Day-ahead optimal operation method of hydrogen energy system considering heat recovery of hydrogen energy system

Abstract

The present application relates to the operation method of the electric hydrogen regional comprehensive energy system, specifically to a kind of day-ahead optimization operation method of electric hydrogen energy system considering hydrogen energy system heat recovery, including obtaining energy system historical operation data and obtaining typical day source load curve;Device operation model considering hydrogen energy system heat recovery is established according to equipment operating parameters;Energy system model is established according to energy system topology structure;With the minimum system operation cost as the goal, the day-ahead optimization operation model of electric hydrogen energy system considering hydrogen energy system heat recovery is established;The optimization operation model is solved to obtain the day-ahead operation plan of electric hydrogen regional comprehensive energy system.The technical problem that the model in the prior art is only for single device, and the operation characteristics of hydrogen energy equipment variable efficiency, multi-working condition are also insufficient, and the operation of electric hydrogen energy system considering hydrogen energy system heat recovery cannot be maximized.

Description

Technical Field

[0001] This invention relates to a method for operating an integrated regional energy system of hydrogen and electricity, specifically a day-ahead optimization method for an hydrogen and electricity energy system that takes into account the heat recovery of the hydrogen energy system. Background Technology

[0002] With the development of hydrogen fuel technology, hydrogen energy has enormous potential as a terminal energy source, and regional integrated energy systems centered on hydrogen electrolysis have become the most promising form of regional terminal energy system. Utilizing distributed renewable energy sources for hydrogen production through electrolysis can not only meet local hydrogen demand but also facilitate the consumption of distributed renewable energy sources, offering better economic benefits compared to centralized hydrogen production methods.

[0003] Existing research has effectively demonstrated the significant improvement that hydrogen energy systems bring to the economical and low-carbon operation of systems. However, it has not delved into the heat generation characteristics of hydrogen energy systems, leading to low energy utilization efficiency. Hydrogen energy requires multiple energy conversions during production, storage, and consumption, resulting in low energy utilization efficiency and significantly limiting its application and development. On the one hand, on the hydrogen production side, the electrolysis efficiency of traditional commercial alkaline and proton exchange membrane water electrolysis systems is only 51%–70%, with nearly 20%–30% of energy lost as heat. On the other hand, on the hydrogen consumption side, the energy utilization efficiency of methanation is 75–80%, the power generation efficiency of hydrogen fuel cells is around 60%, and the overall efficiency of the power-to-gas-to-power (P2G2P) process is less than 40%. To improve hydrogen energy utilization efficiency, existing technologies have focused on optimizing hydrogen energy utilization, proposing to refine the electricity-to-gas process into two stages: electricity-to-hydrogen production and hydrogen methanation. Priority is given to using hydrogen cogeneration or hydrogen fuel cell vehicles for fuel supply, and surplus hydrogen is then methanated, thereby reducing energy conversion and improving energy efficiency. However, these technologies have not fundamentally solved the problem of low energy efficiency.

[0004] Heat recovery technology offers a fundamental solution to the aforementioned problems. Different types of hydrogen energy equipment, such as water electrolysis, hydrogen fuel cells, and methanation, generate a large amount of high-grade waste heat, which can theoretically be recovered and utilized to improve system energy efficiency. Existing technology centers have established electro-hydrogen conversion and heat models for alkaline water electrolysis and proton exchange membrane water electrolysis, and applied them to the optimized operation of integrated electro-thermal energy systems. However, this technology only analyzes the heat generation characteristics of water electrolysis equipment and does not cover high-temperature water electrolysis or other hydrogen energy equipment. In addition, there are technologies for waste heat recovery and utilization of methanation units and hydrogen fuel cells to achieve multi-stage energy utilization. However, in general, current optimized operation methods for heat recovery in hydrogen energy systems only focus on single equipment and have not systematically considered the impact of heat recovery on the production, storage, and utilization of hydrogen energy. Furthermore, the models in these methods are insufficient in expressing the variable efficiency and multi-condition operating characteristics of hydrogen energy equipment, and cannot accurately characterize the coordinated interaction capabilities of hydrogen energy systems with external power and heating systems. Summary of the Invention

[0005] The purpose of this invention is to provide a day-ahead optimization method for an electro-hydrogen energy system that considers heat recovery from the hydrogen energy system. This method addresses the technical problem that existing models only target a single device and fail to adequately express the variable efficiency and multi-condition operating characteristics of hydrogen energy devices. Consequently, they cannot accurately characterize the coordination and interaction capabilities of the hydrogen energy system with external power and heating systems, and thus cannot maximize the optimization of the operation of the electro-hydrogen energy system that considers heat recovery from the hydrogen energy system.

[0006] The present invention provides an optimized operation method for an electro-hydrogen energy system that considers heat recovery in a hydrogen energy system. The equipment in the electro-hydrogen energy system includes a water electrolysis device, a hydrogen fuel cell, a methanation device, and a combined power and heat device.

[0007] Includes the following steps:

[0008] S1 acquires historical operating data of the energy system and obtains a typical daily source-load curve;

[0009] S2 establishes an equipment operation model that considers heat recovery in the hydrogen energy system based on the equipment operating parameters;

[0010] S3 establishes an energy system model based on the energy system topology;

[0011] S4 aims to minimize system operating costs by establishing a day-ahead optimization operation model for an electric hydrogen energy system that considers heat recovery from the hydrogen energy system.

[0012] S6 solves the optimized operation model to obtain the day-ahead operation plan of the integrated energy system for the hydrogen-electric region.

[0013] Furthermore, the operational data of the energy system includes new energy output data, electricity load data, gas load, heat load, and hydrogen load data.

