US 20050183962 A1
A system and method for generating hydrogen gas is described. The system uses a vessel for holding an electrolyte solution. A membrane is arranged in the vessel to form a chamber, and a cathode electrode is positioned in the chamber and in the electrolyte solution. An electric current is applied to the cathode, and with a cooperating anode, produces hydrogen gas using an electrolysis process. The membrane traps the hydrogen in the chamber, and assists in keeping the hydrogen separate from oxygen or other gasses. The hydrogen gas is exhausted from chamber for further refining, storage, or use.
1. A device for generating hydrogen gas, comprising:
a vessel holding an electrolyte solution;
a membrane in the vessel arranged to form a chamber;
a cathode in the chamber and positioned within the electrolyte solution;
an anode in the vessel but not in the chamber and positioned within the electrolyte solution;
a hydrogen gas collection area in the chamber;
a hydrogen gas exhaustion arrangement coupled to the gas collection area; and
an electric source connected to the cathode and the anode.
2. The device according to
3. The device according to
4. The device according to
5. The device according to
6. The device according to
7. The device according to
8. The device according to
9. The device according to
10. The device according to
11. The device according to
a second membrane arranged to form a second oxygen chamber; and
a second anode in the second oxygen chamber and positioned within the electrolyte solution.
12. The device according to
an oxygen collection area in the vessel; and
an oxygen gas exhaustion arrangement coupled to the oxygen gas collection area.
13. The device according to
14. The device according to
15. The device according to
16. The device according to
17. The device according to
18. The device according to
19. The device according to
20. The device according to
21. A method for generating hydrogen gas, comprising:
generating an electric current;
applying the electric current to a cathode and an anode, the cathode and the anode being immersed in an electrolyte solution;
conducting protons through a membrane;
generating a hydrogen gas at the cathode and an oxygen gas at the anode;
using the membrane as a barrier between the hydrogen gas and the oxygen gas; and
exhausting the hydrogen gas.
22. The method according to
positioning a photoelectric cell in a vessel holding the electrolyte; and
generating the electric current with the photoelectric cell.
23. A device for generating hydrogen gas, comprising:
a vessel having a transparent cover;
a membrane arranged in the vessel to form a hydrogen chamber and an oxygen chamber;
a cathode positioned in the hydrogen chamber;
an anode positioned in the oxygen chamber;
electrolyte solution in the hydrogen chamber, the electrolyte solution at a level sufficient to cover the cathode, but allowing a hydrogen collection space;
electrolyte solution in the oxygen chamber, the electrolyte solution at a level sufficient to cover the anode, but allowing an oxygen collection space;
a solar cell in the vessel and positioned so that light can pass through the transparent cover, the electrolyte solution, and onto the solar cell;
power conduits connecting the solar cell to the anode and to the cathode so that electricity generated by the solar cell drives an electrolysis process;
a hydrogen exhaust coupled to the hydrogen chamber; and
wherein the membrane is a proton-passing membrane, and the membrane restricts hydrogen from passing from the hydrogen chamber into the oxygen chamber, and restricts oxygen from passing from the oxygen chamber into the hydrogen chamber.
24. The device according to
25. The device according to
26. The device according to
27. The device according to
28. A method for generating a gas, comprising:
generating an electric current;
applying the electric current to a cathode and an anode, the cathode and the anode being immersed in an electrolyte solution;
conducting protons through a membrane;
generating the gas at the cathode or the anode;
using the membrane as a barrier to contain the gas; and
exhausting the gas.
This patent application refers to a Disclosure Document filed by the inventor and assigned number 529415 by the US Patent and Trademark Office.
The field of the present invention is hydrogen generation. More particularly, the present invention relates to the generation of a hydrogen gas using an electrolysis process.
Hydrogen production has been primarily carried out by large refineries using oil or natural gas as feed stock for using steam conversion. Some hydrogen manufacturing uses utility-produced electricity for causing an electrochemical reaction. Certain hydrogen producing approaches have proposed a solar assist with utility electricity, or solar-exposed opposing glass sheets with electrically conducting coatings. However, no practical way is known to generate hydrogen on-site for individual and commercial needs, exclusively by renewable energy sources, with no fossil fuel consumption or pollution.
