Powerful cell

Fuel-cell membrane developer PolyFuel has developed a fuel-cell stack that is capable of delivering 500W per litre of stack volume.

Fuel-cell membrane developer PolyFuel has developed a fuel-cell stack that is capable of delivering 500W per litre of stack volume, advancing the state of the art for Direct Methanol Fuel Cells (DMFC).

The tiny stack – which easily fits in the palm of the hand – delivers a peak power of 56W, more than twice that needed to power a typical laptop computer.

‘It is the first time, to my knowledge, that anyone has demonstrated a DMFC stack with this high a power density,’ said Henry Voss, vice president of engineering for PolyFuel and holder of 27 fuel-cell patents. In layman’s terms, explained Voss, this means that fuel-cell power supplies of a size and weight that can be physically integrated into a laptop in the same fashion as today’s Lithium-ion batteries are technically within reach.

The fuel-cell “stack” is a precisely-engineered, dense “sandwich” of repeated thin layers of fuel cell membranes, electrodes, and bipolar plates. The membrane is the heart of the fuel cell, and the various layers of the sandwich are designed to deliver fuel and air to as much membrane surface area as possible, while diffusing away moisture and CO2 byproducts. Certain layers additionally provide a current path to carry off electrons produced at the membrane’s surface, and it’s this current that’s used to power the portable device.

Although the company believes that the new stack is the highest-performing direct methanol fuel-cell stack ever developed, its purpose remains to provide developers of fuel cells or fuel cell components with tangible examples of how a consumer-acceptable fuel-cell design can be accomplished, particularly with PolyFuel’s hydrocarbon membranes.

Power density is a measure of the size of a fuel-cell stack relative to its power. The higher the power density, the smaller the fuel-cell stack can be for a given power level. This stack, developed to a particular customer specification, measures 8.8 by 4.5 by 2.8cm and produces 56W at peak power. To the best of PolyFuel’s knowledge, the stack delivers the highest power density of any portable DMFC stack ever made – over 500W/litre