Projektinfo – Detailed information on energy research

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Fig. 1: Second-generation high-temperature superconductor (right) conducts the same rated current of 200 A without losses as the illustrated copper cable (left).
Second generation leads through the niche
Projektinfo 06/2010
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High temperature superconductors

Approx. 100 years ago, the physicist H.K. Onnes discovered that mercury suddenly loses its electrical resistance below a temperature of 4.2 Kelvin. Subsequently, superconducting metal alloys with transition temperatures of up to 23 K were developed. In the last 30 years, this facilitated pioneering developments, primarily in medical technology, but also in the physical research. However, considering its versatility, superconductivity long remained a niche technology. The main reason is the difficulty of maintaining such low temperatures. As only helium is liquid below 23 K, it is the only possible coolant. However, it is expensive and difficult to handle. Also, a significant amount of energy is required to liquefy it.

The response in 1986 was appropriately positive when the physicists J.G. Bednorz and K.A. Müller developed materials which became superconductive at temperatures as high as 35 K. By contrast to the already known metals and alloys, these materials were surprisingly ceramic substances. Just one year later, the new materials achieved transition temperatures above 77 K. This allowed liquid nitrogen, a widely-available, inexpensive industrial product, to be used as a coolant. This greatly expands the possible areas of application, and it also makes energy technology applications, and in particular efficiency technologies, possible. However, there is still need for further development to turn the brittle ceramic materials into superconductive wires or bands in the required quality and quantity at acceptable costs.


Pilot projects in electricity grids and for motors and generators and applications in industrial processes show that significant energy savings are implemented compared with conventional technology. There is often a secondary benefit, which makes superconductivity particularly attractive compared with conventional technology. For example, superconductors are smaller, lighter and more efficient than conventional conductors, and also allow improvements in processes in some cases. The potential of the technology has been identified around the world. Countries such as the USA, Japan, Korea, China and India have increased their research activity. Germany is among the front runners, having offered significant research subsidies in the nineties. Medium-sized companies in particular can offer highly-developed products and system solutions. In order to maintain and expand this good position, the German Federal Ministry of Economics and Technology promotes the development of the technology and its applications in numerous projects.

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