ARCHIVED - Quantum dots add power to SUNRISE
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December 01, 2010— Ottawa, Ontario
Quantum dots that are far smaller than the period ending this sentence are amping up the ability of Canadian photovoltaic researchers to build more efficient solar cells.
In fact, the SUNRISE (Semiconductors Using Nanostructures for Record Increases in Solar-Cell Efficiency) project places Canadian solar cell development at the leading edge, and could help keep it there in the future, says Dr. Frank Shepherd of the NRC Institute for Microstructural Sciences (NRC-IMS), who co-leads SUNRISE with Dr. Trevor Hall of the University of Ottawa.
Launched in 2008, the three-year project is a collaboration involving NRC, the University of Ottawa, the Université de Sherbrooke, Cyrium Technologies Inc., and OPEL International Inc. Each partner has tackled a different facet of the research and development, addressing every aspect of this novel photovoltaic green technology — from chip design, modelling, fabrication and testing, to packaging of the cells, and assembly and construction of the solar tracker.
This fully functional system is now being tested at the Canadian Centre for Housing Technology (CCHT) in Ottawa, which is jointly operated by the NRC Institute for Research in Construction, Natural Resources Canada, and the Canada Mortgage and Housing Corporation.
Called “concentrated photovoltaic” (CPV), the system employs special “triple junction” solar cell chips made using multiple semiconductor layers of different materials and conductivity to collect and convert the full solar energy spectrum, and sophisticated optics to focus 500 times more sunlight onto their surfaces. These components are packaged in computerized sun-tracking arrays that keep them aimed optimally from dawn to dusk.
The SUNRISE solar tracker, installed at the Canada Centre for Housing Technology, uses sophisticated optics to focus sunlight on high efficiency solar cells.
Optimizing the performance
Optimizing the performance involved several iterations of design, fabrication and testing of different “junctions” within the solar cell. In the SUNRISE system, quantum dots — tiny semiconductors a few nanometres in diameter — are incorporated to fine-tune the performance of the multi-layered “triple-junction” structure — each layer being sensitive to a different part of the solar spectrum. The process for adding the dots to solar cell chips (patented by Cyrium Technologies) helps optimize the cells for the different characteristics of sunlight that occur at different latitudes so that they can perform at peak efficiency wherever they are. These exotic chips — which are now commercialized by Cyrium — performed at double the efficiency of traditional silicon solar cells under test conditions, converting 40 percent of sunlight into energy.
On bright days, the solar cell arrays generate more than two kilowatts of electricity, which under some conditions is more than enough for a typical home. Under these circumstances, the solar tracker installed at CCHT exports excess electricity to the power grid.
Dr. Shepherd says that while SUNRISE has produced a solar power system that — for now — is world-leading, it may provide greater benefits still to come.
The benchmark won’t stand still, he notes. This technology will continue to improve. What we’ve developed here is a test bed that will enable future generations of higher-performance solar cells to be assessed and demonstrated in Canada. In fact, we’ve helped establish an end-to-end capability within Canada, from R&D to manufacturing and commercializing.
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