THERMAL ENERGY STORAGE

Abstract

Provided is a thermal energy storage including a housing having a fluid inlet and a fluid outlet, and a thermal energy storage structure arranged within the housing between the fluid inlet and the fluid outlet, the thermal energy storage structure including thermal energy storage elements and flexible separator elements, the flexible separator elements being arranged such that the thermal energy storage elements are separated into layers, each layer forming a channel between the fluid inlet and the fluid outlet. Furthermore, a method of manufacturing a thermal energy storage and a power plant for producing electrical energy is provided.

Claims

1. A thermal energy storage comprising: a housing having a fluid inlet and a fluid outlet; and a thermal energy storage structure arranged within the housing between the fluid and the fluid outlet, the thermal energy storage structure comprising thermal energy storage elements and flexible separator elements, the flexible separator elements being arranged such that the thermal energy storage elements are separated into layers, each layer forming a channel between the fluid inlet and the fluid outlet, wherein the flexible separator elements are capable of changing form to such an extent that no headroom is formed within the layers due to a compacting of the thermal storage elements.

2. The thermal energy storage according to claim 1, wherein each channel has a predetermined shape.

3. The thermal energy storage according to claim 1, wherein the fluid inlet comprises an inlet fluid distribution structure configured to selectively guide a working fluid towards one or more of the channels.

4. The thermal energy storage according to claim 3, wherein the inlet fluid distribution structure comprises a plurality of fluid inlet conduits.

5. The thermal energy storage according to claim 4, wherein at least one fluid inlet conduit comprises a valve.

6. The thermal energy storage according to claim 1, wherein the fluid outlet comprises an outlet fluid distribution structure configured to selectively receive a working fluid from one or more of the channels.

7. The thermal energy storage according to claim 6, wherein the outlet fluid distribution structure comprises a plurality of fluid outlet conduits.

8. The thermal energy storage according to claim 7, wherein at least one fluid outlet conduit comprises a valve.

9. The thermal energy storage according to claim 1, wherein the flexible separator elements comprise sheets or foils of material through which the working fluid flow is blocked or reduced.

10. The thermal energy storage according to claim 1, wherein the flexible separator elements comprise dense textile sheets.

11. The thermal energy storage according to claim 1, wherein the thermal storage elements comprise a material selected from the group consisting of stone, lava stone, brick, granite, basalt, ceramics, and slag.

12. The thermal energy storage according to claim 1, using air as a working fluid.

13. A power plant for producing electrical energy, comprising the thermal energy storage according to claim 1.

14. A method of manufacturing a thermal energy storage, the method comprising: providing a housing having a fluid inlet and a fluid outlet; and arranging a thermal energy storage structure within the housing between the fluid inlet and the fluid outlet, the thermal energy storage structure comprising thermal energy storage elements and flexible separator elements, the flexible separator elements being arranged such that the thermal energy storage elements are separated into layers, each layer forming a channel between the fluid inlet and the fluid outlet, wherein the flexible separator elements are capable of changing form to such an extent that no headroom is formed within the layers due to a compacting of the thermal storage elements.

Description

BRIEF DESCRIPTION

[0043] Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:

[0044] FIG. 1 shows a side-view of a known thermal energy storage;

[0045] FIG. 2 shows a side-view of a thermal energy storage according to an embodiment of the present invention;

[0046] FIG. 3 shows a side-view of a thermal energy storage according to a further embodiment of the present invention; and

[0047] FIG. 4 shows a side-view of a thermal energy storage according to a further embodiment of the present invention.

DETAILED DESCRIPTION

[0048] The illustrations in the drawings are schematic. It is noted that in different figures, similar or identical elements are provided with the same reference numerals or with reference numerals which differ only within the first digit.

[0049] FIG. 1 shows a side-view of a known thermal energy storage arranged in a housing 10. The thermal energy storage housing 10 comprises a fluid inlet 12 for receiving a working fluid, such as water, hot or cold steam, air, nitrogen or argon, as indicated by arrow 11. The thermal energy storage housing 10 further comprises a diffuser section 14 for evenly distributing the working fluid and for reducing the flow speed of the working fluid. The thermal energy storage further comprises thermal storage elements, such as bricks, stone, lava stone, granite, basalt or ceramics provided as bulk material within the housing 10 to form a thermal energy storage structure 20. The thermal energy storage housing 10 further comprises a nozzle section 16 for increasing flow speed and pressure of the working fluid leaving the thermal energy storage structure 20 in the housing 10 and forwarding it to fluid outlet 18 for ejection from the thermal energy storage, as indicated by arrow 17.

