How much land does solar, wind and nuclear energy require?

What kind of energy system has the smallest impact on the natural world? This seemingly straightforward question is actually bedevilingly complex, as evidenced by the rich discussions and debate at the 5^th annual Breakthrough Dialogue hosted by the Breakthrough Institute, an Oakland-based think tank. [Full disclosure: I worked as Director of Energy and Climate Policy at the Institute from 2008-2012].

The impacts of energy systems on the human and non-human environment are manifold, from climate change to ocean acidification, air pollutants to mining, ecosystem damages to physical land footprint. While averting climate change dominates so much of the discussion about how to shrink the impact of energy systems on the environment, once we limit ourselves to a menu of low-carbon energy sources, real environmental tradeoffs still remain.

When it comes to wind, solar and other renewable energy sources, the diffuse nature of these resources and the relatively large land area requirements that result is often held up as a barrier to widespread adoption. Do we really have enough land to turn en masse to solar and wind energy to power modern economies? Or is land use a showstopper for renewable energy?

The reality is that, excluding biomass (more on that later) and with the exception of a few densely populated countries with relatively poor renewable resources, the land area required for widespread renewable energy adoption is relatively minor, especially compared to other human uses of the landscape.

Let’s look at the numbers…

The recently released MIT Future of Solar Energy study contains this useful infographic, which puts everything into perspective.

Source: The Future of Solar Energy, MIT Energy Initiative 2015

According to the MIT authors, powering 100 percent of estimated U.S. electricity demand in 2050 with solar energy would require roughly 33,000 square kilometers (sq-km) of land. That’s if we spread solar panels evenly across the entire country. If we concentrate solar production in the sunniest regions, the total land footprint falls to 12,000 sq-km.

Those sound like big numbers. On the one hand they are. Massachusetts (where I reside) spans about 27,000 sq-km, for comparison. On the other hand, the United States apparently devotes about 10,000 sq-km of land just to golf courses. And as the infographic illustrates, it’s agriculture and forestry that truly drives humanity’s footprint on the natural landscape.

In reality, no one is calling for 100 percent solar energy. Even the most bullish renewable energy advocates typically envision solar providing less than half and usually no more than a quarter of U.S. electricity. (See: “Is There An Upper Limit to Variable Renewables”) If solar provided one-third of Americans’ electricity in 2050, it would require just 4,000-11,000 sq-km.

In other words: with an area no larger than the amount of land currently devoted to golf courses, we could power a third of the country with solar energy.

Solar panels spanning an area of land no larger than that devoted to golf courses could power one-third of American electricity needs. Image source: Sunkist Country Club

That assumes we build solar farms on undeveloped land, in deserts or other untrammeled areas. If instead, we put solar on one quarter of U.S. rooftops and across parking lots, industrial brownfields, landfills, and other degraded lands, this total land footprint would shrink dramatically.

If carefully sited, it may even be possible to power a third of the country with solar without measurably expanding humanity’s land use footprint. Accomplishing that would end up costing more, as large solar farms in the desert are usually the cheapest way to harness solar’s potential. But if land use is your bellwether, there’s no reason not to embrace solar power.

What about wind energy?

As I discussed with Robert Wilson in this recent column, wind farms span a larger area than an equivalently-productive solar farm. Powering one-third of the country's projected 2050 electricity demand with wind energy could take a land area spanning on the order of 66,000 sq-km, according to land use figures calculated by Australian environmental scientist and Energy Collective contributor Barry Brook.

That’s a lot of land, but only about twice as much land as we’ve already devastated with coal mining or three times as much land as we’ve bombed to shit in military test ranges, according to the MIT study. However, that’s the total land area spanned by the wind farms. Wind turbines are spaced out, however, and wind energy can cohabitate perfectly well with farming, grazing, and other productive uses of the underlying land.

The direct land use impact associated with wind turbine pads, roads, substations and transmission lines is much smaller. According to data collected by the National Renewable Energy Laboratory on dozens of U.S. wind farms completed before 2009, the land area permanently taken out of production by wind farms amounts to just about 1 percent of the total area spanned by the wind farm. Another 2 percent of the total area is temporarily impacted during construction activities, used for staging areas, temporary access roads, etc.

Source: Denholm et al. 2009, National Renewable Energy Laboratory

Powering one-third of the country in 2050 with wind farms would thus truly impact only on the order of 2,000 sq-km, of which less than 700 sq-km would be permanently removed from production. That’s an almost trivially small amount of land, equal to only 7 percent of the land area wasted, er, devoted to golf in this country.

Update June 26, 2015: Wind land use figures in original post were rounded to 60,000 sq-km for one-third of U.S. electricity. More accurate figure of 66,000 sq-km included above, with updates to direct and temporary land area impacted accordingly. End update. If well sited and co-located on already disturbed and productive agricultural lands, wind farms could thus fuel a sizeable fraction of America’s energy demand without expanding the human footprint on the land in any meaningful way, except aesthetically.

Wind farms co-habitate just fine with other productive uses of the land, including grazing and agriculture. Image source: Shutterstock

Indeed, as the MIT infographic makes abundantly clear, and as anyone who has flown over or driven across America’s vast agricultural heartland has seen first hand, farming and forestry are far and away the real drivers of humanity’s impact on the landscape. Croplands span a staggering 1.65 million sq-km in the United States, an area almost as large as France, Spain, Germany and the United Kingdom combined. A majority of the 5.2 million sq-km of forests, grasslands, pasturelands, and rangelands in America are also under active management, placed into service for forestry, grazing and other human activities.

