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Credit: National Geographic

It is a commonly repeated refrain that generating 100% of America’s electricity from renewable sources is not possible because doing so would mean blanketing the country in solar panels or windmills. In contrast to fossil fuels, the argument goes, which require a very small amount of land to generate our power needs, renewables have enormous space requirements that guarantee that they will never be anything more than a niche provider of electricity in a country the size of the United States. Most recently, this idea has been advanced in the documentary Switch, currently touring college campuses around the country.

But how accurate is this argument? On its face it makes intuitive sense: solar panels are large (as are windmills) and neither generate electricity as efficiently as a coal or natural gas power plant. It seems plausible then that renewables would require a large amount of space to generate an amount of electricity comparable to fossil fuels. But what are the numbers? And what happens when the land disturbed by coal mining or natural gas drilling is considered? A brief internet search yields unsatisfying results; arguments seem to be split based on previous opinions towards renewable energy, and when articles do include numbers, they do not appear to be accurate.

Not finding a satisfactory answer to the question already developed, I decided to create my own model of land use for each of seven types of electricity generation: wind, solar PV, concentrated solar, nuclear, natural gas, coal, and woody biomass. The model is based on estimates of capacity factors, plant size, and input requirements from a number of sources including NREL, the EIA, the IAEA, and California Energy Commission. The premise was simple: determine how much land would be required to generate an amount of electricity equal to America’s consumption in 2011 for a total of ten years if each of the seven sources was the only one utilized. The time frame was extended to ten years to better account for the fact that fossil fuels require the disturbance of new land every year in the mining or drilling process; in contrast to renewables which only require disturbance for the initial construction of the plant. Despite the fact that some of this land is reclaimed, it can never be reclaimed to its virgin condition. Because quality data do not exist for the area disturbed by things like pipelines, transmission lines, and compressor stations, this area was not considered and, as a result, the estimates for the fossil fuels should be seen as lower bounds only. However, the land covered by plants and the land disturbed in the mining/drilling process was considered. The total amount of land for each was then laid out on the map below.

Woody biomass is not included in the map because the space required covers multiple United States.

Woody biomass is not included in the map because the space required covers multiple United States.

The results are surprising. Wind is by far the most land intensive, but even this is somewhat misleading. The reason wind farms are so large is because the windmills must be spaced a certain distance apart from one another. This is not because they physically occupy all of that land. In fact, most the land remains usable as farm land which is a big reason some farmers actively seek out wind farms as additional sources of revenue from their land. Solar thermal and solar PV require comparable amounts of land — only about 20% more for solar PV. But surprisingly, if the land disturbed over 10 years by mining is considered, coal requires only 50% less land than Solar PV. If a 20 year time horizon is considered — roughly half the length of the useful life of a coal plant — then they are equivalent in land-use.

Perhaps the most important result is the clear indication that renewables would not actually blanket the country in solar panels or windmills. Natural gas and nuclear clearly require far less land for a comparable amount of electricity than renewables, but that was expected. In terms of space used, nuclear is clearly the most efficient source of power — even accounting for the land needed to mine uranium (but not accounting for land required to store waste) — but solar and wind are certainly feasible options from a spatial perspective.

Finally, why is this posted here in the Biodiversity & Ecosystems section rather than Energy? Because the way in which we generate energy has enormous implications for biodiversity. From the effects of windmills on migratory birds and bats, to the conversion of CRP land to produce additional biofuels, there is a very strong connection between biodiversity preservation and energy generation. This is particularly important to consider when thinking about renewables if they are going to require more space than fossil fuels. While the positive impacts on biodiversity from the long-run carbon reduction of renewables will almost certainly outweigh any local effects of land conversion, it is important not to forget that the siting of these new power generation projects will have implications for local biodiversity.

UPDATE: A commenter has pointed out the following two articles that may be interesting reading for anyone looking to explore this further:

Fthenakis, V., & Kim, H. C. (2009). Land use and electricity generation: A life-cycle analysis. Renewable and Sustainable Energy Reviews, 13(6), 1465-1474.

Jacobson, M. Z., & Delucchi, M. A. (2011). Providing all global energy with wind, water, and solar power, Part I: Technologies, energy resources, quantities and areas of infrastructure, and materials. Energy Policy, 39(3), 1154-1169.

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