DE102013223588A1 - Plant and method for storing energy - Google Patents

Abstract

A system for storing energy comprises a hydrogen generation unit (17) for generating hydrogen, a hydrogen storage device (22) for storing hydrogen with a loading unit (21) for loading a carrier medium with the in the hydrogen production unit ( 17) and with a discharge unit (26) for discharging the hydrogen from the loaded carrier medium, and a heat device (4) for generating and storing heat, the heat device (4) with the discharge unit (26) is connected to provide heat.

Description

The invention relates to a system and a method for storing energy.

From the prior art power generation units are known which generate electricity from regenerative forms of energy. In particular, photovoltaic systems, wind power plants and / or hydroelectric power plants are used for this purpose. The availability of regenerative energies depends on meteorological influences and in particular can not be influenced and is difficult to predict. The generation of electricity from regenerative energies is unstable.

The object of the present invention is to improve the availability of electric current, which has been generated in particular from regenerative forms of energy.

The object is solved by features of claims 1 and 12. The gist of the invention is that a system for storing energy has a hydrogen storage device for storing hydrogen and a heat device for generating and storing heat. The hydrogen storage device enables storage of hydrogen generated in a hydrogen generation unit. In particular, the hydrogen generation unit is designed as an electrolyzer. The electrolyzer allows the decomposition of water into hydrogen and oxygen. The electrolyzer may be alkaline, acidic or PEM (Polymer Electrolyte Membrane) electrolyzer, for example. The electrolyzer may also be a high temperature electrolyzer or a Solid Oxide Electrolysis Cell (SOEC) electrolyzer. The SOEC electrolyzer is in particular directly connected to the heat device. The heat device can be designed in such a way that water vapor is released during the thermal loading, that is when supplying heated heat carrier. This steam is fed directly to the SOEC electrolyzer. This makes it possible to provide water very efficiently for the SOEC electrolyser. The water provided for the SOEC electrolyzer has an improved purity, since the water is supplied to the SOEC electrolyzer in the gaseous state as water vapor. The evaporation step, a desalination of the water and thus a systemic cleaning instead. In the thermal discharge of the heat device, the heat device can absorb water vapor, which is emitted in particular by a hydrogen oxidation unit. This means that the heat device also serves as a water storage unit. In a low energy period of time, water can be bound from the hydrogen oxidation unit with heat release. This water is transferred during an energetic period of heat absorption by thermal loading of the heat device in the vapor state and provided for the electrolysis in the SOEC electrolyser. The hydrogen storage device enables storage of hydrogen generated in the hydrogen generation unit. The hydrogen storage device comprises a loading unit for loading a carrier medium with the hydrogen generated in the hydrogen generation unit. The hydrogen can advantageously be handled together with the carrier medium, that is transported, conveyed and stored in particular. In particular, the hydrogen is bound to the carrier medium, in particular chemically bound. This eliminates the need to handle molecular hydrogen. The handling of molecular hydrogen is complicated and poses a safety risk. The hydrogen storage device comprises a discharge unit with which hydrogen is recharged from the loaded carrier medium. The discharge process in the discharge unit allows the release of hydrogen from the loaded carrier medium. Heat is required to drive and / or assist the release. For this purpose, the heat unit, in particular directly and directly connected to the discharge unit. The heat required for discharging the hydrogen can be provided in an uncomplicated and loss-reduced manner, in particular lossless. In particular, it is not necessary that hydrogen stored in the hydrogen storage device be used to apply the heat needed to discharge the hydrogen. For example, when the released hydrogen is energetically utilized, particularly in a polymer electrolyte membrane (PEM) fuel cell, the heat generated thereby has a temperature level that is too low to permit release of the hydrogen from the hydrogen storage device. In the energetic utilization of released hydrogen in a combustion chamber, however, efficiency losses can result from the fact that the extraction of heat at a high temperature level causes efficiency losses within the combustion chamber. Surprisingly, it has now been found that with the additional heat device, the heat required to release the hydrogen, in particular at the required time and in particular with the required temperature level can be provided. This improves the plant's electricity-to-electricity efficiency. The heat device allows the generation and storage of the heat required for this purpose. In particular, the heat generated during a high-energy period is stored in the heat device. Energy-rich means more energy, especially from regenerated forms of electricity is available than is consumed. This means there is an excess of energy. The excess energy can be stored as hydrogen by means of the carrier medium in the system and / or provided for transport to another system. Energy can also mean that energy is available at relatively low cost. In contrast, a low-energy period is characterized by the fact that energy is available in an insufficient amount or only at comparatively high costs. This means that more energy is needed than is available. The heat device is thus thermally charged during the high-energy period. The heat device is in particular capable of storing the heat over a longer, in particular unlimited, period of time. The heat is stored in particular without loss. In the low-energy period, the heat device can release the stored heat again. The heat device is transferred in a thermally discharged state. In particular, the heat device is suitable to absorb heat by using regenerative forms of energy and / or by electric current. Advantageous is a system with a power generating unit for generating electric power. The power generation unit may be connected to the hydrogen generation unit for providing power for hydrogen production and / or to the heat device for providing power for heat generation. The power generating unit enables the sufficient supply of electric power to the hydrogen generating unit. The power generation unit may be a separate, local unit that allows the generation of electrical power in the system. It is also possible that a locally remotely located unit is provided as a power generating unit, which is connected for example via a power line network to the system. In particular, therefore, a public power line network is to be understood as a power generation unit in the sense of the application. Surprisingly, it has been found that even if the electric power generated by the power generation unit is used for both hydrogen production and heat generation by electrically heating the heat carrier, the power-to-current efficiency improves by about 50%. results. Particularly advantageous is a system in which the power generating unit allows the generation of electricity from renewable energy forms. In particular, the power generation unit is a photovoltaic unit, a wind power plant and / or a hydroelectric power plant. In particular, it is advantageous if the heat device allows thermal loading by means of regenerative energies, ie from regenerative heat such as sunlight. In this case, the power-to-current efficiency improves by up to 80%. The heating by direct sunlight can be improved by concentrating the solar radiation by means of a collector. The thermal loading can - at least partially - also be done by electrical heating, the required electrical power can be provided by the power generation unit. In particular, the heat device is thus embodied and integrated into the system for storing energy that heat generated by the heat device can be absorbed and offset in time, at least partially, to the discharge unit.

