Thermoelectronic Energy Conversion System and Method

Abstract

To provide a novel useful system and method for thermionic energy conversion.SOLUTION: In a thermionic energy conversion system including one or more electron collectors, interfacial layers, encapsulated bodies, and / or electron emitters, a method for thermionic energy generation includes receiving power, emitting electrons, and receiving the emitted electrons, and optionally includes convectively transferring heat and / or any other suitable elements.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] Cross - Reference to Related Applications

[0001] This application claims priority to U.S. Provisional Application No. 63 / 020,986, filed on May 6, 2020, which is hereby incorporated by reference in its entirety.

[0002]

[0002] This application is related to U.S. Patent Application No. 16 / 715,705, filed on December 16, 2019, and U.S. Patent Application No. 16 / 676,131, filed on November 6, 2019, each of which is hereby incorporated by reference in its entirety.

[0003] Government Support Statement

[0003] This invention was made with government support under Contract No. W911NF - 18 - C - 0057 awarded by the U.S. Defense Advanced Research Projects Agency. The government has certain rights in this invention.

[0004] Technical Field

[0004] The present invention generally relates to the field of thermionic energy conversion, and more specifically, to novel and useful systems and methods in the field of thermionic energy conversion.

Background Art

[0005]

[0005] Many typical thermionic energy converters (TECs) have inadequate control of collector temperature and / or electrode spacing. Additionally, the management of work - function - reducing materials (such as cesium) can be difficult in such TECs. Therefore, in the field of thermionic energy conversion, there is a need to create novel and useful systems and methods for thermionic energy conversion.

Brief Description of the Drawings

[0006]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 4

Figure 5

Figure 6A

Figure 6B

Figure 7

DETAILED DESCRIPTION OF THE INVENTION

[0007]

[0014] The following description of the preferred embodiments of the present invention is not intended to limit the present invention to these preferred embodiments, but is intended to enable those skilled in the art to manufacture and use the present invention.

[0008] 1. Advantages

[0015] Variations of this technology can provide several advantages and / or benefits.

[0009]

[0016] First, in variations of this technology, the temperature of the electron collector can be reliably maintained at or near the target electron collector operating temperature (±1 °C, ±5 °C, ±10 °C, ±20 °C, ±30 °C, ±50 °C, ±100 °C, etc.). In a specific example, the interface layer can thermally couple the electron collector to a cooling mechanism and / or other thermal control elements (e.g., directly or indirectly).

[0010]

[0017] Second, variations of this technique can maintain a desired spacing (or range of spacings) between the electron collector and the electron emitter (e.g., establish an appropriate interelectrode gap for efficient thermionic energy converter operation). For example, the interface layer can apply a force to the electron collector to maintain the electron collector in an appropriate position relative to the electron emitter (e.g., press the electron collector against one or more spacer elements that function to maintain the interelectrode gap). In some examples, the interface layer is mechanically compliant, which can accommodate dimensional changes of one or more components (e.g., spacers, electron collectors, electron emitters, enclosures, etc.) due to thermal expansion and / or contraction (e.g., when the system transitions to and / or from the system operating temperature, when the temperature of elements within the system changes during operation).

[0011]

[0018] Third, variations of this technique can store (and / or release) a work function reducing material (e.g., an alkali metal and / or alkaline earth metal such as Cs, Ba, Sr, and / or oxides thereof, materials containing such elements). In a specific example, the work function reducing material can be included in the interface layer, eliminating the need for a separate reservoir (and / or supply) for the work function reducing material within the system.

[0012]

[0019] Fourth, variations of this technique can control the location and / or amount of work function reducing material within the system. In some hot electron energy converters, depending on the location, amount, and / or concentration of the work function reducing material, the work function reducing material can form an unwanted electrical path within the system (e.g., a parasitic shunt and / or short circuit between the collector and emitter), react with components of the system, inappropriately change the work function of the electron collector (e.g., due to an insufficient or excessive coating of the collector surface by the work function reducing material, the work function reduction can be inappropriate or excessive), and / or otherwise affect the operation of the system. Variations of this technique can function to avoid or mitigate one or more such problems through control of the work function reducing material. In specific examples, the structure, temperature, and / or temperature gradient of the interface layer (and / or other elements of the system) can localize the work function reducing material within the interface layer and / or otherwise control the location, amount, and / or concentration of the work function reducing material.

[0013]

[0020] However, variations of this technique can provide other suitable advantages and / or benefits.

[0014] 2. System.

[0021] As shown by way of example in FIG. 1, a hot electron energy conversion system 100 can include one or more electron collectors 110, an interface layer 120, an encapsulation 130, and / or an electron emitter 140. However, the system can additionally or alternatively include any other suitable elements.

[0015]

[0022] In some examples, the system can include one or more elements as described in U.S. Patent Application No. 16 / 883,762, entitled "SYSTEM AND METHOD FOR THERMIONIC ENERGY CONVERSION," filed on May 26, 2020 (e.g., the "emitter module 100" of U.S. Patent Application No. 16 / 883,762 includes an electron emitter, the "collector module 200" of U.S. Patent Application No. 16 / 883,762 includes an electron collector and / or an interface layer, and one or more of the "emitter module 100," "collector module 200," and / or "seal 300" include one or more elements of the enclosure, etc.), which is hereby incorporated by reference in its entirety. For example, system 100 can include an emitter module (e.g., similar to the "emitter module 100" described in U.S. Patent Application No. 16 / 883,762) that includes an electron emitter 140 and a first portion of the enclosure 130, a collector module (e.g., similar to the "collector module 200" described in U.S. Patent Application No. 16 / 883,762) that includes an electron collector 110, an interface layer 120, and a second portion of the enclosure 130, and / or a seal (e.g., similar to the "seal 300" described in U.S. Patent Application No. 16 / 883,762) that includes a third portion of the enclosure 130. The system preferably functions to convert thermal input into electrical energy output.

[0016]

[0023] The electron collector (e.g., anode) preferably functions to collect electrons (e.g., electrons emitted from an electron emitter such as thermally ionically emitted electrons). At least one broad surface of the electron collector preferably faces at least one broad surface of the electron emitter through a gap (electrode gap). The gap preferably defines the separation distance (electrode spacing) between the electron collector and the electron emitter. In some examples, the electrode spacing is preferably between 100 nm and 1 mm, but alternatively may be less than 100 nm or greater than 1 mm. The gap (e.g., average gap, minimum gap, etc.) is preferably greater than a threshold minimum width (e.g., 0.1, 0.2, 0.3, 0.5, 0.75, 1, 2, 3, 5, 7.5, 10, 20, 30, 50, 75, 100, 200, 500, 1000, 0.1 - 0.3, 0.3 - 1, 1 - 3, 3 - 10, 10 - 30, 30 - 100, 100 - 300, and / or 300 - 1000 μm, etc.), but additionally or alternatively, it can be less than 100 nm or have any other appropriate width. The gap (e.g., average gap, minimum gap, etc.) is preferably less than a threshold maximum width (e.g., 1, 2, 3, 5, 7.5, 10, 20, 30, 50, 75, 100, 200, 500, 1000, 3000, 1 - 3, 3 - 10, 10 - 30, 30 - 100, 100 - 300, 300 - 1000, and / or 1000 - 3000 μm, etc.), but additionally or alternatively, it may be greater than 3 mm or have other appropriate widths. For example, the gap can have a width in the range of 0.2 - 20 mm (e.g., 1 - 10, 1 - 3, 3 - 6, 5 - 10, or 10 - 20 mm, etc.), but additionally or alternatively, it may be narrower (or may not exist or substantially not exist). However, the gap width can additionally or alternatively be 20 - 50 mm, 50 - 200 mm, or greater than 200 mm.

