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Power Science Technology

Use of Asphalt Paved Surfaces For Solar Heat 110

vg30e writes "It seems that a company in the Netherlands has found a way to use asphalt paved surfaces as solar heat collectors. Flexible tubes under the surface of the road collect heat from asphalt pavement using water as the working liquid. The heated water is stored underground for later use in defrosting the road, or heating buildings. With all the miles of highway in the continental US, this might be a viable way of collecting massive amounts of thermal energy."
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Use of Asphalt Paved Surfaces For Solar Heat

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  • by 2.7182 ( 819680 ) on Tuesday January 01, 2008 @07:25PM (#21877640)
    Physics professor Roland Winston, proposed this 25 years ago.
    • by madsenj37 ( 612413 ) on Tuesday January 01, 2008 @07:35PM (#21877732)
      The idea is one thing, the implementation another. He may have been a visionary, but the buck stops there.
      • Re: (Score:3, Insightful)

        by lpangelrob ( 714473 )

        It's an interesting idea. There are a lot of factors to weigh in, and the primary one is cost - odds are pretty good that doubling the initial cost of construction of a freeway this way won't result in nearly that much savings on maintenance (even accounting for less resurfacing, potholes, and salt spraying) down the line.

        Then there's the fact that having a pump fail anytime during the cold season would almost certainly result in the destruction of the surface, unless there's some sort of way to engineer

        • by afxgrin ( 208686 )
          We need a cheap way to modify asphalt so that it can be used to generate electricity. It really needs to be done chemically. Then any road repairs or new roads can be done using the new asphalt which would have some type of wire mesh laid down that could convert the collected solar energy. Even if it's inefficient, it doesn't matter, there's so much road out there it would make a difference. Again, a key requirement would be making the cost of said "electro-asphalt" low enough that it would attract buye
          • Re: (Score:3, Funny)

            by bcattwoo ( 737354 )

            Pipes and water just sound like a bad idea in general. Sounds like high maintenance costs, not necessarily suitable for all weather environments, high installation cost, specialized labour and more unions, ... it just sounds impractical.
            Right, certainly not as practical as your apparently low maintenance, all weather, low cost, monkey installed, made from unicorn horns electrical asphalt.
            • by afxgrin ( 208686 )
              Well repairing leaky pipes is a serious pain in the ass. Especially when you pull one damaged section out and it leads to breaking another pipe joint that's also buried. I'd much rather replace wiring than pipes. Again - the whole idea I mentioned depends heavily on the magical unicorn horn asphalt. If that can be developed, I think it'd certainly be more practical. There has to be some chemist out there who would lose sleep trying to make it work.
          • by SQLGuru ( 980662 )
            How about this:
            I'm sure each of you have felt the "bounce" of a big truck passing you by....why not create some sort of mechanical compression layer that absorbs the effect of cars going over the road then converts this into a small amount of electricity.....probably most effective on highways and heavily travelled city streets.

            And, on top of that, it would still allow for some thermal collection since it would be a different layer.


            • As a rule, this idea is usually backwards. In order to gather significant power from this, you're basically increasing the amount of energy the vehicles expend - because for this to work, you have to keep the pavement bouncy enough to generate the power. (Put another way, the vehicle is most efficient if the pavement is very flat and very rigid)

              So you're usually sucking energy FROM poorly maintained oil driven vehicles and putting it TO a grid that at least hypothetically could be powered by nuclear or wi
              • by IdeaMan ( 216340 )
                So combine A and inverse of B:
                Use the heat differential to power a Stirling cycle heat engine that gives energy to the road vehicles.
                #1: Decreased stopping distance: Force sensors in the roadway can detect when the vehicle is decelerating, and simply multiply that force * 3.
                #2: Decreased emissions. Heat->electricity means no emissions.
                #3: Synchronizes vehicle speeds. The system can be set up to only provide power to vehicles that are moving the proper speed.
                And no, that wouldn't necessarily b
            • by afxgrin ( 208686 )
              yeah I was thinking of a way to utilize that energy as well. Maybe with two to three layers of slightly different asphalt. I guess I should do some more research on asphalt. Maybe quartz chunks could be mixed into the centre layer, and can create some sort of piezoelectric charge. That probably won't work because it would be highly dependent on the crystal structure (so if it's ground into chunks, that doesn't leave much of a structure... ), but it's an idea.

