The 7 most promising energy sources.

These are not in order of promise. They are just to lay them out in an argument. Please comment and add to the list (or subtract).

Cars:
1. Cellulosic Ethanol
Corn is so 1985. Cellulosic Ethanol, the process of taking all the excess biomass we have, such as hay, cornstalks, wood chips and grass, and turning it into a fuel, uses the whole plant, doesn't require growing space and is massively more efficient. It also doesn't rely upon fertilizer which removes it from the petroleum industry. Been in production in Canada as a demonstration project since 1997. In Cambridge MA there is a plant ready to start producing 1.4 million gallons a year in 08. Other plants are about to start construction in Kansas (50 million gallons) and Spain. Branson is behind it, Alan Greenspan loves it. It is changing very, very quickly and older ethanol plants are trying to convert to cellulosic technology because of the more realistic resource use. There simply isn't enough grain to get corn as a viable fuel.

http://www.InvestInCellulosicEthanol.com

2. Compressed Air
Provides it's own air conditioning. Costs $1.00 every 100 miles. Can refill without a filling station and uses backup fuel if necessary. They are slated to be rolled out THIS decade in massive quantities. And cheap. (But probably loud.)

http://www.theaircar.com/thecar.html
http://www.gizmag.com/go/7000/

3. Electric Cars
I don't think I need to even go into these. Google search it or http://www.evworld.com/

Other energy:
4. Wind and wave power
Turbines are starting to be built into skyscrapers, under rivers and everywhere else. They can be built on huge scales or small, can cost $1.00 or $5,000,000,000,000, and hold an immense amount of potential for integration into existing buildings. No one has ever had their head cut off by a turbine. Really.

Or Scotland has a great solution. Put these up and down the northeast coast to harness the power of the Atlantic. Low profile, cheap and very low maintenance.

Or how about multiple methods?

5. Plasma
Energy from trash (again) that has a net GAIN in profit? Yes. So simple it's crazy. Trash is delivered to a plant, separated and turned into glass, a hydrogen CO mix and energy. The glass is a usable material, the gas is a fuel and the energy is fed into the grid for a profit. The first plant opens in St. Lucie County Florida in 09. Japan has them running already. Startech has said the biggest problem is overcoming existing investment systems, NOT the technology.

Good post about it:
http://synthesis.typepad.com/synthesis/2006/09/geoplasma_and_p.html

6. Solar
The oldest energy source in the world. But solar technology has a problem. It cannot get to the consumer without someone getting in the way and charging a middleman or fighting a bureaucracy. The era of flexible, thin solar cells is right around the corner, unless we let it keep going the way it has. Every window in a tower could be a solar panel if the competing industries hadn't held it back for so long. Seriously – that is all which is stopping it.

That said, there are many places which are advancing solar as a source. San Francisco is covering Moscone Center in 60,000 sf of solar panels, and has already begun using them in every municipal building. (Diffuse light works with solar panels, so SF is terrific for the technology.)

Treehugger
Powerfilm

6.25 Geothermal
I don't know anything about it, but that it is used everywhere and is massively under appreciated. Nicolas?

6.5 Nuclear
Fix the problems of storage and waste and we've got an inexhaustable supply of energy. See you in 2050, according to most.