[0017]

[0024] The gap can be defined and / or maintained by the spacer 150 (e.g., as described in U.S. Patent Application No. 16 / 676,131, filed Nov. 6, 2019, entitled “SYSTEM AND METHOD FOR THERMIONIC ENERGY CONVERSION”, which is hereby incorporated by reference in its entirety). For example, the electron collector can be pressed against (e.g., by an interface layer) a spacer disposed (and maintained) within the interelectrode gap between the collector and the emitter. However, the gap may be maintained additionally or alternatively by pockets or other mechanical fixtures and / or by other suitable means.

[0018]

[0025] The electron collector is preferably coupled (e.g., mechanically, electrically, thermally, chemically, etc.) to the interface layer. The electron collector is preferably coupled to the interface layer along at least one broad surface that does not face the electron emitter, although the electron collector may be coupled to the interface layer along any suitable broad surface. The electron collector is preferably conductive and / or semiconductive. For example, the electron collector can be a metal (e.g., a high melting point metal and / or a low work function metal such as tungsten, molybdenum, platinum, nickel, nickel alloy, superalloy, stainless steel, niobium, iridium, tantalum, etc.; a metal that exhibits a low work function alone; a metal that exhibits a low work function when exposed to an environment where the work function decreases, such as an environment of barium, strontium, and / or cesium that optionally contains oxygen, etc.), a semiconductor (an n-type semiconductor, a p-type semiconductor, a collector material such as the collector materials described in U.S. Patent Application No. 16 / 715,705, filed Dec. 16, 2019, entitled "SYSTEM AND METHOD FOR WORK FUNCTION REDUCTION AND THERMIONIC ENERGY CONVERSION", and / or U.S. Application No. 16 / 676,131, filed Nov. 6, 2019, entitled "System and Method for Thermionic Energy Conversion", each of which is hereby incorporated by reference in its entirety), and / or one or more other suitable materials (i.e., made from).

[0019]

[0026] During operation of a typical thermionic energy converter, the temperature of the electron collector may increase (e.g., exceed the optimal operating temperature, exceed the target operating temperature, exceed the phase transition temperature of the collector material, etc.). The temperature increase can occur due to heat transfer from the electron emitter (e.g., radiation, conduction, convection, combinations thereof, etc.), receipt of electrons from the electron emitter, parasitic heat fluxes through the system, and / or other means. The electron collector generally achieves its highest efficiency below a threshold temperature (e.g., a threshold temperature below the electron emitter operating temperature). Therefore, it may be beneficial to cool and / or maintain (e.g., during operation) the electron collector at a target electron collector temperature or temperature range.

[0020]

[0027] The electron collector is preferably coupled to or includes one or more work function reducing materials that can function to reduce the work function of the collector. For example, work function reducing materials present within the system (e.g., retained within an interface layer and / or present as a vapor within the system housing) deposit on, are present on, and / or interact in other ways with the surface of the electron collector. The work function reducing materials preferably include one or more alkali metals and / or alkaline earth metals (and / or their compounds such as oxides and / or fluorides), more preferably coating (e.g., as a single layer or several single layers) or partially coating (e.g., as a partial single layer) one or more surfaces such as the electron collector surface. However, the electron collector can additionally or alternatively include pnictogen fluorides (e.g., nitrogen fluoride such as nitrogen trifluoride, phosphorus fluoride, arsenic fluoride, antimony fluoride, bismuth fluoride, etc.) and / or any other suitable material.

[0021]

[0028] In a specific example, the electron collector can be or include the "electron collector" (or an element thereof) described in U.S. Patent Application No. 16 / 676,131, "SYSTEM AND METHOD FOR THERMIONIC ENERGY CONVERSION," filed on November 6, 2019, which is hereby incorporated by reference in its entirety, and / or the "anode" (or an element thereof) described in U.S. Patent Application No. 16 / 715,705, "SYSTEM AND METHOD FOR WORK FUNCTION REDUCTION AND THERMIONIC ENERGY CONVERSION," filed on December 16, 2019.

[0022]

[0029] However, the system can additionally or alternatively include any other suitable electron collector.

[0023]

[0030] The electron emitter preferably functions to emit electrons (e.g., when the emitter temperature exceeds a threshold temperature). The electrons are preferably emitted into the interelectrode gap (e.g., electrons emitted from the surface of the emitter proximate to the gap), but additionally or alternatively, they may be from any suitable emitter surface and / or any suitable component in any suitable direction. The electron emitter (i.e., the cathode) preferably comprises one or more metals, preferably tungsten, tantalum, rhenium, ruthenium, molybdenum, nickel, chromium, one or more superalloys (e.g., Inconel, Hastelloy, Kanthal, etc.), niobium, platinum, rhodium, iridium, etc., i.e., high melting point metals (i.e., such as, essentially so), but additionally or alternatively, it may be any other suitable metal. However, the electron emitter can additionally or alternatively comprise one or more semiconductor materials, insulating materials, and / or any other suitable materials.

[0024]

[0031] The electron emitter can be bonded to and / or include a work function reducing material, such as an alkali metal and / or alkaline earth metal coating (and / or its oxide and / or fluoride), that functions to reduce the work function of the emitter and / or increase the number and / or energy of the electrons emitted from the emitter. The work function reducing material is preferably on the surface of the emitter proximate to the gap (e.g., only deposited, resident, effective in reducing the work function, etc.), but additionally or alternatively, it may be diffused into the emitter and / or included in the emitter in other ways. However, the electron emitter can additionally or alternatively include a pnictogen fluoride (e.g., nitrogen fluoride such as nitrogen trifluoride, phosphorus fluoride, arsenic fluoride, antimony fluoride, bismuth fluoride, etc.) and / or any other suitable materials.

[0025]

[0032] In a specific example, the electron emitter has and / or is configured to have the "emitter module" described in U.S. Patent Application No. 16 / 676,131, "SYSTEM AND METHOD FOR THERMIONIC ENERGY CONVERSION", filed on November 6, 2019, and / or any suitable component thereof, and / or the "cathode" described in U.S. Patent Application No. 16 / 715,705, "SYSTEM AND METHOD FOR WORK FUNCTION REDUCTION AND THERMIONIC ENERGY CONVERSION", filed on December 16, 2019, which are hereby incorporated by reference in their entirety.

[0026]

[0033] The enclosure preferably functions to isolate the system from the external environment near (e.g., surrounding) the system. The enclosure can additionally or alternatively function to dissipate energy from the electron collector, provide mechanical support to the electron collector and / or the system, and / or provide any other suitable function. The enclosure may be coupled to the interface layer. The enclosure is preferably disposed to face the electron collector through the interface layer. The enclosure is preferably connected and / or otherwise coupled (e.g., mechanically, thermally, etc.) to the interface layer at at least one broad surface of the interface layer, and preferably to the first broad surface of the interface layer facing the second broad surface of the interface layer connected to the electron collector (e.g., as shown in FIGS. 3A - 3B). However, the enclosure can be coupled to the interface layer in any suitable manner.