[0014] Furthermore, the equipment operation model considering heat recovery in the hydrogen energy system includes:

[0015] 1) Low-temperature and high-temperature water electrolysis heat recovery operation models, including

[0016] For a single electrolytic cell, the voltage required for electrolysis can be expressed as:

[0017] U cell (T ED i cell )=U rev +U ohm +U act +U con

[0018]

[0019] In the formula, U cell The electrolysis voltage is related to T. ED and electrolysis current density i cell Related, it can be divided into reversible voltage U rev Ohmic polarization voltage U ohm Activation polarization voltage U act and concentration polarization voltage U con ;U th This is the minimum voltage required for electrolysis theory, and it is temperature-dependent, being 1.29V at 800℃ and 1.48V at 25℃; n e is the molar number of electrons in hydrogen, and F is the Faraday constant;

[0020] The energy flow model for water electrolysis can be expressed as:

[0021]

[0022] In the formula, P ED,el Energy consumption for high-temperature water electrolysis; P ED,H Energy consumption for high-temperature water electrolysis to produce hydrogen; N cell S represents the number of electrolytic cells; cell The effective area of ​​the electrolytic cell;

[0023] The thermodynamic process of low-temperature water electrolysis is characterized by lumped equations, as follows:

[0024]

[0025] In the formula, LED represents low-temperature water electrolysis; C LED This represents the equivalent heat capacity of a low-temperature electrolytic cell; The heat loss of the low-temperature electrolytic cell at time t; The thermal energy that can be recovered from the low-temperature electrolytic cell at time t;

[0026] The specific thermodynamic processes of the high-temperature water electrolysis system are as follows:

[0027]

[0028] In the formula, HED represents high-temperature electrolyzed water; C HED This is the equivalent heat capacity of a high-temperature electrolytic cell; k represents the thermal energy of the discharged gas at time t. rec The heat exchange coefficient between the discharge gas and the feed gas; The heat loss of the high-temperature electrolytic cell at time t; The energy consumption of the high-temperature water electrolysis preheating device at time t is... Let be the heating energy consumption of the high-temperature electrolytic cell at time t, assuming that all heating is done electrically, i.e.:

[0029] P t HED,heat +P t HED,fur =η EB P t EB

[0030] In the formula, Let η be the power consumption for electrolysis heating of water at time t. EB To improve the efficiency of electric heating;

[0031] The thermal steady-state model is established as follows:

[0032]

[0033]

[0034] The heat loss power consumption of water electrolysis Represented as:

[0035]

[0036] In the formula, R ED T is the equivalent thermal resistance of the electrolytic cell. a The ambient temperature;

[0037] Maintain within a certain temperature range, that is:

[0038]

[0039] The final recovered heat energy of the low-temperature and high-temperature water electrolysis systems are expressed as follows:

[0040]

[0041] In the formula, η represents the heat energy recovered from low-temperature and high-temperature water electrolysis at time t, respectively. ED,he The heat exchange efficiency of the heat exchange device;

[0042] 2) Methanation heat recovery operation model, including,

[0043] The reactants and products must satisfy a molar balance relationship, namely:

[0044]

[0045] In the formula, t represents the rate at which the reactor consumes carbon dioxide and hydrogen, respectively. These represent the rate and molar rate of methane production in the reactor at time t, respectively. The molar ratio of methane and hydrogen produced in the reaction; These are the relative molecular masses of carbon dioxide, hydrogen, and methane, respectively.

[0046] The heat generated during the methanation process is represented as follows:

[0047]

[0048] In the formula, η is the heat consumption generated by methanation at time t; MR The efficiency of the methanation reaction is given by ΔH, which is the heat released per mole of methane produced by methanation, and is 165 kJ / mol.

[0049] The final thermal energy recovered by the methanation unit is expressed as follows:

[0050]

[0051] In the formula, η represents the thermal energy recovered by the methanation unit at time t; MR,heat For the heat exchanger efficiency of the methanation unit;

[0052] 3) Hydrogen fuel cell heat recovery model, including,

[0053] The physical model for hydrogen fuel cell cogeneration is characterized as follows:

[0054]

[0055] in:

[0056]

[0057] In the formula, Let t be the amount of hydrogen consumed by the hydrogen fuel cell. The power generation and heat generation of the hydrogen fuel cell at time t are respectively, and η FC,e η FC,h To improve the power generation efficiency and heat production efficiency of hydrogen fuel cells;

[0058] 4) Hydrogen energy system heat recovery model, including,

[0059] The heat recovery and utilization model for a hydrogen energy system is expressed as follows:

[0060]

[0061] In the formula, η represents the thermal energy recovered and utilized by the hydrogen energy system at time t; he The heat exchange efficiency of the heat exchange device.

[0062] Furthermore, the energy system model includes:

[0063] 1) Distribution network power flow model, as follows:

[0064]

[0065]

[0066]

[0067]

[0068]

[0069] In the formula, P represents the squares of the voltages at nodes i and j, respectively; ij Q ij These represent the active and reactive power of branch ij, respectively; P i Q i These represent the net inflow of active and reactive power at nodes i and j, respectively; r ij x ij Let be the resistance and reactance of branch ij, respectively; These are the squares of the minimum and maximum node voltages, respectively, with V0 being the square of the balancing node voltage; S ij,max The maximum transmission capacity of branch ij;

[0070] 2) Heat distribution network power flow model, including,

[0071] The flow balance at each node is represented as follows:

[0072] A DHN W ij =W node

[0073] In the formula, A DHN W is the branch correlation matrix of the heating network nodes. ij For the branch flow matrix, W node For the node flow matrix;

[0074] The nodal head is represented as:

[0075]

[0076] In the formula, p w,i The water head at node i; K is the equivalent roughness parameter of the water pipe; l ij Let be the length of the water pipe at nodes i and j; be the density of water; d be the inner diameter of the water pipe; W ij Let ij be the water flow velocity at node ij;

[0077] The supply and return water temperatures at the node are expressed as follows:

[0078]

[0079] In the formula, T i s T i r These are the supply and return water temperatures for node i, respectively. These are the supply and return water temperatures for the heat source and heat load nodes, respectively. Let be the water flow velocities at the heat source and heat load nodes, respectively; e(i) is the set of nodes ending at node i, and s(i) is the set of nodes starting at node i.

[0080] The heat energy released and absorbed by heat source and heat load nodes is represented as:

[0081]

[0082] In the formula, These are the heat energy released by the heat source and the heat energy absorbed by the heat load, respectively; c w Specific heat capacity of the working fluid;

[0083] 3) Cogeneration unit operation model, including,

[0084] The combined heat and power (CHP) unit model is represented as follows:

[0085]

[0086] In the formula, P CHP Q CHP These represent the power generation and heat generation of the combined heat and power unit, respectively. CHP B CHP C CHP These are the boundary vectors for the operation of the combined heat and power unit;

[0087] The gas consumption of a combined heat and power (CHP) unit is expressed as follows:

[0088]

[0089] In the formula, Let η be the gas consumption of the cogeneration unit at time t. CHP For the operating efficiency of combined heat and power units, LHV gas It has the low calorific value of natural gas.

