METHOD FOR PROVIDING ENERGY AND SORPTION PLANT

Description

[0001] The invention relates firstly to a method according to claim 1 for providing energy, wherein electrical energy is stored as chemical energy and made available for conversion back into electrical energy. Such methods are known, for example, for operating batteries.

[0002] The invention further relates to a sorption system according to claim 3 with refrigerant, liquid

[0003] A solvent, a refrigerant-poor solution and a refrigerant-rich solution, wherein the poor and rich solutions are single-phase mixtures of the solvent and the refrigerant, and comprising an absorber for absorbing the refrigerant in the poor solution while releasing heat, a desorber for driving the refrigerant out of the rich solution behind the absorber while absorbing a first heat flow supplied from the outside, a solvent pump for pumping the poor solution from the desorber into the absorber, a condenser for liquefying the refrigerant from the desorber, a compressor for drawing the refrigerant out of the desorber, an evaporator for evaporating the refrigerant from the condenser while absorbing a second heat flow supplied from the outside before the absorber, a refrigerant receiver behind the condenser, and a refrigerant pump for pumping the refrigerant from the refrigerant receiver to the evaporator.

[0004] Document EP2803923 A2 discloses a sorption system. Wang J et al., "Analysis of a compression-assisted absorption heat transformer", 12th Heat Pump Conference (Proceedings), Rotterdam, 2017, proposes increasing the inlet pressure of the refrigerant to the condenser in such a sorption system used as a heat transformer with the compressor, in order to reduce energy consumption, particularly for meeting hot water demand and for low-temperature heating of living spaces.

[0005] In the background of the invention, Xu ZY et al. disclose "Absorption seasonal thermal storage cycle with high energy storage density through multi-stage output", Energy 167 (2019) ) A seasonal heat storage system based on absorption processes. Furthermore, it is generally known to use sorption systems as heat pumps. Task

[0006] The invention is based on the objective of proposing a novel energy storage device. Solution

[0007] Based on the known method, the invention proposes that in a sorption system with refrigerant and liquid solvent, a refrigerant-poor and a refrigerant-rich solution, wherein the poor and the rich solutions are single-phase mixtures of the solvent and the refrigerant, the liquid refrigerant is evaporated at a high-pressure level and expanded to a low-pressure level, thereby driving an expansion machine, the poor solution absorbs the vaporous refrigerant, and is collected as the rich solution, and that for storage, the refrigerant is instead driven out of the rich solution at the low-pressure level, the remaining poor solution is collected, and the driven-out refrigerant is compressed, liquefied, and collected using electrical energy.

[0008] The inventive method uses a substantially known sorption system as an energy storage device, wherein electrical energy is stored as chemical energy in the expelled refrigerant at the high-pressure level and made available again by expanding the refrigerant to the low-pressure level.

[0009] Preferably, in a process according to the invention, the liquid refrigerant is evaporated and / or the refrigerant is driven out of the rich solution by means of a heat flow supplied to the sorption system from the outside. Such a process according to the invention preferably uses industrial waste heat to increase the electrical energy supplied.

[0010] Based on the known sorption system, the invention proposes providing a shut-off device for the condenser, wherein the compressor is connected to a refrigerant line between the evaporator and the absorber on a pressure side upstream of the shut-off device. Such a sorption system enables two separate operating states of the sorption system by selectively opening or closing the shut-off device or by driving the compressor and the solvent pump, in particular for energy storage on the one hand and energy supply on the other, but also optionally for operation as a heat pump or as a heat transformer.

[0011] For operation of the sorption system as a heat pump, the condenser is disconnected from the refrigerant line using the shut-off device, and the desorber is connected to the absorber via the compressor. For operation as a heat transformer, the compressor remains unpowered, and the desorber is connected to the condenser.

[0012] Preferably, a sorption system according to the invention includes a throttling element for reducing the pressure of the rich solution between the absorber and the desorber. The pressure reduction between the absorber and the desorber is necessary for operation as a heat transformer or as a heat pump.

