Patent Application
20080296169
Under 35 U.S.C. 119, the present application claims the benefit of the earlier filing date and the right of priority to Canadian Patent Application Serial No. 2,590,421, filed May 30, 2007, the disclosure of which is hereby incorporated by reference for any and all purposes.
The present invention relates generally to electrolysis systems and, more particularly, to a high efficiency electrolysis system and methods of using same.
Fossil fuels, in particular oil, coal and natural gas, represent the primary sources of energy in today's world. Unfortunately in a world of rapidly increasing energy needs, dependence on any energy source of finite size and limited regional availability has dire consequences for the world's economy. In particular, as a country's need for energy increases, so does its vulnerability to disruption in the supply of that energy. Additionally, as fossil fuels are the largest single source of carbon dioxide emissions, a greenhouse gas, continued reliance on such fuels can be expected to lead to continued global warming. Accordingly it is imperative that alternative, clean and renewable energy sources be developed that can replace fossil fuels.
Hydrogen-based fuel is currently one of the leading contenders to replace fossil fuel. There are a number of techniques that can be used to produce hydrogen, although the primary technique is by steam reforming natural gas. In this process thermal energy is used to react natural gas with steam, creating hydrogen and carbon dioxide. This process is well developed, but due to its reliance on fossil fuels and the release of carbon dioxide during production, it does not alleviate the need for fossil fuels nor does it lower the environmental impact of its use over that of traditional fossil fuels. Other, less developed hydrogen producing techniques include (i) biomass fermentation in which methane fermentation of high moisture content biomass creates fuel gas, a small portion of which is hydrogen; (ii) biological water splitting in which certain photosynthetic microbes produce hydrogen from water during their metabolic activities; (iii) photoelectrochemical processes using either soluble metal complexes as a catalyst or semiconducting electrodes in a photochemical cell; (iv) thermochemical water splitting using chemicals such as bromine or iodine, assisted by heat, to split water molecules; (v) thermolysis in which concentrated solar energy is used to generate temperatures high enough to split methane into hydrogen and carbon; and (vi) electrolysis.
Electrolysis as a means of producing hydrogen has been known and used for over 80 years. In general, electrolysis of water uses two electrodes separated by an ion conducting electrolyte. During the process hydrogen is produced at the cathode and oxygen is produced at the anode, the two reaction areas separated by an ion conducting diaphragm. Electricity is required to drive the process. An alternative to conventional electrolysis is high temperature electrolysis, also known as steam electrolysis. This process uses heat, for example produced by a solar concentrator, as a portion of the energy required to cause the needed reaction. Although lowering the electrical consumption of the process is desirable, this process has proven difficult to implement due to the tendency of the hydrogen and oxygen to recombine at the technique's high operating temperatures.
A high temperature heat source, for example a geothermal source, can also be used as a replacement for fossil fuel. In such systems the heat source raises the temperature of water sufficiently to produce steam, the steam driving a turbine generator which, in turn, produces electricity. Alternately the heat source can raise the temperature of a liquid that has a lower boiling temperature than water, such as isopentane, which can also be used to drive a turbine generator. Alternately the heat source can be used as a fossil fuel replacement for non-electrical applications, such as heating buildings.
Although a variety of alternatives to fossil fuels in addition to hydrogen and geothermal sources have been devised, to date none of them have proven acceptable for a variety of reasons ranging from cost to environmental impact to availability. Accordingly, what is needed is a new energy source, or a more efficient form of a current alternative energy source, that can effectively replace fossil fuels without requiring an overly complex distribution system. The present invention provides such a system and method of use.
The present invention provides a method and apparatus for achieving high output efficiency from an electrolysis system using a plurality of electrolysis cells all located within a single electrolysis tank. Each individual electrolysis cell includes a membrane which separates the portion of the electrolysis tank containing that electrolysis cell into two regions. Additionally, each electrolysis cell includes a plurality of metal members and a plurality of high voltage electrodes. The plurality of metal members includes at least a first and second metal member contained within the first region of the electrolysis cell and at least a third and fourth metal member contained within the second region of the electrolysis cell. The plurality of high voltage electrodes includes at least a first high voltage anode contained within the first region of the electrolysis cell and interposed between the first and second metal members, and a first high voltage cathode contained within the second region of the electrolysis cell and interposed between the third and fourth metal members. The high voltage applied to the high voltage electrodes is pulsed.
