CN108666600B - All-vanadium redox flow battery SOC detection method based on thermochemical measurement - Google Patents
All-vanadium redox flow battery SOC detection method based on thermochemical measurement Download PDFInfo
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- 229910052720 vanadium Inorganic materials 0.000 title claims abstract description 44
- 238000001514 detection method Methods 0.000 title claims abstract description 26
- 238000005259 measurement Methods 0.000 title claims abstract description 26
- 230000008859 change Effects 0.000 claims abstract description 76
- 239000003792 electrolyte Substances 0.000 claims abstract description 68
- 238000006243 chemical reaction Methods 0.000 claims abstract description 32
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- 238000003411 electrode reaction Methods 0.000 claims abstract description 16
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- 239000007788 liquid Substances 0.000 claims description 20
- 238000007599 discharging Methods 0.000 claims description 11
- 239000000376 reactant Substances 0.000 claims description 11
- 238000012360 testing method Methods 0.000 claims description 8
- 238000002474 experimental method Methods 0.000 claims description 7
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 claims description 5
- 239000000463 material Substances 0.000 claims description 4
- 238000010521 absorption reaction Methods 0.000 claims description 2
- 229910001456 vanadium ion Inorganic materials 0.000 claims description 2
- 230000008569 process Effects 0.000 abstract description 5
- 238000011897 real-time detection Methods 0.000 abstract description 5
- 238000004364 calculation method Methods 0.000 description 5
- 238000012423 maintenance Methods 0.000 description 3
- 238000007086 side reaction Methods 0.000 description 3
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000005086 pumping Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000002835 absorbance Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000013499 data model Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 230000017525 heat dissipation Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
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- 238000004448 titration Methods 0.000 description 1
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- UUUGYDOQQLOJQA-UHFFFAOYSA-L vanadyl sulfate Chemical compound [V+2]=O.[O-]S([O-])(=O)=O UUUGYDOQQLOJQA-UHFFFAOYSA-L 0.000 description 1
- 229940041260 vanadyl sulfate Drugs 0.000 description 1
- 229910000352 vanadyl sulfate Inorganic materials 0.000 description 1
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Abstract
The invention relates to the field of all-vanadium redox flow batteries, in particular to an all-vanadium redox flow battery SOC detection method based on thermochemical measurement. The method aims at the requirement of real-time detection of the SOC (State-of-charge) State of positive and negative electrodes in the application process of the all-vanadium redox flow battery, measures the specific heat capacity and density of positive and negative electrode electrolytes, the internal resistance of the positive and negative electrodes and the enthalpy change of the positive and negative electrode reactions at different temperatures in an off-line manner, respectively establishes an energy conservation equation for the positive and negative electrodes in a galvanic pile by utilizing a first thermodynamic law, associates the temperature change of the electrolytes at the inlet and the outlet of the positive and negative electrodes of the galvanic pile with the change of reaction heat, measures the temperature change of the electrolytes at the inlet and the outlet of the positive and negative electrodes of the galvanic pile, reaction current and electrolyte flow in real time, calculates the heat change of the positive and negative electrode reactions in a sampling time period in real time, and calculates and obtains the change law.
Description
Technical Field
The invention relates to the field of all-vanadium redox flow batteries, in particular to a thermochemical measurement-based SOC (State-of-charge) detection method for an all-vanadium redox flow battery.
Background
The all-vanadium redox flow battery is one of the first choice of large-scale energy storage technology, the real-time detection of the SOC state is very important, and the high-efficiency SOC online detection method can effectively improve the utilization rate of the capacity and avoid the corrosion and damage of the electrode material caused by side reaction. At present, an open-circuit voltage method is mainly applied in engineering, and the SOC states of the anode and the cathode of a battery are estimated by collecting voltage; meanwhile, although many SOC detection methods based on spectrum, electrolyte conductivity, absorbance and the like can be used for the all-vanadium redox flow battery system with low power level in a laboratory, the SOC detection methods are limited by instruments, and cannot be effectively applied to the all-vanadium redox flow battery system applied to engineering at present. The invention provides a method for acquiring and analyzing the temperature of a positive electrode liquid inlet and a negative electrode liquid outlet of a galvanic pile in real time by utilizing variables which can be acquired in real time at present and considering the simplicity and practicability in application, so as to realize the real-time calculation and detection of SOC.
