Collecting Solar Energy from Asphalt Roads
Have you walked barefoot across a parking lot on a hot summer day? You don’t have to be a space scientist to know the fact that blacktop is remarkably good at soaking up the sun’s heat because you have felt the heat underneath your feet. Researchers at Worcester Polytechnic Institute (WPI) are trying to tap that heat for alternative energy source. Asphalt roads can be used for source of electricity and hot water in future!
Blacktop stays hot for a longer duration of time and this property can help in generating the electricity even after the sun goes down. This can be an added advantage over traditional solar-electric cells. We already have stretches of prepared roads running in acres and parking lots that can be taken advantage of for energy creation. Roads and lots are typically resurfaced every 10 to 12 years and the retrofit could be built into that cycle. One more advantage is that pulling out heat from asphalt can cool the road thus reducing the city’s ‘heat island’ effect. Asphalt solar collectors will not muddle with your artistic sense because they will be invisible unlike roof-top solar panels.
Rajib Mallick, associate professor of civil and environmental engineering at Worcester Polytechnic Institute (WPI) and his research team which also includes Sankha Bhowmick of UMass studied energy generating capacity of asphalt using computer models and by conducting small- and large-scale tests. They used slabs of asphalt for their tests. They embedded thermocouples for measuring heat penetration, and used copper pipes, to determine how efficiently that heat could be transported to running 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 lab they exposed small slabs to halogen lamps which can simulate the sunlight while larger slabs were placed in the real environment i.e. outside for sunlight and wind. The tests confirmed that asphalt soaks up a substantial amount of heat and the highest temperatures are experienced a few centimeters below the surface. At this spot heat exchangers can be placed for the maximum amount of energy. They also tried to increase the heat absorption by using highly conductive aggregate like quartzite. They also take into account to lessen the phenomenon of reflection by using special paint. The research team has also taken into account that they have to replace the copper pipe with some other material which will be a better heat exchanger. That heat exchanger will maximize the heat absorption already trapped in asphalt.