Method for providing electricity and heat using a fuel cell system

Abstract

The invention presented relates to a method (100) for providing electrical current and heat by means of a fuel cell system (200). The presented method (100) comprises executing (101) a mathematical model of the fuel cell system (200), determining (103) performance parameters optimized for a given state, and setting (105) the determined performance parameters on at least one fuel cell stack (201) of the fuel cell system (200), wherein the mathematical model is switchable between at least four given states, wherein in a first state the mathematical model models an operating situation in which the fuel cell system (200) is to be optimized to provide electrical current and thermal energy, wherein in a second state the mathematical model models an operating situation in which the fuel cell system (200) is to be optimized only to provide electrical current, wherein in a third state the mathematical model models an operating situationin which the fuel cell system (200) is to be optimized to provide only thermal energy, and wherein the mathematical model in a fourth state models an operating situation in which the fuel cell system (200) is to be optimized for an operating situation without a requirement for electrical energy and without a requirement for thermal energy.

Description

[0001] The presented invention relates to a method for providing electrical current and heat by means of a fuel cell system and a fuel cell system according to the attached claims. State of the art

[0002] Electrical systems are increasingly being used to supply single-family homes, multi-family homes and entire neighborhoods.

[0003] To relieve the strain on the electricity grids, concepts for local generation and increasing local consumption are needed.

[0004] Combined heat and power plants in combination with local electricity generation through photovoltaics are currently well-known solutions.

[0005] In the future, solid oxide fuel cell systems will be able to replace combined heat and power plants at least partially, as they offer significant advantages in overall efficiency.

[0006] Currently, no optimized operating strategies are known for individual solid oxide fuel cell systems that take into account different requirements such as lifetime, price (two-stage, internal and external of a district), operating costs and modulation speed. Disclosure of the invention

[0007] Within the scope of the presented invention, a fuel cell system and a method for providing electricity and heat using the presented fuel cell system are introduced. Further features and details of the invention will become apparent from the respective dependent claims, the description, and the drawings. Features and details described in connection with the method according to the invention naturally also apply in connection with the fuel cell system according to the invention, and vice versa, so that the disclosure regarding the individual aspects of the invention always refers, or can refer, to each other.

[0008] The invention presented here serves in particular to provide a means of supplying electrical current and heat by means of a fuel cell system.

[0009] Thus, according to a first aspect of the presented invention, a method for providing electrical current and heat by means of a fuel cell system is presented.

[0010] The presented method comprises executing a mathematical model of the fuel cell system, determining performance parameters optimized for a given state, and setting the determined performance parameters on at least one fuel cell stack of the fuel cell system, wherein the mathematical model is switchable between at least four given states, wherein in a first state the mathematical model models an operating situation in which the fuel cell system is to be optimized to provide electrical current and thermal energy, wherein in a second state the mathematical model models an operating situation in which the fuel cell system is to be optimized only to provide electrical current, wherein in a third state the mathematical model models an operating situationin which the fuel cell system is to be optimized to provide only thermal energy, and wherein the mathematical model in a fourth state models an operating situation in which the fuel cell system is to be optimized for an operating situation without a requirement for electrical current and without a requirement for thermal energy.

[0011] In the context of the presented invention, a performance parameter is understood to be an operating parameter for adjusting the power to be provided by a fuel cell system or a fuel cell stack.

[0012] The presented method is based on a mathematical model that implements a control concept, by means of which an operating strategy can be used to optimize the fuel cell system taking into account several objectives.

[0013] The mathematical model can receive the following input variables: Price signals for e.g. electricity, gas and heat as actual values, forecast values ​​and historical data, for e.g. a day, a week or a year looking ahead or looking back.

[0014] The price signals can be subdivided into external price signals provided by an external market participant, in particular electricity prices, such as flexible purchase and sale prices, probably inflexible gas prices and usually fixed heat prices.

[0015] Furthermore, internal price signals are included, such as those coming from a consumer in the form of electricity demand and heat demand.

[0016] The mathematical model couples electricity and heat demand to determine performance parameters, particularly taking into account the current season, and is based on the general consideration that designing a fuel cell system for optimized heat energy supply is less practical than designing it for optimized electrical power supply. Since fuel cell systems, especially solid oxide fuel cell systems, generate only a small amount of heat due to their efficiency, heat energy can be supplied via auxiliary systems such as heat pumps, external electric heaters, or similar devices.

[0017] Due to seasonal fluctuations within a year, fuel cell stacks of a fuel cell system may be switched on or off.

[0018] It may be provided that the mathematical model includes a two-stage optimization approach for each state, with maximum autarky and minimum operating costs specified as optimization goals in a first stage, and minimum operating costs and minimum greenhouse gas emissions specified as optimization goals in a second stage.

[0019] For example, the following control algorithms can be used, each differing in its optimization goal.

