Military has keen interest in fuel cell technology

The Seventh Grove Fuel Cell Symposium, held in London, from 11 to 13 September, examined the prospects for commercialisation of fuel cells, with papers presented on a variety of new materials technology, such as hydrogen storage and protection against corrosion of the electrodes. At present, one of the greatest drawbacks of fuel cells is their cost. However, as far as the military is concerned this is not such a critical factor, being more concerned with the advantages of fuel cells, such as quiet operation, low infrared signature, high power density, and environmental considerations, said Clive Seymour of Intensys Ltd, a company that carries out military research into fuel cells. Hydrogen fuel cells are being considered for use as emergency power backup for nuclear submarines, and auxiliary power for warships, where fuel cells capable of producing up to two megawatts of power would be used, down to individual power packs for infantry soldiers.

The military have specific requirements that fuel cells need to be able to achieve, such as the ability to use a range of logistic fuels, to operate in a wide range of climatic conditions and under battlefield conditions, to be able to withstand physical abuse, and have high availability, reliability and maintainability, said Seymour. One example of the flexibility that is required of fuel cells is that those on board warships should be able to use F76 Dieso, the diesel fuel used to power the ships, as well as Avcat, which is commonly used to power the helicopters on board, but is also used to power vessels if required, and marine gas oil, which the navy uses from around the world if the other two fuels have run out. “The system design must recognise the specific nature of each fuel and must have the flexibility to cope with each of them,” said Seymour.

With regard to infantry use of hydrogen fuel cell technology the military requirements are just as stringent. “The dismounted soldier of the near future is considered to be a weapons platform in his own right,” said John Moore of Power Sources Ltd. Each has to carry a considerable weight, including high tech electronic weaponry requiring a lightweight power source. “No battery either in service today or due to enter in the near future, can provide for the energy demand envisaged for the future dismounted soldier at an acceptable weight,” said Moore. However, despite the advantages that fuel cells can provide, they alone are not the answer, he said. Air breathing fuel cells, as opposed to the pressurised cells used in vehicles, are considered to be the most suitable for a number of reasons, including the dangers of carrying a pressurised container into battle. But this means that they need constant good air conditions in which to operate – rendering them unsuitable for the decrease in air quality which may be likely in a battle, and for immersion in water or mud. The UK, French and US military are currently considering their use for recharging battery packs during battle situations, where their intermittent use will be less vulnerable to changes in air quality.

Non military uses of fuel cells that were discussed included the state of current research into the storage of hydrogen for fuel cells, including the use of carbon nanotubes – much like carbon graphite, but, instead, formed into tubes – which, unfortunately, is currently considered to have low hydrogen absorption, despite early over-optimistic predictions, said Dr John Speight of Birmingham University in the UK. Storage of hydrogen as a liquid is thought to be promising, although there is a 40% penalty in terms of energy due to the liquefying process, said Speight.

Use of diesel or direct methanol fuel cells (DMFCs) was also discussed, including one paper presented by Professor Ray Gorte of the University of Pennsylvania describing a system using copper anodes (see related story), although this appears to have the potential for problems with coking from sulphur when diesel with realistic levels of sulphur, such as 1000ppm, is used.