Alternative energy hits the road

August 12, 2008

Anyone who has walked barefoot across a parking lot on a hot summer day knows that blacktop is exceptionally good at soaking up the sun's warmth. Now, a research team at Worcester Polytechnic Institute (WPI) has found a way to use that heat-soaking property for an alternative energy source.

Through asphalt, the researchers are developing a solar collector that could turn roads and parking lots into ubiquitous—and inexpensive–sources of electricity and hot water.

The research project, which was undertaken at the request of Michael Hulen, president of Novotech Inc. in Acton, Mass, which holds a patent on the concept of using the heat absorbed by pavements, is being directed by Rajib Mallick, associate professor of civil and environmental engineering.

On Monday, Aug. 18, 2008, team member Bao-Liang Chen, a PhD candidate at WPI, will present the results of research aimed at evaluating the potential for transforming stretches of asphalt into a cost-effective energy source at the annual symposium of the International Society for Asphalt Pavements in Zurich, Switzerland. The study looks not only at how well asphalt can collect solar energy, but at the best way to construct roads and parking lots to maximize their heat-absorbing qualities.

"Asphalt has a lot of advantages as a solar collector," Mallick says. "For one, blacktop stays hot and could continue to generate energy after the sun goes down, unlike traditional solar-electric cells. In addition, there is already a massive acreage of installed roads and parking lots that could be retrofitted for energy generation, so there is no need to find additional land for solar farms. Roads and lots are typically resurfaced every 10 to 12 years and the retrofit could be built into that cycle. Extracting heat from asphalt could cool it, reducing the urban 'heat island' effect. Finally, unlike roof-top solar arrays, which some find unattractive, the solar collectors in roads and parking lots would be invisible."

Mallick and his research team, which also includes Sankha Bhowmick of UMass, Dartmouth, studied the energy-generating potential of asphalt using computer models and by conducting small- and large-scale tests. The tests were conducted on slabs of asphalt in which were imbedded thermocouples, to measure heat penetration, and copper pipes, to gauge how well that heat could be transferred to flowing water. Hot water flowing from an asphalt energy system could be used "as is" for heating buildings or in industrial processes, or could be passed through a thermoelectric generator to produce electricity.

In the lab, small slabs were exposed to halogen lamps, simulating sunlight. Larger slabs were set up outdoors and exposed to more realistic environmental conditions, including direct sunlight and wind. The tests showed that asphalt absorbs a considerable amount of heat and that the highest temperatures are found a few centimeters below the surface. This is where a heat exchanger would be located to extract the maximum amount of energy. Experimenting with various asphalt compositions, they found that the addition of highly conductive aggregates, like quartzite, can significantly increase heat absorption, as can the application of a special paint that reduces reflection.

Finally, Mallick says the team concluded that the key to successfully turning asphalt into an effective energy generator will replacing the copper pipes used in the tests with a specially designed, highly efficient heat exchanger that soaks up the maximum amount of the heat absorbed by asphalt. "Our preliminary results provide a promising proof of concept for what could be a very important future source of renewable, pollution-free energy for our nation. And it has been there all along, right under our feet."

Source: Worcester Polytechnic Institute

Explore further: Mussels and sponges in the deep sea can thrive on oil with the help of symbiont bacteria

Related Stories

Cities throw shade at rising heat

March 29, 2017

Rudy Lane is a two-lane road that curves through the leafy suburb of Windy Hills east of Louisville, Ky. Broadway is a main drag downtown where the federal and state courthouses bump up against the 1920s-era Brown Hotel.

Not all cool pavements are created equal

May 18, 2017

Cool pavements can help keep cities cool, right? Yes, but according to new research from the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab), many reflective pavements have some unexpected drawbacks ...

Recommended for you

EU fines Google a record 2.42 billion euros

June 27, 2017

The European Union's competition watchdog slapped a record 2.42 billion euro ($2.72 billion) fine on internet giant Google on Tuesday for breaching antitrust rules with its online shopping service.

