The present invention generally relates to a method for using nanoporous materials to convert mechanical motion and/or heat into electrical energy. In one embodiment, the present invention relates to the use of a nanopore confinement effect that results from a fluid infiltrating a porous material as a means to generating electrical energy. In another embodiment, the present invention relates to the use of a nanopore confinement effect that results from a continuous solid phase infiltrating a porous material as a means to generate electrical energy. In still another embodiment, the present invention relates to the use of a thermoelectric effect that results from a fluid infiltrating a porous material as a means to generate electrical energy. In yet another embodiment, the present invention relates to the use of a thermoelectric effect that results from a continuous solid phase infiltrating a porous material as a means to generate electrical energy. In yet another embodiment, the present invention relates to applying the foregoing mechanoelectric effect or thermoelectric effect to high surface area and/or small-structured solids as a means of enhancing and/or supplementing otherwise inefficient and/or insufficient electrical energy generation.
One type of conventional ion separation generators include water drop electrostatic generators. As drops of an ionized aqueous liquid separate from a body of the liquid, they carry excess ions. Therefore, charge separation can be achieved. According to this method, liquid ionization is achieved using electrodes. In general, as an electric field is applied across the liquid phase, the cations and anions in the liquid are attracted to the oppositely charged electrodes, and thus the ion distribution becomes heterogeneous. Alternatively, charge separation can be achieved in ionic liquids through an electrostatic effect. In this case, as a liquid flows over a solid surface or through a nozzle, ion mobility at the solid-liquid interface double layer is lower than that of the bulk liquid phase. Thus, the liquid flow carries excess charges. In either case, mechanical work is done by gravitational force or by external loading so as to overcome the electrical forces associated with charge separation. Accordingly, mechanical energy is converted into electrical energy. Thus, the device is mechanoelectrical. Systems such as these suffer from a number of problems that render them impractical. Among these problems is their very low power generation efficiency and rate.
The electrostatic effect can be amplified by the large surface area of a nanoporous material. For instance, if the electrostatic charge separation at a solid-liquid interface double layer occurs in a nanochannel or a nanopore, similar mechanical-to-electrical energy conversion can be observed. Due to the large surface area, the overall energy conversion efficiency can be improved. However, charge separation in this system is still caused by the difference in ion mobility in the interfacial double layer relative to a bulk electrolyte. Moreover, to form a double layer, the size of the nanochannel and/or nanopore must be larger than, or at least comparable to, the double layer thickness. Thus this technique cannot be extended to microporous materials of the smallest nanopores and the largest specific surface areas.
In view of the foregoing, there is a need in the art for a device and method for efficiently generating electrical energy using mechanoelectrical and/or thermoelectrical principles.
The present invention generally relates to a method for using nanoporous materials to convert mechanical motion and/or heat into electrical energy. In one embodiment, the present invention relates to the use of a nanopore confinement effect that results from a fluid infiltrating a porous material as a means to generating electrical energy. In another embodiment, the present invention relates to the use of a nanopore confinement effect that results from a continuous solid phase infiltrating a porous material as a means to generate electrical energy. In still another embodiment, the present invention relates to the use of a thermoelectric effect that results from a fluid infiltrating a porous material as a means to generate electrical energy. In yet another embodiment, the present invention relates to the use of a thermoelectric effect that results from a continuous solid phase infiltrating a porous material as a means to generate electrical energy. In yet another embodiment, the present invention relates to applying the foregoing mechanoelectric effect or thermoelectric effect to high surface area and/or small-structured solids as a means of enhancing and/or supplementing otherwise inefficient and/or insufficient electrical energy generation.
In one embodiment, the present invention relates to a mechanoelectric power generating device comprising: a nanoporous material disposed within a containment means, wherein the nanoporous material is capable of separating ions according to size; an electrolyte containing anions and cations disposed within the containment means, wherein the electrolyte is made up of anions and cations that differ in size so that the smaller ion is capable of permeating the nanoporous material, and wherein the larger ions are substantially excluded from the nanoporous material, and wherein the electrolyte is capable of being contained within the containment means; a loading means located and/or disposed within the containment means, wherein the loading means is capable of imparting a mechanical load upon the contents of the containment means, the load being sufficient to cause at least a portion of the electrolyte to at least partially infiltrate the nanoporous material; and at least one contact in electrical communication with the containment means, the electrolyte and/or the nanoporous material, wherein the contact is capable of harvesting any excess electrical charge.
