Paving roads with solar panels is a classic example of a 'simple, easy, wrong' solution. It seems that some people have gross misconceptions about the barrier to solar panels. People living in crowded cities think there is some sort of shortage of space. In a broad sense this is of course very far from the truth. The barrier to solar is cost per kw/hr. As that goes down, solar installations go up.
> Paving roads with solar panels is a classic example of a 'simple, easy, wrong' solution.
You are likely not seeing the same "problem" that the powers that be in France are seeing. When looked at through the lens of graft, corruption and cronyism, it's 'simple, easy, and profitable'. Whether it ever delivers worthwhile amounts of power at efficient costs is entirely secondary.
Always nice to know that certain elements of the human condition are universally true - was just talking the other day about graft, etc in Boston as compared to DC. Now we can include France in the discussion.
> People living in crowded cities think there is some sort of shortage of space.
Too true. When I spent some time in an urban technology research lab, the researchers and students gravitated strongly toward projects described as "a little tiny $X that you can carry with you." Their focuses narrowed from stage performances to screen-based art. In the Indra's web of city life, the wide, open space of rural areas was not only forgotten, but incomprehensible and unavailable as a resource for deployment.
Looked at from the other direction, as solar installations go up, the cost per kWh goes down. So a public entity doing one very large installation seems like a good way to help push costs lower, especially for that particular installation. And if they're looking for a lot of urban public space to build on, why not roads?
because the panels then need to support and run the wear of cars (which my guess is expensive). roads are repaired quite often because they have to deal with temperature contraction and expansion and also huge shifting weights rolling across them all the time.
Right, but that's all structure and doesn't (er, shouldn't) fundamentally affect the cost of the PV cells themselves. Regardless, I agree that it's not necessarily the most cost-effective choice, I just don't think that it's a response to some perceived lack of space either.
Roads require maintainance and solar panels require maintenance -- couldn't innovation (conceivably) produce a maintenance schedule that can maintain both these things under one process at less cost than maintaining each separately?
Why would you complicate something so "easy" like putting solar panels on the side of the roadway? It's going to be so much less efficient for so many reasons ( orientation, dirt, cars shade, scratches) and maybe dangerous for the cars.
Absolutely. Why not put them on the sides or overhead. Granted overhead adds cost, but at least there is no abrasion, and virtually permanent shade. Are they piezo active somehow, why make them part of the roadbed for any reason?
Also wouldn't the surface be less safe for driving in inclement weather, what's tire grip look like under bad weather conditions with this surface?
Exactly. Arizona State University recently covered a bunch of walkways and parking lots with solar panels to both shade the lots while soaking up that delicious Arizona sun, which seems both effective and obvious. Putting it on the ground is not the best idea, and not even the most obvious idea. It's just mind-boggling.
Actually there are some aspects that are admittedly simpler when you lay them on the ground, like for instance cleaning them with vehicles. Vertical panels next to the roads would still be equally bad idea as there is a lot of chemicals and sand and air movement that would create you all kinds of problems, and plus you would have a lot more issues with vandals (or just people throwing half-empty bottles and other heavy garbage from cars), they'd obstruct the view, could be potential safety issue because of lights reflection in the night, etc.
That's true. However, keep in mind that a solar roadway tile has to be "hardened" and its surface has to provide traction when wet. Both of those reduce the amount of light which actually reaches the photovoltaic cell. In other words, a clean tile is probably about as efficient as a dusty solar panel.
>> something so "easy" like putting solar panels on the side of the roadway?
I'm not even sure that's the correct goal.In the end Global warming , is , well, Global. So they key to solving it is making clean energy the default choice for the china, india, etc.
Is buying more solar panels helpful - sure it does help reduce the costs of solar panel manufacturing/installation. But is it one of the best places to invest, if the EU/france want to help ? i'm not sure - because there may be over investment in that area - since it's already economically viable on a large scale.
I wonder though, maybe there are areas of under investment with lots of potential ?
