Australian engineers are claiming a new world record for conversion of sunlight to electricity.
The team from the University of NSW's Australian Centre for Advanced Photovoltaics (ACAP) recorded an efficiency of 34.5%, which they say is a record for unfocused sunlight and getting close to the theoretical limits for such a device.
They used a 28 sq cm four-junction mini-module – embedded in a prism – which splits the incoming rays into four bands using a hybrid four-junction receiver, to extract the maximum energy from each beam of sunlight.
The result, is a significant improvement on the previous record of 24%, achieved by Alta Devices in the USA, over a larger surface area of 800 sq cm.
“This encouraging result shows that there are still advances to come in photovoltaics research to make solar cells even more efficient,” said Senior Research Fellow Dr Mark Keevers.
“Extracting more energy from every beam of sunlight is critical to reducing the cost of electricity generated by solar cells as it lowers the investment needed, and delivering payback faster.”
ACAP set another world record two years ago with a 40% electricity conversion rate, using mirrors to concentrate the light – a technique known as concentrator photovoltaics(CPV) – and then similarly splitting out various wavelengths.
“What’s remarkable is that this level of efficiency had not been expected for many years,” said ACAP Director Professor Martin Green.
“A recent study by Germany’s Agora Energiewende think tank set an aggressive target of 35% efficiency by 2050 for a module that uses unconcentrated sunlight, such as the standard ones on family homes. So things are moving faster in solar cell efficiency than many experts expected, and that’s good news for solar energy. But we must maintain the pace of photovoltaic research in Australia to ensure that we not only build on such tremendous results, but continue to bring benefits back to Australia.”
Keevers and Green caution that this type of technology is to find its way on to rooftops of homes and offices soon, as the cells require more effort to manufacture and therefore cost more than standard crystalline silicon cells with a single junction.
However, they are working on new techniques to reduce the manufacturing complexity and create cheaper multi-junction cells, and they feel the spectrum-splitting approach is perfect for solar towers, which use mirrors to concentrate sunlight which is then converted directly into electricity.
[Dr Mark Keevers with one of the spectrum splitting, four-junction mini-modules developed at UNSW.]
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