Electrolysis: processes – compositions used therein – and methods – Electrolytic synthesis – Preparing nonmetal element
Reexamination Certificate
2000-12-14
2002-10-29
Bell, Bruce F. (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic synthesis
Preparing nonmetal element
C205S629000, C205S633000, C205S634000, C205S637000, C204S252000, C204S253000, C204S255000, C204S256000, C204S257000, C204S258000, C204S263000, C429S010000, C429S010000, C429S006000, C429S006000, C429S006000, C429S006000
Reexamination Certificate
active
06471850
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an electrochemical cell system, and especially relates to the use of an electrochemical cell system capable of operating in a low gravity environment.
BRIEF DESCRIPTION OF THE RELATED ART
Electrochemical cells are energy conversion devices, usually classified as either electrolysis cells or fuel cells. An electrolysis cell functions as a hydrogen generator by electrolytically decomposing water to produce hydrogen and oxygen gases, and functions as a fuel cell by electrochemically reacting hydrogen with oxygen to generate electricity.
Referring to
FIG. 1
, a partial section of a typical proton exchange membrane fuel cell
10
is detailed. In fuel cell
10
, hydrogen gas
12
and reactant water
14
are introduced to a hydrogen electrode (anode)
16
, while oxygen gas
18
is introduced to an oxygen electrode (cathode)
20
. The hydrogen gas
12
for fuel cell operation can originate from a pure hydrogen source, methanol or other hydrogen source. Hydrogen gas electrochemically reacts at anode
16
to produce hydrogen ions (protons) and electrons, wherein the electrons flow of from anode
16
through an electrically connected external load
21
, and the protons migrate through a membrane
22
to cathode
20
. At cathode
20
, the protons and electrons react with the oxygen gas to form resultant water
14
′, which additionally includes any reactant water
14
dragged through membrane
22
to cathode
20
. The electrical potential across anode
16
and cathode
20
can be exploited to power an external load.
The same configuration as is depicted in
FIG. 1
for a fuel cell is conventionally employed for electrolysis cells. In a typical anode feed water electrolysis cell (not shown), process water is fed into a cell on the side of the oxygen electrode (in an electrolytic cell, the anode) to form oxygen gas, electrons, and protons. The electrolytic reaction is facilitated by the positive terminal of a power source electrically connected to the anode and the negative terminal of the power source connected to a hydrogen electrode (in an electrolytic cell, the cathode). The oxygen gas and a portion of the process water exit the cell, while protons and water migrate across the proton exchange membrane to the cathode where hydrogen gas is formed. In a cathode feed electrolysis cell (not shown), process water is fed on the hydrogen electrode, and a portion of the water migrates from the cathode across the membrane to the anode where protons and oxygen gas are formed. A portion of the process water exits the cell at the cathode side without passing through the membrane. The protons migrate across the membrane to the cathode where hydrogen gas is formed.
The typical electrochemical cell includes a one or more individual cells arranged in a stack, with the working fluid directed through the cells via input and output conduits formed within the stack structure. The cells within the stack are sequentially arranged, each including a cathode, a proton exchange membrane, and an anode. In certain conventional arrangements, the anode, cathode, or both are gas diffusion electrodes that facilitate gas diffusion to the membrane. Each cathode/membrane/anode assembly (hereinafter “membrane electrode assembly”, or “MEA”) is typically supported on both sides by flow fields comprising screen packs or bipolar plates. Such flow fields facilitate fluid movement and membrane hydration and provide mechanical support for the MEA. Since a differential pressure often exists in the cells, compression pads or other compression means are often employed to maintain uniform compression in the cell active area, i.e., the electrodes, thereby maintaining intimate contact between flow fields and cell electrodes over long time periods.
In certain arrangements, the electrochemical cells can be employed to both convert electricity into hydrogen, and hydrogen back into electricity as needed. Such systems are commonly referred to as regenerative fuel cell systems.
Electrochemical cell systems are generally operated within a gravitational field. Gravity aids in pulling water away from the electrode surface when the electrochemical cell is used in fuel cell mode, whereas in the electrolysis mode, gas and water exit the cell stack together thereby necessitating gravity-induced phase separation.
It is sometimes desirable to operate electrochemical cell systems in a low gravity environment, or even in a zero gravity environment. However, in typical configurations, water may collect on an electrode thereby inhibiting oxygen access to the electrode, in the fuel cell mode, and alternative water/gas separation methods would be needed in the electrolysis cell mode. Solutions addressing each of these requirements would necessitate excess equipment costs, add to system complexity, and consume electricity.
While existing electrochemical cell systems are suitable for their intended purposes, there still remains a need for improvements, particularly regarding operation of electrochemical cell systems in low gravity or zero gravity environments.
SUMMARY OF THE INVENTION
The above-described drawbacks and disadvantages are alleviated by an electrochemical cell comprising a hydrogen electrode; an oxygen electrode; a membrane disposed between the hydrogen electrode and the oxygen electrode; and a compartmentalized storage tank having a first fluid storage section and a second fluid storage section separated by a movable divider, wherein the compartmentalized storage tank is in fluid communication with the electrochemical cell.
The present invention further relates to an electrochemical cell including a hydrogen electrode; an oxygen electrode; an electrolyte membrane disposed between and in intimate contact with the hydrogen electrode and the oxygen electrode; an oxygen flow field disposed adjacent to and in intimate contact with the oxygen electrode; a hydrogen flow field disposed adjacent to and in intimate contact with the hydrogen electrode; a water flow field disposed in fluid communication with the oxygen flow field; and a media divider disposed between the oxygen flow field and the water flow field.
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A. Leonida, Proceedings of the European Space Power Conference, Hydrogen/Oxygen SPER Electrochemical Devices for Zero-G Applications, esa SP-294, vol. 1, Aug. 1989. esa SP-294, vol. 1, Aug. 1989.
J. McElroy, Journal of Power Sources , 29 (1990) pp. 399-412, Hydrogen-Oxygen Proton-Exchange Membrane Fuel Cells and Electrolyzers. No Month Available.
Molter Trent M.
Shiepe Jason K.
Bell Bruce F.
Cantor & Colburn LLP
Proton Energy Systems, Inc.
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