April 30, 2006

Professor David Faiman in front of his photovoltaic cells apparatus: When people say that the existing supply of fossil fuels will last another 30 or 40 years… this doesn’t mean that life as we know it will last 30 or 40 years.As the world continues to become more and more dependent on fossil fuels, with the US alone consuming 17 million barrels each day, the question of the future looms larger every day: What is the world going to do when oil runs out?

Solar power has usually been dismissed as a possible answer to the problem because of its high cost and relatively low efficiency. But a new type of solar power cell being developed in Israel by one of the world’s foremost experts in the field promises to change that.

In Professor David Faiman’s world of concentrator photovoltaic cells (CPV cells), solar power just might be the answer to the fuel dilemma.

“Traditional photovoltaic cells do two things: collect sunlight and generate electricity from it,” said Faiman of Ben-Gurion University’s Jacob Blaustein Institutes for Desert Research in Sde Boker. “What we’ve done is simply split those two functions, so that the sunlight is collected and concentrated by a dish-shaped mirror, and a small number of concentrator cells generate electricity from that highly concentrated sunlight. Photovoltaic material is far too expensive to waste on something that can be accomplished with cheap glass and steel.”

Faiman’s apparatus, which resembles an enormous satellite dish, rises high above his modest offices in the middle of the Negev desert. Each of the dish’s mirrors can concentrate the sun’s energy by a factor of about 20 before reflecting it up to the solar cells that hang suspended over the apex of the dish. When all 50 of the mirrors used for the project are uncovered (sometimes only one or two are used for testing purposes), the cells are on the receiving end of the light of a thousand suns.

The dish, which weighs about 10 tons, is wheel-mounted onto a rotating base so that it can turn around, following the sun over the course of a day. The dish’s motors move it using a minute amount of the power that it generates.

A recent Faiman research paper analyzed the weather conditions in California and the southwestern United States, concluding that the economics of building concentrator solar power plants there were nothing short of phenomenal. The paper was published in a journal called Energy Policy instead of Faiman’s usual Solar Energy Materials and Solar Cells because he thought that “there’s more of a chance Governor Schwarzenegger will pay attention to a journal with the name Energy Policy.”

“This kind of power plant will cost a little less than $1,000 per kilowatt to build, which is exactly the same as the cost of current fossil fuel plants – except that you wouldn’t have to buy any fuel,” Faiman told ISRAEL21c. “If the electricity were sold at Israel’s going rate of nine cents per kilowatt-hour, the profit margin would be such that the entire investment in solar energy infrastructure could be paid off within twenty years. And all that while, the country could be building more solar power plants using some of the profit from existing ones.”

This kind of state-wide approach to investing in solar power was recently proposed by Dov Raviv (the “father” of the Arrow anti-missile project), who co-authored the Energy Policy paper with Faiman.

Existing solar power plants produce power at three to four times the current rate of nine cents per kilowatt-hour. They survive through government subsidies and laws forcing power companies to purchase solar energy at inflated prices “in the name of greendom,” as Faiman put it. Concentrator solar cells promise to make solar energy into more than just an ‘environmentalists’ toy.”

The new technology, developed under a three million euro grant from the EU, is the result of a partnership between the Ben Gurion University of the Negev, the German Fraunhofer Institute (who developed the concentrator cells), and other European institutions.

CPV cells use gallium arsenide as their principal photovoltaic material, whereas traditional solar cells are made of crystallized silicon. Gallium arsenide cells were developed alongside silicon photovoltaics in the Sixties but largely abandoned due to their high cost.

But because the cells used with the concentrating mirror are very small – around 1000-2000 times smaller than traditional solar panels used in power generation – cost ceases to be the limiting factor that it was when vast amounts of photovoltaic material were required in order to collect sunlight in its dilute form. Despite their high price, gallium arsenide cells are used without any focusing mechanisms in applications like the space station, where cost is not an issue.

The efficiency of silicon cells, 10% to begin with, increases to only about 20% when dealing with concentrated solar energy. The efficiency of gallium arsenide cells, on the other hand, increases with even higher concentrations of sunlight, starting at around 20% and easily doubling this figure. More advanced versions of CPV cells are being developed with projected efficiencies of 40-50%.

The current generation of CPV cells is single-junction – meaning that they have only one “sandwich” of photovoltaic material which does not capture the full spectrum of sunlight. By adding additional layers of material, with each layer slightly tweaked to capture different parts of the sun’s spectrum, scientists hope to create a CPV cell that will utilize much more of the sun’s potential energy.

This summer, Faiman’s team will install a full-fledged prototype concentrator cell module at the apex of the solar mirror and enter the final phase of testing. He plans to publish a paper on his project by the end of the year which he hopes will be ‘sensational’.”

Faiman, born in England, came to Israel by way of Illinois, Oxford and Geneva 34 years ago. He currently lives in Sde Boker in a “passive solar” house, which is built with angles and window sizes precisely calculated so that all of the house’s heating and cooling needs are taken care of by the sun.

“When people say that the existing supply of fossil fuels will last another 30 or 40 years at current rates of consumption, this doesn’t mean that life as we know it will last 30 or 40 years – and aside from that, the rate of consumption goes up all the time,” he said. “Unless the world starts installing infrastructure for solar energy now, we’ll shortly be faced with a very serious problem when fossil fuel prices skyrocket and the world rapidly spirals into chaos.”

Faiman envisions a place for fossil fuels in his ideal solar world. It would be kept, literally, for a rainy day, when there isn’t enough sunlight to run solar generators. “It would be nice to save fossil fuels for more important things than burning them,” he says. “Like the whole petrochemical (plastics) industry, for example.”

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Jason Harris

Jason Harris

Executive Director