Fuel cell efficiency

A new design for fuel cells could make them fault tolerant and resilient to adverse environmental and internal influences.

A team from Imperial College London is developing the technology through a project sponsored by the Engineering and Physical Sciences Research Council (EPSRC).

Current fuel cells are designed with electrodes connected in a series. The weakest link in the cell dictates performance and reliability.

Imperial College chemist Anthony Kucernak and his team will redesign fuel-cell stacks so they can switch out bad units and allow the cell to continue operation.

'We will do it with a series parallel geometry,' he said. 'The stack will look like a normal stack but the electrodes will be in parallel with one another.'

While electrodes in a current fuel-cell stack are integrated with one expensive insulated gate bipolar transistor, the Imperial team proposes integrating less expensive multiple field-effect transistors with each and every electrode in the stack.

'The idea is to replace one monolithic piece of electronics with lots of smaller ones, which are actually a lot cheaper per amount of power they handle,' said Kucernak.

He added that this will make the entire fuel-cell stack more reliable because its condition will not depend on one transistor.

The fuel-cell design could also make it possible to nurse poorly performing electrodes. Kucernak said that the power electronics could look after the condition of each electrode its associated with.

'If an electrode isn't performing particularly well, rather than have it on a full duty cycle, we can ramp it back so the electrode isn't put under as large a strain as the other electrodes,' he said.

Kucernak added that this will make fuel cells run for much longer.

'When you have any sort of system, if you drive it at full performance, then it will fail much quicker,' he said. 'But if you can actually not run it at the full performance but at half performance, you might be able to eke it out for quite a bit longer.'

The four-year project includes partners Applied Technologies Capital, SPC, Imperial Innovations and the Defence Science and Technology Laboratory (DSTL).

Kucernak said the DSTL could use the fuel-cell design in a range of military applications in the future.

'The major interest is replacing the batteries that a lot of the armed forces have to carry around,' he said. 'If you think about infantry men on the field, a large percentage of what they have to carry on their backs is batteries to power all the electrical equipment that they've got because they can't carry around generators. So there is a desire to replace that with systems that have a higher energy density.'

Kucernak added that the technology also has potential to be used in the consumer automotive market.

'A power plant for a car might be something where this system is also very useful.' he said. 'It would be a system that doesn't give up all at once but degrades gracefully so you can run your car much longer.'

Siobhan Wagner