Energy storage system and method of operating the same by flowing a heated liquid through it and using a purge gas to prevent deposition

Abstract

Energy storage systems are disclosed. The system can store energy as heat in a high temperature liquid, and when the high temperature liquid is transported through an array of conduits, the heat can be converted into electricity by absorbing radiation emitted from the high temperature liquid through one or more photovoltaic devices. Some aspects described herein relate to reducing deposition of sublimated material from the conduits onto the photovoltaic devices.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application Serial No. 62 / 740,664, filed on October 3, 2018, entitled DEPOSITION PREVENTION BY SWEEP GAS, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The disclosed embodiments relate to energy storage systems, and more particularly, to energy storage systems configured to store heat in a high temperature liquid. Background Art

[0004] Energy storage systems are used to store energy generated by various energy sources such as renewable energy (e.g., solar, hydroelectric, wind, and / or geothermal energy) and / or other energy sources (e.g., fossil fuels, natural gas, nuclear energy, coal, etc.). In some applications, energy storage systems are used for grid-scale storage to help balance the difference between energy supply and demand. For example, some renewable energy sources can generate energy during periods of low energy demand, and excess energy can be stored until demand increases, at which time the stored energy can be supplied to meet the increased demand. Various methods for energy storage include pumped hydroelectric energy storage, compressed air energy storage, and electrochemical energy storage in one or more batteries. Summary of the invention

[0005] In one embodiment, the energy storage system includes: a conduit constructed and arranged to transport a liquid, a photovoltaic device, a gap between the conduit and the photovoltaic device, a gas inlet constructed and arranged to guide a purge gas into the gap, and a gas outlet constructed and arranged to guide the purge gas out of the gap. The flow of the purge gas from the inlet to the outlet passes through the gap between the conduit and the photovoltaic device.

[0006] In another embodiment, a method includes delivering a liquid through a conduit positioned on a first side of a gap opposite a photovoltaic device, and flowing a purge gas through the gap between the conduit and the photovoltaic device.

[0007] In yet another embodiment, an energy storage system includes: an array of conduits, the array of conduits being constructed and arranged to transport a liquid from a first end of the array to a second end of the array; a plurality of photovoltaic devices; and a plurality of gaps formed in the array of conduits. Each gap includes an opening at at least one end of the array of conduits, and each gap is constructed and arranged to accommodate at least one of the plurality of photovoltaic devices. The plurality of photovoltaic devices can be selectively moved into and out of the plurality of gaps.

[0008] It should be understood that the above concepts and the additional concepts discussed below can be arranged in any suitable combination, as the present disclosure is not limited in this respect. In addition, other advantages and novel features of the present disclosure will become apparent through the following detailed description of multiple non-limiting embodiments when considered in conjunction with the accompanying drawings.

[0009] In the event that this specification and the documents incorporated by reference include contradictory and / or inconsistent disclosures, this specification shall prevail. If two or more documents incorporated by reference include contradictory and / or inconsistent disclosures relative to each other, the document with the later effective date shall prevail. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown in various figures may be represented by a like reference numeral. For clarity, not every component is labeled in every drawing. In the drawings:

[0011] Figure 1 is a schematic diagram of an energy storage and conversion system according to some embodiments;

[0012] Figure 2 is a perspective view of an energy conversion system according to some embodiments;

[0013] Figure 3 yes Figure 2 A perspective view of a portion of an energy conversion system;

[0014] Figure 4 is a schematic cross-sectional view of a portion of an energy conversion system according to some embodiments;

[0015] Figure 4A Depicted Figure 4 The energy conversion system along a portion of route 4A-4A;

[0016] Figure 5 is a schematic cross-sectional view of a portion of an energy conversion system including a purge gas system according to some embodiments;

[0017] Figure 6 is a schematic cross-sectional view of a portion of an energy conversion system including a plurality of intermediate layers according to some embodiments; and

[0018] Figure 7 is a schematic cross-sectional view of a photovoltaic device according to some embodiments. DETAILED DESCRIPTION

[0019] Aspects described herein relate to energy storage systems, such as grid-scale energy storage. The inventors have realized that, although the costs associated with generating energy from many renewable energy sources (e.g., solar and wind energy) are close to the costs associated with conventional energy sources (e.g., fossil fuels), in many cases, when renewable energy is needed, it is not available. For example, the generation of solar and wind energy depends on weather conditions. In other cases, the cost of generating energy (including from non-renewable energy) at low energy demand may be lower. Therefore, the inventors have realized many benefits associated with energy storage systems, which can store energy (e.g., energy generated by one or more renewable energy sources and / or energy generated during low-cost periods) and release the energy at a later desired time (e.g., when energy demand increases). In this way, the energy storage system described herein can provide the distributability of energy generated by various energy sources. Although some systems have been developed to provide such grid-scale energy storage, such as pumped hydroelectric systems and electrochemical systems, the inventors have recognized and realized many disadvantages associated with these methods. For example, pumped hydroelectric energy storage systems are geographically restricted, and electrochemical systems are generally expensive and inefficient.

[0020] In view of the above, the inventors have recognized and appreciated the many benefits associated with energy storage systems configured to store energy as heat. In particular, thermal storage can be substantially cheaper than electricity storage in electrochemical systems and is not as geographically limited as pumped hydroelectric systems. Furthermore, in some cases, for example, based on the cost per unit of stored energy and / or the cost per unit of stored electricity, the systems described herein can allow for cheaper electricity storage compared to existing systems.

