The problem with changing to alternative sources is that we must address all the problems that currently plague our existing energy sources, namely fossil fuels be that oil, gas, or coal. We (Earth) need an energy source that is greenhouse gas free, renewable, and abundant.
I used to believe that the answer was in cold fusion, with a short half life and an abundance of deuterium in our oceans it seemed only to require technology and material science to catch up. However, in the last two or three years I have changed my mind. I now believe that the best path is that of the hydrogen fuel cell. I creates electricity by stripping the electron from the hydrogen atom and making it travel by a different path to reunite with the proton and oxygen to create water vapor as the end-product. Well to a certain extent water vapor is still a greenhouse gas, however the atmosphere will expel the excess water in the form of precipitation and therefore should be fairly innoculous by-product of energy production.
The problem with the hydrogen fuel cell is three-fold. Cost of fuel cell unit is high, production of hydrogen fuel, distribution of hydrogen fuel. The cost of the fuel cell will decrease sharply as we build more and more of them, not only that they will become more efficient at energy conversion as we work out the bugs. A parallel to this is the computer, the first computer I bought cost $2000 and was an IBM with 8MB of RAM and ran at 25Mhz. Now computers are much better and cost much less, this happens to most all products that have high consumer purchasing. The real issue is the production of hydrogen, if we use fossil fuels to create them nothing is gained, however one of the best ways to create hydrogen, although not currently the most common way, is to pass electricity through water. Generate electricty using water elevation (dams), windmills, geothermal and solar. Use this electricity to create hydrogen (The Battery) and distribute this battery to the fuel cell that converts it back into electricity. Obviously we need more green facilities to produce the electricity and they should be near large quantities of water for conversion into H2. Distribution facilities are already in place, we should use existing gas stations for filling of hydrogen fuel cars. At first they could have both products but as gasoline was phased out the same station could deliver hydrogen.
Not only would hydrogen fuel cells work great in cars but they could also power our homes as well, think about it no more power outage because of broken wires, your own personal generator using hydrogen to power your home. I see this fuel and energy conversion cell as our future, there are other possibilities but this one is ready to go, all we need is somebody with foresight to grasp this opportunity and make the next Rockefeller. IMHO