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A thermal energy storage device is provided which comprises a first container and a second container, each having at least an obverse wall, a reverse wall, first side wall connecting the obverse wall and reverse wall, and an internal space, wherein the obverse wall and/or reverse wall has a substantially planar surface, wherein the internal space of the first container and/or the internal space of the second container contains a phase change material and wherein the first and second container are stacked to define a flow path for a fluid in an internal space of the thermal energy storage device, characterized in that the flow path allows a fluid to flow in a serpentine manner from an inflow port of the thermal energy storage device over the complete obverse wall and/or reverse wall of the first container, over the first side wall of the first container, over the complete obverse wall of the second container, over the first side wall of the second container and then over the complete reverse wall of the second container. Moreover, a system is provided.
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In the prior art, thermal energy storage devices are known in which a heat exchanger is submerged in a phase change material ("PCM"). The disadvantage is that a very sophisticated and costly heat exchanger design is required to extract heat from the bulk of the phase change material. In addition, when using phase change materials with different melting temperatures, it becomes difficult to ensure stratification. Equipping such thermal energy storage devices with a complex pipe arrangement can on the one hand ensure stratification, but on the other hand impedes retrofitting measures, i.e. reduces the retrofitting flexibility of the thermal energy storage device and makes the thermal energy storage device more difficult and costly to produce.
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In thermal energy storage devices which comprise an encapsulated phase change material, heat transfer between a heat transfer fluid and the phase change material is generally not very high. Reducing the size of the capsules (or containers) which contain the phase change material can improve heat transfer because smaller diameters increase the total volume to surface area ratio, but this approach increases the number of capsules needed to obtain a certain energy density and thus increases manufacturing costs and the risk of encapsulation failure and leakage of phase change material (e.g. into potable water) significantly.
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GB 2 622 643 A discloses a thermal energy storage device comprising a chamber and a plurality of containers containing a phase change material, wherein the chamber comprises at least one fluid inlet, at least one fluid outlet, a flow path for the transport of a heat transfer fluid from the fluid inlet to the fluid outlet, and a plurality of supports configured to support the containers within the flow path, wherein the plurality of supports enables a direct contact between the heat transfer fluid and a surface of the containers and can be configured such that the plurality of containers are arranged in a staggered configuration. The staggered configuration advantageously generates a turbulent flow of the heat transfer fluid, thereby enhancing heat transfer. The disadvantage of this thermal energy storage device is that its energy density and heat transfer properties (regarding a heat transfer between the heat transfer fluid and the phase change material within the containers) are low. If the thermal energy storage device further comprises pipes to ensure stratification, the pipes impede retrofitting of containers containing a phase change material, i.e. reduce flexibility of use of the thermal energy storage device.
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Starting herefrom, it was an objective of the present invention to provide a thermal energy storage device which overcomes at least one disadvantage of the prior art. Preferably, the thermal energy storage device should provide a high safety and flexibility of use, should be producible in an easier and less expensive manner, should have an improved heat transfer between a heat transfer fluid and the phase change material and/or should provide a higher energy density. Moreover, a system comprising at least one thermal energy storage device with said property should be provided.
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The objective is solved by the thermal energy storage device having the features of claim 1 and the system having the features of claim 15. The dependent claims illustrate advantageous embodiments.
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According to the invention, a thermal energy storage device is provided, comprising
- a) a first container having at least an obverse wall, a reverse wall, first side wall connecting the obverse wall and reverse wall, and an internal space, wherein the obverse wall and/or reverse wall has a substantially planar surface;
- b) a second container having at least an obverse wall, a reverse wall, first side wall connecting the obverse wall and reverse wall, and an internal space, wherein the obverse wall and/or reverse wall has a substantially planar surface;
- wherein the internal space of the first container and/or the internal space of the second container contains a phase change material,
- wherein the first and second container are stacked to define a flow path for a fluid in an internal space of the thermal energy storage device,
- characterized in that the flow path allows a fluid to flow in a serpentine manner from an inflow port of the thermal energy storage device over the complete obverse wall and/or reverse wall of the first container, over the first side wall of the first container, over the complete obverse wall of the second container, over the first side wall of the second container and then over the complete reverse wall of the second container.
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The thermal energy storage device according to the invention provides a high safety, is producible in an easier and less expensive manner than prior art thermal energy storage devices, provides a high energy density and has an improved heat transfer between a heat transfer fluid and the phase change material than prior art thermal energy storage devices.
