CN114041036A - Energy storage device and method of storing energy - Google Patents

Energy storage device and method of storing energy Download PDF

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Publication number
CN114041036A
CN114041036A CN202080044788.XA CN202080044788A CN114041036A CN 114041036 A CN114041036 A CN 114041036A CN 202080044788 A CN202080044788 A CN 202080044788A CN 114041036 A CN114041036 A CN 114041036A
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China
Prior art keywords
energy storage
energy
thermal
storage element
heat
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CN202080044788.XA
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Inventor
萨沙·萨维奇
弗拉迪米尔·瓦西里耶夫
迪伦·卡斯凯利
谢尔盖·潘切施尼
埃里希·赫罗尔德·基西
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E2s Power Co
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E2s Power Co
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Priority claimed from PCT/EP2020/057977 external-priority patent/WO2020254001A1/en
Publication of CN114041036A publication Critical patent/CN114041036A/en
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/14—Thermal energy storage

Abstract

An energy storage device is provided with at least one energy storage unit (1). The energy storage unit (1) comprises a heat storage element (3) made of a solid material and an electric heating device (5) for heating the heat storage element (3). According to a first concept, the electrical heating device (5) is adapted to heat the heat storage element (3) by generating an electrical current within the material of the heat storage element (3). According to a second concept, a gas-electric insulator (8) is provided to electrically insulate the electric heating device (5) from the thermal storage element (3). Furthermore, a method for storing energy by means of such an energy storage device is provided.

Description

Energy storage device and method of storing energy
Technical Field
The present invention relates to an energy storage device for storing thermal energy. The invention also relates to a method of storing energy by means of such an energy storage device.
Background
For power generation, renewable energy sources such as wind energy and solar energy are increasingly used. However, a problem often associated with renewable energy sources is the continued availability of the generated electricity. For example, the wind is intermittent and does not blow continuously for 24 hours and 7 days per week. Solar energy is available only during the day and is highly dependent on weather conditions, especially cloud cover. Therefore, in order to make renewable energy sources more attractive and to increase the availability of the electrical energy generated from these sources, it is necessary to store energy. Today, different energy storage technologies are available, ranging from batteries, pump storage systems, compressed air storage, and various energy storage technologies that use heat, whether high-end or low-end. With these energy storage technologies, energy is stored in the form of, for example, thermal energy, compressed air, or chemical energy during periods of renewable energy surplus, and is subsequently converted to electrical energy and used during periods of high renewable energy demand and/or low availability.
The main problems facing today's energy storage systems are their efficiency and relatively low energy storage density (energy stored per unit surface or volume).
Systems for storing energy based on compressed air are disclosed for example in WO 2004/072452A 1, DE 102011112280 a1, US 2012/0085087 a1, DE 4410440 a1, WO 2016/176174 a1 and CN 103353060 a.
In the not yet published PCT application No. PCT/EP2018/052377 of the same applicant, an energy storage device is proposed in which a thermal storage element made of a solid material is arranged inside a gas container. The heat storage element may be heated by an electrical heating device. Thus, the device allows the combined storage of thermal energy and compressed gas. The stored compressed gas has been heated and can therefore be used directly, for example, to drive a gas turbine.
With respect to large scale applications, molten salt energy storage systems based on liquid salt heating are known. In these systems, salt is heated during periods of high energy availability and used when energy is needed to produce heated steam for driving a steam turbine.
Most currently available energy storage systems for steam generation have the common disadvantage of using an intermediate medium to charge the thermal storage and/or extract the heat for steam generation. The intermediate medium (e.g. air, molten salt, etc.) is heated by a separate energy source and the heat accumulated in the storage is used to generate steam by a heat transfer process. The intermediate medium is thus heated by heat transfer from the heat storage and the obtained heat energy is then transferred to the steam in the heat exchanger. These indirect processes of transferring energy from the storage device to the steam provide additional parasitic losses and significantly reduce system efficiency. Furthermore, the additional equipment required to circulate the intermediate medium makes the system complex and less robust.
Recently, energy storage devices using solid storage materials in the form of stones or concrete have been proposed in order to store thermal energy. The stored thermal energy can be used during periods of high demand to generate steam for heating or to drive a steam power plant in order to convert the stored thermal energy back into electrical energy.
In some publications, solid materials, such as graphite (WO 2005/088218A 1; US 4,136,276A), metals (iron-EP 1666828A 2, steel-WO 91/14906A 1) or MGA (WO 2014/063191A 1) are proposed as storage materials. In some publications, it is proposed to heat solid storage materials by resistive heaters (WO 2005/088218 a1, WO 91/14906 a1 and WO 2012/038620 a1) or by induction (US 4,136,276 a).
In order to generate steam based on stored thermal energy, it is proposed in WO 2005/088218 a1 to provide a conduit for guiding water along the storage material. In the device disclosed in EP 1666828 a2, a conduit is provided within a metallic storage material. In WO 91/14906 a1, separate blocks with baffles are used. A difficulty with the tubing is the thermal contact resistance between the tubing and the storage material, which may require overheating of the storage material to achieve the desired steam parameters. Providing conduits in the storage material is only suitable for metal storage materials with a medium heat capacity. The block with baffles results in an overall oversize of the whole system to ensure the steam has the required quantity and parameters.
Control of steam parameters is a particular challenge, which is only addressed in some publications, for example in WO 2005/088218 a 1. However, the typically proposed solutions usually require expensive equipment, such as thermal valves, i.e. valves regulating the flow of hot steam.
Disclosure of Invention
It is an object of the present invention to provide an energy storage device for storing energy which can be charged and discharged efficiently. Furthermore, the energy storage device should be easy to use for existing power plants, in particular gas and/or coal power plants.
This object is solved by each of the energy storage devices according to claims 1 and 8. A method of storing energy by means of one of such energy storage devices is claimed in claim 18. Further embodiments of the device and the method are provided in the dependent claims.
In the following, an energy storage device according to the independent claim 8 is referred to as an energy storage device according to the first inventive concept, and an energy storage device according to claim 1 is referred to as an energy storage device according to the second inventive concept.
Therefore, according to a first inventive concept, an energy storage device is provided with at least one energy storage unit, particularly precisely with an energy storage unit, which comprises:
a thermal storage element made of a solid material for storing thermal energy; and
an electric heating device for heating the heat storage element by means of electric energy.
The electrical heating means is adapted to heat the heat storage element by generating an electrical current within the solid material of the heat storage element.
Heating the thermal storage element by means of the current generated within the solid material of the thermal storage element allows a very direct and therefore particularly efficient charging process of the energy storage device. This means that the thermal energy is generated directly from the thermal storage element itself, i.e. the current is converted into thermal energy by resistive or inductive heating by the solid material. The heat storage element therefore has a certain electrical conductivity. Thus, no thermal energy transfer from the heating element to the thermal storage element with possible associated losses occurs. No intermediate medium is required for heating the heat storage element by the electric heating device. Furthermore, no electrical insulation is required between the electrical heating device and the thermal storage element, since in an energy storage device the thermal storage element is heated by means of indirect resistive heating by heat dissipation.
Heating of the heat storage element by means of an electric current generated directly in the solid material is particularly suitable with at least 10-4A preferred resistivity of Ω m and not more than 1 Ω m. In this case, the solid material of the thermal storage element is electrically conductive, but has sufficient resistance to be directly heated using a direct or alternating voltage. Materials with the preferred resistivity shown are rare in practice.
In order to generate an electric current within the solid material of the heat storage element, in a preferred embodiment the electric heating device may comprise a contact electrode attached to the heat storage element. In this case, the electrical heating device is adapted to apply a voltage difference between the at least two contact electrodes in order to generate an electrical current through the solid material of the thermal storage element from at least one contact electrode to at least one other contact electrode. By such an embodiment, a very direct and thus efficient heating of the heat storage element may be achieved. The contact electrode is preferably directly attached to the solid material of the thermal storage element. By having an electrical heating device with contact electrodes directly attached to the heat storage element, it is also possible to apply a direct or alternating current for the charging process. Therefore, no frequency converter is required. Furthermore, no cooling means are required to cool the inductor, which is also related to heat losses, compared to the use of an induction coil.
