EFFECTIVE CHARGING PROCESS OF AN ENERGY CONVERSION SYSTEM

Abstract

Provided is an arrangement for storing heat energy and in particular providing electric energy from heat energy, the arrangement including: a storage for storing heat energy having a charging inlet and a charging outlet; a tank for holding water for a steam generator, in particular heat recovery steam generator, the tank having an inlet and an outlet, a storage-steam-generator pipe between the charging outlet of the storage and the inlet of a heat recover steam generator; a storage-steam-generator valve within the storage-steam-generator pipe, in particular within a first portion of the storage-steam-generator pipe allowing to temporarily open the storage-steam-generator pipe.

Claims

1. An arrangement for storing heat energy, in particular from electric energy, and in particular providing electric energy from heat energy, the arrangement comprising: a storage for storing heat energy having a charging inlet and a charging outlet; a tank for holding water for a heat recovery steam generator, the tank having an inlet and an outlet, a storage-steam-generator pipe between the charging outlet of the storage and the inlet of a heat recovery steam generator; a storage-steam-generator valve within the storage-steam-generator pipe, in particular within a first portion of the storage-steam-generator pipe, allowing to temporarily open the storage-steam-generator pipe such as, during a charging process, to supply fluid exiting from the charging outlet of the storage to the heat recovery steam generator, wherein the outlet of the tank is connected to a water inlet of the steam generator, wherein the fluid comprises air.

2. The arrangement according to claim 1, wherein the arrangement is adapted to close the storage-steam-generator valve during a discharging process to discharge the storage and during most of a charging process to charge the storage.

3. The arrangement according to claim 1, wherein the arrangement is adapted to open the storage-steam-generator valve during a portion of the charging process, at which a temperature of fluid exiting from the storage at the charging outlet of the storage rises above a first threshold and/or a first threshold rate, but is below a second threshold and/or a second threshold rate.

4. The arrangement according to claim 1, wherein the storage-steam-generator pipe comprises a second portion connected on one end to the first portion of the storage-steam-generator pipe via a first T-junction and on another end to the steam generator.

5. The arrangement according to claim 1, further comprising: an electric heater or another heat source, having a charging inlet and a charging outlet for the fluid for heating the fluid during a charging process of charging the storage, wherein the charging outlet of the heater is connected with the charging inlet of the storage.

6. The arrangement according to claim 4, further comprising: a heater-steam-generator pipe arranged between a second T-junction connecting to a discharging outlet of the heater and the first T-junction.

7. The arrangement according to claim 6, further comprising: a heater-steam-generator valve within the heater-steam-generator pipe, wherein the arrangement is adapted to close the heater-steam-generator valve during an entire charging process and to open the heater-steam-generator valve during a discharging process.

8. The arrangement according to claim 1, wherein the steam generator is connected with the tank and having a fluid inlet and a fluid outlet, the arrangement further comprising: a steam-generator-outlet valve in a steam generator outlet pipe downstream the steam generator outlet.

9. The arrangement according to claim 6, further comprising a charging pipe system comprising: an upstream charging pipe including an upstream-charging-pipe valve connected via the second T-junction to the charging inlet of the heater; a downstream charging pipe connected via a third T-junction to the charging outlet of the storage and passing through a fourth T-junction and including a downstream-charging-pipe valve and connected to a fifth T-junction connected to the steam generator outlet pipe and a blower pipe including a blower, wherein the fourth T-junction is also connected to the first portion of the storage-steam-generator pipe.

10. The arrangement according to claim 9, further comprising: an upstream discharging pipe including an upstream-discharging-pipe valve and connected on one end to a sixth T-junction and on another end to the third T-junction, wherein the upstream charging pipe runs through the sixth T-junction.

11. The arrangement according to claim 10, wherein the arrangement is adapted to open the upstream-charging-pipe valve, the downstream-charging-pipe valve and to close the upstream-discharging-pipe valve, the heater-steam-generator valve, the storage-steam-generator valve, the steam-generator-outlet valve during most of the charging process.

12. The arrangement according to claim 10, wherein the arrangement is adapted to open the upstream-charging-pipe valve, the storage-steam-generator valve, the steam-generator-outlet valve and to close the upstream-discharging-pipe valve, the heater-steam-generator valve, the downstream-charging-pipe valve during a portion of the charging process.

