It’s the world’s fastest growing source of renewable electricity, but until now most solar panels have been installed on the roofs of buildings or on arrays on the ground.
Now engineers in the Netherlands have developed a new way of installing the panels beneath the road, and have created a test track along 70 metres of bike path near the Dutch town of Krommenie near Amsterdam.
The project called Solaroad took cheap mass-produced solar panels, and sandwiched them between layers of glass, silicon rubber and concrete.
"This version can have a fire brigade truck of 12 tonnes without any damage," said Arian de Bondt, a director at Ooms Civiel, one of the consortium of companies working together on the project. "We were working on panels for big buses and large vehicles in the long run."
The solar panels are connected to smart meters, which can optimise their output, and feed the electricity to street lighting or into the grid.
"If one panel is broken or shadow or dirt, it will only switch off that PV panel," said Jan-Hendrik Kremer, Renewable Energy Systems consultant at technology company Imtech. "The other panels will get the highest energy possible at that moment into the grid."
The research group spent the last five years developing the technology. They said the greatest challenge was creating a slab that was suitable for paving but also tough enough to endure outdoor conditions. They developed at translucent resin which gives grip to the smooth glass surface without blocking the sun.
"We made a set of coatings, which are robust enough to deal with the traffic loads but also give traction to the vehicles passing by,” said Stan Klerks, a scientist at Dutch research group TNO. He said the slabs also had to "transfer as much light as possible on to the solar cells so the solar cells can do their work."
The group is continuing to develop the technology and hope to make it cost-effective within five years.
"Solar panels on roofs are designed to have a lifetime, which is typically 20/25 years,” said project manager Sten de Wit. "This is the type of lifetime that we also want for these types of slabs. If you have a payback time of 15 years then afterwards you also have some payback of the road itself so that makes the road cheaper in the end.”
The Netherlands has over 140,000-km of roads. The groups said this represents massive opportunity for the country. But if other countries were to also adopt the technology it could become a significant source of global electricity in the future.