DEVICE FOR THERMAL ENERGY STORAGE

Description

Technical field

[0001] The invention relates to a device for storing thermal energy with a basin that has a storage area filled with a storage fluid and covered with an insulating layer. State of the art

[0002] Devices for storing thermal energy using water as the energy storage medium are known in the prior art. The water is stored in a basin and covered with an insulating layer to reduce heat transfer from the water to the environment, particularly the ambient air. Thermal energy can be supplied to or removed from the device by pumping water into or out of the basin. For example, German patent DK201870618A1 discloses such a thermal energy storage device in which an additional ballast layer is provided on top of the insulating layer. This ballast layer creates a gradient on the insulating layer, which facilitates drainage and venting. This device further includes maintenance systems for venting and drainage. US patent US4159736A discloses another storage device with a basin according to the preamble of claim 1.

[0003] A disadvantage of the current state of the art, however, is that ventilation and drainage must be carried out directly on the insulation layer using maintenance-intensive systems. The weight of these systems, the ballast layer, and any rainwater is exerted unevenly on the insulation layer, leading to deformations, stresses, and structural weakening. This further increases maintenance requirements. For the same reason, the typically very large surface area of ​​the device cannot be utilized further, which is why the device is preferably installed outside of urban or suburban areas. This, however, results in further heat losses during the transport of water as a heat transfer medium from the storage device to the heat consumers.Furthermore, heat-resistant floats must be provided for the insulation layer, which can withstand the continuous temperature stress caused by the water. Description of the invention

[0004] The invention is therefore based on the objective of designing a device for storing thermal energy in such a way that maintenance work and the material stress on the components involved are minimized, but the surface of the device can still be used for secondary purposes.

[0005] The invention solves the stated problem by mounting the insulation layer on the basin in a height-adjustable manner, and by separating the storage fluid from a usable layer arranged above the insulation layer, which can be raised and lowered with the insulation layer. The insulation layer divides the basin into two spatial areas and forms a liquid-tight barrier between these areas, with the lower storage area being designed as a thermal storage unit. This storage area can also have several layers of storage fluid, which can be separated from one another. In a preferred embodiment, the insulation layer can not only be liquid-tight but also form a thermal barrier. If heat energy is extracted from or supplied to the storage fluid, its temperature changes.This results in a change in the volume and fill level of the storage fluid. Consequently, the insulation layer rises or falls with the fill level, thus preventing the formation of negative pressures and / or an air layer, and ensuring that the insulation layer is always in direct contact with both the storage fluid and the working layer.

[0006] With water as the storage fluid, temperature changes alone can cause fill level changes of several meters, depending on the size and geometry of the device. However, fill level changes in the storage area result not only from heat input and output, but also from the addition or removal of storage fluid. According to the invention, this can be compensated analogously to a heat-induced change. With appropriate dimensioning of the insulation layer and a sufficiently high volume or weight of the functional layer, the pressure applied from the functional layer via the insulation layer to the storage fluid is high enough that the storage fluid remains in a liquid state for an extended period, but can be heated above its boiling point at atmospheric pressure.Since the insulation layer naturally has a large surface area, it can be assembled from individual modules for easier assembly and maintenance. The maximum required stroke of the insulation layer is determined, among other things, by the geometry and volume of the basin and can be easily calculated by a person skilled in the art. In a preferred embodiment, the insulation layer can be not only liquid-tight but also vapor-tight. For example, an earth fill can be provided as the working layer, spaced from the edge of the basin in such a way that it can be raised and lowered along with the insulation layer.

[0007] To ensure a homogeneous distribution of the weight load across the insulation layer and improve the device's static properties, it is proposed that the working layer be a body of water. Since the storage fluid and the body of water are separated from each other by the insulation layer in a liquid-tight manner, no buoyancy acts on the insulation layer, which in turn simplifies height-adjustable mounting. Furthermore, using a body of water as the working layer eliminates areas of higher stress. The body of water above the insulation layer protects it from harmful environmental influences such as frost, hail, etc., and also eliminates the need for the normally required drainage system. The body of water can be still water, such as a pond or lake, or flowing water, such as a stream or river.The body of water can subsequently be used for secondary purposes, for example, for floating photovoltaic systems or as a fish pond. Temporary, smaller accumulations of water, such as rain puddles, are expressly not considered bodies of water within the meaning of the invention. Furthermore, using a body of water as a working layer has the advantage that the volume or weight of the working layer can be easily determined by the height of the water column above the insulation layer.

[0008] If the temperature of the storage fluid changes, air can escape from the fluid and accumulate directly beneath the insulation layer. This causes uneven pressure on the insulation layer and locally increased wear. However, any penetrating air can be efficiently removed if a vent is provided for the storage area within the insulation layer's support structure. Since the pressure from the load-bearing layer, particularly the water, is naturally distributed homogeneously across the surface of the insulation layer, persistent air pockets far from the edges can be avoided and simply vented away. Therefore, the vent can preferably be located at the highest point of the support area to ensure efficient venting of the entire side of the insulation layer facing the storage area.For example, the insulation layer can have grooves leading to ventilation to allow air pockets to escape from the edges.

