Thermal Power of Asphalt Roads & Parking Lots Could Be Tapped for Electricity
by Matthew McDermott, New York, NY on 08.14.08
photo by Chad Johnson
The idea, if not the practice, of using the heat absorption capabilities of asphalt roadways to heat water is not new. About nine months ago we reported on a Dutch civil engineering company which places water pipes underneath and then pump it to nearby buildings for heating. Additionally, the system is constructed so that it can actually pump cold water in the summer for use in cooling.
In a similar vein, researchers at Worcester Polytechnic Institute are investigating whether roadways might also be able to generate electricity. Science Daily provides the details:
Tests Done to Determine Maximum Heat Absorption of Asphalt
The entire project is being directed by Rajib Mallick, associate professor of civil and environmental engineering at WPI, and is studying the heat absorption capabilities of asphalt using computer models, as wells as small and large scale practical tests. The goal of these tests is to measure heat penetration into the asphalt to determine the best location for heat exchangers, as well as testing how well heat can be transferred to water contained in copper pipes embedded in the asphalt.
The tests show that maximum heat occurs only a few centimeters into the asphalt. It was also determined that by adding highly conductive aggregates, such as quartzite, heat absorption can be increased significantly. Reflection-reducing paint can also increase heat absorption.
Water heated in such a system could be used as is for heating buildings (like the Dutch have done) or by feeding it to a thermoelectric generator to produce electricity.
Roadway Energy Systems Could Be Retrofit as Roads Resurfaced
Mallick says that because roads and parking lots are resurfaced every 10-12 years, a roadway energy system could be retrofitted at the same time. Furthermore, extracting heat from asphalt could reduce the ‘heat island’ effect in urban environments.
While we certainly have an abundance of roads and parking lots in the United States, I wonder if the cost and maintenance of such systems would be prohibitive.
Some other things that stick out to me: If maximum heat absorption occurs just a few centimeters and that’s where you want to put your heat exchanger, would you have to move the whole system every time the road got resurfaced after installation? Or to resurface the road? What would be the wear and tear on such a system in highly trafficked areas?
Any civil engineers out there want to weigh in on this one?
via :: Science Daily
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I wonder if it would be more effective to use the impact or pressure-based electricity generators that were featured in those two european nightclubs?
Speed bumps, bridges, or other elevation changes like thatcould suddenly become generators, at least for nearby lights and whatnot.
I dunno, just a thought, as the heat thing seems very sensitive and sensitive isn't exactly what you want to implement, especially on roads as poorly maintained as many of those around America.
I'm not a civil engineer, but I stayed... oh, never mind. A few things I would have a question about.
In addition to the heat exchanger would the system require any additional structure like a steel grid to protect the exchanger from damage?
How deep do the conductive aggregates allow the heat exchanger to be buried? 2 cm below the road surface would make the system susceptible to damage by heavy vehicles.
Asphalt may become too expensive for road building, We may revert to more dirt/oil/gravel, all of which, I should think, would at least increase albedo.
pressure based generators basically steal kinetic energy from one source and turn it into electricity. On a dance floor- it comes from the dancers movements, but on a highway- it comes from (for the most part) gas powered cars. Its not an efficient way to produce electricity unless its positioned in areas where we want the vehicles to slow down/stop anyway (this would also save on brake wear). Otherwise your just stealing momentum from cars and forcing them to accelerate to overcome the moving plates.
I think they could use the temperature difference between the top layer and bottom layer in conjunction with a thermo-couple mesh to generate DC. Thiese systems have poor efficiency but they are reliable (with no moving parts) and can be built to last. And with such high surface area, they coul provide enough juice to power the lights during the night and whatnot.