Agriculture and forestry has thus already disturbed three to four orders of magnitude more land area than would be impacted if we powered two-thirds of the country with wind and solar together. That’s no reason to ignore the imperative to responsibly site wind and solar energy in order to limit their ecological impact, but it also means that discussions about shrinking humanity’s physical footprint on the planet should center on agriculture and forestry, not solar or wind energy.

That’s also why biomass makes so little sense from an ecological perspective.

Corn ethanol supplies only about 4 percent of transportation fuel in the United States, yet already requires 66,000 sq-km of agricultural lands, about five to ten-times more land than would be required to derive two-thirds of the country’s electricity from wind and solar. Biomass for electricity is just as bad, requiring an order of magnitude more land than solar power, according to Brook.

While energy density is thus no reason to turn our backs on wind or solar energy, biomass is another story. From an ecological perspective, we would be wise to severely limit the use of biomass, perhaps to high-value uses without other alternatives, such as a bio-based replacement for high-density jet fuel.

Nuclear power is of course the densest form of energy harnessed yet by humankind. A ton of nuclear fuel used in a light-water reactor contains more than 200,000 times more energy than a ton of coal, making nuclear five orders of magnitude more energy dense than fossil fuels.

Nuclear fuel is so compact that only two grams of natural uranium, about the weight of two paperclips, would fuel 100 percent of an average British person’s energy needs for a day, according to Cambridge University engineering professor David Mackay. Four grams of uranium would be sufficient to meet a fuel-hungry American’s daily needs. Slightly more than 3 pounds would power your life for an entire year.

Uranium weighing as little as this three pound sack of potatoes could fuel an American's entire energy needs for a year. Image source: Sun-Glo of Idaho

That incredible density means that everything associated with the nuclear fuel cycle—from the size of the reactors themselves to the impact of mining to the amount of spent nuclear fuel that must be stored or reprocessed at the end of the cycle—scales down accordingly.

To fuel one-third of the United States’ 2050 electricity demand with nuclear power would require only 440 sq-km, according to the land use figures compiled by Brook. Update, June 26, 2015: It was brought to my attention that the land use figures used by Brook and Bradshaw assume "fourth generation" nuclear reactor designs and are thus not appropriate for comparison to current generation solar and wind here. Brook and Bradshaw assume a land use intensity of 0.1 sq-km per terawatt-hour per year (sq-km/TWh/year) of generation for fourth generation nuclear, which was the basis for the calculation above. My apologies for not closely veryifying the assumptions behind the Brook and Bradshaw paper. 

Thanks to commenter "Som Negert" for providing a link to this table compiled by the U.S. Nuclear Regulatory Commission (NRC), which lists the power output and total site area for all nuclear reactors in the United States.

Using NRC data, I calculate that the actual U.S. nuclear fleet spans 1.02 sq-km per TWh per year of generation (assuming an average 90 percent capacity factor for all reactors). That figure includes the full site area for each reactor, including buffer zones and cooling ponds/lakes etc. in addition to the reactor site itself, and is two orders of magnitude less energy dense than Brook and Bradshaw assume. It does not include land area required for uranium mining or spent fuel storage.

Using these real-world figures, I estimate that suppyling one-third of projected 2050 U.S. electricity demand with nuclear reactors would require nearly 1,500 sq-km of land. That's still only 15 percent of the land currently devoted to golf courses in the United States.

Using these updated figures, nuclear energy is still less land-intensive than solar or the total land area spanned by wind farms, but nuclear's land requirements are larger than the land area actually taken out of production by wind farms, and equivalent to the total area disturbed during and after construction of wind farms. At the same time, the cooling ponds/lakes and buffer zones at nuclear sites are also often used as recreational sites or wildlife sanctuaries, so only a portion of the total site area spanned by a nuclear facility is devoted solely to electricity generation. 

The most compact nuclear power facility in the United States is the 84 acre San Onofre site near San Diego, California (now closed), which has a land intensity of as little as 0.017 sq-km/TWh/year.  If every reactor was able to utilize natural cooling and was built on a site as compact as the San Onofre site, powering one-third of U.S. electricity in 2050 would require as little as 24.3 sq-km, demonstrating the incredible potential density of nuclear energy.

But as they say: real-world mileage may vary. End Update.

The density of nuclear energy is a thus major advantage, from an environmental perspective. More nuclear energy means fueling humanity’s energy appetite will require a substantially smaller physical footprint.

Minimizing the land use footprint of our energy system is an important part of considering the most environmentally benign energy portfolio. But it’s only a part. Some advocates of nuclear energy take a philosophical preference for energy density to extremes, arguing that nuclear’s density makes it wholly superior to wind or solar energy. Yet as we’ve seen, land impact is hardly a barrier to widespread use of wind or solar energy, and of course, land use is just one of several important ecological metrics to balance. As Bradshaw and Brook, a staunch nuclear advocate himself, write:

Because there is no perfect energy source … conservation professionals ultimately need to take an evidence-based approach to consider carefully the integrated effects of energy mixes on biodiversity conservation. Trade-offs and compromises are inevitable and require advocating energy mixes that minimize net environmental damage.

Updated June 26, 2015: A reader requested a summary table comparing results, which I've created below.