The Cutting Edge: COMPUTING / TECHNOLOGY / INNOVATION : Enron Plan Focuses Light on the Improving Solar Cell : Energy: Firm says new methods can produce photovoltaic electric power at 25% of existing technologies' costs.


A surprising proposal by Enron Corp. to produce photovoltaic electric power for a quarter of the cost of existing technologies has refocused attention on the steadily improving solar cell.

After more than 15 years of development, photovoltaic cells are commonplace on hand-held calculators, satellites and in remote locations. But photovoltaic energy will have to be as cheap or cheaper than the 5.5 cents per kilowatt-hour that Enron aims to achieve if it is to reach the larger ambition of its proponents--to carve out a major role as a utility-size power generator.

"Time is on our side. A lot of people will be using it in the future," says Richard King, program manager for photovoltaic research at the Department of Energy. But in the meantime, King says, "there is the chicken-and-egg problem."

As long as it costs 25 cents a kilowatt-hour for solar cells to make energy--compared to 3.5 to 4.5 cents for the newest generation of natural gas turbines--utilities and their government regulators will remain reluctant to support large-scale generating arrays. Yet proponents say that the economies of scale from big installations would be a major factor in bringing costs down.

"It's a cottage industry," King says, "and you have to lift it out of that."

That's why the solar power world is abuzz over the Enron proposal. The Houston-based energy giant has proposed to build a 100-megawatt plant at the Department of Energy's Nevada test site near Las Vegas--huge by photovoltaic industry standards. And it says it can do so without research and development subsidies, though it does want a DOE contract to buy the power at the 5.5-cent price and tax-free bonds to help finance construction.

Enron, which just completed a mammoth 1,875-megawatt natural gas generating plant in England, would invest $150-million in the project, with an eye to exporting the technology to the energy-hungry developing world.

One measure of the impact of such a plant: Only 7 megawatts of photovoltaic electricity are now being fed into utility power lines worldwide.

Almost no one questions the technology itself anymore. The first solar cells were 6% efficient--that is, they converted to electricity 6% of the sunlight that fell on them. (The other solar technology, thermal, focuses the heat of the sun on water, oil or liquid salt, which in turn powers electricity-generating turbines.)

Today, standard photovoltaic cells are 12% to 14% efficient. Last week, the Electric Power Research Institute, which manages research for the nation's electric utilities, announced that Amonix Inc. of Torrance has a solar cell system that is more than 20% efficient. In the lab, experimental cells have reached 30%.

Once in place, solar panels have proven to be largely maintenance-free for two decades or more--and, of course, there are no fuel costs.

While Enron declines to give details of its cost-cutting technology, Kelly said the company's plan exploits economies of scale as well as improvements in the non-solar-cell parts of the system. But it would also involve one of the most widely watched research paths: development of so-called thin-film cells.

The most common photovoltaic technology uses crystalline silicon. The material must be expensively treated and formed into glass-hard ingots, which are then sliced with diamond saws and individually wired into a panel. These cells are the most efficient so far but are labor-intensive to produce and waste 20% of the ingot material in the cutting.

With thin-film technology, a very thin layer of the photovoltaic substance is usually sprayed directly on a glass panel, a procedure easily performed in an automated factory. So far, thin-film panels are no more than 6% to 10% efficient. Another approach, called spherical cell technology, has reached 10% efficiency as well.

"But thin film is certainly the technology that a lot of people feel holds the ultimate hope for less cost. . . . It just uses a whale of a lot less material," says Jim Birk, EPRI manager of renewables and hydro.

While utility-scale solar arrays are still not here, a few utilities are already finding uses for photovoltaic power.

The Sacramento Municipal Utility District now gets 2.6 megawatts of its total 844-megawatt load from photovoltaic facilities, including the world's largest existing plant--a 2-megawatt array at Rancho Seco, 30 miles from Sacramento.

Through Southern California Edison, customers who want lights in their mountain cabins without paying to bring in power lines can now lease solar cell systems set up and maintained by the utility.

Edison also recently set up solar panels at a neighborhood school in South Pasadena. The new power will augment existing lines in the area, which have reached capacity. The photovoltaic array is cost-effective compared to the disruption and expense of tearing up the streets to put in larger wires.

The idea is called distributed generation, and many proponents see it as the answer to the power demands of developing nations lacking their own fossil fuels or a way to avoid the high cost of national transmission grids like those in industrialized countries.

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