DE202023000696U1 - Multi-module high-temperature heat storage tank with serial charging and discharging - Google Patents

Abstract

High-temperature heat accumulator, consisting of an electronic control system and shut-off devices, individual storage units ("modules") with solid storage masses and each module with two internal, separate, structured flow paths, as well as external piping systems, characterized in that:
Modules are fluidically configured with one another in such a way that each storage module is loaded with thermal energy independently of the other modules by flowing a heating fluid through one of the two flow paths and at the same time each module is discharged independently of the other modules by flowing a cooling fluid through the other flow path of thermal energy can.

Description

FIELD OF INVENTION

The invention describes a thermal energy store (“high-temperature heat store”), which is used to absorb waste heat from industrial processes or peak power from regenerative electrical energy production in the form of heat and, if necessary, to transfer it to another system at a later date or at the same time for the purpose of reconversion. The heat is stored by heating solids that are in insulated containers.

The need for storage results from the increasing need for energy production from fossil-free sources and from the increasing share of wind and solar energy in the total energy production. These energy sources are subject to strong fluctuations over time, so that base load capability is only partially given. In a wind power plant, only around 15-20% of the nominal output is available on an annual average. This average value is not reached in around two thirds of the operating time. Solar energy is only available during the day. In many processes, industrial waste heat is only available cyclically.

The load profile, on the other hand, shows seasonal, but mainly strong weekly and daily fluctuations. Therefore, in order to adjust renewable electricity production and electricity demand, storage systems for temporary storage for a few days up to a week are primarily required.

Another problem of regenerative energy production is the disposal of excess power. If no storage is available for this, the power generation systems would have to be curtailed.

Up to now, electricity has mainly been stored using batteries, pumped storage power plants or in the form of “power to gas” (production of hydrogen or methane). The storage capacities or the efficiencies of these methods are limited or the methods are very costly and resource-intensive on a large scale.

OBJECT OF THE INVENTION:

• • Der Wärmespeicher soll bei der Aufnahme von thermischer Energie auch stark unterschiedliche Einspeiseleistungen, zum Beispiel Peak-Leistungen aus Windenergie, effizient bewältigen.
• • Der Wärmespeicher soll bei der Abgabe Wärme bei geeigneter, hoher Mindest-Temperatur bereitstellen und hierbei auch gespeicherte Wärme auf niedrigem Temperaturniveau mit verwenden.
• • Die Kapazität des thermischen Energiespeichers soll so gehalten werden, dass die Glättung beziehungsweise Speicherung der zugeführten zyklisch anfallenden Energie zur Überbrückung von mehreren Tagen ohne Einspeisung ausreicht.
• • Der Wärmespeicher soll bei vergleichbarer Grösse oder Kosten gegenüber vorhandenen Systemen eine grössere Energiespeicherdichte haben.
• • Die Wärmespeichermasse sollte bis zu einer Temperatur von 1000°C erwärmt werden können.
• • Sie soll preiswert und ökologisch unbedenklich sein und beliebig viele Ladezyklen ohne Alterung überstehen.
• • Die Wärmespeichermasse soll aus einem Material bestehen, dass einen Wärmeeintrag über Heissgasdurchströmung und auch direkt über eingebettete Widerstandsheizungen ermöglicht.
• • Die Wärmespeichermasse soll derart ausgestaltet sein, dass ein vergleichsweiser geringer Druckverlust beim Durchströmen entsteht, so dass mehrere Einheiten nacheinander durchströmt werden können.

Thermal energy should be stored efficiently and released again for reconversion. It should not be used primarily as heating or process heat, as is usually the case, but to operate a heat engine that generates electricity. In this way, irregularly occurring thermal energy is to be smoothed out in a base-load-capable manner and times without energy feed-in are to be bridged.

• • When absorbing thermal energy, the heat accumulator should also efficiently cope with greatly differing feed-in capacities, for example peak capacities from wind energy.
• • The heat accumulator should provide heat at a suitable, high minimum temperature when it is released and also use heat stored at a low temperature level.
• • The capacity of the thermal energy store should be maintained in such a way that the smoothing or storage of the supplied cyclically occurring energy is sufficient to bridge several days without being fed in.
• • The heat storage should have a greater energy storage density than existing systems with a comparable size or cost.
• • The heat storage mass should be able to be heated up to a temperature of 1000°C.
• • It should be inexpensive and ecologically harmless and withstand any number of charging cycles without aging.
• • The heat storage mass should consist of a material that enables heat input via hot gas flow and also directly via embedded resistance heaters.
• • The heat storage mass should be designed in such a way that there is a comparatively low pressure loss during flow, so that several units can be flowed through one after the other.

The excess output of a wind turbine is recommended for orientation when dimensioning such a storage system. For example, the installed power (peak power) is 3 MW = 72000 kWh/day, the average power is 12000 kWh/day = 0.5 MW, which is defined as the guaranteed minimum power (base load) and would correspond to the engine power of three to four mid-range cars.

