EP2759679A1 - Thermal storage device for the utilisation of low temperature heat - Google Patents

Abstract

The device (100) has a heat pump (10) e.g. chemical heat pump, for receiving thermal energy at an input side (11) in a temperature level between 40 and 120 degree Celsius, preferably 50 and 90 degree Celsius. The pump delivers the thermal energy on an output side (12) in a raised temperature level ranging between 100 and 300 degree Celsius, preferably 120 and 200 degree Celsius. The thermal energy on the output side is partially transferred to a heat storage medium (21), which deposits the thermal energy in a heat storage (20) e.g. latent heat storage. An independent claim is also included for a method for storing thermal energy by a thermal storage device.

Description

The present invention relates to a thermal storage device comprising a first heat pump, a thermally connected to the first heat pump heat storage, and a circuit for performing a thermal cycle and for generating electrical energy by means of a power generating device connected therein, which energized via a guided in the circulation heat transfer medium can be, the circuit is also thermally connected to the heat storage. Furthermore, the invention relates to a method for storing thermal energy by means of a thermal storage device as described above and below.

Due to the relatively high fluctuation of offered and requested electrical energy in the public power supply networks, the storage of electrical energy for delayed retransmission is often considered necessary to enable efficient network operation. For caching the electrical energy various technical solutions are pursued. In addition to large-scale solutions using pumped storage power plants or compressed air storage power plants, the storage of electrical energy by means of electrochemical processes is increasingly being pursued. However, the former power plant types are severely limited in their use because of their size and geographic requirements. In addition, the construction of such power plants requires a relatively large investment. Electrochemical processes are also not yet used industrially because of their relatively high costs.

Complementary or alternative to these technical solutions is the conversion of electrical energy into chemical energy followed by means of electrolysis. However, for such so-called. Power-to-gas applications large plants are to be built, which cause an increased investment. In addition, the technology has not yet been adequately tested and tested in order to make a widespread use on an industrial scale meaningful.

Other approaches to the caching of electrical energy from public utility networks rely on the intermediate storage of thermal energy derived from the electrical energy. Here, in particular, according to the applicant internally known prior art storage solutions are tracked, which cache thermal energy at a relatively high temperature level, to retrieve this energy after caching again by a Rückverstromungsprozess. The temperature level at which the thermal storage takes place is typically in a temperature range of more than 300 ° C. For storage of thermal energy at such a high temperature level, for example, stone or sand fillings or suitable geological formations as storage material in question, by means of which a thermal storage can be formed. The storage of the heat stored therein can be carried out subsequently in a conventional water-steam process, wherein the reconversion takes place approximately by means of a steam turbine-powered generator, which is connected to a water-steam cycle. In order to optimize the storage efficiency, in this case the highest possible temperature level of over 300 ° C, on which the thermal energy storage takes place, is required.

However, such high temperatures not only cause high risks in terms of operational safety, but also high costs for the provision of the technical materials and components that can be used at these temperatures.

In order to avoid these known from the prior art disadvantages, in the present case, a further technical solution for the thermal storage of electrical energy will be proposed. In particular, this solution is intended to achieve efficient intermediate storage of thermal energy using thermal energy, in particular waste heat, which is not otherwise used in a power plant process. Preferably, a thermal intermediate storage of electrical energy in connection with a power plant process should also be enabled efficiently at a relatively lower temperature level. The storage should in this case take place in particular at a temperature level which is generally referred to as low-temperature level, and in a temperature range between 100 ° C and 300 ° C, in particular between 120 ° C and 200 ° C, (the temperature limit values are included).

Compared to these storage solutions according to the invention, the storage solutions, which store the thermal energy at a temperature level of more than 300 ° C, should be referred to as high-temperature heat storage.

This object of the invention is achieved by a thermal storage device according to claim 1 and by a method for storing thermal energy by means of such a pre-described as well as subsequently described storage device according to claim 13.

In particular, the object underlying the invention is achieved by a thermal storage device, comprising a first heat pump, a thermally connected to the first heat pump heat storage, and a circuit for performing a thermal cycle and for generating electrical energy by means of a power generating device connected therein, via a circulated in the heat transfer medium can be energized, the circuit is also thermally connected to the heat storage, and wherein the first heat pump is adapted to receive thermal energy at a temperature level between 40 ° C and 120 ° C, in particular between 50 ° C and 90 ° C, on a first input side and on a first output side thermal energy at a raised temperature level between 100 ° C and 300 ° C, in particular between 120 ° C and 200 ° C, deliver, wherein the thermal energy on the first output side is at least partially transferred to a heat storage medium, which deposits the thermal energy in the heat accumulator.

