U.S. Looks to the Sun for Energy Future

GOLDEN, Colorado, January 6, 2000 (ENS) - The solar photovoltaic industry in the United States wants to regain its lead in solar technology, a lead recently lost to other nations such as Australia, the European Union countries, Japan, and the Republic of Korea. To accomplish that the Department of Energy has published a five-year business plan for photovoltaic (PV) technology and outlined long range strategies and goals through the year 2020 entitled "Energy for the New Milleneum."

"The challenge we face in this century is to enable PV to go as far as any other energy technology here on Earth by making the scientific and technological advances that will put PV on every rooftop and in every corner of the globe," says James Rannels, director of the Solar Energy Technologies office at the Department of Energy's (DOE) National Renewable Energy Laboratory in Golden, Colorado.

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Kannan Ramanathan works at a physical vapor deposition system for making PV cells. These systems are used to make cells from copper indium diselenide. They were used to fabricate 17.7 percent efficient cells - a world record for thin-film solar cells. (Photo courtesy National Renewable Energy Lab)
The plan envisions making photovoltaic absorbers less than one micrometer thick on long, thin, flexible sheets, or mass producing square miles per year of inexpensive, efficient PV modules.

To achieve the goals of the program, the U.S. industry must maintain an annual production growth rate of 25 percent and must ship seven gigawatts of solar panels this year, of which almost half would be used in domestic installations.

Total costs including operation and maintenance to the end user of the solar technologies must drop to $3 per watt by 2010 and to $1.50 by 2020, the DOE plan says.

By 2030, module efficiency must reach 25 percent and system costs must drop to $1 per watt. Currently, costs are variable but much higher.

In today's laboratories expensive experimental cells have achieved efficiencies as high as 24.7 percent, and commercially produced cells typically have efficiencies less than 16 percent. The trick is to develop fabrication processes and device structures that can translate some of the performance features of laboratory cells into manufacturing.

The DOE plan would spend research and development funds on thin films, high-performance devices, silicon materials, characterization techniques, and innovative concepts that will deliver the low-cost, high efficiency photovoltaics of the future.

The plan specifies that its success depends on developing photovoltaics to meet the needs of the utilities for delivery over the existing power grid. Grid-tied systems should produce the high quality alternating current (AC) signal now universally used in homes and businesses instead of the direct current (DC) produced by today's photovoltaics.

Right now, architects, engineers, and builders are incorporating photovoltaics into their building designs. But more must be done for this concept to become widespread, the DOE plan acknowledges.

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The new building at 4 Times Square in New York integrates thin film PV panels into the mirror glass spandrels from the 35th to 48th floor. The panels produce 1.5% of the building‘s electrical needs. (Photo courtesy DOE)
Costs must drop and the PV industry must pay close attention to the needs of the buildings industry, by making sure their products meet codes, standards, and insurance requirements, and that they design new products that meet real building needs.

The DOE's program, the PV industry, and the buildings industry are cooperating to develop cost-effective systems that blend well with building materials and components. There will be

Global PV sales in 1998 exceeded 150 MW, resulting in revenue of $1.5 billion. The annual growth rate of 20 percent over the past five years is just the beginning, the plan states.

At an annual growth rate of 25 percent, global annual shipments would approach 18,000 MW by 2020, with sales of $27 billion.

The DOE plan predicts that U.S. shipments would reach 7,000 MW by 2020.

"The race for technology and market leadership, however, will be hard fought," warns the DOE plan. "Although PV technology is American born and bred, and although the United States has long been the technological leader, any nation that makes the commitment can build a PV industry." Those countries would create domestic jobs, export energy technology, keep energy dollars at home for further domestic investment, and reap the ancillary economic benefits of controlling a technology whose impact will reach well beyond energy.

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PV shingle by United Solar Systems Corporation. The shingle modules blend so well with conventional roofing that they can be used on new homes where covenants would prohibit more typical PV modules. (Photo courtesy United Solar Systems Corporation)
Greater use of PV will offset carbon dioxide emissions, and building a solar infrastructure "will provide insurance against global warming and climate change." A four kW system can supply power for a typical home in the U.S. and displaces the same amount of carbon as a family car.

"But the promise of PV goes well beyond electricity," the DOE plan adds. The technology can be integrated with electrochromic windows to conserve energy while generating electricity, and can be used to electrolyze hydrogen from water which can be used in fuel cells.

But solar cell manufacturing technologies are not environmentally benign. The manufacturing of semiconductor silicon devices - from polysilicon production, crystal growth, ingot slicing, wafer cleaning, device processing, to encapsulation - requires many steps that are energy intensive and use large amounts of water and toxic chemicals.

In a joint paper presented at the 2nd World Conference and Exhibition on Photovoltaic Solar Energy Conversion, July 1998 in Vienna, Austria, six scientists from the National Renewable Energy Laboratory, Sandia National Laboratories, National Agency for New Technologies Energy & Environment, and the Intersoloarcenter said it is time to clean up the photovoltaics industry. The paper is authored by Y.S. Tsuo, J.M. Gee, P. Menna, D.S. Strevkov, A. Pinov, and V. Zadde.

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Solar Cells, Inc., a manufacturer of cadmium telluride solar panels, is working with National Renewable Energy Lab to improve its product. (Photo courtesy Solar Cells, Inc.)
"Because solar electricity generation is a large-area application, it is likely the PV industry will eventually use more silicon than even the integrated-circuits industry. It is important at this stage to review the environmental impact of the rapidly growing silicon PV industry and to find opportunities for improving the energy efficiency and productivity and reducing environmental impact," they said.

These scientists proposed that the silicon PV industry form an association of government laboratories, equipment suppliers, and cell and module manufacturers to promote more environmentally benign manufacturing approaches. "This association can also coordinate PV industry’s interactions with the environmental associations of the integrated-circuits and printed-circuit-board industries."

"In the PV community, there is a sense of excitement and challenge - the same feeling members of the Apollo program must have felt at the start of the moon race," says Rannels. "Like the space program, a balanced, aggressive PV research and development program has the potential to open a new frontier here on Earth."

The DOE's plan, "Energy for a New Millenium" is available online at: http://www.nrel.gov/ncpv/pdfs/25847X.pdf