Nov 24 2010
City temperatures are frequently much higher than the rural or suburban regions close by, chiefly due to the heat radiations given off by the roads. To utilize this solar energy from pavements, a group of engineering scientists from the University of Rhode Island (URI) is harvesting this solar energy to power streetlights, heat buildings and melt ice.
According to Wayne Lee, leader of the joint project, and URI professor of civil and environmental engineering, there are several hundreds of miles of asphalt pavements throughout the country absorbing a lot of heat and showing temperatures of 140 degrees, and if all that heat is captured and harvested it can be utilized for everyday requirements, reducing fossil fuel usage and thereby reducing global warming.
The URI team has decided to tackle the problem in four different ways, both simple and complex. One technique was to drape photovoltaic cells which are flexible, over the top part of Jersey barriers separating highways, which would provide electricity for powering streetlights and lighting up road signs. The PV cells could also be implanted in the roadway in between the Jersey barrier and its adjoining rumble strip. Lee stated that this method could be used as the technology required such as flexible PV solar cells are readily available, and could be installed easily and help in generating electricity. A test program has been planned for the lights outside Bliss Hall in the campus.
The second method involves embedding water filled pipes underneath the asphalt, and allowing the water to be heated by the sun. The heated water would later be taken through pipes to bridge decks, to help in melting the collected ice on the surface and thus decrease the necessity for using road salt. The same water could also be sent to the buildings in the vicinity for fulfilling hot water demands, just like geothermal heat pumps, or be converted to steam to power a turbine in a small scale power plant. A prototype of this system has been constructed by Andrew Correia, a graduate student, to examine its efficiency and effectiveness, facilitated by a funding from Korea Institute for Construction Technology. Correia plans to demonstrate the technology in a real world environment by trying it on different pipe systems and using varied asphalt mixtures. The retention of heat by asphalt causes the water to stay warm even after sun set. He states that sometimes the water becomes hotter than the asphalt road.
The third technique is using a thermo-electric effect for generation of a minimal amount of electricity, wherein two different semiconductors made out of organic polymeric materials are linked to form a circuit. A cold and hot spot are connected and electricity is generated inside the circuit. According to Sze Yang, Uri’s Chemistry Professor, if thermo-electric supplies could be fitted inside the road at various depths some amount of electricity could be generated to be used for defrosting roads. One more technique is to substitute asphalt roads by roads made of huge, resilient electronic blocks containing PV cells, sensors and LED lights, which could generate electricity for the day to day requirements and also emit alerts for maintenance and service needs. Lee remarks that though this technology is available, it is highly expensive. A prototype in Idaho cost around $100,000. He feels that probably Corporate Parking stations may make use of this technology and that this kind of futuristic technology may take several years for gaining acceptance.