Since superconductivity was discovered in 1911, scientists and engineers throughout the world have been striving to develop an understanding of this remarkable phenomenon. Although till now the superconductivity theory is not very clear yet, many research groups are working hard to find high temperature superconductors. Till now HgBa2Ca2Cu3Ox has the highest critical temperature of 133 K (-140 C). I believe superconductor with Tc at room temperature could be found one day. In this report, let's assume superconductivity can be realized at room temperature and the manufacture cost is reasonable. I'll discuss the impact of room temperature superconductor from the energy point of view.
Electric power transmission is the most straightforward application of superconductors. In 2007, national-level losses were 6.5% of total electricity disposition excluding direct use in USA. [1] The energy loss comes from the resistance of copper or aluminum wire cables and transformers. With a room temperature superconductor, we could completely save this energy. Actually the known high-temperature superconductors have been used in electric power transmission in many experimental projects, such as Long Island HTS project. [2] It has been estimated that the waste would be halved using this method, since the necessary refrigeration equipment would consume about half the power saved by the elimination of the majority of resistive losses. By doing this, more current can be routed through existing cable tunnels. In one instance 250 pounds of superconducting wire replaced 18,000 pounds of vintage copper wire, making it over 7000% more space-efficient. Although high voltage transmission is still needed, more efficient transformers could be made of the superconductors. Superconductor cables are energy-efficient, compact and lightweight, and are expected to play important roles in the future power industry.
Stable superconductors at high temperature may have great impact on nuclear power plants as well. Fusion energy is one of the most important future energy resources. Scientists and engineers have to use high magnetic fields to control the extremely hot plasma (150 million °K). [4] Superconductors are one of the key factors in plans to improve the Tokamak (fusion reactor) and finally realize a fusion power plant. If the fusion energy could be used in the power plant, I think we don't need to worry about electrical energy in the future.
The persistent currents in a closed superconducting loop will flow for months, preserving the magnetic field. As we calculated in the lecture, the energy density of magnetic field stored in the wires is B2/(8 π) = 4 x 107 J/m3, assuming B = 10 T. Although this number is still much smaller than the energy density in gasoline (3.5 x 1010 J/m3), it could be a possible solution to store the excrescent electrical energy.
Magnetic levitation, is a system of transportation that suspends, guides and propels vehicles, predominantly trains, using magnetic levitation from a very large number of magnets for lift and propulsion. With a good superconductor, the cost and energy consumption of magnetic levitation will be greatly reduced and the speed could be increased as well. [6] This could become an alternative to airplanes for short distance travel, for example from Bay Area to LA.
5 MW High Temperature Superconductor Ship Propulsion Motor was demonstrated by Snitchler et al. [7] This propulsion motor will deliver superior performance in terms of high efficiency (96%). Maritime transport could be much more energy efficient if superconductor propulsion system was introduced.
There are many possible applications of superconductors, which could reduce the energy consumptions. For instances, quantum computation based on Josephson junction has been proposed and much less power is used for such quantum computer. [8]
Although superconductor is not an energy resources, it could reduce the energy loss and consumption, help to build high efficiency power plant and store electric energy. If one day the superconductor at room temperature or very high temperature could be found, the energy crisis may be partially solved.
© Shuang Li. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] "Frequently Asked Questions - Electricity," U.S. Energy Information Administration.
[2] Long Island HTS Power Cable Project Fact Sheet.
[3] Y. Nanao and N. Maki, "Fundamental Design and Parameter Optimization Study of HTS Generators for Co-Generation systems," Applied Superconductivity, IEEE Transactions on, 16, 1485 (2006).
[5] Oil Crude and Petroleum Products Explained, U.S. Energy Information Administration.
[6] H.-W. Lee, K.-C. Kim and J. Lee, "Review of Maglev Train Technologies," Magnetics, IEEE Transactions on 42, 1917 (2006).
[7] G. Snitchler, B. Gamble, and S. S. Kalsi, "The Performance of a 5 MW High Temperature Superconductor Ship Propulsion," Applied Superconductivity, IEEE Transactions on 15, 2206 (2005).
[8] B. D. Josephson, "The Discovery of Tunneling Supercurrents," Rev. Mod. Phys. 46, 251 (1974).