He is also the author of the famous (and free) "Sustainable Energy (Without the Hot Air)" . The whole book (12Megs) is available HERE
But he has also recorded a number of lectures on the viability and practicality of renewables, particularly he has focussed on the land areas needed to meet specific goals. These are goals that meet specific energy requirements. Here he is talking about systems that are other than window dressing or merely fashion statement technology.
My favourite quote is:- "I'm not anti renewables but I am pro arithmetic"
The recording is 18 minutes but is well worth a watch (unless you are a green dreamer that is)