The International Energy Agency (IEA) ‘underreports (the) contribution solar and wind by a factor of three’ compared to fossil fuels, according to a recent report. I and others have been pointing this out regularly, but it’s good to see this methodological anomaly (if that’s what it is) exposed and explored in more detail in an article by Erik Sauar. His rendition of it is a little complex and convoluted in places, but the basic point is that the IEA make use of primary energy data, which, for fossil fuels, is relatively straight forward: it’s the tonnes of fuel used by power plants, usually rendered as million tonnes of oil (mtoe) to make it comparable in energy content terms. However, for renewables, since you can’t really measure the input raw energy, for wind and solar they just use the output energy to represent the primary mtoe figure. But strictly, to make sensible comparisons (e.g. of the relative carbon emission implications), a way to infer the primary energy for these renewables is needed. One way is to work out the amount of fossil fuel that would have to be used to produce the same energy output. Standard steam-raising fossil plants are very inefficient, typically wasting two thirds of the primary energy fed in to them, rejected as heat into the environment. So you would need about three times more fossil energy input to get the same output as from a similarly rated renewable generator. Hence Sauar’s claim that some renewables are in effect de-rated unfairly by around a third.
Environmental Research Web 6th Jan 2018 read more »