A feasibility assessment method for offshore wind power hydrogen production system

Abstract

The present invention discloses a feasibility assessment method for an offshore wind power hydrogen production system, and relates to the technical field of hydrogen energy application. At present, the assessment method is performed manually, which has a low intelligence level and is greatly affected by subjective factors. It cannot fully reflect the physical structure, and the assessment is not comprehensive, which affects the accuracy of the assessment. The present invention includes the steps of: acquiring data information; constructing an operation model of an offshore wind power hydrogen production system based on a planning scheme with the goal of maximizing operating benefits; evaluating the system economy based on the operation model of the offshore wind power hydrogen production system under the framework of long-term operation simulation of the offshore wind power hydrogen production system; the technical solution can quickly and effectively evaluate the feasibility of hydrogen production in a dedicated offshore wind farm; compared with traditional assessment methods, the assessment is more accurate and comprehensive, and can be performed automatically, thereby improving efficiency, reducing error rates, and reducing labor costs, while reducing the influence of subjective factors on the objectivity of the assessment.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen energy application, and in particular to a feasibility assessment method for an offshore wind power hydrogen production system. Background Art

[0002] In recent years, my country has vigorously developed renewable energy generation such as wind power and solar power to increase the proportion of renewable energy generation in the power structure. Offshore wind power is an important development direction for renewable energy generation and has great potential. However, wind energy has significant intermittent and volatile characteristics, and its consumption has obvious regional and time-concentrated distribution characteristics. Large-scale grid connection of offshore wind power faces many challenges; secondly, the construction of submarine cables is difficult and the construction cost is high, which hinders the further large-scale development and utilization of offshore wind energy. Hydrogen energy is considered to be an ideal energy carrier to ensure energy security and decarbonization. At present, the way to obtain pure green hydrogen is to electrolyze water. Combining offshore wind power with water electrolysis to produce hydrogen can solve the problem of effective wind power consumption, and the produced hydrogen can be transported to shore by pipeline or ship, promoting the decarbonization transformation of the energy and transportation sectors.

[0003] However, the purchase costs of offshore wind farms, electrolysis equipment, and hydrogen storage devices are high. If the equipment capacity is too large, it is difficult to recover the cost. If it is too small, it may not be possible to fully utilize offshore wind energy and generate sufficient economic benefits. At present, the evaluation method is performed manually, with low intelligence and great subjective influences. It cannot fully reflect the physical structure, and the evaluation is not comprehensive, which affects the accuracy of the evaluation.

[0004] Therefore, it is of great significance to judge whether an investment plan is feasible before investing in construction. Summary of the invention

[0005] The technical problem to be solved and the technical task proposed by the present invention are to improve and perfect the existing technical solutions, and provide a feasibility assessment method for offshore wind power hydrogen production system to assess the feasibility of offshore wind power hydrogen production system planning scheme, provide decision-making basis for offshore wind power hydrogen production system planning scheme, and promote the development of offshore wind power. To this end, the present invention adopts the following technical scheme.

[0006] A feasibility assessment method for an offshore wind power hydrogen production system, the offshore wind power hydrogen production system comprising: an offshore wind farm, an offshore hydrogen production platform, an underground hydrogen storage facility, and a hydrogen transport ship, wherein the electricity generated by the offshore wind farm is transmitted to the offshore hydrogen production platform via a submarine cable; the hydrogen produced by electrolyzing water on the offshore hydrogen production platform is transmitted to the underground hydrogen storage facility via a hydrogen transmission pipeline; the hydrogen stored in the underground hydrogen storage facility is transmitted to the hydrogen transport ship via a hydrogen transmission pipeline; the hydrogen transport ship transports the hydrogen to shore; the feasibility assessment method comprises the following steps:

[0007] 1) Get data information

[0008] The data information includes equipment parameters, meteorological parameters and economic parameters. The equipment parameters include the purchase cost, annual operation and maintenance cost, operation life and operation parameters of offshore wind farms, offshore hydrogen production platforms and underground hydrogen storage facilities; the meteorological parameters include the historical wind speed data of the proposed site selection area; the economic parameters include the discount rate;

[0009] 2) Based on the planning scheme, an operation model of the offshore wind power hydrogen production system is constructed with the goal of maximizing the operating benefits;

[0010] The objective function is:

[0011]

[0012] Where W represents the number of weeks in a month; Indicates the amount of hydrogen output from the hydrogen storage system on a certain day; represents the price at which hydrogen is sold;

[0013] Operational constraints include: offshore wind power generation constraints, water electrolysis hydrogen production constraints, and hydrogen energy storage constraints;

[0014] 3) Under the long-term operation simulation framework of the offshore wind power hydrogen production system, the economic performance of the system is evaluated based on the operation model of the offshore wind power hydrogen production system;

[0015] The medium- and long-term simulation framework adopts the Sequential Monte Carlo method; during the evaluation, the system operation sequential characteristics are reflected through the temporal correlation of wind speed, and annual temporal operation scenarios are generated through random sampling for post-processing.

