Speaking of hydrogen energy, this is also quite interesting. Uses a reaction between an aluminum alloy and water to create hydrogen as it is needed, making it much easier to handle. After the reaction, the aluminum oxide can be recycled back and used again, which is where the energy for the process comes from. I didn't see the efficiency figures for that process in this article but have heard him speak about it on a radio show and he said it is currently at 50 percent, hopefully soon to be at 75. It is a process which is already common and industrialized.
info here:
http://news.uns.purdue.edu/x/2007a/0705 ... rogen.html
with videos at the bottom of the page
and here:
http://www.sciencefriday.com/pages/2007 ... 60107.html
you can listen to the radio show I mentioned by downloading, through itunes, the science friday podcast in the second link for free.
cheers.
EDIT: It is actually the recycling of the gallium and the aluminum which is critical. The reaction has the waste products: hydrogen, gallium, and aluminum oxide (alumina). The gallium is not reacted, it is just allows the aluminum to react with the water. The alumina is what can be recycled and re-used as aluminum in the process at 50-75 percent efficiency.