WO2023136819A1 - Built-in electrochemical hydrogen pumping for fuel cell engines - Google Patents

Abstract

Built-in electrochemical hydrogen pumping (EHP) for fuel cell engines is provided. A fuel cell engine with an electronically controlled fuel valve generates electricity for electric vehicles or for industrial uses and has built-in EHP modes available without disassembling the fuel cell engine or the vehicle hosting the fuel cell engine. The built-in EHP modes can be used to apply analytics to performance, diagnose degradation, or recondition the cell stack. Alternatively, the fuel cell engine with built-in EHP modes may connect to an external accessory unit to execute an EHP cycle without disassembly of the fuel cell engine or vehicle. The accessory unit offloads some EHP components from the fuel cell engine or vehicle. An electronic controller of the fuel cell engine or the vehicle supervises and automates built-in EHP cycles and can apply custom EHP cycles to the cell stack of the fuel cell engine.

Description

BUILT-IN ELECTROCHEMICAL HYDROGEN PUMPING

FOR FUEL CELL ENGINES

BACKGROUND

[0001] Conventional electrochemical hydrogen pumping on the cells stacks of polymer electrolyte membrane (PEM) fuel cells can be used to diagnose the health of the cell stack and sometimes even recover lost performance, but disassembling and reconfiguring a conventional fuel cell stack system to perform this procedure introduces some problems and obstacles. The fuel cell system must be removed from service, and in the case of a fuel cell electric vehicle, the fuel cell stack must be disassembled from the vehicle and mounted into a sophisticated test stand that is configured to perform the conventional electrochemical hydrogen pumping procedure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] The detailed description is set forth with reference to the accompanying figures. The use of the same reference numbers in different figures indicates similar or identical items or features.

[0003] Fig. 1 is a diagram of an example fuel cell electric vehicle hosting an EHP- capable fuel cell engine.

[0004] Fig. 2 is a block diagram of the example EHP-capable fuel cell engine of Fig. 1, in greater detail.

[0005] Fig. 3 is a diagram of subsystems of the example EHP-capable fuel cell engine of Figs. 1-2. [0006] Fig. 4 is a diagram of the example EHP-capable fuel cell engine showing electrical lines and connections of a power conditioning system of the EHP-capable fuel cell engine.

[0007] Fig. 5 is a diagram of an example external accessory unit complementary to EHP-capable fuel cell engine.

[0008] Fig. 6 is a flow diagram of a method of performing built-in electrochemical hydrogen pumping in a fuel cell engine.

[0009] Fig. 7 is a flow diagram of a method of manufacturing an EHP-capable fuel cell engine.

DETAILED DESCRIPTION

[0010] This disclosure describes built-in electrochemical hydrogen pumping (EHP) for fuel cell engines and fuel cell electric vehicles. As a maintenance measure, the EHP process can be used for analytics, diagnostics, reconditioning, and even recovery of cell stack components and fuel cell performance. As described herein, the built-in ability to perform the EHP process in-situ, onboard the fuel cell engine - without conventional disassembly of the fuel cell engine - opens the door to additional uses of the EHP process besides analytics, diagnostics, and reconditioning. The easy availability of EHP provided herein enables such additional actions as pressure testing electrode chambers, testing and calibrating sensors, periodically optimizing performance, and so forth, which can be accomplished on a schedule or whenever desired. The built-in EHP capability may also allow automating the EHP processes, to provide automatic nightly or weekly reconditioning of cathode surfaces or the PEM (electrolyte) of the cell stack. The built-in EHP capability can automatically provide ongoing preventative maintenance and keep performance optimized, in addition to providing analytics and diagnostics. This built-in EHP capability is different from conventional application of EHP on fuel cell engines, in which the fuel cell engine must be dismantled and specialty equipment assembled or gathered to perform a conventional EHP process on an as- needed basis due to the time consuming nature of the conventional process.

[0011] The example fuel cell engines described herein generate electricity for an electric vehicle or for industrial uses, while possessing components for built-in EHP modes. The various built-in EHP modes may be used to apply analytics to the performance of the fuel cell engine, to diagnose degradation of cell stack components, such as cathode, anode, and polymer electrolyte membrane (PEM), and to recondition and maintain the cell stack.

[0012] In an alternative implementation, the fuel cell engine with built-in EHP modes may connect to an external accessory unit via an interface to execute EHP cycles without disassembly of the fuel cell engine or the vehicle. The external accessory unit offloads some of the EHP components from the fuel cell engine or from the vehicle, into a single compatible unit that connects to the fuel cell engine or to the vehicle via a single interface. For example, a given external accessory unit may contain EHP power conditioning components for performing the EHP process, and may include the EHP electronic controller, thereby relieving the vehicle of carrying these components at all times. The external accessory unit may also lower the cost burden of including all of the built-in EHP components in the manufacture of every vehicle, since the accessory unit connects easily to each vehicle, and to many different types of vehicles in turn, as desired.

Example Systems

[0013] Fig. 1 shows an EHP-capable fuel cell engine 100 in an example fuel cell electric vehicle (FCEV) 102, both manufactured with the ability to perform in-situ EHP cycles on a cell stack of the EHP-capable fuel cell engine 100. The subsystems of the EHP- capable fuel cell engine 100 in the vehicle 102 are manufactured to provide built-in EHP cycles for analytic, diagnostic, and reconditioning / recovery purposes.

[0014] The example FCEV 102 (“vehicle”) has a high-pressure supply of hydrogen gas 104 used as fuel for the EHP-capable fuel cell engine 100. One or more high voltage batteries 106 store energy from the EHP-capable fuel cell engine 100, and sometimes reclaim energy generated from braking as electrical energy for battery storage. The one or more high voltage batteries 106 may provide supplemental power to the electric (traction) motor 108 via the power distribution unit 110 of the vehicle 102. The main source of electric power for the electric motor 108 powering propulsion of the vehicle 102 is the EHP-capable fuel cell engine 100. The power distribution unit 110 of the vehicle 102 directs various high voltage electric currents of the EHP-capable fuel cell engine 100, high voltage batteries 106, and electric motor 108 along a high voltage power bus 112.

