Electrolytic hydrogen production and fuel cell waste heat gradient utilization system and method based on organic Rankine cycle

Abstract

The invention relates to an electrolytic hydrogen production and fuel cell waste heat gradient utilization system and method based on an organic Rankine cycle, and belongs to the field of new energy. The system comprises a wind power generation unit, a photovoltaic power generation unit, a storage battery energy storage system, an electrolytic hydrogen production device, a hydrogen storage system, a fuel cell power generation unit, a waste heat utilization unit and an organic Rankine cycle device, and can be used for realizing multi-element consumption and gradient utilization of renewable energy sources. The method specifically comprises the following steps: establishing equipment models in a system, wherein an electrolytic bath considers five states of shutdown, cold start, standby, hot start and standby; on the basis of a mixed integer linear programming method, operation constraints of all equipment, renewable energy output prediction and electricity, heat and hydrogen load requirements are integrated, an optimization scheduling model meeting the electricity, heat and hydrogen load requirements and economical efficiency of the system is constructed, output of all the equipment is coordinated, and finally the optimization targets of maximizing the economical efficiency of the system and meeting the electricity, heat and hydrogen load requirements of the system are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of renewable energy hydrogen production and waste heat utilization, and specifically relates to a system and method for electrolytic hydrogen production and fuel cell waste heat cascade utilization based on an organic Rankine cycle. Background Art

[0002] Electrolyzers and hydrogen fuel cells are core components of renewable energy hydrogen production systems. However, their operation generates significant amounts of low-grade waste heat. During the electrolysis of water to produce hydrogen, the electrolyzer's conversion efficiency is not 100%, resulting in a portion of the electricity being lost as heat. Hydrogen fuel cells also generate electricity through electrochemical reactions, releasing significant amounts of heat. Currently, the utilization of this waste heat is extremely limited, often simply used for low-grade heating. Due to a lack of scientific heat management and optimized configuration, significant amounts of heat are lost during transportation and use, failing to fully realize its value. More critically, existing technologies operate the hydrogen electrolysis system and the fuel cell system independently, lacking an effective mechanism for synergistically utilizing their waste heat resources. This lack of cascaded utilization and complementary allocation of waste heat results in significant waste of waste heat resources, reducing the overall energy efficiency of the renewable energy hydrogen production system and hindering efficient energy recycling, resulting in significant energy waste and economic losses. Summary of the Invention

[0003] Based on this, the present invention provides a system and method for cascade utilization of hydrogen production by electrolysis and fuel cell waste heat based on an organic Rankine cycle, which uses wind power generation and photovoltaic power generation to provide electricity to the system, and uses the waste heat generated by hydrogen production by electrolysis and fuel cells to supply heat loads or generate electricity through an organic Rankine cycle device, thereby improving energy utilization efficiency.

[0004] To achieve the above objectives, the technical solutions of the present invention are as follows:

[0005] This invention provides a cascaded system for hydrogen production through electrolysis and fuel cell waste heat utilization based on the organic Rankine cycle (ORC). The system includes wind power generation, photovoltaic power generation, a hydrogen production electrolyzer, a compressor, a hydrogen storage tank, a hydrogen fuel cell, a heat storage tank, a battery, and an ORC power generation device. The system, which includes but is not limited to the aforementioned components, is particularly suitable for low-carbon energy supply scenarios in microgrids and industrial parks.

[0006] The wind power generation unit converts wind energy into electrical energy through a wind turbine generator set to supply power to the electrolytic hydrogen production device and the power load system, and the excess electrical energy is stored in the battery energy storage system;

[0007] The photovoltaic power generation unit converts solar energy into electrical energy through a photovoltaic power station to supply power to the electrolytic hydrogen production device and the power load system, and the excess electrical energy is stored in the battery energy storage system;

[0008] The battery energy storage system discharges electricity to support the power load system when wind power / photovoltaic power output is insufficient or during peak power consumption periods; and stores excess electricity when wind power / photovoltaic power output is excessive.

[0009] Preferably, electrical energy is converted into hydrogen energy through an alkaline electrolyzer or a proton exchange membrane electrolyzer, which is then pressurized by a compressor and stored in a hydrogen storage tank; the waste heat generated during the electrolysis process is recovered through a heat exchanger to meet user heat needs or drive an organic Rankine cycle device to generate electricity.

[0010] Preferably, when there is insufficient electricity from wind power generation and photovoltaic power generation or when electricity consumption is at a peak, the stored hydrogen is converted into electrical energy through a hydrogen fuel cell, which works together with the battery energy storage system to support the power load. The waste heat generated during the operation is recovered through a heat exchanger to meet the user's heat needs or drive the organic Rankine cycle device to generate electricity.

[0011] Preferably, in the waste heat utilization unit, the organic Rankine cycle device uses a low-boiling-point organic working fluid, and automatically starts when the system heat load demand is fully met or the system optimization operation strategy determines that waste heat power generation is more economical, and converts the recovered waste heat into electrical energy through the organic Rankine cycle. The generated electricity is stored in a battery energy storage system or directly supplied to the power load.

