Will plastics help make fuel cells a reality?

Electrophen injection moulded bipolar plates manufactured by Bac2. The UK company says it can deliver a range of standard plate sizes for prototype fuel cell construction within 48 hours.

In September, the German fuel cell developer ZBT opened a new E6m technical centre for development of fuel cell production technologies alongside its existing building at Duisburg university. This includes injection moulding facilities to produce graphite filled thermoplastic (polyamide) bipolar plates.

According to ZBT, which was set up in 2003 and now employs a staff of 70, the new TAZ Test Application and Assembly centre is needed as fuel cell stacks and systems can only be manufactured with high reproducibility by automated, highly precise manufacturing processes.

It says the TAZ centre means it will have complete control of the process cycle from incoming components, material inspection and automated flexible manufacturing, through to quality control and documentation.

ZBT is currently testing components and fuel cell systems for auxiliary power units and decentralised power generation systems under simulated environments in the new facility, which was financed by the federal German state of North-Rhine-Westphalia and the European Union.

One limiting factor in the development of fuel cell applications is the ability to quickly develop prototype power units. That is a challenge that UK-based Bac2 hopes to address by offering its Electrophen conductive polymer bipolar plates in a “blank” format for machining for prototype cells.

It is now able to deliver three sizes of plate – 60mm by 40mm by 1mm, 150mm by 150mm by 2mm and 300mm by 300mm by 3mm. The company says all of the prototype plates can be delivered within 48 hours if in stock, or can be produced on its 80-tonne compression moulding press within 28 days.

Bac2 chairman James Lewis says ElectroPhen plates are made simply by mixing graphite with the resin and moulding. There is no need for the high temperature graphite exfoliation processing techniques employed by some competitor technologies.

The prototype machined plates can be used to optimise final designs prior to commiting to moulded alternatives. The final moulded plates do not require any further machining or processing prior to assembly into fuel cell stacks, which is an important factor when the bipolar plates typically account for up to 30% of the cost of a proton exchange membrane (PEM) fuel cell stack

BaC2 says its ElectroPhen bipolar plates, with in-plane and through-plane conductivity values of 350 S/cm and 20 S/cm respectively, exceed US Department of Energy (DoE) automotive specifications by a comfortable margin. They also provide a flexural strength value of 30MPa and compressive strength of 75 MPa and are stable up to 150 °C.

One of the latest – and unusual – applications of PEM fuel cell stack technology can be found on the Antares DLR-H2 electrically powered aircraft. Developed by the DLR aerospace centre in Germany and powered by a Celtec-P MEA (membrane electrode assembly) from BASF, it took off from Stuttgart airport for the first time in September.

The Celtec-P fuel cell system uses a polybenzimidazole (PBI) membrane with phosphoric acid and operates in a temperature range of 120-180°C. The PBI consists of an interpenetrating network of polyvinylphosphonic acid and was developed by PEMEAS, since acquired by BASF, for direct methanol fuel cells as an alternative to Nafion 117 membranes.

BASF Fuel Cells provided the high temperature MEAs for Antares – it claims to be the sole supplier of this type of MEA – while Serenergy in Denmark assembled the MEAs into the compact, air-cooled stacks. BASF offers three versions of its Celtec-P MEAs ranging from 100W micro fuel cells up to 100W stationary CHP type units and larger backup power supplies reaching up to 10 kW.

While the technology has been demonstrated in the light aircraft power application, DLR expects Celtec-P fuels cells to find real applications in auxiliary combined heat and power (CHP) units, where several cells could replace on-board turbine generators.

A first development step has involved the use of fuel cells for the emergency energy supply to the hydraulic pumps that control DLR’s own Airbus A320 ATRA research aircraft.

In a separate move, the German federal transport and town development ministry has given the green light to the E86m Callux project, which involves a trial of 800 combined heat and power (CHP) cogeneration fuel cell systems in the cellars of single family homes. The project is a part of the 10-year E500m National Innovation Programme for hydrogen and fuel cell technology.

One of the heating equipment suppliers involved is the Germany-based Baxi Innotech subsidiary of the UK Baxi group. It recently acquired European Fuel Cell, which makes the PEMFC stacks for the Baxi Innotech natural gas CHP systems using thermosetting resin bound bipolar plates from Schunk Kohlenstofftechnik.

Aside from Baxi Innotech, boilermakers Vaillant, Viessmann and Swiss-headquartered Hexis are also involved in the Callux project. However, the Hexis Galileo equipment employs the much higher temperature solid oxide (SOFC) type of fuel cell that relies on metal bipolar plates.

At the launch of the Callux project in September, the minister responsible for the programme, Wolfgang Tiefensee, said the aim is to bring fuel cell heating equipment into the market by 2015 to obtain a real alternative to conventional equipment that is capable of saving up to 30% of primary energy.