Electrical power source

Abstract

The invention relates to an electrical power source comprising two flow batteries (1, 2), which are held at different temperatures (T1, T2) from one another and the potential difference of which can be tapped as useful voltage. The electrolyte liquids (15, 16) are conducted comprehensively across the two flow batteries (1, 2). A heat store (42) is additionally incorporated into the energy source and the electrolyte liquids (15, 16) are conducted through said heat store so that they have their respective temperatures (T1, T2) on the input side of the respective flow batteries (1, 2). The heat store (42) is held in the upper region at the higher of the two temperatures (T1, T2) by feed elements (29) arranged in the upper region and in the lower region at the lower of the two temperatures (T1, T2) by feed elements (29) arranged in the lower region. The temperature profile therebetween is established in accordance with the state of charge of the heat store (42).

Description

[0001] Description

[0002] Title of the invention

[0003] Electrical energy source

[0004] field of technology

[0005] The present invention relates to an electrical energy source,

[0006] - the electrical energy source comprises two flow batteries,

[0007] - wherein the flow batteries each have first and second poles,

[0008] - wherein the first poles are electrically connected to each other and a respective useful potential can be tapped at the second poles,

[0009] - where the useful potentials, related to the first poles, have the same sign,

[0010] - where the two flow batteries each have a reaction chamber,

[0011] - wherein the reaction chambers each have a membrane which separates the respective reaction chamber into two fluid chambers,

[0012] - wherein the membranes are permeable to the transfer of electrical charge carriers between the fluid spaces of the respective reaction space,

[0013] - wherein the electrical energy source has two separate circuits for a respective electrolyte fluid,

[0014] - wherein the circuits are closed circuits, each connecting one of the fluid spaces of the two reaction spaces, so that the electrolyte fluids alternately flow through one of the fluid spaces of one reaction space and one of the fluid spaces of the other reaction space,

[0015] - the two circuits have heat exchangers on the inlet side of the reaction chambers, by means of which the electrolyte liquids are brought to a respective temperature,

[0016] - where one of the two temperatures is higher than the other.

[0017] State of the art

[0018] Electrical energy sources come in a wide variety of forms. Examples include generators, photocells, batteries, accumulators, and others.

[0019] A flow battery is known from the entry "Redox Flow Battery" in the German Wikipedia, accessed on April 27, 2023. A flow battery is a type of accumulator. In a flow battery, electrical energy is stored in chemical compounds, with the reactants dissolved in a solvent. The electrical energy is therefore stored in electrolytes. The electrolytes are conducted in two separate circuits, with ion exchange taking place in a galvanic cell via a membrane. In the cell, the substances dissolved in the electrolyte are chemically reduced or oxidized, whereby electrical energy is required to charge the flow battery and electrical energy is released during discharging.

[0020] From an internet entry retrieved by the applicant on April 26, 2023, at https: / / www.sandia.gov / ess / projects / batteries, it is known that flow batteries exist in which the voltage supplied by the battery contains a significant temperature-dependent contribution, so that the battery voltage can be drastically changed simply by changing the temperature. It is explained that the flow battery can be maintained at a low temperature during the charging portion of the battery cycle and at a high temperature during the discharging portion of the battery cycle, thereby maximizing the amount of electrical energy that can be delivered by the battery. It is proposed to pump the electrolyte fluids (of course via the galvanic cell) back and forth between storage tanks, with the storage tanks being maintained at different temperatures.

[0021] US 2019 / 0 252 697 A1 discloses an electrical energy source according to the preamble of claim 1. JP 2020 188 012 A contains a similar disclosure.

[0022] US Pat. No. 7,820,321 B2 discloses an electrical energy source comprising a single flow battery. The flow battery has a first and a second pole and a reaction chamber. A potential can be tapped at each of the two poles. The reaction chamber has a membrane that separates the reaction chamber into two fluid chambers, the membrane being permeable to the transfer of electrical charge carriers between the fluid chambers of the reaction chamber. Furthermore, the electrical energy source has two separate, closed circuits for a respective electrolyte fluid.

