Chemistry: electrical current producing apparatus – product – and – Having magnetic field feature
Reexamination Certificate
1999-11-23
2002-08-20
Kalafut, Stephen (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Having magnetic field feature
C429S006000, C429S006000, C429S006000, C429S006000
Reexamination Certificate
active
06436562
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a method and apparatus for the management and control of various flow streams related to the operation of a fuel cell engine. The present invention relates more specifically to a stream conditioning system that conditions at least one fuel cell reactant stream in communication with the fuel cell of a fuel cell engine. Namely, the present system can condition the temperature and humidity of a reactant stream supplied to, or exhausted from, either the fuel cell's inlet and outlet streams, on either its anode or cathode side, or on both sides, as described in more detail below.
2. Description of Related Art
Fuel cells are electrochemical devices that convert a fuel's energy directly to electrical energy. Fuel cells operate much like continuous batteries when supplied with fuel to the anode (negative electrode) and oxidant (e.g. air) to the cathode (positive electrode). Fuel cells forego the traditional extraction of energy in the form of combustion heat, conversion of heat energy to mechanical energy (as with a turbine), and finally turning mechanical energy into electricity (e.g. using a dynamo). Instead, fuel cells chemically combine the molecules of a fuel and oxidizer without burning, dispensing with the inefficiencies and pollution of traditional combustion.
The utility of fuel cells has been known since at least as early as 1939. Further developments in the fuel cell field have included the development of proton exchange membrane (PEM) fuel cells, phosphoric acid fuel cells, alkaline fuel cells, and fuel cells incorporating reformer technology to crack hydrocarbons such as gasoline to obtain hydrogen to feed the fuel cell.
Fuel cells generally require two independent flow circuits for delivering reactant streams to the anode and the cathode of the fuel cell. In PEM fuel cells, these flow circuits include an anode circuit for feeding the fuel, generally hydrogen, to the fuel cell; and a cathode circuit for feeding the oxidant, typically air from the ambient, to the fuel cell. In order to maintain proper operating conditions for the fuel cell, the temperatures and humidities of the anode and cathode circuits must be precisely controlled to avoid drying out the electrolyte or otherwise damaging the fuel cell, and thereby stopping the flow of electricity from the fuel cell.
Fuel cells have found application in a number of fields. Stationary cells are used in the utility industry and in commercial/residential settings. An area of particular interest has been the application of fuel cell technology in electrically-powered transport vehicles, including automobiles. In automotive applications, weight and space are at a premium, and therefore, the fuel cell and its supporting systems must be as small and lightweight as possible. Moreover, because automotive applications subject equipment to a wide and rapidly fluctuating range of operating conditions such as temperature and humidity, equipment utilized in such applications must be capable of withstanding and operating under a variety of conditions. Equipment utilized in automotive applications must also be sufficiently rugged to withstand the vibrations and stresses induced by over-the-road use.
Systems for conditioning the flow circuits of a fuel cell have been proposed. For example, U.S. Pat. No. 3,516,867 to Dankese discloses a fuel cell system including a dehumidifier and a humidifier for conditioning the fuel cell's reactant streams. The humidification portion of this system achieves moisture transfer through a partition. This type of humidification system has been found inefficient for automotive applications, mainly because of the large surface areas required to transfer the necessary quantity of moisture to the reactant streams, and because of the undesirable weight of such large-scale systems. In addition, large quantities of heat energy are consumed in vaporizing moisture in this type of humidification system, which energy consumption reduces system efficiency.
U.S. Pat. No. 3,669,751 to Richman discloses a fuel cell, hydrogen generator, and heat exchanger system, wherein reactant air to be supplied to the fuel cell is brought into evaporative contact with a wet electrolyte to humidify the reactant air. The system of Richman suffers similar disadvantages to that of Dankese; namely, the requirement of large surface areas for effecting moisture transfer and the resulting weight of system components, as well as the consumption of considerable energy in vaporizing the moisture.
In addition to cathode humidification, existing fuel cell technology requires the humidification of the hydrogen fuel stream input to the fuel cell's anode in order to prevent drying out the electrolyte within the fuel cell. This requirement of anode humidification adds additional components to a fuel cell's gas management system, resulting in undesirable increased weight and expense. Moreover, known humidification systems such as membrane humidifiers or systems utilizing airflow through beds of wetted spheres consume considerable energy in vaporizing water to provide the required humidification. Therefore, it has been found that known methods of anode humidification are unsuited to automotive applications.
Thus it can be seen that a need yet exists for a lightweight, efficient means of conditioning fuel cell reactant streams of a fuel cell engine.
Yet another need exists for a stream conditioning system for conditioning the oxidant flow to the cathode inlet of a fuel cell.
A need further exists for a method and apparatus for conditioning the anode inlet to a fuel cell, which minimizes the weight and expense of associated components.
It is to the provision of such a fuel cell engine stream conditioning system meeting these and other needs that the present invention is primarily directed.
BRIEF SUMMARY OF THE INVENTION
Briefly described, in a preferred form, the present invention is a stream conditioning system for a fuel cell gas management system or fuel cell engine. The stream conditioning system manages species potential in fuel cell reactant streams. A species transfer device is located in the path of at least one reactant stream of a fuel cell's inlet or outlet, which transfer device conditions that stream to improve the efficiency of the fuel cell. A species transfer device can also be located in the paths of both the fuel cell's inlet and outlet streams. In addition, the typical fuel cell has both an anode side and a cathode side, each side having reactant inlet and outlet streams. The conditioning system of the present invention can be used to condition a reactant stream on either the anode or cathode side, or both sides.
A reactant stream to be conditioned by the present species transfer device is defined as incorporating a potential of a species. Potential is used throughout as a term of relationship, describing the relative potential of a species between two or more streams. Potential will typically be used in context of one stream having a high potential of something (species), and another stream having a lower potential in that something (species) than the one stream, which context can be read as one stream having a higher potential of the species than does the other stream. Species is used throughout as a term describing a component of a stream that the transfer device seeks to remove from that stream, and transfer from that stream to another stream.
The present stream conditioning system communicates with at least two streams, one stream having a higher potential of a species than a lower potential stream. Yet, only one of the two streams need be in the flow path of the fuel cell; that is, only one stream need be a fuel cell reactant stream. The other of the streams can be an exhaust stream, or other such stream, provided to the conditioning system simply to enable transfer of the species from or to this other stream from or to the fuel cell reactant stream. A stream in the flow path of the fuel cell may be
Deveau Todd
Emprise Technology Associates Corp.
Kalafut Stephen
Troutman Sanders LLP
Vorndran Charles
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