Can Asphalt Generate Solar Energy?

A research team led by Rajib Mallick at Worcester Polytechnic Institute (WPI) says it has found a way to use asphalt’s heat-absorbing properties as an alternative energy source.


Prof. Mallick, associate professor of civil and environmental engineering at WPI, states the advantages that asphalt has as a solar collector:

• Blacktop stays hot and could continue to generate energy after the sun goes down, unlike traditional solar-electric cells.
  
• Since installed roads and parking lots already exist, the need to find additional land for solar farms is eliminated.
  
• Because “roads and lots” are typically resurfaced every 10 to 12 years, they could easily and cost-effectively be retrofitted for “energy generation.”
  
• Extracting heat from asphalt would cool pavement and reduce the urban ‘heat island’ effect.
  
• Unlike roof-top solar arrays, which some people find unattractive, solar collectors in roads and parking lots would be invisible.
  

Mallick and his research team, which also includes Sankha Bhowmick of University of Massachusetts, 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.”

Via: Ceramin Tech Weekly and WPI New Release