In another possible embodiment, the electrical heating device comprises an induction coil for inducing an electrical current in the thermal storage element. The induction coil is used to induce a current in the solid material of the heat storage element by electromagnetic induction. In many embodiments, the use of an induction coil, which typically comprises several windings, allows not only the direct generation of an electric current within the solid material of the thermal storage element, but also a simple production of the energy storage device. Thus, induction heating improves charging efficiency because it is a fast and straightforward process.
A channel may be provided which extends through the heat storage element and is adapted to guide a fluid, in particular water and/or steam, through the energy storage device in order to transfer thermal energy from the heat storage element to the fluid. The channels may also be referred to as conduits. The material forming the channel is preferably electrically grounded.
According to a second inventive concept, an energy storage device is provided with at least one energy storage unit, in particular precisely with an energy storage unit, which comprises:
a thermal storage element made of a solid material for storing thermal energy;
an electric heating device for heating the heat storage element by means of electric energy; and
an electrical insulator in the form of a gas insulator for electrically insulating the electrical heating device from the thermal storage element.
The energy storage device according to this second inventive concept is separate and represents an independent invention with respect to the energy storage device according to the first inventive concept as further indicated above. In most applications, it is preferred to use an energy storage device according to the first inventive concept or an energy storage device according to the second inventive concept. However, for certain applications it is also conceivable to combine the two energy storage devices together, for example by providing a single energy storage device having at least one energy storage unit as indicated in relation to the first inventive concept (i.e. where the electrical current is generated directly in the solid material of the thermal storage element) and having at least one energy storage unit as indicated in relation to the second inventive concept (i.e. where a gas electrical insulator is provided to electrically insulate the electrical heating device from the thermal storage element).
In the case of the energy storage device according to this second inventive concept, the electrical heating device preferably comprises a resistive heater arranged near or adjacent to the thermal storage element. In this case, the heat storage element is thus indirectly heated by the electric heating device, which means that heat is transferred from the electric heating device to the heat storage element by heat conduction and/or radiation. The resistive heater is preferably made of a metallic material, but may also be made of an organic material. The electrical insulator serves to electrically isolate the electrical heating device from the thermal storage element, i.e. to prevent short circuits in the thermal storage element, in particular if the thermal storage element has a certain electrical conductivity.
For the energy storage device according to this second inventive concept, it is particularly preferable to use a heat storage element made of a material having a certain electrical conductivity. Preferably, the thermal storage element has a size of less than 10-4Resistivity of Ω m. The heat storage element may for example be made of a metal, such as iron, or comprise graphite.
An electrical insulator is necessary due to the electrical conductivity of the thermal storage element. The electrical insulator should not only protect the thermal storage element from short circuits, but also have good thermal conductivity to ensure energy efficiency. By providing the electrical insulator in the form of a gas insulator, these conflicting and therefore challenging requirements can be met. Preferred gases are air, nitrogen, argon and CO2。
The electrical heating means preferably comprise a resistive heater, e.g. in the form of a resistive strip, i.e. a resistive element having a flat configuration. In order to spatially adapt the heat transfer to the thermal storage element during the charging process, the resistive tracks may have a varying cross-sectional area and/or a varying surface coverage along the surface of the thermal storage element. Alternatively or additionally, the cross-sectional area and/or the surface coverage may also vary along the longitudinal direction of the resistor strip. The embodiment of the resistive track with a varying cross-sectional area and/or varying surface coverage is particularly advantageous if the thermal storage element generally exhibits a specific temperature stratification caused by the discharge process.
In some embodiments, the electrical heating device may further comprise a resistive rod or tube inserted into a hole provided in the thermal storage element. In the space surrounding the rod or tube, the hole is in this case preferably filled with an insulating gas. The hole is preferably a through hole, but may also be a blind hole.
Independently, whether designed according to the first inventive concept or the second inventive concept, the energy storage device preferably comprises an interface unit for connecting the electrical heating device of at least one of the energy storage units to the power supply device. The interface unit preferably comprises cooling means.
The idea of providing an interface unit with a cooling device is generally independent of the design of the energy storage device, as long as it has at least one storage unit for storing thermal energy with a thermal storage element made of a solid material and an electric heating device for heating the thermal storage element by electric energy. Although the idea of an interface unit with a cooling device is preferably used in combination with an energy storage device designed according to the first or second inventive concept, it is also conceivable to use this idea in combination with an energy storage device not designed according to the first or second inventive concept. The idea of an interface unit with a cooling device therefore represents an independent invention with respect to an energy storage device according to the first and second inventive concept as further indicated above.
The electrical heating means may comprise an induction coil for inducing an electrical current directly in the solid material of the heat storage element or in another element arranged near or adjacent to the heat storage element. Alternatively or additionally, the electrical heating means may comprise a resistive heater arranged adjacent or in the vicinity of the heat storage element so as to transfer thermal energy to the heat storage element by thermal conduction and/or radiation.
Regardless of its design, at least a portion of the electrical heating device is typically arranged in close proximity to the thermal storage element and thus may become hot during and/or after charging. Preferably, the respective portion is even arranged within a thermal insulator surrounding the thermal storage element. However, the portions of the power supply device other than the thermal insulator should be prevented from overheating. This may be achieved by providing the interface unit with cooling means. The cooling device serves to cool the connection between, for example, the electrical heating device and the power supply device within the interface unit, so that no thermal energy is transferred from the thermal storage element and/or the electrical heating device to the power supply device, i.e. the power supply device does not overheat. The cooling device may in particular be in the form of a blower.
In order to keep heat losses to a minimum, the interface unit is preferably adapted to mechanically, i.e. physically, disconnect the electric heating means from the power supply means. By mechanically disconnecting the electric heating device from the power supply device, thermal energy can no longer be transferred from the thermal storage element and/or the electric heating device to the power supply device. Furthermore, if the electrical heating device is mechanically disconnected from the power supply, no cooling is required anymore. The interface unit is therefore preferably adapted to automatically disconnect the electric heating means from the power supply means, more preferably to automatically disconnect the electric heating means from the power supply means as soon as the charging process is finished. Advantageously, the interface unit is further adapted to stop the operation of the cooling means if the electric heating means is disconnected from the power supply means. In order to reduce heat losses caused by the cooling process, the interface unit preferably comprises a housing or a box in which the electrical heating device can be connected to the power supply. Furthermore, the interface unit is preferably adapted not only to disconnect, in particular automatically disconnect, the electric heating device from the power supply device, but also to reconnect, in particular automatically reconnect, the electric heating device with the power supply device. In the disconnected state, the respective connecting elements of the electric heating device and the electric power supply device are preferably arranged remote from each other.
Irrespective of whether the energy storage device is designed according to the first inventive concept or the second inventive concept, the energy storage device preferably further comprises a channel adapted to guide a fluid through the energy storage device for transferring thermal energy from the thermal storage element to the fluid. The channel preferably extends along or through the thermal storage element. The fluid may be, inter alia, water and/or steam. Preferably, the fluid is water, which is converted into steam, in particular superheated steam, by the transfer of thermal energy. The transfer of thermal energy from the thermal storage element to the fluid is hereinafter referred to as an energy discharge process.
A channel is herein considered to be a laterally closed or open conduit for conducting a fluid. The channels typically have inlets and outlets arranged at respective ends of the channels. If the channel is closed laterally, the inlet and outlet are the only way of entry into the channel. Thus, the channel is circumferentially surrounded by the confining material and may form, for example, a circular cross-section. In certain embodiments, the channel, which may also be referred to as a conduit, may be formed from, i.e., defined by, the material of the thermal storage element. Furthermore, the channel may also be provided in the steam generating block and defined by the material of the steam generating block. A conduit or tube defining a passage may also be provided. Even if not preferred in all embodiments, it is generally conceivable that the pipe or tube extends through the heat storage element or the steam generating block.
Similar to the charging process, the discharging of the energy storage device can be performed in a particularly efficient manner: the fluid used for driving the turbine, for example, may be led directly through a channel or pipe in order to be heated. With the aid of the turbine, the stored thermal energy can be converted, for example, into mechanical work and returned as electrical energy. In this process, preferably no intermediate medium is used to transfer thermal energy from the heat storage element to the medium driving the turbine. The medium driving the turbine is preferably a fluid which is led through a channel of the energy storage device.
