Science and Technology
Photovoltaic pavements have returned to the forefront of discussions on energy infrastructure by allowing roads, parking lots, bike paths, and other already impermeable areas to be evaluated as surfaces for local electricity generation, without opening new fronts of territorial occupation.
Although the proposal is advancing in tests and commercial applications, the technology still does not represent a wide replacement of conventional asphalt on high-traffic highways, mainly because it needs to prove safety, durability, and competitiveness compared to traditional solar panels.
Among the best-known solutions is Wattway, developed by Colas from research with the French National Institute of Solar Energy and laboratories linked to CEA-Liten, with modules installed on existing road surfaces.
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To operate in this environment, the panels need to combine electricity generation, adhesion, mechanical resistance, and protection for vehicles and pedestrians, maintaining acceptable performance even under tire pressure, dirt, water, shading, and intense temperature variations.
Countries like the United States, France, Germany, and Switzerland are linked to initiatives, partnerships, and demonstration projects, but not to a consolidated exchange of entire highways for solar panels on a large scale.
In addition to these experiences, Wattway itself reports international operations by partners in markets such as Japan, Germany, Switzerland, and Italy, as well as installations in more than a hundred locations worldwide.
With solar cells protected by layers of resin, glass, or composite materials, photovoltaic pavements are designed to generate energy on circulation surfaces, without losing essential characteristics of a safe road.
Unlike panels installed on rooftops, facades, or solar plants, the modules are at ground level, in a horizontal position, subject to braking, impacts, debris accumulation, constant vehicle passage, and temporary shading.
According to Colas, the Wattway modules can be glued directly onto existing infrastructure, which reduces the need for a complete road reconstruction and facilitates applications in urban areas, parking lots, access roads, and controlled sections.
Similarly, the company claims that the surface was designed to maintain skid resistance and allow the passage of vehicles, including trucks, an essential condition for any use in a real road environment.
This combination makes the technology attractive in places where installing conventional panels is difficult due to lack of space, landscape restrictions, absence of available land, or the need to produce energy close to the point of consumption.
On the other hand, placing solar cells on the ground imposes losses that roofs, facades, and inclined plants usually do not face, as solar orientation, ventilation, cleaning, and inclination are limited by the road function.
In Normandy, the most cited experiment took place in Tourouvre-au-Perche, where a 1 km stretch of the RD5 was inaugurated in December 2016 with 2,800 m² of photovoltaic panels.
Funded by the French Ministry of the Environment, the project served as a public evaluation of the technology on a real road, aiming to observe electricity generation, module resistance, and behavior under daily traffic.
The initial official estimate predicted a generation of 280,000 kWh per year, a volume associated with the public lighting of a city of about 5,000 inhabitants, within a technical demonstration program.
In the same statement, the French government indicated that the solar route would be monitored under average traffic of cars and heavy vehicles, reinforcing the experimental nature of the implementation in the Normandy section.
The result, however, exposed significant limits after the inauguration, with subsequent reports of module deterioration, noise, dirt, damage to part of the cover, and electrical production below the initially disclosed expectation.
In 2017, the generation was around 150,000 kWh, before declining in the following years, according to data cited by the Global Construction Review while monitoring the developments of the French project.
This history does not eliminate the technical value of the experiment, but changes the perspective on its application, as it indicates that durability, cost, maintenance, and energy performance remain decisive points for similar projects.
Instead of confirming the direct replacement of asphalt with solar panels over large areas, the French case showed that the technology requires prolonged monitoring, frequent maintenance, and rigorous comparison with conventional photovoltaic alternatives.
In the United States, the most well-known installation linked to Wattway occurred in Georgia, in partnership with The Ray, Georgia Department of Transportation, and Colas, in an area associated with Interstate 85.
Implemented in 2016 at the West Point Visitor Information Center, the project received a technical update in 2019 and began serving as a pilot for installation improvements, electrical architecture, and module resistance.
According to the Ray C. Anderson Foundation, the system installed in Georgia generated 8,420.74 kWh in the first year after implementation, a result used to evaluate performance in a more controlled environment.
