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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."
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.
---Technology will liberate us if it doesn't enslave us first.
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