Accomplishments in Photovoltaic Manufacturing R&D
Successful efforts within the PV Manufacturing R&D Project were recognized by the solar industry. Key highlights from the project are summarized below.
Overall, the project resulted in a more than 50% reduction in manufacturing costs and a substantial return on investment for both the U.S. government and the industries involved. A number of companies participating in the project were able to make technological advances that helped them attract millions of dollars in private investment capital.
Solar Cells and Modules
Advances in solar cells and modules were made that significantly reduced the cost of solar modules while increasing their reliability and performance. Below are examples of the progress made in cell and module technology.
Dow Corning—Developed a clear, protective laminate (encapsulant) for solar modules that provides electrical, high-temperature, and ultraviolet stability with no discoloration. In short, the new laminate allowed the sun's rays (and other environmental elements) to strike the solar module without overheating it and reducing electrical performance.
SolarWorld—Developed a new boron coating process for solar cells that replaced the more expensive and complex traditional aluminum backing.
SunPower—Introduced an antireflective glass to its module design, resulting in a module with a 223-watt power output and a corresponding 17.9% total-area efficiency.
Half the cost of producing a solar module is incurred in wafer production and another 20% is added in the cell processing steps. New manufacturing processes developed by project partners marked significant progress in module cost reduction. A few notable examples follow.
BP Solar—Developed a solar module manufacturing process called "Mono2 technology" that boosts the power production of silicon solar modules by 8% without increasing costs. The company also developed a wire process for cutting solar wafers that reduced the amount of silicon that ended up as "sawdust." The wire-process equipment is standard in the silicon industry today.
Evergreen Solar—Developed a unique manufacturing process for crystalline silicon wafers using a "dual string-ribbon" growth process. One element of the system, a new contact-printing machine, increased throughput by 70%.
GE Energy—Developed a metal wrap-through process for GE solar cell manufacturing that allows GE to make individual "molded wafers." The molded wafers enable a more efficient use of space on the module (i.e., less wasted space) than the traditional wafer design, increasing the conversion efficiency of the module and reducing costs.
Shell Solar—Added a thin (125 microns) wafer-cutting wire to its pilot production mode, giving an increase of almost 8% in watts produced per kilogram of silicon for a significant cost improvement; demonstrated a production increase of more than 6% for about 500 saw runs.
Sinton Consulting—Developed an in-line monitoring tool that measures indicators of cell performance during manufacture of silicon blocks and wafers. Use of the WCT-100 tool allows unacceptable materials to be pulled from the manufacturing line before incurring the expense of converting the wafer to a cell. Several of these tools have been sold to industry, resulting in cost savings within a month of purchase.
Spire—Developed the SPI-Assembler™ 5000, a machine that assembled and soldered silicon cells into strings, which replaced a step that had formerly been done manually. The machine resulted in a fivefold decrease in module costs.
The integration of solar modules onto a rooftop also contributes to greater cost. Many innovative system-integration technologies were developed under the project, including those described below.
PowerLight (Now SunPower)—Developed lightweight and insulating PowerGuard tiles that can be roof-mounted without mechanical fastening. This new systems-integration technology significantly reduced the cost of large commercial PV systems.
Schott Solar—Developed "plug and play" system integration features for solar modules. Schott's "free-standing" PV array roof-mounting system requires no roof penetration and allows modules to track the sun or adapt to severe weather conditions. Schott also developed new PV array circuit-combiner boxes and fasteners used to secure mounting brackets to residential roofs.
New inverters, charge controllers, power supplies, and other PV system components were introduced by this project, including some notable examples below.
Ascension Technology/ASE Americas (now RWE SCHOTT Solar)—Developed a PV module called the SunSine™ 300 with a built-in alternating current inverter. PV modules naturally produce direct current and require an inverter to produce the alternating current used by the electrical grid. The SunSine 300 represented the first time a PV module and inverter were sold as a self-contained unit.
Xantrex Technology—Developed a high-reliability, system-integrated 500-kW PV inverter suitable for use in a multi-megawatt PV power plant.