DE102013110117A1 - High-temperature heat storage - Google Patents

Abstract

The invention relates to a heat store (1) for storing heat energy in at least one heat storage block (2) and a removal device (3) for removal of stored heat energy. For uniform energy extraction from the memory is proposed that the heat storage block (2) and the removal device (3) are separated and designed to be displaceable relative to each other. At least one heat exchanger surface (4) for heat transfer from a fluid (5) or an electric heating element (6) into the heat storage block (2) may be provided in the heat storage block (2) and the removal device for removal of heat energy from the heat storage block (2) (3) at least one evaporator surface (7), for generating a phase change in a heat transfer fluid (8).

Description

The invention relates to a heat storage for storing heat energy in at least one heat storage block and at least one removal device for removing stored heat energy, and a method for controlling or regulating a withdrawal rate from such a heat storage.

Such heat storage with a feed device for the energy to be stored in the form of heat for long-term stable and uniform power output are known. They consist of a highly heat-resistant solid, which is capable of storing heat when heated, and means for decoupling the stored heat, preferably in the form of superheated steam or superheated steam. For example, the former can be used for the provision of district heating. The latter is necessary for the operation of steam turbines for power generation.

Currently, many different technologies are being used to store energy on a large scale. These technologies are necessary to facilitate the further development of renewable energies, e.g. Sun can drive wind, water, tides, etc. While most of these energy sources are abundant, they are not always when needed. Therefore, they must be stored on a large scale, so that even longer periods of undersupply can be covered by these stores. If this does not succeed, the security of supply must continue to be ensured by means of conventional shadow power plants, which in turn are then under-utilized for a long time. Maintaining the operational readiness of these shadow power plants is a very expensive backup solution.

A generic heat storage is from the DE 2117103 A known. The stored heat energy is stored in a single metallic block. This block is inductively heated, a spray nozzle protrudes into a cylindrical recess, which serves to evaporate the water introduced from the spray nozzle. The generated steam is condensed and fed back into the spray nozzle in a cycle.

From the German utility model DE 7010442 U a boiler is known for heating water. It has a thermal storage core and means for heating the core to a temperature above the boiling point of water. Above the core, a steam and water space is arranged. A tube extends from the steam and water space above the core into the core. In addition, means are provided which provide said space with a water supply source and passage into the tube. The system of water supply is self-regulating such that it maintains a pressure equal to the supply pressure, which can be very low. The water can be removed for this purpose from an auxiliary reservoir and fed to the system.

The resulting steam is condensed by the supplied cold water. The water is thereby heated and can be supplied from the space above the core as hot water to a heater. This prior art system limits the removable temperature or medium substantially to the removal of hot water. Steam is not provided. The quantities of heat removed are thus at a temperature level below the boiling point.

The DE 6806870 U relates to an electrically heated heat storage furnace. The memory core consists of memory blocks of ceramic material, which are crossed by metallic channels that form a heating coil for the generation of hot water, steam or the like. This document is based on the object to ensure a good heat transfer from the memory core to the heater even at low storage temperatures. For this purpose, metallic channels forming the heating register are provided with enlarged surfaces. The metallic channels forming the heating register are arranged vertically in the ceramic material, whereby nothing is said about the switching of the channels and even more about the presence and configuration of any vapor collecting space.

The GB 1344486 A describes a water heating system in which horizontal evaporator tubes are embedded in thermal storage blocks made of refractory material. The memory blocks are electrically heated. The horizontally arranged evaporator tubes are connected with their open end to a vertical steam pipe. The vertical steam tube forms a U which terminates with one open end in a closed condensate tank and the other end in an open part of a container. The container and the closed condensate tank are approximately at the same level. The heat is dissipated from the condensate compartment via a heat exchanger. Since the steam pipe ends above the condensate level, the resulting condensate is fed via a separate line to the U-shaped end of the steam line, thereby resulting in a condensate circuit as soon as the condensate level in the condensate tank exceeds the open top end of the condensate return line.

The invention has for its object to dramatically increase the temperature level and thus the heat storage amount of solid heat storage without the associated negative impact of these high temperatures also exposed materials, such as steel, ie the steel pipes to accept, otherwise the long-term durability of a drastically limit such energy storage.