Advantageous is a system in which the heat device has a carbon dioxide storage unit. The carbon dioxide storage unit used is in particular a thermochemical storage system which contains at least one alkaline earth metal carbonate. Upon heating the carbonate compound, particularly during a high energy period, heat is absorbed, an alkaline earth metal oxide is formed, and carbon dioxide gas is released. Thus, during the high-energy period, heat is consumed by releasing carbon dioxide and simultaneously forming an alkaline earth oxide. This thermochemically loads the carbon dioxide storage unit. The carbon dioxide gas can be released into the atmosphere. It is also possible to feed the carbon dioxide gas to another use. The thermochemical carbon dioxide storage unit allows to bind carbon dioxide in a chemical reaction while giving off heat. Accordingly, the release of carbon dioxide is possible under heat absorption. The alkaline earth metal carbonates used are in particular magnesium carbonate, calcium carbonate or strontium carbonate. Upon absorption of heat, magnesium carbonate releases carbon dioxide and forms magnesium oxide. Accordingly, calcium carbonate is formed from calcium carbonate with the release of carbon dioxide and strontium oxide from strontium carbonate with the release of carbon dioxide. Mixtures of said alkaline earth metal carbonates and / or mixtures of said alkaline earth metal carbonates with other solids can also be used. Heat is required for the release of carbon dioxide. This heat can be done, for example, by a separate heating device, in particular using electric current and / or in particular by direct use of radiation energy of the sun. In particular, radiation energy of the sun can be bundled in order to improve the generation of radiant heat, in particular to make it more effective. In particular, the release of carbon dioxide from the at least one alkaline earth carbonate takes place in a solar furnace, which is designed in particular as a shaft furnace, annular furnace or rotary kiln. The solar furnace is most suitably designed so that the effluent, heated carbon dioxide is used to preheat the unreacted alkaline earth carbonate. The implementation of calcium carbonate to calcium oxide takes place at process temperatures between 500 ° C and 1300 ° C, in particular between 800 ° C and 1100 ° C and in particular between 900 ° C and 1000 ° C. The conversion of magnesium carbonate to magnesium oxide takes place at temperatures between 300 ° C and 1000 ° C, in particular between 350 ° C and 900 ° C and in particular between 450 ° C and 850 ° C. The reaction of strontium carbonate to strontium oxide takes place at temperatures between 800 ° C and 1500 ° C, in particular between 1000 ° C and 1300 ° C and in particular between 1200 ° C and 1300 ° C. The alkaline earth metal oxides can be stored indefinitely and lossless, excluding carbon dioxide and water. It is also possible to transport the alkaline earth metal oxides, for example via a pipeline network and / or in closed containers on the road, on tracks and / or by water. To release heat stored in the carbon dioxide storage unit, carbon dioxide is supplied to the alkaline earth oxide. As a result, the alkaline earth carbonate is re-formed under high heat of reaction. This means that a large amount of heat is released. The carbon dioxide storage unit is a heat storage. A designed as a heat storage carbon dioxide storage unit is in Ströhle, Jochen, et al. Chem. Eng. Technol., 2009, 32, no. 3, 435-442 , known.

Particularly advantageous is a system in which the thermochemical carbon dioxide storage unit is connected via a heat pipe directly to the discharge unit. Thereby, the stored in the carbon dioxide storage unit during the high-energy period of heat, which is released during a low-energy period by thermal discharge, be transmitted directly to the discharge unit. The provision and transfer of heat during the low-energy period of the carbon dioxide storage unit to the discharge unit is loss-reduced, in particular lossless, and uncomplicated possible.

A system in which the heat device has a carbon dioxide-based hydrogen storage unit is advantageous. The carbon dioxide-based hydrogen storage unit is directly connected to receive hydrogen, in particular with the hydrogen generation unit. That is, the hydrogen generation unit is connected to both the hydrogen storage device, particularly the charging unit, and the carbon dioxide-based hydrogen storage unit of the heating device. This makes it possible, especially during the high-energy period, to bind hydrogen in the loading unit to the carrier medium and in the carbon dioxide-based hydrogen storage unit to carbon dioxide. Carbon dioxide serves as a carrier medium in the heat device. Hydrogen may be stored in the bound form and made available at a later time, especially during a low energy period.

Particularly advantageous is a system in which the carbon dioxide-based hydrogen storage unit is a carbon dioxide hydrogenation unit. The carbon dioxide hydrogenation unit enables a catalytic reaction of carbon dioxide with the hydrogen from the hydrogen generation unit into a hydrogenated carbon compound, especially methane, formic acid, methanol, ethanol, or hydrocarbon chain compounds of different chain length, such as ethane, propane, butane. A carbon dioxide-based hydrogen storage unit is known, for example, from DE 10 2009 018 126 A1 known. In particular, catalysts are used in the carbon dioxide hydrogenation unit. In particular, such a catalyst has at least one of Ni, Pb, Pt, Cu, Zn, Ru, Fe, Co and Ir. Hydrogenation of carbon dioxide in the carbon dioxide hydrogenation unit for carbon monoxide occurs at process temperatures between 25 ° C and 800 ° C, especially between 150 ° C and 600 ° C. The process pressure of hydrogen is between 0.1 bar and 500 bar, in particular between 10 bar and 50 bar.

