Thermal energy storage system comprising a packed bed hot storage unit and a packed bed cold storage unit and method of operating a thermal energy storage system

Abstract

The invention relates to a system and method for storing electrical energy based on a closed thermodynamic cycle. It makes it possible to store electrical energy in a very efficient, economic and safe way. No environmentally harmful or expensive materials are required. The system comprises a compressor, a turbine and two packed bed storage units operating at different temperature levels. To charge the packed bed storage units, the cycle is operated as a counterclockwise heat pump process. In this process, the heat generated at the outlet of the compressor is expanded into the first packed bed storage unit at a high temperature level and stored therein. The "cold" generated during the subsequent expansion of the gaseous working medium in the turbine is stored in the second packed bed storage unit. This requires mechanical energy provided by an electric motor. To enable the energy storage system to deliver power, the cycle is operated in reverse (i.e. as a clockwise working cycle). Before entering the compressor, the working medium is cooled using the cold stored in the second packed bed storage unit, and after compression, heat is absorbed from the high-temperature packed bed storage system. The high-pressure hot working medium is expanded by means of the turbine, thereby generating energy.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for storing electrical energy (electrical storage system) based on a known thermodynamic cycle. The heat source is a high-temperature heat storage unit; the heat sink is a low-temperature heat storage unit (cold storage unit), which will be referred to as cold storage unit in the following. Furthermore, the cycle comprises at least one compressor and a turbine. The compressor and the turbine are connected to an electric machine (electric motor, generator or motor-generator). BACKGROUND

[0002] With the increase of electrical energy production via solar and wind energy, the storage of electrical energy becomes more important. Various systems are known, such as pumped storage power plants and battery storage systems, (accumulators), chemical storage systems and high-temperature heat storage systems. Without solving the advantages and disadvantages of the known storage systems, it is obvious that there is a huge and growing demand for reliable, safe and profitable storage systems.

[0003] The present invention relates to a heat storage system. Such heat storage systems are described in detail in US 2016 / 0298455 Al, US 2019 / 0195671 Al, US 2019 / 0212070 Al and US 2019 / 0195571 Al. The cycle described therein comprises one adiabatic compression and one adiabatic expansion, one isobaric heat transfer at high temperature and one isobaric heat transfer at low temperature. This cycle is called Joule process or “Brayton cycle”.

[0004] The cycle is operated as a counterclockwise (heat pump) cycle to charge such a heat storage system. The compressor is driven by an electric machine. The high-temperature heat generated in the beginning or intermediate stage of the compressor is stored in the high-temperature heat storage system. The gaseous working medium has a very low temperature, for example -70°C, after expansion in the turbine. This very cold working medium is used to cool the liquid heat carrier of the cold storage unit; the cold storage unit is charged.

[0005] To discharge the heat storage system, the system is operated as a clockwise thermodynamic “work” cycle. The generated work is converted into electrical energy by the electric machine operated by the turbine. After the working medium is adiabatically compressed (and thus also heated) in the compressor, the working medium is further heated by heat from the high-temperature heat storage unit before being discharged into the turbine. Then, the working medium is cooled by the cold storage unit before returning to the compressor. Details can be found in the above-mentioned published patent applications.

[0006] In the high-temperature thermal storage units described in US 2016 / 0298455 A1, US 2019 / 0195671 A1, US 2019 / 0212070 A1 and US 2019 / 0195571 A1, liquid salts or liquid salt mixtures are used as storage medium. The operating temperature of this high-temperature thermal storage medium is determined by the melting point (200°C to 320°C) and the decomposition point (560°C to 570°C) of the salt or salt water mixture. The temperature interval is therefore limited in the range in which the salt storage system operates as a thermal storage unit, i.e. between approximately 230°C and 570°C, which limits the storage capacity of the high-temperature thermal storage unit.

[0007] US 2018 / 0187597 A1, EP 2 390 473 A1 and EP 2 400 120 A1 describe a thermal energy storage system comprising two tanks, wherein each tank is used for a liquid thermal storage medium on the hot side and on the cold side.

[0008] The temperature of the working medium is therefore also determined at the turbine inlet, and the conversion efficiency of thermal energy into electrical energy is correspondingly relatively low. Both have a negative impact on the current-to-current efficiency.

[0009] Cold storage units also work with liquid storage media (e.g. hexane) at low temperatures of approximately -50°C or below. The lower limit of the operating temperature of the cold storage unit is determined by the freezing / melting point of the liquid storage medium. Since the thermal storage medium must not evaporate into a vapor, there is also an upper limit to the temperature.

[0010] In these systems, it is particularly disadvantageous that multiple gas-liquid heat exchangers are required. In order for the thermodynamic cycle using salt and coolant as thermal carriers to still be effective, a gas-gas heat exchanger (recuperator) must be installed between the turbine outlet and the compressor inlet.

