Output of Dutch solar bike lane exceeds expectations | Hacker News Reader

Output of Dutch solar bike lane exceeds expectations

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80 pointsRafert94 comments

Roads are quite a good place to place solar panels, logistically speaking. Yes they are 30% less efficient, but they are also closer to where the electricity will be used, and the marginal opportunity cost of real estate is zero since road use is retained. You don't need new land and you don't need to worry about transporting power at great distances. I'm glad such experiments are being conducted to see how well this idea performs in practice. It's good they started with bike lane as opposed to truck roads. It will give them opportunity to iterate on the panels resiliency.

Not sure why you are being downvoted, but I thing your comment makes a lot of sense, and I'd like to know why some think otherwise.

The economics of solar panels in roads are horrible, given current technology.

Here's an excellent engineering analysis of this exact project: https://www.youtube.com/watch?v=HOZBrHqTJk4

I wrote a comment there. Panels on roads, if they can suffer being driven on well, can be economical when rooftop spaces run out. Rooftops are only sufficient for 25% of Netherland's electricity demand. I notice now there is a couple of inaccuracies but they are only minor ones financially. The benefit from saved real estate is too big.

Local council governments may have access to its road real estate, but have no legal right to install panels on roofs. Netherland land value, per square meter, is €4,907. There is a local property tax is 0.05% - 0.3%. (http://www.shelteroffshore.com/index.php/property/more/prope...), and a wealth tax of 1.3% per year. Assuming 1.4% total taxes per square meter, the revenue received by the government is €68 per square meter. Since building the solar panel on the road means they don't have to build solar panels on real estate that can generate tax revenue, the benefit is €10 of generated electricity, plus the €68 of tax revenue that is preserved (assuming all municipal building rooftops are exhausted, already). That makes a payback of €78 per year. In 15 years, this would equate to €1170, compared to building a solar array on free land. The savings would be even greater compared to the local government renting rooftops to place solar panels.

Logistically speaking, there's a nightmarish level of complexity introduced here. Put a country's food distribution network on top of its energy production system? Put solar cells where you know they'll be constantly driven over by heavy machinery? Replace some of the most durable materials known to man (asphalt and concrete) with glass encased electronics?

These things aren't impossible, but it's such an uphill battle that I wouldn't hold my breath. (http://jalopnik.com/why-the-solar-roadway-is-a-terrible-idea...)

I gather from their website that the solar panels are embedded on top of the concrete roadway, so it would seem to have the same strength.

Durability, not strength. Asphalt is very durable and it fails in predictable ways, it's difficult to design glass that fails gracefully. Yes, it's a surmountable engineering challenge but this project has more than it's fair share of things that fall in the "technically not impossible" or "we'll figure it out later" categories.

Asphalt is cheap, but not really that durable. 3-5 years in you generally see some cracking and should start matence. 5-7 years you generally need some patches and 15-20 you need to replace the surface. Though that's assuming good conditions and reasonable traffic patterns in some areas you need to resurface within 10 years. Concrete on the other hand generally lasts twice as long.

From a material perspective glass is much closer to concrete than asphalt. Ex: http://en.m.wikipedia.org/wiki/Glass_brick the point being glass withstands sunlight and the elements without issue, it's being driven on that's going to be an issue. And luckily that kind of stress is much easer to simulate in a lab vs weathering.

PS: That or ice which can handle heavy loads with little issue.

Point granted, we use asphalt because it's a cheap and I should know better. I would still expect it to last longer than wildly complicated solar panel/computer/light displays that have many more modes of failure.

For this to work you have to do several things to the glass at the same time, none of which come easy: make it strong, make it hard (probably need to get to 8 or 9 on Moh's hardness scale), make it tough, and have it grip rubber as well as asphalt does even when it's wet. Considering scratch resistant and grippy compete with eachother this is not looking hopeful.

Yea, I don't think this is a good idea yet. However, train tracks might be a good option if you could get it durable enough but where having traction issues. The ~1m distance between rails is generally just wasted space and the US has ~400,000 miles of rail if say 20% efficiency over 1/2 of that distance that's ~320GWh per day which is a fair bit of power.

The advantage being rail lines need to trainsport electricity for electric trains, so you get dual use from those power lines.

