EP2574738A1 - Assembly for storing thermal energy - Google Patents

Abstract

The system has a circuit for a working gas, where circuit has a cold storage device (16), a thermal fluid energy machine (13), a heat accumulator (14) and another thermal fluid energy machine (15). The former thermal fluid energy machine is switched as working machine. The latter thermal fluid energy machine is switched as a power machine in the flow direction of the working gas from cold storage device to the heat accumulator. A humidifying unit (18) is provided between the latter thermal fluid energy machine and the heat accumulator for the working gas in a line.

Description

The invention relates to a system for storing thermal energy having a circuit for a working gas. This circuit can be designed to be open, so that it sucks air as working gas from the environment and blows them back into the environment; that is, the environment belongs to the cycle. It is also possible a closed circuit in which any working gas (including air) can be used. In the circuit, the following units are connected in the order indicated by a working gas line: a cold storage, a first thermal fluid energy machine, a heat storage, and a second thermal fluid energy machine. In the flow direction of the working gas seen from the cold storage to the heat storage while the first thermal fluid energy machine is connected as a working machine and the second thermal fluid energy machine as an engine.

The terms engine and work machine are used in the context of this application so that a work machine mechanical work to meet their purpose. A thermal fluid energy machine used as a work machine is thus operated as a compressor or as a compressor. In contrast, an engine performs work, wherein a thermal fluid energy machine for performing the work converts the thermal energy available in the working gas. In this case, the thermal fluid energy machine is thus operated as a motor.

The term "thermal fluid energy machine" forms a generic term for machines that can draw thermal energy from or supply thermal energy to a working fluid, in the context of this application, a working gas. By thermal energy is meant both thermal energy and cold energy. Thermal fluid energy machines (Also referred to below as fluid energy machines in the following) can be designed, for example, as reciprocating engines. Preferably, hydrodynamic thermal fluid energy machines can be used, the wheels allow a continuous flow of the working gas. Preferably, axially acting turbines or compressors are used.

The above-mentioned principle is, for example, according to the US 2010/0257862 A1 described. Here piston machines are used to carry out the method described above. According to the US 5,436,508 It is also known that by means of the above-mentioned systems for storing thermal energy and overcapacities in the use of wind energy for the production of electrical power can be cached to retrieve them when needed again.

The object of the invention is to provide a system for storing thermal energy of the type specified (for example, conversion of mechanical energy into thermal energy with subsequent storage or conversion of the stored thermal energy into mechanical energy), with or with the high efficiency at the same time reasonable expense of the units used is possible.

This object is achieved with the above-mentioned system according to the invention in that between the first thermal fluid energy machine and the heat storage a humidification for the working gas is provided in the line. In the context of this invention, the moistening unit is understood to mean a device through which the working gas can flow, in which steam is supplied to the working gas. Here, the air should be moistened to at most the saturation limit of water vapor. The application of a humidification of the working gas (eg air) has the advantage that the power output of working as the engine Fluid energy machine can be increased with the same size. If required power output therefore smaller and therefore less expensive components for the system can be used. In addition, it is possible to use the hot humidified air emerging from the second fluid energy machine for a supply of heat to the water used in the humidifying unit, so that this energy is not lost to the process as a whole. As a result, the efficiency of the system according to the invention can be advantageously increased.

The cycle of the system according to the invention for storing thermal energy is used with its moistening unit to convert the energy stored in the heat storage and cold storage on the second thermal fluid energy machine into mechanical energy. This can be used, for example, for driving an electric generator. The stored thermal energy is then used in times of great demand for electrical energy to make these available by means of the system.

However, increased use of renewable energy can also mean that the total electricity produced is not in demand at the moment of production. In this case, the system for storing thermal energy can be used to convert the electrical energy into mechanical energy, for example via an electric motor, and into thermal energy via the fluid energy machines. However, it should be noted that reversing the process does not use the humidification tower. This must therefore be bypassed for example by means of suitable bypass lines. Another possibility is to provide for the charging process of the cold storage and the heat storage in the system a separate circuit. This can also be equipped with additional fluid energy machines.

