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The World’s First Solar Panel Road- Not Such A Bright Idea After All!

September 25, 2018

By Paul Homewood



h/t Joe Public

Readers might remember this headline from two years ago:


A solar panel road, claimed to be the world's first, has opened in France. The 1km (0.6-mile) stretch of road in the small Normandy village of Tourouvre-au-Perche is paved with 2,880 photovoltaic panels 


At the time even the Mail pointed out some of the drawbacks, which should be obvious to even those with half a braincell.


  • The horrific cost
  • The even more horrific maintenance cost
  • The fact that solar panels won’t let power street lights at night (which is presumably when they are needed!)
  • The fact that the solar panels are flat, and therefore cannot efficiently harvest the sun
  • The loss of power when cars drive over them
  • Problems caused by frost and snow.

None of this stopped the virtue signalling Segolene Royale, one time socialist French Energy Minister and Ex Ex Mrs Hollande, from opening the ridiculous thing.

But now reality has caught up with the April 1st type nonsense, as The Conservation reveals:


Four years ago a viral campaign wooed the world with a promise of fighting climate change and jump-starting the economy by replacing tarmac on the world’s roads with solar panels. The bold idea has undergone some road testing since then. The first results from preliminary studies have recently come out, and they’re a bit underwhelming.

A solar panel lying under a road is at a number of disadvantages. As it’s not at the optimum tilt angle, it’s going to produce less power and it’s going to be more prone to shading, which is a problem as shade over just 5% of the surface of a panel can reduce power generation by 50%.

The panels are also likely to be covered by dirt and dust, and would need far thicker glass than conventional panels to withstand the weight of traffic, which will further limit the light they absorb.

Unable to benefit from air circulation, its inevitable these panels will heat up more than a rooftop solar panel too. For every 1°C over optimum temperature you lose 0.5% of energy efficiency.

As a result a significant drop in performance for a solar road, compared to rooftop solar panels, has to be expected. The question is by how much and what is the economic cost?

The road test results are in

One of the first solar roads to be installed is in Tourouvre-au-Perche, France. This has a maximum power output of 420 kW, covers 2,800 m² and cost €5m to install. This implies a cost of €11,905 (£10,624) per installed kW.

While the road is supposed to generate 800 kilowatt hours per day (kWh/day), some recently released data indicates a yield closer to 409 kWh/day, or 150,000 kWh/yr. For an idea of how much this is, the average UK home uses around 10 kWh/day. The road’s capacity factor – which measures the efficiency of the technology by dividing its average power output by its potential maximum power output – is just 4%.

The solar road is unveiled in Tourouvre au Perche. Christophe Petit Tesson/EPA


In contrast, the Cestas solar plant near Bordeaux, which features rows of solar panels carefully angled towards the sun, has a maximum power output of 300,000 kW and a capacity factor of 14%. And at a cost of €360m (£321m), or €1,200 (£1,070) per installed kW, one-tenth the cost of our solar roadway, it generates three times more power.

In America, a company called Solar Roadways has developed a smart highway with solar panels, including sensors and LED lights to display traffic warnings about any upcoming hazards, such as a deer. It also has heating pads to melt snow in winter.

Several of their SR3 panels have been installed in a small section of pavement in Sandypoint, Idaho. This is 13.9 m² in area, with an installed capacity of 1.529 KW. The installation cost is given as $48,734 (about £37,482), which implies a cost per installed kW of €27,500 (£24,542), more than 20 times higher than the Cestas powerplant.

Solar Roadway’s own estimates are that the LED lights would consume 106 MWh per lane mile, with the panels generating 415 MWh – so more than 25% of the useful power is consumed by the LEDs. This would reduce performance even further. The heating plates are also quoted as drawing 2.28 MW per lane mile, so running them for just six days would cancel out any net gain from the solar panels.

And this is before we look at the actual data from the Sandypoint installation, which generated 52.397 kWh in 6 months, or 104.8 kWh over a year. From this we can estimate a capacity factor of just 0.782%, which is 20 times less efficient than the Cestas power plant.

