How Would SAI Impact Renewable Energy?

Transitioning from fossil fuels to renewable power is key for cutting greenhouse gas emissions – the root cause of climate change. As of 2024, approximately one third of the world’s electricity is derived from renewable sources, and prices for electricity from wind and solar are falling. The IEA forecasts that the share of renewable electricity generation will increase to about 46% by 2030.

Despite international agreements to reduce greenhouse gas emissions, they continue to rise, and global warming could exceed 2°C above pre-industrial average by mid-century. The limited progress on tackling climate change has spurred some groups to call for more research into sunlight reflection methods – or solar geoengineering – in general and SAI in particular.

Offsetting 1°C of warming with SAI would require reflecting about 1% of incoming sunlight.¹ This would also scatter sunlight, decreasing the proportion of direct sunlight that reaches the surface and increasing diffuse (scattered) sunlight.² Researchers have found that reflecting about 1% of the sunlight that reaches the surface would lead to two to three times more diffuse sunlight.³

Implementing SAI would also lead to other changes in the climate, such as changing winds, rainfall patterns, and cloud cover, which could affect different forms of renewable energy.⁴ In this article, we focus specifically on the impacts of SAI on solar, wind, and hydroelectric power.

Diffusing the sun’s power

The Earth receives vast amounts of energy from the sun, which scientists began harnessing for electricity in the 19th century. Two main categories of solar technology are in use today: photovoltaic (PV) cells and concentrating solar power.

Solar panels are made up of dozens of PV cells. These cells generate electricity by absorbing particles of light from the sun. The absorbed light dislodges electrons within the cell, which then flow and generate electricity.

Several factors affect PV cell functionality. PV cells can produce power from both direct and diffuse sunlight, but they work best in direct sunlight. PV cells are also less efficient as temperatures rise, so climate change can affect the electricity produced by solar panels.⁴

Concentrating solar power arrays use mirrors to concentrate direct sunlight, which heats a liquid. This produces steam, which spins a turbine and generates electricity. They require clear skies, large amounts of land, and are typically used for large-scale power generation.

SAI would affect PV cells and concentrating solar power differently.⁵ It would decrease the total incoming sunlight that would reach the surface, lowering temperatures and shifting some direct sunlight to diffuse sunlight.⁴ While decreased sunlight would lower solar energy production overall, reduced direct sunlight would decrease production from concentrating solar power in particular.⁴ Lower temperatures under SAI could slightly improve the efficiency of PV cells but reduce that of concentrating solar power.⁶

The overall impact of SAI would decrease solar energy potential around the world by a few percentage points, but the effects would vary regionally.⁶ The impact on the solar industry would also vary depending on investment in solar energy infrastructure.

Regional shifts in wind power

People have been harnessing wind power for thousands of years to propel ships and grind grain. Modern wind turbines generate electricity as wind spins large blades that drive a generator.

To generate more power, wind turbines are getting larger, with the tallest currently under construction expected to reach 364 m high including the blades. These larger turbines generate more power, as their blades can capture more wind.

The power that a wind turbine generates depends strongly on the wind speed. Higher wind speeds can increase power output, but turbines are shut down at very high speeds to avoid damage.⁷

The impacts of climate change on wind speeds are regionally variable and highly uncertain. There have been few studies on how SAI might affect wind, but there is evidence that these effects would also vary regionally.⁸

A recent analysis suggests that SAI could drive changes to wind patterns, increasing or decreasing regional wind energy production by up to 12%, while having little effect on global wind energy potential overall.⁸

The power of water

Long before the Industrial Revolution, people used flowing water to power machines to mill grain, process minerals, and even make paper. In the 18th century, water’s power was used to spin cotton in one of the world’s first factories. Hydropower use increased substantially in the 20th century with the building of large dams and is still the largest source of clean energy in the world.

Hydropower relies on channelling water through turbines, typically using dams across rivers. The dams retain large amounts of water that can be released through the turbines during times when energy is in demand. This flexibility to demand makes hydropower stand out among sources of renewable energy.

Hydropower provides about 14% of electricity worldwide, with some countries deriving more than 90% of their electricity from this energy source. However, hydropower depends on a stable and substantial source of surface water, making it vulnerable to climate change. The earlier melting of snow and glaciers, as well as intensifying floods and droughts, are affecting the reliability of hydropower.⁹

SAI has the potential to slow or reverse some of these climate change impacts, such as glacier melt, potentially increasing the reliability of hydropower.⁴ However, these results vary by region⁴ with some areas potentially experiencing worsened droughts and so reduced hydropower potential.¹⁰

SAI’s impacts on renewable energy – variable and uncertain

There is broad agreement among researchers that implementing SAI, or other sunlight reflection methods, would not replace the need to eliminate CO₂ emissions. The scaling up of renewable energy is key for this.

However, there are large uncertainties in how SAI would affect renewable energy resources. Researchers broadly agree that the impacts of SAI on renewables would vary both regionally and seasonally.⁴ Understanding these impacts in more detail will require improved models and scenarios for the future of renewable energy.