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The higher safety is provided because the phase change material is located within the container, i.e. is encapsulated in the container and the number of containers which the thermal energy storage device comprises can be kept relatively small. This also reduces production costs. Moreover, an easier and less expensive production is achieved because stratification can be ensured without a complex pipe arrangement. The high energy density is achieved by having a phase change material in the internal space of each container of the thermal energy storage device and can be further improved by a close stacking of the containers of the thermal energy storage device. The improved heat transfer is obtained by the flow path of the thermal energy storage device which allows a fluid to flow in a serpentine manner from an inflow port of the thermal energy storage device over the complete obverse wall and/or reverse wall of the first container, over the first side wall of the first container, over the complete obverse wall of the second container, over the first side wall of the second container and then over the complete reverse wall of the second container. This ensures an outstanding thermal contact to an area of each container which is as high as possible.
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In a preferred embodiment, in a cross-sectional plane perpendicular to the obverse wall and/or reverse wall of the first container, the first side wall of the first container has a substantially convex shape, wherein the substantially convex shape is formed by
- i) one curved line connecting the obverse wall with the reverse wall of the first container; or
- ii) a plurality of lines connecting the obverse wall with the reverse wall of the first container, wherein the plurality of lines comprises or consists of curved lines and/or straight lines, wherein the plurality of lines preferably connect the obverse wall with the reverse wall via n connection points between every two of the plurality of lines, wherein n is an integer ≥ 1, preferably ≥ 2, optionally ≥ 3.
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Particularly preferably, in a cross-sectional plane perpendicular to the obverse wall and/or reverse wall of the second container, the first side wall of the second container, wherein optionally, in a cross-sectional plane perpendicular to the obverse wall and/or reverse wall of each container of the thermal energy storage device, the first side wall of each container has a substantially convex shape, especially formed as defined above.
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This embodiment increases the surface contact area between the fluid flowing along the flow path and each container. Thus, heat transfer is further improved. Additionally, in the (narrow) gap between the containers (which can be wide), a laminar flow pattern develops. Thus, a laminar flow of fluid along the flow path is even better ensured, resulting in less flow turbulence. Less flow turbulence has the advantage that firstly, transmission of thermal energy to the fluid in the flow path is more homogeneous allowing a uniform extracting of heat from the PCM. In addition, noise production during flow is decreased. This improves withdrawal of fluid at a desired temperature from the thermal energy storage device and results in a more quiet operation of the thermal energy storage device.
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In a preferred embodiment, a length of the obverse wall and reverse wall of each of the first and second container is larger than a length of their first side wall and the first and second container are stacked so that the reverse wall of the first container faces the obverse wall of the second container, wherein the first and second container are stacked in a substantially horizontal direction, wherein the substantially horizontal direction is within ± 10°, preferably within ± 5°, more preferably within ± 2 °, perpendicular to gravitational force vectors. If the thermal energy storage device comprises more than two containers, this kind of stacking can be applied to all containers of the thermal energy storage device. The advantage is that the height of the thermal energy storage device is reduced compared to known thermal energy storage devices, i.e. it can be provided in a more compact manner regarding its height. In addition, containers of thermal energy storage devices usually contain, beside a phase change material, a certain percentage (e.g. 10 vol.-% in relation to the total volume of the internal space of the container) of a gas (e.g. air). With the horizontal stacking and the indicated dimensions of the container (i.e. longer obverse wall and reverse wall than first side wall), the surface of the container facing the flow path and under which the gas is present is smaller than with a vertical stacking of the containers. Since gas is generally a bad thermal conductor, this implies that the horizontal stacking further improves thermal transfer between the phase change material within the internal space of the container and the fluid flowing in the flow path of the thermal energy storage device.
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Preferably, the flow path allows a substantially laminar flow of a liquid heat transfer fluid.
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The flow path can have, over the first side wall of each container, a maximum height of 10 mm, preferably 5 mm, more preferably 3 mm, wherein the maximum height refers to a maximum length of the flow path in a direction parallel to a direction of flow over the obverse wall and/or reverse wall of each container. The smaller this maximum height, the lower is the volume which the flow path occupies in this space (over the first side wall of each container), resulting in a larger volume available for the containers of the thermal energy storage device and a larger heat storage capacity of the thermal energy storage device.
