Energy system

Abstract

The invention relates to an energy system, comprising a functional unit having at least one electrolysis cell (EC) and an additional functional unit having at least one fuel cell (FC) made of solid oxide, wherein the two functional units (EC) and (FC) are combined in one device, waste heat of the (FC) is used to extract the hydrogen from a (LOHC), and the (EC) and (FC) as a whole are equipped with a water reservoir and an oxygen reservoir in such a way that water and steam from the (FC) are temporarily stored in an insulated container and made available to the electrolysis cell operation and in such a way that the oxygen from the (EC) is temporarily stored and supplied to the fuel cell operation while being mixed with or without air.

Description

[0001] Energy system

[0002] Description

[0003] The invention relates to an energy system, in particular for supplying municipal facilities.

[0004] State of the art

[0005] The increasing proportion of electrical energy from wind or solar power increases the need for intermediate energy storage. The availability of renewable energies depends on meteorological influences and, in particular, cannot be influenced or predicted. The generation of electrical power from renewable energies is inconsistent. Hydrogen is a suitable storage option. When the supply of inexpensive and / or renewable electrical energy exceeds demand, it can be produced through electrolysis in an electrolysis cell. When the supply of inexpensive and / or renewable electrical energy falls below demand, it can be used to generate electricity. The hydrogen reacts electrochemically with an oxidizing agent, usually oxygen, in a fuel cell. This hydrogen can be used in the implementation of the energy transition, including in the private sector.The transport of hydrogen, for example, in gas pipelines, is fraught with problems. While gas pipelines should generally be suitable for this type of hydrogen transport, the energy density of the hydrogen that could be pumped through these pipes is approximately one-third to one-quarter that of natural gas. Faster flow or higher pressure are only possible to a limited extent. Furthermore, the booster stations consume energy. Proximity hydrogen production for a sustainable energy supply is desirable and could potentially be produced more cost-effectively than imported hydrogen.

[0006] It is known that a combination of a solar cell, which generates an electric current, and an electrolysis cell, in which water is split into hydrogen and oxygen using this electric current, can produce hydrogen and oxygen, which can then be stored and converted back into electrical energy in a fuel cell when needed. This mixture of hydrogen and oxygen—known as oxyhydrogen—is highly explosive. Handling this mixture requires stringent safety requirements. Furthermore, the technical complexity is considerable.

[0007] It is also known that biological structures can produce hydrogen directly from water using solar energy. The use of biological systems to generate hydrogen from water using sunlight for industrial hydrogen production is complicated by the fact that the hydrogen does not escape as hydrogen gas, but rather is bound to certain organic structures and must first be released. A further disadvantage is that these organic structures are not sufficiently stable.

[0008] DE 196 36 738 A1 discloses a combination system in which a fuel cell battery is combined with a heat engine. SOFC fuel cells, with operating temperatures between 700°C and 1,000°C, are particularly used as high-temperature fuel cells. In the SOFC fuel cell, the chemical reaction of a fuel gas, such as hydrogen or a CO / water vapor mixture, with an oxidizing gas (air) is split by a solid electrolyte into two partial electrochemical reactions in the electrodes located on either side of the electrolyte. Depending on the chemical potential difference, a cell voltage of approximately 1 V is established between the electrodes. By serially and partially interconnecting the relatively small individual cells via metallic connecting elements, technically usable power outputs are achieved.The waste heat from the SOFC fuel cell is used by conduction and / or radiation to heat a heat engine, such as a Stirling engine. The heat engine's working fluid is passed through the SOFC fuel cell in a closed system for heating.

[0009] DE 10 2004 038 435 A1 discloses a method and a device for converting chemical energy into electrical energy using a high-temperature fuel cell and a downstream combined cycle power plant. In this method, the fuel gas slip from the fuel cell and the process steam from the fuel cell accompanying the fuel gas slip are converted into kinetic energy in a gas turbine. Steam compression in the gas turbine and the condensation of the evaporation in a condenser increase the turbine's efficiency. The exhaust gas flow leaving the gas turbine feeds thermal energy into a steam circuit, which additionally absorbs thermal energy from the fuel cell's cooling circuit to reheat the steam, thereby utilizing all of the fuel cell's thermal energy for electricity generation.