Another advantage of the energy storage device according to the first and second inventive concepts is the use of solid materials for storing thermal energy. Solid materials generally allow the storage of large amounts of thermal energy in a relatively small space. Thus, the use of solid materials for storing thermal energy enables the energy storage device to be designed in a particularly compact manner.
A thermal storage element is an element specifically designed for storing thermal energy. Thus, the storage of thermal energy is generally the primary and preferably sole purpose of the thermal storage element.
If the channel extends through the heat storage element, it is preferably completely surrounded by the solid material of one or several heat storage elements (e.g. if there is more than one energy storage unit) along the entire longitudinal extension of the main part thereof. The channel is preferably completely surrounded along at least 60%, more preferably at least 80% of its longitudinal length by the solid material of the one or several heat storage elements.
The fluid is preferably water and/or steam. The use of water and/or steam as a fluid is particularly safe and allows a direct drive of the steam turbine. In a particularly preferred embodiment, the fluid entering the energy storage device and in particular the at least one energy storage unit is water in the liquid phase and the fluid leaving the energy storage device and in particular the at least one energy storage unit is water in the gas phase, i.e. steam. Thus, the energy storage device and in particular the at least one energy storage unit is preferably adapted to boil water and more preferably to boil water and further heat the obtained steam. In other words, the fluid in the form of liquid water preferably enters the energy storage device and in particular the at least one energy storage unit, and the fluid in the form of superheated steam preferably leaves the energy storage device and in particular the at least one energy storage unit. Such an embodiment of the energy storage device is particularly suitable in combination with a steam turbine to convert stored thermal energy into mechanical energy, which may be further converted into electrical energy.
In particular, in the energy storage device according to the first inventive concept, the solid material of the heat storage element is preferably a material having not only a good heat storage capacity but also a certain electrical conductivity so as to allow heating by an electrical current within the material.
The energy storage device according to both inventive concepts may comprise only a single energy storage unit. However, embodiments are preferred in which the energy storage device comprises a plurality of energy storage cells. Particularly preferred is an embodiment with a plurality of energy storage units, so that by applying a corresponding number of energy storage units, the energy storage device can be expanded according to the needs of the user. In embodiments having a plurality of energy storage units, the heat storage element of each energy storage unit preferably comprises at least one planar surface, such that the heat storage elements of different energy storage units are adapted to abut each other with their respective planar surfaces. The heat storage element may in particular have a substantially cuboid shape, in particular a plate-like shape. The abutment of the plurality of heat storage elements need not be direct but may also be indirect, for example with electrical heating means and/or steam generating blocks arranged therebetween. The electrical heating device and/or the steam generating block have a substantially flat configuration in order to be adapted to be arranged between the flat surfaces of at least two adjacent heat storage elements. In this way, a modular and easily expandable construction of the energy storage device can be achieved.
In another also preferred embodiment, each of the one or several energy storage units may have a substantially tubular shape, the central tube forming the channel and the thermal storage element concentrically surrounding the tube. By such a design, the at least one energy storage unit can be easily manufactured and in many cases can be arranged on site in a space-saving manner.
In a particularly preferred embodiment, each heat storage element has a substantially cuboid shape and each electric heating device has a substantially flat configuration. In this embodiment, steam generating blocks are additionally provided, each having a substantially rectangular parallelepiped configuration and comprising channels for guiding a fluid. The electric heating device of the present embodiment is adapted to be arranged between the heat storage elements and the steam generating block is adapted to be arranged between the heat storage elements, so that the energy storage device can be modularly designed with any number of heat storage elements, electric heating devices and steam generating blocks. Due to the modularity of this design, an energy storage device which can be designed according to the first or second inventive concept can be easily adapted to the current needs, in particular with regard to the thermal storage capacity.
If the channel is formed of an electrically conductive material, such as a metal, and extends through the thermal storage element designed according to the first inventive concept, the energy storage device preferably additionally comprises an electrical insulator in order to electrically insulate the channel from the thermal storage element. Since metals are preferably used to form the channels, in order to achieve high thermal conductivity, the material forming the channels typically has a much higher electrical conductivity than the thermal storage material. By providing an electrical insulator around the channel, the occurrence of a bypass current through the material forming the channel can be avoided during heating of the thermal storage element. The material of the electrical insulator should have a high resistivity, i.e. at least higher than the resistivity of the solid material of the thermal storage element. Furthermore, the electrical insulation should have a good thermal conductivity in order to be able to transfer thermal energy from the thermal storage element to the fluid in the channel efficiently. The electrical insulation is preferably in the form of a thin layer that completely surrounds the channel within the thermal storage element.
In a preferred embodiment, whether they are designed according to the first or second inventive concept, the channels are arranged in a steam generating block which is adapted to be arranged directly adjacent to the heat storage element and preferably has a substantially cuboid, in particular plate-like, configuration.
In other, also preferred embodiments, the channel may extend through the thermal storage element. The channels may particularly extend through the thermal storage element such that the temperature distribution within the thermal storage element remains substantially uniform throughout the thermal storage element during transfer of thermal energy from the thermal storage element to the fluid. This may be achieved, for example, if at least one energy storage unit is a multi-pass energy storage unit. A multi-pass energy storage unit is one such energy storage unit: wherein the channel does not extend in a straight line through the heat storage element but comprises at least one curved, meandering curve or the like, such that at least a part of the solid material is able to transfer thermal energy to at least two different adjacent parts of the channel during discharging. The multi-pass energy storage unit has the advantage that the temperature distribution within the thermal storage element remains more uniform during discharging. A more uniform temperature distribution means less thermal stress, thereby extending the useful life of the thermal storage element. In a multi-pass energy storage unit, the channels preferably have a two-dimensional or three-dimensional, single, double or multiple wire meandering, spiral or spiral form.
The channel may also extend through the heat storage element such that a temperature stratification is formed between the inlet and the outlet of the channel during transfer of thermal energy from the heat storage element to the fluid. The temperature stratification is preferably such that the temperature of the heat storage element increases continuously in a direction from the inlet to the outlet of the channel. Such temperature stratification may be achieved, for example, if the at least one energy storage unit is a single-pass energy storage unit. A single pass energy storage unit is one in which the channels extend through the heat storage element in substantially a single straight line, such that each section of solid material is able to transfer thermal energy to only one adjacent section of channels during discharging. Thus, the temperature distribution within the solid material of the heat storage element is not uniform during discharging. In the outlet region of the channel, the heat storage element generally has a higher temperature than in the inlet region of the channel, i.e. there is a pronounced temperature gradient within the heat storage element. Any energy storage unit having temperature stratification, including single pass energy storage units, is particularly suitable for controlling the temperature of the fluid at the exit of the channels.
The energy storage device may comprise an energy storage unit, in particular an energy storage unit with a stratified temperature distribution, e.g. the following single pass energy storage unit: which is arranged in series with and downstream of at least one further energy storage unit. The at least one further energy storage unit may be an energy storage unit with a uniform or stratified temperature distribution, for example a single-pass or multi-pass energy storage unit. Preferably, at least two energy storage units arranged in series are heated to different temperatures. In order to control the temperature of the fluid during discharging, the arrangement of energy storage units in series and downstream of one another is particularly advantageous.
Alternatively or additionally, an energy storage unit, in particular an energy storage unit with a uniform temperature distribution, for example a multi-pass energy storage unit, may be arranged in parallel with at least one further energy storage unit. The at least one further energy storage unit may again be an energy storage unit with a uniform or stratified temperature distribution, e.g. a single pass or multi pass energy storage unit. Preferably, at least two energy storage units arranged in parallel are heated to different temperatures. The parallel arrangement of the energy storage units allows the fluid flow through the energy storage units to be regulated, e.g. by a pump and/or a valve, in order to obtain a desired fluid temperature after mixing the two fluid flows.
As already mentioned above, the arrangement of the series and parallel energy storage units can of course be combined with one another in any desired manner in order to achieve particularly good adjustable, precise and/or stable temperature control of the fluid during the discharging process. The temperatures of the thermal storage elements arranged in series or in parallel preferably differ by at least 50 c, even more preferably by at least 100 c.
The energy storage device according to either of the two inventive concepts preferably additionally comprises a turbine for converting thermal energy stored in the thermal storage element into electrical energy by means of the heated fluid. The turbine is preferably a steam turbine, but may also be, for example, a gas turbine. In the case of a steam turbine, the fluid is preferably water. In the case of a gas turbine, the fluid is preferably air.
