Chemistry: electrical current producing apparatus – product – and – Having magnetic field feature
Reexamination Certificate
1998-11-23
2001-05-08
Kalafut, Stephen (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Having magnetic field feature
C429S006000, C429S006000
Reexamination Certificate
active
06228518
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the methods and apparatus of generating energy through low-cost, efficient processes. More specifically, the invention relates to components of a fuel cell for generating electricity.
BACKGROUND
Methanol fuel cells promise to provide efficient and low-cost electrical current from methanol without burning the fuel. Therefore, pollution from combustion is not created by the use of such fuel cells. The fuel cells are more than twice as efficient as gasoline engines; they run cool, without the need for insulation and structural reinforcement; and rely on a relatively inexpensive fuel. The methanol fuel cells which were designed initially produced about 5 kW, running up to 200 continuous hours, and up to 3,000 intermittent hours, without suffering any loss in performance. The goal is to produce units which can generate up to 40 kW, which would be enough to power a full-size automobile, and which can run for at least 1,000 continuous hours.
The biplate is a two-sided component which is placed between the membrane electrode assemblies (MEA) in a fuel cell stack. One side of the biplate is oriented to face the anode of one MEA, and the other side of the biplate is oriented to face the cathode of another MEA. The biplate provides electrical contact to both of the MEA. It also acts to separate air or oxygen provided to the cathode of one MEA and the fuel provided to the anode of the other MEA. As such it forms part of the fuel cell compartment containing either fuel or air.
The endplate is a fuel cell component which forms part of the last fuel cell compartment in a stack, if a stack is present. If the cells are not stacked, the endplate is simply a wall of the fuel cell. The endplate provides electrical contact between an electrode of the fuel cell and the electrical load which spans the fuel cell or stack of fuel cells. The endplate is simply a single-ended biplate. Thus, both fuel cell components, biplates and endplates, are electrically conductive elements. These plates were typically formed of machined graphite.
Fuel cell components designed for use in hydrogen/air fuel cells needed to be both thermally conductive and electrically conductive. Hydrogen/air stacks could only release the heat generated internally through the stack material. Prior systems often used cooling plates inserted between biplates for the specific purpose of withdrawing heat from the stack in such fuel cells.
At this time, cost is the major factor limiting methanol fuel cell commercialization. An important component of the total cost of methanol fuel cells is the machined graphite biplates and endplates used in conventional cells. This material is relatively expensive, representing up to one third of the cost of a fuel cell. It is also relatively heavy. The weight of these components in fuel cells makes up a significant fraction of the total weight of the fuel cell.
SUMMARY OF THE INVENTION
The invention results from the use of a newly designed fuel cell component assembly in liquid feed fuel cells. The components are made of a material which is more easily manufactured and less dense than that of the electrically conductive elements which carry electrical current.
The resulting fuel cells are less costly to manufacture, made of less costly materials, and lighter than conventional cells. The new components demonstrate that the improvements which are possible are extremely practical in nature, and can be used in fuel cells for automobiles, lawn mowers, portable electrical devices, stand-alone power generators, and in replacement of the internal combustion engine generally. The invention also finds use in fuel cells used in the space shuttle and other high-end applications.
As used herein, a “biplate” is a two-sided separator which prevents fluid communication between compartments of fuel cells which cannot be in fluid communication for the cell to function properly. For example, a biplate can prevent fluid communication between the adjacent negative and positive electrodes of a fuel cell. A biplate may also prevent fluid communication between the last compartment of a fuel cell in a stack and the exterior of the fuel cell. This last aspect of the definition of biplate includes the specific fuel cell components which are found at each end of a stack of cells, also referred to as the endplates. “Endplates” are merely biplates which are not between fuel cell compartments, but are found at the terminus of a fuel cell stack.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. All publications, patent applications, patents and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods and examples are illustrative only and not intended to be limiting.
Other features and advantages of the invention will be apparent from the following detailed description, and from the claims.
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patent: 5063122 (1991-11-01), Rohr
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patent: 5599638 (1997-02-01), Surampudi et al.
patent: 5624769 (1997-04-01), Li et al.
patent: 5773162 (1998-06-01), Surampudi et al.
patent: 5789093 (1998-08-01), Malhi
California Institute of Technology
Fish & Richardson P.C.
Kalafut Stephen
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