[0020] For the first scenario, the initial stage is characterized by both internal electricity demand (i.e., high internal electricity prices) and direct heat demand (i.e., high heat prices for a consumer). Therefore, using the fuel cell system is advantageous compared to purchasing external electricity, as the fuel cell system operates at maximum efficiency, providing both electricity and waste heat in a cost-effective and environmentally friendly manner.

[0021] Accordingly, the optimization goals here are to achieve a high degree of self-sufficiency and cost minimization.

[0022] In a second stage, opposing effects can be triggered by high gas costs, so that purchasing electricity and generating heat on-site becomes cheaper than operating the fuel cell system once a certain gas price is exceeded.

[0023] Accordingly, the optimization goal here is cost minimization.

[0024] Furthermore, regarding greenhouse gas emissions from an external electricity mix, if there is a high proportion of renewable energies in the external electricity mix, the energy costs are generally lower than the operation of a solid oxide fuel cell system with fossil fuels, although this is not valid if the fuel cell system is operated with green hydrogen.

[0025] Accordingly, the optimization goal is to reduce greenhouse gas emissions, whereby a high external electricity price acts as a reinforcing external effect, so that selling electricity externally becomes profitable when internal demand has already been met.

[0026] Accordingly, the optimization goal of cost minimization also applies.

[0027] For the second condition, where there is a need for electrical current but no need for thermal energy, the operation of the fuel cell system is generally possible, e.g. by using a thermal bypass or by not using the thermal energy, but this will be with reduced fuel or cost efficiency.

[0028] For the first stage, there is a demand for electricity, i.e., a high internal electricity price, but no demand for heat, i.e., a low heat price for each consumer.

[0029] Accordingly, unrestricted operation of the fuel cell system is only possible when the optimization goal is "high self-sufficiency". Cost optimization requires a comparison with the external electricity price, which may lead to a reduction in the overall operating time.

[0030] Accordingly, the optimization goals here are high self-sufficiency and cost minimization.

[0031] In the third state, where there is no electricity demand but a direct heat demand, such as in a situation where intermediate electricity storage via sector coupling is no longer possible, there is no internal electricity demand in the first stage, meaning a low internal electricity price. However, there is a heat demand, meaning a high heat price for each consumer. Due to the low thermal output of a fuel cell system, unrestricted operation is not practical in this case and should only be implemented in exceptional circumstances, as the overall efficiency becomes extremely low. Accordingly, the third state should be avoided as much as possible, for example, by using electric auxiliary heaters or heat pumps to convert electricity into heat, thus shifting the third state into the first.

[0032] Accordingly, the optimization goals of high self-sufficiency and cost minimization apply.

[0033] For the fourth state, in which there is no demand for either electricity or heat, after a certain "threshold time," which could be, for example, hours or days, at least one fuel cell stack of the fuel cell system can first be placed in standby mode and then switched off. This can be done particularly depending on the current season, so that the number of active fuel cell stacks is aligned with the current needs of a consumer.

[0034] The control algorithms described above can be used for both the operation and design of a fuel cell system, taking seasonal dependencies into account. The design of auxiliary storage systems, such as thermal storage units or batteries, and the design of electric auxiliary heaters or heat pumps can also be optimized using these control algorithms.

[0035] It may also be provided that the mathematical model includes a seasonal interaction between electricity demand and heat demand.

[0036] By taking the current season into account when forecasting the demand for heat and electricity, a particularly accurate and predictive adjustment of the fuel cell system's performance parameters can be achieved.

[0037] It may also be provided that the mathematical model, when determining performance parameters optimized for a given state, takes into account historical data for a demand for electrical current and / or heat energy.

[0038] By taking historical data into account when forecasting the demand for heat and electricity, a particularly accurate and predictive adjustment of the performance parameters of the fuel cell system can be achieved.

[0039] It may also be provided that the mathematical model includes a multi-objective optimization to maximize the lifetime of the fuel cell system, minimize operating costs, minimize greenhouse gas emissions and minimize resource consumption.

[0040] By formulating a multi-objective problem in a mathematical model, a fuel cell system setting can be achieved that addresses the various problems in the best possible way.

[0041] It may also be provided that the mathematical model is switchable between a setting optimized for a quantity of supplied electrical current and a setting optimized for a quantity of heat energy.

[0042] By using a model that can be switched between a setting optimized for a certain amount of electrical current supplied and a setting optimized for a certain amount of thermal energy, the respective optimized performance parameters can be determined and, if necessary, used to adjust the fuel cell system.

[0043] It may also be provided that the mathematical model for providing electrical power and / or thermal energy takes into account a number of additional power plants, including a fuel cell system, a photovoltaic system, a heat pump, an auxiliary heater and / or a wind turbine.

[0044] It may also be provided that the mathematical model for providing electrical current and / or heat energy takes into account a number of electricity storage devices and / or a number of heat storage devices.

[0045] By taking additional components, such as power plants and / or storage, into account when setting up the fuel cell system, a particularly resource-efficient and cost-efficient overall system can be provided.

