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Use of Asphalt Paved Surfaces For Solar Heat
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."
Physics professor Roland Winston, proposed this 25 years ago.
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.
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.
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.
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.
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Except that your analogy is ridiculous. The proposed heat pump is a closed system. Stick the water in once and you're done. Using a pump to circulate it requires very little power compared to what can be saved in heating by using the heated water.
Yes, the construction costs will be high, but that's what a lifecycle cost analysis is for.
So they're using a series of tubes to make renewable energy? Seems like you can do anything on the internets these days...
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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.
Here's a link to our supplier's page with installation photos for those curious. http://www.invisibleheating.co.uk/photos-of-asc-installation-g.asp
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. ;)
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.
A fool throws a stone into a well and a thousand sages can not remove it.