Terrapower - a possible solution?

I've just been pointed to a TED talk by Bill Gates on a possible solution to the global warming problem. See http://www.ted.com/talks/bill_gates.html. Its well worth a look as it sets out the problem very clearly. TED talks are great by the way - type TED into youtube. The amount of CO2 generated (and hence amount of global warming that will occur) is proportional to:

• The number of people on the planet
• The amount of services (light, heat, transport etc) each person uses
• How efficient each of these services is (how much energy each one requires)
• How much CO2 is generated per unit of energy

As Bill puts it - the first 3 items will never be zero. The only way to stop emitting CO2 into the atmosphere (from human burning of fossil fuels) is to go after the fourth point. Hence you have the drive for renewable energy.

Clearly this requirement is perfectly aligned with the higher level sustainability requirements - although note having renewable energy does not mean we have a totally sustainable way of life (e.g. think about land usage pressures, threats to biodiversity etc).

So how do we get sustainable energy for the planet. Well I suppose that's the biggy. Bill is urging us to look for as many solutions as possible. He favours the high density energy production (e.g. Terrapower) as opposed to diffuse production (wind, solar, biofuels) just because it seems more economically viable. Diffuse sources gobble up land. On the plus side they don't require as much distribution, but then they do not give an uninterpretable supply. I'd tend to agree - high density solutions seem more realistic without subsidy. If it is economically viable - market forces will make it happen. If not - it requires sheer will power and political will power at that  - making it much less likely to happen.

Terrapower (not maybe the best name?) - also called a travelling wave reactor - is the conversion of Uranium 238 to energy. Uranium 238 is 96% of enriched uranium. The uranium 235 gets "burnt" in the reactor to create nuclear power. The 238 is not "burned" and becomes the waste. So not only is this very efficient - it runs off current nuclear waste! Sounds too good to be true. The main downer on it is that is hasn't been demonstrated yet - so who knows - maybe that is the solution.

Bill's other point is to back as many horses as possible as Terrapower may not work out. If 50 years is the time horizon where we must have a solution - else "something very bad" - then it is clearly the 1st problem to solve to get to a fully sustainable system