Energy storage unit

Abstract

The present invention relates to an energy storage unit (1) for the reversible storage and withdrawal of chemical and thermal energy, comprising a double-walled tubular reactor body (2) which spans an annular space (10) and an interior space (7) fluidly connected to the annular space (10). An annular space connection (17) opens into the annular space (10), and an interior space connection (16) opens into the interior space (7), via which connection a gas stream (19) can flow through the energy storage unit (1) in different flow directions. Arranged in the interior space (7) is a reaction material (9) over which the gas stream (19) can flow, comprising a metal-metal oxide reaction material pairing. The metal oxide can be reduced to the metal by flowing over it with a hydrogen-containing gas stream (19), releasing water vapor, and the metal can be oxidized to the metal oxide by flowing over it with a water-vapor-containing gas stream (19), releasing hydrogen.In the annular space (10) there is arranged a thermal storage material (12) over which the gas flow (19) can flow, through which thermal energy can be absorbed from the gas flow (19) or released to it depending on the temperature difference between the thermal storage material (12) and the gas flow (19).

Description

The present invention relates to an energy storage unit for reversibly storing and storing chemical and thermal energy and to an associated method for reversibly storing chemical and thermal energy into and storing chemical and thermal energy from the energy storage unit.A successful conversion of the fossil energy system into a renewable energy system is hardly conceivable without the increased use of hydrogen and entails the need to store large amounts of hydrogen. The storage of hydrogen is associated with great technical challenges. Due to its physical properties, either complex and cost-intensive apparatuses are necessary in order to store hydrogen in a space-saving manner at very high pressures or low temperatures, or large storage volumes have to be accepted in order to store hydrogen without pressure.In order to avoid these disadvantages, approaches are known from the prior art which track indirect storage of hydrogen. In this case, not the hydrogen itself, but the chemical energy contained in the hydrogen is stored by storing a reaction product which has originated from a reversible reaction of a reactant with hydrogen.The reaction product present as a solid can then be stored and stored simply and economically. For storing (discharging) the chemical energy, the reversible reaction is reversed. In this reverse reaction, the reaction product reacts again to give the starting reactant with liberation of hydrogen.Viewed functionally, such an indirect hydrogen storage device allows the storage of hydrogen-although not hydrogen itself, but rather the chemical energy of the hydrogen bound is reversibly stored in a suitable reaction product. Chemical energy is understood to mean an energy form which is stored in a reaction material in the form of a chemical compound and can be released by chemical reactions.For the indirect storage of hydrogen, use is made in particular of metal-metal oxide reaction pairings. For storing the chemical energy of hydrogen, the metal oxide is reduced by hydrogen in an endothermic reaction to pure metal, while the hydrogen is oxidized to water vapor. This process step is also referred to below as endothermic storage of hydrogen. The pure metal thereby enables a pressureless, cost-effective, harmless and (almost) loss-free storage of the chemical energy of the hydrogen at a relatively high energy density. If the chemical energy is now to be released again and thus stored (discharged), the corresponding exothermic back reaction is initiated. For this purpose, the pure metal is treated with steam and oxidized to metal oxide, the steam being simultaneously reduced to hydrogen. This process step is also referred to below as exothermic storage of hydrogen. The stored (released) hydrogen can now be supplied to the desired use.DE 10 2015 007 645 A1 describes how hydrogen can be temporarily stored with the aid of such a metal-metal oxide energy storage unit. By means of an electrolyser, hydrogen is provided, supplied to the energy storage unit and stored there in the form of pure metal as chemical energy. The water vapor formed during the storage of the hydrogen is in this case fed back to the electrolyser. To save out the chemical energy, the energy storage unit is supplied with water vapor from a fuel cell. The hydrogen released in this process is supplied to the fuel cell for power generation. The metal-metal oxide reaction material is present in a reactor through which flow can take place in a packed layer of pellets over which a hydrogen-containing or water vapor-containing gas flows.WO 2014 173 665 A1 likewise shows such a metal-metal oxide energy storage unit, but with a different reactor design. The metal-metal oxide reaction material is present here in the form of small particles in a fluidized bed in the interior of a double-walled fluidized bed reactor. In the annular space of the double-walled fluidized-bed reactor surrounding the inner region, a heat accumulator is provided as a temperature control medium in order to temporarily store thermal energy. During the exothermic storage of hydrogen, thermal energy is released in the fluidized bed and stored in the heat store through the inner wall of the fluidized bed reactor. During the endothermic storage of hydrogen, thermal energy is stored out of the heat store and introduced through the inner wall into the interior of the fluidized bed reactor.The object of the present invention is to provide an improved energy storage unit for reversibly storing and storing chemical and thermal energy, in particular with regard to an improved heat storage capacity, lower pressure losses in the reactor, a simple scalability and low production costs of the energy storage unit.This object is achieved by the energy storage unit for reversibly storing and storing chemical and thermal energy according to claim 1, the energy storage device according to claim 10 and the method according to claim 15 for reversibly storing chemical and thermal energy into and storing chemical and thermal energy from an energy storage unit according to the invention.The energy storage unit according to the invention comprises for reversibly storing and storing chemical and thermal energya double-walled tubular reactor body having an inner wall and an outer wall, which body spans an annular space between the inner wall and the outer wall and an inner space which is connected fluidically to the annular space and extends within the inner wall,(at least) one annular space connection opening into the annular space and (at least) one inner space connection opening into the inner space, via which a gas stream can flow through the energy storage unit in different flow directions,a reaction material which is arranged in the interior of the reactor body and can be overflowed by the gas stream and has a metal-metal oxide reaction material pair, wherein the metal oxide in the reaction material can be reduced by overflow