Recent advances may make systems more popular


September 29, 1991|By Michael Pollick

Sun power makes sense right now for Sam Droege. That's because Baltimore Gas and Electric Co. wants nearly $10,000 to hook up his Davidsonville log cabin home to the nearest electric power pole, a half-mile away.

Mr. Droege's answer was to spend $9,000 on a solar electric system, avoiding the utility altogether. Mr. Droege's 26-foot-by-26-foot home won't feature an electric stove or heater, but it will have a few of the gizmos of modern society, including a washing machine.

Still, it will take a cheaper solar system than that to convert the rest of us to solar. And that's exactly what a number of big-name players are working on.

Power from "the grid," as solar advocates refer to electric utilities, now costs between 5 cents and 12 cents per kilowatt hour -- 8.35 cents in the mid-Atlantic states. The current cost for solar electric power is in the neighborhood of 25 cents to 35 cents per kilowatt hour.

But solar cell research is proceeding at a brisk pace. Within a decade, industry experts say, technological breakthroughs should lower the price of solar power to half of today's levels, making solar cheap enough to entice some suburban homeowners who are "on the grid."

Photovoltaic power, or PV, "is definitely going to get big," says Jack Stone, who is in charge of PV research at the National Renewable Energy Laboratories in Golden, Colo.

Already, he says, solar can compete head-on with diesel generation in remote areas, because it is more reliable and because operating and maintenance costs are much less. Solar is being used to power portable street signs, billboard lights -- even some Baltimore stoplights.

The "next step," he said, is the U.S. residential market. That's going to be a big step. Only 20,000 to 30,000 U.S. homes use PV as their main source of power, according to Home Power magazine, whose husband-and-wife editing team surveys subscribers from their own remote home near Hornbrook, Calif.

The worldwide solar industry attracted interest -- and millions of dollars in investment -- during the oil embargo of the 1970s. The end of tax credits for solar power put a damper on sales in the mid-'80s, and the industry has yet to live up to its promise.

But the industry has been quietly improving the way it makes solar modules, and the modules' efficiency. And technological improvements are expected to drive down costs dramatically.

"There are about 60 companies worldwide who are in a race to pick the right technology and develop low-cost manufacturing," says Bill Howley, chief of staff at the largest PV module maker in the world, Siemens Solar Industries of Camarillo, Calif.

Siemens, part of the West German industrial giant Siemens A.G., is working hard to stay ahead of challenger Solarex Corp. of Rockville, which is backed by U.S. oil giant Amoco Inc.

The basis for solar electric power is the photovoltaic effect, first discovered in 1839 by a French scientist, Edmund Becquerel. PV cells employing this principle have been used for more than a quarter of a century to power satellites.

A silicon solar cell is actually a sandwich of two types of specially prepared silicon, a positive type in back and a negative type in front.

The science

When sunlight hits the cell, it excites electrons in the positive region. Some travel through the junction with the negative material and get trapped there, creating a voltage difference between the back and front of the sandwich. If you connect the negative and positive regions through an electrical load such as a light bulb, electrons will flow through and generate electricity. This is a continuous process, because the sunlight continues to make electrons move.

Today, 90 percent or more of the solar modules being sold are made from solid chunks of the highest-quality silicon. Siemens grows its own crystals in tanks, while No. 2 Solarex Corp. buys high-grade silicon scrap and melts it into bricks at its main plant in Frederick.

Either way, making the solar module is a time-consuming process that requires slicing the silicon into thin wafers, making individual cells out of the wafers, and piecing the cells together into 2-foot-by-4-foot panels with glass covers.

Both Siemens and Solarex are beginning to sell a new type of module called "thin film," made by spraying solar electric material onto a glass plate in much the same way that one would apply a spray tint.

There are trade-offs, though. While the crystal-built modules cost more to make, they are much more efficient, converting 11 percent or more of the sunlight that hits them into electricity. The thin films currently are only 5 percent efficient.

Both companies are working to push up those percentages. Solarex Chairman and Chief Executive John Corsi believes his company can increase thin film's efficiency in two giant steps -- to 10 percent and eventually to 18 percent.

The dark horse in the race is Texas Instruments, which has a joint venture with Southern California Edison to develop solar technology.

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