Agricultural integrated energy system scheduling method considering biomass energy and air source heat pump

Abstract

The invention relates to an agricultural integrated energy system (IAES) low-carbon economic dispatching method considering biomass energy power generation and air source heat pump energy supply, which is characterized by comprising the following steps of: firstly, proposing an IAES topological structure considering the energy supply of a biomass energy power plant and an air source heat pump; secondly, mathematical modeling is conducted on key equipment in the IAES, such as a biomass energy power plant, a cogeneration device, a carbon capture device and an air source heat pump; secondly, considering the power grid electricity price and the wind power electricity price in the peak-valley normal period, considering the carbon transaction cost into the daily operation cost, and performing day-ahead low-carbon economic dispatching on the IAES; finally, simulation verification shows that the provided optimal scheduling method can excavate the IAES carbon emission reduction potential to the maximum extent and considers the system operation economy.

Description

Technical Field

[0001] The present invention belongs to the field of optimized scheduling of integrated energy systems, and specifically relates to a low-carbon economic scheduling method for an integrated agricultural energy system taking into account biomass power generation and air source heat pump energy supply. Background Art

[0002] As "coal to electricity" gradually becomes the main trend of clean heating transformation in northern agricultural bases, due to the characteristics of high power and strong rigidity of electric heating loads in agricultural bases, and the existence of cold storage in agricultural bases also generates a large amount of electric refrigeration loads and other production loads, its large-scale development will have an impact on the relatively weak distribution network in rural areas, bringing great peak-shaving pressure to the power grid and creating safety hazards.

[0003] The agricultural integrated energy system couples multiple energy sources internally, and uses heat pumps and other devices as well as waste crop straw to generate biomass energy, which can greatly improve the flexibility of source measurement, reduce the peak load pressure of the power grid, meet the terminal multi-energy load demand, and further optimize the low-carbon economy of the agricultural base. Therefore, it is very necessary to conduct low-carbon economic scheduling research on the agricultural integrated energy system considering biomass energy generation and air source heat pump energy supply. Summary of the invention

[0004] The present invention proposes a low-carbon economic dispatching method for an agricultural integrated energy system that takes into account biomass power generation and air source heat pump energy supply, which reduces the impact of the agricultural integrated energy system on the distribution network, reduces the peak-shaving pressure of the distribution network, and combines a stepped carbon trading mechanism to further tap the carbon emission reduction potential of the agricultural integrated energy system, further reducing carbon emissions while ensuring the economy of the system.

[0005] In order to realize the proposed low-carbon economic dispatch method of agricultural integrated energy system, it is necessary to model and analyze the system through the following process:

[0006] In order to meet the high electric heating and cooling load in the agricultural base, break the barriers of the single energy system in the agricultural comprehensive energy system, realize the complementarity of different energy sources, and effectively give play to the advantages and potential of different energy sources, the equipment in the agricultural comprehensive energy system includes photovoltaic (PV), biomass power plant (BPP), combined heating and power (CHP) device with integrated absorption chiller, low-temperature waste heat power generation device based on organic Rankine cycle (ORC), air source heat pump, electric refrigerator, electric energy storage, thermal energy storage, carbon capture and storage (CCS) and power-to-gas (P2G) devices. While the agricultural comprehensive energy system is connected to the gas grid and distribution network, considering the principle of local consumption, the agricultural comprehensive energy system has signed an agreement with distributed wind farms near rural areas, providing a new way to consume wind power and increasing its own green electricity purchase. BPP, in conjunction with CCS devices, has reduced the system's carbon emissions and participated in the carbon trading market under the stimulation of tiered carbon trading.

