A system for utilizing abandoned wind power with electrical complementary combined cooling, heating and power

Abstract

A system for utilizing abandoned wind power with electrical complementary combined cooling and heating supply includes a wind farm that supplies power to the power grid. The abandoned wind power is stored as thermal energy through a heat storage electric boiler. The heat storage electric boiler supplies part of the energy to an absorption chiller to supplement the refrigeration application powered by the power grid. The remaining thermal energy is used for heating the urban heat load, and the thermal energy required for the remaining urban heat load is supplemented by a gas boiler. An "electrical complementary - combined cooling and heating supply" model is established according to the characteristics of abandoned wind power and cooling and heating loads. Then, considering the heating and cooling costs, an economic model of "electrical complementary - combined cooling and heating supply" is constructed. Finally, through case analysis, the economy is compared with the traditional "gas boiler - air conditioner" heating and cooling model. The results show that the proposed mode can reduce carbon emissions while consuming abandoned wind power, achieving the purpose of improving the system benefits.

Description

Technical Field

[0001] The present invention relates to the field of abandoned wind utilization in the field of wind power, and particularly relates to a system for utilizing abandoned wind by electrical complementary combined heat and cold supply. Background Art

[0002] At present, fossil energy is gradually exhausted. As a renewable energy source, wind energy is widely used in the power industry. Wind power generation has the advantages of low cost, no pollution, and reliable technology. It is expected that by 2050, the installed wind power capacity in China will exceed 1 billion kilowatts. However, the problem of abandoned wind in China's wind power is still severe. Taking Xinjiang as an example, the abandoned wind power in the whole region in 2020 was 4.97 billion kWh, and the abandoned wind rate was as high as 10.3%, far higher than the national average abandoned wind level. The ability of the power grid to absorb abandoned wind needs to be further improved.

[0003] To further promote the consumption of wind power, converting the electric load into a heat load for electric heating, and using a heat storage electric boiler to store heat and supply heat to absorb abandoned wind has received extensive attention from scholars. In response to this problem, there is existing technology that combines heat storage with wind power heating using a heat storage electric boiler to absorb abandoned wind, but there is no comparative analysis with traditional heating methods; a combined heating model of wind power - heat storage electric boiler is established, and it is solved and proved that the proposed method can effectively absorb abandoned wind. Regarding the problem of using a combined heat and power system to absorb abandoned wind, the heat storage technology is combined with the combined heat and power mode to establish an optimized dispatching model for combined cooling, heat and power generation with multi - energy complementarity, which proves the advantages and functions of multi - energy complementarity power generation; a combined cooling, heat and power system with electrical energy, wind energy, solar energy, natural gas and energy storage as the energy complementarity form is established, and different control strategies are proposed according to the grid - connected mode and island operation mode to improve the utilization rate of comprehensive energy; a coordinated dispatching control strategy for combined heating of electricity and coal boilers to absorb abandoned wind is proposed, an integrated benefit analysis model is established, and the effectiveness and economy of the strategy are proved through the analysis of a wind power heating project example.

[0004] Based on the above research, at present, many literatures use a single combined heat and power system or a heat storage electric boiler to absorb abandoned wind, and few literatures combine the two to establish an abandoned wind absorption model. On this basis, the present invention first analyzes the characteristics of abandoned wind, heating and refrigeration, and then improves the current gas heating mode using a gas boiler, a heat storage electric boiler and an absorption refrigeration system to obtain an "electrical complementary - combined heat and cold supply" abandoned wind absorption mode, and proposes a control strategy for this mode, establishes a heating and refrigeration economic model including a heat storage electric boiler, a gas boiler and an absorption refrigeration machine, and takes a wind farm in Xinjiang as an example for case analysis to verify the effectiveness of the "electrical complementary - combined heat and cold supply" abandoned wind absorption mode proposed by the present invention. Summary of the Invention

[0005] In order to solve the problems existing in the above - mentioned prior art, the purpose of the present invention is to provide a system for utilizing abandoned wind by electrical complementary combined heat and cold supply

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A waste wind utilization system for electrical complementary combined cooling and heating supply includes a wind farm that supplies power to the power grid. The waste wind is stored as heat energy through a heat storage electric boiler. The heat storage electric boiler supplies part of the energy to an absorption chiller to supplement the refrigeration application powered by the power grid, and the remaining heat energy is used for heating the urban heat load. The heat energy required for the remaining urban heat load is supplemented by a gas boiler.

[0008] Further, the system is specifically as follows: An electric-gas boiler-absorption chiller heating and cooling model is constructed. The system equipment includes a heat storage electric boiler, an absorption chiller, and a gas boiler. The cooling load is borne by the absorption chiller and industrial air-conditioning refrigeration, and the heating load is borne by the gas boiler and the heat storage electric boiler. The electric energy W sw (t) generated by the wind farm is connected to the power grid, and part of the waste wind power is converted into heat through the heat storage electric boiler; part of the heat Q xs (t) is used to produce β2Q xs (t) of cooling capacity through the absorption chiller to maintain the cooling load demand of the refrigeration application, and another part of the heat Q xr (t) and the heat supplied by the gas boiler are used together to heat users, and the remaining heat is stored in the heat storage tank of the heat storage electric boiler. At this time, the heat output of the gas boiler is Q rq .

