Creating a "Super" Future
Solar panels and wind turbines. Energy Star–certified appliances. CFL and LED light bulbs. All the typical ways to save energy seem to focus on how it’s generated or how it’s used. Consumers do not generally consider the delivery system in between—unless the power goes out.
But the travel of electricity from power plant to home or office has room for improvement, too. Six percent of all electricity generated in the United States is lost during transmission each year. That may not seem like much, but consider this: power plants are only 35 percent efficient in converting energy into electricity in the first place, so every little bit counts.
One of the culprits of transmission loss is a proven occurrence: electrical resistance. It’s essentially friction that hinders the motion of electrons through a material. That’s why superconductors hold so much promise. They’re super, in part, because they offer no resistance. But there’s a catch: a superconductor needs to be cooled to, and maintained at, an extremely low temperature to display this unique property.
There’s still much scientists need to discover about the superconducting phenomenon before it can make a serious impact on electrical transmission. That’s where Matthew C. Sullivan comes in. The professor in IC’s Department of Physics and Astronomy is working to unlock the game-changing potential of superconductivity, not just for the energy industry but for transportation and recreation, too. And he’s doing it with the help of his undergraduate research assistants.
The “Super” of Superconductivity
Superconductors are elements, metal alloys, and certain ceramics that display unique magnetic and electrical properties when cooled to extremely low temperatures (some near absolute zero, or about -452 degrees Fahrenheit, others as “high” as -218°F, and most between that range). When properly cooled, superconductors offer no resistance to electrical current, which means there is no loss in power as electricity flows through them. The most common use for superconductors today is in magnetic resonance imaging (MRI) machines—used in nearly every hospital in the U.S.—but they are also used in limited commercial capacity in cell phone towers and some electrical transmission cables and wires. The extremely low temperatures needed to maintain this physical state limits large-scale use in cell towers and power lines, however.
Sullivan’s research is focused on understanding why superconductors behave the way they do and perhaps identifying materials that reach a superconducting state at warmer temperatures.
“The hope is that if we can understand the mechanism by which the electrons undergo this superconducting transition from the normal state to the superconducting state, we can understand how to make materials that have higher transition temperatures,” Sullivan said. “The overarching goal would be to eventually make superconductors that can superconduct at room temperature. Even dry ice temperature [-109.3°F] would be fine.”
Should such superconductors be discovered and commercially viable, Sullivan foresees “an explosion and a revolution in how electronic circuitry works, how electric power is transmitted from power plants to homes, and how power is transmitted inside cities.”
“High temperature” superconducting cables could eliminate the need for electrical substations and transformers that convert currents from low voltage to high voltage and back (electricity transmitted in high voltages over long distances loses less energy than low voltages). Even the electronics that are the endpoint of so much electricity could see a spike in performance.
“If you were able to replace the inside of your computers with superconducting wires, they would run at terahertz speed instead of gigahertz speed,” Sullivan noted.
Another current use for superconductors is in particle accelerators such as the Large Hadron Collider in Switzerland, where the Higgs boson particle was confirmed in 2012. They are also behind the levitation in some of the maglev (magnetic levitation) train systems online throughout the world. Enabling objects to levitate is perhaps one of the most visually interesting and impressive qualities of superconductors, and one that Sullivan has a lot of fun demonstrating.
Before late night talk show hosts Stephen Colbert and Jimmy Fallon went head-to-head at the 11:35 p.m. time slot, the two had instigated a mock feud on their old programs. One flashpoint of the feigned dispute was their respective Ben & Jerry’s ice cream flavors. In 2011 Sullivan was invited onto The Colbert Report to propel the host’s Americone Dream ice cream into the future and one-up his rival.
By using liquid nitrogen to cool a small puck made of a superconducting ceramic and inserting it into a mini-cup of the ice cream, Sullivan was able to suspend the carton in place above a magnetic track. With a light tap, the carton traveled back and forth along the metal pathway. Colbert was ecstatic. “It’s levitating!” he cried. “Eat it, Fallon! Eat the future!”
Sullivan’s appearance on The Colbert Report was an amusing variation on in-person demonstrations he’s done for years. But it was the videos he had posted on YouTube that racked up views and led to his invitation to Colbert’s show. There are differences between Sullivan’s YouTube demos and other superconductor videos on YouTube: the materials Sullivan uses to create superconductors retain the exact magnetic field they had before they entered the superconducting state. That “pinned” field works against the fields of the magnets on the track to produce the levitating effect.
“You can also turn the track upside down, and [the puck] will suspend underneath the track [rather than fall to the floor], all in an effort to stay exactly where it was when it was cooled down,” Sullivan said.
Could this trait of superconductivity ever be used to levitate vehicles, like cars or something smaller? Fans of Back to the Future Part II have been waiting for the day when they could buy their own hover board. Though the hover technology in the fictional time-travel movie is never explained, it would be entirely feasible, if unlikely, with technology today, Sullivan said—as long as there were a lot of properly cooled superconductors in our rides and magnets in our roads, or vice versa.
“The only thing that seems a little farfetched at this time is being able to hover over any particular surface that you want. That I’m not clear on how we would do,” he said. In the meantime, more realistic applications for joyrides may be at amusement parks. In 2013, Sullivan was featured on a Travel Channel program about roller coasters of the future. The technology he talks about on the show is already being used in some mass transit venues and may one day be applied to roller coasters as well.
Sullivan’s demonstrations of superconductivity often captivate freshman physics students and lead to requests from them to join his lab. Erin Jolley ’17 admits it was the “wow” factor that initially prompted her to join Sullivan’s team, but she’s since gone deeper into the research. Last year, she started growing crystals to be used in the superconductors and was the first in Sullivan’s lab to successfully grow them in bulk.
Superconductor crystals must be grown at very high—and very specific—temperatures, Jolley explained, and the material needs to melt a little before it’s cooled slowly to yet another specific temperature to ensure it crystalizes.
“But it’s very finicky, so I was messing with the temperature and time constraints to see how adjusting them affected growth,” she said.
She discovered that although the temperatures were specific, the time it took wasn’t.
“They didn’t have to be in as long as we thought they did, which was helpful because we could grow more in a shorter period of time,” she said.
Solving the Mysteries
Superconductivity was discovered over 100 years ago in 1911, and in 1957 the first widely accepted theory about it was finally formulated. But the waters of that theory became murky when, in 1986, the so-called “unconventional” superconductors were discovered.
One of the many questions yet to be answered is the critical temperature at which a material becomes a superconductor. The critical temperature for the unconventional materials that Sullivan works with is unusually high, and it’s still not known why. Another mystery is the mechanism that makes them superconduct in the first place.
Although five Nobel Prizes have gone to researchers examining superconductors over the last century, Sullivan noted that current progress in the field is incremental.
“My lab is trying to add a small piece to this puzzle of trying to understand how these materials actually superconduct because they defy the logic that was understood back in the 1950s,” Sullivan said.
For more on hover boards, read The Future is Hovering.