Cella Energy has developed a way of storing and delivering hydrogen in pellet form, making it attractive for use in powering fuel cells.
The development came out of work into the use of nanotechnology to improve the performance of hydrogen storage materials that Stephen Bennington, Managing Director of Cella Energy, was doing at University College London (UCL) and the Rutherford Appleton Laboratory in the UK.
Bennington chose to work with ammonia borane, which had come out of US Department of Energy-funded research into hydrogen storage. “The pre-cursor chemicals were cheap and readily available and material stored huge amounts of hydrogen and released it at sensible temperatures,” he says. However, ammonia borane had a couple of problems. For rapid hydrogen release it needed to be heated to 120-150°C but it melted at 100°C. “The result would be a horrible foaming mess,” explains Bennington. The other problem was that it took 5-10 minutes for the hydrogen to be released once the material had been heated.
The group worked on solving these problems and the resulting product is a polymer-based composite material. Cella uses a freeze drying process to get the right micro- and nanostructure. The structure is important for the speed of release of the hydrogen and so that the hydrogen can get out without swelling the pellets. “The important breakthrough is that it doesn’t melt and it remains solid throughout the hydrogen release. But it’s porous enough for the hydrogen to get out without damaging the structure,” says Bennington. Cella was spun out of the Rutherford Appleton Laboratory in 2011 with connections with UCL and Oxford University. The company has 20 staff and is based in the UK with a facility atthe Kennedy Space Center in the US.