[0009] Further, it is assumed that every 15 minutes is a time period, is the waste wind power absorbed and consumed by the heat storage electric boiler, Q L is the cooling capacity required for the cooling load in a certain time period, Q R is the heat required for the heating load in a certain time period, W G is the power purchased from the power grid in a certain time period, β1 is the power purchase refrigeration efficiency of the air conditioner, β2 is the refrigeration efficiency of the absorption chiller, β3 is the waste wind heating efficiency, Q S(t-1) is the remaining heat in the heat storage tank of the heat storage electric boiler in the previous time period, Q S(t) is the remaining heat in the heat storage tank of the heat storage electric boiler in this time period. Then Q LR =Q L / β2 is the heat required to be absorbed when the cooling load is all supplied by the absorption chiller, is the heating capacity of the heat storage electric boiler to absorb waste wind; the control strategy is as follows:

[0010] Compare the sum of the remaining heat in the heat storage tank in the previous time period and the heating capacity of the electric boiler to absorb waste wind with the heat required for heating and cooling. Taking the principle of giving priority to meeting the heat required for refrigeration, three cases are considered according to the size of the heat required for heating and cooling;

[0011] 1) When Q S(t-1) +Q qf ≥Q LR +Q R At this time, the heating capacity of the electric boiler and the remaining heat of the heat storage tank can simultaneously meet the heat required for heating and cooling, so there is no need to purchase electricity for refrigeration, nor is there a need for a gas boiler for heating. That is: W G = 0, Q rq = 0, Q S(t) = Q S(t-1) +Q qf -(Q LR +Q R ); (1)

[0012] 2) When Q LR ≤Q S(t-1) +Q qf <Q LR +Q R At this time, the heating capacity of the electric boiler and the remaining heat of the heat storage tank can only meet the heat required by the chiller, and the heat required for heating is supplied by the heat storage electric boiler and the gas boiler. That is: W G = 0, Q rq = Q R -(Q S(t-1) +Q qf -Q LR ), Q S(t) = 0; (2)

[0013] 3) When Q S(t-1) +Q qf <Q LR At this time, the heating capacity of the electric boiler and the remaining heat of the heat storage tank cannot meet the heat required for refrigeration, so electricity needs to be purchased for refrigeration at this time, and all the heat required for heating is supplied by the gas boiler. That is: W G = [Q L -(Q S(t-1) +Q qf )·β2] / β1, Q rq = Q R , Q S(t) = 0. (3)

[0014] Furthermore, the heat storage electric boiler model can be regarded as a combined configuration of an electric boiler model and a heat storage device model. The capacity of the heat storage device is determined according to the maximum heat load, and the capacity of the electric boiler is configured with the goal of maximizing the system life cycle benefit. The objective function of the system is:

[0015] maxF = M RS +M C -M RC -M LC -M YW (4)

[0016] wherein, F represents the system life cycle revenue; M RS —— heating revenue; M C —— carbon emission revenue; M RC —— heating cost; M LC —— cooling cost; M YW —— system operation and maintenance cost.

[0017] Furthermore, 1) The heating revenue is represented by the product of the heating area and the heating cost per unit area:

[0018] M RS = C1·S (5)

[0019] wherein, C1 represents the heating cost per unit area; S represents the heating area.

[0020] 2) The carbon emission revenue is represented by the product of the carbon emission revenue per unit and the reduced carbon emissions:

[0021] M C = C2·W C (6)

[0022] wherein, C2 represents the carbon emission revenue per unit; W C —— the reduced carbon emissions of the system.

[0023] Furthermore, the construction cost and operation cost of the heating and cooling systems of the said system

[0024] 1) Since the existing heating method is by gas boiler for heating, the construction cost of the gas boiler does not need to be considered for the heating system cost. Only the construction cost of the heat storage electric boiler and the fuel cost consumed during heating operation need to be considered. That is, the heating system cost is:

[0025] M RC = C xr + C gr = E xr ·H xr + Q rl ·H rl (7)

[0026]

[0027] E xr = E cr + E d (9)

[0028] wherein, C xr —— the construction cost of the heat storage electric boiler; C gr —— the heating operation cost; E xr —— the capacity of the heat storage electric boiler; Hxr —— Unit price of heat storage electric boiler; Q rl —— Total fuel consumption of the boiler; H rl —— Unit price of the fuel consumed by the boiler —— Unit price of the fuel consumed by the gas boiler —— Total gas consumption of the gas boiler —— Abandoned wind power price —— Total abandoned wind power consumed by the heat storage electric boiler; E cr —— Capacity of the heat storage device in the heat storage electric boiler; E d —— Capacity of the electric boiler in the heat storage electric boiler

[0029] 2) The cost of the refrigeration system includes the construction cost of the absorption refrigeration system, the fuel cost consumed during operation, and the electricity purchase cost for refrigeration. That is, the cost of the refrigeration system is:

[0030]