              Another idea could be mixing iron into the top
        • Maybe instead of purpose built pipes you could use semi-porous asphalt or concrete (which already exist) wrapped in a layer of sealed asphalt. Then the small channels in the asphalt act as the pipes. There'd be no pipes to maintain or replace. Force water in from one side and pull it from the other. Just don't try it in freezing temperatures.
    • When our business laid down a new concrete parking slab for a dock building, we used a pigmented concrete and did this very same thing. Loops of tubes laid down before the pouring, and now we can run cold city water through it in the summer to heat it up before it hits the boilers, and run excess warm water through them to de-ice it in the winter. It also helps that we're in a business that uses a lot of steam and hot water.
  • by LWolenczak ( 10527 ) <> on Tuesday January 01, 2008 @07:26PM (#21877648) Homepage Journal
    This could help reduce the overall temperature of blacktop services... which have this side effect in very hot summers of melting.
    • Re: (Score:1, Insightful)

      by Anonymous Coward
      The problem we have isn't an availability of energy. We have more energy than we know what to do with. The problem is an economical way of converting it to the desired form, and moving it to the places where it is needed. Oh, and do that without ruining our planet, hopefully.
      That said, this is another solution in search of a problem; I can't imagine that it would be even remotely economical to embed tubes in asphalt during construction. Then, remember how roads get cracks in them? That's gonna tear you
      • The article mentions that the system can be used as a de-icer, meaning it actually does work on the "moving [energy] to the places where it is needed" problem.

        That said, using the roads as solar collectors isn't that bad an idea in general. Roads cover a significant amount of square footage, which is left mostly vacant most of the time (outside of cities). May as well use that space for something the rest of the time.
        • What do you use as a qualifier for GOOD as in a good idea?

          It sounds like an interesting idea to me that should be explored but if it turns out to double or tipples the costs of the road, there there might be a problem. We are having trouble paying to maintain them now. And as for generating energy, if it is three times as expensive as traditional methods, then it would be waisting money again. And by energy, I'm not just talking about electricity or heating large buildings with hot water or something like t
          • We don't have trouble paying for road maintenance, we choose not to. Totally different thing. Locally we have a narcissist that gets his jollies by filing anti tax initiatives to see his name and picture in the papers. Then you've got the portion of the populace that doesn't think twice about supporting a bloated runaway military budget, but can't stand the idea of his money going to fund things for the common good.

            It isn't an inability to pay, or even a difficult time finding the money, it's that people wo
            • Choice or not, we wait until bridges fall down before we get worried about it. There is actually enough taxes collected from the Use taxes associated with roads. The Gas and Diesel taxes, the DOT taxes on tires and so on. The problem is that the money goes to things other then roads. So your right, it is more of a choice then an ability but when you have people robbing the till for social programs and stuff that normal citizens should be providing for themselves, we have trouble maintaining the roads. It is
          • We just did a rebuild of a strech of our expressway, first they laid down rebar, reinforcing bars. I don't see where installing some plastic tubing in with the rebar would make a huge difference in costs. Did you know that when they build the Hoover dam, they laid in pipes to cool the concrete as it cured [], if they didn't it would be hot enough to burn you still today. Next they laid down concrete, not the ususal concrete but a drier concrete that was spread over the rebar with a machine that looked like an
            • A couple of things, first, it isn't necessary to use concrete for roads in every place. In places where there is extreme heat or cold, concrete works best, in places with already firm bases (the types of dirt used for foundations) for the roads, moderate temperatures, Asphalt works great. So while in the places with concrete already, it probably wouldn't be too much more to put the pipes in unless your talking about destroying repairable roads to redo them with piping. Then it just doesn't make sense at all
  • Here in Texas, most of the roads are cement*, but I guess you could apply the same principle. Why would you store heat in Texas, it's here in abundance. Come take some.