If the system is provided with bypass lines, they must be suitable for this, the first thermal fluid energy machine and to switch the second thermal fluid energy machine so that the heat storage is in the flow direction of the working gas in front of the cold storage. This can be achieved by reversing the flow direction in the piping system. Another possibility is that the bypass lines in each case directly in front of or behind the heat storage or cold storage in the circuit open, so that only within the thermal storage, the flow direction of the working gas is reversed. It is important to reverse the flow direction in the thermal storage (cold storage or heat storage), so that the cold-warm front is moved in the storage medium of the thermal storage during charging or discharging the thermal storage in the opposite direction.

If an additional circuit is used for charging the thermal storage, it also passes through the same heat storage and cold storage. Suitable valve mechanisms ensure that only the circuit for charging or the circuit for discharging is connected to the thermal storage. Another possibility is that in the thermal storage each two conduit systems are included for two circuits. In this case, a changeover is not required and it can be done in principle even a simultaneous charging and discharging of the thermal storage.

In one case, however, the charging of the heat accumulator and the cold accumulator in the system is achieved in that the heat accumulator can be connected via a second line between a third thermal fluid energy machine and a fourth thermal fluid energy machine, wherein in the direction of flow of the working gas from the third fluid thermal energy machine for the fourth thermal fluid energy machine seen the third thermal fluid energy machine as a working machine and the fourth thermal fluid energy machine is connected as an engine. This allows in the manner already described, the charging of the heat storage, when the working gas flows through the second line in said flow direction. In addition, behind the fourth thermal fluid energy machine, the cold storage can be provided in the second line, which is then fed by the emerging from the fourth fluid energy machine working gas and can absorb the stored in the working gas cooling energy.

According to a further embodiment of the invention, it is provided that behind the second thermal fluid energy machine, a water separator is arranged in the line. By relaxation and cooling of the working gas and the absorption capacity of the same for water vapor decreases so that it condenses. This can then be collected in said water, wherein the separated water still has a temperature of about 50 ° C. This temperature level is thus still above the ambient temperature, so that the stored in the collected water thermal energy can be recycled to the process. If the water vapor were blown into the environment and instead use feed water for the moistening tower from the environment, this thermal energy would be lost to the process. The water separator thus serves to increase the efficiency of the realized by the inventive system process. In order to make the water from the water separator available to the process again, it is advantageously provided that the water separator is connected to the moistening unit via a feed line.

According to another embodiment of the system according to the invention can be provided that the leading away from the second fluid energy machine line leads through a first heat exchanger located in the evaporator. The working gas, which leads away from the second fluid energy machine, has temperatures of about 200 ° C. This heat can be used to provide the humidification tower with thermal energy necessary for the evaporation of the water in the humidification tower. This heat energy is the Process therefore advantageously provided again and thus does not escape into the environment unused. This advantageously further increases the efficiency of the process realized by the plant. In addition, by the cooling of the working gas in the humidification tower, a downstream water separator can operate more effectively, since the water can be more easily separated from the cooled working gas.

Yet another embodiment of the invention provides that an additional heat storage is provided in a branch line, wherein the leading away from the additional heat storage branch line leads through a second heat exchanger located in the evaporator. The stored energy in the additional heat storage can thus additionally support the process of evaporation of water in the humidification unit. The thermal energy input, which takes place indirectly via the additional heat storage, thus advantageously leads to a further increase in the humidity in the humidification unit. This leads to the already described increase in the efficiency of the realized by the inventive system process.

The additional heat storage as well as the heat storage and the cold storage can be powered by external heat and cold sources. Here, for example, offers district heating from a power plant. However, it is particularly advantageous if the additional heat storage and the heat storage and the cold storage are charged by various heat pump processes. For this purpose, the additional heat accumulator can advantageously be connected via an additional line between a fifth thermal fluid energy machine and a sixth thermal fluid energy machine, the fifth thermal fluid energy being seen in the direction of flow of the working gas from the fifth thermal fluid energy machine to the sixth thermal fluid energy machine Machine is connected as a working machine and the sixth thermal fluid energy machine as an engine. It stands thus advantageous for the charging of the additional heat storage a separate heat pump cycle available, the fifth and sixth fluid energy machine can be optimized for the temperatures to be generated in the additional heat storage. Of course, the supplemental heat storage may also be charged by the first or by the third fluid energy machine, if an appropriate interconnection via lines or bypass lines is made possible. It is always necessary to weigh up the costs of components compared to increasing the efficiency for the individual processes. In this weighing economic considerations are in the foreground.

