Anyone who’s taken a barefooted tryst across a paved parking lot knows that blacktop can reach sweltering temperatures when exposed to the summer sun. Now researchers at the Worcester Polytechnic Institute have found a way to use to employ the heat-soaking properties of asphalt as an energy source by inserting heat exchangers a few centimeters below its surface. The development may pave the way for an inexpensive source for electricity and hot water that re-imagines our existing auto infrastructure as a massive conduit for solar-thermal energy.
The United States’ highway network consists of a tremendous expanse of roads and streets stretching 4 million miles. All day long these transit routes soak up the sun’s rays, storing an immense amount of energy that is left to dissipate by nightfall. The concept of asphalt-absorbed solar energy is enticing because it offers an inexpensive way to collect solar energy by utilizing an extensive infrastructure that already exists.
Rajib Mallick has taken the helm of a group of researchers at Worcester Polytechnic and touts the many benefits of using roadways as solar collectors:
“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’s team envisions a network of highly conductive water pipes that would run beneath our roadways, taking advantage of their untapped solar potential. Once heated, this water can be used as-is to heat buildings or can be passed through a thermoelectric generator to produce electricity.
The key to making this technology efficient will be to find the optimum materials for heat conductivity; to do this the team has been experimenting with various compositions of asphalt as well as specially designed heat exchangers that will soak up the maximum amount of thermal energy. Mallick states that “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.”
+ Worcester Polytechnic Institute
Via sciencedaily.com
Photo Credit: dusted
While this sounds real cool, I don\’t understand why they want to use water for this. This planet already has massive drinkable water shortages in some areas, pumping it all through our highway system would just make the shortages much worse. I\’d think there would be another way to convert the heat into energy.
I agree that a non-water option would be nice, but I don’t think we would be using drinking water for this. It sounds like the water is just being used to transport and store the energy. I would think there are various forms of re-purposed non-potable water that could be used.
I know when I lived in AZ the roads got hot and stayed hot for a very long time. We never had “Cold” water in the summer it was always warm. Hopefully these researcher will be able to find a way to make this technology efficient and affordable so states and municipalities will start using it.
This is a great concept, but a large proportion of highway infrastructure is too far from populations to provide building heating. It would work for the large parking lots which surround malls and big box stores, but the highest heating occurs in the summer when you need to cool the buildings rather than supply heat to them. In the winter when you need to heat the building, the asphalt is frozen.
You might be able to use the summer heat to drive an absorption chiller to cool the building. Or you might be able to use the heat in an Organic Rankine Cycle power plant.
The problem is that even though the asphalt is baking hot, it is still a low-temperature heat source.
Mixed feelings on this one, also. My first thought is that asphalt paving is an environmental horror to begin with, the surface water and air heating included, and the idea of promoting it for any reason is backwards. Reground tires would be much better. I even thing concrete is better, although one can argue that either way, certainly.
On the other hand, one has to admit that if you are going to have these streets, some of that heat should be captured. Use hot water not in a stream but in a closed loop to generate electric power, in my view.
Water would be used because it’s readily available and it’s has superb thermal transfer properties for this type of project. It would quickly and readily absorb more heat than any other comparably available or comparably priced heat transfer media (air, etc.).
This is a brilliant idea. In addition, potable water wouldn’t need to be used. Were it not highly corrosive, sea water could be used whenever it is available. Gray water could be used. Water pumped into cities could suck heat away from the highways and into a power generation facility before being filtered and treated for being drinking water. There are a lot of possibilities to tap into an otherwise wasted resource. To criticize this concept because it uses water is short sighted.
See http://peswiki.com/index.php/Directory:Solar_Pavement
how do the heat exchangers manage under the weight of cars and trucks? asphalt roads crack and develop potholes, which is normal road wear-and-tear, does that mean the heat exhcnagers need to be replaced everytime the road is re-done?
what is the life span for these heat exchangers?
The technology for any of this equipment is there. The trransfer media in the system could even be fed by the run-oof from the roads itself.
Excellent concept.
Hi – Just wanted to make a correction – It is actually Worcester Polytechnic Institute, not “Worchester”. You can also call it WPI or even Worcester Tech. Worcester is pronounced, “Woosta”.
I actually had Prof. Mallick as a Civil Engineering major at WPI for a couple classes and some friends have worked for him – he is very passionate about his research and extremely knowledgeable. The applications seem like they could potentially have some impact especially in urban centers where highways are very close to the end user.
This site got a lot of good press from both GreenBUILD this week and from the WPI Alumni Newsletter, The Bridge.
Thanks for correction mkengineer!
I’ve updated the post accordingly.