[0090] Furthermore, the current day-optimized operating model is as follows:

[0091]

[0092]

[0093]

[0094]

[0095]

[0096]

[0097] In the formula, These are the system energy purchase cost, operation and maintenance cost, carbon emission cost, load curtailment penalty cost, and energy sales revenue at time t, respectively. Let t be the unit price at which the system purchases electricity from the upper-level power grid. Let be the interaction power between the system and the upstream power grid at time t. When the power is at a certain time, it indicates that electricity is purchased from the upstream power grid; conversely, it indicates that electricity is fed back to the grid. To address the absolute value nonlinear term in the formula, an auxiliary variable is introduced. And add constraints Linearize it; c gas,buy This refers to the unit price for purchasing gas. Let N be the amount of natural gas purchased at time t; N is the set of all equipment, including water electrolysis, hydrogen fuel cells, CHP, etc. Let P be the unit maintenance cost of the nth device. t,n c represents the power consumption of the nth device at time t. em For the unit carbon emission cost, λ e , λ gas Carbon emissions per unit of electricity and gas consumption, respectively, λ H For the unit carbon emissions of hydrogen industrial production, the system can reduce carbon emissions from industrial hydrogen production by selling hydrogen to the hydrogen energy market; e,p c heat,p c gas,p c H,pThe penalty prices per unit for abandoned electricity, heat, gas, and hydrogen are respectively. These represent the system's abandoned power, abandoned heat, abandoned gas, and abandoned hydrogen at time t, respectively; c H,sell This refers to the unit price of hydrogen sold. Let t be the amount of hydrogen sold by the system at time t;

[0098] The constraints of this model include:

[0099] Constraints for the safe operation of heating networks

[0100] W ij ≤W ij,max

[0101] p w,i,min ≤p w,i ≤p w,i,max

[0102]

[0103] In the formula, W ij,max p represents the maximum water flow velocity at node ij. w,i,max p w,i,min These represent the maximum and minimum head at node i, respectively; T s These represent the maximum and minimum water supply temperatures at node i, respectively. These are the maximum and minimum return water temperatures at node i, respectively;

[0104] Combined heat and power (CHP) unit ramp-up constraints:

[0105]

[0106] In the formula, These are the maximum ramping power of the combined heat and power unit;

[0107] Device operating power consumption constraints:

[0108]

[0109] In the formula, P π t Let π be the power consumption of the device at time t; u π t Let π be the 0-1 state variable of the device at time t; a value of 1 indicates that the device is working. These are the maximum and minimum power consumption of device π, respectively;

[0110] Gas flow balance constraints:

[0111]

[0112] In the formula, G t Let t be the total gas load of the gas network. The density of methane;

[0113] Hydrogen energy balance constraints

[0114]

[0115] In the formula, m t H Let t be the hydrogen load of the system at time t;

[0116] Furthermore, the thermoelectric relationship of hydrogen in a hydrogen fuel cell can be approximated by the following expression:

[0117]

[0118] In the formula, p1, p2, q1, and q2 are the linear fitting coefficients for the electrical power and thermal power of the hydrogen fuel cell, respectively.

[0119] The model established in this invention is not only for a single device, but also expresses the operating characteristics of hydrogen energy equipment such as variable efficiency and multiple operating conditions. It can accurately characterize the coordination and interaction capabilities of hydrogen energy systems with external power systems and heating systems, and thus maximize the optimization of the technical issues of operating the hydrogen energy system with heat recovery. Attached Figure Description

[0120] Figure 1 This is a schematic diagram of the alkaline water electrolysis heat recovery principle in an embodiment of the present invention;

[0121] Figure 2 This is a schematic diagram of the high-temperature water electrolysis heat recovery principle in an embodiment of the present invention;

[0122] Figure 3 Schematic diagram of heat recovery principle in high-temperature water electrolysis;

[0123] Figure 4 This is a diagram showing the production characteristics of low-temperature and high-temperature water electrolysis in the embodiments of the present invention;

[0124] Figure 5 This is a schematic diagram of the heat recovery principle of a hydrogen fuel cell in an embodiment of the present invention.

[0125] Figure 6 A graph showing the relationship between the input and output power of a hydrogen fuel cell.

[0126] Figure 7 A schematic diagram of the IEEE 33 hydrogen energy system simulation network used in the simulation experiment in this embodiment of the invention;

[0127] Figure 8 This is a schematic diagram of the day-ahead source load prediction curve used in the simulation experiment of this invention.

[0128] Figure 9This is a schematic diagram of the optimized operation results of water electrolysis obtained from simulation experiments in an embodiment of the present invention;

[0129] Figure 10 This is a schematic diagram of the optimized operation results of the electro-hydrogen system obtained from the simulation experiment in this embodiment of the invention. Detailed Implementation

[0130] The present invention will be further described below with reference to embodiments, but it should not be construed that the scope of the present invention is limited to the following embodiments. Various substitutions and modifications made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention should be included within the scope of protection of the present invention.

[0131] This embodiment includes the following steps:

[0132] An optimized operating method for an electro-hydrogen energy system considering heat recovery in a hydrogen energy system, the equipment of which includes a water electrolysis unit, a hydrogen fuel cell, a methanation unit, and a combined heat and power (CHP) unit.

[0133] Includes the following steps:

[0134] S1 acquires historical operating data of the energy system and obtains a typical daily source-load curve;

[0135] S2 establishes an equipment operation model that considers heat recovery in the hydrogen energy system based on the equipment operating parameters;

[0136] S3 establishes an energy system model based on the energy system topology;

[0137] S4 aims to minimize system operating costs by establishing a day-ahead optimization operation model for an electric hydrogen energy system that considers heat recovery from the hydrogen energy system.

[0138] S6 solves the optimized operation model to obtain the day-ahead operation plan of the integrated energy system for the hydrogen-electric region.

[0139] The operating data of the energy system includes new energy output, electricity load, gas load, heat load, and hydrogen load.