[0031] In the formula, C xs —— Construction cost of the absorption chiller; C gl —— Cooling operation cost; H xs —— Unit price of the absorption chiller; E xs —— Capacity of the absorption chiller —— Gas consumption of the absorption chiller; W G —— Electricity purchase quantity required to meet the cooling load; H d —— Unit price of electricity purchase

[0032] Furthermore, the maintenance cost of the system is related to the capacity of the system equipment, which refers to the maintenance cost caused by equipment loss. Then this cost is positively correlated with the construction cost of the system. Therefore, the system maintenance cost can be expressed as:

[0033] M YW =(C rq +C xr )·ρ1 + C xs ·ρ2 (11)

[0034] In the formula, ρ1—— Maintenance ratio of the boiler during the heating period; ρ2—— Maintenance ratio of the chiller during the heating period

[0035] Furthermore, the constraint conditions of the system are:

[0036] Heat constraint

[0037] The heating heat is supplied by the gas boiler and the heat storage electric boiler at the same time. Then the heat load demand heat is equal to the total heating heat of the two boilers, that is:

[0038] Q R (t)=Qrq (t) + Q xr (t) (12)

[0039] Wherein, Q R (t)——Heat load demand heat; Q rq (t)——Heat provided by gas boiler; Q xr (t)——Heating heat provided by heat storage electric boiler;

[0040] Cooling capacity constraint

[0041] The cooling capacity is supplied by absorption chiller and purchased electricity refrigeration, that is:

[0042] Q L (t) = Q xs (t)·β2 + W G (t)·β1 (13)

[0043] Wherein, Q L (t)——Cooling load demand cooling capacity; Q xs (t)——Heat absorbed by absorption chiller; W G (t)——Purchased electricity quantity;

[0044] Available abandoned wind constraint

[0045] The abandoned wind electricity quantity is the difference between the theoretical electricity generation and the actual electricity generation, and the available abandoned wind volume does not exceed the total abandoned wind electricity quantity, that is:

[0046]

[0047] Wherein, ——The abandoned wind volume consumed by the heat storage electric boiler, that is, the available abandoned wind volume.

[0048] Compared with the prior art, the beneficial effects of the present invention are:

[0049] The present invention aims at the problems of serious abandoned wind and the difficulty of "thermal-electric decoupling" in traditional heating methods, and proposes an "electricity-gas complementary - combined cooling and heating" abandoned wind consumption mode that combines heat storage electric boilers, gas boilers, and absorption chillers. First, an "electricity-gas complementary - combined cooling and heating" model is established according to the characteristics of abandoned wind and cooling and heating loads. Then, considering the heating and cooling costs, an "electricity-gas complementary - combined cooling and heating" economic model is constructed. Finally, through case analysis, the economy of the proposed model is compared with that of the traditional "gas boiler - air conditioner" heating and cooling model. The results show that the proposed model can reduce carbon emissions while consuming abandoned wind, achieving the purpose of improving system benefits. Description of the drawings

[0050] Figure 1 Schematic diagram for calculating the abandoned wind electricity quantity on a typical day;

[0051] Figure 2 System energy flow structure diagram;

[0052] Figure 3 Flow chart for abandoning wind and accommodating it;

[0053] Figure 4 Relationship between the total income of the system life cycle and the capacity of the electric boiler;

[0054] Figure 5 Comparison chart of abandoned wind power and cooling and heating loads;

[0055] Figure 6 Diagram of the regenerative electric boiler accommodating abandoned wind;

[0056] Figure 7 Cooling load demand diagram;

[0057] Figure 8 Heating load demand diagram. Specific implementation manner

[0058] The technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners:

[0059] As Figure 1-8 shown, the "combined supply" model

[0060] 1.1 Heating characteristics

[0061] The present invention uses abandoned wind to generate heat for heating nearby communities. The size of the heating load is related to the heating area. The heat demand for the heating load during a certain period is as follows:

[0062] Q R = k·S·Δt (1)

[0063] In the formula, Q R —— Heat demand for the heating load during a certain period; k—— Heating coefficient, taking different values in different scenarios, and generally taking 50 for the heating coefficient of residential buildings; S—— Heating area; Δt—— Calculation period of the heating quantity.

[0064] 1.2 Cooling characteristics

[0065] A large amount of heat is generated when the factory data center computer room and equipment components are working. If the heat is not dissipated in time, it will cause harm to the equipment and reduce the service life of the equipment to a certain extent. The heat dissipation problem of the data center building has traditionally been solved by using industrial air conditioners for refrigeration, which increases the cost expenditure to a certain extent.

[0066] The present invention uses an absorption refrigeration unit for refrigeration to achieve the purpose of dissipating heat for equipment, further absorbing curtailment of wind power, and enhancing the system's ability to absorb curtailment of wind power. Compared with the cooling load of general buildings, the cooling load of the data center computer room changes relatively stably throughout the year. In the present invention, the cooling capacity required for the cooling load during a certain period is regarded as a constant, that is:

[0067] Q L =K (2)

[0068] In the formula, Q L —— The cooling capacity required for the cooling load during a certain period; K —— A constant, and its value varies depending on the application scenario.