With an efficiency of the downstream reconversion of 50%, a heat storage tank would then have to be able to absorb an excess output of 0.5 MW/50% =1 MW for one day in order to bridge a day without feeding it in.

STATE OF THE ART:

An existing low-cost solution for storing energy is to convert electricity into heat, store it in a solid, and later convert it back into electricity in a heat engine ("power to heat to power"). High temperature solid heat storage can absorb sensible heat (temperature change) or latent heat (phase change from solid to liquid).

With the help of a resistance heater and a fan, the electrical energy can be converted into a hot gas stream and thus into thermal energy. The hot gas, mostly air, is then fed into an insulated housing filled with the heat storage mass to charge the storage. In some systems, the heating devices are embedded in the heat storage mass or integrated in special channels here and transfer the heat to charge the storage tank by radiation or direct contact with the heat storage mass. Rock fill can be heated to around 800°C, steel and concrete to around 650°C, special granulates and ceramics to 1500°C. In the case of rock fill and granules, the heat transfer fluid flows through the gaps, in the case of steel and concrete either along the surface or through pipes. Shaped stones can also be provided with flow channels.

There are also systems in which bundled sunlight is used directly to heat up or melt a latent heat transfer medium.

The storage systems available on the market are mostly optimized to return a maximum amount of heat to the system, electricity is a by-product. The reason for this is that a storage tank must first be heated to a minimum temperature at which a downstream turbine can be operated (approx. 35°C). When discharging the accumulator and operating a turbine, only the temperature range above this minimum temperature can be used. The stored heat below the minimum temperature can only be used for process or heating purposes. Large usable temperature ranges and high discharge efficiencies can only be achieved with very high maximum temperatures.

The storage devices according to the prior art are operated between these defined maximum and minimum temperatures. The flow paths are used in both directions, the flow direction is reversed for unloading. If the charging does not take place via integrated electric heating rods, then there are only the operating modes "charging" alternating with "discharging". This partly with parallel loading or unloading of several modules. There are also manufacturers where several modules are connected in series for charging.

Overall, the design of the storage according to the prior art means that in most storages, the downstream heat engine is stopped after the emptying cycle. The direction of flow is reversed and the storage tank then has to be recharged.

In the case of storage systems that have integrated heating elements and heat up the storage mass by direct contact or radiation, the downstream heat engine can be operated continuously. However, the only possible heat source here is electricity. Recirculation of hot gases, for example from industrial waste heat, cannot be used here.

State-of-the-art heat accumulators differ from one another essentially in the type of sensitive heat accumulator material used, which is mainly steel, salt, concrete, aluminium, ceramic shaped bricks, special granulates or rock fill.

• • Aus DE102009012318A1 ist ein Latent-Wärmespeichersystem mit einer Mehrzahl von Speicherbehältnissen bekannt
• • WO2013167158A1 handelt von einem Langzeitwärmespeicher, wobei es im wesentlichen um die Geometrie und die Art der Isolierung zur langfristigen Speicherung von Wärme zu Heizzwecken geht.
• • DE102011017311A1 beschreibt eine einfache Bauart mit Schüttgutfüllung und Wärmeeinspeisung via Wärmepumpe.
• • EP3245466B1 beschreibt ein Verfahren einer modular aufgebauten Wärmeenergiespeicheranlage mit zwei Kreisläufen.
• • EP 2 698 505 A1 beschreibt ein Verfahren mit zwei Speichern und zwei Rohrleitungssystemen, entsprechend einer zweistufigen nachgeschalteten Stromerzeugung.
• • In WO2012127179A1 wird eine serielle Verschaltung einzelner Teileinheiten beschrieben, in denen sich eine „Wärmefront“ durch ein Schüttgut fortbewegt. Die Anlage ist darauf abgestellt, in allen Modulen ein möglichst hohes Temperaturniveau zu speichern und dann wieder abzugeben.
• • US20220170386A1 beschreibt eine Anlage mit Formkeramiken, die per Strahlungsheizung bis 1500°C arbeitet.

The essential patents on the subject:

• • Out of DE102009012318A1 a latent heat storage system with a plurality of storage containers is known
• • WO2013167158A1 is about a long-term heat accumulator, which is essentially about the geometry and the type of insulation for long-term storage of heat for heating purposes.
• • DE102011017311A1 describes a simple design with bulk material filling and heat input via a heat pump.
• • EP3245466B1 describes a method of a modular thermal energy storage system with two circuits.
• • EP 2 698 505 A1 describes a process with two reservoirs and two piping systems, corresponding to a two-stage downstream power generation.
• • In WO2012127179A1 a serial connection of individual sub-units is described, in which a "heat front" moves through a bulk material. The system is designed to store the highest possible temperature level in all modules and then release it again.
• • US20220170386A1 describes a system with molded ceramics that works with radiant heating up to 1500°C.