In another embodiment, the present invention relates to a thermoelectric power generating devices comprising: a conductive means that is capable of conducting charge to and from a nanoporous material, wherein the conductive means is disposed in a containment means; a nanoporous material disposed within the containment means, wherein the nanoporous material is capable of separating charge and/or containing excess charge, wherein the nanoporous material and the conductive means are in thermal and electrical communication with the containment means; a temperature control means designed to permit control of the temperature of the containment means, the conductive means, and the nanoporous material; and a means for harvesting excess charge from the conductive means and/or containment means.
a) a schematic diagram of a mechanoelectrical device formed in accordance with one embodiment of the present invention;
b) is a graph illustrating the measured output voltage as a function of time for the device of
a) is a schematic diagram of a thermoelectric device formed in accordance with one embodiment of the present invention;
b) is a graph illustrating the measured output voltage as a function of temperature for the device of
a) is a schematic diagram of a thermoelectric device formed in accordance with another embodiment of the present invention;
b) is a graph illustrating the potential difference, at two different m values, as a function of a change in temperature (ΔT), where m is the mass of the nanoporous carbon electrode;
The present invention generally relates to a method for using nanoporous materials to convert mechanical motion and/or heat into electrical energy. In one embodiment, the present invention relates to the use of a nanopore confinement effect that results from a fluid infiltrating a porous material as a means to generating electrical energy. In another embodiment, the present invention relates to the use of a nanopore confinement effect that results from a continuous solid phase infiltrating a porous material as a means to generate electrical energy. In still another embodiment, the present invention relates to the use of a thermoelectric effect that results from a fluid infiltrating a porous material as a means to generate electrical energy. In yet another embodiment, the present invention relates to the use of a thermoelectric effect that results from a continuous solid phase infiltrating a porous material as a means to generate electrical energy. In yet another embodiment, the present invention relates to applying the foregoing mechanoelectric effect or thermoelectric effect to high surface area and/or small-structured solids as a means of enhancing and/or supplementing otherwise inefficient and/or insufficient electrical energy generation.
Nanoporous materials, as used herein, includes materials having average pore sizes or microchannel/microtube sizes from about 0.5 nm to about 1,000 nm, and can be either electrically conductive or electrically non-conductive. Nanoporous materials within the scope of the present invention include microporous materials with pore sizes smaller than about 2 nm, mesoporous materials with pore sizes larger than about 2 nm but smaller than about 50 nm, macroporous materials with pore sizes larger than about 50 nm, as well as clusters or stacks of nanodots, nanoparticles, nanowires, nanorods, and nanolayers and other nano and/or micro-structured materials having high surface areas. Nanoporous materials within the scope of the present invention also include micro/nano-electromechanical systems (MNEMS) devices containing micro and/or nano-channels/tubes. The only limitation on the kinds of materials that can comprise a nanoporous material of the present invention is that appropriate material(s) must be capable of being formed into one or more of the foregoing structures.
Exemplary nanoporous materials within the scope of the present invention include, but are not limited to, nanoporous oxides, nanoporous silicon, nanoporous carbons, zeolites or zeolite-like materials such as silicalites, porous polymers, porous metals and alloys, natural clays, or any combination of two or more thereof. In another embodiment, exemplary nanoporous materials within the scope of the present invention include, but are not limited to, silica, titania, alumina, zirconia, magnesia, Nb2O5, SnO2, In2O3, ZnO, kaolins, serpentines, smectites, glauconite, chlorites, vermiculites, attapulgite, sepiolite, allophane, imogolite, zeolites, silicalite, silicon, silicones, polypyrrole, binary compounds (e.g., sulfides and nitrides), polyurethanes, acetates, amorphous carbons, semi-crystalline carbons, crystalline carbons, carbon nanotubes, graphene layers, iron, steel, gold, silver, copper, or any suitable combination of two or more thereof. In still another embodiment, exemplary nanoporous materials within the scope of the present invention include, but are not limited to, diatoms, radiolarii, and abalone shell. Additionally, nanoporous materials within the scope of the present invention include, but are not limited to, polymers such as latex, polyolefins, and polyurethanes.
