Researchers at The University of New South Wales (UNSW Australia) have achieved what is claimed to be record solar system energy conversion efficiency of 40.4% (presented on 8 December at the Australian PV Institute’s Asia-Pacific Solar Research Conference at UNSW and to be published by Progress in Photovoltaics journal).
This exceeds the record solar photovoltaic module efficiency of 36.7% reported in July by Fraunhofer Institute for Solar Energy Systems ISE of Freiburg, Germany, using four-junction solar cells of concentrated photovoltaic (CPV) solar system maker Soitec of Bernin, France. The 40% efficiency is the latest achievement by UNSW solar researchers spanning four decades, including the first photovoltaic system with over 20% efficiency in 1989.
The efficiency of the UNSW system was achieved in outdoor tests in Sydney, before being independently confirmed by the US National Renewable Energy Laboratory (NREL) at their outdoor test facility in the USA.
“We used commercial solar cells, but in a new way, so these efficiency improvements are readily accessible to the solar industry,” says Dr Mark Keevers, the UNSW solar scientist who managed the project.
“The new results are based on the use of focused sunlight, and are particularly relevant to photovoltaic power towers being developed in Australia,” says Martin Green, UNSW’s Scientia Professor and Director of the Australian National Energy Agency-supported Centre for Advanced Photovoltaics (ACAP). Green was formerly a director of CSG Solar, which was formed to commercialize the UNSW’s thin-film polycrystalline-silicon-on-glass solar cell. His group's contributions to photovoltaics include developing record-efficiency silicon solar cells as well as spinning off several companies.
According to the Australian government’s funding documents the central receiver concentrator photovoltaic (CSPV) technology combines a CPV receiver with an optimized heliostat collector field (an array of sun-tracking mirrors). The heliostats concentrate sunlight onto the photovoltaic cells in the central receiver at the top of a mast alongside the heliostat field. By using large arrays of inexpensive mirrors, the CSPV technology can side-step cost issues facing other solar technologies and significantly reduce the cost of large-scale solar energy, it is claimed.
The power towers are being developed by Australian firm RayGen Resources Pty Ltd, which provided design and technical support for the high-efficiency prototype. Another partner in the research was Boeing subsidiary Spectrolab Inc of Sylmar, CA, USA, which manufactures multi-junction solar cells and panels for concentrated photovoltaic and spacecraft power systems, and provided some of the cells used in the project.
A key 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 to 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.
The work was funded by the Australian Renewable Energy Agency (ARENA) and supported by the Australia–US Institute for Advanced Photovoltaics (AUSIAPV). “We hope to see this home-grown innovation take the next steps from prototyping to pilot-scale demonstrations,” says ARENA’s CEO Ivor Frischknecht. “Ultimately, more efficient commercial solar plants will make renewable energy cheaper, increasing its competitiveness.”
