SYSTEM FOR STORING ENERGY
A system for storing energy, including a heat accumulator, which includes a storage region and an outer wall surrounding the storage region, said storage region having a heat storage medium, an intermediate region between the storage region and the outer wall being at least partially filled with a gaseous medium and a support material, and the intermediate region being coupled to a pump device such that a pressure of the gaseous medium can be regulated is provided.
This application claims priority to PCT Application No. PCT/DE2014/100244, having a filing date of Jul. 10, 2014, based on DE 10 2013 107 463.4, having a filing date of Jul. 15, 2013, the disclosure of both are herewith incorporated by reference in their entireties.
FIELD OF TECHNOLOGYThe following relates to a system for storing energy.
BACKGROUNDVarious systems are known for storing energy, for example a heat accumulator for storing thermal energy.
Heat accumulators in the interior of a house, for example, are known, said heat accumulators holding a large volume of water in a steel or plastic container. The container is insulated with a thermal insulation, which is usually 20 to 40 cm thick. The water in the heat accumulator is heated for example by means of a solar thermal system. Connected to the heat accumulator is a heating system, by means of which the house can be heated in winter.
Further heat accumulators are disclosed in documents U.S. Pat. No. 3,823,305, DE 37 25 163 A1, DE 10 2011 107 315 A1, U.S. Pat. No. 4,520,862 and DE 1934283.
SUMMARYAn aspect relates to improved technologies for storing energy. In particular, heating of a building is to be enabled with a heat accumulator.
A system for storing energy is provided. The system comprises a heat accumulator. The heat accumulator comprises a storage region, which comprises a heat storage medium, and an outer wall surrounding the storage region. An intermediate region between the storage region and the outer wall is filled at least partially with a gaseous medium and a support material. Furthermore, the intermediate region is coupled with a pumping device, in such a way that a pressure of the gaseous medium can be controlled. In one embodiment, the system comprises only the heat accumulator. Further components can be provided in other embodiments. The intermediate region with the controllable gas surrounding by the outer wall is also referred to as vacuum insulation.
The heat accumulator can be coupled with a device which introduces energy into the heat storage medium, in such a way that the heat storage medium is heated. The heating of the heat storage medium can take place for example by means of electrical energy. The heated heat storage medium releases the thermal energy to the surroundings, for example in the form of thermal radiation or convection. The thermal energy is able to penetrate through the intermediate region and the outer wall and thus heat the surroundings of the heat accumulator.
The pumping device enables a control of the heat release. The thermal conductivity of a gaseous medium is closely linked to the mean free path length of the molecules. At a given temperature, the thermal conductivity is independent of pressure in a wide pressure range and therefore of the gas density. If the mean free path length of the molecules becomes greater than the spacing of differently temperature-regulated walls between which a heat transfer is taking place, the thermal conductivity becomes pressure-dependent. Thus, if the intermediate region is evacuated, i.e. the pressure of the gaseous medium falls below a threshold value, the thermal conductivity of the medium diminishes with falling pressure. The heat transfer from the heat storage medium to the surroundings outside the outer wall can thus be almost completely prevented. If the surroundings are to be heated, the pressure of the gaseous medium can be increased in order to enable a heat transfer. The heat transfer from the heat storage medium to the surroundings can thus be controlled by means of the selection of the pressure of the gaseous medium.
The gaseous medium can be a pure gas, for example hydrogen or helium, or can be present as a gas mixture, for example air. The threshold value from which the thermal conductivity of the gaseous medium becomes pressure-dependent depends on the specific gas or gas mixture. The heavier a gas molecule, the shorter the mean free path length.
A support material is disposed at least partially in the intermediate region. This makes it possible to generate a supported vacuum in the intermediate region. The mean free path length of the gas molecules is (greatly) reduced in the supported vacuum. It is thus not necessary to reduce the pressure excessively in order to achieve a high thermal insulation. The support material can be constituted for example as a fine-porous material and/or as a heat-insulating material. The support material can for example be constituted in the form of solid elements, for example one or more plates, or as free-flowing bulk material. The plate(s) can for example comprise glass fibers, a silicate, silica or a combination of the aforementioned materials. The bulk material preferably has a uniform density, an essentially identical grain size and/or an identical material composition. Hollow glass microspheres, for example, can be used as the bulk material. An inlet opening can be formed in an upper region in the outer wall, through which the bulk material can be introduced into the intermediate region. Furthermore, an outlet opening can be formed in the bottom region of the outer wall, through which the bulk material can be removed from the intermediate region. The thickness of the outer wall can be reduced in the presence of a supported vacuum without its stability being adversely affected. The outer wall can for example comprise a 1 to 2 mm thick stainless steel wall. Provision can be made such that the support material completely fills the intermediate region. For example, one or more plates can be disposed in the intermediate region in such a way that the latter is completely filled. In this case, the gaseous medium can for example be located essentially in pores and/or gaps between components of the plates. The thermal insulation by means of the supported vacuum can be more effective roughly by a factor 20, 30 or 50 than insulation with conventional materials with which no pressure reduction takes place.