[0011] When using molten salts, the high-temperature thermal storage unit requires at least three heat exchangers to safely prevent solidification of the liquid salt. An additional gas-liquid heat exchanger is required for the cold storage unit. Each heat exchanger deteriorates the efficiency of the overall process due to the temperature differences.

[0012] In addition, the operation of such a complete system is very complex, since during input as well as during switching between loading and unloading it must be ensured that the temperature in the high-temperature heat exchanger is always sufficiently high at every point so that the salt cannot solidify by any means. Not only must the interaction between the compressor and turbine sides of the cycle be precisely determined, but also the interaction between the mass flow of the liquid or pump of the tank system on the cold side and on the hot side. Therefore, great attention is given to this problem in the aforementioned patent family.

[0013] Salt storage systems, which are usually shown in the literature only in a very simplified manner as a double tank system with heat exchanger and pump, are in practice complex systems with large adiabatic tanks, special cooling foundations, high requirements for the pumps for the liquid salt and for the system to prevent solidification and the circulation system. The work required for maintenance and repair is also high. Corrosion is another challenge. In addition, the electrical consumption of the salt pump and the coolant pump in the cooling tank must also be considered as separate consumptions in the overall performance or current-to-current efficiency. SUMMARY

[0014] It is an object of the present application to provide a thermal storage system which avoids the disadvantages of the prior art. In particular, a rather good current-to-current efficiency can be achieved with lower costs and lower requirements for material and component safety.

[0015] Advantages of the present application

[0016] The operation of the thermal energy storage system is relatively simple, safe and economical, since the operating pressure in the cycle is relatively low and the mineral storage material is non-toxic and easy to handle.

[0017] Due to the good setup of the storage material, the gaseous heat carriers of the high-temperature thermal storage unit and the cold storage unit have to overcome only a relatively low flow resistance, the energy requirement of the fans is low. In view of the baffles and the lines, this is less than 100 mbar, and according to the specific design, it can often even be less than 50 mbar, even in very large systems. The storage system works at ambient pressure. This means that the wall thickness of the storage modules and the lines can be very small.

[0018] The main difference in using such a high-temperature thermal storage unit as a cold storage unit is that at temperatures below 0°C, preferably a heat transfer medium other than air is used, since moisture in the air cools at low temperatures and in particular freezes the baffles and the fans. This is why the corresponding cold storage unit is preferably designed as a closed system with nitrogen N2, carbon dioxide CO2, argon Ar or helium He, or a different gas or gas mixture that does not condense or freeze at the required operating temperature.

[0019] Compared to the use of a salt storage system and a coolant, by using a packed bed storage system as a high-temperature thermal storage unit and / or as a cold storage unit, the cycle can be operated at much lower pressures.

[0020] This results in a packed bed cold storage unit that is preferably integrated directly into the heat pump process and, since the temperature difference in the heat exchanger is omitted, not only the heat exchanger can be omitted, but also the efficiency is increased.

[0021] The packed bed storage system according to the present application makes it possible to achieve a temperature range of 900°C and above (assumption: storage temperature of the high-temperature heat storage unit is 800°C, storage temperature of the cold storage unit is -100°C).

[0022] In the known system with liquid salt and liquid storage medium in the cold storage unit, the maximum temperature range is approximately 650°C (= 570°C to (-80°C)). The temperature range has a direct influence on the current-to-current efficiency. This is one reason why the current-to-current efficiency of the thermal energy storage system according to the present application is significantly higher than that of the aforementioned known system.

[0023] If one looks more closely at thermodynamics, it can be determined that the proposed packed bed storage system can optimize the temperature interaction of the hot side and the cold side, so that the maximum pressure on the hot side can be approximately 8 bar to 14 bar (using nitrogen N2) when the same process medium is in circulation, which is far below the necessary pressure when using a salt storage system, i.e. more than 60 bar (using nitrogen N2) and more than 30 bar (using other gases (e.g. argon Ar)). This leads to considerable simplifications in material selection, required wall thickness, etc. and safety.

[0024] The above task is achieved by the method for loading and unloading according to claims 9 to 12, which differ only in the direction of the circulation. The first heat transfer system and the second heat transfer system can remain unchanged. This means that a simple and robust operation is conceivable.

[0025] Further advantages and advantageous variants can be found in the following description and their description. BRIEF DESCRIPTION OF DRAWINGS

[0026] The accompanying drawings show the following:

[0027] Figures 1 to 5 : block diagram of an example variant of a thermal energy storage system according to the present application;

[0028] Figures 6 to 11 : explanatory block diagram;

[0029] Figure 12 : T-S diagram of a thermal energy storage system according to the prior art and a thermal energy storage system according to the present application;

[0030] Figure 13 and 14 : cross-section of an example variant of a storage module according to the present application. DETAILED DESCRIPTION

[0031] In the drawings, identical reference numerals have been used, where possible, to designate identical elements and only the components and parts necessary for understanding the present application are shown. Other equipment normally required for operating such a system is not shown. Of course, also a safety valve has to be provided, the low pressure part has to be tightly closable, so that in case of a turbine failure, a compensation vessel etc. no excessive pressure is built up in the cold storage module. Also no further coolers required for a stable operation are shown.

