In the European Union alone there are 10.5 million kilometers of roads that could potentially be used to capture the sun’s energy. However, these expanses of pavement are only occupied by vehicles some 10% of the time. Given this fact, it’s no wonder that France announced in February it plans to cover 1,000 kilometres (620 miles) of roads with solar panels. The program is a collaboration between French road builder Colas and the National Institute of Solar Energy.
The French project, called Wattway, is going to generate clean renewable energy on roadways by collecting the substantial solar energy that hits these surfaces but which is currently not utilized. According to Colas, the manufacturer of the panels, a 1-kilometre section of the surface can produce enough power for a town of 5,000 people. French authorities estimate that solar roads could generate enough electricity to provide power to 5 million people, or about 8 percent of its population.
The French announcement spread quickly over the world media. This will be the first time a roadway of this length has been paved with solar panels. To date, only an experimental bike path has been installed, a 2014 project in the Netherlands. This 70-metre (230-foot) solar-panel path, called SolaRoad, in Krommenie, a village northwest of the Dutch city of Amsterdam, is the first of its kind. It has generated enough energy to power a one-person household for an entire year only in 6 months (3,000 kWh). The $3.7 million bike path, designed by the research group TNO, is the world’s first public road to include embedded solar cells . This prototype will be studied for three years.
Solar Roadways Incorporated, a startup company based in Sandpoint, Idaho, is also developing solar powered road panels to create a smart highway. Last year Solar Roadways created the world’s largest solar panel when the company finished a prototype parking lot in Idaho. The company has received three rounds of U.S. government funding (plus $2 million in venture capital) to test its technology.
Differences in Technologies
France is going to create the Wattway by installing material directly on existing pavement without any need for civil engineering work. Wattway is a patented French innovation that is the fruit of 5 years of research undertaken by Colas, world leader in transport infrastructure, and the INES (French National Institute for Solar Energy). Wattway is composed of cells inserted in superposed layers that ensure resistance and tire grip. The composite material is just a few millimeters thick, making it possible to adapt to thermal dilation in the pavement, as well as vehicle loads, a guarantee of durability and safety. By combining road construction and photovoltaic techniques, Wattway pavement provides clean, renewable energy in the form of electricity, while allowing for all types of traffic.
The “SolaRoad” project in Netherlands was built in prefabricated slabs of concrete approximately eight by 11 feet, topped with crystalline silicon solar cells coated in a thin layer of translucent tempered glass. Allowing as much sunlight as possible to hit the solar cells was a particular design challenge on a surface that must also be safe and practical for cyclists. More than 150,000 cyclists rode over the solar panels during the trial, and they only noticed one fault – a small section of a coating, which provided grip to the surface, has become delaminated due to temperature fluctuations. The panels are designed not only let in as much light as possible, but also to last at least 20 years – a similar lifespan to rooftop solar panels.
The American Solar Roadways design has a hexagonal panel design shown in mock-ups with built-in LEDs programmed to display lane lines and crosswalks. The heating elements are planned to keep roads a few degrees above freezing and the underground channels running alongside the solar roads would house electrical cables.
Despite the fact that there are differences in technologies, there is something in common between the manufacturers. They all produce electrical energy without overtaking farmland or natural landscapes.
Solar panels conquer the world
Since the Wattway project was sanctioned by France’s Agency of Environment and Energy Management, France is demonstrating that the era of attainable solar power is here. All roads, parking lots, driveways, playgrounds, bike paths, and sidewalks can be modernized with solar energy harvesting panels. France´s government level promises to bring solar power to hundreds of miles of roads in the country over the next five years.
While broad-minded entrepreneurs see endless possibilities for solar energy, skeptics raise questions about cost, efficiency, and durability. There are certainly challenges that need to be taken into consideration, and capabilities that still need to be developed. For example, how to do underground repairs, such as sewer network maintenance, in big cities? How easy and costly is the dismantling of street pavement and re-installing it compared to asphalt or concrete? Is there a potential problem of shading on heavily used highways, which could make the solar roads ineffectual? Should we even consider using solar panels on highways, or just pave smaller roads between towns and at locations such as industrial sites?
When panels lie flat on roads, they aren’t as efficient as those in dedicated solar parks, or even on rooftops. Should the panels be at a 30-degree angle when mounted at thee ground, in order to harvest enough energy? To these and many other questions risen, engineers are now looking for cost-effective answers.
Skeptics will certainly continue raising their voices during the years of solar road development, but many believe road-based renewable energy will soon be mundane and will including ice-melting and electric car charging solar capabilities.