WO2014124747A1

WO2014124747A1 - Heat accumulator and heat-accumulator power plant

Info

Publication number: WO2014124747A1
Application number: PCT/EP2014/000376
Authority: WO
Inventors: Lars Zoellner; Klaus Knop
Original assignee: Carbon-Clean Technologies Gmbh
Priority date: 2013-02-12
Filing date: 2014-02-12
Publication date: 2014-08-21
Also published as: DE102013004330A1

Abstract

The invention relates to an electrically heatable heat accumulator (2) for converting electrical energy into thermal energy and for the storage of the thermal energy and time-shifted transfer of the thermal energy to a heat-accumulator power plant (22, 23), wherein the transferred thermal energy is converted back into electrical energy via mechanical energy in the heat-accumulator power plant (22, 23), and/or for the time-shifted output of process heat, comprising a plurality of heat accumulator modules (1), wherein each heat accumulator module (1) has at least one electrical heating resistor (3) for converting electrical energy into thermal energy, at least one heat-storage material that can be heated by the heating resistor (3), and flow channels for a heat-transfer fluid (13) and wherein heat accumulator modules (1) can be individually controlled and can be supplied with current independently of each other for the partial or complete charging of the heat accumulator (2).

Description

Heat storage and heat storage power plant

The invention relates to an electrically heatable heat accumulator for converting electrical energy into thermal energy, in particular for using overcapacities in a power grid and / or for ensuring the grid stability of a power grid, and / or for converting fluctuating electrical energy from renewable energy sources, such as wind energy. and / or solar energy, and for the storage and time-shifted transmission of thermal energy to a heat storage power plant, wherein the transmitted thermal energy is converted back into electrical energy in the heat storage power plant via mechanical energy, and / or for time-delayed extraction of process heat. Moreover, the present invention relates to a heat storage power plant with at least one heat accumulator of the aforementioned type.

The development and utilization of renewable renewable energy sources, such as wind and solar energy, but also geothermal and tidal energy, alternatively or in parallel to conventional energy production from fossil fuels, always wins against the background of long-term exhausting fossil fuels and global warming by climate gases more important.

In the area of the use of renewable energy sources for power generation is disadvantageous that the natural supply situation is difficult to predict and subject to natural fluctuations. For example, due to changes in weather, daily or seasonally, either energy generation peaks or else energy production valleys occur in regenerative energy production. The fluctuating electricity production, due in particular to weather, daily or seasonal influences, is offset by a non-constant demand for electricity by the consumer.

If electricity from renewable energy sources is fed into a public power grid, power generation peaks and power generation valleys can lead to significant problems, since adapting power plant technology to fluctuating amounts of electricity fed into the power grid is only possible with considerable effort. For example, occur in the production of electrical energy from wind energy weather-related unpredictability of electricity production, conventionally operated power plants are driven in peak times when wind down with maximum load, while, for example, in times in which sufficient wind is available to generate electricity, the energy purchase quantities can be so low that the power plant must be underloaded, resulting in higher carbon dioxide emissions. Moreover, if operators of wind turbines can not feed the electricity due to impending network overload in the power grid, a shutdown of the wind turbine is required, resulting in a decrease in the efficiency of the operation of the wind turbine.

Therefore, in the field of using regenerative energy sources for power generation, there is a need for an economical and efficient method for storing regeneratively generated and / or excess electrical energy against the background of the balancing of production peaks and production valleys.

EP 1 577 548 A1 and EP 1 577 549 A1 disclose processes for storing energy and generating electricity, wherein a heat accumulator is heated by means of renewable energy, such as wind energy or solar energy. If necessary, the heat is used in the heat storage to generate steam that is fed directly to a thermodynamic process in a steam turbine, the steam generation is optionally complemented conventionally. A similar method is known from WO 2009/1 12421 A1, wherein a heat storage, a heating element for storing energy from the power grid in the heat storage and a heat exchanger having a primary side and a secondary side are provided in a device for using excess capacity in the power grid, wherein the primary side is thermally coupled to the heat storage for the removal of heat from the heat storage and wherein the secondary side is connected in a power plant and the power plant comprises a gas turbine.

US 5,384,489 describes an apparatus in which electrical energy is generated by wind energy, with which a heating element is operated to heat a fluid in a storage tank, and a device to withdraw the stored energy from the tank again. The energy extracted from the storage tank is used for space heating / room cooling, for cooling in general, Desalination, but preferably used for steam generation to generate electricity.

Object of the present invention is to provide a heat storage and a heat storage power plant of the type mentioned, the heat storage should have a low memory complexity. The heat storage and the heat storage power plant should allow a simple and cost-effective use of excess capacity in the power grid. In particular, the reduction of excess capacity in the power grid and the provision of electrical power at short-term high consumption peaks should be as flexible and as short a time as possible.

The above objects are achieved by an electrically heatable heat storage with the features of claim 1 and by a heat storage power plant with the features of claim 12. Advantageous embodiments emerge from the subclaims.

In a preferred embodiment of the invention, the heat storage device has a plurality of heat storage modules, each heat storage module having at least one electrical heating resistor for converting electrical energy into heat energy, at least one heat storage material heatable by the heating resistor, and flow channels for a heat transfer fluid, and wherein partial or complete loading of the heat accumulator several heat storage modules, preferably all heat storage modules, individually or individually controllable and can be energized independently. For this purpose, a corresponding electrical circuit and at least one switch and, preferably, a control or regulating device for controlling or regulating the number of the energized heat storage modules can be provided. The number of energized heat storage modules is determined depending on the available or a power grid to be taken amount of electricity. This allows reacting very quickly to varying amounts of electricity. Depending on the availability of excess electricity in a power grid, the number of heat storage modules energized can be changed in order to be able to extract the largest possible amount of electricity from the power grid.

The heat storage according to the invention allows a very fast network stabilization and is characterized by a low storage complexity. Through Men of a heat storage module or multiple heat storage modules can be different amounts of electricity very quickly converted into thermal energy, which is then transferred time-shifted in more fuel-intensive times to the heat transfer fluid. Subsequently, the reconversion takes place in the heat storage power plant.