• Aufnehmen von thermischer Energie auf einem Temperaturniveau zwischen 40 °C und 120 °C, insbesondere zwischen 50°C und 90°C, durch die erste Wärmepumpe an einer ersten Eingangsseite;
• Abgeben von thermischer Energie auf einem angehobenen Temperaturniveau zwischen 100 °C und 300 °C, insbesondere zwischen 120°C und 200°C, auf einer ersten Ausgangsseite;
• Übertragen wenigstens eines Teils der thermischen Energie auf der Ausgangsseite auf ein Wärmespeichermedium;
• Deponieren der thermischen Energie des Wärmespeichermediums in dem Wärmespeicher.

Furthermore, the objects on which the invention is based are solved by a method for storing thermal energy by means of such a thermal storage device, which has been described above and also below, and which comprises the following steps:

• Receiving thermal energy at a temperature level between 40 ° C and 120 ° C, in particular between 50 ° C and 90 ° C, through the first heat pump on a first input side;
• Emitting thermal energy at a raised temperature level between 100 ° C and 300 ° C, in particular between 120 ° C and 200 ° C, on a first exit side;
• Transferring at least a portion of the thermal energy on the exit side to a heat storage medium;
• Deposit the thermal energy of the heat storage medium in the heat storage.

According to the invention, therefore, the storage of electrical energy via a thermal storage process with simultaneous integration of low-temperature heat at a temperature level between 40 ° C and 120 ° C, in particular between 50 ° C and 90 ° C. The integration takes place by means of a first heat pump, which in addition to the electrical energy is also able to absorb low-temperature heat at the designated energy level, and at a first output side at a correspondingly elevated temperature level between 100 ° C and 300 ° C, in particular between 120 ° C and 200 ° C, give.

The proposed solution makes it possible in particular to efficiently store electrical energy in a power range which is relevant in terms of power plant technology. The solution of the invention differs in particular by a kraftwerkstauglichen use of a heat pump, which can deliver heat even at a relatively high temperature level. Conventional heat pumps suitable for this use are typically only available up to a temperature range on the heat release side of a maximum of 60 to 70 ° C.

The inventive solution also allows the integration of low-temperature waste heat at a temperature level between 40 ° C and 120 ° C, in particular between 50 ° C and 90 ° C, which is typically discarded in conventional power plant processes. Such low temperature waste heat is produced in numerous power plant as well as industrial processes, and according to the present invention can be efficiently integrated into a storage process. The waste heat losses are not taken into account in conventional determinations of the efficiency of a power plant process.

According to a first particularly preferred embodiment of the invention, the first heat pump is designed to receive and convert electrical energy in a power range of more than 1 MW. Here, the first heat pump is particularly suitable for large-scale applications, in particular for power plant processes, to convert amounts of electricity into thermal energy, which are relevant for the power supply of the public power supply networks.

According to a further embodiment of the thermal storage device, it is provided that the ratio of the thermal energy dissipated on the output side of the first heat pump to the electrical energy which is the first Heat pump required for their operation, between 1.5 and 7, in particular between 2 and 5 is located. The ratio corresponds to the coefficient of performance (COP), which represents the ratio of heat provided at high temperature level to electrical energy used. Accordingly, the first heat pump is configured to receive electrical energy and to provide a significantly greater amount of heat at a higher temperature level. The additionally required differential energy comes from the heat that is supplied to the first heat pump on the first input side as low-temperature heat. Since this is typically taken as waste heat, it can be made very cheap or even free of charge. The heat pumping process requires a smaller amount of electrical energy to provide a relatively larger amount of thermal heat to then buffer it.

According to a further embodiment of the thermal storage device is provided that the heat storage is designed as a sensitive heat storage and / or as a latent heat storage. Sensible heat storage can have, for example, water, pressurized water, thermal oil or even solids as a heat storage medium. Latent heat storage can have, for example, metal or salt melts and organic substances as heat storage media. The phase transition, which is used for energy storage, should be carried out in the temperature range of 100 ° C to 300 ° C, in particular in the temperature range of 120 ° C to 200 ° C. Alternatively or even further, the heat accumulator can also be used as a heating system, e.g. be designed as a district heating system.

According to another aspect of the present invention, the cycle for performing the thermal cycle may be operated as an Organic Rankine Cycle (ORC) or as a Kalina Cycle. Both methods are particularly suitable for reconverting the heat from the heat storage in the temperature range from 100 ° C to 300 ° C, especially from 120 ° C to 200 ° C.

