Tuesday, April 15, 2003

Technology lighting way for solar


New research promises cheaper energy source

By Matthew Fordahl
The Associated Press

SAN JOSE, Calif. - Every minute, the sun bombards Earth with enough energy to supply its power needs for a year. Yet only two one-hundredths of a percent of all the electricity fed into the U.S. grid originates from sunlight.

The world still largely relies on diminishing supplies of environmentally unfriendly and politically destabilizing fossil fuels. Despite decades of research, it's still cheaper to burn coal than to get power from the sun.

But photovoltaic technology is improving efficiency and lowering costs for solar power, and experts believe the development will in the next few years drive solar adoption far faster than any government incentives or environmental concerns.

"Today, if solar energy were available in a quantity and at a cost comparable to fossil fuel, it would be a revolutionary change," said Stephen Empedocles, business development director at Nanosys Inc. The Palo Alto, Calif.-based startup is working on photovoltaic cells so small and cheap they can be sprayed or painted onto surfaces.

Solar power research is proceeding on two fronts: Making cheaper versions of crystalline silicon cells that comprise 80 percent of the solar market, and creating less-expensive photovoltaic technologies with the reliability and efficiency of crystalline silicon.

All the research is built on semiconductors, which absorb the sun's photons. Electrons are bumped along a predictable path by those photons until the current flows into something useful, such as an appliance.

This photovoltaic effect, first noticed in 1839, is the same way the flow of current is manipulated in computer logic and memory chips.

In fact, money-saving advances in the chip industry, such as increasing the size of silicon wafers and perfecting how they are sawed from ingots, are now being exploited in photovoltaics, said Dan Shugar, president of PowerLight Solar Electric Systems.

Since the 1950s, the uses for solar power have exploded. It's no longer limited to such specialty uses as satellites, remote cabins and highway call boxes. "Now, it's cost-effective against grid power for homes and businesses in states that have the incentives," he said.

Yet manufacturing costs remain relatively high, making solar power as much as five times more expensive than energy from fossil fuels - before tax credits and other incentives that states such as California offer.

To lower costs, companies and researchers are trying different types of semiconducting materials, including amorphous silicon and gallium arsenide. These materials are also more flexible than crystalline silicon.

But there's a catch: Such photovoltaics harness about 8 percent of the total energy in sunlight, compared with about 15 percent for crystalline silicon.

Ways to boost efficiency include layering photovoltaic cells so they capture a wider portion of the sun's range of energy. Another involves using lenses and reflectors to concentrate more sunlight on each cell.

These techniques do raise the overall cost, but the Boeing Co. subsidiary Spectrolab, which makes solar power systems for satellites, has used them to reach a record efficiency of more than 34 percent - in the lab. Researchers found sunlight can be concentrated as much as 500 times.

The most futuristic approach involves arranging nanosize semiconductors in a matrix of plastic-like materials that are expected to be much less expensive to produce.

Though some are skeptical about the future technologies, companies that sell today's solar-power systems note that traditional photovoltaics are dropping in price and eventually pay for themselves even at today's costs. PowerLight even touts some of its systems as added protection for roofs.

"Those other technologies are really interesting and I hope they succeed, but we don't need those to succeed for us to succeed," Shugar said. "We're not betting our future on one technology horse."

Location matters in today's solar savingsThough the cost of making traditional solar cells has decreased dramatically over the past 20 years, buying electricity generated by fossil fuels is still cheaper than installing a solar-powered generator at a home or business.

Still, solar systems eventually pay for themselves.

How long it takes is mostly a matter of geography.

A medium-size system, which costs about $52,500, would pay for itself in 11 years in San Jose, where buyers would receive about $20,520 in rebates from the California Energy Commission and $3,478 in state tax credits, according to BP Solar, which sells solar panels. The calculation assumes a monthly electricity bill of $200 to $250.

By comparison, the same system under the same circumstances in Tampa, Fla., would take 32 years to pay off because of the absence of rebates or tax credits. In less sunny Lincoln, Neb., it would take 33 years. In rainy Seattle, 35 years.

Many manufacturers also offer warranties of 20 years or more.

Another savings driver: Some utilities charge industrial users more for electricity during peak periods, which are usually during summer afternoons when air conditioners are running full speed.

That's the same time that solar power generation peaks.




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