[0027]

[0034] The enclosure preferably defines a chamber surrounding an electron emitter, an electron collector, and / or an interface layer. This chamber is preferably fluidly isolated from the surrounding environment (e.g., the atmosphere) surrounding the system and / or the enclosure. The chamber environment is preferably at a lower pressure (e.g., a perfect vacuum or a partial vacuum) compared to the surrounding environment, but it may also be at the same pressure and / or a higher pressure. The chamber can enclose one or more species (e.g., barium, cesium, oxygen, sodium, strontium, zirconium, etc.) that interact with one or more surfaces (e.g., the emitter surface, the collector surface, etc.) to change (e.g., reduce) the work function of the surface. In some examples, one or more such species can be stored as a filling material (e.g., as detailed below) such that the filling material generates a vapor pressure of the species within the chamber. In variations where one or more species are present in a fluid phase (e.g., a gas), the pressure (and / or partial pressure) of each species (and / or all species combined), such as during normal system operation, is above a first threshold pressure (e.g., 1×10 -6 、2×10 -6 、5×10 -6 、1×10 -5 、2×10 -5 、5×10 -5 、1×10 -4 、2×10 -4 、5×10 -4 、1×10 -3 、2×10 -3 、5×10 -3 、1×10 -2 、2×10 -2 、5×10 -2 、1×10 -1 、2×10 -1 、5×10 -1 、1, 2, 5, 10, 20, 50, 100, 200, 500, 760, 800, 10 -6 ~10 -2 、10 -3 ~10 -1 、0.05~5、0.75~15、and / or 5~100 Torr, 800 Torr or more, 10 -6 Torr or less), and above a second threshold pressure (e.g., 1×10-6 , 2×10 -6 , 5×10 -6 , 1×10 -5 , 2×10 -5 , 5×10 -5 , 1×10 -4 , 2×10 -4 , 5×10 -4 , 1×10 -3 , 2×10 -3 , 5×10 -3 , 1×10 -2 , 2×10 -2 , 5×10 -2 , 1×10 -1 , 2×10 -1 , 5×10 -1 , 1, 2, 5, 10, 20, 50, 100, 200, 500, 760, 800, 10 -6 ~10 -2 , 10 -3 ~10 -1 , 0.05~5, 0.75~15, and / or 5~100 Torr, 800 Torr or more, 10 -6 Torr or less), less than, and / or can be any suitable pressure (or partial pressure). In a specific example, during normal system operation, the system includes the vapor pressure of one or more species present in a fill material (e.g., cesium) of 0.1~10 Torr (e.g., 0.2~5, 0.5~2, and / or about 1 Torr, etc.). However, the chamber can alternatively or additionally have any other suitable properties.

[0028]

[0035] In a variation, the enclosure can include one or more of a collector lead, an emitter lead, a cooling element, a seal, and / or other components described in U.S. Patent Application No. 16 / 676,131, "SYSTEM AND METHOD FOR THERMIONIC ENERGY CONVERSION," filed on November 6, 2019, which is hereby incorporated by reference in its entirety. However, the enclosure can include and / or be arranged in any suitable manner.

[0029]

[0036] The seal preferably functions to mechanically (preferably not electrically) couple the electron emitter to the electron collector (and / or the enclosure, the interface layer, or other components). The seal can additionally or alternatively function to isolate the chamber environment from the ambient environment (e.g., in cooperation with other parts of the enclosure). The seal preferably includes one or more electrically insulating materials, more preferably materials that can withstand the seal temperature during TEC operation (e.g., without melting, deforming, decomposing, and / or reacting with other species present in the chamber environment). The material is preferably glass and / or ceramic (e.g., bulk ceramic, deposited ceramic, etc., crystalline ceramic and / or amorphous ceramic). For example, the seal can include one or more boride, carbide, oxide, and / or nitride materials, and / or any other suitable material. In a specific example, the seal includes one or more of alumina (e.g., sapphire, amorphous alumina, etc.), aluminum nitride, silica, silicate glass, silicon, silicon carbide, silicon nitride, and / or any other suitable material. However, the seal can additionally or alternatively include any other suitable material.

[0030]

[0037] The encapsulation body preferably includes (and / or is thermally coupled thereto) one or more cooling elements 131 that can function to facilitate heat removal from the electron collector (and / or any other suitable element of the system). Heat removal is preferably achieved convectively (e.g., in cooperation with an air flow module, in cooperation with a cooling fluid, etc.), but may additionally or alternatively include radiative heat removal, conductive heat removal, and / or heat removal by other suitable mechanisms. The cooling element preferably maintains the electron collector and / or the interface layer at a temperature below a target temperature (e.g., 0 to 100, 100 to 200, 200 to 400, 400 to 600, 200 to 275, 250 to 350, 325 to 400, and / or 275 to 325 °C, such as a target temperature of 300 °C) during operation, e.g., between the target temperature and a lower temperature (e.g., the ambient environmental temperature (“room temperature”), 0, 10, 20, 25, 30, 50, 75, 100, 150, 200, 250, 0 to 25, 25 to 50, 50 to 100, 100 to 200, and / or 200 to 300 °C, etc.). The cooling element is preferably thermally coupled to the electron collector (e.g., by an interface layer). In some examples, the cooling element can function to induce turbulence (e.g., in a heat transfer fluid such as air, water, glycerol, etc.) and / or otherwise increase fluid interaction (e.g., heat transfer) with the cooling element, and preferably includes one or more surface modifiers that include (e.g., are made of) metal. Such surface modifiers can include fins (e.g., parallel plates), baffles, ribs, dimples, and / or any other suitable structures.

[0031]

[0038] The cooling element(s) can include passive cooling elements (e.g., heat sinks, heat spreaders, heat pipes, etc.) and / or active cooling elements (e.g., forced air, forced liquid, thermoelectric coolers, etc.). In some examples, the system can include one or more temperature control elements (e.g., including a cooling element) as described in U.S. Patent Application No. 16 / 883,762, filed May 26, 2020, titled “SYSTEM AND METHOD FOR THERMIONIC ENERGY CONVERSION,” which is hereby incorporated by reference in its entirety (e.g., elements of one or more “airflow modules 13” as described in U.S. Patent Application No. 16 / 883,762).

[0032]

[0039] As an example, as shown in FIGS. 3A, 3B, and 4, the cooling element(s) is preferably disposed proximal to the interface layer (and / or electron collector) and / or configured to prioritize cooling of the interface layer and / or electron collector (e.g., over other elements of the system). Such a configuration can provide advantages over alternative arrangements where the cooling element(s) are disposed proximally and / or prioritize cooling of other elements of the system. Such other elements can include seals, elements disposed near and / or at the heating cavity opening, and / or any other suitable elements. For example, this configuration can maintain the interface layer at a temperature below a threshold temperature, such as 450, 400, 350, 300, 250, 200, 150, 100, 50, 50 - 150, 100 - 200, 150 - 250, 200 - 300, and / or 300 - 450 °C, or some other suitable temperature (and in some examples, above a second threshold temperature of 400, 350, 300, 250, 200, 150, 100, 50, 0, 0 - 100, 50 - 150, 100 - 200, 150 - 250, 200 - 300, and / or 300 - 400 °C) during operation of the thermionic energy converter, for example, which can result in an improvement in device efficiency and / or localization of a larger work function reduction material proximal to (e.g., inside) the interface layer.