[0013] Alternatively, preferably, a sorption system according to the invention comprises an expansion machine for expanding the refrigerant between the evaporator and the absorber, and a solution collector for collecting the rich solution between the absorber and the desorber. Such a sorption system allows operation as an energy storage device: To charge the energy storage device, the refrigerant is driven out of the rich solution collected in the solution collector in the desorber, compressed to high pressure in the compressor, liquefied in the condenser, and collected in the refrigerant collector. To discharge, the refrigerant is evaporated in the evaporator, expanded back to low pressure in the expansion machine, and absorbed in the poor solution in the absorber, which is then collected in the solution collector.

[0014] Energy is expended to drive the refrigerant out of the solvent and to compress it to a high-pressure level; this energy is released again by expanding the refrigerant to low pressure and dissolving it in the poor solution.

[0015] Preferably, such a sorption system according to the invention comprises at least one further solvent pump for each of the poor and / or rich solutions from the absorber to the solution collector, from the desorber to the solution collector, from the solution collector to the absorber, and / or from the solution collector to the desorber. By means of the further solvent pump(s), the concentration of the solution in the solution collector can be further reduced during charging of the energy storage device and further increased during discharging.

[0016] Preferably, in such a sorption system according to the invention, the solution collector is a stratified storage tank. In the solution collector, the concentration of the refrigerant in the solution then increases with increasing height. Thus, a solution with a minimal refrigerant concentration can be drawn from the bottom of the solution collector to discharge the energy storage system, and a richer solution can be drawn from a higher extraction point to charge the energy storage system.

[0017] Preferably, in such a sorption system according to the invention, a single fluid energy machine serves optionally as either the compressor or the expansion machine. By using the fluid energy machine for dual purposes, as either a compressor or an expansion machine depending on the operating condition, a second fluid energy machine is not required, thereby reducing the number of moving parts, the mechanical complexity, and the size of the sorption system.

[0018] Preferably, a sorption system according to the invention comprises a first heat exchanger that serves as both the desorber and the absorber, and / or a second heat exchanger that serves as both the condenser and the evaporator. Due to the dual use of the first and / or second heat exchanger depending on the operating condition, a second heat exchanger is not required in each case, which in turn reduces the number of components and the size of the sorption system.

[0019] In an operating method for a sorption system according to the invention, in a first operating state the compressor is unpowered and the condenser is disconnected from the refrigerant line by means of the shut-off device, the refrigerant pump pumps the refrigerant and the evaporator drives the refrigerant out, and in another operating state the compressor instead feeds the refrigerant into the refrigerant line. The sorption system according to the invention enables these two operating states.

[0020] Preferably, in an operating method according to the invention, a throttling element expands the rich solution downstream of the absorber, and the solvent pump pumps the poor solution. In the first operating state, the condenser liquefies the refrigerant, the refrigerant pump pumps the refrigerant, and the refrigerant evaporates in the evaporator. In such an operating method, the sorption system operates as a heat transformer in the first operating state and as a heat pump in the second. Preferably, during the transition to the first operating state, a portion of the refrigerant boiled off from the other operating state is collected in the refrigerant receiver. By boiling off a portion of the refrigerant, the pressure level of the sorption system operating as a heat transformer is reduced to the pressure level operating as a heat pump.

[0021] Furthermore, preferably in such an operating procedure, the condenser is temporarily connected to the refrigerant line in the high-pressure section of the sorption system to lower the low-pressure level. This makes achieving the required pressure reduction particularly easy.

[0022] Alternatively, preferably in an operating method according to the invention, energy is discharged in the first operating state by successively an expansion machine expanding the refrigerant in the refrigerant line and releasing the energy, the lean solution absorbing the refrigerant, and a solvent collector collecting the rich solution from the absorber; and in the other operating state, energy is charged by successively the solvent pump pumping the rich solution from the solvent collector into the desorber, the compressor being driven and feeding the refrigerant into the condenser, the condenser liquefying the refrigerant, and the refrigerant collector collecting the refrigerant. In such an operating method, the sorption system functions as an energy storage device.

