From: Phil Pugliese (via tml list)

>  Ian,
>
> Could you elaborate a bit more as to how this could be
> performed/executed?

It's easier to store hydrogen as a compound than as a liquid -- MgH2, for example, contains about 0.11 kg/l of hydrogen (compared to 0.07 for liquid H2). The drawback is that the chemical storage is very heavy (total weight is 1.45 kg/l) and you need to release the hydrogen from the chemical bonds, which isn't instant. Also, metal hydrides are solids so you'll need spaces to allow the released hydrogen to flow, which will reduce packing density.

The reason for using metal hydrides is because the energy required to extract the hydrogen is fairly low; if energy isn't a problem (fusion) solid ammonia is 0.14 kg/l, and ordinary water is 0.11.