A lightweight method of storing hydrogen in solid form for use in fuel-cell propulsion systems has been developed at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France.
ESRF says 1kg (2.2lb) of lithium borohydride (LiBH4) will contain about 185g of hydrogen and the compound has a density of 678kg/m³ (42lb/ft³), which is lighter than water, kerosene and diesel at 998, 810 and 800kg/m³, respectively.
Only half as much hydrogen is needed to deliver the same power output as hydrocarbon fuel, but in its normal gaseous state it requires double the volume of kerosene.
About 3.23m³ of LiBH4 would deliver the same amount of energy as 1m³ of kerosene.
"Among the many materials competing for hydrogen this is probably the lightest. Lithium, boron and hydrogen, these are the lightest elements you can find," says ESRF director of beamline research Vladimir Dmitriev.
With LiBH4 the hydrogen is released when the compound is heated to around 300ºC (500º) or more. But the researchers have created new forms of the compound that could release hydrogen at a lower temperature.
This required pressures of up to 200,000bar (2.89 million lb/in²), but they expect to be able to produce this more unstable version at the atmospheric pressures used to mass-produce chemical pellets.
US company Protonex uses a solid hydride system for hydrogen storage in its Procore UAV fuel cell, but details of the hydride's chemical composition are not available.