[0015] The layout of components in the example vehicle 102 of Fig. 1 is only one example for the sake of introduction. The various components of the example vehicle 102 may be arranged in numerous different layouts and may have many more incidental components not shown in Fig. 1. For example, the vehicle 102 may have a low voltage battery (e.g., 12 volts) to power conventional automotive functions. The low voltage battery (not shown) may be charged by a DC/DC step down transformer from the EHP-capable fuel cell engine 100 and/or from the high voltage batteries 106. The supply of high-pressure hydrogen gas 104 (gas tank) may have a filler port on the outside of the vehicle 102 to replenish the supply of hydrogen gas 104.

[0016] Each of the major components shown in Fig. 1 may have numerous subcomponents. For example, the EHP-capable fuel cell engine 100 has its own inherent electrical system, and may have its own electronics, including one or more DC/DC converters or “power conditioning system” to modify the voltage and/or current of the electricity it generates for the power distribution unit 110, for the electric motor 108, for the high voltage batteries 106, or for performing an EHP process. The DC/DC converter(s) of the EHP- capable fuel cell engine 100 are to be differentiated from the power distribution unit 110 of the vehicle 102. The power distribution unit 110 of the vehicle 102 may be in communication with the DC/DC converters of the EHP-capable fuel cell engine 100 and call for specific voltages and currents from the EHP-capable fuel cell engine 100 depending on the state of the vehicle: starting, accelerating, maintaining highway speed, braking, decelerating, idling, stopping, and so forth.

[0017] Fig. 2 shows the example EHP-capable fuel cell engine 100 in greater detail. Each cell of a fuel cell stack 200 has an anode 202 and a cathode 204 on either side of an intervening polymer electrolyte membrane (PEM) 206. A fuel processing system 208 for providing the hydrogen gas 104 to the fuel cell stack 200 has an electronically controlled fuel valve 210 and may have other valves capable of assuming a valve configuration 212 for EHP mode.

[0018] An air processing system 214 for providing oxygen to the fuel cell stack 200 has a blower 216, turbocharger, or compressor for injecting air (including oxygen) into the fuel cell stack 200. The air processing system 214 has valves capable of assuming an EHP mode valve configuration 218.

[0019] An exhaust system 220 determines the disposition of a water vapor end product of the fuel cell stack 200 during operation, and in some implementations may have plumbing to recirculate unreacted hydrogen gas 104 back to the anodes 202 of the fuel cell stack 200 in conjunction with the fuel processing system 208. The exhaust system also has valves capable of assuming an EHP mode valve configuration 222. [0020] An electronic controller 224 of the EHP-capable fuel cell engine 100 manages and supervises all the operations of the EHP-capable fuel cell engine 100 during routine operation. In an implementation, the electronic controller 224 has a discrete EHP controller 226 that configures: the first valves of the fuel processing system 208, including the electronically controlled fuel valve 210, the second valves of the air processing system 214, and the third valves of the exhaust system 220 into the EHP mode valve configurations 212, 218, 222 via electronic signals, directives, or instructions. The EHP controller 226 of the overall electronic controller 224 also communicates in detail with the power conditioning system 228 of the EHP-capable fuel cell engine 100 to perform an EHP cycle.

[0021] The power conditioning system 228 of the EHP-capable fuel cell engine 100 has one or more DC/DC converters 230 and an EHP power manager 232. The power conditioning system 228 of the EHP-capable fuel cell engine 100 is not the same component as the power distribution unit 110 of a vehicle 102 that may be hosting the EHP-capable fuel cell engine 100. However, the power conditioning system 228 of the EHP-capable fuel cell engine 100 and the power distribution unit 110 of the vehicle 102 may share, swap, or mutually coordinate some power functions, depending on implementation.

[0022] The example EHP-capable fuel cell engine 100 may also have a cooling system 234, including a water circulator 236 and cooling plates, for example, among the heatproducing anodes 202 and cathodes 204 of the EHP-capable fuel cell engine 100. In routine operation, and during an EHP mode, the EHP-capable fuel cell engine 100 produces heat, which usually must be heat-sinked, cooled, and/or dissipated, or else utilized in some way to prevent destructive heat damage to components of the EHP-capable fuel cell engine 100.

[0023] During routine operation of the EHP-capable fuel cell engine 100 producing electric power, the fuel processing system 208 supplies the hydrogen gas 104 to the anodes 202 of the fuel cell stack 200 at well-calculated pressures. The fuel processing system 208 may also filter the hydrogen gas 104 prior to entry of the hydrogen gas 104 into valves of the fuel processing system 208. In an implementation, the fuel processing system 208 may control the pressure of the hydrogen gas 104 at the anodes 202 in real time along a continuum of possible pressure values, based on the current states and power requirements of the vehicle 102 or other non-vehicular load being powered by the EHP-capable fuel cell engine 100.

[0024] In an implementation, the pressure of the hydrogen gas 104 at the anodes 202 is precision-controlled by the electronically controlled fuel valve 210. The electronically controlled fuel valve 210 has a variable orifice that is fully adjustable to any opening size via electronic control. The size of the opening provided by the variable orifice of the electronically controlled fuel valve 210 can be any diameter along a continuum from fully open to fully closed. The electronically controlled fuel valve 210 and the opening size of its orifice may be electrically actuated by a solenoid, servo, linear actuator, rotary actuator, and so forth. In an example implementation, a small electric motor drives a train of reduction gears with a potentiometer connected to the mechanical output shaft, for example. Electronics provide a closed-loop servomechanism for variably actuating the electronically controlled fuel valve 210 to any size opening along the continuum, from fully open to fully closed. Other mechanisms may be used to electronically control the orifice size of the electronically controlled fuel valve 210. The electronically controlled fuel valve 210 may be under dynamic control of the electronic controller 224 based on: feedback from one or more pressure sensors and/or pressure transmitters in one or more of the fuel line segments of the fuel processing system 208, current power requirements of the vehicle 102 and its electric motor 108, various states of the vehicle 102, directives from the EHP controller 226 during an EHP mode or cycle, feedback from one or more other pressure sensors and/or pressure transmitters in the air processing system 214 and exhaust system 220, and temperature information from the cooling system 234, among other parameters that may be polled to determine a current orifice size. Other sensor inputs and state information may also enter into control directives for the electronically controlled fuel valve 210.