The working gas can be fed either in a closed or an open circuit. An open circuit always uses the ambient air as working gas. This is sucked from the environment and released at the end of the process also in this, so that the environment closes the open circuit. A closed circuit also allows the use of a different working gas than ambient air. This working gas is guided in the closed circuit. Since a relaxation in the environment with simultaneous adjustment of the ambient pressure and the ambient temperature is eliminated, the working gas in the case of a closed circuit must be passed through a heat exchanger, which allows a release of heat of the working gas to the environment.

It can be provided, for example, that the circuit for the storage of thermal energy in the cold storage and the heat storage is designed as an open circuit and there works as a motor engine thermal fluid energy machine is constructed of two stages, wherein between the steps a water separator for the working gas is provided. This takes into account the fact that humidity is contained in the ambient air. By a relaxation of the working gas in a single stage, it may happen that the humidity due to the strong cooling of the working gas to eg - 100 ° C freezes and in this case the thermal fluid energy machine damaged. In particular, turbine blades can be permanently damaged by icing. However, a relaxation of the working gas in two steps makes it possible to separate condensed water in a water separator behind the first stage, for example at 5 ° C, so that it is already dehumidified in a further cooling of the working gas in the second turbine stage and prevents or at least reduces ice formation can be. Advantageously, the risk of damaging the second fluid energy machine is thereby reduced.

If a closed circuit is used and, as already described, a heat exchanger installed in the circuit, the use of a water separator and a two-stage fluid energy machine as an engine can be omitted. As a working gas in this case, for example, dehumidified ambient air can be used, the humidification is excluded by the closed nature of the circuit. But other working gases can be used.

It is advantageous in the thermal charging of the heat accumulator and the cold accumulator, if before the first or third (depending on the configuration) fluid energy machine of the additional heat storage is traversed by the working gas. That is, the working gas is fed by the additional heat storage warmed up in the first fluid energy machine. As a result, the additional heat storage can serve in addition to the heating of the humidifying another task. The use of the additional heat accumulator has the following advantages. If the system is used to store the thermal energy, the additional heat storage is passed before passing in this case as a working machine (compressor) working first / third fluid energy machine. As a result, the working gas is already warmed above ambient temperature. This has the advantage that the working machine has to absorb less power in order to achieve the required temperature of the working gas. Specifically, the heat storage to be heated to over 500 ° C, which is advantageous subsequent to the preheating of the working gas can also be done with commercially available thermodynamic compressors that allow a compression of the working gas to 15 bar. Advantageously, therefore, can be used on components for the units of the system, which are available on the market without costly modifications. Advantageously, the working gas in the additional heat storage to a temperature between 60 ° C and 100 ° C, particularly advantageously heated to a temperature of 80 ° C. In contrast, heating of the working gas to about 190 ° C is particularly advantageous for the supply of heat in the humidification tower.

As already mentioned, the working gas in the cycle of the heat storage and cold storage can be compressed to 15 bar, which can reach temperatures of the working degree of up to 550 ° C.

Finally, it can be provided according to a particular embodiment of the invention, that behind the second thermal fluid energy machine, a heat exchanger is provided in the line, which is fed as a coolant with water for the moistening. In this way, further heat energy can be withdrawn from the working gas flowing through the line, with which the feed water for the moistening unit is preheated. Thus, this energy is made available to the process again, whereby its efficiency advantageously further increases. In particular, when providing an open circuit, the humidification needs comparatively much feed water, since the water is at least partially discharged into the environment after passing through the circuit. But even in a closed circuit leaks in the circuit or the drying of the channels in the heat storage and the cold storage when switching from unloading to charging mode can lead to new feed water must be entered into the humidification.

Figur 1

ein Ausführungsbeispiel der erfindungsgemäßen Anlage mit Bypassleitungen als Schaltbild und

Figur 2 und 3

ein anderes Ausführungsbeispiel der erfindungsgemäßen Anlage mit getrennten Kreisläufen für das Laden und Entladen der thermischen Speicher anhand von weiteren Schaltbildern.