According to another aspect of the present invention, the working fluid of the first heat pump is identical to the heat transfer medium in the circuit. Working fluids are generally classified as wet (negative slope), isentropic (vertical saturation curve) or dry (positive slope) according to the slope of their saturation curve in a T-S plot. Wet working fluids (such as water and CO2) cause partial condensation in isentropic expansion and thus generally require overheating. Only slightly wet, dry and isotropic fluids do not generally undergo a two-phase regime during expansion, and overheating can therefore be generally avoided. The invention provides for the use of a slightly wet, dry and isotropic working fluid, in particular comprising fluoroketones (eg CF3CF2C (0) CF (CF3) 2), refrigerants (chlorinated and / or fluorinated hydrocarbons (eg R245ca)), hydrocarbons (eg butane, pentane ) and other organic solvents (eg toluene).

According to a further particularly advantageous embodiment of the invention it is provided that the first heat pump, a second heat pump is connected upstream thermally, which is adapted to receive thermal energy at a temperature level between 0 ° C and 60 ° C on a second input side and on a second output side thermal energy at a raised temperature level between 40 ° C and 120 ° C, in particular 50 ° C to 90 ° C, deliver. Such a two-stage heat pump system according to the invention is particularly suitable for first simply raising ambient heat or heat at a relatively low temperature level in order to be able to provide heat to the first heat pump having a temperature level between 40 ° C. and 120 ° C., in particular between 50 ° C. and 90 ° C, has. In this case, the second heat pump can be designed in particular as a commercially available heat pump. Such a two-stage Interconnection is also particularly suitable if the first heat pump requires a required minimum temperature level on its first input side in order to work sufficiently efficiently.

According to a further particularly preferred embodiment of the invention it is provided that the heat transfer medium and the heat storage medium are substantially identical, in particular both can enter into thermal interaction with the heat storage. In this case, in particular transfer losses, which result from the additional interposition of further heat exchangers, avoid. In addition, a compact and characterized by a few technical components thermal storage device can be realized. Furthermore, it is possible to combine functional components of the first heat pump with functional components of the cycle process by means of such an embodiment in order to consequently realize a particularly simple design.

According to a further particularly preferred embodiment of the invention it is provided that the thermal storage device comprises a compressor-expander unit, which is simultaneously encompassed by both the first heat pump and the circuit. In particular, the first heat pump comprises the compressor section and the circuit comprises the expander section. Both can co-operate with a single motor / generator unit to either receive electrical energy or re-supply it in a re-currentization process. In a particular embodiment of the invention, the flow direction at the compressor expander unit when heat absorbed by the first heat pump is equal to that of the circuit in operation for reconversion. The fact that the compressor-expander unit can simultaneously perform functions of the first heat pump as well as functions in the circuit for reconverting, consequently, a particularly simple designed thermal storage device can be provided.

According to the embodiment, such a compressor expander unit can be constructed from two separate working machines, which are switched on and off depending on the direction of flow. However, the use of only one machine is particularly advantageous. This can e.g. can be achieved by working machines operating on the displacement principle (for example screw compressor, screw expander or reciprocating compressor, piston expander). Such machines can be operated in principle in both directions of flow. In this respect, a particularly advantageous embodiment of the thermal storage device is characterized in that the thermal storage device comprises a work machine which has both the function of a compressor and the function of an expander, and which is simultaneously encompassed by both the first heat pump and the circuit. Additional pump units which require or support the individual processes may be provided accordingly. Here, the use of only a single pumping unit is possible, which can work in both directions of flow. It is also possible to provide only one pump unit, which is connected in the circuit. Suitable circuits of adjusting means, such as valves, can support or even effect advantageous flow guidance.

The necessary for these embodiments, the thermal storage devices heat storage are preferably designed as directly flowed through and thus directly loadable and dischargeable heat storage. An intermediate circuit can advantageously be dispensed with.

According to a further embodiment of the thermal storage device according to the invention it is provided that a heat exchanger is fluidly connected both with the first heat pump, as well as with the circuit, the heat exchanger depending on the operating state can serve as a source of cold or as a heat source. When heat is absorbed by the first heat pump, the heat exchanger serves as a heat source, thus allows to absorb heat and supply the first heat pump. When operating the circuit for power generation, the heat exchanger is used in particular as a source of cold in the cycle process. Such a reversible operation possibility of the processes of the first heat pump and the circuit allow a large reduction in the number of required functional components and complexity of their interconnection.

According to a likewise particularly preferred embodiment of the thermal storage device is provided that the first heat pump is designed as a chemical heat pump. Such chemical heat pumps are described, for example, in: Thermochemical Energy Storage and Conversion: A State of the Art Review of the Experimental Research under Practical Conditions, Renewable and Sustainable Energy Reviews, Cot-Gores, J., Castell, A., Cabeza, LF, 16, 5207-5224, 2012 ; as in: A Review of Chemical Heat Pump Technology and Applications, Applied Thermal Engineering, Wongsuwan, W., Kumar, S., Neveu, P., Meunier, F., 21 (2001), 1489-1519 ,

Such chemical heat pumps use in particular the pressure or the temperature dependence of adsorption and absorption processes.