[0010] DE 10 2008 036 368 A1 discloses a device for generating and storing hydrogen, the device comprising a container containing water of a predeterminable layer thickness and provided with at least one translucent wall, a catalyst in operative connection with water, and a light source, wherein a collecting space provided above the water surface for hydrogen-containing gas formed in situ on the catalyst surface is in operative connection with at least one gas storage device.

[0011] The waste heat from a solid oxide fuel cell (SOFC) with relatively high waste heat temperatures of up to 1000°C can be used to extract hydrogen from the hydrogen storage medium (LOHC) and then generate electricity. SOFC fuel cells can also function as electrolysis cells, which can operate well for longer periods because the partial pressure of oxygen then decreases. Hydrogen systems are available on the market for self-sufficient power supply; they can be installed as photovoltaic systems on a building roof. Excess electricity is converted into hydrogen using an electrolysis system and then stored in pressure cylinders. If the electricity from the photovoltaic systems is insufficient, hydrogen is passed through a fuel cell and converted into electricity. At the same time, for safety reasons, the storage system, which comprises a large number of pressure cylinders, must be stored outdoors.

[0012] A disadvantage of the known energy systems is that local energy supply, especially through photovoltaics, is difficult to store.

[0013] The object of the invention is therefore to provide an energy system that makes it possible to supply municipal structures with both electricity and heat.

[0014] Disclosure of the invention

[0015] The invention is disclosed by the features of the main claim. Embodiments and further developments are the subject of the further claims following the main claim.

[0016] An energy system is disclosed comprising a device in the form of an energy supply unit that can supply municipal structures with both electricity and heat. This is achieved using a dual-function fuel electrolysis cell with day-night or summer-winter operation.

[0017] The energy system comprises an energy storage system configured as a hydrogen storage device for storing hydrogen, and a heat device for generating, converting, and storing heat. The hydrogen storage device enables the storage of hydrogen generated in a hydrogen generation unit. In particular, the hydrogen generation unit is configured as an electrolyzer. The electrolyzer enables the decomposition of water into hydrogen and oxygen.

[0018] The design of the fuel electrolysis cell exhibits the aforementioned dual function, whereby day-night or summer-winter operation can occur. If oxygen is fed into a fuel cell instead of air, higher efficiency or a higher energy yield is made possible. This suggests storing the oxygen from the electrolysis operation in summer or day operation for winter or night operation. Therefore, a container is placed between the two cell functions to temporarily store the oxygen until it is needed on the other side. It is important that the oxygen for the fuel cell system, i.e. FC operation, is mixed with a lot, little, or no air - i.e. rarely or possibly never. This depends on the oxygen availability. In the case of a long electrolysis or EC period, the oxygen production would require a very large container that is also under pressure.For economic reasons, a limit makes sense here, but not for specific applications. Oxygen should not be added to the FC in its pure form, as the resulting increase in energy density would lead to increased heating.

[0019] Electrolysis cells require ultrapure water, so a conventional electrolysis cell is equipped with a water purification and evaporation unit. The water vapor generated by the fuel cell operation is temporarily stored in a closed container and thus pre-purified before being fed into the electrolysis process. If the time between the two phases is short, the container can be insulated from water and the water vapor temporarily stored. The calorific value of hydrogen is 33.3 kWh / kg, and the heating value is 39.6 kWh / kg, if pure water vapor were added. This would result in energy savings of at least 10%. Given the impending water shortage, this means one water load per supply unit and no wastewater. In areas with water scarcity, which may become more prevalent due to climate change, intermediate water storage is essential. Water can be easily stored. The hydrogen content is 111 g / liter.That's an energy consumption of 3.6 kWh / liter. A house with, say, four people, depending on the power supply, would need 150 liters of water for the electricity storage.

[0020] Particularly with SOFC technology (SOFC stands for Solid Oxide Fuel Cell), hydrogen may not be fully processed. Since the hydrogen supply and water removal take place on the same side, the hydrogen can be "flushed away" and collected in the water tank. This tank is designed to absorb the hydrogen and then return it to the electrolysis process or fuel cell process.

