Handbook of Energy Storage for Transmission or ... - W2agz.com

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Figure 4
Low-Speed Horizontal-Shaft Steel Flywheel (Courtesy Of Satcon Power Systems)
Figure 5
High-Speed Vertical-Shaft Composite Power Flywheel
High-speed rotors typically use more exotic materials such as graphite composites and
fiberglass, which are lighter but stronger and allow much higher rotational velocities.
These wheels typically spin at speeds above 10,000 rpm, and some designs exceed
100,000 rpm.
The physical construction varies with vertical and horizontal shafts, flywheel speeds, and
simply from one manufacture to another. Figure 6 shows the relative physical size and
profile of several commercially available flywheel systems. Note that the Satcon unit
profile also includes a standby generator, which is connected on the same shaft as the
flywheel and generator.
Rotor Bearings
The bearings support the flywheel rotor and keep it in position to freely rotate. The
bearings must constrain five of the six degrees of freedom for rigid bodies, allowing only
rotation around the axis of the rotor. The construction of the bearings is important in
flywheel performance. Speed of the flywheel is limited in large part by the friction on
Flywheels Page 6