13. The arrangement according to claim 10, wherein the arrangement is adapted to open the upstream-discharging-pipe valve, the heater-steam-generator valve, the steam-generator-outlet valve and to close the upstream-charging-pipe valve, the storage-steam-generator valve, the downstream-charging-pipe valve during the discharging process.

14. The arrangement according to claim 1, the arrangement further comprising: a steam turbine, connected to the steam generator.

15. A method for storing heat energy, in particular from electric energy, and in particular providing electric energy from heat energy, the method comprising: storing heat energy in a storage having a charging inlet and a charging outlet; holding water for a heat recovery steam generator in a tank having an inlet and an outlet; temporarily opening a storage-steam-generator valve within a storage-steam-generator pipe arranged between the charging outlet of the storage and a fluid inlet of the heat recovery steam generator, such as, during a charging process, to supply fluid exiting from the charging outlet of the storage to the heat recovery steam generator, wherein the outlet of the tank is connected to a water inlet of the steam generator, wherein the fluid comprises air.

Description

BRIEF DESCRIPTION

[0047] Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:

[0048] FIG. 1 schematically illustrates an arrangement for storing heat energy from electric energy and also providing electric energy from heat energy according to an embodiment of the present invention during a charging process;

[0049] FIG. 2 schematically illustrates an arrangement for storing heat energy from electric energy and also providing electric energy from heat energy according to an embodiment of the present invention during an end of a charging process;

[0050] FIG. 3 schematically illustrates an arrangement for storing heat energy from electric energy and also providing electric energy from heat energy according to an embodiment of the present invention during a discharging process;

[0051] FIG. 4 schematically illustrates the storage including a temperature profile within the storage;

[0052] FIG. 5 schematically illustrates temperature profiles within a storage as considered in embodiments of the present invention; and

[0053] FIG. 6 schematically illustrates a conventional heat storage system.

DETAILED DESCRIPTION

[0054] The arrangement 1 illustrated in FIGS. 1 to 3 for storing heat energy from electric energy and also providing electric energy from heat energy comprises a storage 3 for storing heat energy having a charging inlet 5 and a charging outlet 7. The charging inlet 5 corresponds to a discharging outlet during a discharging process and the charging outlet 7 corresponds to a discharging inlet during a discharging process. The arrangement 1 further comprises a tank, in particular water tank 9, for holding water for a steam generator 11, in particular a heat recovery steam generator 11, wherein the tank 9 has an inlet 13 and an outlet 15. The arrangement 1 further comprises a storage-steam-generator pipe 17 between the charging outlet 7 of the storage 3 and the heat recovery steam generator 11. For this purpose, the heat recovery steam generator 11 has a fluid inlet 19 via which fluid passing through the storage-steam-generator pipe 17 enters the steam generator 11. Furthermore, the steam generator 11 comprises a water outlet 21 via which water which has been heated within a heat exchanger of the steam generator 11 using the fluid entered at the fluid inlet 19 can pass to the water tank 9. In particular, the steam generator 11 is configured to heat up water which has exited via the water outlet 15 of the water tank and is conveyed via a water inlet 23 into the steam generator 11. The heat exchanger of the steam generator 11 thereby heats up the water by heat exchange using heat from the fluid having entered the steam generator at the fluid inlet 19.

[0055] Thus, the storage-steam-generator pipe 17 is arranged between the charging outlet 7 of the storage 3 and the fluid inlet 19 of the heat recovery steam generator 11. The heated water is then stored in the water tank 9.

[0056] The arrangement 1 further comprises a storage-steam-generator valve 25 (V4) within the storage-steam-generator pipe 17, in particular within a first portion 27 of the storage-steam-generator pipe 17.

[0057] During a first portion of a charging process, as is depicted in FIG. 1, the storage-steam-generator valve 25 (V4) is closed, it can however be opened during a second portion, or an end portion of the charging process as will be explained with reference to FIG. 2 below.

[0058] The valve states are indicated in FIGS. 1 to 3 with a bar indicating a closed state and without a bar indicating an opened state. In FIGS. 1 to 3, the flow direction of the fluid (as well as the flow direction of the water between the water tank 9 and the steam generator 11) is indicated by arrows. In pipe sections without any arrow, the flow of the fluid is essentially zero.