[0046] According to a second aspect, the presented invention relates to a fuel cell system for providing electrical current and thermal energy. The fuel cell system has the same advantages that have already been described in detail in relation to the method for providing electrical current and heat by means of a fuel cell system according to the first second aspect of the invention.

[0047] The presented fuel cell system comprises a number of fuel cell stacks and a computing unit, the computing unit being configured to execute one possible embodiment of the presented method.

[0048] In the context of the presented invention, a computing unit is to be understood as a computer, a processor, a control unit or any other programmable circuit.

[0049] It may be intended that the fuel cell system is a solid oxide fuel cell system.

[0050] Further advantages, features, and details of the invention will become apparent from the following description, in which exemplary embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description can each be essential to the invention individually or in any combination.

[0051] They each show schematically: Fig. 1. a possible design of the presented procedure, and Fig. 2. A representation of a possible design of the presented fuel cell system.

[0052] In Fig. Figure 1 shows a method 100 for providing electricity and heat using a fuel cell system.

[0053] The procedure 100 comprises an execution step 101 in which a mathematical model of the fuel cell system is executed, a determination step 103 in which performance parameters optimized for a given state are determined, and a setting step 105 in which the determined performance parameters are set on at least one fuel cell stack of the fuel cell system.

[0054] The mathematical model is switchable between at least four predefined states, wherein in a first state the mathematical model models an operating situation in which the fuel cell system is to be optimized to provide electrical current and thermal energy, wherein in a second state the mathematical model models an operating situation in which the fuel cell system is to be optimized only to provide electrical current, wherein in a third state the mathematical model models an operating situation in which the fuel cell system is to be optimized only to provide thermal energy, and wherein in a fourth state the mathematical model models an operating situation in which the fuel cell system is to be optimized for an operating situation without a requirement for electrical energy and without a requirement for thermal energy.

[0055] In Fig. Figure 2 shows a fuel cell system 200 for providing electrical current and heat energy.

[0056] The fuel cell system 200 is a solid oxide fuel cell system and comprises a large number of fuel cell stacks or so-called “SOFC clusters” 201 and a computing unit 203.

[0057] The computing unit 203 is configured to execute procedure 100 according to Fig. 1 to execute.

Claims

[1] Method (100) for providing electricity and heat using a fuel cell system (200), wherein the method (100) comprises: - Executing (101) a mathematical model of the fuel cell system (200), - Determining (103) performance parameters optimized for a given state, - Setting (105) the determined performance parameters on at least one fuel cell stack (201) of the fuel cell system (200), where the mathematical model can be switched between at least four predefined states, wherein the mathematical model in a first state models an operating situation in which the fuel cell system (200) is to be optimized to provide electrical current and thermal energy, wherein the mathematical model in a second state models an operating situation in which the fuel cell system (200) is to be optimized only to provide electrical current, wherein the mathematical model in a third state models an operating situation in which the fuel cell system (200) is to be optimized only to provide thermal energy, wherein the mathematical model in a fourth state models an operating situation in which the fuel cell system (200) is to be optimized for an operating situation without a requirement for electrical energy and without a requirement for heat energy. [2] Method (100) according to claim 1, characterized by , that the mathematical model includes a two-stage optimization approach for each state, where in a first stage maximum self-sufficiency and minimum operating costs are specified as optimization goals, and where in a second stage minimum operating costs and minimum greenhouse gas emissions are specified as optimization goals. [3] Method (100) according to claim 1 or 2, characterized by , that the mathematical model includes a seasonally dependent interaction between electricity demand and heat demand. [4] Method (100) according to any one of the preceding claims, characterized by , that the mathematical model takes into account historical data for a demand for electrical current and / or heat energy when determining performance parameters optimized for a given state. [5] Method (100) according to any one of the preceding claims, characterized by, that the mathematical model includes a multi-objective optimization to maximize the lifetime of the fuel cell system, minimize operating costs, minimize greenhouse gas emissions and minimize resource consumption. [6] Method (100) according to any one of the preceding claims, characterized by , that the mathematical model is switchable between a setting optimized for a quantity of supplied electrical current and a setting optimized for a quantity of heat energy. [7] Method (100) according to any of the preceding claims, characterized by , that the mathematical model for providing electrical power and / or thermal energy takes into account a number of additional power plants, the number of which includes a fuel cell system, a photovoltaic system, a heat pump, an auxiliary heater and / or a wind turbine. [8] Method (100) according to any one of the preceding claims, characterized by , that the mathematical model for providing electrical current and / or heat energy takes into account a number of electrical storage devices and / or a number of heat storage devices. [9] Fuel cell system (200) for providing electrical power and thermal energy, the fuel cell system (200) comprising: - a number of fuel cell stacks (201), - a computing unit (203) wherein the computing unit (203) is configured to execute a method (100) according to any one of claims 1 to 8. [10] Fuel cell system (200) according to claim 9, characterized by , that the fuel cell system (200) is a solid oxide fuel cell system.

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