PROBLEMS:

1. 1. Bei der Aufladung der bisherigen Speicher mittels heissem Fluid ist der Wärmeaustausch nur bei hohen Temperaturdifferenzen zwischen Speichermedium und zugeführtem Fluidstrom effizient. Diese nimmt im Laufe der Aufheizung mit zunehmender Angleichung der Temperaturen ab, der Aufladestrom verlässt den Speicher dann zusehends wieder mit erheblicher Restenergie, die entweder verloren geht oder unnütz zirkuliert und dann für die gesamte Luftmenge hochtemperaturgeeignete Ventilatoren erfordert.
2. 2. Bei der Entladung kann nur die Energiemenge oberhalb eines gewissen Temperaturniveaus rückverstromt werden. Die gespeicherte Energie niedrigerer Temperatur kann nicht mehr genutzt werden, um eine Turbine oder eine andere Wärmekraftmaschine anzutreiben. Es verbleibt darum meist für den Grossteil der gespeicherten Wärme nur die Nutzung als Heiz- oder Prozesswärme. Die vielfach gepriesene Kraftwärmekopplung ist in diesem Zusammenhang tatsächlich nur eine Notlösung.
3. 3. Die Restwärme im zurückkehrenden Fluidstrom während des Entladezyklus liegt nämlich unterhalb der Temperatur der Wärmespeichermasse. Sie kann dem Speicher daher nicht wieder zugeführt werden, ausser, es würde gleichzeitig wieder nachgeheizt werden. Sie kann nur die erneute Energieentnahme aus dem Speicher im weiteren Verlauf reduzieren. Dies aber nur bis zur Schwelle der Eintritts-Temperatur des zurückkehrenden Fluides. Das Fluid kann dem Speicher keine Wärmeenergie entnehmen, die kälter ist, als es selbst.
4. 4. Bei der Ausnutzung von Überschussleistung zur Erwärmung weiss man nicht, wie lange diese zur Verfügung steht. Im ungünstigen Fall führt man dem Speicher erhebliche Mengen an Energie zu, aber erreicht nur einen sehr kleinen Abstand zwischen der erzielten Temperatur und der erforderlichen geeigneten Mindesttemperatur (z.B. 10h Aufheizung auf 550°C, effiziente Entladung 2h möglich bis 400°C).
5. 5. Bei Zeiten mit nur kleiner verfügbarer Aufladeleistung kann unter Umständen weder die gesicherte Mindestleistung direkt zur Verfügung gestellt werden, noch kann ausreichend Wärme zur ergänzenden Rückverstromung aus dem Speicher bereitgestellt werden.
6. 6. Stark schwankender Wärmeeintrag bei dem regelmässig ein verwertbares Temperaturniveau unterschritten wird.
7. 7. Speichermassenspezifische Nachteile: Bei Erwärmung durch elektrische Heizungen ist dies nicht in grobkörnige Schüttungen möglich. Für die Erhitzung von groben Schüttungen oder Oberflächen von Festkörpern sind unter Umständen Sekundärkreisläufe von Zweitmedien erforderlich, wodurch Verluste entstehen. Wenn Gasströme durch Schüttungen hindurchgehen, suchen sie sich den Weg des geringsten Widerstandes und führen zu Totbereichen und ungleichmässiger Wärmeverteilung.
8. 8. Bisherige modulare Speicher mit serieller Verschaltung sind derart ausgeführt, dass eine „Warmfront“ mit zunehmender Erhitzung sich nach und nach im Inneren eines jeden Moduls fortpflanzt, bis jeweils die Maximaltemperatur erreicht ist. Bei diesen Apparaten macht es daher keinen Sinn, Energie auf vergleichsweise niedrigem Temperaturniveau einzuspeisen. Temperaturmesseinrichtungen am Einlass oder Auslass können keinen repräsentativen Wert über die gesamte Wärmespeichermasse darstellen, sondern nur zwischen „aufgeladen“ und „entladen“ unterscheiden.
9. 9. Das Nacheinander-Durchströmen mehrerer Module ist nur begrenzt möglich: Entweder ist der Druckverlust in den Strömungswegen vorhandener Speicher zu gross, so dass nur wenige weitere Module durchströmt werden können, oder, das Heizfluid überträgt die Wärme erst nach Auskopplung an einen Sekundärkreislauf an die Wärmeträgermasse, so dass Umschalten zwischen Modulen nicht machbar ist.
10. 10. Wenn ein mit Höchsttemperatur aufgeladener Speicher Wärme an ein Gas abgibt, kann eine eventuell gewünschte niedrigere Gastemperatur nur durch Zumischung von Kaltluft erreicht werden. Das Konstanthalten der Temperatur der ausgekoppelten Wärme ist problematisch.
11. 11. Ein kontinuierlicher Betrieb einer nachgeschalteten Wärmekraftmaschine erfordert die Entkoppelung von Beladung und Entladung. Dies liess sich bislang nur mit elektrischer Widerstandsheizung per direktem Kontakt oder Strahlungsübertragung realisieren. Abwärme per Umluftkreislauf, zum Beispiel aus industriellen Prozessen, kann dann nicht genutzt werden.

