STACK DRAINAGE FOR REDOX FLOW BATTERY

Abstract

A system includes one or more redox flow batteries and includes a stack of several electrochemical cells. The electrochemical cells include a cathode compartment and an anode compartment. The cathode compartment is in fluidic communication, via a feed circuit, with one or more tanks of electrolyte called catholyte. The anode compartment is in fluidic communication, via a feed circuit, with one or more tanks of electrolyte called anolyte. The feed circuit of the catholyte, respectively the anolyte, includes a pump for circulating the catholyte, respectively the anolyte, from the tank to the cathode, respectively the anode compartments. The system includes a catholyte drainage pump and an anolyte drainage pump, the catholyte, respectively. The anolyte drainage pump is controlled by a catholyte, respectively anolyte presence detector, in at least a part of the feed circuit of catholyte, respectively anolyte.

Claims

1. A system comprising one or a plurality of redox flow batteries comprising a stack of a plurality of electrochemical cells, said electrochemical cells comprising a cathode compartment and an anode compartment, the cathode compartment being in fluidic communication via a feed circuit with one or a plurality of tanks of electrolyte called catholyte, the anode compartment being in fluidic communication via a feed circuit with one or a plurality of tanks of electrolyte called anolyte, the feed circuit of the catholyte, respectively of the anolyte, comprising a circulation pump of the catholyte, respectively of the anolyte, from the tank to the cathodic or anodic compartments, said system comprising a catholyte drainage pump and an anolyte drainage pump, the catholyte, respectively anolyte drainage pump being servo-controlled by a presence detector for detecting the presence of catholyte, respectively of anolyte in at least part of said feed circuit of catholyte, respectively of anolyte, the feed circuit of the catholyte, respectively the anolyte, comprising a circulation authorization device for either letting or not letting circulate the catholyte, respectively the anolyte, from the catholyte, respectively the anolyte tank, to the cathode, respectively anode compartments.

2. The system according to claim 1, wherein the circulation authorization device is a three-way solenoid valve connecting either the tank to the circulation pump or connecting the electrochemical cells to the drainage pump.

3. The system according to claim 1, wherein said drainage pump is positioned on a circuit at least in part dedicated to the drainage of the catholyte, respectively the anolyte, called drainage circuit.

4. The system according to claim 1, wherein said circulation pump is positioned on a circuit at least in part dedicated to the circulation of the catholyte, respectively the anolyte, towards the electrochemical cells, called the feed circuit.

5. The system according to claim 1, wherein said catholyte, respectively anolyte presence detector is a device for measuring the liquid level of the catholyte, respectively the anolyte, in at least a part of said feed circuit and/or cathode, respectively anode compartments.

6. The system according to claim 1, wherein, when the presence detector detects the presence of the catholyte, respectively the anolyte, the drainage pump for the catholyte, respectively the anolyte, is in operation and the catholyte, respectively the anolyte circulates in the drainage circuit of the catholyte, respectively of the anolyte, and feeds the inlet of the tank of the catholyte, respectively of the anolyte.

7. A method for producing electricity using one or a plurality of redox flow batteries comprising a stack of a plurality of electrochemical cells, said electrochemical cells comprising a cathode compartment and an anode compartment, the cathode compartment being in fluidic communication via a feed circuit with one or a plurality of tanks of electrolyte called catholyte, the anode compartment being in fluidic communication via a feed circuit with one or a plurality of tanks of electrolyte called anolyte, the feed circuit of the catholyte, respectively the anolyte, comprising a pump for circulating the catholyte, respectively the anolyte from the tank to the cathode, respectively anode compartments, said system comprising a catholyte drainage pump and an anolyte drainage pump, the drainage pump for the catholyte, respectively the anolyte, being servo-controlled by a measuring device for measuring the presence of catholyte or anolyte in at least a part of said catholyte or anolyte feed circuit, said drainage pump being in operation when the presence of catholyte or anolyte is detected by the measuring device, the feed circuit of the catholyte, respectively the anolyte, comprising an authorization device for either letting or not letting circulate the catholyte, respectively the anolyte, from the tank of catholyte, respectively of anolyte, to the cathode, respectively anode compartments.

8. The method according to claim 7, wherein the charging or discharging mode of the flow batteries, the catholyte, respectively the anolyte flows from the catholyte, respectively the anolyte tank to the cathode, respectively the anode compartments, and in that in the standby mode of the flow batteries, the catholyte, respectively the anolyte, is drained from the feed circuit of the catholyte, respectively of the anolyte, and/or from the cathode, respectively anode compartments, to the catholyte, respectively the anolyte tank.

9. The method according to claim 7, wherein, in the charging or discharging mode of the flow batteries, the catholyte, respectively the anolyte flows from the outlet of the catholyte, respectively the anolyte tank to the cathode, respectively the anode compartments and then to the inlet of the catholyte, respectively the anolyte tank, and in that in the standby mode of the flow batteries, the catholyte, respectively the anolyte, flows from the feed circuit of the catholyte, respectively the anolyte, and/or from the cathode, respectively the anode compartments, to a zone near the inlet of the catholyte, respectively the anolyte tank.