[0023] Furthermore, preferably in such an operating method according to the invention, the refrigerant is stored at a maximum of 50 °C when storing energy in the refrigerant collectors. The sorption system then does not require complex insulation to maintain the temperature level of the refrigerant. Examples of implementation

[0024] The invention is explained below with reference to exemplary embodiments. The figures show Fig. 1 a first sorption system according to the invention, Fig. 2 the operation of the first sorption system as a heat transformer, and Fig. 3 the operation of the first sorption system as a heat pump, as well as Fig. 4 a second sorption system according to the invention, Fig. 5 the discharging of the second sorption system as an energy storage device, and Fig. 6 the charging of the second sorption system.

[0025] The in Figure 1The first sorption system 1 according to the invention is operated with water as a solvent and ammonia as a refrigerant and has a circuit with a low-pressure section 2 and a high-pressure section 3. The low-pressure section 2 has a desorber 4 and a refrigerant vapor line 5 from the desorber 4 to a condenser 6, the high-pressure section 3 has an evaporator 7 and an absorber 8.

[0026] A refrigerant pump 9 is arranged downstream of the condenser 6 to pump the liquid refrigerant collected in a refrigerant receiver 10 from the low-pressure section 2 to the high-pressure section 3 and on to the evaporator 7. A solvent pump 11 pumps the remaining lean solution from a separator 12 downstream of the desorber 4 into the absorber 8. A control valve 13 between the absorber 8 and the desorber 4 throttles the rich solution flow from the high-pressure section 3 into the low-pressure section 2.

[0027] Upstream of the condenser 6, a bypass 14 branches off from the refrigerant vapor line 5 into a refrigerant line 15 between the evaporator 7 and the absorber 8. A compressor 16 is arranged in the bypass 14 to transfer the gaseous refrigerant from the low-pressure section 2 to the high-pressure section 3. The compressor 16 is protected against backflow from the high-pressure section 3 to the low-pressure section 2 by a check valve 17.

[0028] Between branch 18 of bypass 14 and condenser 6, a shut-off device 19 in the form of a butterfly valve is arranged in the refrigerant vapor line 5. Parallel to bypass 14, another bypass 20 branches off between shut-off device 19 and condenser 6 to refrigerant line 15, which can be closed with another butterfly valve 21.

[0029] In the operating state of the first sorption plant 1 as a heat transformer according to Figure 2The shut-off device 19 is open and the compressor 16 is unpowered. In the refrigerant receiver 10, the liquid refrigerant has a temperature of 29 °C; in the evaporator 7, it draws a heating power of 4 from a waste heat stream. MW The waste heat flow cools down from 80 to 54 °C.

[0030] In absorber 8, the refrigerant is absorbed in the poor solution, thereby providing a heating output of 3.5 MW a heating medium that is heated from 60 °C to 80 °C. The rich solution absorbs a further heating power of 4 from the waste heat stream in the desorber 4. MW The waste heat flow cools further from 54 to 45 °C. Condenser 6 liquefies with a capacity of 4.5 MW the refrigerant driven out in the desorber 4, which is collected in the refrigerant collector 10.

[0031] In the operating state of the first sorption plant 1 as a heat pump according to Figure 3The compressor 16 will have a capacity of 3.8 MW The actuator is driven, the shut-off device 19 is closed. The low-pressure section 2 is below 4.1 bar, the high-pressure section 3 under 20 bar. The rich solution cools a waste heat flow from 60 to 40 °C in the desorber 4; the solvent pump 11 pumps 85 m 3< / h Poor solution in the absorber 8. There, the poor solution absorbs the refrigerant pumped by the compressor 16 into the refrigerant line 15 and thereby heats a heating medium from 80 to 120 °C.