with a hydrogen-containing gas stream with liberation of water vapor to form the metal, and the metal in the reaction material can be oxidized by overflow with a water-vapor-containing gas stream with liberation of hydrogen to form the metal oxide, anda thermal storage material which is arranged in the annular space of the reactor body and can be overflowed by the gas stream and by means of which thermal energy can be absorbed by the gas stream or emitted to the latter depending on the temperature difference between the thermal storage material and the gas stream.Through the synergistic cooperation of the features of the invention, a number of surprising advantages can be achieved:According to the invention, the gas stream not only overflows the reaction material in the interior, but also the thermostorage material in the annular space. This direct and direct contact between the thermal storage material and the gas stream enables very good heat transfer. The grittiness (i.e. the temperature difference between the thermal storage material and the gas stream) can be reduced and thus more thermal energy can be stored or stored. In this way, the thermal efficiency of the storage process can be improved, since little (unused) waste heat leaves the energy storage unit during the exothermic storage of hydrogen and less heat energy has to be used for external preheating of the supplied hydrogen during the endothermic storage of hydrogen.The invertibility of the flow direction in which the gas stream flows through the energy storage unit thereby enables a simple adaptation to the thermal requirements of the hydrogen storage or discharge process and thus the intermediate storage of a maximum amount of thermal energy, which further improves the thermal efficiency of the storage process:For storing hydrogen (or its chemical energy), the gas stream flows through the energy storage unit in a first flow direction. The initially (strongly) hydrogen-containing gas stream is supplied to the annular space via one of the annular space connections and discharged from the inner space via one of the inner space connections. The relatively cold gas stream thus initially overflows the relatively warm thermal storage material (which was brought to a high temperature level in advance), is heated in the process and in this way brought to the temperature required so that the endothermic reaction can be started during the subsequent overflow of the reaction material and the reaction material can be reduced with the formation of water vapor. When flowing through the interior, the hydrogen content of the gas stream is reduced and the content of the water vapor is increased as a result of the endothermic reaction. In this way, chemical energy is stored in the energy storage unit and at the same time thermal energy is stored from the energy storage unit.In order to store the previously stored hydrogen, the energy storage unit is flowed through in a second flow direction opposite the first flow direction. For this purpose, an initially (strongly) water-vapor-containing gas stream is fed to the interior via one of the interior connections and removed from the annulus via one of the annulus connections. The gas stream thus initially overflows the reduced reaction material. In an exothermic reaction, the reaction material is oxidized to form hydrogen. The gas stream is heated, the water vapor fraction falls and the hydrogen fraction in the gas stream rises. Subsequently, the relatively warm hydrogen-containing gas stream flows through the annular space and heats the relatively cold thermal storage material when it overflows. The thermal energy stored in the thermal storage material is temporarily stored in the energy storage unit and is thus available if the gas stream has to be preheated at a later point in time during the renewed storage of hydrogen, as described further above. In this way, chemical energy is stored out of the energy storage unit and at the same time thermal energy is stored in the energy storage unit.A gas stream contains water vapor or hydrogen when the water vapor fraction or hydrogen fraction in the gas stream is at least 5 volume percentThe energy storage unit can also be easily scaled by adapting the length, the inner wall diameter and / or the outer wall diameter of the tubular reactor body, wherein the ratio of reaction material to thermostorage material can be specifically adapted to the desired application via the volume ratios of interior space to annulus space. The simple geometry of the reactor enables cost-effective production.Furthermore, the construction of the double-walled reactor body and the arrangement of the reaction material in the inner region and the thermostorage material in the annular space make it possible for the outer wall of the reactor to be exposed only to relatively low temperatures. (The highest temperatures occur in the exothermic storage of hydrogen in the reaction material in the interior.) In this way, the heat loss via the outer wall can be reduced, which benefits the storage efficiency. Furthermore, the use of less temperature-stable and thus more cost-effective materials for the outer wall of the reactor body is made possible.Selected aspects of the energy storage unit are to be illuminated in more detail below:The formulation that a gas stream flows over the reaction material or the thermal storage material expresses that the gas stream comes into direct and direct contact with the reaction material or thermal storage material as it flows through the reactor body by flowing past it, flowing through it and / or flowing around it.Tubular reactor bodies are also referred to in process engineering as flow pipes, and double-walled tubular reactor bodies are accordingly referred to as double-walled flow pipes.In the case of the double-walled tubular reactor body, the inner wall forms an inner tube, the outer wall an outer tube enclosing the inner tube. Preferably, the inner tube and the outer tube have a circular cross section and are arranged concentrically with respect to one another. The annular space extends between the inner tube and the outer tube.The formulation that the interior of the reactor body is fluidically connected to the annular space expresses that there is a fluid connection between the interior and the annular space, which permits a fluid or a gas stream to flow from the annular space into the interior and vice versa.The metal-metal oxide reaction material pairing of the reaction material consists of a metal and the associated metal oxide, which can be converted (transferred) into one another by reversible reactions. When the metal-metal oxide reactant pairing is fully oxidized, all of the metal is oxidized to metal oxide, such that the metal-metal oxide reactant pairing is fully present as metal oxide. When the metal-metal oxide reaction material pairing is completely reduced, it is completely present as pure metal.If the thermal storage material is warmer than the gas stream overflowing it, thermal energy is emitted to the gas stream, whereby the latter is heated. This effect is utilized in endothermic storage of hydrogen when a hydrogen-containing gas stream, which is cooler than the thermostorage material, is