Patent Application
20190109331
The invention relates to an improved fuel cell system having an active ventilation subsystem with accurate leak sensing capabilities via a more robust structure at a lower cost.
Fuel cell systems are increasingly being used as a power source in a wide variety of applications. Fuel cell systems have been proposed for use in power consumers such as vehicles as a replacement for internal combustion engines, for example. Fuel cells may also be used as stationary electric power plants in buildings and residences, as portable power in video cameras, computers, and the like.
Fuel cells are electrochemical devices which combine a fuel such as hydrogen and an oxidant such as oxygen to produce electricity. The oxygen is typically supplied by an air stream. The hydrogen and oxygen combine to result in the formation of water. Other fuels can be used such as natural gas, methanol, gasoline, and coal-derived synthetic fuels, for example.
The basic process employed by a fuel cell is efficient, substantially pollution-free, quiet, free from moving parts (other than an air compressor, cooling fans, pumps and actuators), and may be constructed to leave only heat and water as by-products. The term “fuel cell” is typically used to refer to either a single cell or a plurality of cells depending upon the context in which it is used. The plurality of cells is typically bundled together and arranged to form a stack with the plurality of cells commonly arranged in electrical series. Since single fuel cells can be assembled into stacks of varying sizes, systems can be designed to produce a desired energy output level providing flexibility of design for different applications.
Different fuel cell types can be provided such as phosphoric acid, alkaline, molten carbonate, solid oxide, and proton exchange membrane (PEM), for example. The basic components of a PEM-type fuel cell are two electrodes separated by a polymer membrane electrolyte. Each electrode is coated on one side with a thin catalyst layer. The electrodes, catalyst, and membrane together form a membrane electrode assembly (MEA).
As is known, hydrogen is supplied to the fuel cells in a fuel cell stack to cause the necessary chemical reaction to power the vehicle using electricity. However, the fuel cell system and stack require appropriate ventilation in the event of any hydrogen leaks from the fuel cell stack. Moreover, the fuel cell system must also be able to accurately detect any leakage of hydrogen from the fuel cell stack so that appropriate safety measures may be taken. Accordingly, there is a need for a robust fuel cell system which can provide appropriate ventilation and leak detection of the fuel cell stack at a lower cost with fewer parts.
In one embodiment of the present disclosure, a fuel cell system is provided which includes a fuel cell stack disposed within an enclosure, a compressor, an inlet air filter, an inlet passageway connecting the inlet air filter to an inlet of the compressor, a flow restrictor and a hydrogen sensor disposed along a ventilation line running from the enclosure back to the inlet passageway. The compressor further includes a compressor outlet in fluid communication with the fuel cell stack and a compressor inlet in fluid communication with the inlet air filter. The compressor may be configured to draw an ambient air stream through the inlet air filter towards the fuel cell stack thereby creating a vacuum in the inlet passageway. The flow restrictor is configured to couple the inlet passageway to the ventilation line running from the enclosure to the inlet passageway.
The enclosure may, but not necessarily, further define a ventilation aperture having a ventilation filter disposed proximate to the ventilation aperture. It is understood that the enclosure, may but not necessarily further define a BOP (balance of plant) enclosure and a fuel cell stack enclosure. The BOP enclosure may house some air management components as well as fuel management components for the fuel cell system. The fuel cell stack enclosure may include the fuel cell stack itself.
In the first embodiment, the ventilation line, the flow restrictor, and the hydrogen sensor may be in fluid communication with the BOP enclosure via a BOP ventilation line and are also in fluid communication with the fuel cell enclosure via a fuel cell ventilation line. The BOP ventilation line and the fuel cell ventilation line merge into one line which is the second portion of the ventilation line upstream of the flow restrictor and the hydrogen sensor. Moreover, the hydrogen sensor may be in communication with a fuel cell system controller operatively configured to provide driver alerts in the event the exhaust ventilation stream contains hydrogen levels which exceed a predetermined threshold. One example threshold may determine if a severe hydrogen leak is present such that the hydrogen levels exceed a relatively high value based on the hydrogen sensor data. Another example threshold may determine if a mild hydrogen leak is present such that the hydrogen levels exceed a relative low value based on hydrogen sensor data. In a non-limiting example of where a severe hydrogen leak is detected, the fuel cell system controller may, but not necessarily, shut down the entire fuel cell system. Similarly, in the non-limiting example where a mild hydrogen leak is detected, the fuel cell system controller, may but not necessarily, actuates a driver warning light such that the vehicle may be taken in for service.