[0012] The method for electrolysis hydrogen production and fuel cell waste heat cascade utilization based on the organic Rankine cycle includes:

[0013] S1: Establish a multi-energy flow coupled system model including wind power generation, photovoltaic power generation, hydrogen production electrolyzer, compressor, hydrogen storage tank, hydrogen fuel cell, heat storage tank, battery and organic Rankine cycle power generation device;

[0014] S2: During the electrolyzer modeling phase, a refined model is established that considers the switching logic of the five operating states (shutdown, cold start, standby, hot start, and hydrogen production), including constraints such as state transition time, upper and lower limits of operating power, and waste heat recovery.

[0015] S3: In the hydrogen fuel cell modeling phase, a detailed hydrogen fuel cell model is established, including constraints such as start-stop constraints, operating power limits, and waste heat recovery.

[0016] S4: Considering the upper and lower operating limits of the equipment, establish mathematical models of the compressor, hydrogen storage tank, battery and heat storage tank;

[0017] S5: Organic Rankine cycle system modeling stage, building a heat-to-electricity conversion model based on the organic working fluid characteristic curve;

[0018] S6: In the optimization solution phase, based on the mixed integer linear programming (MILP) method, the operating constraints of each device, the output forecast of renewable energy, and the electricity, heat, and hydrogen load requirements are integrated to build an optimal scheduling model that meets the system's electricity, heat, and hydrogen load requirements and economic efficiency. The output of each device is coordinated to ultimately achieve the optimization goals of maximizing system economic efficiency and meeting the system's electricity, heat, and hydrogen load requirements.

[0019] Preferably, in S2, the refined mathematical model of the hydrogen production electrolyzer is as follows:

[0020] Considering that the hydrogen production electrolyzer switches between five states: shutdown, cold start, standby, hot start, and hydrogen production, the state of the hydrogen production electrolyzer is represented by the logical variable δ:

[0021]

[0022] When the hydrogen production electrolyzer is in the hydrogen production state, the relationship between its hydrogen production mass rate and power consumption can be expressed as:

[0023]

[0024] When in the shutdown state, the relationship between its hydrogen production mass rate and power consumption can be expressed as:

[0025]

[0026] In the standby state, the relationship between the hydrogen production mass rate of the hydrogen production electrolyzer and its power consumption can be expressed as:

[0027]

[0028] In the hot start state, the hydrogen production electrolyzer starts to produce hydrogen by electrolysis at the first moment. The relationship between its hydrogen production mass rate and power consumption is the same as that of the electrolyzer in the hydrogen production state, which can be expressed by formula (2).

[0029] In the cold start working state, the hydrogen production electrolyzer starts cold starting from the shutdown state and needs a certain time L to preheat until the temperature in the small chamber reaches the electrolysis requirement before electrolysis and hydrogen production begins. Assuming that the hydrogen production electrolyzer starts cold starting at time k0, the relationship between its hydrogen production mass rate and power consumption can be expressed as:

[0030]

[0031] Where, is the hydrogen production mass rate of the hydrogen production electrolyzer, P e is the power consumed by the hydrogen production electrolyzer, a1, a2, a n , a, b1, b2, b n , b are fitting coefficients, P eminand P emax Respectively represent the minimum and maximum values ​​allowed for the power consumption of the hydrogen production electrolyzer. STB It indicates the power consumed to maintain the temperature in the electrolytic cell chamber when the alkaline electrolytic cell is in standby mode.

[0032] Electrolytic cell heat generation model:

[0033]

[0034] P heat_el (k) = (1-η el (k))*P e (k) (7)

[0035] Where η e is the hydrogen production efficiency of the hydrogen production electrolyzer, NHV is the higher calorific value of hydrogen, P heat_e is the heat generation power of the hydrogen production electrolyzer.

[0036] Preferably, in S3, the refined mathematical model of the hydrogen fuel cell is as follows:

[0037] When a hydrogen fuel cell is in operation, the relationship between its output power and the mass rate of hydrogen consumption can be expressed as:

[0038]

[0039] When the hydrogen fuel cell is in the shutdown state, the relationship between the gas production power and the hydrogen mass consumption rate can be expressed as:

[0040]

[0041] Hydrogen fuel cell heat generation model:

[0042]

[0043] P heat_f (k) = (1-η f (k))*P f (k) (11)

[0044] Where η f is the fuel cell power generation efficiency, P heat_f is the heat generation power of the fuel cell.

[0045] In the electricity-heat-hydrogen cogeneration system method, in S4, the mathematical model of the compressor is as follows:

[0046]

[0047] Where, represents the mass rate of hydrogen entering the compressor, Indicated at reference pressure The power consumed by the compressor, β c Indicates the pressure under which the compressor works normally, β0 is the standard atmospheric pressure, γ c Indicates the dissipation rate of hydrogen from the alkaline electrolyzer to the compressor.

[0048] To ensure the normal operation of the compressor, the operating power required during its operation must meet the following conditions:

[0049]

[0050] Where, is the rated power of the compressor.

[0051] In the electricity-heat-hydrogen cogeneration system method, in S4, the mathematical model of the hydrogen storage tank is as follows:

[0052]

[0053] Where, E tk Indicates the quality of hydrogen in the hydrogen storage tank, is the hydrogen required by the system, usually understood as the hydrogen sold, and Δt is the sampling time.

