TOKYO - JFE Steel Corporation today announced that it has succeeded in manufacturing silicon feedstock (SOG*1) silicon) used in ingot wafers for solar cells. The company has started construction of a commercial plant with capacity of 100 tons/year and has also begun designing a plant to mass produce the material.
The Kyoto Protocol, which was adopted in 1997 to provide a mechanism for counteracting global warming, took effect in February 2005. Japan's CO2 emissions are forecast to reach 1.31 billion tons by 2010, which will be 150 million tons over its target of 1.16 billion tons under the protocol. The national plan adopted in April 2005 to achieve the Kyoto Protocol targets therefore calls for the adoption of new energy sources to cover 47 million tons, or approximately 1/3 of the 150 million ton excess. These new energy sources include solar cells, wind power and biomass generation. Solar cells alone are expected to reduce CO2 emissions by at least 2.6 million tons.
Solar cells are gaining wider usage around the world, particularly rapid in Germany and other European countries, which lead conservation efforts and have systems for purchasing excess generation capacity at high prices. The result has been global tightening supplies of polysilicon and other feedstock used in the production of solar cells.
JFE Steel began using a proprietary unidirectional solidification process to produce silicon ingots in 2001 and has since become one of the world's leading ingot manufacturers in terms of production volume. To stabilize increasingly tight supplies of feedstock, it began to investigate techniques for producing SOG silicon in-house from metallic silicon, thereby providing an alternative to polysilicon. Prototypes created with 100% metallic silicon have achieved the same high conversion efficiency*2) as conventional polysilicon units, leading to the startup in October of a commercial plant with capacity of 100 tons/year. JFE Steel has also begun designing a mass production plant.
The manufacturing technology used in the commercial plant is the result of a research and development project commissioned by the New Energy and Industrial Technology Development Organization (NEDO), and conducted until 2001. JFE Steel improved on this technology and boosted its refining capacity so as to meet increasingly demanding quality requirements.
JFE Steel will use the new technology and increased capacity to provide stable supplies of high-performance, high-quality polycrystal silicon ingot wafers.
*1) SOG silicon:
Solar grade silicon. Silicon feedstock of sufficient quality for utilization only in solar cells, in contrast to polysilicon, which can be used in both semiconductor wafers and solar cell wafers. Unlike polysilicon, which is manufactured in chemical plants using only one method, a chemical vapor deposition (CVD) process based on the Siemens method, there are several ways to produce SOG silicon, including the metallurgical process developed by JFE Steel.
*2) Conversion efficiency:
The rate at which solar cells convert irradiated light energy to electrical energy. For example, conversion efficiency of 10% means that 1 kW/m2 of light energy (the energy from sunlight on a clear day) will produce 100 W of electrical energy when irradiated on a 1 m2 solar cell.
Solar Cell Panel Production Flow Chart
Global Solar Cell Production by Year