By utilizing the temperature change rule of the electrolyte flowing through the inside of the galvanic pile, the calculation of the mass change of the positive and negative pole reactants and the prediction of the SOC state can be realized by utilizing the offline measurement of the specific heat capacity and the density of the positive and negative pole electrolytes, the enthalpy change of the positive and negative pole reactions at different temperatures and the internal resistance of the positive and negative pole half cells, and the online measurement of the volume flow of the electrolytes, the charging and discharging current and the temperature values of the electrolytes at the inlet and the outlet of the galvanic pile based on the first law of thermodynamics and the energy conservation equation of.
A researcher firstly performs specific heat capacity and density experimental determination on the battery by using positive and negative electrolytes with specified concentration, calculates the internal resistance of the battery according to a battery charging and discharging curve, then establishes an energy conservation equation of the internal positive electrode and the negative electrode of the all-vanadium redox flow battery pile, and constructs temperature change rate, temperature convection heat transfer, ohmic heat dissipation, reaction heat and external heat exchange. Furthermore, researchers respectively measure the enthalpy change of the positive and negative electrode reactions at different temperatures through experiments, and fit a data model of the enthalpy change and the temperature based on the measured values. Furthermore, sampling measurement is carried out on the volume flow of the positive electrode and the negative electrode of the online running all-vanadium redox flow battery system, the charging and discharging current and the temperature of the positive electrode electrolyte and the negative electrode electrolyte entering and exiting the galvanic pile at sampling time points, and the change of the mass of the positive electrode reaction substance and the negative electrode reaction substance in the time of adjacent sampling points can be calculated by utilizing an energy conservation equation constructed offline and the enthalpy change value at the corresponding temperature, so that the change rate of the SOC and the real-time SOC state value can be obtained.
Disclosure of Invention
The invention aims to provide an all-vanadium redox flow battery SOC detection method based on thermochemical measurement, which realizes real-time detection of the SOC state of a positive electrode and a negative electrode by measuring the temperature change of electrolyte at an inlet and an outlet of the positive electrode and the negative electrode of a galvanic pile of the all-vanadium redox flow battery in real time. The method is simple to use, and the SOC states of the positive and negative electrolytes can be determined by real-time calculation only by using a necessary temperature sensor in the all-vanadium redox flow battery system through the idea of combining thermochemistry measurement and energy conservation. The SOC detection system of the all-vanadium redox flow battery designed by the method can effectively detect the real-time state of SOC, and is beneficial to long-term stable operation of the battery and reduction of the operation and maintenance cost of electrolyte.
The technical scheme of the invention is as follows:
a thermochemical measurement-based SOC detection method for an all-vanadium redox flow battery is characterized in that temperature sensors are installed at an inlet and an outlet of electrolyte of a positive electrode and a negative electrode of a galvanic pile, the temperature value of each sampling point is collected on line, the real-time heat change of the reaction of the positive electrode and the negative electrode is calculated by utilizing an energy conservation equation of the positive electrode and the negative electrode of the galvanic pile constructed off line, the material variation of the reactant of the positive electrode and the negative electrode in a sampling period is obtained based on the relation between the enthalpy change of the positive electrode and the negative electrode and the temperature obtained by an off-line experiment.
According to the thermochemical measurement-based SOC detection method for the all-vanadium redox flow battery, temperature sensors are respectively arranged at the inlet and outlet positions of positive and negative electrolytes of a galvanic pile, flowmeters are respectively arranged in positive and negative pipelines, an ammeter is arranged between the battery and a PCS system, the sensors are connected with a control system of the all-vanadium redox flow battery, and real-time collection of temperature, flow and current data can be ensured.