[0025] Fig. 3 shows a schematic diagram of the example EHP-capable fuel cell engine 100 presented in Figs. 1-2, including various flow lines and valves for gases. The approximate domains of the fuel processing system 208, air processing system 214, and exhaust system 220 are shown in dashed boxes.

[0026] The example fuel processing system 208 includes a hydrogen gas filter 302 in a flow line to the anode 202. For hydrogen gas 104 entering the fuel processing system 208, the flow line has a pressure sensor/transmitter 304, and a temperature sensor/transmitter 306 providing input to the electronic controller 224 and EHP controller 226. A flow valve 308 allows hydrogen gas 104 into the flow line or closes off the supply of hydrogen gas 104. The electronically controlled fuel valve 210 provides precision-control of pressure of the hydrogen gas 104 at the anode 202 during routine operation of the EHP-capable fuel cell engine 100 and provides precision-control of pressure of the hydrogen gas 104 at both the anode 202 and the cathode 204 during an EHP cycle.

[0027] Although the EHP controller 226 has electronic control lines to most of the components in Fig. 3, the control line 314 between the EHP controller 226 and the electronically controlled fuel valve 210 is shown explicitly in Fig. 3 to underscore the role of the electronically controlled fuel valve 210 during an EHP mode. During routine operation generating electric power, the EHP-capable fuel cell engine 100 is programmed to always maintain a higher pressure of the hydrogen gas 104 at the anode than the pressure of the oxidant (air) at the cathode 204. This provides basic functionality, control, and safety for fuel cells in general, but during an EHP cycle, hydrogen gas 104 is present at the same pressure at both anode 202 and cathode 204. In this scenario, the electronic controller 224 that is not in EHP mode tries to raise the pressure of the hydrogen gas 104 at the anode 202 to keep that pressure higher than the pressure at the cathode 204, but in an EHP mode, this again raises the pressure at the cathode 204 creating a runaway pressure feedback loop as the electronic controller tries to keep the pressure at the anode 202 higher that at the cathode 204. A conventional mechanical fuel regulator valve cannot overcome this runaway pressure feedback loop, or at least cannot provide the pressure control needed for an EHP process without retrofitting numerous impractical mechanical parts, but the variable orifice of the electronically controlled fuel valve 210, described herein, that is electronically adjustable to any opening size provides the pressure control that makes EHP feasible as a built-in capability of the EHP-capable fuel cell engine 100.

[0028] In an implementation, the fuel processing system 208 also has a second pressure sensor/transmitter 310 downstream from the electronically controlled fuel valve 210, thereby providing the pressure of the hydrogen gas 104 at the surface of the anodes 202. The fuel processing system 208 also has a purge valve 312 on the exhaust side of the anodes 202, adjustable to provide backpressure and/or exhaust flow of unused hydrogen gas 104. In some implementations, the fuel processing system 208 has a recirculation loop (not included in Fig. 3) to return unreacted hydrogen gas 104 back to the inputs of the anodes 202 to be used as fuel.

[0029] The example air processing system 214 has an air filter 316 in a flow line to the cathodes 204. Air entering the air processing system 214 via the air filter 316 is inducted into the blower 216 (or turbocharger or compressor). An air pressure sensor/transmitter 318 resides in the flow line between the blower 216 and the cathode 204. During routine operation of the EHP-capable fuel cell engine 100 generating electric power, the air pressure is controlled to provide stoichiometric reaction ratios with the amount of hydrogen gas 104 being consumed at the anodes 202, and to provide a slightly higher pressure of the hydrogen gas 104 at the anode 202 than the pressure of the air at the cathode 204. A second air pressure sensor/transmitter 320 of the air processing system 214 may be situated in the exhaust flow line coming from the cathodes 204, providing an exhaust pressure value to the electronic controller 224. The air processing system 214 may have a bypass loop 322 with a cathode bypass valve 324 to partially offload volumes of air incoming to the blower 216 and the cathode 204.

[0030] The exhaust system 220 may handle the gaseous outputs from the anodes 202 and from the cathodes 204 in various ways. The combined outputs contain air and some hydrogen gas 104; and water vapor as a reaction product of the energy/electri city /heat power production. The exhaust system 220 has an exhaust valve also known as the cathode exhaust valve 326.

[0031] The electronic controller 224 manages the operation of the EHP-capable fuel cell engine 100, and supervises the various states of the components, the production of electricity between anodes 202 and cathodes 204 of the fuel cell stack 200 (not shown as such in Fig. 3), and the pressures of the gases in the system: hydrogen gas 104 as fuel, air containing oxygen as oxidant, and water vapor. The power conditioning system 228 of the EHP-capable fuel cell engine 100, and elements of the cooling system 234, are not shown in Fig. 3. The EHP-capable fuel cell engine 100 may have cooling plates adjacent to anodes 202 and cathodes 204. Instances of the PEM 206 (electrolyte) between each anode 202 and cathode 204 are also not shown in Fig. 3.

EHP Modes of the EHP-Capable Fuel Cell Engine

[0032] In an example EHP mode described below, the EHP controller 226 configures the EHP-capable fuel cell engine 100 to move hydrogen ions (H⁺) from the cathode side to the anode side of the fuel cell stack 200 through the PEM 206. This direction of movement of the hydrogen ions may run counter to the routine direction of the hydrogen ion transport from anode side to cathode side during power production. But this reversal of usual hydrogen ion transport may be used to reverse some cumulative polarizations and oxidations on the electrode surfaces and in the PEM 206 that create resistance to operation and degradation of performance over time. Such EHP modes can therefore be used to recover or recondition these elements of the fuel cell stack 200 or can be used for analytics and diagnostics. In other example EHP modes, the hydrogen ions may be pumped in the same direction through the PEM 206 as during routine operation of the EHP-capable fuel cell engine 100.

