A method for predicting power generation and time of expansion power generation system

Abstract

The invention discloses a method for predicting the power generation and time of an expansion power generation system, which comprises: determining the minimum working pressure of a gas storage tank and the minimum operating liquid level of a heat storage tank; collecting the air pressure of the gas storage tank in real time; the air temperature of the gas storage tank; the absolute humidity of the air in the gas storage tank; the air pressure at the outlet of a final expander; the air temperature at the outlet of the final expander, the absolute humidity of the air at the outlet of the final expander, and the air density of the gas storage tank; the current power generation value; the liquid level of the heat storage tank; the temperature of the heat storage tank, the pressure of a heating medium, the outlet temperature of a heat pump, the outlet temperature of a heating medium of an n-stage heat exchanger, and the density of a heating medium; calculating the remaining power generation of the gas storage tank; calculating the remaining power generation of the heat storage tank; calculating the remaining power generation of the expansion power generation system and the remaining power generation time of the heat storage tank; solving the technical problems that the remaining power generation and the remaining power generation time of the expansion power generation system cannot be grasped during the operation of the expansion power generation.

Description

Technical Field

[0001] The present invention belongs to the technical field of compressed air energy storage, and in particular relates to a method for predicting the amount of power generated and time of an expansion power generation system. Background Art

[0002] As the scale of renewable energy power generation grows, the problems of intermittent and volatile power generation and even anti-regulation become more and more prominent. Effective technical solutions are urgently needed to solve the problem of large-scale grid connection of renewable energy. Large-scale power storage technology is an effective way to solve this problem. Compressed air energy storage system is considered to be one of the most promising large-scale power storage technologies, with the advantages of large energy storage scale, long storage cycle and low environmental pollution.

[0003] The compressed air energy storage system includes an energy storage power consumption system and an energy release power generation system. The energy storage power consumption system uses a compressor to pressurize the air to a higher pressure during the low electricity consumption period, and then stores it in the gas tank after cooling. The energy release power generation system heats the air in the gas tank to a certain temperature during the peak electricity consumption period, and then sends it into the air expander to drive the generator to provide electricity to the power grid. Its work capacity is composed of two parts: the work done by the compressed air in the gas tank and the work done by the heat in the heat storage tank. Both parts of the work capacity are limited and can no longer generate power after reaching the limit conditions. This is different from the conventional power generation form. The existing technology only monitors the equipment operating parameters such as the pressure temperature of the gas tank and the temperature and liquid level of the heat storage tank during the expansion power generation operation. The remaining power generation capacity and remaining power generation time of the expansion power generation system cannot be grasped, which is not conducive to the operation of related units and the arrangement of power grid operation mode according to the power generation capacity in advance, and is not conducive to the coordinated control of the energy storage system and new energy power generation. Summary of the invention

[0004] The technical problem to be solved by the present invention is: to provide a method for predicting the power generation and time of an expansion power generation system, so as to solve the technical problems that during the expansion power generation operation, only the pressure temperature of the gas storage tank and the temperature and liquid level of the heat storage tank can be monitored, and the remaining power generation and remaining power generation time of the expansion power generation system cannot be grasped, which is not conducive to arranging the operation of related units and the operation mode of the power grid in advance according to the power generation capacity, and is not conducive to the coordinated control of the energy storage system and new energy power generation.

[0005] The technical solution of the present invention is:

[0006] A method for predicting the amount of power generated and time of an expansion power generation system, comprising:

[0007] Step 1, determine two limiting values ​​of the compressed air energy storage power generation system, the minimum working pressure of the air storage tank and the minimum operating liquid level of the heat storage tank;

[0008] Step 2: Real-time collection of the air pressure Pgg of the gas storage tank; the air temperature Tgg of the gas storage tank; the absolute humidity dgg of the air in the gas storage tank; the air pressure Pge of the final expander outlet; the air temperature Tge of the final expander outlet, the absolute humidity dge of the air at the final expander outlet, and the air density ρg of the gas storage tank; the current power generation value Wn; the liquid level Ht of the heat storage tank; the temperature Ttg of the heat storage tank, the pressure Pte of the heating medium, the outlet temperature Tte of the heat pump, the outlet temperature Tte1.....Tten of the heating medium of the n-stage heat exchanger, and the density ρt of the heating medium;

[0009] Step 3, calculate the remaining power generation capacity of the gas storage tank;

[0010] Step 4, calculating the remaining power generation of the heat storage tank;

[0011] Step 5: Calculate the remaining power generation of the expansion power generation system and the remaining power generation time of the heat storage tank.

