Australian engineers have set a global record for the amount of solar energy able to be produced by a photovoltaic cell.
Dr Mark Keevers and Professor Martin Green, Senior Research Fellow and Director, respectively, of University of New South Wales’s Australian Centre for Advanced Photovoltaics have taken the world closer than ever before to the theoretical limits of sunlight-to-electricity conversion, using a new solar cell configuration to achieve a sunlight-to-electricity conversion efficiency of 34.5%.
The feat was accomplished using a 28cm2, four-junction mini-module – embedded in a prism – that extracts the maximum energy from sunlight. It does this by splitting the incoming rays into four bands, using a hybrid four-junction receiver to squeeze even more electricity from each beam of sunlight.
“This encouraging result shows that there are still advances to come in photovoltaics research to make solar cells even more efficient,” Keevers says. “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.”
The new UNSW result, confirmed by the US National Renewable Energy Laboratory, is almost 44% better than the previous record – made by Alta Devices of the USA, which reached 24% efficiency, but over a larger surface area of 800cm2.
“What’s remarkable is that this level of efficiency had not been expected for many years,” Green says.
“A recent study by Germany’s Agora Energiewende think tank set an aggressive target of 35% efficiency by 2050 for a module that uses un-concentrated 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,” he added. “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.”
The 34.5% result with the 28 cm2 mini-module is already a world record, but scaling it up to a larger 800cm2 – thereby leaping beyond Alta Devices’ 24% – is well within reach.
“There’ll be some marginal loss from interconnection in the scale-up, but we are so far ahead that it’s entirely feasible,” Keevers says.
The theoretical limit for such a four-junction device is thought to be 53%, which puts the UNSW result two-thirds of the way there.
Due to increased manufacturing costs, multi-junction solar cells of this type are unlikely to find their way onto the rooftops of homes and offices soon, although the UNSW team is working on new techniques to reduce the manufacturing complexity.
However, the spectrum-splitting approach is perfect for solar towers, like those being developed by Australia’s RayGen Resources, which use mirrors to concentrate sunlight which is then converted directly into electricity.
Images: From UNSW.
1: Dr Mark Keevers with one of the spectrum splitting, four-junction mini-modules developed at UNSW.
2: A diagram of the spectrum-splitting, four-junction mini-module developed at UNSW.