The heat accumulator according to the invention has a modular construction with a plurality of electrically heatable heat storage modules, wherein each heat storage module has at least one separate electrical heating resistor and wherein the total heat content of the heat storage substantially equal to the sum of the heat contents of the heat storage modules. By energizing the heating resistor, electrical energy from the heating resistor can be converted into heat energy, which is at least partially transferred to the heat storage material and then stored predominantly by the heat storage material and to a lesser extent by the heating resistor.

The heat transfer fluid can be used as a working fluid in a power plant process. The heat storage power plant may, for example, at least one of the heat accumulator upstream compressor for compressing the heat transfer fluid and at least one turbine downstream of the heat storage for expanding the heated heat storage in the heat transfer fluid performing mechanical work and a generator for converting the mechanical work into electrical energy. In this embodiment, the heat transfer fluid, which is preferably compressed air, flows through the heat accumulator and then serves as working fluid in the power plant process. The heat accumulator may be formed in this context as a pressure vessel and / or it may be the flow channels for the heat transfer fluid under pressure. Alternatively, water as a working fluid of a steam cycle can flow through the heat accumulator and be expanded in a steam turbine of the heat storage power plant. Also, the heat transfer fluid can be used as working fluid in combined gas and steam processes. Also, an indirect heat transfer from the thermal storage medium flowing through the heat transfer fluid to a working fluid of the power plant process is possible. For this purpose, a heat transfer between the heat transfer fluid and the working fluid is preferably carried out via at least one heat exchanger downstream of the heat exchanger. For example, hot air from the heat accumulator may be provided to generate steam as a working medium for a steam process and / or a combined gas and steam process. The heat storage module preferably has one or more heating resistors, wherein each heating resistor is preferably formed by a high-resistance wire or rod made of electrically conductive material, in particular iron or steel, such as structural steel or reinforcing steel, which is used as reinforcement in reinforced concrete. Also stainless steels can be used. Preferably, the heating resistor consists of an iron-aluminum alloy, wherein a passivating or corrosion-inhibiting surface layer of the heating conductor can be formed by aluminum. As a material for the heating resistor and a chromium-nickel alloy can be used. The wire or rod then forms a heating conductor of the heat storage module. The heating resistor is preferably formed in one piece, but may also consist of a plurality of electrically interconnected conductor sections. In addition, the heating resistor need not be designed as a high-resistance wire or high-resistance rod. As a heating resistor, for example, a heating cartridge may be provided, namely a cylindrical metal cartridge as a housing with an inside turned heating coil. It is essential that the heating resistor is heated according to the invention by energization and can deliver its heat directly to the working fluid.

Each heating resistor can be connected via connection contacts of the heat storage module with a power grid. If the heat storage module has a plurality of heating resistors, these can be electrically connected to one another in any circuit arrangement, with basically two connection contacts already being sufficient to supply several or all of the heating resistors of a heat storage module. However, it can also be provided that, in the case of a plurality of heating resistors, each heating resistor can be connected to the power supply system via separate connecting contacts.

The heat storage capacity of the heat storage module is preferably in the range between 0.5 MWh and 10 MWh, more preferably between 1 MWh and 5 MWh. The loading capacity of the heat storage module related to the volume of the heat storage module can be between 0.1 MW _t hermisc m ³ to 5 MW _t hermic / m ³ , preferably between 0.5 MWthermisch m ³ to 1, 5 MWthermisch m ³ , in particular approximately 0, 8 MWthermisch / m ³ , amount. The total heat storage capacity of the heat accumulator may be more than 10 MWh, preferably more than 100 MWh, more preferably more than 500 MWh. The specified performances refer to the thermal storage capacity or the heat content of the heat accumulator at a maximum storage temperature in the range between 900 ° C and 1,300 ° C, preferably in the range between 1000 ° C and 1200 ° C, more preferably in the range of 1100 ° C. With a power range of more than 100 MWh, the heat storage power plant according to the invention competes with pumped-storage power plants and compressed-air storage power plants and can be used industrially for power generation / storage. Here, the heat storage power plant according to the invention over pumped storage power plants and compressed air storage power plants is characterized by a significantly low system complexity and in particular does not rely on the presence of specific geographic conditions, so that compared to pumped storage power plants and compressed air storage power plants significantly cheaper use of excess capacity in the power grid with high efficiency, ie at low energy conversion losses. In principle, however, the heat storage system according to the invention can also be used for non-large-scale applications with storage capacities of less than 20 MWh.

Preferably, each heat storage module of the heat accumulator has the same dimensions. The heat storage module may be parallelepiped-shaped and, depending on the material used of the heat conductor, a base area of preferably about 1 m ² to 16 m ² , at a height of preferably 1 m for simple heating conductors made of steel or iron up to a height of 4 m for high-strength heaters, such as silicon carbide. In the aforementioned dimensioning of the heat storage module, a high stability of the shape of the heat conductor in the heat storage module is ensured.

Although basically each heat storage module of the heat storage individually, d. H. irrespective of the other heat storage modules, can be controlled and energized, it is within the scope of the invention that a plurality of heat storage modules of the heat accumulator in an electrical circuit in series and / or parallel switchable and thus are jointly controlled or energized. For this purpose, the heating resistors of the heat storage modules are electrically connected to one another via connection contacts. To form a series or parallel connection of the heating resistors, at least one switch can be provided. In order to change the number of heat storage modules connected in series and / or in parallel as a function of the desired current consumption, a control or regulating device may be provided.

Incidentally, at least one further switch can be provided, which allows the amount of electricity converted into heat in the heat accumulator to be replaced by required wise change the number of energized heating resistors or the number of energized heat storage modules to change and control. In other words, a switch can be provided with which individual heat storage modules or their heating resistors can be connected to the power supply or disconnected from the power supply, if necessary, to remove more or less electric power from the power supply and to convert it into heat. It can be provided a control and / or regulating device that allows a largely automated control and / or regulation of the heat storage capacity.

The modular design of the heat accumulator according to the invention opens up the possibility that the heat accumulator has at least one flow cell for the heat transfer fluid, wherein the flow cell has a plurality of preferably superimposed heat storage modules and wherein the heat storage modules of a flow cell in the discharge of the heat storage are subsequently flowed through by the heat transfer fluid.