In the prior art certain electrochemical systems have been used. One technique to create hydrogen uses utility grid electricity with a photo assist. Others use photovoltaic sources wired to a separate electrolyzer. The major hydrogen production methods used today are based on reforming natural gas using steam. This requires high temperatures, utility electricity, and considerable fossil fuel energy consumption. Hydrogen may be produced in a large refinery in a process similar to gasoline production from crude oil. Burning coal is also used to produce hydrogen, usually through the steam process. Each of these processes is dependent upon natural resources that have limited supplies and yield pollutants into the earth's environment, especially the air.
One means of hydrogen production began in Switzerland by Michael Gratzel, at the Laboratory of Phototonics and Intefaces at EPEL, Switzerland. This method employs the use of two catalyzed glass surfaces so hydrogen is produced on one surface and oxygen on the other as solar energy passes through. The upper surface is transparent, and may be coated with platinum particles to produce hydrogen. The lower surface evolves oxygen. This process is feasible but it works at a 3% or lower efficiency rate, which is an unacceptable efficiency rate at this time. This system has not been commercially utilized because of coating system inefficiencies and lack of equipment production techniques.
Certain procedures have used photoelectro means. For example, U.S. Pat. No. 6,471,834 to Roe et al. (2002) discloses an apparatus and method of performing electrolysis electrically. It separates the electrolyte into its chemical components. This design functions using direct current (DC) electricity using cathodes in conjunction with incident light energy to increase efficiency. A copper photo collector/cathode is coated with a thin layer of metal, preferably nickel, by electroplating deposition. During the electrolysis process the cathode is irradiated with light. This reduces the amount of DC electrical energy necessary to separate a given quantity of electrolytic material. This approach also requires electroplating or vapor deposition of a metal, preferably nickel, onto a conductive surface, such as a sheet of copper, which becomes near black and serves both to collect and absorb the light and simultaneously acts as a general surface. Such black surfaces will increase heat in the unit, which heat must likely be reduced. This system appears to be unsuited for residential or commercial production of hydrogen gas.
U.S. Pat. No. 6,409,893 to Holzbock (2002) proposes a work electrode and a counter electrode arrangement. One electrode has an electrochemically active surface facing the other electrode. The second electrode's surface is catalytically active. The catalytically active surface of the counter electrode contains at least one polymer and/or at least some salt of polymer doped in an electrically conductive polymer electrolyte system. This approach focuses on developing special electrodes. This design generally uses have heavy, thick electrodes to allow the flow of sufficient current. Since the catalytic activity of carbon is low, it should have a large surface and be catalytically activated. Employing platinum as the catalytically active substance is economically disadvantageous. The system also uses iodine. Iodine has a very slow reaction rate, and shortens the life of the cell because of iodine's reaction with platinum. The loss of this platinum makes the system economically disadvantageous.
U.S. Pat. No. 4,011,149 to Nozik (1977) proposes the use of a thin film where electrodes are deposited on either side of a thin solid polymer electrolyte sheet to make photoelectrolysis of water by solar radiation. This system is similar to Roe's above. Several devices are outlined which essentially employ the electrical conductor thin film layer as the electrode with a counter electrode to complete the circuit. The Nozik process for producing hydrogen from solar radiation comprises the exposure of one electrode to solar radiation. The counter-electrode is in contact with the chemically inert thin film semi-conducting layer. This layer is supported on at least one inner thin film layer that applies a bias between the electrode and the counter electrode to collect hydrogen. The thin electrodes are likely difficult and expensive to manufacture, especially when planning for large markets outside of laboratory work.
U.S. Pat. No. 6,395,252 to Getty et al. (2002) shows a very different method of making hydrogen. This method comprises the reaction of a metal catalyst in a degassed aqueous organic acid solution within a reaction vessel under anaerobic conditions requiring constant temperature and specific pH. This method requires a continuous supply of degassed aqueous organic acid solution as an example of competing hydrogen production techniques. This process has received some academic attention but little has been done to commercialize this process.
