I made a horrible mistake in my Los Angeles Times op-ed last weekend, reproducing some figures from the Breakthrough Institute (TBI) without checking them up first. Although TBI spotted their error first and alerted me, the correction did not come soon enough to prevent Joe Romm from Climate Progress rightly taking me to task for it.
Here is the offending paragraph:
Take Japan again. According to some recent number crunching by the Breakthrough Institute, a centrist environmental think tank, phasing out Japan’s current nuclear generation capacity and replacing it with wind would require a 1.3-billion-acre wind farm, covering more than half the country’s total land mass.
Actually what seems to have happened is that TBI converted 1.3 million into 1.3 billion, so they were out by three orders of magnitude! I thought that their figure sounded a little on the high side, but – what the hell – I was busy with the climate negotiations in Bangkok, so I ran with it. Another lesson learned.
Anyway, this does all raise the question of what the true figure might be if we do actually look at the basic numbers. With a little help from Chris Goodall’s latest contribution, here we go:
- Generous assumption: 3 MW is produced per square kilometre of land (well-spaced large turbines, offshore-style)
- Japan’s total land area = 377,915 km2 (CIA World Factbook)
- Multiply 1 and 2 above together, and Japan’s total theoretical wind generation capacity is 1,133,745 MW
- There are 8760 hours in a year, so Japan could generate 9,931,606,200 MW hours of electricity per year, or 9,932 billion kW-hrs (the same as terawatt hours) over its entire land area
- Japan actually generates 982 billion kW-hrs, of which 27% is nuclear (pre-Fukushima disaster, 2009 figures – source: EIA.gov) = 265.14 billion kW-hrs
- To express this as a percentage: 265.14/99.32 = 2.66% of Japan’s land area needed for a wind farm to replace current nuclear generating capacity
How does this compare with TBI’s corrected estimate, posted on their blog?
Alternatively, replacing the generation lost from a complete phase-out of nuclear power entirely with wind energy would require wind generation to increase from its current levels, 3.257 billion kWh (0.3% of total electricity), to 267 billion kWh (27% of total electricity).
According to NREL’s wind farm area calculator, the installation of these wind turbines would require 38,000 acres taken out of production on a wind farm, and a total of 1.3 million acres for the entire wind farm.
What on earth is an ‘acre’? If we are to convert this using Google to a proper metric number, 1.3 million acres = 5,260 square kilometres = 1.4% of Japan’s land area. So by my calculations, TBI is now being overly generous, and underestimating the area of Japan that would need to be devoted to wind to replace current nuclear generating capacity. Perhaps they are overcompensating somewhat. (It should also be borne in mind that this ‘land take’ for a wind farm does not preclude the land in between the turbines being used for farming, for example.)
So what about CO2 emissions? If we assume coal replaces nuclear (a pessimistic assumption), and use a general carbon intensity of coal (UK figures) of 0.91 kg/kWh, then 265.14 billion kW-hrs (Japan’s 2009 nuclear electricity) multiplied by 0.91 = 241.27 billion kg, which in turn = 241 million tonnes of additional CO2 per year. If the lost nuclear generation capacity were to be replaced by gas, with a carbon intensity of 0.36 kg/kWh… well, I’ll let you do the ‘math’!