New solar cells capture heat and light



solar cells

A prototype of solar micro-concentrator from the Australian National University.

Credit: Images courtesy of the Australian National University

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Solar cells may soon be able to deliver energy as both heat and electricity, thanks to a new project at the Australian National University.

Developed in collaboration with Tianjin University in China, the project is working on technology to capture otherwise wasted heat from the sun. These innovative solar cells are expected to be commercially available within the next three years and should deliver a highly competitive, cost-effective combined solar heating and electricity system.

"Simultaneous provision of heat and electrical power is an attractive feature of our concentrators," said Igor Skryabin from the Australian National University in Canberra. "Collaboration with Tianjin University will ensure access to Chinese markets and manufacturing industries," he said.

Traditionally, solar cells work by using mirrors and lenses to concentrate the sun's energy onto a receiver, which then converts the energy into electricity. Like any object placed in the sun, however, the cells heat up.

This is problematic as solar cells work best at lower temperatures. Typically, the heat is removed by air flowing around the cells.

Such systems are inefficient and wasteful, Skryabin explained. For instance, in a 20 per cent efficient solar cell, 20 per cent of the sun's energy is converted into electricity, while the rest is lost as heat.

In a clever move, the new cells are designed to trap this heat, making it available for other uses. The new technology is made by immersing the cells in a cooling liquid - a channel filled with a transparent mineral oil, which absorbs the sunlight's heat and carries it away from the cells, simultaneously cooling the cells and harvesting heat.

This hybrid system is expected to capture up to 70 per cent of the sunlight that shines on the cell.

Randeep Singh, a mechanical engineer from the Royal Melbourne Institute of Technology who is not involved with the research, is excited by the project.

"This research has the potential to break new grounds in solar technology," he said.

He cautioned, though, that the idea is not without its challenges. "Immersing solar cells in cooling fluid will decrease the sunlight reaching the cells ... Maintaining their temperature within the optimum range will also decide this project's technical and economical feasibility," he said.

Martin Green, an engineer from the University of New South Wales in Sydney, also predicts technical hurdles.

"Heat and moisture are key factors in determining the longevity of any engineered system. Combining the two is likely to reduce the operating life of the system to well below that expected from conventional solar cells," he said.