Department of Climate Change Chief Scientific Advisor, Professor David MacKay FRS, is responsible for ensuring the best science and engineering advice underpins DECC's policy and decision-making.
If you like this, there is an hour-long presentation with much more detail at: http://www.youtube.com/watch?v=GFosQtEqzSE
From his book about the same subject, http://www.withouthotair.com/"Sustainable Energy - without the hot air" presents the numbers that are needed to answer these questions: How huge are Britain's renewable resources, compared with our current energy consumption? How big do renewable energy facilities have to be, to make a significant contribution? How big would our energy consumption be if we adopted strong efficiency measures? Which efficiency measures offer big savings, and which offer only 5 or 10%? Do new much-hyped technologies such as hydrogen or electric cars reduce energy consumption, or do they actually make our energy problem worse?
Via Chuck Sherwood, Senior Associate, TeleDimensions, Inc