THERMAL STORAGE INSTALLATION USING SALTS

Abstract

THERMAL STORAGE INSTALLATION USING SALTS The invention relates to a thermal storage installation (1) using salts, comprising a frame (2) supporting a plurality of upper tanks (3) for storing hot salts and a plurality of lower tanks (7) for storing cold salts, characterized in that the upper tanks (3) are arranged horizontally on an upper part (4) of the frame (2), the inner tanks (7) are arranged horizontally on a lower part (5) of the frame (2), and in that it comprises pumping elements configured to pump and transfer salts from at least one lower tank (7) to at least one upper tank (3), a heat supply means configured to heat the salts during the transfer from the lower tanks (7) to the upper tanks (3),and a heat exchanger (6) in fluidic communication with at least one upper reservoir (3) and with at least one lower reservoir (7). Figure for the abbreviation: Figure 1,

Description

Title of the invention: THERMAL STORAGE INSTALLATION USING SALTS Technical field of the invention

[0001] The present invention can be included in the technical field of thermal storage installations using molten salts in various compositions, in particular those installations which aim to reduce the footprint or the horizontal surface occupied by the storage volume obtained.More specifically, the subject of the invention relates to a thermal storage installation by sensible heat comprising a plurality of tanks coupled to an upper part of a frame, and a plurality of tanks coupled to a lower part thereof, so that the transfer of molten salts from the upper tanks to the lower tanks occurs by gravity through a vertical evaporator arranged in an intermediate part between them, preferably a single-pass evaporator provided with an internal helical coil through which circulates water / steam heated by the molten salts which, in turn, fall through the housing of said evaporator. Technological background

[0002] Dual-tank storage systems are widely known in the state of the art, particularly in the solar thermal power plant sector.

[0003] The hot salt is then used to generate steam or heat a thermal fluid. How the salt is heated depends on the type of plant, typically directly in a solar receiver or indirectly through a transfer fluid circulating through a solar field of cylindrical parabolic collectors.

[0004] A significant disadvantage of this type of solution and other known solutions for thermal salt storage is that they require a large horizontal surface area per unit of stored energy. Statement of the invention

[0005] The present invention aims to solve some of the problems mentioned in the state of the art. The subject of the invention relates to a thermal storage installation using salts, comprising a frame supporting a plurality of upper hot salt storage tanks and a plurality of lower cold salt storage tanks.

[0006] More particularly, the upper tanks are arranged horizontally on an upper part of the frame, the internal tanks are arranged horizontally on a lower part of the frame, and the installation comprises pumping elements designed to pump and transfer salts from at least one of the lower reservoirs to at least one of the upper reservoirs.

[0007] When pumping salts from the lower reservoir to the upper reservoir, the installation includes a heat supply means designed to heat the salts during transfer from the internal reservoirs to the upper reservoirs.

[0008] Preferably, the upper and lower reservoirs have a rectangular cross-section to increase the volume stored per horizontal surface.

[0009] In a preferred embodiment, the heat supply means is embodied in one or more electric heating devices, resulting in a power-to-heat type embodiment.

[0010] In an alternative embodiment, the heat supply means is a heat exchanger powered by a heat transfer fluid which transfers heat to the salts which also circulate through this heat exchanger during their transfer from the lower reservoir to the upper reservoir. This embodiment can be described as heat to heat.

[0011] The subject of the invention relates to a thermal storage installation using salts, comprising a frame supporting a plurality of upper tanks for storing hot salts and a plurality of lower tanks for storing cold salts, said installation being characterized in that the upper tanks are arranged horizontally on an upper part of the frame, the internal tanks are arranged horizontally on a lower part of the frame, and in that it further comprises pumping elements configured to pump and transfer salts from at least one lower tank to at least one upper tank, a heat supply means configured to heat the salts during the transfer from the lower tanks to the upper tanks, and a heat exchanger in fluid communication with at least one upper tank and with at least one lower tank,wherein said heat exchanger is once-through and comprises an internal coil and is configured to gravity transport molten salts from the upper reservoir to the lower reservoir through the exterior of the internal coil.

[0012] In a preferred embodiment, the stored molten salts are used to generate steam or transfer heat to another heat transfer fluid in order to recover the heat stored in the salts. For this purpose, the present invention discloses a gravity solution by means of a vertical single-pass evaporator, preferably provided with a helical coil fed by water or by the other heat transfer fluid, where the salts fall internally through the annular housing of said evaporator heating the fluid circulating through the coil. The housing is of the annular type and does not require deflectors to direct the flow as it descends by gravity.

[0013] The heat exchanger is an evaporator provided with an internal coil of helical configuration arranged inside an annular housing of said evaporator, such that, the molten salts pass through the annular housing and the internal coil is configured to be supplied with water which is converted into steam when it passes through said internal coil.