[0032] To switch from operating mode as a heat transformer to operating mode as a heat pump, the shut-off valve 21 is first opened, the shut-off device 19 is closed and the refrigerant pump 9 is switched off.

[0033] To switch from the operating state as a heat pump to the operating state as a heat transformer, the shut-off valve 21 is closed, the shut-off device 19 is opened, the compressor 16 is taken out of operation and the condenser 6 and the refrigerant pump 9 are put into operation.

[0034] The rich solution absorbs the refrigerant pumped into the refrigerant line 15 by the refrigerant pump 9 until refrigerant is expelled at the low pressure determined by the condenser.

[0035] The first sorption system 1 can be operated as a heat transformer in summer and as a heat pump in winter: For example, a district heating operator can use the heat transformer to raise industrial waste heat or geothermal heat from a low temperature level to a higher temperature level from spring to autumn and feed it into the district heating network. In winter, when heat demand is at its highest, the heat pump can raise all available waste heat to the higher temperature level.

[0036] Even those in Figure 4 The second sorption system 22 shown according to the invention is operated with water as a solvent and ammonia as a refrigerant and has a low-pressure section 23 at 2.4 bar and a high-pressure section 24 under 20 bar The low-pressure section 23 has an absorber 25 and a desorber 26, the high-pressure section 24 has an evaporator 27 and a condenser 28.

[0037] Between the absorber 25 and the desorber 26, the second sorption unit 22 has a solution collector 29. The solution collector 29 is designed as a layered reservoir in which the poor solution collects at the bottom and the rich solution at the top. A first solvent pump 30 pumps the poor solution from the solution collector 29 into the absorber 25. Further solvent pumps 31 pump the rich solution from the solution collector 29 into the desorber 26, and the remaining poor solution from the desorber 26 as well as the rich solution from the absorber 25 into the solution collector 29.

[0038] A refrigerant pump 32 is arranged downstream of the condenser 28 to pump the liquid refrigerant collected in a refrigerant receiver 33 to the evaporator 27. In a refrigerant line 34 between the evaporator 27 and the absorber 25, an expansion machine 35 expands the refrigerant from the high-pressure section 24 to the low-pressure section 23.

[0039] Downstream of the generator 26, a compressor 36 pumps the gaseous refrigerant into the refrigerant line 34. The compressor 36 is protected against backflow from the high-pressure section 24 into the low-pressure section 23 by a check valve 37. A line with a shut-off device 38 in the form of a butterfly valve is arranged between the refrigerant line 34 and the condenser 28.

[0040] For discharging energy from the second sorption plant 22 according to Figure 5 The shut-off device 38 is closed, and the condenser 28 and compressor 36 are out of operation. The refrigerant pump 32 pumps the liquid refrigerant from the refrigerant receiver 33 into the evaporator 27, where it cools a waste heat stream from 60 to 50 °C. In the expansion machine 35, the refrigerant vapor is expanded to low pressure and delivers a power output of 440 kWab. In the absorber 25, the poor solution from the solution collector 29 absorbs the refrigerant and heats a cooling medium from 20 to 31 °C.

[0041] To charge energy into the second sorption plant 22 according to Figure 6 The shut-off device 38 is open and the condenser 28 and the compressor 36 are in operation. A flow of 127 [units of measurement missing] cools the generator 26. m 3< / h the rich solution from the solution collector 29 reduces the waste heat flow from 60 to 40 ° C The compressor 36 pumps the expelled refrigerant into the condenser 28, the liquid refrigerant is heated to 28°C. C collected in refrigerant collector 33.

[0042] The second sorption unit 22, for example, allows the storage of surplus electricity from wind and solar power plants. The second sorption unit 22 can be operated at a constant temperature, e.g., ambient temperature. In this case, the condenser 28 can also be used as an evaporator 27, and the liquid refrigerant can also be evaporated there during the discharge process. The efficiency of the energy storage system is then low: only about 50% of the electrical energy supplied during the charging process can be recovered during discharge.