Moreover, it is an object of the invention to propose a method which allows the system parts gentle and uniform removal of heat from the heat storage.

[A01] The device task is solved in a heat storage for storing heat energy in at least one heat storage block and at least one removal device for removing stored heat energy, characterized in that the heat storage block and the removal device are separated and slidable relative to each other. As a result of the separation, temperature differences between the removal unit and the heat storage block can not cause any mechanical stresses between the two parts otherwise formed as a unit. The structural separation of the extraction unit and heat storage block allows an increase of the storage temperature to a level which is free from the limits of the materials used in the extraction unit.

Consequently, the present invention is characterized by an extremely high possible storage temperature and thus energy density, as well as the highest possible efficiency of the overall process, which is achieved by the constant output temperature / output over a wide temperature range of the storage.

So this is done by separating the actual energy storage, i. the memory block and the device necessary for energy dissipation, i. reached the extraction unit.

The energy storage takes place in a memory block of a ceramic material, which allows long-term stable very high storage temperatures. The ideal material has a maximum temperature resistance to store more energy through higher temperatures, as well as a high specific gravity / spec. Heat capacity to store a maximum of energy per room unit. For this purpose, different materials are suitable, which can be found in the technical parameters, such as the spec. Heat capacity and temperature resistance as well as differ in cost. Chamotte with a high content of Al2O3 (eg grade A40t) allow, for example, already application temperatures of about 1,450 ° C. At the same time they offer with a spec. Density of up to 2.15 g / cm ³ also a comparatively high spec. Heat capacity. However, there are also technical ceramics used whose temperature range can be much higher, but usually disadvantages in terms of spec. Have heat capacity, which can completely or partially cancel the advantage of higher temperature.

[A02] In an embodiment of the invention it is provided that at least one heat exchanger surface for heat transfer from a fluid or an electric heating element are provided in the heat storage block in the heat storage block. Alternatively, heat can be stored in the heat storage block either by means of a fluid or by means of an electrical element, a so-called heating cartridge in the heat storage block. The feed takes place via the at least one heat exchanger surface, which is advantageously designed as a surface storage material, so that there are no material differences that can lead to mechanical stresses. As the fluid, both high-temperature gases and liquid metals can be used.

The heat is presently preferably introduced into the storage block via electric heating cartridges. However, it is also possible that the heat to be stored, as soon as technically suitable and economically useful fluids, e.g. Liquid metals, are available to use fluids for storage. The high temperatures may well be e.g. be produced with parabolic trough solar systems. The liquid medium is passed under low pressure in ceramic tubes through the heat storage. The direct introduction of concentrated thermal radiation is also possible via focusing and reflection.

In any case, from the point of view of economic efficiency and the achievable efficiency, it makes sense and is necessary to achieve the highest possible storage temperature.

[03] In a further embodiment of the invention, it is proposed that for removal of heat energy from the heat storage block, the extraction unit has at least one evaporator surface for generating a phase change in a heat transfer fluid or for further overheating of a fluid that has already exceeded the point of phase change. To remove the stored energy evaporator surfaces are provided in the extraction unit, where there is a phase transformation of a liquid passing. In general, this liquid will be water, but at other temperature levels, other liquids are also applicable. at Using water as a liquid, it is advantageous to increase the temperature level when this phase change takes place at higher pressures.

However, this basic principle is opposed by the materials available today, with the exception of the storage material itself. Here, first of all, the lack of creep rupture strength of the available steels should be mentioned. First and foremost, this limits the maximum temperature that these steels may be exposed to. Since the discharge of the stored heat i.d.R. takes place in the form of superheated steam or superheated steam under very high pressures of a few hundred bar, high-strength pipes are necessary.

[A04] Advantageously, it is therefore provided in a further embodiment of the invention that the evaporator surface is preferably formed by the inner surface of at least one tube, which is preferably embedded in a block whose material corresponds in particular to the material of the heat storage block.

This is the basic principle of this invention. The memory block, in which there are no metallic components except the heating element itself, is separated from the device for heat extraction and can thus be heated to the maximum temperature of the storage material or the maximum temperature of the devices for heat input, for example. The heating cartridges themselves, without the to damage steel used in the device for heat extraction.

