Chemistry: electrical current producing apparatus – product – and – With pressure equalizing means for liquid immersion operation
Reexamination Certificate
1998-08-31
2001-10-30
Kalafut, Stephen (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
With pressure equalizing means for liquid immersion operation
C429S006000, C429S068000, C429S127000, C429S208000, C429S233000
Reexamination Certificate
active
06309771
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to improved methods and systems for electrochemically producing electrical power using metal-air fuel cell battery technology.
2. Description of the Prior Art
More than ever, there is a great need in the art for ways and means of reliably producing small and large amounts of electrical energy for powering various types of electrical systems and devices. It can be helpful to classify these various types electrical systems and devices (conventionally called “electrical loads”) into four different market areas, namely: the Portable Electronics Market which includes products such as portable computers, cellular phones, camcorders, cassette tape players, etc. requiring less than 100 Watts; the Portable Electric Power Tools Market which includes products such as lawn mowers, screw drivers, drills, saws, etc. requiring more than 100 W but less than 1.0 kiloWatt; the Transportation Market which includes products such as power passenger vehicles, buses, golf carts, motorcycles, boats, etc. requiring more than 1.0 kiloWatt but less than 100 kiloWatt; and the Stationary Power Market which includes products such as multi-megawatt systems for powering homes, schools, factories, office buildings, and other distributed generation applications, requiring more than 10 kiloWatt, but less than 200 kilowatts.
Presently, there exists a number of different concepts and techniques for producing electrical power. Among these various concepts and techniques, the technique of Electrochemical Energy Conversion is most popular in the contemporary period inasmuch as it enables the direct production of electrical power from chemical compositions with relatively high energy density on a weight basis (measured in Watt Hours per Kilogram) with relatively high current densities (measured in Amperes per Centimeters2). Examples of devices based on the Electrochemical Energy Conversion concept include: battery cells; fuel cells; and fuel cell batteries (FCB).
Early storage batteries employed lead-acid cells, and then other combinations such a nickel with iron, cadmium, zinc or hydrogen and silver-iron, zinc-bromine, zinc-chlorine were developed with increasing energy quantities per weight. Presently, conventional battery cells are based on one of the following composition pairs: lead acid; nickel-cadmium; and nickel-metal hydrides (NiMH) As battery developers seek to improve energy storage capacity and energy stored per kilogram, they continue to focus on the use of materials. The development of the zinc-air battery is indicative of this research approach.
The electrochemical storage battery is a well known device having many applications. The storage, or secondary battery, is characterized in being capable of accepting direct-current (DC) electrical energy in a changing phase, retaining the energy in the form of chemical energy in the charge retention phase and releasing its energy on being connected to an external load in the discharge phase. The storage battery is capable of repeatedly performing these three phases over a reasonable life cycle.
The structure of the storage battery is typically a construction including one or more identical units called cells. Each cell contains plates referred to as positive (anode) and negative (cathode) electrodes contained in an electrolyte. When a charged storage battery cell is discharged through a load, the plates and the electrolyte undergo a chemical change wherein the negative cathode loses electrons and the positive anode gains electrons, thereby providing a current flow. During charging, the original conditions of the battery are restored by passing through it a current opposite to that produced during the discharge.
Conventional battery technologies based on lead acid, nickel-cadmium, or nickel-metal hydrides have limited operation time, long recharge time, low energy density, hazardous chemical materials requiring special encapsulation containers and careful disposal, fixed electrode areas, and in electrical automobile applications, conventional battery systems result in limited driving distances. Nickel-metal hydride (NiMH) batteries are attractive insofar that they eliminate cadmium, a very toxic substance; however, they deliver less power, have a faster self-discharge rate, and are less tolerant of overcharging.
Because of the enormous market potential, the shortcomings of conventional batteries represent a great opportunity to innovators and entrepreneurs to introduce battery products based on radically new concepts which overcome those shortcomings. Indeed, there is ample evidence of intense R&D activities and significant investments directed towards battery development.
Lithium-polymer batteries promise substantial improvements in energy density. Lithium battery systems employ a lithium anode, a polymer electrolyte and a composite cathode such as CuO, CuS, or FeS. Battery cells of this type are described in the Aug. 19, 1991, Electronic Engineering Times in the publication “Batteries Slim Down For Portability” by Colin Mackay and Robert Kline, Jr. at page 52. However, a major drawback with this battery cell design is that lithium's high reactivity with liquid electrolytes erodes the electrodes of such battery cells. While recent developments in solid state electrolytes have reduced this problem, a number of problems still remain, namely: dendrite formation on the electrodes; and the hazardous effects of lithium on the environmental.
Zinc-air battery technology is environmental friendly, but current batteries are limited to fixed area, resulting in low perceived specific power rating.
Batteries which are reliable, environmentally benign, have energy densities in excess of 200 Watt-hour per kilograms (lead-acid has only 35), and can be recharged faster, can find uses not only in portable electronics but also in consumer appliances, electric vehicles, and in the utilities industry; however, batteries with all of these desirable characteristics do not yet exist.
All conventional batteries, including conventional zinc-air batteries, are designed to have a fixed area, and thus a fixed stored energy determined by the voltage times the charge per unit volume. Traditional battery designers continue to adopt the fixed area design methodology and, therefore, are hindered by fundamental constraints including: (1) the larger the battery capacity, the longer it takes to recharge; (2) every unit weight of the anode is nearly matched by the weight of the cathode, the weight of the electrolyte, as well as the weight of the container; this overhead is the source of low energy density; (3) pulse power is inversely related to the energy capacity; and (4) only one set of electrodes are available for the sequential discharge and recharge cycles.
Fuel Cells have been known for more than one hundred years. Conventional fuel cells are electrochemical devices that convert chemical energy of the fuel directly into usable electricity and heat without combustion of the fuel. The electrochemical reactions are not reversible (i.e. rechargeable). Fuel cells are similar to battery cells in that both produce a DC current by using an electrochemical process. Both fuel cells and batteries have positive and negative electrodes (i.e. the anodes and cathodes) and an ionic conductor or electrolyte. The primary difference between fuel cells and battery cells is that battery cells have only a limited amount of stored energy whereas fuel cells will continue to produce electrical power output as long as fuel and oxidant are supplied thereto.
Conventional fuel cells operate by combining hydrogen with oxygen to release electricity (i.e. charge), heat, and water. The supply of fuel can be pure hydrogen. Hydrogen can also be extracted from natural gas, or other hydrocarbons by using a reformer. Fuel cells emit essentially none of the sulfur and nitrogen compounds released by conventional “combustion-based” electrical power generating methods employing fossil and like kinds of fuel.
Presently, several different conven
Chang Yuen-Ming
Faris Sadeg M.
Tsai Tsepin
Yao Wayne
Brill Esq. Gerow D.
Crispino Esq. Ralph J.
Kalafut Stephen
Perkowski Esq. Thomas J.
Reveo Inc
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