U.S. Pat. No. 6,544,400 to Hockaday et al. (2002) shows a system for delivering hydrogen by a controlled fuel stream to applications using wicking to control the contact to create a feedback mechanism. This requires a highly controlled monitoring of the process and does not appear to be designed for production of adequate quantities of hydrogen production necessary for commercial applications.
The main disadvantage of the above prior solar-to-hydrogen conversion systems is that they do not make hydrogen directly, but require a separate electrolyzer. Separate electrolyzer systems can consume as much as 38% to 40% of the electricity put in; thus industry style electrolyzers are currently only approximately 60% efficient, and typically rely on grid electricity. A distinct disadvantage is that utility grid electricity generally consumes natural gas, oil, or coal with the resultant air and environmental pollutions associated with the use of these limited natural resources.
In prior-art systems poor coatings on substrates have led to further problems. Some photoelectrochemical processes use flat glass sheets with a thin catalytic coating to attract solar energy to make electrical current. These experimental coating systems have not been proven effective over time nor have they been developed to full usefulness at this time. It has proven difficult to apply the catalytic coatings to semiconductor surfaces. The glass in this process is heavy and it has been shown that there is difficulty joining the edges to maintain adhesion of the several sheets.
The problems of previous efforts of producing hydrogen include high capital expenditures, fossil fuel consumption, pollution, low production, low efficiency, non-durable equipment, long distance energy transmission, and they do not make distributed energy on-site. Accordingly, there exists a need for an efficient, scalable system for generating hydrogen gas.
Briefly, the present invention provides a system and method for generating hydrogen gas. The system uses a vessel for holding an electrolyte solution. A membrane is arranged in the vessel to form a chamber, and a cathode electrode is positioned in the chamber and in the electrolyte solution. An electric current is applied to the cathode, and with a cooperating anode, produces hydrogen gas using an electrolysis process. The membrane traps or confines the hydrogen in an open area of the chamber, and assists in keeping the hydrogen separate from oxygen or other gasses. The hydrogen gas is exhausted from the chamber for further processing, storage, or use.
In a preferred example, the hydrogen generation system has a transparent cover and has a photovoltaic panel in the vessel. The photovoltaic panel generates the electricity for powering the electrolysis process. The photovoltaic panel may be submerged in the electrolyte solution, which acts to concentrate light rays onto the panel. Other structures, such as the cover, may be configured to further concentrate light rays onto the panel. In some examples, oxygen gas may also be collected, stored, and used. The generation system may also use an external electricity source for powering the electrolysis process when insufficient electricity is produced by the internal photovoltaic cell. The external power is preferably a renewable source, such as solar, wind, or hydro.
Advantageously, the hydrogen generation system may be configured to generate hydrogen gas using only renewable sources of energy. Further, the generation system is deployable in a contained vessel, and provides a simple membrane structure for keeping the hydrogen gas separated from the oxygen and from other contaminates.
Referring now to
Two electrodes are placed in the electrolyte solution 5. A cathode 9 is positioned in the hydrogen chamber 3, and an anode 8 is positioned in the oxygen chamber 4. An electric source 11 is coupled to the cathode 9 and the anode 8, which causes an electrolysis process. More particularly, the electrolysis process splits water molecules into its elements, with hydrogen gas forming at the cathode 9, and oxygen gas forming at the anode 8. The respective gases bubble through the electrolyte solution 5, and the hydrogen case collects in the hydrogen volume 7, while the oxygen gas collects in the oxygen volume 6. A hydrogen outlet 13 is used to exhaust hydrogen gas, and an oxygen outlet 15 is used to exhaust oxygen gas.
The membrane 17 is selected to restrict the passage of the hydrogen gas. In this way, the membrane acts to trap or confine hydrogen gas in the hydrogen collection volume 7. The membrane may also restrict the passage of oxygen, and thereby keeps the hydrogen gas from mixing with oxygen in the oxygen collection volume 6. The membrane may also be selected to facilitate the electrolysis process. For example, the membrane 17 may be a proton-exchange membrane that allows protons to pass during the electrolysis process. It will be appreciated that the composition, characteristics, and dimensions of the membrane may be selected according to specific electrolysis requirements.