[0059] The storage-steam-generator pipe 17 comprises a second portion 29 which is connected on one end to the first portion 27 of the storage-steam-generator pipe 17 via a first T-junction 31 and on another end to the fluid inlet 19 of the steam generator 11. The arrangement 1 further comprises an electric heater 33 having a charging inlet 35 (being a discharging outlet) and having a charging outlet 37 (being a discharging inlet) for the fluid for heating the fluid during a charging process (illustrated in FIG. 1) for charging the storage 3. Therein, the charging outlet 37 is connected with the charging inlet 5 of the storage 3.

[0060] The arrangement 1 further comprises a heater-steam-generator pipe 39 arranged between a second T-junction 41 connecting to the discharging outlet 35 of the heater 33 and further connected to the first T-junction 31.

[0061] The arrangement 1 further comprises a heater-steam-generator valve 43 (V3) within the heater-steam-generator pipe 39, wherein the arrangement 1 is adapted to close the heater-steam-generator valve 43 (V3) during an entire charging process (as is illustrated in FIG. 1) and to open the heater-steam-generator valve 43 during a discharging process, as is illustrated in FIG. 2.

[0062] The arrangement 1 further comprises a steam generator 11, in particular a heat recovery steam generator, which is connected via the water outlet 21 to the water tank 9 and which has the fluid inlet 19 and further has a fluid outlet 45. Furthermore, a steam-generator-outlet valve (V6) is provided in a steam-generator-outlet pipe 49 downstream the steam-generator-fluid outlet 45.

[0063] The arrangement 1 further comprises a charging pipe system comprising an upstream charging pipe 51 including an upstream-charging-pipe valve 53 (V1) connected via the second T-junction 41 to the charging inlet 35 of the heater 33. The charging pipe system further comprises a downstream charging pipe 55 connected via a third T-junction 57 to the charging outlet 7 of the storage 3 and passing through a fourth T-junction 59 and including a downstream-charging-pipe valve 61 (V5) and connected to a fifth T-junction 63 connected to the steam-generator-outlet pipe 49 and a blower pipe 65 including a blower 67. The fourth T-junction 59 is also connected to the first portion 27 of the storage-steam-generator pipe 17.

[0064] The arrangement 1 further comprises an upstream discharging pipe 67 including an upstream-discharging-pipe valve 69 (V2) and connected on one end to a sixth T-junction 71 and on another end to the third T-junction 57. The upstream charging pipe 51 runs through the sixth T-junction 71.

[0065] During most of the charging process (illustrated in FIG. 1), the arrangement is adapted to open the upstream-charging-pipe valve 53 (V1), the downstream-charging-pipe valve 61 (V5), and to close the upstream-discharging-pipe valve 69 (V2), the heater-steam-generator valve 43 (V3), the storage-steam-generator valve 25 (V4), and the steam-generator-outlet valve 47 (V6). As can be taken from FIG. 1 illustrating a first portion of a charging process, the fluid is driven by the blower 67 running through the pipe sections 65, 51, running through the heater 33, running through storage 3, running through pipe section 55 and again running through the pipe section 65 back to the blower 67.

[0066] During charging the storage, the temperature of the fluid exiting at the charging outlet 7 of the storage increases with time. When the temperature of the fluid at the outlet 7 of the storage is above a first threshold or if a temperature change of the temperature of the fluid exiting at the storage outlet 7 is above a first-rate threshold, the arrangement may switch to another valve setting, as is illustrated in FIG. 2.

[0067] In particular, comparing FIGS. 1 and 2, the valve settings of the valves 25 (V4), 47 (V6) and 61 (V5) have changed. Thus, the arrangement is adapted to open the upstream-charging-pipe valve 53 (V1), the storage-steam-generator valve 25 (V4), the steam-generator-outlet valve 47 (V6) and to close the upstream-discharging-pipe valve 69 (V2), the heater-steam-generator valve 43 (V3) and the downstream-charging-pipe valve 61 (V5) during an end portion of the charging process (illustrated in FIG. 2). Thereby, the fluid exiting at the storage outlet 7 runs through the storage-steam-generator pipe 17, in particular its first portion 27 and its second portion 29 to enter at the fluid inlet 19 the steam generator 11. Thereby, the partially heated fluid can heat up water in a not illustrated heat exchanger which is then stored within the water tank 9.

