Declining populations free up agricultural land for large amounts of solar in densely populated countries

The global population is expected to increase from 8 billion people today to 9.7 billion by mid-century. Strong growth is particularly evident in Africa, which will add a billion people.

However, in many countries, population is stable or even falling. There are nine countries with populations larger than 20 million people that are expected to have lower populations in 2050 than today: China, Russia, Japan, Germany, Italy, South Korea, Spain, Ukraine and Poland. The combined population of these countries is expected to fall by 10%, from 2 billion people today to 1.8 billion people in 2050.

A country with a falling population requires less food. In principle, agricultural space could be freed up for other purposes. And one of these purposes could be hosting solar farms. Let us explore how much solar PV energy could be harvested from freed-up agricultural land. Solar panels are over 100 times more efficient at converting solar energy into useful energy than biomass energy from sugar cane, which is the world’s largest crop by mass. With solar PV, relatively small areas of agricultural land can produce large quantities of electricity.

We make the following assumptions for 2050:

· The world reaches zero fossil fuel consumption.

· Solar and wind drive electrification of transport, heating, and industry.

· Solar and wind drive electrolytic production of large amounts of hydrogen for chemicals [ammonia, metals, ceramics, plastics, synthetic aviation fuels, etc.] including energy exports from sunbelt countries to Europe and elsewhere.

· Everybody in the world catches up to the per capita energy consumption of high-income countries.

· Agricultural land is freed up for solar PV farms in the same ratio as population decline. Typical electricity consumption today in high-income countries is 7-12 MWh per person per year. This needs to double or triple to get rid of all fossil fuel consumption, depending upon participation in the chemical industry. We assume that the energy consumption of 9.7 billion people reaches 20 MWh per person per year (all needs inclusive) in mid-century. Thus, an affluent, fully electrified, and fully decarbonized world will need about 200,000 TWh per year of electricity. For comparison, global electricity consumption today is about 30,000 TWh per year.

We maximize energy harvest per unit area by assuming dense arrays of high-efficiency solar panels with low [10 degrees] tilt scattered all over the globe, but mainly in sunbelt countries. The nominal power of each block of solar panels is assumed to be 200 W per m2 and their efficiency to be 20% efficiency. The blocks of solar panels are scattered throughout agricultural regions. The annual energy yield (MWh/MW) for each region is calculated using the capacity factor calculator in the Global Solar Atlas. Table 1 shows (B) the projected population in 2050; (C) the expected population decline from 2022 to 2050; (D) the agricultural land in 2022; (E) the freed-up agricultural land in 2050 caused by population decline; (F) the potential solar generation from the free-up land; and (G) the required generation in 2050 to provide 20 MWh of electricity per person per year.

A B C D E F G

Population in 2050 (millions) Population decline by 2050 Agricultural land in 2022 (1000 km2) Freed-up land in 2050 (1000 km2) Potential extra generation (TWh/year) Required generation (TWh/year)

For all countries except South Korea, solar generation on freed-up agricultural land (Column F) is sufficient (or much more than sufficient) to provide the energy required (Column G) to operate a fully decarbonized economy. Indeed, the total area of potentially available land across the 9 countries is sufficient to provide two thirds of the energy required (143,000 TWh) by a fully electrified, decarbonized, affluent, global population of 10 billion people in 2050.

In addition, of course, there will also be large energy contributions from rooftop solar, floating solar, solar farms in arid areas, solar in combination with agriculture (agrivoltaics), wind, hydro and other sources.

This is a naive calculation for illustrative purposes only. Importantly, Russia and Ukraine export large fractions of their agricultural output, and so declining populations in those countries do not lead to a declining need for agricultural production. Additionally, countries might devote newly available agricultural land to other purposes, including agriculture for export, increasing agricultural self-sufficiency, alternative crops with lower yield [such as meat], forests, and restoring ecosystems.

However, there is a real opportunity in China, Japan, Germany, Italy, Spain, and Poland, to harvest substantial fractions of required solar energy from agricultural land freed up by declining populations.

Authors: Prof. Andrew Blakers /ANU) & Prof. Ricardo Rüther (UFSC).

Andrew.blakers@anu.edu.au and rruther@gmail.com

ISES, the International Solar Energy Society is a UN-accredited membership NGO founded in 1954 working towards a world with 100% renewable energy for all, used efficiently and wisely.