[0021] There are mainly five processes:

[0022] 1 ) A photovoltaic system generates electricity, which is used to produce hydrogen via an electrolysis cell,

[0023] 2) The hydrogen is stored in LOHC (liquid-organic hydrogen carrier) and

[0024] 3) Stored in a non-pressurised state in a [disused] fuel oil tank or other suitable container; this storage device has a specially shaped membrane which separates unloaded LOHC from loaded LOHC and deforms accordingly when, for example, a loaded LOHC is fed in on one side and the unloaded LOHC is removed on the other side;

[0025] 4) Release of hydrogen during fuel cell operation, with the resulting waste heat the hydrogen is released from the LOHC and converted into electricity;

[0026] 5) The waste heat from these processes is used to generate hot water and heat the heating system; the waste heat generated is in the range of over 100°C. This at least makes hot water supply possible. Since the amount of heat generated is greater than the hot water supply requires, a certain amount of heating is also possible. There are two options for this:

[0027] I) The waste heat, preferably from fuel cell operation (winter or night, even with direct supply of hydrogen gas from pipelines), but if possible also from other functions that would not be sufficient for heating, is mixed with cold waste heat from the heat pump in such a way that a heat pump can be supplied with the appropriate intake temperature, thus increasing its efficiency. The heat pump therefore no longer has any contact with the outside. If necessary, heat is received from outside via a heat exchanger. If the circulating medium is a refrigerant, air is less suitable. This is done according to the strategy of ideally adjusting the intake heat so that the heat generated corresponds to the demand.This can be adjusted using artificial intelligence, taking into account the parameters: power density of the available waste heat, temperature of a refrigerant, desired room temperature and outside temperature or other external parameters or even the available electricity, e.g. from batteries or photovoltaics.

[0028] II) The residual heat is transferred to a well-insulated heat storage tank and extracted from there when heating is required. This can either be done directly, e.g., as an additional heat source on particularly cold days, or with a heat pump (HP). The HP allows only a fraction of the heat pump's output volume to be extracted from the heat storage tank, depending on the temperature in the heat storage tank. This occurs in such a way that the volume flow from the heat storage tank (T1) and the cold heat pump exhaust flow (T2) normally drawn in by the HP mix to create a flow with an optimal temperature for HP operation, depending on peripheral, weather, and seasonal parameters.

[0029] The energy system according to the invention has the advantage that the ideal or optimal mixing ratio for heating can be set, if necessary also depending on the heating period, is extremely flexible and is based on a) the outside temperature, and b) the efficiency of the heat pump, or the available power from a battery or photovoltaics (PV), c) the condition of the heat storage and / or d) the length of the remaining winter to be expected. To achieve this, the aim is to regulate everything optimally. It is to be expected that other factors such as weather forecasts, daytime and nighttime temperature variations, etc. will also come into play. Therefore, the control system has a weather factor, a time factor, a heat factor and a system factor. This indicates increased complexity and speaks in favor of control and regulation with artificial intelligence. e) A heat storage system is used in new houses, e.g.as a bed of gravel, sand or a layer of earth with pipes running through it under a house. The entire area of ​​the house or part of it can also be used, or even, for example, a cellar room in the case of retrofitting, or insulated liquid containers (water) located in the cellar, the water from a cistern can be used or placed next to the house. f) If the water from the cistern is used, it must be a minimum size and the temperature there must not exceed approximately 30°C, or up to 50°C depending on the time of year and how the water is used, e.g. for watering plants. Alternatively, a second cold cistern can be used. The advantage is that rainwater constantly flows in, thus constantly supplying fresh water with a higher temperature. The cistern must therefore be constructed in such a way that cold water flows out and the new water remains.Ice can certainly form in cisterns, provided the fixtures and structure are resistant to it. The pipes in the cistern can be laid on or near the cistern wall to capture or utilize geothermal energy. This also allows the crystallization heat to be utilized. g) The waste heat can be used for cooking by producing steam from the waste heat and directing it to the cooking area. h) Heat can also be supplied to the storage tank or the entire process from external sources and other sources.