[0007] Wheat, corn, soybeans, peanuts and other crops are grown inside the agricultural integrated energy system. The crop straw can be used as a rich biomass resource, and the slag produced after its combustion can be used as fertilizer to feed back to the land within the agricultural integrated energy system. In the past, biomass power plants required a lot of investment in the acquisition, transportation, storage and pretreatment of biomass materials, while the agricultural integrated energy system can complete the industrial chain closed loop of biomass power generation and eliminate the process of biomass acquisition and transportation. Biomass itself is considered to have zero carbon emissions, and the CO2 produced during its combustion is equivalent to the CO2 absorbed during its growth. The flue gas produced by combustion can be captured by CCS, and the CO2 is sent to the P2G equipment, which can achieve negative carbon emissions and further tap the carbon reduction potential of the agricultural integrated energy system. Limited by the seasonality of crop harvesting, the calorific value contained in the harvested crop straw is calculated on an annual basis:

[0008]

[0009] Where L CS is the total calorific value of crop straw harvested in a year, N is the number of crop types whose straw can be harvested, and s i is the planting area of ​​the i-th type of crop, m i is the weight of harvestable straw per unit area of ​​the i-th type of crop, L i is the calorific value per unit mass of the i-th type of crop straw.

[0010] In order to improve the stability and storage performance of crop straw, reduce its volume and humidity, and make it more suitable for biomass power generation, it needs to be pre-treated, usually by drying, crushing and pressing. Considering the sustainability of biomass power plants and making them participate in day-ahead scheduling, the total calorific value of biomass particles that can be used for power generation every day is L CSD .

[0011]

[0012] Where E CSD and Q CSD is the total value of electric and thermal energy dispatched by biomass power generation on the day before, and The efficiency of biomass energy conversion from electricity to heat.

[0013] BPP satisfies the requirement that the total electric energy delivered during the daily dispatch cycle is equal to E CSD , which can improve the flexibility of the source side and further tap the potential of source-load matching. The model involved in scheduling is:

[0014]

[0015] in is the output power of BPP, δ BPP (t) is the working status flag of BPP, which is a 0-1 variable; and is the maximum and minimum output power of BPP; and It is the minimum continuous working time and maximum number of switching times per day of BPP.

[0016] The flue gas generated by BPP power generation can eventually absorb and store CO2 in the absorption tower through a monoethanolamine (MEA) aqueous solution to complete the biomass energy carbon capture and storage (BECCS) process. In addition to BPP, flue gas from CHP can also undergo the above process in the agricultural integrated energy system. CO2 is released by heating in the regeneration tower, and the released MEA solution can be sent back to the absorption tower for the next round of CO2 absorption. The released CO2 can be sent to the P2G system for fixation.

[0017] Compared with other types of heat pumps, air source heat pumps have the advantages of easy installation, strong adaptability, low initial investment, and no need for geothermal loops. They have been used to a certain extent in heating and industrial parks in the north. As an energy conversion unit, air source heat pumps provide the required cooling and heating loads in the agricultural comprehensive energy system. This article focuses on the energy flow of the equipment, so it mainly considers the power load consumed by the heat pump unit and the output cooling and heating loads. Its working model is:

[0018]

[0019] in and are the electrical power consumed by the heat pump and the heating and cooling power respectively; and are heating and cooling efficiency respectively; and They are heating and cooling working status flags, both are 0-1 variables; and They are the maximum power for heating and cooling respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the operation framework diagram of the agricultural integrated energy system considering biomass power generation and air source heat pump.

[0021] Figure 2 This is the workflow diagram of BECCS combined with P2G. DETAILED DESCRIPTION

[0022] This scheduling method adopts a reward-and-punishment type tiered carbon trading mechanism, which is more fair and can further tap the low-carbon potential of the system. The BPP in the agricultural integrated energy system is considered to have zero carbon emissions in the carbon trading mechanism. The carbon emission source is the gas turbine, so a carbon emission quota is set for the gas turbine. The gas turbine can generate electricity and heat at the same time. By introducing a conversion coefficient, the carbon quota of the gas turbine is:

[0023]

[0024] Among them C QUO is the total carbon emission quota of the agricultural comprehensive energy system, ε QUO is the carbon quota factor per unit thermal power, and γ is the electric-to-heat conversion coefficient of the gas turbine. The part of the agricultural integrated energy system that exceeds the carbon emission quota needs to be purchased in the carbon trading market, while the part that is lower than the carbon emission quota can be sold in the carbon trading market to obtain income. The overall carbon trading model is as follows:

[0025]

[0026] where f CETis the carbon trading cost; χ is the carbon trading base price; α and β are the penalty and reward coefficients respectively; l is the interval length; C tran Carbon trading volume.