According to a further or further inventive idea, it is provided that the heat storage is designed as a thermo-chemical heat storage. Such a heat accumulator may, for example, comprise a bed of a solid or a liquid. Such a bed or the liquid can in turn receive a heat storage medium, which may be, for example, steam or ammonia. The absorption capacity depends on the pressure and temperature level. The uptake and subsequent release of heat storage medium may be by chemical reactions, reversible adsorption processes and absorption processes.

When taking up the heat storage medium, heat is released, while desorption requires heat in return. When loading the heat accumulator so far typically a heat sink is provided, which may be, for example, the heat exchanger described above. Accordingly, there is, for example, the heat storage medium condensed there, whereby about the partial pressure of the heat storage medium drops in the cycle of the chemical heat pump.

At the same time, the heat accumulator can be supplied with heat during charging, in particular with waste heat. Such heat can be supplied to the heat storage, for example, via a further heat exchanger or in particular by the heat exchanger described above.

A lowering of the partial pressure in the heat storage leads to a desorption of the heat storage medium, for example on the bed of solids or the liquid, wherein the heat storage heat storage medium loses the circulation. If the heat storage medium is, for example, water, the heat storage is thus increasingly dried. Since the process of desorption of the heat storage medium is associated with a heat absorption, heat, in particular waste heat is supplied in order to avoid a decrease in the temperature level in the heat storage.

The electrical energy consumption when loading such a thermo-chemical heat storage is very low, since only recirculation components, eg. Pumps, must be operated. The electrical energy requirement is therefore significantly lower than the energy demand for a conventional heat pump. A complete charge of the heat accumulator corresponds, for example, to a complete desorption of the heat storage medium in the heat accumulator.

For the discharge of the heat storage for power generation, the heat accumulator is supplied with an increased partial pressure of the heat storage medium, whereby a chemical reaction, an adsorption or absorption of this heat storage medium takes place approximately at the bed or liquid of the heat accumulator. This results in an increase in the temperature level, wherein this temperature increase can be suitably fed into the circuit for the reconversion. The discharge of the heat accumulator can also be done by operating a recirculation unit, for example a pump unit. However, the power requirement through this recirculation unit is low in comparison to the released thermal energy, which can be converted into electrical energy by the reconversion.

According to a particularly preferred first embodiment of the method according to the invention, it is provided that, furthermore, a step of transmitting thermal energy after it has been stored out of the heat accumulator is included in the heat transfer medium of the circuit. Consequently, the thermal energy in the recycle circuit can be efficiently utilized.

In the following, the invention will be described in detail with reference to the following

Figures are explained. It should be noted that the figures are to be understood only schematically and do not represent a restriction on the feasibility of the invention.

It should also be noted that components with the same reference numerals have the same technical effect.

Furthermore, the invention is as claimed below, claimed as well as the invention, which results from combination of the individual features shown below, as far as this combination is to be taken under the inventive concept.

Figur 1

eine schematische Schaltansicht einer ersten Ausführungsform der erfindungsgemäßen thermischen Speichereinrichtung;

Figur 2

eine weitere Ausführungsform der erfindungsgemäßen thermischen Speichereinrichtung in schematischer Schaltansicht;

Figur 3

eine weitere Ausführungsform der erfindungsgemäßen thermischen Speichereinrichtung in schematischer Schaltansicht;

Figur 4

eine diagrammatische Darstellung der thermodynamischen Zustandsänderungen des Arbeitsfluids bei Betrieb einer thermischen Speichereinrichtung, wie sie in Figur 3 dargestellt ist, entsprechend einem T-S-Diagramm.

Figur 5

eine weitere Ausführungsform der erfindungsgemäßen thermischen Speichereinrichtung in schematischer Schaltansicht;

Figur 6

eine rechnerische Darstellung des Strom-zu-Strom Wirkungsgrades (Power-to-Power-Efficiancy, PtP-E) in Abhängigkeit der von der ersten Wärmepumpe aufgenommenen thermischen Abwärme (Waste Heat Temperature, WHT);

Figur 7

eine flussdiagrammatische Darstellung einer Ausführungsform des erfindungsgemäßen Verfahrens zur Speicherung von thermischer Energie mittels einer vorab wie auch nachfolgend dargestellten thermischen Speichereinrichtung.

Hereby show:

FIG. 1

a schematic circuit diagram of a first embodiment of the thermal storage device according to the invention;

FIG. 2

a further embodiment of the thermal storage device according to the invention in a schematic circuit diagram;

FIG. 3

a further embodiment of the thermal storage device according to the invention in a schematic circuit diagram;

FIG. 4

a diagrammatic representation of the thermodynamic state changes of the working fluid in operation of a thermal storage device, as shown in FIG. 3 is shown, corresponding to a TS diagram.

