Solar Road Setbacks

“Would you like to drive slower, add to noise pollution and waste money? Then solar roads are for you,” says Joanne Nova.¹ Solar power highways are hitting a roadblock. Nearly three years after France built a 0.6 mile stretch of photovoltaic road in Normandy, the government is deeming it a disappointing experiment. The reason: after nearly three years of use, Normandy's photovoltaic highway is delivering disappointing results. ²

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World's first solar powered road

Billed in 2016 as the 'world's first solar powered road' and called 'Wattway,' France installed, near the village of Tourouvre-au-Perche, solar panels on the driving surface of a 0.6 mile stretch of road used by 2,000 motorists per day. The panels were covered by a transparent coating to protect them from automobile weight and road wear. When completed, the road was supposed to power up to 5 million homes. But that first 0.6 mile stretch, which engineers had originally estimated would power up to 5,000 homes hasn't lived up to expectations. ² After installation, it was clear that the panels couldn't hold up under the wear and tear of highway traffic. The 2,800 square meters of solar panels peeled away and splintered and many of them were removed after being declared too damaged to repair. The road has deteriorated to a terrible state, it isn't producing anywhere near the amount of energy it had previously pledged to, and the traffic it has brought with it is causing noise problems. Leaves fall on the road, then cars grind the leaves on the beautiful polymer surface. The road isn't angled towards the sun, gets brutally hot, and both reduce efficiency. If the top polymer layer were thicker and tougher, less solar energy would get through. Planting trees beside the road would cool it, but the shade would hide the sun.¹

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Even rotting leaves and thunderstorms appear to pose a risk in terms of damage to the surface of the road

Even rotting leaves and thunderstorms appear to pose a risk in terms of damage to the surface of the road. What's more, the road is very noisy, which is why the traffic limit had to be lowered to 70 kmh.¹ The road was meant to produce about 150,000 kWh a yer, which is enough to provide light up to 5,000 people every day. Instead, it made less than 80,000 in 2018, and fewer than 40,000 by July 2019. There proved to be several problems with this goal. The first was that Normandy is not historically known as a sunny area. At the time, the region's capital city of Caen only got 44 days of strong sunshine a year, and not much has changed since. Storms have wreaked havoc with the systems, blowing circuits. But even if the weather was in order, it appears the panels weren't built to capture them efficiently. ¹ Solar panels need to be tilted at an angle to the horizontal and facing due south, in the northern hemisphere, not magnetic south. There are well known formula for calculating the correct angle of tilt. There is a quick and dirty rule of thumb for the angle, it is: add 15 degrees to the latitude. The other thing they always forget about with solar roads is the dirt and scuff marks on the panel surfaces which can reduce output to less than 15%. Shading is a major issue in photovoltaics. A single pole—an antenna, for instance, casting a shadow across an array can ruin its output. The last thing you want to do is put PV panels under your car. ³

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Other Examples:

Experts have lobbed skepticism at the glitzy promise of solar roadways since they were first announced. Other experiments in the realm have gone similarly awry. In China, one six-foot panel of a 0.6 mile solar highway was stolen prompting the government to abandon the project. In Missouri, where the company Solar Roadways was meant to test a small patch of sidewalk at a rest stop along Route 66, negotiations between the Department of Transportation and the company broke down. ² In Idaho a solar road had an 83% failure rate. Despite massive internet hype, the prototype of the solar road can't be driven on, hasn't generated any electricity and 75 percent of the panels were broken before they were even installed. Of the panels installed to make a 'solar footpath,' 18 of 30 were dead on arrival due to a manufacturing failure. A short rain shower caused another four panels to fail, and only five panels appear to be presently functional. The prototype appears to be plagued by drainage issues, poor manufacturing controls and fundamental design flaws. ⁴ The project generated an average of 0.62 kilowatt hours (kWh) of electricity per day since it began publicly posting power data in late March. To put that in perspective, the average microwave blow drier consumes about 1 kWh per day. ⁵ One success: a solar bike path in the Netherlands has been declared a success. Dubbed the SolaRoad, the bike path is exactly what its name suggests. The electricity generated by SolaRoad is used for various purposes such as traffic management systems, public lighting, households, and electric mobility.¹

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Summary:

After years of development and millions of dollars (including government funding), all of the solar roadways installed to date do not produce cost-effective energy production. The roads are expensive and produce far less electricity than could be produced if the money was used on a solar farm, or simply by placing then by the side of the rod. ⁶ In spite of the problems with roadways, the concept has some potential in other areas. The technology has already been used on bike paths and there are possible benefits for home driveways. Most cars are kept at work during the day. What does this mean for the future of energy generating roads? It's safe to assume companies will continue exploring experimental roadways—they might just have to temper their expectations.²

References

1. Joanne Nova, “Solar road is $6m epic disaster—4% capacity, broken and so noisy speed limits were cut,” joannenova.com.au, August 19, 2019
2. Liz Stinson, “France's solar roadway experiment has failed,” curbed.com, July 25, 2019
3. Craig Morris, “Solar roadways need to be stopped,” Erneuerbareenergien, March 6, 2014
4. Andrew Follet, “Solar road is a total and epic failure, 83% of its panels break in a week,” dailycaller.com, October 18, 2016
5. Andrew Follet, “Idaho's $4.3 million solar road generates enough power to run one microwave,” dailycaller.com, April 3, 2017
6. Maverick Baker, “Solar roadways: an engineering failure,” Interesting Engineering, May 18, 2017

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