The first embodiment may further include an enclosure exhaust passage configured to directly transfer a ventilation exhaust stream from the enclosure to the atmosphere and may further include an air flow meter disposed on the inlet passageway proximate to the inlet air filter. The air flow meter may be configured to determine whether the fuel cell system's ventilation is able to adequately draw in air.
In yet another embodiment of the present disclosure, a fuel cell system is provided which includes a fuel cell stack disposed in an enclosure, a compressor, an inlet passageway, a flow restrictor, a ventilation filter affixed to the flow restrictor and a hydrogen sensor disposed on a ventilation line. The compressor outlet may be in fluid communication with the fuel cell stack while the compressor inlet is in fluid communication with the inlet air filter via the inlet passageway. The compressor may therefore be configured to draw in an ambient air stream through the inlet air filter towards the fuel cell stack. As a result, a vacuum is created within the inlet passageway. The flow restrictor of may be configured to couple the inlet passageway to the ventilation line running from the enclosure to the inlet passageway while also controlling the air flow from the ventilation line to the inlet passageway.
In the second embodiment, the enclosure may, but not necessarily, further define a ventilation aperture or more than one ventilation aperture. Similarly, in the second embodiment, the enclosure, may but not necessarily further define a BOP (balance of plant) enclosure and a fuel cell stack enclosure. Where the enclosure further defines a BOP enclosure and a fuel cell stack enclosure. The BOP enclosure may house some air management components as well as fuel management components for the fuel cell system. The fuel cell stack enclosure may include the fuel cell stack itself.
In the second embodiment, the ventilation line, the flow restrictor, and the hydrogen sensor may be in fluid communication with the BOP enclosure via a BOP ventilation line. It is also understood that the ventilation line, the flow restrictor, and the hydrogen sensor may also be in fluid communication with the fuel cell enclosure via a fuel cell ventilation line. The BOP ventilation line and the fuel cell ventilation line may merge into one ventilation line which is the second portion of the ventilation line. The first portion of the ventilation line (having two lines—the BOP ventilation line and the fuel cell ventilation line) is upstream of the flow restrictor and the hydrogen sensor such that the single hydrogen sensor may determine if there are any hydrogen leaks in the entire fuel cell system via the second portion of the ventilation line. In this location, the hydrogen sensor may be in communication with a fuel cell system controller operatively configured to provide driver alerts in the event the exhaust ventilation stream contains hydrogen levels which exceed a predetermined threshold. The predetermined threshold may, but not necessarily, be one of a variety of thresholds as previously described.
Similar to the first embodiment, the second embodiment of the fuel cell system may further include an enclosure exhaust passage configured to directly transfer a ventilation exhaust stream from the enclosure to the atmosphere via enclosure exhaust outlet as well as an air flow meter disposed on the inlet passageway proximate to the inlet air filter where the air flow meter may be configured to determine whether the fuel cell system's ventilation is able to adequately draw in air.
The present disclosure and its particular features and advantages will become more apparent from the following detailed description considered with reference to the accompanying drawings.
These and other features and advantages of the present disclosure will be apparent from the following detailed description, best mode, claims, and accompanying drawings in which:
Like reference numerals refer to like parts throughout the description of several views of the drawings.
Reference will now be made in detail to presently preferred compositions, embodiments and methods of the present disclosure, which constitute the best modes of practicing the present disclosure presently known to the inventors. The figures are not necessarily to scale. However, it is to be understood that the disclosed embodiments are merely exemplary of the present disclosure that may be embodied in various and alternative forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for any aspect of the present disclosure and/or as a representative basis for teaching one skilled in the art to variously employ the present disclosure.