Engineers use replica to pinpoint California dam repairs

June 26, 2017

Inside a cavernous northern Utah warehouse, hydraulic engineers send water rushing down a replica of a section of a dam built out of wood, concrete and steel—trying to pinpoint what repairs will work best at the tallest ...

18 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

Doug_Huffman
2.8 / 5 (5) Aug 12, 2008
'Renewable, pollution-free energy.' Renewable but still limited to 1350 W m^2 the Solar Constant and its derivative 'insolation' 4kWh day^-1.

And "pollution-free" from asphalt?! Asphalt is perhaps the very best repository for 'pollution' since it can be diluted in time and space.
Plurk
4.7 / 5 (6) Aug 12, 2008
Though indeed an interesting angle, this is hardly a new development. Since a few years a couple of (cost effective) projects are already in place in the Netherlands, cooling and heating buildings and keeping roads free of ice in the winter. And that's just implementations I am aware of. This article makes it sound like something new while it is not.
Sean_W
3.7 / 5 (9) Aug 12, 2008
"Roads and lots are typically resurfaced every 10 to 12 years and the retrofit could be built into that cycle."

They may be replaced every 10 to 12 years but they start to crumble almost immediately. I think that a new type of road surface would be needed for this to work - one that actually lasts a couple of years. But then if that was developed, the energy you save by not having to patch every year and resurface every decade would save a lot of energy. Unfortunately it would also mean that politicians would need to come up with a new source of pork projects and make work schemes for their regions so there is not much chance of that being a welcome innovation.
NeilFarbstein
3.4 / 5 (8) Aug 12, 2008
If dirt were dollars we wouldn't worry anymore..
whatever device you put under asphalt roads is going to fall apart from the constant stress of cars riding over it.
slash
3.8 / 5 (5) Aug 13, 2008
Good luck finding empty parking lots!

Seriously: If there was an area with a sufficient number of parking lots with a sufficient percantage of sun-exposure over ther day, then probably you won't need all of them - just build a solar farm on the area that is currently unused and you'll get a more efficient source of energy that is a lot cheaper to set up and maintain! The same is mostly true for roads, where maintenance costs for such devices migth easily exceed the net worth of the energy being generated.

My estimation may be off, but without some hard numbers noone will ever be able to prove me wrong!
Doug_Huffman
2.5 / 5 (4) Aug 13, 2008
If dirt were dollars...If froggies had wings...If wishes were fishes...If beggars had horses. I'll remember "If dirt were dollars..." Has a good alliteration.
DGBEACH
4.3 / 5 (3) Aug 13, 2008
Good luck finding empty parking lots!

They obviously would install these things where cars DON'T park...duh
whatever device you put under asphalt roads is going to fall apart from the constant stress of cars riding over it.

As Plurk stated, there are places on this planet (yes there are other inhabited/civilized places besides the U.S.A.!) where this is already being done successfully. I guess it just depends on how competent the civil engineering is in the country.
earls
4.5 / 5 (2) Aug 13, 2008
Again, the issue is energy storage. There's a million and one obvious processes like this to capture the sun's energy, but if you don't use it, you lose it, and when the sun's gone, so is your power.

I would assume, understandably, that people currently utilize some sort of classical energy storage scheme, but it's nowhere close to as efficient as it should be to truly make this an alternative energy source. Yet.
slash
2.5 / 5 (2) Aug 13, 2008
Good luck finding empty parking lots!

They obviously would install these things where cars DON'T park...duh

Apparently they DO intend to put this under parking lots - check the very first paragraph of this article:
Through asphalt, the researchers are developing a solar collector that could turn roads _and_parking_lots_ into ubiquitous and inexpensive sources of electricity and hot water.
jaggspb
4.8 / 5 (4) Aug 13, 2008
Again, the issue is energy storage. There's a million and one obvious processes like this to capture the sun's energy, but if you don't use it, you lose it, and when the sun's gone, so is your power.


