HTS wire and Cryocoolers

HTS wire

Being ceramics, HTS are difficult to turn into useful conductors (in this regard they are different from LTS that are metal alloys and cheaper to manufacture). Of the many potential high-temperature superconductors only three are prospects for being manufactured into useful lengths of long wire - BSCCO and YBCO. 

• Generation 1 Wire - BSCCO
  BSCCO or Bi2 Sr2 Ca2 Cu3 O10+d (also referred to as “generation one”) is available in long lengths and is the current mainstay of device manufacture. While it superconducts at liquid nitrogen temperatures its production involves a batch process and significant quantities of silver. It is therefore relatively much more expensive than other conductors (such as copper) and is not seen as being able to reach the price and performance targets required to enable a large scale HTS industry.
   
• Generation 2 Wire - YBCO
  The industry is transitioning to YBCO (also referred to as “generation two” conductor). It can be produced in a semi-continuous process and uses much cheaper raw materials. This holds out the prospect for HTS conductor to eventually compete with copper and even get close to LTS on a price/performance base. Like BSCCO, YBCO superconducts at liquid nitrogen temperatures, but performs better than BSCCO at high currents and in high magnetic fields. Pilot plants commenced producing long lengths of wire in 2008.
   

MgB2

Magnesium Diboride Superconductors (MgB2) requires much lower temperatures to become a superconductor (below 40K) and is less tolerant to the high magnetic fields and currents than the BSCCO and YBCO conductors. Its lower operating temperature means that its application will be limited to magnet systems, not in power systems. It is however less complex to manufacture into a wire and is potentially cheaper. The challenge right now is to produce long lengths with uniform performance.

Cryocoolers

Affordable and reliable cryocooling is an essential enabling technology for HTS. Every HTS device requires a cryocooler and since it can represent a third of the cost of device it represents an important component in an overall system. As HTS systems moved into industrial settings more robust coolers will be required, and New Zealand has developed such a cooler. This potentially represents a significant opportunity both in for HTS equipment and in other industrial gas applications.