Capturing solar energy from asphalt pavements

Summary:Massachusetts researchers have found a new method for capturing solar energy. They're using heat from asphalt and other paved surfaces to produce electricity. 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.' This is an excellent idea because parking lots stay hot at night -- at least during summer -- and 'could continue to generate energy after the sun goes down, unlike traditional solar-electric cells.' Furthermore, there is no need to find land to build solar farms. Finally, there would be another advantage. Unlike rooftop solar panels, solar collectors in roads and parking lots would be invisible. Now it remains to be seen if this research team can convince the industry to change the way they're building roads. But read more...

Massachusetts researchers have found a new method for capturing solar energy. They're using heat from asphalt and other paved surfaces to produce electricity. 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.' This is an excellent idea because parking lots stay hot at night -- at least during summer -- and 'could continue to generate energy after the sun goes down, unlike traditional solar-electric cells.' Furthermore, there is no need to find land to build solar farms. Finally, there would be another advantage. Unlike rooftop solar panels, solar collectors in roads and parking lots would be invisible. Now it remains to be seen if this research team can convince the industry to change the way they're building roads. But read more...

This research work has been led by Rajib Mallick, Associate Professor of Civil and Environmental Engineering at the Worcester Polytechnic Institute (WPI), at the request of Michael Hulen, president of Novotech in Acton, MA. Mallick was helped by Bao-Liang Chen, a PhD candidate at WPI, and worked with Sankha Bhowmick, Associate Professor of Mechanical Engineering at the University of Massachusetts in Dartmouth.

Here is a quote from Mallick. "Asphalt has a lot of advantages as a solar collector. 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."

Of course, it looks like a good idea. But how does this work? "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."

The research team thinks that turning asphalt into an energy collector is a very simple process which just implies to replace "the copper pipes used in the tests with a specially designed, highly efficient heat exchanger."

Here is Mallick's conclusion. "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."

This research work will be presented on August 19, 2008, during a conference organized by the International Society for Asphalt Pavements (ISAP). The International ISAP Symposium on Asphalt Pavements and Environment will be held on August 18-20, 2008 in Zurich, Switzerland. Here is a link to the technical program (PDF format, 12 pages, 182 KB). The WPI researchers will present a paper called "Capturing solar energy from asphalt pavements" during the session 5a named "Energy Saving and Production."

Sources: Worcester Polytechnic Institute news release, August 11, 2008; and various websites

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