The invention also relates to a method for storing energy by means of an energy storage device, in particular by means of one of the energy storage devices as described above, wherein the energy storage device has at least one energy storage unit comprising a thermal storage element made of a solid material, has a channel adapted to conduct a fluid through the energy storage device for transferring thermal energy from the thermal storage element to the fluid, and has an electrical heating device for heating the thermal storage element by means of electrical energy. The method comprises the following steps:
heating the heat storage element, for example by a resistive heater or by using an electrical heating device to generate an electrical current within the solid material of the heat storage element; and
a fluid, in particular water and/or steam, is guided through a channel (which may in particular be part of a steam generating block) in order to transfer thermal energy from the heat storage element to the fluid, i.e. to heat the fluid.
The channel, which may also be referred to as a tube, may particularly extend along or through the heat storage element.
The heated fluid is preferably used to drive a turbine, in particular a steam turbine.
Before heating the heat storage element, the channel is advantageously purged by a gas, in particular by air. Purging the channels with gas allows for the removal of possible residues of fluids or other substances from the channels. The presence of fluid and/or other substances within the channels during heating of the thermal storage elements is generally undesirable because such substances may evaporate uncontrollably during charging and even damage the channels. Overheating of the channels due to uneven temperature distribution can be prevented by the described purging process. Purging is preferably performed by low velocity air.
In a preferred embodiment, at least two energy storage units are arranged in parallel with one another and are heated to different temperatures by means of respective electrical heating devices, wherein the fluid is guided through the respective channels in at least two fluid streams, and wherein the at least two fluid streams are regulated such that, after mixing of the two fluid streams with one another, a resulting predetermined target pressure, mass flow and/or temperature of the fluid is achieved, which is preferably between the temperatures of the at least two energy storage units. The two parallel fluid flows through the energy storage unit with thermal storage elements of different temperatures allow a particularly good adjustable, precise and/or stable temperature control of the fluid during discharging. The control of the mass flow and the pressure is preferably provided by one or several pumps and/or one or several valves arranged at the cold end of the system, i.e. upstream of the energy storage unit, in particular of the thermal storage element. The system preferably does not include any pumps and/or valves at the hot end.
In a further preferred embodiment, at least two energy storage units are arranged in series, a second energy storage unit being arranged downstream of the first energy storage unit, wherein the first energy storage unit is heated to a different temperature than the second energy storage unit by means of a respective electrical heating device, and wherein the temperature of the second energy storage unit corresponds to a predetermined target temperature of the fluid. Thus, the predetermined target temperature is typically the temperature of the fluid as it exits the most downstream energy storage unit of the at least two energy storage units arranged in series. Preferably, the predetermined target temperature is the temperature of the fluid as it leaves the energy storage device, and particularly preferably the temperature of the fluid as it enters the turbine. The control of the mass flow and the pressure is preferably provided by one or several pumps and/or one or several valves arranged at the cold end of the system, i.e. upstream of the energy storage unit, in particular of the thermal storage element. The system does not include any pumps and/or valves at the hot end.
Drawings
Preferred embodiments of the present invention will now be described with reference to the accompanying drawings, which are for illustrative purposes only and are not limiting. Shown in the drawings are:
fig. 1 is a schematic illustration of a (multi-pass) energy storage cell of an energy storage device according to an embodiment of the invention, wherein the electrical heating device has contact electrodes;
FIG. 2 is a schematic view of a (multi-pass) energy storage unit of an energy storage device according to another embodiment of the invention, wherein the electric heating device has an induction coil;
FIG. 3a is a schematic illustration of a (single pass) energy storage unit of an energy storage device according to yet another embodiment of the invention, with electrical insulation between the channels and the thermal storage elements;
FIG. 3b is a cross-sectional view of the energy storage unit of FIG. 3a along plane III-III;
FIG. 4 is a schematic illustration of a (single pass) energy storage unit of the energy storage device of FIG. 2 and a water pump for pumping water through the energy storage device;
FIG. 5 is a schematic diagram of an energy storage apparatus according to yet another embodiment of the invention, comprising three single pass energy storage units arranged in series;
FIG. 6 is a schematic illustration of an energy storage device according to yet another embodiment of the present invention, including a multi-pass energy storage unit, a water pump, and a steam turbine;
FIG. 7 shows a graph of storage temperature versus time along the main heat propagation direction of a thermal storage element in the case of a thermal storage element with temperature stratification;
fig. 8 is a perspective view of a (multi-pass) energy storage cell of the energy storage device of the present invention with a straight channel extending through the thermal storage element;
fig. 9 is a perspective view of a (multi-pass) energy storage cell of the energy storage device of the present invention, wherein a straight channel extends through the heat storage element, the channels being connected by a connecting element to form two serpentine channels;
FIG. 10 shows a graph of storage temperature versus time along the main heat propagation direction of a heat storage element in the case of a heat storage element with a uniform temperature distribution;
FIG. 11 is a schematic diagram of an energy storage apparatus according to yet another embodiment of the invention, including multi-pass and single-pass energy storage cells arranged in series;
FIG. 12 is a schematic diagram of an energy storage device according to yet another embodiment of the invention, including two multi-pass energy storage cells arranged in parallel;
FIG. 13 is a schematic diagram of an energy storage apparatus according to yet another embodiment of the invention, including multi-pass and single-pass energy storage cells arranged in parallel;
FIG. 14 is a schematic perspective view of an energy storage unit according to yet another embodiment of the invention, including a gas electrical insulator between the electrical heating device and the thermal storage element;
FIG. 15 is a schematic perspective view of an energy storage unit according to another embodiment of the invention, wherein an electrical heating device is disposed between two thermal storage elements;
fig. 16 is a schematic perspective view of an energy storage unit according to another embodiment of the invention, wherein an electrical heating device is arranged between two stacks of thermal storage elements;
FIG. 17 is a schematic perspective view of a variation of an electrical heating device for the energy storage device of the present invention;
FIG. 18 is a schematic perspective view of another variation of an electrical heating device for the energy storage device of the present invention;
FIG. 19 is a schematic perspective view of an energy storage unit according to another embodiment of the invention in which a plurality of cylindrical resistive heaters are disposed between a plurality of cylindrical thermal storage elements;
fig. 20a is a schematic cross-sectional view of an energy storage device of the invention with an interface unit for connecting and disconnecting the electric heating device to and from the power supply;
FIG. 20b the energy storage device of FIG. 20a in an open state of the interface unit;
FIG. 21 is a schematic perspective view of two rectangular parallelepiped heat storage elements and a plate-like vapor generation block stacked on each other;
FIG. 22 is a schematic perspective view of a plurality of hexagonal heat storage elements and a plate-like steam generating block abutting one another;
FIG. 23 is a schematic perspective view of three heat storage elements and a plate-shaped steam generation block abutting each other, each heat storage element having a cross-section of a circular sector;
FIG. 24 is a schematic perspective view of a plurality of rectangular parallelepiped heat storage elements and a plurality of plate-shaped steam generation blocks stacked on one another;
FIG. 25 is a schematic perspective view of a plurality of rectangular parallelepiped heat storage elements and a plurality of plate-like steam generation blocks stacked one upon another in another configuration compared to FIG. 24;
FIG. 26 is a schematic perspective view of a vapor generation block of the energy storage device of the present invention having a serpentine channel;
FIG. 27 is a schematic perspective view of a vapor generation block of the energy storage device of the present invention having a plurality of straight channels within the block;
FIG. 28 is a schematic perspective view of a vapor generation block of the energy storage device of the present invention wherein a plurality of straight channels inside the block are interconnected by tubes outside the block to form a serpentine channel;
FIG. 29 is a schematic perspective view of a thermal storage block with an integrated serpentine channel;
FIG. 30 is a schematic perspective view of a heat storage block with an integrated straight channel;
FIG. 31 is a schematic perspective view of a heat storage block with integrated straight channels interconnected by tubes external to the block to form serpentine channels;
FIG. 32 is a schematic perspective view of an energy storage device of the present invention having a modular construction with a plurality of stacked thermal storage elements, electrical heating devices, and steam generation blocks; and
FIG. 33 is a schematic perspective view of an energy storage device of the present invention having a similar modular construction as FIG. 32, but with an alternative arrangement and with increased heat storage capacity.