Existing problems and technical improvements:

1. 1. When charging the previous accumulator using hot fluid, the heat exchange is only efficient if there are high temperature differences between the storage medium and the fluid flow supplied. This decreases in the course of heating up as the temperatures become more equal, the charging current then leaves the storage tank with considerable residual energy, which is either lost or circulates uselessly and then fans that are suitable for high temperatures are required for the entire air volume.
2. 2. When discharging, only the amount of energy above a certain temperature level can be converted back into electricity. The stored energy at lower temperatures can no longer be used to drive a turbine or other heat engine. Most of the stored heat can therefore only be used as heating or process heat. In this context, the widely praised combined heat and power system is actually only an emergency solution.
3. 3. The residual heat in the returning fluid flow during the discharge cycle is namely below the temperature of the heat storage mass. It can therefore not be returned to the storage tank unless it is reheated at the same time. It can only reduce the renewed energy withdrawal from the storage in the further course. However, this only up to the threshold of the entry temperature of the returning fluid. The fluid cannot take thermal energy from the storage that is colder than itself.
4. 4. When using excess power for heating, one does not know how long this will be available. In the worst case, the storage tank is supplied with considerable amounts of energy, but only a very small gap between the temperature achieved and the required suitable minimum temperature is achieved (e.g. 10 hours of heating to 550°C, efficient discharge of 2 hours possible to 400°C).
5. 5. At times when only a small amount of charging power is available, it may not be possible to provide the guaranteed minimum power directly, nor can sufficient heat be provided from the storage facility for additional conversion into electricity.
6. 6. Heavily fluctuating heat input that regularly falls below a usable temperature level.
7. 7. Disadvantages specific to the storage mass: When heated by electric heaters, this is not possible in coarse-grained fills. Secondary circuits of secondary media may be required for the heating of coarse bulk materials or surfaces of solid bodies, which results in losses. When gas flows pass through beds, they seek the path of least resistance, resulting in dead zones and uneven heat distribution.
8. 8. Previous modular storage devices with serial connection are designed in such a way that a "warm front" with increasing heating gradually propagates inside each module until the maximum temperature is reached. With these devices, it therefore makes no sense to feed in energy at a comparatively low temperature level. Temperature measuring devices at the inlet or outlet cannot represent a representative value for the entire heat storage mass, but only distinguish between "charged" and "discharged".
9. 9. Flowing through several modules one after the other is only possible to a limited extent: Either the pressure loss in the flow paths of the existing storage tank is too great, so that only a few more modules can be flowed through, or the heating fluid only transfers the heat to the after coupling to a secondary circuit Heat transfer mass so switching between modules is not feasible.
10. 10. If a storage tank that has been charged with a maximum temperature gives off heat to a gas, a possibly desired lower gas temperature can only be achieved by mixing in cold air. Keeping the temperature of the extracted heat constant is problematic.
11. 11. A continuous operation of a downstream heat engine requires the decoupling of loading and unloading. Until now, this could only be achieved with electrical resistance heating via direct contact or radiation transmission. Waste heat from the circulating air cycle, for example from industrial processes, cannot then be used.

SOLUTION OF THE PROBLEMS:

• 12. The sensible heat storage mass essentially consists of a combination of metal pipes and fine bulk goods. This combines the advantages of fast reaction time, high energy storage density (= little space required), low flow resistance and simple construction with inexpensive materials.
• 13. In addition, a latent heat storage mass can be provided, which is embedded in the bulk material in encapsulated form.
• 14. The charging and discharging streams are separated from each other, using different piping systems, and can therefore operate simultaneously and independently.
• 15. The residual heat after delivering the energy to a downstream heat engine is not waste heat, but is fed back to the storage tank.
• 16. The heat storage mass is divided into several separate and individually controllable areas in which different temperatures can prevail. Small volumes reach the desired final temperature more quickly when heat is applied in a concentrated manner.
• 17. The heat is distributed in a targeted and comparatively homogeneous manner in each module, not in the form of a warm front migrating through it.
• 18. A different operating mode can be selected as required, in which there is a switch between parallel, successive or serial flow (or a combination thereof) of several sub-areas, each with different individual temperatures.
• 19. Certain modules of the heat accumulator have a practicable minimum temperature (e.g. 500°C) for as long as possible, which enables reconversion using a heat engine.
• 20. The successive flow through several storage areas with a gradual temperature change serves to utilize otherwise unusable low-temperature thermal energy: The discharging current returning to the storage unit flows through different storage areas one after the other and releases its residual heat below the temperature range required for reconversion. The charging flow is preheated in counterflow with this low temperature.