[0023] Summary of the invention

[0024] The object of the present invention is to provide a design of an electrical energy source comprising flow batteries and advantageously utilizing the temperature dependence of the battery voltages. This design optimizes the energy balance of the electrical energy storage device and also allows for the consideration of influences on the thermal balance of the electrical energy source that occur during charging and discharging.

[0025] The object is achieved by an electrical energy source having the features of claim 1. Advantageous embodiments of the electrical energy source are the subject of dependent claims 2 to 4. According to the invention, an electrical energy source of the type mentioned at the outset is designed in that

[0026] - that the electrical energy source has a heat storage device containing a storage medium,

[0027] - that the heat exchangers each have a feed element and a take-off element,

[0028] - that the respective feed element is kept at the respective temperature to which the respective electrolyte liquid is brought by means of the respective heat exchanger, in particular a respective fluid is passed through the respective feed element which has the respective temperature when fed to the respective feed element,

[0029] - that the respective electrolyte fluid flows through the respective removal element, that the feed elements which are kept at the higher of the two temperatures are arranged exclusively in an upper region of the heat accumulator and the feed elements which are kept at the lower of the two temperatures are arranged exclusively in a lower region of the heat accumulator and that the removal elements by means of which the respective electrolyte fluid is brought to the higher of the two temperatures are arranged at least in the upper region of the heat accumulator and the removal elements by means of which the respective electrolyte fluid is brought to the lower of the two temperatures are arranged at least in the lower region of the heat accumulator.

[0030] This means that influences on the thermal balance of the electrical energy source that occur during charging and discharging can be absorbed and buffered by the heat storage device.

[0031] In its simplest form, the electrical energy source functions exclusively as an energy source, thus offering no storage option for electrical energy. However, it is possible to design the electrical energy source in such a way that electrical energy storage is also possible.This is achieved in that the two circuits have storage vessels and influencing elements on the outlet side of the reaction chambers, by means of which the amount of respective electrolyte fluid can be adjusted. This electrolyte fluid is transported from the storage vessel on the outlet side of the reaction chamber of one flow battery via the heat exchanger on the inlet side of the reaction chamber of the other flow battery and the reaction chamber of the other flow battery into the storage vessel on the outlet side of the reaction chamber of the other flow battery, so that a fill level of the storage vessel on the outlet side of the reaction chamber of one flow battery decreases and a fill level of the storage vessel on the outlet side of the reaction chamber of the other flow battery increases. The influencing elements can be pumps. This design is always feasible. In the case of pumps, the amount of electrolyte fluid transported can be adjusted by appropriately controlling the pumps.Alternatively, two of the influencing elements can be pumps and two valves. This configuration is feasible if there is a height difference between the storage vessels on the inlet and outlet sides of the valves, so that when the respective valve is open, the respective electrolyte fluid flows by gravity from the storage vessel on the inlet side of the respective valve via the reaction chamber on the outlet side of the respective valve into the storage vessel on the outlet side of the aforementioned reaction chamber. In this case, the amount of flowing electrolyte fluid can be adjusted by the extent to which the respective valve is opened.

[0032] Preferably, the supply elements maintained at the higher of the two temperatures are combined into a single supply element, and the supply elements maintained at the lower of the two temperatures are also combined into a single supply element. This simplifies the overall design of the electrical energy source. The consumption elements must, of course, remain separate from each other, at least with regard to the electrolyte flows, since otherwise separate circuits would no longer exist. From a mechanical and structural point of view, they can also be combined if necessary.

[0033] Preferably,

[0034] - that the removal elements extend within the heat storage unit from the upper area of ​​the heat storage unit to the lower area of ​​the heat storage unit,

[0035] - that the removal elements, by means of which the respective electrolyte liquid is brought to the higher of the two temperatures, are flowed through by the respective electrolyte liquid within the heat storage device from bottom to top and

[0036] - that the removal elements, by means of which the respective electrolyte liquid is brought to the lower of the two temperatures, are flowed through by the respective electrolyte liquid within the heat storage device from top to bottom.

[0037] This design maximizes the efficiency of the heat storage system.