The support material is understood in the sense that a supported vacuum is generated with the creation of an underpressure. As described above, this means that the mean free path length of the molecules is shortened. In addition, the support material can be constituted to perform a statically bearing function. As a result of the reduction of the pressure in the intermediate region, forces act on the outer wall that are dependent on the pressure difference between the external pressure and the pressure in the intermediate region. The support material can be constituted to take up these forces and to prevent the deformation of the outer wall. In this case, the support material thus performs two functions. It supports both the vacuum and also mechanically the outer wall. Such a support material can also be referred to as a statically bearing support material. Furthermore, the support material can serve as radiation protection (against thermal radiation).
The intermediate region can be filled at least partially with at least two different support materials. A support material can be a statically bearing support material. Another support material can be a statically non-bearing support material. The support materials can be disposed in several layers. The statically non-bearing support material can also be referred to as a filler material or insulation material. The non-bearing support material (insulating material) can also serve as radiation protection (against thermal radiation).
According to an embodiment, the intermediate region can be filled at least partially or completely with four support materials. The four support materials can be disposed in such a way that two support materials are directly adjacent to the outer wall and have no contact with the storage region. The two support materials constitute an outer support layer. Two other support materials can be disposed directly adjacent to the storage region and have no contact with the outer wall. They constitute an inner support layer. The heat transfer coefficients of the four support materials can be the same or different. Furthermore, the heat transfer coefficients of the two support materials of the outer layer can be the same or different Finally, the heat transfer coefficients of the two other support materials of the inner layer can also be the same or different.
Provision can be made such that one end of the statically bearing support material lies adjacent to the storage region and another end of the statically bearing support material lies adjacent to the inner side of the outer wall. The statically bearing support material extends over the entire length of the intermediate region between the storage region and the outer wall. A support is thus formed. A plurality of such supports can also be disposed in the intermediate region. The region between the supports can be filled at least partially with an insulation material. The thermal insulation can thus be adapted. Costs and/or material can be saved. A further insulation material can be provided directly adjacent to the storage region. The region between the columns is thus filled (in part) with a double ply. The further insulation material can be temperature-dependent, i.e. have a melting temperature or sublimation temperature greater than 600° C., preferably greater than 800° C., more preferably greater than 1000° C. In the case where the storage region comprises a solid heat storage medium, for example a concrete core, the further insulation material can have a melting temperature or sublimation temperature in the range from 1000° C. to 1400° C. The maximum heat release of the storage region can be adjusted by the choice of the further insulation material. The further insulation material can be plate-shaped, for example a plate containing silica.
The use of a several plies of support layers (same or different materials) has the following advantages: the maximum heat transfer coefficient can be dimensioned, a greater range of the heat transfer coefficient can be adjusted, thinner insulating thicknesses can be used, a higher storage capacity (maximum temperature) of the heat accumulator is possible and the volume of the heat accumulator can be reduced.
The greater range of the heat transfer coefficient is possible due to the use of different materials beside one another (e.g. statically bearing and statically non-bearing). In the case of statically non-bearing materials, the thermal conduction can be further reduced. A lower heat transfer coefficient can be achieved, right up to a multi-ply arrangement (multilayer arrangement) in which virtually only thermal radiation still has to be prevented.
The heat accumulator can be connected rigidly to a floor of a building. Provision can be made such that the heat accumulator is integrated into foundations of a building. Furthermore, provision can be made such that a bottom side of the storage region is completely surrounded by the outer wall. An insulation can be formed at a bottom side of the heat accumulator. Provision can be made such that a support material is disposed beneath the storage region inside the intermediate region, for example in the form of the aforementioned plate or plurality of plates. By regulating the pressure of the gaseous medium, a thermal insulation in the bottom region can thus also be guaranteed. The storage region can for example stand on the plate (or the plates). Alternatively or in addition, a chamber can be constituted beneath the heat accumulator. The chamber can comprise a chamber wall which surrounds a chamber region. The chamber region can be filled at least partially with a further gaseous medium and a further support material. Furthermore, the chamber region can be coupled with the pumping device or a further pumping device, in such a way that a pressure of the further gaseous medium can be controlled. A heat release in the direction of the bottom can thus be controlled. The embodiments in respect of the gaseous medium and the support material apply accordingly to the further gaseous medium and the further support material. Provision can in particular be made such that the gaseous medium and the further gaseous medium as well as the support material and the further support material are the same. Furthermore, the insulation at the bottom side can, alternatively or in addition, comprise one or more foam glass plates, which for example are stacked upon one another.