[0140] In this embodiment, the equipment operation model considering heat recovery in the hydrogen energy system is as follows:

[0141] 1) Low-temperature and high-temperature water electrolysis heat recovery operation model

[0142] Water electrolysis technology is divided into two main categories: low-temperature water electrolysis, represented by alkaline electrolysis and proton exchange membrane electrolysis, and high-temperature water electrolysis, represented by high-temperature solid oxidation electrolysis. Both types of electrolysis technology have the potential for heat recovery and utilization. Among them, the heat recovery principle of low-temperature electrolysis technology is similar; taking the heat recovery and utilization of alkaline water electrolysis as an example... Figure 1This is a schematic diagram of the heat recovery principle of an alkaline water electrolysis system. The electrolyte enters the alkaline electrolysis tank via a circulating pump to electrolyze and generate hydrogen and oxygen. The reaction temperature is approximately 70–90°C. Due to the relatively low reaction temperature, the electrolysis voltage, in addition to producing hydrogen, must overcome the electrolytic polarization reaction. This energy is ultimately dissipated as heat, causing the electrolyte temperature to rise. The high-temperature electrolytic waste liquid (60–80°C) after the reaction can recover the residual heat through a heat exchange device, simultaneously cooling the alkaline solution. The cooled, low-temperature electrolytic waste liquid can be treated and then reused in the next electrolysis cycle, thereby improving the utilization rate of the alkaline solution. Therefore, the heat source for heat recovery in alkaline water electrolysis is the heat released during the electrolysis reaction, and the recovery medium is the high-temperature electrolytic waste liquid.

[0143] Unlike low-temperature water electrolysis systems, high-temperature water electrolysis systems, in order to ensure the required temperature of the raw material gas and the reaction in the electrolyzer, include auxiliary equipment in addition to the high-temperature electrolyzer to provide the necessary heat energy supply, such as preheating devices, heat exchange devices, and electric furnaces. Figure 2 This is a schematic diagram of the heat recovery principle of high-temperature water electrolysis. Room temperature liquid water H₂O(l,T) a The heat is absorbed by the preheating device and heat exchange device 1 to form high-temperature water vapor H2O(g,T). ED The gas is electrolyzed in a high-temperature electrolytic cell to generate high-temperature hydrogen and oxygen. The high-temperature product is then used to heat the feed gas through a heat exchange device 1 to achieve preliminary recovery and utilization of waste heat, reducing the gas temperature to T. out (100~130℃). This part of the gas is cooled to room temperature through heat exchange device 2, and the waste heat is further recovered to the heating network. The final product is processed and stored in hydrogen storage tank and oxygen storage tank.

[0144] Low-temperature and high-temperature water electrolysis operate on the same electrolysis reaction principle; therefore, the following variable descriptions will not differentiate between low-temperature and high-temperature water electrolysis. For a single electrolysis cell, the voltage required for electrolysis can be expressed as:

[0145] U cell (T ED i cell )=U rev +U ohm +U act +U con (1)

[0146]

[0147] In the formula, U cell The electrolysis voltage is related to T. ED and electrolysis current density i cell Related, it can be divided into reversible voltage U rev Ohmic polarization voltage U ohm Activation polarization voltage U act and concentration polarization voltage U con;U th This is the minimum voltage required for electrolysis theory, and it is temperature-dependent, being 1.29V at 800℃ and 1.48V at 25℃; n e U is the molar number of electrons in hydrogen, and F is the Faraday constant. For low-temperature water electrolysis, the electrolysis voltage U is... cell Greater than U th Therefore, under low-temperature conditions, the electrolysis reaction is exothermic; while for high-temperature electrolysis, U cell The situation is much more complex. When U cell >U th At that time, the electrolysis process is exothermic, when U cell th At this time, the high-temperature water electrolysis system exhibits endothermic behavior. According to the energy flow model of water electrolysis, it can be expressed as:

[0148]

[0149] In the formula, P ED,el Energy consumption for high-temperature water electrolysis; P ED,H Energy consumption for high-temperature water electrolysis to produce hydrogen; N cell S represents the number of electrolytic cells; cell This represents the effective area of ​​the electrolytic cell. Eliminating i in the formula... cell P can be obtained ED,el P ED,H and T ED The relationship function between the three is as follows:

[0150]

[0151] Based on the empirical equations for low-temperature and high-temperature water electrolysis, the P values ​​for different types of electrolyzed water can be derived. ED,el P ED,H and T ED See the functional relationship Figure 3 .

[0152] Fig 3The output characteristics of low-temperature and high-temperature electrolysis systems

[0153] During operation, the thermodynamic processes of low-temperature water electrolysis can be characterized using lumped equations, as follows:

[0154]

[0155] In the formula, LED represents low-temperature water electrolysis; C LED This represents the equivalent heat capacity of a low-temperature electrolytic cell; The heat loss of the low-temperature electrolytic cell at time t;​ Let t represent the recoverable thermal energy from the low-temperature electrolyzer at time t. For high-temperature water electrolysis systems, due to auxiliary heating devices and internal thermal circulation systems, the thermodynamic processes differ from those of low-temperature water electrolysis, as detailed below:

[0156]

[0157] In the formula, HED represents high-temperature electrolyzed water; C HED This is the equivalent heat capacity of a high-temperature electrolytic cell; k represents the thermal energy of the discharged gas at time t. rec The heat exchange coefficient between the discharge gas and the feed gas; The heat loss of the high-temperature electrolytic cell at time t; The energy consumption of the high-temperature water electrolysis preheating device at time t is... Let be the heating energy consumption of the high-temperature electrolytic cell at time t. In this embodiment, it is assumed that all heating is done electrically, i.e.:

[0158] P t HED,heat +P t HED,fur =η EB P t EB (7)

[0159] In the formula, Let η be the power consumption for electrolysis heating of water at time t. EB To optimize the efficiency of electric heating, and considering that the thermal time constant of the electrolytic cell is typically much larger than the scheduling timescale, the following thermal steady-state model can be proposed:

[0160]

[0161]

[0162] It can be seen that the electrolyzer exhibits significant heat storage characteristics, and its heat storage capacity depends on the equivalent heat capacity. For low-temperature and high-temperature water electrolysis, the heat loss power consumption during water electrolysis... It can be represented as:

[0163]

[0164] In the formula, R ED T is the equivalent thermal resistance of the electrolytic cell. a This refers to ambient temperature. For normal operation of the electrolytic cell, It needs to be within a certain temperature range, that is:

[0165]

[0166] Considering the operating efficiency of the heat exchanger and water pump, the final recovered heat energy of the low-temperature and high-temperature water electrolysis systems can be expressed as follows:

[0167]

[0168] In the formula, η represents the heat energy recovered from low-temperature and high-temperature water electrolysis at time t, respectively. ED,he The heat exchange efficiency of the heat exchange device.