[0012] The method for determining the minimum working pressure of the gas tank is: when the expander air intake valve is fully opened and the power generated by the expansion generator is the minimum power (Wl), the pressure of the gas tank is the minimum working pressure of the gas tank.

[0013] The method for determining the minimum operating liquid level of the heat storage tank is: the heat pump does not cavitation due to low inlet pressure caused by the drop in the liquid level of the heat storage tank, and the minimum operating liquid level is determined to be equal to the minimum cavitation margin of the heat pump.

[0014] The air temperature measurement method of the gas tank is as follows: if there is one gas tank, the air temperature is measured at no less than 3 points, covering the bottom, middle and top of the gas tank, and the mathematical average is finally taken; if there are more than one gas tank, each gas tank has an air temperature measurement point, and the mathematical average is finally taken. The temperature uses a contact PT100 thermal resistor temperature sensor, and the probe penetrates vertically into 1 / 3 of the diameter of the gas tank.

[0015] The measurement method of air pressure, air humidity and air density of the gas tank is as follows: if there is one gas tank, the measuring point is at the outlet of the gas tank pipeline; if there are more than one gas tank, each gas tank is set with a measuring point, and the mathematical average is finally taken; the pressure is measured by a resistive strain gauge pressure sensor; the flow measurement adopts an inserted vortex gas flow sensor installed in the straight pipe section of the pipeline; the density measurement adopts a resonant tuning fork online density meter.

[0016] The calculation method of the remaining power generation capacity of the gas tank is:

[0017] Apgu=(((Pgg-Pgl) / Pgg)*V*ρg*(hgg-hge))

[0018] Where: Apgu is the remaining power generation of the gas tank, Pgl is the minimum working pressure of the gas tank, V is the volume of the gas tank, hgg is the air enthalpy value corresponding to the air pressure, temperature and absolute humidity of the gas tank, and hge is the enthalpy value corresponding to the air pressure, temperature and absolute humidity at the outlet of the final expander.

[0019] The calculation method of the remaining power generation of the thermal storage tank is:

[0020]

[0021] In the formula: Aptu is the remaining power generation of the heat storage tank, Vu is the available heating medium volume capacity, hte0 is the calorific value corresponding to the pressure and temperature of the heating medium at the heat pump outlet, hte1.......hten is the calorific value corresponding to the heating medium at the n-stage heat exchanger outlet, η i is the heat transfer efficiency of the i-stage heat exchanger.

[0022] Calculate the remaining power generation of the expansion power generation system and the remaining power generation time of the heat storage tank:

[0023] Appu=Apgu+Aptu

[0024] tpu=Appu / Wn

[0025] Where: Appu is the remaining power generation of the expansion power generation system; tpu is the remaining power generation time of the expansion power generation system.

[0026] Beneficial effects of the present invention:

[0027] The present invention combines the characteristics of compressed air energy storage, determines the corresponding limiting power generation conditions, and calculates the remaining power generation of the expansion power generation system provided by the gas storage tank and the heat storage tank in real time by monitoring parameters such as the pressure temperature of the gas storage tank and the temperature and liquid level of the heat storage tank. The remaining power generation time of the power generation system is calculated according to the current power generation power, and the operation of the relevant units and the operation mode of the power grid can be arranged in advance according to the power generation capacity prediction, so as to better realize the coordinated control of the energy storage system and the new energy power generation and improve the new energy consumption capacity.

[0028] Advantages of the present invention:

[0029] The relationship between the pressure and temperature of the gas tank of the expansion generator set, the temperature and liquid level of the heat storage tank and other parameters and the remaining power generation and remaining power generation time of the expansion power generation system are revealed, and the amount of power and time that the expansion power generation system can generate are calculated in real time, making the power generation capacity of the expansion generator measurable and observable.

