How much of Japan’s land area would be needed to replace nuclear with wind?

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:

  1. Generous assumption: 3 MW is produced per square kilometre of land (well-spaced large turbines, offshore-style)
  2. Japan’s total land area = 377,915 km2 (CIA World Factbook)
  3. Multiply 1 and 2 above together, and Japan’s total theoretical wind generation capacity is 1,133,745 MW
  4. 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
  5. Japan actually generates 982 billion kW-hrs, of which 27% is nuclear (pre-Fukushima disaster, 2009 figures – source: = 265.14 billion kW-hrs
  6. 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’!


  1. tim73

    The average capacity is only about 20-30 percent on average from a wind turbine and it varies quite a lot during the day. So if it is rated 2 MW, you get 400-600 kW on average but it could be 100 kW for a most of the day and then 1300 kW for few hours.

    In Texas 2008 February, they lost 1700 MW of wind turbine power and had to shutdown 1100 MW within TEN minutes from large customers to avert the grid collapse. That was because most of the backup coal plants were under maintenance.

    Wind power cannot replace nuclear or coal alone, it needs backup (coal) power or storing the energy somehow for low supply, high demand situations. That means usually pumping water up into dams. There is also the costs of building the complex grid to carry to maximum wind power, which you get mostly few times per month.

    1. MightyDrunken

      A report which looked at onshore wind farms around the USA found a capacity factor from 1 to 11MW/km2 giving an average of 3.0 ± 1.7 MW/km2. The figure is highly variable because there is no definition for the area occupied by a wind farm, most of this area is just open space suitable for farming. If you calculate the capacity factor for the Thanet offshore Wind Farm it comes to 11MW/km2, so about 3MW/Km2 if you assume a capacity factor of 30%.

      On your mention on the downside of wind power the backup is not a problem for the moment as there is currently little wind power and plenty of gas. In fact coal and nuclear are bad backups for wind as they are not easily varied.

  2. Dr. Richard Tetley

    Mark Lynas,
    Actually the offending paragraph includes the last sentence, “Going for solar instead would require a similar land area, and would in economic terms cost the country more than a trillion dollars.” So unfortunately those that read the article without the disclaimer might think that solar energy is not a credible energy source. So before I write my letter to the editor correcting your article in my local paper you might indicate to me that the entire paragraph is incorrect, not just the portion regarding wind power. I assume that the land mass needed for solar is better estimated at 1.3 million acres by the Breakthrough Institute. I do, however, find that number is remarkably close to the estimate for wind power, which seems unlikely. It would be helpful to get a reply indicating that the whole paragraph was misleading. I am sorry that this error has been perpetuated by reprinting of the Los Angeles Times article in many, many smaller newspapers. Without a reply I will have to make my own assumptions regarding the last sentence of the erroneous paragraph. I can be found at . It is unfortunate that this error occurred.
    Richard Tetley
    Eugene, Oregon, USA

    Entire 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. Going for solar instead would require a similar land area, and would in economic terms cost the country more than a trillion dollars.”

    1. Mark Lynas (Post author)

      Hi Richard – yes, I’m certain this must be wrong too, but I haven’t attempted the figure for solar, only wind. You could try using the NREL calculator that is linked above. But feel free to write your letter to various editors!


  3. Alexandre

    I’m no big fan of nuclear, but gien the present urgency in reducing GHG emissions, I would not start by replacing nuclear by wind power in Japan.

    How about replacing Fossil Fuels first?

  4. dp

    There’s area and then there’s Romm area. Good thing he doesn’t design parking lots – nobody would be able to get their doors open.

    Here’s some data on what is already built.

    And the conclusions (section 6) of this document found on the calculator page Romm’s article referenced, the 1.2 million acres is pretty close on an area/MW basis using 1MW generators:

    In Washington State the new Kittitas eyesore sites 52 400′ towers on 5,400 acres.

  5. jam

    You have made one error of assumption, one error of understanding, and one error of interpretation.

    1. Assumption: offshore-style
    I would submit that if the turbines are off-shore, then there is zero usage of Japan’s land area.

    2. Understanding: per square kilometre of land
    Furthermore, assuming that you are referring to on-shore turbines only, the terrain of Japan would indicate that most, if not all, of the wind turbines would be sited on ridge lines. Turbine spacing on ridge lines can be anywhere from 2.5 to 5 rotor diameters. A 3 MW turbine will have on the order of a 100 m diameter rotor. Even being conservative (100 m x 5 = 500 m), there would be two turbines per kilometer. The width of the line is almost irrelevant at a simple 5 m wide road.