That's still bundling something fragile with infrastructure that carries heavy machinery. Transporting electricity is a solved problem, we can put a solar farm in the middle of nowhere with current technology. And if we're looking for land that's already owned we could put solar cells underneath long range transmission lines 1000x easier than we could embed them in roads or in train tracks.

Thick pices of tempered glass are vary durable and could easily outlast asphalt as a road surface. Right now the decreased efficiency makes this a non starter, but long term if solar keeps getting cheaper it may become a reasonable supplement to the power grid.

PS: Bullet resistant glass is surprisingly clear dispite how thick it is.

I wonder what the stopping distance is on this glass?

Not as big as wet glass or icy glass ;)

Materials scientists do fascinating things with glass, but making it competitive with rocks for road surfaces seems like a waste of effort.

Personally I think Elon Musk's solutions for this problem (decentralized clean power generation) are a bit more compelling, especially the part about putting solar panels on our rooftops instead of in our roads.

http://fusion.net/story/129075/elon-musk-reminded-everyone-l...

Is it important that they started with bike lanes and not full roadways? A bicycle vs. a delivery truck present radically different loads to the roadway.

The road is much wider, and pose greater disruption to transport during installation - If the experiment fails because it can't even take bicycle loads, and bicycle wear and tear, there would be bigger waste. If 70m works (physically, politically, economically), do 100m. If 100m works, go for 500m. If that works, do a 50m prototype on a road. Something like that.

It would also be far more costly. As roadways have way higher requirements then bikes.

Strangely enough, glass lasts a very long time in terms of actual time from the perspective of geologic longevity. Pieces of glass will tell humanity's story long after buildings and roads crumble to dust. I understand that shards resting peacefully and a pathway that is used constantly are very different things, but I never cease to be amazed at the strength of glass and how much it has strengthened in my own life time. Just a thought.

In a country with sun nearly all day, on a bike path (not a road), run in a place without shade trees or houses. So they got a few KWH. If instead of a mile of 'solar bike path' you made a proper installation anywhere along that path in an empty lot, you'd do better, it would be cheaper, transmission costs would be less, and on and on.

This fixation on "we're already using land area for roads; solar panels need land area; lets combine them!" is not an engineering decision - its politics and public relations.

The main purpose of roads is to handle vehicle traffic. Here I see solar panels covered with glass and I just don't get it how it can be used for anything else but to generate hype. Even if the glass was somehow more damage resistant than asphalt there is still the question of grip. And even if you invented transparent asphalt to put the panels beneath, it would only be trasparent for a day or two, until dirt accumulates. They are probably cleaning this 70m strip every day but can't do the same for the entire road network.

Part of the experiment is to test the traction surface. They had a problem with a bicyclist slipping, so they switched from stick-on surface to spray-on surface.

The article says they use an angled surface and natural precipitation to keep the glass clean. I can only imagine how much dirt builds up on a highway over a day. A similar complication would be dirt or sand being blown onto the roadway by wind, or washed there by rainfall.

US roads are home to several critical subterranean infrastructures: water, sewer, electrical, natural gas, and internet. Our roads are constantly being cut open, trenched, and patched to do maintenance and repairs to these systems.

In the US, we have large amounts of unused space on top of our buildings. Placing panels on the top of buildings puts the electricity near its consumption point and reduces building cooling costs.

The issues with placing solar panels on roofs is the high cost of installation. I would guess the cost of installing panels on busy streets would be similar to the cost of installing them on rooftops.

Rooftop is great for medium and low density residential. Higher density residential and industrial and it starts to get difficult.

The municipality here is in the process of disposing of their ~30 MW power plant (mostly coal + oil peaker), that serves ~20,000 people. Rooftop would handily meet summer needs, winter heating is another question (there is space, it would be too costly). A nearby mill has a 100 MW natural gas plant and occupies considerably less area than is served by the municipal plant.

US power plant data is here: http://www.eia.gov/state/maps.cfm

>Higher density residential and industrial and it starts to get difficult.

Rooftop solar may not be profitable for individual building owners, but is still likely to be a good thing across the community. A more "socialized" model where the costs are borne and the generated power reaped across the grid, rather than per-building, makes more sense. Particularly since we're talking about this as an alternative to solar panels in roads.

> Our roads are constantly being cut open, trenched, and patched to do maintenance and repairs to these systems.

