DE102014221148B4 - Operating method of a redox flow system and a motor vehicle as well as a redox flow system and a motor vehicle with a redox flow system - Google Patents

Abstract

Operating method of a redox flow system (10), comprising the steps: - storing active material (AM) in at least one active material storage (210, 310), the active material storage (210, 310) storing active material (AM) for an anode (120) or for a cathode (130) of at least one redox flow cell (100) of the redox flow system (10); - adding solvent (L) to the active material (AM) upstream of the redox flow cell (100) ;- Solvent removal downstream of the redox flow cell (100), at least part of the solvent (L) being removed again; and- providing the removed solvent (L) for re-addition to the active material (AM) upstream of the redox flow cell (100).

Description

The technology disclosed herein relates to an operating method of a redox flow system and a motor vehicle as well as a redox flow system and a motor vehicle with a redox flow system.

The technology disclosed here relates to a redox flow system with at least one redox flow cell. A redox flow cell includes an anode and a cathode separated by an ion-permeable separator. Such redox flow cells themselves are known. They are used, for example, in redox flow batteries. In a redox flow battery or redox flow battery, the redox flow cell or redox flow cell is flowed through by two energy-storing electrolyte solutions that contain active materials or redox pairs in ion form. The electrolyte solutions are stored in external tanks. The electrolyte in the cathode fluid circuit is called catholyte, and the electrolyte in the anode fluid circuit is called anolyte. In addition to batteries with electrolyte tanks for the catholyte solution and anolyte solution, structures are also known in which vanadium is used as the anolyte solution and atmospheric oxygen flows through the cathode. The energy converter is supplied with oxygen on the cathode side, which means that the catholyte solution can be omitted. Redox flow cells are also used in some redox flow fuel cell systems.

The disadvantage of such redox flow systems is that the electrolyte solutions used so far have a relatively low energy storage capacity. The active materials are present in previously known electrolytes mainly in dissolved form (electrolyte solution). The amount of active materials of the previously known electrolytes is therefore limited by the solubility limit. As a result, with reasonable effort, only an energy density can be achieved that makes its use for mobile applications uncompetitive.

An “electrolyte” is generally a chemical compound that is dissociated into ions in the solid, liquid or dissolved state. “Electrolyte” also refers to the solid or liquid material that contains the mobile ions.

For example, from the US 2010/0047671 A1 A redox flow system is known in which semi-solid or solid particles are transported to the redox flow cell so that the stored energy is converted there. Compared to semi-solid or solid particles, electrolytes with dissolved active materials can be transported through the fuel cell system comparatively easily and with little energy expenditure.

It is an object of the present invention to reduce or eliminate the disadvantages of the previously known solution. In particular, it is an object of the technology disclosed here to provide a redox flow system for mobile applications, which can provide energy for long journeys of a vehicle with a preferably low weight.

The task(s) is/are solved by the subject matter of the independent patent claims. The dependent claims represent preferred embodiments.

The technology disclosed here relates to a redox flow system with at least one redox flow cell. A redox flow cell includes an anode and a cathode. The anode and cathode are separated from each other by an ion-selective separator.

The ion-selective separator can be designed, for example, as a proton exchange membrane (PEM). A cation-selective polymer electrolyte membrane is preferably used. Materials for such a membrane are: Nation®, Flemion® and Aciplex®. To simplify matters, a system with a redox flow cell is often discussed here. If a component of the system is listed below in the singular, the plural should also be included. For example, a plurality of redox flow cells and sometimes a plurality of system components can be provided.

The redox flow system includes at least one active material storage for storing a redox active material. The redox active material (hereinafter: active material) is the redox couple that reacts in the redox flow cell and is responsible for generating the cell voltage.

In principle, all active materials that are present in both oxidized and reduced form in the liquid phase can be considered for the redox flow system disclosed here. Pairings with the highest or lowest possible reference potential, a low formula weight and the ability to exchange several electrons per formula turnover are particularly interesting. Active materials that dissolve well in the solvent, preferably water, are preferably used. Such active materials are known from the prior art. For example, a redox flow battery system is conceivable in which vanadium is used as the active material in the anolyte and catholyte. Other redox flow systems work, for example, with vanadium and chromium, with zinc and bromine or with vanadium and oxygen.