[0033]

[0040] However, the cooling element can additionally or alternatively include any other suitable element having any suitable configuration.

[0034]

[0041] In some examples, the enclosure may include (and / or be thermally coupled to) one or more heating elements 132. For example, the enclosure can include a heating element disposed proximal to the interface layer relative to the cooling element (e.g., as shown in FIG. 4). However, the enclosure may additionally or alternatively include a cooling element disposed proximal to the interface layer relative to the heating element, and / or may have any other suitable arrangement of heating and cooling elements. (Preferably, cooperating with one or more cooling elements) The heating element can function to enable and / or improve the temperature control of other elements of the system, such as the interface layer (e.g., thereby enabling excellent control over the filling material contained within the interface layer, such as control of the vaporization of liquid cesium stored in the interface layer). For example, by varying the heat output of the heating element, the temperature of the interface layer can be controlled (e.g., enabling the temperature of the interface layer to be maintained within a desired temperature range for efficient system operation. For example, a range where the minimum and maximum are each within the range of 100 to 300 °C and / or a temperature range that is each 0 to 200 °C lower than the electron collector temperature, etc.). However, the system can additionally or alternatively include other suitable heating elements having other suitable functions (and / or may not include a heating element).

[0035]

[0042] The interface layer preferably functions to couple the electron collector to the enclosure (and / or any suitable component of the enclosure and / or an external system such as an external load), e.g., thermally, electrically, mechanically, and / or chemically. At least one broad face of the interface layer preferably contacts (e.g., touches, makes a mechanical connection, etc.) the electron collector, and at least one broad face preferably contacts the enclosure. At least one broad face that contacts the electron collector is preferably different from (e.g., the two broad faces face each other across the interface layer) at least one broad face that contacts the enclosure, although the same broad face(s) may contact the electron collector and the enclosure. The interface layer can be a point contact (e.g., one or more discrete points), an edge contact, a surface contact, a volume contact, and / or any suitable contact. In some embodiments, the interface layer can include (and / or function as) a "collector bridge" as described in U.S. Patent Application No. 16 / 676,131, filed November 6, 2019, "SYSTEM AND METHOD FOR THERMIONIC ENERGY CONVERSION," which is hereby incorporated by reference in its entirety. The interface layer preferably is in fluid communication (e.g., fluid contact) with the chamber environment (e.g., fluidly coupled to the interelectrode gap).

[0036]

[0043] In a specific example, the interface layer is adhered (e.g., using an adhesive, or using adhesion forces such as surface tension or wetness generated by a work function reducing material or a filler, etc.), processed (e.g., defined by growth and / or deposition, etching, etc.), integrated (e.g., partial and / or complete intercalation), attached and / or fixed, welded, fitted (e.g., including the structural retention function of the interface layer, and / or other fitting elements such as complementary male and female parts, screw parts, etc.), mechanically connected, electrostatically and / or magnetically coupled, contacted with no or substantially no bonding force and / or mechanism, and / or contacted with the collector and / or enclosure in other ways. However, the interface layer (and / or a separate interface layer) can contact any suitable component and be configured in any way.

[0037]

[0044] The interface layer is preferably compliant (e.g., deformable). Such compliance functions to accommodate mechanical changes in one or more system components (e.g., deformation in response to forces such as thermal expansion and / or contraction, forces resulting from pressure differences, etc.), and preferably does not substantially degrade the operation and / or functionality of the system. The interface layer is preferably elastically deformable, but additionally or alternatively, it can be inelastically deformable, elastically deformable, and / or have any suitable deformation. The interface layer can expand and / or contract. When the interface layer expands and / or contracts, the separation distance (and / or orientation) between the electron collector and the electron emitter preferably remains substantially constant (e.g., does not change; changes by less than a threshold amount of 0% or more, such as 1%, 2%, 5%, 10%, 20%, 0.1 - 1%, 1 - 2%, 2 - 5%, 5 - 10%, 10 - 20%, 20 - 30%, etc.). However, alternatively, it can change substantially, such as by a threshold amount (e.g., 1%, 2%, 5%, 10%, 20%, 0.1 - 1%, 1 - 2%, 2 - 5%, 5 - 10%, 10 - 20%, 20 - 30%, etc.) or more (e.g., the separation distance and / or orientation can reach when the interface layer reaches the operating temperature). The spring constant of the interface layer (e.g., modeling the interface layer as a Hooke's spring) is preferably 10 - 500 kN / m, such as 25, 50, 75, 100, 150, 200, 250, 300, 400, 10 - 50, 50 - 100, 100 - 200, and / or 200 - 500 kN / m, but it can be less than 10 kN / m or greater than 500 kN / m, and / or can have any other suitable value. In some examples, the interface layer can include (e.g., be made of) one or more springs (e.g., cantilever springs, coil springs, etc.) such as micro - machined and / or nano - machined springs. However, the interface material can additionally or alternatively include any other suitable elements configured to achieve the desired compliance.

[0038]

[0045] The interface layer preferably includes one or more interface materials (e.g., made of, composed of). The interface material is preferably compatible with one or more electron collector materials (e.g., group IV semiconductors such as Si, Ge, SiC and / or their alloys, group III-V semiconductors such as GaAs, GaSb, GaP, GaN, AlSb, AlAs, AlP, AlN, InSb, InAs, InP, InN, and / or their alloys, group II-VI semiconductors such as ZnTe, ZnSe, ZnS, ZnO, CdSe, CdTe, CdS, MgSe, MgTe, MgS, and / or their alloys, etc.) (e.g., does not react, reacts at a rate less than the threshold reaction rate, does not diffuse, has a diffusion coefficient (and / or interdiffusion coefficient) less than the threshold diffusion coefficient, etc.). In a specific example, the interface material has a low diffusion coefficient to the collector material (e.g., at 0 °C, 100 °C, 200 °C, 300 °C, 400 °C, 500 °C, etc.; at the electron collector operating temperature; at the interface layer temperature; at the enclosure temperature, etc.), and its diffusion coefficient (and / or interdiffusion coefficient) is about 1×10 -9 cm 2 / second or less, such as 1×10 -15 、1×10 -15 、2×10 -15 、5×10 -15 、1×10 -14 、2×10 -14 、5×10 -14 、1×10 -13 、2×10 -13 、5×10 -13 、1×10 -12 、2×10 -12 、5×10 -12 、1×10 -11 、2×10 -11 、5×10 -11 、1×10 -10 、2×10 -10 、5×10 -10 or less. However, the interface material (e.g., at 0 °C, 100 °C, 200 °C, 300 °C, 400 °C, 500 °C, etc.; at the electron collector operating temperature; at the interface layer temperature; at the enclosure temperature, etc.), the diffusion coefficient (and / or interdiffusion coefficient) to the collector material is about 1×10 -9It may be larger and / or may have any suitable diffusion coefficient. The interface material can include one or more of a metal (e.g., nickel, tantalum, zirconium, titanium, tungsten, molybdenum, rhenium, hafnium, iron, copper, etc.), a precursor of a work function reducing material, an alloy (e.g., tungsten-rhenium, tungsten-rhenium-hafnium carbide, inconel, hastelloy, inconeloy, monel, nimonic, stellite, cupronickel, steel, stainless steel, etc.), a carbonaceous material (e.g., graphite), and / or any suitable material. The precursor of the work function reducing material is preferably an oxide of the work function reducing material (e.g., chromate, dichromate, oxide, superoxide, peroxide, aluminate, silicate, borate, titanate, vanadate, vanadite, ferrate, permanganate, manganate, etc.). However, the precursor of the work function reducing material can additionally or alternatively include a sulfide, nitride, azide, halide, and / or any suitable anion salt of the work function reducing material, and / or any other suitable precursor.