[0169] 2) Methanation heat recovery operation model

[0170] Methanation is a strongly exothermic reaction. The intense heat of reaction can lead to reduced reaction efficiency and even catalyst sintering, making reactor temperature control crucial. Methanation units typically consist of multiple reactors operating in cascade, with cooling and circulation systems used for temperature control between the reactors. Figure 4 This diagram illustrates a common methanation process, consisting of two methanation reactors and a supplementary methanation reactor. The feed gas enters the two methanation reactors via a circulating compressor and preheating device. The reacted gas is cooled by a heat exchanger before entering the next reactor to continue the reaction. The final reaction gas passes through a gas-liquid separator to separate methane and water vapor, forming the final product gas. Heat exchangers exist between the reactors to cool the reaction gases and achieve heat recovery.

[0171] According to the principle of methanation reaction, the reactants and products must satisfy a molar balance relationship, that is:

[0172]

[0173] In the formula, t represents the rate at which the reactor consumes carbon dioxide and hydrogen, respectively. Let n be the rate and molar rate of methane production in the reactor at time t, respectively; CH4-H The molar ratio of methane and hydrogen produced in the reaction; These are the relative molecular masses of carbon dioxide, hydrogen, and methane, respectively.

[0174] Therefore, the heat generated during the methanation process is as follows:

[0175]

[0176] In the formula, η is the heat consumption generated by methanation at time t; MR ΔH represents the efficiency of the methanation reaction; ΔH is the heat released per mole of methane produced by methanation, which is 165 kJ / mol.

[0177] The final thermal energy recovered by the methanation unit can be expressed as:

[0178]

[0179] In the formula, η represents the thermal energy recovered by the methanation unit at time t; MR,heat The efficiency of the heat exchanger in the methanation unit.

[0180] 3) Hydrogen fuel cell heat recovery model

[0181] Hydrogen fuel cells generate electricity through the redox reaction of hydrogen and oxygen in a hydrogen fuel cell stack. The generated electricity is then transmitted to the power grid via a converter. Simultaneously, waste heat from the stack can be recovered through a heat exchange device and connected to a district heating network, achieving combined heat and power (CHP) with an overall efficiency of 80-90%. The principle of heat recovery in hydrogen fuel cells is explained in [link to documentation]. Figure 5 .

[0182] This embodiment selects a high-temperature solid oxide hydrogen fuel cell as the research object. The physical model of hydrogen fuel cell cogeneration can be characterized by the following empirical equation:

[0183]

[0184] in:

[0185]

[0186] In the formula, Let t be the amount of hydrogen consumed by the hydrogen fuel cell. The power generation and heat generation of the hydrogen fuel cell at time t are respectively, and η FC,e η FC,h This relates to the power generation and heat production efficiency of hydrogen fuel cells. The thermoelectric relationship of hydrogen in a hydrogen fuel cell is as follows: Figure 6 As shown, by performing a linear fit, the following approximate expression can be obtained:

[0187]

[0188] In the formula, p1, p2, q1, and q2 are the linear fitting coefficients for the electrical power and thermal power of the hydrogen fuel cell, respectively.

[0189] 4) Hydrogen energy system heat recovery model

[0190] The hydrogen energy system incorporates a thermal energy management system. This system controls the cooling mass flow rate and temperature of the water electrolysis, hydrogen fuel cell, and methanation equipment, thereby controlling the operating temperature of the equipment and the recovered thermal energy. The hydrogen energy system is connected to an external heating network via a heat exchange device and a heat pump, achieving coupling with the external heating system. Based on the law of conservation of energy, this embodiment establishes a heat recovery and utilization model for the hydrogen energy system, as detailed below:

[0191]

[0192] In the formula, η represents the thermal energy recovered and utilized by the hydrogen energy system at time t; he The heat exchange efficiency of the heat exchange device.

[0193] The energy system model in this embodiment is as follows:

[0194] 1) Distribution network power flow model

[0195] The Lindistflow power flow model is widely used in radial distribution network power flow calculation and modeling, as detailed below:

[0196]

[0197]

[0198]

[0199]

[0200]

[0201] In the formula, P represents the squares of the voltages at nodes i and j, respectively; ij Q ij These represent the active and reactive power of branch ij, respectively; P i Q i These represent the net inflow of active and reactive power at nodes i and j, respectively; r ij x ij Let be the resistance and reactance of branch ij, respectively; These are the squares of the minimum and maximum node voltages, respectively, with V0 being the square of the balancing node voltage; S ij,max This represents the maximum transmission capacity of branch ij.

[0202] 2) Heat distribution network flow model

[0203] For a heating network, the water flow balance at each node can be expressed as:

[0204] A DHN W ij =W node (25)

[0205] In the formula, A DHN W is the branch correlation matrix of the heating network nodes. ij For the branch flow matrix, W node Let be the flow matrix of the nodes. The head at each node can be represented as:

[0206]

[0207] In the formula, pw,i The water head at node i; K is the equivalent roughness parameter of the water pipe; l ij Let be the length of the water pipe at nodes i and j; be the density of water; d be the inner diameter of the water pipe; W ij Let be the water flow velocity at node ij.

[0208] Heat distribution networks typically have short distribution distances, so heat loss during heat transfer can be ignored. Therefore, for each node, the supply and return water temperatures can be expressed as:

[0209]

[0210] In the formula, These are the supply and return water temperatures for node i, respectively. These are the supply and return water temperatures for the heat source and heat load nodes, respectively. Let be the water flow velocities at the heat source and heat load nodes, respectively; e(i) is the set of nodes ending at node i, and s(i) is the set of nodes starting at node i.

[0211] For each heat source and heat load node, the released and absorbed heat energy can be expressed as:

[0212]

[0213] In the formula, These are the heat energy released by the heat source and the heat energy absorbed by the heat load, respectively; c w is the specific heat capacity of the working fluid.

[0214] 3) Cogeneration unit operation model

[0215] A combined heat and power (CHP) unit generates electricity and heat by burning natural gas. Its mathematical model can be expressed as:

[0216]

[0217] In the formula, P CHP Q CHP These represent the power generation and heat generation of the combined heat and power unit, respectively. CHP B CHP C CHP These are the boundary vectors for the operation of the combined heat and power (CHP) unit. The gas consumption of the CHP unit can be expressed as:

[0218]

[0219] In the formula, Let η be the gas consumption of the cogeneration unit at time t. CHP For the operating efficiency of combined heat and power units, LHV gas It has the low calorific value of natural gas.

