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. 2,590,490, 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 source. 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 an electrolysis system and method of using same. In addition to an electrolysis tank and a membrane separating the tank into two regions, the system includes a plurality of metal members and a plurality of high voltage electrodes. The plurality of metal members includes at least a first metal member and a second metal member contained within the first region of the electrolysis tank and at least a third metal member and a fourth metal member contained within the second region of the electrolysis tank. The plurality of high voltage electrodes includes at least a first high voltage anode contained within the first region of the electrolysis tank and interposed between the first and second metal members, and at least a first high voltage cathode contained within the second region of the electrolysis tank and interposed between the third and fourth metal members. The high voltage applied to the high voltage electrodes is pulsed. 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 high voltage pulses occur at a frequency between 50 Hz and 1 MHz, and more preferably at a frequency between 100 Hz and 10 kHz. Preferably the high voltage pulses have a pulse duration of between 0.01 and 75 percent of the time period defined by the frequency, and more preferably a pulse duration of 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. The metal members and the high voltage electrodes are fabricated from any of a variety of materials, although preferably the material 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. The metal members and the high voltage electrodes can utilize any of a variety of surface shapes and can be either positioned parallel to one another or not parallel to one another.
In at least one embodiment, the concentration of electrolyte in the liquid is between 0.05 and 10 percent by weight. In at least one other embodiment of the invention, the concentration of electrolyte in the liquid is between 0.05 and 2.0 percent by weight. In yet at least one other embodiment of the invention, the concentration of electrolyte in the liquid is between 0.1 and 0.5 percent by weight.
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.
Separating tank 101 into two regions is a membrane 105. Membrane 105 permits ion/electron exchange between the two regions of tank 101 while keeping separate the oxygen and hydrogen bubbles produced during electrolysis. Maintaining separate hydrogen and oxygen gas regions is important not only as a means of allowing the collection of pure hydrogen gas and pure oxygen gas, but also as a means of minimizing the risk of explosions due to the inadvertent recombination of the two gases. Exemplary materials for membrane 105 include, but are not limited to, polypropylene, tetrafluoroethylene, asbestos, etc. In at least one embodiment, membrane 105 is 25 microns thick and comprised of polypropylene.
As noted herein, the present system is capable of generating considerable heat. Accordingly, system components such as tank 101 and membrane 105 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 membrane 105) 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 electrolysis tank 101 are gas outlets 107 and 109. As hydrogen gas is produced at the cathode and oxygen gas is produced at the anode, in the exemplary embodiment shown in
The electrolysis system of the invention uses a combination of metal members and high voltage electrodes. The metal members include at least two metal members within each region of the electrolysis tank. The high voltage electrodes include at least one high voltage cathode interposed between at least two metal members within one region of the tank, and at least one high voltage anode interposed between at least two metal members within the other region of the tank. Assuming multiple high voltage cathodes and/or multiple high voltage anodes, all cathodes are kept in one region of tank 101 while all anodes are kept in the other tank region, the two tank regions separated by membrane 105.
In the embodiment illustrated in
As previously noted, the high voltage cathode (or cathodes) is positioned between at least one pair of metal members and the high voltage anode (or anodes) is positioned between at least one pair of metal members. Thus in the exemplary embodiment shown in
In one preferred embodiment, electrodes 115/117 and metal members 121/123/125/127 are comprised of titanium. In another preferred embodiment, electrodes 115/117 and metal members 121/123/125/127 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 both the high voltage anodes and the high voltage cathodes, nor does the same material have to be used for all of the metal members. 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 the faces of the metal members is a large percentage of the cross-sectional area of tank 101, typically on the order of at least 40 percent of the cross-sectional area of tank 101, and often between approximately 70 percent and 90 percent of the cross-sectional area of tank 101. The high voltage electrodes (e.g., electrodes 115 and 117) may be larger, smaller or the same size as the metal members (e.g., metal members 121, 123, 125 and 127).
Typically the voltage applied to high voltage electrodes 115/117 by source 119 is within the range of 50 volts to 50 kilovolts, and preferably within the range of 100 volts to 5 kilovolts. Rather than continually apply voltage to the electrodes, source 119 is pulsed, preferably at a frequency of between 50 Hz and 1 MHz, and more preferably at a frequency of between 100 Hz and 10 kHz. The pulse width (i.e., 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. Thus, for example, for a frequency of 150 Hz, the pulse duration is preferably in the range of 0.67 microseconds to 5 milliseconds, and more preferably in the range of 66.7 microseconds to 3.3 milliseconds. Alternately, for example, for a frequency of 1 kHz, the pulse duration is preferably in the range of 0.1 microseconds to 0.75 milliseconds, and more preferably in the range of 10 microseconds to 0.5 milliseconds. The frequency and/or pulse duration can be changed during system operation, thus allowing the system output efficiency to be continually optimized. Although voltage source 119 can include internal pulsing means, preferably an external pulse generator 129 controls a high voltage switch 131 which, in turn, controls the output of voltage source 119. Other means for pulsing the voltage source are clearly envisioned, for example using a switching power supply coupled to an external pulse generator or using a switching power supply with an internal pulse generator.
As described herein, the electrolysis process of the invention generates considerable heat. It will be appreciated that if the system is allowed to become too hot for a given pressure, the fluid within tank 101 will begin to boil. Additionally, various system components may be susceptible to heat damage. Although the system can be turned off and allowed to cool when the temperature exceeds a preset value, for example using a control system coupled to a thermocouple or other heat monitor which triggers the control system when the system (or tank fluid) exceeds the preset value, this is not a preferred approach due to the inherent inefficiency of stopping the process, allowing the system to cool, and then restarting the system. A more efficient, and preferred, approach uses means which actively cool the system to maintain the temperature within an acceptable range. 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 tank 101 is surrounded by coolant conduit 133, 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 should be understood that 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,
After process termination, electrolysis can be re-initiated when desired. Prior to electrolysis re-initiation, if desired the water in the electrolysis tank can be removed (step 715) and the tank refilled (step 717). Prior to refilling the tank, a series of optional steps can be performed. For example, the tank can be washed out (optional step 719) and the electrodes can be cleaned, for example to remove oxides, by washing the electrodes with diluted acids (optional step 721). Spent, or used up, electrodes can also be replaced prior to refilling (optional step 723).
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 production efficiency of the process and therefore the system output. 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, pressure, electrode size, electrode composition, electrode shape, electrode configuration, electrode separation, metal member size, metal member composition, metal member shape, metal member configuration, high voltage setting, pulse frequency and pulse duration.
After the initial set-up is completed, electrolysis is initiated (step 809) and the output of the system is monitored (step 811), for example the rate of temperature increase. System optimization can begin immediately or the system can be allowed to run for an initial period of time (step 813) prior to optimization. The initial period of operation can be based on achieving a predetermined output, for example a specific rate of temperature increase, or achieving a steady state output (e.g., a specific temperature). Alternately the initial period of time can simply be a predetermined time period, for example 3 hours.
After the initial time period is exceeded, assuming that the selected approach uses step 813, the system output is monitored (step 815) 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 817) followed by the optimization of the pulse frequency (step 818). Then the voltage of the high voltage supply is optimized (step 819). In this embodiment after optimization is complete the electrolysis process is allowed to continue (step 821) without further optimization until the process is halted, step 823. In another, and preferred, alternative approach illustrated in
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 |
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2,590,490 | May 2007 | CA | national |