Detailed Description
In the following, features having the same or similar design and/or the same or similar function are denoted by the same reference numerals.
A first embodiment of an energy storage device according to the first inventive concept is shown in fig. 1. The energy storage device comprises an energy storage unit, which here has the form of a multi-pass energy storage unit 1. The multi-pass energy storage unit 1 comprises a thermal storage element 3, a channel 41, which may also be referred to as a tube, an electric heating device 5, a thermal insulator 6 and a housing 2.
The thermal storage element 3 is made of a solid material, i.e. a material which is always in the solid state during charging and discharging. Preferably, the thermal storage element has at least 10-4A resistivity of Ω m and not more than 1 Ω m.
The channel 41 has an inlet for introducing a fluid in the form of liquid water W and has an outlet through which the heated water leaves the multi-pass energy storage unit 1 in the form of steam S, in particular superheated steam S.
The thermal insulator 6 is provided directly and preferably over the entire outer surface of the thermal storage element 3 to prevent the stored thermal energy from dissipating to the outside. The housing 2 serves to receive and hold the thermal storage element 3 and the thermal insulator 6.
The electrical heating means 5 comprise two contact electrodes 51 directly attached to the solid material of the thermal storage element 3. The contact electrodes 51 are attached to two surfaces of the thermal storage element 3, which are arranged on opposite sides of the thermal storage element 3. The electric heating device 5 is connected to an electric power supply device 9 (source G of electric current), which may be, for example, a solar or wind energy system and/or a public power supply. During periods of high supply power, the electrical heating means 5 heats the thermal storage element 3 by applying a voltage difference across the contact electrode 51, which results in an electrical current being generated within the solid material of the thermal storage element 3. The current in turn causes resistive heating of the thermal storage element 3. Thus, the electrical energy from the electrical energy supply means 9 is converted into thermal energy stored in the thermal storage element 3 in a very direct and therefore efficient manner.
In an alternative embodiment, the electric heating device 5 may also comprise a connection to the channel 41 (see dashed lines in fig. 1) in order to electrically ground the channel 41.
During periods of high energy demand, the thermal energy stored in the thermal storage element 3 may be converted back into electrical and/or mechanical energy. For this purpose, liquid water W is introduced into the channel 41 via an inlet by means of, for example, a pump, and is guided through the channel 41 so as to pass through the heat storage element 3 to an outlet of the channel 41. On its way through the channel 41, heat energy is transferred from the heat storage element 3 to the water, whereupon the water is heated and evaporated into steam S. The steam S is further heated, i.e. superheated, on the way towards the outlet of the channel 41.
A turbine, in particular a steam turbine 14 (see fig. 6), may be connected to the outlet of the channel 41. The superheated steam S drives the steam turbine 14 for converting thermal energy back into electrical energy and/or into mechanical energy. The steam turbine 14 may have several low-pressure and high-pressure sections and/or include several low-pressure and high-pressure turbines, as is well known to the skilled person. In the steam turbine 14, the steam S is cooled. A thermal expansion valve may additionally be present in order to convert the already cooled vapor S back into its liquid phase. Liquid water W may then be introduced into the channel 41 again. Thus, the energy storage device preferably comprises a closed cycle for circulating water during discharging. In other alternative embodiments, an open cycle (open circle) may be provided.
The second embodiment of the energy storage device according to the first inventive concept as shown in fig. 2 differs from the energy storage device in fig. 1 in the design of the electric heating device 5. The induction coil 52 is used here to induce a current within the solid material of the thermal storage element 3, rather than to generate a current in the thermal storage element 3 through a pair of contact electrodes. The induction coil 52 comprises a plurality of windings, which are preferably wound around the heat storage element 3 in order to induce a current as uniformly as possible within the heat storage element 3. An induction coil 52 also surrounds the channel 41.
The multi-pass energy storage unit 1 as shown in fig. 2 is shown in a state before the charging process, i.e. in an unheated state. In order to achieve as uniform a heating of the heat storage element 3 as possible, the channel 41 is purged with low-velocity air a. In so doing, possible residues of residual water and/or other unwanted substances are removed from the channels 41 and therefore no longer lead to uncontrolled evaporation and associated overheating hot spots during the charging process.
Fig. 3a and 3b show a particularly preferred embodiment of an energy storage apparatus according to the first inventive concept, wherein a single pass energy storage unit 1 having a substantially tubular shape is used. The production of a tubular shaped single pass energy storage unit 2 has proven to be particularly easy and thus cost-effective. Furthermore, a single-pass energy storage unit 2 having such a shape can be arranged in a space-saving manner in many practical cases. The embodiments shown in fig. 3a and 3b may also be applied to an energy storage device according to the second inventive concept.
As can be seen from fig. 3a, the channels 41 extend along a substantially straight line through the thermal storage element 3. Or in other words, the channel 41 extends through the heat storage element centrally and parallel to the longitudinal central axis of the heat storage element. Therefore, the temperature distribution within the heat storage element 3 during discharging becomes uneven, i.e., there is a significant temperature gradient, i.e., temperature stratification, in the heat storage element 3 from the inlet to the outlet of the channel 41. Such an uneven temperature distribution (or temperature stratification) may be advantageous in order to maintain a constant temperature of the steam S at the outlet of the channel 41.
The energy storage device as shown in fig. 3a and 3b further comprises an electrical insulator 7 for electrically insulating the channel 41 from the thermal storage element 3, the channel 41 preferably being a metal channel, i.e. a channel formed of a metallic material, in all embodiments. The electrical insulator 7 serves to prevent bypass currents in the channel 41 during charging. The electrical insulator 7 is preferably represented by a thin layer of an electrically insulating but thermally conducting material. Possible examples of materials for the electrical insulator 7 are nitrides such as AlN and SiN and carbides such as SiC.
In the embodiment shown in fig. 4, the energy storage device additionally comprises a pump 10 for delivering water W to and through the channel 41.
Fig. 5 shows an embodiment of the energy storage apparatus according to the first or second inventive concept, wherein three single pass energy storage units 2 are arranged in series. The advantage of the energy storage device of fig. 5 is similar to the advantage of fig. 3a and 3b, i.e. the temperature profile gradient from inlet to outlet, for controlling the outlet temperature of the steam S. In the embodiment of fig. 5, the thermal stress is reduced due to the division into three single pass energy storage units 2. The arrangement of fig. 5 also allows the heat storage elements 3 of different single pass energy storage units 2 to be heated to different temperatures during charging.
Fig. 6 shows an embodiment with a single multi-pass energy storage unit 1. Water W is transported by the pump 10 in an open or closed loop through the multi-pass energy storage unit 1 and to the steam turbine 14 to drive the steam turbine.
Regardless of the type of energy storage unit, two discharging concepts can be implemented:
discharge of thermal storage with temperature stratification.
Discharge of thermal stores with uniform temperature distribution.
The first concept is illustrated in fig. 4 to 6. In fig. 4, a particularly simple system with a single heat storage element 3 and a single straight channel 41 extending through the heat storage element 3 is shown. The temperature distribution along the main heat propagation direction PD of the thermal storage element 3 for different times during the discharging process is shown in fig. 7. At the beginning of discharging (t)0) The temperature along the thermal storage element 3 is constant and during discharging the temperature of the storage material near the entrance of the channel 41 becomes significantly lower than the temperature of the storage material near the exit, i.e. there is temperature stratification within the element along the main direction PD. The temperature distribution (average temperature in a cross-section perpendicular to the flow direction) has a propagation along the flow directionThe form of the propagating wave. As can be noted in FIG. 7, the temperature at the outlet of the channel 41 is at t0To t3Is kept constant, which means that the steam S is at t0To t3At a constant temperature out of the thermal storage element 3.
The same effect as shown in fig. 7 can also be observed in each thermal storage element 3 shown in fig. 5 (preferably with different amplitude) and along the main direction PD of the multi-pass energy storage unit 1 shown in fig. 6 (which is here oriented perpendicular to the flow direction).
To obtain a uniform temperature distribution, the system may have a plurality of straight channels extending in parallel but with opposite flow directions, i.e. with alternating inlets and outlets, as shown in fig. 8. In the embodiment shown in fig. 8, a single rectangular parallelepiped heat storage element 3 has a plurality of straight channels 41, but the flow direction of each adjacent channel 41 is opposite. Thus, the temperature of the heat storage will vary over time as shown in fig. 10, i.e. for the entire heat storage element 3 and at t0To t3It is substantially uniform at all times.