[0030] The energy system according to the invention comprises a dual-function cell designed as a solid oxide fuel cell (SOFC), namely with at least one electrolysis function (EC) and one fuel cell function (FC). The solid oxide fuel cell (SOFC) has a dual function and, for this purpose, has an integrated or attached reactor arranged at the at least one electrolysis cell (EC) and the at least one fuel cell (FC). The waste heat from fuel cell operation is fed to the reactor, extracting the hydrogen and converting it into electricity, thus enhancing the energy system as a municipal utility.

[0031] Additionally, a water storage tank, or an isolated water and steam storage tank, is connected to the (FC) and (EC). This tank collects the water and / or steam supplied by the fuel cell (FC) and passes it on to the EC as needed. The energy system includes an oxygen storage tank for the temporary storage of O2. The oxygen storage tank is designed as a container connected to the fuel cell (FC) at an air inlet and to an oxygen outlet of the electrolysis cell (EC).

[0032] The waste heat from the electrolysis cell (EC) and fuel cell (FC) functions, from LOHC loading and from LOHC release can be used to generate hot water. The waste heat can be stored in a heat storage system, whereby the heat storage comprises the storage media, gravel, sand, earth, liquids or water. The storage media gravel, sand and earth are installed as thermally insulated fill or as a thermally insulated part of a foundation beneath a building and / or arranged over part or the entire area of ​​the building or in basement rooms or stored in insulated storage tanks. A cistern can be used as a heat source. A heat pump circuit is designed with which almost 100% to almost 0% of a heat pump flow can be extracted from the heat storage system and / or absorbs heat from the environment.The quantities sucked in depend on the outside temperature, the available heat in the storage tank, the duration of the remaining winter, the weather forecast, the type and size of the heat storage tank, the type of heat source and its size and can be regulated and controlled by a control and regulation device in a classic or via Kl methods.

[0033] The steam from the waste heat can be used to power a stove, for example. The heat storage unit is heated from its exterior by burning residual materials such as waste wood, wood, sewage sludge, and non-toxic waste with air or pure oxygen from the electrolysis cell (EC). CO2 can be collected by burning it with oxygen. The generated energy can be made available to heat-using companies such as drying companies, electroplating companies, or even sewage treatment plants that can utilize waste heat. These companies, in particular, can store and sell hydrogen in LOHCs.

[0034] Further advantages and advantageous embodiments of the invention can be found in the following description of the figures, the drawings and the claims.

[0035] An exemplary embodiment of the inventive solution is explained in more detail below with reference to the attached schematic drawings. It shows:

[0036] Fig. 1 shows an energy system in a schematic representation,

[0037] Fig. 2 shows the energy system with waste heat, also in a schematic representation,

[0038] Fig. 3 shows the energy system for summer and winter operation,

[0039] Fig. 4 shows a heat supply from residual heat,

[0040] Fig. 5 shows a schematic representation of the energy system using a heat pump.

[0041] Figure 1 depicts an energy system comprising at least one solid oxide fuel cell (FC). Waste heat from the FC is used to extract hydrogen from a LOHC. Water or steam from the FC is stored in an insulated container, a reactor. The diagram includes a cathode 1, an anode 2, an electrolyte 3, and a reactor 4. The diagram shows a setup for possible winter operation of the FC.

[0042] Fig. 2 shows the energy system with reactor 4, which has at least one electrolysis cell EC for electrolysis operation. Waste heat 5 for hot water 5.1, as well as for heat storage and waste heat 5.2, are schematically shown. The hydrogen generated by electrolysis is stored in reactor 4. The illustration shows a possible summer operation EC. The use of LOHC has the advantage that LOHC cannot be ignited and is far less toxic than gasoline or diesel.