STRUCTURE OF THE INVENTION:

1a shows the basic structure of the system, 2 until 4 show details on this. The system consists of a battery of individual but interconnected heat storage units [1 to 6] (“modules”). In the following figures, six cuboid modules are provided as an example. The representation of the modules in cuboid form is only intended to illustrate the functionality. A cylindrical shape could also be provided in an advantageous embodiment in terms of reducing heat losses and minimizing the cost of materials. In this case, the memory can be constructed from concentric or layered modules or modules arranged in sectors or a combination thereof. Cuboid modules, on the other hand, can be expanded more easily with additional modules. Examples of possible geometries are in 1b shown.

The heat storage system contains two media circuits that are independent of one another: a loading circuit [14] and a discharging circuit [12,13]. Both circuits meet in the modules without touching or mixing.

Each heat storage module, for example in 4 shown as a section, essentially consists of a thermally insulated container [16], which contains a heat storage mass [20] or a combination of several heat storage masses and the two pipe units [17 and 18] for loading and unloading. Exemplary designs of the internal piping systems are in 2 until 4 shown.

An advantageous embodiment of the invention provides that the two internal pipe systems [17 and 18] often span the entire length of a module and are deflected several times by 180°, thus forming a matrix-shaped bundle of parallel lines that evenly run through the storage module. Both pipe systems are at an angle of 90° or 180° to each other. They do not touch but penetrate each other. In the 2 and 3 The pipe systems shown take up the same space as in 4 shown. These piping systems transfer the heat from the charging stream to the store or from the store to the discharging stream, with the heat being evenly distributed in the store.

In addition, there are external piping systems outside the modules for distributing the charging and discharging flows, as well as an external collecting pipe that discharges the gas flows exiting the modules or directs them to another module (not shown in Fig 4 ). The modules are also connected to one another on the input side by return current lines or bypass lines. For the charging current, these are lines [7] and [9] on the input side, for In the discharge circuit, these are lines [10] and [11] ( 5 until 11 ). As shown, some of these can also be located inside the modules to reduce heat loss.

According to the state of the art, the gaps [20] inside each module between the individual tubes are filled with a suitable heat-storing bulk material with a low pore volume, for example quartz sand (specific heat capacity: 0.83 kJ/kgK). Typical values for the thermal conductivity of dry quartz sand are 0.3 W/mK (pore volume/solid volume = 1) to 0.6 W/mK (pore volume/solid volume = 0.5)

An additional optional advantageous embodiment is that a large part of the spaces between the individual tubes are first filled with shaped bricks, such as fireclay (specific heat capacity: 1.0 kJ/kgK) or soapstone (specific heat capacity: 0.98 kJ/kgK). , and that only the remaining volume, i.e. the gaps between the stones and pipes, are filled with bulk material.

Optionally, in an advantageous embodiment, latent heat storage tubes ("melt cores") [19] arranged horizontally in a grid-like manner can also be provided. These are pressure-resistant, hermetically sealed tubes that contain a latent heat storage material such as aluminum or certain types of salt. This melts or solidifies at certain temperatures and stores or releases energy through the phase change. The dimensions of these tubes should be selected so that the enclosed medium can expand when it melts or solidifies and, if necessary, there is a small residual volume for an inert, compressible filling gas on the liquid surface.

The horizontal position ensures that the melted material inside spreads out in the liquid phase over the entire length.

Ultimately, each storage module is densely interwoven with a network of pipes and melting cores, with fine bulk material and optionally stones in the spaces between them. All fixtures off 4 . inside the thermally insulated container [16] together form the heat storage mass. The higher the proportion of metal pipes in comparison to the bulk material mass, the greater the heat storage density. The diameters and wall thicknesses of the pipe systems [17 and 18] should therefore also be generously dimensioned in order to reduce the flow resistance.

BASIC OPERATION OF THE INVENTION

Loading and unloading of the modules with heat takes place independently of each other through two different media circuits in their own piping systems, which in 1 are shown. The internal piping systems are in 2 and 3 shown as an example.

During the charging process, a heated heat transfer fluid [20] circulates between the heat source and the heat accumulator. It is fed to one or more modules through an external distribution pipe system [7], where it flows through the internal heat input pipe system ( 2 ), heats up the heat storage mass and leaves the module at a reduced temperature through an external pipe collection system [8]. After reheating at a heat source, the medium returns to the heat accumulator.

The structure of the heat storage mass, which is evenly traversed by steel piping systems, which account for a large proportion of the total heat storage capacity, ensures a rapid response to temperature changes and an even distribution of temperature changes throughout the storage material volume. There is therefore no so-called "heat front" as in many other storage systems, but rather a homogeneous temperature change per module.

The removal of the stored heat is analogous to the charging, but by means of a different media circuit: An initially cold heat transfer medium [21] circulates between the storage and the heat engine in a different pipe system. It is fed to one or more heated modules through a central inlet pipe [12] and a distribution pipe [10], flows through the heat discharge pipe system ( 3 ), absorbs heat and leaves the system at a higher temperature through the outlet pipe [13]. After dissipating energy in a heat engine, it returns cooled to storage.