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Moreover, the flow path can have, over the obverse wall and/or reverse wall of each container, a maximum height of 50 mm, preferably 40 mm, more preferably 30 mm, even more preferably 20 mm, especially 10 mm, wherein the maximum height refers to a maximum length of the flow path in a direction perpendicular to a direction of flow over the obverse wall and/or reverse wall of each container. The smaller this height, the higher the packing density of the containers will be, resulting in a higher energy density and more compact structure of the thermal energy storage device. This is especially beneficial for smaller houses and apartments because the structure is more compact than known domestic hot water cylinders as thermal energy storage device. For example, it is estimated that about 200L of DHW can be discharged from a 100L thermal energy storage device according to the invention.
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The inflow port can be configured as a manifold. Preferably, the thermal energy storage device further comprises an outflow port, wherein the outflow port is more preferably configured as a manifold. The advantage is that a more laminar flow of fluid flowing within the container and out of the container can be ensured.
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The thermal energy storage device can have walls (which e.g. form a vessel). The walls can comprise an insulation material, e.g. on a surface of the walls which is directed to an outside of the thermal energy storage device. This improves energy efficiency over time.
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In this case, one of the walls can contact a second side wall of the first and second container, optionally of each container of the thermal energy storage device. The second side wall of each container is a side wall of the container which connects the obverse wall and reverse wall of each container at a location opposite of the first side wall.
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Moreover, one of the walls can contact a third side wall of the first and second container, optionally of each container of the thermal energy storage device. The third side wall of each container connects the obverse wall and reverse wall of each container and is located perpendicular to the first side wall of each container.
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Furthermore, one of the walls can contact a fourth side wall of the first and second container, optionally of each container of the thermal energy storage device. The fourth side wall of each container connects the obverse wall and reverse wall of each container and is located perpendicular to the first side wall of each container and opposite to a third side wall of the container.
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Alternatively, the first container and second container, optionally all containers of the thermal storage device, each comprise a frame (which e.g. forms a vessel by frames of each container of the thermal energy storage device contacting each other). The containers comprising a frame allow an ordered arrangement of the containers without requiring a specifically designed heat exchanger and without a need for the thermal energy storage device to comprise (separate) walls because the frame forms the walls of the thermal energy storage device. This allows the provision of the thermal energy storage device in a less cost-intensive manner and also allows a modular configuration of the thermal energy storage device. The frame can comprise an insulation material, e.g. on a surface of the frame which is directed to an outside of the thermal energy storage device. This improves energy efficiency over time.
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In this case, each frame can contact a second side wall of each container. The second side wall of each container connects the obverse wall and reverse wall of each container at a location opposite of the first side wall.
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Moreover, each frame can contact a third side wall of the first and second container, optionally of each container of the thermal energy storage device. The third side wall of each container connects the obverse wall and reverse wall of each container and is located perpendicular to the first side wall of each container.
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Furthermore, each frame can contact a fourth side wall of the first and second container, optionally of each container of the thermal energy storage device. The fourth side wall of each container connects the obverse wall and reverse wall of each container and is located perpendicular to the first side wall of each container and opposite to a third side wall of the container.
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Each frame can have a height which is maximally 50 mm, preferably 40 mm, more preferably 30 mm, even more preferably 20 mm, especially 10 mm, larger than the height of each of the first container and second container, wherein the height of each container refers to a maximum dimension of the container from its obverse wall to its reverse wall perpendicular to the flow path. This height of the frame defines a height of the flow path along the obverse wall and/or reverse wall of each container in the thermal energy storage device. The smaller this height, the higher the packing density of the containers will be, resulting in a higher energy density and more compact structure of the thermal energy storage device.
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Besides, each frame can have a length which is maximally 10 mm, preferably 5 mm, more preferably 3 mm, larger than the length of each of the first container and second container, wherein the length of each container refers to a maximum dimension of the container in a direction of its obverse wall and/or its reverse wall parallel the flow path. This length of the frame defines the height of the flow path along the first side wall of each container in the thermal energy storage device. The smaller this maximum height, the better a laminar flow can be ensured and the better can be ensured that heat is homogeneously transferred to the fluid flowing in the flow path (resulting in a more homogeneous temperature distribution within said fluid).