For example, vanadium can be provided as the active material. The active material storage provides the active material for the anode or for the cathode. The at least one active material storage can be connected (fluidly) to the anode or to the cathode. Two memories are preferably provided, with one memory storing the active material for the catholyte and one memory storing the active material for the anolyte.

The redox flow system further comprises at least one solvent addition unit which is arranged upstream of the redox flow cell or the anode or the cathode.

The solvent addition unit is suitable for adding solvent to the active material. Such a solvent addition unit can be designed, for example, as a mixer to which the active material is fed via a screw conveyor or a conveyor belt.

The solvent addition unit is designed such that a measurable volume of solvent is introduced from the solvent tank into a mixing container and a measured amount of active material, in powder, paste or liquid form, is added so that a preferably homogeneous concentration is set. The mixing unit is preferably designed as a magnetic mixer. This means that a closed container can be used and leakage problems can be avoided.

For example, the solvent can be applied as a spray to powdered active material, for example in a mixer.

The solvent addition unit is preferably arranged downstream or in the active material storage. The at least one solvent addition unit can be formed integrally with the active material storage. The term “downstream” refers to the flow of the active material.

The redox flow system further includes at least one solvent removal unit. The solvent removal unit is arranged downstream of the redox flow cell or the anode or the cathode. The solvent removal unit is suitable for removing or separating the solvent, in particular from an electrolyte solution.

The redox flow system further comprises at least one return circuit which is suitable for feeding the solvent removed from the electrolyte to the solvent addition unit. The recycling can provide the removed solvent for re-addition to the active material upstream of the redox flow cell or the anode or the cathode.

The return can, for example, comprise a pipeline element which connects the solvent removal unit to the solvent addition unit. Furthermore, the return can include a tank for (intermediate) storage of solvent. In a further embodiment, the solvent addition unit, the solvent removal unit and/or the tank for storing the solvent are housed in a housing.

The technology disclosed herein further includes an operating method for a redox flow system. The operating method preferably includes the step: storing at least one active material (AM) in at least one active material memory, the active material memory providing active material for an anode or for a cathode of at least one redox flow cell of the redox flow system.

The operating method for a redox flow system includes the step: adding solvent to the active material, in particular in a solvent addition unit upstream of the anode or the cathode and preferably downstream or in the active material storage.

Furthermore, the operating method includes the step: solvent removal or solvent removal downstream of the redox flow cell or the anode or the cathode, in particular in a solvent removal unit. At least part of the solvent is removed again.

Furthermore, the operating method includes the step: providing the removed solvent for re-addition to the active material upstream of the redox flow cell or the anode or the cathode, in particular by recycling the removed solvent into the solvent addition unit.

The solvent addition unit and/or the solvent removal unit can also be functionally integrated into other components of the redox flow system and do not have to be structurally a separate unit.

The technology disclosed here relates in particular to a system and a method in which the active material is or can be stored, in particular in an active material storage, as a dry powder, paste, pellets and/or a highly concentrated solution. The active material is particularly preferred as a highly concentrated solution stored, which has a concentration of at least 3 molar, more preferably 17 molar, and particularly preferably 30 molar.

The active material can preferably be brought into solution in the solvent addition unit. The resulting electrolyte solution, comprising the solvent and the active material, can then be fed to the at least one redox flow cell. The active materials are preferably brought into solution only for the passage through the cell stack or stack or energy converter which has the at least one redox flow cell. In other words, the dry or almost dry active material is brought into solution before the stack and the solvent is completely or largely removed after the stack. The removed solvent is then directed to a point in front of the stack and used there again to bring the dry active material into solution. This creates a closed solvent cycle in which the solvent can be continuously reused. This process can be applied on both the cathode side and the anode side. Alternatively, it is possible to obtain a suspension by adding solvent, which can then be fed to the at least one redox flow cell.