At a glance, it looks like the solar road system uses semi-modular panels. That could possibly make road work much easier than it is on asphalt, which requires a ridiculous array of equipment to cut away the offending area before work begins, then lay down an entirely new replacement section once work is complete.

Roads, bike lanes, etc are all terrible places to put solar. Look at the difficulties people have with floor heating via hot water pipes, which is a simpler problem to solve and despite that is still problematic.

Comments to the article are not so enthusiastic:

- 25% more solar exposure in the area this april--should be considered, too

- with the frost, the glass-like surface turned into a frictionless slide

I'd love to see some financial analysis:

1) cost of producing the same amount of electricity with Netherlands' most common electricity production

2) cost of building this vs. a normal bike path, and time for recovering the cost considering #1

3) expected life of this system + anual maintenance cost

4) cost of a typical roof installation for the same surface

5) Cost of a normal bike path with ordinary solar cells of equal area next to it

6.) CO2 and energy saving.

5.1 Cost of a normal bike path with ordinary solar cells on top of it (providing shade, and shelter from the rain, with presumably greater efficiency)

This is actually what I envisioned before I looked up some pictures (if there were any in the article, they didn't load for me).

It seems more practical, in particular for a bike path.

That's already well-studied, for parking lots with shade structures.

I'm astonished how many people are weighing in to trash a small project researching something new that might be interesting!

I'm definitely not trashing it - I'm enthusiastically interested in whether it's viable. What I'd love to know is what the expected cost structure, at scale might be, in comparison to other options.

There probably won't be a win on a purely mathematical/financial level at first. 3000 kWh in 6 months is only about $300 worth of electricity at 10 cents/kWh. I don't care how low the cost of paving gets, it's not going to compete with the cheapest form of energy in human history (burning stuff - traditionally wood, then peat, then coal as the availability of fuel inevitably dwindled, and now to deep sea exploration, fracking and tar sands that are only economical if externalities aren’t considered).

The real win (as I see it) is in converting economies from continuous financial outlays going up in smoke to one-time investments with exponential returns spread over similar time frames. Automation and amortization are the future. Each time a drag on the economy like inefficiency, unsustainability or rent seekers are innovated around, the truth that sustainability is cheaper eventually proves itself in their absence.

Even if some of these clever experiments cost 10 times more than the market rate at first, it will click for people that maybe they can lower their own energy usage by half through minor lifestyle changes (whose side effects include greater health and happiness), and drop that by half again with more efficient devices. So most people can get down to 1/4 of their current usage for next to nothing essentially, and now we're only talking a factor of 2.5 times more expensive to go from an unsustainable to a sustainable society. Then if we live with that liberated mindset long enough, the Moore’s law of alternative energy takes care of the discrepancy in a matter of decades. This is already happening and probably unstoppable at this point except through excessive lobbying and fast tracking, which we are seeing as well.

This still doesn't tell us why we should put solar panels in bike paths instead of on rooftops. A solar roadway seems far from sustainable. Those efficiency gains you claim decrease the roadway cost would be even more effective combined with rooftop solar.

For that matter, why not put the panels over the path, on an awning? Thin film panels could be built into tarps that are stretched over the roadway between anchored poles. You could reduce the coverage price to something commensurate with lighting.

And, solar panels are becoming more efficient every year, so it does not make sense to me to embed them in a bike path that will last decades.

The most efficicient in terms of both finance and environment, to use solar panels is probably to replace them as soon as they have paid for themselves.

What are you doing with the old panels then? As long as they are still making some reasonable amount of power, it doesn't seem like recycling/reprocessing/discarding the materials could be better for the environment that continuing to use them.

That's all harder to figure out if you don't have vast unoccupied spaces to put solar panels, but at the moment we do have that.

As a subset of 1), don't forget: cost of buying it from the French who have a nice surplus thanks to their massive nuclear capability (as the British already do [1]).

[1] http://en.wikipedia.org/wiki/HVDC_Cross-Channel "As of 2005 imports of electricity from France have historically accounted for about 5% of electricity available in the UK."

See also: "France was the biggest energy exporter in the EU in 2012, exporting 45TWh of electricity to its neighbours." http://en.wikipedia.org/wiki/Nuclear_power_in_France

Really? On their website[0] they claim their glass surface doesn't require snow removal because the heating elements melt it and as such asphalt roads have a cost of snow removal that apparently comes for free with these.