According to this invention, the removal of the stored heat then takes place by means of a removal device made of a likewise highly heat-resistant block, i. the so-called heat extractor, in which pipes are embedded as a heat exchanger, in which the introduced medium, i.d.R. is the water is evaporated or else in the example. Injected steam is further overheated. The superheated, under very high pressure steam is then used for the operation of steam turbines for power generation. Of course, the heating of any other gases or liquids in this way is possible. Alternatively, it is also possible to dispense with the heat-resistant block and to work only with a tube collector bundle for heat removal. The tube collector bundle can additionally be equipped with exchanger surfaces.

[A05] The measure that the heat storage block, the removal device is at least partially enveloping, serves to increase the withdrawal power. The design and dimensioning of the degree of coupling between the heat storage block and removal device can be influenced in many areas. The functions of the coupling as a function of the distance between the heat storage block and removal device is adjustable by the design of the area in which the heat storage block encloses the removal device. For example, in the case of a cylindrical envelope, the coupling increases linearly with the reduction of the distance, while if the sampling device is immersed in a conical trough, the coupling increases progressively with the distance.

The heat transfer between the heat storage block and the heat extractor is carried out at very high temperatures mainly by thermal radiation. The heat output, which is transmitted by thermal radiation to the heat extractor, is controllable and / or controllable by a controllable distance between the movable heat extractor and the actual heat storage. The objectives of this controllability are on the one hand the regulation of the output power of the memory. Even more important, however, is to increase the temperature of the heat extractor, regardless of the actual storage temperature, beyond the limits imposed by the creep rupture of the heat exchanger embedded therein.

From the mechanical decoupling of energy storage and heat extractor results that the temperature of the memory can be much higher than in all other known concepts, since no steel-based metallic materials are exposed directly to this high temperature. So are storage temperatures, like the o.g. To reach 1,450 ° C with known from the high-temperature furnace construction technology and also to exceed when using suitable materials.

[A06] As an advantageous form of wrapping is proposed in an embodiment of the invention that the heat storage block in the region of the envelope concave and the sampling device is at least partially convex.

[A07] A reduction of heat losses is achieved when the heat storage block and the removal device are arranged in a common housing, which preferably has a negative pressure. The negative pressure causes a better isolation from the environment. Heat conduction and convection, which could lead to heat loss, are reduced.

[A08] In a further embodiment of the invention, it is provided that the heat storage block and the removal device are arranged in a common, preferably vertical axis, wherein the distance from the heat storage block and the removal device can be changed by a motor is formed and preferably the weight of the moving part of the heat storage block or the removal device is at least partially compensated. The possibility of changing the distance between the removal device and the heat storage block, allows a regulation and / or control of the heat released quantities in a wide range.

At the same time, it is possible to keep the output power of the memory constant over a wide temperature range of the memory, since the heat sinking by decreasing storage temperature and thus the decreasing radiation power of the heat storage is counteracted by reducing the distance between the heat exchanger and heat storage. The ideal extraction temperature is thus achieved via a simple control whose reference variable is the desired extraction temperature and whose actuator is the device for changing the distance and whose controlled variable is the actual temperature of the heat extractor. This goes up to the mechanical contact between heat extractor and heat storage, whereby in the course of further cooling, the decreasing heat radiation is increasingly replaced by direct heat conduction between the two bodies. If the storage tank temperature falls below the value of the defined and adjustable ideal temperature for removal, then the output power and the achievable maximum output temperature from the storage tank decrease as the temperature continues to fall and thereby also the efficiency of the overall process. In terms of optimum overall efficiency, the output temperature should always be kept at the technically feasible maximum. If the greatest possible memory range is in the foreground, then the memory can also be cooled further at the expense of efficiency.

In this case, the stored energy can be exploited to an unavoidable minimum. For example, by a combination operation, by using very high storage temperatures in favor of the optimum efficiency for generating superheated steam. If the temperature of a storage block falls below the optimum temperature for steam superheating, the residual temperature via heat exchangers can be used almost lossless for water evaporation, especially in multi-stage steam superheating, or at the end of the temperature scale to provide heat for heating purposes.