[0033] In one implementation, the EHP controller 226 begins an EHP cycle by closing the cathode exhaust valve 326, opening the cathode bypass valve 324, and running the (cathode) air blower 216 of the air processing system 214 at a predetermined speed. This valve configuration 218 of the cathode bypass valve 324 of the air processing system 214, and valve configuration 222 of the cathode exhaust valve 326 of the exhaust system 220 creates a circular loop from the inlet of the cathode 204 to the exit, or outlet, of the cathode 204 in which no new air is introduced into the loop because no air is being consumed by the EHP-capable fuel cell engine 100 during EHP processes. The fuel purge valve 312 of the anode 202 in the fuel processing system 208 is opened to introduce hydrogen gas 104 into the circulation loop formed by the states of the other valves. This valve configuration 212 of the fuel purge valve 312 of the fuel processing system 208 raises the cathode side pressure of the hydrogen gas 104 to almost the same pressure as on the anode side, and to a pressure above the outside ambient atmospheric air pressure. This pressure gradient with respect to ambient atmospheric pressure further ensures that no new air (oxygen) is introduced into the system during an EHP cycle. Adding oxygen at this point would result in rapid and uncontrolled reactions at the catalyst sites of the anode 202 and cathode 204. Without adequate heat removal from the cooling system 234, this would lead to severe damage to the components of the EHP-capable fuel cell engine 100, and possibly to fire.

[0034] With hydrogen gas 104 at both the anode 202 and cathode 204 during the EHP cycle being described, the EHP controller 226 supervises the electronically controlled fuel valve 210 to automatically maintain a proper pressure of the hydrogen gas 104 for the EHP process using electronic signals and feedback from sensors 310, 320, 318, for example. Since the variable orifice of the electronically controlled fuel valve 210 can adaptively respond in proportion to pressure changes of the hydrogen gas 104, the pressure at the anode 202 and cathode 204 remains at a controlled level. Mechanical/physical fuel regulators of conventional fuel cell engines cannot perform this task in a practical manner.

[0035] Fig. 4 shows the example EHP-capable fuel cell engine 100 with electrical lines and connections of the power conditioning system 228 of the EHP-capable fuel cell engine 100. Components of the power conditioning system 228 used to perform an EHP cycle in the EHP-capable fuel cell engine 100 may also reside outside the EHP-capable fuel cell engine 100 depending on implementation. For example, one or more DC/DC converters 230 may reside in the power distribution unit 110 of the vehicle 102 (Fig. 1), or in an external accessory unit to be described below.

[0036] In a preferred embodiment, the EHP power manager 232 of the power conditioning system 238 applies a DC current via the DC/DC converter(s) 230 at a reverse polarity to that used for routine power generation in the EHP-capable fuel cell engine 100. In an implementation, the power conditioning system 238 and its DC/DC converter(s) 230 are bidirectional, possessing the ability to apply a DC current to the anodes 202 and cathodes 204 in either direction, with switchable lead polarities. The example EHP-capable fuel cell engine 100 may provide different EHP modes for applying different types of EHP cycles to the fuel cell stack 200. Example Electrochemical Hydrogen Pumping (EHP) Cycles

[0037] Electrochemical hydrogen pumping in general is the process of moving hydrogen ions from one side of the PEM 206 (electrolyte) to the other side using electrical energy. Since the hydrogen gas 104 ionizes and deionizes at the electrodes during EHP, the net effect is transport of the hydrogen gas 104 from the anode side to the cathode side (or vice versa) through the PEM 206 (electrolyte). The amount of energy required, and the amount of hydrogen moved, is dependent upon the voltage and current applied. The direction of movement, that is, from anode to cathode or from cathode to anode, is dependent upon the polarity of the current applied.

[0038] In routine operation, a fuel cell stack 200 is the source of electrical energy during fuel cell operation: hydrogen gas 104 (the fuel) releases electrons on the anode side of the fuel cell creating an electron flow for an electrical circuit:

dewhile the hydrogen ions (also known as hydrogen cations, hydrons, protons, or H⁺) travel through the PEM 206 (electrolyte) to the cathode 204 to combine with oxide anions being formed by reduction of oxygen gas at the cathode 204. The reduction of the oxygen is accomplished by the electrons that were generated at the anode 202 and have flowed through an electrical circuit (wires) of the vehicle 102 or other electrical load:

From the two electrochemical half-reactions above, the overall chemical reaction of the EHP- capable fuel cell engine 100 in generating electric power is a combination of the hydrogen gas 104 with oxygen gas through the agency of the fuel cell stack 200, resulting in electricity, water vapor, and heat:

2H₂ + O₂ - 2H₂O vapor + electron flow + heat [0039] Electrochemical hydrogen pumping (EHP), on the other hand, does not form or dissociate water, and so does not combine hydrogen gas with oxygen via the fuel cell. Instead, an electric current is applied to the fuel cell stack 200 to drive EHP, as opposed to the fuel cell stack 200 generating electricity during routine operation. During one example mode of an EHP cycle, the negative (anode) lead of a DC current mediated by the power conditioning system 228 is connected to the cathode side of the fuel cell stack 200 in the presence of hydrogen gas 104, and the positive (cathode) lead of the DC current is connected to the anode side of the fuel cell stack 200, also in the presence of the hydrogen gas 104. The power source of the DC current may be the high voltage batteries 106 of the vehicle 102, as mediated by the DC/DC converter(s) 230, or the power source may be external to the vehicle, as when one type of external accessory unit is used to interface with the vehicle 102 and perform the EHP process.

[0040] The DC current applied by the power conditioning system 228 during an EHP cycle moves electrons through the fuel cell stack 200 and transports hydrogen ions (H⁺) through the PEM 206, instead of the fuel cell stack 200 generating electric current and transport of ions as during routine operation of the EHP-capable fuel cell engine 100.