The heat storage modules of a flow cell can be energized individually and can be energized independently of the other heat storage modules of the flow cell. Preferably, however, it is provided that all or more heating resistors of the heat storage modules of a flow cell with at least one switch in an electrical circuit in series and / or parallel switchable and thus can be supplied with current.

The heat accumulator according to the invention preferably has a plurality of throughflow cells through which the heat transfer fluid can flow separately, wherein the flow of the heat transfer fluid through each flow cell can be individually shut off or regulated. In this context, it may be provided that each flow cell can be individually controlled for partial or complete loading of the heat accumulator and the heat storage modules of each flow cell can be supplied with current independently of the heat storage modules of the other flow cells. It is understood that a corresponding circuit and, preferably, a correspondingly designed control or regulating device can be provided in order to allow one or more flow cells to flow through the heat transfer fluid as required. This allows the heat that is removed from the heat storage and provided in the heat storage power plant for reconversion, in a fast and easy way to adapt to the actual power requirements. For example, subsequently only one flow-through cell can be flowed through by the heat transfer fluid until this throughflow cell has been discharged and the storage temperature of the storage modules of this throughflow cell has reached or fallen below a predetermined minimum value. Then, the next flow cell is released and flows through the heat transfer fluid, while the last flowed through (s) discharged cell (s) is blocked for the heat transfer fluid or become. The loading of the flow cells by energizing the heat storage modules can be carried out with a time delay to the discharge of the flow cells. Regardless, it is of course also possible for a plurality of throughflow cells to be flowed through simultaneously by the heat transfer fluid in order to heat a larger volume flow of the heat transfer fluid.

In order to control or regulate the flow of the heat transfer fluid through adjacent flow cells, at least one adjustable shut-off element can be provided between two adjacent flow cells, wherein a flow path of the heat transfer fluid is released by a flow cell and closed by the other flow cell by adjusting the shutoff. Several flow cells can be arranged next to each other and can be flowed through by appropriate position of the shut-off elements of the heat transfer fluid below.

A development of the invention can provide that a plurality of heat storage modules is arranged side by side in a geometric heat storage row, wherein the heating resistors of the heat storage modules of the heat storage row are connected in series in an electrical circuit. In this case, heating resistors connected in series are flowed through by the same current, so that the heating resistors are heated equally during energization. The total electrical resistance of the heat storage modules of a heat storage row then corresponds to the sum of the individual resistances of the heat storage modules.

It is also expedient if each flow cell has a plurality of heat storage rows arranged one above the other, wherein the heat storage modules of the superimposed heat storage rows are subsequently flowed through by the working fluid and wherein the heat storage rows with at least one switch, if necessary, are electrically connected in series or in parallel and / or wherein the number of energized heat storage rows is changed as needed. This allows very flexible adjust the time to load the heat storage modules and the heat storage capacity of the existing capacity in the power grid.

In order to minimize the heat transfer to the environment as possible, a heat insulation enclosing the flow cell and / or the heat storage can be provided. Preferably, a common thermal insulation is provided which encloses all flow cells of the heat accumulator. The thermal insulation may have a multilayer structure with a vacuum formed between two layers, so that an unwanted heat transfer is reduced as much as possible.

The proportion of the heat content of the at least one heating resistor to the total heat content of the heat storage module may be less than 20%, preferably less than 10%, in particular less than 5% in a preferred embodiment of the invention. In other words, this means that the heat storage capacity of the heat storage module to more than 80%, preferably more than 90%, more preferably more than 95%, is determined by the heat storage material.

However, in an alternative embodiment of the invention, the heat accumulator according to the invention may also provide at least one heat storage module which has at least one electrical heating resistor and flow passages surrounding the heating resistor for a heat transfer fluid, in particular a working fluid of the thermal power plant, wherein the heating resistor by the removal of electrical energy from a Power supply is energized and the electrical energy is converted into heat energy and stored by the heating resistor, wherein the working fluid is heatable by direct heat transfer from the heating resistor and wherein the proportion of heat content of the at least one heating resistor in the total heat content of the heat storage module is at least 30%, in particular at least 50% , Preferably, in this embodiment of the invention, the proportion of heat content of the at least one heating resistor in the total heat content of the heat storage module is more than 60%, more preferably more than 70%. If the heat storage module has a plurality of heating resistors or heating conductors, the proportion of heat content of all heating resistors in the total heat content of the heat storage module amounts to at least 30%, in particular at least 50%, more preferably more than 60%, more preferably more than 70%. The aforementioned values refer to a (maximum) storage temperature in the range between 900 ° C and 1300 ° C, preferably in the range between 1000 ° C and 1200 ° C, more preferably in the range of 1100 ° C. The heat content or the heat storage capacity or the thermal energy of the heating resistor is defined here as the product of the specific heat capacity and the mass of the heating resistor and a specific temperature of the heat accumulator. In an analogous manner, the total heat content of the heat storage module from the heat content of all components and components of the heat storage module is determined at the specific temperature, the heat storage module in particular internals or bulk material may have a deviating from the material of the heating resistor second heat storage material. The heat energy is given here in the Sl unit system in Joule [J].

The heat transfer between the heating resistor and the heat storage material of a heat storage module can preferably be effected by forced convection and / or radiation. Preferably, the heater and heat storage material are not in direct contact with each other and are substantially spaced apart so that heat transfer may be predominantly or entirely by forced convection and / or radiation but not by heat conduction. This takes into account the fact that the heating resistor on the one hand and the heat storage material on the other hand generally have a different thermal expansion, so that at a spacing of heat conductor and heat storage material damage to the usually less dimensionally stable heat storage material due to moving through a longitudinal extent relative to the heat storage material Heat conductor is excluded.