According to the thermochemical measurement-based SOC detection method for the all-vanadium redox flow battery, the density and specific heat capacity of positive and negative electrolyte, the internal resistance of positive and negative half batteries and the enthalpy change of positive and negative reactions at different temperatures are measured in an off-line manner, and a relational expression of the positive and negative reaction enthalpy change and the temperature is established.
The method for detecting the SOC of the all-vanadium redox flow battery based on thermochemical measurement is characterized in that based on density, specific heat capacity, internal resistance and enthalpy change obtained off-line, an energy conservation equation is respectively established for a positive electrode and a negative electrode of a galvanic pile by utilizing a first law of thermodynamics, and a relation between temperature change and reaction heat change is established.
The method for detecting the SOC of the all-vanadium redox flow battery based on thermochemical measurement comprises the steps of measuring inlet and outlet temperatures of electrolytes of positive and negative electrodes of a galvanic pile, flow rates of positive and negative electrode pipelines and charging and discharging currents in real time on line, calculating heat changes of the reactions of the positive and negative electrodes at corresponding temperatures in a sampling period in real time based on an energy conservation equation, and calculating and detecting the SOC state of the positive and negative electrodes based on the thermochemical enthalpy changes of the positive and negative electrodes measured off line.
The method for detecting the SOC of the all-vanadium redox flow battery based on thermochemical measurement comprises the steps of calculating the change of the mass of positive and negative electrode reactions in sampling time by utilizing the real-time heat change generated by the positive and negative electrode reactions and the standard enthalpy change value of the positive and negative electrode reactions under different temperature conditions obtained in an off-line mode, and obtaining the change of the SOC and the real-time SOC state based on the change of the mass.
The method for detecting the SOC of the all-vanadium redox flow battery based on thermochemical measurement is used for measuring and collecting the inlet and outlet temperatures of electrolytes of the anode and the cathode of a galvanic pile respectively, so that the SOC states of the anode and the cathode are independently detected.
The design idea of the invention is as follows:
the invention relates to an all-vanadium redox flow battery SOC detection method based on thermochemical measurement, which integrates thermochemical and thermodynamic theories, and is characterized in that the specific heat capacity and density of electrolyte, and the enthalpy change and internal resistance of positive and negative electrode reactions are measured through an off-line experiment, and the relation between the enthalpy change of the positive and negative electrode reactions and the temperature change of the positive and negative electrodes of an electrolyte entering and exiting a galvanic pile in sampling time is constructed by utilizing an energy conservation equation; then, the inlet and outlet temperatures of the positive and negative electrolyte of the galvanic pile are measured in real time on line, and the heat change of the positive and negative reactions in the sampling time is calculated on line by utilizing the charge and discharge current and the volume flow value; and finally, calculating the variation of the reactant according to the enthalpy change and temperature change relation obtained offline, and obtaining the SOC variation of the anode and the cathode and the real-time SOC state. The invention is based on thermodynamics and thermochemistry theory, realizes that the change quantity of reactants and the real-time SOC state are obtained by measuring the temperature change on line by constructing the relation between the temperature change rule and the reaction heat absorption and release, can complete the real-time detection of the SOC by only utilizing conventional necessary devices such as a temperature sensor, a flowmeter and the like, improves the operation stability of the system and simultaneously considers the advantages of low operation and maintenance cost.