[0069] 1.3 Characteristics of curtailment of wind power

[0070] The randomness, volatility, and reverse load characteristics of wind power output will have an impact on the power system

[11] . For the calculation of curtailment of wind power, there is no unified method in the world. Generally, the curtailment of wind power is considered to be the difference between the theoretical power generation and the actual power generation. As Figure 1 shown in the schematic diagram of the calculation principle of curtailment of wind power for a typical day, it can be analyzed that curtailment of wind power on a typical day mostly occurs in periods such as 0:00 - 5:00, 9:00 - 11:00, 15:00 - 17:00, 22:00 - 24:00, etc., that is, during low load periods. Therefore, curtailment of wind power has reverse load characteristics.

[0071] In summary, the curtailment of wind power during a certain period is:

[0072]

[0073] In the formula, W qf —— Curtailment of wind power of the wind farm; t1 —— The starting time of the calculation period; t2 —— The ending time of the calculation period; P ll —— Theoretical power generation power of the wind farm; P sj —— Actual power generation power of the wind farm.

[0074] With the rapid development of wind power, due to the large volatility of wind power output, the slowdown of electricity demand, and the fact that most wind farm aggregation areas are in regions with relatively small loads, since 2010, serious problems of curtailment of wind power and power rationing have emerged in China. In 2020, the annual curtailment rate of wind power in Xinjiang was still as high as 10.3%, and there is still a certain gap from the goal of basically solving the problem of clean energy consumption.

[0075] 1.4 “Electrical complementary - combined cooling and heating supply” model

[0076] Taking a wind power station and a heating company in Xinjiang as examples, a heating and cooling model of electric-gas boiler-absorption chiller is constructed. The system equipment includes a heat storage electric boiler, an absorption chiller, and a gas boiler. The cooling load is borne by the absorption chiller and industrial air conditioners, and the heating load is borne by the gas boiler and the heat storage electric boiler.

[0077] The system energy flow structure diagram is as Figure 2 shown. The working principle of the system is to connect the electric energy W sw (t) generated by the wind farm to the power grid, and convert part of the curtailed wind power into heat through the heat storage electric boiler. Part of the heat Q xs (t) is used to produce β2Q xs (t) of cooling capacity through the absorption chiller to meet the cooling load demand of the data center building, and the other part of the heat Q xr (t) is used together with the heat supplied by the gas boiler to heat users. The remaining heat is stored in the heat storage tank of the heat storage electric boiler, as Figure 2 shown. At this time, the heat output of the gas boiler is Q rq .

[0078] Assume that each 15 minutes is a time period, is the curtailed wind power absorbed and consumed by the heat storage electric boiler, Q L is the cooling capacity of the cooling load demand in a certain time period, Q R is the heat of the heating load demand in a certain time period, W G is the electricity purchased from the power grid in a certain time period, β1 is the refrigeration efficiency of the air conditioner purchased with electricity, β2 is the refrigeration efficiency of the absorption chiller, β3 is the heating efficiency of curtailed wind power, Q S(t-1) is the remaining heat in the heat storage tank of the heat storage electric boiler in the previous time period, Q S(t) is the remaining heat in the heat storage tank of the heat storage electric boiler in this time period. Then Q LR =Q L / β2 is the heat required to be absorbed when the cooling load is all supplied by the absorption chiller, is the heat output of the heat storage electric boiler absorbing curtailed wind power. The control strategy is as follows:

[0079] Compare the sum of the remaining heat in the heat storage tank in the previous time period and the heat output of the electric boiler absorbing curtailed wind power with the heat required for heating and cooling. Taking the principle of giving priority to meeting the heat required for refrigeration, three cases are considered according to the size of the heat required for heating and cooling.

[0080] 1) When Q S(t-1) +Q qf ≥Q LR +Q RWhen the heat output of the electric boiler and the remaining heat in the heat storage tank can simultaneously meet the heat requirements for heating and cooling, there is no need to purchase electricity for refrigeration, nor is there a need for the gas boiler to provide heat for heating, that is: W G = 0, Q rq = 0, Q S(t) = Q S(t-1) + Q qf -(Q LR + Q R ).

[0081] 2) When Q LR ≤ Q S(t-1) + Q qf < Q LR + Q R At this time, the heat output of the electric boiler and the remaining heat in the heat storage tank can only meet the heat requirements of the chiller, and the heat required for heating is supplied by the heat storage electric boiler and the gas boiler, that is: W G = 0, Q rq = Q R -(Q S(t-1) + Q qf - Q LR ), Q S(t) = 0.

[0082] 3) When Q S(t-1) + Q qf < Q LR At this time, the heat output of the electric boiler and the remaining heat in the heat storage tank cannot meet the heat requirements for refrigeration, so electricity needs to be purchased for refrigeration at this time, and all the heat required for heating is supplied by the gas boiler, that is: W G = [Q L -(Q S(t-1) + Q qf )·β2] / β1, Q rq = Q R , Q S(t) = 0.