However, it takes more energy to melt snow than to push it to the side[1] which they simply ignore and that makes me question what other things they're leaving out in order to tell a good story. I'd really like to see the numbers crunched for how many snowy days a year will cause the system to consume as much energy as it produces.

[0] - http://solarroadways.com/snow.shtml [1] - https://what-if.xkcd.com/130/

It takes moe energy to melt snow than push it to the side? This is northwestern Europe, where the snow never gets more than a few centimeters deep, and the temperatures never go more than a few degrees below freezing. I could definitely see heating a surface by a few degrees being cheaper than bringing a plow or other snow clearing machinery out to some path.

Now, northern Canada would probably be a different story.

Can confirm, in the Netherlands on bike lanes black ice is a much bigger problem than snow. Heating should work fine against black ice while shoving isn't very effective.

The enthalpy of fusion for water is 335 J/g. The specific heat capacity of ice at -10C is 2.1 J/(gK). So the major part in melting the water isn't heating it until it melts - it is the melting itself that is expensive.

That said, I do see some value in solar ways in the space savings.

Why not awnings over the bike path? This can be done in ways that look awesome and do not ruin the scenery and the view from the bike path. Thin film collectors in the form of tarps suspended from poles would make the installation cost commensurate with installing light poles. You'd need significant R&D in the aerodynamics, etc. However, you already need significant R&D for collector roadways, and you're starting out with an inherently disadvantaged design.

It takes moe energy to melt snow than push it to the side?

Physics. We're talking the energy of phase change vs. mechanical energy. They're both factors of the mass. The XKCD what-if calculations apply just as well to varying amounts of snow. It will always take less energy to push it aside than it does to melt it.

If you are thinking about saving the cost of the equipment and driver, then that's fine. However, physics again rears its ugly head, and you are not going to be making the power to melt the snow from the roadway itself. What you are proposing is to embed all roads with heating elements, which is clearly very wasteful by the calculations in the links in the gp post. Embedding all roads with resistive heating elements is the last thing a country that wants to reduce its carbon footprint should do.

However, that does not compute the cost of having to drive over with a shoveling machine, let alone the cost of building and maintaining a shoveling machine, or the cost of calling workers at 4pm to show up to drive the shoveling machine....

Moreover, and perhaps more importantly, it doesn't snow that often in the Netherlands, so our dearly bought shoveling machine is now idling 359 days of the year - it will still be deprecated and replaced after 10 years though.

Environmental science lives in the real world ;-)

So the resistive heating elements that will add significant cost the the production of the panels will be embedded in the bike paths and are only useful 6 days per year?

Wow, you actually are posting that as if I hadn't mentioned that issue in the gp post.

"If you are thinking about saving the cost of the equipment and driver, then that's fine."

I can't tell if this is intellectual dishonesty or poor reading comprehension.

I notice their site doesn't show any pictures of snow melting.

Snow melting systems that work are available.[1] The power requirements are well understood, and the documents linked have tables and calculation rules. The second document[2] is for electrically powered snow melting.

The big win on power consumption is good controls. Both a snow sensor and temperature sensors are needed, or huge amounts of energy go into heating cold, dry concrete.

[1] http://www.viega.us/xbcr/en-us/Viega_S-no-ice_Snow_Melting_S... [2] http://www.pentairthermal.com/Images/EN-RaychemElectroMeltSn...

The FAQ of the project at http://www.solaroad.nl/en/faq/ is worth reading. Among others, it explains that the €3.5M spent wasn't only used to produce this stretch of road (unfortunately without going into detail), and that covering _all_ rooftops in the Netherlands would only cover 25% of Dutch _electricity_ demand.

Given European clean energy goals, more square meters are needed. Those are hard to come by in a densily populated country such as the Netherlands.

Is this a sure win? No, but if it works, it can be a useful part of the energy mix. Also, if it works, I guess scaling it up will not meet much nimby resistance, unlike he alternatives of huge wind parks or sacrificing land or water area for solar arrays.

Sounds like the first comment hit the nail on the head: there being 25% more sunlight hours than expected.

Interesting points:

1. > That is more than the upper limit calculated on the basis of laboratory tests.

Does this mean the panels generated more than they were tested to generate?