The invention has the advantages and beneficial effects that:
1. the method is simple and easy to implement, relevant parameters of the electrolyte and the battery can be obtained through an off-line experiment, meanwhile, temperature, flow and current data can be collected on line in real time, the change rate of the anode reactant and the cathode reactant to time can be calculated in real time by utilizing an energy conservation equation based on the first law of thermodynamics, and the real-time SOC state of the anode electrolyte and the cathode electrolyte can be obtained on line based on the change rate. The method does not introduce any high-cost and complex measuring instrument and equipment, can realize the detection of the SOC state only by collecting the temperature change of the electrolyte through the temperature sensor, has simple process, and can completely meet the engineering application requirement with accuracy, thereby having extremely strong application value. Meanwhile, the method can independently and respectively detect the SOC states of the half-cell, namely the anode and the cathode, overcomes the limitation that the traditional open-circuit voltage method only detects the SOC of the single cell, and can provide reference basis for the design of capacity rebalance control.
2. The method combines thermochemistry and thermodynamics theories, has complete theoretical support, simple required process, feasible technology and easy operation, and is suitable for large-scale application of the all-vanadium redox flow battery. At present, the method has the limitation that the self-discharge reaction and the side reaction at the final stage of charging generate extra heat, so as to cause the enthalpy change calculation error of the positive and negative electrode reactions and correspondingly cause the SOC calculation error, so the use of the method requires that an ion conduction membrane with low vanadium permeability is adopted for a battery, and the charge cut-off voltage is reasonably controlled so as to avoid the generation of a large amount of side reactions.
Drawings
FIG. 1 is a flow chart of implementation steps of an all-vanadium redox flow battery SOC detection method based on thermochemical measurement.
FIG. 2 is a schematic diagram illustrating application of the thermochemical measurement-based SOC detection method for the all-vanadium redox flow battery. In the figure, 1 a positive pole liquid storage tank; 2 a negative pole liquid storage tank; 3, electric pile; 4, pumping one; 5, pumping a second pump; FM, flow meter; TT, temperature sensor; A. and (4) an ammeter.
Detailed Description
In the specific implementation process, as shown in fig. 1, the SOC detection method of the all-vanadium redox flow battery based on thermochemical measurement according to the present invention includes measuring specific heat capacity and density of the positive and negative electrolytes, internal resistance of the positive and negative electrodes, and enthalpy change of the positive and negative electrodes reaction in an off-line experiment, offline constructing an energy conservation equation for the positive and negative electrodes of the galvanic pile using the above parameters, online measuring inlet and outlet temperatures of the positive and negative electrolytes of the galvanic pile, and flow rates of the positive and negative electrode pipelines of charge and discharge current, calculating heat change caused by the positive and negative electrode reactions in real time using the energy conservation equation, and comparing the calculated heat change with a standard enthalpy change obtained offline to:
(1) and measuring physical and thermochemical reaction parameters of the positive and negative electrolytes off line. Firstly, preparing positive and negative electrolytes according to the electrolyte concentration of the practically-operated all-vanadium redox flow battery system, and measuring the specific heat capacity C of the electrolytes by using a solution thermodynamic method and equipmentpAnd a density ρ; then, a single cell test platform is built according to the actual operation all-vanadium redox flow battery system structure and selected materials, a voltage change curve is obtained under different charging and discharging conditions, and the integral single cell and the internal resistance R of the positive electrode and the negative electrode are obtained according to the voltage change curve+And R-(ii) a Further, a reaction calorimeter is used for measuring the standard enthalpy change value delta of the positive and negative pole reactions at different temperaturesrH+And ΔrH-Respectively fitting the positive and negative electrode enthalpy changes and the temperature relation deltarH+/-＝f(T)。
Negative electrode V3++e-→V2+ ΔrH_(J/mol)
Positive electrode
ΔrH+(J/mol)
(2) And (5) constructing an energy conservation equation. Respectively constructing an energy conservation equation for the anode and the cathode of the galvanic pile by using the physical and thermochemical parameters obtained in the step (1) and using a first thermodynamic law, wherein the energy conservation equation is as follows:
wherein V is the volume (L) of the positive electrode or the negative electrode, Q is the flow rate (L/s) of the positive electrode or the negative electrode, and T isinThe temperature is the inlet temperature (DEG C) of electrolyte of the anode or the cathode of the pile, T is the outlet temperature (DEG C) of the electrolyte of the anode or the cathode of the pile, I is charging and discharging current (A), R is the internal resistance (omega) of the anode or the cathode, and J is the heat absorbed or released by the reaction of the anode or the cathode.