If a reduced number of inlets and outlets should be provided for the same heat storage element 3 as shown in fig. 8, a curved connecting element 42 may be provided to connect adjacent inlets and outlets of the heat storage element 3 as shown in the embodiment shown in fig. 9. In this case, two serpentine channels 41 are provided, each having an inlet and an outlet. Again, a uniform temperature of the heat storage element 3 may be achieved by changing the flow direction in adjacent portions of the channel 41.
Therefore, a discharge with temperature stratification would have particular advantages for controlling steam parameters. The discharging with a uniform temperature distribution may have particular advantages due to the low temperature gradient within the thermal storage element 3. However, a combination of a plurality of such thermal storage elements 3, which may be of different or identical types, as explained below with reference to fig. 11 to 13, is particularly advantageous. The energy storage devices shown in fig. 11 to 13 may be according to any of the first or second inventive concepts or even represent a combination thereof.
The energy storage devices as shown in fig. 11 to 13 each comprise a first energy storage unit 1 arranged in series (fig. 11) or in parallel (fig. 12 and 13) with a second energy storage unit 1. In each of fig. 11 to 13, the first energy storage unit 1 is an energy storage unit 1 having a uniform temperature distribution during discharging. In fig. 11 and 13, the second energy storage unit 1 is an energy storage unit 1 with temperature stratification between the inlet and the outlet during discharging. In fig. 12, the second energy storage unit 1 is also an energy storage unit 1 with a uniform temperature distribution during discharging. In the present exemplary embodiment of fig. 11 to 13, the energy storage unit 1 with a uniform temperature distribution is realized in each case by an exemplary provision of a multi-pass energy storage unit 1, and the energy storage unit 1 with temperature stratification is realized in each case by an exemplary provision of a single-pass energy storage unit 1. In the following and with respect to fig. 11 to 13, the description is directed to single-pass and multi-pass energy storage units 1, but it is to be understood that these embodiments are merely examples, and that each single-pass energy storage unit 1 may generally be replaced by any other energy storage unit 1 having temperature stratification, and that each multi-pass energy storage unit 1 may generally be replaced by any other energy storage unit 1 having uniform temperature distribution.
The single pass energy storage unit 1 is arranged downstream of the multi-pass energy storage unit 1. This embodiment combines the above-mentioned advantages of a uniform temperature distribution (i.e. the advantages of the multi-pass energy storage unit 1 herein) with the above-mentioned advantages of temperature stratification (i.e. the advantages of the single-pass energy storage unit 1 herein). The multi-pass energy storage unit 1 and the thermal storage element 3 of the single-pass energy storage unit 1 are preferably heated to different temperatures during charging. The temperature of the multi-pass energy storage unit 1 is preferably higher than the temperature of the single-pass energy storage unit 1.
For example, the multi-pass energy storage unit 1 shown in fig. 11 may be charged to the maximum possible temperature of the respective solid material of its thermal storage element 3. The multi-pass energy storage unit 1 is then used as a preheater and evaporator and also as a superheater for a certain time. The once-through energy storage unit 1 is charged to a temperature equal to the required temperature of the steam S. The once-through energy storage unit 1 then functions as a superheater. At the initial stage of the discharging process, the multi-pass energy storage unit 1 is charged with energy, and the output temperature of the steam at the outlet of the multi-pass energy storage unit 1 may exceed the temperature required for the steam S. In this case, this superheated steam will further charge the once-through energy storage unit 1 and maintain it at the desired temperature. Once the temperature at the outlet of the multi-pass energy storage unit 1 falls below the desired temperature of the steam S, the single pass energy storage unit 1 begins to operate as a superheater and maintain the desired steam temperature.
Different thermal storage elements 3 may be made of different materials to optimize the overall cost of the energy storage device. In each case, the outlet element at the lowest temperature may, for example, be made of a cheaper material than the element arranged upstream. It is also possible, for example, to arrange more than two elements (N elements) made of different materials and heated to different temperatures into a chain. The main advantage of this storage method compared to other methods is that the temperature of the output steam S is self-controlled, i.e. no active control elements are required.
A pump 10 to maintain the required mass flow and pressure is arranged on the cold side of the system. No hot valves and pumps or any other expensive equipment are required at the hot end of the system.
Fig. 12 shows another preferred embodiment of the invention, in which two multi-pass energy storage units 1 are arranged in parallel. During charging, the thermal storage elements 3 of the two multi-pass energy storage units 1 are heated to different temperatures. During the discharging process, the water W is guided in two separate flows through the process energy storage unit 1 and converted into steam S. The two streams of steam S are then combined and mixed within the steam collector 11. Each flow is delivered by a pump 10 arranged upstream, i.e. on the cold side, of the respective multi-pass energy storage unit 1. The resulting output temperature of the mixed steam S at the outlet of the steam collector 11 can be adjusted by corresponding control of the pump 10. In this way, the output temperature of the mixed steam S can be easily adjusted to a temperature between the temperatures of the two multi-pass energy storage units 1. By arranging the pump 10 upstream of the heat storage element 3, i.e. on the cold side of the system, the technical requirements on the pump 10 are reduced. Instead of two pumps, it is of course also possible to use, for example, a single pump 10 and two valves 12 and 13, as shown in the example of fig. 13.
For example, the first multi-pass energy storage unit 1 as shown in fig. 12 may be charged to the maximum possible temperature of the respective solid material of its thermal storage element 3. The second multi-pass energy storage element 1 may be charged to a temperature below that of the first multi-pass energy storage unit 1. The water flow W is split between the two multi-pass energy storage units 1 such that the resulting steam mixture at the output of the steam collector 11 has the required mass flow and the required temperature.
The embodiments of fig. 11 and 12 can of course be combined with one another in order to achieve a constant and well-adjustable output temperature of the steam S before it is led to, for example, a steam turbine.
In the embodiment of fig. 13, the multi-pass energy storage unit 1 is arranged in parallel with the single-pass energy storage unit 1. Also, the two energy storage units 1 are preferably heated to different temperatures during the heating process. The advantage of the multi-pass energy storage unit 1 is the combination of high heat capacity and extended life due to uniform temperature distribution and less thermal stress during discharging. An advantage of the single pass energy storage unit 1 is its temperature stability. By adjusting the mass flow of the water flow W through the two energy storage units 1, which is here done by means of the valves 12 and 13 and the valves 12 and 13 are also arranged upstream of the energy storage units 1, i.e. the cold side of the system, the temperature of the steam S at the output of the steam collector 11 can be adjusted and controlled. The high heat storage capacity is thus combined with a particularly good adjustable and controllable output temperature of the steam S. In this embodiment a single pump 10 is used to deliver both water streams. Instead of a single pump and two valves, it is of course also possible to use, for example, two pumps 10, as shown in the example of fig. 12.
Fig. 14 illustrates an embodiment of an energy storage device according to the second inventive concept. The energy storage device comprises a heat storage element 3 having a rectangular parallelepiped shape with a central through hole extending through the entire heat storage element along a straight line on a longitudinal central axis3. Arranged within the through hole is a resistive heater 53 of the electric heating means 5. In order to prevent short circuits that may occur within the solid material of the thermal storage element 3, an electrical insulator 8 in the form of a gas insulator is provided, which surrounds the resistive heater 53 along the entire length of the resistive heater 53. The material of the heat storage element 3 has a thickness of less than 10-4Preferred resistivity of Ω m. In order to keep the resistive heater 53 centered within the through hole of the thermal storage element 3, a spacer 81 made of a dielectric material is provided.
Thus, in the embodiment of fig. 14, the space between the resistive heater 53 and the material of the thermal storage element 3 is filled by an electrical insulator 8, which may be realized by a non-conductive gas (air, nitrogen, argon, carbon dioxide, or the like). The current (ac or dc) heats the resistive heater 53 and transfers heat by radiation to the inner surface of the heat storage element 3 and then by conduction to the interior of the solid material of the heat storage element 3. In the present embodiment, the resistive heater 53 has a circular cross section.
Fig. 15 shows an embodiment in which the resistive heater 53 has a rectangular cross section and is located between two rectangular parallelepiped heat storage elements 3. The resistive heater 53 may be formed of a meander-shaped strip as shown in fig. 15. In other embodiments, the resistive heater 53 may also be formed by a cylindrical element such as a tube or by any other shaped element.
