As I write this post, the electricity demand in the UK is 37.5 GW [=37,500,000,000 Watts]. The industry claims that wind turbines typically supply about 30 to 40% of their capacity, while the National Wind Watch in the US claims 15 to 30%. In other words, a large wind turbine rated at 3MW [3,000,000 Watts] would will typically generate 1MW from its 50m blades that give it a total height of about 130m [about 30% higher than St Paul’s Cathedral in London]. So 37,500 such wind turbines would be required to meet current electricity demand in the UK, or one for every 1.6 miles on a square grid covering the country, which is why blending of energy sources is essential [see posting on May 15th, 2013 on Energy diversity].
We can do similar calculations for solar panels, which typically produce 250 Watts /square metre but for only perhaps 4 hours per day in the UK, so that 150 square kilometres of solar panels would be needed to meet current demand, if the sun was shining which it is not – another reason for blending energy sources.
Fossil fuel fired power stations make up 70% of the blend in the UK and are responsible for about 25% of the UK carbon emissions. The UK government aims to reduce carbon emissions by 80% by 2050 (based on 1990 levels), so about 65% of the UK powerstations have to be changed in the next 35 years to provide a more sustainable blend of energy sources. This is not long given the scale of the infrastructure projects required and the situation is the same in many countries around the world. So there is plenty for engineers to do once the decisions have been made on the blend.