That said, it should be pointed out that this panel is in a town square. If there is one thing we can conclude, it’s that a section of pavement surrounded by buildings in a snowy northern town is not the best place to locate a solar installation. However, perhaps there’s a bigger point – solar roads on city streets are just not a great idea.

The driveway prototype which inspired Solar Roadways. Dan Walden/Wikimedia Commons, CC BY-SA

Running out of road

Roads don’t actually represent as large an area as we assume. The UK department of transport gives a breakdown of the length of the UK’s different road types.

Assuming we can clad these in solar panels, four lanes of every motorway, two lanes on the A & B roads and half a lane for C & U roads (a lot are single track roads and just won’t be suitable) we come up with a surface area of 2 billion m².

Which sounds like a lot, until you realise that buildings in the UK’s urban areas occupy an area of 17.6 billion m². So just covering a fraction of the UK’s rooftops with solar panels would immediately yield more power than putting them on roads. That’s quite apart from the benefits that a more elevated position would yield for greater power generation.

All of this suggests that only a small fraction of the road network would actually be suitable. And, given the relatively small size of the road network, solar roads could only ever become a niche source of power and never the shortcut to our future energy supply.


I have little doubt though that someone, somewhere has made a lot of money has made an awful lot of money out of French taxpayers for this charade. Which was, after all, the whole purpose of the exercise all along.

  1. Ian Magness permalink
    September 25, 2018 10:46 pm

    It seems strangely reassuring that somewhere there are people even more deluded than ourselves.
    Oh, I forgot Drax….

    • david permalink
      September 26, 2018 3:59 am

      I can not get the council to fix the potholes in my road. I will suggest they repair them with solar panels…give it the old green spin.

      • Ian Magness permalink
        September 26, 2018 2:26 pm

        Great idea David! In east Surrey, we can’t get the potholes fixed because the council spent all its money (and I mean £millions) on miles of average speed camera schemes for, er, “road safety”. We have been told that there is no cash for potholes until they have recoupled the camera outlay via fines.
        I wish this were a joke – but it’s not. The French may be ahead of us in lunacy but, really, we aren’t far behind.

    • September 26, 2018 12:20 pm

      I bet the folks on the coastal plains of North and South Carolina have not forgotten Drax. They have faced the water from Hurricane Florence and not just that which fell on them at the time. The water which fell upland has now reached them by way of rivers with denuded banks..Drax’s actions will also cause the riverbanks to erode and the meanders to straighten out.

  2. John F. Hultquist permalink
    September 26, 2018 4:39 am

    Makes me think of this:

    Stuck in the Middle with You”

    Clowns to the left of me!
    Jokers to the right!
    Here I am stuck in the middle with you.

    From a song written by Scottish musicians Gerry Rafferty and Joe Egan and originally performed by their band Stealers Wheel.

    • Gerry, England permalink
      September 26, 2018 1:45 pm

      That sounds just like attending a gathering of MPs.

    • Ian Magness permalink
      September 26, 2018 2:37 pm

      John H. and Stonyground,
      You were fans but you forgot to mention how ahead of his time Gerry Rafferty was. As you know, after Stealers Wheel, Gerry had the blockbuster hit “Baker Street”. The B side? “Big change in the weather”. How did he know?

  3. Stonyground permalink
    September 26, 2018 7:54 am

    Stealers Wheel also did a song that went:

    Everyone’s agreed to have a good time, nobody is stepping out of line.
    Everyone’s agreed that everything will turn out fine.

    It could have been written about the kind of group think that leads to a fiasco like this where nobody wants to stick their head above the parapet and point out what a stupid idea it is.

  4. Malcolm Bell permalink
    September 26, 2018 7:55 am

    What effect does driving on wet glass have on vehicle adhesion? Perhaps like driving on ice!

    What weight can they carry – like a forty tonne lorry?

    Access to under road services (had etc) might be a problem.

    Being made of flat panels the road will be uneven – like one made of paving slabs.

    Most roads are tupically at least half in shadow – hence “the sunny side of the street”.

    Typical “green” thought – pious but potty.

