String ribbon
Encyclopedia
String Ribbon solar cells is proprietary technology developed by Evergreen Solar
.
The name describes the manufacturing process, where high temperature resistant wires are pulled through molten
silicon to form a multi-crystalline ribbon
of silicon crystals. The ribbon is then cut into lengths which are treated with traditional processes to form solar cell
s.
String Ribbon has the capability of using less silicon compared to other wafer production methods as wafers are manufactured to the approximately correct specification avoiding the need for sawing of silicon blocks. Silicon accounts for more than 50% of manufacturing costs in producing first generation solar cells, where much of the silicon is discarded as waste at the sawing stage of manufacture. Employing the string ribbon process allows the manufacture of PV grade silicon wafers to the approximate dimensions while avoiding the waste encountered when sawing wafers from ingots. This manufacturing process uses about half the amount of input silicon required by traditional processes.
String Ribbon technology offers a less expensive manufacturing technique but is not capable of achieving the same electrical performance as wafer technology. Typically a cut wafer will convert 15-16% of the incoming light into electricity where String Ribbon Solar Cells are capable of converting 13-14%. In research laboratories the technology has reached as high as 18.3%, however it cannot be produced commercially to this specification. Wafer technologies have reached as high as 25% in laboratory conditions.
While String Ribbon technology has certain advantages as to the shape of the crystals, the overall thickness varies enough so that not every 'silicon strip' can be processed directly into a solar cell. In addition to this drawback, the growth process is thermally very inefficient. The radiating area/gram of crystal is extremely high, leading to very high energy expenses which offset the reduced silicon use/expense.
Evergreen Solar
Evergreen Solar, Inc. is a publicly-held U.S. company which specializes in solar energy. It trades on the NASDAQ under the ticker symbol ESLRD....
.
Technology description
String ribbon is a method of producing multi-crystalline silicon strips suitable for the photovoltaic industry.The name describes the manufacturing process, where high temperature resistant wires are pulled through molten
Mölten
Mölten is a comune in South Tyrol in the Italian region Trentino-Alto Adige/Südtirol, located about 60 km north of Trento and about 12 km northwest of Bolzano .-Geography:...
silicon to form a multi-crystalline ribbon
Ribbon
A ribbon or riband is a thin band of material, typically cloth but also plastic or sometimes metal, used primarily for binding and tying. Cloth ribbons, most commonly silk, are often used in connection with clothing, but are also applied for innumerable useful, ornamental and symbolic purposes...
of silicon crystals. The ribbon is then cut into lengths which are treated with traditional processes to form solar cell
Solar cell
A solar cell is a solid state electrical device that converts the energy of light directly into electricity by the photovoltaic effect....
s.
String Ribbon has the capability of using less silicon compared to other wafer production methods as wafers are manufactured to the approximately correct specification avoiding the need for sawing of silicon blocks. Silicon accounts for more than 50% of manufacturing costs in producing first generation solar cells, where much of the silicon is discarded as waste at the sawing stage of manufacture. Employing the string ribbon process allows the manufacture of PV grade silicon wafers to the approximate dimensions while avoiding the waste encountered when sawing wafers from ingots. This manufacturing process uses about half the amount of input silicon required by traditional processes.
String Ribbon technology offers a less expensive manufacturing technique but is not capable of achieving the same electrical performance as wafer technology. Typically a cut wafer will convert 15-16% of the incoming light into electricity where String Ribbon Solar Cells are capable of converting 13-14%. In research laboratories the technology has reached as high as 18.3%, however it cannot be produced commercially to this specification. Wafer technologies have reached as high as 25% in laboratory conditions.
While String Ribbon technology has certain advantages as to the shape of the crystals, the overall thickness varies enough so that not every 'silicon strip' can be processed directly into a solar cell. In addition to this drawback, the growth process is thermally very inefficient. The radiating area/gram of crystal is extremely high, leading to very high energy expenses which offset the reduced silicon use/expense.
Production estimates
| Year | Production Capacity | Production | Installed Capacity |
|---|---|---|---|
| 2006 | - | 28 MW | - |
| 2007 | 107 MW | 66.2 MW | - |
| 2008 | 188 MW | 125 MW |