Why do people feel the need to hit the home run on energy? Is it because we have been spoiled by crude/coal as a big source?

Chances are that any energy policy of the future will use a more diverse and level range of sources than some single source that provides the bulk.

If this process is used to provide hot water to buildings, then you already have an energy benefit. Just because it won't provide hot water all day AND night should not invalidate it as being useful.
Velanarris
1.5 / 5 (2) Aug 13, 2008
Again, the issue is energy storage. There's a million and one obvious processes like this to capture the sun's energy, but if you don't use it, you lose it, and when the sun's gone, so is your power.


Why do people feel the need to hit the home run on energy? Is it because we have been spoiled by crude/coal as a big source?

Chances are that any energy policy of the future will use a more diverse and level range of sources than some single source that provides the bulk.

If this process is used to provide hot water to buildings, then you already have an energy benefit. Just because it won't provide hot water all day AND night should not invalidate it as being useful.


Well that'd be a downer if you run out of hot water in the late afternoon wouldn't it?

Besides, in areas like MA, home of the developing company, the biggest obstacle would be the winter. Where asphalt works contrary and holds the cold of the ice and snow sitting on it unless you're spending energy to heat the asphalt which is completely counter productive.
Soylent
not rated yet Aug 13, 2008
Good luck finding empty parking lots!
They obviously would install these things where cars DON'T park...duh

Apparently they DO intend to put this under parking lots - check the very first paragraph of this article:
Through asphalt, the researchers are developing a solar collector that could turn roads _and_parking_lots_ into ubiquitous and inexpensive sources of electricity and hot water.


Is it so hard to understand that a parkinglot consists both of parking spaces and roads connecting them where you aren't allowed to dawdle?
jaggspb
3.5 / 5 (2) Aug 13, 2008

Well that'd be a downer if you run out of hot water in the late afternoon wouldn't it?

Besides, in areas like MA, home of the developing company, the biggest obstacle would be the winter. Where asphalt works contrary and holds the cold of the ice and snow sitting on it unless you're spending energy to heat the asphalt which is completely counter productive.


I just used the hot water portion as an example. If the tech is cost effective enough it should be used regardless because cumulative effects exist. Just like trickle charges have a big impact on energy usage on a large scale.

My point was just because it doesn't produce 100MW of power doesn't mean it isn't useful tech to explore. I'm by far a greeny but from a logic perspective it is well just that, logical.
Velanarris
not rated yet Aug 13, 2008

I just used the hot water portion as an example. If the tech is cost effective enough it should be used regardless because cumulative effects exist. Just like trickle charges have a big impact on energy usage on a large scale.

My point was just because it doesn't produce 100MW of power doesn't mean it isn't useful tech to explore. I'm by far a greeny but from a logic perspective it is well just that, logical.


I don't disagree, all energy is good energy as it's needed to continue civilization, and more of it is required to expand and develop advanced civilization. There are just far too many hurdles, and too many parallel deployments to say this is new or revolutionary science.

Especially as cold weather is the downfall of this idea when it comes to practical application in most regions.

This is however a great idea for equatorial zones, where they have an abundance of heat.
jaggspb
not rated yet Aug 13, 2008

I don't disagree, all energy is good energy as it's needed to continue civilization, and more of it is required to expand and develop advanced civilization. There are just far too many hurdles, and too many parallel deployments to say this is new or revolutionary science.

Especially as cold weather is the downfall of this idea when it comes to practical application in most regions.

This is however a great idea for equatorial zones, where they have an abundance of heat.


I think we are on the same page then. You are right about different forms of energy are more practical to certain regions over others.
Soylent
5 / 5 (1) Aug 13, 2008
Why do people feel the need to hit the home run on energy?


Because not getting access to power when its needed represents a huge degradation of lifestyle and won't be accepted as long as there are better alternatives even if they're dirtier. Because getting power when you don't need it is useless.