Advantageously, the generation system 1 provides sufficiently pure hydrogen gas without complex gas separation equipment. Instead, the generation system 1 uses a simple membrane to keep the hydrogen separated from other gases, which enables the efficient collection of commercial grade hydrogen gas using known gas-processing techniques. It will be understood that further purifying and processing of the hydrogen gas may be desirable for some uses. Also, the energy source 11 is preferably a renewable electricity source, such as a photovoltaic cell, wind turbine, or hydro turbine, so the generation system 1 is environmentally friendly, and may be used to generate hydrogen in a wide variety of locations.
Generation system 1 uses electric energy that is generated by an energy source 11 that is outside the vessel 2. For example, the energy source may be photovoltaic cells, a wind turbine, or a hydro turbine placed a distance from the vessel. It will be appreciated that these energy sources may be used individually, or may be used in any combination. It will also be understood that the energy source may include electricity from a commercially available power grid or generator. In another example, a hydrogen generator 1 a uses an energy source which is internal to the vessel 2. More particularly, the energy source is a photovoltaic cell or panel 19 connected to the cathode 9 and the anode 8. The vessel 2 includes a transparent portion for allowing light rays to project onto the photovoltaic cell 19. It will be understood that cells may be arranged to form a photovoltaic panel if additional surface area is desirable. The light causes the photovoltaic cell to generate electricity, which drives an electrolysis process to generate hydrogen gas. Although the photovoltaic panel 19 is shown in the electrolyte solution, it will be appreciated that its position also may be otherwise selected according to lighting patterns.
Generation system 1 a may optionally connect to an external energy source 18. The energy source 18 may be, for example, the commercial power grid or generator, a solar array, a wind turbine, or a hydro turbine. The energy source 18 may also include switching controls (not shown) for selectively coupling the energy source to the anode 8 and the cathode 9. For example, the switching controls may be set to preferably allow the internal solar panel to provide power, but may switch to a wind turbine during periods of insufficient light.
Significantly, generation system 1 a provides a single vessel 2 for producing commercial grade hydrogen. An internal solar panel 19 generates electricity that drives an electrolysis process, while a membrane 17 traps the hydrogen gas and keeps it separate from the oxygen and sufficiently pure. Hydrogen gas may be exhausted into known containment or transport structures for storage or use. For example, the generation system 1 a could include a hydrogen storage tank for collecting hydrogen gas. The hydrogen may be piped to a fuel-cell where the hydrogen gas is converted into electricity as needed. In this way, the generation system 1 a enables the generation and storage of energy from renewable sources, such as solar, hydro, and wind, when those sources are available. At other times, for example when it is dark and there is no wind, the fuel cell uses the stored hydrogen energy to produce electricity.
In use, as shown in the flowchart of
Anode and cathode electrodes are separated by a membrane 17, which is preferably a proton-passing membrane. By adjusting the characteristics or dimensions of the membrane, the electrolysis process may be moderated or otherwise controlled. The generated electricity is applied to the anode and cathode electrodes in the electrolyte solution, which causes hydrogen to be produced at the cathode electrode and oxygen to be produced at the anode. The hydrogen gas bubbles through the electrolyte solution and is trapped by the membrane in a hydrogen collection volume, and the oxygen may bubble through the electrolyte and be trapped by the membrane in an oxygen collection volume. Since the membrane may be selected to restrict passage of both hydrogen and oxygen, the membrane keeps the generated hydrogen and oxygen from mixing. Preferably, the same membrane is used for controlling the electrolysis process and for trapping the hydrogen gas, although separate membranes may be used.
The hydrogen may then be exhausted for further processing, storage, or use. In a similar manner, the oxygen may be exhausted as waste, or collected for processing, storage, or use. Although the system and process is described for generating hydrogen gas, other electrolytes and membranes may be selected for the production of other gases.
