EEVblog #850 - French Wattway Solar Roadways BUSTED

[SeanB]

Would be interesting to see Colas put the panels through the standard roadway accelerated test that is used with every new construction or application method. Basically a section is made in the yard to the exact spec, 50m long. then you run a bogie over it on standard truck tyres and axles, with a load equal to the maximum allowable axle loading ( here that would be 22 tons or so per axle) using a long steel guide beam and a heavy electric motor so you basically run it back and forth 24/7 for 6 months, every week taking readings on wear of the road, deflection, tyre wear, power use and such.

This test gives you a fair indicator of how this surface will fare in the typical 15 year road life cycle before replacement. In most cases a tar road will have deep rutting and compaction after 5 months of this, and a concrete road will exhibit major edge damage and joint failure, along with severe surface wear.

A solar road tile will not survive this standard test, and any stick on coat will fail long before the end as well from the cold flow of the tar underlay. The picture of an empty truck on the tile is fine, now just start the engine and, with the brakes on, do a 5 cycle dry steer on the tile and see if it survives when you put a dual front steer on it loaded to the legal axle load with crusher mix. 12 tons load per steering axle, which can damage standard good tar that has not had a long enough time to outgas, or on a very hot day.

[Kilrah]

I guess the only thing that would put this to rest is someone actually building it and honestly publishing the data.

But that would require time, investment, and most importantly, honesty and accepting you've been wrong in the end, so it'll never happen (well yeah it will, but only on a full scale implementation so you get to harvest all the money from building an entire system before people get to see how useless it is, then you can say "oh well too bad, but now it's there anyway so let's just use it", and get the 2nd half of the money through the utterly expensive maintenance it will require ).

Is this the new American dream?   Figure out some BS idea that has a hint of reality and milk investors for everything you can with fancy marketing?

What happens to these jokers went the house of cards finally falls?  Do they walk on to the next BS idea and repeat?

Yep my conclusion too. Best concise description I've ever read about it.

[sarepairman2]

i wonder how resistant these solar panel road ways are to nuclear combat/solar flares/terrorism vs current infrastructure.


i would appreciate if you evaluated this issue. many governments are putting in serious $$$ into hardening their infrastructure, which is kind of a hidden cost.

perhaps a well designed distributed power generation system could harden nations. or weaken them, i dont know.

power generation in the hands of the people reminds be a little bit of the Chinese "great leap forward".

[ruurdjan]

i meant that they would stay in goverment control no matter what. and you would not have a protest about the "gobbermint stealing oah ruufs"
as in, we can send in some national guard to restore power to our city and we can use them to make serious grid planning decisions without trying to push mad legislation.

What's all this talk about government stealing people's roofs?
The government has tons of land and building that don't have solar panels. Put panels on that land first.
People's homes are their homes, if you want panels on them offer incentives for people to take it up. Works well in many countries.

I think you'll find that the total roof area of all government buildings is totally dwarfed by the total area of all federal roadways.
US example: http://www.gsa.gov/portal/content/104501
10.000 buildings across the US (let's assume they can put solar panels on leased buildings). Average area? No idea... Let's say 100m2 for argument's sake. So that's 1 Million m2.
Total length of all US interstates (federal owned - https://en.wikipedia.org/wiki/Interstate_Highway_System): 77.000km. Average wdths - again, no idea but let's say 6 lanes plus two shoulders (https://en.wikipedia.org/wiki/Interstate_Highway_standards) = 6*12ft + 2*10ft = 92ft = 28 meter.
Total area: 28*70 Million: 2000 square  meter.
A 2000-fold difference (less than I expected).

I'd be interested in a non-monetary calculation of efficiency - stating 'it's bullshit' just based on $$ doesn't take into account the cost of the environment (which we can't really reasonably express in $$).

Engineering-wise - I'd agree, it's a very hard case to make. But that for me just means we should try harder, not abandon the idea.

[EEVblog]

yes but you could never make a radical change this way, I am just saying that road ways might allow for that if there is enough of them.

Having "enough" of something that doesn't work properly and has a negative return, is not a solution you want at any cost.

I think there is a strong benefit to them, of course I am not saying that NOW is the right time to implement them.

It will never be the right time to implement them. That is the entire point.
If you have numbers to prove that solar roadways are viable, then present them.