[0021] In some embodiments, the energy storage system described herein can store heat in a high temperature liquid, such as liquid silicon, liquid iron, liquid aluminum oxide, liquid silicon dioxide, liquid ferrosilicon, liquid boron, liquid metal oxides (e.g., iron oxides), liquid salts, oils, or other suitable liquid materials. The liquid can be heated to a first high temperature using energy from one or more energy sources (including renewable energy sources and / or non-renewable energy sources), and the liquid can be stored in a first liquid storage tank configured to maintain the liquid at a first temperature. In some applications, the first liquid storage tank can be constructed and arranged to provide a low surface area to volume ratio for the liquid contained therein, which can help reduce heat loss from the liquid while storing the liquid in the first liquid storage tank.

[0022] Energy can be recovered from the high temperature liquid via one or more photovoltaic devices. In particular, the high temperature liquid can be transported through a series of conduits, such as pipes, tubes, channels or other structures. Since the present disclosure is not very limited, the heat transfer from the liquid to the conduit can heat the conduit to an appropriate temperature so that the conduit emits electromagnetic radiation with a wavelength of any suitable range (including but not limited to visible light (400nm to 700nm), infrared radiation (700nm to 1mm) and / or any other suitable range of wavelengths). In particular, the conduit can be heated to a temperature sufficient to generate a significant energy flux radiated from the conduit. For example, in some embodiments, the energy flux radiated from the conduit can be about 5-10kW / m 2 About 10kW / m 2 , which may correspond to kilowatts or megawatts of power recovered from the system depending on the particular system size. In some cases, these energy fluxes may correspond to conduits being heated to a temperature of about 1400° C. to about 2600° C., 2000° C. to about 2600° C., or another suitable range of temperatures.

[0023] The radiation emitted from the conduit can be absorbed by one or more photovoltaic devices to convert the radiation into electricity. In this way, the system can convert energy stored in the liquid in the form of heat into electricity. In some embodiments, one or more photovoltaic devices may include a multi-junction photovoltaic device, which can provide absorption of radiation of a wider range of wavelengths, thereby improving the efficiency of conversion from heat in the liquid to electricity. For example, a multi-junction photovoltaic device may be included in the energy storage system of some embodiments.

[0024] In some embodiments, the high temperature liquid transported by the conduit may be at a temperature of about 1400°C to about 2600°C (e.g., about 2400°C for a system utilizing liquid silicon). To accommodate these high temperatures, the conduit may be formed of a suitable high melting point material having a melting temperature higher than the temperature of the high temperature liquid contained therein. Suitable types of materials may include, but are not limited to, graphite, tungsten, silicon carbide, silicon nitride, aluminum nitride, zirconium carbide, other refractory carbides, nitrides, borides, and / or oxides. However, the inventors have recognized and appreciated that at these high temperatures, the vapor pressure of many materials (including carbon) may be relatively high compared to the vapor pressure of the material at room temperature. These elevated vapor pressures may result in undesired sublimation or evaporation of the conduit material during high temperature operation and recapture of previously stored energy. The sublimated material may then be deposited onto any exposed surface at a lower temperature. This may include sublimation and deposition of the material onto the photovoltaic device of the system, which may prevent subsequent absorption of radiation by the photovoltaic device and reduce the performance of the photovoltaic device. In fact, the inventors have realized that even very thin layers of material (e.g., as thin as a few atomic layers) deposited onto a photovoltaic device may dramatically reduce the performance of the photovoltaic device. Therefore, some aspects described herein relate to reducing the deposition of sublimated sublimated material onto a photovoltaic device, which can provide improved system efficiency, reduced system maintenance requirements (e.g., for cleaning or replacement of photovoltaic devices), and / or longer system life. For example, in some cases, the embodiments described herein can provide a system with an expected life of 30 years or more.

[0025] In some embodiments, one or more conduits may be separated from the corresponding photovoltaic device by an intermediate layer, and the intermediate layer may be formed of a material having a vapor pressure lower than that of the conduit material when both the intermediate layer and the conduit are at their elevated operating temperature (e.g., about the temperature of the high temperature liquid contained in the conduit). In this way, the intermediate layer can reduce the vapor pressure of materials within the system that may interact with the photovoltaic device, which can result in significantly reduced sublimation. The intermediate layer can be formed as a film, one or more tubes, one or more chambers, a wall, a foil structure, a coating disposed on one or more conduits, a combination of one or more of the foregoing structures, and / or any other structure that provides a barrier between the conduit and the photovoltaic device to reduce the vapor pressure of the adjacent photovoltaic device and correspondingly reduce the deposition of sublimated material onto the photovoltaic device.

[0026] According to some aspects, an intermediate layer between one or more conduits conveying high temperature liquid and one or more photovoltaic devices can act as a diffusion barrier, which physically blocks sublimated atoms from the conduits from diffusing to and depositing on the photovoltaic devices. For example, in one embodiment, one or more conduits can be formed of graphite, and the intermediate layer can be formed of tungsten, and the tungsten intermediate layer can block the diffusion of sublimated carbon atoms to the photovoltaic devices, thereby reducing or substantially preventing the undesired deposition of materials on the photovoltaic devices. Additionally, due to the tungsten or other intermediate layer having a reduced vapor pressure compared to the conduit material at these temperatures, the gas space between the barrier and the photovoltaic device will exhibit a reduced local pressure of the sublimated material compared to the gas space between the barrier and the conduit. Of course, although specific materials are mentioned above, other materials that may be suitable for the intermediate layer may include, but are not limited to, rhenium, tantalum, and / or alloys of tungsten, rhenium and / or tantalum, and any other suitable material (e.g., carbide, nitride, boride and / or oxide) having a vapor pressure less than the corresponding vapor pressure of the material of the corresponding conduit through which the high temperature liquid is contained.