You have to look at the whole solution and see which partial solutions are worth while and how they interact. Ignoring storage and transmission costs doesn't make them go away.

If your complementary heat source is natural gas or heating oil, both of which are very easy to store and use when appropriate, you clearly do save some energy when you can substitute for them. If your alternative heat source is a heat pump you won't save nearly as much energy because electricity is hard to store and power companies will overproduce than risk any shortages; you might save a bit of natural gas or hydro, but your not going to save any coal or nuclear energy as they can't accomodate such changes.

This system needs seasonal heat store even more than solar panels or passive space heating does(capable of collecting heat for far longer into the winter than asphalt-based collectors). If seasonal heat store can't be made cost effective and reliable enough your partial solution isn't very useful, especially if we move from relatively costly and increasingly scarce natural gas and oil to abundant (low grade) coal and even more abundant uranium and thorium.

Is it because we have been spoiled by crude/coal as a big source?


You say spoiled like it should be regarded as a luxury to not sit shivering in the dark. There'll always be enough fissionable material to prevent that and there's an enormous amount of lower grade coals. If you want to prevent the use of all that coal you need to successfully compete with it.
Javaman
not rated yet Aug 14, 2008
Why do people feel the need to hit the home run on energy?


Because not getting access to power when its needed represents a huge degradation of lifestyle and won't be accepted as long as there are better alternatives even if they're dirtier. Because getting power when you don't need it is useless.

You have to look at the whole solution and see which partial solutions are worth while and how they interact. Ignoring storage and transmission costs doesn't make them go away.


Thats exactly the point. This system isn't intended to be Earths Savior, it is intended to reduce the dependence on coal, not replace it. The concept of the national grid is that SEVERAL sources add energy into it, so that when one source is disabled, nobody loses power.

"You say spoiled like it should be regarded as a luxury to not sit shivering in the dark."

Your just being dramatic.
Soylent
5 / 5 (1) Aug 17, 2008
Thats exactly the point. This system isn't intended to be Earths Savior, it is intended to reduce the dependence on coal, not replace it.


But it doesn't reduce dependence on coal if it cannot replace baseload at any where near an acceptable cost.

The concept of the national grid is that SEVERAL sources add energy into it, so that when one source is disabled, nobody loses power.


But that's not even remotely feasible.

Weather is highly correlated over very large areas so distributing your wind, solar and wave plants widely doesn't help very much. The entire Europe or United states would appear to a grid operator as only a handful of enormous power plants that turn on and off at random with a few hours time to adapt.

You'd need to massively overbuild your power generation to make the odds of not having enough power tolerable. With current storage technology surplus power would be largely wasted as it is inefficient and costly to store electrical power(nuclear and coal are both cheaper than just the storage component alone). It's a leap of faith to assume that users who can tolerate intermittent power, like EVs are going to become cost effective and widely adopted and that variable rates will cause people to charge their EVs when cost effective instead of when convenient.

The current US grid is a number of approximately state-sized grids without much export/import capacity between them. Power-lines are expensive; they cost about ~$1 million/km. We're easily talking hundreds of trillions of dollars to build the behemoth your asking for even before you add power-plants or storage.

Interdependency across the entire nation through enormously long power lines is a very fragile system. An earth quake, a tree falling on the power lines, a storm, any random luddite with an axe to grind can plunge a large part of the country into rolling blackouts and brown outs. Adding more excess capacity and more additional routes in the national grid may be the only option to mitigate and that would be enormously expensive.

In the US it would merely be a pork barrel project that's unlikely to amount to anything when people start getting annoyed at paying many times the rate they payed for the old system of coal, nuclear, hydro and NG generation(all of which are still abundant).

If you tried to force Africa or India into doing this it would not merely be an inconvenience; they can't afford it, you'd kill people.

Alternative power sources absolutely must be competitive; plunging in head first without very carefully demonstrating that to be the case is likely to be a disaster.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.