[0009] The water volume of a body of water used as a service layer can decrease, for example, due to environmental influences. If the water level falls below a minimum, its secondary use and the protective function for the insulation layer can no longer be guaranteed. Therefore, to regulate the water volume, it is proposed that an inflow be provided above the insulation layer. This ensures sufficient filling of the body of water regardless of weather conditions such as rain, snow, wind, etc. Additionally, the water volume can be regulated and adjusted to the basin size and the fill level of the storage area. As an additional function, the thickness of the water layer can also be influenced by controlled water supply via the inflow, for example, to increase the thermal insulation properties of the water body and thus reduce heat loss.

[0010] If the basin does not have sufficient volume to hold the water, there is a risk of uncontrolled overflow. This can cause damage in the immediate vicinity of the device and restrict the secondary use of the water. However, uncontrolled overflow can be prevented if a water overflow is provided at a predetermined basin height. In the simplest case, this overflow can be a sloping open or closed channel or area. When the water level reaches the height of this overflow, excess water is drained away by gravity. For this purpose, the overflow can have a suitable gradient. Together with the water inlet, the water level can thus be set to a level suitable for the device and maintained over the long term.

[0011] A particularly preferred method for raising or lowering the insulation layer depending on the storage fluid level is to mount the insulation layer on the tank via a bellows-type construction, allowing for height adjustment. The bellows construction can be made, for example, of stainless steel or plastic sealing membranes and is tightly connected to the tank wall. Because the bellows construction is essentially free of fixed points, thermally induced stresses can be effectively compensated. To provide additional safety in the event of leaks, the bellows can be constructed with at least two layers, thus providing multiple sealing levels.The space between the individual layers of the bellows structure is filled with insulating material, such as air, thus providing additional thermal insulation, especially when additional convection dampers are incorporated into the bellows. To compensate for pressure fluctuations in the air-filled space between the bellows, caused by movements resulting from changes in the storage level, the bellows structure can also include a vent. Under favorable design conditions, the vent can be located within the insulation layer, providing a common vent for both the bellows structure and the storage area itself. This allows any air pockets that may accumulate under the insulation layer to be easily removed.In a preferred embodiment, the bellows can not only compensate for fluctuations in the fill level, but also absorb forces parallel to the surface of the working layer or the body of water, such as those that can occur, for example, due to a temperature change in the storage fluid. For this purpose, the bellows can, for example, be mounted on a floating suspension or be designed to allow limited freedom of movement parallel to the surface of the working layer or the body of water.

[0012] In a preferred embodiment, the height-adjustable support for the insulation layer on the basin and / or the insulation layer itself can be multi-layered. This multi-layered design allows the outer layers to act as sacrificial layers, thus extending the service life of the support and / or the insulation layer despite accelerated degradation due to high temperatures. This is particularly relevant if the support and / or the insulation layer is made of plastic or has an outer plastic layer. A multi-layered design is especially recommended for the support of the insulation layer on the basin, as this support, which can preferably be a bellows, must be flexible.

[0013] If the insulation layer is composed of individual modules, particularly advantageous structural and energy storage conditions arise when each module comprises a frame filled with insulating material. Due to these features, thermal bridges are reduced despite the modular design of the insulation layer, which would otherwise be detrimental to the energy efficiency of the device according to the invention. The individual modules can be connected to one another via the frames. In a preferred embodiment of the invention, the modules are flexibly connected to one another via their frames so that the insulation layer can better absorb forces parallel and perpendicular to the liquid surface. The frame must be liquid-tight; for this purpose, it can be made, for example, of metal, preferably stainless steel sheets, or of a polymer. Suitable insulating materials include, for example, polyurethane foams, foamed glass gravel, or similar materials.

[0014] The invention also relates to a method for manufacturing a device according to the invention. In this method, the basin is filled with a liquid, for example, the storage liquid, onto whose liquid surface the interconnected modules of the insulation layer are applied. Subsequently, the liquid surface is lowered to the level of the storage area, the insulation layer is mounted on the basin in a height-adjustable manner, and the basin area above the insulation layer is filled to form a usable layer, for example, a body of water. Each module is thus initially located on a conveyor belt leading to the basin and is positioned above an assembly pit. Above the assembly pit, the modules or module connections are tightly joined together in a multi-layered configuration, for example, by welding.After the welding work is completed, the modules are pulled further towards the liquid surface, for example, using winches. This requires temporarily flooding the entire basin, specifically above the storage area level. Upon reaching the liquid surface, the modules are supported by mounting brackets to prevent damage. Once all modules are joined together and floating on the liquid surface, the resulting insulation layer is aligned towards the center of the basin, and the water level of the storage area is lowered to the required height. A bellows-type structure can be used to adjust the height of the insulation layer within the basin, fitting tightly against both the basin edge and the insulation layer. The water can then be added in a controlled manner, creating a body of water above the insulation layer. Brief description of the invention