    • September 26, 2018 7:59 am

      Those were precisely my thoughts. I wonder why none of the establishment people think of these things; and the photo shows a lot of such green idiots.

    • Ben Vorlich permalink
      September 26, 2018 8:32 am

      Can’t say I’d like to cycle or motorcycle over a stretch of solar panels on a rainy day. I would like to drive into a low sun either the reflection of sunlight as well as the sun itself would make safe driving impossible.

  5. Bitter@twisted permalink
    September 26, 2018 8:09 am

    Criminally stupid politicians and and our money are soon parted.

  6. Ian permalink
    September 26, 2018 8:46 am

    But “Something Must Be Done”, or we’ll see more confused and hungry beluga whales swimming up the Thames, a phenomenon the BBC suggested could be due to climate change whilst noting, without any sense of irony, that it could also be due to the noise from offshore wind farms!

  7. Tim Spence permalink
    September 26, 2018 8:48 am

    Rule 1. Keep your wallet away from politicians
    Rule 2. Keep politicians away from science
    Rule 3. When a committee designs a Horse, expect a Camel.

  8. September 26, 2018 9:21 am

    The French solar road is old tech. The Swedes want to be able to charge up their EVs as they drive along.

    Not many hours of daylight in the Swedish winter…

    • September 26, 2018 10:13 am

      Sounds like Scalextrix!

      • Gerry, England permalink
        September 26, 2018 1:47 pm

        Some trams used to pick up power from a ground conductor instead of an overhead cable. All part of the plan to regress human society.

  9. Dave Ward permalink
    September 26, 2018 10:17 am

    Elon Musk’s Solar Roof Tiles aren’t doing very well either:

    • Athelstan permalink
      September 26, 2018 12:40 pm

      Well! what a surprise that is – not.

  10. September 26, 2018 12:25 pm

    Pardon the intrusion from one who lives neither in the UK nor Idaho, BUT, I have noticed that wet glass is very slippery. It would not be my choice for road surface. Any method to account for that would likely also reduce the light. So would etching caused by salt and other chemicals used in the winter. What about snowplow blades?

    • Gerry, England permalink
      September 26, 2018 1:51 pm

      Could spread some sand over the surface.

      • September 26, 2018 3:05 pm

        That should effectively block the solar radiation from reaching the cells. My point!!

  11. Athelstan permalink
    September 26, 2018 12:39 pm

    This extraordinarily, outrageously pathetic green boondoggle is just what happens when, a government allows the virtue signalling eco-amazons aka SJW’s pond life free access to the coffers filled by the poor old taxpayers. Public sector profligacy and violation – example as above, should be made a punishable offence.

  12. John Scott permalink
    September 26, 2018 3:59 pm

    Aside from the foregoing comments I note the following:

    1) Roads have a camber to drain away rain and prevent hydroplaneing,
    2) Roads are dirty and this will stop a lot of the sun’s rays reaching the receptors
    3) Driving on glass will be worse than driving on ice, using salt, grit or sand will etch the surface of the panels further reducing transmission
    4) Even an imbecile would know the cost and maintenance of the panels will be huge
    5) Obviously there was never a business case done

  13. saparonia permalink
    September 26, 2018 9:37 pm

    It’s the thought that counts

  14. Teddy permalink
    September 27, 2018 9:47 am

    Bluefield Solar Income Fund interim report stated that 55MWp subsidy free solar PV capacity was added to the UK grid in the first half of 2018, 36 MWp of which is of utility scale. This is a very small amount but is there something happening in the price of solar that is beginning to change the outlook for it?

  15. mikewaite permalink
    September 27, 2018 1:37 pm

    Don’t discourage this experiment. Rather, insist that the UK Govt, to maintain its determination to be “world leaders” in combating climate change, should install, say 500m, in a very prominent place, a road leading to Whitehall or Parliament Square, or perhaps a slight hill near Hampstead where the incredibly well paid BBC journalists live.
    Then wait and see what the politicos , journalists and cab drivers think of it as they attempt
    to drive and brake on a wet November evening with the lights of Westminster reflecting off the glassy surface.

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