heated by the thermostorage material and in this way brought to the temperature required for the endothermic reaction. (The thermal storage material must, of course, be brought to the required higher temperature level beforehand.)If, on the other hand, the thermal storage material is colder than the gas stream flowing over it, it absorbs thermal energy from the gas stream, as a result of which the latter is cooled. This effect is utilized in the exothermic storage of hydrogen when a hydrogen-containing gas stream, which is hotter than the thermal storage material, is cooled by the thermal storage material and in this way thermal energy is temporarily stored there.The reaction material, like any material containing mass, also acts to a certain extent as a thermal store. A thermostorage material in the sense of the present invention is not understood, however, as meaning a material which represents a reaction material having a metal-metal oxide reaction material pairing in the sense of the invention, which can be reduced to the metal by overflowing with a hydrogen-containing gas stream with liberation of water vapor.According to a preferred embodiment of the energy storage unitthe reaction material is present in the form of a bed of reaction material shaped bodies which have in particular a diameter of 4 to 30 mm, preferably 5 to 18 mm, and / orthe thermal storage material is in the form of a bed of thermal storage material shaped bodies which have in particular a diameter of 4 to 30 mm, preferably 5 to 18 mm.In this way, the reaction material and / or the thermostorage material is present as a bulk layer of shaped bodies (also referred to as pellets), through which a gas stream can flow with only slight pressure losses and at the same time has a very large contact area between the gas stream and the reaction material or the thermostorage material, which is detrimental to the reaction speed and to the heat exchange. In addition, an energy storage unit which is designed as a fixed-bed reactor with a packed layer of pellets can be scaled in a simple manner. Furthermore, in particular in comparison with fluidized-bed reactors, complicated apparatuses for gas-solid separation can be dispensed with.The reaction material shaped bodies can be designed in particular as porous pellets, the structure and production of which is described in detail, for example, in DD 94984 A1 and which can have a framework structure (e.g. made of aluminum oxide, calcium, chromium, copper, manganese, nickel, silicon oxide, rhodium and zirconium) in which the reaction material is incorporated.In the case of non-spherical shaped bodies, the smallest cross section is used as diameter.According to a further advantageous embodiment of the energy storage unit according to the inventionthe metal-metal oxide reaction material pairing is designed as an iron-iron oxide reaction material pairing, a tungsten-tungsten oxide reaction material pairing, a tin-tin oxide reaction material pairing, a nickel-nickel oxide reaction material pairing, a copper-copper oxide reaction material pairing, a manganese-manganese oxide reaction material pairing, and / or cerium-cerium oxide reaction material pairing,the thermal storage material is designed as a latent heat storage device and comprises in particular a metal salt, an inorganic salt, a high-temperature phase change material (PCM), calcium chloride, aluminum and / or potassium nitrate, and / orthe thermal storage material is designed as a sensitive heat store and comprises in particular a ceramic, in particular an aluminum oxide and / or a zirconium oxide, a refractory material, in particular silicon carbide and / or magnesia, gravel, volcanic rock and / or high-temperature concrete.The metal-metal oxide reaction material pairings listed have proven to be particularly suitable for practice, wherein in particular the iron-iron oxide reaction material pairings represent an extraordinarily good compromise between economic efficiency and stability.Furthermore, it can be advantageously provided thatthe inner wall has at least one aperture which establishes a fluidic connection between the interior space and the annular space, andthe at least one aperture is in particular configured as a circular aperture having a diameter of 3 to 10 mm, as a slot-shaped aperture having a width of 2 to 6 mm and a length of 4 to 100 mm, or as a circular-segment-shaped aperture having an opening angle of 90 to 300° and a clear width of 2 to 6 mm.In this way, the interior space can be fluidically connected to the annular space without additional piping complexity. In this case, it should be ensured that the diameters or the inside widths of the apertures are smaller than the diameters of the reaction material shaped bodies or of the thermal storage material shaped bodies.Particularly advantageously, the inner wall has a plurality of apertures, which each produce a fluidic connection between the interior space and the annular space.The number and / or the size of the apertures in the inner wall can vary along the longitudinal extent of the tubular reactor body in order to realize a desired flow guidance in this way. Furthermore, different aperture geometries (circular, slot-shaped, circular segment-shaped) can also be combined with one another.Advantageously, flow guide plates can be provided in the interior and / or in the annular space in order to realize as uniform a flow through the interior or the annular space as possible.According to a further advantageous embodiment of the invention, the reactor body (in particular at one of its end-face ends) has a connecting line which fluidically connects the interior space to the annular space.In this way, it can be achieved that the gas stream initially flows completely through the interior (or the annular space) before it enters the other space, that is to say the annular space (or the interior), and flows completely through the latter, as a result of which the efficiency of the energy storage unit can be increased.Furthermore, it can be provided thatthe inner wall of the reactor body is made of a metallic material, in particular of a highly alloyed steel, and / or of a mineral material, in particular of a ceramic, of chamotte stone and / or volcanic rock, and / orthe outer wall of the reactor body is made of a metallic material, in particular of a low-alloy steel sheet.In particular, high-temperature-resistant materials are used as the inner wall material, since very high temperatures can occur in the interior during the exothermic storage of hydrogen. The outer wall, on the other hand, can be made of less temperature-resistant and thus more cost-effective materials, which benefits the economy of the energy storage unit.For the purposes of the present invention, a low-alloy steel is understood to mean a steel in which the sum of the alloying elements does not exceed a content of 10 percent by mass, in particular of 5 percent by mass.The requirements for the temperature resistance of the material of the outer wall can be reduced still further in an advantageous manner in that the outer wall of the reactor body is lined on the side facing the annular space by a mineral material, chamotte stone and / or volcanic rock.Energy