In each module, supplied heat is contained in the two internal piping systems themselves ( 2 and 3 ), stored in the melting cores and in the stone/bulk material combination. The two internal piping systems, the bulk material and the housing of the fusible cores store sensible heat. The melting material inside the melting cores stores sensible and latent heat.

When heating up (loading) a module, the internal charging pipe system [17] heats up first and transfers this heat to the bulk material and, if necessary, to the stones contained therein as well as to the unloading pipe system [18]. The melting cores [19] heat up through contact with the bulk material [20].

Fusible cores [19] should only be provided in modules where correspondingly high temperatures prevail. Aluminum, for example, has a melting point of 660°C. Alternatively, it can be provided in downstream modules with a low temperature that melting cores with a different melting material with a lower melting temperature are used.

Since the heat input takes place through a different pipe system than the heat discharge, it can take place according to the invention for each module independently and at the same time as the heat discharge. This is advantageous if the amount of heat supplied does not correspond to that to be dissipated, for example because it is only available cyclically or fluctuatingly.

This configuration also allows the charging stream to use a different medium than the discharging circuit. The former could, for example, also use oil, the latter, for example, steam. A secondary circuit for extracting energy for steam turbines is then unnecessary.

An additional heat input into the modules can advantageously take place directly in the individual modules by means of electrical heating devices. The electrical heating devices can also be arranged externally, in the inflow of the heating fluid.

1. 1. stark fluktuierende Beladeströme effizient zu verteilen und zu speichern, und
2. 2. gespeicherte Wärmeenergie auf niedrigem Temperaturniveau mit zur Rückverstromung auszunutzen, weil
3. 3. Module unterschiedliche, individuelle Temperaturen haben können, die
4. 4. Bei Bedarf nacheinander durchströmt werden und somit
5. 5. Zu einer stufenweisen Temperaturänderung der Gasströme führen,
6. 6. Wodurch eine Gegenstromwärmeübertragung zwischen Be- und Entladestrom realisiert wird, die
7. 7. Simultan oder zeitversetzt zwischen Beladung und Entladung stattfindet.

In addition to the simultaneous charging and discharging, the main point of the invention is the flexible connection of the modules to one another, which makes it possible

1. 1. Efficiently distribute and store strongly fluctuating loading currents, and
2. 2. to utilize stored thermal energy at a low temperature level for reconversion, because
3. 3. Modules can have different, individual temperatures
4. 4. If necessary, flow through them one after the other and thus
5. 5. Lead to a gradual change in temperature of the gas streams,
6. 6. By which a countercurrent heat transfer between charging and discharging is realized, the
7. 7. Simultaneously or with a time lag between loading and unloading.

The main advantage of the modular structure described is that small sub-areas can be controlled individually. The charging and discharging can always take place anywhere in the system with the highest temperature differences, and thus with the highest efficiency of heat transfer.

The activation or deactivation and the flow sequence of the individual modules is controlled electronically and automatically with valves. Temperature sensing devices on each module are linked to a central electronic controller that actuates valves to control the flow paths to and between the modules. This is not shown in the illustrations.

OPERATING MODES LOADING PROCESS:

5 until 8th show advantageous examples of the loading process. A first flow of medium [20] circulates between the heat source and initially cold storage. It is fed to one or more modules through the external distribution piping system [7]. After dissipating heat to the accumulator, it returns cooled down to the heat source through the external manifold [8]. The modules are charged with heat either in parallel (simultaneously) or one after the other (successively) or according to the invention in series (serial) or according to the invention from a combination thereof.

5 shows an example with successive charging of individual modules. The amount of heat supplied is concentrated here through the external distribution or loading pipe [7] and given to module 5, and the temperature only rises there. When a desired temperature of the storage mass is reached, a switch is made to another module. The medium then leaves the system through an external manifold [8] and returns to the heat source. This mode is advantageous if a lower amount of heat that is available for a longer period of time is fed in, but it should be ensured that at least one module should always have a minimum temperature.

6 shows an example with simultaneous (parallel) charging of modules 1-6. Here, the amounts of heat supplied and the temperature increases in the modules involved are the same; the maximum temperature is only reached somewhere in the system at the end of the charging process. This Operating mode is advantageous if a very large amount of heat (e.g. peak power from wind energy) is to be distributed evenly.

Since the efficiency of the heat exchange is greatest with high temperature differences, it decreases continuously in these two operating modes in the modules involved, and a lot of heat then circulates uselessly in the charging flow. The manufacturers of conventional systems do not address this point when naming the "storage efficiency".

