
France to build 1000 km of roads with solar panels - gipkot
http://www.solarcrunch.org/2016/01/france-to-build-1000-km-of-road-with.html
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nkoren
Let's do this Jeopardy-style.

Answer: "Roads."

Question: "What surface or environment -- by virtue of having no control over
shading or solar angle, and by maximising dirt, wear-and-tear, and difficulty
of maintenance -- is more or less the worst place on earth to mount
photovoltaic panels?"

I mean, I _know_ that roads occupy a stupid amount of surface area, and I
understand the desire to do something better with that area. (Tip: just build
less of them.) But seriously, as far as solar panels are concerned, they have
_nothing_ else going with them.

~~~
giarc
During the day, when the sun shines the brightest the roads will have the most
amount of traffic, shading the panels from the sun. Doesn't make sense to me.

Why not just spend this money and put solar panels on industrial buildings or
state owned buildings?

~~~
Qwertious
Most roads don't have much traffic - with a 3 second gap between each car and
the cars going at 60KM/hr, the vast majority of the road will be open at any
one time. And obviously, when the sun's high up the shadows will be the
smallest.

>Why not just spend this money and put solar panels on industrial buildings or
state owned buildings?

Proof of concept. Varying solar tech research to find unexpected gains. Maybe
it turns out that putting solar panels on roads is actually extremely cost-
effective, when you properly adapt the solar panels to road conditions?

~~~
dheera
There is a _lot_ more area coverage in roads than state-owned buildings.
Convert all roads and you can easily power the entire country many times over.
If the government is going to foot the bill and make solar power happen
immediately, roads have the advantage that they are immediately available land
for solar generation. Build solar off-road and you have to choose between a
legal battle of evicting civilians from their private property, or destroying
government-owned nature reserves. Convert roads and you conveniently dual-
purpose existing land area while minimizing environmental impact.

~~~
lotharbot
> _" There is a lot more area coverage in roads than state-owned buildings"_

and there's a lot more area coverage in state-owned buildings without solar
than in state-owned buildings with solar, or that will get solar in a
reasonable timeframe. It's not like we're running out of rooftops and need to
find alternatives.

Even if the government did manage to cover all of their rooftops, there's
still plenty of residential rooftop area that can easily be converted with
proper incentives. I'm pretty sure we can generate enough solar power to
handle all of the needs that solar is suitable for before we come anywhere
close to running out of rooftops.

Even if I'm mistaken about how many open roofs there are and how much solar
capacity they could handle, there are a lot of other and better options before
you get to "put PV cells on the ground underneath semis".

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comboy
Very relevant:
[https://www.youtube.com/watch?v=obS6TUVSZds](https://www.youtube.com/watch?v=obS6TUVSZds)

Many of you probably know EEVblog. In this video he does the math.

Spoilers: as common sense suggests, those roads are not such a good idea (at
least with currently available technology).

~~~
nkoren
Interesting analysis -- although his numbers actually go off-track in a number
of places. The flubs the math on the maximum power output (it's actually about
20% worse than he estimates) while making too strong a case against LED
lighting (you can use reflective baffles to send the light at the appropriate
shallow angles; there's no need to waste energy projecting lane-markings
straight up. Also, an "intelligent" road which presumably has built-in car
sensors needn't project lane markings indefinitely -- just a few hundred
metres in front of whatever cars are present. During low-traffic periods this
could save a lot of energy).

But all of that is beside the point. What's interesting is that in his
analysis, he makes the same mistake that the solar roadways people make (and
which I've just made here), of chasing technical details too far down the
rabbit hole. That's just not necessary: a simple financial analysis leads to a
much quicker and more certain refutation.

For any given amount of money invested, you can either build A.) a solar
roadway, or B.) a conventional roadway plus a solar farm. If the LTV (lifetime
value) of A is greater than the LTV of B, then A is a good idea. If it isn't,
then it isn't. It took me about 5 minutes of high-level analysis to conclude
that the LTV of solar roadways was orders of magnitude worse than the LTV of
conventional roads + solar farms -- sufficiently so that no amount of
technical fiddling would ever close the gap. That's pretty much the end of the
story.