[0054] To ensure safe and efficient operation, the quality of hydrogen in the hydrogen storage tank must meet the following constraints:

[0055]

[0056] E tk (0) = E tkmin (17)

[0057] Where, and They represent the lower and upper limits of the hydrogen storage tank capacity respectively.

[0058] In the electricity-heat-hydrogen cogeneration system method, in S4, the mathematical model of the battery is as follows:

[0059] E b (k+1)=E b (k)-P b (k)Δt (18)

[0060]

[0061] Where, E b is the remaining energy in the lithium battery pack; P b is the battery charging and discharging power, when P b When it is negative, it means the lithium battery is charging; when P b When it is positive, it means the lithium battery is discharging. and Respectively represent the minimum and maximum values ​​of battery charge and discharge power. and Respectively represent the lower and upper limits of battery capacity.

[0062] Assuming that at the end of each day, the lithium battery energy storage state is forced to return to its initial value, it can be expressed as:

[0063] E b (n d ×N s +1)=E b (1) (21)

[0064] Preferably, in S4, the mathematical model of the heat storage tank is as follows:

[0065] E h (k+1)=E h (k)-P h (k)Δt (22)

[0066]

[0067] Where, E h Indicates the power in the heat storage tank, P h Charge and discharge heat power for the heat storage tank, and They represent the minimum and maximum values ​​of the charging and discharging power of the heat storage tank respectively. and Respectively represent the lower and upper limits of the heat storage tank capacity.

[0068] In the electricity-heat-hydrogen cogeneration system method, in S5, the mathematical model of the organic Rankine cycle is as follows:

[0069] P ORC,e (k) = η ORC P ORC (k) (25)

[0070]

[0071] Where, P ORC,e represents the input thermal power of the organic Rankine cycle device, P ORC is the output power of the organic Rankine cycle, η ORC is the conversion efficiency of the organic Rankine cycle, Indicates the rated thermal power of the organic Rankine cycle.

[0072] In the electricity-heat-hydrogen cogeneration system method, in S6, the electricity-heat-hydrogen system optimization scheduling model considering the output of renewable energy and the uncertainty of electricity, heat, and hydrogen loads is as follows:

[0073] (1) Objective function

[0074] Aims to maximize the economic efficiency of the electricity-heat-hydrogen system (represented by the first and second terms of the objective function) while meeting the electricity, heat and hydrogen load demands as much as possible.

[0075]

[0076] Where, σ ele is the grid-connected electricity price, N y is the total length of sampling time, P g is the grid-connected power, is the selling price of hydrogen, J load 、J hydrogen and J heat They represent the penalty costs when the electric load, hydrogen load and thermal load are not met.

[0077] (2) Constraints

[0078] Power constraints for wind turbines, photovoltaics, electric loads, hydrogen loads, and thermal loads:

[0079] 0≤P w (k)≤P wmax (k) (28)

[0080] 0≤P v (k)≤P vmax (k) (29)

[0081] 0≤P load1 (k)≤P load (k) (30)

[0082] 0≤P hload1 (k)≤P hload (k) (31)

[0083] 0≤P heat1 (k)≤P heat (k) (32)

[0084] Grid-connected power fluctuation constraints:

[0085] -ξ g ≤E g (k+1)=P g (k+1)-P g (k)≤ξ g (33)

[0086] System electric power balance constraints:

[0087] P w (k)+P v (k)+Pf (k) = P g (k)+P load1 (k)+P e (k)+P c (k)+P b (k) (34)

[0088] Other constraints:

[0089] Electrolyzer operation constraints: (2) to (7)

[0090] Hydrogen fuel cell operation constraints: (8) to (11)

[0091] Compressor operating constraints: (14)

[0092] Hydrogen storage tank constraints: (16) to (17)

[0093] Battery constraints: (19) to (21)

[0094] Heat storage tank constraints: (23)~(24)

[0095] Organic Rankine cycle operating constraints: (26)

[0096] Where, P w and P v Represent the actual output of wind farm and photovoltaic power station respectively, P wmax and P vmax They represent the maximum output of wind farm and photovoltaic power station respectively, P load1 and P load They represent the actual power load provided by the system and the power load required by the system, P hload1 and P hload They represent the hydrogen load actually provided by the system and the hydrogen load required by the system, P heat1 and P heat They represent the heat load actually provided by the system and the heat load required by the system, ξ g is the maximum allowable grid-connected power fluctuation value, E g Indicates the actual grid-connected power fluctuation value.

[0097] Preferably, in S6, a mixed integer linear programming (MILP) method is used for solving, ultimately achieving the optimization goal of maximizing the system economy and meeting the system's electricity, heat, and hydrogen load requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0098] Figure 1 This is a system diagram of the electrolysis hydrogen production and fuel cell waste heat cascade utilization based on the organic Rankine cycle of the present invention.

[0099] Figure 2This is a flow chart of the method for electrolysis hydrogen production and fuel cell waste heat cascade utilization based on the organic Rankine cycle of the present invention. DETAILED DESCRIPTION

[0100] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0101] The electrolysis hydrogen production and fuel cell waste heat cascade utilization system based on the organic Rankine cycle includes a wind power generation unit, a photovoltaic power generation unit, a hydrogen production electrolyzer, a compressor, a hydrogen storage tank, a hydrogen fuel cell, a heat storage tank, a battery and an organic Rankine cycle power generation device.