And you said you think there is a "strong benefit to them". How can you possibly know that? No need to answer, because it's a rhetorical question, the answer is you can't. Why? Because there is zero data that solar roads are in any way practical as a road surface. And the evidence as solar production system actually shows the opposite to "strong benefit".
You obviously think the concept has a strong benefit, but sorry, that doesn't cut it.

[EEVblog]

Engineering-wise - I'd agree, it's a very hard case to make. But that for me just means we should try harder, not abandon the idea.

See my previous post about providing numbers to prove this will ever be a viable solution. I'm betting you can't provide such numbers.
The idea should be abandoned, it is demonstrably lunacy.

[Kilrah]

It will never be the right time to implement them. That is the entire point.

I agree with you 99%, but I'd still say cautious and as we say, never say "never".

Playing Devil's advocate here of course, but how would the numbers bode with panels with 80% efficiency?
Of course it will always be more energy efficient to run them in a place where there isn't anything covering or rolling on them, but if it's the only place they are accepted there might still probably be a point in the future where a combination of some secondary aspects can push the currently negative return into the positive, even if only slightly. Could be evolutions in completely unrelated fields that aren't even taken into account or thought of today.
While putting panels overhead like in the Korean solution makes so much more sense, maybe there'll be a day where just laying a layer of panels on the road and only needing a conventional cleaning truck to run on them every once in a while during quiet times at night to keep them clean becomes cheaper and simpler than building structures to put panels on top of them then dealing with more difficult access to clean them, even when factoring the drop in efficiency.

[Brumby]

In an effort to approach the subject from a different perspective, I started to think - "What would it take for solar roadways to become viable?"

.... and the more attributes that were considered, the more it became obvious that many of the improvements that might be developed for solar roadways, simply put the more traditional solar installations that much further ahead.

The only time they could be 'viable' is if there was nowhere else that could be used and economics became second to power delivery.

.... and we'd be in a right royal mess if it ever got to that.

[nwvlab]

Playing Devil's advocate here of course, but how would the numbers bode with panels with 80% efficiency?

State of the art multijunction solar cells can't even reach 50% (http://www.nrel.gov/ncpv/images/efficiency_chart.jpg). And I'm talking about cells, because the panel efficiency is even lower. Furthermore, they cost a lot and they are used in those applications where there is almost no other ways to have electric energy at discrete power levels, such as satellites.

Single junction solar cells have a theoretical maximum efficiency smaller than 34%. That's the Shockley–Queisser limit.

We should not only look at the efficiency, but also we should consider the energy payback time (if it's longer than the device lifetime and if you can obtain energy by other means, it's better not to use them!), and reliability.

For instance, if they had a good reliability, organic solar cells, despite they have a much lower efficiency, could be more suitable, because they are very cheap (roll to roll manufacture) and the energy payback time is short (much shorther than single junction silicon cells). And there is plenty of unused space.
Unfortunately, they have a very poor reliability (especially if you plan to use them in a such harsh environment as roadways)... By the way, even if they had the best reliability ever, you should avoid using them in applications where shading is frequent (i.e. don't put on a road!), because it is very stressful for them.

[Kilrah]

Playing Devil's advocate here of course, but how would the numbers bode with panels with 80% efficiency?

State of the art multijunction solar cells can't even reach 50% (http://www.nrel.gov/ncpv/images/efficiency_chart.jpg). And I'm talking about cells, because the panel efficiency is even lower.
Single junction solar cells have a theoretical maximum efficiency smaller than 34%. That's the Shockley–Queisser limit.

I'm only playing on Dave's insistance about never. Maybe in 50 years we'll have solar cell technology that's got nothing in common with today's, is based on things we don't even know of now and for which 80% efficiency is peanuts, comes for the price of a piece of paper and with which mechanical resistance is not a concern, nobody knows.

To me declaring that something will never be possible is as much of a broken statement as saying solar roadways are viable today

[EEVblog]

It will never be the right time to implement them. That is the entire point.

I agree with you 99%, but I'd still say cautious and as we say, never say "never".

I did concede in the video that there are perhaps niche case uses.