[0030] Arrange the unit operation in advance and in an orderly manner according to the remaining power output and operating time of the expansion generator set.

[0031] Provide sufficient time to process the grid operation mode to prevent the impact of sudden load reduction on the grid.

[0032] Based on the compressed air energy storage system power generation output forecast and the new energy power generation output forecast, the coordinated control between the energy storage power generation system and new energy can be better strengthened, and the new energy consumption capacity can be improved.

[0033] It solves the technical problems that during the expansion power generation operation, only the pressure temperature of the gas tank and the temperature and liquid level of the heat storage tank can be monitored, and the remaining power generation capacity and remaining power generation time of the expansion power generation system cannot be grasped, which is not conducive to the operation of related units and the arrangement of power grid operation mode in advance according to the power generation capacity, and is not conducive to the coordinated control of the energy storage system and new energy power generation. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the process of the present invention;

[0035] Figure 2 It is a schematic diagram of the hardware system composition of the present invention. DETAILED DESCRIPTION

[0036] The invention discloses a compressed air energy storage system for expansion and power generation. Figure 1 , including: an air storage tank (1), an air intake regulating valve (2), a multi-stage expansion machine (3), a generator (4), a heat storage tank (5), a heat pump (6), a multi-stage heat exchanger (7), and a cold storage tank (8). The air storage tank stores high-pressure compressed air, which is connected to the first-stage heat exchanger through a pipeline for heating and then goes to the first-stage expansion machine of the multi-stage expansion machine. The compressed air is discharged from the first-stage expansion machine after doing work, and enters the second-stage expansion machine after being heated by the second-stage heater, and so on, until it is discharged from the last-stage expansion machine. The heat storage tank stores heat through a heat exchange medium, which enters each stage of the heat exchanger to heat the compressed air after being pressurized by a heat pump, and enters the cold storage tank after the heat exchange medium is cooled. The number of multi-stage heaters is equal to the number of multi-stage expansion machines, and is arranged at the corresponding expansion machine inlet. The high-temperature and high-pressure compressed air enters the expansion machine to drive the expansion machine to rotate, and the expansion machine drives the generator to rotate through the shaft to generate electricity.

[0037] The multi-stage expander (3) comprises a first-stage expander 301, a second-stage expander 302, a third-stage expander 303, and so on, and n-th-stage expander stages.

[0038] The multi-stage heat exchanger (7) includes a first-stage heat exchanger 701, a second-stage heat exchanger 702, a third-stage heat exchanger 703, ... an n-th-stage heat exchanger.

[0039] A method for predicting the amount of power generated and time of an expansion power generation system, specifically comprising:

[0040] The first step is to determine the two limiting values ​​of the compressed air energy storage power generation system, the minimum working pressure of the air storage tank and the minimum operating liquid level of the heat storage tank, as follows:

[0041] Determine the minimum working pressure (Pl) of the gas storage tank by fully opening the expander intake valve and the gas storage tank pressure when the expansion generator generates the minimum power (Wl) as the minimum working pressure of the gas storage tank.

[0042] The minimum power generation power (Wl) of the expansion generator is 10% of the rated power of the expansion generator. When the expansion generator operates at 10% of the rated power, 1. the flow rate of compressed air will be reduced due to high-speed rotation, causing the expander body to overheat, 2. the efficiency of the expander body will be reduced, and 3. the pressure of the air tank will be low, which will cause the efficiency of the entire compressed air energy storage system including the compressor to be low.

[0043] Determine the minimum operating liquid level (Hl) of the heat storage tank. The restriction condition is that the heat pump does not cavitation due to low inlet pressure caused by the drop in the liquid level of the heat storage tank. Therefore, the minimum operating liquid level (unit: meter) is determined to be equal to the minimum cavitation margin of the heat pump (unit: meter). That is, when the liquid level of the heat storage tank gradually decreases during operation, when it is equal to the minimum operating liquid level (Hl), stop the system operation.

[0044] The second step is to collect Pgg, Tgg, dgg, Pge, Tge, dge, ρg, Wn, Ht, Ttg, Pte, Tte, Tte1.....Tten, ρt in real time.