[0102] The wind power generation unit converts wind energy into electrical energy through a wind turbine generator set to supply power to the electrolytic hydrogen production device and the power load system, and the excess electrical energy is stored in the battery energy storage system.

[0103] The photovoltaic power generation unit converts solar energy into electrical energy through a photovoltaic power station to supply power to the electrolytic hydrogen production device and the power load system, and the excess electrical energy is stored in the battery energy storage system.

[0104] The battery energy storage system discharges electricity to support the power load system when wind power / photovoltaic power output is insufficient or during peak power consumption periods; and stores excess electricity when wind power / photovoltaic power output is excessive.

[0105] The electrolysis hydrogen production and storage system converts electrical energy into hydrogen energy through an electrolyzer, which is then pressurized by a compressor and stored in a hydrogen storage tank. The waste heat generated during the electrolysis process is recovered through a heat exchanger to meet user heat needs or drive an organic Rankine cycle (ORC) device to generate electricity.

[0106] The hydrogen fuel cell converts stored hydrogen into electrical energy when renewable energy generation is low or electricity consumption is at peak, and works together with the battery energy storage system to support the power load. The waste heat generated during operation is recovered through a heat exchanger to meet user heat needs or drive the organic Rankine cycle device to generate electricity.

[0107] The waste heat utilization unit and the organic Rankine cycle device use a low-boiling-point organic working fluid and automatically start when the system heat load demand is fully met or the system optimization operation strategy determines that waste heat power generation is more economical, and convert the recovered waste heat into electrical energy through the organic Rankine cycle. The generated electricity is stored in a battery energy storage system or directly supplied to the power load.

[0108] In short, this electrolysis hydrogen production and fuel cell waste heat cascade utilization system based on the organic Rankine cycle builds an energy system with multi-energy complementarity and efficient utilization.

[0109] At the power generation and storage level, wind power generation units capture wind energy through wind turbines and convert it into electricity, powering the hydrogen electrolysis unit and the power load system. Excess electricity is stored in batteries. Photovoltaic power generation units achieve the same function by converting solar energy into electricity through photovoltaic power plants. Battery energy storage systems play a role in "peak shaving" and "valley filling," storing electricity when renewable energy is generating excess power and discharging it during periods of insufficient power generation or peak demand, ensuring a stable power supply.

[0110] In the hydrogen production, storage, and fuel cell segment, the electrolysis hydrogen production and storage system converts electrical energy into hydrogen energy through an electrolyzer. This hydrogen energy is then compressed and stored in a hydrogen storage tank. Excess heat from the electrolysis process is recovered through a heat exchanger to meet user heat needs or drive organic Rankine cycle power generation. During energy downturns and peak electricity demand, the hydrogen fuel cell converts stored hydrogen into electricity, collaborating with the battery to ensure power supply. Excess heat from the operation is also recovered and reused.

[0111] In the waste heat utilization unit, the organic Rankine cycle device uses a low-boiling-point organic working fluid as a medium. When the system heat load demand is met, or when waste heat power generation is determined to be more economical through optimized operation strategy, it automatically starts and efficiently converts the recovered waste heat into electrical energy. The generated electricity is either stored in batteries or directly supplied to the power load, realizing the cascade utilization of energy and maximizing benefits.

[0112] The method for electrolysis hydrogen production and fuel cell waste heat cascade utilization based on the organic Rankine cycle includes:

[0113] S1: Establish a multi-energy flow coupled system model including wind power generation, photovoltaic power generation, hydrogen production electrolyzer, compressor, hydrogen storage tank, hydrogen fuel cell, heat storage tank, battery and organic Rankine cycle power generation device;

[0114] S2: During the electrolyzer modeling phase, a refined model is established that considers the switching logic of the five operating states (shutdown, cold start, standby, hot start, and hydrogen production), including constraints such as state transition time, upper and lower limits of operating power, and waste heat recovery.

[0115] S3: In the hydrogen fuel cell modeling phase, a detailed hydrogen fuel cell model is established, including constraints such as start-stop constraints, operating power limits, and waste heat recovery.

[0116] S4: Considering the upper and lower operating limits of the equipment, establish mathematical models of the compressor, hydrogen storage tank, battery and heat storage tank;

[0117] S5: Organic Rankine cycle system modeling stage, building a heat-to-electricity conversion model based on the organic working fluid characteristic curve;

[0118] S6: In the optimization solution phase, based on the mixed integer linear programming (MILP) method, the operating constraints of each device, the output forecast of renewable energy, and the electricity, heat, and hydrogen load requirements are integrated to build an optimal scheduling model that meets the system's electricity, heat, and hydrogen load requirements and economic efficiency. The output of each device is coordinated to ultimately achieve the optimization goals of maximizing system economic efficiency and meeting the system's electricity, heat, and hydrogen load requirements.