Because there's always a risk folks would steal the Solar Panels (not unheard of in France). If it's below the road, maybe it makes it a little bit harder and more dangerous.
Anything between the solar cell and sunlight torpedoes efficiency. So never mind stealing them; they're useless under some layer of plastic or whatever. This whole project is pointless.
A few things to point out:
1. putting solar on the ground means that it is less efficient (cars blocking rays) than raising it above the roadway and providing shade to the roadway.
2. Dirt on the panels makes them less efficient, roads are dirty
3. Expensive to fix. It is cheaper to fix asphalt than photovoltaic.
Agreed, it seems that the economics simply don't add up. The article is also particularly deceptive, as it claims that 4 metres are enough to power one household, and 1km to "light a settlement of 5000 people". However, that means just powering the streetlights of a settlement of 5000, as 1000/4 = 250 only. It's interesting at least as an example of environmental action purely driven by an attempt to get cheap political support (pun intended). I wonder if such an experiment could at least drive further research and innovation.
I doubt that 4 meters of solar roadway would be able to power a household after 6 months of normal use (not to mention that the placement of solar panels on the road is such a stupid idea that it beggars belief).
I think you can ignore the effect of shadows from cars. If you look at satellite images of highways, the percentage of the road covered by cars is actually quite small (<5%, by length, I would estimate.) The reduced efficiency due to not orienting the panels at the optimum angle will be much greater.
Solar panels are connected in series to improve efficiency and reduce costs of inverters. Single panel under shadow degrades the whole set. It behaves as a resistance.
Which is why you add bypass diodes. If you don't have bypass diodes, and have enough other cells in series, you can actually burn out a section of panel by casting a shadow on it.
That's a poor comparison, it's not about efficency at any one stage, it's a question of total cost vs total gain. If the cost of this road surface over it's lifetime is less than traditional road surface plus the equivelent solar cells over there lifetime then it's a good idea.
Given that asphalt construction is made out of mostly waste materials, is nearly 100% recyclable, can be patched in-situ, requires very little maintenance, requires very little skill to install/maintain, and is much more durable than glass, there's no way the TCOs are even remotely comparable.
Asphalt is a product from crude oil; as such it's got finite supply and is likely to go up significantly in costs over time. It's actually used on roofs which are becoming less common for various reasons and breaks down in sunlight.
PS: Nothing says they need to use glass, just a cheap durable and translucent substance.
OK, can you name a cheap, somewhat durable, and translucent substance that's not glass?
The typical translucent substances people use in practice are various kinds of glass, plexiglass (not durable; scratches up a lot), transparent ceramics of various sorts (generally not cheap), gems like sapphire (not cheap, especially for large-scale applications). Anything I'm missing?
Lacquer wood finish comes to mind, though tar is hardly durable. Not 100% on the specifics but people already use concrete sealant on roads so traction and cost wise it's in the ballpark.
Don't forget Silicon is really quite tough so your really looking for something that can sit outside for 20 years vs. trying to protect fragile components.
The hard problem in road surfaces is not the sitting outside for 20 years. Glass, even cheap crappy glass, handles this last just fine; see windows in houses. The hard problems are dealing with repeated time-varying mechanical stress and dealing with thermal expansion (windows can play fast and loose with this by leaving expansion space around the glass inside the frame).
It won't be. Tarmac is an incredibly well-designed material to use for roads. Glass + silicon is not (to put it mildly). Not to mention that the sheer cost of solar panels makes this a ludicrously expensive project (why didn't they just make a solar farm instead and save some of the money to pay for tarmac -- it's a much better way to spend your money).
Tarmac is cheap and easy to apply, other than that it's a poor road surface. In heavy use coupled with poor conditions Tarmac can need resurfacing in as little as 5 years (10-20 is more common). Worse, it can significantly increase fuel consumption for heavy vesicles as the road surface deforms.
Concrete is better for fuel consumption and can last 2-4 times as long, but needs regular gaps for heat expansion which can cause noise issues and poor ware patterns. It's also far more expensive and end of life roads often spend long periods in poor repair.