Preferably the high voltage pulses occur at a frequency between 50 Hz and 1 MHz, and more preferably at a frequency of between 100 Hz and 10 kHz. The pulse duration is preferably between 0.01 and 75 percent of the time period defined by the frequency, and more preferably between 1 and 50 percent of the time period defined by the frequency. Preferably the high voltage is between 50 volts and 50 kilovolts, more preferably between 100 volts and 5 kilovolts.
Preferably the liquid within the tank is comprised of one or more of; water, deuterated water, tritiated water, semiheavy water, heavy oxygen water, and/or any other water containing an isotope of either hydrogen or oxygen. Preferably the liquid within the electrolysis tank includes an electrolyte with a concentration in the range of 0.05 to 10 percent by weight, more preferably in the range of 0.05 to 2.0 percent by weight, and still more preferably in the range of 0.1 to 0.5 percent by weight.
The electrodes and the metal members can be fabricated from a variety of materials, although preferably the material for each is selected from the group consisting of steel, nickel, copper, iron, stainless steel, cobalt, manganese, zinc, titanium, platinum, palladium, aluminum, lithium, magnesium, boron, carbon, graphite, carbon-graphite, metal hydrides and alloys thereof.
In at least one embodiment, the electrolysis system is cooled. Cooling is preferably achieved by thermally coupling at least a portion of the electrolysis system to a portion of a conduit containing a heat transfer medium. The conduit can surround the electrolysis tank, be integrated within the walls of the electrolysis tank, or be contained within the electrolysis tank.
In at least one embodiment, the electrolysis system also contains a system controller. The system controller can be used to perform system optimization, either during an initial optimization period or repeatedly throughout system operation.
A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings.
A typical electrolysis system used to decompose water into hydrogen and oxygen gases utilizes relatively high concentrations of electrolyte. The present invention, however, has been found to work best with relatively low electrolyte concentrations, thereby maintaining a relatively high initial water resistivity. Preferably the water resistivity prior to the addition of an electrolyte is on the order of 1 to 28 megohms. Preferably the concentration of electrolyte is in the range of 0.05 percent to 10 percent by weight, more preferably the concentration of electrolyte is in the range of 0.05 percent to 2.0 percent by weight, and still more preferably the concentration of electrolyte is in the range of 0.1 percent to 0.5 percent by weight.
The electrolysis system of the invention includes multiple electrolysis cells, an electrolysis cell defined herein as having at least two metal members and a high voltage cathode interposed between the two metal members within a first region of the cell, and at least two metal members and a high voltage anode interposed between the two metal members within a second region of the cell, the two cell regions separated by a membrane. In the embodiment illustrated in
Membranes 105-107 permit ion/electron exchange between the two regions of each cell while keeping separate the oxygen and hydrogen bubbles produced during electrolysis. Maintaining separate hydrogen and oxygen gas regions is important as a means of minimizing the risk of explosions due to the inadvertent recombination of the two gases. Additionally, separating the regions allows the collection of pure hydrogen gas and pure oxygen gas. Accordingly similar polarity electrodes are grouped together with the membranes keeping groups separate. Exemplary membrane materials include, but are not limited to, polypropylene, tetrafluoroethylene, asbestos, etc.
As noted herein, the present system is capable of generating considerable heat. Accordingly, system components such as the electrolysis tank (e.g., tank 101) and the membranes (e.g., membranes 105-107) that are expected to be subjected to the heat generated by the system must be fabricated from suitable materials and designed to indefinitely accommodate the intended operating temperatures as well as the internal tank pressure. For example, in at least one preferred embodiment the system is designed to operate at a temperature of approximately 90° C. at standard pressure. In an alternate exemplary embodiment, the system is designed to operate at elevated temperatures (e.g., 100° C. to 150° C.) and at sufficient pressure to prevent boiling of liquid 103. In yet another alternate exemplary embodiment, the system is designed to operate at even higher temperatures (e.g., 200° C. to 350° C.) and higher pressures (e.g., sufficient to prevent boiling). Accordingly, it will be understood that the choice of materials (e.g., for tank 101 and membranes 105-107) and the design of the system (e.g., tank wall thicknesses, fittings, etc.) will vary, depending upon the intended system operational parameters, primarily temperature and pressure.
Other standard features of the electrolysis tank are gas outlets for any hydrogen and oxygen gases generated within the tank. In the exemplary embodiment shown in
In the embodiment illustrated in
Preferably and as shown, the faces of the individual electrodes and the individual metal members are parallel to one another. It should be understood, however, that the faces of the individual electrodes and the individual metal members do not have to be parallel to one another.