Another arrangement with resistive heaters 53 between stacks of rectangular parallelepiped thermal storage elements 3 is shown in figure 16. Due to their flat surfaces, the heat storage elements 3 may be arranged such that they directly abut each other and heat transfer from the resistive heater 53 to the heat storage elements 3 is optimal. In all arrangements, the resistive heater 53 may be supported by a dielectric spacer, such as spacer 81 shown in fig. 14.
In some embodiments, the resistive heater 53 may be formed of resistive strips having a varying cross-sectional area and/or varying surface coverage along its longitudinal direction, as shown in fig. 17 and 18. In the variant of fig. 17, the cross-sectional area of the resistive heater 53 increases from left to right, which in use results in more heat being generated to the left than to the right. Similarly, the surface coverage of the resistive heater 53 shown in fig. 18 decreases from left to right, again resulting in less heat being generated towards the right in the figure in use. The embodiment of the resistive heater 53 as shown in fig. 17 and 18 is particularly advantageous, for example, in combination with a thermal storage element 3 having temperature stratification during discharging, as shown in fig. 7. According to one of the modifications shown in fig. 17 and 18, such a change in temperature can be equalized by the resistive heater 53 during charging.
Fig. 19 shows an embodiment in which a plurality of cylindrical heat storage elements 3 are provided. Between these heat storage elements 3, cylindrical resistive heaters 53 are arranged, and the cylindrical resistive heaters 53 are electrically insulated from the heat storage elements by surrounding electrical gas insulators 8. The resistive heaters 53 are preferably connected in parallel to the power supply 9.
Fig. 20a and 20b show an embodiment of an energy storage device according to the second inventive concept, i.e. with a gas electrical insulator 8 between the resistive heater 53 and the thermal storage element 3. Of course, the energy storage device as shown in fig. 20a and 20b may alternatively or additionally also be designed according to the first inventive concept.
The thermal storage element 3 and the resistive heater 53 of the energy storage device of fig. 20a and 20b are located inside the thermal insulator 6. Electrical power is supplied and distributed to the plurality of resistive heaters 53 through a power bus 17 also disposed inside the thermal insulator 6. Therefore, the electric heating means 5 and in particular the electric power bus 17 inside the thermal insulator 6 also get hot during charging and should therefore be made of a heat resistant material. Outside the thermal insulation 6, (cold) supply lines 19 connect the electrical energy bus 17 to standard electrical devices, such as bus bars, transformers and/or the public power grid. The standard electrical equipment is typically made of a low thermal resistance material (e.g., copper) and needs to be protected from heat.
In order to prevent the cold supply lines 19 from heating up, an interface unit 20 with a blower 22 is provided. The blower 22 serves to cool the connection between the electrical energy bus 17 and the supply line 19 by air or by another coolant. In order to keep heat losses to a minimum, the connection between the electrical energy bus 17 and the supply lines 19 is preferably arranged in a cooling tank 21. The cooling tank 21 is arranged outside the thermal insulator 6 and attached to the housing 2.
Therefore, during charging, the connection between the high temperature power bus 17 and the low temperature power supply line 19 is forcibly cooled by the blower 22. As long as the energy charging process is relatively fast, the overall heat loss is small. Once the charging process is complete and the supply of electrical energy is no longer required, the power supply line 19 may be physically disconnected from the electrical energy bus 17 so that no heat transfer from the energy bus 17 to the power supply line 19 may occur. Thus, the blower 22 may be turned off at the same time. In order to physically disconnect the power supply line 19 from the electrical energy bus 17, the interface unit 20 is adapted to decouple the respective coupling elements of the power supply line 19 and the electrical energy bus 17 such that in the decoupled state the coupling elements are arranged away from each other, as shown in fig. 20 b. Thus, by physically, i.e. mechanically, disconnecting the electrical power bus 17 and thus the electrical heating device 5 from the power supply line 19, heat losses can be kept to a minimum. After the charging process is completed, i.e. during storage and during discharging, the cooling box 21 is prevented from overheating by natural convection. As a protective measure, the blower 22 may be switched on temporarily if the temperature inside the cooling box 21 rises above a certain threshold. The interface unit 20 is preferably adapted to automatically disconnect the power bus 17 from the power supply lines 19.
Fig. 21 shows an embodiment according to the first or second inventive concept, in which the thermal storage element 3 has a rectangular parallelepiped shape. A plurality of channels 41 is arranged within the steam generating block 4, which has a cuboid-shaped, in particular plate-shaped, configuration. The channels 41 extend in a straight line parallel through the steam generating block 4. The steam generating block 4 is sandwiched between the two heat storage elements 2. Due to the flat and equally sized outer surfaces of the heat storage element 2 and the steam generating block 4, an optimal transfer of thermal energy from the heat storage element 3 to the steam generating block 4 is achieved during discharging. By arranging more heat storage elements 3 and steam generating blocks 4 on top of the upper heat storage element 3, the energy storage device can easily be expanded to increase its thermal capacity. The entire heat storage element block 3 and the steam generating block 4 are held together by gravity.
Another easily expandable embodiment of the energy storage device is shown in fig. 22, in which the thermal storage elements 3 have a hexagonal shape, in each case with six side surfaces. Between each pair of adjacent side surfaces is arranged a steam generating block 4.
The energy storage device shown in fig. 23 includes three heat storage elements 3. The cross section of these heat storage elements 3 is shaped in each case as a circular sector. These three elements are for example arranged to form a circle, wherein the steam generating block 4 is arranged between each pair of radial surfaces.
A preferred embodiment of the energy storage device is shown in fig. 24 and 25, in which a plurality of rectangular parallelepiped heat storage elements 3 are stacked on each other, and the steam generating block 4 is arranged between the heat storage elements 3. The steam generating block 4 may be arranged along a horizontal (fig. 24) or vertical (fig. 25) surface of the heat storage element 3. The arrangement of the channels 41 in the separate steam generating block 4 results in an easier construction and an improved thermal stress distribution.
Fig. 26 to 28 show a possible preferred design of a steam generating block 4 for use in one of the embodiments shown in fig. 21 to 25, for example.
The steam generating block 4 as shown in fig. 26 comprises a single serpentine channel 41 covering the entire plate-shaped steam generating block 4.
In the steam generating block 4 of fig. 27, a plurality of straight channels 41 extend in parallel through the steam generating block 4. The construction of the steam generating block 4 as shown in fig. 27 is particularly simple.
A further variant of a steam generating block 4 with straight parallel channels 41 and thus simple construction is shown in fig. 28. However, in order to have a serpentine channel with a single inlet and a single outlet, the openings of the channels 41 are connected by connecting elements 42 in the form of bent tubes.
Fig. 29 to 31 show different variants of a thermal storage element 3 with integrated channels 41 for guiding a fluid in order to transfer thermal energy to the fluid during discharging.
In the variant of fig. 29, the heat storage element 3 comprises an internal serpentine channel 41. The heat storage element 3 has a single inlet and a single outlet. To simplify the construction of the heat storage element 3 of fig. 29 in order to be able to access the interior of the channel 41 for e.g. cleaning purposes and/or to reduce thermal stresses, the heat storage unit 3 may be divided into two parts along the dash-dotted line as shown in fig. 29. In this case the channel 41 will be formed by a groove in the abutting surface of one or both parts of the heat storage element 3. In the variant of fig. 30 and 31 it is also possible to provide two portions each divided into channels in the form of grooves.
In the heat storage elements 3 of fig. 30 and 31, two channels 41 extend in each case along a straight line and in parallel through the respective element. The serpentine channel is realized in fig. 31 by connecting the two openings by means of a connecting element 42.
In fig. 32 and 33, two particularly preferred embodiments of the energy storage device according to the second inventive concept are shown. In both embodiments, a plurality of rectangular parallelepiped heat storage elements 3 stacked on one another are provided. The steam generating blocks 4 with channels 41 for releasing thermal energy through the fluid are arranged vertically (fig. 32) or horizontally (fig. 33) between the thermal storage elements 3. The plate-shaped steam generating block 4 is designed according to the embodiment shown in fig. 28, i.e. with straight parallel channels 41 interconnected by connecting elements 42. For supplying a fluid, e.g. water W, to the steam generating block 4, a common supply pipe 15 is provided, and for collecting a heated fluid, e.g. superheated steam S, from the steam generating block 4, a common collection pipe 16 is provided. The steam generating block 4 is connected in parallel to a supply pipe 15 and a collection pipe 16.
