VEHICLE POWER SYSTEMS AND METHODS EMPLOYING FUEL CELLS

Power systems and methods described herein can provide power system management and power delivery, among other functionality. The power systems and methods for a vehicle can employ a fuel cell, such as a Solid Oxide Fuel Cell (SOFC), as a power source in conjunction with another power sources, such as one or more vehicle batteries, capacitors, etc. The fuel cell can be conditionally used to provide power to the electrical system, thereby reducing the load on the vehicle batteries.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appended drawings where like numerals reference like elements is intended as a description of various embodiments of the disclosed subject matter and is not intended to represent the only embodiments. Each embodiment described in this disclosure is provided merely as an example or illustration and should not be construed as preferred or advantageous over other embodiments. The illustrative examples provided herein are not intended to be exhaustive or to limit the claimed subject matter to the precise forms disclosed. Similarly, any steps described herein may be interchangeable with other steps, or combinations of steps, in order to achieve the same or substantially similar result.

Prior to discussing the details of various aspects of the present disclosure, it should be understood that the following description includes sections that are presented largely in terms of logic and operations that may be performed by conventional electronic components. These electronic components may be grouped in a single location or distributed over a wide area. It will be appreciated by one skilled in the art that the logic described herein may be implemented in a variety of configurations, including but not limited to, hardware, software, and combinations thereof. In circumstances were the components are distributed, the components are accessible to each other via communication links.

The following description sets forth one or more examples of an electrical power system for vehicles and the like. The power systems and methods described herein can provide power system management and power delivery, among other functionality. Generally described, examples described herein are directed to power systems and methods for a vehicle that employ a fuel cell, such as a Solid Oxide Fuel Cell (SOFC), as a power source in conjunction with another power sources, such as one or more vehicle batteries, capacitors, etc. The fuel cell can be conditionally used to provide power to the electrical system, thereby reducing the load on the vehicle batteries.

In some examples described herein, the electrical power system, based on information from a combination of data sources, operates the power system in order to meet the operational needs of the vehicle. Some of the information that may be collected and/or utilized by the power systems and methods include but are not limited to hours of vehicle operation, historical driver operation data, load data, GPS location and optional topography data, weather data, etc., and fuel cell characteristic data, such as power output ramp curve data, operational temperature data, etc. In some embodiments, the fuel cell is started in advance of full load demand of the vehicle so that the fuel cell is capable of providing full output capacity in order to at least meet such demand.

Although exemplary embodiments of the present disclosure will be described hereinafter with reference to a heavy duty truck, it will be appreciated that aspects of the present disclosure have wide application, and therefore, may be suitable for use with many other types of vehicles, including but not limited to light and medium duty vehicles, passenger vehicles, motor homes, buses, commercial vehicles, marine vessels, etc. Accordingly, the following descriptions and illustrations herein should be considered illustrative in nature, and thus, not limiting the scope of the present invention, as claimed.

As briefly described above, embodiments of the present disclosure are directed to power systems and methods suitable for use in a vehicle.FIG. 1schematically shows a vehicle20, such as a Class 8 tractor, that comprises a powertrain system24. In the embodiment shown inFIG. 1, the powertrain24includes an internal combustion engine26, a transmission32, and a clutch assembly36. The transmission32may be a manual transmission, an automated manual transmission, or an automatic transmission that includes multiple forward gears and a reverse gear operatively connected to an output shaft42. The clutch assemblies36may be positioned between the internal combustion engine26and the transmission32to selectively engage/disengage the internal combustion engine26from the transmission32. In use, the internal combustion engine26receives fuel from a fuel source46and converts the energy of the fuel into output torque. The output torque of the engine is converted via the transmission32into rotation of the output shaft42.

The vehicle20also includes at least two axles such as a steer axle50and at least one drive axle, such as axles52and54. The output shaft42of the transmission32, which may include a vehicle drive shaft46, is drivingly coupled to the drive axles52and54for transmitting the output torque generated by the engine26to the drive axles52and54. The steer axle50is operatively coupled to a power steering system60. In one embodiment, the power steering system60includes an electrically driven steering pump. The steer axle50supports corresponding front wheels66and the drive axles52and54support corresponding rear wheels68, each of the wheels having service brake components70. In some embodiments, the service brake components include air brake components of the air brake system72, such as an electrically driven compressor, compressed air supply/return lines, brake chambers, etc. The service brake components70may also include wheel speed sensors, electronically controlled pressure valves, and the like, to effect control of the vehicle braking system.

