Solar Roadways Project Beats $1M Goal, Should Enter Production

Lucas123 (935744) writes "It appears an Idaho-based company that created prototype panels for constructing roads that (among other features) gather solar power, will be going into production after it exceeded its crowdfunding goal of $1M. ... Solar Roadways' Indiegogo project has already exceeded $1.6 million. The hexagonal-shaped solar panels consist of four layers, including photovoltaic cells, LED lights, an electronic support structure (circuit board) and a base layer made of recyclable materials. The panels plug together to form circuits that can then use LED lights to create any number of traffic patterns, as well as issue lighted warnings for drivers. The panels also have the ability to melt snow and ice. Along with the crowdfunding money, Solar Roadways has received federal grant money for development."

Comments

Thermodynamically Impossible

[Cassini2]

Isn't it impossible for solar cells to melt significant snow?

The black road surface will effectively capture almost all of the sun's energy. In the northern U.S. and Canada, roads routinely get covered in snow.

The solar cell can capture a portion of the sun's incoming energy, and potentially use it to power heaters to melt the snow. This approach has several problems. Firstly, the solar cells / heater mechanism is less energy efficient than a black road surface. Secondly, if the snow falls when it is dark, the solar cell will stop working (unless it has some big batteries are present, and even they won't last long in a heavy snow fall.) Lastly, the best sun occurs in the summer, and the snow hits in the winter, when less solar energy is available.

About the only way a solar cell can keep up with incoming snow is if the solar array is much larger than the area of snow being melted. However, even then, you still have the problem of the solar array getting covered in snow ...

Re:Thermodynamically Impossible

[Maury Markowitz]

> Isn't it impossible for solar cells to melt significant snow?

Yes. Obviously if there is enough energy in the sunlight to melt the snow, the snow would melt already.

Heating snow to clear it is multiply-times less efficient than scraping it off with a snowplow.

This whole idea is the dumbest thing I've seen in years, designed by someone who knows nothing about solar power or road engineering. Ask anyone on the planet who's ever had a re-lay a cobblestone road surface how well they think this will work.

Re:Thermodynamically Impossible

[Anonymous Coward]

Seriously, cobblestone?

I'm a transportation engineer (I'm posting this anonymously so the details of my employment are not associated to my account) though with very little experience designing pavements. What my experience tells me though is that regardless of the panel itself it needs some sort of frame to hold it down.

Vehicles generate thousands of pounds of force parallel to the pavement face when they brake. This is what causes rippling in pavement at intersections when the asphalt is too soft or weak. So they've got the friction to stop the car what transfers that force to the ground (and prevents the ground from shifting)? Naturally you are going to need some sort of frame with very positive connection to the ground. That sounds unbelievably expensive. Current roadway costs are near $2 million dollars per lane mile (a 12 wide width of pavement 1 mile long). The materials that make up the roadway are generally pretty cheap (various engineered sands and gravels) and are applied to the roadway using large heavy equipment with very little human labor. You've now replaced that with presumably the same base system (you still have the same loads) a metal frame to hold the panel in place and the panel (these systems would replace the hard surface ie the asphalt or concrete). Even a minimal frame material wise is going to massively expensive. Steel is very very expensive in rough bar form (in comparison to things like concrete and asphalt), let alone in machined frames that require manual hand labor to install. What happens when a frame is bent? How's it anchored? Even massively damaged pavements are usually traversable, a missing or damaged panel sounds like a 2' circumference 1' deep pothole that will rip a tire off a vehicle at speed.

The next question is durability. They say they've tested them with truck loads, have they done the standard AASHTO pavement test that involves driving a semi around (in a 1/4 mile loop track) on them for 5 years straight to demonstrate long term durability? What about studded snow tires? What about an accident where a car flips at 70 mph and imparts forces that literally pulverize concrete to powder? What if the car then burns (a typical car fire approaches 3000 degrees) What about an accident where hazardous or corrosive products are spilled? What happens when a car being chased by the cops has it's tires shredded but then keeps driving on rims for 20 miles until the rims literally weld themselves to the rotor (the typical result on standard pavement is about a half inch groove from every rim for the length the car ran without rubber)? What about road debris coming off cars and hitting other cars (I've seen sections of concrete a foot thick destroyed by heavy objects falling off semis)?

How long are the panels good for? We design asphalt roads for 20 years and concrete for 40-50 years. And though the asphalt requires perodic treatments as part of it's life cycle unless a mistake was made they generally last that long. Most of the interstates lasted far longer than the 40 years they were designed for, in my state we've still got original interstate in locations that is approaching 60 years old.

