Rooftop solar PV could supply two-thirds of world’s energy needs, and lower global temperatures

Covering rooftops across the planet with solar panels could deliver 65 per cent of current global power consumption and almost completely replace fossil fuel-based electricity, and it could also lower global temperatures by 0.13 degrees.

These are the findings from a new study from researchers at the University of Sussex that found rooftop solar PV could generate 19,500 terawatt hours (TWh) of electricity per year. (Australia consumes around 250 TWh of electricity a year).

By using nine advanced Earth system models, geospatial data mining, and artificial intelligence techniques, the researchers were able to estimate the global rooftop area at a resolution of 1 kilometres to evaluate the technological potential of rooftop solar PV.

The researchers outlined their full methodology in an article published in the journal Nature, involving a lot of artificial intelligence machine learning that helped to determine that rooftops currently cover 286,393 kilometres-squared (km²) of the globe.

Of this 286,393km², 30 per cent is unsurprisingly located in East Asia and 12 per cent by North America. China and the United States similarly comprised the largest collection of rooftops, with 74,426km² and 30,928km² respectively.

They were then able to extrapolate the generation potential of rooftop solar PV if every suitable rooftop was used, which resulted in annual electricity generation potential of 19,483TWh.

Unfortunately, this number is based on current building stocks, which means that poorer and undeveloped regions would not be able to benefit to the same degree as more industrialised nations.

For example, Africa, despite having the world’s highest solar energy resources, has very limited building stock, which means that the rooftop solar installation potential for Africa amounts to only 1,188GW, only 7 per cent of the global total.

Conversely, the macro-regions cumulatively boast much lower solar radiation levels, but have an installation potential of 4,339GW, constituting 25 per cent of the total rooftop solar potential.

The researchers were also able to use their findings to calculate the impact a global coverage of rooftop solar would have on global warming. While figures differed depending on the models and scenarios used, complete rooftop solar coverage based on current building stocks could mitigate global warming by 0.13–0.05 °C.

Importantly, the researchers also warned that solar power offers taxpayers better value for money than nuclear and urged policymakers around the globe to prioritise rooftop solar.

“Solar is now outcompeting nuclear power in cost, deployment speed, and environmental risks,” said Prof Felix Creutzig, a University of Sussex climate and policy researcher and one of the authors of the report.

“Given its immediate carbon reduction benefits governments should consider shifting incentives toward rooftop PV instead of nuclear. This goes for cooler countries like the UK as well as those with more obvious solar potential.

“Beyond carbon savings, reducing fossil fuel dependence also means cleaner air and better energy security. With so much untapped potential in solar it’s hard to see how governments can justify investing in nuclear, or as yet unproven carbon capture projects.”