Heat store with heat storage cassettes

1 . A heat store for storing electrical energy as thermal energy, comprising:

at least one electric heating device for converting electrical energy into thermal energy;

a plurality of heat storage cassettes, wherein each heat storage cassette comprises a cassette frame and a plurality of heat storage rods held in the cassette frame,

wherein each heat storage cassette comprises retainers for holding the heat storage rods in a predetermined position, and wherein at least one end of each heat storage rod is left unfixed so as to allow a free thermal expansion of the heat storage rods in a longitudinal direction of the heat storage rods inside the cassette frame;

wherein, in a fully assembled state of the heat storage cassettes, each cassette frame is closed in the longitudinal direction of the held heat storage rods, so that it is not possible for the heat storage rods to exit the cassette frame in the longitudinal direction, and

wherein a clearance delimited by one of the cassette frames in the longitudinal direction of the held heat storage rods is greater than a length of the heat storage rods so as to allow the free thermal expansion of the heat storage rods in the longitudinal direction,

wherein, in cases where the cassette frame has receiving holes for the heat storage rods, the clearance includes the space that extends into the receiving holes whereas, in cases where the cassette frame does not comprise receiving holes for the heat storage rods, the clearance extends between opposite parts of the cassette frame.

2 . The heat store according to claim 1 ,

wherein the clearance and the length of the heat storage rods are chosen so that a gap remains in the longitudinal direction that is greater than a thermal expansion length of the heat storage rods when the heat storage rods are heated over a design temperature range of the heat store.

3 . The heat store according to claim 1 ,

wherein the retainers of one of the cassette frames comprise at least one guide rail, and

wherein each guide rail extends perpendicularly to the longitudinal direction of the heat storage rods and comprises a plurality of holes, wherein one of the heat storage rods extends through each hole.

4 . The heat store according to claim 1 ,

wherein each cassette frame has a base side and an opposite end side, and

wherein the cassette frame comprises, on the base side and/or on the end side, a frame part with receiving holes or receiving recesses for supporting the heat storage rods, wherein the frame part with receiving holes or receiving recesses forms part of the retainers.

5 . The heat store according to claim 1 , further comprising:

a plurality of heat storage modules, wherein each heat storage module comprises a module frame which is configured to hold a plurality of the heat storage cassettes and at least one electric heating device without fixation.

6 . The heat store according to claim 5 ,

wherein the module frame respectively has a plurality of receiving grooves on two opposite sides for a respective projection of one of the heat storage cassettes, so that every heat storage cassette is held in two opposite receiving grooves.

7 . The heat store according to claim 5 ,

wherein, in order to hold the electric heating device, the module frame comprises on two opposite sides at least one respective heating-device receiving groove for a respective edge section of the electric heating device.

8 . The heat store according to claim 5 ,

wherein at least some of the heat storage modules are arranged next to one another with a gap that allows thermal expansion, so that heat transfer fluid flowing through them flows through them successively, and their module frames are not rigidly fixed to one another.

9 . The heat store according to claim 5 ,

wherein the heat storage cassettes of one of the heat storage modules stand on a base plate of this heat storage module, wherein the base plate bears the weight of the heat storage cassettes, wherein the heat storage cassettes are prevented from tipping over by receiving grooves on sides of the heat storage module and edge sections of the heat storage cassettes which project into the receiving grooves.

10 . The heat store according to claim 5 ,

wherein at least one of the heat storage modules is arranged horizontally so that the longitudinal direction of the heat storage rods is oriented horizontally, wherein the retainers bear the weight of the heat storage rods and support each heat storage rod in at least two places, without a fixing of the heat storage rod, in order to ensure the free thermal expansion of the heat storage rods in the longitudinal direction.

11 . The heat store according to claim 1 ,

wherein the heat storage cassettes are arranged upright so that the longitudinal direction of the heat storage rods is oriented vertically,

wherein the heat storage rods stand on a cassette frame base so that they are free to expand thermally in a vertical direction,

wherein the retainers form a protection against tilting for the heat storage rods.

12 . A heat store for storing electrical energy as thermal energy, comprising:

at least one electric heating device for converting electrical energy into thermal energy;

a plurality of heat storage cassettes, wherein each heat storage cassette comprises a cassette frame and a plurality of heat storage rods held in the cassette frame,

wherein each heat storage cassette comprises retainers for holding the heat storage rods in a predetermined position, and wherein at least one end of each heat storage rod is left unfixed so as to allow a free thermal expansion of the heat storage rods in a longitudinal direction of the heat storage rods inside the cassette frame;

the heat store further comprising a plurality of heat storage modules, wherein each heat storage module comprises a module frame which is configured to hold a plurality of the heat storage cassettes and at least one electric heating device without fixation.

13 . The heat store according to claim 12 ,

wherein, in a fully assembled state of the heat storage cassettes, each cassette frame is closed in the longitudinal direction of the held heat storage rods, so that it is not possible for the heat storage rods to exit the cassette frame in the longitudinal direction, and

wherein a clearance delimited by one of the cassette frames in the longitudinal direction of the held heat storage rods is greater than a length of the heat storage rods so as to allow the free thermal expansion of the heat storage rods in the longitudinal direction,

wherein, in cases where the cassette frame has receiving holes for the heat storage rods, the clearance includes the space that extends into the receiving holes whereas, in cases where the cassette frame does not comprise receiving holes for the heat storage rods, the clearance extends between opposite parts of the cassette frame.

14 . The heat store according to claim 13 ,

wherein the clearance and the length of the heat storage rods are chosen so that a gap remains in the longitudinal direction that is greater than a thermal expansion length of the heat storage rods when the heat storage rods are heated over a design temperature range of the heat store.

15 . The heat store according to claim 12 ,

wherein, in order to hold the electric heating device, the module frame comprises on two opposite sides at least one respective heating-device receiving groove for a respective edge section of the electric heating device.

16 . The heat store according to claim 12 ,

wherein at least some of the heat storage modules are arranged next to one another with a gap that allows thermal expansion, so that heat transfer fluid flowing through them flows through them successively, and their module frames are not rigidly fixed to one another.

17 . The heat store according to claim 12 ,

wherein the heat storage cassettes of one of the heat storage modules stand on a base plate of this heat storage module, wherein the base plate bears the weight of the heat storage cassettes, wherein the heat storage cassettes are prevented from tipping over by receiving grooves on sides of the heat storage module and edge sections of the heat storage cassettes which project into the receiving grooves.

18 . A heat store for storing electrical energy as thermal energy, comprising:

a heat storage module including:

a plurality of heat storage cassettes, each of the plurality of heat storage cassettes including:

a cassette frame which in cross section is closed on all four sides, wherein the cassette frame includes retainers for holding heat storage rods in predetermined positions;

a plurality of heat storage rods inserted into the cassette frame so that each heat storage rod is held in position by the corresponding retainers, wherein at least one end of each heat storage rod is left unfixed so as to allow a free thermal expansion of the heat storage rods in a longitudinal direction of the heat storage rods inside the cassette frame; and

projections protruding from opposite sides of the cassette frame; and

a module frame having a plurality of receiving grooves on two opposite sides for a respective projection of one of the heat storage cassettes, so that every heat storage cassette is held in two opposite receiving grooves.

19 . The heat store of claim 18 , the heat storage module further including at least one electric heating device for converting electrical energy into thermal energy, wherein the at least one electric heating device is held in the module frame without fixation.

20 . The heat store of claim 18 , including a plurality of heat storage modules.