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Electronic
energy storage and future transportation
Principal
Investigator: Dr. Lei Yu
and Dr. Daniel Davis
Subcontractor:
Dr. Rober Hebner, University of Texas at Austin
Sponsoring
Agency: National
Institute of Standards and Technology
Period: September 1, 2000
~ August 31, 2001
Introduction:
The
National Institute of Standards and Technology
(NIST) provides the measurement capability the
U.S. needs to introduce advanced technology
into the economy.
In order to do this effectively, NIST
must anticipate when new measurement
technology is going to be needed.
One technology trend that may require
significant new measurement technology is the
trend toward hybrid vehicles that operate with
a variety of sources of power and energy
storage devices.
These may constitute a huge market as
fuel availability and increasing concerns over
air quality make it economical for cars,
trucks, and busses to be very different in the
future than they are today.
To
assure that the necessary metrology is in
place, NIST needs to have a good understanding
of the emerging technology.
With that understanding, NIST staff can
assure that appropriate measurement capability
is available as needed.
This proposed project, involving
students and staff from Texas Southern
University and the University of Texas at
Austin, will provide information NIST staff
members can use to improve their assessment of
any need for increased involvement in this
technology.
Technology
Background:
One of the
current trends in advanced transportation is to
recover the energy used in braking rather than
dissipating it as heat.
Each time a bus, truck, train, or car
stops, the entire kinetic energy it had must be
dissipated as heat.
Fuel must then be used to re-accelerate
the vehicle.
Being able to save that fuel, by storing
and re-using the vehicle’s kinetic energy,
improves fuel economy.
It also has the potential to do much
more.
If, for
example, the prime power source is an internal
combustion engine, whether the fuel is gasoline,
diesel, or a compressed hydrocarbon gas, the
engine runs best and pollutes least at nearly
constant engine speed. Acceleration and deceleration generally increase pollution.
By adding the energy storage device,
pollution should be decreased.
Even
the sources considered “non-polluting” like
fuel cells and batteries have improved
performance with energy storage.
These sources tend to have a more limited
life and reduced efficiency when used to power
highly variable loads.
A storage device can serve as a nearly
constant load to the primary source while
providing the power profile needed by the load.
Advances
in supporting technology have made one storage
device particularly attractive today.
This device is a kinetic energy storage
device powering a generator.
This is the concept that provides power
for the electricity utility grid.
The utility grid, however, is so large
that load changes tend to be a very small
fraction of the overall load.
Here that is no longer true.
The development of a small device that
can support wide load changes has resulted
primarily from three advances.
The first
advance is the development of strong composite
materials.
The fundamental need for strength of
materials is obvious from the basic equation of
rotational kinetic energy, Er,
Er = Iw2/2.
The amount
of energy stored scales as the square of the
rotational velocity,
w.
So, high rotational speed means
high-energy storage in a small volume if the
materials can tolerate the stresses.
New composite materials have made this
approach feasible.
Second,
high rotational speed requires high-speed
low-loss bearings.
The development of magnetic bearings and
their associated control algorithms has made it
possible to use a levitated flywheel to store
kinetic energy.
Mechanical backup bearings are still
needed to handle the largest shock loads. This combination of bearings has helped make this technology
possible.
Finally, the system cannot work unless the capability
exists to regulate and control the power flow.
With the rapid development of power
electronics, power conditioning is
increasingly available at the current and
voltage levels as well as the variable and
rather high frequency used in this source.
These electronics allow good computer
control of the entire power system, providing
the capability to maintain nearly optimum
operational conditions.
Proposed
Program:
The
students and staff of the School of Technology
at Texas Southern University will initiate a
study to model the likely fuel savings and
reduced air pollution possible using flywheel
energy storage in a vehicle.
This project will build upon expertise
developed in a number of research projects
concerning fuel consumption and emission
evaluation and modeling.
In
a project for the Texas Department of
Transportation (TxDOT) entitled “Collection
and Evaluation of Modal Traffic Data for
Determination of Vehicle Emission Rates Under
Certain Driving Conditions,”
the staff collected on-road emission data,
evaluated various existing emission estimation
models with on-road emissions, and developed
an emission estimation model to evaluate
emission implications of alternative traffic
control and management strategies. The newly
developed emission model establishes
relationships between the on-road vehicle
exhaust emissions and a vehicle’s
instantaneous speed and acceleration rate.
This emission model, originally developed to
evaluate emission implications of alternative
traffic control and management strategies, can
be used to predict the influence of
alternative vehicle technologies.
In
a project for the U.S. Department of
Transportation titled “Quantitatively
Estimating Air Quality Improvements and Energy
Savings of Alternative Traffic Control
Strategies,” TSU staff estimated the
potential reductions of vehicle emission and
fuel consumption resulting from alternative
traffic control strategies and/or vehicle
routing logic.
In
this proposed program, staff at Texas Southern
University will first conduct a comprehensive
literature review to identify existing
models/methods for estimating fuel consumption
and vehicle exhaust emissions under different
technologies.
Then, TSU staff will propose a new
model for estimating fuel savings and air
pollution reductions under flywheel energy
storage in a vehicle.
The evaluation model will be able to
evaluate effects of applications of flywheel
energy storage in vehicles on network-wide air
pollution under various driving, technology,
and traffic control conditions.
The
technical staff at the Center for
Electromechanics at the University of Texas at
Austin will provide technical data on the
performance of current and possibly future
energy storage approaches to the staff at
Texas Southern University to support the
modeling efforts.
The Center is currently working with
Houston Metro to install a flywheel-based
energy storage system on a bus.
This project should provide performance
data useful to the modeling effort
Research
Information
For further
information about the research, please contact
Dr. Lei Yu by telephone at(713) 313-7282 or by e-mail at
yu_lx@tsu.edu.
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