[0083] The flow chart of wind abandonment and consumption is as Figure 3 shown:

[0084] 2 Economic analysis of "electrical complementary - combined cooling and heating supply"

[0085] Since the current heating method in Xinjiang is mostly gas boiler heating, the capacity of the gas boilers of the heating company is determined. What needs to be configured is the capacity of the heat storage electric boiler, and the capacity of the refrigeration unit needs to be configured according to the cooling load demand to break the constraint of "determining electricity by heat".

[0086] 2.2 Objective function

[0087] The heat storage electric boiler model can be regarded as a combined configuration of an electric boiler model and a heat storage device model. The capacity of the heat storage device is determined according to the maximum heat load, and the capacity of the electric boiler is configured with the goal of maximizing the system life cycle benefit. The objective function of the system is:

[0088] maxF = M RS + M C - M RC - M LC - M YW (4)

[0089] In the formula, F——system life cycle benefit; M RS ——heating benefit; M C ——carbon emission benefit; M RC ——heating cost; M LC ——cooling cost; M YW ——system operation and maintenance cost.

[0090] 2.1.1 Heating and carbon emission benefits

[0091] 1) The heating benefit is expressed as the product of the heating area and the heating cost per unit area:

[0092] M RS = C1·S (5)

[0093] In the formula, C1——heating cost per unit area; S——heating area.

[0094] 2) The carbon emission benefit is expressed as the product of the carbon emission benefit per unit and the reduced carbon emissions:

[0095] M C = C2·W C (6)

[0096] In the formula, C2——carbon emission benefit per unit; W C ——reduced carbon emissions of the system.

[0097] 2.1.2 Construction cost and operation cost of heating and cooling systems

[0098] 1) Since the existing heating method is by gas boiler for heating, the construction cost of the gas boiler does not need to be considered for the heating system cost. Only the construction cost of the heat storage electric boiler and the fuel cost consumed during heating operation need to be considered. That is, the heating system cost is:

[0099] M RC = C xr + C gr = E xr ·H xr + Q rl ·H rl(7)

[0100]

[0101] E xr =E cr +E d (9)

[0102] In the formula, C xr —— Construction cost of the regenerative electric boiler; C gr —— Heating operation cost; E xr —— Capacity of the regenerative electric boiler; H xr —— Unit price of the regenerative electric boiler; Q rl —— Total amount of fuel consumed by the boiler; H rl —— Unit price of the fuel consumed by the boiler; —— Unit price of the fuel consumed by the gas boiler; —— Total amount of gas consumed by the gas boiler; —— Abandoned wind power price; —— Total amount of abandoned wind power consumed by the regenerative electric boiler; E cr —— Capacity of the heat storage device in the regenerative electric boiler; E d —— Capacity of the electric boiler in the regenerative electric boiler.

[0103] 2) The cost of the refrigeration system includes the construction cost of the absorption refrigeration system, the fuel cost consumed during operation, and the electricity purchase cost for refrigeration. That is, the cost of the refrigeration system is:

[0104]

[0105] In the formula, C xs —— Construction cost of the absorption chiller; C gl —— Cooling operation cost; H xs —— Unit price of the absorption chiller; E xs —— Capacity of the absorption chiller; —— Gas consumption of the absorption chiller; W G —— Electricity purchase quantity required to meet the cooling load; H d —— Unit price of electricity purchase.

[0106] 2.1.3 System maintenance cost

[0107] The maintenance cost of the system is related to the capacity of the system equipment and refers to the maintenance cost caused by equipment wear. Therefore, this cost is positively correlated with the construction cost of the system. So the system maintenance cost can be expressed as:

[0108] M YW =(C rq +C xr )·ρ1 + C xs ·ρ2 (11)

[0109] In the formula, ρ1 represents the maintenance ratio of the boiler during the heating period; ρ2 represents the maintenance ratio of the chiller during the heating period.

[0110] 2.2 Constraints

[0111] During the operation of the system, it should meet the heat constraint, cold constraint, and available abandoned wind constraint.

[0112] 2.2.1 Heat Constraint

[0113] The heating heat is supplied by the gas boiler and the heat storage electric boiler simultaneously. Then, the heat load demand heat is equal to the total heating heat of the two boilers, that is:

[0114] Q R (t) = Q rq (t) + Q xr (t) (12)

[0115] In the formula, Q R (t) represents the heat load demand heat; Q rq (t) represents the heat supplied by the gas boiler; Q xr (t) represents the heating heat supplied by the heat storage electric boiler.

[0116] 2.2.2 Cold Constraint

[0117] The cooling capacity is supplied by the absorption chiller and the purchased electricity refrigeration, that is:

[0118] Q L (t) = Q xs (t)·β2 + W G (t)·β1 (13)

[0119] In the formula, Q L (t) represents the cold load demand cold quantity; Q xs (t) represents the heat absorbed by the absorption chiller; W G (t) represents the purchased electricity quantity.

[0120] 2.2.3 Available Abandoned Wind Constraint

[0121] The abandoned wind power is the difference between the theoretical power generation and the actual power generation, and the available abandoned wind volume does not exceed the total abandoned wind power, that is:

[0122]

[0123] In the formula, —— represents the abandoned wind volume absorbed by the heat storage electric boiler, which is the available abandoned wind volume.