~~~
shalmanese
That's enough for all right thinking people to agree it's a dumb idea but not
enough to convince someone who isn't well versed in the field. For that, you
need to go into far more detail.

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bane
I mean, that's cool and all. But why build the road surface out of fragile
panels? Why not just build a regular road and provide it cover with a roof
made out of panels? Now drivers get to drive in the shade and it's probably
less expensive.

Even cheaper, just put the panels up along side the road, perhaps on shoulders
or other already owned rights of way.

Even cheaper, just give the money to everybody so they can put panels and
batteries on their houses and businesses and over parking lots.

~~~
zardo
Even cheaper, just solicit bids for utility scale solar, (and write so
distributed roof top solar is allowed to compete).

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malandrew
This is asinine for all the reasons others have already stated. The only place
solar panels could make sense is on the road shoulder. Even then they need to
be robust enough to handle having an 18 wheeler park on them. Or you only make
them strong enough to park cars on them and replace them when 18 wheelers do
need to stop on them with the savings earned from not over-engineering them to
withstand 18-wheelers.

That said, I do think roads are a prime place to combine with energy
distribution infrastructure. On top of energy distribution, we don't need cars
with batteries if they can instead function like slot cars getting their
energy from the road surface below. This greatly reduces the weight of cars
such that they are much cheaper to accelerate and decelerate and the stored
kinetic energy is much lower making them much safer. Basically roads need a
safe "automotive third rail". PG&E in California in partnership with the
California DoT is the ideal company to pioneer this approach.

Moving batteries around is great short term, but long term we really should be
electrifying roads.

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JoeAltmaier
Trust the French to do something so romantic and pointless.

~~~
option_greek
Why is it pointless ?

~~~
jacquesm
Because roads that carry a lot of traffic will need resurfacing before the
solar panels have reached their economic break even point.

There are a lot of bull-shit renewable energy projects, which is a real pity
because there are also a lot of good ones and the bad ones give all of those
projects a bad rap.

~~~
Rexxar
I don't know if this project is bull-shit or not. But a big part of solar
electricity cost is installation cost and emplacement cost, not the solar
panel. By using "free" space and installing those panel while
building/repairing the road we can save on those two important cost.

The question is : is it enough to offset the drawbacks ?

~~~
barney54
No. Areas to put solar panels are not that scarce.

~~~
marshray
Just put them properly angled and positioned in the highway medians instead.

This is not hard people.

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malandrew
This is asinine for all the reasons others have already stated.

That said, I do think roads are a prime place to combine with energy
distribution infrastructure. On top of energy distribution, we don't need cars
with batteries if they can instead function like slot cars getting their
energy from the road surface below. This greatly reduces the weight of cars
such that they are much cheaper to accelerate and decelerate and the stored
kinetic energy is much lower making them much safer. Basically roads need a
safe "automotive third rail". PG&E in California in partnership with the
California DoT is the ideal company to pioneer this approach.

Energy distribution is actually a power company's biggest strategic asset and
they should be focusing on this, especially in the face of a world where
energy production is being massively distributed through such approaches as
home solar.