[0043] The illustration includes a cathode 1, an anode 2, an electrolyte 3, and a reactor 4. Waste heat 5 for hot water 5.1 and for heat storage, and 5.2 waste heat, in particular for the extraction from the LOHC, is schematically illustrated. Fig. 3 schematically illustrates the energy system according to the invention with fuel cell operation and electrolysis operation. The energy system has at least one electrolysis cell EC and at least one fuel cell FC made of solid oxide. The two functional units EC and FC are combined in one device. Waste heat from the FC is used to extract the hydrogen from an LOHC.The entire system, with a water reservoir and an oxygen reservoir, is equipped in such a way that water or steam from the FC is temporarily stored in an insulated container and made available to the electrolysis cell operation as needed. Oxygen from the EC is temporarily stored and mixed with air as needed, fed to the fuel cell operation. The fuel cell operation on the right side of the diagram shows the winter FC operation of an SOFC fuel cell, as well as the directions of movement of H2, H2O, and O2, in contrast to the summer EC operation on the left side. Water and a residual amount of H2 can be stored and used for summer operation.

[0044] The oxygen O2 produced during electrolysis can be fed back into the fuel cell system. Thus, the EC and FC systems are implemented in a single cell, or rather, an isolated container, with a sustainable resource supply. The container for the two cell functions of the EC and FC is designed to temporarily store the oxygen until it is needed on the other side of the energy system. The oxygen for the fuel cell system, i.e., the FC system, is mixed with a lot, little, or no air—in other words, rarely or possibly never. This depends on the oxygen availability.

[0045] Fig. 4 shows the heat supply from the residual heat generated by the LOHC-EC-FC system or solely from the waste heat of fuel cell operation.

[0046] Figures 4 and 5 show: The waste heat from the LOHC system (especially in summer) is fed to the heat storage tank 30 and extracted from it again when the heat pump 10 / HP is operating. This heat is extracted only to the extent required by the current heating situation. The residual heat from the LOHC system or the residual heat from the FC (after hot water generation) can also be fed directly to the heat pump or mixed with external heat or cold. In addition, heat can also be supplied to the heat storage tank from outside, for example, through combustion processes.

[0047] Refrigerants are pumped through the circuit. Heat from the outside is fed into the energy system via heat exchangers. Waste heat in the range of over 100°C is generated. This at least makes hot water supply possible. Since the amount of heat generated is greater than the hot water supply requires, a certain amount of heating is also possible. This means that the residual heat goes into a well-insulated heat storage tank and is extracted from there again when heating is required. This can happen either directly, e.g. as an additional heat source on particularly cold days, or with a heat pump HP. The HP allows only a fraction of the heat pump's output volume to be taken from the heat storage tank, depending on the temperature in the heat storage tank. This happens in such a way that the volume flow from the heat storage tank (T1) and the air T2 normally drawn in by the HP mix to create a flow with the optimal temperature for the HP function.

[0048] The energy system can also run without the exemplary branch concerning the heat storage unit 30. This means that 100% of the energy flows through the LOHC system 20. The distribution valve 15 controls the flows into the heat storage unit 30, the LOHC system 20, and the external flow 18. Information can be evaluated about which energy flow is coming from the LOHC system and how this flow is controlled. The heat supply from hydrogenation, FC, and EC 40 is schematically represented by an arrow.

[0049] Fig. 5 shows a schematic of the structure of the energy system with a heat pump WP / 10, a LOHC system 20, and a heat storage unit 30. A pump is integrated into the heat pump 14, or a compressor can generate the pumping power. 15 denotes a distribution valve. A heat mixing valve 16 is provided. The heat 17 from the LOHC system or from other sources can be introduced and stored in the heat storage unit 30. Heat from other sources 18 is utilized. A distribution valve distributes the flows according to a K1 system specification. The heat mixing valve 16 controls the mixing temperature at the outlet with the aid of the K1, which can also introduce heat from outside. All features presented in the description, the following claims, and the drawings can be essential to the invention both individually and in any combination with one another.