storage units which are particularly suitable for practice can be realized ifthe axial extent of the annular space is 5 to 10 times larger than the largest diameter of the annular space of the reactor body, and / orthe largest diameter of the annular space is 1.5 to 4 times larger than the largest diameter of the interior of the reactor body.The invention is also manifested in an energy storage device which has an energy storage unit according to the invention and furthermore comprises:a first source of a hydrogen-containing first gas stream which is fluidically connectable to the (at least one) annular space connection (such that the first gas stream can be supplied to the energy storage unit via the (at least one) annular space connection),a first depression for the first gas stream, which is fluidically connectable to the (at least one) interior connection (such that the first gas stream can be discharged via the (at least one) interior connection of the energy storage unit),a second source of a water-vapor-containing second gas stream, which can be fluidically connected to the (at least one) interior connection (such that the second gas stream can be supplied to the energy storage unit via the (at least one) interior connection), anda second depression for the second gas stream, which is fluidically connectable to the (at least one) annular space connection (such that the second gas stream can be discharged via the (at least one) annular space connection of the energy storage unit).In order to store chemical energy in the energy storage unit, the first gas stream flows through the latter in a first gas flow direction. The first gas stream originates from the first source, flows through the annular space connection with a relatively high hydrogen content into the annular space, then flows through the interior while reducing the reaction material and leaves the energy storage unit with a relatively low hydrogen content and a relatively high water vapor content through the interior space connection in order to be supplied to the first depression.In order to store chemical energy from the energy storage unit and to provide hydrogen, a second gas stream flows through the energy storage unit in an opposite, second gas stream direction. The second gas stream originates from the second source, flows into the interior space with a relatively high water vapor fraction through the interior space connection, oxidizes the reaction material and is heated and forms hydrogen, then flows through the annular space with heating of the thermal storage material and leaves the energy storage unit with a relatively high hydrogen fraction through the annular space connection in order to be supplied to the second depression.The energy storage unit can be integrated and incorporated in a wide variety of processes. Against this background, a further preferred embodiment comprisesthe first source of the hydrogen-containing first gas stream comprises a pyrolysis plant, a gasification plant and / or an electrolysis plant,the first sink for the (water vapor-containing) first gas stream comprises a gasification plant, an electrolysis plant, a turbine and / or a vapor store,the second source of the water-vapor-containing second gas stream comprises a gasification plant, a steam generator, a fuel cell, an internal combustion engine, a combustion boiler, a gas turbine and / or a steam accumulator, and / orthe second sink for the (hydrogen-containing) second gas stream comprises an internal combustion engine, a fuel cell, a combustion boiler, a gas turbine and / or a production process for steel or a chemical.Particularly preferably, the energy storage unit is integrated into a pyrolysis plant and / or a gasification plant in which hydrogen can be obtained from hydrocarbons and organic oxygen compounds, e.g. from organic residues and / or plastics, by means of a pyrolysis step and / or by means of a gasification step. The gasification plant can function both as a first source for the hydrogen-containing first gas stream and as a first sink for the water-vapor-containing first gas stream. This is because the first gas stream containing water vapor can be injected into the gasification step, since process vapor is typically required in these process steps. The pyrolysis plant can function as a first source for the hydrogen-containing first gas stream.The gasification plant can also function as a second source for the second gas stream containing water vapor. Because process steam is typically required in the gasification process, gasification plants typically have steam generators which can be used as a second source for the second gas stream containing water vapor.According to a further preferred embodiment of the energy storage device, it is provided thatthe energy storage device comprises a first heat exchanger having a cold side and a warm side,the cold side of the first heat exchanger is arranged fluidically between the first source and the annular space connection of the energy storage unit, andthe warm side of the first heat exchanger is arranged fluidically between the interior connection of the energy storage unit and the first depression.In this way, the energy efficiency of the energy storage device can be improved since the first heat exchanger can be used in storing hydrogen to preheat the first gas stream entering the energy storage unit.The first gas stream emerging from the energy store can be cooled in this way to such an extent that the water vapor contained in the first gas stream condenses to liquid water. This is particularly advantageous if a low-temperature electrolyser functions both as the first source of the hydrogen-containing first gas stream and as the first sink of the water-containing first gas stream.A low temperature electrolyser (e.g. a PEM electrolyser, an AEM electrolyser or an AEL electrolyser) requires liquid water as input and provides hydrogen at typically less than 100°C as output. If, on the other hand, a high-temperature electrolyser (e.g. a solid oxide electrolyser (SOEC)) acts as the first source of the hydrogen-containing first gas stream and as the first sink of the water-containing first gas stream, this first heat exchanger can be dispensed with. This is because a high-temperature electrolyser requires water vapor as input and supplies hydrogen at a temperature level of up to 900° C. as output.The energy efficiency of the energy storage device is still favourable ifthe energy storage device comprises a second heat exchanger having a cold side and a warm side,the cold side of the second heat exchanger is arranged fluidically between the second source and the interior connection of the energy storage unit, andthe warm side of the second heat exchanger is arranged fluidically between the annular space connection of the energy storage unit and the second depression.In this way, when storing hydrogen, the second gas stream entering the energy storage unit can be preheated to such an extent that liquid water is converted into water vapor.According to a further preferred embodiment of the energy storage device, it can be provided for further increasing the energy efficiency thatthe energy storage device comprises a third heat exchanger