[0038] Short description of the drawings

[0039] The above-described properties, features, and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more readily understood in connection with the following description of an embodiment, which is explained in more detail in conjunction with the drawings.

[0040] FIG 1 shows an electrical energy source, FIG 2 shows another electrical energy source and

[0041] FIG 3 Temperature curves.

[0042] Description of the embodiments

[0043] According to FIG 1, an electrical energy source has two flow batteries 1, 2. The two flow batteries 1, 2 each have first poles 3, 4 and second poles 5, 6. The first poles 3, 4 are electrically connected to one another. A respective useful potential P1, P2 can be tapped at the second poles 5, 6. The two useful potentials P1, P2 have the same sign relative to the first poles 3, 4 (or the corresponding common potential PO). According to the illustration in FIG 1, the two useful potentials P1, P2 are positive, i.e. greater than the common potential PO. However, it could also be the other way around.

[0044] The two flow batteries 1, 2 each further comprise a reaction chamber 7, 8. The reaction chambers 7, 8 each comprise a membrane 9, 10. The respective membrane 9, 10 separates the respective reaction chamber 7, 8 into two fluid chambers 11, 12 and 13, 14, respectively. The membranes 9, 10 are permeable to the transfer of electrical charge carriers between the fluid chambers 11, 12 and 13, 14 of the respective reaction chamber 7, 8. However, they are not permeable to the electrolyte fluids 15, 16 located in the fluid chambers 11 to 14.

[0045] The electrical energy source further comprises two separate circuits 17, 18. The two circuits 17, 18 are closed circuits. One of the two electrolyte fluids 15, 16 circulates in each of them. One circuit 17 connects the fluid chambers 11 and 13 to one another. The connection is such that the electrolyte fluid 15 is first conducted via a line section 19 from the fluid chamber 11 to the fluid chamber 13 and then via a line section 20 from the fluid chamber 13 to the fluid chamber 11. The other circuit 18 connects the fluid chambers 12 and 14 to one another. The connection is such that the electrolyte fluid 16 is first conducted via a line section 21 from the fluid chamber 12 to the fluid chamber 14 and then via a line section 22 from the fluid chamber 14 to the fluid chamber 12.As a result, the electrolyte fluids 15, 16 alternately flow through one of the fluid chambers 11, 12 of one reaction chamber 7 and one of the fluid chambers 13, 14 of the other reaction chamber 8. Pumps 23, 24 required to pump the electrolyte fluids 15, 16 are always operated in both directions and in the same way. They can, in principle, be arranged at any location in the circuits 17, 18. The arrangement shown in line sections 20 and 22 is not mandatory. They could equally well be arranged in line sections 19 and 21.

[0046] When the electrolyte liquid 15 flows through the fluid space 11, it is either oxidized or reduced. When the electrolyte liquid 15 is oxidized in the fluid space 11, the electrolyte liquid 16 is reduced in the fluid space 12, the electrolyte liquid 15 is reduced in the fluid space 13, and the electrolyte liquid 16 is oxidized in the fluid space 14. Conversely, when the electrolyte liquid 15 is reduced in the fluid space 11, the electrolyte liquid 16 is oxidized in the fluid space 12, the electrolyte liquid 15 is oxidized in the fluid space 13, and the electrolyte liquid 16 is reduced in the fluid space 14.

[0047] The two circuits 17, 18 have heat exchangers 25 to 28 on the inlet side of the reaction chambers 7, 8. The electrolyte fluids 15, 16 are brought to a temperature T1 by means of the heat exchangers 25 and 26. The electrolyte fluids 15, 16 are brought to a temperature T2 by means of the heat exchangers 27 and 28. The temperature T2 is higher than the temperature T1.

[0048] The structure of heat exchanger 25 is explained in more detail below. Similar designs apply to the other heat exchangers 26 to 28.