[0220] The day-ahead optimization operation model established in this embodiment is as follows:

[0221] (1) The objective of the optimization model proposed in this embodiment is to minimize the operating cost C of the regional integrated energy system. The operating cost includes energy purchase cost, operation and maintenance cost, carbon emission cost, load curtailment penalty cost, and energy sales revenue, as detailed below:

[0222]

[0223]

[0224]

[0225]

[0226]

[0227]

[0228] In the formula, These are the system energy purchase cost, operation and maintenance cost, carbon emission cost, load curtailment penalty cost, and energy sales revenue at time t, respectively. Let t be the unit price at which the system purchases electricity from the upper-level power grid. Let be the interaction power between the system and the upstream power grid at time t. When the power is at a certain time, it indicates that electricity is purchased from the upstream power grid; conversely, it indicates that electricity is fed back to the grid. To address the absolute value nonlinear term in the formula, an auxiliary variable is introduced. And add constraints Linearize it; c gas,buy This refers to the unit price for purchasing gas. Let N be the amount of natural gas purchased at time t; N is the set of all equipment, including water electrolysis, hydrogen fuel cells, CHP, etc. Let P be the unit maintenance cost of the nth device. t,n c represents the power consumption of the nth device at time t. em For the unit carbon emission cost, λ e , λ gas Carbon emissions per unit of electricity and gas consumption, respectively, λ H For the unit carbon emissions of hydrogen industrial production, the system can reduce carbon emissions from industrial hydrogen production by selling hydrogen to the hydrogen energy market; e,p c heat,p c gas,p c H,p The penalty prices per unit for abandoned electricity, heat, gas, and hydrogen are respectively. These represent the system's abandoned power, abandoned heat, abandoned gas, and abandoned hydrogen at time t, respectively; c H,sell This refers to the unit price of hydrogen sold. Let t be the amount of hydrogen sold by the system at time t.

[0229] (2) Constraints

[0230] Constraints for the safe operation of heating networks

[0231] To ensure the safe and stable operation of the heating network, the following constraints must be met:

[0232] W ij ≤W ij,max (37)

[0233] p w,i,min ≤p w,i ≤p w,i,max (38)

[0234]

[0235] In the formula, W ij,max p represents the maximum water flow velocity at node ij. w,i,max p w,i,min These are the maximum and minimum head at node i, respectively; These represent the maximum and minimum water supply temperatures at node i, respectively. These represent the maximum and minimum return water temperatures at node i, respectively.

[0236] 1) Climbing constraints of cogeneration units

[0237]

[0238] In the formula, These are the maximum ramping power of the combined heat and power (CHP) unit.

[0239] 2) Equipment operating power consumption constraints

[0240] To ensure the safe and stable operation of the system, the power consumption of the devices in the system must meet the following requirements:

[0241]

[0242] In the formula, P π t The power consumption of device π at time t, including water electrolysis, hydrogen fuel cells, methanation devices, etc.; u π t Let π be the 0-1 state variable of the device at time t; a value of 1 indicates that the device is working. These represent the maximum and minimum power consumption of device π, respectively.

[0243] 3) Gas flow balance constraint

[0244] In the formula, G t Let t be the total gas load of the gas network. The density is that of methane.

[0245] 4) Hydrogen energy balance constraints

[0246] Hydrogen produced by water electrolysis can be used for hydrogen loads, sold to the hydrogen energy market, methanation, or hydrogen fuel cell reactions, as detailed below:

[0247]

[0248] In the formula, Let t be the hydrogen load of the system at time t.

[0249] This embodiment also includes a simulation of the distribution process in this invention, using the IEEE 33 hydrogen energy system simulation network for the simulation, such as... Figure 7 As shown in the table. The hydrogen energy system is connected to the grid at node N10, the heating network at node H3, and the gas network at node G1. Photovoltaic and wind turbines are connected to the grid at nodes N22, N25, and N33, respectively. The CHP unit is connected to the grid at node N18, the heating network at node H7, and the gas network at node G6. Electricity purchased from the upstream grid is subject to time-of-use pricing. System and equipment parameters are shown in Table 1. Parameters for low-temperature and high-temperature water electrolysis are shown in the table below.

[0250] Figure 8 The regional day-ahead source-load forecast curves used for simulation include new energy output, electricity load, gas load, heat load, and hydrogen load.

[0251] In the simulation, commercial software was used to solve the optimized operation model and obtain the day-ahead operation plan of the integrated energy system for the hydrogen-electric region.

[0252] To study the impact of hydrogen energy system heat recovery on the operation of regional integrated energy systems, this embodiment sets up the following scenarios for comparative analysis.

[0253] Scenario 1: The water electrolysis device uses low-temperature water electrolysis, and heat recovery of the hydrogen energy system is not considered;

[0254] Scenario 2: The water electrolysis device uses low-temperature water electrolysis, while also considering heat recovery from the hydrogen energy system;

[0255] Scenario 3: The water electrolysis device uses high-temperature water electrolysis, without considering heat recovery from the hydrogen energy system;

[0256] Scenario 4: The water electrolysis device uses high-temperature water electrolysis, while also considering the heat recovery and utilization of the hydrogen energy system.

[0257] Figure 9The figures show the operating results of the low-temperature and high-temperature electrolyzed water electrolyzers in scenarios 2 and 4, respectively, regarding temperature and heat recovery. As can be seen from the figures, there are significant differences in the operating results of low-temperature and high-temperature electrolyzed water after considering heat recovery, mainly reflected in the heat recovery capacity (QED) and operating temperature (TED). Regarding heat recovery QED, the maximum heat recovery power consumption of low-temperature electrolyzed water is approximately 700kW, while that of high-temperature electrolyzed water is 500kW. The heat recovery capacity of low-temperature electrolyzed water is higher than that of high-temperature electrolyzed water for the same capacity. This is mainly because a portion of the heat generated by high-temperature electrolyzed water is used for internal heat circulation, resulting in less output heat energy.

