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Shedding new light on solar power

Posted: 23 Feb 2010     Print Version  Bookmark and Share

Keywords:Solar power  cell  technologies 

SunTech Power makes silicon-based solar modules using both less expensive polycrystalline silicon and its more expensive monocrystalline form. Its markets are residential and commercial applications, including building-integrated photovoltaic (BIPV). Its global headquarters is in Wuxi, China, and the firm has regional headquarters in California and Switzerland. It is building a 30MW plant in Arizona and is expanding its manufacturing plants in China with a goal of 1.4GW (photovoltaic cell and module capacity) by mid-2010.

SunTech's most exciting technology is a silicon-cell variation that it calls Pluto.

Figure 2

Figure 2: SunTech BIPV (Building Integrated Photovoltaic) installation. [Photo courtesy SunTech Power].

The company licensed the technology from the University of New South Wales in Australia. Like standard silicon cells, Pluto cells have metal lines to collect electrons, but Pluto's metal lines are both much narrower and closer together than standard metal lines. There are two benefits: the metal lines shade less of the underlying silicon, and the electrons have a shorter distance to travel to find a line (some electrons get lost along the way). SunTech is now producing Pluto cells that achieve efficiencies of about 17% for polycrystalline silicon and about 19% for monocrystalline silicon, values that have been confirmed by Germany's Fraunhofer Institute.

One very forward-looking SunTech product is a glass-on-glass thin-film product that can be used as the glazing on the side of an office building. It serves as a window (and, like sunglasses, comes in varying degrees of opacity) and has contacts at the sides of the windows. The efficiency is low— about 6%— and the technology is currently expensive, but it makes it possible to turn the side of a skyscraper into a giant solar plant.

SolarWorld has been producing and marketing silicon solar cells in the United States since 1977; its history is thus longer than the 25- or 30-year field life that solar firms typically claim for their photovoltaic installations. Today it manufactures what it likes to the call "the workhorse of the industry," a very reliable monocrystalline silicon cell with an efficiency of 14%.

To make its cells, SolarWorld etches the surface of the wafer to create pyramidal structures. The surface area that is able to capture incoming light is thereby increased. At some angles, the light is reflected from the pyramid faces, giving a second chance for it to be captured. This gives slightly higher efficiency, particularly in early morning and late afternoon.

The company pays attention to details, large and small. For example, its products are produced in the United States, and virtually all of the components are purchased within the United States, which reduces transportation costs substantially. Its plants are also highly automated, with the result that labour costs are only 10 per cent of their total costs.

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