Further details of the invention are described below with reference to the drawing. The same or corresponding drawing elements are in each case provided with the same reference numerals and are explained only to the extent that there are differences between the individual figures. Show it:

FIG. 1

an embodiment of the system according to the invention with bypass lines as a circuit diagram and

FIGS. 2 and 3

another embodiment of the system according to the invention with separate circuits for charging and discharging the thermal storage using other circuit diagrams.

A plant for storing thermal energy according to FIG. 1 has a conduit 11, with which a plurality of units are connected to each other such that they can be traversed by a working gas in an open circuit. The working gas is drawn in through a valve A from the environment and flows through a first thermal fluid energy machine 13, which is designed as a hydrodynamic compressor. Furthermore, the line then leads via a valve B to a heat accumulator 14. This is connected via the line 11 via a valve C with a second thermal fluid energy machine 15, which is designed as a hydrodynamic turbine. From the turbine, the line 11 leads via a valve D to a cold storage 16. From the cold storage 16, the line opens into the environment. In the described operating state, the valves A to D are thus opened. Valves E to H are closed (more on that below)

The first and second fluid energy machines 13 and 15 are mechanically coupled to each other via a shaft 21 and are driven by an electric motor M fed by a wind power plant 22 as long as the generated electrical energy in the power grid is not in demand. During this operating state of the heat accumulator 14 and the cold storage 16 charged, as will be explained in more detail later, and the system is flowed through line 11, wherein the units are flowed through in the above order.

If the demand for electrical energy in relation to the currently generated amount of electrical energy is greater, the power generated by the wind power plant 22 is fed directly into the grid. In addition, the system supports the power generation in another operating state by the heat accumulator 14 and the cold storage 16 are discharged and the shaft 21 by the fluid energy machines 18 and 19, a generator G is driven. For this purpose, the valves A to D are closed and opened for the valves E to H. As a result, portions of the conduit 11 are no longer flowed through, but instead open bypass lines 19, which change the flow of the working gas.

The working gas flows through the cold storage 16 and passes through a bypass line 19 via the valve E to the first fluid energy machine (compressor). After leaving the compressor, the working gas is passed through a valve F through a humidifying unit 18, which is provided in a further bypass line 19 and leads to the heat accumulator 14. Therefore, the heat accumulator 14 is already supplied with humidified air, which leaves the heat accumulator 14 via the bypass line 19 through a valve G and the second fluid energy machine 15 (turbine) is supplied. Here, the mechanical energy for driving the first fluid energy machine 13 (compressor) and the generator is obtained. About the bypass line 19 through a valve H, the working gas returns to the environment, previously the working gas is dehumidified via a water separator 17. The separated, about 50 ° C warm water is supplied via a feed pump 23 a of the humidifying 18. In addition, heat can be introduced into the humidification unit, which is derived, for example, as district heating from a power plant. This is in FIG. 1 indicated by a heat exchanger 33a.

The structure of the heat accumulator 14 and the cold accumulator 16 (also the additional heat accumulator according to FIG. 3 ) in the system according to FIG. 1 is equal in each case and is explained in greater detail by an enlarged detail on the basis of the cold accumulator 16. Provided is a container whose wall 24 is provided with an insulating material 25 having large pores 26. Inside the container concrete 27 is provided, which acts as a heat storage or cold storage. Within the concrete 27 pipes 28 are laid parallel running through which the working gas flows and thereby emits heat or absorbs heat (depending on the mode and storage).

Based on the system according to Figures 2 and 3 the thermal charging and discharging process will be explained in more detail. In FIG. 2 First, a two-stage charging process is shown, which works on the principle of a heat pump. Shown in the Figures 2 and 3 an open circuit, however, as indicated by dash-dotted lines, using an optional heat exchanger 17a, 17b could be closed. The states in the working gas, which in the embodiment of the Figures 2 and 3 consists of air, are each shown on the lines 30, 31, 32 in circles. At the top left is the pressure in bar. Top right, the enthalpy is given in KJ / Kg. Bottom left is the temperature in ° C and bottom right is the mass flow in kg / s. The direction of flow of the gas is indicated by arrows in the relevant line.

