The greatest problem to overcome is the amount of energy it takes to create energy sources. Ethanol (manufactured from corn) is the US' leading alternative fuel for automobiles. Unfortunately, it takes more energy to grow, harvest, convert and distribute it than can be generated by it. Therefore it's actually a wasteful fuel. When the goal is to produce energy, you simply cannot go into a negative position.

The Waste Vegetable Oil (WVO) conversion on diesel engines I spoke about in the Oil Storm thread is one of the most interesting innovations. It won't scale for mass production, simply because as fat as we are, we don't eat THAT much greasy food. But it is a brilliant idea for the minority who will adopt it, mainly because it is re-using spent fuel that would otherwise pollute the ecosystem, because it can be found for free or on the cheap if you know where to look, and its mere existence gets enviro-newbies to think "you can do THIS with THAT?!?!?!?"

There is no silver bullet to solve the energy crisis, but we must get serious about two things:
1) Employing a variety of alternatives that don't take more energy to create than what is produced.
2) Adapting our refinery capacity to make use of Heavy Crude, which is spoiling in the ground while we barter life and limb for Light Crude. It won't last forever, but it can certainly get us through the next century while we figure out the long-term solution.

Once we figure out how to convert the moon into energy, then we'll have a limitless supply of energy. At least, until that limit is reached.