[EEVblog]

I'm only playing on Dave's insistance about never. Maybe in 50 years we'll have solar cell technology that's got nothing in common with today's, is based on things we don't even know of now and for which 80% efficiency is peanuts, comes for the price of a piece of paper and with which mechanical resistance is not a concern, nobody knows.

The physics won't change:
1) Flat solar cells on the road will not be as efficient as properly installed angled ones.
2) The dirt and grime blocking the won't magically disappear, unless we get hover conversions.
3) The maintenance and installation issues won't magically go away.

[ornea]

Dave, you should subtitle (in french) your video and send it to our french ministers...

If someone wants to provide the French subtitle file then I can upload it.

Better yet, dub into french. It would be a hoot to hear dubbed with the same passion and enthusiasm as Dave put into this one.

[Kilrah]

The physics won't change:
1) Flat solar cells on the road will not be as efficient as properly installed angled ones.
2) The dirt and grime blocking the won't magically disappear, unless we get hover conversions.
3) The maintenance and installation issues won't magically go away.

No, but it's impossible to say all of these will never become an acceptable compromise either.

1) Sure, but what if it's no more possibility to install properly angled ones (because politics or space availability e.g. all houses are already equipped, other land reserved for different uses)?
2) Dirt and grime is also an issue on other installations, and roads could actually be easier to clean
3) No, but they could become easy enough compared to other options to make it interesting.

Again it's only the never I can't concieve, only a "not in the foreseeable future".

No issues about the rest, incidentally I'd go further and say that right now even just researching it is a blatant waste of time and effort given that in the current state of things and foreseeable evolutions it only takes quick calculations to show there isn't a chance as you've shown. I put it in the same facepalm-worthy category as attempts at things like electric airplanes which have been demonstrated recently, for which it's obvious that given the current battery technology and foreseeable short term evolutions they're completely pointless. Spending a couple of years now making some custom developments (motors, controllers and things) based on existing general purpose designs to make it work in that application only to show it off when you know you've got nothing to power it to do anything useful makes absolutely no sense, the required developments are minor and can be done quickly enough that you'd better just keep that idea on a shelf until a solution to the major problem is there, or about to be. You'll have more than enough time to build your plane and develop your simple custom electronics between the moment the magic battery with 10x the performance enters production and actually becomes available for you to use. And given that likely won't be before years, anything done today will be obsolete when the time for it comes, given advances in other technological aspects you'll be able to do it better and cheaper if you do it at the right time e.g. once you've actually got all the required parts and technologies at your disposal, so really a total waste.

Unfortunately there's a thing called marketing that craves for "shiny new exciting" but useless things and will justify any level of engineering stupidity and somehow manage to put value in that wasted time... 
On the other hand that allows people who would probably be bored or not have a job to do something that they probably find cool or like, so well...

[EEVblog]

Better yet, dub into french. It would be a hoot to hear dubbed with the same passion and enthusiasm as Dave put into this one.

Dos Youtube even support audio dubbing?

[nctnico]

The one thing Dave doesn't address but is very likely the reason why solar roadways actually DO make sense: SPACE.

Because the ridiculous number of practical downsides of using them as a road surface completely trumps the fact that it might make sense in theory.
You shouldn't invest in something that just makes sense in theory, if the practical downsides are already known, and demonstrably will not get better with time.

Still... what if roads end up to be the only place left to place additional solar panels? This is very unlikely in Australia because there is a lot of space out there where you could build a huge solar farm but in Europe there is not much space for solar panels. And there is always the 'great but not in my back yard effect'. In the NL they already have trouble putting wind turbines several tens of kilometers off-shore because people complain their view over the sea will be affected. The same goes for solar panels mounted at their optimum angle: the space available for that is very limited in cities where it has to look pleasant as well.

[Kilrah]

Dos Youtube even support audio dubbing?

Just upload a separate video with different soundtrack.

[EEVblog]

Still... what if roads end up to be the only place left to place additional solar panels?

Another theoretic what-if question.
I'd be staggered that if all rooftops and suitable public land, and roads and parking lots covered etc didn't cater for all our solar supply needs.
There are just so many other much much much better options than driving on solar panels, it the absolute last desperate resort, and IMO not even worthy of a "what if" discussion.
But go ahead, argue away, good luck trying to come up with solutions for driving on solar panels that that low enough maintenance that doesn't make it a net negative investment.
Solar roadways doesn't magically become a viable idea because we have run out of space and its the only option.