[0119] Among them, in S2, the refined mathematical model of the hydrogen production electrolyzer is as follows:

[0120] Considering that the hydrogen production electrolyzer switches between five states: shutdown, cold start, standby, hot start, and hydrogen production, the state of the hydrogen production electrolyzer is represented by the logical variable δ:

[0121]

[0122] When the hydrogen production electrolyzer is in the hydrogen production state, the relationship between its hydrogen production mass rate and power consumption can be expressed as:

[0123]

[0124] When in the shutdown state, the relationship between its hydrogen production mass rate and power consumption can be expressed as:

[0125]

[0126] In the standby state, the relationship between the hydrogen production mass rate of the hydrogen production electrolyzer and its power consumption can be expressed as:

[0127]

[0128] In the hot start state, the hydrogen production electrolyzer starts to produce hydrogen by electrolysis at the first moment. The relationship between its hydrogen production mass rate and power consumption is the same as that of the electrolyzer in the hydrogen production state, which can be expressed by formula (2).

[0129] In the cold start working state, the hydrogen production electrolyzer starts cold starting from the shutdown state and needs a certain time L to preheat until the temperature in the small chamber reaches the electrolysis requirement before electrolysis and hydrogen production begins. Assuming that the hydrogen production electrolyzer starts cold starting at time k0, the relationship between its hydrogen production mass rate and power consumption can be expressed as:

[0130]

[0131] Where, is the hydrogen production mass rate of the hydrogen production electrolyzer, P e is the power consumed by the hydrogen production electrolyzer, a1, a2, a n , a, b1, b2, b n , b are fitting coefficients, P eminand P emax Respectively represent the minimum and maximum values ​​allowed for the power consumption of the hydrogen production electrolyzer. STB It indicates the power consumed to maintain the temperature in the electrolytic cell chamber when the alkaline electrolytic cell is in standby mode.

[0132] Electrolytic cell heat generation model:

[0133]

[0134] P heat_el (k) = (1-η el (k))*P e (k) (7)

[0135] Where η e is the hydrogen production efficiency of the hydrogen production electrolyzer, NHV is the higher calorific value of hydrogen, P heat_e is the heat generation power of the hydrogen production electrolyzer.

[0136] In S3, the refined mathematical model of the hydrogen fuel cell is as follows:

[0137] When a hydrogen fuel cell is in operation, the relationship between its output power and the mass rate of hydrogen consumption can be expressed as:

[0138]

[0139] When the hydrogen fuel cell is in the shutdown state, the relationship between the gas production power and the hydrogen mass consumption rate can be expressed as:

[0140]

[0141] Hydrogen fuel cell heat generation model:

[0142]

[0143] P heat_f (k) = (1-η f (k))*P f (k) (11)

[0144] Where η f is the fuel cell power generation efficiency, P heat_f is the heat generation power of the fuel cell.

[0145] In the electricity-heat-hydrogen cogeneration system method, in S4, the mathematical model of the compressor is as follows:

[0146]

[0147] Where, represents the mass rate of hydrogen entering the compressor, Indicated at reference pressure The power consumed by the compressor, β c Indicates the pressure under which the compressor works normally, β0 is the standard atmospheric pressure, γ c Indicates the dissipation rate of hydrogen from the alkaline electrolyzer to the compressor.

[0148] To ensure the normal operation of the compressor, the operating power required during its operation must meet the following conditions:

[0149]

[0150] Where, is the rated power of the compressor.

[0151] Among them, in said S4, the mathematical model of the hydrogen storage tank is as follows:

[0152]

[0153] Where, E tk Indicates the quality of hydrogen in the hydrogen storage tank, is the hydrogen required by the system, usually understood as the hydrogen sold, and Δt is the sampling time.

[0154] To ensure safe and efficient operation, the quality of hydrogen in the hydrogen storage tank must meet the following constraints:

[0155]

[0156] E tk (0) = E tkmin (17)

[0157] Where, and They represent the lower and upper limits of the hydrogen storage tank capacity respectively.

[0158] Wherein, in said S4, the mathematical model of the battery is as follows:

[0159] E b (k+1)=E b (k)-P b (k)Δt (18)

[0160]

[0161] Where, E b is the remaining energy in the lithium battery pack; P b is the battery charging and discharging power, when P b When it is negative, it means the lithium battery is charging; when P b When it is positive, it means the lithium battery is discharging. and Respectively represent the minimum and maximum values ​​of battery charge and discharge power. and Respectively represent the lower and upper limits of battery capacity.

[0162] Assuming that at the end of each day, the lithium battery energy storage state is forced to return to its initial value, it can be expressed as:

[0163] E b (n d ×N s +1)=E b (1) (21)

[0164] Among them, in S4, the mathematical model of the heat storage tank is as follows:

[0165] E h (k+1)=E h (k)-P h (k)Δt (22)

[0166]

[0167] Where, E h Indicates the power in the heat storage tank, P h Charge and discharge heat power for the heat storage tank, and They represent the minimum and maximum values ​​of the charging and discharging power of the heat storage tank respectively. and Respectively represent the lower and upper limits of the heat storage tank capacity.

