It’s like that serendipitous combination of chocolate and peanut butter, only the Dept. of Energy’s National Renewable Energy Lab and Optony are purposely setting out to combine their leading edge efforts to bring down the costs of solar power by wedding the former’s record-setting thin-film solar photovoltaic (PV) cells with the latter’s concentrating solar power (CSP) system.
NREL and Optony announced July 14 that a joint research team will carry out a three-phased project to develop new thin-film solar cells compatible with Optony’s optical systems design.
To date, CSP systems have been concentrating sunlight on high-priced, flat panel silicon solar cells that are doped with exotic metals, such as gallium arsenide, the latest generation of which have conversion efficiencies of 40%, meaning that 40% of the sunlight that strikes the panel is converted to electricity.
While they are less efficient – NREL’s world record-setting thin-film copper indium gallium diselenide (CIGS) solar cell came in at a test conversion efficiency of 19.9%, putting them just shy of the 20% efficiency typical of silicon PV flat panels. In addition, thin film cells are cheaper to produce, more flexible in terms of how they can be used, and can also capture and convert light into electricity in lower light conditions and when sunlight strikes them at a wider range of angles as compared to silicon-based flat panels.
Developing thin-film cells that can withstand and dissipate the tremendous heat they’ll be exposed to as a result of having sunlight concentrated on their surfaces by the mirrors used in Optony’s CSP systems will be the key to combining the two solar power technologies.
“If you’ve ever taken a magnifying glass to ants, it’s a lethal thing,” senior NREL scientist Scott Ward said in a press release. “You can imagine what a hostile environment it is for a cell to operate under 500 to 1,000 suns concentration, and it’s expensive to create an optical system that will provide that kind of concentration ratio.”
The mirrors used in CSP systems magnify and concentrate sunlight’s strength as much as 1,000 times. Silicon isn’t a very good conductor of heat, which poses problems for such systems.
In contrast, thin-film cells can be deposited on a variety of materials that are better heat conductors. They also have the advantage of being cheaper to produce. “In this respect, thin-film cells are superior in design to the silicon solar cells,” noted NREL senior scientist Miguel Contreras, who developed the thin-film cells that hold the world efficiency record. “The cheaper thin-film cells and low-cost optics should lead to a less expensive product or a lower dollar per watt of electricity.”
By the end of the three-phase project, NREL and Optony, which was awarded a $250,000 grant from the DoE’s Technology Commercialization and Development Fund to work on the project, hope to have a concentrating photovoltaic (CPV) product suitable for large-scale manufacturing,
“The system will not only be cheaper to manufacture, but also more reliable,” Dong Wang, an Optony vice president who will be working on-site as part of the R&D team at NREL, stated optimistically.