having a cold side and a warm side,a coolant can flow through the cold side of the third heat exchanger, andthe warm side is arranged fluidically between the interior connection of the energy storage unit and the first depression.Thermal energy can thus be decoupled via the coolant, in order to be used, for example, in a near-end or district heating network. The first gas stream can be cooled to such an extent that the water vapor contained in the first gas stream condenses into liquid water. As already discussed above, this can be particularly advantageous if a low-temperature electrolyser functions both as the first source of the hydrogen-containing first gas stream and as the first sink of the water-containing first gas stream.Furthermore, the invention manifests itself in the method according to the invention for reversibly storing chemical and thermal energy in an energy storage unit according to the invention and for storing chemical and thermal energy from an energy storage unit according to the invention, having the following steps: A) flowing through the energy storage unit with a first gas stream in a first flow direction by supplying the first hydrogen-containing gas stream via the (at least one) annular space connection and discharging the first gas stream via the (at least one) inner space connection, wherein the first gas stream is heated (to a temperature of in particular 400° to 900° C.) when flowing through the annular space by the thermal storage material and thus thermal energy is stored from the energy storage unit and the first gas stream reduces the reaction material (in an endothermic reaction) when flowing through the inner space, with conversion of hydrogen to water vapor and thus chemical energy is stored in the energy storage unit by reduction of the reaction material, and B) flowing through the energy storage unit with a second gas stream in a second flow direction opposite the first flow direction by supplying the second gas stream containing water vapor via the (at least one) inner space connection and discharging the second gas stream via the (at least one) annular space connection, wherein the second gas stream oxidizes the reaction material (in an exothermic reaction) to hydrogen by reacting water vapor when flowing through the interior, and therefore chemical energy is stored out of the energy storage unit by oxidizing the reaction material, and the second gas stream is cooled down when flowing through the thermal storage material when flowing through the annulus, and thus thermal energy is stored in the energy storage unit.Furthermore, it can advantageously be provided that an inert gas stream flows through the energy storage unit in order to selectively heat up the thermal storage material in the annular space. Nitrogen can be used as inert gas, for example--in principle, all gases which do not react with the reaction material are suitable. The thermal energy transferred from the inert gas stream to the thermal storage material can be provided by waste heat from industrial processes. In order to make it possible for the inert gas flow to flow only through the annular space-and not also through the interior space-corresponding valves, connections and / or other flow guidance devices can be provided on the energy storage unit. Furthermore, it can be provided that the second gas stream has an inert gas fraction in order to adapt the second gas stream better to the requirements of the second depression. In particular, if the second depression is designed as an internal combustion engine, the second gas stream may have an argon and / or nitrogen fraction in view of this background.Exemplary embodiments of the invention are explained in more detail below with reference to the drawings. This shows FIGS. 1A & 1B show an energy storage unit according to a first embodiment, FIGS. 2A & 2B show an energy storage unit according to a second embodiment, FIGS. 3A & 3B show an energy storage device according to a third embodiment during the storage of hydrogen (FIG. 3A ) or during the storage of hydrogen (FIG. 3B ), wherein the hydrogen is provided for storage by a low-temperature electrolyser, FIGS. 4A & 4B show an energy storage device according to a fourth embodiment during the storage of hydrogen (FIG. 4A ) or during the storage of hydrogen (FIG. 4B ), wherein the hydrogen is provided for storage by a SOEC electrolyser, FIGS. 5A & 5B show an energy storage device according to a fifth embodiment during the storage of hydrogen (FIG. 5A ) or during the storage of hydrogen (FIG. 5B ), wherein the hydrogen is provided by a pyrolysis plant for storage.FIGS. 1 and 2 each schematically show an energy storage unit 1 when storing hydrogen (FIGS. 1A and 2A ) and when storing hydrogen (FIGS. 1B and 2B ).The energy storage units 1 are each designed as standing double-walled flow tubes, i.e. each have a double-walled tubular reactor body 2. An inner tube 3 forms the inner wall 4, an outer tube 5 concentrically enclosing the inner tube 3 forms the outer wall 6 of the double-walled reactor body 2, The cylindrical inner space 7 bounded by the inner wall 4 is filled with reaction material shaped bodies 8 each having a diameter of 4 to 30 mm, which have a pairing of iron and iron oxide reaction material-the reaction material 9 is thus present in the form of a bed.The annular space 10 which stretches between the inner wall 4 and the outer wall 6 is pre-filled with shaped thermal storage material bodies 11 (as which the thermal storage material 12 is present), which likewise each have a diameter of 4 to 30 mm.At its end faces, the double-walled reactor body 2 is closed in each case by means of a dome-shaped (dome-shaped) cap 13, 14. Supports 15 are attached to the lower cap 13 to allow the reactor body 2 to be positioned upright. Furthermore, the lower cap 13 has an interior connection 16 which opens into the interior 7.In the energy storage unit 1 according to the first embodiment shown in FIGS. 1A and 1B, an annular space connection 17 opening into the annular space 10 is provided in the upper cap 14. Furthermore, the inner wall 4 has a plurality of apertures 18 which fluidically connect the interior 7 to the annular space 10. The apertures 18 are distributed uniformly in the axial and radial direction over the inner wall 4, are circular and have a diameter of 3 to 10 mm.A gas stream 19 can flow through the energy storage unit 1 in two different flow directions.In order to store previously stored chemical energy, a steam-containing gas stream 19 is introduced into the interior 7 via the interior connection 16, as shown in FIG. 1A. While the steam-containing gas stream 19 flows over the shaped reaction material bodies 8, iron is oxidized to iron oxide in an exothermic reaction and steam is simultaneously reduced to hydrogen. The water vapor fraction in the gas stream 19 falls, the hydrogen fraction rises and the gas stream 19 is heated. The gas stream 19 flows through the apertures 18 in the inner wall 4 into the annular chamber 10. Flow guide plates can be provided in the interior 7 and / or the annular space 10 in order to achieve as uniform a flow through the interior 7 and / or the annular space 10 as possible. While the gas stream 19 flows