Covering highways with solar panels could cut global emissions and accidents, study finds

Groundbreaking research suggests covering the world's highways with solar roofs could reduce CO2 emissions by 28%, generate electricity and improve road safety

Covering the world’s highways with solar panel roofs could dramatically reduce carbon dioxide emissions and decrease traffic accidents, according to a new study. This ambitious estimate, which analyzed the costs and benefits of installing solar roofs on a global scale, suggests a potential reduction in carbon emissions by 28%, significantly decreasing the reliance on fossil fuels.

The research, published in Earth’s Future, envisions a network of elevated solar panels above highways and major roads, capable of generating electricity while shielding vehicles from harsh weather conditions. Ling Yao, a remote sensing scientist at the Chinese Academy of Sciences and the lead author of the study, stated:

“There are some pilot programs for photovoltaic highway roofs, but not on the scale we’ve envisioned. Covering the Earth’s highways with solar roofs could generate 17.58 petawatt-hours of electricity annually, equivalent to over 60% of the world’s electricity consumption in 2023.”

The study’s authors emphasize the need for innovative solutions to reduce carbon emissions and meet the 1.5-degree Celsius warming target set by the Intergovernmental Panel on Climate Change (IPCC). Between 2012 and 2021, solar panels accounted for 40% of the new renewable energy sources installed. As solar panel costs continue to decrease, creative projects like Yao’s could facilitate the global transition to sustainable energy.

Inspiration for a sustainable future

The idea for this groundbreaking study came to Yao during his evening commute over an overpass, when he thought:

“Roads are connected like a network. Why not turn our roads into a network of photovoltaics?”

Covering highways with solar roofs utilizes already developed land to generate electricity, reducing the demand for greenhouse gas-emitting energy sources and, in turn, lowering carbon emissions. The Earth is covered by over 2 million miles (3.2 million kilometers) of highways, enough to circle the equator 251 times.

While solar-covered parking lots have increased in recent years, paved roads covered with photovoltaic panels are still in their infancy. Some countries have initiated small pilot projects, but extensive stretches of highways covered by solar panels remain a distant goal.

Researchers examined the world’s highways and major roadways, calculating the cost to build and maintain a network of solar panels in each country or region. Their analysis was based on polysilicon photovoltaic panels with a maximum output of 250 watts, tilted 10 degrees toward the outer lanes of highways.

According to Yao, installing solar roofs on the world’s highways would require 52.3 billion solar panels, generating up to 17,578 terawatt-hours annually, more than four times the annual energy production of the United States. Covering major roadways would generate an additional 13,570 terawatt-hours per year.

The cost per megawatt-hour and the potential for energy generation vary geographically, with most installations located near densely populated areas with extensive highways, such as Eastern China, Western Europe, and the Eastern United States.

Environmental impact and road safety

Installing photovoltaic roofs over global highways could produce enough energy to replace the equivalent of 9.66 gigatons of carbon dioxide generated by fossil fuels annually, about two-thirds of the United States’ greenhouse gas emissions in 2022. Yao remarked:

“It really surprised me. I didn’t realize that highways alone could support the deployment of such large photovoltaic installations, generating more than half of the world’s electricity demand and greatly easing the pressure to reduce global carbon emissions.”

Highway solar roofs could also reduce road accident fatalities worldwide by 10.8%, particularly in regions with high rainfall, by protecting drivers and roads from rain and snow. Enhanced road safety would also reduce the economic costs of accidents.

Despite the promising outlook, installing solar roofs on highways could face significant obstacles, including high costs—potentially up to four times the cost of equivalent ground-mounted installations—and maintenance expenses. Practical issues, such as cleaning billions of solar panels, pose additional challenges.

However, Yao remains optimistic that small pilot programs will gain traction and that some countries will implement solar roofs on a large scale. He envisions photovoltaic roofs being more easily installed along long, straight stretches of highways, such as those in the southwestern United States.

Source: American Geophysical Union