So far the company has demonstrated the process only on relatively small, 15-centimeter-wide solar modules. Its goal for early next year is to build a factory to produce, first, 30-centimeter modules, and later--most likely sometime after June--prototypes of modules that are about three-quarters of a square meter (60 by 120 centimeters). The larger size is necessary for bringing the product in line with standard module sizes, making them cheaper to install. The factory will be designed to produce enough cells per year to generate 20 megawatts of electricity at first, and eventually 40 megawatts. A typical wind turbine, in comparison, might generate two megawatts of electricity.

The first of the company's large cells will have efficiencies of 10 to 12 percent, Stanbery estimates, or slightly better than other thin-film solar cells. In 10 years, he expects those figures to increase to 13 to 15 percent, or good enough to compete with some types of conventional silicon solar cells. Stanbery also expects to manufacture cells for less than First Solar, a Phoenix, AZ-based maker of a different type of thin-film solar cell that has seen high demand for its products. (See "Thin Film's Time in the Sun.")

Ultimately, the most important figure is the cost of electricity from the cells once they've been installed--the bottom-line cost for customers. Heliovolt is at too early a stage to provide concrete information, since this cost depends on a number of factors in addition to the cost of the modules, including the cost of installation and other hardware. But the company's target is to reach 15 cents per kilowatt hour of electricity by 2010. That's less than the cost of grid electricity in half of the world's markets, according to an industry report. This goal puts the company in a race with conventional solar cells, which, according to the report, could reach similar costs by that time. Currently, the cost of solar electricity is about 25 cents per kilowatt hour. To further cut costs, Heliovolt intends to incorporate the solar modules into building materials, such as the glass facades on skyscrapers.