Road surfacing can play a significant role in the large-scale generation of solar energy. In the SolaRoad consortium, TNO is working on technology and constructions that incorporate solar cells in the road. After successful trials with bike paths and roads in the Netherlands, Dutch companies and knowledge institutes are now working with Belgian and German partners in the EU Interreg project “Rolling Solar” to perfect solar road surfacing. Extensive trials are taking place at the Brightlands Chemelot Campus in Geleen to accelerate integration of PV into the infrastructure.
Solar road surface suitable for more than 10% electricity demand
The three countries together have more than a million kilometres of roads. That makes it attractive to equip them where possible with solar cells for generating renewable energy. TNO has previously calculated that covering suitable sections of the 140,000 kilometres of roads in the Netherlands would be enough to meet more than ten percent of the Dutch electricity requirement.
"We want to equip as much of the road surface as possible with solar cells without causing any inconvenience."
The world’ s longest solar bike path
“Harvesting the sun from the road surface fits in with our philosophy of equipping as much of the existing infrastructure surface as possible with solar cells without inconveniencing road users or road authorities”, says Arian de Bondt, director of SolaRoad.
The consortium – initiated by TNO and including construction company Strukton, installation company SPIE, and the VLAQ Group – previously carried out trials with bike paths in Krommenie (2014), Blauwestad (2017), Haaksbergen (2018), Geldermalsen (2021), and three sites in France.
SolaRoad has since applied the concept to a bike path between Utrecht and Hilversum over a length of more than 300 metres: the longest solar bike path in the world. Testing is intended to determine whether the yield can be improved, and especially whether the road surface will require little maintenance over the course of a seven-year period.
“We are also carrying out trials with heavy traffic,” says Arian de Bondt, “but for the time being we are concentrating on perfecting its use for bike paths. Thanks to the progress we’ve made in SolaRoad, they now generate around 120 kilowatt hours of renewable electricity per square metre annually.
For road authorities – which usually means provinces or municipalities – this is interesting as a means of powering street lighting, for example. And the increasing number of electric bikes means that installing charging points is also an obvious step. This is also an attractive option in the Rolling Solar project with our two neighbouring countries.”
The Netherlands leads the way
Rolling Solar is a project within the Meuse-Rhine Euroregion Interreg programme, financed by the European Regional Development Fund (ERDF), the Dutch Ministry of Economic Affairs, and the Dutch Province of Noord Brabant, and coordinated by TNO.
It aims to promote cross-border cooperation on solar cells in the infrastructure through knowledge-sharing. This is intended to result in the large-scale generation of renewable electricity close to the user.
"It’s now about making everything cost-effective and robust."
TNO expert Ando Kuypers explains: “In the Netherlands, but also at EU level, road authorities and governments are increasingly interested in using the infrastructure not just for mobility but also to generate green electricity.
TNO has carried out trials to equip noise barriers with solar cells, collaborating on this with the Rijkswaterstaat and ProRail. The technology has been developed and it’s is now about making everything cost-effective and robust. This offers great opportunities for the business sector. The Netherlands is already frontrunner in the deployment of solar road surfacing. It fits in perfectly as part of the energy transition and it also creates new economic activity.”
Trials of thin-film technology
The first generations of solar cells in bike paths consisted of crystalline silicon. This is still relatively expensive because the cells are coated with a protective layer and manual assembly of the structure is a lot of work.
At the Brightlands Chemelot campus in Geleen, experiments are therefore also taking place with thin-film PV laminates from Solliance, in which TNO is an important partner. It would appear that thin film is less vulnerable, more flexible, and easier to integrate into the road surface. In Geleen, its performance is being compared with that of silicon in the road.
Both materials are installed in the test stretch. The energy output is then measured, as well as the effects of cold and heat, moisture, traffic, and other influences. The trials also provide a lot of information about bonding of the layers in the construction, cabling, and connectors.
Within the Rolling Solar project, SolaRoad and TNO are working with a large number of parties, including Hasselt University, the Jülich Research Centre, RWTH Aachen University, the imec research organisation, Zuyd University of Applied Sciences, HELMo University College, and companies from a number of EU countries. The aim is for manufacturers and construction companies to soon be able to produce and install solar road surfacing in a cost-effective manner.
"If we would incorporate solar cells into all the bike paths in the Netherlands, we would prevent five million tonnes of CO2 emissions per year."
Arian de Bondt explains: “The Netherlands has an estimated 35,000 kilometres of bike paths. If we incorporate solar cells into all of them, we can generate some 15 terawatt hours of electricity a year and prevent five million tonnes of CO2 emissions. The benefits are obvious.”
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