[0049] According to FIG. 1, the heat exchanger 25 has a feed element 29 and a removal element 30. The feed element 29 is maintained at temperature T1, i.e., the temperature to which the electrolyte liquid 15 is brought by the heat exchanger 25. In particular, it is possible for a fluid 31 to be passed through the feed element 29 for this purpose, which fluid 31 has a temperature T1 when fed to the feed element 29. The removal element 30 is part of the circuit 17. The electrolyte liquid 15 flows through it. The feed element 29 and the removal element 30 are thermally coupled to one another, so that the temperature T1 of the feed element 29 is transferred to the electrolyte liquid 15.

[0050] In order to produce different potentials P1, P2, the potentials P1, P2, relative to the common potential PO, must depend to a significant extent on the temperature T1, T2 in the respective reaction chambers 7, 8. Suitable electrolyte fluids 15, 16 are known. Purely as an example, the electrolyte fluids used in a vanadium redox accumulator are mentioned.

[0051] In the embodiment of FIG 1, the two circuits 17, 18 have further heat exchangers 32, 33 between the heat exchangers 25 to 28 arranged on the inlet side of the reaction chambers 7, 8 of the flow batteries 1, 2 and the reaction chamber 8, 7 of the other flow battery 2, 1. By means of the further heat exchangers 32, 33, the temperatures of the electrolyte liquids 15, 16 of the respective circuit 17, 18 are brought closer to one another. For this purpose, the heat exchanger 32 is preferably flowed through on the one hand by the electrolyte liquid 15, which flows in the line section 19 from the reaction chamber 7 to the reaction chamber 8, and on the other hand by the electrolyte liquid 15, which flows in the line section 20 from the reaction chamber 8 to the reaction chamber 7.In an analogous manner, for this purpose, the heat exchanger 33 is flowed through on the one hand by the electrolyte liquid 16, which flows in the line section 21 from the reaction chamber 7 to the reaction chamber 8, and on the other hand by the electrolyte liquid 16, which flows in the line section 22 from the reaction chamber 8 to the reaction chamber 7.

[0052] FIG 1 also shows storage vessels 34 to 37 on the outlet side of reaction chambers 7 and 8. Storage vessels 34 to 37 are components of circuits 17 and 18.

[0053] An embodiment of an electrical energy source according to the invention is explained below in conjunction with FIG. 2. The above explanations made in conjunction with FIG. 1 also apply to this embodiment. However, in FIG. 2, poles 3 to 6 and potentials P0, P1, and P2 are not shown, as these are not necessary for understanding the modifications of the embodiment of FIG. 2 compared to the embodiment of FIG. 1.

[0054] In the embodiment according to FIG. 2, the storage vessels 34 to 37 are also present on the outlet side of the reaction chambers 7, 8. Furthermore, the two circuits 17, 18 have influencing elements 38 to 41 on the outlet side of the reaction chambers 7, 8 instead of the pumps 23, 24. The influencing elements 38 to 41 can be arranged downstream of the storage vessels 34 to 37 as shown in FIG. 2. Alternatively, the influencing elements 38 to 41 can be arranged upstream of the storage vessels 34 to 37.

[0055] The influencing elements 38 to 41 can be operated jointly and in a similar manner. In this case, the electrical energy source operates in the same manner as explained above in connection with FIG. 1. However, the influencing elements 38 to 41 can also be operated in a similar manner only in pairs. In particular, the influencing elements 38 and 39 are always operated jointly and in a similar manner, and the influencing elements 40 and 41 are also always operated jointly and in a similar manner. However, the operation of the influencing elements 38 and 39 can be selected independently of the operation of the influencing elements 40 and 41.

[0056] In the following, we will first explain what happens when only the influencing element 38 and the influencing element 39 are operated.