[0016] As a preferred technical means: In step 2), offshore wind power generation constraints:

[0017] The theoretical power of wind power generation is obtained by sweeping through area A at speed v; due to the Beta limit, the correction factor c is introduced p ; Then the maximum theoretical power of the wind turbine is:

[0018]

[0019] In the formula, ρ represents the density of air, A is the area swept by the blade, v is the wind speed, c p is the Beta limit; the relationship between the actual power output of the wind turbine and the wind speed is:

[0020]

[0021]

[0022] In the formula, represents a collection of wind turbines; A collection representing years; Represents the set of seasons in a year; A collection representing the months of a season; Represents a set of days of the week; represents the set of hours in a day; P r and v r denote the rated output power and rated wind speed of the wind turbine, P i,y,s,m,d,h represents the power output of wind turbine i at the hth hour of the mth day of the mth month of the sth season of the yth year;

[0023] Assuming that each turbine uses the same wind power curve; not considering the effects of wind shear, air density changes, wake effects, and turbulence caused by other turbines; the power output of the entire wind farm is expressed as:

[0024]

[0025] In the formula, represents the power output of the entire wind farm, and N represents the number of wind turbines in the wind farm.

[0026] As a preferred technical means: In step 2), the electrolysis of water to produce hydrogen is constrained by:

[0027] Since the wind farm is off-grid and dedicated to hydrogen production, all the electricity it needs comes from the wind farm; the rate at which the electrolyzer can produce hydrogen is as follows:

[0028]

[0029] In the formula, E elec Indicates the electrical energy consumed to produce 1 unit of hydrogen by electrolysis; E pcl Indicates the electrical energy consumed in purifying water, compressing hydrogen and other losses;

[0030] The size of the electrolyzer, i.e. the rated capacity P elz,max , its rated capacity constraints are as follows:

[0031]

[0032] In fact, to ensure efficient operation, the electrolyzer should be shut down when the input power is too low; the lower limit of wind farm power generation P farm,low It is set to 5% of the rated capacity of the electrolytic cell, as shown in formula (7):

[0033] P farm,low =0.05P elz,max (7)

[0034] At the chosen size of the hydrogen electrolyser, if the wind farm produces enough electricity, the electrolyser operates at its rated capacity, i.e.:

[0035]

[0036] After comprehensive analysis, the actual hydrogen production rate of the electrolyzer is shown in formula (9):

[0037]

[0038]

[0039] As a preferred technical means: in step 2), hydrogen energy storage constraints:

[0040] Offshore wind energy has seasonal fluctuation characteristics, and the supply and demand of hydrogen energy are unbalanced in time and space. Therefore, the hydrogen storage system of the offshore wind power hydrogen production system should have the characteristics of seasonal energy storage;

[0041]

[0042]

[0043]

[0044]

[0045] Where S is the number of seasons in a year; M is the number of months in a quarter; W is the number of weeks in a month; D is the number of days in a week; H is the number of hours in a day; Indicates the amount of hydrogen stored in the hydrogen storage system on a certain day; Indicates the amount of hydrogen input into the hydrogen storage system on a certain day; represents the amount of hydrogen output from the hydrogen storage system on a certain day; equations (11)-(13) describe the change of hydrogen storage in the hydrogen storage system in a year;

[0046]

[0047] The meaning of formula (14) is that the amount of hydrogen stored in the hydrogen storage system at the end of the year should be the same as at the beginning of the year;

[0048]

[0049]

[0050]

[0051] In the formula, m HS,max Indicates the capacity of the hydrogen storage system; n in,max / n out,maxrepresents the upper limit of the mass flow of hydrogen input / output of the hydrogen storage system; equation (15) is the capacity constraint of the hydrogen storage system; equations (16) and (17) are the upper and lower limit constraints of hydrogen input / output of the hydrogen storage system.

[0052] 5. A feasibility assessment method for an offshore wind power hydrogen production system according to claim 4, characterized in that: in step 3), when the economic performance is assessed, the steps include:

[0053] 301): Input data, set iterative convergence conditions and the operating life cycle Y of hydrogen energy technology application; initialize y=1, and perform annual operation simulation calculation;

[0054] 302): Construct the long-term dynamic operation boundary of the electric-hydrogen complementary system for the yth year, generate simulation parameters such as component purchase price and hydrogen transaction price, etc. Based on this, perform simulation calculation of the operation within the year, and set the iteration pointer k=1;

[0055] 303): For the kth iteration, the time series random simulation and Latin hypercube sampling technology are used to generate 8760 hours of wind speed curves to obtain the medium- and short-term operation scenarios of the offshore wind power hydrogen production system; the specific process is to first standardize the annual historical wind speed data to remove the change trend, then use the standardized data and the general wind speed time series generation method to generate a standard wind speed time series, and then restore the standard wind speed time series to finally obtain the simulated wind speed time series with annual and daily change trends;

[0056] 304): Based on the offshore wind power hydrogen production operation model, the optimal time series energy flow calculation under the annual operation scenario is carried out, the system operation status evaluation is completed and the economic indicators are statistically analyzed;

[0057] 305): Calculate the annual value of the economic index and make a convergence judgment; if the convergence condition is met, the annual simulation algorithm is terminated and goes to step 6; otherwise, set k=k+1 and return to step 303);

[0058] 306): Update the component aging status and the annual dynamic operation boundary parameters; if y=Y, the annual simulation algorithm is terminated and go to step 307); otherwise, set y=y+1 and return to step 302);

[0059] 307): Output economic evaluation indicators such as annual cost, net present value, and investment payback period.