[0027] In addition to providing a lower vapor pressure of the sublimated material adjacent to the photovoltaic device, the intermediate layer can also form an emitting surface configured to radiate energy (e.g., visible light and / or infrared radiation) toward the photovoltaic device. For example, the intermediate layer can be positioned adjacent to one or more conduits that carry a high temperature liquid, and heat from the conduits can be transferred to the intermediate layer (e.g., via conduction, convection, and / or radiative heating). As described above, when heated, the intermediate layer can radiate the absorbed energy toward the photovoltaic device, which can then absorb the radiation and convert it into electricity.

[0028] According to some aspects, the undesirable deposition of the sublimated material from one or more conduits to one or more photovoltaic devices of the system can be reduced or avoided by removing the sublimated atoms from the system before the atoms can be deposited on one or more photovoltaic devices. In some embodiments, this removal of the sublimated material can be realized by making the purge gas flow in the gap between one or more conduits and one or more photovoltaic devices. The purge gas can form a moving air curtain between one or more conduits and one or more photovoltaic devices, and the moving air curtain entrains the sublimated atoms and moves the sublimated atoms away from the photovoltaic device before the sublimated atoms can be deposited on the photovoltaic device. According to a specific embodiment, the purge gas can include any suitable non-reactive gas. For example, the purge gas can include one or more inert gases, such as argon, krypton, and / or xenon, and / or a combination of non-reactive gases. In some applications, compared with the purge gas including lighter gases, it is preferred to include heavier gases with atoms and / or molecules with larger cross-sections to provide improved entrainment of sublimated atoms and correspondingly reduced deposition of sublimated atoms. However, it should be understood that the present disclosure is not limited to purge gases comprising the specifically disclosed gases and heavy atoms and / or molecules.

[0029] In some embodiments, purge gas can flow into the gap between one or more conduits and one or more photovoltaic devices through a gas inlet, and purge gas can flow out of the gap through a gas outlet spaced apart from the gas inlet. In addition, according to an embodiment, the system may include multiple inlets and multiple outlets spaced around and / or along the length of the system. In either case, when flowing out of the gas inlet, the purge gas can entrain and transport sublimated gas atoms to the gas outlet, and the entrained sublimated gas can be removed from the gap at the gas outlet so that the sublimated atoms cannot reach the photovoltaic device. In some cases, the purge gas can be recycled so that it can flow into and out of the gap multiple times. In such an embodiment, the purge gas can pass through a filter after leaving the gap through the gas outlet, and the filter can be configured to remove sublimated gas atoms from the purge gas before the purge gas is directed back to the gas inlet.

[0030] According to some aspects, the velocity of the purge gas in the gap between one or more conduits of the system and one or more photovoltaic devices can be controlled to reduce and / or avoid deposition of sublimated gas atoms onto the photovoltaic devices. For example, in some embodiments, the velocity of the purge gas (v 吹扫 ) is controlled to be greater than the drift velocity (v) of any sublimated gas atom in the gap 漂移). In certain embodiments, the velocity of the purge gas can be controlled based on the geometry of the particular system. For example, the system can include one or more pairs of gas inlets and gas outlets, and each gas outlet can be spaced a distance L from the corresponding gas inlet. In addition, the gap between the conduit and the photovoltaic device can have a width w, which can correspond to the minimum distance that the sublimated atoms must travel to deposit on the photovoltaic device. In some such embodiments, the velocity of the purge gas can be controlled so that L / v 吹扫 <w / v 漂移 (That is, the time for the purge gas to travel from the gas inlet to the gas outlet is less than the time for the sublimated atoms to diffuse through the gap). According to certain embodiments, a suitable velocity of the purge gas can be from about 0.01 m / sec to about 10 m / sec (e.g., from about 0.5 m / sec to about 3 m / sec). For example, such a purge gas velocity can be used in conjunction with a system gap width of about 1 mm to about 1 m. However, it should be understood that other purge gas velocities and gap spacings can be used, as the present disclosure is not limited in this regard.

[0031] According to certain embodiments, the drift velocity of the gas may be determined in any suitable manner to select a suitable velocity for the purge gas. In some cases, the drift velocity of the gas (e.g., in a zero velocity environment) may be determined based on the average temperature of the gas. In some cases, as will be appreciated by one of ordinary skill in the art, the drift velocity may correspond to the thermal velocity of the gas, which may be determined according to classical principles of statistical mechanics. For example, the drift velocity of a gas atom or molecule having mass m at temperature T may be given by the most likely velocity v=(2k B T / m) 1 / 2 , RMS velocity v = (3k B T / m) 1 / 2 and / or the velocity v corresponding to the average velocity of the gas atoms or molecules = (8k B T / πm) 1 / 2 To limit, where k B =1.38×10 -23 J / K is the Boltzmann constant.In some embodiments, the velocity of the purge gas and the gap size can be selected so that the time for the purge gas to leave the system is shorter than the expected time for sublimated atoms to diffuse through the gap using one or more of these thermal velocity values.

[0032] In some embodiments, the purge gas can act as a thermal barrier between the conduit and the photovoltaic device to help avoid non-radiative heat transfer from the conduit to the photovoltaic device, which can reduce heating of the photovoltaic device that could otherwise damage the photovoltaic device. Notably, the inventors have realized that since most heat transfer at the operating temperature of the system (e.g., about 2400° C.) occurs via radiative heat transfer, this reduction in non-radiative heating of the photovoltaic device due to the purge gas may not significantly affect the efficiency of the system. In particular, since the rate of radiative heat transfer varies proportionally to the fourth power of temperature, compared to conduction and convection, which vary linearly with temperature, radiative heat transfer may prevail above a certain elevated temperature.