[0015] The invention is illustrated in the drawing as an example. It shows Fig. 1 shows a schematic section through a device according to the invention and Fig. 2 shows a schematic representation to illustrate a method for manufacturing a device according to the invention based on individual insulation layer modules. Ways to implement the invention

[0016] An inventive device for storing thermal energy comprises an upwardly open basin 1, which has a storage area 4 filled with a storage fluid 2 and covered with an insulating layer 3. The insulating layer 3 is mounted on the basin 1 via a bellows construction 5 so as to be height-adjustable and separates the storage fluid 2 in a liquid-tight manner from a usable layer arranged above the insulating layer 3, preferably a body of water 6. The body of water 6 can be a still body of water, such as a pond or a lake, or a flowing body of water, such as a stream or river, and thus be used for a secondary purpose, for example for floating photovoltaic systems, or as a fishpond. In order to be able to regulate the water volume of the body of water 6, both an inlet 7 and an overflow 8 are provided above the insulating layer 3.The fluid level and temperature of the storage fluid 2 can be adjusted via a storage inlet 9 and a storage outlet 10. The fluid level of the storage fluid 2 can also change when heat is extracted from the storage fluid 2 via a heat exchanger (not shown in the drawing).

[0017] To reliably remove any air that may be released by outgassing of the storage fluid 2 or during filling or emptying of the storage area 4, which could potentially lead to the formation of air pockets accumulating under the insulation layer 3, a vent 11 for the storage area 4 is provided in the area where the insulation layer 3 is mounted. For clarity, this vent 11 is only indicated by a circular cross-section. It is understood, however, that such a vent 11 can include a vent pipe (not shown in detail) leading away from the storage area 4. Although the vent 11 can, in principle, serve as a common vent for both the storage area 4 and the bellows assembly 5, a separate vent 12 for the bellows assembly 5 is also provided in this embodiment.

[0018] With regard to Fig. 2A method for manufacturing a device according to the invention is described. The basin 1 is filled with a liquid such that the liquid surface is above the level of the storage area 4. Several individual modules 13 can be provided to form the insulating layer 3. The modules 13 are guided to the basin 1 on a conveyor track 14 and transported, for example, via mounting rollers 15 and mounting supports (not shown). Above a mounting pit 16, the modules 13 are tightly joined together, for example, using a welding device 17. The modules 13 are then pulled further towards the liquid surface, for example, with the aid of winches. Upon reaching the liquid surface, the modules 13 are supported by means of mounting brackets 18 to prevent damage.Only after the modules 13 reach the liquid surface are the temporary mounting supports under the modules 13 removed, allowing the modules 13 to float on the liquid surface. Once all modules 13 have been connected and are floating on the liquid surface, the resulting insulation layer 3 is aligned towards the center of the basin, and the fill level of the storage area 4 is lowered to the required height. The insulation layer 3 is then sealed to the bellows structure 5 in a liquid-tight manner, and the surface water can be added in a controlled manner, creating a body of water 6 above the insulation layer 3.

Claims

1. Device for storing thermal energy with a basin (1) that has a storage area (4) filled with a storage fluid (2) and covered with an insulation layer (3), characterized in that the insulation layer (3), which can be raised and lowered with the fill level of the storage area (4), is mounted on the basin (1) in a height-adjustable manner and separates the storage fluid (2) in a liquid-tight manner from a use-layer arranged above the insulation layer (3) and capable of being raised and lowered with the insulation layer, in such a way that the insulation layer (3) is always in direct contact with both the storage fluid (2) and the use-layer.

2. Device according to claim 1, characterized in that the use-layer is a body of water (6).

3. Device according to claim 1, characterized in that a vent (11) for the storage area (4) is provided in the region where the insulation layer (3) is mounted.

4. Device according to claim 2 or 3, characterized in that a water inflow (7) is provided above the insulation layer (3).

5. Device according to one of claims 2 to 4, characterized in that a water overflow (8) is provided at a predetermined basin height.

6. Device according to one of claims 1 to 4, characterized in that the insulation layer (3) is mounted on the basin (1) in a height-adjustable manner via a bellows construction (5).

7. Device according to one of claims 1 to 5, characterized in that the insulation layer (3) has individual modules (13), which comprise a frame filled with an insulating material.

8. Method for manufacturing a device according to claim 7, characterized in that the basin (1) is filled with a liquid, onto the surface of which the interconnected modules (13) of the insulation layer (3) are applied, after which the liquid surface is lowered to the height of the storage area (4), the insulation layer (3) is mounted on the basin (1) in a height-adjustable manner, and the basin area above the insulation layer (1) is filled to form a use-layer.