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Bean curd ingredient paves way for low-cost solar panel

Posted: 30 Jun 2014     Print Version  Bookmark and Share

Keywords:tofu  magnesium chloride  cadmium chloride  solar panel 

Physicist Dr. Jon Major experimented on an active ingredient used in making bean curd, or tofu, to reduce the cost of making solar panels.

A researcher at the University of Liverpool's Stephenson Institute for Renewable Energy, Major's findings on magnesium chloride as a low-cost substitute for cadmium chloride in the production of solar cells was recently published in Nature.

Though both toxic and pricey, cadmium chloride is applied in a thin layer to the surface of solar cells to boost their efficiency. It's tolerated because it increases the conversion rate of sunlight to energy from a relatively piddly 2 per cent to 15 per cent.

When asked about the ugly trade-offs that almost always accompany a material substitution, Major said magnesium chloride is about the closest thing to a free lunch one could possibly hope for. "All of our test devices performed near identically with either magnesium chloride and cadmium chloride. We're getting cell efficiencies using the magnesium chloride process that are as good as anything we've had using the cadmium chloride process."

He went on to say that there are no obvious barriers to wide-scale adoption of the process, only that the manufacturers will choose to do so. "Magnesium chloride is low cost, easily obtainable as it's extracted from seawater, and can simply be substituted for cadmium chloride in the existing process," he stressed.

 Magnesium chloride

Dr. Jon Major has applied for a patent on the use of magnesium chloride, a common chemical used in the processing of tofu, in solar cell manufacturing. (Source: University of Liverpool)

The application of magnesium chloride is straightforward: There's no need to control the thickness of the magnesium chloride or worry about toxicity, so it can be sprayed on the solar panel's surface at a bench. Researchers optimised the annealing process in order for the cell to get the best energy conversion efficiency.

Pressed on the expected cost savings, Major said that it's difficult to quote a definitive figure, as industrial contacts are naturally reluctant to give out that information. "All I can say is that we anticipate it to be significant. Magnesium chloride costs $0.001 per gram compared to $0.3 per gram for cadmium chloride. And the same deposition processes can be used without the need for a fume cupboard."

The operative question here is why hasn't magnesium chloride been considered before to improve solar cell efficiency, particularly given the severe drawbacks of cadmium chloride?

"We're not sure," said Major. "All we can say is that because the cadmium chloride process gives such good cell efficiencies nobody has felt the need to replace it."

It well might be a case of "if it isn't broken don't fix it."

"The cadmium chloride process has been established as the process route for 25 years now so often the assumption is that all other alternatives had been investigated," Major explained. "It's only when you look through the research literature you realise that, bar a few notable exceptions, not a great deal of research has gone into looking for alternatives."

As for tofu, which he swore off after a bad experience when an undergraduate, Major says he's thinking about giving it another go. "It's obviously full of good stuff. And maybe it will make me more efficient!"

- Karen Field
  EE Times

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