[0032] Figure 1 The thermal energy storage system in the first example variant shown comprises a compressor 102, an electric motor 100 and a turbine 104. A first heat exchanger 116 is positioned between the "outlet" 151 of the compressor 102 and the "inlet" 153 of the turbine 104.

[0033] Between the "outlet" 155 of the turbine 104 and the "inlet" 157 of the compressor 102 is a second heat exchanger 126. The terms "outlet" and "inlet" are indicated in quotation marks, because this is based on a counter-clockwise "heat pump" cycle. However, the system can also be configured as a clockwise "work" cycle. In this way, the compressor 102 operates as an expansion turbine, the turbine 104 operates as a compressor and also the flow direction of the working medium is reversed.

[0034] The first heat exchanger 116 is connected via a first heat transfer system 159 with the packed bed high temperature heat storage unit 112-HM. In Figure 1 In the figure only two lines 118 of the first heat transfer system 159 are visible.

[0035] The second heat exchanger 126 is connected via a second heat transfer system 161 with the packed bed cold storage unit 112-KM. In Figure 1 In the figure only two lines 128 of the second heat transfer system 161 are visible.

[0036] Both heat transfer systems 159, 161 work with a gaseous heat carrier, which transfers heat to the solid storage material of the high temperature heat storage unit 112-HM during charging and takes heat from the heat storage material during discharging. When charging the cold storage unit 112-KM, the heat carrier removes heat from the storage material, so that it cools down. During discharging, it emits heat onto the storage material of the cold storage unit 122-KM and thus cools down.

[0037] The second heat transfer system 161 can for example be operated with argon, nitrogen N2, CO2, and other gases or gas mixtures as heat carrier. In the first heat transfer system 159, also air can be used as heat carrier.

[0038] The high-temperature heat storage unit 112-HM and the cold storage unit 122-KM essentially have the same structure. The structure and function thereof are described in DE 10 2010 055 997 Al and WO 2012 / 017041 Al, which are hereby incorporated by reference.

[0039] The thermal energy storage system is shown in Figure 2 The respective flow directions of the three gaseous media are indicated by arrows in Figure 2 During charging, the electric machine 100 is used as a motor; it drives the compressor 102. A counterclockwise heat pump cycle thus takes place.

[0040] In the first heat exchanger 116, a heat transfer from the hot working medium 108 to the likewise gaseous heat carrier of the first heat transfer system 159 takes place. The high-temperature heat storage unit 112-HM is charged with the heat carrier of the first heat transfer system 159, which is heated by this heat transfer.

[0041] In the second heat exchanger 126, a heat transfer from the very cold working medium 108 (e.g., a temperature of -100°C) leaving the turbine 104 to the gaseous heat carrier of the second heat transfer system 161 takes place. The cold storage unit 122-KM is charged, i.e., cooled, using the heat carrier of the second heat transfer system 161, which is cooled by this heat transfer.

[0042] The discharge of the thermal energy storage system according to the present invention is illustrated by Figure 3 the second example variant shown in Fig. 2. In the second example variant, the compressor 102 and the turbine 104 are not mechanically connected; instead, both the compressor 102 and the turbine 104 are each connected with an electric machine 100, 101. The function of all example variants is essentially the same, so the charging and discharging is illustrated by one variant. Since the functional principle of all variants is the same, or at least there is a significant commonality, the skilled person can transfer this to another variant.

[0043] During discharging, the "turbine" 104 works as a compressor and is driven by the electric machine 101. In the first heat exchanger 116, the working medium, which has been heated by the compression in the "turbine" 104, is further heated. This is achieved by passing the heat carrier of the first heat transfer system 159 through the heat storage material of the high-temperature heat storage unit 112-HM and being heated to 1000°C or more. This high heat is transferred to the working medium in the first heat exchanger 116.

[0044] As a result, the heat carrier of the second heat transfer system 161 in the second heat exchanger 126 cools the working medium before it enters the turbine 104, which works as a compressor at 155, thus discharging the cold storage unit 122-KM.

[0045] Figure 4Another variant is schematically shown. This variant takes into account the fact that it is generally not possible to construct a single or multi-stage turbine 104 such that it works effectively or very effectively when operated as a compressor. This applies correspondingly to a single or multi-stage compressor 102.

[0046] This variant comprises two compressors 102-B, 104-E and turbines 104-B, 102-E. There are two electric machines 100, 101 which can work in generator and motor mode. The couplings 105 are connectable with the electric machines via the required system components (compressor and turbine) and the inactive couplings are decoupled.

