High velocity forming of fuel cell plates
A production process, based on high velocity metal forming, can
manufacture fuel cell bipolar plates in a fraction of the time normally
required, according to a technology firm in the USA. This could also
make fuel cell production cheaper.
American Trim (Amtrim), based in Lima, worked with the Ohio State University (OSU) and General Motors to devise the system, which involves accelerating a sheet of metal into a die to instantaneously form a detailed shape.
‘High velocity metal forming allows materials to be formed while they are in the hyper plastic state,’ explains Steve Hatkevich, Director of Research and Development at Amtrim. ‘This, coupled with the uniform strain distribution, allows deeper forms to be achieved versus traditional approaches.’
The technique was developed by Dr Glenn Daehn at OSU, and Amtrim has spent the past five years making his system more robust. ‘The actuator (which delivers forming force to the substrate) was [initially] complex and had a limited life,’ notes Hatkevich. Amtrim claims to have extended its life to over 100,000 uses.
Once fully optimised, the researchers believe their machinery could create a bipolar fuel cell plate in six seconds, as opposed to the 15 minutes required in non-automated processes. ‘The capital cost of HVMF equipment is around 10% of the cost of traditional forming equipment, and the energy requirement is less than 10%,’ adds Hatkevich.
The bipolar plate, used to channel hydrogen to the anode and oxidants to the cathode, forms the largest part of a polymer electrolyte membrane fuel cell – up to 150 plates go into a single cell. It is traditionally made from a carbon-polymer or graphite using injection moulding or CNC milling, which can be time-consuming and costly.
The HVMF enables the use of cheaper metals. The materials investigated by Amtrim so far include stainless steel and iron alloys, as well as aluminium and copper.
Dr Dan Brett, Co-Director of The Centre for CO2 Technology at University College London, UK, says the speed of production and potential dimensional tolerance of the Amtrim plates shows promise.
‘However, are they thinking about the internal fuel cell environment? It is very corrosive, and only a few metals would be suitable. They would also need to be coated, which would add another [costly] step to the process.’
The company aims to build a full-scale commercial machine by the end of 2009.
Further information: Amtrim