10. The method according to claim 7, wherein in the standby mode of the flow batteries, drainage is activated when the measuring device detects the presence of catholyte, respectively of anolyte, for example by measuring the liquid level, in at least a part of said feed circuit and/or a part of said cathode, respectively anode compartments.

11. A compact electrochemical cell assembly, comprising in a container the system of claim 1.

12. The assembly according to claim 11, characterized in that it can be transported.

Description

[0030] The invention will be described more precisely in relation to the figures, without limiting the scope of the invention. In the present invention, reference is made independently to the different elements by the reference numbers thereof in the figures, without any limitation of the scope of the invention. References to an element with multiple reference numbers mean that the description generally applies to the element bearing the reference sign. Thereby e.g. a reference to the tank 10, 20 means that the description applies generally and independently or simultaneously to the tank 10 and to the tank 20.

[0031] FIG. 1 schematically shows an embodiment working in the ON mode.

[0032] The system comprises catholyte tank 10 and an anolyte tank 20. The catholyte tank is in fluidic communication, via a feed system 13, with the cathode compartments of a plurality of electrochemical cells 30. The anolyte tank 20 is in fluidic communication, via a feed system 23, with the anodic compartments of a plurality of electrochemical cells 30. The feed system 13 for the catholyte comprises a feed pump 15 and a device for letting the fluid through, e.g. a three-way solenoid valve 12, directing the catholyte from the tank 10 to the electrochemical cells 30 in charge/discharge operating mode. The anolyte feed system 23 comprises a feed pump 25 and a device for letting the fluid through, e.g. a three-way solenoid valve 22, directing the anolyte from the tank 20 to the electrochemical cells 30 in charge/discharge operating mode. Said mode makes it possible to feed the stacks (plurality of electrochemical cells 30) with electrolyte thus leading to the normal operation of the battery in charge and discharge mode.

[0033] FIG. 2 schematically illustrates an embodiment working in standby mode. In standby mode, the outlet solenoid valves 12, 22 of the tanks rotate independently so as to isolate the tanks 10, 20, respectively. The solenoid valve 12, 22 rotates so as to bring the catholyte, respectively the anolyte, into contact with a drainage pump 14, 24, respectively. The feed of the drainage pump 14, 24 is connected to one or a plurality of detectors of the presence of the electrolyte in question, e.g. one or a plurality of detectors of liquid level. The electrolyte presence detector(s) can typically be positioned between the solenoid valve 12, 22 and the feed pump 15, 25, respectively. In general, each drainage pump 14, 24 can be independently servo-controlled by one or a plurality of sensors for the presence of electrolyte. When the detector detects the presence of residual electrolyte in a feed circuit, the detector sends a signal, typically via a Battery Management System (BMS, not shown in the figures), to supply the drainage pumps 14, 24 so as to substantially empty the feed circuits 13, 23, respectively and the stacks 30, of residual electrolytes. Such system makes possible to not have to position the stacks 30 above the tanks 10, 20 for ensuring a drainage and an isolation of the stacks 30, which reduces the self-discharge of the flow battery, more particularly when the container is compact and/or placed or intended for being placed in a constrained vertical environment.

[0034] Typically, the containers are 20 feet, 20 feet HO (High Cube), or 40 feet containers. More generally, a container or an environment constrained in height can be concerned. Thereby, such a constrained environment does not allow the electrolyte tanks to be positioned freely, and more particularly below the level of the electrochemical cells.

[0035] Typically, according to the invention, the positioning in space of the electrolyte tanks with respect to the electrochemical cells does not make possible a liquid drainage by gravity of the catholyte, respectively of the anolyte, contained in the electrochemical cells.

[0036] Advantageously, according to the invention, the electrolyte tanks are positioned below the liquid level of catholyte, respectively anolyte, contained in the electrochemical cells.

[0037] Experiments were carried out. According to a system of the prior art, without the implementation of a drainage servo-controlled by an electrolyte presence detector and the fluidic isolation of the electrolytes, a loss of 420 Ah is observed. With a system according to the present invention, including a drainage circuit servo-controlled by an electrolyte presence detector, and isolated, reduces the loss to 234 Ah. The inventors were thus able to improve the storage stability of the redox flow battery system by reducing the self-discharge phenomenon during the standby phases.

[0038] System or process according to the invention or equivalent terms means a system or a method as defined in the present invention, including according to any of the variants, particular or specific embodiments, independently or according to any of the combinations thereof, even according to the preferred features.

[0039] Other goals, features and advantages of the invention will become clear to a person skilled in the art from reading the explanatory description which refers to the figures which are given only as an illustration and which do not, in any way, limit the scope of the invention.