Between each pair of stacks of heat storage elements 3, a resistive heater 53 of a common electric heating device 5 is arranged. The plurality of resistive heaters 53 are arranged in parallel and extend along a vertical plane. In each case, the resistive heater 53 is formed by a meander-shaped strip with a flat surface and is surrounded by an electrical insulator 8 in the form of a gas insulator. To supply power to the resistive heater 53, a first power bus 17 and a second power bus 18 are provided. The resistive heater 53 is connected in parallel to the first power bus 17 and the second power bus 18.
The advantages of the embodiments of fig. 32 and 33 are in particular the easy scalability and construction of the energy storage device. The structure is modular so that the energy storage device can use the same type of elements to accommodate any required storage capacity.
The present invention is of course not limited to the foregoing embodiments and may be variously modified. For example, the embodiments of fig. 1 to 33 may be arbitrarily combined. Any embodiment combining the first and second inventive concepts is easily conceivable. Possible energy storage devices may include one or more multi-pass and/or one or more single-pass energy storage cells arranged in series and/or parallel. The thermal storage elements 3 of different energy storage units may also be made of different solid materials and/or different shapes. A number of further modifications are possible.
Reference numerals
1 energy storage unit 12 valve
13 valve
2 casing 14 steam turbine
3 Heat storage element
15 supply pipe
4 steam generating block 16 collecting pipe
41 channel
42 connecting element 17 Power bus
18 electric energy bus
5 electric heating device 19 cold power supply circuit
51 contact electrode
52 Induction coil 20 interface unit
53 resistive heater 21 cooling tank
22 blower
6 thermal insulator
7 electric insulator W water
8 electric insulator S steam
81 spacer A air
9 main heat propagation direction of power supply device PD
10 Pump
11 steam collector

Claims (22)

1. An energy storage device having at least one energy storage unit (1), the energy storage unit (1) comprising:
a thermal storage element (3) made of a solid material for storing thermal energy;
-electrical heating means (5) for heating the thermal storage element (3) by electrical energy; and
an electrical insulator (8) for electrically insulating the electrical heating device (5) from the thermal storage element (3),
is characterized in that:
the electrical insulator (8) is a gas insulator.
2. The energy storage device of claim 1, wherein the thermal storage element (3) has less than 10-4Resistivity of Ω m.
3. The energy storage device of claim 1 or 2, wherein the electrical heating device (5) comprises a resistive strip with varying cross-sectional area and/or varying surface coverage along the surface of the thermal storage element (3).
4. Energy storage device according to claim 1 or 2, wherein the electrical heating device (5) comprises a resistive rod or tube (53) inserted in a hole provided in the thermal storage element (3).
5. The energy storage device as claimed in one of the preceding claims, wherein the energy storage device comprises a plurality of energy storage units (1), and wherein the heat storage elements (3) of each energy storage unit (1) comprise at least one flat surface, such that the heat storage elements (3) are adapted to abut each other with their respective flat surfaces.
6. The energy storage device as defined in claim 5, wherein each of the thermal storage elements (3) has a substantially cuboid shape, in particular a plate-like shape.
7. The energy storage device of claim 5 or 6, wherein the electrical heating device (5) has a substantially flat configuration so as to be arranged between flat surfaces of at least two adjacent thermal storage elements (3).
8. An energy storage device having at least one energy storage unit (1), the energy storage unit (1) comprising:
a thermal storage element (3) made of a solid material for storing thermal energy; and
an electric heating device (5) for heating the thermal storage element (3) by means of electric energy,
wherein the electrical heating device (5) is adapted to heat the heat storage element (3) by generating an electrical current within the solid material of the heat storage element (3).
9. The energy storage device of claim 8, wherein the thermal storage element (3) has at least 10-4A resistivity of Ω m and not more than 1 Ω m.
10. Energy storage device according to claim 8 or 9, wherein the electrical heating device (5) comprises a contact electrode (51) attached to the thermal storage element (3).
11. Energy storage device according to one of the preceding claims, wherein the energy storage device comprises an interface unit (20) for connecting the electrical heating device (5) of at least one of the energy storage units (1) to a power supply device (19), and wherein the interface unit (20) comprises a cooling device (22) and is preferably adapted to mechanically disconnect the electrical heating device (5) from the power supply device (19).
12. The energy storage device according to one of the preceding claims, wherein the solid material of the thermal storage element (3) forms a miscible interstitial phase system, and in particular is made of a miscible interstitial alloy.
13. The energy storage device of one of the preceding claims, wherein the at least one energy storage unit (1) comprises a channel (41), the channel (41) being adapted to guide a fluid (W, S) through the energy storage device for transferring thermal energy from the thermal storage element (3) to the fluid (W, S), and preferably extending along or through the thermal storage element (3).
14. The energy storage device of claim 13, wherein the channel (41) is arranged in a steam generating block (4), the steam generating block (4) being adapted to be arranged directly adjacent to the heat storage element (3) and preferably having a substantially cuboid configuration, in particular a plate-like configuration.
15. The energy storage device of claim 13 or 14, wherein the channels (41) extend through the heat storage element (3) such that the temperature distribution remains substantially uniform throughout the heat storage element (3) during transfer of thermal energy from the heat storage element (3) to the fluid (W, S).
16. The energy storage device of claim 13 or 14, wherein the channel (41) extends through the heat storage element (3) such that a temperature stratification is formed between an inlet and an outlet of the channel (41) during transfer of thermal energy from the heat storage element (3) to the fluid (W, S).
17. The energy storage device as claimed in one of the preceding claims, wherein each heat storage element (3) has a substantially cuboid shape and each electric heating device (5) has a substantially flat configuration, wherein steam generating blocks (4) are provided, each having a substantially cuboid configuration and comprising channels (41) for guiding a fluid (W, S), and wherein the electric heating devices (5) are adapted to be arranged between the heat storage elements (3) and the steam generating blocks (4) are adapted to be arranged between the heat storage elements (3), such that the energy storage device can be modularly designed with any number of heat storage elements (3), electric heating devices (5) and steam generating blocks (4).
18. Method for storing energy by means of an energy storage device, in particular by means of an energy storage device as claimed in one of the preceding claims, having at least one energy storage unit (1), the energy storage unit (1) comprising: a thermal storage element (3) made of a solid material; a channel (41) adapted to guide a fluid (W, S) through the energy storage device for transferring thermal energy from the thermal storage element to the fluid (W, S); and an electric heating device (5) for heating the thermal storage element (3) by electric energy, the method comprising the steps of:
-heating the heat storage element (3) using the electric heating device (5); and
-guiding a fluid (W, S) through said channel (41) in order to transfer thermal energy from said thermal storage element (3) to said fluid (W, S).
19. A method according to claim 18, wherein the heated fluid (W, S) is used to drive a steam turbine.
20. Method according to one of claims 18 or 19, wherein the channel (41) is purged by a gas, in particular by air (a), before heating the heat storage element (3).
21. Method according to one of claims 18 to 20, wherein at least two energy storage units (1) are arranged in parallel with each other and heated to different temperatures by respective electric heating devices (5), wherein the fluids (W, S) are guided through respective channels (41) in at least two fluid flows, and wherein the at least two fluid flows are regulated, preferably by one or several control devices arranged upstream of the energy storage units (1), such that: after mixing the two fluid streams with each other, the resulting predetermined target pressure, mass flow and/or temperature of the fluids (W, S) is achieved.
22. Method according to one of claims 18 to 21, wherein at least two energy storage units (1) are arranged in series, a second energy storage unit being arranged downstream of a first energy storage unit, wherein the first energy storage unit is heated to a different temperature than the second energy storage unit by means of a respective electrical heating device (5), and wherein the temperature of the second energy storage unit corresponds to a predetermined target temperature of the fluid (W, S).
CN202080044788.XA 2019-06-17 2020-03-23 Energy storage device and method of storing energy Pending CN114041036A (en)

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EP18004723 2019-06-17
PCT/EP2020/057977 WO2020254001A1 (en) 2019-06-17 2020-03-23 Energy storage device and method for storing energy

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