Please create an account to participate in the Slashdot moderation system

 


Forgot your password?
Close
typodupeerror
×
Earth

Los Angeles Tests Reflective 'Cool Pavement' On Streets (dailynews.com) 123

Posted by EditorDavid from the awesome-asphalt dept.
mikeebbbd writes: As reported in the Los Angeles Daily News, during the current heatwave various officials swooped down on streets coated with an experimental light-gray sealer that makes the old asphalt into a "cool street" -- and it works, with average temperature differences between coated streets and adjacent old asphalt around 10F. At a large parking lot, the temperature reduction was over 20F. If the material holds up and continues to meet other criteria, LA plans to use it on more pavement rehab projects, which could eventually make a difference in the heat island effect. The "CoolSeal" coating is apparently proprietary to a company named GuardTop LLC, costs $25-40K/mile, and lasts 5-7 years. At that price, it's might not be used a lot, at least at first; typical slurry seals run $15-30K/mile.
This discussion has been archived. No new comments can be posted.

Los Angeles Tests Reflective 'Cool Pavement' On Streets More

Los Angeles Tests Reflective 'Cool Pavement' On Streets

Comments Filter:

  • Wonderful (Score:3)

    by Mr D from 63 ( 3395377 ) on Sunday June 25, 2017 @11:41AM (#54686635)
    Lighter color coatings reflect more heat. Complete with expert testimonials!

    “I feel a slight difference on the street and inside my apartment,” said Priscilla Corleto, 24, walking Gatsby, her small white Shih Tzu. “Without the AC, it seems cooler.

    • Re: (Score:2)

      by Jamu ( 852752 )
      43% of the sun's radiation heat is visible, so it should be possible to have a black surface that reflects less heat than a white one. Even one that's perfectly white. Although if the surface could convert the visible light into the infrared or ultraviolet, you can have a black surface that relects all the heat. That would be cool (sorry) to compare to a white surface that absorbs everthing except visible light.
    • I don't know if it's possible to reflect heat, but I'm sure the lighter color reflects more LIGHT.

      • Re: (Score:3)

        by Nutria ( 679911 )

        Isn't "heat" just slightly longer waves of red light?

        • Re: (Score:3)

          by Jamu ( 852752 )
          Heat is disorganised energy.

        • Isn't "heat" just slightly longer waves of red light?

          Heat is kinetic energy. Temperature is a measure of the average kinetic energy of a system. It also happens that individual atoms/molecules can transition between energy levels by emitting/absorbing infrared radiation [stackexchange.com]. That's the way that heat from something like the sun can travel through the vacuum of space to reach Earth.

          • I'd correct you, but I'd have to get into all sorts of subtle stuff like the difference between internal energy/enthalpy and heat in the first and second laws. I liked the answer up above -- heat is disorganized energy -- better.

      • I don't know if it's possible to reflect heat, but I'm sure the lighter color reflects more LIGHT.

        Maybe 'absorb less' would have been more appropriate. That could also be considered, in relative terms, rejection of some heat compared to a higher absorbing surface.

      • It very much is possible to reflect heat, play around with a thermal camera sometimes.

    • Lighter color coatings reflect more heat. Complete with expert testimonials!

      Who could have imagined that a lighter color would be more reflective? Science Marches On!

  • Plant a tree, save the Earth... (Score:5, Insightful)

    by __aaclcg7560 ( 824291 ) on Sunday June 25, 2017 @11:42AM (#54686637)

    Might be cheaper to plant trees and landscaping in an urban environment. Several tech companies are using rooftop gardens to put the heat to better use.

    https://www.wired.com/2015/03/facebook-moves-new-garden-roofed-fantasyland/ [wired.com]

    • Re:Plant a tree, save the Earth... (Score:5, Informative)

      by ShanghaiBill ( 739463 ) on Sunday June 25, 2017 @12:04PM (#54686747)

      Might be cheaper to plant trees and landscaping in an urban environment.

      That is absurd. There is absolutely no way you are going to plant trees along a mile of urban roadway for $25-$40k. You need to add at least two zeros. Even more in LA where no plant life survives without water, so you would need to trench for irrigation pipes, and pay for ongoing maintenance.

      • There is absolutely no way you are going to plant trees along a mile of urban roadway for $25-$40k. You need to add at least two zeros.

        Good point. When they built the sound walls along the 280 in Silicon Valley, the cost was ~$1M per mile. My father didn't like the work because there was only an 18-inch gap between the slow lane and the scaffolding.

