Are Glowing, Solar Smart Roads the Future? 193
cartechboy (2660665) writes "We were just talking about glow-in-the-dark roads and how they were having issues already. Now there's a company called Solar Roadways that's looking to make glowing, solar, smart roads. Back in 2009 the Department of Transportation awarded Solar Roadways $100,000 to prototype road systems with embedded digital signage and dividing lines, all powered by the sun. As it turns out, the company's prototype performed well — so well that Solar Roadways is now looking to go big-time, and it's asking for your help to do so. At the heart of the Solar Roadways project sit a vast number of hexagonal tiles. The bottom of those tiles consist of solar panels and circuit boards, covered with a thick sheet of tempered glass. The panels contain LED lights, which can be configured to mark traffic lanes, send messages, or fulfill other functions. The panels also have heating elements to help melt snow and ice during colder months. Are these smart roads the future, or just another pipe dream?"
Shit doesn't work (Score:2, Informative)
Re: Shit doesn't work (Score:3, Informative)
According to this article, unless I didn't read it correctly, the solar technology they're talking about involves solar panels under a glass surface roadway. The article you cite only references the use of glow in the dark paint.
Re:Road hazard much? (Score:5, Informative)
From the FAQ:
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.
Re:Pipe Dream I suspect (Score:5, Informative)
I have put in driveway snowmelt systems and a typically driveway needs at a minimum ~100 kbtu/hr boiler to keep the driveway clear. Scaling that up to a road way and it would be astronomical.
That was my thought as well. Phase change is a bitch, so I anticipated this was a marketing gimmick. I decided to run some quick calculations to determine how much snow could be melted by a 1 m^2 solar heating roadway plate thing.
Solar Roadways is in Idaho, so I decided to use their location for stats. I decided to use an average insolation value [solar-electric.com] of 2 kWh/day in December in Idaho. I disregarded the fact that these plates won't be tilted to compensate for latitude, which will give the roadway an artificially improved performance stat. I used an enthalpy of fusion for water [wikipedia.org] as 334 kJ/kg. I used a 50 kg/m^3 value for the density of freshly-fallen snow [sciencelearn.org.nz]. Finally, I decided to let the road panel have a 15% PV efficiency as well as a 100% solar panel coverage (neither of which is likely to be realistic for a road tile thing, but again this is in favor of the roadway panel).
So, how much snow can this melt per day? Call it 6.5 cm [google.com]. In practice, I'm guessing the answer is closer to "0", because the instant the panel is covered by snow it will cease generating energy. Also, snowstorms are not known to occur during bright, bright, sunshiny days. It seems Solar Roadways expects their panels to be hooked to the grid and pull power to melt snow.
Therefore, this exercise devolves to "why haven't we installed electric radiant heat in our existing roadways to melt snow?"
Well, if we have a four lane standard US highway (12 ft lanes) and we need to melt that same 6.5 cm of freshly fallen snow, it would require 4.4 MWh [google.com] (yes, megawatt-hours). In Idaho, it looks like an average wholesale rate for 1 MWh of electricity [eia.gov] is approximately $150. So... call it $600 per km to melt a few cm of snow... once? And this is for light, fluffy, happy snow, not the slushy sleety shit that has the density of neutronium and gives grandpa a heart attack when he tries to shovel it.
Unless I dropped a few orders of magnitude here (please let me know if I did), it seems the answer to this is "just use the fucking salt instead, like we have been doing." In conclusion, perhaps the LED roadway is useful, but the snow melting bit really seems to be a gimmick.