[0033] In some embodiments, a plurality of conduits for conveying high temperature liquids may be arranged into an array including one or more gaps, the gaps being constructed and arranged to accommodate one or more photovoltaic devices, and one or more photovoltaic devices may be moved into and out of the gaps. For example, when energy generation is desired, one or more photovoltaic devices may be moved and / or actuated into corresponding gaps in the conduit array, and high temperature liquid may be conveyed through the conduit to generate electricity via radiation emitted from the conduit and absorbed by the photovoltaic device, as described above. In some embodiments, the gap may be configured as an extension channel formed in the conduit array, and the photovoltaic device may be formed as an extension rod insertable into the cavity. The inventors have realized that when electricity generation is not desired, such a configuration including a movable photovoltaic device may be advantageous in avoiding unnecessary exposure of the photovoltaic device to elevated temperatures and / or sublimated atoms that may be deposited on the photovoltaic device. In addition, in some applications, a system including a movable photovoltaic device may provide simple maintenance, repair and / or replacement of one or more photovoltaic devices without taking the entire system offline.

[0034] In addition, the inventors have recognized and appreciated that, in some cases, one or more photovoltaic devices in an energy conversion system may not absorb all electromagnetic radiation that may be emitted from one or more conduits of the system, and such unabsorbed radiation may result in an undesirable loss of system efficiency and / or heating of the photovoltaic device. Therefore, the inventors have realized many advantages associated with a system including one or more reflective layers, which are constructed and arranged to reflect at least a portion of the radiation that is not absorbed by the photovoltaic device back to the conduit (e.g., the gap between the conduit and the photovoltaic device). For example, in some embodiments, the reflective layer may be disposed behind one or more photovoltaic devices in the energy conversion system, and the photovoltaic device may be positioned between the reflective layer and the gap between the photovoltaic device and the conduit that transports the high-temperature liquid. The reflective layer may be configured to reflect radiation that is not absorbed by the photovoltaic device back to the gap so that the radiation can then be absorbed by the photovoltaic device or by the conduit or other suitable member within the system to avoid heat loss that can reduce system efficiency. For example, if the reflected radiation is absorbed by the conduit, it can help keep the conduit at a higher temperature so that the conduit can continue to emit additional radiation that can then be absorbed by the photovoltaic device. In some embodiments, the reflective layer can be configured such that its reflectance spectrum substantially overlaps with the emission spectrum from the conduit (or other suitable emitting member).

[0035] Turning to the drawings, specific non-limiting embodiments are described in further detail. It should be understood that the various systems, components, features, and methods described with respect to these embodiments may be used alone and / or in any desired combination, as the present disclosure is not limited to only the specific embodiments described herein.

[0036] Figure 1 is a schematic diagram of an energy storage system 100 of an embodiment. As described above, the system includes a first liquid storage tank 102, which is constructed and arranged to contain a high-temperature liquid 104 (e.g., liquid silicon) at a temperature of about 2400°C or other suitable temperature. The first liquid storage tank 102 is fluidly coupled to an energy conversion system 106 via a pipe 122, and the pipe 122 may include any suitable structure for transporting the high-temperature liquid 104. The energy conversion system 106 includes one or more conduits through which the high-temperature liquid flows, and in some embodiments includes an array of conduits 108 through which the high-temperature liquid flows. When the liquid flows through the array, the conduit is heated and emits radiation. The emitted radiation is then absorbed by one or more photovoltaic devices 110 to convert the radiation into electricity, which can be transported to an external system 124.

[0037] In some applications, the high temperature liquid 104 can be maintained in the first storage tank 102 until energy recovery is desired, at which time the high temperature liquid can be delivered to the energy conversion system 106. In some embodiments, the first storage tank can be configured to hold a large amount of high temperature liquid 104, which can advantageously provide a small surface area to volume ratio of the first storage tank. As described above, such a configuration can help avoid heat losses while storing the liquid in the first storage tank. In an exemplary embodiment, the first storage tank 102 can have a diameter or other lateral dimension of about 1m to about 100m, and a height of about 1m to about 100m. In some embodiments, the surface area to volume ratio can be about 1.2m -1 About 0.15m -1 In still other embodiments, the size of the tank and appropriate insulation materials may be selected so that less than 1% of the energy stored in the high temperature liquid is lost as heat per day.

[0038] After exiting the array 108 of the energy conversion system 106, the liquid (now at a lower temperature due to the emission of radiation within the array 108) flows into the pump 112, which pumps the lower temperature liquid 114 to the second reservoir 116. For example, in one embodiment where the high temperature liquid is liquid silicon at a temperature of about 2400°C, the liquid silicon can be stored in the second reservoir at a temperature of about 1900°C. In some applications, the pump 112 can also be used to control the flow of the high temperature liquid 104 from the first reservoir 102 to the energy conversion system 106. In some embodiments, the pump 112 can be configured to move liquid from the first reservoir 102 into the first end of the conduit array 108 of the energy conversion system 106, to move liquid from the second end of the conduit array into the second reservoir 116; and to move liquid from the second reservoir through the heater 118 and into the first reservoir 102. Exemplary pumps that may be suitable for pumping liquid throughout system 100 are described in U.S. Patent Application Publication No. 2018 / 0045197, which is incorporated herein by reference in its entirety.

[0039] When energy is provided to the system from an external energy source 120 (which may be any suitable renewable or non-renewable energy source), the lower temperature liquid 114 may be pumped through a heater 118. The heater may use energy from the external energy source 120 to heat the liquid using any suitable heating method (e.g., induction heating, resistive heating, etc.) and raise the temperature of the liquid to the temperature of the high temperature liquid 104. After heating, the high temperature liquid may be pumped into the first liquid storage tank 102, where the liquid may be held until it is pumped through the system to recover electricity when desired.

