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New Solar Cell Sets Record For Energy Efficiency
Lucas123 writes "After three years of work, German and French researchers have achieved a new world record on converting sunlight to energy through a photovoltaic cell, achieving a 44.7% rate of efficiency, which was measured at a concentration of 297 suns. The efficiency rating means the solar cell collects 44.7% of the sun's spectrum's energy, from ultraviolet to the infrared spectrum, which is converted into electrical energy. The team of researchers said the technology places them on the path to achieving their roadmap of 50% efficiency in solar energy conversion."
Here is a graph of solar cell efficiency showing the different kinds of materials used to make them. The typical solar cell is silicon (blue on the graph) and maxes out at 27.6% efficiency.
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Multi-junction cells are expensive to produce, using techniques similar to semiconductor device fabrication, usually metalorganic vapour phase epitaxy but on "chip" sizes on the order of centimeters. In cases where outright performance is the only consideration, these cells have become common, they are widely used in satellite applications for instance, where the power-to-weight ratio overwhelms practically every other cost.
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"...a photovoltaic cell, achieving a 44.7% rate of efficiency, which was measured at a concentration of 297 suns"
This means that they use mirrors to focus the light onto the panel. Since high-efficiency panels tend to be expensive, the more light you can concentrate on it, the better. The fact that it can handle a near 300 fold increase in throughput is a good thing. These are not going to be used on a residential roof flat panel anytime soon.
Capacity factor for PV solar in the U.S. is about 0.145. That is, if you plop down a 1000 Watt panel angled at your latitude, and measure its power generation for a year, it'll average out to 145 Watts. It incorporates everything - weather, angle of the sun, night, etc. Across the country, it ranges from about 0.185 in the desert southwest, to 0.11 in New England.
From the Wikipedia article, in 2012 Germany had 32.6 GW of installed PV solar capacity, and it generated 28 GWh of electricity. A year is 8766 hours, so that's an average generation rate of 28000 GWh / 8766 h = 3.19 GW. So their PV solar capacity factor is 0.098 (Numerous hits on Google reporting instantaneous generation and generation over 24 hours notwithstanding - those don't matter, only the long-term cyclical average does, a natural cycle of seasons being one year.)
Basically, Germany is a terrible place to install PV solar. The only reason it's viable there is because their green energy initiatives have driven up the cost of their electricity to about $0.34/kWh (vs about $0.20/kWh for France and the UK). Numerous studies put the cost of electricity from PV solar at about 2x-5x the cost from other sources. So normally it wouldn't be cost-effective. But if you raise electricity prices to 3x what it is in the U.S., suddenly PV solar becomes financially viable.
They use Fresnel lenses, not mirrors : http://www.soitec.com/en/technologies/concentrix/components/
PS: I worked with Concentrix (now Soitec). Cool company.