Motor vehicles – Power – Electric
Reexamination Certificate
1998-12-23
2001-04-10
Swann, J. J. (Department: 3611)
Motor vehicles
Power
Electric
C429S010000
Reexamination Certificate
active
06213234
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a hybrid electric vehicle having a combination fuel cell and a gas turbine power generator and in particular, to a hybrid electrical vehicle having a combination fuel cell and a gas turbine power generator wherein the majority of the power to propel the vehicle under steady-state urban driving conditions is derived from the fuel cell.
BACKGROUND ART
The most popular power source for automotive applications is an internal combustion engine connected to a mechanical drive train which in turn rotates at least one wheel to drive the automobile. However, state and federal automotive emission laws are becoming increasingly more difficult to meet using current internal combustion engines powered by hydrocarbon fuels which emit large quantities of carbon dioxide, carbon monoxide, and various nitrogen oxides as by-products. Additionally, even the most efficient internal combustion engines are not very efficient, having a maximum efficiency of approximately 35% or less. The efficiency of an internal combustion engine increases as the energy output increases. During urban driving cycles where the required power output is the lowest, the efficiency is even lower.
As an alternative, electric vehicles were developed with the electric energy stored in large battery packs that replace the internal combustion engine and powered the automobile. The stored energy drives at least one electric motor which in turn rotates at least one drive wheel. However, there are still many drawbacks with the expensive battery packs such as long recharge periods, minimal driving distances before recharging, lack of power for passing and climbing hills, and excessively large and heavy battery packs.
Hybrid vehicles have been designed wherein for example, the automobile is continuously powered by a relatively low-powered, fuel-burning power source such as turbogenerator which can be run near or at peak efficiency. When extra power is required, for example, during acceleration or hill climbing, the surge power is provided by a storage device which stores energy during steady state driving conditions such as driving at a constant speed on a level road. Prior art storage devices include flywheels, pressurized fluid accumulators, batteries, and capacitors. The fundamental problem with these systems is that maximum efficiency is still limited by the fuel burning combustion engine whether it be internal combustion, spark ignited, diesel or a gas turbine.
A relatively new technology proposed for powering automobiles is the use of fuel cells to provide electric power. A fuel cell creates electricity through a chemical reaction wherein a hydrocarbon fuel oxidizes and forms carbon dioxide and water as by-products. Fuel cells have an efficiency of approximately 70-80%, much more efficient than internal combustion engines at the relatively low power requirements of urban driving. However, for a fuel cell to provide all the necessary power to an automobile to climb hills, drive at highway speeds, and supply passing power, the fuel cell would be too large, expensive, and heavy for an automobile. See for example ASME 97-GT-340, Parametric Study of Fuel Cell and Gas Turbine Combined Cycle Performance by Stephenson, Dawn and Ritchey, Ian.
DISCLOSURE OF INVENTION
The present invention solves the above-mentioned problems and provides a clean-burning, efficient, economical, automotive power source by converting a substantial portion of the fuel consumed by the vehicle directly to electrical energy using a fuel cell at very efficient conversion rates without the prohibitive cost of the existing fuel cell vehicle. At higher power requirements, a gas turbine generates additional power.
Accordingly, a hybrid electric vehicle is provided with an electric motor drivingly connected to a at least one driven wheel. The vehicle has a source of hydrocarbon fuel, a fuel cell for converting the hydrocarbon fuel and oxygen contained in air directly to electric energy and fuel cell exhaust gas, and a gas turbine engine powered by fuel cell exhaust gas as well as by directly burning hydrocarbon fuel. An electric generator is coupled to the gas turbine to provide electrical energy which in conjunction with the electrical output of the fuel cell powers the vehicle's electric motor. A power controller responsive to a demand signal from a vehicle occupant regulates the operation of the fuel cell and the gas turbine to cause the fuel cell and the fuel cell exhaust gases to provide vehicle power when the vehicle's need are generally below the maximum fuel cell power output level, and to provide hydrocarbon fuel to the gas turbine to generate additional power as required up to a maximum sustainable power level. The fuel cell and the gas turbine are sized relative to the vehicle such that the maximum electrical power output of the fuel cell is no greater than about 50% and, preferably, no greater than about 25%, of the maximum sustainable power level.
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Rosen Harold A.
Willis Jeffrey W.
Brooks & Kushman P.C.
Capstone Turbine Corporation
Dunn David R.
Swann J. J.
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