[0040] Figure 2A perspective view of an energy conversion system 200 including an array of conduits 202 is shown, through which a high temperature liquid can flow from a first end 204 of the array to a second end 206 of the array. The array 202 includes a plurality of gaps 208, and each gap is constructed and arranged to accommodate a photovoltaic device 210. The gaps 208 can be formed as open channels that extend from the first end 204 of the array to the second end 206 of the array, and in some embodiments extend completely through the second end 206 of the array. In either case, each gap includes at least one end that can be open to the outside of the array to accommodate one or more corresponding photovoltaic devices. The photovoltaic devices 210 can be formed as extended rods so that the photovoltaic devices can extend along at least a portion of each gap, and in some embodiments extend along substantially the entire length of each gap. In some embodiments, the energy conversion system 200 can include a housing 212, and the housing can include an opening 214 aligned with the gaps 208 to allow the photovoltaic devices to be inserted into and removed from the conduit array 202.

[0041] Now refer to Figure 3 , describing in more detail Figure 2 Some aspects of the energy conversion system 200. In particular, Figure 3 2 is a perspective view of a portion of a conduit array 202 showing a plurality of individual conduits 203 arranged to define a gap 208 in which a photovoltaic device 210 may be accommodated. The photovoltaic device may be selectively inserted into or removed from the gap 208 as indicated by arrow 216. In particular, the photovoltaic device 202 may extend in a direction parallel to the conduits 203, and the photovoltaic device may be moved in that direction to selectively move the photovoltaic device into or out of the gap 208. In some cases, the photovoltaic device may be partially accommodated in the gap such that a portion of the photovoltaic device remains outside of the gap 208. Furthermore, while the depicted embodiment includes photovoltaic devices that may be moved into and out of the gap, it should be understood that other configurations may be suitable, such as a configuration in which the conduit array is movable relative to one or more fixed photovoltaic devices to selectively position the photovoltaic device in the gap of the conduit array when energy recovery is desired. As described above, such an arrangement in which the photovoltaic device is selectively movable relative to the conduit can be advantageous for avoiding unnecessary exposure of the photovoltaic device to high temperature conditions within gap 208 when the system is not recovering previously stored energy, and / or for repair, maintenance, and / or replacement of the photovoltaic device.

[0042] Although the photovoltaic device 210 is depicted as a prismatic rod structure having a rectangular cross-section in the above embodiments, it should be understood that other configurations may be suitable. For example, other cross-sectional geometries such as circular, triangular, or other polygonal geometries may be suitable. Alternatively or additionally, the photovoltaic device 210 may include a planar or plate-like structure, a layered structure, and / or may include one or more channels formed through at least a portion of the length of the photovoltaic device. Therefore, it should be understood that the present disclosure is not limited to photovoltaic devices and / or corresponding conduit arrays of any particular shape or geometry. In addition, although Figures 2 to 3 The embodiment shown in includes photovoltaic devices 210 that are removable from the conduit array 202, but other configurations are also contemplated, including configurations in which one or more photovoltaic devices are permanently mounted in the array.

[0043] Figure 4 4 is a cross-sectional top view of an embodiment of an energy conversion system 400, the energy conversion system 400 including an array 402 of conduits 404 through which a high temperature liquid can flow, as described above. Similar to the above embodiments, the conduits 404 are arranged to define gaps 406 in which photovoltaic devices 408 can be permanently and / or selectively accommodated.

[0044] In the depicted embodiment, an intermediate layer 410 is provided between the conduit 404 forming each gap 406 and the corresponding photovoltaic device positioned in the corresponding gap to isolate the photovoltaic device from the conduit. As described above, the intermediate layer can help reduce the vapor pressure of the sublimated material in the gap 406. The intermediate layer 410 can also help reduce and / or avoid the diffusion of the sublimated material from the conduit 404 through the gap 406 and diffuse to the diffusion on the photovoltaic device 408. For example, one or more intermediate layers in the system can act as a physical barrier to reduce or prevent diffusion into the gap 406. As shown, in some embodiments, a plurality of intermediate layers 410 can be arranged so that the conduit 404 is positioned between the relative parts of the intermediate layer to form an overall array structure. In this way, the intermediate layer 410 can at least partially surround the conduit 404, which can help accommodate the sublimated material and avoid the deposition of the sublimated material on the photovoltaic device 408.

[0045] Figure 4The embodiment depicted in also includes a plurality of gas flow ports 412 positioned around the photovoltaic device. As described in more detail below, the gas flow ports 412 may be gas inlets and / or gas outlets through which a purge gas may flow into or out of the gap 406, respectively, to entrain and remove any sublimated atoms in the gap. As shown, the gas ports 412 may be located around the photovoltaic device 408, but other arrangements may be suitable, including arrangements of the gas ports on other components of the system, as the present disclosure is not limited to any particular configuration or arrangement of the gas ports.

[0046] Figure 4A Depicted along Figure 4 4A-4A of the cross-sectional view of the energy conversion system 400. In the depicted embodiment, the photovoltaic device 408 may include a plurality of gas ports 412 distributed along its length (e.g., a gas inlet or gas outlet through which a purge gas can flow). Therefore, it should be understood that the plurality of gas inlets may be distributed around the periphery of the photovoltaic device and / or along the length and / or width of the photovoltaic device in any suitable manner to provide the desired flow geometry of the purge gas. For example, some embodiments may include gas ports distributed along the length of the photovoltaic device and gas ports distributed around the circumference or other periphery of the photovoltaic device to achieve the desired flow of the purge gas within the gap. For example, other embodiments in which the photovoltaic device has a flatter geometry may include gas ports distributed along the length of the photovoltaic device and across the width.

