Superconductors

A superconductor is an element, a metallic alloy, or a compound that will conduct electricity without resistance below a certain temperature. The key is without resistance because resistance produces losses in the energy flowing through the material.

Once set in motion, electrical current will flow “forever” in a closed loop of superconducting material. This makes it the closest thing we know to a perpetual motion machine we have today.

Superconductivity was first observed in 1911 by a Dutch physicist named Heike Kamerlingh Onnes. He used mercury and cooled it to the temperature of liquid helium, which is 4 degrees Kelvin. Absolute zero, the coldest temperature that theoretically exists, is O degrees Kelvin. When the mercury reached this temperature, its resistance suddenly disappeared, meaning that electrical current flowed freely through it.

In 1933, Meissner and Ochsenfeld discovered what has come to be known as the “Meissner effect.” A magnet moving by a conductor induces electric current in the conductor. The is the basis for conventional generators. With a superconductor, however, the magnet is repulsed as the induced current exactly mirrors the field that would otherwise have penetrated the superconductor. This is known as diamagnetism and can cause a magnet to actually be levitated above a superconductor material.

Over time, and a great deal of research, it has become possible to create superconductors out of a variety of compounds that show the effect at higher temperatures. Ceramic compounds, thought to be a natural insulator, have been found to have superconductive capability. The current world record is now 138 Kelvin for an esoteric compound of mercury, thallium, barium, calcium, copper, and oxygen under quite severe lab conditions.

The first company to commercialize “high temperature” superconductors was Illinois Superconductor in 1989. they introduced a depth sensor for medical equipment that operated at the temperature of liquid nitrogen, about 77 degrees Kelvin. Other devices, including one capable of detecting even the weakest magnetic fields have been developed since. Again, these are fairly esoteric uses under confined conditions. As we think back to the physicists who developed the Laws of Thermodynamics and what they were doing, we wonder if there are other potential uses that are more relevant commercially.

The concept of magnetic levitation (the Meissner Effect) was introduced earlier. It is one area where superconductors perform very well. Trains can be made to “float” on strong superconductor magnets, thus eliminating the friction between train and tracks.

Conventional electromagnets would be huge and waste much of the energy as heat. In Japan in 1997, the ministry of Transport introduced the Yamanashi MAGLEV Test Line and in 2003, the test train reached a speed of 361mph.

The worlds’ first MAGLEV train was a shuttle in Birmingham, England. It shut down in 1997 after 11 years in operation. Other lines include on in Shanghai at Pudong International Airport, and one will begin in late 2004 at Old Dominion University in the US. However, widespread use to this point has been limited by political and environmental concerns. Strong magnetic fields can create a biohazard, and the impact is under research.

Other potential uses for MAGLEV technology include building MAGLEV systems along the right-of-way of existing interstate highways to carry both passengers and freight more efficiently and cheaply without being as dependent on fossil fuels. Another, more or less futuristic idea is to use low pressure tunnels for the vehicles, thus cutting down air friction. The vehicles would theoretically travel at super speeds at up to 2000mph, again carrying freight and/or passengers. The technology has been extended to things like cheaply transporting water, carrying crushed rock in mining operations, and even in space flight. The idea here would be to move the rocket over a MAGLEV line in a low pressure tunnel until it reached a certain speed, then curve it upward for launch, at which time the conventional rockets would kick in. The amount of conventional rocket fuel would be considerably lessened, making it cheaper to launch a space vehicle.

Biomagnetism is another use for superconductors and one that we are more familiar with. Current MRI’s use superconductor magnets to impinge a magnetic field into the body. Hydrogen atoms present in the body (water and fat) accept the energy then release it at a frequency that can now be detected by computers and displayed, thus giving a picture of what is going on in the body. This technology has been known for a long time, but superconductors and faster computers now make it feasible.

Another instrument relying on superconductors is called a superconducting quantum interference device or SQUID. It is capable of detecting a change in a magnetic field one billion times weaker than the force that moves the needle of a compass. The device is used to probe the body without the need for the strong magnetic fields of the MRI. One such use is to look at the brain.

Another use for superconductors is creating super-colliders or atom-smashers on steroids. The research on high-energy particles relies on the ability to accelerate sub-atomic particles to speeds approaching the speed of light. One super-collider is now operational in Europe and is called the Large Hadron Collider (LHC). Other colliders include Fermilab, HERA, and RHIC Heavy Ion Collider.

A future use for superconductors is in electric generators. With superconductors, a generator is above 99% efficient and about half the size of a conventional generator. It uses much less fossil fuel and would generate more electricity more cheaply. It goes without saying that the environmental fallout of using fewer fossil fuels would also be significantly lessened.

Other applications now under research include using superconductors to increase the speed and processing power or computers, using the technology in superconducting X-Ray detectors, light detectors, digital routers, electric storage capability and on and on. The US Navy is looking at using smaller motors based on superconductor technology. One producing 5000hp was recently introduced that takes up far less space and uses far less fuel than a conventional motor.

The uses of superconductor technology seems only limited by the inventiveness of the researchers looking at new applications. Will we, one day, go to our local MAGLEV station in New York on a cold wintery day and, in less than an hour, disembark in sunny Miami? All for less energy than a gallon of gasoline? Don’t bet against it!

By Karla Soule