9.7 Summary Ë 363been comprehensively studied. The research status of stiffness, rotational loss, and
stability characteristics is reviewed in this chapter. The stiffness work in our group has
also been described. It is found that axial stiffness of a RSB is reduced by no more than
8% at different speeds, which is thought to result from the high cooling efficiency in
liquid nitrogen. An efficient calculation method of radial stiffness has been proposed,
and the calculation error is just 2.86% compared with experimental results.
HTSB applications to FESS, rotor support for machine, laser beam deflection
polygon scanner, centrifuge, liquid hydrogen tank, and non-contact mixer have been
introduced. The first industrial application of HTSB was realized by Nexans Super-
Conductors GmbH to support the rotor of a 4-MW HTS generator in 2006. A liquid
nitrogen pump is one of the new applications of HTSB, while other applications like
a high-speed motor, wind power generation and an electric aircraft engine, are also
promising. A liquid nitrogen pump prototype with HTSB was developed to verify the
application feasibility. Experiment shows that operation of this pump is very stable
without abnormal vibration or noise and that the flow rate and head increase with
rotational speeds.
Among the wide applications of HTSB, FESS is the most popular and most
promising one. Because of the passive stability, low rotational loss, and potential high
rotational speed of HTSB, HTS FESS owns distinct advantages of high energy density,
high efficiency, longevity of service, simple control, low maintenance, etc., which
provides a new approach to the global energy crisis. Several large-scale (over 5 kWh)
HTS FESS prototypes have been developed by Boeing, ATZ and ISTEC to demonstrate
the technical advantages. As a high*quality power source, HTS FESS is very promising
for EVs, spaceflight, and UPS.
A FESS model with two axial ASBs is made to demonstrate the working principle
of the storage system. With a 1.4-kg levitated steel plate as spinning flywheel, a
lamp could be lighted by the stored energy in the FESS model, which is useful
to demonstrate the mutual conversion processes of electrical energy to mechanical
energy. In order to develop a large-scale FESS prototype, a measurement set-up for
HTSB was first designed. As a basic platform, it was able to measure the force and
stiffness characteristics of HTSB under conditions of different cooling methods and
working temperatures. Based on the research results of the HTSB, a 5-kWh HTS FESS
prototype was designed and manufactured. It is planned to apply it in a regenera-
tive braking system subway for energy savings. Furthermore, the 5-kWh HTS FESS
prototype also has good application prospects in renewable energy, power grid, UPS,
electromagnetic launch, and EVs.
For the practical applications of HTSB and FESS, continuous work is being
conducted on the load capacity, force density, rotational loss, stability, and new
designs. Once the reasonable compromise between performance and cost is achieved,
HTSB and FESS will immediately become widely commercial, because there are great
demands for highly efficient energy storage technologies, from many fields of energy,
transportation, military, etc.