The generation system applies electrical energy, preferably from a renewable source, into a vessel or case for photoelectrochemical hydrogen production. There is no separate electrolyzer as in known systems. This solar direct electrochemical process uses solar exposure on immersed photovoltaic cells to power anodes and cathodes in the electrolyte to produce the fuel gas, hydrogen. By eliminating the traditional electrolyzer, the overall cost to produce hydrogen is reduced as electrolyzers are expensive and can reduce efficiency by consuming as much as 40% of the available electricity. In the present process, the original high capital cost of the electrolyzer is eliminated. The primary concentrating process is a combination of aqueous electrolyte solution and lenses that provide solar concentration. Also the vessel or case may receive electricity from wind turbine or hydro turbines to augment the solar power.
The disclosed generation system uses an electrolysis process to generate hydrogen from an electrolyte solution. In an electrolyte-water solution the hydrogen ions have a positive (+) charge and these become attracted to the negative (−) cathode to produce hydrogen. The oxygen ions have a negative (−) charge and they become attracted to the positive (+) anode to produce oxygen. The hydrogen ions are attracted to the negative electrode where they receive electrons, become stressed by over loading and combine to form the hydrogen molecule. Likewise, the negative oxygen ions migrate toward the positive terminal in the electrolyte to give up an electron and combine to form the oxygen molecules. Electro catalysts such as platinum may be used as an electrode or a coating on an electrode to reduce the amount of energy needed to break apart and oxidize hydrogen gas.
In the hydrogen generation system, as the splitting of the water takes place, hydrogen and oxygen are produced on separate sides of the membrane and collected in separate containers or chambers. Thus, the gases are respectively channeled from the high concentration pressure in the electrolyte toward two separate low pressure reservoirs for hydrogen and oxygen. These gasses are then processed and transferred to storage tanks.
With the hydrogen and oxygen molecules cleanly separated and stored, their potential energy exists for future use. Employing fuel cells, hydrogen and oxygen may be recombined to generate clean electrical energy that is free of fossil fuel and pollution. Such fuel cell produced energy is used as electricity for homes, business, industry, as well as to power automobiles and trucks. Hydrogen may also be used in industry as fuel for combustion purposes that yields no pollution or residue.
Accordingly, the direct photoelectrochemical process combined with wind and hydro turbine energy can be used to produce hydrogen while requiring no fossil fuel such as natural gas, oil, or coal. This technology is an improvement compared to prior art and other current efforts to use just solar to make hydrogen. This present hydrogen generation process is an improvement over systems that rely on metal or glass coated plates, some of which focus only on solar assist rather than direct solar electrochemical reaction. Some systems reformulate natural gas using steam to extract hydrogen from natural gas, oil, or coal. The consumption of such fossil fuels depletes the store of such natural resources in the earth and in making hydrogen, yields environmental pollutants. This pollution negatively affects humans and the earth environment everywhere.
In addition, the present process produces hydrogen energy on-site for local energy needs. The requirement for traditional distribution equipment, related pollution, and the associated costs are eliminated. For example, hydrogen may be used in fuel cells for electrical generation for residential use or for automobile and truck energy. The proposed hydrogen production process is accomplished on-site, at a residence or business, government, or military defense facility and at any location where power is required, and without consuming any utility grid electricity. Although it may use only renewable solar, wind, and hydroelectric sources of energy, if needed, it can consume utility grid electricity for producing hydrogen. Furthermore, the present electrochemical hydrogen generator has the additional advantages in that it eliminates the traditional electrolyzer used to make hydrogen with electricity, thereby eliminating the 40% inefficiency in the operation of the electrolyzer.
The disclosed generation system is also scalable. It is easily mass produced and arranged in multiple units, thus reducing the overall cost to the consumer.