[0045] Pgg is the air pressure of the gas tank, Tgg is the air temperature of the gas tank, dgg is the absolute humidity of the air in the gas tank, Pge is the air pressure at the outlet of the last stage expander, Tge is the air temperature at the outlet of the last stage expander, dge is the absolute humidity of the air at the outlet of the last stage expander, ρg is the air density of the gas tank, Wn is the current power generation value, Ht is the liquid level of the heat storage tank, Ttg is the temperature of the heat storage tank, Pte is the heating medium pressure, Tte is the outlet temperature of the heat pump, Tte1...Tten is the outlet temperature of the heating medium of the n-stage heat exchanger, and ρt is the density of the heating medium.

[0046] Air temperature measurement requirements for gas tanks: If there is one gas tank, the air temperature should be measured at no less than 3 points, covering the bottom, middle and top of the gas tank, and the mathematical average should be taken for calculation. Because the air in the gas tank does not flow out stably during operation, the temperature at different heights in the gas tank is different. If there are multiple gas tanks, each gas tank has an air temperature measurement point, and the mathematical average should be taken for calculation.

[0047] The requirements for measuring the air pressure, air humidity and air density of the gas tank are as follows: If there is only one gas tank, the measuring point is at the outlet of the gas tank pipeline. If there are multiple gas tanks, each gas tank has a measuring point, and the mathematical average is finally calculated.

[0048] The temperature adopts contact PT100 thermal resistance temperature sensor, the probe is vertically inserted into 1 / 3 of the diameter of the gas tank, and outputs 4~20mA signal.

[0049] The pressure adopts resistance strain gauge pressure sensor, with a range of 0-25MPa and an output signal of 4-20mA

[0050] The flow measurement uses an inserted vortex gas flow sensor installed in the straight section of the pipeline. Because the pipeline will produce unstable flow during the adjustment process, the amplifier is separated from the sensor. The sensor uses an interference cancellation circuit and an anti-vibration sensor head, has anti-environmental vibration performance, and outputs 4-20mA signals.

[0051] Density measurement uses a resonant tuning fork online density meter, which outputs 4-20mA signal.

[0052] The third step is to calculate the remaining power generation capacity of the gas tank:

[0053] Apgu=(((Pgg-Pgl) / Pgg)*V*ρg*(hgg-hge))

[0054] In the formula: Apgu is the remaining power generation of the gas tank, Pgl is the minimum working pressure of the gas tank, V is the volume of the gas tank, hgg is the air enthalpy value corresponding to the air pressure, temperature and absolute humidity of the gas tank, and hge is the enthalpy value corresponding to the air pressure, temperature and absolute humidity at the outlet of the final expander;

[0055] The fourth step is to calculate the remaining power generation of the heat storage tank:

[0056]

[0057] In the formula: Aptu is the remaining power generation of the heat storage tank, Vu is the available heating medium volume capacity, hte0 is the calorific value corresponding to the pressure and temperature of the heating medium at the heat pump outlet, hte1.......hten is the calorific value corresponding to the heating medium at the n-stage heat exchanger outlet, η i is the heat transfer efficiency of the i-stage heat exchanger

[0058] According to the current liquid level (Hg) and the minimum liquid level (Hl), the available heating medium volume capacity (Vu) is calculated through the shape of the heat storage tank (generally a spherical tank or a cylindrical tank).

[0059] Step 5: Calculate the remaining power generation of the expansion power generation system and the remaining power generation time of the heat storage tank: Appu = Apgu + Aptu

[0060] tpu=Appu / Wn

[0061] Where: Appu is the remaining power generation of the expansion power generation system.

[0062] tpu is the remaining power generation time of the expansion power generation system.

[0063] When Appu≤Apcu, an alarm for the remaining power generation of the compressed air energy storage system is issued.

[0064] When tpu≤tcu, an alarm for the remaining power generation time of the compressed air energy storage system is issued.

[0065] Apcu is the alarm value of the remaining power generation of the compressed air energy storage system; tcu is the alarm value of the remaining power generation time of the compressed air energy storage system.