[0043] However, if heat is available at a higher temperature than the ambient temperature, efficiency can be significantly increased. During charging, refrigerant can then be driven out of the rich solution at a considerably higher low-pressure level. Due to the increased low-pressure level, the compressor requires 36 times less electricity to compress the refrigerant from low pressure to high pressure.

[0044] If a higher-temperature heat source is used to evaporate the refrigerant during discharge of the storage unit, a higher high pressure is generated. Conversely, if the absorber 25 is cooled by a recooler that dissipates heat to the environment, the lean solution can absorb refrigerant at a low low-pressure level. The expansion machine thus has a high pressure differential available and, depending on the temperature conditions, can even generate more electricity than was consumed during charging by partially converting the low-temperature heat into electricity.

[0045] Another sorption system can be used as a heat transformer or heat pump, as well as an energy storage unit. When there is a surplus of electricity and low heat demand, some of the refrigerant, compressed to high pressure, is condensed and stored in the refrigerant receiver 33. This reduces the amount of refrigerant supplied to the absorber and thus reduces the amount of heat released at high temperatures. When electricity is needed, the compressor output is reduced, saving electricity, and refrigerant from the refrigerant receiver 33 is evaporated in the high-pressure section and supplied to the absorber.

[0046] The characters are 1 Sorption unit 2 Low-pressure section 3 High-pressure section 4 Desorber 5 Refrigerant vapor line 6 Condenser 7 Evaporator 8 Absorber 9 Refrigerant pump 10 Refrigerant receiver 11 Solvent pump 12 Separator 13 Control valve 14 Bypass 15 Refrigerant line 16 Compressor 17 Check valve 18 Branch 19 Shut-off device 20 Bypass 21 Shut-off valve 22 Sorption unit 23 Low-pressure section 24 High-pressure section 25 Absorber 26 Desorber 27 Evaporator 28 Condenser 29 Solvent receiver 30 Solvent pump 31 Solvent pump 32 Refrigerant pump 33 Refrigerant receiver 34 Refrigerant line 35 Expansion unit 36 ​​Compressor 37 Check valve 38 Shut-off device

Claims

1. A method for supplying energy, wherein in an operating state for storage, electrical energy is stored as chemical energy and after switching to an operating state for supply, the electrical energy is supplied, wherein in a sorption system (22) with a refrigerant and liquid solvent, having a refrigerant-poor solution and a refrigerant-rich solution, wherein the poor and rich solutions are single-phase mixtures of the solvent and the refrigerant, a. in the operating state for supply, the liquid refrigerant is evaporated at a high-pressure level and expanded to a low-pressure level, thereby driving an expansion machine (35), the poor solution absorbs the gaseous refrigerant and is collected as the rich solution, and b. in the operating state for storage, the refrigerant is instead driven out of the rich solution at the low-pressure level, the remaining poor solution is collected, and the driven-out refrigerant is compressed to the high-pressure level by means of electrical energy, liquefied, and collected.

2. The method according to the preceding claim, wherein by means of a heat stream supplied to the sorption system (22) from the outside, the liquid refrigerant is evaporated and / or the refrigerant is driven out of the rich solution.

