Another renewable limit is GEOPOLITICAL. (I love renewables and this is painful to admit). Many smaller countries with large populations simply *cannot* power themselves. When one considers how diffuse wind and solar are, there is simply NOT ENOUGH LAND for smaller countries! Australia is fine with all our deserts and our (comparatively) low population. But the UK could not power itself without nuclear. This is simply the laws of physics of scattered, diffuse renewable energy supplied in a small area with a larger population like the UK. In today’s economic and geopolitical environment when many nations are starting to reconsider globalisation and are trying to invent more home-grown solutions to energy security, renewables simply cannot cut it for large populations in small lands. Such countries simply demand too much power for each scrap of land! Let me hand you over to David MacKay.
“David John Cameron MacKay, FRS (born April 22, 1967), is the professor of natural philosophy in the department of Physics at the University of Cambridge and chief scientific adviser to the UK Department of Energy and Climate Change (DECC). Before being appointed to the DECC, MacKay was most well known as author of the book Sustainable Energy — Without the Hot Air.”
David gives the following example in his famous TED talk.
You have a road with a 60 mile an hour (100kmph) speed limit. The cars on the road burn fuel at around 30 miles per gallon (which is the European average car efficiency, and why we are using imperial measurements). Along the side of the road is a ribbon of biofuel fields to fuel this particular road. The cars are about 80 meters apart. Now, the question is, how WIDE would the biofuel strip be to fuel this road of 60mh, 30 mpg, 80 meter apart cars, 24/7? (Length doesn’t matter really because we’re talking about average WIDTH to fuel these cars and if the length of the road extends, so does the biofuel strip along side it.)
It’s a strange example, but physicist David MacKay wants us to think about renewable energy in a new way. If the biofuels grow 1200 litres of biofuel per hectare per year, then the strip along side this one, busy road would need to be 8km wide to fuel this one road!
Please watch David Mackay’s TED talk here.