[0060] As a preferred technical means: in step 305), a stability criterion is used to judge convergence; CI is used to represent the convergence index, and the convergence judgment is expressed as the following formula:

[0061] CI≤δ (18)

[0062] In the formula, δ represents the set convergence accuracy threshold; when CI is less than or equal to this threshold, the medium- and long-term simulation algorithm converges and stops the cycle; otherwise, the cycle continues; the calculation formula of the convergence index CI is as follows:

[0063]

[0064]

[0065] In the formula, I E,k (i) represents the value of the kth economic index obtained by statistics of the first i scenarios, and there are K economic indexes in total; It represents the calibration value of the kth economic index, which is used to convert the index quantity with units into dimensionless quantity to realize the normalization of the index; R,m (i) represents the value of the mth reliability index obtained by statistics of the first i scenarios, It represents the calibration value of the mth economic index. There are M reliability evaluation indicators in total.

[0066] As the preferred technical means: the calculation method of economic indicators is as follows:

[0067] Assuming that the construction time is not considered, the investment cost C0 is:

[0068]

[0069] In the formula, C0 represents the total investment cost; represents the investment cost of a wind farm, including wind turbines and submarine cables; represents the investment cost of the offshore hydrogen production platform, including the offshore platform, power control and regulator, seawater purification device, water electrolysis device and power supply system; represents the investment cost of the hydrogen storage system, including underground hydrogen storage structures and related facilities and hydrogen transmission pipelines;

[0070] Annual operation and maintenance cost C y,O&M for:

[0071]

[0072] In the formula, represents the operation and maintenance cost of the wind farm in year y; represents the operation and maintenance cost of the offshore hydrogen production platform in year y; represents the operation and maintenance cost of the hydrogen storage system in year y;

[0073] The cost of offshore wind power hydrogen production system includes two parts: equipment planning investment cost system operation and maintenance cost; the economic benefits of the system are measured by equivalent annual value cost (ACS) y The calculation formula is as follows:

[0074] ACS y =CRF·C0+C y,O&M (twenty three)

[0075]

[0076] In the formula, CRF represents the capital recovery factor, i represents the discount rate, and Y represents the life cycle of the equipment;

[0077] The payback period PBP meets:

[0078]

[0079] In the formula, F represents the annual operating income, F y represents the operating income in the yth year; assuming that the annual hydrogen production, hydrogen price, and operation and maintenance costs of the offshore wind power hydrogen production system remain unchanged, the average annual operating income is:

[0080] R a =F1-C 1,O&M =F2-C 2,O&M =…=F PBP -C PBP,O&M (26)

[0081] Then formula (25) is simplified to:

[0082]

[0083] Further simplification yields:

[0084]

[0085] And calculate the net present value (NPV); when the NPV is greater than zero, the plan is feasible, and the larger the NPV, the better the plan and the better the investment benefit; the calculation formula is:

[0086]

[0087] Beneficial effects: The present invention proposes a structure of an offshore wind power hydrogen production system and establishes an analysis model, which can quickly and effectively evaluate the feasibility of hydrogen production in a dedicated offshore wind farm; the proposed evaluation method performs a refined mathematical modeling of the timing operation of the offshore wind power hydrogen production system, which can more accurately reflect the impact of the system's physical structure and operating characteristics on its economic efficiency compared to traditional evaluation methods; in addition, the evaluation model takes into account the seasonal characteristics of offshore wind power output and the impact of seasonal energy storage on the system's economic benefits, making it more in line with actual conditions; based on the historical data of key system operation parameters, a Latin hypercube sampling method is used to generate multiple groups of operation scenarios, so that the system's operation simulation is as consistent with actual conditions as possible; the above sampling scenarios and operation models are combined through a medium- and long-term simulation framework based on the sequential Monte Carlo method, and when the convergence conditions are reached, the various economic evaluation indicators of the system are calculated to achieve an economic evaluation of the offshore wind power hydrogen production system, which can effectively solve the feasibility evaluation problem of the offshore wind power hydrogen production system. The technical solution is accurate and comprehensive in evaluation, and can be carried out automatically, which improves efficiency, reduces error rates, reduces labor costs, and reduces the impact of subjective factors on the objectivity of the evaluation. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] Figure 1 It is a structural schematic diagram of an offshore wind power hydrogen production system of the present invention;

[0089] Figure 2 It is a schematic diagram of the process of the present invention.

[0090] Figure 3 It is a mid- and long-term operation simulation framework diagram of the offshore wind power hydrogen production system of the present invention. DETAILED DESCRIPTION

[0091] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0092] In the description of the present invention, it should be understood that the terms “include” and “comprises” indicate the presence of described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0093] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0094] It should be further understood that the term "and / or" used in the present specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects are in an "or" relationship.