The case cover 16 and bottom of case 12 are attached by slide-in compression connectors 26 at all junctures and sealed with adhesive. The case may be manufactured in various sizes, and may be arranged in a set of multiple units for additional generation capacity, depending on hydrogen production requirements. A float system 80 may be used for automated or semi-automated water and electrolyte replacement as needed during hydrogen production. Cooling-heat transfer chips 104 are available as needed to accommodate cooling or warming needs. Cooling-heat transfer chips 106 in the liquid electrolyte may also create a stirring or agitation of the electrolyte solution to enhance electrolysis. Suitable cooling-heat transfer chips can be obtained from Cool Chips, PLC, Gibraltar.
An aqueous electrolyte 20 fills the case cavity on both sides of the membrane 24. The electrolyte comprises water and sulfuric acid, for example. In one example the electrolyte is a 10% solution, but other concentrations may be used as needed to control production of hydrogen. Other electrolytes such as polymer composite types may also be employed. Another electrolyte which may be incorporated is a polymer material from Ballard, Burnaby, BC, Canada, which is capable of conducting an electric current in the presence of water, without acid. A preferred membrane 24 may be from 50 microns to 125 microns thick while various thicknesses may be chosen to alter yield of hydrogen and oxygen. This membrane is a product of DuPont Chemical Co of Fayetteville, N.C.
A frame 22 is constructed of high density polypropylene or ABS or other plastic, to hold the membrane. The frame is constructed by mating two plastic sections. The two sections are then pressed together with the membrane 24 secured between. Epoxy adhesive is used to hold the assemblage in place in the case. The case 12 parts are mated by press friction fit and bonded with epoxy 26. It will be appreciated that the membrane may be secured and attached using other methods and materials. Device 10 is shown with two membranes, each positioned to form an oxygen chamber 46. Since the device 10 generates a greater volume of hydrogen than oxygen, the hydrogen chamber 40 is larger than the oxygen chambers 46.
A photovoltaic cell 28 is located at the base of the case 12. In one example the cell is a US—64 made by ECD Uni-Solar, Auburn Hills, Mich. This photovoltaic cell has a triple-junction amorphous silicon alloy with a transparent weather resistant fluoropolymer ETFE elastomer covering. Optionally, for some operating conditions, a cell 28 may include a triple-junction silicon photovoltaic cell with up to 34 percent efficiency and can accept solar concentrations up to 400 suns. This latter photocell is manufactured by Spectrolab, Inc, Sylmar, Calif. Such silicon cells may have a clear coating 102, or a coating product, CARC—22, from Paired Helix, Co., La Mesa, Calif.
Submersing the photovoltaic cells in the electrolyte solution acts to concentrate solar energy into the photovoltaic cell. It will be understood that adjustments to case dimensions may be used to obtain a greater degree of light concentration. Light concentration may be achieved either without a cover or with the concentrating cover 16. Such aqueous submersion of photo cells increases electrical generation from the cell.
The case 12 may be of molded plastic or other materials and is manufactured in various sizes as needed. The function of the case 12 is to hold all other parts and provide a sturdy attachment to a support structure, such as to a tracking base of a tracking system, to a building, or to the ground. The case also acts as the vessel that holds the fluid electrolyte solution, and may enable the transfer and concentration of light rays onto a photovoltaic cell.
A cover 16 functions to protect the apparatus and may also act to concentrate solar radiation. The case may be provided in multiple sections that are mated together during the assembly process. These mating parts may function by slide-in compression fittings at all junctures, although other assembly techniques may be used. A single case may contain all components necessary for the production of hydrogen and electricity. The frame of this case may be attached to a building or to the ground. Cases may then be assembled in multiple units in a master frame consisting of an array of several cases. Float 80 mechanism is attached to automatically provide water and electrolyte replacement as needed during hydrogen production. Cooling-heat transfer devices 104 may be attached to the case to stabilize temperature as required by local weather conditions.
An aqueous electrolyte 20 fills the case cavity on both sides of membrane 24 to provide a source of water for splitting water into hydrogen and oxygen. Positive and negative electrical charges emanate through the electrolyte between anode 34 and cathode 36, causing the water to split into hydrogen and oxygen. Electrolytes 20 may comprise both aqueous and polymer materials. Electrolytes may also be nonaqueous polymers capable of conducting an electric current. Polymer composites that have been used to synthesize polymeric electrolytes include polyacrylonitrile, polyvinyl pyrrolidone, and polyethylene oxide. These have low dielectric constants which lead to high degrees of ion association in polymeric electrolytes. When the base polymers are amorphous ionic conductivity is increased.