[HackedFridgeMagnet]

Still... what if roads end up to be the only place left to place additional solar panels?

There is so much energy incident on earth via the sun that this wont happen.

Surely they will integrate them into residential roofing in the medium term, not just put them on top and you will never need a solar road.

It's not that you cant do it, it's just that it clearly isn't the best solution, now or in the future.

Picture of suburbs of Sydney. Plenty of unused roof space here.

[rsjsouza]

Me thinks there is a construction mafia in collusion with politicians and some greasing going on to get these ludicrous projects on the taxpayer dollar. 

Precisely. This is a bad joke of a compulsory crowdfunding project paid by the taxpayers...

The idea may have taken off in France due to the events in Fukushima. France has a very large nuclear installed capacity and the public opinion may naturally be open to alternative ideas, thus easing approval.

I've yet to see any data at all on the South Korean system, or even a capacity figure.

With the current tensions in the region, I don't expect you will see public data anytime soon.

The one thing Dave doesn't address but is very likely the reason why solar roadways actually DO make sense: SPACE.

Because the ridiculous number of practical downsides of using them as a road surface completely trumps the fact that it might make sense in theory.
You shouldn't invest in something that just makes sense in theory, if the practical downsides are already known, and demonstrably will not get better with time.

Still... what if roads end up to be the only place left to place additional solar panels?

I can see this being a tougher issue with smaller countries such as Holland, Japan, etc. which will always have to balance accounts with energy imports. That does not make roadways practical in their current shape, but certainly lowers the minimum compromise level.

[nctnico]

Still... what if roads end up to be the only place left to place additional solar panels?

Another theoretic what-if question.
I'd be staggered that if all rooftops and suitable public land, and roads and parking lots covered etc didn't cater for all our solar supply needs.
There are just so many other much much much better options than driving on solar panels, it the absolute last desperate resort, and IMO not even worthy of a "what if" discussion.

Also @HackedFridgeMagnet: As I wrote before, space is not available in all places. When I visited New Zealand with a co-worker from Australia he and the NZ people told me you could drive 20 minutes outside the city and walk in the woods for days without meeting a single person. Especially in In the north-west part of Europe that is just impossible. It is difficult to wrap your head around these differences in population density and what effect they have on available space for things like large scale solar farms. For example: the NL is the second largest exporter of agricultural products in the world. This means that solar panels will have to earn a whole lot of money in order to use precious land for solar panels instead of growing some kind of plants. Land just isn't free.

Ofcourse it is very likely heavy trucks will wreck solar roads but on many multi lane roads the trucks are only allowed in one or two lanes. In Germany for example you can clearly see the right most lane(s) is(are) constructed differently for that reason.

[lem_ix]

Very disturbing, but just what people want. Expect a facebook version of these solar tiles at some point, you can read your wall while driving !  ( probs will have to take power off the grid to run it tho ... )

Meanwhile real progress is made on passion and sweat of engineers. 

[G7PSK]

There are many kilometres of dykes in the Netherlands much of which has a south facing side which could be covered in solar panels instead of roads.

[SeanB]

There are many kilometres of dykes in the Netherlands much of which has a south facing side which could be covered in solar panels instead of roads.

And as a bonus they do not need to be walk on proof, just able to withstand a Category 9 storm that regularly trundles in from the Atlantic. That is probably easier than making one that will withstand a truck.

[nctnico]

There are many kilometres of dykes in the Netherlands much of which has a south facing side which could be covered in solar panels instead of roads.

And as a bonus they do not need to be walk on proof, just able to withstand a Category 9 storm that regularly trundles in from the Atlantic. That is probably easier than making one that will withstand a truck.

Note that most dykes are inside the country because -roughly speaking- the west part of the NL is basically a swamp below sea level and canals to transport the water out are sandwiched between two dykes. The idea isn't bad but there are a few issues:
- The 'not in my back yard' principle applies so people will complain their view gets ruined
- I'm not sure what the building restrictions are on dykes. They may look like heaps of dirt overgrown by grass but dykes are probably the most critical piece of infrastructure in the NL.
- Dykes may be inhabited by plants and or animals which may not be disturbed and many are also used to keep cattle.