[0095] It should be understood that, although the terms first, second, third, etc. may be used to describe preset ranges, etc. in the embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are only used to distinguish preset ranges from each other. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0096] The word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0097] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0098] See also Figure 1 The present invention provides an offshore wind power hydrogen production system, which is composed of an offshore wind farm, an offshore hydrogen production platform, an underground hydrogen storage facility, and a hydrogen transport ship. The electricity from the offshore wind farm is transmitted to the offshore platform through a submarine cable; the hydrogen produced by electrolyzing water on the offshore platform is transmitted to the underground hydrogen storage facility through a hydrogen transmission pipeline; the hydrogen stored in the underground hydrogen storage facility is transmitted to the hydrogen transport ship through a hydrogen transmission pipeline; and the hydrogen transport ship transports the hydrogen to the shore.

[0099] The specific structural features of the offshore wind power hydrogen production system are as follows:

[0100] An offshore wind farm consists of a certain number of wind turbines and a power transmission system. The wind turbines include blades, fans, towers and foundations, which can convert wind energy into electrical energy; the power transmission system is the submarine cable from the wind turbines to the offshore platform.

[0101] The offshore hydrogen production platform consists of an offshore platform, power control and regulator, a seawater purification device, a water electrolysis device and a power supply system. Its function is to convert electrical energy into hydrogen energy through water electrolysis.

[0102] The hydrogen storage system consists of underground hydrogen storage structures (underground caves, depleted oil reservoirs, etc.) and related facilities and pipeline systems, which are used to store hydrogen produced by offshore hydrogen production platforms. In addition, the storage capacity should be designed in accordance with technological progress and the capacity of hydrogen transport ships.

[0103] Hydrogen tankers are used to transport hydrogen produced by offshore hydrogen production systems to shore.

[0104] See also Figure 2 The present invention provides a feasibility assessment method for an offshore wind power hydrogen production system, which evaluates the feasibility of a planning scheme by calculating various indicators through medium- and long-term simulation of system operation, and includes the following steps:

[0105] S1. Obtain relevant information required for planning and feasibility assessment of offshore wind power hydrogen production system;

[0106] Specifically include:

[0107] (1) Equipment parameters, such as the purchase cost, annual operation and maintenance cost, operating life, and operating parameters of offshore wind farms, offshore hydrogen production platforms, and underground hydrogen storage facilities;

[0108] (2) Meteorological parameters, such as historical wind speed data for the proposed site area;

[0109] (3) Economic parameters, such as discount rates.

[0110] S2. Based on the planning scheme, an operation model of the offshore wind power hydrogen production system is constructed with the goal of maximizing the operating benefits;

[0111] (1) Objective function

[0112]

[0113] Where W represents the number of weeks in a month; Indicates the amount of hydrogen output from the hydrogen storage system on a certain day; The price at which hydrogen is sold. The sale of hydrogen is the only revenue for offshore wind power hydrogen production systems. Any government incentive support for new technologies and very low carbon energy production is included in this price, and additional revenue from the sale of oxygen by-product is not taken into account.

[0114] 2) Operational constraints

[0115] (1) Offshore wind power generation model

[0116] The theoretical power of wind power generation is obtained by sweeping through area A at speed v. Due to the Beta limit, the correction factor c is introduced p . Then the maximum theoretical power of the wind turbine is:

[0117]

[0118] In the formula, ρ represents the density of air, A is the area swept by the blade, v is the wind speed, c p is the Beta limit. The relationship between the actual power output of a wind turbine and wind speed is:

[0119]

[0120]

[0121] In the formula, represents a collection of wind turbines; A collection representing years; Represents the set of seasons in a year; A collection representing the months of a season; Represents a set of days of the week; Represents a set of hours in a day. r and v r denote the rated output power and rated wind speed of the wind turbine, P y,s,m,d,t represents the power output of wind turbine i at hour h of day d of month m of season s of year y. This formula usually represents the power curve.

[0122] Assuming that each turbine uses the same wind power curve; not considering the effects of wind shear, air density changes, wake effects, and turbulence caused by other turbines. The power output of the entire wind farm can be expressed as:

[0123]

[0124] In the formula, represents the power output of the entire wind farm, and N represents the number of wind turbines in the wind farm.

[0125] (2) Hydrogen production model by water electrolysis

[0126] Since the wind farm is off-grid and dedicated to hydrogen production, the electricity for all other services (including water purification and hydrogen compression) must come from the wind farm. In theory, the electrolyzer can produce hydrogen at the rate shown below:

[0127]

[0128] In the formula, E elec Indicates the electrical energy consumed to produce 1 unit of hydrogen by electrolysis; E pcl Represents the electrical energy consumed in purifying water, compressing hydrogen and other losses.