Advantageous is a system in which the heat device has a release unit for releasing stored hydrogen. Release is understood to mean in particular a splitting of a hydrogenated carbon compound. During release, carbon dioxide and hydrogen are predominantly formed, especially exclusively. In particular, the release unit is a catalytic reactor to split the stored hydrogen. The released hydrogen can in particular be fed to a hydrogen oxidation unit, in particular a fuel cell, for generating electric current. The released carbon dioxide can be supplied to the carbon dioxide storage unit. Under heat release, carbon dioxide can be reacted with the alkaline earth oxide to form alkaline earth carbonate in the carbon dioxide storage unit. However, release can also mean oxidation of a hydrogenated carbon compound. The release unit is in this case connected to the discharge unit. This makes it possible to provide heat generated in the discharge of the hydrogen in the discharge unit for discharging the carrier medium. In particular, the release unit is a combustion chamber for oxidizing the stored hydrogen.

Advantageous is a system in which the heat device is designed as a circulatory system. In particular, the cycle system comprises a carbon dioxide-based hydrogen storage unit, a release unit, one between the carbon dioxide-based hydrogen storage unit and the release unit. Unit arranged tank for storage and / or storage of the hydrogenated carbon compound produced in the carbon dioxide-based hydrogen storage unit. In particular, the carbon dioxide storage unit is provided between the release unit and the carbon dioxide-based hydrogen storage unit. For storing and providing the hydrogenated carbon compound may also serve a line connection to a gas supply such as biogas. For example, the hydrogenated carbon compound produced in the carbon dioxide-based hydrogen storage unit may be fed into a gas network and removed therefrom as needed. The carbon dioxide source used is in particular an incinerator for the combustion of organic material. It is also possible for coal, gas and / or petroleum to be burned in a combustion power plant to provide carbon dioxide. It is also possible that exhaust gas, in particular, purified exhaust gas of a biogas combustion plant, serves as a carbon dioxide source. As a carbon dioxide storage unit may serve a container in which carbon dioxide is stored in gaseous, liquid, supercritical or solid form.

Particularly advantageous is a system with a hydrogen oxidation unit for generating electrical power. The electric current is made possible in particular by the oxidation of hydrogen with oxygen to form water. With the hydrogen oxidation unit, electric power can be directly generated, especially when the hydrogen oxidation unit is a PEM fuel cell. In the PEM fuel cell electric current is obtained in a temperature range between -20 ° C and 250 ° C, in particular between 20 ° C and 180 ° C of hydrogen and oxygen. Alternatively, a SOFC (Solid Oxide Fuel Cell) fuel cell may also be used as the hydrogen oxidation unit. In the SOFC fuel cell, the generation of electric current at a temperature between 200 ° C and 1200 ° C, in particular between 400 ° C and 900 ° C of hydrogen and oxygen. The hydrogen oxidation unit may also serve for the indirect generation of electrical current, for example when the hydrogen oxidation unit is a combustion chamber. Hot combustion gases of the combustion chamber may be used to drive a turbine to generate electrical energy.

Advantageous is a system in which the unloading unit for conveying unloaded carrier medium is connected to the loading unit such that unloaded carrier medium discharged from the unloading unit can be conveyed to the loading unit for loading with hydrogen. In particular, the hydrogen storage device has a closed loop system for the carrier medium. In particular, a carrier medium buffering unit for storing the discharged carrier medium may be provided between the unloading unit and the loading unit. In particular, a carrier medium storage unit for storing the loaded carrier medium may be provided between the loading unit and the unloading unit. The stored loaded carrier medium is an energy store. If necessary, the loaded carrier medium can be released. The bound hydrogen is released and converted into a hydrogen oxidation unit. This results in an improved buffering effect of the hydrogen storage device. Advantageous is a system in which the carrier medium storage unit is integrated into the loading unit. This is especially the case when the carrier medium is present as a solid. Alternatively, the carrier medium storage unit may have a separate, in particular external, tank, which in particular has at least one tank line for connection to an external line system. This is particularly advantageous if the carrier medium is present as a liquid. This makes it possible to store the carrier medium largely unpressurized. For example, a container, as it is known for storing liquid hydrocarbons such as fuels and / or fuel oil can be used. It is also conceivable that the carrier medium can be dispensed into a dedicated line system or transport system and provided for unloading at another location. In the discharge unit, at least partial heat of the heat device is used to release hydrogen. The released hydrogen is released to the hydrogen oxidation unit to generate electric power. If the carrier medium is a solid, the discharge unit is designed so that hydrogen can be released and released from a material made of specific metal alloys. If it is a sorptive carrier medium, the unloading unit allows the desorption of hydrogen from a porous solid to release hydrogen. When an LOHC support medium is used, the hydrogen is released by a catalyzed dehydrogenation reaction from an organic molecule or from a mixture of organic molecules. This means that the release of the hydrogen takes place by a material conversion of the loaded carrier medium by means of discharge in the discharge unit by means of a catalysed dehydrogenation reaction. In the loaded state, the carrier medium is in particular a saturated, polycyclic compound, in particular a perhydro-dibenzyltoluene or a perhydrobenzyltoluene, which can be used as pure substances, isomeric mixtures or mixtures with one another. Alternatively, the loaded carrier medium is a saturated polycyclic compound containing heteroatoms such as nitrogen or oxygen, especially perhydro-N-ethylcarbazole, perhydro-N-propylcarbazole, perhydro-N-isopropylcarbazole, perhydro-N-butylcarbazole, or mixtures of these substances. Alternatively, as loaded Supported medium may also be used a saturated organic oligomer or polymer, which can be converted by catalytic dehydrogenation in oligomers or polymers with extended π-conjugated electron system. The unloading of the loaded carrier media in the discharge unit takes place in particular in a pressure-stable chemical reactor at a process temperature between 100 ° C and 450 ° C, preferably between 150 ° C and 420 ° C and in particular between 180 ° C and 390 ° C. The process pressure is between 0.1 and 30 bar, in particular between 1 and 10 bar, wherein in particular a metal-containing catalyst can be used which contains in particular platinum and / or palladium. Importantly, the catalyst is capable of releasing hydrogen released from the LOHC carrier as hydrogen gas. In addition to platinum and / or palladium, in particular metals such as chromium, iron, cobalt, nickel, copper, iridium or ruthenium are suitable. The discharged, liquid carrier medium can be discharged from the discharge unit in particular into a carrier medium intermediate unit, which can be arranged in particular externally to the system. The buffered, discharged carrier medium can be used in particular at a later time for a renewed loading by hydrogen, ie for hydrogen storage in the system, in particular in the hydrogen storage device. Furthermore, a carrier medium storage unit may be provided for storing the loaded carrier medium. If a metal hydride storage medium is used as the carrier medium, the installation space required for the provision of the loading unit, carrier medium storage unit and discharge unit is integrated. In particular, the three units mentioned are structurally combined in one component. The loading in the loading unit with the solid carrier medium takes place opposite the discharge in the unloading unit at reduced temperature but higher pressure.