[0047] In Figure 4 and Figure 5 In the example variant shown, only the first heat exchanger 116 and the first heat transfer system 159 are present. Unlike the above variant example, the circulating working medium flows directly through the cold storage unit 112-KM. The second heat exchanger 126 and the second heat transfer system 161 are omitted and the circulating working medium flows directly through the cold storage unit 122-KM.

[0048] This has a number of advantages. Perhaps the most obvious is that the investment costs and space requirements are much lower. In addition, the current-to-current efficiency of the thermal energy storage system is improved since the temperature difference is omitted in the process of transferring from the storage material to the heat carrier of the second heat transfer system 161 and from this heat carrier to the circulating working medium in the second heat exchanger 126.

[0049] On the high temperature side, charging and discharging remain unchanged and take place as described above. As a result of the working medium flowing through the cold storage unit 122-KM, charging and discharging of the cold storage unit 122-KM takes place.

[0050] In Figure 4 the thermal energy storage system is discharging. This is based on the switch positions of the armatures 106-1 to 106-4 and the flow directions of the working medium and heat carrier of the heat transfer systems 159 and 161. During discharging, the compressor 104-E is driven by the electric machine 101. Coupling 105-4 is closed and coupling 105-3 is open. The turbine 102-E drives the electric machine 100 which feeds power into the power grid via line 99. Coupling 105-1 is closed and coupling 105-2 is open.

[0051] The armatures 106-1 and 106-4 are open. The armatures 106-2 and 106-3 are closed so that the unused compressor 102-B and the unused turbine 104-B are disconnected from the cycle.

[0052] To load the thermal energy storage system, the compressor 102-B is driven by the motor 100. The coupling 105-3 is closed, while the coupling 105-4 is open. The turbine 104-B drives the motor 101, which powers the grid through the line 98. The coupling 105-2 is closed, while the coupling 105-1 is open.

[0053] The armatures 106-2 and 106-3 are open. The armatures 106-1 and 106-4 are closed, so that the unused compressor 104-E and the unused turbine 102-E are disconnected from the cycle.

[0054] Figure 5 The example variant shown is to some extent Figure 1 A variant of the form shown, in which, as Figure 4 As shown and described in its associated description, the working medium flows directly through the cold storage unit; the second heat exchanger 126 and the second heat transfer system 161 are omitted.

[0055] Figures 6 to 12 is a somewhat more detailed illustration, in particular of the high-temperature heat storage unit 112-HM, the cold storage unit 122-KM, the first heat transfer system 159, and the second heat transfer system 161.

[0056] Figure 6 The high-temperature heat storage unit 112-HM and the first heat transfer system 159 are shown in more detail. The high-temperature heat storage unit 112-HM comprises a plurality of high-temperature heat storage modules HM1 to HM5, the number of which is freely selectable. Basically, the number of modules can be as many as one wishes, i.e. the amount of heat to be stored can be increased as many as one wishes via the number of modules. Each module HM is connected to the first heat transfer system 159 by two lines (without reference signs).

[0057] Figure 6 The first heat transfer system 159 shown is an open system, which means that it works with ambient air as a heat carrier. Ambient air can be sucked in via the line 165, or air from the high-temperature heat storage unit 112-HM can be discharged into the environment. The high-temperature heat storage unit 112-HM contains a blower HF and flaps H1 to H11. Using the flaps H2 to H5, the flow direction of the heat carrier can be reversed. A second blower (not shown) that conveys in the opposite direction can also be installed.

[0058] For the sake of understanding, the lines within the high-temperature heat storage unit 112-HM are not numbered. The first heat transfer system 159 is connected to the first heat exchanger 116 by the line 118. It is conceivable to allocate the part of the first heat exchanger 116 that the air from the heat carrier passes through to the first heat transfer system 159.

[0059] In Figure 6 which the shutters H1 to H11 are positioned such that the storage module HM1 is loaded, wherein ambient air is used as heat carrier. The ambient air required for the loading is sucked through the fan HF via the line 165.1 and the open shutter H1 and is supplied via the open shutter H2 to the first heat exchanger 116. In the first heat exchanger 116, the circulating working medium 108 gives off its high-temperature heat to the ambient air (heat carrier).

[0060] The now hot air is fed into the module HM1 through the line and the open shutter H6. In the module HM1, the heat carrier "air" simultaneously passes through the storage material (e.g. sand, gravel, stones, ceramic particles, metal oxide / silicate particles, etc.) in the module HM1 and transfers heat to the storage material. The cooled air then leaves the module HM1 of the high-temperature heat storage unit 112-HM. As soon as the module HM1 is completely loaded, the module HM2 is activated, since the shutter H6 is closed and the shutter H7 is open. In this way, the modules HM1 to HM5 can be loaded continuously.