wobei
T₂ die Temperatur am Verdichterausgang,
T₁ die Temperatur am Verdichtereingang,
η _c der isentropische Wirkungsgrad des Kompressors,
n das Druckverhältnis (hier 15:1) und
K die Kompressibilität ist, die bei Luft 1,4 beträgt.In the model calculation for the circulation of the second line 31 according to FIG. 2 enters the working gas with 1 bar and 20 ° C in a (previously charged) additional heat storage 12 and leaves it with a temperature of 80 ° C. Compression by means of the third fluid energy machine 34 operating as a compressor leads to an increase in pressure to 15 bar and, consequently, also to a temperature increase to 540 ° C. This calculation is based on the following formula $${\mathrm{T}}_{\mathrm{2}}\mathrm{=}{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="imgf0002.png,imgf0003.png"\; state="\{\{state\}\}">T</figure-callout>}}_{\mathrm{1}}\mathrm{+}\left({\mathrm{T}}_{\mathrm{2}\mathrm{s}}\mathrm{-}{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="imgf0002.png,imgf0003.png"\; state="\{\{state\}\}">T</figure-callout>}}_{\mathrm{1}}\right)\mathrm{/}{\mathrm{\eta }}_{\mathrm{c}}\mathrm{;}{\mathrm{T}}_{\mathrm{2}\mathrm{s}}\mathrm{=}{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="imgf0002.png,imgf0003.png"\; state="\{\{state\}\}">T</figure-callout>}}_{\mathrm{1}}{\mathrm{\pi }}^{\left(\mathrm{K}\mathrm{-}\mathrm{1}\right)\mathrm{/}\mathrm{K}}\mathrm{.}$$

in which
T _{2 is} the temperature at the compressor outlet,
T _{1 is} the temperature at the compressor inlet,
η _c the isentropic efficiency of the compressor,
n the pressure ratio (here 15: 1) and
K is the compressibility, which is 1.4 in air.

The isentropic efficiency η _c can be assumed to be a compressor with 0.85.

The heated working gas now passes through the heat storage 14, where the majority of the available thermal energy is stored. During storage, the working gas cools to 20 ° C, while the pressure (apart from flow-related pressure losses) is maintained at 15 bar. Subsequently, the working gas is expanded in two series-connected stages 35a, 35b of a fourth fluid energy machine 35 so that it arrives at a pressure level of 1 bar. The working gas cools to 5 ° C after the first stage and to -100 ° C after the second stage. The basis for this calculation is also the formula given above.

In the part of the line 31, which connects the two stages of the fourth fluid energy machine 35a, 35b in the form of a high-pressure turbine and a low-pressure turbine, a water separator 29 is additionally provided. This allows for a first relaxation, a drying of the air, so that the humidity contained in this second stage 35b of the fourth fluid energy machine 35 does not lead to icing of the turbine blades.

In the further course, the relaxed and therefore cooled working gas withdraws heat from the cold storage 16 and is thereby heated to 0 ° C. In this way, cold energy is stored in the cold storage 16, which can be used in a subsequent energy production. If one compares the temperature of the working gas at the outlet of cold storage 16 and on Input of the additional heat storage 12, it is clear why in the case of a closed circuit, the heat exchanger 17b must be provided. Here, the working gas can be reheated to an ambient temperature of 20 ° C, whereby the environment heat is removed, which is provided to the process. Of course, such a measure can be omitted if the working gas is sucked directly from the environment, since this already has ambient temperature.

Thus, when passing through the circuit of the second line 31, a preheating can be done by the additional heat storage 12, an additional circuit is realized by an additional line 30, with which the additional heat storage 12 can be charged. The additional heat storage 12 must therefore be connected to both the circuit of the second line 31 and to the circuit of the additional line 30. A connection to the second line 31 takes place through the valves I, while a connection to the additional line 30 is ensured by opening the valves K. When passing through the additional line 30, the air is first passed through a fifth fluid energy machine 36, which operates as a compressor. The compressed air is passed through the additional heat storage 12, wherein the flow direction corresponding to the indicated arrows runs exactly opposite to the circuit formed by the second conduit 31. After the air was brought from ambient pressure (1 bar) and ambient temperature (20 ° C) through the compressor to 4 bar and a temperature of 188 ° C, the air is cooled by the additional heat storage 12 back to 20 ° C. Subsequently, the air is decompressed through the stages 37a, 37b of a sixth fluid energy machine 37, which operates as a turbine, in two stages. Here, too, a water separator 29 is provided in the additional line 30 connecting the two stages 37 a, 37 b, which works in the same way as that in the second line 31. After relaxing the air via the sixth fluid energy machine 37, this has a temperature of -56 ° C at ambient pressure (1 bar). In the event that the Circuit of the additional line 30, as shown in phantom, should be executed closed, therefore, a heat exchanger 17c must be provided so that the air from -56 ° C can be heated by heat to the environment to 20 ° C.