over the thermal storage material shaped bodies 11, it emits thermal energy to the relatively cool thermal storage shaped bodies 11. The cooled, hydrogen-containing gas stream 19 then leaves the energy storage unit via the annular space connection 17.For storing (loading) the energy storage unit 1 with chemical energy-see FIG. 1B-a gas stream 19 flows through the energy storage unit 1 in the opposite direction. Via the annular space connection 17, the hydrogen-containing gas stream 19 is fed to the annular space 10 and heated when the relatively warm thermal storage material shaped bodies 11 overflow. The heated gas stream 19 flows through the apertures 18 into the interior 7. When the reaction material shaped bodies 8 are overflowed, iron oxide is reduced to iron and hydrogen is oxidized to water vapor in an endothermic reaction. The hydrogen content in the gas stream 19 falls, and the water vapor content rises. The gas flow 19 leaves the energy storage unit 1 via the interior connection 16.The second embodiment of the energy storage unit 1 illustrated in FIGS. 2A and 2B differs from the embodiment illustrated in FIGS. 1A and 1B substantially in the embodiment of the fluidic connection between the interior 7 and the annular space 10 and the positioning of the annular space connection 17.According to the exemplary embodiment shown in FIGS. 2A and 2B, the inner wall 7 has no apertures. The fluidic connection between the interior 7 and the annular space 10 is realized by a connecting line 20 arranged in the upper cap 14.The annular space connection 17 is arranged in the lower cap 13. Thus, of course, a gas stream 19 can also flow through the energy storage unit 1 according to FIGS. 2A and 2B in two different flow directions.To save chemical energy, a water-vapor-containing gas stream 19 is fed to the interior 7 via the interior connection 16. The gas stream 19 flows through the entire interior 7 (wherein iron is oxidized to iron oxide and water vapor is reduced to hydrogen in an exothermic reaction) and is deflected in the connecting line 20 in the upper cap 14 and conducted into the annular space 10. When flowing through the annular space 10, the thermal storage material 12 is heated and the gas stream 19 is cooled before it leaves the energy storage unit 1 via the annular space connection 17.For storing chemical energy, a gas stream 19 flows through the energy storage unit 1 in the opposite direction of flow-cf. FIG. 2B.FIGS. 3A to 5B show three different embodiments of an energy storage device 21 according to the invention having an energy storage unit 1 according to the invention when storing hydrogen (FIGS. 3A, 4A, 5A ) or when storing hydrogen (FIGS. 3B, 4B, 5B ).FIGS. 3A and 3B show an energy storage device 21 having two sources Q 1, Q 2, two sinks S 1, S 2, three heat exchangers HX 1, HX 2, HX 3 each having a cold side and a warm side, and an energy storage unit 1.A low-temperature electrolyser PEM functions as a first source Q 1 for the first hydrogen-containing gas stream G 1 and as a first sink S 1 for the first water-containing gas stream G 1 when storing hydrogen. The course of the first gas stream G 1 is indicated in FIG. 3A by connecting arrows between the individual components.A fuel cell BZ functions as a second source Q 2 for the water(vapor) containing second gas stream G 2 and as a second sink S 2 for the hydrogen containing second gas stream G 2 when storing hydrogen. The course of the second gas stream G 2 is indicated in FIG. 3B by connecting arrows between the individual components.Alternatively, a heat engine, in particular an internal combustion engine, or an industrial process could also function, for example, as second source Q 2 for the water(steam) containing second gas stream G 2 and as second sink S 2 for the hydrogen containing second gas stream G 2.A line fluidically connects the hydrogen outlet of the low-temperature electrolyser PEM via a first three-way valve V 1 to the annular space connection 17 of the energy storage unit 1, wherein the cold side of the first heat exchanger HX 1 is fluidically connected therebetween. The internal space port 16 is fluidly connected to the water inlet of the low temperature electrolyser PEM via a second three-way valve V 2 and a pipe, with the warm side of the first heat exchanger HX 1 and the warm side of the third heat exchanger HX 3 being fluidly interposed therebetween.The annular space connection 17 of the energy storage unit 1 is fluidically connected via the first three-way valve V 1 via a line to the hydrogen inlet of the fuel cell BZ, the warm side of the second heat exchanger HX 2 being interposed therebetween. The internal space port 16 is fluidly connected to the water outlet of the fuel cell BZ via the second three-way valve V 2 with the cold side of the second heat exchanger HX 2 interposed therebetween. A coolant line is fluidically connected to the cold side of the third heat exchanger HX 3 for supplying a heat collector V.The oxygen outlet of the low-temperature electrolyser PEM may be connected to an oxygen inlet of the fuel cell BZ via an oxygen accumulator.For storing chemical energy (storing hydrogen), as shown in FIG. 3A, the low-temperature electrolyser PEM is fluidically connected to the energy storage unit 1 as a first source Q 1 and as a first sink S 1 of the first gas stream G 1 by corresponding switching of the two three-way valves V 1, V 2, such that the first gas stream G 1 flows through the energy storage unit 1 in the first flow direction.Water and electricity E are supplied to the electrolyser PEM for the production of hydrogen or a hydrogen-containing gas stream. The hydrogen-containing first gas stream G 1 emerging from the low-temperature electrolyser PEM passes the first heat exchanger HX 1, is heated there and enters the energy storage unit 1 via the annular space connection 17. When flowing through the energy storage unit 1, the reaction material 9 is reduced and thus chemical energy is stored. In order to avoid repetitions, a detailed description of the processes running in the energy storage unit 1 is omitted at this point and reference is made to the corresponding explanations above.The first gas stream G 1, now containing water vapor, exits the energy storage unit 1 via the interior connection 16 and passes the warm side of the first heat exchanger HX 1 in order to dissipate thermal energy to the first gas stream G 1, containing hydrogen, which flows through the cold side. Subsequently, the water-vapor-containing first gas stream G 1 passes through the third heat exchanger HX 3 and emits further thermal energy to the coolant circulating in the coolant line before the water-(vapor)-containing first gas stream G 1 is fed again via the water inlet to the electrolyser PEM. The water (vapor-containing) first gas stream G 1 can be cooled to such an extent that the water vapor condenses to water.For storing the chemical energy (storing hydrogen), the two three-way valves V 1, V 2 are switched, as shown in FIG. 3B, in such a way that the fuel cell BZ is fluidically connected to the energy storage unit 1 as a second source Q 2 and as a second sink S 2 of the second gas stream G 2, such that the second gas stream G 2 flows through the energy storage