The DOE report’s comparison of land used for wind farm with land requirements of other energy sources is cogent and worth quoting at some length:
“Coal mining is estimated to disturb more than 400,000 hectares of land every year for electricity generation in the United States, and it destroys rapidly disappearing wildlife habitat. In the next 10 years, more than 153,000 hectares of high-quality mature deciduous forest are projected to be lost to coal mining in West Virginia, Tennessee, Kentucky, and Virginia, according to the National Wildlife Federation (Price and Glick 2002).
“Wind farm development also requires large areas of land, but the land is used very differently. The 20% Wind Scenario (305 GW) estimates that in the United States, about 50,000 square kilometers (sq-km) would be required for land-based projects and more than 11,000 sq-km would be needed for offshore wind farm projects. However, the footprint of land that will actually be disturbed for wind development projects under the 20% Wind Scenario ranges from 2% to 5% of the total amount (representing land needed for the turbines and related infrastructure). Thus the amount of land to be disturbed by wind development under the 20% Wind Scenario is only 1,000 to 2,500 sq-km (100,000 to 250,000 hectares)—an amount of dedicated land that is slightly smaller than Rhode Island. For scale comparisons, available data for existing coal mining activities indicate that about 1,700,000 hectares of land is permitted or covered and about 425,000 hectares of land are disturbed (DOI 2004). An important factor to note is that wind energy projects use the same land area each year; coal and uranium must be mined from successive areas, with the total disturbed area increasing each year. In agricultural areas, land used for wind generation projects has the potential to be compatible with some land uses because only a few hectares are taken out of production, and no mining or drilling is needed to extract the fuel.”
I commented on the discrepancy between the DOE report and the article, and the author of the Scientific American piece, David Biello, said he had assumed a capacity factor of 25% for the wind turbines, “based on historic experience in Europe from 2000-2008.” There are four problems with this:
1) Average wind speeds in Europe are lower than in the U.S. A typical American wind farm today has an average capacity factor of 35% or more.
2) Technology development and innovation continue in the wind turbine industry at a rapid pace. It is unreasonable to assume that turbines built a decade from today will be no more productive than those of the past. For this reason, the DOE report assumed an average capacity factor of 43% for turbines operating in 2030.
3) Even if one assume a capacity factor of only 25%, as Mr. Biello does, the land requirement for 20% is far less than his article states. The DOE report assumes U.S. electricity demand of 5.8 trillion kilowatt-hours (kWh) in 2030. With turbines operating at 25% capacity factor to generate 20% of that amount (1.16 trillion kWh), roughly 530 GW of wind would be needed (rather than the 305 GW calculated by the report), or 1.74 times as much capacity. Multiplying 1.74 by the 61,000 sq-km in the DOE report yields a land requirement of 106,000 sq-km, still only slightly more than one-quarter of the 400,000 claimed by Mr. Biello.
4) The DOE report was the work of more than a year’s labor by an extensive team of the foremost American experts on wind energy. It remains the gold standard on whether wind power can supply 20% of U.S. electricity (it can) and the physical and technical requirements need to achieve that level of wind generation.
By Tom Gray, www.awea.org/blog/