[0027] Green power purchase certificates have great development prospects in my country. However, my country still generally adopts the "certificate-electricity separation" trading model, and most consumers are not willing to consume green certificates. This paper adopts the "certificate-electricity integration" model to bundle green electricity and green certificates for sale. When purchasing electricity from wind farms in the agricultural comprehensive energy system, green certificates are purchased at the same time. This accelerates the economic return of wind farms and makes it easier for consumers to trace the source of green electricity.

[0028] In order to increase users' enthusiasm for purchasing green electricity and enhance its competitiveness in the market, setting a reasonable green electricity quota ratio for energy purchasers can not only increase the consumption rate of new energy, but also establish a good corporate image. In the agricultural comprehensive energy system, its quota should meet the following conditions:

[0029]

[0030] in and The agricultural integrated energy system purchases electricity from wind farms and power grids respectively. is the gas purchase power in period t; θ is the set green electricity quota ratio.

[0031] The agricultural integrated energy system aims to minimize the daily purchase and sale of energy while meeting the power balance of electricity, heat, cooling and gas:

[0032]

[0033] is the daily energy purchase cost of the system, The cost of purchasing green certificates for the system, Proceeds from selling energy for the agricultural integrated energy system.

[0034] Taking into account the mechanism of "one region, one price" for natural gas, in order to avoid and When the values ​​are taken at the same time and the solution cannot be found, the following constraints are satisfied:

[0035]

[0036] The following five scenarios are set up for comparative analysis. Scenario 1: Including BPP and BECCS system and ORC-based low-temperature waste heat power generation device, but only considering the traditional carbon trading mechanism; Scenario 2: Including BPP and ORC-based low-temperature waste heat power generation device, no BECCS system and considering the step-by-step carbon trading mechanism; Scenario 3: Including BPP and BECCS system, not including ORC-based low-temperature waste heat power generation device, considering the step-by-step carbon trading mechanism; Scenario 4: Including CCS system and ORC-based low-temperature waste heat power generation device, no BPP and considering the step-by-step carbon trading mechanism; Scenario 5: Including BPP, BECCS system and ORC-based low-temperature waste heat power generation device, and considering the step-by-step carbon trading mechanism. The optimization scheduling results under each scenario are shown in Table 1.

[0037] Optimize scheduling results in each scenario

[0038]

[0039] As shown in Table 1, in scenario 5, the system's carbon emissions of 29748kg are the lowest among all scenarios, which is 445kg lower than scenario 1 under the traditional carbon trading mechanism, 1363kg lower than scenario 2 without BECCS, and 2324kg lower than scenario 4 without BPP. This shows that BECCS combined with the step-by-step carbon trading mechanism can maximize the carbon reduction potential of the system. In terms of operating costs, scenario 1 has the lowest cost because the impact of the traditional carbon trading mechanism on the operation of the agricultural integrated energy system is not as significant as that of the step-by-step carbon trading. Among the other four scenarios considering the step-by-step carbon trading, the operating cost of scenario 5 is lower than that of other scenarios, achieving the goal of low-carbon economic operation of the agricultural integrated energy system.

[0040] Air source heat pumps and electric refrigeration machines bear most of the cooling and heating loads in the agricultural integrated energy system. Since the preservation of vegetables in the agricultural integrated energy system requires the cold storage to work for a long time, there is still a large cooling load at night, and when the temperature rises at noon, the cooling load will increase sharply. The change of heat load is relatively stable compared to the cooling load, but its average value is still high. Electric refrigeration machines can provide relatively stable cooling loads, while the remaining large amount of cooling and heating loads require air source heat pumps to flexibly supply energy.

