362 Ë 9 HTS Maglev bearing and flywheel energy storage system
a hybrid electric drive ground combat vehicle [87]. The US Navy has contracted a
ship-based hypervelocity railgun of 64-MJ muzzle kinetic energy [88]. The ESC of our
HTS FESS units can satisfy those electromagnetic weapon systems well. The key point
is the design and manufacture of the compulsator to the HTS FESS unit to satisfy the
pulsed power demand of EM launch or weapon system. Furthermore, the possible
applications of HTS FESS as pulse power supply also includes plasma experiments,
laser experiments, ion accelerator, pre-acceleration of spacecraft, etc.
9.6.6Electric vehicle
The HTS FESS prototype can be used as the energy supply for an electric vehicle (EV)
or hybrid electric vehicle (HEV). The applications in EV/HEV require small size and
light weight of the HTS FESS unit. Compared with the application in an EM launch
system or UPS system, the ESC is more important for an EV/HEV system. For example,
the commercial product, Model S EV of Tesla Motors Inc., has an ESC of 60 kWh and
85 kWh, with maximal output power of 222–310 kW [89]. Under the normal driving
mode, the maximal range per charge can be achieved is 390 and 500 km for an ESC
of 60 and 85 kWh, respectively. An I/O power of 200–300 kW can be conveniently
achieved with a single HTS FESS unit, but the ESC is a problematic issue. Because
of the limitation of size and structure of a vehicle, it is better to choose a distributed
design of HEV FESS, i.e. an array of HTS FESS units. For example, a HTS FESS array
for an EV can consist of 20 HTS FESS units, each with ESC of 3 kWh and I/O power
of 15 kW, which can achieve the similar operation performance as the Model S EV of
60 kWh ESC. Besides the ESC and power, the resistance to vibration and the need for
cryogenic working conditions are more essential problems for the HTS FESS units in
EV/HEV.
9.7 Summary
As one of the most important applications of HTS Maglev technologies, HTSB exhibits
outstanding advantages, like the lowest rotational loss in all kind of bearings (COF is
as low as 10−^7 ) [13] and very high speed up to 520,000 rpm [14]. It has low noise, long
lifetime, no abrasion, and no need for lubricant. It is stable at all directions, and does
not need an active control system. Even in the case of power failure, it has enough
time to stop the rotor safely before the HTS stator quenches. It has good environment
adaptation and can be applied in a vacuum environment which is impossible for
gas-suspended bearing.
Due to the excellent performances, HTSB attracts research interests all over the
world. HTSB characteristics, such as magnetic force, stiffness, damping, rotor dyna-
mics, stabilization, force creep, temperature dependence, and rotational loss, have