Compared to the previously known solutions, a comparatively small volume of solvent is required to transport the dissolved active materials through the stack. Since most of the solvent is in the solvent cycle and the active materials are stored in semi-solid or solid form or as a highly concentrated solution, a large part of the solvent can be saved with an electrolyte storage device compared to conventional redox flow systems. For mobile applications, such as a motor vehicle, up to 200 to 300 liters of solvent could be saved, which can lead to a significant reduction in the weight of the entire system. Due to the reduced vehicle weight, improved longitudinal and lateral dynamics as well as increased safety can also be achieved. In addition, the system disclosed here has potential for savings in terms of installation space. With the system disclosed here, motor vehicles can advantageously be realized which, with a storage capacity, can cover ranges that are already suitable for series production without increasing the total weight of the motor vehicle to a total weight that is not suitable for series production.

The redox flow system preferably comprises two active material storage units, two solvent addition units and two solvent removal units. An active material storage, a solvent addition unit and a solvent removal unit are preferably provided in the anode fluid circuit and an active material storage, a solvent addition unit and a solvent removal unit in the cathode fluid circuit.

In other words, the redox flow system preferably includes an active material storage that stores the active material to form the catholyte. The active material for forming the catholyte is brought into solution in the solvent addition unit by adding solvent, whereby the catholyte is formed. The catholyte flows through the cathode and is then reduced in the solvent removal unit of the cathode fluid circuit. At the same time, the anode fluid circuit includes an active material reservoir for storing active material, which together with the solvent forms the anolyte, which ultimately flows through the anode before the solvent is removed in the solvent removal unit of the anode fluid circuit.

The redox flow system can further have at least one residual storage container which is designed to store the converted active material after the reaction in the redox flow cell and after solvent removal. In other words, the residual storage container is designed to store the active material extracted and converted from the electrolyte solution. The spent active material can, for example, be present as a highly concentrated solution or in semi-solid or solid form. In one embodiment, the residual storage container and the active material storage can be accommodated in a storage housing or in a storage volume, for example separated by a partition. In a further embodiment, the converted active material is fed back to the active material storage.

The redox flow system is preferably operated continuously or in shifts. If the redox flow system is designed, for example, as a redox flow battery, then, for example, the converted active material can be stored in the at least one active material storage. When the battery is charged, the converted active material is then converted into usable or convertible active material. In shift operation, for example, the completely discharged or converted active material can be collected in the residual storage container.

The technology disclosed here further includes a motor vehicle with a redox flow system disclosed here. However, the disclosed technology is not limited to mobile applications. The technology disclosed here can also be used, for example, for stationary redox flow systems to store energy.

• - Verdampfung oder Verdunsten des Lösungsmittels, insbesondere unter Unterdruck;
• - Ausfällung des umgewandelten Aktivmaterials aus der umgewandelten Elektrolytlösung;
• - Umkehrosmose mittels einer semipermeablen Membran;
• - Zentrifugieren der umgewandelten Elektrolytlösung;
• - Lösungsmittelextraktion, beispielsweise durch Einbringen von mindestens einem zusätzlichen Lösungsmittel; und/oder
• - Filtration.

The removal of the solvent from the electrolyte solution converted in the at least one redox flow cell may, for example, include one or more of the following methods:

• - Evaporation or evaporation of the solvent, especially under negative pressure;
• - Precipitation of the converted active material from the converted electrolyte solution;
• - Reverse osmosis using a semi-permeable membrane;
• - centrifuging the converted electrolyte solution;
• - Solvent extraction, for example by introducing at least one additional solvent; and or
• - Filtration.

For example, the undissolved active materials can be separated from the electrolyte by mechanical separation (e.g. using a membrane filter or a centrifuge). In a further step, the solution can then be broken down into the components solvent and active material, for example by fractional distillation and/or by reverse osmosis. The necessary heat of evaporation for the distillation can be provided, for example, from the heat released during the subsequent condensation (heat pump principle).

For example, the solvent can be provided with a precipitation additive so that the solubility of the active material is exceeded and precipitation of the active material occurs. The precipitated active material is separated mechanically (e.g. using a filter or a centrifuge). The solvent mixture (solvent + additive) can be separated, for example, by fractional distillation. Alternatively, the solvent mixture can be broken down into the components, for example by reverse osmosis. If a precipitation additive is used, an additional tank can be provided for storing the precipitation additive.

