How Much Solar Is Needed?
With challenges to solar farms, some people ask, how many solar farms do we need to build? Since I was recently asked, I suggest some proposed scenarios on how much land is required for solar arrays.
Both rooftop solar and farm-scale solar are necessary if we are to meet projected national targets of renewable energy by 2050. That is, if we want X amount of solar in our renewable energy mix, then we need Y amount of surface area for solar arrays. If you don’t accept the targets, then none of this math matters.
Start with the Solar Futures Study (Sept. 2021)from the US Department of Energy:
Landing Page: https://www.energy.gov/eere/solar/solar-futures-study
Let's pretend we really want to act responsibly on the climate crisis by converting much of our electrical consumption to renewable energy. What does the imminent role of solar energy look like? A summary of the Solar Futures Study suggests staggering numbers, with implications for vast economic growth.
The study finds that with aggressive cost reductions, supportive policies, and large-scale electrification, solar could account for as much as 40% of the nation’s electricity supply by 2035 and 45% by 2050.
The Solar Futures Study modeled the deployment of solar necessary for a decarbonized grid. Preliminary modeling shows that decarbonizing the entire energy system could result in as much as 3,000 GW of solar due to increased electrification.
To reach these levels, solar deployment will need to grow by an average of 30 gigawatts alternating current (GWac) each year between now and 2025 and ramp up to 60 GW per year between 2025 and 2030—four times its current deployment rate—to total 1,000 GWac of solar deployed by 2035.
Although land acquisition poses challenges, land availability does not constrain solar deployment in the decarbonization scenarios. In 2050, ground-based solar technologies require a maximum land area equivalent to 0.5% of the contiguous U.S. surface area. This requirement could be met in numerous ways including use of disturbed lands. The maximum solar land area required is equivalent to less than 10% of potentially suitable disturbed lands, thus avoiding conflicts with high-value lands in current use. Various approaches are available to mitigate local impacts or even enhance the value of land that hosts solar systems. Installing PV systems on waterbodies, in farming or grazing areas, and in ways that enhance pollinator habitats are potential ways to enhance solar energy production while providing benefits such as lower water evaporation rates and higher agricultural yields.
Water withdrawals decline by about 90% by 2050 in the decarbonization scenarios. The water savings result from the low water use of solar and other clean energy generation technologies, compared with fossil fuel and nuclear generators.
Per the study, in 2050 ground-based solar technologies require a maximum land area equivalent to 0.5% of the contiguous U.S. surface area.
So how much space is 0.5% of the contiguous U.S. surface area?
US: 2.43B acres
2.43 x 0.005 = 0.01215
0.5% of US: 12.15M acres
12,150,000 acres =18,984 square miles
Nearly the size of Lake Michigan at 22,300 sq. mi.
Great Lakes: 60.32M acres
60,320,000 acres = 94,250 square miles
Here’s a visual perspective on US land needed for solar development by 2050. If you accept the target, what’s needed is to cover an area equivalent to the size of Lake Michigan, sans Green Bay, with solar panels?
Or from another perspective…
Green: solar required is 15,600 sq. mi. from combined rooftop and open land.
Red: 3,100 sq. mi. (solar rooftop potential).
Again, since I was asked, let me add a note on efficiency and how it relates to farmland. In Indiana, you can grow corn for ethanol or you can install solar panels for renewable energy. Without going deep this time, “In Indiana, solar yields roughly thirty times the energy per acre.” Compared to using land to grow corn for ethanol, solar arrays are vastly more efficient.
Let me touch briefly on rooftop solar energy. I agree it is often preferred over open land. However, we can’t just point a finger with scorn at solar farms and wish for more rooftop solar. The greatest impediment to rooftop solar is the Indiana Statehouse. Last year (two decades after the start of the 21st Century) Indiana’s elected officials affirmed the State’s disinterest in supporting solar energy with its so-called 21st Century Indiana Energy Policy Task Force. I wrote about it here: https://www.nightwise.org/single-post/my-dad-on-the-roof.
While it has allowed large solar installations, the Statehouse undermined reasonable incentives for rooftop solar. A current push among Indiana solar advocates is to encourage a concept called Community Solar. That’s where a group of people who would like to be part of the solution can join a solar collective if they are unable to install solar on a rooftop themselves. That would include renters, people who can invest only smaller amounts or for shorter time frames, people who live in shady or wooded areas, people with HOA restrictions, schools, churches, low income populations, etc. You invest in community solar, and your return from energy that goes into the grid is a reduction in your electric bill.
But the Statehouse doesn’t allow real community solar. Some politicians assert rooftop solar puts the burden on ratepayers who don’t have solar. That’s claimed despite the reality that it is the private investors who are the ones who pay for and build the extra capacity to get the utilities through peak demand. By deferring the need for extra power plants and diesel generators, the solar contribution instead saves ratepayers from the increased construction that would further fossilize the old carbon-based system.
So…I ask everyone to please keep a heads-up about any opportunity to support Community Solar. It’s not the “subsidy” that Indiana Statehouse politicians claim. Details from Solar United Neighbors are at https://www.solarunitedneighbors.org/go-solar/community-solar/.