Advantageous is a system in which the hydrogen is bound to the carrier medium in the loading unit. In particular, hydrogen is chemically bound to the carrier medium. For example, chemical bonding of the hydrogen may be accomplished by the carrier medium present in the loading unit being a metal hydride reservoir containing a metal alloy-derived material that absorbs and chemically binds hydrogen. Alternatively, the carrier medium may also be a liquid organic hydride. In this case, the chemical bonding of the hydrogen in the loading unit takes place by means of a catalytic hydrogenation reaction to an organic molecule or to a mixture of organic molecules. Such organic hydrides, which are referred to in the English literature as liquid organic hydrogen carrier (LOHC) are from the EP 1 475 349 A2 known. This form of hydrogen storage has the particular advantage that LOHC carrier media are in liquid form under the process conditions used. The physico-chemical properties of LOHC carrier media are highly similar to conventional liquid fuels, allowing pumps to be used for transport and storage for fuel and fuel logistics storage. Hydrogen storage in chemically bound form in an organic liquid allows pressureless storage under normal conditions for long periods of time without significant hydrogen loss. As LOHC carrier media in particular polycyclic aromatic compounds with a π-electron system or multiple π-electron systems, which are converted in the loading unit of the hydrogen storage device by hydrogenation in the respective saturated, polycyclic compounds. In particular, dibenzyltoluenes and benzyltoluenes as pure substances, isomeric mixtures or mixtures of these substances with one another can be used as LOHC carrier media. It is also possible to use as LOHC carrier media polycyclic, heteroaromatic compounds having a π-electron system or multiple π-electron systems, which are converted in the loading unit by hydrogenation into the respective saturated, polycyclic compounds containing heteroatoms such as nitrogen or oxygen contain. In particular, N-ethylcarbazole, N-propylcarbazole, N-isopropylcarbazole, N-butylcarbazole or mixtures of these substances with one another serve as LOHC carrier media. As LOHC carrier media are organic oligomers or polymers with extended π-conjugated electron systems, which are converted in the loading unit by hydrogenation in the respective saturated compounds possible. When using liquid organic hydrides, the at least partial hydrogenation of the discharged LOHC carrier medium takes place in a pressure-stable chemical reactor as a loading unit at a temperature between 50 ° C and 400 ° C, in particular between 120 ° C and 300 ° C, in particular between 150 ° C and 280 ° C. The hydrogenation, ie the loading, takes place at a process pressure of from 2 bar to 200 bar, in particular at from 10 bar to 100 bar, and in particular in the presence of a metal-containing catalyst. Suitable catalysts for the loading of the LOHC carrier medium are in particular those which comprise the element ruthenium and / or nickel. Catalysts are also possible which have other elements or additional elements in addition to ruthenium and / or nickel. Essential are those elements that can attach hydrogen and transferred to LOHC carrier medium. In addition to ruthenium and / or nickel, in particular metals such as chromium, iron, cobalt, copper, iridium, palladium or platinum are possible as catalysts.

Advantageous is a system with a control unit, which is at least with the heat device and the discharge unit in bidirectional signal connection. This makes it possible to detect with the control unit the respective state of the heat device and the discharge unit. This means that it is possible via the control unit to detect how much heat is available in the heat device. At the same time it can be determined if there is a heat demand in the discharge unit. The control unit can directly control the supply of heat from the heat device to the discharge unit to facilitate a discharge operation in the discharge unit.

In order to monitor the overall process and / or the overall energy storage system, the control unit can be integrated with other components of the installation, in particular the carbon dioxide storage unit, the power generation unit, the hydrogen generation unit, the loading unit, the carrier storage unit, the release unit. Unit, be connected to the carbon dioxide-based hydrogen storage unit and / or hydrogen oxidation unit.

