Flywheels for transportation applications Dean Flanagan Flywheel Energy

Flywheels for transportation applications Dean Flanagan Flywheel Energy Systems Inc. www. flywheelenergysystems. com EV 2011 VÉ Conference & Trade Show Special Session: Emerging Energy Storage Technologies 26 September 2011

Today • Order of presentation 1. The organization 2. Flywheel technology review 3. Transportation applications • Take away 1. Short term energy storage is useful in many transportation applications 2. Flywheels are useful short term energy storage devices

The organization Flywheel Energy Systems Inc. • founded March 1993 as an Ontario corporation • a Canadian controlled private company • extensive high speed rotating machines expertise Transportation research and product development Industrial motors and drives

Flywheel = high voltage mechanical battery The flywheel energy storage device incorporates the following core elements: • a high inertia energy storage rotor (“rotor”) • a variable speed permanent magnet synchronous AC motor/generator (“motor”) • a bi-directional PWM IGBT based inverter (“inverter”) • the rotor provides the energy storage rating • the motor provides the power rating • the inverter provides the DC link voltage rating

Mechanical plant (note the presence of r 2 and ω2 in the equations for energy and stress) Solid disk Pierced disk Kinetic energy (J) Polar inertia (kg·m 2) Peak stress (Pa) Electrical plant (similar to a traction drive system except the motor operates in vacuum) Copyright© 2011 Flywheel Energy Systems Inc.

Charge sustaining hybrid vehicle “sweet spot” of 10 -20 seconds 5 x 106 cycles Important note for flywheels: no erosion of performance characteristics (energy, power, efficiency) with age or cyclic use Addressable end-use typically falls within a 10 sec – 10 min timeframe

Transportation applications Short term energy storage solutions for transportation applications • Spacecraft • Marine • Rail • Lifting devices • Off road • On road • Motorsports

Rail

Two rail applications • On-board storage for catenary-free operation – Remove “visual pollution” of catenary wires – 30 meter tram requires 500 -600 k. W for 20 seconds • Wayside storage for metro’s and light rail – All modern metro’s and light rail systems employ regenerative braking – Present regenerative braking systems frequently fail to harvest as much as 75%-90% of the available kinetic energy resource simply because there is no place for the regenerated energy to go – Harvesting the unusable kinetic energy resource requires MW’s for 10 to 20 seconds

Power mismatch when a = constant

Wayside storage is needed to optimize regenerative braking systems Harvest Deploy Braking power and accelerating power required for a 144, 000 kg three-car consist from or to 72 km/h at 1 m/s 2 acceleration.

Why are you still using chemicals for energy storage? On road

More power, less energy

High DOH hybrids provide improved efficiency without performance erosion J. Gonder et al. , "Lower-Energy Requirements for Power-Assist HEV Energy Storage Systems—Analysis and Rationale, " NREL, PR-540 -47682, 2010.

Transit bus ESS power and SOC PRMS ≈ 28 k. W d. P/dt > 500 k. W/s di/dt > 800 A/s -60 k. W facility charge power limit ΔSOCmax ≈ 350 Wh A 10 minute slice from a 90 minute measured data set. Input power profile developed by Cross. Chasm Technologies for a charge sustaining series hybrid transit bus operating on a TTC route.

The application space What Vehicle mass (kg) Service life (years) Operating life (hours) Cycle life (cycles) Power (k. W) Time (s) Wayside rail 144, 000 30 180, 000 5, 000 On-board rail 30, 000 30 180, 000 5, 000 500 – 600 Class 7 hybrids 15, 000 12 – 18 80, 000 3, 000 120 – 200 500 – 800 10 – 20 Class 5 – 6 hybrids 7, 000 – 12, 000 10 – 15 40, 000 1, 500, 000 80 – 140 400 – 600 10 – 20 Class 3 – 4 hybrids 4, 500 – 7, 000 10 – 15 25, 000 1, 000 50 – 90 250 – 400 10 – 20 Class 1 – 2 hybrids 1, 300 – 4, 500 10 – 15 25 – 75 100 – 300 10 – 20 5, 000 200, 000 3, 000 Energy (Wh) 8, 000 10 – 20 3, 000 20

The benefits • • • Long service life and high cycle tolerance Preference for rapid charge and discharge High round trip efficiency No capacity fade No power fade No efficiency fade Wide temperature tolerance Low maintenance cost No end of life disposal costs Low total cost of ownership No high voltage exposure during maintenance operations and first responder interventions

Take away 1. Short term energy storage solutions are useful in many transportation applications 2. Flywheels are useful short term energy storage devices