The heat storage material may be formed by molded blocks, which may have a plurality of throughflow openings for the heat transfer medium and / or a plurality of through openings for the heating conductor. In this embodiment, the shaped bricks may have separate openings for the heat transfer medium on the one hand and for the heating conductor on the other. This ensures that first channels for the heating element and second channels for the heat transfer fluid are fluidly separated from each other, so that the heating element does not come into contact with the heat transfer fluid. Particularly in the case of corrosive heat carrier fluids, this has an advantageous effect on the service life of the heat storage module. The stones can also be recesses on the edges and / or depressions in such a way that, when assembling or collapsing the shaped bricks between adjacent bricks, a plurality of flow openings for the heat transfer medium and / or, preferably, a plurality of through openings for the heating conductor are formed. Also, the channels for the heating conductor and the channels for the heat transfer fluid can run in different directions. For example, horizontally extending first channels may be provided for the heating conductor between two superimposed rows of stones of the conglomerates and the two rows passing through vertically extending second channels for the heat transfer fluid.

As already described above, it is expedient if the heating conductor is not firmly connected to the shaped bricks, but guided freely movable in the through holes. This is advantageous with regard to a different thermal expansion of heat conductor and heat storage material. If the heat conductor does not bear against the shaped bricks, it can not lead to abrasion of the molded bricks at a different thermal expansion.

If the heating resistor is flowed around directly by the heat transfer fluid, corrosion of the heating resistor may occur at high temperatures in the heat accumulator. To prevent this, an inert gas, in particular nitrogen, can be used as the heat transfer fluid. There it may be expedient to guide the heat transfer fluid in a (closed) circuit. This results in lower costs associated with providing the heat transfer fluid and can help to reduce the complexity of the heat storage power plant.

Alternatively, the heating element can also be embedded in the molded block material, which can be done, for example, by sheathing the heating conductor with a ceramic material and then firing the sheathed heating conductor with the material of the shaped block.

In an alternative embodiment of the invention, the heat storage material may also be pourable or free-flowing. For example, it is possible to use sand as a cost-effective heat storage material. The heating conductor can then be embedded in the bed. The bed can also have ceramic channels, which are fired by heating and are provided for flow through the heat transfer medium and / or for the implementation of the heat conductor. Form stones can be made of chamotte or other ceramic material. The material of the heating resistor may have a specific heat capacity of 0.4 kJ / (kgK) to 0.8 kJ / (kgK), while the specific heat capacity of the material of the mold holding elements is in the range between 1.0 kJ / (kgK) and 1, 4 kJ / (kgK) can lie. The abovementioned values of the specific heat capacities are based on the maximum storage temperature during the heating of the heat transfer fluid, which is preferably in the range between 900 ° C. and 1300 ° C., more preferably in the range between 1000 ° C. and 1200 ° C., particularly preferably in the range of about 1 100 ° C, lies.

Each heat storage module may have a composite formed from a plurality of interconnected molded blocks as a heat storage material. The heating resistor is then passed through the composite, preferably meandering, so that a sufficiently large heat transfer surface for the heat transfer from the heating element is created on the heat storage material. As a result, a very short loading time of the heat storage module is achieved. The molding compound in the heat storage module can be achieved by preferably in three spatial directions connected blocks. The heating resistor can then traverse the composite in three directions, preferably in a different way.

In another embodiment of the heat accumulator according to the invention it is provided that the heat storage module comprises at least one shape retaining element made of a material with compared to the heating resistor of lower electrical conductivity for stabilizing the heating resistor and / or mutual insulation of adjacent conductor sections of the heating resistor, wherein the proportion of heat content of at least a shape-retaining element in the total heat content of the heat storage module according to the invention less than 70%, in particular less than 50%. The material of which the shape-retaining element consists has no or practically insignificant electrical conductivity and, in particular, serves to spatially support, fix and stabilize the heating resistor. Preferably, a plurality of shape-retaining elements are provided, in which case the proportion of the heat content of all shape-retaining elements in the total heat content of the heat storage module is less than 70%, in particular less than 50%. The above values refer to the above mentioned maximum storage temperatures. Accordingly, the proportion of the heat content of the at least one heating resistor and the proportion of the heat content of the at least one shape-holding element, a ratio of greater than 1: 2, preferably greater than 1: 3, to each other. Preferably, however, a plurality of shape-retaining elements are provided, so that the stated proportions always refer to the heat content of all shape-retaining elements.

The shape-retaining element may consist of chamotte or another ceramic material. If a plurality of shape-retaining elements are provided for stabilizing the heating resistor, they may be web-shaped or rod-shaped and arranged in a plurality of parallel planes, wherein openings are formed between the shape-retaining elements of adjacent planes for conductor sections of the heat conductor which are in particular orthogonal to the planes. The shape-retaining elements of adjacent planes can then be arranged running in a crosswise manner with respect to each other.

The material of the heating resistor preferably has a smaller specific heat capacity than the material of which the shape holding elements consist. The material of the heating resistor may have a specific heat capacity of 0.4 kJ / (kgK) to 0.8 kJ / (kgK), while the specific heat capacity of the material of the mold holding elements is in the range between 1.0 kJ / (kgK) and 1, 4 kJ / (kgK) can lie. The abovementioned values of the specific heat capacities are based on the maximum storage temperature during the heating of the heat transfer fluid, which is preferably in the range between 900 ° C. and 1,300 ° C., preferably in the range between 1,000 ° C. and 1,200 ° C., more preferably in the range from 1,100 ° C, lies. However, in comparison to the material of which the shape-retaining elements are made, the material of the heating resistor has a higher density, so that the weight fraction of the heating resistor in the total weight of the heat storage module can be greater than the weight fraction of the shape-retaining elements in the total weight, in each case based on a specific volume of the heat storage module. Based on the specific volume of the heat storage module, this leads to a higher heat content of the heating resistor compared to the heat content of the mold holding elements. This makes it possible to achieve a small size of the heat storage module according to the invention with a high heat storage capacity.

In order to reduce the component complexity of the heat storage module, the heat storage module can be formed only by a rod or wire-shaped heating conductor as a heating resistor and by a plurality of molded bricks and / or shape-retaining elements. The heating element can be formed in one or more pieces and can be connected via two connection contacts for a current supply to a power grid.

It is expedient if the heating resistor and the molded blocks and / or shape-retaining elements are not separated to the outside by a housing which is sealed with respect to the heat-transfer fluid, so that the heating resistor and the shape-retaining elements can be bypassed or flowed through freely by the heat transfer fluid.