      • It would have been cheaper to plant trees back when they were planning this stuff. It would have also increased water retention; Los Angeles receives almost 100% of its current water needs every year in the form of rainfall, and damned near 100% of that runs off into the ocean immediately (with predictable negative consequences for marine life) because they have covered their sprawling collection of dunes and tar pits in concrete and asphalt.

        • hindsight is 20/20, but what you can do is vote for the representative that has similar views and attend public meetings and voice your concerns.
          I happen to be voicing my concerns on the lack of tree's and over the last 2 years, I am finally being heard and they have started some basic plantings.

          if you don't voice your views in a government forum
          and if you don't vote for your local rep's
          then you will get what others want.

      • That is absurd. There is absolutely no way you are going to plant trees along a mile of urban roadway for $25-$40k. You need to add at least two zeros. Even more in LA where no plant life survives without water, so you would need to trench for irrigation pipes, and pay for ongoing maintenance.

        25k-40k is about what the average person makes in a year. Surely one person could plant trees along a mile long stretch in a year even if all they had was a single shovel. You can buy 12 inch seedlings for under $1 a piece so it would cost less than $1k to put one every 6 feet. It would take a few years before they got large enough to provide shade but it's not absurd to think that it's possible to do something like this especially considering in most cases, the state already has caretakers that mow and

        • Well, I got some slight knowledge of this: reference point is South Florida
          A) trees can't be 6 feet apart, trunk to trunk should be about 30'
          B) native species to the area are needed and have a cost basis of about $40

          C) ( blocked views ) you can not plant a tree on a corner
          C1) nor can it be 75 feet from the corner
          C2) drivers side can not be 85 feet from the corner
          C3) Corner does not start at the swale or hellstrip, starts at the property line

          D) digging a hole is not easy, you got top sandy earth then coral.

          E

          • A) trees can't be 6 feet apart, trunk to trunk should be about 30'

            This makes it even cheaper.

            B) native species to the area are needed and have a cost basis of about $40

            C) ( blocked views ) you can not plant a tree on a corner
            C1) nor can it be 75 feet from the corner
            C2) drivers side can not be 85 feet from the corner
            C3) Corner does not start at the swale or hellstrip, starts at the property line

            D) digging a hole is not easy, you got top sandy earth then coral.

            E) Native species are in tune to drought, so watering is an option, not a requirement. the city has a truck that waters plants.

            F) North side plantings incur a liability of blocking the sun on private land ( sun rights ), so if I have solar, how will the city compensate me.
            F1) South Side plantings cover the pavement.

            G) if a driver hit's a tree planted by the city, does the driver have a legal right to claim anything to the city? ( this is where DOT studies come into play ) and does the city have to buy insurance for this.

            As for the rest of this, I almost added an disclaimer to my post that this was not counting any political or lawyer BS.

            I also should have included a link to this article: https://www.bloomberg.com/view... [bloomberg.com]

            My uncle used to put up new telephone poles. I believe it was only a two man crew. It was in the dakotas which was very rocky and hard to dig. They would drop a stick of dynamite in the ground, cover it with a heavy mat and blow it up.

            We have one of the highest levels ever of

      • Re: (Score:3)

        by Reziac ( 43301 ) *

        Actually, many of the highways in the desert north of Los Angeles used to be lined with elm trees -- which when I was living there, were big mature healthy trees despite getting no supplemental water whatsoever. (Judging from a few specimens where I was able to count rings, they were planted in the 1940s.)

        Used to be, you ask? The tree-topping craze killed most of them, and your tax dollars paid for it, since L.A. County contracted with a tree trimmer who severely cut back all these formerly-healthy trees. C

      • Re: (Score:1)

        by MercTech ( 46455 )

        Back before people expected the Gub'mint to do everything; planting trees along the boulevard was an Arbor Day project for school age kids and Boy Scout troops. And, yes, trees along a roadway muffle noise and mitigate the heat radiating from the roadways.

    • we're currently ignoring the whole water shortage thing here in Arizona. It'll bite us in the next 20 years. The wealthier parts where I'm at are crazy with how much green there is. It's like they terraformed the landscape. You can do that when water's cheap due to subsidies but that's not going to last forever.
      • Arizona is absurd. I just read where they are going to plant a zillion trees in order to cool Phoenix down. In different issue of the same magazine, I read about the severe water shortages and high cost of the Central Arizona Project. I thought trees needed water.

    • Why not both? Planting trees is a good thing for various reasons, but it doesn't seem like a reason not to make other kinds of improvements.