[0039]

[0046] In an example where the interface layer includes a metal (titanium, hafnium, zirconium, iron, nickel, aluminum, calcium, magnesium, beryllium, strontium, barium, radium, etc.) and a precursor of a work function reducing material, the metal can react with the precursor of the work function reducing material (e.g., at a specific chamber pressure such as achieved during normal operation of the TEC when the interface layer reaches the reaction temperature) to release the work function reducing material.

[0040]

[0047] In a specific example, the interface layer may include a sacrificial metal (e.g., titanium, hafnium, zirconium, iron, nickel, aluminum, calcium, magnesium, beryllium, strontium, barium, radium, etc.) and a work function reduction material precursor (e.g., cesium chromate (Cs2Cr04)). The sacrificial metal can be included in the interface layer as a structural component, as a coating, in a sacrificial metal reservoir, as a non-structural component, and / or in another manner. When the interface layer reaches a threshold temperature (e.g., room temperature, target operating temperature, reaction temperature, etc.), a portion of the sacrificial metal indicated by "M" reacts with Cs2Cr04 to produce Cs and M2(Cr04) x and may be generated.

[0041]

[0048] In some variations, the interface layer can be (partially and / or wholly) coated. The coating can function to change the electrical, thermal, mechanical, chemical, and / or other properties of the interface layer and / or the interface material (and / or the interface with other elements of the system). For example, the coating can function to improve the heat conduction and / or electrical conduction between the interface layer and the element it contacts (e.g., the collector and / or the enclosure). The coating can be the same as or different from the interface material (e.g., it can include one or more of the interface materials, and can include the materials described above with respect to the interface material and materials different from the interface material). The coating can be deposited, grown, plated (e.g., electroplated), dip-coated, spray-coated, roll-coated, and / or the interface material can be coated in another manner. In a first specific example where the interface material includes tungsten and / or cobalt, the coating can include copper. In a second specific example where the interface material includes copper, the coating can include nickel. However, any suitable coating can be used for any interface material.

[0042]

[0049] The interface layer can additionally or alternatively serve the function of storing one or more filling materials (e.g., serving as a reservoir for the filling materials). The filling materials are preferably fluids (e.g., liquids, gases, supercritical fluids, etc.), more preferably condensed phases such as liquids, but can additionally or alternatively include solids, plasmas, and / or materials in any other phase of matter. In some embodiments, the filling materials can modify (e.g., determine, increase, decrease, etc.) the physical and / or chemical properties (thermal conductivity, electrical conductivity, deformability, spring constant, diffusivity, etc.) of the interface layer. For example, the filling materials can function to increase the bond (e.g., thermal, electrical, etc.) between the collector and the enclosure. The filling materials preferably wet the interface layer partially or completely, but can alternatively be non-wetting with respect to the interface layer. The wettability of the filling materials with respect to the interface layer can be controlled based on the structure of the interface layer (e.g., nanoscopic structure, mesoscopic structure, macroscopic structure, etc.), the interface material, the filling materials, the surface energy of the interface layer, the surface treatment of the interface layer, and / or any suitable properties of the interface layer.

[0043]

[0050] The filling materials are preferably work function reducing materials (e.g., alkali metals and / or alkaline earth metals such as cesium, barium, strontium, etc.), and the interface layer functions as an integral reservoir for the work function reducing materials (e.g., an integrated cesium reservoir). However, the filling materials can additionally or alternatively include materials corresponding to one or more "anode layers" (preferably work function adjusting layers, but additionally or alternatively any other suitable anode layers such as semiconductor layers, electron protection layers, electron trapping layers, chemical protection layers, etc.) described in U.S. Patent Application No. 16 / 676,131, filed on November 6, 2019, "SYSTEM AND METHOD FOR THERMIONIC ENERGY CONVERSION", which is hereby incorporated by reference in its entirety.

[0044]

[0051] The shape of the interface layer (e.g., a three-dimensional structure that defines, delimits, encloses, etc.) can be and / or can include one or more structures among a prism (e.g., a right prism), a frustum of a cone, a cylindrical shape, a cylindrical tube, an arbitrary shape, and / or an appropriate geometry. The broad surface of the interface layer in contact with the electron collector preferably has substantially the same shape as the broad surface of the electron collector with which they are in contact, but may have a shape different from the broad surface of the electron collector. The broad surface of the interface layer in contact with the electron collector preferably has substantially the same size as the broad surface of the electron collector with which they are in contact (e.g., the lateral and / or longitudinal spread differs by at most 1%, 5%, 10%, 20%, 30%, 40%, etc.), but may have a size different from the broad surface of the electron collector (e.g., larger or smaller).

[0045]

[0052] The thickness of the interface layer can be selected based on the physical and / or chemical properties of the interface layer (e.g., under normal conditions during system operation such as in the presence of high temperature and / or cesium). For example, a thin interface layer (e.g., thinner than a first threshold thickness) exhibits non-linear (e.g., inelastic) mechanical properties, while a thick interface layer (e.g., thicker than a second threshold thickness) may require a large amount of filling material (e.g., to achieve a desired state such as filling the filling material completely or substantially completely, e.g., 50%, 75%, 85%, 90%, 95%, 98%, 30 - 60%, 50 - 100%, 50 - 80%, 70 - 85%, 80 - 90%, 90 - 95%, and / or 95 - 100%, etc., filling the material within a threshold ratio relative to the maximum capacity), exhibit a large temperature gradient or temperature difference (e.g., greater than a threshold gradient or threshold temperature difference), cause large expansion and / or contraction with temperature changes, and / or otherwise cause disadvantages. Therefore, the thickness is preferably selected to avoid and / or balance such potential disadvantages. The thickness of the interface layer is preferably between 0.05 and 10 mm, and can be, for example, 0.1 mm, 0.2 mm, 0.3 mm, 0.5 mm, 0.75 mm, 1 mm, 1.25 mm, 1.5 mm, 2 mm, 3 mm, 4 mm, 5 mm, 7.5 mm, 9 mm, 0.05 - 0.5 mm, 0.1 - 1 mm, 0.5 - 10 mm. However, the thickness of the interface layer can be less than 0.05 mm, greater than 10 mm, and / or any other appropriate thickness.