unit 1 in the second flow direction (opposite the first flow direction).The water(vapor) containing second gas stream G 2 exiting from the fuel cell BZ flows through (passes through) the second heat exchanger HX 2, is heated there and enters the energy storage unit 1 via the interior connection 16. When flowing through the energy storage unit 1, the reaction material 9 is oxidized and thus chemical energy is stored. In order to avoid repetitions, a detailed description of the processes running in the energy storage unit 1 is also omitted at this point and reference is made to the corresponding explanations above. The now hydrogen-containing and hot second gas stream G 2 exits from the energy storage unit 1 via the annular space connection 17 and passes the warm side of the second heat exchanger HX 2 in order to there discharge thermal energy to the water(steam)-containing second gas stream G 2 which flows through the cold side. Subsequently, the hydrogen-containing second gas stream G 2 is fed back to the fuel cell BZ via the hydrogen inlet.The energy storage device 21 shown in FIGS. 4A and 4B differs from the energy storage device shown in FIGS. 3A and 3B substantially in that a high-temperature electrolyser SOEC is used instead of a low-temperature electrolyser as the first source Q 1 and first sink S 1 of the first gas stream. Furthermore, the first heat exchanger HX 1 and the third heat exchanger HX 3 are omitted. FIGS. 4A and 4B show, analogously to FIGS. 3A and 3B, the energy storage device 21 when storing chemical energy (FIG. 4A ) or when storing chemical energy (FIG. 4B ).FIGS. 5A and 5B show another embodiment of an energy storage device 21 having two sources Q 1, Q 2, two sinks S 1, S 2, a heat exchanger having a cold side and a warm side, and an energy storage unit.A residue utilization system 22 having a pyrolysis system PYRO, a gasification system VERZ and a gas processing system REIN functions as the first source Q 1 and first sink S 1 of a first gas stream G 1.For storing chemical energy into the energy storage unit-cf. FIG. 5A in this regard-a hydrogen-containing first gas stream G 1 can be obtained in the residue utilization system 22 from hydrocarbons and / or organic oxygen compounds (e.g. from plastic waste), which can be supplied via the cold side of the first heat exchanger HX 1, a first three-way valve V 1 and the annular space connection 17 of the energy storage unit 1 in order to then flow through the latter in a first flow direction. The (oxidized) water-vapor-containing first gas stream G 1 can then be taken from the energy storage unit 1 via the interior connection 16 and a second three-way valve V 2, conducted through the warm side of the first heat exchanger HX 1 (and cooled) and fed to the gasifier VERW.In order to store the chemical energy (store hydrogen), a steam generator STEAM of the residue utilization system 22 can function as a second source Q 2 of a second gas stream G 2.For this purpose, the water-vapor-containing second gas stream G 2 is supplied from the steam generator STEAM via the (correspondingly connected) second three-way valve V 2 and the interior connection 16 of the energy storage unit 1, flows through the latter in the opposite second gas stream direction (and is reduced and heated in the process) and leaves the latter via the annular space connection 17 and the first three-way valve V 1 as a hydrogen-containing second gas stream G 2, which can be supplied to a second depression S 2 for the use of the hydrogen.List of reference characters1 Energy storage unit 2 Reactor body 3 Inner tube 4 Inner wall 5 Outer tube 6 Outer wall 7 Inner space 8 Reaction material shaped bodies 9 Reaction material 10 Annular space 11 Thermal storage material shaped bodies 12 Thermal storage material 13 Lower cap 14 Upper cap 15 Supports 16 Inner space connection 17 Annular space connection 18 Aperture 19 Gas stream 20 Connecting line 21 Energy storage device Q 1 First source Q 2 Second source S 1 First depression S 2 Second depression HX 1 First heat exchanger HX 2 Second heat exchanger HX 3 Third heat exchanger G 1 First gas stream G 2 Second gas stream PEM, The electrolyzer FC fuel cell V 1 first three-way valve V 2 second three-way valve E electricity 22 waste material utilization system PYRO pyrolysis system VERZ gasification system REIN gas treatment systemReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2015 007 645 A1

[0007] WO 2014 173 665 A1

[0008] DD 94984 A1

[0028]

Claims

Energy storage unit (1) for reversibly storing and storing chemical and thermal energy, comprising - a double-walled tubular reactor body (2) having an inner wall (4) and an outer wall (6), which extends between the inner wall (4) and the outer wall (6) an annular space (10) and an inner space (7) which is fluidically connected to the annular space (10) and extends within the inner wall (4), - at least one annular space connection (17) which opens into the annular space (10) and at least one inner space connection (16) which opens into the inner space (7) and through which a gas stream (19, G1, G2) can flow through the energy storage unit (1) in different flow directions, - an inner space (7) which is arranged in the inner space (7) of the reactor body (2) and is arranged by the gas stream (19, G1, G2), A reaction material (9) which can be overflowed with a metal-metal oxide reaction material pairing, wherein the metal oxide in the reaction material (9) can be reduced to the metal by overflow with a hydrogen-containing gas stream (19, G1, G2) with liberation of water vapor and the metal in the reaction material can be oxidized to the metal oxide by overflow with a water-vapor-containing gas stream (19, G1, G2) with liberation of hydrogen, and - a thermal storage material (12) which is arranged in the annular space (10) of the reactor body (2) and can be overflowed by the gas stream (19, G1, G2) and by means of which thermal energy can be absorbed by the gas stream (19, G1, G2) or can be discharged to the gas stream (19, G1, G2) as a function of the temperature difference between the thermal storage material (12) and the gas stream (19, G1, G2).Energy storage unit (1) according to Claim 1, wherein - the reaction material (9) is present in the form of a bed of reaction material shaped bodies (8) which have in particular a diameter of 4 to 30 mm, preferably 5 to 18 mm, and / or - the thermal storage material (12) is present in the form of a bed of thermal storage material shaped bodies (11) which have in particular a diameter of 4 to 30 mm, preferably 5 to 18 mm.Energy storage unit (1) according to one of the preceding claims, wherein - the metal-metal oxide reaction material pairing is designed as an iron-iron oxide reaction material pairing, a tungsten-tungsten oxide reaction material pairing, a tin-tin oxide reaction material pairing, a nickel-nickel oxide reaction material pairing, a copper-copper oxide reaction material pairing, a manganese-manganese oxide reaction material pairing and / or cerium-cerium oxide reaction material pairing, - the thermal storage material (12) is designed as a latent heat storage unit and in particular comprises a metal salt, an inorganic salt, a high-temperature phase change material (PCM), calcium