    *Here, they use asphalt to fill in potholes.
    • Re: (Score:1, Troll)

      by dltaylor ( 7510 )
      It snows in El Paso in January/February, and in Amarillo more than that. Texas is a hell of a lot bigger than Austin, or whatever small part of it you're familiar with. Even in the winter, the road surface is usually enough warmer than the snow-covered ground to provide some useful energy.

      There's another source of heat in addition to the solar input. Passing vehicles emit heat from the exhaust (including the catalytic converters) and there's heat built up from the mechanical stresses, 'specially the "big
      • by LWATCDR ( 28044 )
        The real problem is what do you do with that heat? Yes you could use it to deice the roads but in the summer when you have the most gain you have the least use for the heat. The heat of the road is like lost of other energy around use. Just not concentrated enough to be of much use.
        Yes parts of Texas can get down right chilly Even Dallas can get a bit nippy.
    • Funny, here in Chicago they do the opposite. Use cement to patch a hole in an asphalt road.

    • I believe you mean concrete.
    • Re: (Score:3, Interesting)

      by eth1 ( 94901 )
      Actually, here in TX, you could use this to *cool* the roads. The extreme heat tends to crack and buckle the concrete. You'd also get some pretty hot water (even from the light-colored concrete). It's energy, and I'm sure someone could use it!
  • by victim ( 30647 ) on Tuesday January 01, 2008 @07:37PM (#21877742)
    There is apparently a bridge in Fukui [] which does just this.

    Sorry for that link to Treehugger, they are a black hole of links and I would not normally link, but they had the best English language article I could find in 3 seconds of googling.
  • Nothing new... (Score:4, Informative)

    by tgd ( 2822 ) on Tuesday January 01, 2008 @07:42PM (#21877770)
    Its not uncommon for some very high end houses to do this during the summer and reverse the process (to keep the driveway ice/snow free) during the winter.
    • That's called geothermal heating, or a heat pump. It's not common but it's not rare either, the driveway part is a bit over the top. Usually in rural areas a pond is dug which effectively becomes a solar collect several acres in size, a swimming hold and a source of fish. Sometimes depending on the condition and depth of the aquifer an array of pipes are just buried in the ground for a heat source and sink.
      • by tgd ( 2822 )
        No, its not called geothermal heating or a heat pump... thats something entirely different.

        These are systems initially installed for the express purpose of keeping a large parking area and driveway clear of snow, which some more innovative people have taken to using for production of hot water as well during the summer.
  • by Anonymous Coward on Tuesday January 01, 2008 @07:49PM (#21877806)
    The article talks about storing energy in ground water. It isn't such a crazy idea. We used to do that kind of thing. Until the 1950s, the conventional way to keep food cool was in an ice box. Ice would be harvested in the winter and stored in ice houses. The ice would be delivered to householders in the spring, summer and fall. It worked well but was labor intensive.

    The idea of storing heat in the summer and cold in the winter is viable technically. The capital costs are impressive though. To keep my house cool over the hot summer months would take many cubic yards of ice. The container would be very expensive but maybe not more than most people are willing to spend on an in-ground pool.

    It could work. Cheap energy allowed us to forget things we used to do. Expensive energy would cause us to bring them back. The ice box, in some form, could easily return.
    • Re: (Score:2, Informative)

      by Mr. Slippery ( 47854 )

      The idea of storing heat in the summer and cold in the winter is viable technically...To keep my house cool over the hot summer months would take many cubic yards of ice.

      Which is why you use the ground [] instead. It spends all winter getting cool and remains cooler than the air in summer; it spends all summer getting warm and remains warmer than the air in winter.

      • Re: (Score:1, Informative)

        by Anonymous Coward
        The wiki article you link to describes heat pumps. A heat pump allows you to work against fifty degrees (approx.) rather than the ambient air temperature. That is really efficient for air conditioning. The only energy you need would be that required to pump air and water. For heating, you have to supply the energy necessary to get from fifty to seventy. (Yes, I realize the explanation is over simplified.)

        The idea of storing ice is that you have to pump much less water. You could do the thing in the ot
  • by Colin Smith ( 2679 ) on Tuesday January 01, 2008 @07:51PM (#21877824)
    And they've been around for decades. You can buy a system today, in all civilised countries. They work in exactly the same way as your refrigerator.
  • by youthoftoday ( 975074 ) on Tuesday January 01, 2008 @08:26PM (#21878052) Homepage Journal
    So they're using a series of tubes to make renewable energy? Seems like you can do anything on the internets these days...
    • by j235 ( 734628 )
      I'm surprised Al Gore didn't invent this one too!