[A09] The physical laws of heat transfer from heat storage block to the sampling device can be adapted within wide ranges, if in a well formed by the heat storage block a quantity of heat-conducting fluid is provided. Preferably, a liquid metal is selected as the fluid, so that the liquid metal transfers heat by means of convection. The physical laws of heat radiation are decisive only for those partial surfaces in which the intermediate space between the heat store and the removal device is not filled with liquid metal.

• • Solange die Speichertemperatur im Bereich oberhalb der Zieltemperatur des Wärmeauskopplers liegt, erreicht man den derzeit technisch höchstmöglichen Wirkungsgrad für den gesamten Kraftwerksprozess.
• • Die spezifischen Kosten pro kWh gespeicherter Wärme sinken erheblich, da die auf diese Weise sehr viel höhere Speichertemperatur auf die Kosten des Speichers selbst keinen nennenswerten Einfluss hat. Lediglich durch eine verstärkte Isolierung muss höheren Speichertemperaturen Rechnung getragen werden, will man nicht höhere Wärmeverluste hinnehmen, die durch das höhere Temperaturgefälle zur Umgebung ansonsten entstehen würden.
• • Der Speicher kann sehr wartungsfreundlich konstruiert werden, so dass alle möglicherweise wartungs- oder reparaturbedürftigen Bauteile, nach Entfernung der Isolierung, von oben zugänglich sind. So kann sowohl der Wärmeauskoppler als auch die Heizpatronen ohne Herunterfahren des Speichers unter Einhaltung entsprechender Sicherheitsmaßnahmen ausgebaut und gewechselt werden.
• • Die erhöhte Energiedichte durch die höhere Temperatur ermöglicht kleinere Speicher bei gleichem Energieinhalt.
• • Die Lebensdauer der eingesetzten metallischen Werkstoffe im Wärmeauskoppler kann durch die regelbare Temperatur des Wärmeauskopplers bestimmt werden. Durch entsprechende Wahl der Temperatur kann entweder der Wirkungsgrad und die Leistung oder die Lebensdauer favorisiert werden.
• • Da der Speicher und der Wärmeauskoppler aus nur wenigen einfachen Bauteilen besteht, sind deren Herstellkosten vergleichsweise gering. Die notwendigen Regel- und Stellglieder sind ebenfalls sehr einfach auszulegen und zu bauen. So können durch den Einsatz von Gegengewichten die notwendigen Kräfte und damit die Aktuatoren für die Bewegung des Wärmeauskopplers sehr klein gehalten werden. Die Temperatur des Speichers und des Wärmeauskopplers wird intervallweise oder permanent gemessen, um daraus die notwendige Stellgröße für die Korrektur ableiten zu können.

[A10] The method task is solved by a method for controlling or controlling a withdrawal rate from a heat storage by changing a distance of the heat storage block and the removal device. This results in particular the following advantages:

• • As long as the storage tank temperature is in the range above the target temperature of the heat extractor, the currently highest technical efficiency is achieved for the entire power plant process.
• • The specific cost per kWh of stored heat drops significantly, as the much higher storage temperature in this way has no significant impact on the cost of the store itself. Only through a reinforced insulation higher storage temperatures must be taken into account, you do not want to accept higher heat losses that would otherwise arise due to the higher temperature gradient to the environment.
• • The storage tank can be designed to be very easy to maintain so that any components requiring maintenance or repair can be accessed from above once the insulation has been removed. Thus, both the heat extractor and the heating cartridges can be removed and replaced without shutting down the memory in compliance with appropriate security measures.
• • The increased energy density due to the higher temperature allows smaller storage tanks with the same energy content.
• • The service life of the metallic materials used in the heat extractor can be determined by the controllable temperature of the heat extractor. By appropriate choice of temperature, either the efficiency and the performance or the lifetime can be favored.
• • Since the memory and the heat extractor consists of only a few simple components, their production costs are comparatively low. The necessary control and actuators are also very easy to design and build. Thus, the use of counterweights, the necessary forces and thus the actuators for the movement of the heat extractor can be kept very small. The temperature of the Memory and the heat extractor is measured at intervals or permanently, in order to derive the necessary manipulated variable for the correction.

