Composites being considered for solar backsheet applications

BioSolar has launched a composites-based material for use as the backsheet of crystalline silicon photovoltaic solar cells.

BioSolar Inc. (Santa Clarita, Calif., USA) has announced the launch of a composites-based material for use as the backsheet of crystalline silicon (c-Si) photovoltaic solar cells, the most commonly used solar cell type on the market.

Solar cell backsheets are required to withstand cycling of heat and damp conditions to maintain the integrity of the cell structure. Backsheets are traditionally manufactured of layers of Kevlar, polyester and Kevlar in a multilayer format that can be expensive and cumbersome to produce.

BioSolar's alternative is a bio-based nylon 11 derived from castor beans with a platelet-type talc filler at loadings of up to 40 percent. The backsheet is produced via extrusion, a process with which the company can align the talc platelets to provide desired moisture and dielectric properties.

Dr. Stan Levy, vice president and chief technology officer at BioSolar, says the company is working with a testing partner to assess the viability of the material and will submit the backsheets to UL test 1703, known as the Damp Heat Test. In this test, the material is subjected to an environment of 85°C/185°F ad 85 percent humidity for 1,000 hours. The material is expected to pass this test and Levy says BioSolar may add 1,000 hours to the evaluation to further establish the material's robustness. In-house testing, he says, has already proved the material's viability.

Savings, says Levy, could be in the 20 to 25 percent range, compared to Kevlar/polyester combinations. Extrusion of the material is being done by an outside firm right now, but BioSolar hopes to bring that function in-house soon. Assuming all UL testing goes well, BioSolar will start taking orders in Q3 for delivery in Q4 2010.

Looking ahead, BioSolar is evaluating use of glass fiber in the bio-based nylon 11, and is working on a clear material to be used in the facesheet covering and protecting solar cells. The company also would like to develop backsheet material for thin-film solar cells, which are rapidly gaining favor in the solar energy community.