Provision can be made such that the heat accumulator is disposed in the building in such a way that it is surrounded on all sides by the external building wall. For example, the heat accumulator is disposed essentially centrally in the building in order to enable uniform heating of the building. Provision can be made such that the heat accumulator is constituted free-standing in the building. Furthermore, provision can be made such that the heat accumulator is surrounded, for example completely, by an internal building wall of the building. The heat accumulator can be integrated into the wall construction of the building. For example, the heat accumulator can extend over several stories of the building. The shape of the heat accumulator can be adapted here to the geometry of the building. The heat accumulator can for example have a curved shape. Provision can be made such that heat conducting elements are disposed at the outer wall of the heat accumulator, said heat conducting elements extending into the building in order to distribute the heat.
Provision can be made such that a part of the heat accumulator is disposed outside the building or is located beneath the building, for example in the cellar. Through the use of different support materials, the maximum heat insulation can be kept in the outer part by a particularly small mean free path length of the support material and the heat release can also be controlled in the interior of the building.
According to another embodiment, the building can be constituted with a vacuum insulation. The vacuum insulation can comprise outer walls and/or a floor (e.g. for a cellar). The vacuum insulation can be coupled with the pumping device. The vacuum insulation leads to good thermal insulation of the building and can be controlled. Furthermore, the vacuum insulation is somewhat thinner than conventional thermal insulation systems. It is also easy to install. Moreover, it enables the use of smaller heat accumulators in the building. The embodiments in respect of the vacuum insulation of the heat accumulator apply analogously to the vacuum insulation of the building.
The heat accumulator can be free from connections to a heating system of the building. Furthermore, the building itself can be free from a heating system. Provision can be made such that heating of the building is achieved exclusively by means of the heat accumulator. It is advantageous for this if the external building wall is constituted with a thick (good) thermal insulation. In addition, provision can be made to install a plurality of heat accumulators in the building. Provision can be made here such that each of the plurality of heat exchangers is constituted in each case with a pumping device. Alternatively, a common pumping device can be provided, which is coupled to the plurality of heat accumulators. According to an embodiment, the heat accumulator can be configured to release heat stored in the heat storage medium essentially over the entire area of the outer wall. The release of the heat takes place, for example, distributed essentially uniformly over the entire area of the outer wall. According to an alternative embodiment, a plurality of zones can be constituted in the intermediate region, in such a way that a release of the heat stored in the heat storage medium takes place with differing intensity via the outer wall. The different zones can be constituted for example by different thicknesses of the support material, in particular of the plates, and/or by different materials. Furthermore, the intermediate region can be divided by means of a plurality of intermediate walls into a plurality of intermediate sub-regions closed off from one another. The pressure in the intermediate sub-regions can be controlled independently of one another, for example by means of one or more pumping devices coupled to the sub-regions, so that the heat release can thus be controlled.
The outer wall of the heat accumulator can be made of a metal or a metal alloy, especially stainless steel, of a glass or of a plastic. The outer wall can be constituted in one part or multi-part. Expansion elements can be constituted between the elements of the outer wall, which take up an expansion of the heat transfer medium during heating. The outer wall can for example have a corrugated shape. The outer wall can be constituted by a foil, for example a metal foil. The outer wall can be free from silvering on an inner side.
A gas tank can be coupled to the pumping device, said gas tank accommodating the gaseous medium during pumping out (i.e. reduction of the pressure). If the pressure is to be subsequently raised, the gaseous medium stored in the gas tank can be discharged again into the intermediate region.
The pumping device can be constituted as a vacuum pump, for example a displacement pump, a molecular pump or a turbo-molecular pump.
The heat accumulator can be constituted as a long-term heat accumulator. A long-term heat accumulator is configured to store heat in the hot season, for example when there is strong solar radiation, and to heat a (well insulated) building in the cold season with the stored heat.
Provision can be made for a cooling element, for example a cooling pipe, to be disposed at an outer side of the outer wall. The outer wall can thus be cooled if need be, if the heat release from the storage region is undesirable high. A plurality of cooling elements can also be provided. Cooling of the building can if necessary be carried out with the cooling element. Provision can be made such that the cooling element is coupled with a cold water pipe of a building or a rainwater tank outside the building.