(3) Sensor placement and online measurement. As shown in fig. 2, the positive electrodeThe liquid tank 1 is provided with VO2+/VO2 +The negative electrode liquid storage tank 2 is internally provided with a V-containing liquid2+/V3+The positive electrolyte and the negative electrolyte are respectively connected with the electric pile 3 through pipelines, the first pump 4 is arranged on the liquid flow path of the positive electrolyte, and the second pump 5 is arranged on the liquid flow path of the negative electrolyte. The flow meter FM and the temperature sensor TT are respectively arranged on the anode and cathode pipelines and the anode and cathode electrolyte inlets and outlets of the galvanic pile, the ammeter A is arranged in a loop of the PCS (power control system) and the galvanic pile 3, and the sensors are connected with the all-vanadium redox flow battery control system to realize real-time data acquisition.
(4) And SOC is calculated on line. Inputting the positive and negative electrode energy conservation equation established in the step (2) into a battery control system, and utilizing adjacent sampling time t1And t2Measured temperature value T1And T2Calculating the heat change dJ caused by the reaction of the positive electrode and the negative electrode as follows:
using the change dJ of heat of positive and negative electrodes and the reaction of positive and negative electrodes at T2Change in enthalpy at temperaturerH(T2) Respectively calculating the concentration change quantity delta c and t of the anode reactant and the cathode reactant and the product according to the following formulas2Time-point concentration c:
c(t2)＝c(t1)+Δc
in the formula, VtCalculating the SOC states of the anode and the cathode according to the concentration of vanadium ions in each valence state of the anode and the cathode, wherein the SOC states are the total volume (L) of the electrolyte of the anode or the cathode:
therefore, the system and the method only utilize the temperature sensor which is necessary for the all-vanadium redox flow battery system to realize the real-time detection of the SOC, can effectively improve the utilization rate of the electrolyte and reduce the difficulty and the cost of operation and maintenance.
In order to make the technical solution and advantages of the present invention more clear, the following detailed description is given with reference to specific embodiments.
Example 1
In the embodiment, 1.6mol/L vanadyl sulfate and 2.6mol/L sulfuric acid are used as the anode and cathode electrolytes. Firstly, the specific heat capacity and the density of the positive and negative electrolytes are measured in an off-line experiment, wherein the specific heat capacity is 3.2J/g ℃, and the density is 1.35g/cm3(ii) a And then, building a single cell testing platform, wherein the size of a half cell is 10cm multiplied by 0.3cm, and the total volume of positive and negative electrolyte is 1L respectively. Measuring a battery voltage change curve under different charging and discharging currents to obtain the internal resistances of the positive electrode and the negative electrode which are both 5m omega; building a three-electrode test platform, respectively measuring the enthalpy changes of the positive and negative electrode reactions at different temperatures by utilizing a thermochemical measuring instrument, and respectively fitting a relational expression delta between the enthalpy changes of the positive and negative electrodes and the temperaturerH+/-(t); based on the first law of thermodynamics, the physical parameters and the thermochemical parameters are utilized to construct an energy conservation equation of the positive electrode and the negative electrode, and the energy conservation equation is input into a battery control system.