      "We're going to take all that heat and put it into, what I like to call, a 'Locked Box'".
    • Yes, in the olden days they used to pump all the air out of the tubes and make radios out of them.
  • by Anonymous Coward on Tuesday January 01, 2008 @08:31PM (#21878084)
    I use this same technique to heat my pool. When filling it up in the summer I get together all my hoses and connect them. After laying this ultra long on my driveway I simply run water slowly though it from the tap into the pool. The water heats as it travels the hose and by the time it gets to the pool its actually quite warm.
    • Re: (Score:3, Insightful)

      by YrWrstNtmr ( 564987 )
      I use this same technique to heat my pool. When filling it up in the summer...

      Why do you empty it in the fall? Treat it well when you're done for the season, and you don't have to blow 15-20-30,000 new gallons in the spring.
      • Re: (Score:1, Informative)

        by Anonymous Coward
        Ha, yes well this was before I got a permanent pool, before I had one of those huge rubber ones with the inflatable ring on the top. It was fair sized about 3.5 feet deep mabey 16 feet across. In hind site it did wast a lot of water but that is quite cheep here in New England and it only cost about 600$ compared to the few thousand it cost to get a permanent one professionally installed.
      • He's probably not emptying it completely at the end of the year, unless it's a collapsible pool. We would drain about 12 inches at the end of the season to make the pool easier to cover and to prevent damage over the winter (Michigan winters, gotta love 'em). The water left in the pool gave it its structural integrity.
  • Freezing? (Score:3, Insightful)

    by Dan East ( 318230 ) on Tuesday January 01, 2008 @08:35PM (#21878098) Journal
    If any of that water were to freeze it would turn the roadway into a cratered, cracked and potholed disaster.

    Dan East
    • Re: (Score:3, Insightful)

      by hjf ( 703092 )
      you would have to be really stupid to use tap water on a system like that. add some antifreeze and that's it.
      • How many millions of gallons of the stuff are we going to *make*? How much of an impact will all those chemicals have when, not if, but when they leak? Continuing upkeep and environmental cleanup have to be added in. Then there's producing all this wonderful stuff, the chemicals, steels, seals, wire, pumps, generators, etc. It takes energy, materials and labor which costs money. Once you've added up the total cost of owner ship then you compare that to the benefits.

        Has anyone projected our energy needs to 2
        • You can have antifreeze that isn't toxic to the environment when spilled. A lot of the brine road department treat roads with is runoff from pulp piles at alcohol distilleries. IT normally runs into the rivers and ground without the slightest issues.

          As for turning roads into eclectic generators, I'm willing to be that it would cost a lot more then you could ever recover from it. This idea is actually pretty old. But this doesn't mean we shouldn't study it to see if recent advances in tech make it more pract
    • you say that like it's different from what we have now.
  • Do they get in the way loop detectors used in the roads?
    • If the tubes are nonferrous (which they'd likely be), they wouldn't cause a problem. However, if the pavement contained these tubes, it would preclude adding a loop detector after teh fact unless you can build the detector into an added top layer, which may reduce the tube system's effectiveness.

  • I think the maintenance issues will sink this idea on the large scale. The pipes have to be close to the surface to take advantage of the heat, but that's where they are exposed to the most stress from both traffic and weather-related expansion and contraction.
    • And while here in southern Louisiana we'd love to get some energy from the horrid summer heat, the shifting ground and perpetual sinking of our landscape will surely crack or damage the daylights (ha!) out of the pipe system. Either way, it's nice to see a working effort.
    • Re: (Score:3, Insightful)

      Yup, it's the operating costs stupid.
      4 minutes MTBF.

      KGO morning Traffic report: "We've got quite a back up on 101 northbound, they've been chasing a leak in lane 3 for 2 weeks; hopefully they'll find it, and we can get back to using the road as a - um - road thingy."