The circuits of the second line 31 and the additional line 30 are set independently. Therefore, the third and fourth fluid energy machines are mechanically coupled via the shaft 21 to a motor M1 and the fifth and sixth fluid energy machines via the other shaft 21 to a motor M2. With overcapacities of the wind turbine 22, the electrical energy can first drive the motor M2 to charge the additional heat storage 12. Subsequently, by operation of the motor M1 and simultaneous discharge of the additional heat accumulator 12, the heat accumulator 14 and the cold accumulator 16 can be charged. Subsequently, by the operation of the motor M2 and the additional heat storage 12 can be recharged. When all accumulators are fully charged, an effective discharge cycle can be initiated to generate electrical energy (cf. FIG. 3 ). However, should the excess capacity of the wind power plant 22 end without the additional heat storage 12 could be charged, the energy available in this can be replaced by other heat sources (see. FIG. 3 ).

Also conceivable is an additional heat accumulator 12, which can be supplied by separate line systems for the second line 31 and the additional line 30. This would create two independent circuits without valves I and K being used. In this way, the auxiliary heat storage 12 could be simultaneously charged and discharged. It is therefore conceivable in this case, a simultaneous operation of the motors M1, M2. This operating regime has two advantages. On the one hand, even larger overcapacities of the wind power plant 22 can be absorbed by simultaneous operation of the motors M1, M2 at full load, resulting in greater flexibility of the system. In addition, could through To ensure simultaneous operation of both motors that the three thermal storage 12, 14, 16 are always filled simultaneously and not one after the other. Thus, the charging process can be stopped at any time at full operability of the discharge process, if no excess capacity in the electrical network are no longer available and instead creates a need for additional electrical energy.

through FIG. 3 the discharge cycle of the heat accumulator 14 and the cold accumulator 16 can be followed, wherein the generator G electrical energy is generated. For the discharge cycle, the first fluid energy machine 13 and the second fluid energy machine 15 are available, which are described in the charging processes described above (see FIG FIG. 2 ) were not used. This allows the optimization of the efficiency of the fluid energy machines, but also leads to higher investment costs for the purchase of the system. Therefore, the higher investment cost of using additional fluid power machines versus the gain in efficiency achieved by optimizing each to the appropriate operating condition using four fluid power machines is to be weighed. The heat storage 14, the cold storage 16 and the additional heat storage 12 are the same as in FIG. 2 and are flowed through only in the opposite direction. In the Figures 2 and 3 Thus, the same system is shown, for reasons of clarity, only the system components and lines involved in the running process are shown. Furthermore, the alternative of a closed circuit is shown in phantom.

The working gas is passed through the cold storage 16. It is cooled from 20 ° C to -100 ° C. This measure serves to reduce the power consumption in order to operate the first fluid energy machine operating as a compressor. The power consumption is reduced by the factor corresponding to the temperature difference in Kelvin so 293K / 173K = 1.69. In the example, the compressor compresses the working gas at 10 bar. The temperature rises to 89 ° C. Technically acceptable would be a compression of up to 15 bar. The compressed working gas first passes through the moistening unit 18 and then the heat accumulator 14 and is thereby heated in the moistening unit to 145 ° C. and in the heat accumulator 14 to 530 ° C. Subsequently, the working gas is expanded by the second fluid energy machine 15, which thus operates in this operating state as a turbine. There is a relaxation to 1 bar, wherein there is still a temperature of 201 ° C in the working gas at the output of the first fluid energy machine. Therefore, the working gas can still be passed through a heat exchanger 33b in the evaporation unit to emit heat there for the evaporation of the water. As a result of the further cooling of the working gas, it is possible to deposit at least part of the air humidity via the water separator 17. The separated water still has a temperature of about 50 ° C and is pumped via a feed pump 23b back into the humidification unit. The dehumidified air leaves the circuit and is blown into the environment. Alternatively it can be provided that, as indicated by dash-dotted lines, a closed circuit is realized by the line 32. In this case, a heat exchanger 17a ensures that the working gas, which still has a temperature of 50 ° C, is cooled to ambient temperature (20 ° C). The heat exchanger can also be used to warm up fresh water, which can be pumped via a feed pump 23c into the humidification unit.

