The Advantages & Disadvantages of Superconductors

Most materials people use are insulators, like plastic, or conductors, like an aluminium pot or a copper cable. Insulators show very high resistance to electricity. Conductors like copper show some resistance. Another class of materials show no resistance at all when cooled to very low temperatures, cooler than the coolest deep freezer. Called superconductors, they were discovered in 1911. Today, they are revolutionising the electric grid, cell phone technology and medical diagnosis. Scientists are working to make them perform at room temperature.

The electric power grid is among the greatest engineering achievements of the 20th century. Demand, however, is about to overwhelm it. For example, the North American blackout of 2003, which lasted about four days, affected over 50 million persons and caused about £3 billion in economic loss. Superconductor technology provides lossless wires and cables and improves the reliability and efficiency of the power grid. Plans are underway to replace by 2030 the present power grid with a superconducting power grid. A superconducting power system occupies less real estate and is buried in the ground, quite different from present day grid lines.

Wide-band telecommunications technology, which operates best at gigahertz frequencies, is very useful for improving the efficiency and reliability of cell phones. Such frequencies are very difficult to achieve with semiconductor-based circuitry. However, they have been easily achieved by Hypres's superconductor-based receiver, using a technology called rapid single flux quantum, or RSFQ, integrated circuit receiver. It operates with the aid of a 4-kelvin cryocooler. This technology is showing up in many cell phone receiver transmitter towers.

One of the first large-scale applications of superconductivity is in medical diagnosis. Magnetic resonance imaging, or MRI, uses powerful superconducting magnets to produce large and uniform magnetic fields inside the patient's body. MRI scanners, which contain liquid helium refrigeration system, pick up how these magnetic fields are reflected by organs in the body. The machine eventually produces an image. MRI machines are superior to x-ray technology in producing a diagnosis. Paul Leuterbur and Sir Peter Mansfield were awarded the 2003 Nobel Prize in physiology or medicine, "for their discoveries concerning magnetic resonance imaging," underlying the significance of MRI, and by implication superconductors, to medicine.

Superconducting materials superconduct only when kept below a given temperature called the transition temperature. For presently known practical superconductors, the temperature is much below 77 Kelvin, the temperature of liquid nitrogen. Keeping them below that temperature involves a lot of expensive cryogenic technology. Thus, superconductors still do not show up in most everyday electronics. Scientists are working on designing superconductors that can operate at room temperature.