And constructing an SOC detection test platform, selecting a single battery as a test target, arranging a temperature sensor and a flow meter on the anode and cathode pipelines respectively, and connecting the temperature sensor and the flow meter with an ammeter into a battery control system to realize real-time data acquisition. Operating the all-vanadium redox flow battery system, wherein the SOC state of the anode at a certain time is 10%, the temperature of electrolyte at a liquid inlet of the anode of the galvanic pile is 26.5 ℃, the temperature of electrolyte at a liquid outlet of the anode of the galvanic pile is 27 ℃, charging the battery at constant current of 100A, measuring the temperature of the liquid outlet of the anode of the galvanic pile to be 28.5 ℃ after 120s, and calculating the change of the reaction heat of the anode in 120s through an energy conservation equation:
dJ＝7kJ
calculating by using the offline fitted anode temperature and enthalpy change relational expression to obtain the corresponding anode enthalpy change at 27 ℃:
ΔrH(27℃)＝123kJ/mol
v within 120s5+The concentration variation is as follows:
from V5+Initial SOC state obtained with initial concentration of 0.16mol/L, at 120s V5+The concentration is 0.22mol/L, and the SOC state of the positive electrode is as follows:
and testing and verifying the calculated value obtained by the SOC detection method. Collecting a positive electrolyte sample at 120s on line, carrying out off-line titration analysis test, and obtaining two decimal points of an analysis result, wherein V in the positive electrolyte5+The concentration is 0.22mol/L, V4+The concentration is 1.38mol/L, namely the SOC of the positive electrolyte at the moment is 13.75 percent.
The embodiment result shows that the method can effectively utilize temperature change measurement caused by reaction heat to carry out online detection on the SOC state, and by utilizing thermodynamics and thermochemistry theories, the method can finish independent detection on the SOC state of the positive electrode and the negative electrode only by collecting the temperature, the flow and the charging and discharging current of a positive electrode liquid inlet and a negative electrode liquid outlet of a galvanic pile, has the advantages of good detection continuity, simple and easy operation, simple process and low cost, and can be suitable for SOC online detection in the application of a large-scale all-vanadium redox flow battery system.
Claims (3)
1. A thermochemical measurement-based SOC detection method for an all-vanadium redox flow battery is characterized in that temperature sensors are installed at an inlet and an outlet of electrolyte of a positive electrode and a negative electrode of a galvanic pile, the temperature value of each sampling point is collected on line, the real-time heat change of the reaction of the positive electrode and the negative electrode is calculated by using an energy conservation equation of the positive electrode and the negative electrode of the galvanic pile constructed off line, the material variation of reactants of the positive electrode and the negative electrode in a sampling period is obtained based on the relation between the enthalpy change of the positive electrode and the negative electrode and the temperature obtained by an off-line experiment, and the real-time;
(1) measuring physical and thermochemical reaction parameters of the positive and negative electrolytes off line; firstly, preparing positive and negative electrolytes according to the electrolyte concentration of the practically-operated all-vanadium redox flow battery system, and measuring the specific heat capacity C of the electrolytes by using a solution thermodynamic method and equipmentpAnd a density ρ; then, a single cell test platform is built according to the actual operation all-vanadium redox flow battery system structure and selected materials, a voltage change curve is obtained under different charging and discharging conditions, and the integral single cell and the internal resistance R of the positive electrode and the negative electrode are obtained according to the voltage change curve+And R-(ii) a Further, a reaction calorimeter is used for measuring the standard enthalpy change value delta of the positive and negative pole reactions at different temperaturesrH+And ΔrH-Respectively fitting the positive and negative electrode enthalpy changes and the temperature relation deltarH+/-＝f(T)；
Negative electrode V3++e-→V2+ ΔrH-(J/mol)
(2) Constructing an energy conservation equation; respectively constructing an energy conservation equation for the anode and the cathode of the galvanic pile by using the physical and thermochemical parameters obtained in the step (1) and using a first thermodynamic law, wherein the energy conservation equation is as follows:
wherein V is the volume of the anode or the cathode, and the unit is L; q is the flow of the anode or the cathode, and the unit is L/s; t isinThe temperature is the inlet temperature of electrolyte of the anode or the cathode of the pile, and the unit is; t is the outlet temperature of electrolyte of the anode or the cathode of the pile, and the unit is; i is charging and discharging current, and the unit is A; r is the internal resistance of the anode or the cathode, and the unit is omega; j is reaction absorption or release of positive or negative electrodeThe amount of heat of;