[0057] In this case, the electrolyte liquid 15 is transported by means of the influencing element 38 from the storage vessel 34 on the outlet side of the reaction chamber 7 via the removal element 30 of the heat exchanger 27 (see FIG. 1) on the inlet side of the reaction chamber 8 and the reaction chamber 8 itself into the storage vessel 35. This reduces a fill level F1 of the storage vessel 34. A fill level F2 of the storage vessel 35 increases to the same extent. In an analogous manner, the electrolyte liquid 16 is transported by means of the influencing element 39 from the storage vessel 36 on the outlet side of the reaction chamber 7 via the removal element 30 of the heat exchanger 28 (see FIG. 1) on the inlet side of the reaction chamber 8 and the reaction chamber 8 itself into the storage vessel 37. This reduces the filling level F3 of the storage vessel 36. The filling level F4 of the storage vessel 37 increases to the same extent.As a result, flow battery 2 is operated, but flow battery 1 is not. This reduces the charge state of the electrical energy source. Therefore, charge is removed from the electrical energy source.

[0058] When the influencing elements 40 and 41 are operated, the reverse process occurs. This increases the charge state of the electrical energy source. Thus, charge is supplied to the electrical energy source.

[0059] The extension of the basic principle to include the storage vessels 34 to 37 and the influencing elements 38 to 41 means that the electrical energy source can also be used as an electrical energy storage device in addition to being a pure electrical energy source.

[0060] The electrical energy source can thus be operated in three "pure" operating modes. In the first of these "pure" operating modes, all four influencing elements 38 to 41 are operated in the same way. This "pure" operating mode is essentially the same operating mode as the electrical energy source in FIG. 1. In the second of these "pure" operating modes, only the influencing elements 38 and 39 are operated in the same way. Influencing elements 40 and 41 are not operated in this operating mode. In the third of these "pure" operating modes, the situation is reversed. Here, only the influencing elements 40 and 41 are operated in the same way. Influencing elements 38 and 39 are not operated in this operating mode. These two further "pure" operating modes are possible with the electrical energy source in FIG. 2, but not with the electrical energy source in FIG. 1.In addition to these “pure” operating modes, a mixed operation is also possible with the electrical energy source of FIG 2, in which all four influencing elements 38 to 41 are operated, but the influencing elements 38 and 39 are controlled more strongly or less strongly than the influencing elements 40 and 41.

[0061] In the illustration according to FIG. 2, all four influencing elements 38 to 41 are designed as pumps. However, two of the influencing elements 38 to 41 can also be designed as pumps and two as valves. This configuration is not shown separately.

[0062] To optimize the thermal energy balance, the electrical energy source, as shown in FIG. 2, also has a heat accumulator 42. The heat accumulator 42 contains a storage medium 43, for example, a thermal oil or water or a salt that melts at a low temperature, for example, sodium acetate trihydrate, sodium sulfate, sodium hydroxide, or alum. The melting point of the storage medium 43 can be between the two temperatures T1 and T2. However, the melting point of the storage medium 43 can also be below temperature T1. Furthermore, the boiling point of the storage medium 43 should, if possible, be above temperature T2. However, exceptions to these rules are possible.

[0063] In the embodiment according to FIG 2, the feed elements 29, which are maintained at temperature T2, are arranged exclusively in an upper region of the heat accumulator 42. Conversely, the feed elements 29, which are maintained at temperature T1, are arranged exclusively in a lower region of the heat accumulator 42. The removal elements 30, by means of which the electrolyte liquids 15, 16 are brought to temperature T2, are arranged at least in the upper region of the heat accumulator 42. Conversely, the removal elements 30, by means of which the electrolyte liquids 15, 16 are brought to temperature T1, are arranged at least in the lower region of the heat accumulator 42.

[0064] Preferably, the removal elements 30 are not arranged exclusively in the upper or lower region of the heat accumulator 42, but extend, as shown in FIG 2, within the heat accumulator 42 from the upper region of the heat accumulator 42 to the lower region of the heat accumulator 42. In this case, the removal elements 30, by means of which the electrolyte liquids 15, 16 are brought to the temperature T2, are flowed through from bottom to top by the electrolyte liquids 15, 16 within the heat accumulator 42. Conversely, in this case, the removal elements 30, by means of which the electrolyte liquids 15, 16 are brought to the temperature T1, are flowed through from top to bottom by the electrolyte liquids 15, 16 within the heat accumulator 42.

[0065] As shown in FIG. 2, the feed elements 29 that are maintained at temperature T2 are combined into a common feed element. Likewise, the feed elements 29 that are maintained at temperature T1 are combined into a common feed element.