chloride, aluminum and / or potassium nitrate, and / or - the thermal storage material (12) is designed as a sensitive thermal storage unit and in particular a ceramic, in particular, an aluminum oxide and / or a zirconium oxide, a refractory material, in particular silicon carbide and / or magnesia, gravel, volcanic rock and / or high-temperature concrete.Energy storage unit (1) according to one of the preceding claims, wherein - the inner wall (4) has at least one aperture (18) which establishes a fluidic connection between the interior space (7) and the annular space (10), and - the at least one aperture (18) is in particular designed as a circular aperture having a diameter of 3 to 10 mm, as a slot-shaped aperture having a width of 2 to 6 mm and a length of 4 to 100 mm, or as a circular-segment-shaped aperture having an opening angle of 90 to 300° and a clear width of 2 to 6 mm.Energy storage unit (1) according to Claim 4, wherein the inner wall (4) has a plurality of apertures (18), which each produce a fluidic connection between the interior space (7) and the annular space (10).Energy storage unit (1) according to one of the preceding claims, wherein the reactor body (2) has a connecting line (20) which fluidically connects the interior space (7) to the annular space (10).Energy storage unit (1) according to one of the preceding claims, wherein - the inner wall (4) of the reactor body (2) is made of a metallic material, in particular of a high-alloy steel, and / or of a mineral material, in particular of a ceramic, of chamotte stone and / or volcanic rock, and / or - the outer wall (6) of the reactor body (2) is made of a metallic material, in particular of a low-alloy steel sheet.Energy storage unit (1) according to one of the preceding claims, wherein the outer wall (6) of the reactor body (2) is lined on the side facing the annular space (10) by a mineral material, chamot brick and / or volcanic brick.Energy storage unit (1) according to one of the preceding claims, wherein - the axial extent of the annular space (10) is 5 to 10 times greater than the largest diameter of the annular space (10) of the reactor body (2), and / or - the largest diameter of the annular space (10) is 1.5 to 4 times greater than the largest diameter of the inner space (7) of the reactor body (2).Energy storage device (21) having an energy storage unit (1) according to one of the preceding claims, comprising - a first source (Q1) of a hydrogen-containing first gas stream (G1), which can be fluidically connected to the at least one annular space connection (17), - a first depression (S1) for the first gas stream (G1), which can be fluidically connected to the at least one interior space connection (16), - a second source (Q2) of a water-vapor-containing second gas stream (G2), which can be fluidically connected to the at least one interior space connection (16), and - a second depression (S2) for the second gas stream (G2), which can be fluidically connected to the at least one annular space connection (17).Energy storage device (21) according to Claim 10, wherein - the first source (Q1) of the hydrogen-containing first gas stream (G1) comprises a pyrolysis plant (PYRO), a gasification plant (VERW) and / or an electrolyser (PEM, SOEC), - the first sink (S1) for the water-vapor-containing first gas stream (G1) comprises a gasification plant (VERW), an electrolyser (PEM, SOEC), a turbine and / or a steam accumulator, - the second source (Q2) of the water-vapor-containing second gas stream (G2) comprises a gasification plant (VERW), a steam generator (STEAM), a fuel cell (BZ), an internal combustion engine, a combustion boiler, a gas turbine and / or a steam accumulator, and / or - the second depression (S 2) for the hydrogen-containing second gas stream (G 2) comprises an internal combustion engine, a fuel cell (FC), a combustion boiler, a gas turbine and / or a production process for steel or a chemical.Energy storage device (21) according to Claim 10 or 11, wherein - the energy storage device (21) comprises a first heat exchanger (HX1) having a cold side and a warm side, - the cold side of the first heat exchanger (HX1) is arranged fluidically between the first source (Q1) and the at least one annular space connection (17) of the energy storage unit (1), and - the warm side of the first heat exchanger (HX1) is arranged fluidically between the at least one interior connection (16) of the energy storage unit (1) and the first depression (S1).Energy storage device (21) according to one of Claims 10 to 12, wherein - the energy storage device (21) comprises a second heat exchanger (HX2) having a cold side and a warm side, - the cold side of the second heat exchanger (HX2) is arranged fluidically between the second source (Q2) and the at least one interior connection (16) of the energy storage unit (1), and - the warm side of the second heat exchanger (HX2) is arranged fluidically between the at least one annular space connection (17) of the energy storage unit (1) and the second depression (S2).Energy storage device (21) according to one of Claims 10 to 13, wherein - the energy storage device (21) comprises a third heat exchanger (HX3) having a cold side and a warm side, - a coolant can flow through the cold side of the third heat exchanger (HX3), and - the warm side is arranged fluidically between the at least one interior connection (16) of the energy storage unit (1) and the first depression (S1).Method for reversibly storing chemical and thermal energy into and storing chemical and thermal energy from an energy storage unit (1) according to one of the preceding claims, having the following steps: A) flowing through the energy storage unit (1) with a first gas stream (G1) in a first flow direction by supplying the first hydrogen-containing gas stream (G1) via the at least one annular space connection (17) and discharging the first gas stream (G1) via the at least one interior space connection (16), wherein the first gas stream (G1) is heated to a temperature of in particular 400° to 900° C. when flowing through the annular space (10) through the thermal storage material (12) and thus thermal energy is stored out of the energy storage unit (1) and the first gas stream (G1) reduces the reaction material (9) while converting hydrogen to water vapor when flowing through the inner space (7) and thus chemical energy is stored in the energy storage unit (1) by reducing the reaction material (9), and B) flows through the energy storage unit (1) with a second gas stream (G2) in a second flow direction opposite the first flow direction by supplying the second gas stream (G2) containing water vapor via the at least one inner space connection (16) and discharging the second gas stream (G2) via the at least one annular space connection (17), wherein the second gas stream (G2) oxidizes the reaction material (9) to hydrogen while flowing through the interior space (7) and thus chemical energy is stored out of the energy storage unit by oxidizing the reaction material (9), and the second gas stream (G2) is cooled down through the thermal storage material (12) while flowing through the annular space (10) and thus thermal energy is stored in the energy storage unit (1).

Images