Christiana Chang lives where temperatures rarely dip low enough to produce snow let alone ice.
Yet in a lab at the University of Houston she is in the midst of perfecting something that just may garner a smile from those in regions where wintery weather wreaks havoc on commutes.
Self-heating roads.
They’re the subject of her master’s thesis and an idea she has been working on since earning her bachelor’s degree in mechanical engineering from UH in 2008. In just two years on the project, already she has had big breakthroughs.
“We have been able to raise the surface temperature of concrete enough to get ice to melt,” the Houston native boasted. Her results, showing a rise from 14 degrees Fahrenheit to near 32, were recently published in a technical note in the Journal of Smart Materials and Structures. It details her efforts to embed conductive carbon nanofiber paper in concrete to achieve deicing results.
“It is just like the coil on your stove,” Chang explained of how the nanofiber paper works with the concrete. “All we have to do is apply electricity on either side of the paper. Since we are passing current through something that is resistive, it is going to convert that to heat energy.”
Designed to mimic the depth of real roads, the paper rests three inches below the surface of a four by 10 inch slab of concrete. Another inch stands between it and the ground below. In tests where she applied just six watts of power to the paper in the model, the temperature on the surface of the concrete slab rose nearly 20 degrees in two hours.
They are findings that have caught the attention of national media, including New Scientist magazine, as well as been picked up by numerous Internet bloggers interested in how her self-heating roads hold up to traditional methods such as salting and plows.
Prior to earning her second, more advanced degree in mechanical engineering later this year, she will work to deliver for them when she takes testing from a small-scale model in a modified freezer in the lab to a road-sized footprint on a stretch of real roadway in Alaska.
But in the meantime, Chang has ideas about how to improve on the technology. For starters, she wants to ensure the paper inside the concrete can last the life of the road. So she is exploring ways to coat the paper with a polymer that may help it stay durable despite the constant strains of road traffic.
And along with her adviser, Gangbing Song, a professor of mechanical engineering, she is hopeful to keep its cost competitive or better than what is out there. Yet, with the cost of carbon nanofiber paper at $100 for an 11-by-11 sheet, it will take a little work.
But Chang and Song aren’t worried.
“The performance of the paper is there,” Chang said. “When we heat it and just measure the paper temperature, it gets close to 120 degrees Celcius (248 F).”
They are hopeful the intense heat created by the paper will allow it to be used far beyond its 11-by-11 imprint—instead spacing out pieces of the paper to achieve the same effect. This, coupled with advances in the production of the paper that are expected to bring down its $100 sticker price, could give them their advantage.
“Last year, the 11-by-11 inch sheet was $500, but now, just in the one year, they have improved the technology pretty quickly to where they are about a $100 a sheet,” Chang said, noting technology continues to improve due to its use as a material in electrical components.
Although they are continuing to perfect the idea, what’s been seen so far is promising.
“The development of self-heating concrete using carbon nanofibers has many advantages that are being shown through our research,” said Song. “Not only do carbon nanofibers resist corrosion better than their metal counterparts, they also greatly increase electrical conductivity. This can be done using much lower voltage during the heating process, which is safer and cheaper to use. It is for these reasons we feel it is holds promise for use on much larger scales in some of the country’s coldest climates.”