The inventive method for storing energy is characterized in particular by the fact that heat is provided by means of the heat device in the discharge unit, the heat required for the discharge of a hydrogen storage unit and the release of hydrogen from this hydrogen storage unit is. The method further comprises the steps of: generating hydrogen by means of a hydrogen generation unit, loading a carrier medium with the hydrogen generated in the hydrogen generation unit by means of a loading unit, storing the loaded carrier medium by means of a carrier medium storage unit, generating and storing heat by means a heat device and discharging the hydrogen from the loaded carrier medium by means of a discharge unit. In particular, the discharged hydrogen is supplied to a hydrogen oxidation unit for generating electric power. Alternatively, the hydrogen can be compressed and transferred to a hydrogen pressure tank, used at a later time and / or transported in this storage form to another location. In this bound form, the hydrogen stored on the loaded carrier medium may be provided, for example, at a hydrogen filling station. For this purpose, the hydrogen is released from the loaded carrier medium with the supply of heat and provided to the confusion.

Advantageous is a method in which the generation and storage of heat during a high-energy period, wherein the storage of the heat by thermal loading of a heat storage, which is designed as a carbon dioxide storage unit is carried out. Additionally or alternatively, a thermal discharge, that is, a discharge of the stored heat from the carbon dioxide storage unit, take place during a low-energy period. By providing heat during the low energy period, hydrogen may be released from the loaded carrier medium in the discharge unit during the low energy period and utilized for power generation.

Advantageous is a method in which heat is absorbed and stored by emptying a carbon dioxide storage unit, in particular by forming a metal oxide from a metal carbonate.

Further advantageous is a method in which heat is released and discharged by filling the carbon dioxide storage unit, in particular by forming a metal carbonate from a metal oxide.

Advantageous is a method that allows a regulation of the heat input from the heat device to the discharge unit due to a current thermal loading state of the heat device and / or a current discharge state in the discharge unit.

Further advantageous embodiments, additional features and details of the invention will become apparent from the following description of an embodiment with reference to the drawing. Show it:

1 a schematic representation of the system according to the invention for storing energy.

In the 1 shown schematically and as a whole with 1 The designated energy storage system includes a power generation unit 2 in the form of a photovoltaic system. The power generation unit 2 is suitable to energy from regenerative energy sources 3 is provided to use for generating electric power. The energy sources 3 represent regenerative, in particular unsteady forms of energy. As a power generation unit 2 In addition to the above-mentioned photovoltaic unit, in particular a wind power plant and / or a hydroelectric power plant into consideration. Alternatively, during a high-energy period of time, electrical energy may be obtained from an electrical network at a comparatively low cost instead of or in addition to the regenerative energy sources 3 be used to power the plant 1 save.

The direct energy effect of the regenerative energy source 3 on the power generation unit 2 and a heat device 4 is through the arrows 5 symbolically represented. The heat device 4 is designed as a circulatory system. The cycle system comprises a carbon dioxide based hydrogen storage unit 6 over a line 7 with a tank 8th for a hydrogenated carbon compound. The Tank 8th is over a line 9 with a release unit 10 connected to release the stored hydrogen. The release unit 10 is over a line 11 with a carbon dioxide storage unit 12 connected. The carbon dioxide storage unit 12 is over a line 13 with the hydrogen storage unit 6 connected. The release unit 10 has a heat pipe 14 on. About the heat pipe 14 can heat out the release unit 10 be dissipated. To the release unit 10 is alternatively a hydrogen line 15 connected to hydrogen from the release unit 10 dissipate. As will be explained later, in alternative embodiments, for the release unit 10 either the heat pipe 14 or the hydrogen pipe 15 intended. For the sake of completeness, in 1 both lines 14 . 15 shown.

The carbon dioxide storage unit 12 is designed so that a heat input that is required to release carbon dioxide, direct sunlight 5 and / or electric power is possible. This is the power generation unit 2 via an electrical line 16 with the carbon dioxide storage unit 12 connected.

Another power line 16 is between the power generation unit 2 and a hydrogen generation unit 17 intended. The hydrogen generation unit 17 is designed as an electrolyzer. The electrolyzer 17 is over a pipeline 18 with a water storage 19 connected. The water storage 19 may represent a storage tank or a connection to a public water supply. About the pipeline 18 can water from the water storage 19 the hydrogen production unit 17 be supplied. Hydrogen, which is gaseous as H ₂ in the hydrogen generation unit 17 can be generated via a first pipeline 20 a loading unit 21 a hydrogen storage device 22 be supplied. Via a second pipeline 39 may be hydrogen from the hydrogen generation unit 17 into the hydrogen storage unit 6 be encouraged. This means that the carbon dioxide-based hydrogen storage unit 6 for receiving hydrogen via the pipeline 39 with the hydrogen generation unit 17 directly connected. Furthermore, to the hydrogen generation unit 17 a pipeline 23 connected for connection to an oxygen consumer 24 , The oxygen consumer 24 can also be omitted. It is also possible that the oxygen consumer 24 is connected via a pipeline with an oxygen storage for storing the oxygen generated in the hydrogen generation unit. Such an oxygen storage may be the oxygen consumer 24 also replace. At the oxygen consumer 19 another pipe may be connected to oxygen from the oxygen consumer 24 dissipate.

The hydrogen storage device 22 is used to store hydrogen and includes the loading unit 21 for loading a carrier medium with the hydrogen present in the hydrogen production unit 17 has been generated. The carrier medium used according to the embodiment shown is a liquid carrier medium comprising the system dibenzyltoluene / perhydro-dibenzyltoluene, as disclosed by Brückner et al., ChemSusChem, 2013, DOI: 10.1002 / cssc.201300426. The hydrogen storage device 22 further comprises a carrier medium storage unit 25 for storing in the loading unit 21 loaded carrier medium. The hydrogen storage device 22 further includes a discharge unit 26 for discharging the hydrogen from the loaded carrier medium and a carrier medium storage unit 27 for storing the unloaded carrier medium. It is also possible to use the carrier media storage unit 25 and the carrier medium storage unit 27 as a single carrier medium storage unit. This means that, in particular, only a single tank is used whose hydrogen content is variable during a process. Thus loaded, unloaded and partially discharged carrier medium is present as a mixture in this single carrier medium storage unit. The loading unit 21 , the carrier media storage unit 25 , the discharge unit 26 and the carrier medium storage unit 27 are each about piping 28 connected with each other. These may be pipelines 28 act as they are known to promote diesel fuel or heating oil. Through the pipes 28 can the carrier medium along a cycle direction 29 in the hydrogen storage device 22 circulate. Together with the carrier medium, the hydrogen in the pipelines 28 circulate.

