Solar Junction Breaks Concentrated Solar World Record with 43.5% Efficiency

Solar Junction, a company headquartered in San Jose, California has once again broken the efficiency world record for production-ready solar cells, which was confirmed by the United States’ National Renewable Energy Laboratory (NREL) last week. The new record, 43.5%, is 1.2% higher than the previous record.

According to the company, it achieved this new record by partitioning the solar spectrum more appropriately, thus maximizing efficiency. Its technology is, specifically, a concentrated photovoltaic cell. A photovoltaic cell is the part of a solar panel that generates electricity, and this type is designed for enormous amounts of sunlight to be concentrated onto it. It is 5.5 mm x 5.5 mm and its efficiency remained above 43% when the equivalent of 400 suns and 1,000 suns was concentrated onto it, but it was, unfortunately, slightly worse with 1,000 suns focused on it.

What is 1,000 suns and how do concentrator photovoltaics (CPV) work?: The sun shines a certain amount of energy onto each 5.5 mm x 5.5 mm surface on the earth, and that is, of course, how much sunlight the 5.5 mm x 5.5 mm cell is exposed to, but, to save money on the expensive photovoltaic material, a small piece of it is used (like the 5.5 mm cell mentioned) to generate electricity while concentrators (such as mirrors, for example) are used to concentrate 400 to 1,000 times the amount of sunlight the cell would normally be exposed to onto it. Sadly, this concept does not work for traditional solar cells due to excessive degradation unless someone could find a way to keep them cool.

Funding: This project was partially funded by the United States Department of Energy (DOE), which often funds alternative energy and energy storage research and development. This is done, in addition to loaning money to companies that want to construct alternatively-fueled power plants, to accelerate technological advancement in the field of alternative energy in order to make alternative energy sources more competitive with conventional energy sources. In February, Solar Junction made it onto a short list of finalists that could receive DOE loan guarantees under the DOE Loan Guarantee Program (LGP).

Brief History: Over the past few years, the CPV cell efficiency record has improved an average of 0.4% annually. Two months before this advancement, Solar Junction achieved a 41.4% efficiency. That advancement was also made under the company’s PV Incubator subcontract.

The CEO, Jim Weldon, said:

We’ve delivered on milestone after milestone and attribute this to our superior performing technology platform, driven by our dedicated, hard-charging technical team, supported by our integrated in-house manufacturing line that has enabled, and will continue to enable, multiple iterations of product improvement on an accelerated timeline. With A-SLAM™, we have a highly extensible technology that is actually delivering a clear and continued path to higher efficiencies in both the short and long term. That bodes well for CPV.

The company plans to scale in-house manufacturing of III-V multi-junction solar cells based on lattice-matched 1eV materials up to 250 MW of electricity generation capacity and start shipping commercial cells this year. Multi-junction solar cells, very simply, consist of several p-n (or positive-negative) junctions so that the cell can cover more of the solar spectrum. Learn more via the link above.

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