Let the sunshine in

In 2015, materials scientist Rob Moore adjusts the instrumentation at SSRL beam line 5-4 at the SLAC National Accelerator Laboratory in Menlo Park, Calif. Arkansas State University graduate students will get to work with scientists at the California lab as part of a Department of Energy research grant.

JONESBORO — When it comes to solar panels, it takes more than Windex to keep them clean.

Arkansas State University assistant professor of mechanical engineer Robert Fleming, will be studying the science of solar panel soiling thanks to a $360,000 two-year grant from the U.S. Department of Energy’s Established Program to Stimulate Competitive Research (DOE EPSCoR) program.

“Really, what happens with solar panels is dirt and grime accumulates on them, which over time blocks a substantial part of light that should be making it into panel,” Fleming said.

Eventually, the clouding effect can reduce the solar panel’s ability to produce power by as much as 35 percent.

Solar panels, or solar photovoltaic modules (PV modules) can be kept clean by hand – having someone sponge dust and grime off the panels – but on an industrial scale, hand cleaning is unfeasible, Fleming said.

“Some of the large solar arrays are in places where water is scarce,” Fleming said, “like the Southwest, or Africa.”

The cost of cleaning solar panels cuts into the profitability of the power production, as does the gradual loss of solar input due to the loss of coating clarity.

The loss of productivity makes it harder for solar to compete with other energy sources such as coal or combustible fuels, Fleming said.

“Solar panels harness the limitless energy of the sun to generate electricity. The efficiency with which the power is generated means a lower utility bill for the consumer,” said Abhijit Bhattacharyya, inaugural dean of the College of Engineering and Computer Science at A-State. “Efficiency depends on many factors including anti-soiling coatings that keep the panels clean. Not much is known about the science and technology of how that happens.”

“The US Department of Energy-EPSCOR program has determined that Dr. Drew Fleming’s project on anti-soiling coatings will deliver a better understanding of the science and technology of the coatings. Dr. Fleming is one of our outstanding researchers in the College of Engineering and Computer Science,” Bhattacharyya said.

“I look forward to his work and that of his research group to generate new knowledge right here in the upper delta region of Arkansas in collaboration with some of the best laboratories in the world – the SLAC National Accelerator Laboratory and the Lawrence Livermore National Laboratory in California,” Bhattacharyya said.

Fleming said Thursday the award is technically still under negotiation, but the selection of his project as one under negotiation for an award was announced by the DOE around July 15 as part of $21 million the DOE allocated for research in EPSCoR eligible states.

DOE EPSCoR a federal-state partnership program designed to enhance the capabilities of designated states and territories to conduct sustainable and nationally competitive energy-related research, according to the DOE Office of Science website.

The grant will be officially awarded after negotiations, Fleming said.

Prior to joining the faculty at ASU in 2019, Fleming spent five years developing anti-soiling coating technologies for PV applications at a company called WattGlass in Northwest Arkansas.

“While there, I realized that there was very little understanding of the interaction mechanisms that governed soiling and soil accumulation on PV modules, especially in context of the disparity of climates and local soil compositions where PV modules might be installed,” Fleming stated in a description of the research project.

Since manual washing of solar panels is not the best method to keep solar fields operating at their peak, the industry is looking for a coating that prevents loss of clarity within the glass covering.

Glass is the best material for solar panels because, unlike plastics, it is less susceptible to fading. Think old car headlights versus glass windows of the same age.

“The industry is seeking a cutting-edge coating, but there is no current widespread solution. One of the biggest impediments to developing coatings is a lack of foundational knowledge of the process of how different soils interact on a molecular level with the surface of the panels,” Fleming said.

To design a coating, scientists need to better understand the mechanisms at a fundamental level.

That’s where Fleming’s research project begins.

“We want to understand how different types of soil accumulate in the PV industry, and we’ll be working with the DOE laboratories, using advanced x-rays to understand how the soil interacting with the coating surfaces,” he said.

In this project, soiling interactions between PV cover glass materials and a large library of standardized soil compositions will be investigated. This funding opportunity encouraged collaboration with Department of Energy National Laboratories, and Fleming has partnered researchers at the

SLAC National Accelerator Laboratory in Menlo Park, Calif., and Lawrence Livermore National Laboratory in Oakland, Calif.

The partnership with SLAC enables access to advanced x-ray analysis tools at the Standard Synchrotron Radiation Lightsource; the collaboration with LLNL will support advanced computational modeling to help interpret experimental results.

ASU researchers will be the primary participants on this project, with the national lab staff acting in mentoring/advisory roles.

“I expect to fund multiple graduate and undergraduate students as a part of this project, where they will have the opportunity to work on-site at DOE National Labs,” Fleming said.

“What I have found from previous experiments is the interaction between glass and common soil results in changes of the surface chemistry,” Fleming said. “At SLAC, the have the ability to perform powerful, sensitive x-ray spectroscopy. The changes are very difficult to interpret by eye.”

In the laboratory, researchers will also be able to simulate on atomic level what is involved in the chemical reactions, and be able to model what reactions happen.

The standard warranty for solar panels in the industry is 25 years, and there has been a push for panel life to be extended to 50 years.

Fleming said his research would be a step making getting PV modules truly economical.

The ultimate goal of the research won’t be a coating product for solar panels, but knowledge of how the environment changes solar panel coatings.

“The end goal is fundamental knowledge of the interaction mechanisms,” Fleming said. “Once know those, that knowledge will give us insight into how design productions.”

“I am very excited and look forward to his contributions but I am even more excited at the prospect of the very impact experiences the funding will provide to the student researchers who will be part of the project,” Bhattacharyya said.