[0066] Case: The system power generation capacity is 10MW and the gas storage capacity of the gas tank is 6000m 3 The initial pressure and temperature are set to 10MPa and 30℃ respectively. The minimum working pressure of the gas storage tank is 2MPa and the temperature is 0℃. The heat storage tank is cylindrical with a bottom area of ​​33m 2 The initial water level, pressure and temperature are 5m, 0.2MPa and 120℃ respectively, and the lowest liquid level is 0.4m.

[0067] Step 1: Through the real-time monitoring system, collect data Pgg = 9.741MPa, Tgg = 27.702℃, dgg = 0%, Pge = 0.087MPa, Tge = 21.026℃, dge = 0%, ρg = 112.313kg / m 3 , Wn=10.076MW, Ht=4.179m, Ttg=119.957℃, Pte=0.199MPa, Tte=119.7℃, Tte1....Tten=110.7℃, 102.7℃, 94.2℃, 86.1℃, ρt=943.1kg / m 3 .

[0068] Step 2: According to the air parameters in the air storage tank Pgg = 9.741MPa, Tgg = 27.702℃, dgg = 0%, hgg = 27.883kJ / kg. According to the air parameters at the outlet of the final expander Pge = 0.087MPa, Tge = 21.026℃, dge = 0%, hee = 23.009kJ / kg.

[0069] The rated power of the expansion generator is 10MW, and the minimum load is 1MW. Under the minimum load condition, when the expander intake valve is fully opened, the pressure of the gas storage tank, that is, the minimum working pressure, is 2MPa, and the temperature in the gas storage tank is 0℃.

[0070] Calculate the remaining power generation capacity of the gas tank:

[0071] Apu=((Pgg-Pgl) / Pgg)*V*ρg*(hgg-hge)=((9.741*106 -2*10 6 ) / (9.741*10 6 ))*112.313*6000*(27.883-23.009)=2610119.1kJ=725kW·h

[0072] Step 3: The lowest operating liquid level of the heat storage tank, i.e. the lowest NPSH of the heat pump, is H1 = 0.4m. Calculate the available heating medium volume capacity Vu = (4.179-0.4)*33 = 137.918m3.

[0073] According to the outlet heating medium temperature of the n-stage heat exchanger Tte1 = 110.7 ° C, Tte2 = 102.7 ° C, Tte3 = 94.2 ° C, Tte4 = 86.1 ° C, the corresponding calorific value hte1 = 465.733 kJ / kg, hte2 = 431.701 kJ / kg, hte3 = 395.593 kJ / kg, hte4 = 361.413 kJ / kg is obtained by looking up the table. According to the outlet temperature of the heat pump Tte = 119.7 ° C, the corresponding calorific value hte = 503.794 kJ / kg is obtained.

[0074] Calculate the remaining power generation capacity and remaining power generation time of the thermal storage tank:

[0075]

[0076] Step 4: Calculate the remaining power generation and remaining power generation time of the expansion power generation system:

[0077] Appu=Apgu+Aptu=725+5041.44=5766.47kW·h.

[0078] tpu=Appu / Wn=5766.47*3600 / 10076=2060s.

[0079] Features of the present invention:

[0080] 1) The work done by the expansion power generation system is the work done by the compressed air in the gas storage tank plus the work done by the heat in the heat storage tank.

[0081] 2) By monitoring the pressure and temperature of the gas storage tank, the liquid level temperature of the heat storage tank and other parameters, the remaining power generation in the expansion power generation system is calculated and predicted.

[0082] 2) The remaining power generation time in the expanded power generation system is predicted by the remaining power generation amount and the current power generation value in the expanded power generation system.

[0083] 4) A method for determining the minimum working pressure is provided, which is to fully open the expander air intake valve to maintain the pressure of the minimum load of the expander generator, and the minimum load of the expander generator is 10% of the rated power of the expander generator.

[0084] 5) The minimum operating liquid level of the heat storage tank (Hl) is equal to the minimum NPSH of the heat pump.

[0085] 6) The heating medium of the heat storage tank can be water, thermal oil or molten salt.

