Celling point

UK researchers claim to have made a breakthrough in the design of fuel cells that could transform the commercial prospects of the fledgling clean-energy technology.

Compact mixed-reactant (CMR) fuel cells are designed to be smaller, lighter and need fewer components – including costly platinum – than conventional alternatives.

Their developer, Cambridge-based CMR Fuel Cells, claimed that when formed into a array of cells – a ‘stack’ – they can increase performance by up to tenfold and cut costs by 80 per cent.

CMR was this week spun out of technology incubator Generics as a standalone firm to commercialise the new fuel cell architecture.

It claimed the base technology could eventually be applied to almost any type of fuel cell across a range of industries, including power generation and the automotive sector.

But the company’s initial focus will be on direct methanol fuel cells for portable electronic devices said chief executive Michael Priestnall.

‘We are looking at developments in areas such as battery chargers, laptops and power tools. There are also specific applications for portable military equipment.’CMR cells are less prone to failure or accidental damage when dropped because of their simpler design and reduced number of components, he claimed.

The size, cost and complexity of fuel cells has been a persistent barrier to their widespread commercial roll-out.

CMR’s system has been under development for several years within Generics, where Priestnall was head of fuel cell consulting.

CMR was born as an independent business after raising capital from investment house Conduit Ventures and the Carbon Trust, which claimed its technology could make a significant contribution to the development of clean energy sources. Generics has retained a stake in the new company.

The fuel cell industry is ferociously competitive, with researchers around the worldracing to solve the type of technical issues that CMR is addressing.

Priestnall admitted that it was still early days for the company. ‘I would characterise us as moderate-to-high risk, but with the potential for an enormously high pay-off.’However, he claimed CMR’s core technology could become a global design standard for all fuel cells.

‘We’ve had cells in the lab running for weeks,’ he said. ‘At the fundamental electro-chemical level it works. What we are concentrating on now is engineering it into a stack that can outperform the alternatives. We are confident we can achieve that.’

How it works: breaking down the barriers

Compact mixed-reactant technology literally breaks down the barriers between the elements that make a fuel cell work.

Fuel cells rely on the energy produced by the electrochemical reactions of a fuel – for example methanol or hydrogen – and an oxidant at two electrodes coated with a catalyst.

In conventional cells, the fuel is delivered separately from the oxygen by using a sophisticated engineered structure comprising a membrane and barrier plates designed to keep the two apart.

This is because for the cell to work the fuel needs to react at the anode, and the oxygen at the cathode. If both reacted on the same electrode, the result would be heat rather than electricity.

The plates alone account for about 90 per cent of the size and weight and up to one third of the cost of conventional fuel cell stacks, according to CMR.

Seepage between the two electrodes has long been recognised as a problem, and researchers around the world have successfully identified ‘selective catalysts’ that will react with the fuel or oxidant while ignoring the other.

This work has been designed to improve the performance of conventional fuel cell designs. But CMR decided that if the catalysts can act selectively there is no need to separate the fuel and oxidant at all and the barriers can come down.

CMR fuel cells deliver a continuous mixture of fuel and oxygen through a stack of porous cells, eliminating the need for the flow plates.

The anode and cathode are coated with a selective catalyst which reacts appropriately with the fuel/oxygen blend as it passes through the assembly.

A conventional fuel cell would use platinum for both the anode and the cathode because of the precious metal’s efficiency at reacting with the fuel and the oxygen.Platinum is removed from the cathode entirely, resulting in significant cost savings. The core element of the fuel cell – the cell repeat unit – is reduced from a thickness of 2mm to 0.2mm.

According to CMR, the continuous through-flow also boosts the performance of the reactants across the catalyst surfaces.