particles, known as nanoparticles, to do the cleaning work for them. Their idea is to coat the solar panels with arrays of transparent but electrically conducting nanoparticles. These particles provide an electrical field that can modify the electrical properties of the dust particles. Once these dust particles are charged, an electrical field can be used to attract them and sweep them away from the panels without the use of water.

While the concept may appear simple, several factors determine whether the technology will ultimately be viable. The first consideration is that the nanoparticles themselves be transparent.

“If we are coating the solar panel, we don’t want to block the light, so that is one of the first things we have to address,” Das said. Already in the UNLV Department of Electrical and Computer Engineering scientists have a system in place to create any type of nanoparticle at any density, but this technology is currently tailored for the purposes of constructing devices and integrated circuits, not requiring the creation of large areas of nanoparticles.

“It’s really high cost, so this cannot be useful for large-scale photovoltaic applications,” Das said. At present, however, the scientists are using this methodology to see if their water-less cleaning concept will work. “And then we will move on and develop a low-cost technology for the new solution.”

Using the tools already available, the scientists have synthesized nanoparticles of indium tin oxide and zinc oxide. Both these compounds are efficient conductors of electricity but are also transparent — a rare property. The team is also working on developing a low-cost technique, because the existing technique used for project demonstration would be highly expensive.

“They wouldn’t cover much of a surface area and the PV panels are, of course, huge,” Das said. “And we would need to create a technology that is much, much less expensive.”

Fine-Tuning the Process

The scientists have performed multiple experiments to fine-tune the process of creating the nanoparticles that will be best suited for this application. The scientists’ synthesis process produces charged nanoparticles. Using in-house equipment, the scientists have demonstrated that the charged nanoparticles can be moved around using an electric field. “We were very encouraged to see that once the particles are charged, they can be efficiently manipulated using electric field,” Das said.

The Das team is currently working on developing a low-cost technique for creating the transparent nanoparticles. Once the nanoparticles are created, one of the key goals of the project is to determine how to charge the dust particles and how to measure that charge.

“Unless we can measure it we can’t know if we are charging it properly,” Das said.

Once the scientists have perfected this process they plan to build a large area of nanoparticles, which will be specifically charged. Dust particles would then accumulate on this area and be charged by the nanoparticles.

“Our hope is that the focused electric field could actually charge the dust particles sufficiently so that we can move them,” Das said.

The scientists continue to work on the many challenging aspects of the project: creating the nanoparticles, charging and measuring the dust particles, and transferring the dust with an electric field.

”We are very encouraged by the achievements we have made so far, and hopeful that will be able to develop a low cost technology for charging and electrically manipulating dust particles,” Das said. “We believe that this will be a big step towards sustainable generation of solar energy.”