Moreover, the invention preferably advantageously provides that the heating resistor is formed into a spatial structure defining the geometry of the heat storage module. Preferably, a wire extending in a plurality of spatial directions is provided as a heating conductor, wherein strip-shaped shape holding elements can then be arranged between adjacent conductor sections of the heating conductor in order to stabilize the heating conductor and prevent conductor sections from bending when the heat storage power plant is erected and / or during later operation and a short circuit connection is formed, through which a high current can flow, which leads to a destruction of the heating conductor.

As an alternative to a meandering heating conductor, it may be helical or have a different profile. At the location of a wire and rods of an electrically conductive material at the ends can be connected to each other, so that there is a continuous heating conductor.

The dimensions of the heat storage module are determined in this context by the dimensions of the space created by straight and / or bent portions of the heat conductor. It is expedient that the space structure is cuboid, preferably cuboid, so that heat storage modules can be stacked in a simple manner. In this way, on the one hand, the transport of the heat storage modules to a construction site of the heat storage power plant is simplified and on the other created the possibility to reduce the space required for the heat storage at the site by stacking several heat storage modules on top of each other.

Specifically, there are a variety of ways to design and develop the heat accumulator according to the invention and the heat storage power plant according to the invention, reference being made on the one hand to the dependent claims and on the other hand to the following detailed description of preferred embodiments of the invention with reference to the drawings. The features of the invention described above and discussed below with reference to the drawings may be combined as needed, even if not expressly described.

In the drawing show

1 is a schematic view of a heat storage module of a heat storage device according to the invention for a heat storage power plant in a perspective view obliquely from above,

FIG. 2 shows a schematic cross-sectional view of a possible embodiment of the heat storage module, a schematic side view of the heat storage module shown in FIG. 2, FIG.

4 is a schematic representation of a heat storage row of a heat accumulator according to the invention, wherein the heat storage row has a plurality of heat storage modules,

5 is a schematic representation of a flow cell of a heat accumulator according to the invention with a plurality of superposed heat storage rows,

Fig. 6, 7 are each a schematic side view of an inventive

A heat accumulator with a plurality of juxtaposed arranged and subsequently flowed through by a working fluid of a heat storage power flow cells, a schematic representation of a heat accumulator of the type shown in Figs. 6 and 7, wherein the working fluid is fed to a gas turbine, after flowing through the heat accumulator

9 is a schematic representation of a first embodiment of a

Heat storage power plant with a heat accumulator of the type shown in Fig. 8, 10 shows an alternative embodiment of a heat storage power plant with a heat accumulator of the type shown in Fig. 8,

11 shows a composite of molded bricks for a heat storage module according to the invention, the molded bricks forming a heat storage material of the heat storage module, in a schematic side view, FIG.

Fig. 12 is a plan view of the composite shown in Figure 1 1 and

13 shows the course of a heating conductor through the composite shown in FIGS. 1 and 2.

FIG. 1 schematically shows a heat storage module 1 of a heat accumulator 2 shown in more detail in FIGS. 6 to 8. The heat storage module 1 has a heating conductor 3 as a heating resistor, wherein the heating conductor 3 is bent in all spatial directions X, Y, Z of FIG. 1 meandering and forms a spatial structure that determines the geometry and dimensions of the heat storage module 1. The spatial structure in the present case has a cube shape, but in principle may also have a different shape. However, the cube shape is advantageous because it allows the stacking of a plurality of heat storage modules 1 in a simple manner and thereby simplifies the transport and assembly. The heating conductor 3 is formed by a high-resistance wire or high-resistance connected at the ends rods made of an electrically conductive material such as iron or steel. The cube-shaped heat storage module 1 may have an edge length of about 1 m.

The metallic heating conductor 3 represents an electrical resistance in the heat storage module 1, wherein the material of the heating conductor 3 also fulfills a heat storage function. Preferably, however, the heat storage function is predominantly fulfilled by a heat storage material of the heat storage module 1, wherein the heat storage material may be chamotte or another ceramic material.

The heating conductor 3 is electrically contactable via a connection contact 4, 5, which are shown only schematically in FIG. 1 and which may be the ends of the heating conductor 3 in the simplest embodiment. Between straight and angled conductor sections of the heating element 3 schematically shown flow channels 6 are provided for a heat transfer fluid 13, the as a working fluid of a heat storage power plant 22, 23 shown schematically in Figs. 9 and 10 can be used.

According to FIG. 9 and FIG. 10, the heating conductor 3 can be supplied with electricity from a power network, the electrical energy 25 being converted into heat energy and by the heating conductor 3 and preferably a heat storage material of the heat storage module 1, not shown in FIG , is stored. When time-shifted flow through the heat storage module 1, the heat transfer fluid 13 can then be heated by direct or indirect heat transfer from the heating 3 and / or heat storage material, the proportion of heat content of the heating element 3 in the total heat content of the heat storage module 1 at a certain temperature in the range of 900 ° C. to 1300 ° C may be less than 20%, preferably less than 10%, in particular less than 5%. The heat storage material then essentially determines the heat storage capacity of the heat storage module. 1

In another embodiment, the heat storage module 1, however, it is also possible in principle that the heating element 3 takes over the actual heat storage function, in which case the proportion of heat content of the heating element 3 in the total heat content of the heat storage module 1 more than 50%, preferably more than 60%, more preferably more than 70%.

Here, the heat content of the heating conductor 3 and the heat content of the heat storage material is based on the volume of the heat storage module 1, wherein the heat storage module 1 temperature range under consideration preferably has a total storage capacity of between 0.5 and 2 MWh / m ^3, in particular of approximately 1 MWh / m ³ , may have.

As can be seen from FIGS. 2 and 3, a spatial arrangement of the heating conductor 3 can be stabilized with shape-retaining elements 7, 8 which are not electrically or only insignificantly conductive. While the heating conductor 3 is preferably made of iron or steel, the shape holding elements 7, 8, for example, chamotte or other ceramic material and are in the embodiment shown web or rod-shaped and arranged in several parallel planes one above the other. It can be provided that the proportion of the heat content of the shape retaining elements 7, 8 in the total heat content of the heat storage module 1 at a given temperature is less than 50%. Between the shape retaining elements 7, 8 adjacent levels openings 9 for formed orthogonal to the planes extending portions of the heating element 3. The shape holding elements 7, 8 of adjacent planes are arranged running crosswise to each other. The selected structure of the heat storage module 1 with a plurality of mold holding elements 7, 8 surrounding a meandering heating element 3, leads to a high inner surface of the heat exchanger module 1, so that the heat transfer from the heat storage module 1 to a working fluid 13 improves and a very rapid heating the working fluid 13 is ensured.