Glass is actually a fairly competitive surface. Though, to expensive for most uses, people have used to for see though driveways etc.
> Tarmac is cheap and easy to apply, other than that it's a poor road surface. In heavy use coupled with poor conditions Tarmac can need resurfacing in as little as 5 years (10-20 is more common). Worse, it can significantly increase fuel consumption for heavy vesicles as the road surface deforms.
Yes, but because it's cheap this isn't a big problem. Not to mention that glass will not last 5-20 years on a highway. It is much softer than the stones and other crap which will be scraped against it with car tyres. It will start to crack when it's hot. It will lose any grip very quickly (thus making it a public safety hazard) and won't function as a useful solar panel much faster than it will stop working. A driveway and a highway are very different problems to solve.
> Concrete is better for fuel consumption and can last 2-4 times as long, but needs regular gaps for heat expansion which can cause noise issues and poor ware patterns. It's also far more expensive and end of life roads often spend long periods in poor repair.
Yeah, concrete is good as well. I forgot to mention it.
> Glass is actually a fairly competitive surface. Though, to expensive for most uses, people have used to for see though driveways etc.
See above. I don't agree. And I don't see why people are trying to convince themselves that it isn't a stupid idea.
However, it's the kind of problem begging for a good solution. One option would be an ablative surface like asphalt where glass chunks are suspended in a clear resin. Probably a health hazard. Another is to only add panels down the center of a lane, which might push a marginal solution into feasibility.
It is beyond stupid on so many levels only a politician could love it. The sad part is how much money politicians can waste without oversight, especially on dubious expenditures. They would get so much more bang for their buck putting up a solar array along the highway.
However this really sounds as if the politicians bought a bill of goods and simply could not comprehend they don't understand the issues. As in, they are the smartest people they know so they are incapable of being sold a bill of goods that are bogus.
In other words, if it does appear idiotic for all the technical reasons, it would follow other reasons are at play. (Call me a cynic, but "pork-barrel" immediately comes to mind.)
I prefer to look at it this way: effectiveness of their ideas is one of the least important things they optimize for. They're driven by constraints that have little to do with actual value to society.
That's just the start. How about, the worst possible case for transmitting power to where its needed - a huge line. A real solar plant can be put where demand is. Also, the angle of the cells is necessarily straight up. Works on the equator, sucks every other place on the planet. And so on.
This is an example of stupid thinking - "Roads are flat; solar cells are flat; lets combine them!" It ignores all the other requirements for a good (efficient, positive return) solar installation.
The "1000 km" title is misleading. The tiles will be mostly installed on parking space near commercial centers and on a few low-speed connecting roads.
I find it actually a great idea, especially with more electrical cars looking for plugs at those locations.
Their PR is unfortunately low quality and low on facts, though critical thinking would also try to look at the "why".
The futur or "solar roads" is clearly not highways and express lanes. It's slow speed, commercial areas - as badly presented by Colas.
For the context, land use in Europe is so different than in the US. Suburbs don't crawl as much and space is more of a premium.
Thinking at a really local level, for a new retail space like this: https://goo.gl/maps/BRkQ5qNyaQU2 - the fields around the center are either here to stay or would be built on.
About 80% of this commercial space is parking lots. It's wasted space. Why not use it to produce power? Why use additional fertile or constructible terrain to add solar tiles?
Since 2015, businesses in France also have to build either gardens or solar panels on their rooftops (new constructions and redevelopments). So that's turning 90% of space used into something productive or "user-friendly". Again why not do it?
The pricing of those solar tiles is interesting: 6 euros per max watt produced on location. Cheap enough - and you get free power for parking users.
It's also great PR for solar to get inserted in people's lives at such locations.
> About 80% of this commercial space is parking lots. It's wasted space. Why not use it to produce power?
You didn't get my point obviously. Parking spaces are to park on. When a car is on a parking space, it's blocking the light from tiles under it and also casting a shadow.