FIG. 5

a further embodiment of the thermal storage device according to the invention in a schematic circuit diagram;

FIG. 6

a computational representation of the power-to-power efficiency (Power-to-Power Efficiency, PtP-E) as a function of the heat absorbed by the first heat pump thermal waste heat (Waste Heat Temperature, WHT);

FIG. 7

a flowchart representation of an embodiment of the method according to the invention for storing thermal energy by means of a previously described as well as below thermal storage device.

FIG. 1 shows a circuit diagram of a first possible embodiment of the thermal storage device 100 according to the invention, which in addition to a first heat pump 10, a heat storage 20 and a circuit 30 for performing a thermal cycle process, by means of which the reconverting of the thermal energy stored in the heat storage 20 is made possible. The first heat pump 10 is adapted to thermal energy at a temperature level between 40 and 120 ° C, in particular between 50 ° C and 90 ° C, receive on a first input side 11 and on a first output side 12 thermal energy at a raised temperature level between 100 ° C and 300 ° C, in particular between 120 ° C and 200 ° C, deliver. The first input side 11 corresponds in this case to a first heat exchanger 17 and the first output side 12 to a further heat exchanger 18.

During operation of the thermal storage device 100, the thermal energy on the first output side 12 is at least partially transferred to a heat storage medium 21, which supplies the thermal energy absorbed in this way to the heat accumulator 20 and deposits it in the meantime. According to the embodiment, the heat storage medium 21 is located in a suitable fluid line system, which is thermally connected to the first output side 12, and can also interact thermally with the heat accumulator 20 at the same time. It should be noted that the heat storage medium can be designed both in terms of a heat storage medium 20 located in the heat storage, as well as a medium which mediates the heat transfer between the first output side 12 of the first heat pump 10 and the heat storage 20. In another embodiment, can also be dispensed with the heat storage medium 21 and the associated fluid conduit system, wherein the output side 12 is connected directly to the heat accumulator 20, or is integrated in this. According to this configuration, the working fluid of the heat pump 10 transfers the heat directly to the heat storage 20.

After temporary storage of the thermal energy in the heat accumulator 20, at a subsequent point in time, this thermal energy can again be withdrawn in order to supply it to the circuit 30. In this case, as is achieved in the present case by a suitable thermal connection, the thermal energy is transferred to the heat transfer medium 32 located in the circuit 30 by means of a heat exchanger 37 become. The circuit is designed to carry out a thermal cycle and the heat transfer medium 32 is capable of energizing the power generating device 31 connected to the circuit 30.

The power generating device 31 is presently designed as an expander 36 which interacts mechanically with a power generator (G). As a source of cold is used in this thermal cycle another heat exchanger 38, which is also connected in the circuit 30. For fluid conveyance or for assisted fluid transport, the circuit 30 provides a pump 35, which acts on the heat transfer medium 32 located therein with a flow.

According to the embodiment, the thermal storage device 100 can consequently absorb heat at the first input side 11 of the first heat pump 10 and decouple it at an elevated temperature level via the first output side 12 of the first heat pump 10. Here, the heat pump 10 is provided both thermal heat at the first input side 11, as well as electrical energy, which in the present case for the operation of a motor (M) is provided, which drives a compressor 15. The compressor 15 is adapted to provide thermal heat at a raised temperature level between 100 ° C and 300 ° C, especially between 120 ° C and 200 ° C.

In the present case, the first heat pump 10 is furthermore designed as a closed circuit, in which a circulating medium not provided with reference numerals is circulated. To change the pressure of this cycle medium, an adjusting means 16 is connected as a pressure change unit in the first heat pump 10.

According to the invention, as already explained above, the use of a slightly wet, dry and / or isentropic working fluid (heat pump medium), in particular fluoroketones (eg CF 3 CF 2 CF (CFC) 2), refrigerant (chlorinated and / or fluorinated hydrocarbons (eg R245ca)), hydrocarbons (eg butane, pentane) and other organic solvents (eg toluene) provide.

According to the embodiment, the first heat pump 10 can thus increase the total heat output by it and increase it to a temperature level suitable for intermediate storage in the heat accumulator 20 by simultaneous absorption of electrical energy and thermal energy, which is typically provided in the form of waste heat energy.

FIG. 2 shows a further embodiment of the thermal storage device 100 according to the invention in a schematic circuit diagram. Here, the in. Differs FIG. 2 shown embodiment of the in FIG. 1 embodiment shown only to the effect that the first heat pump 10, a second heat pump 40 is connected upstream thermally, the second heat pump 40 is adapted to receive thermal energy at a temperature level between 0 ° C and 60 ° C at a second input side 41 and at a second Output side 42 thermal energy at a raised temperature level between 40 ° C and 120 ° C, especially between 50 ° C and 90 ° C. The second input side of the second heat pump 40 is presently designed as a heat exchanger 47. The second output side of the second heat pump 40 in this case corresponds to the heat exchanger 17, which also represents the first input side 11 of the first heat pump 10.