[0041] Due to the high efficiency of air source heat pumps, dual air source heat pumps are used in this scheduling strategy. Heat pump 1 is almost in full power output state throughout the whole process. Since the peak-to-valley difference of the heat load is small and the average is large, the larger capacity heat pump 1 bears the "base load" part of the heat load. The working state of heat pump 2 is more flexible. Since the power of the cold load is small during the valley period and the energy supply priority of the electric refrigerator is not high, the electric refrigerator has a certain spare capacity. Heat pump 2 will switch to heating during the peak period of heat load and choose cooling during the non-peak period of heat load. This configuration of dual heat pumps combined with electric refrigerators improves the internal energy supply flexibility and operation economy of the agricultural comprehensive energy system.

[0042] As described above, the present invention has been described in detail. Obviously, the present invention is not limited to the given embodiments. As long as they do not substantially deviate from the inventive point and effect of the present invention and various modifications that can be made by technicians familiar with the field are also included in the protection scope of the present invention.

Claims

1. Considering the dispatching method of agricultural integrated energy system with biomass energy and air source heat pump; Firstly, the integrated energy system in agricultural scenario should be modeled as a whole. In order to meet the high electric heating and cooling load in agricultural base, break the barrier of single energy system in agricultural integrated energy system, realize the complementarity of different energy sources, and effectively play the advantages and potential of different energy sources, the equipment in agricultural integrated energy system includes PV, BPP, CHP device with integrated absorption chiller, low temperature waste heat power generation device based on ORC, air source heat pump, electric chiller, electric energy storage, thermal energy storage, CCS and P2G. When agricultural integrated energy system is connected to gas grid and distribution network, considering the principle of local consumption, agricultural integrated energy system signs an agreement with distributed wind farms near rural areas, which provides a new way for wind power consumption and increases its own green electricity purchase. BPP and CCS devices reduce carbon emissions of the system under the stimulation of step-by-step carbon trading and participate in the carbon trading market.

2. According to the content of claim 1, specific mathematical modeling is performed on its internal key equipment: Wheat, corn, soybeans, peanuts and other crops are planted in the agricultural integrated energy system. The crop straw can be used as a rich biomass resource, and the slag produced after its combustion can be used as fertilizer to feed back to the land in the agricultural integrated energy system. In the past, biomass power plants required a lot of investment in the acquisition, transportation, storage and pretreatment of biomass materials. The agricultural integrated energy system can complete the industrial chain closed loop of biomass power generation, eliminating the process of biomass acquisition and transportation. Biomass itself is considered to have zero carbon emissions. The CO2 produced during its combustion is equivalent to the CO2 absorbed during its growth. The flue gas produced by combustion can be captured by CCS, and the CO2 is sent to the P2G equipment, which can achieve negative carbon emissions and further tap the carbon reduction potential of the agricultural integrated energy system. Limited by the seasonality of crop harvesting, the calorific value contained in the harvested crop straw is calculated on an annual basis: Where L CS is the total calorific value of crop straw harvested in a year, N is the number of crop types whose straw can be harvested, and s i is the planting area of ​​the i-th type of crop, m i is the weight of harvestable straw per unit area of ​​the i-th type of crop, L i is the calorific value per unit mass of the i-th type of crop straw; In order to improve the stability and storage performance of crop straw, reduce its volume and humidity, and make it more suitable for biomass power generation, it is necessary to pre-treat it, usually by drying, crushing and pressing. Considering the sustainability of biomass power plants and making them participate in day-ahead scheduling, the total calorific value of biomass particles that can be used for power generation every day is L CSD : Where E CSD and Q CSD is the total value of electric energy and thermal energy dispatched by biomass power generation on the day before, and The efficiency of biomass energy conversion from electricity to heat; BPP satisfies the requirement that the total electric energy delivered during the daily dispatch cycle is equal to E CSD , which can improve the flexibility of the source side and further tap the potential of source-load matching. The model involved in scheduling is: in is the output power of BPP, δ BPP (t) is the working status flag of BPP, which is a 0-1 variable; and P is the maximum and minimum output power of BPP; and The minimum continuous working time and maximum number of switching times per day of BPP; The flue gas generated by BPP power generation can eventually absorb and store CO2 in the absorption tower through a monoethanolamine (MEA) aqueous solution to complete the biomass energy carbon capture and storage (BECCS) process. In addition to BPP, the flue gas from CHP can also undergo the above process in the agricultural integrated energy system. CO2 is released by heating in the regeneration tower. The released MEA solution can be sent back to the absorption tower for the next round of CO2 absorption, and the released CO2 can be sent to the P2G system for fixation. Compared with other types of heat pumps, air source heat pumps have the advantages of easy installation, strong adaptability, low initial investment, and no need for geothermal loops. They have been used to a certain extent in heating and industrial parks in the north. As an energy conversion unit, air source heat pumps provide the required cooling and heating loads in the agricultural comprehensive energy system. This article focuses on the energy flow of the equipment, so it mainly considers the power load consumed by the heat pump unit and the output cooling and heating loads. Its working model is: in and are the electrical power consumed by the heat pump and the heating and cooling power respectively; and are heating and cooling efficiencies, respectively; and They are heating and cooling working status flags, both are 0-1 variables; and They are the maximum power for heating and cooling respectively.