The discharge unit 26 is about the heat conduction 14 with the release unit 10 the heat device 4 connected. Through the heat pipe 14 can heat from the release unit 10 the heat device 4 directly to the discharge unit 26 be supplied. Heat is generated in the release unit 10 if this is designed as a combustion unit, for example for methane. When burning Methane does not produce hydrogen. This means that in this case the hydrogen line 15 for removal to the hydrogen from the release unit 10 is not required. Unless the release unit 10 is designed as a catalytic reactor, hydrogen is via the hydrogen line 15 dissipated and carbon dioxide over the line 11 the carbon dioxide storage unit 12 fed. Alternatively, carbon dioxide can also be completely or partially released into the ambient air. In the catalytic cleavage in the release unit 10 no heat is generated. In this case, the heat pipe 14 not required or not used.

The discharge unit 26 is over another heat pipe 30 with the carbon dioxide storage unit 12 the heat device 4 directly connected. Through the heat pipe 30 can heat from the carbon dioxide storage unit 12 the heat device 4 directly to the discharge unit 26 be supplied. The discharge unit 26 is over a pipeline 31 with a hydrogen oxidation unit 32 connected. The pipeline 31 serves to transport hydrogen from the unloading unit 26 to the hydrogen oxidation unit 32 , The hydrogen is in the discharge unit 26 taken from the carrier medium. Furthermore, via the hydrogen line 15 the release unit 10 the heat device 4 directly with the hydrogen oxidation unit 32 connected. The one in the release unit 10 liberated hydrogen can be the hydrogen oxidation unit 32 be fed directly.

According to the embodiment shown, the hydrogen oxidation unit is 32 designed as a PEM fuel cell. The hydrogen oxidation unit 32 is with an oxygen source 33 and / or connected to an air source. The oxygen source 33 can via a pipeline with the oxygen consumer 24 be connected. This makes it possible for oxygen to be generated during hydrogen production in the hydrogen production unit 17 obtained directly from the hydrogen oxidation unit 32 is returned. In this case, the oxygen consumer can 24 and the oxygen source 33 be designed as a common, integrated oxygen storage.

The hydrogen oxidation unit 32 is over a power line 36 to a power grid 37 connected. Instead of the power grid 37 may also be provided a single power consumer. The power grid 37 serves to supply multiple, in particular a plurality of up to 1000 or 10000 or more individual power consumers, especially private households or commercial enterprises. The power grid may thus be, for example, a local power grid that serves to power a commercial area with one or more industrial companies and / or one or more private households. The power grid 37 can also be part of the public electricity grid. This makes it possible for electrical current to flow in the hydrogen oxidation unit 32 has been generated, over the power line 36 and the power grid 37 is fed.

The attachment 1 furthermore comprises a, in particular central, control unit 38 for the controlled operation of the plant 1 , The control unit 38 is in particular with the heat device 4 , in particular with the carbon dioxide storage unit 12 , and with the discharge unit 26 each in bidirectional signal connection. This makes it possible for the control unit 38 the thermal loading state of the heating device 4 on the one hand and the current process parameters in the unloading unit 26 on the other hand. The control unit 38 ensures that, for example, when a discharge is to take place, heat from the carbon dioxide storage unit 12 the heat device 4 over the heat conduction 30 the discharge unit 26 provided. In the event that there is a heat requirement for discharge and a thermal load condition in the heat device 4 should not be sufficient, can be through the regulatory unit 38 Also, an additional thermal loading may be initiated by, for example, the power generation unit 2 over the power line 16 electric current for electrically heating the heat device 4 provides. This is the control unit 38 in bidirectional signal connection with the power generation unit 2 , In the event that the release unit is designed as a combustion unit for combustion of methane, via the heat pipe 14 the discharge unit 26 heat generated during the combustion of methane in addition to the heat resulting from the carbon dioxide storage unit 12 provided. The control unit 38 is in particular with the release unit 10 and / or the carbon dioxide hydrogenation unit 6 the heat device 4 , with the power generation unit 2 and / or with the electrolyzer 17 in bidirectional signal connection.

Subsequently, the inventive method for storing energy based on the operation of the system 1 explained in more detail. The sun as a regenerative energy source 3 emits sunbeams as energy 5 by means of a photovoltaic system as a power generation unit 2 be used for power generation. In parallel, the solar radiation, ie the radiant heat of the sun is used to in the heat device 4 especially in the carbon dioxide storage unit 12 one adequate large amount of calcium carbonate (CaCO ₃ ) to burn calcium oxide (CaO) and carbon dioxide (CO ₂ ). The carbon dioxide formed on burning the calcium carbonate becomes the hydrogen storage unit 6 with hydrogen from the electrolyzer 17 converted to methane (CH ₄ ).