• - Betreiben des hier offenbarten Redox-Flow-Systems, und
• - Zuführen von Rekuperationsenergie zu der Lösungsmittelentfernungseinheit.

The technology disclosed here further relates to an operating method of a motor vehicle, which comprises the steps:

• - Operating the redox flow system disclosed here, and
• - Supplying recuperation energy to the solvent removal unit.

Recuperation energy is generally understood to mean the energy recovered during the operation of a motor vehicle, for example the energy that is recovered for braking during a braking process by using an electric motor, which is therefore used as a generator.

Alternatively or additionally, the recuperation energy can be used to charge a battery, preferably a redox flow battery.

• 1 eine schematische Darstellung des Redox-Flow-Systems 10, und
• 2 eine schematische Ansicht eines weiteren Redox-Flow-Systems 10.

The technology disclosed here will now be explained using figures. Show it

• 1 a schematic representation of the redox flow system 10, and
• 2 a schematic view of another redox flow system 10.

1 shows schematically the redox flow system 10 with a redox flow cell 100 as well as the anode fluid circuit 200 and the cathode fluid circuit 300. The example shown here can be, for example, a redox flow battery 10, which is used as the active material AM Vanadium is used in the anode fluid circuit 200 and in the cathode fluid circuit 300.

If AM or oxygen and vanadium are used as active materials or as a redox pair, the catholyte fluid circuit 300 would be omitted. Instead of the catholyte fluid circuit 300, such a redox flow battery would have a cathode 130 through which atmospheric oxygen would flow. Such a system could then also be referred to as a fuel cell.

The redox flow system 10 shown here includes a redox flow cell 100 with an anode 120 and a cathode 130, which are separated from each other by the ion-selective separator 150. The structure of the redox flow cell 100 is known from previously known redox flow batteries and will not be discussed further here. The anode fluid circuit 200 and the cathode fluid circuit 300 are constructed the same. An active material storage 210, 310 is arranged in both fluid circuits 200, 300, which is connected to the corresponding areas of the anode 120 and the cathode 130.

The solvent addition units 220, 320 can preferably be arranged immediately adjacent to the respective active material storage 210, 310. In a further embodiment, the solvent addition units 220, 320 can be formed in the active material storage 210, 310 or integrally with them. The solvent addition unit 220, 320 can be, for example, a mixing device 220, 320, to which active material is supplied in semi-solid or solid form by means of a mechanical conveyor, such as a screw conveyor. Furthermore, it is also conceivable that the active material is of high consistency centered solution is present which can be conveyed to the mixer 220, 320 via other suitable means.

It is also possible to provide the solvent addition unit 220, 320 at a distance from the active material storage 210, 310. In the embodiment shown here, the solvent addition unit 220, 320 is arranged upstream of the redox flow cell 100. From the solvent addition units 220, 320, the electrolyte AML created by mixing or bringing into solution, i.e. the anolyte and the catholyte, flows through corresponding feed lines 230, 330 to the redox flow cell 100. The electrolyte AML can be used, for example Feed pumps 260, 360 are transported. The electrochemical reactions that are the cause of the cell voltage that can ultimately be taken from the system 10 then take place in the redox flow cell 100. The electrolyte AM'L converted in the electrochemical reaction leaves the redox flow cell 100 and flows through corresponding derivatives 250, 350 to the solvent removal units 240, 340, which are arranged downstream of the redox flow cell 100. For example, an electrolyte solution or an electrolyte suspension can be used as the electrolyte.

In the solvent removal units 240, 340, the solvent L is at least partially removed from the spent electrolyte AM'L. The converted electrolyte AM'L is thereby concentrated. The converted active material AM' can, for example, be added back to the active material storage 210, 310. Unused active material AM and converted active material AM` are then stored in the active material memory 210, 310. During the charging process, converted active material AM' is converted back into “unused” active material AM.

The solution L removed or obtained from the reacted electrolyte AM'L is fed to the solvent addition units 220, 320 through the return 270, 370. The returns 270, 370 can, for example, include a storage tank 272, 372 in which solvent L is temporarily stored.

