I went to an interesting talk last night hosted by the Cambridge Society for the Application of Research. It was given by local professor Dr David MacKay promoting his new book "Sustainable Energy: without the hot air". Although you can buy a copy you can download the whole thing in Creative Commons licensed glory from his website.
The book is basically a scientific approach to the problem of how we manage the energy deficit and move to sustainable energy future. He started his talking about the current problems with "Greenwashing" and the dangers of an emotive approach to promotion of alternatives. The big elephant in the room is of course the role Nuclear could play in the equation with most of the environmental lobby against it without having the answers to fill the shortfall in energy.
The principle problem with renewables is the low energy density (a limit of physics) which lead to the Wales unit. If we were to provide all our energy we would have to convert all farm land to biomass, have several Wales sized wind farms both on and off shore as well as ship in solar energy from significant chunks of the Libyan dessert.
The flip side of the problem of course is reducing demand. The big runners seem to be all electric transport and more efficient heating and cooling by using Heat Pumps. Current car usage is very inefficient in term of power budget and there is much more to be done in the field. The current hybrids really only scratch the surface of what is possible and from MacKay's point of view can only be a stepping stone to fully electrified personal vehicles. I was impressed by the numbers on Heat Pumps which claim greater the 100% efficiency by virtue of tapping energy from the environment. The question remains if we will reach a limit by permanently refrigerating outside while we are kept warm inside the buildings.
The overall conclusion of the talk was a positive one. If we added nuclear and "clean" coal to the mix ("sustainable" equals will last for 1000 years at current demand) and reduced the area set aside for renewables to be more realistic at the same time as aggressively reducing consumption by transport and heating it is a scientifically doable thing. Whether we will is another question all together.