GE’s ecomagination* Initiative and Lexan* EXL9330 Resin Help Keep Solar-Panel Battery Connection Boxes Protected and Looking Good

With oil and natural gas prices soaring, interest in alternative energy sources like photovoltaics (solar technology) is climbing rapidly. Solar energy is cleaner, less polluting, and does not negatively impact the environment. It can be a good source of primary or supplemental energy in both urban and rural locations. China is becoming a major manufacturer and exporter of solar devices, exporting over 90 percent of these units around the globe. A newly ratified Renewable Energy Law in China is expected to drive domestic consumption of solar technology rapidly.

When well-known solar-panel manufacturer - Canadian Solar Inc.’s Chinese subsidiary, CSI Solar Technologies Ltd. - needed a tough but good-looking cover material for its solar-module battery connection box, the company selected GE’s Lexan* EXL9330 resin. No domestic polycarbonate (PC) that CSI tested could meet all of the company’s specifications for low-temperature toughness, aesthetics, electrical properties, and flame-retardancy that supports global environmental initiatives. Since solar modules are positioned outdoors in a variety of harsh conditions, their components must be able to withstand weathering and possible damage while also maintaining high-quality, long-term aesthetics. Since CSI’s units are sold around the world, the module also had to be able to meet global standards for quality and safety.

GE-Plastics and Canadian Solar Inc.

Founded in 2001 as a spin-off from Automation Tooling Systems Inc. — one of the world’s leading factory automation companies and solar producers — Canadian Solar Inc. (CSI) is a solar-energy manufacturer and application developer that serves customers globally. The company’s headquarters, R&D, and customer-service operations are located in St-Laurent, Quebec, Canada, while manufacturing operations are located in Changshu, Jiangsu, China. CSI has become a major provider of integrated solar devices for specialty applications, such as telecommunication signaling and automobiles. These applications are often used in severe conditions and subjected to extreme temperatures, vibration, and chemical exposure. Hence materials used in the company’s solar components must be tough, dependable, and aesthetically pleasing.

CSI was faced with the challenge of finding a material that would meet international standards, since 90 percent of China's solar cell production is for export. The box is mounted on the back of solar modules and holds batteries, which collect and temporarily store electricity generated by the photovoltaic cells in the module, then transmit the energy to a central control device. The company required the box provide low-temperature impact strength to –40 C, good weatherability without the need for paint, dimensional stability, a comparative tracking index (CTI) of two, and a UL94 5VA flame-retardancy listing at three mm in a formulation that meets global environmental standards.

Initially, CSI evaluated flame-retardant PC materials produced by companies based in China. However, no product tested by CSI met all of their performance requirements. The company then turned to GE. As one of its ecomagination* initiatives — a new global effort to help customers solve tough environmental challenges — a local GE team from China worked closely with CSI to understand the application’s requirements, so CSI could identify a candidate material that met their criteria. GE then worked with sales to provide an immediate supply, and provided processing support to help ensure the application launched smoothly and successfully.

The material chosen for the battery connection box housing was GE’s Lexan EXL9330 resin, a copolymer of PC and siloxane. This material combines the best of PC and silicone chemistry to produce a thermoplastic resin with exceptional low-temperature toughness to –60 C, excellent and long-term weatherability, excellent dimensional stability, a CTI value of two required by the customer, and UL94 5VA flame retardancy at three mm walls.

GE’s Lexan EXL9330 uses a non-halogenated (non-brominated, non-chlorinated) flame-retardant package that is intended for conformance with environmental standards such as the Restriction of Certain Hazardous Substances (RoHS) and Waste Electrical & Electronic Equipment (WEEE). This grade is currently being evaluated under European TUV Rheinland standards and will then be submitted for review under the International Electrotechnical Commission (IEC) standards.

According to Brian Lu, General Manager of CSI Solar Technologies Inc., “At CSI we pride ourselves in working closely with our customers to understand their needs and provide a solar solution that works. We received this same level of service from GE in helping us identify the right material for our solar-module battery connection box. Since our products are shipped around the world, it was very important that the polymer we chose meet global safety requirements. And because our solar modules often are mounted in challenging environments, we needed a cover material that would function well and maintain aesthetics long-term. GE’s Lexan EXL9330 resin does all of this and more. We were also very pleased we could find a formulation that is intended for conformance with tough environmental standards. Photovoltaics is one of the cleanest energy-producing technologies, so we wanted to use materials that could help support environmental initiatives.”

GE’s Lexan EXL9330 resin is an opaque PC / siloxane. It carries UL flame-retardancy ratings of F1 / V-0 / 5VA in a non-halogenated, formulation that is intended for conformance with environmental standards such as ROHS and WEEE. The thermoplastic copolymer can be used interchangeably in a tool cut for conventional flame-retarded PC since it has the same shrinkage value. At the end of product life, the parts molded of this material can be disassembled and recycled.

Details at www.csisolar.com.

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+31 164 29 20 97

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