[0168] Wherein, in said S5, the mathematical model of the organic Rankine cycle is as follows:

[0169] P ORC,e (k) = η ORC P ORC (k) (25)

[0170]

[0171] Where, P ORC,e represents the input thermal power of the organic Rankine cycle device, P ORC is the output power of the organic Rankine cycle, η ORC is the conversion efficiency of the organic Rankine cycle, Indicates the rated thermal power of the organic Rankine cycle.

[0172] In S6, the optimal dispatch model of the electricity-heat-hydrogen system considering the uncertainty of renewable energy output and electricity, heat, and hydrogen loads is as follows:

[0173] (1) Objective function

[0174] Aims to maximize the economic efficiency of the electricity-heat-hydrogen system (represented by the first and second terms of the objective function) while meeting the electricity, heat and hydrogen load demands as much as possible.

[0175]

[0176] Where σ ele is the grid-connected electricity price, N y is the total length of sampling time, P g is the grid-connected power, is the selling price of hydrogen, J load 、J hydrogen and J heat They represent the penalty costs when the electric load, hydrogen load and thermal load are not met.

[0177] (2) Constraints

[0178] Power constraints for wind turbines, photovoltaics, electric loads, hydrogen loads, and thermal loads:

[0179] 0≤P w (k)≤P wmax (k) (28)

[0180] 0≤P v (k)≤P vmax (k) (29)

[0181] 0≤P load1 (k)≤P load (k) (30)

[0182] 0≤P hload1 (k)≤P hload (k) (31)

[0183] 0≤P heat1 (k)≤P heat (k) (32)

[0184] Grid-connected power fluctuation constraints:

[0185] -ξ g ≤E g (k+1)=P g (k+1)-P g (k)≤ξ g (33)

[0186] System electric power balance constraints:

[0187] P w (k)+P v (k)+P f (k) = P g (k)+P load1 (k)+Pe (k)+P c (k)+P b (k) (34)

[0188] Other constraints:

[0189] Electrolyzer operation constraints: (2) to (7)

[0190] Hydrogen fuel cell operation constraints: (8) to (11)

[0191] Compressor operating constraints: (14)

[0192] Hydrogen storage tank constraints: (16) to (17)

[0193] Battery constraints: (19) to (21)

[0194] Heat storage tank constraints: (23)~(24)

[0195] Organic Rankine cycle operating constraints: (26)

[0196] Where, P w and P v Represent the actual output of wind farm and photovoltaic power station respectively, P wmax and P vmax They represent the maximum output of wind farm and photovoltaic power station respectively, P load1 and P load They represent the actual power load provided by the system and the power load required by the system, P hload1 and P hload They represent the hydrogen load actually provided by the system and the hydrogen load required by the system, P heat1 and P heat They represent the heat load actually provided by the system and the heat load required by the system, ξ g is the maximum permissible grid-connected power fluctuation value, E g Indicates the actual grid-connected power fluctuation value.

[0197] Among them, in S6, the mixed integer linear programming (MILP) method is used for solution, and ultimately the optimization goal of maximizing the system economy and meeting the system's electricity, heat, and hydrogen load requirements is achieved.

[0198] In summary, modeling and optimization are carried out around multi-energy flow coupling to achieve efficient energy utilization. First, a multi-energy flow coupling system model is established, which includes equipment such as wind power generation and photovoltaic power generation. In the electrolyzer and hydrogen fuel cell modeling stages, refined models are established respectively. The former considers the switching logic and related constraints of five operating states such as shutdown and hydrogen production, while the latter includes constraints such as start-stop, power limit, and waste heat recovery. At the same time, for equipment such as compressors and hydrogen storage tanks, mathematical models are established considering the upper and lower limits of operation. The organic Rankine cycle system constructs a heat-to-electricity conversion model based on the characteristic curve of the organic working fluid. Finally, in the optimization solution stage, the mixed integer linear programming method is used to integrate the operating constraints of each device, the output forecast of renewable energy, and the load demand of electricity, heat, and hydrogen to construct an optimized scheduling model, coordinate the output of equipment, and achieve the dual goals of maximizing system economy and meeting the load demand of electricity, heat, and hydrogen.

Claims

1. An electrolysis hydrogen production and fuel cell waste heat cascade utilization system based on an organic Rankine cycle, characterized in that: The system includes: a wind power generation unit, a photovoltaic power generation unit, a battery energy storage system, an electrolytic hydrogen production device, a hydrogen storage system, a fuel cell power generation unit, a waste heat utilization unit and an organic Rankine cycle device; The wind power generation unit converts wind energy into electrical energy through a wind turbine generator set to supply power to the electrolytic hydrogen production device and the power load system, and the excess electrical energy is stored in the battery energy storage system; The photovoltaic power generation unit converts solar energy into electrical energy through a photovoltaic power station to supply power to the electrolytic hydrogen production device and the power load system, and the excess electrical energy is stored in the battery energy storage system; When wind power generation and photovoltaic power generation are insufficient or during peak power consumption periods, the battery energy storage system discharges to support the power load system.

2. The electrolysis hydrogen production and fuel cell waste heat cascade utilization system based on the organic Rankine cycle according to claim 1 is characterized in that: Electrical energy is converted into hydrogen energy through an alkaline electrolyzer or a proton exchange membrane electrolyzer, which is then pressurized by a compressor and stored in a hydrogen storage tank. The waste heat generated during the electrolysis process is recovered through a heat exchanger to meet user heat needs or drive an organic Rankine cycle device to generate electricity.

