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Future World – How Many Windmills Would We Need?

Edward A. Reid Jr.
Posted On:
Jun 6, 2017  at  at 8:51 AM
Energy Policy, Climate Change

The US currently consumes approximately 97 quadrillion British Thermal Units (BTU) of energy in all forms each year (97 Quads). Since this quantity of energy and the forms of energy which constitute it vary over time, this analysis will use rounded numbers to avoid the impression of unjustified accuracy or precision.

Current US energy consumption, by fuel source, is approximately:

  Natural Gas 29 Quads
  Coal 14 Quads
  Oil 36 Quads
  Renewables 10 Quads
  Nuclear 8 Quads


Current US electricity consumption is approximately 12 quads.



The objective of the climate change movement is to eliminate fossil fuel consumption by the end of the century, if not before. The climate change movement is also not supportive of nuclear power generation or additional hydroelectric generation. Achieving their goal would require replacing the useful energy services provided by approximately 87 quads of current US energy consumption with renewable sources of energy. As shown above, current US energy consumption produces only approximately 31 quads of useful energy services. The balance of the energy consumed is rejected as the result of process inefficiencies. Therefore, approximately 21 quads of additional renewable energy would be required to replace the useful energy services currently provided by fossil fuels and nuclear, assuming 100% utilization efficiency. At a more realistic utilization efficiency level of 60%, approximately an additional 35 quads of renewable energy would be required.

One scenario would provide the entire 35 quads of additional renewable energy with wind generation. If we assume a mix of onshore and offshore wind generation, an average wind turbine capacity of 3 MW and an average wind turbine capacity factor of 35%, the incremental generating capacity required would be approximately:

35,000,000,000,000,000 BTU/yr

3MW/WT * 0.35 * 1,000,000 W/MW * 3.413 BTU/Whr * 8766 hours/yr. = 35,000,000,000,000,000 BTU/yr

31,000,000,000 BTU/yr = 1,200,000 wind turbines

Normal electric industry practice would provide a capacity reserve margin of approximately 20%, to allow for weather extremes and equipment outage for maintenance and repair. This would increase the number of additional wind turbines required to approximately 1,450,000.

Hourly variations in electricity demand can average approximately 60%, which would require either additional generation capacity or storage capacity equal to approximately 30% of peak demand. Seasonal demand is also higher in summer and winter than in spring and fall, requiring additional, longer term, storage.

Current US electric generating capacity is approximately 1,000 Gigawatts (GW), of which 70 GW is wind generators and 80 GW is hydroelectric generators. Replacing the remaining 850 GW with 3 MW wind turbines at a 35% capacity factor would require approximately 800,000 wind turbines.

Therefore, it would require approximately 2.3 million wind turbines to replace existing fossil and nuclear generated electricity and the current direct uses of coal, oil and natural gas. That is approximately 30 times the current installed wind generation capacity. Other scenarios might rely on a combination of wind and solar initially, with later additions of Ocean Thermal Energy Conversion and Wave Energy. Regardless, this would be a monumental task.