Furthermore, a storage tank can be arranged in the derivatives 250, 350, in which converted electrolyte material AM'L can be temporarily stored. The temporarily stored electrolyte material AM'L can, for example, be supplied to the solvent removal unit 240, 340 in recuperation phases. The recuperation energy from the electrical machine can then be used, for example, to remove the solvent, whereby the solvent L can be recycled in an energy-efficient manner.

In the embodiment shown here, the components 210, 220 and 240 as well as 310, 320 and 340 are arranged adjacent to one another. In a further embodiment, however, these components can also be spaced apart and connected to one another by lines.

2 shows a further embodiment of a redox flow system 10. The structure is essentially similar to that of the redox flow system 10 1 . Deviating from the design according to 1 In the embodiment shown here, the converted active material AM` is not fed back to the active material storage 210, 310. In the embodiment shown here, the spent active material AM' is stored in the residual storage container 280, 380 after solvent removal in the solvent removal unit 240, 340. The system shown here is not a continuous system, but rather a system that is operated in shifts.

The foregoing description of the present invention is for illustrative purposes only and not for the purpose of limiting the invention. Various changes and modifications are possible within the scope of the invention without departing from the scope of the invention and its equivalents.

Claims (9)

Operating method of a redox flow system (10), comprising the steps: - Storing active material (AM) in at least one active material memory (210, 310), the active material memory (210, 310) storing active material (AM) for an anode (120) or for a cathode (130) of at least one redox flow cell (100) of the redox flow system (10); - Addition of solvent (L) to the active material (AM) upstream of the redox flow cell (100); - Solvent removal downstream of the redox flow cell (100), at least part of the solvent (L) being removed again; and - Providing the removed solvent (L) for re-addition to the active material (AM) upstream of the redox flow cell (100). Procedure according to Claim 1 , wherein the active material (AM) is stored in the active material storage (210, 310) as dry powder, paste, pellets and / or highly concentrated solution. Procedure according to Claim 1 or 2 , wherein the removal of the solvent (L) from the electrolyte solution (AM'L) converted in the redox flow cell (100) comprises one or more of the following process steps: - Evaporation or evaporation of the solvent (L), especially under negative pressure; - Precipitation of the converted active material (AM') from the converted electrolyte solution (AM'L); - Reverse osmosis using a semi-permeable membrane; - Centrifugation of the converted electrolyte solution (AM'L); - solvent extraction; and/or - filtration. Operating procedure of a motor vehicle, with the steps: - Operating a redox flow system (10) with a method according to one of the preceding claims, and - Supplying recuperation energy to a solvent removal unit (240, 340), in which at least part of the solvent (L) is removed again. Redox flow system (10) with: - at least one redox flow cell (100), which has an anode (120) and a cathode (130), which are separated from each other by an ion-selective separator (140); - at least one active material memory (210, 310) for storing a redox active material (AM), the active material memory (210, 310) providing active material (AM) for the anode (120) or for the cathode (130); - at least one solvent addition unit (220, 320) which is arranged upstream of the redox flow cell (100), the solvent addition unit (220, 320) being suitable for adding solvent (L) to the redox active material (AM); - at least one solvent removal unit (240, 340) which is arranged downstream of the redox flow cell (100), the solvent removal unit (240, 340) being suitable for removing solvent (L); and - at least one return line (270, 370) which is suitable for feeding the removed solvent (L) to the solvent addition unit (220, 320). Redox flow system (10). Claim 5 , wherein the at least one active material storage (210, 310) is designed to store the active material (AM) as dry powder, paste, pellets and / or highly concentrated solution. Redox flow system (10). Claim 5 or 6 , wherein an active material storage (210, 310), a solvent addition unit (220, 320) and a solvent removal unit (240, 340) are provided in the anode fluid circuit (200) and in the cathode fluid circuit (300). Redox flow system (10) according to one of the Claims 5 until 7 , wherein the redox flow system (10) further has at least one residual storage container (280, 380) which is designed to contain the converted active material (AM') after the reaction in the redox flow cell (100) and after solvent removal save. Motor vehicle with a redox flow system (10) according to one of the previous ones Claims 5 until 8th .

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