[0061] It is also possible to load several modules HM simultaneously in a parallel manner. For this purpose, only the respective shutters have to be opened. For example, when the modules HM3 and HM4 are loaded in parallel, the shutters H8 and H9 have to be opened; the shutters H6, H7 and H10 remain closed in order to prevent a passage through the modules HM1, HM2 and HM5.

[0062] It is generally advantageous if, before the temperature rise following the complete loading of a module HM and before the temperature rise following the loading of a module has reached the outlet surface of the wall of storage material (this is the case when the thermocline has reached the outlet surface of the wall of storage material; see the description of Figure 13 and 14 ), the successive second loading of the module behind the almost completely loaded module is activated. This can prevent heat losses.

[0063] Figure 7 An exemplary switching position of the high-temperature heat storage unit is shown, in which this type of operation is possible. In this case, more shutters are required than in the example variant shown in Figure 6 . The additional shutters are marked with H12, H13, H14, H15, H16, H17, H18 and H19. In this switching variant, several modules can be loaded or unloaded in parallel or also successively.

[0064] Figure 7The loading of modules HM2 and HM3 is shown, wherein modules HM2 and HM3 are loaded successively. In this variant, ambient air flows through the open baffle H1 as heat carrier medium 118, then flows through the blower HF and baffle H2, and is heated in the heat exchanger 116. Via the corresponding pipeline and baffle H7, the hot air is now supplied to module HM2 and flows through the storage material here. If the thermocline reaches the outlet surface of the heat exchanger from the storage system wall, the temperature of the air leaving module HM2 is higher than the temperature of module HM2 if it has not yet been fully loaded. In order not to lose this heat, only partially cooled air is supplied to the module HM3, which has not yet been fully loaded, via the open baffle H12. After the air dissipates the remaining heat into the storage material in module HM3, the completely cooled air leaves the high-temperature heat storage unit via the open baffles H18, H19 and H11.

[0065] If the first heat transfer system 159 is operated as a closed system, loading is also possible. Then, the dampers H1 and H11 are closed, and the damper H4 is opened. Then, the heat carrier circulates in the first heat transfer system 159.

[0066] Of course, loading is also possible if the first heat transfer system 159 is operated as a closed system. If a suitable gas (e.g., nitrogen N2, argon Ar, or carbon dioxide CO2) is used as the heat carrier, the system must be closed. Baffles H1 and H11 are omitted in closed system operation.

[0067] Figure 8 FIGURE 1 illustrates the cold storage unit 122-KM and the second heat transfer system 161 in greater detail. The cold storage unit 122-KM comprises a plurality of cold storage modules KM1 to KM5, wherein the number of modules can be freely determined. Essentially, the number of modules can be as large as desired, i.e., the amount of cold storage can be freely determined by the number of modules. Each module KMI is connected to the second heat transfer system 161 via two pipelines (not referenced). The number of modules HM and KM does not necessarily have to be equal.

[0068] The second heat transfer system 161 is a system that is always closed because it cannot work with ambient air as a heat carrier. The cold storage unit 122-KM includes a blower KF and baffles K2 to K15. The baffles K2 to K5 allow the flow direction of the heat carrier to be reversed.

[0069] For ease of understanding, the pipelines within the cold storage unit 122 -KM have no reference numerals. The second heat transfer system 161 is connected to the second heat exchanger 126 via a pipeline 128 .

[0070] Figure 8The second heat transfer system 161 is shown when the cold storage unit 122-KM, in particular the module KM2, is loaded. The heat carrier is cooled in the second heat exchanger 126 and the heat carrier is fed into the module KM2 via one of the lines 128 and the open flap K7. When passing through the module KM2, the heat carrier cools the storage material and the heat carrier is warmed up.

[0071] After leaving the module KM2, the heat carrier is fed into the module KM3 via the open flap K13, i.e. in this example the heat carrier successively passes through the two modules KM2 and KM3. The "heated" heat carrier is then fed via the open flaps K18, K19 and K4 into the blower KF. The blower KF transports the heat carrier back to the second heat exchanger 126 via the open flap K2 and the further line 128. There the heat carrier gives off its heat to the working medium of the cycle 108 flowing against the flow direction; the heat carrier is cooled and then fed back to one or more modules KM.

[0072] In Figure 9 , the unloading of the module HM2 of the high temperature storage unit 112-HM is shown as a closing process, i.e. the flaps HI and H11 are closed.

[0073] The flow direction is reversed when unloading. This can be achieved via a second blower working in the opposite direction to the loading process, or via the same blower HF, wherein by this blower HF the flow direction is reversed by the flaps H2 to H5. I.e. when unloading, the heat carrier (air, nitrogen, argon, etc.) sucked from the first heat exchanger 116 flows through the open flap H3 and then through the blower HF, which transports the heat carrier via the line to the module HM2 through the open flap H5. The heat carrier passes through the module HM2 and the storage material located therein and flows through the open flap H7 to the first heat exchanger 116. Now the cooled heat carrier is fed back into the blower HF through the duct 118 and the flap H3.

