File:solar-land-requirements.png

Summary

World map: If all energy came from solar panels, how much land would we need?

The land is shown in white.

We would need approximately 0.8% of Earth's surface.

Just for comparison, crop land is about 2.9% of Earth's surface, and pasture land is about 5.4% of Earth's surface.

Methodology

Area required for solar panels, if

• all energy came from solar photovoltaics, and
• everyone on Earth lived a "first-world" lifestyle.

Map projection: equirectangular

First we estimate how much energy would be needed per person: [''']this is a conservative overestimate. People in warm climates might actually need slightly less energy because they don't need heating. The difference is not a lot though oecd.energy.tfc / oecd.population kWh/year energy_per_capita (calculation loading)

Then we estimate how much area that would take energy_per_capita / (area_suitable * sunlight_average * solar_panel.efficiency) km^2 solar_land_per_capita (calculation loading)

Now we use that to generate an isochromic map:

Image generator code:

# load files
pop << data/population.data-float64-8640x4320
earth << data/blue-marble-posterized.png

# convert 'pop' to population density (people per km^2)
pop @@ quantity_to_density

# resize 'pop' to fit the 'earth' background
pop :: earth.r

# make 'pop' represent "for each pixel, what fraction of the land is solar land"
pop *= 0.00053790026 # km^2 per person needed for solar           
pop @@ spread

# darken the background
earth.r *= 0.5
earth.g *= 0.5
earth.b *= 0.5

# show the solar land in white
earth.r += pop
earth.g += pop
earth.b += pop
earth.r <= 1
earth.g <= 1
earth.b <= 1

# save
earth >> data/solar-land-requirements.png



# How much solar land is needed in total?
pop @@ density_to_quantity  # make 'pop' represent "for each pixel, how many km^2 of solar land"
pop @@ stats

From the "stats" output from the last line:

Sum: 4293152.303951

This means there is 4293152 km^2 of solar land.

Divide this by the Earth's surface (510072000 km^2), and you get 0.8%.

Would your city need solar farms?

1 / solar_land_per_capita people per km^2 (calculation loading)

Simple heuristic:

• If your city's population density is greater than this number above, then yes.
• Otherwise, all energy could be generated within the city (rooftops, probably).

But this is an oversimplification. Some things to consider:

• Every city defines its borders differently - this could bias the official stats of "population density".
• If factories are in some industrial area outside the city, their solar panels could be there instead.
• Other factors, shown in the next section:

Limitations of this analysis

• Not all cities have the same area_suited for solar panels.
• Solar panel output varies by latitude.
• Energy requirements for heating depend on latitude.

If we want something really accurate, we might have to analyze things on a city-by-city basis.

Not counted in this map: The land that would be needed for extracting the mineralsyou can help calculate this - analyze your favorite battery chemistry and solar panel chemistry needed to make both the solar panels and energy storage.