(...)(though none that burn fuels are much more than 40% efficient at present, those pesky laws of thermodynamics - but that's still better than the peak gasoline engine efficiency around 30% - 33% better and that's comparing to the gas engine's peak, which only some hybrids see regularly).
In the case of the sun, the fact that my panels are about 14.5% efficient is not a big deal - the input is free anyway and would have been completely wasted otherwise heating my roof.
yeah, these are all points I was wondering about - it might not look like much difference between 30% and 40% efficiency, but if you look in the relative terms, as gasoline engine being point of reference (our current "prime mover"), than electricity generation is 33% more efficient, from the same fossils (10% difference is 1/3 of our base 30% efficiency). Not to mention, if you use so called Combined Heat & Power plants (CHP), where the waste heat is also used (as technologic process heat, or even for doomestic water usage - on metropolitan scale), the efficiency gets as good as in the region of 70+%. It can be also quite cost effectively supplemented & further improved upon by renewables (initial heating of water in steam turbines by concentrated solar, for example). And as electric transport goes, electric power trains have some more advantages over the ones that must accompany ICE engines (for example, nearly flat torque through the whole 0-max RPMs range, thus no transmission required - another weight & mechanical efficiency gain, no idling, less complex=more reliable & less maintenance)
The other thing you mention, re: photovoltaics - I am always puzzled about the excitement, that this or that laboratory "have achieved better efficiency photovoltaic cells", - at the expense of exotic processes or high costs, or exotic materials. I say: why bother? Increasing efficiency is only important, when we have to save fuel, but here, the "fuel" is free, like you said. IMHO, the focus of development should be on making CHEAP, easy to manufacture, environmentaly friendly and long-lasting cells - even if it comes at the cost of slightly lover efficiency. I mean, if your panels were say 10% efficient, Fusor, but would cost you, say, a quarter of what you've paid - you'd just double the square meter area, comparing to what you have, and we are good, no?
regarding hydrogen peroxide - there are good few go-carts powered by that stuff, to be googled for your amusement. But it is dangerous & unstable stuff indeed, and I would prefer not sitting on the tank full of it as well!
BTW, if my memory serves me well, Russian torpedoes on board of one "Kursk" submarine were powered by H2O2, which was quoted as the most probable cause of explosions & the following tragedy, by independent investigation body (ie non-Russian-government one)