3. The electrolysis hydrogen production and fuel cell waste heat cascade utilization system based on the organic Rankine cycle according to claim 1 is characterized in that: When wind power and photovoltaic power generation are insufficient or when electricity consumption is at peak times, the stored hydrogen is converted into electrical energy through hydrogen fuel cells, which work together with the battery energy storage system to support the power load. The waste heat generated during the operation is recovered through a heat exchanger to meet user heat needs or drive the organic Rankine cycle device to generate electricity.

4. The electrolysis hydrogen production and fuel cell waste heat cascade utilization system based on the organic Rankine cycle according to claim 1 is characterized in that: The organic Rankine cycle device uses a low-boiling-point organic working fluid and automatically starts when the system heat load demand is fully met or the system optimization operation strategy determines that waste heat power generation is more economical. The recovered waste heat is converted into electrical energy through the organic Rankine cycle. The generated electricity is stored in a battery energy storage system or directly supplied to the power load.

5. A method for hydrogen production by electrolysis and cascade utilization of fuel cell waste heat based on an organic Rankine cycle, characterized in that: include: S1: Establish a multi-energy flow coupled system model including wind power generation, photovoltaic power generation, hydrogen production electrolyzer, compressor, hydrogen storage tank, hydrogen fuel cell, heat storage tank, battery and organic Rankine cycle power generation device; S2: During the hydrogen production electrolyzer modeling phase, a refined model of the switching logic for the five operating states of shutdown, cold start, standby, hot start, and hydrogen production is established, including constraints on state transition time, upper and lower limits on operating power, and waste heat recovery and utilization. S3: In the hydrogen fuel cell modeling phase, a refined hydrogen fuel cell model is established, which includes start-stop constraints, operating power limits, and waste heat recovery constraints. S4: Considering the upper and lower operating limits of the equipment, establish mathematical models of the compressor, hydrogen storage tank, battery and heat storage tank; S5: Organic Rankine cycle system modeling stage, building a heat-to-electricity conversion model based on the organic working fluid characteristic curve; S6: In the optimization solution phase, based on the mixed integer linear programming method, the operating constraints of each device, the output forecast of renewable energy, and the electricity, heat, and hydrogen load requirements are integrated to build an optimal scheduling model that meets the system's electricity, heat, and hydrogen load requirements and economic efficiency. The output of each device is coordinated to achieve the optimization goals of maximizing the system's economic efficiency and meeting the system's electricity, heat, and hydrogen load requirements.

6. The method for electrolysis hydrogen production and fuel cell waste heat cascade utilization based on organic Rankine cycle according to claim 5, characterized in that: The refined mathematical model of the hydrogen production electrolyzer in S2 is as follows: The hydrogen production electrolyzer switches between five states: shutdown, cold start, standby, hot start, and hydrogen production. The state of the hydrogen production electrolyzer is represented by the logical variable δ: When the hydrogen production electrolyzer is in the hydrogen production state, the relationship between its hydrogen production mass rate and power consumption is expressed as: When the power is turned off, the relationship between the hydrogen production mass rate and the power consumption is expressed as: In the standby state, the relationship between the hydrogen production mass rate of the hydrogen production electrolyzer and its power consumption is expressed as: In the hot start state, the hydrogen production electrolyzer begins to electrolyze and produce hydrogen. The relationship between its hydrogen production mass rate and power consumption is the same as that of the electrolyzer in the hydrogen production state, which is expressed by formula (2); In the cold start working state, the hydrogen production electrolyzer starts cold start from the shutdown state and needs time L to preheat until the temperature in the small chamber reaches the electrolysis requirement before starting electrolysis to produce hydrogen. When the hydrogen production electrolyzer starts cold start at time k0, the relationship between its hydrogen production mass rate and power consumption is expressed as: Where, is the hydrogen production mass rate of the hydrogen production electrolyzer, P e is the power consumed by the hydrogen production electrolyzer, a1, a2, a n , a, b1, b2, b n , b are fitting coefficients, P emin and P emax They represent the minimum and maximum values ​​allowed for the power consumption of the hydrogen production electrolyzer, P STB Indicates the power consumed by the alkaline electrolytic cell to maintain the temperature in the electrolytic cell chamber when the cell is in standby mode; Electrolytic cell heat generation model: P.S heat_el (k)(1-η el (k))*P e (k) (7) Where η e is the hydrogen production efficiency of the hydrogen production electrolyzer, NHV is the higher calorific value of hydrogen, P heat_e is the heat generation power of the hydrogen production electrolyzer; The refined mathematical model of the hydrogen fuel cell in S3 is as follows: When the fuel cell is in operation, the relationship between its output power and the mass rate of hydrogen consumption is expressed as: When the hydrogen fuel cell is in the shutdown state, the relationship between the gas production power and the hydrogen mass consumption rate is expressed as: Hydrogen fuel cell heat generation model: P.S heat_f (k)(1-η f (k))*P f (k) (11) Where η f is the fuel cell power generation efficiency, P heat_f is the heat generation power of the fuel cell.