[0066] For an electrical energy source having a heat accumulator 42, the temperature stratification of the storage medium 43 in the heat accumulator 42 depends on the extent to which the electrical energy source is charged or discharged. This is explained below in conjunction with FIG. 3, which shows the temperature of the storage medium 43 as a function of the height h within the heat accumulator 42.

[0067] In FIG 3, h1 denotes the lowest point of the heat accumulator 42, and h2 the highest point. In the lower region of the heat accumulator 42, i.e. at the location of the corresponding feed element 29, the storage medium 43 always has a temperature T1. Similarly, in the upper region of the heat accumulator 42, i.e. at the location of the corresponding feed element 29, the storage medium 43 always has a temperature T2. The temperature profile in between, however, depends on whether the electrical energy source is charged or discharged. If the electrical energy source is fully charged, the fill levels F1 and F3 are at a maximum and the fill levels F2 and F4 are at a minimum. In this case, a temperature profile approximately corresponding to curve K1 arises. The thermal energy is essentially located in the heat accumulator 42. If the electrical energy source is fully discharged, the fill levels F1 and F3 are at a minimum and the fill levels F2 and F4 are at a maximum.In this case, a temperature curve roughly corresponds to curve K2. The heat energy is essentially located in the electrolyte fluids 15, 16. If the electrical energy source is neither fully charged nor fully discharged, a temperature curve between curves K1 and K2 is established, for example, roughly corresponding to curve K3. The fill levels F1 to F4 also lie between their minimum and maximum values.

[0068] The present invention has many advantages. In particular, electrical energy can be generated in a simple manner – namely, without the need for a heat engine that drives a generator – based on a temperature difference. The mode of operation is similar to the Carnot cycle. The electrical energy source can – at least in some cases – still supply electrical energy even when the operation of a heat engine with corresponding temperature differences would no longer be possible. In the case of the embodiment according to FIG. 2, electrical energy can also be stored and released. Furthermore, switching between the various operating modes is possible very quickly, i.e., highly dynamically.Furthermore, such flow batteries 1, 2 can also be cascaded and further loops with heat exchangers 25 to 28 can be installed in the heat storage 42 in order to be able to bring the electrolytes 15, 16 to their respective target temperature T1 or T2 again and again, even when passing through flow batteries 1, 2 several times.

[0069] Although the invention has been illustrated and described in detail by the preferred embodiments, the invention is not limited by the disclosed examples, and other variations may be derived therefrom by those skilled in the art without departing from the scope of the invention.

