Question about the energy density of hydrogen fuel cells.

Lithium battery technologies are kicking tuchis in the high energy density
world. beating NiMH over 2:1 in both W/kg and W/l. Just the same they are
not primary sources, just rechargeable batteries.

Strictly speaking, hydrogen is not a primary source either, as it does
not occur in nature in free form. Hydrogen is just a way of storing
energy created through chemical reaction using primary sources, e.g.
oil, coal, solar or hydro-electric. So not much differences with
batteries really. In fact in case of solar and hydroelectric, the
intermediate stage in hydrogen production is electricity, just as it is
with producing charged battery materials inside the battery.
Methanol and specially ethanol fuel cells might have a valid claim
to use primary sources as both materials can be produced from naturally
growing sources (corn etc) using a natural process - fermentation, so
amount of manipulations is comparable with distilling oil into gasoline.
Even more so are solid-oxide fuel-cells using natural gas, but
unfortunately later are not practical for portable devices, at least yet.

Regards,
Yevgen