This means that during a high-energy period, solar radiant energy can be used to convert 6 moles of CaCO ₃ into 6 moles of CaO releasing 6 moles of CO ₂ . Energy is used in the form of heat in the amount of 297 Wh. Furthermore, the electrolyzer 17 10 kWh of electrical energy supplied. This amount of energy is in the electrolyzer 17 used with an efficiency of 70% for hydrogen production. The generated 7 kWh hydrogen correspond to a molar amount of 106 mol H ₂ . Of these, 82.2 moles of H _{2 are} in the loading unit 21 of the hydrogen storage device 22 used for the hydrogenation of 9.1 mol of dibenzyltoluene to 9.1 mol of perhydro-dibenzyltoluene. In this case, a heat quantity of 1.6 kWh is released. The remaining 23.8 moles of hydrogen are converted to 6 moles of methane in a sabatizing process with the 6 moles of carbon dioxide liberated to calcium oxide on firing the calcium carbonate. It releases 275 Wh of heat. The resulting high-energy products, ie 9.1 moles of perhydro-dibenzyltoluene, 6 moles of CaO and 6 moles of methane, are stored in tanks or silos. The methane can alternatively be fed into a public pipeline network.

For the release of the stored hydrogen during a low-energy period, 6 moles of methane are burned with oxygen to form carbon dioxide and water. Methane combustion does not produce hydrogen. This releases 1.34 kWh of heat. With the help of the liberated carbon dioxide 6 moles of CaO are reacted with the release of 297 Wh to 6 moles of CaCO ₃ . The total amount of heat available is 1.6 kWh. This amount of heat is the discharge unit 26 , which is designed as a LOHC hydrogen release unit supplied. There are released from the 9.1 moles of perhydro-dibenzyltoluene 81.2 moles of hydrogen. This is used in a fuel cell with an efficiency of 55% to generate 2.95 kWh of electricity. The current-to-current efficiency is 29.5%. Compared with an arrangement known from the prior art, the current-to-current efficiency improves by 11%.

Instead of methane as a reaction product in the hydrogen storage unit 6 For example, the carbon dioxide formed on burning the calcium carbonate can be converted to methanol. As a result, the current-to-current efficiency can be increased to 38.5%.

Alternatively, it is also possible to react the carbon dioxide with hydrogen to formic acid. The current-to-current efficiency is then 38.5%.

The conversion of the carbon dioxide to methanol or formic acid means that no heat is released in a later release of carbon dioxide, which is carried out by catalytic cracking and not by combustion. In the two cases mentioned, the charge for the discharge of hydrogen in the discharge unit 26 required heat exclusively, so completely, on the metal carbonate formation in the carbon dioxide storage unit 12 made available.

Table 1 summarizes the efficiency as well as the masses of LOHC carrier medium, CaO and the carbon carrier used, which are required for a storage of 10 kWh of electricity. Table 1: methane methanol formic acid efficiency 29.5% 38.5% 38.5% Mass LOHC 2.6 kg 1.3 kg 2.3 kg Mass CaO 336 g 1.2 kg 1.9 kg Mass C carrier 96 g 0.7 kg 1.6 kg

The release of heat by contacting the Erdalkalimetalloxids with carbon dioxide by introducing carbon dioxide into a bed of alkaline earth metal oxide, the latter may be present as a fixed bed, in particular in the form of a fluidized bed, a fluidized bed or a flow stream. The carbon dioxide used in this step is at least partially derived from the release unit 10 , Calcium carbonate / calcium oxide and magnesium carbonate / magnesium oxide are particularly preferred in the carbon dioxide storage unit 12 used. These are low-cost materials that are available in almost unlimited quantities Are available. The substances are toxicologically and ecotoxicologically harmless. Even an accident of the solar furnace, the storage system or a possibly used transport system for the storage and transport of the alkaline earth carbonate and / or alkaline earth oxide compounds does not constitute a danger to the environment.

According to an embodiment, not shown, the hydrogenated carbon compound is not localized, in particular spatially removed from the hydrogen storage device 22 generated. This means that in particular the carbon dioxide-based hydrogen storage unit 6 removed to the hydrogen storage device 22 is arranged and the hydrogenated carbon compound by means of a supply line or other suitable transport logistics such as by ship transport, rail transport or trucks to the tank 8th is transported. It is particularly advantageous in terms of carbon dioxide balance, if the outside of the plant 1 the tank 8th supplied hydrogenated carbon compound has been formed using regenerative energy and / or using renewable resources, such as methane from a biogas plant and / or from a power-to-gas plant, formic acid from biomass, formic acid and / or methanol by carbon dioxide Hydrogenation or carbon monoxide hydrogenation with regenerative hydrogen from solar and / or wind power plants or biodiesel.

The release unit 10 allows that from the tank 8th supplied hydrogenated carbon compound by cleavage in carbon dioxide and hydrogen or by oxidation in carbon dioxide and water to convert. In both variants, the carbon dioxide formed is the carbon dioxide storage unit 12 fed. It is also possible to deliver the formed carbon dioxide - at least partially - directly to the environment. According to the embodiment shown, the release unit 10 a unit for the oxidation of the hydrogenated carbon compound, in particular a combustion chamber for burning methane. In particular, in the combustion chamber, the heat of combustion formed in the oxidation of the hydrogenated carbon compound is at least partially utilized to release hydrogen in the discharge unit 26 to drive or assist. In this case, all hydrogenated carbon compounds, in particular methane, formic acid, methanol, ethanol or hydrocarbon compounds of different chain lengths and mixtures of these substances with one another or mixtures of said substances with other hydrogenated carbon compounds are suitable.