[0068] During a discharging process, as is illustrated in FIG. 3, the arrangement is adapted to open the upstream-discharging-pipe valve 69 (V2), the heater-steam-generator valve 43 (V3), the steam-generator-outlet valve 47 (V6) and to close the upstream-charging-pipe valve 53 (V1), the storage-steam-generator valve 25 (V4) and the downstream-charging-pipe valve 61 (V5). Thereby, the flow direction through the storage 3 and the heater 33 is reversed compared to a charging process and the fluid heated by the storage is entering the fluid inlet 19 of the steam generator. The steam generator 11 in turn generates steam which is used in a steam turbine to produce electric energy.

[0069] To achieve constant power consumption, the exiting heat transporting fluid has to be cooled before it enters the heater, or the mass flow has to increase as soon as the temperature of the cold and of the heat storage rises at the end of the charging process. Embodiments of the present invention use the existing heat recovery steam generator as a heat exchanger to transfer the thermal energy from the heat transporting fluid to the feedwater (inside the water tank of the water-steam cycle). Thereby, the heat transporting fluid is cooled and the heat is not lost to the environment but stored inside the water tank 9 until the heat storage 3 is being discharged and the steam is being produced.

[0070] To be able to guide the heat transporting fluid through the steam generator when charging the heat storage 3, two additional valves, namely valves V3, V4 are installed in the arrangement illustrated in FIGS. 1 to 3. Further, a connection between the steam generator and the water tank has been installed, i.e., the water pipe 22 from the water outlet 21 of the steam generator to the water tank inlet 13. Furthermore, a water pipe 24 connecting the water tank outlet 15 to the water inlet 23 of the steam generator is introduced. As soon as the temperature of the heat transporting fluid at the cold end (for example outlet 7) of the heat storage 3 begins to rise (in particular above a selectable threshold), the valve 61 (V5) is closed, while the valves 25 (V4) and 47 (V6) are opened (see FIG. 2). For discharging the heat storage 3 (see FIG. 3), the valves 53 (V1) and 25 (V4) have to be closed, while the valves 69 (V2) and 43 (V3) have to be opened.

[0071] It is possible to use only parts of the heat recovery steam generator as a heat exchanger, i.e., only the economizer.

[0072] According to embodiments of the present invention, in a thermal energy storage plant, a steam generator is used as a heat exchanger. Thereby, most of the volume of the heat storage can be used without significant heat losses to the environment. Also, since the feedwater is pre-heated, the response time of the discharging process (especially water-steam cycle) may be reduced because the feedwater needs less energy to be evaporated. Due to the higher feedwater temperature and the subsequent higher average head addition temperature, the efficiency of the steam cycle may increase.

[0073] At all times during charge and discharge, the blower which makes the heat transporting fluid flow through the piping system may be protected from high temperatures, because the fluid is cooled. Because the temperature difference between the openings of the heater can be kept constant, the power consumption during the charging process can be kept constant as well. This may be important in order to make accurate purchases at the electricity market.

[0074] FIG. 4 schematically illustrates the storage 3 including a temperature profile 4 within the storage 3 when the storage is essentially discharged, i.e., essentially empty of any heat energy. The ordinate 12 illustrates the temperature while the abscissa 14 indicates the location within the storage 3. The arrow 6 shows a shifting direction of the temperature profile when charging, the arrow 8 shows the shifting direction of the temperature profile when discharging.

[0075] FIG. 5 also illustrates the storage 3 in addition of a temperature profile 10 within the storage 3 when the storage is essentially charged. During an end of a charging process as illustrated in FIG. 5, the temperature of the fluid exiting at the charging outlet 7 of the storage 3 has increased. When in this situation the valve setting of FIG. 2 is applied, the heat energy comprised within the fluid having the elevated temperature can be recovered by heating up water using the steam generator 11. Thus, according to embodiments of the present invention, the charging process is continued for a longer time than is conventionally applied.

[0076] FIG. 6 illustrates in a schematic form a conventional energy storage system, wherein elements similar in structure or function are indicated with the same reference sign but preceded by the number 1.

[0077] 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.

[0078] 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.