(3) sensor placement and online measurement; the positive liquid storage tank is internally provided with a liquid containing VO2+/VO2 +The negative electrode liquid storage tank is internally provided with a liquid storage tank containing V2+/V3+The positive electrolyte and the negative electrolyte are respectively connected with the pile through pipelines, the first pump is arranged on the liquid flow path of the positive electrolyte, and the second pump is arranged on the liquid flow path of the negative electrolyte; the flow meter FM and the temperature sensor TT are respectively arranged on a positive electrode pipeline, a negative electrode pipeline, a positive electrode electrolyte inlet and a negative electrode electrolyte outlet of the galvanic pile, the ammeter A is arranged in a loop of the power control system and the galvanic pile, and the sensors are connected with the all-vanadium redox flow battery control system to realize real-time data acquisition;
(4) SOC is calculated on line; inputting the positive and negative electrode energy conservation equation established in the step (2) into a battery control system, and utilizing adjacent sampling time t1And t2Measured temperature value T1And T2Calculating the heat change dJ caused by the reaction of the positive electrode and the negative electrode as follows:
using the change dJ of heat of positive and negative electrodes and the reaction of positive and negative electrodes at T2Change in enthalpy at temperaturerH(T2) Respectively calculating the concentration change quantity delta c and t of the anode reactant and the cathode reactant and the product according to the following formulas2Time-point concentration c:
c(t2)＝c(ti)+Δc
in the formula, VtIs the total volume of the electrolyte of the anode or the cathode, and the unit is L; calculating the SOC states of the positive electrode and the negative electrode according to the concentrations of the vanadium ions in the valence states of the positive electrode and the negative electrode:
therefore, the SOC is detected in real time by using a temperature sensor which is necessary for the all-vanadium redox flow battery system;
wherein:
measuring the density and specific heat capacity of the positive and negative electrolytes, the internal resistance of the positive and negative half batteries and the enthalpy change of the positive and negative reactions at different temperatures in an off-line manner, and constructing a relational expression of the enthalpy change of the positive and negative reactions and the temperature;
based on density, specific heat capacity, internal resistance and enthalpy change obtained off-line, respectively establishing an energy conservation equation for the anode and the cathode of the galvanic pile by utilizing a first law of thermodynamics, and constructing a relation between temperature change and reaction heat change;
the inlet and outlet temperatures of positive and negative electrolyte of the galvanic pile, the flow of the positive and negative pipelines and the charging and discharging current are measured on line in real time, the heat change of the positive and negative reactions at the corresponding temperature in a sampling period is calculated in real time based on an energy conservation equation, and the SOC state of the positive and negative electrodes is calculated and detected based on the thermochemical enthalpy change of the positive and negative electrodes measured off line;
and calculating the change of the mass of the positive and negative electrode reactions in sampling time by using the real-time heat change generated by the positive and negative electrode reactions and the standard enthalpy change values of the positive and negative electrode reactions under different temperature conditions obtained in an off-line manner, and solving the change of the SOC and the real-time SOC state based on the change of the mass.
2. The thermochemical measurement-based SOC detection method for all vanadium redox flow batteries according to claim 1, wherein temperature sensors are respectively arranged at the inlet and outlet positions of positive and negative electrolytes of a galvanic pile, flowmeters are respectively arranged in positive and negative pipelines, an ammeter is arranged between the batteries and a PCS system, and the sensors are connected with a control system of the all vanadium redox flow batteries and can ensure real-time collection of temperature, flow and current data.
3. The method for detecting the SOC of the all-vanadium redox flow battery based on thermochemical measurement according to claim 1, wherein the temperatures of the inlet and outlet of electrolytes of the anode and the cathode of the galvanic pile are measured and collected respectively, so that the SOC states of the anode and the cathode are detected independently.
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