The opponents of nuclear energy claim that Japan could produce much of its electricity from wind. (See the debate at Climate Progress). Others, such as the Breakthrough Institute , offers estimates of how of the country's land area would have to be covered with turbines to generate enough electricity. Below is my estimate of how much of the country would be required – about 10%. Since Japan gets about one quarter of its electricity from nuclear power about 2.5% of the land area would need to provide the equivalent amount of power. This would come from about 50,000 turbines.

My producution figures are almost certainly far too low. I use a high estimate of the average number of watts of electricity produced per square metre of land and my figures assume constant hourly production. But of course wind is highly erratic, so far more wind turbines would have to be installed to meet the total need. The actual production of onshore turbines - which are generally less productive than offshore wind farms - would probably be much less than 3 watts per square metre. Japan would also need extensive grid links with other Asian countries to protect against long periods of low wind speed by giving the country to import large quantities of electricity. Unlike Britain, Japan does not have a single electricity network. This would further enhance the problems of dealing with regional shortages and surpluses of wind power.

I’d be very grateful for any corrections to these numbers.One point for clarification. The figures I give are for typical production of working turbines, properly spaced over large areas so that one turbine does not steal the wind of another. Pack the turbines more closely and you might get higher total production, but at much higher cost. Wind farms really do need lots and lots of space. The world’s biggest offshore installation, the planned London Array, will need over 230 square kilometres to provide 1000 megawatts of maximum generating capacity. Some turbines will be spaced over a kilometre apart.

Wind a 3 watts (1) per sq metre b 3 megawatts per sq kilometre Japan c 377,835 sq kilometres Total wind production if all of onshore Japan given over to turbines d 1,133,505 megawatts production if all of Japan used for wind farms (2) e 8,760 hours per year f 9,929,503,800 megawatt hours per year g 1,000,000 terawatt hours per megawatt hour h 9,930 terawatt hours per year Share of Japanese land area needed i 1,075 terawatt hours per year used in Japan (3) j 10.8% share land area of Japan needed

Notes

(1) This figure is achieved by the best UK offshore wind farms (2) The land area multiplied by the electricity production per sq.m. (3) Estimates of this figure vary slightly