> Why use additional fertile or constructible terrain to add solar tiles?
Because they won't have cars park on them. They will also be at an optimal angle and cleaner.
On a parking lot, not 100% is used by cars. Lots of space for driving/walking through and around.
The example above show the paring lot partially full with a lot of space for solar panel roads: https://goo.gl/maps/ZR5kNMZYGbE2
Also, in France, we're limited in farming space. Sure, it's going to go away eventually, while we outsource farming elsewhere, but replacing fields with solar panels is not as obvious of a tradeoff as it could be elsewhere in the world.
Why not just make covered parking, and put solar panels on top? Then you can just use "regular" solar panels, which will be a lot cheaper, last a lot longer, and produce a lot more electricity. Plus, covered parking! The additional structure will be costly, but I wouldn't be surprised if it ended up being the same total cost as the tiles.
Or they could COVER the parking lot with these panels, which would not only generate more electricity, but would also be far more durable, provide shade/cover, and reduce the need for air conditioning systems to be run when because you'll no longer be climbing into a hot car.
Do a search on YouTube for "EEVBlog solar roadways". Solar roads are a great way to get people excited about solar, and a terrible way to produce electricity.
> edit: also part of the breakthrough here is that the upper layer is made of recycled glass and resin and is not slippery.
I personally doubt this will solve the softness issues (it will wear down quickly). But if it's not being used on highways, the wearing isn't as serious of an issue. I still think just building a solar farm is a much better idea.
> Bit surprised by the negativity around this on HN.
The "solar freaking roadways" people just pissed me off so much with their dumb crap. Not to mention that so many politicians took them seriously, lording them as an example of innovation. As a result, myself (and probably quite a few other people on HN) have built up a massive amount of skepticism when people talk about ideas like this, because we know they're a bad idea and wish people would stop pushing it.
putting solar panels under the cars in parking lots seems like possibly the silliest thing ever - not only does it block the light from getting to the solar panels, but covered parking is desirable - if they just put the panels above the cars they would get more light and the cars and people would have some protection from the weather.
Horizontal placement, dust, scratches vs brittleness, mechanics of moving load bearing by tiling vs continuous surface, cost of PV turn it into a joke. We'd be better off putting them above the roads than on the roads.
Gah, what a terrible idea. Making a durable, safe road surface that's also useful as a solar source? Why not just put a solar roof on the entire road instead? It'd probably be cheaper, and almost certainly safer and more efficient.
If we wanted to generate electric power off of road surfaces, why not embed piezoelectric or some other compression-to-energy mechanism instead? Cars rolling over the road apply a tremendous amount of physical energy to the surface. Capture that energy. It's probably more than you'd get from solar.
> Cars rolling over the road apply a tremendous amount of physical energy to the surface. Capture that energy.
This is a misunderstanding of thermodynamics.
There is no energy to be captured without adding friction to the existing situation. Even capturing the vibration would tax the vehicles traveling over the road.
This is similar to the old "smart steps" concept[1], which takes extra energy (beyond the energy already required to take a step) from the person walking on it.
> There is no energy to be captured without adding friction to the existing situation.
The point is that there is already added friction (we want cars to grip roads and feet to have cushioned impact) and wear (asphalt is a liquid). Cars already compress roadways, brake on them, etc. To the other extent, a flexible base could reduce some of the wear by adding flexibility.
For "Smart Steps" yes, they consumer energy from the walker, but the walker also has less impact on joints. Running tracks prefer absorbing surfaces (rubber) for the increased friction vs concrete - not absorbing energy.
Your point is true, if we were to replace all the asphalt roads with a new form of road.
I suspect the energy and material requirements for making an energy-capturing dampening system that feels similar to asphalt to the vehicles overhead would far outweigh the benefits (I'm picturing some sort of electrolyte putty with thousands of wire leads every meter, funneling microamps of energy into a the heavier wire in a conduit underneath).
