Patent Application
20170062847
A power generator includes a fuel cell having a proton exchange membrane for generating electricity from hydrogen and oxygen. An oxygen generator is coupled to the proton exchange membrane for providing oxygen to the proton exchange membrane. A hydrogen producing fuel may be used to provide hydrogen to the proton exchange membrane.
Fuel cell based power generators that use a proton exchange membrane (PEM) fuel cell and water-scavenging, self regulating, chemical hydride based hydrogen generator are sensitive to ambient humidity. This sensitivity may restrict the operation of the power generator to locations with adequate moisture in the environment. Low water content in PEM resulting from normal ambient humidity may also limit the maximum power that can be generated as opposed to power generator with sufficient water. In addition, the shelf life of such fuel cells may suffer from a continuous hydrogen discharge through the PEM.
In the following description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments which may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural, logical and electrical changes may be made without departing from the scope of the present invention. The following description of example embodiments is, therefore, not to be taken in a limited sense, and the scope of the present invention is defined by the appended claims.
The functions or algorithms described herein may be implemented in software or a combination of software and human implemented procedures in one embodiment. The software may consist of computer executable instructions stored on computer readable media such as memory or other type of storage devices. The term “computer readable media” is also used to represent any means by which the computer readable instructions may be received by the computer, such as by different forms of wired or wireless transmissions. Further, such functions correspond to modules, which are software, hardware, firmware or any combination thereof. Multiple functions may be performed in one or more modules as desired, and the embodiments described are merely examples. The software may be executed on a digital signal processor, ASIC, microprocessor, or other type of processor operating on a computer system, such as a personal computer, server or other computer system.
A power generator is shown generally at 100 in
The electrolytic oxygen generator 115 functions as an oxygen-selective permeable membrane, allowing oxygen-ion permeation at elevated temperature but blocking other gases. Water generated by the electricity generating reaction is trapped between the fuel cell 110 cathode and the electrolytic oxygen generator 115 membrane. The effect of the membrane is three-fold. First, since the oxygen generator 115 membrane is effectively impermeable to water vapor, the fuel cell 110 power output is no longer sensitive to ambient humidity, because no water is lost to the ambient at low ambient humidity. Second, the water vapor raises the humidity of the fuel cell 110 cathode, which promotes a larger water concentration gradient within the membrane, driving more water vapor to a fuel cell 110 anode where it can react with the chemical hydride and generate more hydrogen, which is consumed by the fuel cell 110, thus increasing power output. Power output is also increased because higher water content in the membrane results in higher ionic conductivity (reduced ionic resistance), reducing resistive losses. Rough estimates of power output improvement may be 10×. Third, the oxygen generator 115 membrane effectively blocks hydrogen discharge to ambient which increases the shelf life and attainable total electricity. In one embodiment, the power generator 100 may be precharged with a desired amount of water vapor to enable it to operate at desired power levels.
In various embodiments, fans or pumps may be used to control the flow of air, oxygen and hydrogen. At 130, a fan or pump are indicated in the ambient air flow path 120. At 140, a valve and optional fan are indicated to control oxygen flow to the fuel cell 110 anode. At 150, an optional fan or pump is shown to help circulate water vapor and hydrogen (H2) around one or more sections of fuel 125 and in particular transport H2 to the fuel cell 110 cathode. Control electronics are shown in block form at 160. The control electronics 160 may be used to control valves, fans/pumps, and heaters in power generator 100. The positions, types and sizes of the valves and fan/pump may be varied between different embodiments. In one embodiment, power generator 100 has a size that is approximately the same as a BA5390/U battery, about 62.2×111.8×127 mm.
At elevated temperatures and oxygen pressure or voltage gradient, membranes made of certain solid oxide (ex., SrCo0.8Fe0.2O3-δ) can transport significant oxygen ions. The oxygen molecules dissociate in one side and recombine in another side. One example structure for an oxygen generator 115 is illustrated at 200 in
Oxygen is transported into the hollow fibers 220 and is delivered to the fuel cell 110. In further embodiments, the oxygen generator membrane may take the shape of membrane stack layers, or yet other shapes conducive to generating a desired amount of oxygen in a compact and efficient form wherein size limitations may apply.
In one embodiment, the oxygen generator is a mixed conductor, which means that an oxygen generator membrane 510 in
At high temperature (400-1000 C), the membrane 510 adsorbs and dissociates oxygen molecules from an ambient air 520 or oxygen containing gas feed side. The dissociated oxygen is ionized. The ions 525 are transferred through the membrane as illustrated in
In one embodiment, ambient air is provided to the membrane 510. In this embodiment, the ambient air is sufficient for PEM fuel cell applications at a 10-100 W level. In a further embodiment, compressed air is provided to the membrane 510 by means of a pump or pressurized source of air.
An ion conductor type oxygen transport membrane is illustrated at 610 in
The membrane 610 is a dense metal oxide(s) in one embodiment, which is non-gas-permeable (or the gas permeation is extremely small). The membrane thickness can be from microns to centimeters in various embodiments.
Some examples of mixed conductor electrodes 510 include but are not limited to SrCo0.33Fe0.67O3-δ, SrCo0.8Fe2O3-δ, Sr0.7Mo0.3CoO3, Sr0.97Fe0.8Ti0.2O3-δ, Sr0.97Fe0.4Ti0.6O3-δ, SrCo0.8Ti0.2O3-δ, Ba0.5Sr0.5Co0.8Fe0.2O3-δ, BaBiCo0.2Fe0.8-xO3-δ(x=0.1˜0.5), LaCo(M)O3-δ, LaCo0.9Cr0.1O3-δ, and many other mixed conducting oxides with similar characteristics. Such similar characteristics may include the ability to obtain O2 from gasses containing O2, such as ambient air, and also to be substantially water and water vapor impermeable. Some examples of ion conductor electrodes 610 include but are not limited to LaCaAlOx, LaSr Ga MgOx, BiYOx, CeGdOx, ZrSeOx, and YSZ to name a few.
In one embodiment, the control electronics may be a computer system 700 having one or more components of a block diagram as shown in
Computer-readable instructions stored on a computer-readable medium such as memory 720 are executable by the processing unit 710 of the system 700. In some embodiments, the system may be a digital signal processor, ASIC, microprocessor, or other type of processor operating on a computer system, such as a personal computer, server or other computer system, and may be formed on a single circuit board, chip or substrate.
The Abstract is provided to comply with 37 C.F.R. §1.72(b) to allow the reader to quickly ascertain the nature and gist of the technical disclosure. The Abstract is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.
This application is a divisional of U.S. Patent Application Ser. No. 12/062,315, filed on Apr. 3, 2008, the disclosure of which is incorporated herein in its entirety by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12062315 | Apr 2008 | US |
| Child | 15258745 | US |