First heat pump 10 and second heat pump 40 are therefore thermally coupled to each other via a heat exchanger 17. In order to increase the temperature level of the heat coupled into the second heat pump 40, the second heat pump 40 provides a compressor 45, which in turn can be operated electrically via a motor (M). Further, the second heat pump 40 may also have a working as a pressure change unit actuating means 46 which is adapted to the in the second heat pump 40 circulated fluid to pressurize with a flow.

FIG. 3 shows a further advantageous embodiment of the thermal storage device 100 according to the invention, wherein according to the embodiment, the first heat pump 10 is connected to the circuit 30 thermally. Furthermore, the heat pump 10 and the circuit 30 have common components that are suitable for the process engineering coupling of both processes.

According to the embodiment, the first heat pump 10 is designed as a compressor 15 driven by a motor (M). The motor (M) can also be operated as a generator (G) in another operating mode. In this respect, the motor (M) can also be used as a power generating device 31. The compressor 15 is mechanically connected to an expander 36 via a common shaft, which may possibly also have a coupling, so that, depending on the operating mode, the motor (M) or generator (G) in each case with the compressor 15 and the expander 36th interacts mechanically. In this respect, the present embodiment has a compressor expander unit 50 which is simultaneously encompassed by both the first heat pump 10 and the circuit 30.

During operation of the motor (M) for current consumption and simultaneous mechanical interaction with the compressor 15, recorded on the first input side 11 thermal energy can be raised to a higher temperature level. The temperature level is suitable for thermal intermediate storage in the heat accumulator 20. The thermal energy provided by the operation of the compressor 15 is transferred to the heat storage medium 21, which is also the heat pump medium circulated in the first heat pump 10 at the same time. After delivery of the thermal energy in the heat storage 20, the heat storage medium 21 interacts with a working as a pressure change unit actuating means 16 and flows back to the first input side 11 of the heat pump circuit.

The first input side 11 is designed as a heat exchanger 60, which can be used both as a heat source as well as a source of cold depending on the operating condition.

If, for example, no more thermal energy is supplied to the first input side 11, a removal of thermal energy from the heat accumulator 20 can take place. It is necessary to provide the heat exchanger 60 with cold so far that it can be used in the circuit 30 as a source of cold. Accordingly, thermal energy can now be taken from the heat accumulator 20, which in the present case is guided via the expander 36 and used to operate the power generating device 31 as a generator (G). After relaxation via the expander 36, the heat transfer medium 32 can be supplied to the heat exchanger 60. In order to close the circuit 30 and to guide the heat transfer medium 32 back to the heat accumulator 20, the heat exchanger 60 is connected to another line that allows this return, this line be provided with a pump 35 for acting on the heat transfer medium 32 with a flow can.

According to the embodiment, it is also possible for the actuating means 16 and pump 35 included in the embodiment to be replaced by a single unit, which can be operated in respectively opposite directions. Here, it is also useful or necessary that the two cable guides shown are formed as a single cable routing.

It is also conceivable in accordance with the invention that the compressor expander unit 50 has only one working machine which can fulfill both the function of the compressor 15 and that of the expander 36. In this case, it may again be necessary for the work machine to be in the same position Currents can be used accordingly. Here, it is also useful again or required that the two cable guides shown are formed as a single wiring.

FIG. 4 schematically shows the thermodynamic state changes of the working fluid in operation of a thermal storage device 100, as shown in FIG. 3 is shown in a TS diagram. The individual designated states in the diagram shown here correspond to those in FIG FIG. 3 81, 82, 83, 84 and 91, 92, 93, and 94, which indicate locations at which the working fluid has a specific state. Here, the phase boundary line for a nearly isentropic working fluid (right branch of the phase boundary line) is shown as a thick line. This phase boundary line encloses down the area of a two-phase mixture. Next is shown as a thickened line on the isothermal temperature level 86, an idealized phase transition, as it can be done in a latent heat storage, for example, wherein the melting and solidification of the storage material is carried out at a temperature level. Since in real conditions the solidification temperature differs slightly from the melting temperature, the phase transition is shown as a thickened line to better illustrate this slight temperature difference.

The operating process is shown here for a subcritical operation, i. the maximum working fluid temperature is always below its critical temperature.