[0050] The thermal energy storage may be charged with thermal energy by feeding a hot working fluid, such as hot steam, to the fluid inlet 12. The working fluid will flow through the thermal energy storage in the thermal energy storage structure 20 and thereby heat up the thermal storage elements. The cooled working fluid leaves the storage via the fluid outlet 18. After the charging is completed, the storage may be left in a standstill period of hours or even days until the stored thermal energy is needed and discharged by feeding a cold working fluid, such as water, to the fluid inlet 12. After flowing through the thermal energy storage structure 20 within housing 10, the heated working fluid is ejected from the thermal energy storage through fluid outlet 18.

[0051] FIG. 1 also shows a curve indicating the temperature distribution within the thermal energy storage structure 20 after charging. The ideal curve shows a constant high temperature section 30 within the thermal energy storage structure 20 and ends with a steep drop section 32 towards the lower temperature 34 at the cold end of the structure 20. In reality, however, the curve will have a sloped section 36 connecting the high temperature section 30 and the low temperature section 34. This is due to the natural convection within the structure 20 as discussed in the introduction. Over time, the sloped section 36 will be longer and longer, i.e. the high temperature section will be shorter and shorter. This and other problems can be avoided by the thermal energy storages according to embodiments of the present invention as described hereinafter.

[0052] FIG. 2 shows a side-view of a thermal energy storage according to an embodiment of the present invention. The thermal energy storage according to this embodiment is generally similar to the thermal energy storage shown in FIG. 1 and discussed above. Thus, the detailed description of common features will not be repeated here. However, the thermal energy storage according to this embodiment differs from the thermal energy storage shown in FIG. 1 in that it comprises flexible separator elements 22 arranged within the thermal energy storage structure such that the thermal energy storage elements are separated into layers 24. Each layer 24 forms a separate channel between the fluid inlet and the fluid outlet. The flexible separator elements are formed of mineral textile sheets or similar dense textile and thereby provide two important effects. First of all, natural convection within the storage structure 20 is significantly reduced by the separation into layers 24. Furthermore, the flexibility of the separation elements 22 assures that the structure 20 can stay compact even if some of the thermal energy storage elements move, crack or collapse. In other words, the channels 24 are able to change their shape over time in such a way that an empty space or headroom above the thermal storage elements within the channels 24 is avoided. Such empty spaces would cause convection within the layers 24 and in turn within the entire structure 20. Thus, the flexible separation elements 22 provide a significantly better reduction of natural convection within the storage structure 20 in comparison to rigid separator plates, such as steel plates.

[0053] A further advantage of the flexible separator elements 22 is shown in FIG. 3 which shows a side-view of a thermal energy storage according to a further embodiment of the present invention. Here, the separator elements 22 are arranged in a somewhat bent or curved fashion (or banana-like shape) to provide channels 24 extending downwards from the fluid inlet 11 and then up towards the fluid outlet 18. Thereby, as also shown in FIG. 3, it is possible to position the fluid inlet 12 and fluid outlet 18 above the vertical middle of the structure 20, which may e.g. be beneficial when the structure is arranged below ground level.

[0054] FIG. 4 shows a side-view of a thermal energy storage according to a further embodiment of the present invention. In this embodiment, the fluid inlet 12 comprises an inlet fluid distribution structure formed by a plurality of fluid inlet conduits 13a, 13b. Similarly, the fluid outlet 18 comprises an outlet fluid distribution structure formed by a plurality of fluid outlet conduits 19a, 19b. Although FIG. 4 shows two fluid inlet conduits 13a, 13b and two fluid outlet conduits 19a, 19b, it is emphasized that any number of fluid inlet conduits and fluid outlet conduits may be used, e.g. three, four, five, six, seven, eight, nine, ten or more. Each conduit 13a, 13b, 19a, 19b may comprise a valve (not shown) for selectively opening and closing the corresponding conduit. Thereby, it is possible to selectively charge/discharge one or more of the channels 24.

[0055] Generally, the thermal energy storage according to embodiments of the present invention is capable of storing thermal energy for a long standstill period while maintaining a uniform temperature distribution within the structure. Thereby, an extended lifetime of the thermal energy storage elements 20 is achieved and a constant temperature of the output fluid from the storage can be provided. Furthermore, the thermal energy storage of embodiments of the present invention provides a high degree of flexibility as the channels can be shaped in a variety of ways, e.g. to accommodate constraints set by the chosen location for the storage.

[0056] The thermal energy storage may advantageously be used for temporarily storing excess energy at power production plants when production temporarily exceeds demand, e.g. in connected with a wind power plant which is susceptible to varying wind speeds and wind directions.

[0057] 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.

[0058] 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.