Of course it adds friction, but that friction could be pretty negligible. You don't need to capture all the energy introduced by a heavy vehicle passing over the surface. Just capture a little of it.
Some technical ideas are stupid in a trolly way: it's difficult to actually put numbers to the reason this is bad, because you have not actually put forth a proposal, only an idea, and we would require a detailed physical simulation of your proposal to be able to demonstrate with proof "This is a fucking stupid idea".
Nevertheless, design enough things and mess around with energy capture schemes enough and you do develop some intuition in the matter of how hard it would be to implement, how much you would actually get back, how negligible that is. That intuition is screaming at us that this is a waste of time, your idea is bad, and you should feel bad.
What is easy to point out that you're trying to shift the burden for electrical power generation from solar/nuclear/coal, on to scarce and expensive oil, mediated through low efficiency automotive engines, and in the process increase road construction costs by orders of magnitude.
The only free lunch you get in automotive regenerative power for every car that passes, is on the downslope of very long hills at high speed. You can regenerate power here through the wheels (and that's slowly being put into the fleet as we start to use wheelhub motors & large battery banks), or through in-road baffles. You could do the same thing at traffic lights, but they don't have a predictable deceleration curve and speeds are much lower (making it feel choppy) and it's not an environment where you want to mess with people's sense of acceleration, for safety reasons.
That's just dumb, I'm sorry. There are losses in any process. Any power generated by this Rube Goldberg idea, would cost far more in lost power to the car. There is no free lunch.
Roads already flex and compress in response to the moving weight of vehicles traveling on them. That's basic materials engineering. Where does that energy currently go? Thermal loss. Can we convert some of that thermal loss into captured electricity?
Vehicles are already losing friction energy to roads. This doesn't need to add to it.
Power plants like to generate superheated steam to drive turbines. And now we suppose a tenth of a degree of warming in the pavement is worth going after?
Go back to engineering school for a few more years, is my advice to anybody trying to get energy out of roads. That potato clock we made in 2nd grade generates more energy.
Thank you, that was my point as soon as I heard about "our" roads being made into non efficient solar panels.
However, given the few experiments conducted so far, it seems that it wouldn't be any more efficient than solar panels, moreover, the technology to cover roads with piezoelectric sections hasn't been tested out of research, AFAIK.
Roads don't need to be covered with piezo surfaces. The piezo could be underneath the surface, relying on compression transmitted through from the surface. It should work with existing concrete and asphalt surfaces.
So let's take the conservative end of this - 1,000 lane-kilometers.
Assume a lane is about 4 meters. Thus we have 4 square kilometers as a target, if we assume a square meter of road is exactly as good as a square meter of dirt.
About 1€ per square meter. For farmland on the expensive, 'stunning' end of the spectrum.
Put it there. Whole program. Forget about the roads. Now you don't have to shut down FOUR THOUSAND KILOMETERS of active traffic-bearing road, or employ an army of thousands of installers, or repeatedly install it because it "lasts up to ten years". You don't have to deal with an extra layer of glass-polymer tile on top, you don't have to run all of the wiring in the least efficient and least maintainable manner possible, you don't have to do a bunch of things that become necessary if you stick it in the road.
1m^2 of solar panel at 20% efficiency achieves about 200 watts at theoretical best insolation. Solar panels are presently priced around 0.25€ per watt, so we arrive at a cost of around 50€ per square meter panel, or 50x as much as the land to place the panels on.
4 million Euros wouldn't be more than a tiny fraction of a program like this. Using the roads has the potential to increase costs by a factor 10x-1000x over using simple panels.
> Wattway cells collect solar energy using a thin film of polycrystalline silicon, but are resistant to the passage of heavy goods vehicles and offer sufficient traction to prevent skids.
Ah. It is "sufficient". Okey Dokey.
Edit: Oh, and never let science get in the way of politics!
As pointed out by other posters it's not the most efficient way of getting power for various reasons, so this must be mostly motivated by political reasons.
I really hope it's not slippery at all, I ride my motorbike all the time and a small skid has more consequences than with a car.