The storage of heat in heat storage 20 takes place at the isothermal temperature level 86 in the range between 100 ° C and 300 ° C, in particular between 120 ° C and 200 ° C. Particularly advantageous is an isothermal storage, as is possible by latent heat storage or thermo-chemical heat storage, ie it is a phase transition or a physical or chemical reaction to store the heat used. In the heat pump cycle, at least for the most part, condensed working fluid is present at point 91 in front of the heat exchanger 60. The temperature level of the heat absorption 87 is between 40 ° C and 120 ° C, in particular between 50 ° C and 90 ° C. After heat absorption, the working fluid is present in the TS diagram at point 92, ie evaporation or overheating has taken place. After the compressor 15, the working fluid is at point 93 at a higher temperature. The heat is transferred to the heat accumulator 20 until the point 94 is reached. Then there is a further heat release or pressure change until the initial state 91 is reached again.

The thermal circuit for reconversion is also in Fig. 4 shown. Here, working fluid is compressed in the liquid phase from point 81 to point 82. Then there is a heat absorption from the heat storage 20 until the point 83 is reached. By the expansion in the expander 36 work is performed and discharged through the power generating device 31 to the outside. After expansion, the working fluid is present at point 84 and reaches the initial state 81 again due to the removal of heat with condensation.

FIG. 5 shows a further particularly preferred embodiment of the thermal storage device 100 according to the invention, wherein the heat pump 10 and the heat accumulator 20 are interconnected in a closed circuit. The heat pump 10 is designed as a chemical heat pump, wherein the heat accumulator 20 is designed as a thermo-chemical heat storage. The system of first heat pump 10 and heat storage 20 allows by suitable adsorption and desorption processes, or chemical and physical reactions in the heat storage 20, the provision of thermal energy, which in turn can be provided to the circuit 30.

In order to charge the heat accumulator 20 with thermal energy, a heat exchanger 17 is provided on the first input side 11 of the first heat pump 10. About this may be appropriate Heat to be added or removed. Furthermore, the first heat pump 10 comprises a turbomachine 19 (compressor), which moves the heat storage medium 21 guided in this circuit between the heat accumulator 20 and the first inlet side 11, that is to say it applies a flow. Depending on the flow state or coupled-in thermal heat can be absorbed in the heat storage by absorption or adsorption and corresponding desorption processes, or by chemical and physical reactions thermal energy (typically by desorption) or thermal energy are emitted (typically by absorption or adsorption). The heat released during operation of the first heat pump 10 can also be temporarily stored in the heat storage.

FIG. 6 FIG. 12 shows an idealized calculation of the current-to-current efficiency (PtP-E) as a function of the temperature level of the heat provided to the first heat pump 10, which in the present case is provided as waste heat. This temperature level (WHT) relates to typical temperature levels of waste heat in a power plant process.

The calculations for this are based on simplified assumptions, however, which make a comparison of different heat storage methods and the related thermal storage devices make sense.

The curve labeled C is based on relatively conservative assumptions about the efficiencies of individual components of the thermal storage device 100. Here, it is assumed that the circuit 30 is operated as ORC (Organic Rankine Cycle). The grade of the heat pump (ie, the efficiency to Carnot efficiency ratio) and the cycle 30 were assumed to be 50%. The heat storage temperature in the heat storage 20 was assumed to 140 ° C, heat losses are 10%, the heat storage capacity is 25 K, the condensation temperature of the ORC 35 ° C. Despite these relatively conservative assumptions, the Efficiency at a temperature level of more than 90 ° C already about 40%.

Further optimized efficiencies of individual components were set forth for Case B, which assumed that the heat pump grade and the ORC are 60%, the heat storage temperature 130 ° C, heat losses 5%, heat storage modesty 15 K, the condensation temperature of the ORC 30 ° C. Under such assumptions, efficiencies of the thermal storage device 100 of more than 50% can already be achieved with amounts of waste heat at a temperature level of more than 70 ° C.

Further technical improvements, such as are possible by a greatly reduced power consumption, are shown in the curve according to case A. It was assumed that the heat pump has a significantly higher power-to-heat efficiency. Such can be achieved, for example, by a chemical heat pump, as described above, as the first heat pump 10. The required current consumption was only estimated in the present case. It is essential, however, that the chemical heat pump primarily absorbs thermal energy, without requiring electrical energy such as through consumption by a compressor. The estimate shows that even at temperature levels of 50 ° C and above, a current-to-current efficiency of over 70% can be achieved.

• Aufnehmen von thermischer Energie auf einem Temperaturniveau zwischen 40 °C und 120 °C, insbesondere zwischen 50°C und 90°C, durch die erste Wärmepumpe an einer ersten Eingangsseite (Verfahrensschritt 201);
• Abgeben von thermischer Energie auf einem angehobenen Temperaturniveau zwischen 100 °C und 300 °C, insbesondere zwischen 120°C und 200°C, auf einer ersten Ausgangsseite (Verfahrensschritt 202);
• Übertragen wenigstens eines Teils der thermischen Energie auf der Ausgangsseite auf ein Wärmespeichermedium (Verfahrenschritt 203);
• Deponieren der thermischen Energie des Wärmespeichermediums in dem Wärmespeicher (Verfahrensschritt 204).