3. According to claim 1, the agricultural comprehensive energy system should consider the impact of the carbon trading mechanism and the green certificate trading mechanism in scheduling. Here, a reward-and-punishment type ladder carbon trading mechanism is adopted. While being more fair, it can also further tap the low-carbon potential of the system. The BPP in the agricultural comprehensive energy system is considered to have zero carbon emissions in the carbon trading mechanism. The carbon emission source is the gas turbine, so a carbon emission quota is set for the gas turbine. The gas turbine can generate electricity and heat at the same time. The conversion coefficient is introduced, and the carbon quota of the gas turbine is: Among them C QUO is the total carbon emission quota of agricultural comprehensive energy system, ε QUO is the carbon quota factor per unit thermal power, γ is the electric-to-heat conversion coefficient of the gas turbine, the part of the agricultural comprehensive energy system that exceeds the carbon emission quota needs to be purchased in the carbon trading market, and the part that is lower than the carbon emission quota can be sold in the carbon trading market to obtain income, then the overall carbon trading model is as follows: where f CET is the carbon trading cost; χ is the carbon trading base price; α and β are the penalty and reward coefficients respectively; l is the interval length; C tran is the carbon trading volume; Green power purchase certificates have great development prospects in my country. However, my country still generally adopts the "certificate-electricity separation" trading model, and most consumers are not willing to consume green certificates. Here, the "certificate-electricity integration" model is adopted to bundle green electricity and green certificates for sale. When purchasing electricity from wind farms in the agricultural comprehensive energy system, green certificates are purchased at the same time. This speeds up the economic return of wind farms and makes it easier for consumers to trace the source of green electricity. In order to increase users' enthusiasm for purchasing green electricity and enhance its competitiveness in the market, setting a reasonable green electricity quota ratio for energy purchasers can not only increase the consumption rate of new energy, but also establish a good corporate image. In the agricultural comprehensive energy system, its quota should meet the following conditions: in and The agricultural integrated energy system purchases electricity from wind farms and power grids respectively. is the gas purchase power in period t; θ is the set green electricity quota ratio.

4. The proposed scheduling strategy has been transformed into a mixed integer linear problem. After modeling the key equipment in the agricultural integrated energy system, including BPP, CHP, air source heat pump and BECCS, and introducing the step-by-step carbon trading mechanism and green certificate trading mechanism, the carbon trading cost and green certificate purchase are taken as part of the objective function. Finally, under the conditions of satisfying equipment output constraints and energy balance constraints, the objective function is: is the daily energy purchase cost of the system, The cost of purchasing green certificates for the system, Proceeds from selling energy for agri-energy systems; The proposed low-carbon economic dispatch strategy can obtain the optimal solution through the precise mathematical programming algorithm, and the CPLEX solver in the YALMIP toolbox is called on the MATLAB platform to solve it.

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