The race to develop cost-effective solar power has sped up with the announcement of the world鈥檚 most efficient photovoltaic cell yet.
Spectrolab, a subsidiary of Boeing based in California, US, has created a photovoltaic cell capable of converting 36 per cent of the Sun鈥檚 rays into electricity. By contrast, ordinary existing solar cells are between 10 and 15 per cent energy efficient.
Solar power experts have welcomed the development, but point out that much work remains to be done before the Sun鈥檚 energy can be much more widely harnessed. In particular, the design used by Spectrolab is still relatively expensive to manufacture and it is not suitable for use in every location.
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The company鈥檚 Improved Triple Junction concentrator cells focus the Sun鈥檚 rays to boost the energy received by the solar panel. Efficiency is further boosted by the use of multiple layers, each of which is capable of absorbing photons of different wavelengths.
But the record energy conversion rate was achieved by modifying alloy elements in the top and middle layers. 鈥淲e adjusted the band gaps of the middle cell and the top cell to achieve maximum performance,鈥� says Nasser Karam, Spectrolab鈥檚 vice president of advanced technology.
Karam told New Scientist that Spectrolab hopes to further develop the technique to create cells that are up to 40 percent efficiency: 鈥淭here is still room for improvement.鈥�
Down to Earth
Spectrolab鈥檚 main business is making compact and highly efficient solar cells for use on spacecraft. But it hopes to adapt its technology for use on Earth.
Although highly efficient, concentrator cells are more complex, and therefore more expensive to make, than conventional silicon solar cells. They also require a Sun tracker to keep sunlight focused on the cells and need special cooling because of the intense heat generated.
Tom Markvart, a solar energy researcher at Southampton University, UK, adds that this type of solar cell is only suitable for use in bright conditions. 鈥淵ou need a fairly high degree of concentration,鈥� he told New Scientist. 鈥淵ou wouldn鈥檛 use it in the UK, for example, because you can鈥檛 focus sunlight diffused by clouds.鈥�
But the technology might be useful for addressing energy shortages in some places, says Keith Barnham, a solar cell researcher at Imperial College London, UK. 鈥淭here is an awful lot of the world not on the electricity grid, where solar power makes a lot of sense,鈥� he says.