[A11] However, it is also advantageous to use the heat accumulator for heating purposes in buildings. This is where the advantages of the high storage temperature come into their own. The sampling device can be controlled at any time so that the introduced water does not evaporate, but only heated. Thus, the memory takes over the function of a water heater and can thus replace the usual boiler including hot water tank.

A preferred embodiment of the invention will be explained by way of example with reference to a drawing. The figures of the drawing show in detail:

1 a schematic perspective view of a heat accumulator according to the invention,

2 a schematic plan view of the heat storage according to the invention,

3 a vertical section through the heat accumulator according to the invention under load according to section line AA in 2 .

4 a vertical section through the heat accumulator according to the invention under load according to section line BB in 2 .

5 a vertical section through the heat storage according to the invention according to section line CC in 6 in the decoupled state and

6 a schematic plan view of the heat storage according to the invention 5 ,

In the 1 shown schematic perspective view of the heat accumulator according to the invention 1 shows the structure of the heat storage 1 in a heat storage block 2 and a sampling device 3 , The heat storage block 2 and the sampling device 3 lie on a common central axis 16 and are in this axis 16 displaceable relative to each other. For the sake of clarity, the drives to enable this displacement are not shown. The removal device 3 indicates at its top 21 several supply lines 22 for supplying water. The in the removal device 3 steam is formed via the steam pipe 23 from the sampling device 3 taken.

2 shows a plan view of the heat accumulator according to the invention. That for the production of steam by supply line 22 supplied water first flows into annular manifolds 24 which makes it into vertically oriented tubes 10 is directed. The in the removal device 3 generated steam is then through the steam line 23 taken.

The heat storage block 2 is by means of four heating elements 6 heated, the evenly distributed in the corner areas of the memory block 2 are arranged.

The more detailed structure of the heat storage block 2 and the sampling device 3 can be the vertical section through the heat storage according to the invention under load according to section line AA of 3 remove. That through the supply lines 22 the removal device 3 supplied water is from the ring distributors 24 through pipes 10 first vertically into a block 11 of a material 12 passed, in which the pipes 10 embedded, and so a Tauscherkopf 25 form. There follows the line 10 in vertical section in about the outer contour 26 of the exchange head 25 , then rising vertically in a steam room 27 to flow into. Between the case 15 the removal device 3 and the exchange head 25 is an insulator 28 arranged, which reduces heat losses to the environment of the heat accumulator.

In 4 is a vertical section shown, the heat storage 1 diagonal cuts, so that also in the heat storage block 2 provided heating cartridges or heating elements 6 are visible. The heating function of the heating element 6 may also be from a fluid passed through 5 be taken over, which has the appropriate temperature. Also the memory block 2 is from a good thermal insulator 28 in the case 15 surrounded, so that also an uncontrolled heat loss from heat storage block 2 is avoided. The housing 15 of removal device 3 and heat storage block 2 Partially wrap themselves. Like that 3 and 4 can be seen, they are telescopically mutually displaceable. This allows the distance 17 between heat storage block 2 and removal device 3 change. For modification, suitable drives are provided which the skilled person can form, for example, as piston-cylinder units or spindle nut drives which are synchronized with one another.

From the steam room 27 the generated steam is collected by means of a collecting bell 30 taken and over steam line 23 for example, supplied to generate electrical energy of a turbine.

The material 13 of the heat storage block 2 is preferably a dense high temperature resistant mass, which is suitable to absorb a corresponding amount of heat energy. The material 12 the removal device 3 can be made of the same material exist, so that both materials have a similar expansion behavior. The outer contour of the exchange head 25 is bell-shaped convex and immersed in a correspondingly negatively shaped trough of the material 13 of the heat storage block 2 one. The heat transfer between the heat storage block 2 and the sampling device 3 initially based primarily on thermal radiation. But it can also be based on convection, if the space between sampling device 3 and the heat storage block 2 is filled by a fluid, preferably a liquid metal. In 3 in the form of blackening is such a liquid medium 31 shown. The upper mirror of the medium 31 is located below the top of the trough 18 ,

The representations of the 3 and 4 thus show the state in which from heat storage block 2 Heat over the exchange head 25 is removed. Ie that the exchange head 3 with the heat storage block 2 thermally coupled.

