France's solar road: International solar experts give their analysis | RenewEconomy

France’s solar road: International solar experts give their analysis

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The construction of a solar road in France is turning numerous heads due to the novelty value of the project. Solar experts have a different view.

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PV Magazine


The construction of a solar road in France is turning numerous heads due to the novelty value of the project, however, solar experts have a different view, seeing the construction as economically unviable, and actually damaging to the solar industry.

A 340 kW solar road is currently under construction in Normandy, France. It will be one kilometer long, with a surface of 2,800 m2, according to Michel Salion from the Colas-Wattway press team, a subsidiary company of Bouygues S.A. Although advertised on the French Ministry of Ecology website as having the capacity to deliver 17,963 kWh per day, in actual fact it will generate just 767 kWh per day.

In fact, Segolène Royal, French Minister of Ecology, announced that one kilometer of the solar road will deliver enough electricity for 5,000 houses. This is also wrong. With 767 kWh per day – official data from Michel Salion – it will just be able to power 50 French homes. The cost of one kilometer of the solar road is EUR 5,000,000, which works out as EUR 100,000 per each home that is powered by the road.

The erroneous statistics generated a lot of hype all over the world, however, solar experts have offered differing analysis of the project.

“Solar roads in France are much less efficient, and more costly, than PV on rooftops and parking structures, and in PV power plants,” commented  Mark Jacobson, director of the Atmosphere Energy Program at Stanford University and founder of The Solution Project.

For Jenny Chase, Head of solar analysis at Bloomberg New Energy Finance (BNEF), “French solar roads seem like a way to subsidize French companies, not a way to make electricity.”

Chase categorically denied the idea of solar roads popping up on four continents, while tweeting in response to a Bloomberg article earlier in the month. While BNEF founder Michael Liebreich, offered an alternative, somewhat satirical, headline: French company gets subsidy to build solar roadway with approximately 170-year payback.

Within the article, Liebreich wrote that the French solar road is “a state-funded experiment with zero chance of becoming commercially viable,” and the “170-year payback is with 0% finance, no maintenance and panels that last 170 years.”

“So these panels, which currently cost EUR 21 per W, will perform substantially worse and have a shorter lifetime than normal EUR 1/W PV. But that’s ok because… they’re made in France?” continued Chase.

Colas said one year ago that the cost of the solar road would be EUR 6 per W. But that was just for the modules, without the Balance of System (BoS) and inverter costs. “The solar road is a technically and economically non-sense,” added solar analyst Pietro Radoia.

“The road is the worst place for solar panels. France can install PV over rooftops. Colas is in a monopolistic situation, without competition bringing the cost down.” Chase also indicated that the Wattway would still be extremely expensive to use for bike lanes or parking lots across the country.

“Even if you’re short of land, you’ll put solar over roads, not on them,” continued Liebreich. This sentiment was echoed by Eric Vidalenc, from the French Environment Agency (ADEME), who said that solar above the bike lanes “would protect bikers from the rain.”

And even the installation of the road comes with unexpected challenges. Notably rain, as the glue for the Wattway does not stick when it gets wet, which is problematic in the rainy Normand region. A tent was erected to protect the construction from water, but it has limited effectiveness during windy days.

Yet with all of these challenges and economic viability worries of the project, Ségolène Royal announced plans to build 1,000 kilometers of solar roads. “It’s stunning how political leaders can promote such a trap for the unguarded.” Said Association négaWatt spokesman Thierry Salomon.

“It’s a public relations gag,” summarizes Philip Hiersemenzel, a German clean tech spokesman and advisor. While the President of the French Council of Energy has questioned whether the French taxpayers have been properly informed about the cost of the project.

The French Alternative Energies and Atomic Energy Commission (CEA) is Wattway’s scientific partner. However, Liebreich points out that “renewables energies are no longer alternative energies,” while also noting that the solar road project can wrongly make real clean energy innovation appear unviable and novelty.

Maybe it is best summed up by Australian engineer Dave Jones who alikens the project to testing windmills on a planet without atmosphere or creating submarine solar under the Channel between France and the U.K.

Source: PV Magazine. Reproduced with permission.

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  1. Karl-Friedrich Lenz 3 years ago

    It doesn’t matter what one kilometer of the road costs. The figure that would matter is the amount of extra cost compared to a road without solar panels.

    Obviously, it doesn’t make sense for the cost of this solar technology to be at EUR 14,705 per kW, which is the result of dividing 5 million by 340 kW. Large scale solar project costs have been under EUR 1,000 in Germany for years. There may be some additional cost from making these panels suited for carrying traffic, but not by an order of magnitude.

    Is the above analysis based on the 5 million for 340 kW figure, disregarding the cost of building a road in the first place?

    • Objectif Terre 3 years ago


      “Can Wattway be installed on any type of road? Are there any constraints (roadway condition, tight curves, etc.)?
      Wattway can be installed on any road with asphalt pavement that is recent, with no cracks, ruts, deformation, or asbestos. The road must comply with stipulated technical and commercial specifications.”

      21€/W = without the cost of the road.

      • Karl-Friedrich Lenz 3 years ago

        Strange, I see a quote of EUR 6/W in the FAQ. Still much more expensive than a rooftop project, but at least in a range that makes sense at first sight.

