BioSolar makes PV backsheet from beans and cotton

15 Aug 2008

Backsheets made from renewable biomaterials could be more cost effective than petroleum-based films for crystalline silicon solar cells.

biomaterial backsheet

BioBacksheet, a solar cell backsheet derived from cotton and castor beans, could drastically improve the cost-effectiveness of solar cells by replacing traditional backsheet materials, according to its US developer BioSolar.

"As far as PV module components are concerned, there has not been anything similar to BioBacksheet," David Lee of BioSolar told optics.org. "Our eventual goal is to reduce the cost compared with petroleum-based components by as much as 50%."

Backsheets are used to protect the back of PV solar modules, and are commonly made from petroleum-based films. As oil prices fluctuate, so the cost of such materials affects the ultimate cost of solar cell manufacture. BioSolar has been working to produce bio-based materials from renewable resources that could be used instead, and so reduce the cost per watt of the power generated.

BioSolar's material blends a type of nylon made from castor beans with a cellulose film derived from cotton rags. Despite such humble origins, the materials are said to meet or exceed the characteristics and performance requirements for the PV industry.

"The thermal properties, moisture barrier properties and mechanical behaviour of the sheet are all equally critical," said Lee. "It also has to provide adequate electrical insulation and good adhesion during and after lamination."

BioSolar believes that the market for backsheets will be worth $1 billion by 2010.

"Our initial production of BioBacksheet should be able to provide a 25% cost saving to PV module manufacturers over their current materials," commented Lee. "Faced with severe pressure to cut costs whenever possible, we feel that module manufacturers will be open to 25% cost savings on any component they are currently using."

BioSolar is currently focusing on providing backsheets to crystalline silicon PV manufacturers, although according to Lee applications in the thin-film sector could also follow.

"BioBacksheet should cover 95% of the present PV market in its current form," he said. "Most non-silicon based thin-film applications require extremely high moisture barrier and high temperature resistance, and we will address that market in the future."