[0129] The size of the electrolyzer, i.e. the rated capacity P elz,max , which is a fixed and important asset installed from the beginning of the project. Its rated capacity constraints are as follows:

[0130]

[0131] In fact, to ensure efficient operation, the electrolyzer should be shut down when the input power (i.e. the real-time output power of the wind farm) is too low. farm,low It is set to 5% of the rated capacity of the electrolytic cell, as shown in formula (7):

[0132] P farm,low =0.05P elz,max (7)

[0133] At the chosen size of the hydrogen electrolyser, if the wind farm produces enough electricity, the electrolyser operates at its rated capacity, i.e.:

[0134]

[0135] After comprehensive analysis, the actual hydrogen production rate of the electrolyzer is shown in formula (8):

[0136]

[0137]

[0138] (3) Hydrogen energy storage model

[0139] Offshore wind energy has seasonal fluctuations, and the supply and demand of hydrogen energy are unbalanced in time and space. Therefore, the hydrogen storage system of the offshore wind power hydrogen production system should have the characteristics of seasonal energy storage.

[0140]

[0141]

[0142]

[0143]

[0144] Where S is the number of seasons in a year; M is the number of months in a quarter; W is the number of weeks in a month; D is the number of days in a week; H is the number of hours in a day; Indicates the amount of hydrogen input into the hydrogen storage system on a certain day; It represents the amount of hydrogen output from the hydrogen storage system on a certain day. Equations (11)-(13) describe the change of hydrogen storage in the hydrogen storage system in a year.

[0145]

[0146] Formula (14) means that the hydrogen storage capacity of the hydrogen storage system at the end of the year should be the same as that at the beginning of the year.

[0147]

[0148]

[0149]

[0150] In the formula, m HS,max Indicates the capacity of the hydrogen storage system; n in,max / n out,max represents the upper limit of the mass flow of hydrogen gas input / output of the hydrogen storage system. Formula (15) is the capacity constraint of the hydrogen storage system; Formulas (16) and (17) are the upper and lower limit constraints of hydrogen gas input / output of the hydrogen storage system.

[0151] S3. Evaluate the economic feasibility of the system under the long-term operation simulation framework of the offshore wind power hydrogen production system.

[0152] See also Figure 3 ,The medium- and long-term simulation framework of the present invention is proposed based on the ,sequential Monte Carlo method. The consideration of the system operation ,sequential characteristics is mainly reflected in the time series correlation of the ,wind speed, and is described by generating annual time series ,operation scenarios through random sampling. Figure 3 The most important thing in the simulation framework is how to judge the convergence of the evaluation index. This embodiment uses a stability criterion to judge the convergence. Using CI to represent the convergence index, the convergence judgment can be expressed as the following formula:

[0153] CI≤δ (18)

[0154] In the formula, δ represents the set convergence accuracy threshold. When CI is less than or equal to this threshold, the medium- and long-term simulation algorithm converges and stops the loop; otherwise, the loop continues. The calculation formula of the convergence index CI is as follows:

[0155]

[0156]

[0157] In the formula, I E,k (i) represents the value of the kth economic index obtained by statistics of the first i scenarios, and there are K economic indexes in total; It represents the calibration value of the kth economic index, which is used to convert the index quantity with units into dimensionless quantity to realize the normalization of the index. R,m (i) represents the value of the mth reliability index obtained by statistics of the first i scenarios, It represents the calibration value of the mth economic index, and there are M reliability evaluation indexes in total. It should be noted that the selection of calibration values ​​can not only normalize each index, but also play the role of index convergence judgment weight. The overall process of economic evaluation of sequential Monte Carlo simulation is as follows:

[0158] Step 1: Input data, set the iterative convergence conditions and the operating life cycle Y of hydrogen energy technology application; initialize y=1 and perform annual operation simulation calculations.

[0159] Step 2: Construct the long-term dynamic operation boundary of the electric-hydrogen complementary system for the yth year, and generate simulation parameters such as component purchase price and hydrogen transaction price; based on this, perform simulation calculations for the operation within the year, and set the iteration pointer k=1.

[0160] Step 3: For the kth iteration, use time series random simulation and Latin hypercube sampling technology to generate 8760 hours of wind speed curves to obtain the medium- and short-term operation scenarios of the offshore wind power hydrogen production system. The specific process is to first standardize the annual historical wind speed data to remove the change trend, then use the standardized data and the general wind speed time series generation method to generate a standard wind speed time series, and then restore the standard wind speed time series to finally obtain a simulated wind speed time series with annual and daily change trends.

[0161] Step 4: Based on the offshore wind power hydrogen production operation model, calculate the optimal time series energy flow under the annual operation scenario, complete the system operation status evaluation and statistically analyze the economic indicators.

[0162] Step 5: Calculate the annual value of economic indicators and make a convergence judgment. If the convergence condition is met, the annual simulation algorithm terminates and goes to step 6; otherwise, set k = k + 1 and return to step 3.

[0163] Step 6: Update component aging status and annual dynamic operation boundary parameters. If y = Y, the annual simulation algorithm ends and goes to step 7; otherwise, set y = y + 1 and return to step 2.

[0164] Step 7: Output economic evaluation indicators such as annual cost, net present value, and investment payback period.

