On paper, the idea of installing solar panels on our road network seemed like a brilliant idea. This brave new world plan went viral a few years ago. It promised this was the solution to climate change with a side benefit of reaping huge financial rewards for the economy.


To bring us all back to earth with a bang, the results from the practical and empirical stats are in and they are not as sunny as they were initially claimed to be.


Solar Panels on Roads Instead of Tarmac

This idea originated from a good place in people’s minds. It was not ever meant to be seen as a mindless cash-grab, only an honest attempt to resolve the world’s energy crisis. The implementation of solar panelled roads in certain parts of the world has exposed some flaws in the concept.

Solar panels on a flat surface are not at their optimum tilt angles. Any solar panel expert will tell you that when shade covers only 5% of the panel it can reduce the power generation by a whopping 50%. Added to this, roads are prone to being covered on a daily basis by dirt, dust, litter, and plant life; the glass would have to be much thicker than usual which would limit their light absorption even further.

There would be no air circulation and when solar panels heat over the optimum temperature by even one degree they lose 0.5% of their energy efficiency. They are just not as effective as they are on top of a roof.


Results Are In

The French city of Tourouvre-au-Perche installed one of the first solar panelled roads – all 2,800 square metres of it – at a cost of €5m. The road was supposed to generate about 800 kWh/day, but the yield was actually closer to 409 kilowatt hours per day. The average home uses approximately 10 per household of that wattage, so only around 40 homes could potentially be powered daily. That is simply not enough to warrant the expenditure.

In contrast to this, Bordeaux’s Cestas solar plant cost €360m to build and has an output of 300,000 kWh/day. This is because the panels are angled towards the sun. At a cost per installed kW, the Cestas solar plant cost one tenth less to build than the solar road at Tourouvre-au-Perche.


Some of the ideas that were posited around with the solar road concept were indeed very proactive. It was said the roads could power their own heat to melt ice and snow and proximal electric lights and hazard signs could be lit up from the generation too. But these natural weather elements are more of a North American blizzard situation and not something that occurs with regularity in New Zealand. The question would be if the solar panels on roads would be capable of generating the kind of heat needed under such conditions in the first place.


What Would Work

As we have covered in a previous article on the possibility of solar panels replacing tarmac surfaces, solar power is the best source of green energy we currently have. But, you know what every country has more of than tarmac? Roof surfaces. If every unshaded building rooftop was covered with solar panels at an optimum tilt, it would immediately yield more solar power energy than if every road was.

Maybe in a few decades, the price of solar panels for roads will become more accessible and the technology can be examined more fully. Until then, continue to look up for a solution to the clean energy crisis,

and not down on the ground.




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