In the illustrated embodiments of the heat storage module 1, it is such that this is formed only by the heating conductor 3, the connection elements 4, 5 (which may be part of the heating element 3) and by the heat storage material, for example formed as a shape retaining elements 7, 8.

As is further apparent from FIGS. 1 to 3, the heat storage module 1 preferably has no insulation and / or no (gas-tight) housing, so that the heat storage module 1 can be flowed through by the heat transfer fluid 13.

The total weight of the heat conductor 3 of a heat storage module 1 relative to the volume of the heat storage module 1 can be between 3000 kg / m ³ and 4000 kg / m ³ , while the total weight of the heat storage material 1, for example the shape-retaining elements, also relates to the volume of the heat storage module 1 7, 8, between 500 kg / m ³ and 700 kg / m ³ can be.

As is apparent from Fig. 4, a plurality of heat storage modules 1 may be arranged in a geometric heat storage row 10, wherein the heating conductors 3 of the heat storage modules 1 are connected in series in an electrical circuit. For this purpose, the connection elements 4, 5 of adjacent heat exchanger modules 1 are electrically connected to each other. The connection element 4 of a first and in Fig. 4 left outside illustrated heat storage module 1 of the heat storage 10 is electrically contacted with the connection element 5 of the last heat storage module 1 of the heat storage row 10, so that the heat storage row 10 shows an electrical total resistance 1 1. The heating conductors 3 connected in series are flowed through by the same current when the heat storage row 10 is energized. The total resistance 1 1 of the heat storage row 10 results from the sum of the individual resistances of the heat storage modules. 1 5 shows a flow-through cell 12 of the heat accumulator 2 shown in FIGS. 6 to 8, which is formed by a plurality of heat storage rows 10 arranged one above the other. In the embodiment shown, the flow-through cell 12 can have, for example, 5 heat storage rows 10 stacked on top of one another, wherein the heat storage modules 1 of the heat storage rows 10 arranged one above the other can be flowed through from below by a heat transfer fluid 13. This is shown schematically in FIG. 8, which shows the supply line of the heat transfer fluid 13 after compression with a compressor 14 via a distributor 15, the supply of the heat carrier fluid 13 taking place from below via the heat exchanger modules 1 of the lowermost row of heat exchangers 10. It is understood that the supply line can also be realized differently.

According to FIG. 5, a plurality of heat storage rows 10 of a flow cell 12 with switches 16 can, if necessary, be electrically connected in series or in parallel and / or the number of heat storage rows 10 energized can be changed as required. In this way, the loading duration of the heat storage modules, that is, the duration of the power consumption, in which a certain amount of electricity is converted into thermal energy, and the storage capacity of the heat accumulator 2 can be changed in a simple manner. According to FIG. 5, a first heat storage module 1 of a lowermost heat storage row 10 is electrically contacted with a last heat storage module 1 of an uppermost heat storage row 10. The resulting total resistance 17 of the flow cell 12 depends on whether the heat storage rows 10 are connected in series or in parallel. By parallel connection of the heat storage rows 10 of the total electrical resistance 17 decreases, so that the duration of the power consumption decreases.

In the figures 6 to 8, the heat accumulator 2 is shown schematically, wherein the heat accumulator 2 in the illustrated embodiment has ten juxtaposed flow cells 12. At least one adjustable shut-off element 18 is provided between adjacent flow-through cells 12, wherein a flow path of the heat transfer fluid 13 through the flow-through cell 12 is released by the shut-off element 18 and closed by the other adjacent flow-through cells 12. According to FIG. 6, the heat transfer fluid 13 only flows through the first throughflow cell 12 shown on the left in FIGS. 6 and 7, wherein the position of the first shut-off element 18 between the first and second flow-through cells 12 Flow through the further downstream flow cells 12 is excluded. When flowing through with the heat transfer fluid 13, the first flow cell 12 cools due to heat transfer from the heating resistors of the heat storage modules 1 of the first flow cell 12 to the heat transfer fluid 13. If a predetermined minimum temperature of the heat transfer is reached, the first shut-off element 18 according to FIG adjusted, so that the heat transfer fluid 13 subsequently flows only through the second flow cell 12 and is heated. The downstream in the flow direction further shut-off elements 18 of the further flow cells 12 are in a position which excludes a flow through the heat transfer fluid 13. Once the heat storage modules 1 of the second flow cell 12 are discharged or cooled, the heat storage modules 1 of the third flow cell 12 are released by changing the position of the arranged between the second flow cell 12 and the third flow cell 12 shut-off element 18 for a flow with the heat transfer fluid 13. This process is repeated until the last flow cell 12 (shown on the far right in FIGS. 6 and 7) is discharged accordingly. Subsequently, it is necessary to recharge the flow cells 12, which takes place by energizing the heating resistors of the heat storage modules 1. It is understood that a discharge of the flow cells 12 by heat transfer to the heat transfer fluid 13 and a loading of the flow cells 12 by energization do not require that all flow cells 12 of the heat accumulator 2 are already unloaded or loaded.

In Fig. 8, the heat accumulator 2 is shown in perspective, wherein the heat accumulator 2 may have a thermal heat storage capacity of more than 100 MWh, for example, of 500 MWh. The heat storage line is based on the thermal energy of the heat accumulator 2 at a maximum storage temperature between 900 ° C and 1300 ° C, preferably 1100 ° C to 1200 ° C, to which the heat storage fluid 13 can be heated in the heat storage 2.

After flowing through a flow zone 12, the heat transfer fluid 13 can be supplied to a turbine 20 via a collector 19, wherein the heat transfer fluid 13 is expanded by performing mechanical work and the mechanical work is converted into electrical energy with a generator 21 shown in FIGS. 9 and 10 , As can be seen from FIGS. 6 and 7, a common insulation 22, which houses the flow-through cells 12, can be provided in order to reduce heat losses due to unwanted heat transfer to the environment. In principle, each flow-through cell 12 can also be surrounded by a gas-tight or pressure-tight housing and thus encapsulated.

