of 14.0% w/w, 46.2 g/litre. Cryo-compressed Cryo-compressed storage of hydrogen is the only technology that meets 2015 DOE targets for volumetric and gravimetric efficiency (see "CcH2" on slide 6 in ). Furthermore, another study has shown that cryo-compression exhibits interesting cost advantages: ownership cost (price per mile) and storage system cost (price per vehicle) are actually the lowest when compared to any other technology (see third row in slide 13 of ). For example, a cryo-compressed hydrogen system would cost $0.12 per mile (including cost of fuel and all other associated costs), while conventional gasoline vehicles cost between $0.05 and $0.07 per mile. Like liquid storage, cryo-compressed uses cold hydrogen (20.3 K and slightly above) in order to reach a high energy density. However, the main difference is that, when the hydrogen would warm-up due to heat transfer with the environment ("boil off"), the tank is allowed to go to pressures much higher (up to 350 bars versus a couple of bars for liquid storage). As a consequence, it takes more time before the hydrogen has to vent, and in most driving situations, enough hydrogen is used by the car to keep the pressure well below the venting limit. Consequently, it has been demonstrated that a high driving range could be achieved with a cryo-compressed tank : more than were driven with a full tank mounted on a hydrogen-fueled engine of Toyota Prius. Research is still underway to study and demonstrate the full potential of the technology. As of 2010, the BMW Group has started a thorough component and system level validation of cryo-compressed vehicle storage on its way to a commercial product. Clathrate hydrates H2 caged in a clathrate hydrate was first reported in 2002, but requires very high pressures to be stable. In 2004, researchers showed solid H2-containing hydrates could be formed at ambient temperature and 10s of bar by adding small amounts of promoting substances such as THF. These clathrates have a theoretical maximum hydrogen densities of around 5 wt% and 40 kg/m3. Glass capillary arrays A team of Russian, Israeli and German scientists have collaboratively developed an innovative technology based on glass capillary arrays for the safe infusion, storage and controlled release of hydrogen in mobile applications. The C.En technology has achieved the United States Department of Energy (DOE) 2010 targets for on-board hydrogen storage systems. DOE 2015 targets can be achieved using flexible glass capillaries