Claims

1. A method for predicting the amount of power generated and the time of power generation of an expansion power generation system, comprising: Step 1, determine two limiting values ​​of the compressed air energy storage power generation system, the minimum working pressure of the air storage tank and the minimum operating liquid level of the heat storage tank; Step 2: Real-time collection of the air pressure Pgg of the gas storage tank; the air temperature Tgg of the gas storage tank; the absolute humidity dgg of the air in the gas storage tank; the air pressure Pge of the outlet of the final expander; the air temperature Tge of the outlet of the final expander, the absolute humidity dge of the outlet of the final expander, and the air density ρg of the gas storage tank; the current power generation value Wn; the liquid level Ht of the heat storage tank; the temperature Ttg of the heat storage tank, the pressure Pte of the heating medium, the outlet temperature Tte of the heat pump, the outlet temperature Tte1 of the heating medium of the n-stage heat exchanger, and the density ρ of the heating medium t ; Step 3, calculate the remaining power generation capacity of the gas storage tank; The calculation method of the remaining power generation capacity of the gas tank is: A pgu =(((Pgg-Pgl) / Pgg)*V*ρg*(hgg-hge)) Where: A pgu is the remaining power generation of the gas tank, Pgl is the minimum working pressure of the gas tank, V is the volume of the gas tank, hgg is the air enthalpy value corresponding to the air pressure, temperature and absolute humidity of the gas tank, and hge is the enthalpy value corresponding to the air pressure, temperature and absolute humidity at the outlet of the final expander; Step 4, calculating the remaining power generation of the heat storage tank; The calculation method of the remaining power generation of the thermal storage tank is: Where: A ptu is the remaining power generation of the thermal storage tank, V u is the available heating medium volume capacity, h te0 is the calorific value corresponding to the pressure and temperature of the heating medium at the heat pump outlet, h te1 .......h ten is the calorific value of the heating medium at the outlet of the n-stage heat exchanger, η i is the heat transfer efficiency of the i-stage heat exchanger; according to the current liquid level Hg and the lowest liquid level Hl, the available heating medium volume capacity V is calculated through the shape of the heat storage tank u ; Step 5, calculating the remaining power generation amount and the remaining power generation time of the expansion power generation system; Calculate the remaining power generation and remaining power generation time of the expansion power generation system: A ppu =A pgu +A ptu t pu =A ppu / Wn Where: A ppu The remaining power generation of the expansion power generation system; t pu It is the remaining power generation time of the expansion power generation system.

2. A method for predicting the amount of power generated and time of an expansion power generation system according to claim 1, characterized in that: The method for determining the minimum working pressure of the gas storage tank is: fully open the expander air intake valve, and the gas tank pressure when the expansion generator power is the minimum power Wl is the minimum working pressure of the gas storage tank.

3. The method for predicting the amount of power generated and the time of power generation of an expansion power generation system according to claim 1, characterized in that: The method for determining the minimum operating liquid level of the heat storage tank is: the heat pump does not cavitation due to low inlet pressure caused by the drop in the liquid level of the heat storage tank, and the minimum operating liquid level is determined to be equal to the minimum cavitation margin of the heat pump.

4. The method for predicting the amount of power generated and the time of power generation of an expansion power generation system according to claim 1, characterized in that: The air temperature measurement method of the gas tank is as follows: if there is one gas tank, the air temperature is measured at no less than 3 points, covering the bottom, middle and top of the gas tank, and the mathematical average is finally taken; if there are more than one gas tank, each gas tank has an air temperature measurement point, and the mathematical average is finally taken. The temperature uses a contact PT100 thermal resistor temperature sensor, and the probe penetrates vertically into 1 / 3 of the diameter of the gas tank.

5. The method for predicting the amount of power generated and the time of power generation of an expansion power generation system according to claim 1, characterized in that: The measurement method of air pressure, air humidity and air density of the gas tank is as follows: if there is one gas tank, the measuring point is at the outlet of the gas tank pipeline; if there are more than one gas tank, each gas tank is set with a measuring point, and the mathematical average is finally taken; the pressure is measured by a resistive strain gauge pressure sensor; the flow measurement adopts an inserted vortex gas flow sensor installed in the straight pipe section of the pipeline; the density is measured by a resonant tuning fork online density meter.

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