A membrane 24 may be sized and its thickness selected to yield desired production of hydrogen and oxygen. The membrane functions to control the flow of protons in the electrolyte. The membrane is a proton-exchange membrane, which serves as a solid electrolyte placed between an anode and a cathode. The proton-exchange membrane conducts protons and it does not conduct electrons. The frame 22 is provided to hold the membrane 24. The frame is constructed in two parts and held together as self mating parts using a friction fit. An adhesive is employed to attach the frame to the case. The membrane is also impermeable to the gases produced in this process. Consequently, it maintains separation between the hydrogen evolved at a cathode 34 and the oxygen evolved at an anode 36. Hydrogen diffuses out of the water into cathode collection chamber 40, and collects at the top of the reservoir. Oxygen produced in the anode chamber rises to the top of its collection chamber 46. In this way, the membrane enables the capture and collection of commercial grade hydrogen without complex separation structures.
The key for direct solar conversion is to find a light-harvesting system that efficiently collects solar energy and directs it into the water-splitting reaction. The present embodiment does this efficiently. Hydrogen is produced as a result of voltage input by solarelectro emission from a photovoltaic cell and is applied directly through cathodes and anodes in an electrolysis reaction inside the case. Also, external electric energy may be provided using windelectro electrical turbine generation or hydroelectic generated electricity. There is no separate electrolyzer employed nor is there any electricity from utility grid required as in traditional electrolysis methodology. In the present process, electricity enters the electrolysis cavity by means of connectors in a protected housing 32 as well as protective coverings and coatings.
A photovoltaic cell 28 may be a triple-junction amorphous silicon alloy with a transparent weather resistant elastomer covering. The bottom layer of the cell absorbs the red light, the middle layer absorbs green light, and the top layer absorbs blue light. This spectrum splitting capability is important in attaining higher efficiencies. The present embodiment also includes the option, for some operating conditions, to include a triple-junction silicon photovoltaic cell with up to 34 percent efficiency that can accept higher concentrations of up to 400 suns, further reducing the output cost. These high efficiency photovoltaic cells are manufactured by Spectrolab, Inc, Sylmar, Calif. In the present embodiment such silicon cells may have a chemical resistant clear coating 102 to protect the cell from degradation. This coating may also enhance electrical generation by concentration of solar energy.
In one example the photovoltaic cell 28 may be installed in strips located to receive the focused and concentrated solar radiation. Such installation reduces the area of photovoltaic cells in the case, yet functions adequately under the concentration process. This cell produces 1.8 volts. The thermodynamic potential for splitting water into H2 and O2 at 25° C. is 1.23 volts as understood in the art. For ambient temperature approximately 1.6 v to 1.8 v is needed for water decomposition. In fact, current commercial electrolyzers operate between 1.7 v and 1.9 v. Converting energy of 1.9 v into a corresponding wavelength of light produces light having a λ of 650 nm, which is in the lower energy red portion of the visible spectra. This means that the entire visible spectrum of light has sufficient energy to split water into hydrogen and oxygen. The selected photovoltaic cell takes advantage of this solar radiation.
The system may include a housing 32 (see
Electricity may be generated external to the system, and conducted into the case to drive the electrolysis process. The external energy preferably is generated using renewable sources, such as wind or water, but may be from a commercial electric grid or generator. Electricity from the wind turbine (
Solar tracking may be used to rotate the hydrogen generation system to increase the intensity of light reaching its internal solar panel. The solar tracking structure shown in
Solar tracking is used in the preferred embodiment and may be used with other embodiments. Solar tracking motion control by double axis means is directed by photodiode 70, connecting wires 74, control boxes, and direct current electric motors 76. The motor gears contact track 56, which also has matching gear teeth, both vertical and horizontal. Where electricity is required for tracking motors, a separate photocell 72 may be employed to power an ultracapacitor 78. The ultracapacitor comes from the semiconductor industry as an electrochemical unit. These capacitors contain large-surface-area electrodes with very small interelectrode gaps, and they have large volumetric capacitances. They offer better service than known batteries, taking less energy to charge them and then holding the charge longer.
