CSU physics professor helps lead major university thin-cell photovoltaic program

Jim Sites

Jim Sites is a physics professor who has worked in photovoltaics research for over 40 years.

His dedication to his craft shows itself in the depth and quality of the photovoltaic research that he oversees at CSU.

Also known as solar energy, photovoltaics transform sunlight into electricity and are one of the most promising large-scale sources of clean energy for the future.

The CSU Photovoltaic lab tests thin-film solar cells.

The Dazzling Effect of Thin-Film Solar Cells

For many years, Sites has focused on the applications of cadmium-telluride and other thin-film solar cells. Most of that work has been done in partnership with mechanical engineering professor W.S. Sampath. Although the majority of solar panels worldwide use silicon, Sites sees thin-film cells as more promising due to lower production costs.

During the production process, thin-film layers are deposited over the glass base of the panels. These layers are cut by lasers to separate each cell, with the result that many solar cells are interconnected on the same layer.

Producing many interconnected cells simultaneously is easier and faster than creating each cell individually, as happens with silicon panels.

“You need less material, and you need less energy for the same amount of power you get out,” Sites explained.

Sites described one way to measure the effectiveness of thin-film solar cells. “We have a factor we call ‘energy payback time,’ which is basically how long you have to run the solar panel in order to recover the energy that you use to make it. That’s down to about half a year for thin films,” shorter than the energy payback time for silicon cells.

Testing equipment at the Photovoltaic lab

CSU’s Investment in Solar Energy Research

According to Sites, CSU has one of the largest university thin-cell programs in the country. Currently he and Sampath lead a team of around 20 students and researchers.

The scale of the program matches its goals, as Sites and his colleagues aim to promote solar-energy growth at a utility scale.

A thin-film solar panel

CSU has multiple facilities dedicated to solar energy research. In addition to the lab that Sites oversees in the Physics department of the main campus, the Foothills campus hosts a field of solar panels and manufactures the thin-film cells used by Site’s and Sampath’s larger team. Much of the photovoltaics work is organized within the CSU site of the National Science Foundation’s Center for Next Generation Photovoltaics, which is affiliated with the CSU Energy Institute, and dedicated to broadly expanding the use of solar energy.

While the Foothills campus is in charge of producing the cells, Sites’ lab tests the cells’ performance. “Outside of one large company, we make the highest efficiency cadmium telluride solar cells,” he noted.

Sites’ lab also collaborates with the National Renewable Energy Laboratory in Golden and First Solar, the largest solar company in the US and the largest producer of thin-film photovoltaic cells worldwide.

Electroluminescent images show the regularity of manufactured cells.

A Bright Future for Solar Energy

Sites said that solar energy usage has almost doubled in the U.S. within the past year.

The increase, according to him, is only from 1% to 2%. But the trend is promising and Sites expects solar power to form an increasing percentage of the world’s energy usage.

He noted that the price for solar energy infrastructure has been dropping. “I think it’s safe to say that it’s competitive in a large part of the world,” he said.

The average lifespan of a solar panel is also increasing. Currently, panels will last for 25 years or more, but Sites is confident that number will only continue to grow.

Thin-film solar cells from one of the earlier batches produced by the university

Sites sees potential for solar energy production all across the U.S.

“The actual ratio of sunshine you get in New Jersey compared to Colorado isn’t extreme, so that even in places you don’t think of as being as sunny as Arizona, or southern California, photovoltaics still work pretty well.”

He envisioned our future world as being interconnected by shared solar energy, with sunnier regions passing along power to less sunny ones.

Sites with one of the largest solar panels in the lab

Next Steps for Solar

As with any nascent technology, there are still obstacles that researchers must overcome in order to make widespread solar energy production feasible.

The major challenge that Sites identified is storing solar energy so that it can be used at night, when panels are not generating power.

But Sites seemed confident that solar energy, especially thin-film panels, will succeed in the long term. “Having the Energy Institute to kind of help bring things together has been real helpful,” Sites remarked.

Collaboration and an interdisciplinary approach, like that fostered by CSU and the Energy Institute, will help photovoltaic research continue to develop and innovate.

More information about the CSU Photovoltaics Lab is available here.