“Extreme” Plug-In Flywheel Hybrid Promises a Possible 250 MPG
23 February 2005
AFS Trinity Power Corporation has unveiled a flywheel-supported hybrid technology that the company anticipates will enable fuel economy in the 200–250 mpg range.
The Extreme Hybrid drivetrain—under development for light duty and heavy duty vehicles—is a plug-in hybrid that gets most of its power from the grid. The flywheel system provides greater efficiency in energy capture and release from regenerative braking, thereby extending the operational range of the vehicle in all-electric mode.
The hybrid drivetrain system consists of five primary elements:
Advanced lithium batteries that are recharged at night with off-peak power from the power grid
An advanced flywheel for improved energy capture (up to 80%) and storage from regenerative braking
Advanced power-conversion and management electronics
A high efficiency steady-state Internal Combustion Engine
An electric powertrain
A flywheel is a rotating, kinetic store of energy. As energy is drawn from the system, the rotating components slow down, and as the system is charged, they speed up. Flywheel energy storage grows in proportion to the flywheel mass and the square of its rotational velocity.
The trick for a vehicle flywheel system is optimizing size and weight, durability of materials, rotational speed, speed of energy capture and discharge, and cost.
AFS Trinity’s approach is to use a flywheel within a flywheel. Its ARC (Active Rotating Containment) flywheel—for which it received a patent in 2002—uses a slower, heavier rotating outer flywheel to contain a much faster, lighter inner flywheel.
The result is more power per pound, more efficient energy transfer and a neutral gyroscopic effect which will allow vehicular operation without having to use counter-rotating pairs of separate flywheel systems.
When the flywheel hybrid vehicle runs on electricity alone it will not rely solely on its batteries; the flywheel and ultracapacitors will do the heavy lifting, providing high power over a short duration for acceleration or for quickly capturing regenerative braking energy.
This capability addresses one the limitations of the current chemical batteries used in plug-ins: the difficulty in absorbing or releasing high currents when they are in a deeply discharged state.
The flywheel thus buffers and protect the batteries, leaving them to do only what they do best: provide low-current longer running time in electric-only mode.
Power from the batteries will be “sipped” by the vehicle, not “gulped”. Although all of the subsystems are important, the high performance energy storage system is the critical part of a plug-in hybrid drive train.—AFS Trinity CEO Edward W. Furia
AFS Trinity expects that a driver will be able to operate the vehicle in electric-only mode for 40 miles, and at any time may flip a switch to run the vehicle as a conventional hybrid with a 500-mile range.
If Trinity can meet the 40 mile range mark with acceptable speed and performance, then it will be able to satisfy the daily driving needs of many drivers solely on electricity and thus deliver that extreme fuel efficiency.
We need to cure our addiction to oil. Our current 20 mpg national average vehicle fuel efficiency is embarrassing. While 50 miles per gallon in cars like the Toyota Prius is great for today, to address our transportation energy needs in the near future our national average fuel economy should be more than 200 miles per gallon.—Edward W. Furia
An Extreme Hybrid drivetrain for passenger cars is expected to begin development this year, be demonstrated in a prototype vehicle in two years and be ready for licensing to U.S. and foreign carmakers in three.
AFS Trinity Power Corporation is a flywheel energy company, created in 2000 through the combination of two pioneers: American Flywheel Systems (AFS)—the recipient of the first patent ever given for a flywheel battery (1992)—and Trinity Flywheel Power (Trinity). The company has devoted more than $45 million, 75% of it from private sources, to the development of kinetic energy storage, power management and UPS power backup technologies.
AFS Trinity is currently engaged in or has participated in development programs with a number of private and government organizations including DARPA, NASA, the U.S. Navy, U.S. Army, U.S. DOT, California Energy Commission, Oak Ridge National Laboratories, Lawrence Livermore National Labs, Lockheed and Honeywell.
Flywheel Energy Systems, 1997 paper
Plug-In Vehicles-Today’s Car for Tomorrow’s Technology, Electricity Innovation Institute
Analysis and Control of a Flywheel Hybrid Vehicular Powertrain, 2004 (Contact authors for a copy of the paper)
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