7. The method for electrolysis hydrogen production and fuel cell waste heat cascade utilization based on organic Rankine cycle according to claim 5, characterized in that: The mathematical model of the compressor in S4 is as follows: Where, Indicates the mass rate of hydrogen entering the compressor, P c ref Indicates the reference pressure The power consumed by the compressor, β c Indicates the pressure under which the compressor works normally, β0 is the standard atmospheric pressure, γ c represents the dissipation rate of hydrogen from the alkaline electrolyzer to the compressor; To ensure the normal operation of the compressor, the operating power required during its operation must meet the following conditions: Where, P c rat is the rated power of the compressor; The mathematical model of the hydrogen storage tank in S4 is as follows: Where, E tk Indicates the quality of hydrogen in the hydrogen storage tank, is the hydrogen required by the system, Δt is the sampling time; To ensure safe and efficient operation, the quality of hydrogen in the hydrogen storage tank must meet the following constraints: AND tk (0)=E tkmin (17) Where, and They represent the lower and upper limits of the hydrogen storage tank capacity respectively.

8. The method for electrolysis hydrogen production and fuel cell waste heat cascade utilization based on organic Rankine cycle according to claim 5, characterized in that: The mathematical model of the battery in S4 is as follows: E b (k+1)=E b (k)-P b (k)Δt (18) Where, E b is the remaining energy in the lithium battery pack; P b is the battery charging and discharging power, when P b When it is negative, it means the lithium battery is charging; when P b When it is positive, it means the lithium battery is discharging. b min and P b max Respectively represent the minimum and maximum values ​​of battery charge and discharge power, and Respectively represent the lower and upper limits of battery capacity, At the end of each day, the lithium battery energy storage state is forced to return to its initial value, expressed as: AND b (n d ×N s +1)=And b (1) (21) The mathematical model of the heat storage tank in S4 is as follows: E h (k+1)=E h (k)-P h (k)Δt (22) P h min ≤P h (k)≤P h max (24) Where, E h Indicates the power in the heat storage tank, Ph is the heat storage tank charging and discharging power, P h min and P h max Respectively represent the minimum and maximum values ​​of the heat storage tank charging and discharging power, and Respectively represent the lower and upper limits of the heat storage tank capacity.

9. The method for electrolysis hydrogen production and fuel cell waste heat cascade utilization based on organic Rankine cycle according to claim 5, characterized in that: The mathematical model of the organic Rankine cycle in S5 is as follows: P.S ORC,e (k)6η ORC P.S ORC (k) (25) Where, P ORC,e represents the input thermal power of the organic Rankine cycle device, P ORC is the output power of the organic Rankine cycle, η ORC is the conversion efficiency of the organic Rankine cycle, Indicates the rated thermal power of the organic Rankine cycle.

10. The method for electrolysis hydrogen production and fuel cell waste heat cascade utilization based on organic Rankine cycle according to claim 5, characterized in that: The optimal dispatch model of the electricity-heat-hydrogen system in S6 considering the uncertainty of renewable energy output and electricity, heat, and hydrogen loads is as follows: (1) Objective function Aims to maximize the economic efficiency of the electricity-heat-hydrogen system while meeting the electricity, heat and hydrogen load requirements. Where σ ele is the grid-connected electricity price, N y is the total length of sampling time, P g is the grid-connected power, is the selling price of hydrogen, J load 、J hydrogen and J heat They represent the penalty costs when the electric load, hydrogen load, and heat load are not met; (2) Constraints Power constraints for wind turbines, photovoltaics, electric loads, hydrogen loads, and thermal loads: 0≤P w (k)≤P wmax (k) (28) 0≤P v (k)≤P vmax (k) (29) 0≤P load1 (k)≤P load (k) (30) 0≤P hload1 (k)≤P hload (k) (31) 0≤P heat1 (k)≤P heat (k) (32) Grid-connected power fluctuation constraints: -ξ g ≤E g (k+1)DP g (k+1)-P g (k)≤ξ g (33) System electric power balance constraints: P w (k)+P v (k)+P f (k)=P g (k)+P load1 (k)+P e (k)+P c (k)+P b (k) (34) Other constraints: Electrolyzer operation constraints: (2) to (7) Hydrogen fuel cell operation constraints: (8) to (11) Compressor operating constraints: (14) Hydrogen storage tank constraints: (16) to (17) Battery constraints: (19) to (21) Heat storage tank constraints: (23)~(24) Organic Rankine cycle operating constraints: (26) Where, P w and P v They represent the power supply and the actual power supply of photovoltaic power generation, P wmax and P vmax Represent the maximum power supply of wind power generation and photovoltaic power generation, P load1 and P load They represent the actual power load provided by the system and the power load required by the system, P hload1 and P hload They represent the hydrogen load actually provided by the system and the hydrogen load required by the system, P heat1 and P heat They represent the heat load actually provided by the system and the heat load required by the system, ξ g is the maximum allowable grid-connected power fluctuation value, E g Indicates the actual grid-connected power fluctuation value; The mixed integer linear programming method is used to solve S6, and ultimately the optimization goals of maximizing the system economy and meeting the system's electricity, heat, and hydrogen load requirements are achieved.

Images