[0165] The calculation method of economic indicators is as follows:

[0166] Assuming that the construction time is not considered, the investment cost C0 is:

[0167]

[0168] In the formula, C0 represents the total investment cost; represents the investment cost of a wind farm, including wind turbines and submarine cables; It represents the investment cost of the offshore hydrogen production platform, including the offshore platform, power control and regulator, seawater purification device, water electrolysis device and power supply system; Represents the investment cost of the hydrogen storage system, including underground hydrogen storage structures and related facilities and hydrogen pipelines, etc. The cost of hydrogen transport ships is not considered here.

[0169] Annual operation and maintenance cost C y,O&M for:

[0170]

[0171] In the formula, represents the operation and maintenance cost of the wind farm in year y; represents the operation and maintenance cost of the offshore hydrogen production platform in year y; It represents the operation and maintenance cost of the hydrogen storage system in year y. It is worth noting that since all the electricity consumed by the facilities comes from offshore wind farms, there is no electricity purchase cost.

[0172] The cost of offshore wind power hydrogen production system mainly includes two parts: equipment planning investment cost system operation and maintenance cost. Here we use the equivalent annual value cost to measure the economic benefits of the system. y The calculation formula is as follows:

[0173] ACS y =CRF·C0+C y,O&M (twenty three)

[0174]

[0175] In the formula, CRF represents the capital recovery factor, i represents the discount rate, and Y represents the life cycle of the equipment.

[0176] The payback period (PBP) is the time required for the accumulated economic benefits to equal the initial investment costs. It can be divided into static payback period and dynamic payback period. The static payback period is the time required to recover the entire investment with the net income of the project without considering the time value of money. The dynamic payback period is calculated by converting the net cash flow of each year of the investment project into present value according to the benchmark rate of return, which is the fundamental difference between it and the static payback period.

[0177] Investors are generally very concerned about the speed of investment recovery. In order to reduce investment risks, they all hope to recover their investments as soon as possible. The dynamic investment recovery period is a commonly used economic evaluation indicator. The dynamic investment recovery period makes up for the shortcoming of the static investment recovery period that does not consider the time value of funds, making it more in line with the actual situation. The present invention uses the dynamic recovery period, and its calculation method is as follows:

[0178] The payback period PBP should meet the following requirements:

[0179]

[0180] In the formula, F represents the annual operating income. Assuming that the annual hydrogen production, hydrogen price, and operation and maintenance costs of the offshore wind power hydrogen production system remain unchanged, the average annual operating income is:

[0181] R a =F1-C 1,O&M =F2-C 2,O&M =…=F PBP -C PBP,O&M (26)

[0182] Then formula (25) can be simplified as:

[0183]

[0184] Further simplification yields:

[0185]

[0186] Although the payback period takes into account the time value of money, it does not focus on the cash flow that may occur after the payback period is reached. Therefore, in order to evaluate the cash flow after the payback period and assess the feasibility of the project, it is also necessary to refer to the net present value (NPV).

[0187] The net present value is the algebraic sum of the present values ​​of net cash flows in each year calculated at the industry benchmark discount rate or other set discount rate during the project calculation period. The net present value method is a method of evaluating the pros and cons of a plan based on the size of the net present value. If the net present value is greater than zero, the plan is feasible, and the larger the net present value, the better the plan and the better the investment return. The calculation formula is:

[0188]

[0189] A specific embodiment of the present invention is provided below. Assume that an offshore wind power hydrogen production system is planned to be built in a certain area. Relevant information required for economic evaluation of the offshore wind power system is obtained. Table 1 shows the main economic parameters of the hydrogen energy equipment, and Table 2 shows the technical parameters of each device.

[0190] Table 1 Economic parameters of each equipment

[0191]

[0192] Table 2 Technical parameters of simulation operation

[0193]

[0194]

[0195] 2) Economic feasibility assessment of basic planning scheme

[0196] based on Figure 1 The typical structure, model and method of offshore wind power hydrogen production are shown in Table 3. The economic feasibility of the offshore wind power hydrogen production system is simulated through medium- and long-term operation, and the index results are obtained.

[0197] Table 3 Economic indicators of offshore wind power hydrogen production system

[0198]

[0199] It can be seen that the annual cost and income of offshore wind power hydrogen production are 181,380,000 yuan and 274,450,000 yuan respectively, and the corresponding project net present value is 993,560,000 yuan. The net present value is positive and the value is large, indicating that the offshore wind power hydrogen production project has strong economic profitability. This can also be reflected in the investment payback period. The operating life of the wind farm is 25 years, and the investment begins to generate positive returns in the 10th year.

[0200] 3) Comparative analysis of the economic feasibility of different hydrogen storage capacity solutions

[0201] In order to verify the impact of different hydrogen storage scales on the economic feasibility of offshore wind power hydrogen production projects, this example evaluates and analyzes the economic indicators under different schemes, including only net present value and investment payback period. The specific schemes and related indicator results are shown in Table 4.

[0202] Table 4 Economic index results under different hydrogen storage scales

[0203]

[0204]

[0205] It can be seen that as the storage capacity increases, the net present value decreases and the investment payback period increases. The growth rate of the investment payback period within a storage period of 2-30 days is slower than that of 30-60 days, so a shorter storage period is more economical.