[0014] The heat exchanger has an internal coil of helical configuration arranged within an annular housing of said evaporator, such that the molten salts pass through the annular housing and the internal coil is configured to be supplied by the transfer fluid.

[0015] The transfer fluid comprises salts.

[0016] Note the absence of a hot salt pump for transfer, since the transfer occurs by gravity through the evaporator. The installation reduces the number of rotating equipment and salt valves sensitive to failure and wear.

[0017] The heat supply means comprises one or more electric heating devices installed in a portion of the transfer from the lower tank to the upper tank.

[0018] The arrangement of the lower cold and upper hot tank groups on two levels allows the gravity flow of salts through the evaporator and facilitates the use of the lower tanks (lowest point of the installation) as a collection and drainage system. This is a closed system where the salt circulates between the storage tanks and uses the cold storage of the lower tanks as a collection system, by gravity of the molten salts, particularly relevant in the event of loss or interruption of the electrical supply, thus providing greater safety.

[0019] Furthermore, this arrangement allows for a reduced system footprint, while being compact and taking advantage of the intermediate space, critical for installation in existing congested installations. For example, in addition to the evaporator, the intermediate storage space between the upper and lower parts can be used to install equipment such as:

[0020] - a deaerator,

[0021] - pumps,

[0022] - an electrical and control room,

[0023] - auxiliary equipment.

[0024] It is noted that the vertical configuration of the installation described above separates the hot and cold sides, allowing greater temperature jumps and thus reducing the necessary flow of salts, making the volume required for the same storage capacity smaller.

[0025] Furthermore, the proposed once-through evaporator does not need or include an integrated reboiler, except for a separator which is only required during startups. Conventional reboiler evaporators have a high recirculation rate (between 4 and 10 times the generated vapor flow), which requires the reboiler to be installed at a high height to generate natural circulation or the use of continuous recirculation pumps. This is not necessary with the evaporator of the present invention, since the once-through evaporator only requires one type of recirculation pumps used only during startups, which are not the aforementioned continuous recirculation pumps.

[0026] Similarly, the proposed single-pass evaporator contains in a single unit the equivalent of an economizer, the evaporator itself and a superheater, which, in the configurations used based on box and tube exchangers, are separated, occupying more space.

[0027] Preferably, the upper reservoirs comprise an upper main reservoir and a plurality of upper secondary reservoirs connected thereto, and the inner reservoirs comprise a lower main reservoir and a plurality of lower secondary reservoirs connected thereto, the main reservoirs being in fluid communication with each other for transferring salts from the lower main reservoir to the upper main reservoir. Therefore, vertical pumps are preferably installed in the lower main reservoir which stores cold salts.

[0028] In addition, the installation may comprise a covering circuit which channels a covering gas to at least one upper tank and at least one lower tank. This inerting or covering is carried out at very low pressure, more precisely, of the order of millibars.

[0029] The installation comprises an inerting circuit which channels an inert gas towards at least one upper tank and towards at least one lower tank.

[0030] All equipment can be prefabricated on the frame or platform of maximum size equal to that of a 40-foot container. The various platforms that make up the frame can be installed on pillars, preferably made of concrete or metal, creating the structure that contains and supports the equipment.

[0031] The solution is a compact installation with a storage space comprising different intermediate levels where all the elements necessary for its proper functioning, including electrical, instrumentation and control equipment, are installed. List of figures

[0032] To complete the description and to help better understand the features of the invention, in accordance with a preferred example of a practical embodiment of this, a set of drawings is attached, as an integral part of said description where, for illustrative and non-limiting purposes, the following elements are represented:

[0033] [Fig. 1] represents a front perspective view of a preferred embodiment of the installation of the present invention, where the upper tanks, the lower tanks, the evaporator and the inerting circuit, among others, are illustrated.

[0034] [Fig.2] represents a side perspective view of the preferred embodiment of [Fig.l].

[0035] Detailed description of an embodiment of the invention

[0036] A detailed description of an example of a preferred embodiment of the subject of the invention is given below with the aid of the attached figures 1 and 2 described above.

[0037] As illustrated in [Fig.l], the subject of the invention relates to a thermal storage installation 1 using salts, comprising a frame 2 supporting a plurality of upper tanks 3 for storing hot salts and a plurality of lower tanks 7 for storing cold salts, the upper tanks 3 being arranged horizontally on an upper part 4 of the frame 2, the internal tanks 7 being arranged horizontally on a lower part 5 of the frame 2.

[0038] More specifically, as shown in [Fig.l] and [Fig.2], the installation comprises a heat exchanger 6 in fluid communication with at least one upper tank 3 and with at least one lower tank 7, said heat exchanger 6 being single-pass and comprising an internal coil 8, and being configured to transport by gravity the molten salts from the upper tank 3 to the lower tank 7 through the exterior of the internal coil 8.

