I've been thinking a lot about sustainable energy recently, since it is such a hot topic and I like to give in to trends...or maybe it's just that I think a lot of the ideas being implemented aren't good enough, if they're even good at all.
I saw a H2 bus in Berkeley the other day, and it got me thinking about the overall energy efficiency of such systems. Sure, the systems prevent local pollution where the H2 bus is run, but globally, a lot of energy is wasted in manufacturing and transporting the energy. One study shows that the overall energy efficiency of a diesel bus is at least two times higher than that of the hydrogen bus, at least as implemented in California.
But, there are some really good ideas. My personal favorite is the solar powered Stirling engine. We can use the heat of the sun, concentrated using mirrors, and the cool of the earth to easily generate power. Here is an example. Deserts, where there is minimal property value, would finally find their niche in our economy.
Another popular idea is using algae to produce fuels. Down side is we'd still be using fuel (aka burning stuff). Up side is that algae consumes the CO2, so it's a net neutral.
Finally, something that's flown onto my radar recently: Polywell, or IEC (Bussard) Fusion. It's all very physics-based, but might lead somewhere interesting.