    3. Interpretation: land area
    As the blockquote from TBI indicates, only 3% of the land area is actually taken out of service. So to say that 2%, 3%, 5%, or 10% – whatever the “real” number happens to be – is ignorant at best and intentionally misleading at worst.

  6. LarryD

    Go one to Goggle Maps and take a look at Japan-terrain. Japan’s population is concentrated in the coastal regions for very good reasons, Japan’s interior is mountainous. And much of it is nature reserves. And being on the Ring of Fire, they have a lot of earthquakes. Anyone bother to design earthquake resistant wind turbines? Or solar farms?

    Then there are the usual, how often is it cloudy, how often is it still, storm effects, etc.

    And Japan doesn’t have much in the way of oil, coal or gas (why do you think they for nuclear in the first place?), so switching to any of those isn’t in the cards. What are they going to use for a back up when the sun doesn’t shine or the wind doesn’t blow?

  7. Andrew King

    Hi Mark… I live downunder in New Zealand. We have a nuclear-free policy down here (which is, at times, blissfully naive in my humble opinion).

    However, the country got right behind the creation of wind farms over the past 20 years or so…and it HAS had a marginal impact on the overall generation of electricity down here.

    Interestingly, New Zealand is almost identical in land-size to Japan and so comparisons can be useful. But their (Japan’s) energy consumption requirements are ‘many multiples’ of what it is here. We’re only a nation of 4.5 million!

    Having said this, roughly 4% of New Zealand’s total energy comes from Wind Turbines. See Wind Energy NZ for a little more information if it is of any interest to you.

    Personally, at the end of the day, I think it is a complete utopian pipe-dream to think that Japan could one day entertain a complete switch-over to wind power – even though the negative (and potentially deadly) aspects of nuclear power stations have certainly been highlighted recently!

    Andrew King

    P.S Mind if I leave a shameless, low-energy plug? I’m the head technician for Winscribe (as opposed to “Wind Scribe”…haha) best speech recognition software

  8. Jimmy Leighton

    As larry says, the biggest issue is the seismic activity in Japan which i think will hinder any long term Wind Farm Development. Perhaps as a complement to existing strategies but not as a major source.

    That said, as per Andrews comment above, NZ also has earthquakes, but i suppose they are much less common.

    At the end of the day, Wind turbines dont look that earthquake resistant, but i suppose the longer term damage from an earthquake damaged turbine is much less than that of a damaged nuclear reactor.

    Interesting times ahead!

  9. Alex

    Just to add to conversation, Fukushima was a design from the 1950’s and had a long record of security violations including terrible maintenance unqualified personnel and forging security reports and somehow this means nuclear power is forever unsafe according to some.

    Also nuclear power has one important benefit no other energy source has namely the creation of medical isotopes used for cancer treatment and painkillers no amount of windmills or solar can ever make up for the loss of such isotopes.

    Like Jimmy said we have some interesting times ahead.

  10. El_Zoido

    Energy Systems form around the energy source.
    You can not simply change the source without changing the system.

    Windpower works superbly in the renewable de-centralized energy system. That system works hand in hand with decentralized sources from solar, biomass (including gas fired plants) & hydropower.

    About the earthquake / typhoon dangers in Japan.
    None of the (few) Enercon wind turbines in the Tohoku area were damaged due to the earth quake and remain operational.

    As for the land use:
    You have to differ between the space required in terms of efficent use (having enough space between the turbines) and the space actually used for the foundation & maintainance roads of the turbine. The last one is the space that is actually blocked from any other form of usage.

    It will take about 27 km² of foundation space to produce 115 TWh by 2020 in Germany. Knowing that most wind farms are located on farmland, you can believe that number.

    In comparison:
    Not to far from where I am, there is an open coal mine that consumes 85 km² of land. You can see it from space and entire villages were moved to dig hundreds of meters down in the ground.

    Japan has alot more wind potential than most areas of Germany, which would mean they could build alot more highly efficent huge turbines along their giant coastline. That means they could propably do more with less land use.

  11. Randy

    Kind of a scary thought, considering that my little state, Vermont, has a questionable reactor that is getting on in years.
    It would help if there were not these ongoing accidents and spills and leaks that are categorically denied.

  12. Gene Preston

    Wind cannot replace nuclear no matter how many MW of wind or how many acres are programmed for wind. This is because wind can be calm for extended periods of time. There is on energy storage technology that can be implemented to provide power during these light wind periods, not even pumped storage. The size and storage area and cost of pumped storage needed to make wind reliable is well beyond what is possible considering both costs and land area needed. Basically all wind is good for is to cause lower amounts of natural gas generation to be used, but that natural gas system must be full capacity to provide reliability. So wind is useful only as an energy source to reduce the cost of natural gas fuel.


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