[0041] In each EHP cycle, applying DC current to the fuel cell stack 200 causes the hydrogen gas 104 at whichever electrode is connected to the positive lead of the DC current, to give up electrons (electrochemical oxidation) to become hydrogen ions:

The hydrogen ions (H⁺) travel through the PEM 206 of the fuel cell stack 200 to whichever electrode is connected to negative polarity of the DC current applied, where the hydrogen ions recombine with electrons from the DC current applied (electrochemical reduction) to become hydrogen gas again:

The overall net reaction during electrochemical hydrogen pumping is: H2 gas (positive electrode)

H2 gas (negative electrode) with hydrogen ions migrating through the PEM 206 toward the negative electrode. When the negative electrode during EHP is the usual anode 202 of the fuel cell stack 200, this migration of hydrogen ions in a reverse direction of their usual flow during power generation can recondition the PEM 206 and electrodes by reversing accumulated charge polarities and reversing accumulated oxidation corrosion at electrode surfaces.

[0042] When the fuel cell is operating to produce electric power, the chemical reactions and transport of hydrogen ions across the PEM 206 may create various polarizations in the materials of the fuel cell stack 200, in which charged species become fixed in the solid aspects of the PEM 206 and the electrodes 202, 204, not to mention other possible unintended corrosions and oxidations of the material elements. These changes may be miniscule but accumulate over time during regular use of the fuel cell stack 200. Thus, the performance of the fuel cell stack 200 may degrade slowly over time. When the flow of hydrogen ions is driven in a reverse direction through the PEM 206 by an externally applied DC current, this reversal tends to break down resistances to ion flow that have built up over time, and reverse accumulated polarizations, oxidations, and corrosions, however miniscule, but widespread throughout the fuel cell stack 200. The EHP process may rejuvenate or “recharge” the performance of the fuel cell to some degree, in addition to providing analytic and diagnostic tools to study the condition of the electrodes 202, 204 and PEM 206.

[0043] The EHP cycles applied can be used as an analytical tool for determining fuel cell and electrode performances at anodes 202 and cathodes 204 through various electrical measurements taken before, during, and after an EHP cycle. The EHP cycles may also be used in the same way for diagnostics: to determine causes for a decrease in performance of the fuel cell stack 200. [0044] An electrochemical hydrogen pumping cycle is a period or “session” of electrochemical hydrogen pumping. As used herein, such an EHP cycle may include applying the DC current with either polarity, or with both polarities in alteration: 1) negative DC current lead of the power source connected to the usual cathode 204 of the fuel cell stack 200, to drive hydrogen ions across the PEM 206 from the usual anode 202 of the fuel cell towards the usual cathode 206 of the fuel cell (conventional direction); or 2) negative DC current lead connected to the usual anode 202 of the fuel cell stack 200, to drive the hydrogen ions across the PEM 206 from the usual cathode 204 of the fuel cell stack 200 towards the usual anode 202 of the fuel cell stack 200; or 3) alternating polarity, in which the polarity of the DC current is switched back and forth at a selected frequencies or time intervals.

[0045] A unidirectional EHP cycle (of single polarity) may be applied over a waveform, such as a sine wave to gradually increase and decrease voltage or current at a selected frequency during the cycle, or in a square wave to apply the voltage or current in an on-off pattern of selected amplitude and frequency. Likewise, a bidirectional EHP cycle may be applied in a sine wave or a square wave, with polarity reversing at each wave, or at each integral number or count, of the applied waves. Of course, the EHP cycle may consist of DC current applied in only one polarity direction, in one on-off cycle as a default. Each wave of a waveform described above, applied in a unidirectional EHP cycle or a bidirectional EHP cycle, may be microseconds, seconds, minutes, or hours long, depending on the purpose of the EHP cycle applied.

[0046] When the EHP-capable fuel cell engine 100 is relatively self-contained, then only a power source (external to the EHP-capable fuel cell engine 100) is needed to perform an EHP cycle on the fuel cell stack 200 of the EHP-capable fuel cell engine 100. In this scenario, an EHP-capable fuel cell engine 100 residing in a vehicle 102 may use energy from the high voltage batteries 106 of the vehicle 102 supplied via the high voltage power bus 112 and the power distribution unit 110 of the vehicle 102 to power the EHP cycle. The power conditioning system 228 of the EHP-capable fuel cell engine 100 possesses the ability to reverse the polarity of DC power received over the high voltage power bus 112 of the vehicle 102, for purposes of performing the EHP process.

[0047] Fig. 5 shows an example external accessory unit 500 complementing the EHP- capable fuel cell engine 100 via an interface 502 hook-up between the two. The external accessory unit 500 may contain some components that would otherwise be built into the EHP-capable fuel cell engine 100 or the vehicle 102 for performing EHP. The external accessory unit 500 assists the EHP-capable fuel cell engine 100 in performing EHP, and also offloads components from the EHP-capable fuel cell engine 100 or from the vehicle 102. The external accessory unit 500 may streamline the vehicle and lower the cost burden of including all the components to perform EHP within every manufactured vehicle 102, since a single external accessory unit 500 can temporarily connect one-at-a-time to numerous vehicles, to perform EHP when desired.

[0048] When the EHP-capable fuel cell engine 100 does not reside in a vehicle 102, but resides in some other industrial setting, the external accessory unit 500 contains or utilizes a power supply 504 external to the EHP-capable fuel cell engine 100 to power the EHP process, instead of using the high voltage batteries 106 built into a vehicle 102. When the EHP-capable fuel cell engine 100 resides in a vehicle 102, but uses the external accessory unit 500 for EHP, the external accessory unit 500 may use either the high voltage batteries 106 of the vehicle 102 to power the EHP process or an external power source, or its own power supply 504 depending on implementation. The external accessory unit 500 may plug into a wall socket to utilize external power from the commercial power grid.

[0049] When the external accessory unit 500 for assisting EHP contains or utilizes a power source or power supply 504 external to the vehicle 102, the power conditioning system 228 of the EHP-capable fuel cell engine 100 residing in the vehicle 102 may have the ability to electrically isolate the EHP-capable fuel cell engine 100 from the high voltage power bus 112 and high voltage batteries 106 of the vehicle. This electrical isolation may be accomplished via nonconducting materials and electromechanical relays or other electronic circuits for disconnecting the fuel cell stack 200 of the EHP-capable fuel cell engine 100 from the usual electrical connections of the power conditioning system 228 used during routine power generation.