Moving batteries around is great short term, but long term we really should be
electrifying roads.

~~~
woah
Lol why would you think that PG&E plus DoT would be able to do any kind of R&D
in an efficient manner?!?

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cyphar
Great. What a lovely waste of money. It's the "solar freaking roadways"
bullshit again. No, making roads solar panels is not a good idea. At all. End
of story. It's always a better idea to spend the money on a solar farm.

1\. Road surfaces need to be resilient to grit and large trucks driving over
them in rain and other shitty conditions. Glass is much softer than rocks, and
it will undoubtedly crack eventually in the constant heating and cooling, not
to mention tree roots and all the other issues that fuck up asphalt. Not to
mention you'd need to clean (or replace) the panels so often you might as well
make the roads out of gold.

2\. In order to actually get the power from the solar panels, you need an
energy grid that is as big as the road network (this isn't a big deal for
small rollouts, but it is an important note to make). In almost all countries,
this is simply impractical (the electricity network is several times smaller
than the road network) and would be an enormous waste of money for very little
gain.

3\. Solar panels are already about 30% efficient at best. However, that metric
only applies for solar panels being hit with direct sunlight. If you lay your
panels flat on the ground (and not on rotating sunflower-like angled panels)
you lose yet another third of the amount of energy you could've gained. Why?
What was the fucking point of that?

TL;DR: Please just build solar farms and stop trying to reuse the road system
for something it wasn't designed for. You're just wasting taxpayer's money.

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dimonomid
Meanwhile, in Woodland, North Carolina, solar farm is rejected because it
would "suck up all the sun’s energy":
[http://thehigherlearning.com/2015/12/14/fact-check-small-
tow...](http://thehigherlearning.com/2015/12/14/fact-check-small-town-rejects-
solar-farm-because-it-would-suck-up-all-the-suns-energy/)

Although there is solar farm, not the road..

~~~
jmelloy
To be fair, that was the fourth solar farm planned to be built juuuust far
enough outside the town that they weren't getting paid for it or able to use
the electricity generated.

~~~
garrettgrimsley
The article the parent comment linked to is a refutation of the news stories
that attacked the town. I'm not sure if they meant to do that.

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awjr
Whereas in the Netherlands they are applying this principle to bike lanes
which by the virtue of the traffic they carry have a longer lifespan.
[http://mic.com/articles/117948/6-months-later-here-s-
what-s-...](http://mic.com/articles/117948/6-months-later-here-s-what-s-
happened-to-the-netherland-s-solar-bike-paths#.WT4jgv2Mj)

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stuaxo
Did they name this website for this one story ? As crunch is what will happen
to those solar sells underneath the wheels of these vehicles.

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frik
Interesting, but this won't survive harsh winter conditions. Imagine a
snowplow in action.

~~~
dudul
Luckily, winters in France don't compare to what can be experienced on the US
East coast.

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mchannon
A few thoughts here:

•Shading. Cars don't occupy 100% of a highway, even when it's stopped bumper-
to-bumper. The faster cars go, the larger the gaps between them. For PV, the
recovery is instantaneous, and for a large road surface, the power output flat
and steady in spite of car movement. The most sunlight will come in from the
best angle during the noon hour, when roads experience little traffic. Morning
and evening rush hour usually suck for sunlight to begin with (the sun's lower
in the sky), so even bumper-to-bumper shading wouldn't be taking much away
from the total.

•Dirt. The technical term for dirt on a solar panel is "dusting". It's a
factor, and even in places where it rains mud on occasion, a pretty minor one.
The rain eventually washes most of the gunk away. A much more significant
factor would be heat buildup. PV's put out more power the colder they are. On
rooftops they can convect that heat away. On road surfaces, not as much.

•Ruggedness. Having broken more solar panels than anyone I know, I can attest
that a PV road surface can be done right. Cars don't jump Mario-style on
surfaces but rather apply predictable compression and shear stresses that
would have about as much effect on the tempered glass surfaces as your
windshield wipers do on your windshield. Even a shattered solar panel still
works almost as well as a new one, believe it or not. The silicon cells
themselves have a diamond crystalline structure and are tough as nails in
compression. If you somehow managed to bend a cell 90 degrees then it would
end badly, but that's simply not happening on this road.

•Solar angle. These won't win any awards for most power output of a given
surface area of solar panels, but per hectare of land, they're probably just
as good as any system. All the sunlight incident on that hectare will hit a
solar panel. Given how cheap solar panels are now (<$1/W), and how expensive
an urban road is ($2000 a linear foot!), the solar road competes not against a
solar rooftop installation (15% efficient) but against a conventional road (0%
efficient).

