What If We Covered All the Roads with Solar Panels?

We sure love our roads. We love them so much that we seem determined to pave the entire world. But maybe roads can become the future of renewable energy. That’s right, roads as energy generators. How? By building them with solar panels. Do we have the technology? Could we power the entire world? What are the drawbacks?

In 2017, the UK promised to run on 100% renewable energy by 2025. Yet they still have a long way to go, with only 33% of their energy having come from renewable sources in 2018. Could solar panel roads be the answer?

Energy is created when photons from the Sun hit a silicon solar panel. Silicon is a semi-conductor and has similar properties to metal and an electrical insulator. So when the Sun’s photons hit the silicon atoms in a solar cell, they transfer their energy to loose electrons which knocks them off the silicon atoms. This generates electricity.

Since 2000, there has been a 200% increase in global renewable energy consumption. Sounds good for the solar industry. However in 2019, of the 17,000 terawatt-hours (TWh) of renewable energy created globally, only 3% came from solar. Turning our abundance of roads into energy creating thoroughfares could move solar to the fastlane for renewable sources. But how much solar road would we need?

In 2016, Waywatt built a 1km (0.6 mi) solar roadway. It generated about 280 megawatt-hours (MWh) per year. That’s enough energy to power 25 homes for 12 months. The UK has around 400,000 km (248,548 mi) of road. If 20% of those roads were converted, that would equal around 81,000 km (50,000 mi) of new solar panel paved roads. The energy from these roads would only account for 5% of the UK’s total energy consumption in a year. The price tag?

Well, a 1 km (0.69 mi) road in Normandy, France, cost €5 million, or approximately 5.5 million US U.S. dollars, to build. And that’s enough to also burn a sizeable hole in a city’s wallet. So let’s hope the cost for solar technology goes down before attempting to build an 81,000 km (50,000 mi) stretch.

How would solar roadways change the world though? The largest change, and the reason behind creating these solar roads, is the reduction of carbon dioxide (CO2), the biggest driver of global climate change.

Many roads are currently paved in asphalt. This material absorbs 80% to 95% of the Sun’s rays, which increases heat on the road and surrounding areas. A phenomenon called the urban heat island effect. Switching over to solar roads would reduce this effect, creating cooler roadways and cooler cities.

As these solar roads stretched over more of the globe, the coal industry would have to shutter its doors and we would need less petroleum for asphalt production. Many people would lose their jobs. Governments would need to create programs to re-tool the workers for the growing demand of solar road construction.

Then there’s the roads themselves. To build these roads, solar panels are placed between layers of glass, silicon rubber, and concrete.
This makes for a slippery road, especially during rain or snow. The roads would need a durable coating to create traction, and that coating would have to be safe for the environment and humans. Or would we develop improved car tires from another material to better grip road surfaces?

Another route is to create smart solar roads. These roads would include technology to keep its surface above freezing, charge electric cars as they drive, and use LEDs for bright road surface markings. There are a lot of road blocks for this new technology. Cost, material, and safety being the big ones. But is it worth it to invest in research and development?

In 2014, the Netherlands built a solar bike path. This 70 meter (220.6 ft) bike path generated 3,000 kilowatt-hours (kWh). In other words, the solar bike path could power a small household for one year. Talk about ‘re-cycling’ your carbon footprint in a powerful way.
Despite current limitations, solar paved roads might still be a possibility in our future.

Though there are other ways to use solar panel technology for renewable energy. Why ground our thinking earthbound? For instance, there is a lot of open space up on our Moon. Is it possible to install solar panels on the Moon, and for us to access that energy?