      • Well, for parking lots specifically you are much better off providing PV shelter structures than relying primarily on an asphalt coating.

        There is a downside for the reflective coatings; it dramatically increases light pollution. By mixing PV and reflective coatings (where needed) you can address both issues.

        • Well I'm sure there are all kinds of things you could do to improve various problems. My point was more, why not keep all the possible solutions in mind, and then use a mixture of the solutions that make sense in whatever situation you come across?

          Maybe spraying a coating onto existing asphalt is a good partial solution that can be used in some circumstances. Maybe planting trees is a good partial solution. It also seems to me that there might be a replacement material for asphalt that wouldn't need an

    • Might be cheaper to plant trees and landscaping in an urban environment

      It sounds like that's the plan. From the fine article:

      Two years ago, the councilman had passed a motion to test a new cool pavement that, with more trees and reflective rooftop solar panels, he thought could counter longer and extreme heat waves.

  • something like powdered limestone or any powdered mineral that will make the "black" color of asphalt less black and closer to white, its not like this company has a monopoly & patent on the colors in nature
    • Comment removed based on user account deletion

      • Re: (Score:3, Informative)

        by Anonymous Coward

        Concrete is much more expensive than asphalt. It's also harder to install and maintain. While slabs of concrete may last longer, it doesn't do much good if it becomes irregular (kathunk kathunk kathunk .. for 100 miles). It can't be resurfaced as easily (no grinding down the top and pouring 2 inches of additional concrete on top) as asphalt either. It has use cases on grades that are steep, or where heavy travel craters the asphalt in hot areas (stop lights, downhill braking, etc).

        • Re: (Score:1)

          by Anonymous Coward

          it also is not immune to temperature, either, even in northern climates. and when it fails, the buckles can be rather spectacular.

    • The tires on all cars are still black anyway. It's going to be hard to keep the lighter colored streets clean of burnouts.

  • The coating make some of the solar-sourced infrared heat NOT get absorbed by the roadway. Does it magically go straight back to space, or does it reflect onto other structures, heating THEM up?

    I suspect mostly the latter in an urban environment. So, how does changing WHAT absorbs the heat affect the overall retention of the heat island?

    Using plants absorbs more CO2, but the heat increases evaporation.

    • Re: (Score:2)

      by caseih ( 160668 )

      Yes as a matter of fact, it would reflect a significant portion back into space. Obviously some of the IR rays would go in all directions and hit buildings and trees and things.

      Nothing magical about that. In fact you can use a solar reflector to freeze water at night.

  • Trees and vegetation reduce the temperature by ten degrees F, cost less and last longer.

    But hey, keep paving over every blade of grass and cutting down every tree in sight then wonder why it's so hot.

    • That is great and all until you realize that the places that need this were built on desert.

    • Re: (Score:1)

      by Anonymous Coward

      Trees and vegetation reduce the temperature by ten degrees F, cost less and last longer.

      But hey, keep paving over every blade of grass and cutting down every tree in sight then wonder why it's so hot.

      I've actually done a lot of work in this area, and the trees and vegetation actually end up costing substantially more in most highway/major street use cases, since there are significant additional costs associated with planting, maintenance, cleanup of debris, and repair to damage caused by the vegetation itself to the road surface.

      There's also the fact that for high volume roads, you can't plant vegetation on the road surface itself, which retains far more heat than do medians, shoulders, etc. There are p

  • Using concrete without a coating of asphalt on top has a similar effect... how about just paving with concrete. It lasts longer, requires less maintenance, and is cooler. If made thick enough it can also be ground down to "resurface" it several times without any need to add more concrete unlike asphalt roads.

    Using asphalt is only done because asphalt is a byproduct of the petroleum refining process and the oil companies have done everything they can to ensure they can sell their waste and force us to use

  • This is going to make chroming the moon considerably less cool.

  • Now Hippies can walk barefoot in July without burning their feet.

  • After playing ambient music as it cruised through space after booster separation, the second stage executed a successful short burn to raise its orbit. In about five minutes it will try releasing satellites.

  • Tokyo, too. (Score:3)

    by lindseyp ( 988332 ) on Monday June 26, 2017 @02:31AM (#54689793)

    They started doing this in Tokyo several years ago. They painted a lot of major roads green. I was worried about them being slippery in the rain, at first, but they turned out to be no worse than bare asphalt, and I believe they helped stem the heat island effect.

  • Won't somebody think of the lizards?!

Slashdot Top Deals

E = MC ** 2 +- 3db

Close