The system of
Cooling-heat transfer in the cases 12 and 14 in
Referring now to
This alterative hydrogen generation system employs a thin electrode 36 such as a stainless steel screen or of other thin electrode material. The membrane 24 is placed just above the thin electrode functioning as separator of the hydrogen and oxygen. Electrode bands 34 are attached around the sides of the case to allow solar exposure on the photovoltaic cell 28. These electrodes 34 may be double layered, depending on the square centimeter surface required to obtain the desired efficiency of hydrogen production. The upper electrode 34 consists of a thin band of (perhaps 12.7 mm wide) stainless steel or other electrode material. The electrodes 34 are held in place by a holder 38. The case 14, has a collection chamber 40, emitting tube 42 and a hydrogen purification module 44, a monitoring and measurement system designed to process the hydrogen to make it available for a wider range of applications. A similar purification module 50 is in place for oxygen processing on the oxygen emitting tube 48. This embodiment also has the float 80 for water and electrolyte replacement. The hydrogen measurement device 44 is a well-known solid-state hydrogen sensor connected to a computer-based data system to record output.
The electrical connectors 52 from the photovoltaic cells lead outside the case 14 in
The system of
The system of
The connections between the photovoltaic cells 28 and the electrodes 34, 36 are accomplished by using wires 30 or an option of strips such as copper or other conductive materials including an option for composite conductors.
Wind concentration is achieved by a funnel device which compresses and concentrates what wind energy may be available to enhance electrical output of the generator and hydrogen production. Wind concentration makes it possible to produce hydrogen from the case in twilight and night conditions when no solar exposure is available. Wind turbine energy generation and photoelectrochemical process combined takes advantage of low sun areas, but also can produce hydrogen twenty four hours a day when wind and hydro energy are available. With traditional stationary solar cell settings, full sunlight is not available to the cells during the entire day. Calculations of available, useable sun range from 5.5 to 6.2 hours per day, even in the strong southern sun locations in the United States. This present embodiment process includes solar tracking to increase solar time exposure for the solar assisted hydrogen producing process.
The present hydrogen generation system also may include local storage of generated hydrogen gas. In one example, the gas may be stored in a flexible bladder storage unit. The bladder has an outer layer that will preferably be a composite polymer layer as padding to protect the entire storage unit. A strong layer, including fibers, will serve as base for an inner layer. An inner coating will include polymer material capable of preventing hydrogen dispersion through the wall of the storage unit. The unit is constructed for storing and carrying a chemically aggressive gas such as hydrogen.
Although the description above contains many specificities, these should not be construed as limiting the scope of the invention, but as merely providing illustrations of some of the presently preferred embodiments of this invention. For example, the case may have other sizes and shapes, such a circular, oval, trapezoidal, triangular, etc. The concentrator can have similar or other shapes than those just listed. The case may be thinner or thicker as desired to improve efficiency. The apparatus for the base frame and tracking mechanism may take other configurations, including fixed position, or rotation on a fixed pole, attached to a roof, or permanently fixed on a post on the ground. Solar tracking may be accomplished by thermal shifting of heat sensitive chemicals. A photodiode tracker is of another nature, such as laser directed power. Hydrogen may be collected directly without purification as there are uses for unprocessed hydrogen. Other types of electrolytes may be employed, such a potassium hydroxide or non-aqueous electrolytes. Certain polymer composite electrodes may also be introduced into these embodiments.
While particular preferred and alternative embodiments of the present invention have been disclosed, it will be appreciated that many various modifications and extensions of the above described technology may be implemented using the teaching of this invention. All such modifications and extensions are intended to be included within the true spirit and scope of the appended claims.