I went to a wonderful seminar given by David MacKay (http://withouthotair.com) at the Armourer's and Brasiers Cambridge Forum. He talked about the physics (i.e. what would it take, not what would it cost) to provide the UK with energy from renewable resources. One of my favorite quotes (and there were many) was:
Burning chemicals should be a thermodynamic crime.
It just makes me laugh.