[0206] above Figure 1-3 The feasibility assessment method for an offshore wind power hydrogen production system shown is a specific embodiment of the present invention, which has embodied the substantial characteristics and progress of the present invention. According to actual use needs and under the guidance of the present invention, equivalent modifications in shape, structure, etc. can be made to the method, which are all within the protection scope of this scheme.

Claims

1. A feasibility assessment method for an offshore wind power hydrogen production system, the offshore wind power hydrogen production system comprising: Offshore wind farm, offshore hydrogen production platform, underground hydrogen storage facility, hydrogen transport ship, the electricity generated by the offshore wind farm is transmitted to the offshore hydrogen production platform through submarine cables; the hydrogen produced by electrolyzing water on the offshore hydrogen production platform is transmitted to the underground hydrogen storage facility through a hydrogen pipeline; the hydrogen stored in the underground hydrogen storage facility is transmitted to the hydrogen transport ship through a hydrogen pipeline; the hydrogen transport ship transports the hydrogen to the shore; it is characterized in that: it is characterized in that: the feasibility assessment method comprises the following steps: 1) Get data information The data information includes equipment parameters, meteorological parameters and economic parameters. The equipment parameters include the purchase cost, annual operation and maintenance cost, operation life and operation parameters of offshore wind farms, offshore hydrogen production platforms and underground hydrogen storage facilities; the meteorological parameters include the historical wind speed data of the proposed site selection area; the economic parameters include the discount rate; 2) Based on the planning scheme, an operation model of the offshore wind power hydrogen production system is constructed with the goal of maximizing the operating benefits; The objective function is: Where W represents the number of weeks in a month; Indicates the amount of hydrogen output from the hydrogen storage system on a certain day; represents the price at which hydrogen is sold; Operational constraints include: offshore wind power generation constraints, water electrolysis hydrogen production constraints, and hydrogen energy storage constraints; 3) Under the long-term operation simulation framework of the offshore wind power hydrogen production system, the economic performance of the system is evaluated based on the operation model of the offshore wind power hydrogen production system; The medium- and long-term simulation framework uses the Sequential Monte Carlo method. During the evaluation, the time series correlation of wind speed is used to reflect the system operation time series characteristics, and annual time series operation scenarios are generated through random sampling for post-processing. In step 2), offshore wind power generation constraints: The theoretical power of wind power generation is obtained by sweeping through area A at speed v; due to the Beta limit, the correction factor c is introduced p ; Then the maximum theoretical power of the wind turbine is: In the formula, ρ represents the density of air, A is the area swept by the blade, v is the wind speed, c p is the Beta limit; the relationship between the actual power output of the wind turbine and the wind speed is: Where N is the set of wind turbines; Y is the set of years; S is the set of seasons in a year; M is the set of months in a season; D is the set of days in a week; H is the set of hours in a day; P ...; M is the set of months in a season; D is the set of days in a week; H is the set of hours in a day; P is the set of wind turbines; Y is the set of years; S is the set of seasons; M is the set of months in a season; D is the set of days in a week; H is the set of hours in a day; P is the set of wind turbines; r and v r denote the rated output power and rated wind speed of the wind turbine, P i,y,s,m,d,h represents the power output of wind turbine i at hour h of day d of month m of season s of year y; Assuming that each turbine uses the same wind power curve; not considering the effects of wind shear, air density changes, wake effects, and turbulence caused by other turbines; the power output of the entire wind farm is expressed as: In the formula, represents the power output of the entire wind farm, N represents the number of wind turbines in the wind farm; In step 2), the electrolysis of water to produce hydrogen is constrained Since the wind farm is off-grid and dedicated to hydrogen production, all the electricity it needs comes from the wind farm; the rate at which the electrolyzer can produce hydrogen is as follows: In the formula, E elec Indicates the electrical energy consumed to produce 1 unit of hydrogen by electrolysis; E pcl Indicates the electrical energy consumed in purifying water, compressing hydrogen and other losses; The size of the electrolyzer, i.e. the rated capacity P elz,max , its rated capacity constraints are as follows: In fact, to ensure efficient operation, the electrolyzer should be shut down when the input power is too low; the lower limit of wind farm power generation P farm,low It is set to 5% of the rated capacity of the electrolytic cell, as shown in formula (7): P farm,low =0.05P elz,max (7) At the chosen size of the hydrogen electrolyser, if the wind farm produces enough electricity, the electrolyser operates at its rated capacity, i.e.: After comprehensive analysis, the actual hydrogen production rate of the electrolyzer is shown in formula (9): In step 2), the hydrogen storage constraint Offshore wind energy has seasonal fluctuation characteristics, and the supply and demand of hydrogen energy are unbalanced in time and space. Therefore, the hydrogen storage system of the offshore wind power hydrogen production system should have the characteristics of seasonal energy storage; Where S is the number of seasons in a year; M is the number of months in a quarter; W is the number of weeks in a month; D is the number of days in a week; H is the number of hours in a day; Indicates the hydrogen storage capacity of the hydrogen storage system on a certain day; Indicates the amount of hydrogen input into the hydrogen storage system on a certain day; represents the amount of hydrogen output from the hydrogen storage system on a certain day; equations (11)-(13) describe the change of hydrogen storage in the hydrogen storage system in a year; The meaning of formula (14) is that the amount of hydrogen stored in the hydrogen storage system at the end of the year should be the same as at the beginning of the year; In the formula, m HS,max Indicates the capacity of the hydrogen storage system; n in,max / n out,max represents the upper limit of the mass flow of hydrogen gas input / output of the hydrogen storage system; Formula (15) is the capacity constraint of the hydrogen storage system; Formulas (16) and (17) are the upper and lower limit constraints of hydrogen gas input / output of the hydrogen storage system; In step 3), when the economic feasibility is evaluated, the following steps are included: 301): Input data, set iterative convergence conditions and the operating life cycle Y of hydrogen energy technology application; initialize y=1, and perform annual operation simulation calculation; 302): Construct the long-term dynamic operation boundary of the electric-hydrogen complementary system for the yth year, generate simulation parameters of component purchase price and hydrogen transaction price; based on this, perform simulation calculation of the operation within the year, and set the iteration pointer k=1; 303): For the kth iteration, the time series random simulation and Latin hypercube sampling technology are used to generate 8760 hours of wind speed curves to obtain the medium- and short-term operation scenarios of the offshore wind power hydrogen production system; the specific process is to first standardize the annual historical wind speed data to remove the change trend, then use the standardized data and the general wind speed time series generation method to generate a standard wind speed time series, and then restore the standard wind speed time series to finally obtain the simulated wind speed time series with annual and daily change trends; 304): Based on the offshore wind power hydrogen production operation model, the optimal time series energy flow calculation under the annual operation scenario is carried out, the system operation status evaluation is completed and the economic indicators are statistically analyzed; 305): Calculate the annual value of the economic index and make a convergence judgment; if the convergence condition is met, the annual simulation algorithm is terminated and goes to step 6; otherwise, set k=k+1 and return to step 303); 306): Update the component aging status and the annual dynamic operation boundary parameters; if y=Y, the annual simulation algorithm is terminated and go to step 307); otherwise, set y=y+1 and return to step 302); 307): Output equal annual cost, net present value, and investment payback period economic evaluation indicators.