It is alternatively possible, the release unit 10 as a unit for splitting the hydrogenated carbon compounds, in particular as a catalytic reactor. In the catalytic reactor, the hydrogenated carbon compound is contacted with a metal-containing catalyst. In this case, hydrogen and carbon dioxide is generated by cleavage of the carbon compound. Due to the release of hydrogen in the catalytic cracking of the carbon compound is the execution of the release unit 10 particularly advantageous as a catalytic reactor. Heat is consumed in catalytic cracking. The heat required for this purpose, for example, directly from the designed as a heat storage carbon dioxide storage unit 12 to provide. This can be an extra heat pipe 40 directly between the carbon dioxide storage unit 12 and the release unit 10 as a heat pipe next to the pipe 11 be provided. The hydrogen thus formed becomes the hydrogen oxidation unit 32 fed. As a catalyst for cleaving the hydrogenated carbon compound, elements such as palladium, platinum, nickel, iron, ruthenium, iridium, cobalt, copper or zinc are suitable. The catalytic cleavage takes place at temperatures of 25 ° C to 1000 ° C, in particular between 40 ° C and 300 ° C. Preferred feedstocks for the cleavage of the hydrogenated carbon compound in the release unit 10 are methanol and / or formic acid.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102009018126 A1 [0008]
• EP 1475349 A2 [0013]

Cited non-patent literature

• Ströhle, Jochen, et al. Chem. Eng. Technol., 2009, 32, no. 3, 435-442 [0005]

Claims (15)

Plant for storing energy comprising a. a hydrogen generation unit ( 17 ) for generating hydrogen, b. a hydrogen storage device ( 22 ) for storing hydrogen comprising i. a loading unit ( 21 ) for loading a carrier medium with that in the hydrogen generation unit ( 17 ) generated hydrogen and ii. a discharge unit ( 26 ) for discharging the hydrogen from the loaded carrier medium, and c. a heat device ( 4 ) for generating and storing heat, wherein the heat device ( 4 ) with the unloading unit ( 26 ) is connected to provide heat. Plant according to claim 1, characterized in that the heat device ( 4 ) a thermochemical carbon dioxide storage unit ( 12 ), wherein the thermochemical carbon dioxide storage unit ( 12 ) contains at least one alkaline earth metal carbonate, in particular magnesium carbonate, calcium carbonate and / or strontium carbonate. Plant according to claim 2, characterized in that the carbon dioxide storage unit ( 12 ) for the delivery of heat with the discharge unit ( 26 ) by means of a heat conduction ( 30 ) is directly connected. Plant according to one of the preceding claims, characterized in that the heat device ( 4 ) a carbon dioxide-based hydrogen storage unit ( 6 ) for receiving hydrogen, in particular with the hydrogen generation unit ( 17 ) is directly connected. Plant according to claim 4, characterized in that the carbon dioxide-based hydrogen storage unit comprises a carbon dioxide hydrogenation unit ( 6 ). Plant according to one of the preceding claims, characterized in that the heat device ( 4 ) a release unit ( 10 ) for releasing stored hydrogen, wherein the release unit ( 10 ) for providing the carbon dioxide resulting from the liberation of the hydrogen with the carbon dioxide storage unit ( 12 ), the release unit ( 10 ) is designed in particular as a catalytic reactor. Plant according to one of the preceding claims, characterized in that the heat device ( 4 ) is designed as a circulatory system, in particular the carbon dioxide storage unit ( 12 ), the carbon dioxide hydrogenation unit ( 6 ), the release unit ( 10 ) and a tank ( 8th ) for a hydrogenated carbon compound as components of the cycle system, wherein the components ( 6 . 8th . 10 . 12 ) of the circulatory system via lines ( 7 . 9 . 11 . 13 ) are interconnected. Plant according to one of the preceding claims, characterized by a hydrogen oxidation unit ( 32 ) for generating electric power, wherein the hydrogen oxidation unit ( 32 ) in particular for feeding the electric current with a power grid ( 37 ) connected is. Installation according to one of the preceding claims, characterized in that the unloading unit ( 26 ) for conveying unloaded carrier medium with the loading unit ( 21 ), in particular a carrier medium buffer unit ( 27 ) for storing the discharged carrier medium between the unloading unit ( 26 ) and the loading unit ( 21 ) and in particular a carrier medium storage unit ( 25 ) for storing the loaded carrier medium between the loading unit ( 21 ) and the unloading unit ( 26 ), and in particular the carrier medium storage unit ( 25 ) has a tank and in particular at least one tank line for connection to an external line system. Installation according to one of the preceding claims, characterized in that in the loading unit ( 21 ) the hydrogen is bound to the carrier medium, in particular chemically. Installation according to one of the preceding claims, characterized by a control unit ( 38 ), with the heat device ( 4 ), in particular with the carbon dioxide storage unit ( 12 ), with a hydrogen storage unit ( 6 ) and with a release unit ( 10 ), with the unloading unit ( 26 ), with a power generating unit ( 2 ) and / or with a hydrogen generation unit ( 17 ) is in bidirectional signal connection. Method for energy storage comprising the method steps - generating hydrogen by means of a hydrogen generation unit ( 17 ), - Loading a carrier medium with the in the hydrogen production unit ( 17 ) generated by means of a loading unit ( 21 ), - storing the loaded carrier medium by means of a carrier medium storage unit ( 25 ), - generating and storing heat by means of a heat device ( 4 ), - discharging the hydrogen from the loaded carrier medium by means of a discharge unit ( 26 ), - providing heat by means of the heat device ( 4 ) in the unloading unit ( 26 ), wherein the heat for the discharge of the hydrogen in the discharge unit ( 26 ) is required. A method according to claim 12, characterized in that the generation and storage of heat during a high-energy period, wherein heat by emptying a carbon dioxide storage unit ( 12 ), in particular by forming a metal oxide from a metal carbonate, is recorded and stored. A method according to claim 12 or 13, characterized in that during a low energy period heat by filling a carbon dioxide storage unit ( 12 ), in particular by forming a metal carbonate from a metal oxide, released and discharged. Method according to one of claims 12 to 14, characterized by a controlled implementation of the method by means of a control unit ( 38 ) such that the heat required for discharging the hydrogen is provided in an automated and demand-adapted manner.

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