[0050] Whether built into the power conditioning system 228 or offloaded to an external accessory unit 500, the DC/DC converter(s) 230 may be specially-purposed for applying EHP to the fuel cell stack 200. This means the DC/DC converter(s) 230 for EHP are capable of applying DC current at amperage and voltage levels needed to drive EHP processes, and at a desired polarity. In most implementations, the DC/DC converter(s) 230 for EHP are capable of switching polarity of the DC current applied to the fuel cell stack 200, under control of the EHP power manager 232.

[0051] The external accessory unit 500 for performing EHP on an EHP-capable fuel cell engine 100 may also contain the EHP controller 226, or an instance of the EHP controller 226 if there is also an instance built into the EHP-capable fuel cell engine 100 being serviced. The external accessory unit 500 may also contain the hardware and software of various analytic tools 506 and diagnostic tools 508 directed to electrical measurements of the fuel cell stack 200 and the EHP-capable fuel cell engine 100 before, during, and after an EHP session performed by the external accessory unit 500.

[0052] The example interface 502 shown in Fig. 5 for connecting the external accessory unit 500 to the EHP-capable fuel cell engine 100 may reside on the EHP-capable fuel cell engine 100, under the hood (for example) of a vehicle 102, under or on the body or chassis of the vehicle 102, or on the external accessory unit 500, if an example unified EHP cable 510 is detachable at both ends. The example unified EHP cable 510 may include high capacity, high amperage DC leads and communication wires to establish communication between the external accessory unit 500 and the EHP-capable fuel cell engine 100 and/or the vehicle 102. The example interface 502 shown in Fig. 5 has a plug receptacle 512 with jacks for communication wires and jacks for DC power leads of the unified EHP cable 510.

[0053] In an implementation, the EHP-capable fuel cell engine 100 is provided with a fully-isolated bi-directional DC/DC converter 230 in the power conditioning system 228. The power conditioning system 228 is connectable to the high voltage power bus 112 of the vehicle 102. The high voltage batteries 106 of the vehicle 102 are requested to connect to the high voltage power bus 112, providing the electrical energy to perform the EHP process via the power conditioning system 228. The amount of DC power, i.e., current at a given polarity, and at a given voltage, to be applied in an EHP session depends on the size of the fuel cell stack 200 of the EHP-capable fuel cell engine 100 being serviced, and on many other factors, such as the EHP mode selected. In one EHP mode, the EHP power manager 232 applies a predetermined amount of current, such as 1.0 A/cm², to the cell stack by carefully raising the voltage, for example from 0 volts/cell to 0.1 volts/cell. When the goal is to move hydrogen ions from the cathode 204 to the anode 202 for reconditioning one or more elements of the fuel cell stack 200, the polarity of the DC current applied is reversed from that of routing fuel cell operation, and DC current moves in the opposite direction from the direction operative when the EHP-capable fuel cell engine 100 is generating electric power.

[0054] The EHP controller 226, which supervises and/or automates each EHP session, may reside in the electronic controller 224 of the EHP-capable fuel cell engine 100, or in the engine control module of a vehicle hosting the EHP-capable fuel cell engine 100, or in the external accessory unit 500, depending on implementation. The logic manufactured into the EHP controller 226 may be state machine-based, with permissives to move from state to state. A fault detection system of the electronic controller 224 during an EHP session may also be state-based, with different faults active or not active based upon the current state, each fault having defined conditions. The EHP controller 226 may be commanded into beginning an EHP session either by an automated process, or manually via a user interface. The EHP controller 226 monitors and controls the EHP process during each EHP session. The electronic controller 224, whether onboard the EHP-capable fuel cell engine 100, the vehicle 102, or the external accessory unit 500, may record and translate the results of an EHP session being applied for analytics, diagnostics, or for reconditioning of the fuel cell stack 200.

Example Processes

[0055] Fig. 6 shows an example method 600 for performing built-in electrochemical hydrogen pumping in a fuel cell engine. In the flow diagram of Fig. 6, operations of the example method 600 are shown in individual blocks. The order in which the operations are described in the example method 600 is not intended to be construed as a limitation, and any number of the described blocks can be combined in any order and/or in parallel to implement the process.

[0056] At block 602, an electronic controller is programmed to execute directives for performing electrochemical hydrogen pumping in a fuel cell engine.

[0057] At block 604, one or more valve states of a fuel processing system of the fuel cell engine are actuated to expose an anode and a cathode of the fuel cell engine to hydrogen gas, based on a first directive from the electronic controller.

[0058] At block 606, one or more valve states of an air processing system of the fuel cell engine are actuated to expose the anode and the cathode of the fuel cell engine to the hydrogen gas, based on a second directive from the electronic controller. In an implementation, the same second directive or another directive from the electronic controller may adjust a running speed of a blower, turbocharger, or compressor of the air processing system to assist maintaining a pressure of the hydrogen gas at the anode and the cathode above the ambient atmospheric pressure.

[0059] At block 608, one or more valve states of an exhaust system of the fuel cell engine are actuated to expose the anode and the cathode of the fuel cell engine to the hydrogen gas, based on a third directive from the electronic controller.

[0060] At block 610, a DC current is applied at the anode and the cathode at a selected polarity to drive an electrochemical hydrogen pumping process across a polymer electrolyte membrane (PEM) of the fuel cell stack, based on a fourth directive from the electronic controller.

[0061] Fig. 7 shows an example process 700 for making an EHP-capable fuel cell engine. In the flow diagram of Fig. 7, operations of the example process 700 are shown in individual blocks. The order in which the operations are described in the example process 700 is not intended to be construed as a limitation, and any number of the described blocks can be combined in any order and/or in parallel to implement the process.

[0062] At block 702, a cell stack is obtained for making a fuel cell engine, the cell stack capable of producing electric power from hydrogen gas.