2. Part of the purpose of the project was to beta test the suitability of their glass surface treatment as a biking/walking surface. (I'm imagining it's textured like a truck bed liner, but transparent.) They did have an incident early on with a bicyclist slipping, related to a stick-on surface, so they switched to a spray-on surface.

3. Commenters slinging arrows at a Conservative strawman for the high price and comparatively low (factor of 500) energy output vs government building rooftops.

1. No, it means that the panels generated more than the predicted upper bound. As a commenter on the source article mentioned, this year's April was one of the most sunny in recorded Dutch weather history, which might have contributed to this fact.

Numbers from the article:

3000 kWh in six months = 684W average

70 kWh per m^2 per year = 8W per m^2

As a comparison point, https://en.wikipedia.org/wiki/Photovoltaic_system#Solar_arra... gives a typical output for a square-meter panel as 0.75kWh per day, or 31W.

That's the wrong 6 months though, since it's including the whole winter and none of the summer. Looking at the graph, April accounted for as much power production as the other 5 months combined.

Could this be the missing link to make electric cars winning the battle? No need for plugs at gas stations, inductive charging [1] while driving on the road will do it.

Am I being too futuristic?

[1] http://en.wikipedia.org/wiki/Inductive_charging#Electric_veh...

No.

And no. The fault isn't Futurism but fantasy.

> The cycle path was opened in November as a pilot project for three years and was followed with great interest, also by foreign media.

I'm not following this new very closely. "Open" means that they allow cyclist, pedestrian (and dogs) to use a small 70m pilot segment, or that they have a 70m segment in the middle of nowhere?

Here's a photo. It's a bike path between two towns, and about 2000 cyclists per day ride on it.

http://www.theguardian.com/environment/2014/nov/05/worlds-fi...

It cost three million euros but can only power three houses? A million euros to use solar to power a house? Am I missing something?

Since this is the first prototype, I'm guessing the R&D cost that much.

You're installing cycle track plus power generation infrastructure in one hit.

Neither of those things is cheap on its own, e.g.:

"Cycle track costs at anywhere between £100,000 and £900,000 [per km]" from https://transportretort.wordpress.com/2011/02/09/how-much-wo...

Government economics, working as designed.

>Government economics, working as designed.

You've been downvoted perhaps because it's not clear if you're being sarcastic, but I agree earnestly.

The primary purpose of government is to organise things that benefit people: and they only need to do this when business can't or won't. Governments should act as a balance to the negative aspects of capitalism.

As such, I genuinely believe that governments should be "uneconomic".

Do you know how much the first Apple Watch to come off the line cost? Billions. R&D cost gets amortized through mass production; this is what it looks like at the beginning.

Consider that the cost of a kilometre of ordinary road is a few million dollars, and that prototypes are orders of magnitude more expensive than a mass produced optimised supply chain with economies of scale.

It's not in the middle of nowhere, it was being used by cyclists. Apparently, over 150,000 cyclists rode over it since it was opened.

Source (Dutch, but includes a photo): http://www.noord-holland.nl/web/Actueel/Nieuws/Artikel/Zonne...

A nitpick, but being a Dutch bike lane, there will not be any pedestrians and dogs on it. Bike lanes are for bikes.

Well, it makes slightly more sense than the solar roads for normal cars and trucks, if only because it doesn't have to be quite as tough, but I do suspect that it would be cheaper to install, easier to maintain and far more efficient in terms of power generation, to put a normal cycle path down and put a roof of solar above it.

Yes, but it wouldn't be as pleasant to ride on the road. Riding a bike with a roof over your head? I don't know, but I appreciate seeing the sky and the horizon when riding a bike.

It wouldn't be a roof exactly. Because you can angle the panels and have much better transmission of light to the panel from not having to have a bike-proof coating, you wouldn't be completely covering the path and you would get the same amount of power from a strip that is thinner than the path, angled and fairly high up, this would cost far less money as it is available off the shelf, so you have more cash to spend on making more of it. Also, if you integrate it with lamp posts for your support pillars, you are not increasing the amount of street clutter either.

Are Dutch bike lanes like US bike lanes? Adjacent to motor vehicle lanes, with no grade separation, and an expectation that motor vehicles will use the lane whenever it is convenient, regardless of right of way? If so, this is really solar panels for the right shoulder, and I would really expect a big truck to break them

The title seems to be inaccurate. The test area is a dedicated bike path, not attached to a standard road.