The decoupled state, in which no significant heat from the heat storage block 2 is taken in the 6 and 5 shown. The 6 shows a vertical section, as previously in 3 shown, but with a much higher distance 17 the removal unit 3 from the heat storage block 2 , In this illustration, the convex profile of the block 11 the removal device 3 and the area 14 correspondingly concave trough 18 of the memory block 13 ,

Had the liquid medium 31 in 3 almost the entire space between the material 12 the removal device 3 and the material 13 the heat storage 2 taken, this is the medium 31 in 6 in the lower part of the hollow 18 collected. A bulkhead 32 forms the upper end of the trough 18 , Because the exchange head 25 through the bulkhead 32 completely from the heat storage 2 is disconnected, finds no heat transfer between memory block 2 and the sampling device 3 instead of.

LIST OF REFERENCE NUMBERS

1

heat storage

2

Heat storage block

3

removal device

4

Heat exchanger surface

5

fluid

6

heating element

7

evaporator surface

8th

Heat transfer fluid

9

Inner surface of the pipe

10

 pipe

11

 block

12

 material

13

 material

14

 Area

15

 casing

16

 axis

17

 distance

18

 trough

19

 fluid

20

21

 top

22

 leads

23

 steam line

24

 distributor

25

 exchanger head

26

 outer contour

27

 steam room

28

 insulator

29

 distance

30

 collecting bell

31

32

 bulkhead

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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.

Cited patent literature

• DE 2117103 A [0004]
• DE 7010442 U [0005]
• DE 6806870 U [0007]
• GB 1344486 A [0008]

Claims (11)

Heat storage ( 1 ) for storing heat energy in at least one heat storage block ( 2 ) and at least one removal device ( 3 ) for the removal of stored heat energy, characterized in that the heat storage block ( 2 ) and the removal device ( 3 ) are separated and designed to be displaceable relative to each other. Heat storage according to claim 1, characterized in that in the heat storage block ( 2 ) at least one heat exchanger surface ( 4 ) for heat transfer from a fluid ( 5 ) or an electric heating element ( 6 ) in the heat storage block ( 2 ) is provided. Heat storage according to claim 1 or 2, characterized in that for the removal of heat energy from the heat storage block ( 2 ) the removal device ( 3 ) at least one evaporator surface ( 7 ) for generating a phase change in a heat transfer fluid ( 8th ) or to further overheat a fluid that has already exceeded the point of phase change. Heat storage according to claim 3, characterized in that the evaporator surface ( 7 ) preferably through the inner surface ( 9 ) of at least one pipe ( 10 ), preferably in a block ( 11 ) whose material ( 12 ) especially the material ( 13 ) of the heat storage block ( 2 ) corresponds. Heat storage according to one or more of the preceding claims, characterized in that the heat storage block ( 2 ) the removal device ( 3 ) is formed at least partially enveloping. Heat storage according to one or more of the preceding claims, characterized in that the heat storage block ( 2 ) in areas ( 14 ) concave and the sampling device ( 3 ) is formed at least partially enveloping convex. Heat storage according to one or more of the preceding claims, characterized in that the heat storage block ( 2 ) and the removal device ( 3 ) in a common housing ( 15 ) are arranged, which preferably has a negative pressure. Heat storage according to one or more of the preceding claims, characterized in that the heat storage block ( 2 ) and the removal device ( 3 ) in a common, preferably vertical axis ( 16 ), the distance ( 17 ) of heat storage block ( 2 ) and the removal device ( 3 ) is designed to be motor-changeable and preferably the weight of the moving part of heat storage block ( 2 ) or the removal device ( 3 ) is formed at least partially compensated. Heat accumulator according to one or more of the preceding claims, characterized in that in one of the heat storage block ( 2 ) formed trough ( 18 ) a quantity of a heat-conducting fluid ( 19 ) is provided. Method for controlling or regulating a removal capacity from a heat accumulator according to one or more of the preceding claims, characterized in that a distance of the heat storage block and removal device is changed. Use of a heat accumulator according to one or more of claims 1 to 9, for heating purposes in buildings.

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