The vehicle20may further include a cab mounted operator interface, such as a control console84, which may include any of a number of output devices88, such as lights, graphical displays, buzzers, speakers, gages, and the like, and various input devices90, such as toggle switches, push button switches, potentiometers, or the like. In some embodiments, the vehicle may further include cab or sleeper mounted electrical systems92, sometimes referred to as “house loads”, including an infotainment system94, an auxiliary A/C unit96, and/or other appliances98of convenience, such as a microwave, a coffee maker, electrical outlets for laptops, etc. In some embodiments, the infotainment system includes a navigational device having GPS or other location capability, CD/DVD or other audio/visual functionality, and optional communications system, including RF and IR based communication links. The RF capabilities of the infotainment system may include but are not limited to 802.x (e.g., 802.11, 802.15, 802.16, etc.), cellular, and Bluetooth/nearfield protocols, among others.

In order to start the internal combustion engine, and to provide power to the control console84and other cab and/or sleeper mounted electrical systems92, etc., the vehicle20also includes a power system100. The power system100in one embodiment includes a power control120and electrical energy source124. The electrical energy source124may include electrical energy storage in the form of one or more batteries126, one or more capacitors128, and combinations thereof, etc. The electrical energy source124also includes a fuel cell130, such as a solid oxide fuel cell (SOFC), to provide an additional source of electrical power for the power system100. The SOFC in one embodiment may be capable of outputting up to about 5 kilowatts of power. The batteries126can be of the lead acid, NiCd, Lithium-ion type or can include any currently known or future developed rechargeable battery technology. The batteries may include starting batteries, deep cycle batteries, combinations thereof, etc. In some embodiments, the power system may include one or more primary batteries for starting the internal combustion engine and one or more auxiliary batteries for providing power to the “house” loads, among others, during engine on and engine off conditions. In this embodiment, the auxiliary batteries may be combined with the capacitors128, the fuel cell130, etc., in order to form an APU or the like.

As will be described in more detail below, the power control120in some embodiments can be used to manage the distribution of power to the associated loads of the vehicle. Further as will be described in more detail below, the power control120may include one or more algorithms that predict energy demands of the vehicle systems, determine the energy storage levels of the electrical energy storage, and operate the power system in order to supply power to the systems of the vehicle20.

The power system100of the vehicle may also include one or more DC/DC converters to supply direct current to any suitable DC load, and may optionally include an inverter to supply alternating current to any suitable AC load. In some embodiments, the DC/DC converter reduces the voltage it receives from electrical energy storage124and/or fuel cell130, and outputs power at this lower voltage to the appropriate loads. The D/C to D/C converter or inverter can output power to other electrical devices on the vehicle20, including electric pumps, electric compressors, of the air brake system72, the power steering system60, or other vehicle systems, such as an electric PTO, etc., as will be described in more detail below. To aid in the distribution of power, additional components may be used, which are not shown but well known in the art, including distribution blocks, distribution panels, fuse blocks, relays, and/or the like.

While the vehicle20ofFIG. 1employs a powertrain utilizing an internal combustion engine as the vehicle motive force, the vehicle20depicted inFIG. 1represents only one of the many possible applications for the systems and methods of the present disclosure. It should be appreciated that aspects of the present disclosure transcend any particular type of land or marine vehicle and any type of powertrain. For example, the vehicle may employ a hybrid powertrain122, as depicted inFIG. 3.FIG. 3illustrates a hybrid powertrain of parallel-type, although hybrid powertrains of the serial-type, or combined hybrid configurations (i.e., hybrids that operate in some manner as a parallel hybrid and a serial hybrid) may also be employed.

In the embodiment shown inFIG. 2, the hybrid powertrain122includes an internal combustion engine26, an electric motor/generator28, a power transfer unit30, and a transmission32. In use, the electric motor generator28can receive electrical energy from the power system100via a high voltage DC bus40and converts the electrical energy into output torque. The electric motor generator28can also operate as a generator for generating electrical energy to be stored in the electrical energy storage. A regenerative braking state of vehicle operation may also be provided by the power transfer unit30, as known in the art.

Turning now toFIG. 3, there is shown in block diagrammatic form one example of the power control120formed in accordance with aspects of the present disclosure. As best shown inFIG. 3, the power control120includes a controller210connected in electrical communication with a plurality of data sources220. As will be described in more detail below, the data sources220may include but are not limited to navigation equipment, communications device, on-board sensors, and/or the like. It will be appreciated that the controller210can be connected directly (wired or wirelessly) to the plurality of data sources220or indirectly via a CAN240. Those skilled in the art and others will recognize that the CAN240may be implemented using any number of different communication protocols such as, but not limited to, Society of Automotive Engineer's (“SAE”) J1587, SAE J1922, SAE J1939, SAE J1708, and combinations thereof. The controller may also communicate with other electronic components of the vehicle20via the CAN240for collecting data from other electronic components to be utilized by the controller210, and as such, can also be considered in some embodiments as data sources220. For example, the controller210may receive data from one or more of an engine controller, a transmission controller, a brake system controller, among others. In operation, as will be described in more detail below, the controller210receives signals from the data sources220, processes such signals and others, and depending on the processed signals, transmits suitable control signals for operating the power system100, including the fuel cell130.