[0047] Now refer to Figure 5 , an energy conversion system 600 including a purge gas of one embodiment is described in more detail. In the depicted embodiment, the conduit 602 is spaced apart from the photovoltaic device 604 via a gap 606 having a width W. A stream of a purge gas 610 is formed in the gap by causing the purge gas to flow into the gap via a gas inlet 612 and flow out of the gap via a gas outlet 614, the gas outlet 614 being formed in the photovoltaic device 604 and spaced apart from the corresponding gas inlet. Although the gas inlet and gas outlet are depicted as channels formed in the photovoltaic device, it should be understood that other configurations may be suitable. For example, some embodiments may include one or more nozzles associated with an inlet or outlet and configured to direct a purge gas stream.

[0048] As shown, the flow of purge gas 610 can be directed in a direction from inlet 612 toward outlet and / or along the length of gap 606, the direction being substantially parallel to the direction along which photovoltaic device 604 extends. In other embodiments, the purge gas can be directed such that at least one component of the velocity of the purge gas flow is along the length of the photovoltaic device and / or along the length of the gap. For example, in such an embodiment, another component of the velocity of the purge gas can be directed along the width of the photovoltaic device, which can help avoid dead zones within the gap where gas flow may stagnate.

[0049] The flow of purge gas 610 within gap 606 can be driven by a blower 618 configured to impart a desired velocity to the purge gas. For example, as previously described, in some embodiments, the velocity of the purge gas can be selected so that the time for the purge gas to travel from gas inlet 612 to gas outlet 614 is less than the diffusion time for sublimated material from conduit 602 to diffuse through gap 606 and deposit onto photovoltaic device 604. In some cases, the velocity v of the purge gas is less than 100%. 吹扫 The purge gas velocity may be selected based on the length L between the gas inlet and the gas outlet and the width W of the gap. For example, as described above, the purge gas velocity may be selected such that L / v 吹扫 <W / v 漂移 , where v 漂移 It is the drift velocity of the material of the sublimation from the conduit. Selecting the purge gas velocity that satisfies this condition can help ensure that the time that purge gas flows from gas inlet 612 to gas outlet 614 is less than the time that the atoms of sublimation diffuse through gap 606. In certain embodiments, the purge gas velocity can be about 0.01m / second to about 10m / second (for example, about 0.5m / second to about 3m / second). In addition, in some embodiments, the length between adjacent inlets and outlets can be less than about 500cm, less than about 100cm, less than about 500cm, less than about 10cm or less than about 5cm. In some embodiments, the length between adjacent inlets and outlets can be up to about 5m. In some cases, suitable purge gas velocity can be set based on the interval between adjacent inlets and outlets and / or the temperature of the high temperature liquid transported by conduit.

[0050] As shown, in some embodiments, the purge gas 610 can be recirculated so that the purge gas can be directed to flow out of the gas outlet 614 and back into the gas inlet 612. For example, the purge gas can flow out of the outlet 614 and flow through the conduit 616 to the cooler 620, which is configured to reduce the temperature of the gas leaving the gap 606. For example, the cooler can reduce the temperature of the gas from a first temperature (which can correspond to the temperature of the liquid transported within the conduit 602 (e.g., about 1800° C. to about 2600° C.)) to a second lower temperature (e.g., less than about 1000° C., less than about 500° C., less than about 100° C., less than about 50° C., or less than about 30° C.). In some embodiments where the photovoltaic device 604 is actively cooled (e.g., to about 35° C. or to another suitable temperature), the cooler can be configured to reduce the temperature of the gas to a temperature below the temperature of the photovoltaic device (e.g., to about 30° C. to 35° C.). After being cooled, the gas then passes through a filter 622, which can remove material from the purge gas, such as sublimated material from the conduit that is entrained by the purge gas flow. It should be understood that the filter 622 can include any suitable filter material, such as porous metal, polymer material, carbon, and / or ceramic material. After filtering, the purge gas can then pass through a blower 618 to be accelerated to a desired speed to enter the gap 606 through the gas inlet 612.

[0051] Also like Figure 5 As shown, in order to further reduce the vapor pressure of the sublimated gas in the gap, in some embodiments it may be desirable to further include an intermediate layer 608 positioned between the conduit 602 and the photovoltaic device 604. The intermediate layer can, for example, help reduce the diffusion of sublimated material through the gap 606 by forming a diffusion barrier to block the diffusion of material from the conduit through the gap. Alternatively or additionally, the intermediate layer can be formed of a material having a vapor pressure lower than that of the conduit material, which can result in less sublimation of the material into the gap. Due to the corresponding reduced vapor pressure of the sublimated material present in the gap, this reduced vapor pressure can be used to reduce the corresponding purge gas speed, gap width, and / or other suitable operating parameters. However, it should be understood that in some embodiments, the intermediate layer 608 may not be included, and the above-mentioned purge gas flow may be sufficient to avoid the deposition of sublimated material onto the photovoltaic device 604. For example, embodiments without the intermediate layer 608 can use a relatively high speed purge gas flow and / or a larger gap width to prevent or reduce the deposition of sublimated material.

[0052] Now refer to Figure 6 , describes in more detail aspects related to the intermediate layer that may be included in the system described herein. In particular, Figure 6706. FIG. 70 is a cross-sectional top view of a portion of an array 700 of conduits 702 defining gaps 706 in which photovoltaic devices 704 are housed. As shown, a plurality of intermediate layers 708 can be positioned along opposite sides of the conduits 702. In this manner, at least a portion of the intermediate layers 708 are positioned between the conduits 702 and the gaps 706, and in some cases, the intermediate layers can at least partially surround the conduits 702. In some embodiments, the arrangement of the intermediate layers can define one or more conduit regions 712 in which the conduits 702 are positioned, and the intermediate layers can provide a physical barrier between the conduits and the gaps 706.