Except in the examples, or where otherwise expressly indicated, all numerical quantities in this description indicating amounts of material or conditions of reaction and/or use are to be understood as modified by the word “about” in describing the broadest scope of the present disclosure. Practice within the numerical limits stated is generally preferred. Also, unless expressly stated to the contrary: percent, “parts of,” and ratio values are by weight; the description of a group or class of materials as suitable or preferred for a given purpose in connection with the present disclosure implies that mixtures of any two or more of the members of the group or class are equally suitable or preferred; the first definition of an acronym or other abbreviation applies to all subsequent uses herein of the same abbreviation and applies to normal grammatical variations of the initially defined abbreviation; and, unless expressly stated to the contrary, measurement of a property is determined by the same technique as previously or later referenced for the same property.
It is also to be understood that this present disclosure is not limited to the specific embodiments and methods described below, as specific components and/or conditions may, of course, vary. Furthermore, the terminology used herein is used only for the purpose of describing particular embodiments of the present disclosure and is not intended to be limiting in any way.
It must also be noted that, as used in the specification and the appended claims, the singular form “a,” “an,” and “the” comprise plural referents unless the context clearly indicates otherwise. For example, reference to a component in the singular is intended to comprise a plurality of components.
The term “comprising” is synonymous with “including,” “having,” “containing,” or “characterized by.” These terms are inclusive and open-ended and do not exclude additional, un-recited elements or method steps.
The phrase “consisting of” excludes any element, step, or ingredient not specified in the claim. When this phrase appears in a clause of the body of a claim, rather than immediately following the preamble, it limits only the element set forth in that clause; other elements are not excluded from the claim as a whole.
The phrase “consisting essentially of” limits the scope of a claim to the specified materials or steps, plus those that do not materially affect the basic and novel characteristic(s) of the claimed subject matter.
The terms “comprising”, “consisting of”, and “consisting essentially of” can be alternatively used. Where one of these three terms is used, the presently disclosed and claimed subject matter can include the use of either of the other two terms.
Throughout this application, where publications are referenced, the disclosures of these publications in their entireties are hereby incorporated by reference into this application to more fully describe the state of the art to which this present disclosure pertains.
With reference to
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Also, the flow restrictor 28 of
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It is understood with respect to all embodiments of the present disclosure, an air passageway 31 (see example of air passageway 31 in
Additionally, the flow rate of the ventilation air stream 52 entering the inlet air passageway 26 from the ventilation line 30 must not disrupt the overall air flow control of the fuel cell system 10 given that the air stream 52 enters the inlet air passageway 26 downstream of the inlet air flow meter 64. However, it is also understood that an additional air flow meter (not shown) may be installed onto the inlet air passageway 26 downstream of the flow restrictor 28 to detect any such undesired disruptions to the air stream which is entering the compressor 16. Since the safe (non-flammable) flow is 10 SLPM and the total airflow for a non-limiting example fuel cell system sized for about 80 kW is about 3700 SLPM at full power. This is the approximate air flow needed for the cathode of the fuel cell stack to provide adequate oxygen to support the electrochemical reactions therein. The flow rate of air stream 52 which enters inlet air passageway 26 must be relatively insignificant relative to the flow rate for inlet air stream 27 such that the flow rate for the combined air streams 29—inlet air stream 27 and ventilation air stream 52 stays within an acceptable deviation range with respect to air flow measurements taken upstream at the inlet air flow meter 62. Accordingly, to the extent that readings from inlet air flow meter 62 have any small errors, such errors could be attributed to flow rate change due to the ventilation air stream 52 which enters inlet passageway 26. Moreover, it is also understood that small errors in the data from the inlet air flow meter 62 could also be attributed to any clogging at the inlet air filter 22 as well. Additionally the high dilution of the ventilation air stream 52 upon its mixture into the inlet airstream 27 such that combined air stream 29 (see non-limiting example in
It is further understood that any hydrogen (represented by example element 63 in
While at least two exemplary embodiments have been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the disclosure as set forth in the appended claims and the legal equivalents thereof.