[0074] Figure 10 and 11 The loading of the cold storage unit 112-KM without the second heat exchanger 126 and without the second heat transfer system 161 is shown (see also Figure 4 and 5 ).

[0075] Figure 10 The direct loading of the module KM1 is shown. After the working medium has left the turbine and has become very cold, the working medium of the cycle is transported into the module KM1 via the line and the open flap K6. When passing through the module KM1, the working medium cools the storage material and heats up. Then the working medium is transported to the compressor.

[0076] Figure 11The successive loading of modules KM2 and KM3 is shown, i.e. the flaps K7 and K13 are open and the working medium passes through the modules KM2 and KM3 in succession. The "heated" working medium reaches the compressor via the open flaps K18, K19.

[0077] In Figure 12 US 2019 / 0195571 Al known heat storage system with liquid salt and liquid coolant as heat storage unit is compared to the heat storage system described in the present invention. Figure 12 Two T-S diagrams for selected actual parameters of terminal temperature difference, pressure loss, and individual consumption are shown, and both methods aim to store the same electrical output or power amount.

[0078] The graph 171 shows the counterclockwise heat pump cycle of the heat storage system known from US 2019 / 0195571 Al for loading.

[0079] The graph 173 shows the clockwise work cycle of the heat storage system known from US 2019 / 0195571 Al for unloading.

[0080] The graph 175 thus shows the counterclockwise heat pump cycle of the heat storage system described in the present invention used during loading.

[0081] The graph 177 shows the clockwise work cycle of the heat storage system described in the present invention during unloading.

[0082] Figure 12 The comparison of the T-S diagrams with the specified pressure ranges (p max = 67.4 bar against p max = 8.5 bar) shows that the heat storage system described in the present invention is very beneficial in terms of system safety. The comparison of the current-to-current efficiencies (62.2% to 57.2%) clearly shows the benefit of the heat storage system described in the present invention.

[0083] Figure 13 A cross section of an example variant of a storage module HM or KM with six walls 167 composed of storage material is shown. The walls 167 are porous so that the heat carriers (air, gas) of the heat transfer system 159 or 161 can flow through the pores. Preferred mineral storage materials (sand, gravel, basalt, ceramic particles, metal oxide / silicate particles, etc.) have an average diameter of less than 8 mm, preferably 1 mm to 3 mm, and are arranged in multiple layers or walls 167 that are simultaneously horizontally traversed. A radial traversal of the storage layers is also possible. The various arrangements and flow directions of the storage material are shown and explained by the applicant in DE 10 2010 055 997 Al and DE 10 2010 033 571 Al.

[0084] The number and thickness of the walls 167 depend on the respective requirements of the storage system (e.g. maximum allowable pressure loss). The thickness is in the range of 0.3 m to 2.5 m.

[0085] The heat carrier is conveyed via lines 179 into three intermediate spaces between the walls 167.

[0086] The heat carrier is conveyed from two intermediate spaces between two walls 167 via lines 181. The lines 181 are connected with intermediate spaces between the casings 183 of the storage modules HM, KM. This allows the heat carrier to pass through all six walls 167 at the same time and through the entire surface of all six walls 167. This significantly reduces the pressure loss and still allows a very good and fast heat transfer from the heat carrier to the storage material and vice versa.

[0087] Figure 13 The inflow and outflow lines 179, 181 are shown above the storage material, but these lines can feed or discharge the heat carrier (gas or air) between the walls from the side or from below. Any combination is possible, e.g. the storage module can be loaded from one side and unloaded from the other side. The storage material can pass through in other ways, e.g. radially or from below to above, as described above.

[0088] Figure 14 A cross section of another example variant of a storage module HM or KM with six walls 167 made of storage material is shown. The walls 167 are porous so that the heat carrier (air, gas) of the heat transfer system 159 or 161 can flow through the walls.

[0089] The loading of the storage module is shown on top of Figure 14 The heat carrier is conveyed via lines 179 into three intermediate spaces between the walls 167.

[0090] The cooled heat carrier is conveyed from two intermediate spaces between two walls 167 via lines 181. The lines 181 are also connected with intermediate spaces between the casings of the storage modules HM, KM. This allows all six walls 167 to be passed through by the heat carrier through their entire surface at the same time. This significantly reduces the pressure loss and also allows a very good and fast heat transfer from the heat carrier to the storage material and vice versa.

[0091] In this example variant, the lines 179 and 181 are connected with the heat transfer system 159 or 161 via baffle boxes, in each of which a baffle is positioned.

