[Voltorb]

It has been well established that hydrogen could only work as an energy carrier. Sure, it's easy to make hydrogen using the electrolysis of water, but this requires more electricity than one would ever get back from that hydrogen in a fuel cell. So much electricity in fact, that the vast majority of commercially produced hydrogen is produced from methane. I don't think we're going to start wasting all our natural gas making hydrogen.

So all we need is lots of electricity, right? Yet most electricity, I think over 80%, in the world is made by burning coal or natural gas... this will run out eventually. Fission reactors create lots of electricity, yet the total reserves of uranium on earth will also run out. The only answer is wind, solar, hydro, and wave power. Combined, these sources produce less than 5% of the world's electricity. We need to get started now, while the energy to construct these types of plants is still cheap.

Assuming we could eventually satisfy all world electricity demand using renewable resources, there is still the small problem of losing the sheer power of the internal combustion engine. Imagine an all electric eighteen wheeler. An all electric freight ship. I suppose it could be done, but it will require a bit of engineering. I don't even know how airplanes would be replaced. You'd probably have to scrap the jet engine all together and make electric propellers.

As far as cold-fusion is concerned--I think its theoretically possible. But if we could even get hot fusion to work, discovering cold fusion would be less than momentous. You are correct in saying that we have gotten energy out of fusion, but the best achieved put out 60% of the energy put in. Fusion has remained 20 years away for the last 50 years, scientists like to joke. But improvements are being made. I hold on to hope.

And if this isn't enough to get you worried, imagine a world without plastic. Shriek! We can save something like 70% of all fossil fuels if we generated all electricity without them. I suggest we get started here, and save the oil for plastic.