New method of storing hydrogen for fuel cells

High hopes for hydrogen storage: this variety of lithium hydride could help unlock the door to a low-carbon future. Picture courtesy EPSRC.

They have developed a lithium compound that may make it practical to store enough hydrogen to enable cars to be driven over 300 miles (480 km) before refuelling. Achieving this range is considered essential for the widespread adoption of fuel cells.

The research was carried out by a team from the universities of Birmingham and Oxford and the Rutherford Appleton Laboratory, under the auspices of the UK Sustainable Hydrogen Energy Consortium (UK-SHEC).

Fuel cells produce carbon-free electricity by harnessing electrochemical reactions between hydrogen and oxygen. Current prototype and demonstration cars powered by fuell cells have a range of around 200 miles. To achieve a 300 mile driving range with current fuel cell technology, space the size of a double-decker bus would be needed to store hydrogen gas at standard temperature and pressure – and storing it as a compressed gas in cylinders or as a liquid in storage tanks would not be practical due to the weight and size implications.

The UK-SHEC research has therefore focused on finding a way of storing hydrogen at a much higher density and within acceptable weight limits. The researchers have harnessed the phenomenon of chemisorption, in which atoms of a gas are absorbed into the crystal structure of a solid-state material and then released when needed.

The team tested thousands of solid-state compounds to find a light, cheap, readily available material that would enable the absorption/desorption process to take place rapidly and safely at typical fuel cell operating temperatures. They have come up with a variety of lithium hydride (specifically Li4BN3H10) that could offer the right blend of properties. Further work is now needed to further investigate the potential of this powder.

“This could be a major step towards the breakthrough that the fuel cell industry and the transport sector been waiting for,” said project co-ordinator Peter Edwards of Oxford University. “It’s due to the vision of combining many of the leading groups in the UK to tackle this, arguably the biggest challenge for the development of hydrogen fuel cell vehicles.”

Edwards said the work could make a key contribution to helping fuel cell cars become viable for mass-manufacture within around 10 years.

The research was carried out as part of SUPERGEN, a multidisciplinary research initiative launched in 2003 that aims to help the UK meet its environmental emissions targets through a radical improvement in the sustainability of power generation and supply.

SUPERGEN is managed by four of the UK research councils with the environmental body, the Carbon Trust. A total of 13 research consortia are now at work or have been announced.