In a preferred embodiment, all of the electrodes and metal members are comprised of titanium. In another preferred embodiment, all of the electrodes and metal members are comprised of stainless steel. It should be appreciated, however, that other materials can be used and that the same material does not have to be used for both the metal members and the high voltage electrodes, nor does the same material have to be used for all of the metal members, nor does the same material have to be used for both the high voltage anodes and the high voltage cathodes. In addition to titanium and stainless steel, other exemplary materials that can be used for the metal members and the high voltage electrodes include, but are not limited to, copper, iron, stainless steel, cobalt, manganese, zinc, nickel, platinum, palladium, aluminum, lithium, magnesium, boron, carbon, graphite, carbon-graphite, metal hydrides and alloys of these materials. As used in the present specification, a metal hydride refers to any compound of a metal and hydrogen or an isotope of hydrogen (e.g., deuterium, tritium).
Preferably the surface area of each of the faces of the metal members (i.e., members 117, 118, 121, 122, 125, 126, 129 and 130 in
In
As previously noted, the electrolysis process of the invention generates considerable heat. To withdraw that heat so that it can be used, and to prevent the liquid within the tank from becoming too hot and boiling at a given temperature, and to prevent possible damage to those system components that may be susceptible to damage, in the preferred embodiments of the invention the system includes means to actively cool the system to within an acceptable temperature range. For example, in at least one preferred embodiment the cooling system does not allow the temperature to exceed 90° C. Although it will be appreciated that the invention is not limited to a specific type of cooling system or a specific implementation of the cooling system, in at least one embodiment the electrolysis tank is surrounded by a coolant conduit 139, portions of which are shown in
As will be appreciated by those of skill in the art, there are numerous minor variations of the system described herein and shown in
It will be appreciated that the supply electronics (i.e., high voltage power supply, high voltage switch, pulse generator) shown in
It should be understood that the electrolysis system of the present invention can be operated in a number of modes, the primary differences between modes being the degree of process optimization used during operation. For example,
Once set-up is complete, electrolysis is initiated (step 809). During the electrolysis process (step 811), and as previously noted, the water is heated by the process itself. Eventually, when operation is no longer desirable, the electrolysis process is suspended (step 813). If desired, prior to further operation the tank can be drained (step 815) and refilled (step 817). Prior to refilling the tank, a series of optional steps can be performed. For example, the tank can be washed out (optional step 819) and the electrodes and/or metal members can be cleaned, for example to remove oxides, by washing with diluted acids (optional step 821). Spent, or used up, electrodes and/or metal members can also be replaced prior to refilling (optional step 823). After cleaning the system and/or replacing electrodes/members as deemed necessary, and refilling the system, the system is ready to reinitiate the electrolysis process.
The above sequence of processing steps works best once the operational parameters have been optimized for a specific system configuration since the system configuration will impact the heat generation efficiency of the process. Exemplary system configuration parameters that affect the optimal electrolysis settings include tank size, quantity of water, type and/or quality of water, electrolyte composition, electrolyte concentration, electrode size, electrode composition, electrode shape, electrode configuration, electrode separation, metal member size, metal member composition, metal member shape, metal member configuration, metal member separation, cell number, cell separation, initial water temperature, high voltage setting, pulse frequency and pulse duration.
After the initial set-up is completed, electrolysis is initiated (step 909) and system output is monitored (step 911), for example absolute temperature or the rate of temperature increase. Although system optimization can begin immediately, preferably the system is allowed to run for an initial period of time (step 913) prior to optimization. The initial period of operation can be based on achieving a predetermined output, for example a specific level of temperature increase, or achieving a steady state output (e.g., steady state temperature). Alternately the initial period of time can simply be a predetermined time period, for example 6 hours.
After the initial time period is exceeded, the system output (e.g., temperature rate increase, steady state temperature, etc.) is monitored (step 915) while optimizing one or more of the operational parameters. Although the order of parameter optimization is not critical, in at least one preferred embodiment the first parameter to be optimized is pulse duration (step 917). Then the pulse frequency is optimized (step 918), followed by optimization of the high voltage (step 919). In this embodiment after optimization is complete the electrolysis process is allowed to continue (step 921) without further optimization until the process is halted, step 923. In another, and preferred, alternative approach illustrated in
Note that the optimization processes described relative to
The optimization process described relative to
As will be understood by those familiar with the art, the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the disclosures and descriptions herein are intended to be illustrative, but not limiting, of the scope of the invention which is set forth in the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2,590,421 | May 2007 | CA | national |
