New 3M Inventions Target Solar Cell Technology

3M^TM is investing $200 million in new plastic film production as its targets a major business opportunity in solar and other renewable energy technologies.

The company recently completed a manufacturing expansion in Singapore for 3M Scotchshield^TM Film, a leading solar film critical to the manufacturing of crystalline silicon photovoltaic (PV) modules. A look at recent patents approvals shows that the Minnesota-based technology powerhouse is also quietly developing new products aimed at reducing cost and improving performance of solar cells

"3M draws upon decades of experience producing similar materials for other industries and applies this heritage to our line of renewable energy products," says Scott Norquist, manager of Energy Generation for the 3M Renewable Energy Div.

3M pioneered solar films 25 years ago, when scientists first developed solar energy and mirror films. The company also has significant experience in developing products for long-term exposure to outdoor environments and has substantial capabilities in weathering technologies.

In early 2009, 3M formed a Renewable Energy Division to coordinate applicable products across the company's 40-plus core technologies. It falls within 3M's Industrial and Transportation Business and focuses on energy generation and energy management. 3M offers films, tapes, coatings, encapsulants, sealants and adhesives for solar energy, wind energy, geothermal and biofuel businesses

3M has made several breakthroughs in concentrating light with inventions such as 3M Solar Concentrator Panels. In addition, 3M Mirror Films demonstrate potential to provide cost savings over similar glass-based systems.

Multilayer Film

Dyneon Scotchshield Film 17 utilizes a multilayer construction consisting of an outer fluoropolymer film bonded to a proprietary PET film, which is bonded to EVA film to complete the multilayer backsheet. This inner EVA layer of the backsheet bonds to EVA cell encapsulants during the PV module lamination process.

A U.S. patent awarded Dec. 29 to 3M Innovative Properties Co. shows the significant technical firepower 3M is putting into this market. The patent describes a multilayer film intended to improve protection of the back of a solar cell while overcome problems associated with previous designs such as high cost or difficulty in applying laminates.

The 3M multilayer film in the patent includes a polyester intermediate layer and outer layers of semi-crystalline fluoropolymer with a tensile modulus of less than 100,000 psi and an olefinic plastic, such as polypropylene. The layers could be produced through a conventional coextrusion process or via thermal lamination.

One of the key aspects of the new approach is the preshrinking of the polyester layer prior to thermal lamination. "Pre-shrinking of the film after the addition of other layers can become exceedingly difficult especially if one or more of the additional outer layers has a softening or melting point that is within the temperature range required to pre-shrink the intermediate layer," according to the 3M inventors.

The thickness of the individual layers within the multilayer film can be varied based on the requirements. 3M says it expects the outer layer of fluoropolymer will be from about 0.5 to 5 mils, preferably 1 to 2 mils thick; the intermediate layer will be from about 1 to 10 mils, preferably 2 to 4 mils; and the outer polyolefin layer will be from 1 to 20 mils or greater. Preferably it is 10 mils or greater.

3M is not the only American corporate giant making a major move in the photovoltaics area. DuPont said it expects its sales in solar energy to exceed $1 billion by 2012.