Last week I mentioned solar roads as a (so far) failed sustainable transport innovation. Specifically, I was talking about projects that have attempted to embed solar panels in the road surface. This is obviously a huge technical challenge, if they’re going to be durable enough to be driven over by heavy traffic. It’s also unnecessary, as there are other ways to make a solar highway.
Solar power along roads can power street lighting and signage, as well as export surplus power to homes and businesses nearby. As more road transport is electrified, it might also be able to serve charging points or on-road systems such as wireless or cabled charging.
Here are four ways I can think of to make a solar highway.
1 – The road surface. I’m aware of solar road projects in the US, France and China. The first didn’t work properly, the French project fell to pieces in a couple of years. The Chinese project had been damaged within a week, though it has apparently fared okay since. The most successful project has been the solar bike path installed in the Netherlands, and of course it’s much easier to accomodate bikes than the tractors that demolished the solar road in France.
Why do companies keep trying it, despite the weight of scepticism? Because if it can be made to work, solar surfaces could automatically clear themselves of snow and ice. Built-in lighting could warn drivers of accidents or delays. China’s system, which includes batteries and panels protected by transparent concrete, might still work. But since the main benefit of solar panels is generating electricity, there are better places to put them than under the wheels of heavy good vehicles.
2 – On the verges. Many road designs have wide verges, and motorways are often levelled into broad embankments. Where a road runs north to south, there are often miles and miles of perfectly oriented slopes that could host PV. There’s a huge new venture being planned in the Netherlands that will see solar installed down both sides of the motorway and on the central reservation, and that got the green light this year. Here’s one being installed in Germany back in 2007:
3 – The sound barriers: where highways pass through urban areas, sound barriers are often added to the sides to reduce noise pollution. Switzerland apparently claim the world first, having added PV to sound barriers back in 1989. A 2017 study by the US Department of Transport found them in 14 different countries, including Britain, though I don’t remember hearing of any beyond a trial a few years ago. (Let me know if you’ve seen one!) There are a variety designs. There are fairly traditional barriers with PV stuck on top, or integrated in zig-zag shelves. The Netherlands has translucent coloured glass ones that can double up as billboards or public art. There are also transparent vertical solar fences that allow light in from both sides, such as this example in Germany:
4 – Over the top. Finally, there are projects that build a canopy over the top of the road and place the panels on that. This protects roads from snow and ice too, and reduces noise. Make them transparent, and you can still benefit from natural light during the day. Belgium added a solar tunnel to a railway line about a decade ago. Croatia has a sound-proofing solar canopy on its A7 highway. In Germany, the village of Goldbach is protected from the noise of a six lane autobahn by a tunnel with solar on the roof. A new project will test the idea of solar road canopies in Germany and Austria over the next three years, with the possibility that they might look something like this: