Solar panels over highways could significantly cut emissions and boost road safety

Solar panels over highways could significantly cut emissions and boost road safety

by Simon Mansfield

Sydney, Australia (SPX) Aug 08, 2024

Covering highways worldwide with solar panel roofs could greatly reduce carbon emissions and improve road safety, according to new research. This study, which assessed the costs and benefits of installing solar roofs over global highways, suggests that such a move could cut carbon emissions by around 28% by reducing reliance on fossil fuels.

The research proposes a network of solar panels elevated above highways and major roads, which would generate electricity while protecting vehicles from adverse weather. This study was published in Earth’s Future, an open-access AGU journal focusing on interdisciplinary research about the planet and its future.

“There are some highway photovoltaic roof pilot programs, but not to the scale that we have imagined,” said Ling Yao, a remote sensing scientist at the Chinese Academy of Sciences and the study’s lead author. “Covering Earth’s highways with solar roofs could generate 17.58 PWh of electricity per year, equivalent to more than 60% of the world’s total electricity consumption in 2023.”

The authors note that innovative solutions like this are essential to achieve the 1.5 degrees Celsius (2.7 degrees Fahrenheit) warming goal set by the International Panel on Climate Change. Solar photovoltaics have become a significant part of new renewable energy installations, comprising 40% of the total between 2012 and 2021. As the cost of solar panels decreases, projects like Yao’s could facilitate the global shift to sustainable energy.

A Vision for a Renewable and Safer Future

Yao was inspired by his evening commute when he conceived this study.

“I suddenly looked down at the road, and thought, ‘The roads are connected to each other. It’s just like a network – the cars can move freely from one place to another,'” he said. “I thought, ‘Why don’t we turn our roads into a network of photovoltaics?'”

Building solar roofs over highways would utilize already-developed land to generate electricity, lowering the demand for greenhouse gas-emitting energy and thus cutting carbon emissions. There are over 3.2 million kilometers (1.9 million miles) of highways on Earth – enough to circle the equator 251 times.

While solar-roofed parking lots have become more common recently, photovoltaic-paved and -roofed roads are still in the early stages. Although some countries have launched small pilot-scale highway photovoltaic projects, extensive solar-panel-covered highways remain a distant goal.

The researchers evaluated highways and major roads worldwide, estimating the costs to build and maintain solar panel networks in each region. Their analysis used polysilicon photovoltaic panels with a maximum power generation of 250 watts, angled at a 10-degree tilt towards the outer lanes of the highway.

Yao stated that installing solar roofs over global highways and major roads would require 52.3 billion solar panels. These panels could produce up to 17,578 terawatt-hours per year, more than four times the annual energy output of the United States. Extending this to major roads could generate an additional 13,570 terawatt-hours per year.

The cost per megawatt-hour and energy potential would vary by location, with most installations near densely populated areas with extensive highways, such as eastern China, western Europe, and the U.S. East Coast.

By installing these solar roofs worldwide, the energy generated could replace up to 9.66 gigatons of fossil fuel-generated carbon dioxide annually, equal to about two-thirds of the U.S. greenhouse gas emissions in 2022.

“This 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,” Yao said.

The study also estimated that solar highway roofs could reduce global traffic deaths by 10.8%, particularly in areas with heavy rainfall, by shielding drivers from the elements. Improved highway safety could also lower the economic costs of traffic accidents.

Overcoming Challenges

Despite the promise, this futuristic highway setup faces obstacles, including high initial costs – potentially up to four times that of ground-based arrays – and maintenance expenses. Practical issues like cleaning billions of solar panels also pose challenges.

Yao remains optimistic, hoping that small pilot programs will expand and that some countries will adopt highway solar roofs on a large scale. He envisions these roofs being most feasible on long, flat highways, such as those in the southwestern United States.

“Actually putting this into practice is the best evidence to make someone believe that this idea is practical,” he said.

Research Report:Roofing Highways With Solar Panels Substantially Reduces Carbon Emissions and Traffic Losses