3. A sorption system (1, 22) with a refrigerant, a liquid solvent, a refrigerant-poor solution and a refrigerant-rich solution, wherein the poor and rich solutions are single-phase mixtures of the solvent and the refrigerant, comprising: a. an absorber (8, 25) for absorbing the refrigerant in the poor solution with the release of heat, b. a desorber (4, 26) for driving the refrigerant out of the rich solution downstream of the absorber (8, 25) while absorbing a first heat stream supplied from outside, c. a solvent pump (11, 30) for pumping the poor solution from the desorber (4, 26) to the absorber (8, 25), d. a condenser (6, 28) for liquefying the refrigerant from the desorber (4, 26), e. a compressor (16, 36) for extracting the refrigerant from the desorber (4, 26), f. an evaporator (7, 27) for evaporating the refrigerant from the condenser (6, 28) while absorbing a second heat stream supplied from outside upstream of the absorber (8, 25), g. a refrigerant collector (10, 33) downstream of the condenser (6, 28), and h. a refrigerant pump (9, 32) for pumping the refrigerant from the refrigerant collector (10, 33) to the evaporator (7, 27), characterized by a shut-off device (19, 38) for the condenser (6, 28), wherein the compressor (16, 36) is connected to a refrigerant line (15, 34) between the evaporator (7, 27) and the absorber (8, 25) at a pressure side upstream of the shut-off device (19, 38), wherein the sorption system (1, 22) can be switched between two operating states for storing or providing energy or for operating as a heat pump or heat transformer by selectively opening or closing the shut-off device (19, 38) or driving the compressor (16, 36) and the solvent pump (11, 30).

4. The sorption system (1) according to the preceding claim, comprising a throttle element for relaxing the rich solution between the absorber (8) and the desorber (4).

5. The sorption system (22) according to Claim 3, comprising an expansion machine (35) for relaxing the refrigerant between the evaporator (27) and the absorber (25), and a solution collector (29) for collecting the rich solution between the absorber (25) and the desorber (26).

6. The sorption system (22) according to the preceding claim, comprising at least one additional solvent pump (31) for pumping from the absorber (25) and / or the desorber (26) to the solution collector (29) and / or from the solution collector (29) to the absorber (25) and / or the desorber (26) .

7. The sorption system (22) according to any one of Claims 3 or 4, wherein the solution collector (29) is a stratified storage tank.

8. The sorption system according to any one of Claims 3 to 7, comprising a single fluid energy machine that is used alternately as the compressor or as the expansion machine.

9. The sorption system according to any one of Claims 3 to 8, comprising a first heat exchanger that is used as both the desorber and the absorber and / or a second heat exchanger that is used as both the condenser and the evaporator.

10. An operating method for operating a sorption system (1, 22) according to any one of Claims 3 to 9, wherein in a first of the operating states: a. the compressor (16, 36) is idle and b. the condenser (6, 28) is separated from the refrigerant line (15, 34) by means of the shut-off device (19, 38), c. the refrigerant pump (9, 32) pumps the refrigerant and d. the evaporator (6, 27) evaporates the refrigerant, wherein in a second of the operating states, instead of features a to d of the first of the operating states e. the compressor (16, 36) is driven and f. the refrigerant is introduced into the refrigerant line (15, 34).

11. The operating method according to the preceding claim, wherein a. a throttle element expands the rich solution downstream of the absorber (8), b. the solvent pump (11) pumps the poor solution, wherein c. in the operating state, one after the other, d. the condenser (6) liquefies the refrigerant, e. the refrigerant pump (9, 32) pumps the refrigerant and f. the refrigerant is evaporated in the evaporator (6) .

12. The operating method according to the preceding claim, wherein upon transitioning to the first of the operating states from the other of the operating states, a distilled portion of the refrigerant is collected in the refrigerant collector (33).

13. The operating method according to the preceding claim, wherein to lower the low-pressure level, the condenser (6) is temporarily connected to the refrigerant line (15).

14. The operating method according to Claim 10, wherein a. in the first of the operating states, energy is discharged in that, one after the other, b. an expansion machine (35) expands the refrigerant in the refrigerant line (34) and delivers energy, c. the poor solution absorbs the refrigerant and d. a solution collector (29) collects the rich solution from the absorber (25) and wherein e. in the other of the operating states, energy is charged in that, one after the other, f. the solvent pump (30) pumps the rich solution from the solution collector (29) into the desorber (26), g. the compressor (36) is driven and introduces the refrigerant into the condenser (28), h. the condenser (28) liquefies the refrigerant and i. the refrigerant collector (33) collects the refrigerant.

15. The operating method according to the preceding claim, wherein the refrigerant collector (10, 33) collects the refrigerant at a maximum temperature of 50 °C.