IPF 2011: What to do with room-temperature superconductivity once we find it?

While researchers are working to understand the origin of superconductivity, technicians are working just as furiously to find new ways this remarkable effect can be put to use.

What are the possible applications for room-temperature superconductors? At this year’s Industrial Physics Forum in Dallas, Texas, George Crabtree from Argonne National Laboratory gave a brief overview of the possibilities.

Power generation and storage hold a tremendous amount of promise. Nearly every step from power generation to delivery can be dramatically improved with the infusion of superconductivity.

The prime example is in power delivery. The US power grid loses nearly 10% of the energy generated to resistance and inefficiencies in the system. Those losses drop dramatically when superconducting wires are used. Not only that, but superconducting wires are so efficient they transfer five times the amount of electricity as a copper wire of the same width.

The current grid’s inefficiency is becoming a major issue in urban areas. As more people move to cities, energy demand naturally follows. But as the need for electricity increases, real estate for the wires becomes scarcer. The wires have to compete with ever-expanding plumbing needs and broadband lines. Smaller, more efficient wires could mitigate the real-estate crunch.

On a much larger scale, superconducting wires could help provide one of the biggest boosts to get renewable energy off the ground. The windiest parts of the US are in the Great Plains, while the sunniest parts of the country are in the Southwest. Most people live east of the Mississippi River and along the West Coast, many miles away from those promising energy sources.

‘You got to move that power, if you want to use it, hundreds or even thousands of miles,’ Crabtree said.

An interstate superhighway for electricity

Superconducting wires would be ideal for moving power over long distances. Crabtree showed a plan for a network of superconducting cables running from the Plains and the Southwest to both coasts through ‘a sort of interstate superhighway for electricity.’

Just as big a challenge as energy transfer is energy storage. Here, too, superconductivity holds much promise. Superconducting magnetic energy storage (SMES) is a new technology currently being developed in labs around the world. By feeding electricity into a superconducting coil, SMES stores the electricity with little loss.

SMES does have some drawbacks. The biggest one pertains to storage capacity. To store the amount of energy that a standard coal plant puts out in a given day, you would need an SMES the size of a football field. But on smaller scales, SMES starts making more sense.

Indeed, SMES can mitigate one of the biggest drawbacks to wind and solar power: intermittency. When the wind dies down, or a cloud passes, power output decreases. SMES systems can smooth out the release of power. Connecting an SMES to each wind turbine or bank of photovoltaic cells would be a big step toward overcoming the intermittency problem.

For some of these applications, the use of superconducting wire is so advantageous that some operators are willing to use cuprate materials, even though the wires require cooling and are brittle. Still, achieving room-temperature superconductivity remains the major goal. ‘I don’t think that there’s anyone in the room saying you couldn’t get a room-temperature superconductor,’ Crabtree said.

The first generation of superconducting wires consisted of BSCCO (bismuth strontium calcium copper oxide) filaments suspended in a silver sheath. This hampered their practicality because of the inherent high costs of silver. Now, layered YBCO (yttrium barium copper oxide) ribbons are one of the most promising areas of development. The raw materials needed to manufacture them are far cheaper, but because of their intricate construction, cost still far outstrips that of traditional copper wires. On top of that, the energy needed to keep the wires sufficiently cool eclipses any power savings offered by superconducting wires.

Despite those disadvantages, tests started in 2008 by the Department of Energy and the Long Island Power Authority have shown that cuprate wires perform well.

The need for room-temperature superconductivity is plainly present, and as the old adage goes, ‘necessity is the mother of invention.’ And even if cheap and easy room-temperature superconductivity is just a pipe dream, the search for it has resulted in incalculable contributions to science.

‘Superconductivity has in many ways led the field of condensed-matter physics for the last century,’ Crabtree said.

Mike Lucibella