Why anyone would pursue such a suboptimal installations is beyond me. Researchers finding ways to waste grant money I guess..

The company leading the project claims commercialization is five years away. They likely are optimistic or biased, but I am not sure they are outright lying.

Prices of solar cells drop fast. Extrapolate a few years, and costs of solar installations will be dominated not by what solar cells cost, but by what it costs to install them.

In this case, something must be installed anyways to build the cycle path. It might well be that installing a (cycle path, solar cells) combination will only be marginally more expensive than installing a traditional cycle path.

Will we get there? If solar cells and the electronics needed to wire than together (which, in this case, are more complex because the road may see highly variable shading patterns) get dirt cheap, we might.

Do you really believe that it is more efficient to build a bike lane paved with solar panels, rather than a bike lane paved with asphalt and separate, dedicated solar facilitates?

EDIT: Looking at the pictures others have posted you still have to use asphalt (or more likely concrete because you need better stability, which is even more expensive) underneath, so there really is nothing saved by doing this. What a waste of money.

How is the presence of asphalt underneath an issue? The deciding factor will be whether the marginal cost of a solar path over an asphalt path will be greater or less than building an equivalent solar facility. That seems like it could go either way.

Very good point. Plus even if the marginal cost is lower than a dedicated solar facility, we don't necessarily have that luxury. We do if we want just 5% sustainable energy, not a problem. But if we want 99% sustainable energy, surface area is a very tricky challenge [0] and so it'd be a matter of the one and the other, instead of the one or the other.

[0] https://www.youtube.com/watch?v=GFosQtEqzSE

Why are you so negative about research?

Would you pay me to research the practicalities of installing solar panels in my basement?

The arguments about this thing not making any sense aren't so far away from the arguments about my basement not being very sunny.

>The arguments about this thing not making any sense aren't so far away from the arguments about my basement not being very sunny.

Actually, they are. At its best, getting sunlight in your basement is impossible. For solar bike lanes, the worst possible outcome is that they are impractical. And that is a purely financial consideration. At some point the benefits of solar (regardless of cost) might outweigt the negatives of using fossil fuel.

You never know, I might live in a glass house.

That it is observably impractical was the point I was trying to make.

My best guess would be that this to test if solar works at all on roads. There were talks of this being really useful on Highway at non-peak hours.

If you end up setting Solar Farms, you're grabbing land from Nature. This way you can re-purpose the land already used (roads, footpaths, Highways) for more than moving person from point A to point B.

Also, it allows roads to be productive even when there's no traffic.

One of the reasons is because of the sheer size of roads. It's kind of a strange facet of our economy, one which may shift this century [0], but as it stands roads tend to outweigh buildings in terms of surface area in most countries.

This is interesting because contrary to popular science which says that we can power the whole world with a tiny fraction of land use dedicated to solar panels, surface area is actually one of the biggest challenges we have in a 99% sustainable energy world that we have to get to.

Check out without the hot air, free book by physicist McKay at Cambridge. He's done a 1h presentation at Harvard which tells you the gist of it, and a 15 minutes TED talk which I'd skip unless you really only have 15 minutes. He covers the surface area challenges of solar and other sustainable energies quite well.

The ability then to one day put extremely cheap solar (e.g. at least 1 order of magnitude cheaper than today) in every new road (whose lifespan is a few decades, so we could on paper replace them all halfway through the century), is very interesting.

Of course there are huge, huge drawbacks. But that's not necessarily because it's impossible, but because we have path dependency. That's why you need prototypes and R&D to see how we can build roads sustainably using new materials, and whether solar panels fit into that picture.

[0] Roads are there for a reason: transport. We're now seeing for the first time ever tools on a scale that can cut down transport on a global scale. Still immature, but it's getting there. The combination of internet, 3d printing and virtual/augmented reality, means we can live global lives locally without having to physically transfer ourselves, information or products. It means we can work & study remotely better and experience entertainment and tourism more locally. And when we do move stuff, there's the option of doing it through new channels (air, with drones), or more efficient channels (self-driving vehicles that can attain higher speeds with smaller gaps safely, calculate more efficient routes and turn transport into a commodity: smaller vehicles transporting people, as opposed to cars being branded products, all of which lead to far fewer roads being necessary). It's a very bold claim but I wouldn't be surprised if roads kept explosively increasing until 2025, and then stagnating and at some point sharply reducing after a shift in human culture, manufacturing and transportation.