Additionally, one of ordinary skill in the art would recognize that any of the foregoing materials alone, or in combination, can be modified with one or more surface coatings as a means of altering its surface properties. To this end, one of ordinary skill in the art would readily recognize that a wide variety of functional groups are available for appropriate surface modifications. Exemplary functional groups include, but are not limited to, hydroxyls, silanes, siloxanes, organically substituted siloxanes, alcohols, phenols, amines, carboxylic acids, sulfates, sulfites, sulfides, nitrates, nitrites, nitrides, phosphates, phosphites, nitrites, isocyanides, isothiocyanides, thiols, or any suitable combination of two or more thereof.
Liquids within the scope of the present invention can be either conductive or non-conductive. Exemplary liquids within the scope of the present invention include, but are not limited to, distilled and/or de-ionized water, waters having one or more dissolved chemicals, molten metals and/or alloys, molten salts (e.g., organic molten salts and inorganic molten salts), oils, oil-based solutions, alcohols, alcohol solutions. In still another embodiment, exemplary liquids within the scope of the present invention include, but are not limited to, benzene, toluene, n-heptane and the like. Molten metals and/or within the scope of the present invention include, but are not limited to, mercury, gallium, lead, copper, iron, nickel, Monel and any combination thereof. Monel is a trademark of Inco Alloys International, of West Va., and can be purchased from any of a variety of sources including Chand Eisenmann Metallurgical, Inc.
Both mechanoelectric and thermoelectric embodiments of the present invention comprise at least one solid electrode in electrical contact with a liquid electrolyte. Generally, contacting an electrode carrying excess charge with a liquid electrolyte results in the formation of a double layer, as shown in
The mechanoelectric embodiments of the present invention operate, in part, on the difference in mobility between anions and cations in a nanoporous material. More specifically, if the nanopore is large enough to accept the smaller ion but small enough to exclude the larger ion, the liquid can comprise and/or assume two differently charged regions (i.e., charge separation). The confined liquid in the nanopores has an excess of the smaller ion, and the bulk liquid outside the nanoporous material has an excess of the larger ion. Excess charge is collected using a large-surface-area electrode. Thus, a considerable portion of the mechanical work that is done in relation to liquid infiltration can be converted to electric energy.
a) illustrates one mechanoelectric embodiment of the present invention. As is shown in
In one example, device 100 comprises about 0.5 grams of nanoporous silicalite (ZSM-5) immersed in about 4.0 grams of an aqueous solution of 27% NaCl, which is sealed in a stainless steel container with a stainless steel piston having an O-ring seal (113 PU70, O-rings Inc.). The ZSM-5 zeolite is hydrothermally synthesized with the molar ratios of 0.01 Na2O/1.0 ethylamine/1.0 SiO2/15 H2O to the reactant. The Na2O is calculated from NaOH. The ethylamine utilized is 70% in H2O (E3754, Sigma-Aldrich). The silicon source is silica sol (LUDOX HS-30 colloidal silica, 30 weight percent, 420824, Sigma-Aldrich). The water is de-ionized water (3234-7, VWR). The reactant is then sealed in a 50 mL stainless steel autoclave and hydrothermally reacted at 180° C. for 18 hours without stirring. The stainless steel autoclave included a cylinder and a cap which are sealed tightly. The cylinder includes an approximately 4 mm thick polytetrafluoroethylene liner.
The silica sol with ethylamine template crystallizes under high temperature and pressure generated in the autoclave. The as-synthesized product is washed with cold de-ionized water, filtered with a Buchner funnel and Whatman filter paper, dried in an oven (1410, VWR) at 100° C. for one hour, and then calcined in a furnace (HTF55322A, VWR) at 550° C. for two hours with a flow of air sufficient to remove the organic template.
