Solar Innovations: Super-Efficient Modules, Quantum Dots, Agave & More
This month’s roundup of solar innovations and breakthroughs in solar technology explores advances as complex as luminescent concentrators equipped with quantum dots and high-efficiency, stacked cells capable of converting nearly 44 percent of incoming sunlight into electricity – and as basic as planting agave under ground-mounted arrays to reduce the impact of dust on performance.
Ultra-high efficiency, stacked cells
Developers: Semprius Inc., Solar Junction, and University of Illinois at Urbana-Champaign
How it works: A developer of high-concentration PV modules, North Carolina-based Semprius this week announced it has produced its first quadruple-junction stacked solar cell using a proprietary micro-transfer printing process. Developed together with high-efficiency solar cell company Solar Junction and Frederick Seitz Materials Research Lab at the University of Urbana-Champaign, the cell relies on a multi-layer microcell stacked onto a single-layer germanium microcell to capture more of the solar spectrum and reach much higher efficiencies than either thin-film or conventional crystalline solar cells.
What it promises: Initial testing shows a sunlight conversion efficiency of 43.9 percent. However, Semprius claims that the process is capable of achieving greater than 50-percent efficiency. Semprius already reached a module-level efficiency of 35.5 percent last September using a lower-efficiency cell. With this new higher efficiency cell capturing more sunlight, Semprius’ high-concentration modules could soon near 40 percent.
Commercial arrival: As a recent graduate of the U.S. Department of Energy’s Sunshot Incubator Program, Semprius is still in a start-up phase. The company has installed systems with customers in six states and eight countries, but its overall commercial impact on the power plant markets it is targeting in global sunbelt regions remains minimal. As with other developers of other high-concentration PV technologies, it is presently unclear whether Semprius will arrive on the big stage – or remain an exotic solar sideshow.
Adding agave to reduce dust on panels
Developer: Stanford University
How it works: Ground-mounted solar arrays located in sunny, arid regions – whether large-scale power plants or even backyard arrays – deal with a lot of dust that reduces the performance of solar panels. Stanford scientists in April discussed new computer modules showing how planting low-lying agave beneath solar arrays in arid regions could help to anchor the soil and reduce dust. Since dust would be reduced, this could also reduce the amount of water needed to clean the panels.
What it promises: Stanford envisions co-locating agave or another biofuel crop with large-scale PV farms in arid regions to help prevent dust, reduce water usage and also provide another stream of income – since the crop could be used to produce ethanol. Clever DIYers with ground-mounted solar arrays in dusty environments could find agave helpful in reducing soiling on their systems.
Commercial arrival: Available now!
Panasonic boosts efficiency of HIT panels
Developer: Panasonic Corp.
How it works: As announced in April, Japan’s Panasonic has achieved a new world record for sunlight conversion efficiency using an HIT [Heterojunction with Intrinsic Thin layer] PV cell of 25.6 percent. According to Panasonic, its HIT cells achieve higher efficiency than standard crystalline silicon-based cells by reducing power generation losses by forming impurity-free amorphous-silicon layers between the crystalline base and p-type and n-type amorphous-silicon layers. The HIT cell also uses a back-contact structure, which reduces shading on the front side of the cell.
What it promises: Higher efficiency crystalline PV panels for rooftops and power plants.
Commercial arrival: Panasonic HIT cells already are commercially available today. The company has not said when the new higher-efficiency lab cell will be mass manufactured. Even for an established player such as Panasonic, this still could take several years.
Luminescent concentrator with quantum dots
Developer: Los Alamos National Laboratory and University of Milano-Bicocca
How it works: Researchers at Los Alamos and Italy’s University of Milano-Bicocca in April published a paper in Nature Photonics describing their use of quantum dots – tiny bits of semiconductor matter – in a luminescent solar concentrator. Luminescent concentrators are slabs of transparent material that include solar cells. In their research, Los Alamos researchers used cadmium selenide/cadmium sulfide quantum dots.
What it promises: Theoretically, luminescent concentrators could be used to develop cool products like architectural glass for homes and buildings that also produce electricity.
Commercial arrival: Laboratory development of luminescent concentrators has been going on for well over a decade. While the addition of quantum dots does not immediately take this technology from the lab to the marketplace, it could make the technology more intriguing to investors who – eventually – could enable commercialization.