We use the materials we do in roads because they are cheap, easy to put down (ie not labor intensive) and easy to fix (a temporary fix can involve dumping and spreading a load of gravel with common construction equipment). This system just screams money, and labor and lack of durability. Maybe I'll be wrong, I suspect I won't be. The ESALs (equivalent single axle loads) that a pavement takes over a life time can be astonishing (trillions of pounds of force over a 20-40 year lifetime). The panel and frame that support this are going to be flexed billions of times a year, fatigue fractures are a very real concern in metals.

Anyway, as I say I might end up wrong, i suspect I won't. I'm astonished people donated a million bucks for this and I believe once they do the real AASHTO testing that will be required before this can be used on roads they will demonstrate

Re:Thermodynamically Impossible

[reg]

As someone with a PhD in Pavement Engineering, and an active researcher into pavement design, let me say this is a classic case of someone thinking that because something looks simple it is. Pavements are the most complex civil engineering structures to design, because they are the only structures designed to fail in fatigue. My wife showed me their video the other day, and all I could do was laugh. Reading their FAQ now, shows they've never asked an actual pavement engineer for their input (and FHWA funding shows nothing, in fact googling shows that they're not even really being funded by the FHWA research budget but by the Small Business Innovation Research (SBIR) program i.e. this is money to promote small business, the research is a secondary goal).

Just a correction for you though - there is not really an AASHTO testing protocol, that was a one off test done 50s and 60s. Now, most proof testing of these types of innovative designs are done by accelerated pavement testing.

Before we even look at the engineering, look at the cost: the highest cost pavement currently are precast concrete slabs, which are similar in some ways to this idea (except they are 50 times the size). They cost about $3 million per lane mile to install. There are over 8 million lane miles of public road in the US, so their idea in their video of covering all the roads in the US would only cost $24 trillion (or nearly twice the US annual GDP) assuming they could get the cost down to that of concrete... Assuming for the moment that the solar panels themselves are cost neutral, just the cost of the glass and support structures would make this impossible to afford.

From an engineering perspective, you have functional and structural criteria. Functional are skid resistance, spray, noise and light reflectivity. The glass would polish, resulting in low skid resistance at high speed, and bad light reflection. Their textured surface would be OK for low speed skid, but really bad for noise and spray, even with drainage between the panels. Many new pavements have a porous top layer for this. Their paving stone like pattern would be really bad for noise (like block paving). Putting LED lights into pressure sensors for animals would be fun, but probably not reliable, and on roads you have to have systems that are reliable because either drivers can trust them, or they are a waste of time.

Structurally, the fact that they refer to gross vehicle mass is a dead giveaway that they don't know the first thing about pavements... The critical number is wheel load. Their panels look to be an awkward size between an interlocking block paver where the wheel load is spread across several blocks, and a concrete slab. The panels would need to be connected in such a way that they can expand and contract, with sufficient load transfer between panels for the entire surface to act as a continuum. With this size of panel there would a lot of flex at the joints, which would break most materials. Concrete slabs get joined using 1 inch dowel bars... Assuming these were placed on existing pavements, maybe they would work, but my guess is that they would get beat up quickly by highway traffic.

Then there is a question of life cycle assessment. Their "numbers" page shows they also know nothing about this either. They just include the benefits... There is no measure of the system, including manufacture, construction, maintenance, etc. They also don't have albedo measurements, etc...

So, to conclude, I don't think this idea is going anywhere fast. Their first step should be to hire a pavement engineer. Then they need to do some lab testing, then use their $1.7 million for an accelerated pavement test to determine if their design can work as a road, before they do any more messing around with electronics... At least their idea is not as silly as the people who want to put piezoelectric generators into pavements to capture all the "wasted" energy...

Regards,
-Jeremy

Re:Deja vu

[phrostie]

I was a bit skeptical when I'd first heard about this.

What I hope happens is that they start off focusing on commercial applications like parking lots and drive ways.
That will give the technology time mature and the price to come down.

otherwise yeah, I suspect we'll be rebuilding a lot of roads as they work the real world bugs out.

Critical piece in The Verge

[De Lemming]

The Verge had a good article criticizing this project. The article doesn't break down the project completely, but points out why their goals are far-fetched, and people should not get too exited.

Also note that when looking at the project, it's not initially clear that a connection with the main electricity grid is still necessary. At night, displaying the signs and defrosting the road is done with electricity from the net. During the day, the solar panels can transfer electricity back to the grid. Their current implementation doesn't include batteries to store electricity locally, and this wouldn't be very environmentally friendly anyway.

Re:Deja vu

[nysus]

That is, in fact, their plan.