They are in the UK, certainly here in Northern Ireland at least. On the way out of Enniskillen there's an estate with them on it, but you can clearly see the difference between the non-solar and solar tiles in the roof. Here's a couple of products [0] and [1] (I'm not affiliated or connected in any way, just been looking into this while planning my own house).
There's also this stuff [2] but I've never actually seen it installed anywhere yet. It takes a completely different approach and is more like a metal roof than slates.
Another excellent idea I read about was storing solar heat in massive batteries underground. The battery being made of brick or stone, or earth. You catch heat in the summer and pipe it below ground, and warm up this underground store/battery (away from the water table). Because earth is also a good insulator the heat is localised. And in winter you reverse the process, drawing out the stored heat.
Roads get very hot in the summer (in some places), and if you could store that heat for residential units in the winter that may be better than turning into electrical energy.
Yeah it probably makes more sense to just use this kind of setup [1] except you ditch the mirrors and just embed the pipes directly into the road vs putting solar panels on the road.
You end up with a lot of similar issues - cost of materials, requires a lot more expertise to install/repair, damage may require replacing larger areas than a few tiles, slick roof surface, etc.
But at least you're not driving on glass or dealing with car accidents on the roof (hopefully)
It's unfortunate that in the most sunny parts, people don't have sloping roofs so panels actually look ugly. Still, roof solar is very popular in southern europe.
Maybe as engineers we are tempted to misunderstand the motivation for building this. As other commenters have pointed out, the main reason for this is political. Perhaps the secondary reason is not so much the actual utility of the solar roadway but the visual impact and the meaning that it represents. I mean, one of the biggest cities on Earth has giant woman made of copper placed on an island just outside it.
A lot of threads point to the dangers and inefficiencies, as well as political motivations.
Does anyone know the economics of paving roads with cement or tar per m^2? The labor and material cost would be transferred and somewhat offset installing solar elsewhere.
I can not speak to the claims of safety, but I would imagine the decision is rational enough not to be endangering lives.
I would be interested to hear this argument out. This was the first thing that came to my mind: are there any savings in the costs of the actual road? If you take those savings into account, what does the net cost / kwh look like?
In addition to the efficiency concerns, France should be thinking about the conflict minerals that are likely in these solar panels. I am supportive of efforts to reduce energy consumption and alternative more environmentally friendly energy sources. And it's exciting to hear about new solutions for energy that appear affordable. But I am hesitant to use technologies that use conflict minerals. Before we make decisions about buying innovative products like solar cells, we need greater awareness about the materials they use and where they are coming from.
This will be a maintenance nightmare. The software concepts of Separation Of Concerns and Object Single Responsibility might be usefully applied to this domain.
Not mentioned is the total cost of the project, estimated at around 2.7 billion Euro for 10-15 years of life expectancy according to the industrial manufacturer (Colas).
There is a very long way, in France, between political declarations of intention and actions, so I'm betting this will never be done. Which would probably be for the best, a predictable failure such as this project would slow down development of renewables in France even more.
Anyone who thinks this through a bit must realize that roads are one of the least optimal places to put solar panels. Solar panels are still not very cheap so putting them where they are not efficient tips the scale further against Solar energy. France on the other hand is one of the main producers of cheap atomic energy. Given all that I cannot see how this can be any more than a publicity stunt.
See this topic (solar roads) is the Perpetual Motion machine of renewable energy. Folks flock to the idea regardless of the implausibility, regardless of the massive evidence that is nonsense. And trying to argue is like trying to argue with a pig; you just get muddy, and after a while you notice the pig likes it.
Was on a long motorcycle trip with a few friends. We had left our home in the US and were traversing Canada which, of course, uses the metric system, unlike the US.
As we passed one sign, it said something to effect of "Dawson City 1500km", which I remarked on over the radio as it was a nice round number (and, of course, quite some distance, and a large number you're unlikely to see on a road sign in the US due in part to the greater length of the mile).
