The University of Arizona

$1M Federal Grant Fuels UA-Developed Solar Technology

University Comunications | November 21, 2012
The reflective glass dishes that collect the sunlight are mounted on frames that track the sun as it moves across the sky. (Artist's conception: REhnu, Inc.)
The reflective glass dishes that collect the sunlight are mounted on frames that track the sun as it moves across the sky. (Artist's conception: REhnu, Inc.)

By taking advantage of existing manufacturing and supply lines and combining cheap components with high-tech technology, the UA's concept offers a realistic chance at successfully competing with fossil fuels in the not-too-far future.

The reflective glass dishes that collect the sunlight are mounted on frames that track the sun as it moves across the sky. (Artist's conception: REhnu, Inc.)
The reflective glass dishes that collect the sunlight are mounted on frames that track the sun as it moves across the sky. (Artist's conception: REhnu, Inc.)
The power-generating unit can easily be upgraded as photovoltaic cells evolve toward more efficiency. (Photo: REhnu, Inc.)
The power-generating unit can easily be upgraded as photovoltaic cells evolve toward more efficiency. (Photo: REhnu, Inc.)

A $1 million award from the Department of Energy could help solar power technology developed at the University of Arizona revolutionize the way sunlight is converted into electrical power. 

The award, one of 10 made in 2012 by the DOE under its Round 7 SunShot Incubator program (see sidebar), is the only one made this year to advance high-concentration photovoltaics, or CPV.
 
The grant was awarded to REhnu Inc., a spin-off company founded by UA optics professor Roger Angel, who also is the director of the UA’s Steward Observatory Mirror Laboratory. REhnu is tasked with commercializing the system from successful prototype to production-ready form. 
 
Unlike conventional photovoltaics, the kind you might have installed on your roof, REhnu’s system collects sunlight with large mirrors and focuses the concentrated light onto a small patch of high-efficiency photovoltaic cells. 
 
“From the outset, our goal has been to develop solar energy technologies that would be cost-competitive with fossil-fuel generation without requiring subsidies,” said Angel, inventor of the concept and founder of REhnu. “This DOE award recognizes the potential of REhnu’s approach and will provide an enormous boost to commercializing this disruptive technology.”
 
Angel’s concept applies expertise gained over the mirror lab’s extensive history of making the world’s largest telescope mirrors to the fabrication of cheap but effective dishes capable of harvesting sunlight more effectively than any other existing technology. REhnu holds an exclusive license from the UA to commercialize his novel approach, which is protected by three UA-held patents. 
 
Peter Strittmatter, Regents’ Professor at the UA department of astronomy and REhnu’s secretary, said: “The prototype we have developed at the UA has been working exceedingly well and now shows great promise for producing electricity at costs competitive with fossil fuels.”
 
“We know what we have has the potential to be game changing, but the specific goal right now is to implement the technology in a form that can succeed in a market that has become extremely competitive,” said REhnu CEO Justin Elliott. 
 
Elliott explained that unlike other CPV technology companies, which have to develop every part of their technology from scratch, REhnu’s approach takes advantage of existing manufacturing and supply lines and thus keep investment costs down. 
 
The solar mirrors developed at the mirror lab focus sunlight onto a 5-inch glass ball and from there to a small array of 36 highly efficient photovoltaic, or PV, cells, developed originally to power spacecraft. They convert a broader range of the solar spectrum into electricity than regular cells to make twice as much electrical power. The ball lens is coated to maximize transparency for the incoming rays.
 
“By taking advantage of Roger Angel’s incredible knowledge of optics, plus access to the mirror lab, we have made a new unique mirror concentrator that allows us to bundle our high-power cells in a separate, small package, and to combine the best of other proven solar technologies in a more effective way,” Elliott said. 
 
“Using largely existing technology not only allows us to go to market at a fraction of what other solar technologies require, but also allows our system to be upgraded and maintained more cheaply and effectively,” he said, adding that the system provides a way to take advantage of the high and steadily increasing efficiency of photovoltaic cell technology using existing supply chains developed for other solar applications. 
 
According to Elliott, the concentrator PV cells REhnu uses hold potential for becoming still more efficient, boosting their current ability to convert 40 percent of solar energy into electricity up to more than 60 percent. Key to REhnu’s approach is its modular design, allowing for cheap upgrades of only certain parts without affecting the rest of the package.
 
“For example, in 10 years we can swap out just the power generator units and upgrade to cells with 50 percent efficiency. Overall, we’d be increasing the power plant’s efficiency by one-third while spending only 10 to 15 percent to get there."
 
Elliott added that the solar electricity industry is limited by the longevity of the photovoltaic material. 
 
“You put them out in the field and they convert sunlight to electricity, but they degrade with every year,” he explained. “That is why existing contracts are limited to 25 years or less.”
 
“We expect our system to last much longer, about 40 years, and we expect it to make about twice as much as energy compared to conventional solar power installations. When the other projects stop, we keep running.”