Research Papers: Gas Turbines: Structures and Dynamics

Design and Analysis of a Unique Energy Storage Flywheel System—An Integrated Flywheel, Motor/Generator, and Magnetic Bearing Configuration

[+] Author and Article Information
Arunvel Kailasan

Gardner Denver, Inc.,
100 Gardner Park,
Peachtree City, GA 30269
e-mail: Arunvel.Kailasan@gardnerdenver.com

Tim Dimond

Rotor Bearing Solutions International, LLC,
3277 Arbor Trace,
Charlottesville, VA 22911-7580
e-mail: tim.dimond@rotorsolution.com

Paul Allaire

Fellow ASME
Rotor Bearing Solutions International, LLC,
3277 Arbor Trace,
Charlottesville, VA 22911-7580
e-mail: paul.allaire@rotorsolution.com

David Sheffler

Department or Mechanical and
Aerospace Engineering,
University of Virginia,
122 Engineer’s Way,
Charlottesville, VA 22904
e-mail: das2jt@virginia.edu

1Corresponding author.

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 10, 2014; final manuscript received August 26, 2014; published online November 11, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 137(4), 042505 (Apr 01, 2015) (9 pages) Paper No: GTP-14-1365; doi: 10.1115/1.4028575 History: Received July 10, 2014; Revised August 26, 2014; Online November 11, 2014

Energy storage is becoming increasingly important with the rising need to accommodate the energy needs of a greater population. Energy storage is especially important with intermittent sources such as solar and wind. Flywheel energy storage systems store kinetic energy by constantly spinning a compact rotor in a low-friction environment. When short-term back-up power is required as a result of utility power loss or fluctuations, the rotor’s inertia allows it to continue spinning and the resulting kinetic energy is converted to electricity. Unlike fossil-fuel power plants and batteries, the flywheel based energy storage systems do not emit any harmful byproducts during their operation and have attracted interest recently. A typical flywheel system is comprised of an energy storage rotor, a motor-generator system, bearings, power electronics, controls, and a containment housing. Conventional outer flywheel designs have a large diameter energy storage rotor attached to a smaller diameter section which is used as a motor/generator. The cost to build and maintain such a system can be substantial. This paper presents a unique concept design for a 1 kW-h inside-out integrated flywheel energy storage system. The flywheel operates at a nominal speed of 40,000 rpm. This design can potentially scale up for higher energy storage capacity. It uses a single composite rotor to perform the functions of energy storage. The flywheel design incorporates a five-axis active magnetic bearing system. The flywheel is also encased in a double layered housing to ensure safe operation. Insulated-gate bipolar transistor (IBGT) based power electronics are adopted as well. The design targets cost savings from reduced material and manufacturing costs. This paper focuses on the rotor design, the active magnetic bearing design, the associated rotordynamics, and a preliminary closed-loop controller.

Copyright © 2015 by ASME
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Fig. 1

Schematic of proposed flywheel design

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Fig. 2

Inner and outer steel spline ring model

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Fig. 3

Total rotor model, including composite energy storage

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Fig. 4

Flywheel rotor finite element model

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Fig. 5

Rotor composite stresses

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Fig. 6

Peak stresses over operating speed range compared to failure

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Fig. 8

Thrust AMB finite element analysis

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Fig. 9

Radial AMB inverted design

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Fig. 10

Radial AMB finite element analysis

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Fig. 11

Rotor finite element model

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Fig. 12

Critical speed map

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Fig. 13

Undamped mode shapes

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Fig. 14

Campbell diagram, rotor with support stiffness

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Fig. 15

Rotor predicted unbalance response

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Fig. 16

Flywheel controller schematic

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Fig. 17

Root locus analysis, radial bearings




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