      Operating costs are often the unthunk Achilles heel. -almost as bad as opportunity cost, and cost of risk.

    • They actually wouldn't necessarily need to be close to the surface - the deeper you go, sure it takes longer to reach the pipes, but you have to remember that you have all year. So by placing them deep you get a more even heat.

      Interestingly enough, it might increase the lifespan of the road by keeping it at a more constant temperature.
  • ... until a pothole develops under a pipe or until the surface is worn away and tires start tearing into the pipes and you start losing coolant in a thousand small leaks all over the system. If you want to screw around with solar heat-based energy generation, passive solar at the focal point of a parabolic collector is much less costly, is much less brittle, and is much easier to repair when it does break.
  • I don't have the story on hand, but I'll try to summarize as best I can:

    There's this farmer out in the middle of nowhere, and one day the government decides they need to run a high way through his farm. They make a proposition to buy the needed land (not the entire farm, mind you), and he says okay, under one condition: That he be able to run pipes under the high way, and do whatever he wants with them. The government, not sure of his intentions, but thinking there's not much harm in it, says okay.

    What the
    • There's this farmer out in the middle of nowhere, and one day the government decides they need to run a high way through his farm. They make a proposition to buy the needed land (not the entire farm, mind you), and he says okay, under one condition: That he be able to run pipes under the high way, and do whatever he wants with them. The government, not sure of his intentions, but thinking there's not much harm in it, says okay.

      What the farmer did, was run pipes from under the highway, right into his hous
  • This is a wonderful idea, until some moron with a jackhammer knocks out the heat to your building. Or worse, the pipes all freeze up due to a "computer monitoring glitch" - rendering all roads with this technology useless as the asphalt buckles and cracks due to the expanding water in the pipes.

    It is time consuming enough when the local DOT decides to start digging up roads. Imagine if they had to lay miles of pipe under it too! Please put this in the recycle bin and move on to the next idea. This one has s
    • by geek2k5 ( 882748 )

      According to the article, this 'flawed' engineering appears to work in an area that doesn't get a lot of sunny days. That tells me that the engineers involved are far from drunk.

      Note that it collects heat in the warm season to be used in the cold season. A jackhammer or backhoe applied to the road or parking lot collectors wouldn't have much impact on the heat already stored. (They could, however, cut off gas lines and underground power lines, a flaw in 'modern' heating systems.)

      Now the potential for fre

      • I admit to being a moron. Actually, airports might be a really good place for this (as described in the article).
  • by LloydPickering ( 1211110 ) on Wednesday January 02, 2008 @06:28AM (#21880756) Homepage
    I work for a company in the UK who installs road energy systems. Figured I'd finally register a slashdot account to respond to this article after lurking around for so long.

    Here's a link to our supplier's page with installation photos for those curious. []

    The pipes are filled with anti-freeze rather than water. We use a vegetable based anti-freeze because of it's non toxicity should it leak.

    The system is divided into zones, or sections which converge to a manifold. Each zone can be turned off individually, so if someone does damage a section of pipe, it can be turned off without affecting the rest of the system. Anyone who has underfloor heating should have this in place too.

    We combine the system with geothermal heating and cooling using boreholes. In the summer excess heat from the building, and from the road is 'dumped' into the boreholes raising the average temperature of the local ground. In the winter we abstract the stored heat which then lowers the temperature back down. The entire system is 'closed loop'. We don't touch the groundwater itself at all, although we do also install open loop geothermal systems.

    Inside the building is a heat pump, which (as stated above) works like a fridge, but in reverse. Its basically just a Copeland compressor. It takes in large quantities of water at ground temperature, say 12 degrees C, and compresses that heat into a tank of water (heating it to say 45-50 degrees C) and the water that returns to the ground will exit at something like 6-8 degrees C. Different systems are designed to work with different temperature gradients, so be aware that those are simply example numbers. The larger the difference in temperature, the more efficient the system which is where the road energy comes in. Storing the excess heat in the summer means for example the average ground temp isn't the aforementioned 12 degrees C it's 15 degrees C instead.

    A more layman style description can be made using orange squash. Imagine you have a large volume of orange squash. If you find a way to remove some of the orange dilute from the squash you end up with a weaker orange squash, and a volume of orange concentrate. The heat pump works on this idea, except with heat instead of orange squash.