[0124] 3 Case Study

[0125] 3.1 Data Selection

[0126] This invention selects data from a wind farm and a heating company in Xinjiang. The gas boiler capacity of the original system is 1.4 MW, and the construction cost is 150,000 yuan. The original system has 5 industrial refrigeration air conditioners with a cooling capacity of 65 kW each, and the construction cost is 140,000 yuan. The heating period is set to 180 days, and the heating area of a certain building in the community is 20,000 m 2 , and the heating cost per unit heating area per month is 30 yuan / m 2 . The typical daily cooling load demand is 0.3 MW, the unit income from carbon emissions is 60 yuan / ton, the unit price of the heat storage electric boiler capacity is 900,000 yuan / MW, the unit price of the absorption chiller capacity is 2,500 yuan / kW. According to the size of the cooling load demand, the absorption chiller capacity of the system is set to 0.4 MW, and the gas unit price is 2.93 yuan / m 3 . The abandoned wind power price is 0.05 yuan / kWh, the purchased electricity unit price is 0.39 yuan / kWh. The annual maintenance ratios ρ1 of the boiler, ρ2 of the absorption chiller, and ρ3 of the air conditioner are all taken as 0.01. The electric cooling efficiency β1 of the air conditioner, the refrigeration efficiency β2 of the absorption chiller, and the heat generation efficiency β3 of the abandoned wind are all taken as 0.98. The normal operation life of the system is 15 years.

[0127] 3.2 Data Analysis

[0128] This invention first assumes that the heat storage device capacity of the heat storage electric boiler is 2 MWh, the initial heat storage of the heat storage tank is 0.35 MWh, and the maximum charge-discharge power is 0.25 MW according to the size of the heat load demand. Through the analysis and calculation of a large amount of data, the optimal electric boiler capacity of 1.537 MW is configured by using the beetle antennae search algorithm, and the relationship curve between the total life cycle income of the system and the electric boiler capacity is obtained as shown in Figure 4 follows:

[0129] Analysis Figure 4 It can be seen that as the electric boiler capacity increases, the total life cycle income of the system shows a trend of first increasing and then decreasing. When the electric boiler capacity is small, the abandoned wind power cannot be utilized to the maximum extent, and the gas boiler undertakes a large heat load, resulting in a large cost and a small system income. If the electric boiler capacity is too large, while meeting the heat load demand, it will cause a problem of capacity waste, making the construction cost and operation and maintenance cost of the heat storage electric boiler large and reducing the system economy. Then, by analyzing the wind power data, heat load, and cooling load data, the comparison diagram of the abandoned wind power and the cooling and heating load, and the diagram of the heat storage electric boiler consuming the abandoned wind are obtained as shown in Figure 5 and Figure 6 follows:

[0130] From Figure 5Analysis shows that the curtailment power is almost greater than the heat load and the cold load at any moment, and there is no curtailment phenomenon during the period from 19:00 to 21:00. According to the proposed control strategy, the heat storage electric boiler absorbs part of the curtailment power for heating. First, it meets the heat demand required for refrigeration, and then cooperates with the gas boiler for heating to meet the heat load demand.

[0131] The curtailment power absorbed by the heat storage electric boiler is calculated to obtain Figure 6 the heat storage electric boiler curtailment absorption diagram as shown. According to the data analysis and calculation, the total curtailment electricity of the system in a heating period is 6791.85 MWh, the curtailment volume absorbed by the system in a heating period is 4329.45 MWh, and 63.74% of the curtailment electricity is absorbed. It can be seen that the heat storage electric boiler has a certain ability to absorb curtailment.

[0132] Then, the analysis of the supply and demand of the cold and heat loads is carried out to obtain Figure 7 、 Figure 8 the cold and heat load demand diagrams as shown.

[0133] When the curtailment power at a certain moment is greater than 0.3 MW, the cold load is fully met by the absorption chiller for refrigeration; when the curtailment power at a certain moment is greater than 0 MW and less than 0.3 MW, the cold load demand is met by the industrial air conditioner purchasing electricity for refrigeration and the absorption chiller for refrigeration; when there is no curtailment, the cold load demand is fully met by the industrial air conditioner purchasing electricity for refrigeration. From Figure 7 it can be seen that the refrigeration power of the absorption chiller can basically meet the cold load demand on a typical day, and the power of the industrial air conditioner purchasing electricity for refrigeration is very small. Using the absorption chiller for refrigeration can effectively reduce the electricity purchase cost of the system and increase the energy utilization efficiency of the system to a certain extent.

[0134] As Figure 8 shown, the present invention selects the data of 48 moments in a day at intervals of 0.5 h to draw the heat load demand diagram of a typical day. Analysis shows that the heating power of the electric boiler in the heat storage electric boiler shows a trend of more at night and less during the day, which is consistent with the trend of the curtailment power on this day. The gas boiler plays a certain auxiliary heating role and cooperates with the heat storage electric boiler to jointly meet the heat load demand.

