Solar Energy System of the Month:

CIS-Solar Cells From the Assembly Line:
Pilot Factory for Thin Layer Modules Starts Production

A new chapter in solar technology history is being written in Marbach on Neckar. The Würth Solar GmbH and Co. KG opened their pilot factory to manufacture CIS Thin Layer Solar Modules on June 19, 2000 .

CIS pilot factory, Technology Park Marbach

Technology Park Marbach. Location of the CIS pilot factory from Würth Solar.
Thin layer modules with an entire surface area of 10,000 square meters will be manufactured here.

Illustration: Würth Solar

The new technology allows the rational production of high quality and long lasting solar cells with low material and energy expenditures. The important features of the product line are efficiency, quality and versatility. Würth Solar wants to bring the first CIS modules on the market as soon as August 2000.

CIS: High Tech for a Sunny Future

The thin layer cells are made predominately out of the elements copper, indium and selenium. The chemical symbol is CuInSe2. In comparison to the well-known, shiny blue, polycrystalline silicon cell, which features a 12-14% rate of efficiency, the material and energy production expenses are considerably lower.

Structure of a CIS solar cell
Structure of a CIS solar cell.
Illustration: Würth Solar

CIS cells, Uses for
Uses for CIS cells

CIS cells are ten times thinner than polycrystalline cells. Their photo active layer is deposited directly on pieces of standard window glass. Just like the red-brown amorphous silicon cells- which are found in calculators and clocks- the CIS cells are produced in thin, material-saving layers. However, the CIS cells considerably outperform the efficiency of standard amorphous silicon cells on an average of 6 percent: in the laboratory of the Center for Sun Energy and Hydrogen Research (Zentrum für Sonnenenergie- und Wasserstoff-Forschung-ZSW) at the University of Stuttgart, a square CIS module with a length of 30 centimeters achieved almost 13% efficiency. That is the current "world record".

Elements are being produced in the new factory that measure 60 by 120 centimeters. The manufacturer wants to raise the efficiency from the current 8 percent to 10, and later even to12 percent. Bernhard Dimmler, technical manager of Würth Solar, has calculated a yearly output of at least 1.2 megawatts of power during the pilot phase. That would conform with approximately 10,000 square meters of module surface, or the electricity consumption of 300 households.

The Turning Point: Solar Technology Production in a Former
Coal-Fired Power Station

The cooperative project from Würth Solar, the EnBW Kraftwerk AG and the ZSW is pointing the way into the future. Using former buildings from the EnBW and in cooperation with the city of Marbach, a model project was developed to convert a power station site. 11 other companies will be active in the future energy and technology park, next to the solar factory, which first gave it momentum.

Solar modules will now be built, where fossil resources once burned. A project on fuel cell technology will also be represented. The technology of yesterday is giving way to the technology of tomorrow. The generators in the former boiler room of the coal-fired power station Marbach I have been shut down. Instead, Würth solar cells are being manufactured here in dust-free rooms.

The system for manufacturing the CIS cells
The system for manufacturing the CIS module being delivered to the boiler room in the former coal-fired power station.
Illustration: Würth Solar

The company sees itself as a development partner and know-how supplier for photovoltaic producers who want to solve system problems with CIS technology. Würth Solar intends to invest approximately 30 million marks in the project; the system technology alone already costs 18 million marks. Another 12 million marks are furthermore estimated for the reconstruction of the building and running costs.

Würth Solar's competative edge is exhibited by their achievement of the layering of a one-thousandth of a millimeter thin light sensitive film. Up until then, CIS cells were layered and alloyed in several steps. At Marbach, this step takes place in one process: copper, indium, and selenium are vaporized at the same time under absolute vacuum conditions at 500° Celsius. The elements then adhere to a plate of two to four millimeter thick window glass, that has already been coated with a backing pin of the metal molybdenum. The layers are then "apportioned" with laser beams and then fixed to the desired tension. Afterwards a transparent contact layer of zinc oxide is applied, the module is then packed between the treated and an untreated glass plate. Sealed in this way, it will be protected against environmental influences for a long time.

The goal is to make solar energy marketable. Würth solar is moving in a new direction.

Logo: Würth Solar

CIS system in the dust-free room
The CIS system in the dust-free room
Illustration: Würth Solar

Bright Prospects for Photovoltaics

Würth is expecting a considerable reduction in costs from the mass production of thin layer modules. CIS modules should soon be offered for much less than customary products. Photovoltaic has already cleared most of the hurdles of profitability anyway. State support and growing environmental awareness are boosting demand. Lower prices would strengthen the trend for one's own solar power station even more.
"We are deliberately investing in future technology, that we regard as elementarily important. But as a company, we have, of course, success as our aim," stated Rolf Bauer, who is responsible for the solar company in the Würth corporation, at the inauguration of the solar factory. Next to production, Würth Solar is also striving for the worldwide distribution of portable systems. These should come into use where no electrical grid is available, such as in developing countries.

Illustrations and material: Würth Solar GmbH & Co. KG. Red. Solarserver. Rolf Hug
Translation: Mary Meier

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