The Land Footprint of PV Solar (and Nuclear and Wind Power)
After I wrote An Ode to PV Solar Power, an article highlighting several unique and fascinating aspects of solar power (namely its physics and modularity), a reader brought up the issue of the high land footprint of solar.
Yes, photovoltaic solar requires more land than other energy sources to generate the same amount of electricity. But I wanted to explore — how much more? I did some research and here’s what I found out.
Solar requires significantly more land than nuclear, and wind requires even more than solar
As a point of comparison, I will use nuclear power, which is the densest source of energy and thus requires the least amount of land use per kWh of electricity generated.
A typical 1GW nuclear power plant with a capacity factor* of about 90% requires 1.3 square miles (3.4km2) of land.
*The capacity factor is the measure of a plant’s productivity. More specifically, the capacity factor of a power plant is equal to the amount of electricity produced for a given time, divided by the amount of electricity that would have been produced if the plant was running continuously at its installed capacity for that time. Here is a comparison of typical capacity factors for different energy sources:
Photovoltaic (PV) solar farms have relatively low capacity factors because unsurprisingly, the PV panels do not generate electricity at night or on cloudy days. The capacity factor of solar PV varies from 17–28%. Thus to generate the same amount of electricity as the aforementioned nuclear plant, a solar farm would need an installed capacity of 3.3–5.4GW, requiring between 45–75 square miles (116–200km2).
Like solar, because of wind power’s intermittence, the capacity factor of wind power is on the lower side and ranges from 32–47%.To match the electricity output of the nuclear power plant, a wind farm would need to have an installed capacity of 1.9–2.8GW.
While wind power has a higher capacity factor than solar power, wind farms require a lot more land because the wind turbines need to be spaced very far apart and thus the equivalent wind farm would require between 260–360 square miles (670–930km2)!
To provide some perspective, my neighborhood, the 11th arrondissement in Paris, is 1.4 square miles (like the 1GW nuclear plant).
The area of all of Paris is 40 square miles (the equivalent solar farm).
The area of the five boroughs of New York City is about 320 square miles (the equivalent wind farm).
Or another way of looking at it:
I did not realize that the land footprint of wind power was so high (and that New York City was so much bigger than Paris)!
So much land, but — as per usual, there’s more to the story
PV solar requires about 50x more area than nuclear to generate the same amount of electricity. However, one of solar’s great advantages is its modularity and flexibility and the fact that the panels do not necessarily need to be installed on the ground directly. Solar panels can be installed on homes and buildings, parking lots, highways, even canals.
Also, a new sector that is developing quickly is agrivoltaics, the dual-use of land for both PV solar and agriculture. As presented by the French company Sun’Agri, the solar panels are elevated on fixed support systems about 4 meters above the crop field. This configuration allows to double up on generating electricity and producing crops for regions with limited land resources. For this agrivoltaics installation in Kenya, the panels help to retain moisture in the soil and boost crop growth.
As these examples demonstrate, solar does not necessarily require direct and unique land.
Moreover, solar farms can also be installed in places that people do not frequent and which are not suitable for agriculture — namely deserts and “brown fields” (closed landfills, old coal mines, even Chrenobyl hosts a a 1MW solar farm).
Wind power requires 200x more land than nuclear — which seems quite astonishing. The direct land footprint of a wind turbine is actually quite small, but for a wind farm generally composed of 50–100 wind turbines (or sometimes up to thousands), the turbines must be spaced very far apart to avoid obstacles and wind turbulence. The general rule-of-thumb for spacing between two turbines is 7 rotor diameters (1 rotor diameter is equal to twice the length of a blade).
A 5MW turbine with a rotor diameter of 125m must be distanced about 875 meters (more than half a mile!) from the closest turbine. That is a lot of “undisturbed land”, no wonder wind power’s land use footprint is 200x that of nuclear! While people do not want to live next to or on a wind farm, this land can and is increasingly being used for other purposes like livestock grazing and agriculture.
For all these reasons and more (namely that these comparisons do not include the land use need for mining and disposal related to nuclear energy), in his paper Renewable energy’s “footprint” myth, Rocky Mountain Institute’s Amory Lovins explains quite well that “land footprint seems an odd criterion for choosing energy systems”.
So what’s the takeaway?
On the one hand, this analysis demonstrates how incredibly energy-dense and reliable nuclear power is.
On the other hand, even though solar and wind are diffuse energy sources and require significantly more land than nuclear, land-use is not necessarily a critical criterion in many situations — and in the case of regions with limited land resources, there are many dual-use land solutions for these technologies.
Beyond land-use, nuclear and renewable sources like solar and wind have their pros and cons (cost, risk, waste, intermittence…) but one major advantage that they share is that they are low carbon-emitting energy sources. And the only way to drastically reduce carbon emissions is to make fossil fuels — which are responsible for 3/4 of global greenhouse gas emissions — a thing of the past and replace them with a mix of these low carbon-emitting energy sources.
Fossil fuels are already a thing of the past for me, that’s why I didn’t even consider them in this analysis.
Further reading
- “The Ultimate Fast Facts Guide to Nuclear”, Department of Energy, 2019.
- “The U.S.Will Need a Lot of Land for a Zero-Carbon Economy”, Bloomberg Green, 2021.
- “When It Comes To Land Impact, Does Solar, Wind, Nuclear, Coal, Or Natural Gas Have The Smallest Footprint?”, FreeingEnergy, 2020.
- “Renewable energy’s footprint myth”, Rocky Mountain Institute, 2011.
