Using commercial solar cells, researchers have converted over 40 percent of the sunlight hitting a solar system into electricity, the highest efficiency ever reported.

Since plant photosynthesis, the thing solar cells want to mimic, is only 5 percent, and the human body is only 25 percent efficient, the world should have switched to solar long ago if anywhere near 40 percent was attainable, right? Efficiency means different things. Electric cars claim to be over 90 percent efficient, for example, because they power the car directly, but that is only when manufacturers frame the result carefully. Gasoline has far more energy density and electric cars require an eight hour charge after driving a few dozen miles, most of the electricity to charge them comes from fossil fuels because solar is too inefficient, and the car efficiency due to batteries begins to drop immediately.

In the actual world, current solar panels are plagued by lots of inefficiencies, though they are nowhere near as bad as wind turbines, and solar will be the future, provided we stop subsidizing panel companies and use that money to find basic research instead. Right now the efficiency is about 10 percent and there is a big environmental downside; since not every location has ample sunlight, to use solar power in the US would mean adding solar panels equivalent to all of the pavement that currently exists. And 20,000 miles of new transmission lines. All without factoring in the environmental damage from mining of rare earth materials and construction, which American environmentalists don't see because it happens in China.

Great solar efficiency in space has been achieved, but it is not helping us much on earth. A test in Sydney has been independently confirmed by the National Renewable Energy Laboratory (NREL) and used commercial solar cells to get a 40 percent efficiency rate, a new record. 

 "The new results are based on the use of focused sunlight, and are particularly relevant to photovoltaic power towers being developed in Australia," said UNSW Scientia Professor and Director of the Advanced Centre for Advanced Photovoltaics (ACAP) Professor Martin Green.

"We used commercial solar cells, but in a new way, so these efficiency improvements are readily accessible to the solar industry," added Dr Mark Keevers, the UNSW solar scientist who managed the project.

Part of the prototype's design is the use of a custom optical bandpass filter to capture sunlight that is normally wasted by commercial solar cells on towers and convert it to electricity at a higher efficiency than the solar cells themselves ever could. Such filters reflect particular wavelengths of light while transmitting others.

Power towers are being developed by Australian company, RayGen Resources, which provided design and technical support for the high efficiency prototype. Another partner in the research was Spectrolab, a US-based company that provided some of the cells used in the project.

Upcoming in the Progress in Photovoltaics journal. The work was funded by the Australian Renewable Energy Agency (ARENA) and supported by the Australia-US Institute for Advanced Photovoltaics (AUSIAPV). Source: University of New South Wales