[0063] At block 704, a fuel processing system is joined with the cell stack, wherein the fuel processing system comprises one or more first valves operable to expose an anode and a cathode of the cell stack to the hydrogen gas in order to render the fuel cell engine capable of performing an electrochemical hydrogen pumping (EHP) process. The one or more first valves include an electronically actuated fuel valve possessing a variable orifice that can open to any diameter between a fully open state and a fully closed state. The electronically actuated fuel valve dynamically controls a pressure of the hydrogen gas at the anode and the cathode as directed by electronic signaling.

[0064] At block 706, an air processing system is joined with the cell stack, wherein the air processing system comprises one or more second valves operable to expose the anode and the cathode to the hydrogen gas in coordination with the one or more first valves.

[0065] At block 708, an exhaust system is joined with the cell stack, wherein the exhaust system comprises one or more third valves operable to expose the anode and the cathode to the hydrogen gas in coordination with the one or more first valves and the one or more second valves.

[0066] At block 710, a power conditioning system is joined with the cell stack, wherein the power conditioning system is capable of applying an electric current from a power source to the anode and the cathode at an amperage and a voltage capable of driving the electrochemical hydrogen pumping process across a polymer electrolyte membrane (PEM) of the cell stack.

[0067] The example process 700 may include joining a power conditioning system capable of utilizing a battery of a vehicle hosting the fuel cell engine as the power source for EHP. The example process 700 may also include j oining a power conditioning system capable of connecting with a power supply of an external accessory unit as the power source. [0068] The example process 700 may further include joining the power conditioning system in a manner that enables electrically isolating the cell stack and the power conditioning system from electrical connections adverse to performing the electrochemical hydrogen pumping process. The power conditioning system may selectively apply the electric current either with a first DC polarity or with a second DC polarity, the first DC polarity being applied via a negative lead of the power source connected to the cathodes of the cell stack and a positive lead of the power source being connected to the anodes of the cell stack. The second DC polarity is applied via a negative lead of the power source being connected to the anodes of the cell stack and a positive lead of the power source being connected to the cathodes of the cell stack.

[0069] The power conditioning system may apply the electric current to the anodes and the cathodes as a DC current in various waveforms or application patterns: such as a sine wave voltage pattern at constant current, a sine wave current pattern at constant voltage, a square wave voltage pattern at constant current, or a square wave current pattern at constant voltage. These waveform patterns of applying the DC current drive the electrochemical hydrogen pumping process across the polymer electrolyte membrane (PEM) of the cell stack and may be used for various analytic, diagnostic, and recovery / reconditioning purposes.

[0070] The process 700 may further include joining an electronic controller to the EHP- capable fuel cell engine to perform various EHP processes in various modes. The electronic controller operates the one or more first valves of the fuel processing system, the one or more second valves of the air processing system, the one or more third valves of the exhaust system, and the power conditioning system to perform the electrochemical hydrogen pumping process across the polymer electrolyte membrane (PEM) of the EHP-capable fuel cell engine. The electronic controller may dynamically supervise the electronically controlled fuel valve of the fuel processing system in real time, based on sensor inputs of pressure, temperature, and other parameters. The other parameters by which the electronic controller may dynamically control the size of the orifice of the electronically controlled fuel valve in real time, may include current states of a vehicle or states of the fuel cell engine, applied DC current characteristics during an EHP session, the selected EHP mode, EHP algorithms, feedback from diagnostic tools, feedback from analytic tools, fuel supply pressure, degree of PEM recovery, degree of electrode recovery, and so forth. [0071] The process 700 may include joining the electronic controller as part of the fuel cell engine, as part of an engine control module or electronic control unit of a vehicle hosting the fuel cell engine, or as part of an external accessory unit connectable to the fuel cell engine via an interface, for performing EHP processes.

[0072] In the foregoing specification, embodiments of the invention have been described with reference to numerous specific details that may vary from implementation to implementation. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. The sole and exclusive indicator of the scope of the invention, and what is intended by the applicants to be the scope of the invention, is the literal and equivalent scope of the set of claims that issue from this application, in the specific form in which such claims issue, including any subsequent correction.

Claims

CLAIMS What is claimed is:

1. An apparatus, comprising: a fuel cell engine for producing electric power from a hydrogen gas; a cell stack of the fuel cell engine; a fuel processing system of the fuel cell engine with one or more first valves operable to expose an anode of the cell stack and a cathode of the cell stack to the hydrogen gas, the one or more first valves including an electronically actuated fuel valve possessing a variable orifice for dynamically controlling a pressure of the hydrogen gas at the anode and the cathode; an air processing system of the fuel cell engine with one or more second valves operable to expose the anode and the cathode to the hydrogen gas in cooperation with the one or more first valves; an exhaust system of the fuel cell engine with one or more third valves operable to expose the anode and the cathode to the hydrogen gas in cooperation with the one or more first valves and the one or more second valves; and a power conditioning system of the fuel cell engine capable of applying an electric current to the anode and the cathode at an amperage and a voltage capable of driving an electrochemical hydrogen pumping process across a polymer electrolyte membrane (PEM) of the cell stack.

2. The apparatus of claim 1, further comprising an electronic controller to supervise operations of the one or more first valves of the fuel processing system, the one or more second valves of the air processing system, the one or more third valves of the exhaust

25 system, a blower, turbocharger, or compressor of the air processing system, and the power conditioning system to perform the electrochemical hydrogen pumping process across the polymer electrolyte membrane (PEM) of the fuel cell engine.

3. The apparatus of claim 2, wherein the electronic controller comprises an electronic control unit onboard or native to the fuel cell engine.

4. The apparatus of claim 2, wherein the electronic controller comprises an engine control module or an electronic control unit of a vehicle hosting the fuel cell engine.

5. The apparatus of claim 2, wherein the power conditioning is capable of: electrically isolating the power conditioning system and the cell stack from electrical connections adverse to performing the electrochemical hydrogen pumping process, based on a first directive from the electronic controller; and applying the electric current via electrical connections to the anode and the cathode at the amperage and the voltage to drive the electrochemical hydrogen pumping process across the polymer electrolyte membrane (PEM) of the cell stack, based on a second directive from the electronic controller.