[0092] Figure 14 The loading of the storage module HM is shown on top of Figure 14The bottom of Figure 1 shows the discharge of the storage module HM. By switching two flaps, the flow direction of the heat carrier of the heat transfer system through the storage wall 167 is reversed. This again reduces the energy losses during loading and discharging. It is possible for the storage module to be integrated directly into the air flow, without the air flow having to be reversed between loading and discharging.

[0093] It is proposed for the external dimensions of the storage modules HM, KM to match the external dimensions of the transport containers. This means that the modules can be manufactured in the factory and transported to the place of use in an affordable manner. Alternatively, the modules can be assembled directly on the construction site. Accordingly, there can of course be considerable dimensions.

[0094] In general, the housing and the support elements are made of steel, but due to the small over- and underpressure relative to the environment, other materials such as concrete can be used for on-site assembly. The filling of the storage material and the closure of the module are preferably carried out after the on-site assembly.

[0095] The arrangement of the storage material in the interior of the module in the form of a gas- or air-permeable wall produces a large inflow surface. This reduces the speed of the gaseous heat carrier on the inflow wall compared to the flow speed in the line. This in turn leads to an exponential reduction in the pressure loss when passing through the storage material. As a result, the energy requirement of the blower of the heat transfer system 159 and 161 is reduced.

[0096] By using a fine-grained / particle-like storage material, the thermocline (threshold layer between hot and cold material in the flow direction) is very narrow (about 5-35 cm). The large surface of the fine-grained storage material facilitates very good heat exchange and high heat output during loading and discharging. The large surface and the narrow thermocline result in the temperature of the heat carrier remaining very stable during the movement of the storage material during discharging. The temperature of the heat carrier only drops more strongly when the thermocline reaches the outlet surface.

[0097] The flexibility of the module structure, the number and size of the storage material walls in the module and the option of loading and discharging the modules in parallel means that not only a large amount of heat can be stored, but also different heat outputs can be selected during loading and discharging. For example, when discharging, a very high heat output can be achieved in a short time (e.g. 100 MW, 2 hours, ten modules are passed through simultaneously in parallel). During discharging, a low output can be achieved over a long period of time (e.g. 20 MW, 10 hours, two modules are simultaneously discharged in parallel, then the next two modules are loaded).

[0098] In order to keep the heat at a useful high level over a long period of time, the modules and the lines must be well insulated from the corresponding heat and must be protected from the passage of the modules in idle mode through natural convection via closed flaps.

[0099] It has proven beneficial to reverse the flow direction through the storage material between loading and unloading.

[0100] If the storage modules are installed in a system comprising the same flow direction regardless of loading and unloading, two suitable switching flaps before and after the storage module can reverse the flow through the storage material. In Figure 14 the arrangement of switching flaps in the module is shown in various transition positions. The storage module is loaded on Figure 14 top, hot gas flows in, is then guided from above through the inflow channel and flows between the storage material walls. After the throughflow, the gas leaves the module through the external flow through the storage material walls or between the module walls and the external storage material walls and up to the outflow pipe and leaves the module in a cooled state. In Figure 14 Figure 14 the arrangement of switching flaps in the module is shown in various transition positions. The storage module is loaded on

[0101] If only one of the two flaps is switched, a bypass is created and the gas can flow through the corresponding switching line. Such a module with a switching flap is also suitable if there is a continuous stable gas temperature or a narrow temperature range behind the module (for example, in order to maintain a chemical process), in which the temperature of the inflow gas fluctuates significantly.

Claims

1. A thermal energy storage system comprising a high-temperature heat storage unit, a cold storage unit, at least one compressor (102), and at least one turbine (104), in, The high-temperature heat storage unit, the at least one turbine (104), the cold storage unit and the at least one compressor (102) are connected to each other via pipelines, so that the gaseous working medium circulating in the pipelines is operated in a counterclockwise heat pump cycle or in a clockwise working cycle in a selectable manner. The outlet (151) of the compressor (102) is connected to the inlet (153) of the turbine (104), the outlet (155) of the turbine (104) is connected to the inlet (157) of the compressor (102), a first heat exchanger (116) is provided between the outlet (151) of the compressor (102) and the inlet (153) of the turbine (104), a second heat exchanger (126) is provided between the outlet (155) of the turbine (104) and the inlet (157) of the compressor (102), the working medium respectively passing through one side of the first heat exchanger (116) and the second heat exchanger (126), It is characterized in that The high temperature heat storage unit (112-HM) and the cold storage unit (122-KM) are packed bed storage units. There is a first heat transfer system (159) between the first heat exchanger (116) and the high temperature thermal storage unit (112-HM), There is a second heat transfer system (161) between the second heat exchanger (126) and the cold storage unit (122-KM), and The heat transfer system (159, 161) operates using a gaseous heat transfer medium.