FIG. 7 shows a flowchart representation of an embodiment of the method according to the invention for the storage of thermal energy by means of a previously described thermal storage device, comprising the following steps:

• Receiving thermal energy at a temperature level between 40 ° C and 120 ° C, in particular between 50 ° C and 90 ° C, through the first heat pump at a first input side (method step 201);
• Outputting thermal energy at a raised temperature level between 100 ° C and 300 ° C, in particular between 120 ° C and 200 ° C, on a first output side (method step 202);
• Transferring at least a portion of the thermal energy on the output side to a heat storage medium (process step 203);
• Depositing the thermal energy of the heat storage medium in the heat storage (step 204).

Further embodiments emerge from the subclaims.

Claims (14)

Thermal storage device (100) comprising a first heat pump (10), a thermally connected to the first heat pump (10) heat storage (20), and a circuit (30) for performing a thermal cycle and for generating electrical energy by means of a power generating device connected therein (31), which can be energized via a in the circuit (30) guided heat transfer medium (32), wherein the circuit (30) also thermally connected to the heat storage (20), characterized in that the first heat pump (10) to is formed to receive thermal energy at a temperature level between 40 ° C and 120 ° C, in particular between 50 ° C and 90 ° C, on a first input side (11) and on a first output side (12) thermal energy at a raised temperature level between 100 ° C and 300 ° C, in particular between 120 ° C and 200 ° C, with the thermal energy on de The first output side (12) is at least partially transferred to a heat storage medium (21), which deposits the thermal energy in the heat accumulator (20). Thermal storage device according to claim 1, characterized in that the first heat pump (10) is adapted to receive electrical energy at a power of at least 1 MW. Thermal storage device according to one of the preceding claims,
characterized in that the ratio of thermal energy dissipated at the output side (12) of the first heat pump (10) to the electrical energy required by the first heat pump (10) for operation is between 1, 5 and 7, in particular between 2 and 5 lies. Thermal storage device according to one of the preceding claims,
characterized in that the heat accumulator (20) is designed as a sensitive heat storage, and / or as latent heat storage. Thermal storage device according to one of the preceding claims,
characterized in that the working fluid of the first heat pump (10) is identical to the heat transfer medium (32) in the circuit (30). Thermal storage device according to one of the preceding claims,
characterized in that the first heat pump (10) a second heat pump (40) is connected upstream thermally, which is adapted to receive thermal energy at a temperature level between 0 ° C and 60 ° C at a second input side (41) and on a second Output side (42) thermal energy at a raised temperature level between 40 ° C and 120 ° C, in particular 50 ° C to 90 ° C. Thermal storage device according to one of the preceding claims,
characterized in that the heat transfer medium (32) and the heat storage medium (21) are substantially identical, in particular both can enter into thermal interaction with the heat accumulator (20). Thermal storage device according to one of the preceding claims,
characterized in that the thermal storage device (100) comprises a compressor-expander unit (50) which is simultaneously encompassed by both the first heat pump (10) and the circuit (30). Thermal storage device according to one of the preceding claims 1 to 7,
characterized in that the thermal storage device (100) comprises a work machine (70) having both the function of a compressor and the function of an expander, and which simultaneously from both the first heat pump (10) and the circuit (30) is included. Thermal storage device according to claim 7, characterized in that a heat exchanger (60) is both fluidically connected to the first heat pump (10), as well as with the circuit (30), wherein the heat exchanger (60) depending on the operating condition as a cold source or as a heat source can serve. Thermal storage device according to one of the preceding claims,
characterized in that the first heat pump (10) is designed as a chemical heat pump. Thermal storage device according to one of the preceding claims,
characterized in that the heat accumulator (20) is designed as a thermo-chemical heat storage. Method for storing thermal energy by means of a thermal storage device (100) according to one of the preceding claims, comprising the following steps: - Receiving thermal energy at a temperature level between 40 ° C and 120 ° C, in particular between 50 ° C and 90 ° C, by the first heat pump (10) at a first input side (11); - Releasing thermal energy at a raised temperature level between 100 ° C and 300 ° C, in particular between 120 ° C and 200 ° C, on a first output side (12); - Transferring at least a portion of the thermal energy on the output side (12) on a heat storage medium (21); - Deposit the thermal energy of the heat storage medium (21) in the heat storage (20). Method according to claim 13,
characterized in that there is further included a step of transferring thermal energy after it has been discharged from the heat accumulator (20) to the heat transfer medium (32) of the circuit (30).

Images