6. The apparatus of claim 1, wherein the power conditioning system is capable of utilizing a battery of a vehicle hosting the fuel cell engine as a power source for driving the electrochemical hydrogen pumping process, or the power conditioning system is capable of connecting with a power supply of an external accessory unit as the power source for driving the electrochemical hydrogen pumping process.

7. The apparatus of claim 6, wherein the electronic controller for performing the electrochemical hydrogen pumping process also resides in the external accessory unit.

8. The apparatus of claim 1, wherein the power conditioning system selectively applies the electric current either with a first DC polarity or a second DC polarity, the first DC polarity applied via a negative lead of a power source connected to the cathode and a positive lead of the power source connected to the anode, and the second DC polarity applied via a negative lead of the power source connected to the anode and a positive lead of the power source connected to the cathode.

9. The apparatus of claim 8, wherein the power conditioning system applies the electric current to the anode and the cathode as a DC current in one of: a constant DC voltage at a varying DC current, a constant DC current at a varying DC voltage, a sine wave voltage pattern at constant current, a sine wave current pattern at constant voltage, a square wave voltage pattern at constant current, or a square wave current pattern at constant voltage; and wherein the applied DC current drives the electrochemical hydrogen pumping process across the polymer electrolyte membrane (PEM) of the cell stack.

10. A process, comprising: obtaining a cell stack for making a fuel cell engine, the cell stack capable of producing electric power from a hydrogen gas; joining a fuel processing system to the cell stack, the fuel processing system comprising one or more first valves operable to expose an anode of the cell stack and a cathode of the cell stack to the hydrogen gas to render the fuel cell engine capable of performing an electrochemical hydrogen pumping (EHP) process, the one or more first valves including an electronically actuated fuel valve possessing a variable orifice for dynamically controlling a pressure of the hydrogen gas at the anode and the cathode; joining an air processing system to the cell stack, the air processing system comprising one or more second valves operable to expose the anode and the cathode to the hydrogen gas in coordination with the one or more first valves; joining an exhaust system to the cell stack, the exhaust system comprising one or more third valves operable to expose the anode and the cathode to the hydrogen gas in coordination with the one or more first valves and the one or more second valves; and joining a power conditioning system to the cell stack, the power conditioning system capable of applying an electric current from a power source to the anode and the cathode at an amperage and a voltage capable of driving the electrochemical hydrogen pumping process across a polymer electrolyte membrane (PEM) of the cell stack.

11. The process of claim 10, wherein joining the power conditioning system to the cell stack further comprises one of rendering the power conditioning system capable of utilizing a battery of a vehicle hosting the fuel cell engine as the power source, or

28 rendering the power conditioning system capable of connecting with a power supply of an external accessory unit as the power source.

12. The process of claim 10, further comprising rendering the fuel cell engine capable of electrically isolating the cell stack and the power conditioning system from electrical connections adverse to performing the electrochemical hydrogen pumping process.

13. The process of claim 10, further comprising rendering the power conditioning system capable of selectively applying the electric current either with a first DC polarity or a second DC polarity, the first DC polarity applied via a negative lead of the power source connected to the cathode and a positive lead of the power source connected to the anode, and the second DC polarity applied via a negative lead of the power source connected to the anode and a positive lead of the power source connected to the cathode.

14. The process of claim 13, further comprising rendering the power conditioning system capable of applying the electric current to the anode and the cathode as a DC current in one of a sine wave voltage pattern at constant current, a sine wave current pattern at constant voltage, a square wave voltage pattern at constant current, or a square wave current pattern at constant voltage to drive the electrochemical hydrogen pumping process across the polymer electrolyte membrane (PEM) of the cell stack.

15. The process of claim 10, further comprising connecting an electronic controller to the fuel cell engine to operate the one or more first valves of the fuel processing system, the one or more second valves of the air processing system, the one or more third valves of the exhaust system, and the power conditioning system to perform the

29 electrochemical hydrogen pumping process across the polymer electrolyte membrane (PEM) of the fuel cell engine.

16. The process of claim 15, further comprising one of: including the electronic controller as an electronic control unit onboard the fuel cell engine, including the electronic controller in an engine control module or an electronic control unit of a vehicle hosting the fuel cell engine, or including the electronic controller in an external accessory unit connectable to the fuel cell engine via an interface.

17. A system, comprising: a fuel cell engine capable of undergoing an electrochemical hydrogen pumping process on a cell stack of the fuel cell engine without disassembly of the fuel cell engine; an accessory unit comprising a power supply and an electronic controller for performing the electrochemical hydrogen pumping process on the cell stack of the fuel cell engine; and an interface for connecting the accessory unit to the fuel cell engine.

18. The system of claim 17, further comprising: a fuel processing system of the fuel cell engine with one or more first valves operable to expose an anode of the cell stack and a cathode of the cell stack to the hydrogen gas for performing the electrochemical hydrogen pumping process, the one or more first valves including an electronically actuated fuel valve possessing a variable orifice for dynamically controlling a pressure of the hydrogen gas at the anode and the cathode;

30 an air processing system of the fuel cell engine with one or more second valves operable to expose the anode and the cathode to the hydrogen gas in cooperation with the one or more first valves; and an exhaust system of the fuel cell engine with one or more third valves operable to expose the anode and the cathode to the hydrogen gas in cooperation with the one or more first valves and the one or more second valves.

19. The system of claim 18, wherein the electronic controller of the accessory supervises the one or more first valves of the fuel processing system, the one or more second valves of the air processing system, the one or more third valves of the exhaust system, and the power supply to perform the electrochemical hydrogen pumping process across a polymer electrolyte membrane (PEM) of the fuel cell engine.

20. The system of claim 17, wherein the power supply of the accessory unit applies an electric current to an anode and a cathode of the fuel cell stack at an amperage and a voltage capable of driving the electrochemical hydrogen pumping process across a polymer electrolyte membrane (PEM) of the cell stack; and wherein the amperage and the voltage are selected to drive the electrochemical hydrogen pumping process for diagnosing or analyzing a condition of the anode, the cathode, or the polymer electrolyte membrane (PEM) of the cell stack, or the amperage and the voltage are selected to drive the electrochemical hydrogen pumping process to recondition a component of the cell stack.

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