[0046]

[0053] The interface layer preferably defines an open volume, but may alternatively be a solid material (e.g., one that does not define an open volume such as pores and / or cavities). In a specific example, the interface layer is a porous element (e.g., defining nanopores, micropores, mesopores, macropores, etc., as shown by way of example in FIG. 2B), an aligned, non-aligned, and / or partially aligned bundle of filaments (e.g., as shown in FIG. 2A), a wire ball as illustrated in FIG. 2F (e.g., a nickel wire, etc.), an aligned, non-aligned, and / or partially aligned fiber and / or bristle (e.g., as shown in FIG. 2G), a structure (e.g., holes, depressions, troughs, valleys, cavities, raised structures, meshes, etc., as shown in FIGS. 2C and 2D), an array of structures (e.g., as shown in FIG. 2E, such as those described in Meza, Lucas R., Satyajit Das, Julia R. Greer. "Strong, lightweight, and recoverable three-dimensional ceramic nanolattices." Science 345.6202 (2014): 1322-1326 and / or Schaedler, Tobias A., et al. "Ultralight metallic microlattices." Science 334.6058 (2011): 962-965, which are hereby incorporated by reference in their entireties), metallic wool (e.g., steel wool, copper wool, etc.), felt (e.g., graphite felt), a layered sheet of material (e.g., a corrugated and / or wrinkled sheet, etc.), a nano- and / or microfabricated structure (e.g., a structure prepared using atomic layer deposition, a mechanically compliant structure manufactured by atomic layer deposition, etc., chemical vapor deposition, physical vapor deposition, sputtering, etching, combinations thereof, etc.), and / or has any suitable structure.

[0047]

[0054] The filling rate (e.g., percentage of the total volume of the interface layer such as porosity, open volume, filling with one or more filling materials, or being fillable) can be selected based on the interface material, filling material, operating parameters (electrical parameters such as voltage, current, power, operating temperatures such as electron collector temperature, interface layer temperature, electron emitter temperature, operating pressure, etc.), the size of the interface layer and / or electron collector, and / or any suitable characteristics. For example, an interface layer with a low filling rate (e.g., lower than a first threshold filling rate) can become inelastic. On the other hand, an interface layer with a high filling rate (e.g., higher than a second threshold filling rate) may have low conductivity (e.g., thermal conductivity, electrical conductivity, etc.) such as the conductivity of the filled and / or unfilled interface layer, and / or the retention of the filling material may be insufficient (e.g., most of the filling material separates from the interface layer due to evaporation, etc., or the interface layer is unfilled, substantially unfilled, or in a filling state lower than the minimum desired filling degree for efficient operation). However, in some embodiments, the filling rate has little or no effect (e.g., 1%, 2%, 5%, 10%, 20% or less, etc.) on the characteristics (e.g., physical and / or chemical characteristics) of the interface layer, the interface layer can be selected and / or designed to function at any filling rate (e.g., one interface layer that functions at any filling rate, multiple different interface layers designed at different filling rates, etc.), and / or any filling rate can be used.

[0048]

[0055] The filling rate is preferably about 75% - 99.5%, for example 99.4, 99.3, 99.2, 99.1, 99, 98, 96, 94, 92, 90, 87.5, 85, 82.5, 80, 77.5, 99 - 99.5, 98 - 99, 95 - 98, 90 - 96, 85 - 90, 80 - 85, and / or 75 - 80%, etc. However, the filling rate may be less than 75%, more than 99.5%, and / or any suitable ratio.

[0049]

[0056] However, the system can additionally and / or alternatively include one or more reservoirs (e.g., work function reducing materials and / or any other suitable filling materials) separate from the interface layer.

[0050]

[0057] The interface layer can additionally or alternatively function to conduct heat (e.g., function as a thermal interface layer). During operation, the interface layer preferably conducts heat from the electron collector (e.g., functions to cool the electron collector), and more preferably conducts heat from the collector to the enclosure (e.g., to the cooling mechanism). However, the interface layer can additionally or alternatively conduct heat to the electron collector (e.g., warm the electron collector to the operating temperature, operate in a feedback loop to maintain the electron collector temperature within a desired temperature range, etc.).

[0051]

[0058] The thermal conductivity of the interface layer can depend on the shape of the interface layer (e.g., unloaded interface layer, interface layer during manufacturing, interface layer with load, during normal operation, etc.), the material of the interface layer, the load on the interface layer (e.g., filling material, filling ratio, etc.), and / or any properties of the interface layer. The thermal conductivity can be isotropic (e.g., the same in the x / y / z directions) and / or anisotropic (e.g., different in the x / y / z directions). The thermal conductivity of the interface layer is preferably at least about 0.5 W / (m*K), such as 0.75, 1, 2, 3, 5, 10, 20, 50, 100, 200, 500, 1000, 2000, 5000, 5 - 20, 1 - 10, 10 - 50, and / or 25 - 200 W / (m*K), etc. However, the thermal conductivity of the interface layer can be less than 0.5 W / (m*K).

[0052]

[0059] In some variations, the interface layer can be configured to modify and / or impart thermal properties of the interface layer using the Leidenfrost effect. The Leidenfrost effect is a phenomenon in which a liquid near a hot surface (e.g., a surface at a temperature and pressure above the Leidenfrost point of the liquid) rapidly evaporates, insulating (e.g., thermally insulating) the unevaporated liquid, thereby creating a vapor layer that slows the evaporation rate of the unevaporated liquid (e.g., compared to the case where the liquid is in direct contact with the surface). In a specific example, the work function reducing material is a liquid that can utilize the Leidenfrost effect when in contact with an electron collector (and / or enclosure). However, any suitable material and / or interface layer can be used to achieve the Leidenfrost effect.

[0053]

[0060] In other variations, the interface layer can be configured so that the Leidenfrost effect does not occur and / or so that the Leidenfrost effect is suppressed. In a specific example, the shape, surface energy, wettability (e.g., of the interface layer with respect to the work function reducing material), interface material, and / or any suitable properties can be selected to wick the work function reducing material, which can function to suppress droplet formation and thereby interrupt the Leidenfrost effect.

[0054]

[0061] In other variations, the interface layer can be configured to operate as a heat pipe (e.g., it can include one or more heat pipes). In a specific example of these variations, the work function reducing material is used as the working fluid of the heat pipe (e.g., the material that evaporates and condenses within the heat pipe) to transfer heat between the electron collector and the enclosure (and / or interface layer). However, any suitable filling material can be used as the working material of the heat pipe, and / or the heat pipe can be configured in another way.

[0055]

[0062] However, the interface layer can be configured to enable the Leidenfrost effect (e.g., in a first mode, for a first set of operating conditions, for a particular material, etc.), not to cause and / or suppress the Leidenfrost effect (e.g., in a second mode, for a second set of operating conditions, for a particular material, etc.), and / or to be configured in another way.