[0053] As described above, the intermediate layer 708 can be formed of a material having a vapor pressure lower than the vapor pressure of the material of the conduit 702 at the elevated operating temperature of the system. For example, for a conduit formed of graphite, the vapor pressure at an exemplary operating temperature of about 2400°C can be about 10Pa. However, the intermediate layer can be formed of a material, such as tungsten, having a vapor pressure much lower than 1Pa at this temperature. Therefore, by placing the intermediate barrier 708 between the conduit and the photovoltaic device 704, the vapor pressure of the sublimated material in the gap 706 can be significantly reduced, which can help reduce the sublimation and corresponding deposition of the material onto the photovoltaic device. Additionally, as previously described, the intermediate layer 708 can act as a physical barrier to prevent or limit the diffusion of material from the conduit 702 to the photovoltaic device 706. For example, any sublimated material from the conduit can be contained between the intermediate layers 708 on either side of the conduit.

[0054] As described above, in some embodiments, the intermediate layer 708 can also serve as an emitting surface from which radiation is emitted into the gap 706 toward the photovoltaic device 704. For example, heat from the conduit 702 (e.g., from a high temperature liquid flowing through the conduit) can be transferred to the intermediate layer 708 via conduction, convection, and / or radiative heating. When heated, the intermediate layer 708 can emit radiation from its surface toward the photovoltaic device.

[0055] According to a particular embodiment, the conduit 702 and / or the intermediate layer 708 can have any suitable dimensions. For example, in some embodiments, the wall thickness of the conduit and the thickness of the intermediate layer 708 can be selected based on the expected sublimation rate of the materials of the conduit and the intermediate layer at the nominal operating temperature of the system. For example, the thickness can be selected so that the conduit and the intermediate layer have a usable service life of about 30 years or more. In an exemplary embodiment, the system can include a graphite conduit with a wall thickness of about 1 mm to 1 cm and a tungsten intermediate layer with a thickness of 10 microns to about 5 mm, which can provide a service life of about 30 years based on the expected sublimation rate of carbon and tungsten at the operating temperature of the array 700.

[0056] Now refer to Figure 7, a photovoltaic device 800 according to an embodiment is described in more detail. In particular, Figure 7 A cross-sectional view of a photovoltaic device formed as a prismatic rod is depicted, which can extend, for example, along the length of a conduit array as described above. Photovoltaic device 800 includes a central core 802, and one or more photovoltaic layers 804 are disposed around the central core 802 on one or more outer surfaces of the central core. Photovoltaic layer 804 can include one or more photovoltaic cells configured to convert radiation (e.g., visible light and / or infrared radiation) into electricity. Various configurations of photovoltaic cells can be suitable, including one or more multi-junction photovoltaic cells, single-junction photovoltaic cells, and / or combinations of different types of photovoltaic cells selected to provide a desired absorption spectrum. Although a photovoltaic device configured as a prismatic rod is depicted, it should be understood that other configurations can be suitable. For example, a photovoltaic device can have a prismatic structure with other cross-sectional shapes (e.g., triangles, rectangles, other regular or irregular polygons, circles, ellipses, etc.), or a photovoltaic device can have a planar configuration (e.g., where the photovoltaic layer is positioned on one or both sides of a substantially flat planar structure). Therefore, it should be understood that the present disclosure is not limited to any particular shape and / or configuration of a photovoltaic device.

[0057] In some embodiments, a reflective layer 806 can be disposed below one or more photovoltaic layers 804 such that the reflective layer 806 is disposed between the central core or other underlying support surface and the one or more photovoltaic layers. For example, the reflective layer 806 can be configured to reflect radiation that is not absorbed by the photovoltaic layer 804 back into the gap and toward one or more conduits ( Figure 7 The reflective layer 806 may be formed of any suitable reflective material, and in some embodiments, the material may be selected to provide a reflective spectrum that at least partially includes, and in some embodiments substantially includes, a corresponding emission spectrum of the radiation emitted by the conduit. In some cases, the reflected radiation may be reabsorbed by the high temperature liquid (e.g., after being absorbed by the conduit), which may help maintain the temperature of the liquid and avoid energy loss. In other cases, the reflected radiation may be subsequently absorbed by the photovoltaic layer 804 after reflecting off one or more additional surfaces (e.g., surfaces of the intermediate layer) in the conduit array (not shown).

[0058] In some applications, it may be desirable to maintain a desired operating temperature of the photovoltaic device. Figure 7As shown, the photovoltaic device may also include one or more cooling channels 808 formed in the central core 802 or other portion of the device, and a cooling fluid below the desired operating temperature of the photovoltaic device may be flowed through the cooling channels. In this way, the cooling channels may help cool one or more photovoltaic layers 806 to maintain the desired operating temperature so that one or more photovoltaic layers do not become damaged when exposed to high temperatures associated with the high temperature liquid flowing through the conduit. In an exemplary embodiment, the cooling fluid may include water at a temperature of about 35°C, and the water may flow through the cooling channels at a volume flow rate suitable for a system of a given size to provide an appropriate degree of cooling for the photovoltaic layer. It should be understood that the central core may include any suitable arrangement of cooling channels, as the present disclosure is not limited in this regard. In addition, in some cases, the reflective layer may help avoid undesired heating of the photovoltaic device by avoiding heat absorption by the photovoltaic device 800 (e.g., by reflecting unabsorbed radiation away from the photovoltaic device).

[0059] Although the present teaching has been described in conjunction with a plurality of embodiments and examples, it is not intended that the present teaching be limited to such embodiments or examples. On the contrary, the present teaching encompasses various alternatives, modifications, and equivalents as will be appreciated by those skilled in the art. Therefore, the foregoing description and accompanying drawings are intended only as examples.