In several embodiments, the controller210may contain logic rules implemented in a variety of combinations of hardware circuitry components and programmed microprocessors to effect control of the power system100. To that end, as further illustrated inFIG. 3, one suitable embodiment of the controller210includes a memory262, a processor268, and a power control module280for providing functionality to the power control120. The memory262may include computer readable storage media in read-only memory (ROM), random-access memory (RAM), and keep-alive memory (KAM), for example. The KAM may be used to store various operating variables while the processor268is powered down. The computer-readable storage media may be implemented using any of a number of known memory devices such as PROMs (programmable read-only memory), EPROMs (electrically PROM), EEPROMs (electrically erasable PROM), flash memory, or any other electric, magnetic, optical, or combination memory devices capable of storing data, including fuel cell operational data282. In some embodiments, the controller210may include additional components including but not limited to a high speed clock, analog to digital (A/D) and digital to analog (D/A) circuitry, input/output circuitry and devices (I/O) and appropriate signal conditioning and buffer circuitry.

As used herein, the term processor is not limited to integrated circuits referred to in the art as a computer, but broadly refers to a microcontroller, a microcomputer, a microprocessor, a programmable logic controller, an application specific integrated circuit, other programmable circuits, combinations of the above, among others. In one embodiment, the processor268executes instructions stored in memory262, such as power control module280, to manage the load demand of the vehicle systems, and in turn, control the operation of the fuel cell130.

The power control module280may include a set of control algorithms, including resident program instructions and calibrations stored in one of the storage mediums and executed to provide desired functions. Information transfer to and from the power control module280can be accomplished by way of a direct connection, a local area network bus and a serial peripheral interface bus. The algorithms may be executed during preset loop cycles such that each algorithm is executed at least once each loop cycle. Algorithms stored in the non-volatile memory devices are executed by the processor to monitor inputs from the sensing devices and other data transmitting devices or polls such devices for data to be used therein. Loop cycles are executed at regular intervals, for example each 3.125, 6.25, 12.5, 25 and 100 milliseconds during ongoing operation of the vehicle. Alternatively, algorithms may be executed in response to the occurrence of an event.

Still referring toFIG. 3, the processor268communicates with various data sources220directly or indirectly via an input/output (I/O) interface286and suitable communication links. The interface286may be implemented as a single integrated interface that provides various raw data or signal conditioning, processing, and/or conversion, short-circuit protection, and/or the like. Alternatively, one or more dedicated hardware or firmware chips may be used to condition and process particular signals before being supplied to the processor268. In some embodiments, the signals transmitted from the interface286may be suitable digital or analog signals to control the fuel cell130.

As shown inFIG. 3, the controller210is a separate controller dedicated to the power system100. However, it will be appreciated that the controller210may be a power control module, which could be software embedded within an existing on-board controller, such as the engine controller, a general purpose controller, etc.

As briefly described above, the data sources220can include but are not limited to on-board sensors, a navigation/GPS device, a communications device, data stores, etc. These data sources and others in some embodiments may be part of the infotainment system94, control console84, etc., described above. The data supplied from these data sources230and others may generally or specifically relate to vehicle operating parameters, operator driving trends and accessory (e.g., house load) usage patterns and characteristics, and external parameters, including present vehicle navigation, traffic patterns, weather data, among others.

Referring now toFIG. 4, there is shown a flow diagram of one example of method carried out by the power system100, and in some embodiments, carried out by one or more control modules, such as the power control module280, when executed by the processor268. As shown inFIG. 4, the method begins at block400, and at block404, the power load demand of the vehicle20is predicted over a predetermined time, route, etc. Generally, the power load demand can be predicted during engine on and/or engine off conditions. In that regard, in some embodiments, via data sources220and others, various states of vehicle operating parameters, operator driving trends and accessory (e.g., “house loads,” etc) usage patterns, and external parameters, including present vehicle navigational data, traffic patterns, weather data, among others, are monitored. From monitoring any combination of these various parameters, a predicted power load demand for the vehicle over time is calculated, referred to herein as the predicted power load demand schedule, an example of which is shown graphically inFIG. 5as510.