[0258] Regarding the operating temperature (TED), low-temperature electrolyzed water heats up approximately from 0:00 to 6:00 and from 11:00 to 16:00, and cools down from 7:00 to 11:00 and from 16:00 to 23:00. High-temperature electrolyzed water only heats up from 11:00 to 15:00 and cools down from 19:00 to 24:00. This indicates that both low-temperature and high-temperature electrolyzed water cool down between 19:00 and 23:00, primarily because hydrogen demand is lower and heat demand is higher during this period. To meet the nighttime heat demand, the electrolyzed water lowers the electrolyzer reaction temperature, increasing heat generation efficiency while releasing the stored heat energy. However, the operating temperatures of low-temperature and high-temperature water electrolysis differ significantly between 0:00 and 8:00. This is mainly because the heat load is higher during this period. High-temperature electrolyzers can achieve greater heat output by operating at low temperatures, while low-temperature water electrolyzers need to increase the reaction temperature to achieve greater hydrogen output in order to meet the peak hydrogen load demand from 8:00 to 9:00. Therefore, the water electrolysis system possesses a certain degree of flexible electrothermal regulation and heat storage capacity, allowing it to control heat recovery and operating temperature according to external energy demand, achieving coordinated operation of electricity, heat, and hydrogen.

[0259] To illustrate the impact of hydrogen energy system heat recovery on grid operation, a comparative analysis is conducted using the operating results of scenarios 3 and 4 as examples. Figure 10 The figures show the results for electricity consumption in water electrolysis, CHP power generation, and wind and solar curtailment in scenarios 3 and 4. As the figures show, wind and solar curtailment in scenario 3 mainly occurs between 3:00 AM and 5:00 AM. This is because the CHP unit operates in a "heat-driven power generation" mode. To meet the high heat load demand during this period, its power output adjustment range is limited. Meanwhile, wind power output is high during this time, making it difficult to absorb a large amount of wind power, thus resulting in curtailment. In scenario 4, the system's nighttime wind curtailment is zero. This is mainly because the hydrogen energy system's heat recovery and utilization reduces the heat output pressure of the CHP unit, increases its power output adjustment range, and further reduces wind curtailment. Therefore, hydrogen energy system heat recovery can effectively promote the coordinated operation of the system's electricity and heat, alleviate the electricity-heat coupling operation characteristics of the CHP unit, and promote wind power absorption.

[0260] Table 1. Results of system operating costs and wind / solar curtailment rates in different scenarios.

[0261]

[0262] *Unit: RMB 10,000

[0263] Table 1 shows the system operating costs and wind / solar curtailment rates for four scenarios. The total operating costs for scenarios 1 and 2 are RMB 93,600 and RMB 70,300, respectively; the total operating costs for scenarios 3 and 4 are RMB 85,300 and RMB 69,500, respectively. Considering hydrogen energy system heat recovery, the total costs are reduced by 24.9% and 18.6%, respectively. The wind / solar curtailment rates for each scenario are 10.25%, 0.22%, 8.8%, and 0.09%, respectively. This indicates that hydrogen energy system heat recovery significantly improves system operating efficiency, mainly because it reduces the heating demand and wind / solar curtailment of the CHP unit, thereby reducing gas and electricity purchase costs. Therefore, hydrogen energy system heat recovery can effectively reduce system operating costs and wind / solar curtailment, further demonstrating the superiority of hydrogen energy system heat recovery.

[0264] Table 2. Impact of heat recovery on the energy efficiency of hydrogen energy equipment

[0265]

[0266] Table 2 shows the impact of heat recovery on the energy efficiency of hydrogen energy equipment. As can be seen from the table, heat recovery can significantly improve the energy efficiency of hydrogen energy equipment, with absolute increases in energy efficiency of low-temperature water electrolysis, high-temperature water electrolysis, hydrogen fuel cells, and methanation being 23.8%, 14.1%, 33.3%, and 12.6%, respectively.