[0056]

[0063] As shown in FIG. 3B, a thermal gradient may exist across the interface layer (e.g., during operation such as operation in a normal state, a desired state, a maximum efficiency state, etc.). The gradient is preferably defined along (or substantially along) the axis between the electron collector and the enclosure (e.g., the interface layer may be hotter on the side closer to the electron collector and / or the broad face of the interface layer, and colder on the side closer to the enclosure and / or the broad face of the enclosure, or vice versa). However, the gradient may be along an axis perpendicular or oblique to the axis between the electron collector and the enclosure, and may be a radial temperature gradient, an azimuthal temperature gradient, and / or any suitable temperature gradient. The maximum temperature difference (ΔT) within the interface layer (e.g., between the hottest location and the coldest location on the surface, point, volume, etc. of the interface layer, preferably between the hottest location near the collector or on it and the coldest location near the enclosure or on it) is preferably at most 200° C. (e.g., ΔT is about 1, 2, 5, 10, 20, 50, 100, 150, 175, 190, and / or 200° C. or less, ΔT is in the range of 0 to 200, 0 to 10, 10 to 30, 20 to 50, 30 to 100, 50 to 150, and / or 100 to 200° C., but alternatively may exceed 200° C. The minimum ΔT within the interface layer (e.g., between the hottest location and the coldest location on the surface, point, volume, etc. of the interface layer, preferably between the hottest location near the collector or on it and the coldest location of the enclosure) is preferably a threshold temperature difference (e.g., ΔT is about 1, 2, 5, 10, 20, 50, 100, 150, 175, 190, and / or 200° C. or more, ΔT is in the range of 1 to 200, 1 to 10, 10 to 30, 20 to 50, 30 to 100, 50 to 150, and / or 100 to 200° C., etc.), but alternatively may be less than 1° C. The temperature difference may function to localize the work function reducing material within the interface layer (e.g., promoting the condensation and / or collection of the work function reducing material in the interface layer as opposed to other components within the chamber).

[0057]

[0064] The coldest (or substantially coldest) location within the chamber (e.g., during system operation under normal conditions) is preferably located within the interface layer (e.g., at least a portion of the interface layer is at a lower temperature than the electron collector, electron emitter, spacer, etc.), which can function to preferentially condense and / or localize a work function reducing material (and / or any suitable material) within the interface layer. However, the interface layer (or a subset thereof) may alternatively (e.g., during system operation under normal conditions) be within a threshold temperature difference of the coldest temperature within the chamber (e.g., exceeding the coldest chamber temperature by 0 - 50, 0 - 10, 10 - 30, and / or 20 - 50 °C), or at some other suitable temperature.

[0058]

[0065] In some variations, the presence of a filling material within the interface layer can provide and / or enhance heat transport across the interface layer. For example, the filling material can provide enhanced thermal conductivity, and / or a fluid (e.g., liquid) filling material can mediate heat transfer by convection. In specific examples (e.g., where the filling material is a liquid metal such as liquid cesium, or contains a liquid metal), both convection and conduction within the filling material can significantly contribute to heat transport across the interface layer.

[0059]

[0066] The interface layer can function, additionally or alternatively, to provide electrical conductivity (e.g., conduct electrons from and / or to the electron collector). Current can be conducted between the electron collector and an external load, enclosure, and / or any suitable endpoint (e.g., from the electron collector). The electrical conductivity (e.g., electron conductivity) of the interface layer can depend on the shape of the interface layer (e.g., an unloaded interface layer, an as - manufactured interface layer, etc.), the material of the interface layer, the load on the interface layer (e.g., filling material, filling rate, etc.), and / or any property of the interface layer. The electrical conductivity (e.g., electron conductivity) can be isotropic (e.g., the same in the x / y / z directions) and / or anisotropic (e.g., different in the x / y / z directions).

[0060]

[0067] In a specific example, the electrical conductivity (e.g., electron conductivity) of the interface layer can be greater than about 1 x 10 4 S / m (e.g., about 10 5 S / m, 10 6 S / m, 10 7 S / m, etc.). However, the electrical conductivity of the interface layer may be less than 10 4 S / m and / or may have any suitable value.

[0061]

[0068] In some variations, the presence of the filling material within the interface layer can provide and / or enhance the electrical conductivity (e.g., electron conductivity) of the interface layer, reduce the contact resistance between the interface layer and the electron collector (and / or the encapsulant), and / or otherwise modify the electrical properties of the interface layer.

[0062]

[0069] In some variations, the system can include multiple interface layers. Each interface layer is preferably different (e.g., different shape, different surface energy, different interface material, different filling material, etc.), but may be the same. The additional interface layer can modify the thermoelectric, mechanical, chemical, and / or any suitable bond between any components (e.g., between the electron emitter and the encapsulant, between the electron collector and the encapsulant, between the first interface layer and the encapsulant, between the electron collector and the first interface layer, etc.). In a specific example (e.g., as shown in FIG. 5), the system can include a porous interface layer (e.g., a work function reduction material reservoir) and a solid interface layer (e.g., a shunt). The shunt can function to offset the interface layer (and the electron collector) from the encapsulant (e.g., a cooling mechanism), thereby changing the operating temperature and / or temperature gradient of the work function reduction material reservoir. In this example, the shunt can be disposed between the work function reduction material reservoir and the encapsulant. In a variation, including a shunt can be particularly beneficial for a Cs plasma thermionic energy converter, but can be used for any thermionic energy converter and / or any suitable system.

[0063]

[0070] In some embodiments, the system includes one or more elements as described in U.S. Patent Application No. 16 / 676,131, filed Nov. 6, 2019, “SYSTEM AND METHOD FOR THERMIONIC ENERGY CONVERSION,” which is hereby incorporated by reference in its entirety. For example, the system can include (e.g., can be) the “thermionic energy generation system 10” (or a subset of its elements) of U.S. Patent Application No. 16 / 676,131, and the “collector contact 250” of U.S. Patent Application No. 16 / 676,131 can include (e.g., as shown in FIGS. 6A - 6B) the interface layer described herein. In a specific example, the collector contact includes a mechanically compliant interface layer that includes a work function reducing filling material such as cesium.

[0064]

[0071] However, the system can alternatively or additionally include any other suitable elements in any suitable configuration.

[0065] 3. Method

[0072] A method of manufacturing a system (and / or any component of the system) may include any suitable steps (e.g., performed one or more times) including material growth, material deposition (e.g., microfabrication such as atomic layer deposition, chemical vapor deposition, physical vapor deposition, sputtering, etching, combinations thereof, nanofabrication, etc.), manual material manipulation (e.g., winding, machining, etc.), broaching (e.g., generation of fine wire shaving using a broach), combustion of an interfacial material precursor (e.g., metal bis(tetrazolato)amine BTA complex), dealloying, nanopurification, gamma ray irradiation, metal sol-gel treatment, generation of metal foams (e.g., gas injection into molten metal, mixing of foaming agents into molten metal, casting of metal using a foaming skeleton, etc.), alignment of structures and / or materials (e.g., bristol, laminated layers, etc.), intercalation of materials (e.g., intercalation of a filling material into an interfacial layer and / or material), coating of an interfacial layer (and / or interfacial material), and / or any other suitable processing step. The interfacial layer can be manufactured on an electron collector, on an encapsulant, and / or separately from the electron collector and / or electron collector encapsulant. However, the system and / or its components can additionally or alternatively be manufactured by any other suitable method.

[0066]

[0073] The operating method 20 preferably includes the steps of receiving power, emitting electrons, and receiving the emitted electrons, and optionally can include the step of convectively transferring heat and / or any other suitable element (e.g., as shown in FIG. 7). This method is preferably performed using the thermionic energy generation system 10 described above, but can additionally or alternatively be performed using any other suitable system.