The predicted power load demand schedule, as represented by line510, is an aggregate of the power demand from the various vehicle subsystems during vehicle operation. These subsystems may include but are not limited to powertrain24, control console84, “house loads” in the form of infotainment systems, appliances (coffee maker, microwave, refrigerator, cook top, washer/dryer, power outlets, etc.) and other electrically powered devices (e.g., heaters, A/C units, air compressors, electric PTOs, etc.). In some embodiments, such as those employing a hybrid powertrain, the predicted power demand schedule also includes upcoming vehicle propulsion power requirements by the electric drive motors28, etc., which may be determined with the assistance of vehicle navigation data, operator driving patterns, etc.

Operator driving patterns in some embodiments may include an average power demand, a ratio between vehicle stop time to the total driving time, etc. In other embodiments, the operator driving pattern is predicted using a driving pattern recognition function based on statistical driving cycle information that can be developed during ongoing operation of the vehicle20. This may include monitoring operator driving patterns to derive statistical driving pattern information from historical driving cycle information. In one or more embodiments, usage patterns of house loads may also be taken into consideration when calculating the predicted power load demand schedule. Again, this may be average power demand, or predicted power demand based on historical data, etc. Further, weather data can be taken into consideration regarding the use of A/C systems, auxiliary lighting, power take-offs, etc.

From block404, the method proceeds to block406, where the power storage levels of the electrical energy storage124are predicted over the same time period as the predicted power load demand schedule. In some embodiments, the predicted power storage levels is an average state of charge (SOC) of the electrical energy storage over time, an example of which is shown graphically inFIG. 5as514and518. As best shown inFIG. 5, the graph illustrates the average SOC (at 50% and 80%) of the electrical energy storage in dashed lines.

In other embodiments, the predicted power storage levels are determined by monitoring the electrical energy storage and predicting a state-of-charge trajectory for the electrical energy storage, which may include one of a charge-sustaining strategy and a charge-depleting strategy. In some embodiments, vehicle navigation data and other data can be additionally or alternatively used to predict potential power source recharging events via regenerative braking, excess alternator amperage, among others. Frequency and duration of such recharging events may impact the predicted power storage levels. It will be appreciated that in some embodiments, the output of one or more engine driven alternators may also be taken into consideration when predicting the power storage levels of the power storage device.

Next, the method proceeds to block408, where the operation schedule of one or more components of the power system100during engine on and/or engine off conditions is determined. In that regard, one or more components of the power system100may be controlled based on the results of the predictive load storage levels and the predictive power load schedule from blocks406and404, respectively.

In one embodiment, the fuel cell operational and characteristic data stored in memory262is used in conjunction with the results of the predictive load storage levels and the predictive power load schedule from blocks406and404, respectively, in order to operate (e.g., turn on; turn off, cycle, etc.) the fuel cell. For example, in some embodiments, the predicted load demand may approach or even exceed a current (e.g., amps) level corresponding to a desired minimum SOC level (e.g., 50%) of the electrical energy storage, which may in some cases affect the short-term and long term operation thereof. Accordingly, to alleviate the possible power shortage or potential harmful operating conditions of the electrical energy storage at low SOC's and to provide a more balanced supply of power, the fuel cell may be operated at strategic times during vehicle operation. The fuel cell, as known in the art, can be started by delivery of oxygen to the cathode side and delivery of fuel to the anode side of the fuel cell.

It is known that fuel cells, and particular, SOFC's, do not output maximum power at the start, but take time to “ramp up” to maximum power. For fuel cells like SOFC's, this ramp up time can occur while the fuel cell material, typically of the ceramic type, is brought up to an efficient operating temperature.

Due to such inherent ramp up power curves of fuel cells, and in particular, solid oxide fuel cells, the power module280in some embodiments, when executed by the processor268, determines a time Tmaxwhen it is desirable for the solid oxide fuel cell to be operating, for example, at its maximum output. And in turn, the power module280in some embodiments, when executed by the processor268, signals the fuel cell at the appropriate time preceding time Tmax, designated as TstartinFIG. 5, given its ramp up power characteristics represented graphically by curves522, and/or other data such as fuel cell operating parameters (e.g., fuel delivery rates, oxygen delivery rates, operating temperatures, etc.). It will be appreciated that in some embodiments, the timing is to allow the fuel cell to reach maximum output prior to possible need. In other embodiments, the control can advantageously use the power characteristics in order to time the start of the fuel cell to more closely match the additional demand. The fuel cell may then be stopped at times during the predictive power load schedule in order to conserve fuel, etc., and restarted when desired.

The principles, representative embodiments, and modes of operation of the present invention have been described in the foregoing description. However, aspects of the present invention which are intended to be protected are not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. It will be appreciated that variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes, and equivalents fall within the spirit and scope of the present invention, as claimed.