[0039] In the preferred embodiment described, the heat exchanger 6 is an evaporator provided with an internal coil 8 of helical configuration arranged inside an annular housing 9 of said evaporator 6, such that, the molten salts pass through the annular housing 9 and the internal coil 8 is configured to be supplied with water which is converted into steam when it passes through said internal coil 8.

[0040] Similarly, the upper reservoirs 3 comprise an upper main reservoir and a plurality of upper secondary reservoirs connected thereto, and the lower reservoirs 7 comprise a lower main reservoir and a plurality of lower secondary reservoirs connected thereto, the main reservoirs being in fluid communication with each other for the transfer of salts from the lower main reservoir to the upper main reservoir by means of pumping elements or pumps.

[0041] As shown in both [Fig.l] and [Fig.2], the heat supply means, in a preferred embodiment, is incorporated in one or more devices of electric heaters 11 installed in a part included in the transfer from the lower tank 7 to the upper tank 3.

[0042] In [Fig.2], it is shown that the installation comprises a cover circuit 10 which channels a cover gas over all the upper tanks 3 and over all the lower tanks 7. This inerting circuit 10 operates at low pressure, in particular of the order of millibars, to obtain a slight overpressure to prevent humid air from penetrating from the street. In an example of an embodiment, the cover circuit 10 is an inerting circuit and the cover gas is an inert gas.

[0043] Finally, all the necessary equipment can be arranged in intermediate levels included in a storage space arranged between the upper part 4 and the lower part of the frame 2 to take advantage of the space and reduce the footprint. For example, the electrical and control room 12, a deaerator, auxiliary equipment and / or different pumps can be installed in this storage space and on the sides or around the heat exchanger 6.

Claims

Claims

1. Thermal storage installation (1) using salts, comprising a frame (2) supporting a plurality of upper tanks (3) for storing hot salts and a plurality of lower tanks (7) for storing cold salts, said installation (1) being characterized in that the upper tanks (3) are arranged horizontally on an upper part (4) of the frame (2), the internal tanks (7) are arranged horizontally on a lower part (5) of the frame (2), and in that it further comprises pumping elements configured to pump and transfer salts from at least one lower tank (7) to at least one upper tank (3), heat supply means configured to heat the salts during the transfer from the lower tanks (7) to the upper tanks (3),and a heat exchanger (6) in fluid communication with at least one upper reservoir (3) and with at least one lower reservoir (7), wherein said heat exchanger (6) is single-pass and comprises an internal coil (8) and is configured to transport by gravity the molten salts from the upper reservoir (3) to the lower reservoir (7) through the exterior of the internal coil (8).,

2. Installation according to claim 1, wherein the heat exchanger (6) is an evaporator provided with an internal coil (8) of helical configuration arranged inside an annular housing (9) of said evaporator (6), such that, the molten salts pass through the annular housing (9) and the internal coil (8) is configured to be supplied with water which is converted into steam when it passes through said internal coil (8)

3. Installation according to claim 2, wherein the heat exchanger (6) has an internal coil (8) of helical configuration arranged inside an annular housing (9) of said evaporator (6), such that the molten salts pass through the annular housing (9) and the internal coil (8) is configured to be supplied by the transfer fluid.

4. An installation according to claim 2, wherein the transfer fluid comprises salts.

5. An installation according to any one of the preceding claims, wherein the heat supply means comprises one or more electric heating devices (11) installed in a part of the transfer from the lower tank (7) to the upper tank (3).

6. Installation according to any one of claims 1 to 4, in which the heat supply means is a heat exchanger supplied by a heat transfer fluid which transfers heat to the salts circulating therein during their transfer from the lower reservoir (7) to the upper reservoir (3).

7. An installation according to any one of the preceding claims, wherein the upper (3) and lower (7) tanks have a rectangular cross-section.

8. An installation according to any one of the preceding claims, wherein the upper tanks (3) comprise an upper main tank and a plurality of upper secondary tanks connected thereto, and the internal tanks (7) comprise a lower main tank and a plurality of lower secondary tanks connected thereto, the main tanks being in fluid communication with each other for the transfer of salts from the lower main tank to the upper main tank.

9. Installation according to any one of the preceding claims, comprising an inerting circuit (10) which channels an inert gas towards at least one upper tank (3) and towards at least one lower tank (7).

10. Installation according to any one of the preceding claims, comprising a storage space (13) arranged between the upper part (4) and the lower part of the frame (2), wherein said storage space comprises one or more elements in a list consisting of: - a deaerator, - pumps, - an electrical and control room (12), - auxiliary equipment.

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