It should be noted, that the above embodiment of the present invention is not limited to use the of ZSM-5 zeolite for the energy generation, and that a variety of other materials can be used and/or replace the ZSM-5. Alternatively, a combination of one or more materials can be used, with such a combination including, or not including, ZSM-5. In one instance, ZSM-5 can be replaced by any nanoporous material with a suitable nanopore size. In other words, the nanopore size should be considerably larger than one type of ion (either the anion or cation) and comparable or smaller than that of the counter ion.
Similarly, it should be noted, that the above embodiment of the present invention is not limited to the electrolytes set forth in the foregoing example. Rather, the electrolytes utilized therein can include any electrolytes and/or polyelectrolytes comprised of positively charged and negatively charged ions having sizes that are different enough to be preferentially accepted/excluded by the chosen nanoporous material. Such materials include, but are not limited to, chlorides, acetate, iodates, nitrates, nitrites, hydroxides, sulfides, pyroantimonates, sulfites, sulfates, metavanadates, tungstates, phosphates, phosphate monobasic/dibasic salts, tetraborates, bromides, bromates, oxalates, chlorates, carbonates, chromates, dichromates, bicarbonates, Fe(CN)64− salts, pyrophosphates (e.g., pyrophosphate tetrabasic or dibasic salts), methyltrioctylammonium salts and related polyelectrolytes, cesium salts and related polyelectrolytes, hexadecyltrimethylammonium salts and related polyelectrolytes, and tetrabutylammonium salts and related polyelectrolytes.
In some embodiments the container and the piston can be insulated with polytetrafluoroethylene tape. Some embodiments optionally include a porous Monel rod (OD: 0.3750 inch; length: 0.75 inch; micron grade: 0.5; available from Chand Eisenmann Metallurgical, Inc.) that can be placed at the bottom of the container to act as an electrode. However, any of a variety of porous metals and/or alloys can be substituted for the rod set forth above. Moreover, the shape of the electrode is not limited to the rod shape set forth above, but rather can be any convenient shape including a disk, a washer, a ribbon, a wire, spherical, ellipsoidal, or irregular.
In other embodiments the voltage of the stainless steel container can be monitored. Monitoring can be continuous, intermittent, a combination of continuous and intermittent. Furthermore, such monitoring can be carried out by any appropriate means. Such monitoring means can include, but is not limited to, a multimeter, a voltmeter, and/or a computer of any appropriate kind. In one specific example, monitoring can be accomplished with an NI 6036E DAQ board, hosted by a computer running Labview software.
In one example the average nanopore size of a silicalite is 0.53×0.56 nm, and the pore size of the Monel electrode is 500 nm. The nanopore size is much larger than the cation but somewhat comparable to the size of the anion. In this example, the dimensions of the Monel rod is 0.1×0.3 inches, and it is used to increase the contact area between the liquid phase and the electrode. The height of the container is about 1.5 inches, and the inner diameter is about 0.75 inch. The size of the sodium cation is 0.095 nm, and the size of the chloride anion is 0.18 nm. The silicalite is hydrophobic, and therefore when no external loading is applied the liquid can not enter the nanopores.
In this example, a compressive load is then applied through the piston using a type-5569 Instron machine. The rate of the crosshead is set to about 1 mm/min. As the piston is compressed into the container, the inner pressure increases. When the capillary effect of nanopores is overcome, the liquid is forced into the nanopores. Since the large anions resist entering the relatively small nanopores, cation infiltration exceeds that of anion infiltration, and as a result charge separation and/or isolation occurs. In this example, the confined liquid inside the nanopores is positively charged, and the bulk liquid outside the nanopores is negatively charged. At the interface of the electrode (the inner surface of the steel container and the pore surface of the porous Monel rod), double layers are formed and countercharges are induced in the solid, leading to a net output voltage between the electrode and the ground.