Possible plant concepts for a heat storage power plant 22, 23 using the heat accumulator 2 will be explained with reference to FIGS. 9 and 10.

In the heat storage power plant 22 shown in FIG. 9, the heat transfer fluid 13 is compressed in the compressor 14 and then passes into a first regenerator 24. The regenerator 24 is provided for preheating the heat transfer fluid 13. Subsequently, the preheated heat transfer fluid 13 flows through the heat accumulator 2, the heat storage modules 1 have previously been heated by removal of electrical energy 25 from a power grid. When flowing through the heat accumulator 2, the heat transfer fluid 13 is heated by heat transfer from the heating conductors 3 and the shape retaining elements 7, 8 of the heat storage modules 1 of the heat accumulator 2 and then passes into a combustion chamber 26. In the combustion chamber 26, a gaseous energy source 27, such as natural gas or Biogas, and / or a liquid energy source 28, such as methanol, are burned. The heat of combustion leads to a further heating of the heat transfer fluid 13, which is subsequently expanded in the turbine 20 while performing mechanical work. The mechanical work is converted by the generator 22 into electrical energy 29, it being understood that the removal of electrical energy 25 from the power grid and the generation of electrical energy 29 and their supply to the power grid are time-delayed, to compensate for excess capacity to enable in the power grid.

After the heat transfer fluid has been 13 relaxed in the turbine 20, it flows through a second regenerator 30, which is heated in the process. After the regenerator 30 has been heated, the flow paths are switched to the first cold regenerator 24 and to the second regenerator 30, so that the cooled heat carrier fluid 13 first re-enters the compressor 14 and, after compression, flows through the hot second regenerator 30, which now heats the heat carrier fluid 13 serves. When switching the first regenerator 24 enters the flow path of the hot heat transfer fluid 13 after exiting the turbine 20 and is recharged. Preferably, as regenerators 24, 30 so-called Pebble Heater provided.

As is further apparent from FIG. 9, the illustrated system concept allows a partial flow of the heat transfer fluid 13 to be supplied to the combustion chamber 26 via a bypass line 31 shown in dashed lines in FIG. 9 in order to correspondingly increase the temperature level of the heat transfer fluid 13 at the exit from the combustion chamber 26 regulate.

The heat transfer fluid 13 is guided in a closed circuit, it also being possible for the heat carrier fluid 13 to be nitrogen, so that corrosion of the heating conductors 3 when flowing through the heat accumulator 2 with the heat transfer fluid 13 can be largely ruled out.

In Fig. 10, another embodiment of a heat storage power plant 23 is shown.

In contrast to the heat storage power plant 22 shown in FIG. 9, a preheating of the heat transfer fluid 13 by means of regenerators 24, 25 is not provided according to FIG. Instead, the residual heat of the heat transfer fluid 13 is used after exiting the turbine 20 in a steam cycle shown schematically 32 for superheating of steam, which is expanded in a steam turbine 33. The mechanical work done in this process is converted into electricity by a further generator 34, which is fed into the power grid at high power demand together with the current generated in the turbine 20 during the expansion of the heat transfer fluid 13 in the turbine 20. The downstream steam cycle 32 allows utilization of the heat energy still contained in the heat transfer fluid 13 after exiting the turbine 20 for power generation, resulting in a higher efficiency in power generation.

FIGS. 11 to 13 each show a composite 35 formed by a plurality of molding blocks 36 arranged next to one another and one above the other for a heat storage module 1. The molded blocks 36 form a heat storage material of the heat storage module 1, wherein at a temperature in the range of 900 ° C to 1300 ° C, in particular in the range of 1 100 ° C to 1200 ° C, more than 80%, preferably more than 90%, on preferably more than 95% of the total total heat content of the heat storage module 1 is formed by the heat content of the molded blocks 36.

Between adjacent juxtaposed molded bricks 36 36 through openings 37 are formed due to the edge side geometry of the bricks, through which the heating element 3 is guided according to Figure 13 meandering. In this case, the heating conductor 3 can once again penetrate the shaped stones 36 in all three spatial directions of the heat storage module 1 in a meandering manner. The heating conductor 3 has a smaller diameter than the passage openings 37, so that an annular gap is formed between the heating conductor 3 and the shaped bricks 36, which can form a throughflow opening for the heat transfer fluid 13. In principle, however, it is also possible to pass the heating conductor 3 on the one hand and the heat transfer fluid 13 on the other hand through separate passage openings 37. It may also be possible for the shaped bricks 36 to have passage openings for the heating conductor 3 and / or for the heat transfer fluid 13. A separation of the heating conductor 3 from the heat transfer fluid 13 may be appropriate to prevent corrosion damage to the heating element 3 due to contact with the heat transfer fluid 13.

On the upper side, the shaped bricks 36 have projections 38, which cooperate with corresponding indentations 39 on the underside of the shaped bricks 36, so that it is possible in a simple manner to stack the bricks 36 one above the other with high stability of the composite 35 and thereby achieve an exact alignment of the bricks To ensure flow openings 38 between the blocks 36.