According to another embodiment, provision can be made such that a heat exchanger device is disposed inside the outer wall, said heat exchanger device being coupled with the storage region in such a way that a heat exchange medium of the heat exchanger device takes up heat from the heat storage medium, and wherein the heat exchanger device comprises a pipe element which penetrates the outer wall and by means of which the mentioned heat exchange medium can be transported into a region outside the outer wall. The heat exchange between the heat exchange medium and the heat storage medium can also take place by means of a controllable vacuum. Provision can be made such that a further intermediate region is formed between the heat storage medium and the heat exchange medium, said further intermediate region being filled with a further gaseous medium. The further intermediate region can be coupled to the pumping device of the heat accumulator. Alternatively, a further pumping device can be coupled with the further intermediate region. The heat release from the heat storage medium to the heat exchange medium can be controlled by controlling the pressure of the further gaseous medium in the second intermediate region. The further gaseous medium can be identical to the gaseous medium of the heat accumulator. Alternatively, the further gaseous medium can be different from the gaseous medium. The further gaseous medium can be a pure gas or can be present as a gas mixture, for example air. Hot drinking water, for example, can be provided with the heat exchanger. A plurality of heat exchanger devices can be disposed inside the outer wall. The plurality of heat exchanger devices can be coupled with a common pumping device or each coupled with a separate pumping device.
The system can furthermore comprise a hot water tank, which is coupled with the heat accumulator in such a way that heat is released from the heat accumulator to the hot water tank in order to heat water in the hot water tank. The hot water tank can be constituted with a vacuum insulation. Overheating of the hot water tank is thus avoided. The embodiments in respect of the vacuum insulation of the heat accumulator apply analogously to the vacuum insulation of the hot water tank.
In another embodiment, the system can furthermore comprise a generator for generating electrical energy, which is coupled with the heat accumulator so that the generator can be operated with heat from the heat accumulator. The generator can be coupled for example with a steam turbine or with a Sterling engine. A steam turbine comprises a rapidly rotating shaft, provided with many turbine blades against which water vapor flows. The water vapor can be heated with the heat from the heat accumulator. A Stirling engine is a thermal engine, in which a working gas such air, helium or hydrogen in an enclosed volume is heated from the exterior in one region and cooled in another in order to perform mechanical work. The heating can again take place by means of the heat from the heat accumulator. Electrical energy can thus be stored more cheaply than in chemical batteries. The Stirling engine can be coupled by means of the pumping device to the heat accumulator.
Provision can be made such that the storage region comprises a solid heat storage medium. In this case, the storage region is constituted by a solid storage core. A solid body as a heat storage medium can be heated to very high temperatures of for example several hundred degrees Celsius. A large quantity of heat can thus be stored in a relatively small space. As a solid heat storage medium, use can be made for example of basalt chips, concrete, soapstone, fireclay or steel. Provision can be made such that one or more heat exchanger devices are disposed in the solid heat storage medium. The one or more heat exchanger devices can be separated by a heat-resistant material from the solid heat storage medium.
When use is made of a solid heat storage medium, provision can be made such that the heat accumulator comprises, for confinement, solely the outer wall and is free from inner walls and further outer walls.
Furthermore, provision can be made such that the solid heat storage medium is evacuated. On account of their production, their machining and processing and their storage, solid bodies generally contain gas molecules not only on their surface, but also in their interior. The molecules can be dissolved in the crystal lattice, accumulated at grain boundaries or enclosed in cavities. If the surroundings of the solid body are evacuated, the gas molecules pass to the surface of the solid body (diffusion) and from there into the evacuated region (desorption). This process is also referred to as outgassing. The outgassing influences the generation and maintenance of a vacuum. Provision can be made such that a vacuum is created in the intermediate region of the heat accumulator, in such a way that the solid heat storage medium itself is evacuated, i.e. does not contain any or only a few gas molecules.
Provision can also be made such that the storage region is coupled with a photovoltaic device, by means of which the heat storage medium can be heated. A photovoltaic device converts light energy into electrical energy. For example, sunlight can be converted by means of a solar cell into electrical energy. The electrical energy can be used to heat the heat storage medium. Provision can for example be made such that a photovoltaic system is installed on a roof of the building, said photovoltaic system being coupled with the heat accumulator. Provision can be made such that the photovoltaic device is constituted with a small-sized inverter. Alternatively, the photovoltaic device can be constituted free from an inverter. In both cases, the heat storage medium can also be heated with direct current.