Claims

1. An energy storage system, comprising: a conduit constructed and arranged to carry a liquid heated to a temperature of 1400°C to 2600°C; photovoltaic devices configured to convert electromagnetic radiation into electricity; a gap between the conduit and the photovoltaic device; a gas inlet constructed and arranged to direct a purge gas into the gap; as well as a gas outlet constructed and arranged to direct the purge gas out of the gap, wherein the flow of the purge gas from the inlet to the outlet is configured to pass through the gap between the conduit and the photovoltaic device at a velocity greater than a drift velocity of the sublimated gas. 2 . The energy storage system according to claim 1 , wherein a component of the velocity of the purge gas along a first direction between the gas inlet and the gas outlet is greater than a drift velocity of the gas in the gap.

3. The energy storage system according to claim 2, wherein the gas inlet and the gas outlet are separated by a first distance, the conduit and the photovoltaic device are separated by a second distance, and wherein the first distance divided by the velocity of the purge gas along the first direction is less than the second distance divided by the drift velocity of the gas in the cavity. The energy storage system according to claim 2 , wherein the photovoltaic device extends along the first direction. The energy storage system according to claim 1 , wherein the purge gas comprises at least one selected from argon, krypton, and xenon.

6. The energy storage system of claim 1, wherein the photovoltaic device comprises a multi-junction photovoltaic cell. The energy storage system of claim 1 , wherein the conduit is formed of graphite.

8. The energy storage system of claim 1, wherein the liquid comprises silicon or ferrosilicon.

9. The energy storage system of claim 1, further comprising a reflective surface, wherein the photovoltaic device is positioned between the reflective surface and the gap.

10. The energy storage system of claim 9, wherein the reflective surface is constructed and arranged to reflect at least a portion of radiation not absorbed by the photovoltaic device toward the gap. 11 . The energy storage system of claim 1 , further comprising a filter coupled to the gas inlet and the gas outlet. 12 . The energy storage system of claim 11 , wherein the purge gas is directed out of the gas outlet, through the filter, and back into the gas inlet.

13. A method for storing energy, comprising: conveying a liquid through a conduit positioned on a first side of the gap opposite the photovoltaic device, wherein the liquid is heated to a temperature of 1400° C. to 2600° C.; and A purge gas is caused to flow through the gap between the conduit and the photovoltaic device at a velocity greater than a drift velocity of the sublimated gas.

14. The method according to claim 13, further comprising: heating the conduit at least in part as a result of conveying the liquid through the conduit; emitting radiation from the conduit into the gap due at least in part to heating the conduit; as well as At least a portion of the emitted radiation is absorbed by the photovoltaic device.

15. The method of claim 14, further comprising reflecting at least a portion of the radiation not absorbed by the photovoltaic device back toward the gap.

16. The method of claim 13, wherein flowing the purge gas through the gap comprises directing the purge gas into the gap through a gas inlet and directing the purge gas out of the gap through a gas outlet.

17. The method according to claim 16, further comprising: passing the purge gas through a filter after the purge gas flows out of the gap through the gas outlet; as well as The purge gas is flowed from the filter to the gas inlet.

18. The method of claim 13, wherein the purge gas comprises at least one selected from argon, krypton, and xenon.

19. The method of claim 13, wherein the temperature of the liquid transported through the conduit is 1800°C to 2600°C.

20. The method of claim 13, wherein a velocity of the purge gas within the gap is greater than a drift velocity of the gas within the gap.

21. An energy storage system, comprising: an array of conduits constructed and arranged to transport a liquid from a first end of the array to a second end of the array, wherein the liquid is heated to a temperature of 1400°C to 2600°C; multiple photovoltaic devices; and A plurality of gaps are formed in the array of conduits, each gap comprising: an opening at at least one end of the array of conduits, wherein each gap is constructed and arranged to accommodate at least one of the plurality of photovoltaic devices and to flow a purge gas therethrough at a velocity greater than a drift velocity of the sublimated gas, and The plurality of photovoltaic devices are selectively movable into and out of the plurality of gaps.

22. The energy storage system of claim 21, further comprising one or more gas inlets constructed and arranged to direct a purge gas into at least one gap of the plurality of gaps.

23. The energy storage system of claim 22, further comprising one or more gas outlets constructed and arranged to direct the purge gas out of the at least one gap.

24. The energy storage system of claim 23, wherein the flow of the purge gas from the one or more gas inlets to the one or more gas outlets is directed at least partially along the length of the gap.

25. The energy storage system of claim 21, wherein the liquid is cooled from a first temperature at the first end of the array to a second temperature at the second end of the array.

26. The energy storage system of claim 25, wherein the first temperature is 1400°C to 2600°C.

27. The energy storage system of claim 26, wherein radiation is emitted into the plurality of gaps due at least in part to cooling of the liquid.

28. The energy storage system according to claim 25, further comprising: a first fluid reservoir fluidly coupled to the first end of the array of conduits and constructed and arranged to store the fluid at the first temperature; a second fluid reservoir fluidly coupled to the second end of the conduit array and the first fluid reservoir, the second fluid reservoir being constructed and arranged to store the fluid at the second temperature; as well as A heater positioned between the first and second fluid reservoirs, the heater being constructed and arranged to heat the fluid from the second temperature to the first temperature.

29. The energy storage system according to claim 28, further comprising a pump, wherein the pump is configured to: moving the liquid from the first reservoir into the first end of the conduit array; moving the liquid from the second end of the conduit array into the second reservoir; and The liquid is moved from the second liquid reservoir, through the heater, and into the first liquid reservoir.

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