[0135] Analyzing the operation of the system from the economic perspective can better prove the feasibility and effectiveness of the "electrical complementary - combined cooling and heating supply" mode. In the traditional heating and cooling mode, the heat load is fully supplied and met by the gas boiler, and the cold load is fully met by the air conditioner purchasing electricity for refrigeration. The heating and cooling cost of the system is the sum of the gas cost required for heating and the electricity cost required for refrigeration. The system construction cost is the sum of the gas boiler cost and the industrial air conditioner construction cost. The system maintenance cost is the product of the construction cost, the maintenance coefficient, and the operation years. By calculating the various economic parameters of the mode proposed in the present invention and the traditional mode, the comparison results are shown in Table 1:

[0136] Table 1 Economic Comparison of Heating and Cooling Modes

[0137]

[0138] The results show that the "electrical complementary - combined heat and power" mode proposed in the present invention is more economical than the traditional mode. At the same time, this mode can bring a carbon emission benefit of 6.7539 million yuan while consuming curtailment of wind power, which not only improves the economy of the system and the utilization rate of wind energy, but also reduces carbon emissions to a certain extent.

[0139] 4 Conclusions

[0140] The present invention proposes an operation strategy for curtailment of wind power utilization by using a thermal energy storage electric boiler and a gas boiler for heating and an absorption chiller for cooling. Through case analysis of the data of a wind farm in Xinjiang, the following conclusions are obtained:

[0141] 1) The "electrical complementary - combined heat and power" curtailment of wind power utilization mode can effectively reduce the curtailment of wind power by nearly 64% in the wind farm and improve the energy utilization rate.

[0142] 2) An economic model with the goal of maximizing the system life - cycle benefit is established, and the capacity of the electric boiler in the optimal thermal energy storage electric boiler is configured to be 1.537 MW by using the beetle antennae search algorithm. The total system life - cycle benefit is 45.1313 million yuan, and its economy is better than that of the traditional heating and cooling system. If the wind power prediction technology is added, it can perform real - time scheduling of the thermal energy storage electric boiler, making the curtailment of wind power more fully utilized, which is also helpful for the dispatching of the power grid and further improves the economic and environmental benefits of the system.

[0143] As mentioned above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any change or replacement that can be thought of without creative work should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope defined by the claims.

Claims

1. An abandoned wind power utilization system for electrical complementary combined cooling and heating supply, characterized in that It includes a wind farm that supplies power to the power grid. The curtailed wind power is stored as thermal energy through a heat storage electric boiler. The heat storage electric boiler supplies part of the energy to an absorption chiller to supplement the refrigeration application powered by the power grid, and the remaining thermal energy is used to heat the urban heat load. The thermal energy required for the remaining urban heat load is supplemented by a gas boiler. The specific system is as follows: an electro-gas boiler-absorption chiller heating and cooling model is constructed, and the system equipment includes a heat storage electric boiler, an absorption chiller, and a gas boiler; the cooling load is borne by the absorption chiller and industrial air conditioners for refrigeration, and the heating load is borne by the gas boiler and the heat storage electric boiler; the electric energy W sw (t) generated by the wind farm is connected to the power grid, and a part of the curtailed wind power is converted into heat through the heat storage electric boiler; a part of the heat Q xs (t) is used to produce β2Q xs (t) of cooling capacity through the absorption chiller to maintain the cooling load demand of the refrigeration application, and another part of the heat Q xr (t) cooperates with the heat supplied by the gas boiler to heat the users, and the remaining heat is stored in the heat storage tank of the heat storage electric boiler. At this time, the heat output of the gas boiler is Q rq ; Assume that each 15 - minute period is a time interval, is the curtailed wind power absorbed and accommodated by the heat storage electric boiler, Q L is the cooling capacity required for the cooling load in a certain period, Q R is the heat quantity required for the heating load in a certain period, W G is the electricity purchased from the power grid in a certain period, β1 is the electricity - consumption refrigeration efficiency of the air conditioner, β2 is the refrigeration efficiency of the absorption chiller, β3 is the waste - wind heating efficiency, Q S(t-1) is the remaining heat in the heat storage tank of the heat storage electric boiler in the previous period, Q S(t) is the remaining heat in the heat storage tank of the heat storage electric boiler in this period, then Q LR = Q L / β2 is the heat required to be absorbed when the cooling load is fully supplied by the absorption chiller, is the heat generated by the heat storage electric boiler absorbing waste wind; The control strategy is as follows: Compare the sum of the remaining heat in the heat storage tank in the previous period and the heat generated by the electric boiler absorbing the curtailed wind power with the heat required for heating and refrigeration. Based on the principle of giving priority to meeting the refrigeration heat requirement, consider three cases according to the magnitude of the heat required for heating and refrigeration. 1) When Q S(t-1) +Q qf ≥Q LR +Q R At this time, the heating capacity of the electric boiler and the remaining heat of the heat storage tank can simultaneously meet the heat required for heating and cooling. Then, there is no need to purchase electricity for refrigeration, nor is there a need for a gas boiler to provide heat for heating. That is: W G = 0, Q rq = 0, Q S(t) = Q S(t-1) +Q qf -(Q LR +Q R ); 2) When Q LR ≤Q S(t-1) +Q qf <Q LR +Q R At this time, the heating capacity of the electric boiler and the remaining heat of the heat storage tank can only meet the heat required by the refrigerating machine, and the heat required for heating is supplied by the regenerative electric boiler and the gas boiler, that is: W G =0, Q rq =Q R -(Q S(t-1) +Q qf -Q LR ), Q S(t) =0; 3) When Q S(t-1) +Q qf <Q LR At this time, the heating capacity of the electric boiler and the remaining heat of the heat storage tank cannot meet the heat required for refrigeration. Then, power purchase for refrigeration is needed at this time, and all the heat required for heating is supplied by the gas boiler, that is: W G =[Q L -(Q S(t-1) +Q qf )β2] / β1, Q rq =Q R , Q S(t) =0.