7 FIG. 12 shows an example of a more advantageous embodiment of the flow switching where this disadvantage is avoided. It includes a partially serial charging. The inflowing hot heat transfer medium initially transfers energy simultaneously to the first three modules. It leaves these areas at a reduced temperature via internal return flow lines [15] and flows into the downstream module 4 via an external bypass line [9]. The heat transfer medium continues to cool down here. This process is repeated in the downstream modules 5 and 6, so that the medium is gradually cooled and the modules 4-6 are heated in stages, each with a lower temperature. The gas flow then leaves module 6 at the lowest temperature and only then flows back to the heat source through the external outlet line [8].

8th shows the consistent application of serial charging: The medium flow reaches module 1 via the external inlet pipe [7]. It then flows to the next module via the internal return flow pipe [15] and external bypass pipe [9]. This is repeated in all subsequent modules up to the last. The gas flow continuously loses temperature, the modules heat up accordingly in a cascade, so that there is finally a temperature gradient from module 1 to module 6. This configuration is feasible if suitable pipe diameters are chosen so that only acceptable pressure losses occur.

On the other hand, charging that results in all modules having the same temperature at the end of charging, namely the maximum temperature, is not desirable. This only means that the capacity of the system is exhausted and it is too small. The electrical heat storage efficiency would be lower because a lot of hot gas would have circulated uselessly between the heat source and the storage to achieve such a state.

OPERATING MODES DISCHARGE PROCESS:

9 until 11 show examples of possible configurations for the discharge process. Due to the charging with thermal energy, there is a temperature gradient from module 1 to 6.

A second flow of medium [21] circulates between the hot heat accumulator and the heat engine. Completely different pipelines are used here than for loading. After dissipating the heat to the machine, the cooled medium flow returns to the storage tank and is routed through the external pipes [12 and 10] to the modules.

In 9 . a parallel discharge of modules 2 and 3 is shown first. The heated medium flow leaves the storage tank with a mixed temperature of both modules through the external discharge pipe [13].

In addition to parallel and successive discharge, an advantageous embodiment also enables serial, i.e. stepwise discharge: 10 shows this process based on modules 6 to 3. The medium flows through the inlet pipe [12] and the external distribution pipe [10] first into the coldest module [6], where it warms up and then moves through a bypass return flow line in succession [11] into the next warmer module. In this way, according to the invention, the medium is heated in stages and the thermal energy at a low temperature level from the coldest module can also be used. According to the invention, this corresponds to a countercurrent heat exchange with serial loading, which has produced a temperature gradient from module 1 to module 6.

In this case, the thermal energy does not have to be extracted up to the hottest module. The heat transfer fluid can be removed from the system as soon as its temperature is sufficiently high (in the example at module 3) to enable reconversion in a heat engine. The temperature level from the modules not involved (modules 1 and 2 in the example) is initially spared. If the temperatures of the previously active modules drop during the course of discharging, residual heating can then also take place through heat extraction from the previously unused, hotter modules. This means that the coldest modules are discharged first and then the hottest.

11 . shows this case of serial charging based on modules 6 to 4. If, in this example, the temperature of the gas after leaving module 4 is not sufficient, a gas flow from an even hotter module can be mixed in. In the example off 11 this is module 2.

Since the purpose of the invention is to enable a constant amount of energy for reconversion, which is based on the nominal output of the downstream heat engine, a deduction of maximum output in parallel from several modules is not necessary, but still possible.

However, there is the case that the residual heat remaining in the storage is not sufficient to operate a heat engine efficiently. For this purpose, in the case of serial discharging, the warmest module can be reheated during discharging, so that a downstream heat engine can continue to be operated continuously and efficiently.

It is also conceivable that waste heat from an industrial process is fed into the storage facility, but its temperature fluctuates and regularly falls below a usable level. This heat with a fluctuating temperature can be directed to different modules in a targeted manner. According to the invention, a discharged gas stream can simultaneously circulate at a constant temperature--as described above--between the storage device and the downstream reconversion system and still ensure their continuous operation.

1. a) Serielle Beladung Modul 3 - 5
2. b) Serielle Beladung Modul 2 - 4
3. c) Serielle Beladung Modul 1 - 3
4. d) Serielle Beladung Modul 2 - 4
5. e) Serielle Beladung Modul 3 - 5
6. f) Serielle Beladung Modul 5 - 6
7. g) Usw.

12 describes an example of the course over time of such a fluctuating introduction of heat. About 40% of the time (horizontal axis) the temperature (vertical axis) is below the minimum usable temperature ("T _min ") for reconversion. With conventional heat storage, a downstream turbine would have to start and stop regularly. In addition, loading would first have to be stopped in order to enable unloading. In contrast, the smoothing of the fed-in thermal energy takes place in the present invention in that the heat is diverted to other modules at specific time intervals (vertical dashed lines). The time axis is divided into sections a to t. Exemplary and advantageous procedure for this case:

1. a) Serial loading modules 3 - 5
2. b) Serial loading modules 2 - 4
3. c) Serial loading modules 1 - 3
4. d) Serial loading modules 2 - 4
5. e) Serial loading modules 3 - 5
6. f) Serial loading modules 5 - 6
7. g) Etc.