Read about it on the "Vision" page of their website: http://www.solarroadways.com/v...

Re:Deja vu

[MrNaz]

I really hate to be skeptical, especially with a project with goals as desirable as this, however I just don't see it happening. Road surfaces receive an enormous amount of wear. The current state of materials technology just isn't able to deliver the properties that such a surface would need to have to provide the described functionality.

Don't get me wrong, I really, really want this to succeed. It's just that we still can't make a solid bitumen road resistant to cracks in the long term, so how can we hope to make electronics and other far more fragile components match or exceed that level of durability without making the costs skyrocket to the point that it is not economically viable. Airports, with their massive budgets, have runways with *some* of that functionality, and they already require regular maintenance. The $ per square meter spent on a runway at an airport is more than a few orders of magnitude more than that spent on public roads.

Anyway, let's watch and hope.

Re:Deja vu

[nysus]

They address this on their website:

"What are you going to do about traction? What's going to happen to the surface of the Solar Roadways when it rains>

Everyone naturally pictures sliding out of control on a smooth piece of wet glass! Actually, one of our many technical specs is that it be textured to the point that it provides at least the traction that current asphalt roads offer - even in the rain. We hesitate to even call it glass, as it is far from a traditional window pane, but glass is what it is, so glass is what we must call it.

We sent samples of textured glass to a university civil engineering lab for traction testing. We started off being able to stop a car going 40 mph on a wet surface in the required distance. We designed a more and more aggressive surface pattern until we got a call form the lab one day: we'd torn the boot off of the British Pendulum Testing apparatus! We backed off a little and ended up with a texture that can stop a vehicle going 80 mph in the required distance."

Not sure how true or relevant this is but they do address it.

Re:Deja vu

[MrNaz]

You missed the whole point of durability that I mentioned.

In Thailand, many of the roads in the southern areas use glass balls as lane markers. They don't get driven over unless a wheel is in on the lane marker, hence, only a small fraction of the actual traffic. Nonetheless, it is plainly obvious that they just don't last. They are chipped and damaged to the point that they don't fulfill their function.

Roads are possibly the most abused surface mankind makes. No type of glass that we have access to could ever stand up to long term road wear. It's just not possible with today's tech. I really think that this is a grant scam, which is unfortunate, because the politicians being scammed will be less favourable to green projects the next time a real idea comes around.

Re:Deja vu

[nysus]

Sorry, I was scrolling up and down the page, got distracted, and copied the answer from the wrong question. Here's what they say:

"How will you replace damaged panels in a highway?

Since our system is modular, repair will be much quicker and easier than our current maintenance system for asphalt roads. We've learned that in the U.S., over $160 billion is lost each year in lost productivity from people sitting in traffic due to road maintenance.

Each of the panels contain their own microprocessor, which communicates wireless with surrounding panels. If one of them should become damaged and stop communicating, then the rest of the panels can report the problem. For instance, "I-95 mile marker 114.3 northbound lane, third panel in, panel number A013C419 not responding".

Each panel assembly weighs 110-pounds. A single operator could load a good panel into his/her truck and respond to the scene. The panel could be swapped out and reprogrammed in a few minutes. The damaged panel would then be returned to a repair center. Think of how this compares to pot hole repair!"

Do simple tests first

[crow]

The should do the simple tests first.

They claim that the glass cover panels can hold up to traffic and provide sufficient traction. Why not mount just the glass covers over a stretch of road and see how it behaves? Until they get the covers right, the rest is irrelevant.

Once they have the ability to make a glass roadway, then they can deal with the question of what to put under it. How about just LEDs for traffic marking? Will they work in the day time? Will they put out too much light pollution?

Once they have the traffic markings working, they can get the heating elements needed for installing where it might snow. I'm under the impression that they have to melt the snow because the panels won't stand up to snow plows. Maybe it will make more sense to run pipes with heated antifreeze solution instead of direct electric heat. Maybe it will make more sense to redesign the glass covers to stand up to snow plows.

Once those are solved, putting in solar panels is a no-brainer that helps the economics of the project work.

In the end, once all the technical issues are solved, it's a matter of economics. What is the cost of a road made with the panels over 50 years as opposed to a traditional asphalt or concrete road when all the maintenance is factored in for each road type?

Considering all the above, I'm convinced that it makes much more sense to put solar on rooftops.

Re:Deja vu

[jklovanc]

Have you ever seen a road that is perfectly flat for any reasonable distance? There are hills and valleys everywhere and on every hill there will be small edged that stick up. The edges will cause roughness and driving noise. They will also cause impacts that may greatly shorten the life of the panels.