A mechanoelectric device in accordance with another embodiment of the present invention is illustrated in
Furthermore, the containment means of the device of
The thermoelectric embodiments of the present invention operate, in part, on the principle that when two dissimilar materials are in electrical contact charge moves across the interface (or the double layer) due to thermal motion. Furthermore, charge mobility changes as a function of temperature. Thus, when two dissimilar materials are in electrical contact a net potential difference is generated. Due to the small contact area of prior art systems, the efficiency of electric energy generation is quite low. However, in accordance with the present invention, a nanoporous solid in electrical contact with a liquid electrolyte is capable of very efficient energy conversion due to the large surface area present.
a) illustrates one thermoelectric embodiment of the present invention. As is shown in
In one example, the device of
a) depicts another thermoelectric embodiment in accordance with the present invention. As can be seen from
Although not restricted thereto, the foregoing example includes the following. A J. K. Baker Norit SX2 nanoporous carbon is used to create large-surface-area electrodes. The as-received carbon material is in powder form, with an average particle size of about 20 μm. The average pore size is about 1 to about 10 nm, and the specific surface area is about 800 m2/g. Nanoporous electrodes are prepared by mixing eight parts nanoporous carbon, one part Soltex ACE acetylene black (AB), and one part Aldrich 182702 polyvinylidene fluoride (PVF). The mixture is then placed in a steel mold and compressed using a type-5569 Instron machine at about 500 MPa for about five minutes at room temperature. This process forms disks having diameters of about 19.0 mm. The masses of the disks are in the range of about 15 to about 60 mg. A thermoelectric system is produced by immersing two substantially identical sandwich cells in a solution of about 30 weight percent sodium chloride, which is placed into two glass containers. The sandwich cells each comprise a copper counter electrode, a porous insulating membrane separator (Sterlitech PTU0247100 PTFE un-laminated membrane filter with the pore size of 200 nm), and a nanoporous carbon electrode.
In this example, the two copper counter electrodes are directly connected by a copper wire, and the two nanoporous carbon electrodes are connected by a copper wire through a 10 kΩ resistor, R0. One container (A) is maintained at room temperature, TA. The other (B) is heated using an Aldrich Z28 controlled-temperature bath, with the temperature increase rate lower than about 0.5° C./min. The voltage, Φ, across the resistor is measured with a NI 6036E DAQ board hosted by a computer with Labview.
Still another alternative thermoelectric embodiment in accordance with the present invention is shown in
Alternatively, the foregoing embodiment can operate in electromechanical mode. According to this variation, the potential difference is manipulated to control the internal pressure of the two assemblies. Thus, by applying a potential, the system can output mechanical work.
In one embodiment, the present invention includes a high repeatability and reliability, simplicity in fabrication. In another embodiment, the present invention includes compatibility with small-scale devices, such as micro-electromechanical systems (MEMS), and with large-scale facilities such as electro-hydraulic systems. In still another embodiment, the present invention can be used to harvest electrical energy from ambient heat and mechanical motions, and/or to control temperatures, and/or to actively damp mechanical vibrations, and the like. In yet another embodiment, the present invention can also be a nanometer-scale power supply.
A thermoelectric system in accordance with the presenting invention is not required to contain a liquid phase. For instance, in embodiments where the liquid is a liquid metal, the temperature can be reduced, thereby solidifying the metal. In this embodiment the metal can still be conductive. Thus, such a system can still operate in thermoelectric mode because charge can still move across the interface of the confined phase (i.e., the solidified metal) and the nanoporous material in a temperature dependent manner.
In some embodiments the same nanoporous material can be used in either a mechanoelectric or thermoelectric system. Furthermore, some mechnoelectric embodiments can function in thermoelectric mode, and vice versa. For instance, as shown in
Although the invention has been described in detail with particular reference to certain embodiments detailed herein, other embodiments can achieve the same results. Variations and modifications of the present invention will be obvious to those skilled in the art and the present invention is intended to cover in the appended claims all such modifications and equivalents.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US2006/032472 | 8/18/2006 | WO | 00 | 6/13/2008 |
Number | Date | Country | |
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60709851 | Aug 2005 | US |