@spivonious: Geothermal isn't too bad for domestic heating, but I don't think it works out for generation of electricity,  And it should be used more, but I think it's just not advertised enough.

 

As for hydrogen fuel cells, the energy required to produce pure hydrogen is quite high in the first place -- so how do you generate that?  There has been some success using solar mirrors to crack it, but it's not really scalable.

Now portable Thorium reactors on the other hand ...

 

Herbie