Bac2 the future for fuel-cell materials

  • 13-Oct-2008 02:08 EDT
Bac2 FuelCellConstruction (1).jpg

The plates are based on Bac2’s conductive polymer, ElectroPhen, developed over a period of three years.

Automotive fuel-cell technology remains a promising alternative energy solution, but it also brings many challenges, including those concerning materials, manufacturing, and associated costs. Fuel-cell materials company Bac2 is now making available to OEMs a range of sample quantities of blank bipolar plates for use in polymer electrolyte membrane (PEM) fuel-cell stacks. Suitable for fuel-cell evaluation and prototyping, two new sizes have been introduced. They measure 150 x 150 x 2 mm (5.9 x 5.9 x 0.08 in) and 60 x 40 x 1 mm (2.4 x 1.6 x 0.04 in), respectively, and complement the original 300- x 300- x 3-mm (11.8- x 11.8- x 0.12-in) version launched earlier this year.

Graham Murray, Technical Director of Bac2, said: "Some customers are requesting sample quantities in various sizes because every fuel-cell application is different, so there is a lot of customization of plates involved. It can be more effective in the development stages to machine a blank plate, only paying for the mold tooling when the final plate design is determined."

The plates are based on Bac2’s conductive polymer, ElectroPhen, developed over a period of three years, which can be machined more simply than metal plates. Their conductivity is markedly in excess of U.S. Department of Energy specifications for use in automotive applications. Once the fuel-cell design has been finalized, the plates can be ordered as fully molded parts that need no further processes or machining.

Bac2’s bipolar plates exhibit in-plane and through-plane conductivity of 350 S/cm and 30 S/cm, respectively. Murray stated that they are stable to 150ºC (302ºF) and have 30-MPa (4350-psi) flexural strength and 75-MPa (10,900-psi) compressive strength. Thermal conductivity is greater than 100 W/m·K, some 10 times better than stainless steel, stated Murray.

He added that polar plates account for between 30% and 50% of the cost of a typical hydrogen or methanol polymer PEM fuel-cell stack. ElectroPhen’s manufacturing process is a two-part mix followed by low-temperature curing. It is described by Murray as being both simple and easily scalable at "significantly" lower cost than alternatives. Plates made from the material are thermally stable, resilient to temperature, and inert toward fuel-cell catalysts and membranes.

ElectroPhen’s basic raw materials are available from major chemical suppliers. "It has a raw state conductivity 1 billion times higher than commonly used resin binders so that no high-temperature processing or surface machining is needed to ensure good conductivity. Where required, Bac2 customizes the material with plasticizers, reinforcers, and conductive fillers to fine-tune it for specific applications," said Murray.

The company is confident that the electrically conductive composite material will make a significant contribution to the early adoption of clean energy from fuel-cell stacks. Bac2 is in the process of developing ElectroPhen commercially and has patents pending in Europe, America, and Japan.

ElectroPhen is made from readily available low-cost constituents, can be pressed or molded to complex shapes, and is sufficiently robust enough for harsh environments. Murray said that the material could be used to produce plates economically using what it terms a "very simple mix-and-mold" process for high-volume production. Chemicals used are commercial off-the-shelf and available in bulk. Bac2 holds patents on the formulation.

In addition to ElectronPhen’s role in fuel cells, Bac2 will find an increasingly wide range of applications for ElectroPhen in electrical and electronic applications, said Murray.

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