Further aspects and features of the invention may relate to an electrically heatable heat accumulator (2) for the conversion of electrical energy into thermal energy at low-consumption times and for the storage and time-shifted transfer of thermal energy to a working fluid of a heat storage power plant (22, 23) comprising at least one heat storage module (1), wherein the heat storage module (1) at least one electrical heating resistor and the heating resistance surrounding flow channels for the working fluid of the heat storage power plant (22, 23), wherein the heating resistor can be energized by the removal of electrical energy (25) from a power grid and the electrical energy is converted into thermal energy and stored by the heating resistor, wherein the working fluid can be heated by direct heat transfer from the heating resistor and wherein the proportion of heat content of the at least one heating Resistance to the total heat content of the heat storage module (1) is at least 30%; and / or wherein the heat storage module (1) has at least one shape-retaining element (7, 8) of a material with lower electrical conductivity compared to the heating resistor for stabilizing the heating resistor and / or for mutual insulation of adjacent conductor sections of the heating resistor, wherein the content of the heat content of at least one shape-retaining element (7, 8) is less than 70% of the total heat content of the heat storage module (1); and / or wherein the heating resistor (3) is formed into a space defining the geometry of the heat storage module (1); and / or wherein a modular construction of the heat accumulator (2) with a plurality of electrically heatable heat storage modules (1) is provided, each heat storage module (1) has at least one separate electrical heating resistor and the total heat content of the heat accumulator (2) substantially the sum of the heat contents the heat storage modules (1) corresponds and wherein the heating resistors of the heat storage modules (1) via terminal contacts (4, 5) are electrically contacted with each other; and / or wherein a plurality of heat storage modules (1) in a geometric heat storage row (10) is arranged and that the heating resistors of the heat storage modules (1) of the heat storage row (10) are connected in series in an electrical circuit; and / or wherein at least one switch (16) for controlling the loading time of a plurality of heat storage modules (1) by forming a series or parallel connection of the heating resistors of the heat storage modules (1) is provided; and / or wherein a plurality of separable and successively flow-through throughflow cells (12) are provided for the working fluid, each flow cell (12) having a plurality of heat storage modules (1) and wherein the heat storage modules (1) of a flow cell (12) subsequently flowed through by the working fluid are; and or wherein each flow cell (12) comprises a plurality of superimposed heat storage rows (10), wherein superimposed heat storage modules (1) of the heat storage rows (10) are flowed through by the working fluid and wherein the heat storage rows (10) with at least one switch (16), if necessary electrically in Row or are switchable in parallel and / or wherein the number of energized heat storage rows (10) is changed as needed; and / or wherein between two adjacent flow cells (12) at least one adjustable shut-off element (18) is provided, wherein by adjusting the shut-off (18) a flow path of the working fluid through a flow cell (12) released and closed by the adjacent other flow cell (12) becomes.

A further aspect of the invention can be a heat storage power plant (22, 23) designed for removing electrical energy (25) from a power grid in low-consumption periods and the delayed delivery of electrical energy (29) at high power demand, with at least one by removal of electrical energy ( 25) from the power grid electrically heatable heat storage (2), with at least one heat storage (2) upstream compressor (14) for compressing a working fluid and at least one heat storage (2) downstream turbine (20) for expanding the in the heat storage (2 ) heated working fluid while performing mechanical work and with a generator (21) for converting the mechanical work into electrical energy (29).

Claims

claims:

1. Electrically heatable heat storage (2) for converting electrical energy into thermal energy and for storing and time-delayed transmission of thermal energy to a heat storage power plant (22, 23), wherein the transmitted thermal energy in the heat storage power plant (22, 23) via mechanical energy is converted back into electrical energy, and / or for time-delayed extraction of process heat, with a plurality of heat storage modules (1), each heat storage module (1) at least one electrical heating resistor (3) for converting electrical energy into heat energy, at least one through the heat resistor (3) heatable heat storage material and flow channels for a heat transfer fluid (13) and wherein for a partial or complete loading of the heat storage (2) heat storage modules (1) are individually energized and independently energized.

2. Heat storage (2) according to claim 1, characterized in that at least one switch (16) for forming a series or parallel connection of the heating resistors (3) of a plurality of heat storage modules (1) is provided.

3. Heat storage (2) according to any one of the preceding claims 1 or 2, characterized in that a plurality of superimposed or juxtaposed heat storage modules (1) form a flow cell (12) of the heat accumulator (2), wherein the heat storage modules (1) of a flow cell (12) are subsequently flowed through by the heat transfer fluid (13).

4. heat storage device (2) according to claim 3, characterized in that a plurality of separate from each other by the heat transfer fluid (13) flow-through flow cells (12) are provided, wherein the flow of the heat transfer fluid (13) through each flow cell (12) is individually shut off or regulated ,

5. heat accumulator (2) according to claim 3 or 4, characterized in that each flow cell (12) for a partial or complete loading of the heat accumulator (2) individually controllable and the heat storage modules (1) each flow cell (12) independently of the heat storage modules ( 1) of the other flow cells (12) can be energized.

6. Heat storage (2) according to one of the preceding claims 3 to 5, characterized in that between two adjacent flow cells (12) at least one adjustable shut-off element (18) is provided, wherein by adjusting the shut-off element (18) a flow path of the heat transfer fluid (13 ) is released through a flow cell (12) and through the adjacent other flow cell.

7. heat accumulator (2) according to any one of the preceding claims 3 to 6, characterized in that each flow cell (12) has a plurality of overexposed heat storage rows (10), each heat storage row comprises a plurality of heat storage modules (1) and the superposed heat storage rows (10) are subsequently flowed through by the heat transfer fluid (13) and wherein the heat storage rows (10) with at least one switch (16), if necessary electrically in series or in parallel are switchable and / or wherein the number of energized heat storage rows (10) is changed as needed.

8. heat storage (2) according to any one of the preceding claims, characterized in that the heat transfer between the heating resistor (3) and the heat storage material by forced convection and / or by radiation.

9. heat storage device (2) according to any one of the preceding claims, characterized in that the heat storage material is formed by molded blocks (36), wherein the molded blocks (36) has a plurality of flow openings (38) for the heat transfer fluid (13) and / or a plurality of passage openings (37) for the heating conductor (3).

10. Heat store (2) according to any one of the preceding claims, character- ized in that each heat storage module (1) in a composite (35) arranged shaped blocks (36), wherein the heating resistor (3) multiple, preferably meandering, through the composite passed through.

1 1. A heat accumulator (2) according to any one of the preceding claims, character- ized in that the proportion of heat content of the at least one heating resistor (3) in the total heat content of the heat storage module (1) less than 20%, preferably less than 10%, in particular less than 5%.

12. heat storage power plant (22, 23) designed for removing electrical energy (25) from a power grid in low-consumption times and the time-delayed delivery of electrical energy (29) at high power demand, with at least one by removing the electrical energy (25) from the mains electricity Heatable heat accumulator (2) according to one of the preceding claims, wherein the heat storage power plant is designed for the return conversion of thermal energy from the heat accumulator (2) via mechanical energy into electrical energy.