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AC Propulsion
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Development and Evaluation of a Plug-in HEV
with Vehicle-to-Grid Power Flow
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CARB Grant Number ICAT 01-2
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| The statements and conclusions in this Report are those of the grantee and not necessarily
those of the California Air Resources Board. The mention of commercial products, their source or their use in connection
with material reported herein is not to be construed as actual or implied endorsement of such products. |
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| Summary |
| The goal of this project was to develop a prototype plug-in hybrid vehicle that would
combine characteristics of a pure electric vehicle with the unconstrained range of a conventional vehicle. This
was accomplished by developing a compatible auxiliary power unit (APU), including an specially designed alternator,
integrating the propulsion system and APU into a vehicle, and demonstrating emission reductions and commercialization
potential. |
| A plug-in hybrid differs from the hybrid vehicles now in production in that it can
connect to the power grid and use grid-supplied energy as well as energy from onboard storage of petroleum-based
fuel such as gasoline or diesel. The plug-in hybrid developed for this project demonstrates four capabilities that
differentiate it from plugless hybrids as well as from conventional vehicles. The project vehicle can: |
1. Provide full performance and 35-mile range with electric propulsion only.
2. Substitute grid energy in place of petroleum energy.
3. Serve as a distributed electric power resource.
4. Use natural gas for generation of electric power.
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| The results of testing conducted under this project indicate that these capabilities
can reduce vehicle emissions. Also, these capabilities demonstrate potential economic and energy benefits that
can assist the commercialization of plug-in hybrids, so that emission benefits can be realized. |
| The Vehicle Technology |
| Volkswagen Jetta was converted to electric propulsion using a 100 kW drive system
and an eight kWh lead-acid battery. The battery charger is integrated with the drive system and operates
on grid power at 100 to 250 VAC. Charge power up to 20 kW is possible. The charger operates bi-directionally,
allowing conversion of electricity from the high-voltage DC bus to 60 Hz AC current at up to 15 kW. The AC
power can be fed to the grid or to other external loads. |
| A custom-built auxiliary power unit (APU) using a small automobile engine was designed
and developed specifically for this project. The APU feeds the high-voltage bus with up to 30 kW of DC current.
This power level allows charge-sustaining operation at any speed up to 80 mph. The APU is series-connected,
it never drives the wheels directly. The APU can operate as a generation source, with its output fed from the vehicle
to external loads including local or large area power grids. |
| Equipped with a wireless internet connection and control algorithms developed under
a separate CARB research contract, the power system in the project vehicle can be controlled remotely to provide
grid support functions. |
| Development of the APU was a major element of this project. The emission-controlled
engine drives a light-weight, high-efficiency alternator designed and developed to meet the power, noise,
and weight requirements of this application. The engine burns gasoline when it operates while the vehicle is being
driven. The engine is also equipped to operate on low-pressure natural gas, and the vehicle is equipped with a
gas connection that allows the APU to draw fuel directly from gas mains while it is parked. Connecting the
project vehicle to an off-board gas source allows it to generate electric power continuously without depleting
the onboard fuel supply or discharging the battery. |
| Vehicle Capabilities |
| The project vehicle was built to demonstrate usability, functionality, and convenience
in daily use as well as the unique capabilities of plug-in hybrids. Driveability, simple controls, and seamless
operation of the hybrid system all received development effort under this project. Vehicle features include cruise
control, power brakes, regenerative braking, power steering, traction control, and bi-directional power. The
vehicle has been tested and evaluated for emissions, efficiency, audible noise, and power quality in stationary
operation; and emissions, range, fuel economy, acceleration, and driveability in mobile operation. |
| The completed vehicle provides 35 miles of range on batteries. The battery charger
allows charging from 110V, 208V, or 240V outlets. A standard 50A electric outlet allows charging in one hour. Fuel
economy of 30 to 35 mpg gives gasoline range of over 500 miles using gasoline. Up to 30 kW DC electric
power is produced by the APU. This power level allows charge sustaining operation at up to 80 mph. Top speed
is governed at 85 mph. Acceleration from 0-60 mph can be achieved in 8.5 seconds. |
| The project vehicle demonstrates full functionality as a replacement for a conventional
car that may be used locally or for long-distance travel. (Storage capacity was compromised in the prototype
vehicle, but this compromise is not inherent to plug-in hybrids.) |
| Emission Results |
| In dynamometer tests conducted by CARB at their El Monte, CA, test facility, the
project vehicle produced emission levels near current ULEV standards over the standard UDDS test cycle. In separate
tests, emissions were measured at steady state operating points, and these brake-specific emission rates, measured
in gms/kWhr are very low as shown in the table. |
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Project Car APU Operating Data,
Stationary Mode, Gasoline Fuel
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Fuel
gal/kWh
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Efficiency
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NMHC
gm/kWh
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CO
gm/kWh
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NOx
gm/kWh
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Project Car APU 5 kW
(gasoline)
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0.148
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20.5%
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0.011
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0.254
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0.154
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Project Car APU 15 kW
(gasoline)
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0.116
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26.0%
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0.003
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0.232
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0.048
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Capstone Microturbine
30 kW1 (natural gas,
max output)
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NA
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NA
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0.078
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0.603
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0.223
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U.S. Generation Avg1
(fossil fuel)
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NA
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NA
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NA
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NA
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2.54
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CA Generation Avg 2
(fossil fuel)
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NA
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NA
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NA
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NA
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0.20
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CARB DG Standard3
2003
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NA
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NA
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0.45
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2.7
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0.23
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CARB DG Standard3
2007
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NA
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NA
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0.009
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0.045
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0.03
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| 1 Source: Capstone White Paper March 6, 2000 |
| 2 Source: CEC Environmental Performance Report, 2001 |
| 3 Distributed Generation Certification Program, Section 94203, California Code of Regulations |
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| It is interesting to note that, because APU operation is de-coupled to a some degree
from the actual driving cycle, the UDDS emissions can be estimated just by multiplying the brake specific emmisions
rates times the energy required by the vehicle over the driving cycle. Such theoretical calculations suggest that
SULEV emission levels over the UDDS should be achievable, and that the relatively high emissions measured over
the actual UDDS test are the result of poor cold-start emission control. |
| The measured brake specific emissions rates also can predict the emissions from the APU
when it is used as a stationary power source. Comparing the brake specific emissions from the project APU to emissions
from other power generating sources shows that the project APU operates with significantly lower emissions
than microturbines or conventional gen-sets, neither of which benefit from the sophisticated and highly
developed emission control systems that are typical of current automotive engines. |
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Funding Source
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Funding Amount
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| ICAT |
$230,071
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| Grantee |
$79,900
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| South Coast Air Quality Management District and National
Renewable Energy Laboratory |
$220,000
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| Volkswagon |
$225,000
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Click here for
the entire final report.
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