2. A feasibility assessment method for an offshore wind power hydrogen production system according to claim 1, characterized in that: In step 305), a stability criterion is used to judge convergence; CI is used to represent the convergence index, and the convergence judgment is expressed as the following formula: CI≤δ (18) In the formula, δ represents the set convergence accuracy threshold; when CI is less than or equal to this threshold, the medium- and long-term simulation algorithm converges and stops the cycle; otherwise, the cycle continues; the calculation formula of the convergence index CI is as follows: In the formula, I E,k (i) represents the value of the kth economic index obtained by statistics of the first i scenarios, and there are K economic indexes in total; It represents the calibration value of the kth economic index, which is used to convert the index quantity with units into dimensionless quantity to realize the normalization of the index; R,m (i) represents the value of the mth reliability index obtained by statistics of the first i scenarios, It represents the calibration value of the mth economic index. There are M reliability evaluation indicators in total.

3. A feasibility assessment method for an offshore wind power hydrogen production system according to claim 2, characterized in that: The calculation method of economic indicators is as follows: Assuming that the construction time is not considered, the investment cost C0 is: In the formula, C0 represents the total investment cost; represents the investment cost of a wind farm, including wind turbines and submarine cables; represents the investment cost of the offshore hydrogen production platform, including the offshore platform, power control and regulator, seawater purification device, water electrolysis device and power supply system; represents the investment cost of the hydrogen storage system, including underground hydrogen storage structures and related facilities and hydrogen transmission pipelines; Annual operation and maintenance cost C y,O&M for: In the formula, represents the operation and maintenance cost of the wind farm in year y; represents the operation and maintenance cost of the offshore hydrogen production platform in year y; represents the operation and maintenance cost of the hydrogen storage system in year y; The cost of offshore wind power hydrogen production system includes two parts: equipment planning investment cost system operation and maintenance cost; the economic benefits of the system are measured by equivalent annual value cost (ACS) y The calculation formula is as follows: ACS y =CRF·C0+C y,O&M (23) In the formula, CRF represents the capital recovery factor, i represents the discount rate, and Y represents the life cycle of the equipment; The payback period PBP meets: In the formula, F represents the annual operating income, F y represents the operating income in the yth year; assuming that the annual hydrogen production, hydrogen price, and operation and maintenance costs of the offshore wind power hydrogen production system remain unchanged, the average annual operating income is: R a =F1-C 1,O&M =F2-C 2,O&M =···=F PBP -C PBP,O&M (26) Then formula (25) is simplified to: Further simplification yields: And calculate the net present value (NPV); when the NPV is greater than zero, the plan is feasible, and the larger the NPV, the better the plan and the better the investment benefit; the calculation formula is:

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