Powercube details for outdoor 40% efficient solar to electricity conversion using commercial cells

A solar research team at the University of New South Wales has converted over 40 per cent of sunlight into electricity, with an innovative take on Australian-designed solar tower technology.

This is a follow up to an article yesterday about record outdoor solar power conversion efficiency.

The team achieved 40.1 per cent efficiency in outdoor testing in Sydney in late October, using a solar ‘Power Cube’ system made up of commercially available solar cells, but with innovative efficiency improvements.

A key part of the ‘Power Cube’ 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 – reflecting particular wavelengths of light while transmitting others – and convert it to electricity at a higher efficiency than the solar cells themselves ever could.

The project funding page is here The concentrated solar power project goal is to reduce the cost of utility scale photovoltaics by developing a technology that splits sunlight into specific wavelength bands (called spectrum splitting) and converts each separate band into electricity using commercially available triple-junction and silicon (Si) solar cells, thereby increasing the overall amount of electricity generated.

The triple-junction solar cells used in the power tower receiver are fabricated on a Germanium (Ge) substrate to ensure good crystal quality, but the downside is that some of the sunlight absorbed in the Ge is wasted as heat.

This project uses an innovative ‘power cube’ receiver to divert some of this lost energy to additional solar cells made from Si, which are relatively inexpensive to produce and potentially increase the overall amount of energy converted from the sunlight by 10 per cent.

They used solar power towers 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 which provided some of the cells used in the project.

“The clever solution combines advanced triple junction cells with cheaper conventional silicon cells to boost power output,” said Ivor Frischknecht, CEO of the Australian Renewable Energy Agency (ARENA), which contributed $550,000 towards the $1.3 million project.

“Light that is normally wasted by triple junction cells is captured by splitting incoming sunlight into different spectra and directing some of it into a silicon cell,” Frischknecht said.

“This approach has achieved a higher efficiency than what is physically possible with a triple junction cell alone.”

Frischknecht said the breakthrough could have practical applications for concentrated solar power PV towers, where sunlight is reflected from a field of sun tracking mirrors towards a central receiver.

“Instead of using mirrors to heat a medium like salt, the high tech receiver converts light to electricity directly, like a rooftop solar panel does,” he said.

“Light that is normally wasted by triple junction cells is captured by splitting incoming sunlight into different spectra and directing some of it into a silicon cell.

“This approach has achieved a higher efficiency than what is physically possible with a triple junction cell alone.”

SOURCES – Arena, Renew Economy, University of New South Wales

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