In the humidifying unit heat is needed, which causes the evaporation of the feedwater. To provide an additional source of energy here, as already possible FIG. 1 indicated, the heat exchanger 33 a are connected to an external heat source. This can be, for example, district heating. But it is also advantageous to use the charged additional heat storage 12. For this purpose, a branch line 38 is provided, which branches off from the line 32 before the cold storage 16. This goes through the additional heat storage 12 and then a heat exchanger 33c in the humidification unit, so that the heat energy stored in the additional heat storage 12 can also be supplied to the humidification unit. The branch line 38 opens behind the heat exchanger 33c in the line 32 behind the heat exchanger 33b. The mass flow of working gas is thus split at the branch line 38, 8.3 Kg / s are passed through the branch line 38 and 4.8 Kg / s through the cold storage 16 humidifying unit 18 and the heat storage 14 are passed.

Claims (10)

Thermal energy storage system comprising a working gas circuit, in which circuit the following units are connected in the order indicated by a working gas line (11): ● a cold storage (16), ● a first thermal fluid energy machine (13), ● a heat storage (14) and ● a second thermal fluid energy machine (15), wherein viewed in the direction of flow of the working gas from the cold storage (16) to the heat storage (14), the first thermal fluid energy machine (13) as a working machine and the second thermal fluid energy machine (15) as an engine is switched,
characterized,
in that a humidification unit (18) for the working gas in the line is provided between the first thermal fluid energy machine (15) and the heat accumulator (14). Plant according to claim 1,
characterized,
that behind the second thermal fluid energy machine, a water separator (17) in the conduit (11) is arranged. Plant according to claim 2,
characterized,
that the water separator (17) is connected via a feed line to the humidification unit (18). Plant according to one of claims 1 to 3,
characterized,
in that the conduit (11) leading away from the second thermal fluid energy machine passes through a heat exchanger (33b) located in the humidifying unit. Plant according to one of the preceding claims,
characterized,
that an auxiliary heat accumulator (12) is provided in a branch line (38), of the auxiliary heat accumulator (12) takes leading away branch line (38) by a in the humidification unit (18) located heat exchanger (33c). Plant according to one of the preceding claims,
characterized,
in that behind the second thermal fluid energy machine (15) there is provided a heat exchanger (17a) in the conduit, which is supplied with water as coolant for the moistening unit (16). Plant according to one of the preceding claims,
characterized,
in that the heat store (14) can be connected via a second line (31) between a third thermal fluid energy machine (34) and a fourth thermal fluid energy machine (35), in the direction of flow of the working gas from the third thermal fluid energy machine ( 34) to the fourth thermal fluid energy machine (35), the third thermal fluid energy machine (34) is connected as a working machine and the fourth thermal fluid energy machine (35) is connected as an engine. Plant according to claim 7,
characterized,
that in the flow direction according to claim 7 behind the fourth fluid energy machine (35) of the cold storage (16) via the second line (31) can be switched. Plant according to one of the preceding claims,
characterized,
in that the auxiliary heat accumulator (12) can be connected via a supplementary line (30) between a fifth thermal fluid energy machine (36) and a sixth thermal fluid energy machine (37), wherein in the direction of flow of the working gas from the fifth thermal fluid energy machine (36) to the sixth thermal fluid energy machine (37) the fifth thermal fluid energy machine (36) is connected as a working machine and the sixth thermal fluid energy machine (37) is connected as an engine. Installation according to one of claims 1 to 6,
characterized,
in that the first thermal fluid energy machine (13) and the second thermal fluid energy machine (16) can be switched via bypass lines (19) such that the heat accumulator (14) lies in the flow direction of the working fluid in front of the cold accumulator (16).

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