Why is it bike lane though? any practical considerations?

I would assume this is because far less weight needs to be borne by the roadway. But that's just my guess.

In the video they explain they use a bike lane to learn before going to real roads. Bikes are much lighter than cars and trucks, and they want to learn what materials work best.

What were the expectations?

According to http://www.solaroad.nl/wp-content/uploads/2013/06/Artikel-So... it was 50 kWh per square meter.

(over what unit time)?

Per year.

Sorry, this is beyond silly. Do they actually have any scientists with some command of mathematics working on this project?

Other than to screw ignorant government morons out of lots of money I could not imagine any reputable scientist or engineer not falling to the floor laughing uncontrollably when presented with the idea of putting solar panel on a sidewalk/bike path.

The whole thing is so utterly ridiculous that the only possible explanation is someone is making millions with this project.

The dynamics of down-voting on HN can be interesting. I have this --possibly flawed-- mental image of emotional impulse voting devoid of any effort to analyze what is being said.

For the benefit of those who didn't take the time to think before down-voting my prior comment I'll try to spell it out here.

A few facts:

- Good commercial cells deliver an efficiency in the 14% to 19% range.

- This efficiency assumes the cells are aimed at the sun

- Optimal winter angle for the Netherlands is approximately 76 degrees from horizontal

- Peak efficiency also assumes the cells are clean and have nothing obstructing or altering light from reaching it's surface at the optimal angle

- In all cases you can Google my claims and verify their veracity

Option #1:

- Cover the solar panels with glass - Scuff-up the surface so people and bikes don't slip and slide all over the place - As an alternative, apply a film to achieve the same effect - Mount them flat on the ground - Place trees around it - Have people, bikes and dogs walk on it

Analysis:

- The cost of encasing panels in concrete and glass modules and installing them is monumental

- The optimal angle for Amsterdam is approximately 76 degrees. Panels mounted flat simply throw away a significant amount of available energy.

- Solar cells laid flat will produce between 20% and 30% less when compared to optimally aimed cells.

- Glass will create problems based on how light enters. You have reflection, diffraction and scattering as possibilities. A percentage of the energy will never reach the cells.

- A non-slip surface will scatter and absorb a significant amount of energy. Based on the images I've seen of these road modules I am going to guestimate that at best 70% of the light entering the road reaches the cells. I base this on years of working with a wide range of optical diffusers.

- Dirt and particles on the cells can have huge efficiency effects. From light scattering to simply blocking and absorption. I'll go ahead and guess that you can't keep a roadway clean 100% of the time, therefore, you probably pay a, say, 20% penalty on average for having dirt, leaves and dog shit on the road. This is entirely a seat-of-the-pants number. It could be 10% or 50%. It isn't going to be zero.

- Power generation is now utilization dependent. With more people on the road more light is blocked and less power is generated. I won't put a number to this. I will rather make a statement: If nobody uses the road, what's the point of building one in the first place or building one that is so much more expensive than simply pouring plain concrete?

- Depending on angle, trees, buildings and even tall vehicles on the road will cast shadows on the panels.

A very rough calculation then says that, at best, our solar roadway will operate at 40% of peak efficiency. If we factor in the constant need for cleaning this number could very well go down significantly. For example, do we have a crew of a few people using gas powered leaf blowers cleaning the roadway a few times a day?

Option #2: Build a light steel structure atop a conventional bike path. Angle the panels for optimal efficiency at that latitude. You might splurge and add active tracking.

Analysis:

- The cost of installation is significantly lower

- By mounting the panels at the optimal collection angle we ensure converting power as near to the efficiency peak for the panel in question

- Angled mounting also aids in reducing surface particulate contamination and makes cleaning potentially as simple as an automated water sprinkler system

- The entire system is far less costly and efficient

- The bike path gets "free" shade as a side effect

So, yeah, the entire idea is absolutely ridiculous if anyone bothers to do a little math. Someone has got to be lining their pockets or whoever is leading this project is simply in denial.

Go ahead and downvote, but, if you do, please show your calculations and how you arrived at the idea that this concept actually makes sense to deploy at scale. I'll bet you can't.

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