An overview of flywheel energy systems with HTS bearings

Passive magnetic bearings Incorporating permanent magnets and ReBaCuO, together with carbon fibre, offer the possibility of increasing the stored, volumetric energy density of FES and unprecedentedly low idling loss of FES. Its stored energy need only satisfy customers' needs for the time it takes to bring on conventional 'back-up'. The FES itself must come up to power quickly enough to avoid any disruption in the customer's operation (e.g., continuous industrial processes involving fragile materials, for example paper forming). Such customers do not care about the price of electricity nearly as much as they care about not ruining their product, damaging their machines or having 'clean ups' that stop or slow output. Firms that engage in electronic commerce and/or telecommunications also value uninterruptible power. Another set of potential customers (construction, electric railroads) may wish to avoid fluctuations in their electrical supply or they may wish to avoid causing harm to others who may hold them liable for poor power quality. Finally, real time prices (e.g., every 15 s) and real time commands, disseminated via internet, and distributed storage might enable reduced system generation costs. Generators and FES makers would have to cooperate to make this feasible. Now, the central techno-economic challenge is to build a high-power, low-loss motor generator that reaches full power in a very short time.