    On the whole, systems are surprisingly economical for commercial customers. In the UK installing a geothermal heating system will generally have a payback period of around 5 years when compared to a natural gas boiler. The extra benefit is that you also get almost free cooling with the system whereas with a gas boiler you have to put in extra chiller units. As a final economic litmus test...we are installing a road energy and geothermal system for a small medical centre in the UK ultimately paid for by the NHS, and I'm sure even those outside the UK know the NHS is pretty frugal. ;)

    • Re: (Score:3, Funny)

      by hoggoth ( 414195 )
      > takes in large quantities of water at ground temperature, say 12 degrees C, and compresses that heat into a tank of water (heating it to say 45-50 degrees C) and the water that returns to the ground will exit at something like 6-8 degrees C...

      > A more layman style description can be made using orange squash. Imagine you have a large volume of orange squash...

      I was having trouble following the process because I am unfamiliar with this "water" material you used in your example. Thank goodness you gave
      • Well, the analogy was aimed more at explaining the *magical* process of turning 12 degree C water into 50 degree C water that a lot of people find rather difficult to understand.

        Thank you for your pedantry.

        As a side note: Anyone with an allergy to citrus may at their own discretion substitute the orange squash in the analogy with any other form of diluted drink of preference.

      • by cromar ( 1103585 )
        I have no idea what be this "orange squash."
        • "Orange squash" is a bit like Sunny Delight, but even nastier. Basically, take some orange concentrate, boil it with sugar (or substitute) into a thick syrup, and sell the syrup. It is then diluted heavily before being drunk. Some squash vendors throw in vitamins, colourings, and various other oddities as well.
    • Figured I'd finally register a slashdot account to respond to this article after lurking around for so long.
      You got a pretty got UID. Only problem is there is no "2". Queue Futurama: Ahhh, what an awful dream. Ones and zeroes everywhere...[shudder] and I thought I saw a two." -- Bender "It was just a dream, Bender. There's no such thing as two". -- Fry Welcome out from the shadow's LloydPickering :)
  • by foniksonik ( 573572 ) on Wednesday January 02, 2008 @11:57AM (#21882684) Homepage Journal
    This article doesn't mention the facts I'm interested in.

    How hot does the water in the pipes get? Is it hot enough that if you swapped out alcohol for the water, the alcohol would turn to steam? (78.3 degrees C) Obviously the surface gets pretty damn hot but does that get through the asphalt into the pipes efficiently enough....

    If so has anyone thought of running a nearby stirling engine to generate actual electricity?

    My thoughts on this were that in a place like California or Nevada, where there are hundreds of thousands of miles of roadway and at least half a year of near cloudless skies, quite a bit of energy could be generated with little or no additional impact on the environment.

    If enough energy was generated you could conceivably even run some public transportation on these roads using an exposed contact system such as a recessed rail... or just run a system parallel to the roads. The cost of transporting the energy to these locations for this use would have dropped to zero thereby making them much more economical.

    • by Forbman ( 794277 )
      Hmm... I think places like the Qualcomm Stadium parking lot in San Diego would be better than roadways for this, as well as shopping centers, parking garages, etc.
      • Those would be fine choices for private installations or proof of concept on a small scale. What I would like to see is a big public works project (contracted out in part of course) to the tune of billions of investment over say 10 years.

        This is the type of thing that once a proof of concept has been delivered and the on-going costs have been derived from a 5 year testbed... it gets rolled out in a massive way as a long term integrated project.

        See I'm thinking of millions of miles of piping laid down as pre
  • He discussed asphalt solar in his 1986 novel O-zone. His characters were using it to make rain (and to drive up the price of oil, IIRC).
  • Some additional thought would need to be made into the selection of aggregate materials for the asphalt. Here in MD, and in many other areas, once the surface coating of the actual asphalt wears or washes away, the exposed aggregate is actually almost white, where the aggregate is of certain types of flint, quartz, limestone, or marble. Many of the aggregates from established quarries would be poorly suited to absorbing heat, necessitating the establishment of new quarries, or having to transport more suita

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