[0070] 1, 2 flow batteries

[0071] 3 to 6 poles

[0072] 7, 8 reaction chambers

[0073] 9, 10 membranes

[0074] 11 to 14 fluid chambers

[0075] 15, 16 Electrolyte fluids

[0076] 17, 18 circuits

[0077] 19 to 22 line sections

[0078] 23, 24 pumps

[0079] 25 to 28 heat exchangers

[0080] 29 Feed element

[0081] 30 Acceptance element

[0082] 31 Fluid

[0083] 32, 33 additional heat exchangers

[0084] 34 to 37 storage vessels

[0085] 38 to 41 influencing elements

[0086] 42 heat storage tanks

[0087] 43 Storage medium

[0088] F1 to F4 Fill levels h, h1 , h2 Heights

[0089] K1, K2, K3 curves

[0090] PO, P1, P2 potentials

[0091] T1 , T2 temperatures

Claims

Claims 1. Electrical energy source, - wherein the electrical energy source comprises two flow batteries (1, 2), - wherein the flow batteries (1, 2) each have first and second poles (3 to 6), - wherein the first poles (3, 4) are electrically connected to one another and a respective useful potential (P1, P2) can be tapped off at the second poles (5, 6), - wherein the useful potentials (P1, P2) relative to the first poles (3, 4) have the same sign, - wherein the two flow batteries (1, 2) each have a reaction chamber (7, 8), - wherein the reaction chambers (7, 8) each have a membrane (9, 10) which separates the respective reaction chamber (7, 8) into two fluid chambers (11 to 14), - wherein the membranes (9, 10) are permeable to a transfer of electrical charge carriers between the fluid spaces (11 to 14) of the respective reaction space (7, 8), - wherein the electrical energy source has two separate circuits (17, 18) for a respective electrolyte liquid (15, 16), - wherein the circuits (17, 18) are closed circuits which each connect one of the fluid spaces (11, 14) of the two reaction spaces (7, 8) to one another, so that the electrolyte liquids (15, 16) alternately flow through one of the fluid spaces (11, 12) of one reaction space (7) and one of the fluid spaces (13, 14) of the other reaction space (8), - wherein the two circuits (17, 18) have heat exchangers (25 to 28) on the inlet side of the reaction chambers (7, 8), by means of which the electrolyte liquids (15, 16) are brought to a respective temperature (T 1 , T2), - wherein one of the two temperatures (T1, T2) is higher than the other, characterized in that - that the electrical energy source has a heat accumulator (42) in which a storage medium (43) is located, - that the heat exchangers (25 to 28) each have a feed element (29) and a take-off element (30), - that the respective feed element (29) is kept at the respective temperature (T1, T2) to which the respective electrolyte liquid (15, 16) is brought by means of the respective heat exchanger (25 to 28), in particular a respective fluid (31) is passed through the respective feed element (29) which has the respective temperature (T1, T2) when fed to the respective feed element (29), - that the respective removal element (30) is flowed through by the respective electrolyte liquid (15, 16), that the feed elements (29) which are kept at the higher of the two temperatures (T1, T2) are arranged exclusively in an upper region of the heat accumulator (42) and the feed elements (29) which are kept at the lower of the two temperatures (T1, T2) are held, are arranged exclusively in a lower region of the heat accumulator (42) and that the removal elements (30), by means of which the respective electrolyte liquid (15, 16) is brought to the higher of the two temperatures (T1, T2), are arranged at least in the upper region of the heat accumulator (42) and the removal elements (30), by means of which the respective electrolyte liquid (15, 16) is brought to the lower of the two temperatures (T1, T2), are arranged at least in the lower region of the heat accumulator (42).

2. Electrical energy source according to claim 1, characterized in that the two circuits (17, 18) have storage vessels (34 to 37) and influencing elements (38 to 41) on the outlet side of the reaction chambers (7, 8), by means of which the amount of respective electrolyte liquid (15, 16) can be adjusted, which is transported from the storage vessel (34, 36) on the outlet side of the reaction chamber (7) of one flow battery (1) via the heat exchanger (27, 28) on the inlet side of the reaction chamber (8) of the other flow battery (2) and the reaction chamber (8) of the other flow battery (2) into the storage vessel (35, 37) on the outlet side of the reaction chamber (8) of the other flow battery (2), so that a filling level (F1, F3) of the storage vessel (34, 36) on the outlet side of the reaction chamber (7) of one flow battery (1) is reduced and a filling level (F2, F4) of the storage vessel (35, 37) on the outlet side of the reaction chamber (8) of the other flow battery (2) is increased.

3. Electrical energy source according to claim 1 or 2, characterized in that the feed elements (29) which are kept at the higher of the two temperatures (T1, T2) are combined to form a common feed element (29) and the feed elements (29) which are kept at the lower of the two temperatures (T1, T2) are combined to form a common feed element (29).

4. Electrical energy source according to claim 1, 2 or 3, characterized in that - that the removal elements (30) extend within the heat accumulator (42) from the upper region of the heat accumulator (42) to the lower region of the heat accumulator (42), - that the removal elements (30), by means of which the respective electrolyte liquid (15, 16) is brought to the higher of the two temperatures (T1, T2), are flowed through by the respective electrolyte liquid (15, 16) within the heat accumulator (42) from bottom to top, and - that the removal elements (30), by means of which the respective electrolyte liquid (15, 16) is brought to the lower of the two temperatures (T1, T2), are separated from the respective electro- lyt fluid (15, 16) within the heat accumulator (42) flows from top to bottom.

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