Claims

1. A day-ahead optimization operation method for an electro-hydrogen energy system considering heat recovery in a hydrogen energy system, characterized in that, The equipment in the electric hydrogen energy system includes water electrolysis devices, hydrogen fuel cells, methanation devices, and combined heat and power devices; Includes the following steps: S1 acquires historical operating data of the energy system, including new energy output data, electricity load data, gas load, heat load and hydrogen load data; S2 establishes an equipment operation model that considers heat recovery in the hydrogen energy system based on equipment operating parameters, including: 1) Low-temperature and high-temperature water electrolysis heat recovery operation models, including For a single electrolytic cell, the voltage required for electrolysis can be expressed as: In the formula, The electrolysis voltage is the same as the voltage at which the electrolysis voltage is applied. and electrolysis current density Related, they can be divided into reversible voltages. Ohmic polarization voltage Activation polarization voltage and concentration polarization voltage ; This is the minimum voltage required for electrolysis theory, which is temperature-dependent, at 1.29V at 800℃ and 1.48V at 25℃. The molar number of electrons in hydrogen. It is Faraday's constant; The energy flow model for water electrolysis can be expressed as: In the formula, Energy consumption for high-temperature water electrolysis; Energy consumption for high-temperature water electrolysis to produce hydrogen; The thermodynamic process of low-temperature water electrolysis is characterized by lumped equations, as follows: In the formula, LED represents low-temperature water electrolysis; This represents the equivalent heat capacity of a low-temperature electrolytic cell; The heat loss of the low-temperature electrolytic cell at time t; The thermal energy that can be recovered from the low-temperature electrolytic cell at time t; The specific thermodynamic processes of the high-temperature water electrolysis system are as follows: In the formula, HED represents high-temperature electrolyzed water; This is the equivalent heat capacity of the high-temperature electrolytic cell; Let t be the thermal energy of the discharged gas. The heat exchange coefficient between the discharge gas and the feed gas; The heat loss of the high-temperature electrolytic cell at time t; The energy consumption of the high-temperature water electrolysis preheating device at time t is... Let be the heating energy consumption of the high-temperature electrolytic cell at time t, assuming that all heating is done electrically, i.e.: In the formula, The power consumption for electrolysis heating of water at time t. To improve the efficiency of electric heating; The thermal steady-state model is established as follows: The heat loss power consumption of water electrolysis Represented as: In the formula, This is the equivalent thermal resistance of the electrolytic cell. The ambient temperature; Maintain within a certain temperature range, that is: The final recovered heat energy of the low-temperature and high-temperature water electrolysis systems are expressed as follows: In the formula, , These represent the heat energy recovered during low-temperature and high-temperature water electrolysis at time t, respectively. The heat exchange efficiency of the heat exchange device; 2) Methanation heat recovery operation model, including, The reactants and products must satisfy a molar balance relationship, namely: In the formula, , t represents the rate at which the reactor consumes carbon dioxide and hydrogen, respectively. , These represent the rate and molar rate of methane production in the reactor at time t, respectively. The molar ratio of methane and hydrogen produced in the reaction; , , These are the relative molecular masses of carbon dioxide, hydrogen, and methane, respectively. The heat generated during the methanation process is represented as follows: In the formula, The heat consumption of methanation at time t; The efficiency of the methanation reaction is given by ΔH, which is the heat released per mole of methane produced by methanation, and is 165 kJ / mol. The final thermal energy recovered by the methanation unit is expressed as follows: In the formula, The thermal energy recovered by the methanation unit at time t; For the heat exchanger efficiency of the methanation unit; 3) Hydrogen fuel cell heat recovery model, including, The physical model for hydrogen fuel cell cogeneration is characterized as follows: In the formula, Let t be the amount of hydrogen consumed by the hydrogen fuel cell. These represent the power generation and heat generation of the hydrogen fuel cell at time t, respectively. To improve the power generation efficiency and heat production efficiency of hydrogen fuel cells; 4) Hydrogen energy system heat recovery model, including, The heat recovery and utilization model for a hydrogen energy system is expressed as follows: In the formula, Let t be the thermal energy recovered and utilized by the hydrogen energy system at time t; The heat exchange efficiency of the heat exchange device; S3 establishes an energy system model based on the energy system topology; 1) Distribution network power flow model, as follows: In the formula, These are the squares of the voltages at nodes i and j, respectively. These are the active and reactive power of branch ij, respectively; These represent the net inflow of active and reactive power at nodes i and j, respectively. Let be the resistance and reactance of branch ij, respectively; These are the squares of the minimum and maximum node voltages, respectively, with V0 being the square of the balanced node voltage. The maximum transmission capacity of branch ij; 2) Heat distribution network power flow model, including, The flow balance at each node is represented as follows: In the formula, This is the branch correlation matrix of the heating network nodes. For the branch flow matrix, For the node flow matrix; The nodal head is represented as: In the formula, is the head of node i; K is the equivalent roughness parameter of the water pipe. Let be the length of the water pipe at nodes i and j; be the density of water; and d be the inner diameter of the water pipe. Let ij be the water flow velocity at node ij; The supply and return water temperatures at the node are expressed as follows: In the formula, These are the supply and return water temperatures for node i, respectively. These are the supply and return water temperatures for the heat source and heat load nodes, respectively. These are the water flow velocities at the heat source and heat load nodes, respectively. Let i be the set of nodes whose last node is node i. Let i be the set of nodes starting with node i. The heat energy released and absorbed by heat source and heat load nodes is represented as: ； In the formula, These are the heat energy released by the heat source and the heat energy absorbed by the heat load, respectively. Specific heat capacity of the working fluid; 3) Cogeneration unit operation model, including, The combined heat and power (CHP) unit model is represented as follows: In the formula, These represent the power generation and heat generation capacity of the combined heat and power unit, respectively. These are the boundary vectors for the operation of the combined heat and power unit; The gas consumption of a combined heat and power (CHP) unit is expressed as follows: In the formula, Let t be the gas consumption of the combined heat and power unit. To improve the operating efficiency of combined heat and power units, It has the low calorific value of natural gas; S4 aims to minimize system operating costs by establishing a day-ahead optimization operation model for an electric hydrogen energy system that considers heat recovery from the hydrogen energy system. The current optimized operating model is as follows: In the formula, These are the system energy purchase cost, operation and maintenance cost, carbon emission cost, load curtailment penalty cost, and energy sales revenue at time t, respectively. Let t be the unit price at which the system purchases electricity from the upper-level power grid. Let be the interaction power between the system and the upstream power grid at time t. When the power source is at a certain time, it indicates that electricity is purchased from the upstream power grid; conversely, it indicates that electricity is fed back to the grid. The absolute value nonlinear term in the expression is addressed by introducing an auxiliary variable. And add constraints Linearize it; This refers to the unit price for purchasing gas. Let be the amount of natural gas purchased at time t; N is the set of all equipment, including water electrolysis, hydrogen fuel cells, and CHP. The unit maintenance cost for the nth device. Let be the power consumption of the nth device at time t; Cost per unit of carbon emissions These are the carbon emissions per unit of electricity consumption and gas consumption, respectively. To reduce the carbon emissions per unit of hydrogen production in the industrial sector, the system can reduce carbon emissions from industrial hydrogen production by selling hydrogen to the hydrogen energy market. The penalty prices per unit for abandoned electricity, heat, gas, and hydrogen are respectively. These represent the system's abandoned power, abandoned heat, abandoned gas, and abandoned hydrogen at time t, respectively. This refers to the unit price of hydrogen sold. Let t be the amount of hydrogen sold by the system at time t; The constraints of this model include: Constraints for the safe operation of heating networks In the formula, The maximum water flow velocity at node ij; These are the maximum and minimum head at node i, respectively; These represent the maximum and minimum water supply temperatures at node i, respectively. These are the maximum and minimum return water temperatures at node i, respectively; Combined heat and power (CHP) unit ramp-up constraints: In the formula, These are the maximum ramping power of the combined heat and power unit; Device operating power consumption constraints: ； In the formula, Let π be the power consumption of the device at time t; Let π be the 0-1 state variable of the device at time t; a value of 1 indicates that the device is working. These are the maximum and minimum power consumption of device π, respectively; Gas flow balance constraints: In the formula, G t Let t be the total gas load of the gas network. The density of methane; Hydrogen energy balance constraints In the formula, Let t be the hydrogen load of the system at time t; S5 solves the optimized operation model to obtain the day-ahead operation plan of the integrated energy system for the hydrogen-electric region.

2. The method according to claim 1, characterized in that, In the hydrogen fuel cell heat recovery model, the hydrogen thermoelectric relationship of the hydrogen fuel cell is expressed by the following approximate expression: In the formula, p1, p2, q1, and q2 are the linear fitting coefficients for the electrical power and thermal power of the hydrogen fuel cell, respectively.

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