[0067]

[0074] The hot ion energy generation method preferably functions to generate electrical output (e.g., supply power to an external load). This method preferably includes the steps of receiving power, emitting electrons, and receiving the emitted electrons. Optionally, this method can arbitrarily include the step of convectively transferring heat. However, this method can additionally or alternatively include any other suitable elements.

[0068]

[0075] The step of receiving power is preferably performed within a heating cavity, more preferably near an electron emitter (e.g., in an inner shell adjacent to the electron emitter). The power is preferably thermal power, but can additionally or alternatively include power from any other suitable source. Optionally, this method can include the step of providing the received power. The power is preferably provided by a power input. The power is preferably provided continuously, but can alternatively be provided at other suitable timings. In one example, the step of supplying power includes operating a burner (e.g., one disposed within the heating cavity) with one or more flames proximate to and / or incident on the flame receiving region of the emitter module, and the step of receiving power includes receiving heat from the flame in this flame receiving region. However, the step of receiving power can additionally or alternatively include any other suitable elements implemented in any suitable manner.

[0069]

[0076] The step of emitting electrons is preferably performed at (and / or near) an electron emitter. When power is received (e.g., when the electron emitter reaches an elevated temperature such as 400 - 500, 500 - 600, 600 - 700, 700 - 800, 800 - 1000, 1000 - 1600, or 1600 - 2000 °C), the electron emitter preferably emits electrons (e.g., thermionically emits electrons). The electrons are preferably emitted into the chamber, more preferably towards an electron collector. However, the step of emitting electrons can additionally or alternatively include any other suitable elements implemented in any suitable manner.

[0070]

[0077] The step of receiving the emitted electrons is preferably carried out by an electron collector. The electrons are preferably received from the electron emitter through a chamber. While receiving the emitted electrons, preferably the electron collector is cooler (optionally with a lower work function) than the electron emitter and can generate electric power from the reception of the emitted electrons. The step of receiving the emitted electrons preferably includes providing the generated electric power to an external electrical load (e.g., via conductive leads of the emitter and collector modules). However, the step of receiving the emitted electrons can additionally or alternatively include any other suitable element carried out in any suitable manner.

[0071]

[0078] This method can optionally include the step of convectively transferring heat. The step of convectively transferring heat can function to cool the electron collector and / or preheat the burner gas. The step of convectively transferring heat is preferably carried out by an air flow module, which can flow one or more fluids (such as air) along an air flow path defined, for example, by one or more ducts of the air flow module, along elements of the system. The elements of the system along which the fluid can flow can include one or more of a cooling element, an outer shell of the emitter module, an inner shell of the emitter module, a burner, and / or any other suitable element. However, the step of convectively transferring heat can additionally or alternatively include any other suitable element carried out in any suitable manner, and / or this method can include any other suitable element carried out in any suitable manner.

[0072]

[0079] This method of operation may include one or more elements (e.g., for "work function reduction" and / or "thermionic energy conversion") disclosed in U.S. Patent Application No. 16 / 715,705, filed December 16, 2019, "SYSTEM AND METHOD FOR WORK FUNCTION REDUCTION AND THERMIONIC ENERGY CONVERSION", which is incorporated herein by reference in its entirety. However, this method of operation may additionally or alternatively include any other suitable elements.

[0073]

[0080] Embodiments of the system and / or method can include all combinations and permutations of various system components and various method processes, and one or more instances of the methods and / or processes described herein can be performed asynchronously (e.g., sequentially), simultaneously (e.g., in parallel), or in any other suitable order by and / or using one or more instances of the systems, elements, and / or entities described herein.

[0074]

[0081] The drawings illustrate the architecture, functionality, and operation of possible implementations of the system and method according to preferred embodiments, exemplary configurations, and variations thereof. In this regard, each block of a flowchart or block diagram can represent a module, segment, step, or portion of code that includes one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative embodiments, the functions recited in the blocks may occur out of the order shown in the figures. For example, two blocks shown in succession may in fact be executed substantially simultaneously depending on the related functionality, or the blocks may be executed in the reverse order. It should be noted that each block of the block diagrams and / or flowchart diagrams, and combinations of blocks in the block diagrams and / or flowchart diagrams, can be implemented by a dedicated hardware-based system that performs the specified function or acts, or by a combination of dedicated hardware and computer instructions.

[0075]

[0082] Those skilled in the art will recognize that modifications and variations can be made to the preferred embodiments of the present invention without departing from the scope of the invention as defined in the following claims, from the foregoing detailed description, the drawings, and the claims.

Claims

1. In a system having a thermionic energy converter (TEC) that defines a chamber, the TEC includes an electron collector disposed within the chamber, an electron emitter facing the electron collector across the chamber, and an interface layer disposed within the chamber, wherein the electron collector is disposed between the electron emitter and the interface layer, the interface layer mechanically couples the electron collector to the chamber, the interface layer defines a reservoir within the chamber, the reservoir contains a work function reducing material, and vapor of the work function reducing material interacts with surfaces of the electron emitter and the electron collector to reduce work functions of the surfaces of the electron emitter and the electron collector. A system characterized by this.

2. The system according to claim 1, wherein the chamber is fluidly isolated from the ambient environment surrounding the TEC.

3. The system according to claim 2, wherein the chamber contains vapor of the work function reducing material.

4. The system according to claim 1, wherein the work function reducing material includes liquid cesium.

5. The system further includes a cooling element thermally coupled to the interface layer, the cooling element is disposed outside the chamber, and the interface layer is disposed between the cooling element and the electron collector. The system according to claim 4.

6. The system according to claim 5, wherein the cooling element is configured to control the temperature of the liquid cesium.

7. The system according to claim 1, wherein the interface layer has a porous metal structure.

8. The system according to claim 7, wherein the work function reducing material has cesium contained within pores of the porous metal structure.

9. The system according to claim 8, wherein the cesium is configured to thermally couple the electron collector to a cooling element disposed outside the chamber.

10. The system according to claim 1, wherein the interface layer includes a metal and a work function reducing material precursor, and the metal and the work function reducing material precursor are configured to react to produce the work function reducing material.

11. The system according to claim 10, wherein the work function reducing material is cesium and the work function reducing material precursor is cesium chromate.

12. In the system according to any one of claims 1 to 11, Comprising a spacer disposed between the electron collector and the electron emitter, The interface layer maintains the electrode gap between the electron collector and the electron emitter by maintaining contact between the electron collector and the spacer. A system characterized by this.

13. The system according to claim 12, wherein the interface layer is mechanically flexible.

14. The system according to claim 13, wherein the interface layer has a spring constant of 10 kN / m to 500 kN / m.

15. The system according to claim 13, wherein the interface layer includes a porous metal structure, and the porous metal structure is mechanically flexible.

16. The system according to claim 3, wherein the vapor of the work function reducing material reduces the work function of the surface of the electron emitter.

17. The system according to claim 8 or 9, wherein the vapor of cesium fluidly couples the electrode gap defined in the chamber between the electron emitter and the electron collector.

18. The system according to any one of claims 7, 8, 9, and 17, wherein the porous metal structure includes nickel-coated copper.

19. The interface layer contacts the electron collector in a wide surface, The system according to claim 12, wherein the interface layer defines a thickness of 0.05 mm to 10 mm along an axis perpendicular to the wide surface.

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