[0050] List of reference symbols

[0051] FC fuel cell operation

[0052] EC electrolysis operation

[0053] SOFC solid oxide fuel cell

[0054] LOHC Liquid organic hydrogen carriers

[0055] T1 temperature i

[0056] T2 Temperature 2

[0057] T3 Temperature 3

[0058] 1 cathode

[0059] 2 anode

[0060] 3 Electrolyte

[0061] 4 reactor

[0062] 5 Waste heat

[0063] 5.1 Waste heat for hot water and heat storage

[0064] 5.2 Waste heat with hydrogen extraction from LOHC

[0065] 10 / WP heat pump

[0066] 14 Pump / Compressor

[0067] 15 Distribution valve

[0068] 16 Heat mixing valve

[0069] 17 Heat of a LOHC system

[0070] 18 Heat from a source

[0071] 20 LOHC system

[0072] 30 heat storage units

[0073] 40 Heat of hydrogenation, FC and EC

Claims

Dr.- Inq. SCHLÜCKER, Eberhard: 74183 Obersulm Claims 1 . Energy system, comprising a functional unit with at least one electrolysis cell (EC) and a further functional unit with at least one fuel cell (FC) made of solid oxide, characterized in that the two functional units (EC) and (FC) are combined in one device and waste heat from the (FC) is used to extract the hydrogen from a (LOHC), and the entirety of (EC) and (FC) are equipped with a water reservoir and an oxygen reservoir such that water and steam from the (FC) are temporarily stored in an insulated container and made available to the electrolysis cell operation, the oxygen from the (EC) is temporarily stored and fed to the fuel cell operation, mixed with or without air.

2. Energy system according to claim 1, characterized in that a fuel cell (SOFC), in which hydrogen is released, and an electrolysis cell are designed as two individual devices independently of one another and are equipped with oxygen and water buffers, thereby forming an energy supply block.

3. Energy system according to one of claims 1 or 2, characterized in that for generating hot water and for cooking with steam, the waste heat from functions of the electrolysis cell (EC) and the fuel cell (FC), the LOHC loading and the hydrogen release from (LOHC) can be used.

4. Energy system according to one of the preceding claims, characterized in that the waste heat preferably comes from the fuel cell operation of a night or winter operation, and / or the electrolysis operation of a sunny phase in a cold period, and / or the storage of the hydrogen in the (LOHC), pure or diluted with air heat or cold WP gas, can be used for a heat pump to heat one or more houses.

5. Energy system according to one of the preceding claims, characterized in that waste heat from the system can be stored in a heat storage device, wherein the heat storage device uses the storage media, gravel, sand, liquids, water or earth.

6. Energy system according to claim 5, characterized in that the storage media gravel, sand or earth are interspersed with pipes, are installed as thermally insulated fill or as a thermally insulated part of a foundation under a building and / or are arranged over part or the entire area of the building or in basement rooms or are stored in insulated storage tanks and / or a liquid storage for the water is arranged outside the building, wherein the water or liquids are also interspersed with pipes.

7. Energy system according to one of the preceding claims, characterized in that a heat pump circuit is designed with which almost 100% to almost 0% of a heat pump flow can be extracted from the heat storage and almost 0% to almost 100% of the heat from the environment, or from the fuel cell operation or a cold heat pump gas flow.

8. Energy system according to one of the preceding claims, characterized in that a reactor (4) is designed for storing H2 after electrolysis with (EC) or extraction by (FC).

9. Energy system according to one of the preceding claims, characterized in that the heat for the heat pump (10 / WP) is taken from a cistern and its surroundings, wherein the cistern and heat pipes located there for the heat pump (10 / WP) form an energetically optimized unit, the maximum temperature of each application and potential icing are taken into account and the geothermal energy of the direct environment is used.

10. Energy system according to claim 8 or 9, characterized in that the amount sucked in by the (10 / WP) depends on the outside temperature, the available heat in the storage, the duration of the remaining winter, the weather forecast, the type and size of the heat storage, the type of heat source and its size and can be regulated and controlled by a control and regulating device in a classic embodiment, or via Kl methods. 11 . Energy system according to one of the preceding claims, characterized in that the heat storage device is heated from its outside by combustion of residual materials such as waste wood, wood, sewage sludge, non-toxic waste, with air or pure oxygen of the electrolysis cell (EC) and, in the case of combustion with pure oxygen, the CO2 is collected.

12. Energy system according to one of the preceding claims, characterized in that hydrogen, which is supplied via pipelines, can be fed to the (FC), electricity is generated and the waste heat can be used for hot water and either for heating or is stored in summer operation and the hot water can be used in the heat storage, whereby a residual or superfluous amount can be discharged.

13. Energy system according to one of the preceding claims, characterized in that a buffer battery is designed to start up the energy system and to bridge interference effects.

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