I studied energy at Stanford and joined the team that spun TerraPower (www.terrapower.com) out of Intellectual Ventures with Bill Gates' backing. I spent a lot of time looking at these nuclear batteries and economically it's very hard to see them working out as anything close to competitive to natural gas, coal, or wind. The amount of security, containment, etc. that you need for a large plant vs. a small plant doesn't vary much, so the costs per kWh don't scale down as you move down in total plant size, they scale up - and the idea as the techcrunch article suggests that you could sell just a "thermal" battery and let the utility or whoever add the actual steam-to-electric conversion on their own is laughable. Utilities don't do anything on their own.

I do hope these guys figured out something novel about the economics -- and I certainly applaud YC for going into energy.