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

Abstract

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 fluctua tions, 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 stor age rotor, a motor-generator system, bearings, power electronics, controls, and a con tainment 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 / kW-li inside-out integrated flywheel energy storage system.The flywheel operates at a nominal speed o f40,000 rpm. This design can potentially scale up for higher energy storage capacity. It uses a single composite rotor to peiform the functions o f 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.

A series hybrid “real inertia” energy storage system

“…Numerous novel flywheel designs have been proposed which could form part of a SHyKESS design and will be investigated. For example, integrated flywheel, motor/generator and magnetic bearing systems in the work of Kailasan et al [46] benefited from reduced shaft lengths. Additional flexibility in the design is present through the choice of flywheel and transmission shaft materials [47] and shape of the flywheel (for example, the use of constant stress flywheel cross sections with or without an outer retaining ring [47]), which are generally characterised by the shape factor K [48].…”

Critical Review of Flywheel Energy Storage System

“…Active magnetic bearing (Figure 11) accommodates coils that can adjust the amount of electromagnetic force in the system, thereby reducing vibrations in the rotating mass [108,109]. This is achieved via a feedback system monitoring the shaft position and increasing the stability of the FESS.…”

Development of a High-Fidelity Model for an Electrically Driven Energy Storage Flywheel Suitable for Small Scale Residential Applications

“…The increase in velocity changes the flow type of a rotating disc in a medium from laminar to turbulent. This transition is determined by Reynolds number 3 × 10 5 , a dimensionless parameter calculated using Equation (16).…”

“…Many publications have addressed the mechanical aspects, such as the bearing systems and rotor dynamics of the flywheels. To name a few, rotor design and analysis of composite rotor FESS is discussed in [16]. Authors in [17] present modelling and simulation of the rotor of a composite flywheel at different speeds.…”