After the update, the foundation reported that the later version had a performance gain of 21%, reaching 144 Wp per square meter, an advancement presented as part of the technical improvement of the solution.
This experience reinforces a trend observed in other markets, where the most viable projects appear in parking lots, low-speed areas, bike paths, access roads, yards, ports, and urban equipment.
In these locations, traffic tends to be more predictable and maintenance causes less impact on circulation, which reduces operational risks compared to extensive highways and high-speed lanes.
In March 2024, the French National Institute of Solar Energy reported that the latest version of Wattway slabs underwent IEC 61215 and IEC 61730 certifications.
Used in the photovoltaic sector to assess the performance and safety of solar modules, these certifications were treated by the French body as a milestone for trafficable solutions applied in pavements.
Despite improving the technical credibility of the solution, the certification does not automatically transform every road into a competitive plant, because generation depends on physical conditions that are difficult to optimize on the ground.
In conventional photovoltaic systems, inclination, solar orientation, ventilation, and cleaning strongly influence production; whereas in pavement, these factors are subordinate to traffic, adherence, and mechanical resistance.
Research on solar pavements also describes the technology as an alternative still maturing, especially when the cost of implementation, lifespan, maintenance, and electricity production are evaluated together.
A review published in Renewable and Sustainable Energy Reviews pointed out that the economic benefits of solar pavements still did not cover the costs over a 20-year horizon in the analyzed models.
Surfaces already occupied by urban infrastructure, but with less operational aggressiveness, appear as the most prudent environments for the use of photovoltaic pavements in distributed generation projects.
Parking lots, bike paths, technical sidewalks, industrial yards, port areas, airports, and low-speed accesses allow for energy generation without competing for new land or exposing the modules to extreme traffic.
Wattway itself started to highlight offers aimed at local self-consumption and autonomous equipment supply, such as lighting, cameras, signage, and electric bicycle charging at specific points.
On its project page, the company cites installations in parking lots, pontoons, bike paths, and pedestrian areas, rather than prioritizing large highway stretches subjected to intense and continuous traffic.
This repositioning helps explain why the idea of transforming 1 km of road into a “smart solar power plant” needs technical, economic, and operational context before being treated as a broad solution.
In theory, the road can produce electricity; in practice, the generation depends on insolation, shading, dirt, plate conservation, electrical connection, maintenance cost, and comparison with common solar panels.
Before implementation on public roads, the adoption of photovoltaic pavements requires a complete technical evaluation, including adherence in rain, weight resistance per axle, drainage, electrical protection, and repair plan.
The surface also needs to avoid additional risks for motorcyclists, cyclists, pedestrians, and heavy vehicles, as well as allow for quick interventions without compromising circulation in strategic areas for long periods.
Another sensitive point involves the public value of the investment, especially when the project uses state resources and needs to demonstrate a concrete advantage over simpler and more established solar alternatives.
In this comparison, not only the differences between traditional asphalt and photovoltaic pavement are considered, but also solar roofs on public buildings, parking lot covers, plants in degraded areas, and panels on highway side strips.
For this reason, the advancement of photovoltaic pavements tends to be gradual, localized, and accompanied by performance monitoring, rather than occurring as a widespread replacement of conventional road infrastructure.
Technology can contribute to distributed generation, especially in places where space is scarce, but it still depends on consistent proof of cost, lifespan, safety, and performance in real traffic.
Solar roads are no longer just a laboratory promise, although they remain far from a widespread replacement of common asphalt with photovoltaic modules on extensive highways subjected to heavy use.
Today, the most concrete path is in controlled applications that generate energy near the point of consumption and reduce the use of new areas, without selling the technology as a universal substitute for asphalt.
A journalist who graduated in 2017 and has been active in the field since 2015, with six years of experience in print magazines, stints at free-to-air TV channels, and over 12,000 online publications. A specialist in politics, employment, economics, courses, and other topics, he is also the editor of the CPG portal. Professional registration: 0087134/SP. If you have any questions, wish to report an error, or suggest a story idea related to the topics covered on the website, please contact via email: alisson.hficher@outlook.com. We do not accept résumés!
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