The thermal energy below the usable level ("T _min ") is also fed in, stored and finally recovered.

According to the invention, thermal energy can be obtained continuously, regardless of whether or not heat is charged, since the discharge from the sufficiently hot modules takes place by means of a different pipe system and the modes of charging and discharging ensure that energy is also at a low temperature level can also be used as long as at least one module has a sufficiently high temperature level.

13 describes an example of a constellation with fluctuating regenerative energy production. In case a), a wind turbine [24] generates electricity and at the same time delivers excess power to the heat storage system. For this purpose, a resistance heater [23] generates heat in a first air circuit [20], which is installed in the loading circuit with the heat accumulator. The heat engine [22] is out of service.

In case b), the wind turbine is not in operation or only generates a small amount of electricity that is not used to charge the storage facility. The energy contained in the heat accumulator is conducted to the heat engine [22] by means of a second medium circuit [21], where it generates electricity [25].

SUMMARY OF BENEFITS:

1. (1) Dividing the entire heat storage capacity into smaller units is advantageous for production, installation, expandability and operation: according to the prior art, cuboid modules can, for example, be installed in commercially available containers and brought to the construction site ready-to-use.
2. (2) The volumetric heat storage density is 4 to 8 times higher than a lava rock heat storage due to the materials used and the smaller void volume. The storage density related to the mass is about twice as high as that of lava rock, but the volume of the storage is only 15...20% of this, assuming a storage temperature of only 750°C. The heat storage density is approx. 30% higher compared to special granules.
3. (3) Significantly higher temperatures can be absorbed than with concrete or pure steel storage tanks.
4. (4) The desired temperatures of the output flow can be kept constant with the same amount of air by switching between the modules. Heat can be taken from where the desired temperature prevails. It is not required in the external Use speed-controlled fans or air mixing devices in the gas cycle.
5. (5) Loading does not have to be interrupted for unloading. No operation on the device is required for switching. The downstream heat engine can therefore be operated continuously.
6. (6) The separation of the charging and discharging currents also enables the input of fluctuating amounts of energy with a regular drop below a usable temperature level with simultaneous continuous discharging according to the invention. As a result, heat can be obtained for longer and more heat can be fed in.
7. (7) Charging is carried out efficiently and in such a way that the residual temperature of the charging current exiting the storage tank is always low. Little residual heat circulates in the loading circuit, which also makes reheating at the heat source more efficient.
8. (8) In contrast to conventional heat accumulators, thermal energy at a low temperature level is also utilized according to the invention by stepwise temperature changes in countercurrent heat exchange. That's why it makes sense for the first time to feed such energy into the storage instead of leaving it unused or only using it for heating purposes.

Reference List

1

module 1

2

module 2

3

module 3

4

module 4

5

module 5

6

module 6

7

Distribution pipeline loading circuit

8th

Collection pipe on the outlet side of the loading circuit

9

Return flow/bypass line loading circuit

10

Distribution pipe discharge circuit

11

Bypass return line discharge circuit

12

Inlet piping discharge circuit

13

Discharge circuit discharge pipe

14

loading cycle

15

internal return flow line loading circuit

16

Thermally insulated module housing

17

internal loading piping system

18

internal discharge piping system

19

Fused cores (latent heat storage)

20

heat storage mass

21

Discharge circuit behind heat engine

22

heat engine

23

Heating device in the loading circuit

24

Renewable energy source. Here: wind turbine

25

Electricity generation at the heat engine

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102009012318 A1 [0017]
• WO 2013167158 A1 [0017]
• DE 102011017311 A1 [0017]
• EP 3245466 B1 [0017]
• EP 2698505 A1 [0017]
• WO 2012127179 A1 [0017]
• US20220170386A1 [0017]

Claims (5)

High-temperature heat accumulator, consisting of an electronic control system and shut-off devices, individual storage units ("modules") with solid storage masses and each module with two internal, separate, structured flow paths, as well as external piping systems, characterized in that: Modules are fluidically configured with one another in such a way that each storage module is loaded with thermal energy independently of the other modules by flowing a heating fluid through one of the two flow paths and at the same time each module is discharged independently of the other modules by flowing a cooling fluid through the other flow path of thermal energy can. Depending on the situation and switchable during operation, several modules from the previous claim can be flown through with a heating fluid in a serial or parallel or successive arrangement or from a combination thereof for charging with thermal energy. Depending on the situation and switchable during operation, several modules from previous claims can be flown through by a cooling fluid in a serial or parallel or successive arrangement or in a combination thereof for discharging thermal energy. By configuring the flow through the individual modules according to the previous claims, a simultaneous or time-delayed countercurrent heat exchange between charging and discharging flow can be implemented, in which the temperatures of the fluids change in stages as they flow through the modules. The heat storage mass contains a defined number of closed containers with a filling of phase change material, which are located in a defined position and arrangement inside the actual heat storage mass.

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