According to another development, provision can be made such that the storage region comprises a heat storage fluid surrounded by an inner wall. In this case, the heat accumulator is constituted double-walled. The intermediate region is formed between the inner wall and the outer wall, said intermediate region being filled at least partially with the gaseous medium and the support material. The heat storage fluid can for example be water. On account of its high specific thermal capacity and its relatively low viscosity, water as a heat storage medium makes acceptable demands on the technology. In particular, it makes the introduction and the removal of the stored thermal energy equally simple. Provision can be made such that the heat accumulator is constituted with a relief valve. The inner wall can be constituted for example by stainless steel.
The storage region can be coupled with a solar thermal system, by means of which the heat storage medium can be heated. The solar thermal system converts sunlight into thermal energy. Provision can for example be made for a solar thermal system to be installed on a roof of the building, said solar thermal system being coupled with the heat accumulator.
Alternatively or in addition, the storage region can be coupled with one or more parabolic collectors. Parabolic collectors bundle the sunlight, in the same way as in a solar thermal power station, and heat a heat transfer medium, for example water or liquid sodium.
Furthermore, provision can be made such that the heat storage medium is paraffin. In this case, the paraffin can if necessary be surrounded by an inner wall. The storage region can be coupled with a solar thermal system or a photovoltaic device in order to heat the paraffin.
Provision can be made such that a solid or a liquid heat storage medium is disposed in the storage region.
Provision can also be made such that the storage region is coupled with a photothermal device. The photothermal system combines the effects of photovoltaics and solarthermics. A solid as well as a liquid heat storage medium or a combination of the two can thus be heated. Furthermore, the storage region can be coupled with a furnace, for example a wood gasification furnace.
Provision can be made such that a solar installation, for example a photovoltaic device, a solar thermal system and/or a photothermal system, or another heating device (e.g. wood gasification furnace) are coupled with a heat pump. The heat pump is disposed for example outside the building. The energy supplied by the solar installation or the heating device is increased, for example while cooling the surroundings, and the increased thermal energy is fed to the storage region in order to heat the heat storage medium.
Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:
The same reference numbers are used for identical components in the following.
In
In the embodiment shown in
Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.
For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements.
Claims
1. A system for storing energy with a heat accumulator, which comprises a storage region, and an outer wall surrounding the storage region, wherein the storage region comprises a heat storage medium, wherein an intermediate region between the storage region and the outer wall is filled at least partially with a gaseous medium and a support material and wherein the intermediate region is coupled with a pumping device, in such a way that a pressure of the gaseous medium can be controlled.
2. The system according to claim 1, wherein the intermediate region is filled at least partially with at least two different support materials.
3. The system according to claim 2, wherein a statically bearing support material and a statically non-bearing support material are disposed in the intermediate region.
4. The system according to claim 2, wherein the support materials are disposed in several layers.
5. The system according to claim 1, also comprising a generator for generating electrical energy, which is coupled with the heat accumulator, so that the generator can be operated with heat from the heat accumulator.
6. The system according to claim 1, further comprising a hot water tank, which is coupled with the heat accumulator in such a way that heat is released from the heat accumulator to the hot water tank in order to heat water in the hot water tank.
7. The system according to claim 1, wherein the heat accumulator is configured to release the heat stored in the heat storage medium essentially over the entire area of the outer wall.
8. The system according to claim 1, wherein a plurality of zones is constituted in the intermediate region, in such a way that a release of the heat stored in the heat storage medium takes place with differing intensity via the outer wall.
9. The system according to claim 1, wherein a heat exchanger device is disposed inside the outer wall, said heat exchanger device being coupled with the storage region in such a way that a heat exchange medium of the heat exchanger device takes up heat from the heat storage medium, and wherein the heat exchanger device comprises a pipe element which penetrates the outer wall and by means of which the mentioned heat exchange medium can be transported into a region outside the outer wall.
10. The system according to claim 1, wherein the storage region comprises a solid heat storage medium.
11. The system according to claim 10, wherein the solid heat storage medium is evacuated.
12. The system according to claim 1, wherein the storage region comprises a heat storage fluid surrounded by an inner wall.
13. The system according to claim 1, wherein the storage region is coupled with a photovoltaic device, by means of which the heat storage medium can be heated.
14. The system according to claim 1, wherein the storage region is coupled with a solar thermal system, by means of which the heat storage medium can be heated.
15. The system according to claim 1, wherein a cooling element is disposed at an outer side of the outer wall.
Type: Application
Filed: Jul 10, 2014
Publication Date: May 26, 2016
Inventor: Jan HOLUB (Weißwasser)
Application Number: 14/903,293