2. A thermal energy storage system comprising a high-temperature heat storage unit, a cold storage unit, at least one compressor (102), and at least one turbine (104), in, The high-temperature heat storage unit, the at least one turbine (104), the cold storage unit, and the at least one compressor (102) are connected to each other via pipelines, so that the gaseous working medium circulating in the pipelines operates in a counterclockwise heat pump cycle or a clockwise working cycle in a selectable manner. The outlet (151) of the compressor (102) is connected to the inlet (153) of the turbine (104), the outlet (155) of the turbine (104) is connected to the inlet (157) of the compressor (102), a first heat exchanger (116) is provided between the outlet (151) of the compressor (102) and the inlet (153) of the turbine (104), the working medium passing through one side of the first heat exchanger (116), It is characterized in that The high temperature heat storage unit (112-HM) and the cold storage unit (122-KM) are designed as packed bed type storage units, There is a first heat transfer system (159) between the first heat exchanger (116) and the high temperature thermal storage unit (112-HM), The first heat transfer system (159) operates using a gaseous heat transfer medium, and The cold storage unit (122-KM) is integrated into the circuit between the outlet (155) of the turbine (104) and the inlet (157) of the compressor (102), so that the working medium flows through the cold storage unit (122-KM).

3. The thermal energy storage system according to claim 1, characterized in that The high-temperature heat storage unit (112-HM) consists of one or more heat storage modules and / or the cold storage unit (122-KM) consists of one or more cold storage modules, in which fine-grained / granular storage material is present.

4. The thermal energy storage system according to claim 2, characterized in that The high-temperature heat storage unit (112-HM) consists of one or more heat storage modules and / or the cold storage unit (122-KM) consists of one or more cold storage modules, in which fine-grained / granular storage material is present.

5. The thermal energy storage system according to claim 3 or 4, characterized in that: The storage material in the hot storage module and / or the cold storage module is arranged in the form of air-permeable or gas-permeable walls (167).

6. The thermal energy storage system according to claim 3, characterized in that The first heat transfer system (159) and the second heat transfer system (161) include at least one blower (HF, KF), a pipe, and a baffle (Hi, Kj), and the first heat transfer system (159) and the second heat transfer system (161) are configured to load or unload one or more of the hot storage modules and / or one or more of the cold storage modules by operating the baffle.

7. The thermal energy storage system according to claim 1, characterized in that The thermal energy storage system includes a first compressor (104E) for operating as a counterclockwise heat pump cycle and a second compressor (102B) for operating as a clockwise working cycle.

8. The thermal energy storage system according to claim 1, characterized in that The thermal energy storage system includes a first turbine (102E) for operating as a counterclockwise heat pump cycle and a second turbine (104B) for operating as a clockwise working cycle.

9. The thermal energy storage system according to claim 1, characterized in that The thermal energy storage system comprises at least one motor (100, 101), and the at least one motor (100, 101) is connected to the compressor (102) and / or the turbine (104).

10. A method for loading a thermal energy storage system according to claim 3, the method comprising the following steps: at least one compressor and at least one turbine operate as a counterclockwise cycle; as well as The first heat transfer system (159) is operated so that the heat carrier passes through the heat storage module sequentially or simultaneously.

11. A method for loading a thermal energy storage system according to claim 4, the method comprising the following steps: at least one compressor and at least one turbine operate as a counterclockwise cycle; as well as The first heat transfer system (159) is operated so that the heat carrier passes through the heat storage module sequentially or simultaneously.

12. A method for loading a thermal energy storage system according to claim 3, the method comprising the steps of: operating at least one compressor and at least one turbine as a counterclockwise cycle; operating the first heat transfer system (159) so that the heat carrier passes through the heat storage module sequentially or simultaneously; as well as The second heat transfer system (161) is operated so that the heat carrier passes through the cold storage module sequentially or simultaneously.

13. A method for unloading a thermal energy storage system according to claim 3 or 4, the method comprising the following steps: operating at least one compressor and at least one turbine as a clockwise working cycle; as well as The first heat transfer system (159) is operated so that the heat carrier passes through the heat storage module sequentially or simultaneously.

14. A method for loading a thermal energy storage system according to claim 3, the method comprising the following steps: operating at least one compressor and at least one turbine as a clockwise cycle; operating the first heat transfer system (159) so that the heat carrier passes through the heat storage module sequentially or simultaneously; as well as The second heat transfer system (161) is operated so that the heat carrier passes through the cold storage module sequentially or simultaneously.

15. The method according to claim 10, characterized in that When the "loading" operating mode and the "unloading" operating mode are alternated, the flow direction of the heat carrier in the first heat transfer system (159) and / or the second heat transfer system (161) is reversed.

16. The method according to claim 10 or 11, characterized in that The hot storage modules and the cold storage modules are loaded and / or unloaded independently.

17. The method according to claim 10 or 11, characterized in that The plurality of hot storage modules and the cold storage modules are switched sequentially or in parallel during loading and / or unloading.

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