2. The system according to claim 1, wherein The heat storage electric boiler model can be regarded as a combined configuration of an electric boiler model and a heat storage device model. Determine the capacity of the heat storage device according to the maximum heat load, and configure the capacity of the electric boiler with the goal of maximizing the system life cycle benefit. The objective function of the system is: maxF = M RS +M C -M RC -M LC -M YW (4) Where F is the system life cycle revenue; M RS is the heating revenue; M C is the carbon emission revenue; M RC is the heating cost; M LC is the cooling cost; M YW is the system operation and maintenance cost.

3. The system according to claim 2, wherein 1) The heating benefit is expressed as the product of the heating area and the heating cost per unit area: M RS = C1·S (5) In the formula, C1 represents the heating cost per unit area; S represents the heating area. 2) The carbon emission benefit is expressed as the product of the unit carbon emission benefit and the reduced carbon emissions: M C = C2·W C (6) Where C2 is the unit carbon emission benefit; W C —— the carbon emission reduction of the system.

4. The system according to claim 3, wherein The construction cost and operation cost of the heating and refrigeration systems of the said system 1) Since the existing heating method is by a gas boiler, the construction cost of the gas boiler does not need to be considered for the heating system cost. Only the construction cost of the heat storage electric boiler and the fuel cost consumed during heating operation need to be considered. That is, the heating system cost is: M RC = C xr + C gr = E xr · H cr + Q r1 · H r1 (7) E xr = E cr + E d (9) In the formula, C xr —— The construction cost of the heat storage electric boiler; C gr —— The heating operation cost; E xr —— The capacity of the heat storage electric boiler; H xr —— The unit price of the heat storage electric boiler; Q rl —— The total amount of fuel consumed by the boiler; H rl —— The unit price of the fuel consumed by the boiler; —— The unit price of the fuel consumed by the gas boiler; —— The total amount of gas consumed by the gas boiler; —— The abandoned wind power price; —— The total amount of abandoned wind power consumed by the heat storage electric boiler; E cr —— The capacity of the heat storage device in the heat storage electric boiler; E d —— The capacity of the electric boiler in the heat storage electric boiler; 2) The refrigeration system cost includes the construction cost of the absorption refrigeration system, the fuel cost consumed during operation, and the electricity purchase refrigeration cost. That is, the refrigeration system cost is: Wherein, C xs —— Construction cost of the absorption chiller; C gl —— Operating cost of cooling supply; H xs —— Unit price of the absorption chiller; E xs —— Capacity of the absorption chiller; —— Gas consumption of the absorption chiller; W G —— Electricity purchase quantity required to meet the cooling load; H d —— Unit price of electricity purchase.

5. The system according to claim 4, wherein The maintenance cost of the said system is related to the capacity of the system equipment and refers to the maintenance cost caused by equipment wear. Then this cost is positively correlated with the construction cost of the system. So the system maintenance cost can be expressed as: M YW = (C rq + C xr ) · ρ1 + C x s · ρ2 (11) In the formula, ρ1 represents the maintenance ratio of the boiler during the heating cycle; ρ2 represents the maintenance ratio of the chiller during the heating cycle.

6. The system according to claim 5, wherein The constraint conditions of the said system are: Heat constraint The heating heat is supplied by the gas boiler and the heat storage electric boiler at the same time. Then the heat load demand heat is equal to the total heating heat of the two boilers. That is: Q R Q(t) = Q rq Q(t) + Q xr Q(t)(12) Where, Q R (t) —— Heat load demand heat; Q rq (t) —— Heat provided by the gas boiler; Q xr (t) —— Heating heat provided by the heat storage electric boiler; Cooling capacity constraint The cooling capacity is supplied by the absorption chiller and the electricity purchase refrigeration. That is: Q L ψ(t) = Q xs ψ(t)·β2 + W G ψ(t)·β1 (13) Where, Q L (t)——Cooling load demand cooling capacity; Q xs (t)——Heat absorbed by the absorption chiller; W G (t)——Purchased electricity quantity; Available curtailed wind constraint The curtailed wind power is the difference between the theoretical power generation and the actual power generation, and the available curtailed wind volume does not exceed the total curtailed wind power. That is: In the formula, —— The air volume of waste heat stored in the electric boiler for consumption, which is the available air volume of waste heat.

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