        Anyway, high costs are expected for low volume experimental projects. It doesn’t matter what exactly the costs are now. The interesting question is how much they can come down producing at scale.

        • Objectif Terre 3 years ago

          EUR 6/W = module cost, without BoS+inverter.
          Source = the Director of Wattway

          CEA hopes to divid by a factor 2 the module cost in the middle term, and by a factor 3 in the long term. So with 6/3 = 2€/W, those modules will cost 4x more than normal 0,5/W modules. Deeply absurd. And it’s just for the modules. BoS cost will stay very high because of the complexity of a solar plant on road.

  2. Ren Stimpy 3 years ago

    This is madness. Everybody knows their best solar resource is the French Foreign Legion. The Legionnaire’s hat is flat which makes it perfect for a solar panel, there are thousands of them and they march out in the desert sun all day long.

  3. John Coller 3 years ago

    Googling “how much do roads cost”, gives the indication that it costs roughly $1.25 million per mile to mill and resurface a 4-lane road, $4 million per mile to expand it to 6-lanes.

    Clearly, EUR 5,000,000 for a mile of road and 340 kW of solar is a high cost, but it is just a pilot project, the high cost of a normal road and low cost of normal solar shows there is at least the potential for it to become viable.

    • Objectif Terre 3 years ago

      21€/W = without the cost of the road. Normal PV: 1€/W
      Liebreich wrote that the French solar road is “a state-funded experiment with zero chance of becoming commercially viable”
      Wattway technical director said that the W attway cost = 7€/W (just the module) + 7€/W (installation) + 7€/W (grid connection) = 21€/W
      Does France really need solar roads?

      • Karl-Friedrich Lenz 3 years ago

        Thanks for the link. Interesting that they manage to spend EUR 7/W only for grid connection. There seems to be a lot of room for improvement in these numbers.

        • Objectif Terre 3 years ago

          Just image that they can divid by a factor 3 the total cost in 2 years. 21/3 = 7€/W. Deeply absurd because normal PV = 1/W. And with good yield and lifespan. #GameOver

  4. john 3 years ago

    Perhaps the person who signs off on this is a misguided person.
    It will just reinforce the story line that solar is useless and in this setting will prove to be.
    The shading issue alone makes this a lunatic idea.
    Put half the panels on decent structures for 1/4 of the cost with twice the output is what every solar institution will be saying.
    I made up the cost and output figures but you get the picture this is madness.

  5. Miles Harding 3 years ago

    It would seem that the French are determined to out-do the “Hydrogen economy” with a proposal that’s totally idiotic.

    In the 1980s, it was doctors and dentists that seemed to get involved in obviously hopeless ‘inventions’. At the time I put it to greed and being clueless about the physics. When they did ask, they didn’t like the answer and seemed convinced that it was a conspiracy to discourage them so that the adviser could swoop in and steal the pots of gold waiting for the intrepid. If they could have heard the laughter in the tea room, they may have thought differently.

    One has to wonder about the mentality of these politicians who are determined to press ahead, despite not being able to find a credible source to back their decision. I attribute this to the political ranks being full of lawyers, economists and stooges that, again, are clueless about the physics of their pet projects and refuse to take advice that conradicts their own vested interests.

    It is incumbent on all of us to hold their feet to the fire and not let them get away with avoiding blame for their own stupid hubris when it blows up in their faces.

  6. David Petitjean 3 years ago

    Comparing the price of a prototype (because that’s what it should compared to, state funded research) to super-high volume solar panels from China where the state is artificially lowering the cost of panels with subsidies is… let’s say, ridiculous at best.

    F-35 Lighting prototype cost 1.1 Trillion and i don’t see people comparing this cost with a the currently mass produced F-16, Eurofighter or Rafale.

    The arguments used here are the same that were used 10 years ago about the solar industry all together. People have gone quieter since. Mass production and standardisation of the solar roads installation will show whether or not it is viable. But for now, no one knows anything. It is also possible that this prototype is mainly there for utility companies to see if and how they can integrate them in their network.

    • Objectif Terre 3 years ago

      Philippe Harelle, Wattway Chief Technology Officer:
      “Dans nos chantiers d’applications on faisait que des petits chantiers de 25, 50, 100 mètres-carrés parcequ’il n’y a pas lieu d’aller plus loin pour tester techniquement le sujet”

      As you can read (and listen), Wattway CTO says that several 25-100 square meters protoypes have been tested. He says 2800 m2 isn’t usefull for testing. The 1 km long project in Normandie isn’t a prototype but a pre-commercial product.

    • Objectif Terre 3 years ago

      “The arguments used here are the same that were used 10 years ago about the solar industry all together.”

      Response here:
      (…) One could thus consider that the costs of this brilliant emerging technology are brought to fall: the industrial scaling up permitted by the construction of 1000 km of roads is precisely what is needed to accelerate the decline in costs. But this is not a reasonable thinking. For the standard photovoltaic CAPEX to decrease by a factor of 6 in 20 years, billions and billions of dollars were poured in Germany, China, Japan, Korea South, Taiwan, United States, etc. And it took 20 years (…)

      Do we need to come back to the 1990s ?

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