•Economic gotchas. The biggest concern I have with this approach is the
balance of system- the miles of copper wire, the mounting hardware, the
inverter assemblies, and the places to store and access them outside the
weather. Inverters wear out after X years, and so the question is at what
point is it just more cost-effective not to replace the inverters? French
electricity will probably justify it, but maybe not Pacific Northwest
electricity (where cheap hydro keeps it ideal for heavy power users).

•Heat vs. Electricity- Let's face it. We run on electricity to a far greater
extent than low-grade heat. Saving a few kWh from cooling and warming a
building using stored heat from a roadway is great, but it's a drop in the
bucket compared to what that space probably uses in electricity. You can swing
the temperature in that building by literally thousands of degrees with
electricity, whereas a couple dozen is the most you can hope for with heat
capture. Electricity can be dispatched thousands of miles away along existing
infrastructure, but that waste heat is limited to a few thousand feet at best.

•Wheel Grip/Slippage [edit]. Conventional PV's have a flat surface since
that's how glass is most cheaply manufactured. If modules are small enough
(apparently these aren't) then a tile/lowered grout approach will still create
a rough enough surface to allow for reasonable braking distance. Glass is
really hard to create coarse surface roughness in when transparency must be
maintained, so I'd be concerned that minimum braking distance would be
increased. Icing conditions would be particularly concerning.

~~~
mapt
"have about as much effect on the tempered glass surfaces as your windshield
wipers do on your windshield."

And this is where you lose me. Either you've never seen a tempered glass
surface, or you've never seen a road, or maybe you just have no idea why roads
are built of the things they're built of.

Asphalt is a pliant surface made of viscous hydrocarbons and filler that
slowly stiffens up over a period of years. You can scratch it, you can embed
pebbles in it, you can heat up the center twenty degrees warmer than the
edges, you can run a metal snowplow over it, you can press furrows in it until
some parts of the road surface have 30 degrees of divergence from other parts
of the road surface. To some extent it's self-leveling, balancing out physical
distortion in one spot with physical distortion in another spot five seconds
later.

The way you cut glass (at least, without a specialist sawblade) is by
scratching it and then applying pressure. The crack propagates and it shatters
into two pieces. This doesn't work with tempered glass at all; The surface is
under so much tension that it tends to shatter into many pieces instead of
two. Roads don't get scratched as exceptional events - it happens many times a
day, with tires, steel bits hanging off, but most problematically, with quartz
pebbles (harder than glass) embedded in tires. Go look at your tires; Rub your
finger along the surface. Now rub your iPhone along that surface.

Melting glass and transporting it in whole sheets is energetically very
expensive. Installation is extremely difficult. Wear characteristics are not
only unworkable, the glass would rapidly become frosted and translucent.

If it was economical to make roads out of glass, we would be doing it. It's
not even economical to make them out of concrete except in isolated
circumstances.

Roadway solar panels are a laughably bad idea. Green inventors are condemnable
when they waste our very limited enthusiasm for green ideas on obvious
technical nonstarters. I've been watching this space for more than a decade
and I'm beginning to despair at the ratio of design/architecture student
renders to even back-of-the-envelope engineering effort.

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datashovel
I would love to hear more details about why folks don't like the idea. Let's
suppose the solar panels are durable enough for heavy vehicles to drive over,
and modular so as to make re/placement reasonable. What are the real problems?

~~~
deelowe
Most don't believe there's a positive ROI. Panels need to stay clean. I
personally think the business model for these is to get Governments to install
them for PR reasons (using public funding).

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Roverlord
Someone tell them to read the hyperloop whitepaper, that way at least the
solar panels won't be wasted on the ground, and they'll be at the cutting edge
of train like things again.

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jmnicolas
How about they experiment on 1 km before 1000 ? I'm very dubious that this can
work, so before they burn my taxes on this kind of things I'd rather they
prove its usefulness.

~~~
dudul
That's exactly what they are doing. The article is lying, the only thing that
was decided is to test the new technology before kicking off the 1000km
project.

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jkot
Such a waste of money!