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Apart from the above, each frame can have a width which is identical to the width of each of the first container and second container, wherein the width of each container refers to a maximum dimension of the container in a direction of its obverse wall and/or its reverse wall perpendicular to the flow path. This implies that the frame contacts each container at sides of each container which are perpendicular to the flow path.
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In a preferred embodiment, each frame of each container is stacked with a neighbouring frame of each container in the thermal energy storage device, so that neighbouring frames contact each other in a liquid-tight manner. For example, the frames can be clamped together and then sealed between each other to avoid a leakage of fluid from the flow path to the outside of the thermal energy storage device. This embodiment has the advantage that the frames of the containers form the walls of the thermal energy storage device and form a vessel. The advantage of this embodiment is that the thermal energy storage device is configured in a modular manner, wherein one frame represents one module. This allows for an easy exchange of one module with another (e.g. an exchange of one frame comprising a container containing a first phase change material with another frame comprising a container container a second phase change material). The advantage is that the thermal energy storage device can be repaired very easily and its thermal storage properties can be changed very easily.
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The thermal energy storage device can comprise at least one of a state of charge analyser which is configured to determine a state of charge of the thermal energy storage device. The advantage is that a state of charge can be communicated to a controller of a system comprising the thermal energy storage device and the system can be configured to react accordingly.
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Moreover, the thermal energy storage device can comprise at least one leak detection analyser which is configured to detect a leakage of phase change material from one of the containers of the thermal energy storage device. The leak detection analyser is optionally selected from the group consisting of a device for measuring an electrical conductance of a liquid, a device for measuring electrical resistance of a liquid, a device for measuring density of a liquid and combinations thereof. The advantage is that an occurrence of a leak can be communicated to a controller of a system comprising the thermal energy storage device and the system can be configured to react accordingly (e.g. issue a warning signal to an operator of the system). This improves safety of operation of the system.
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The thermal energy storage device can further comprise at least one, preferably at least 7, more preferably 10 to 40, additional containers, wherein each of the additional containers has at least an obverse wall, a reverse wall, first side wall connecting the obverse wall and reverse wall and an internal space, wherein the obverse wall and/or reverse wall has a substantially planar surface. The internal space of each of the containers contains a phase change material, wherein the additional containers are arranged in a same stacking manner like the first and second container to define a flow path for a fluid in the internal space of the thermal energy storage device. The flow path allows a fluid to flow from the complete reverse wall of the second container over the complete obverse wall, the complete first side wall and the complete reverse wall of each additional container. Preferably, the first and second container and the additional containers are arranged to form at least two zones, preferably at least three zones, more preferably at least four zones, in the internal space of the thermal energy storage device. In this context, the containers preferably comprise a phase change material which has a melting point which
- i) is identical in each zone and different between the zones; and/or
- ii) zonally increases or zonally decreases in an axial direction of the thermal energy storage device.
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This embodiment allows to adjust the thermal storage properties of the thermal energy storage device.
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The first and/or second container, optionally each container of the thermal energy storage device, can have a height in the range of at least 3 mm, optionally in the range of 3 to 50 mm, preferably 10 to 25 mm, wherein the height of each container refers to a maximum dimension of the container from its obverse wall to its reverse wall perpendicular to the flow path. The smaller the height of each container, the more compact the thermal energy storage device can be provided (e.g. more compact in horizontal length in case of a horizontal stacking of the containers).
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Moreover, the first and/or second container, optionally each container of the thermal energy storage device, can have a length in the range of at least 10 cm, optionally in the range of 10 cm to 200 cm, wherein the length of each container refers to a maximum dimension of the container in a direction of its obverse wall and/or its reverse wall parallel the flow path. The smaller the length, the more compact the thermal energy storage device can be provided (e.g. more compact in vertical height in case of a horizontal stacking of the containers).
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Furthermore, the first and/or second container, optionally each container of the thermal energy storage device, can have a width in the range of at least 10 cm, optionally in the range of 10 cm to 200 cm wherein the width of each container refers to a maximum dimension of the container in a direction of its obverse wall and/or its reverse wall perpendicular to the flow path. The smaller the width, the more compact the thermal energy storage device can be provided (e.g. more compact in horizontal width in case of a horizontal stacking of the containers).
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Besides, the first and/or second container, optionally each container of the thermal energy storage device, can have, at least on regions, an essentially rectangular cross-section or an essentially triangular cross-section, wherein the cross-section lies in a plane which is parallel to the flow path, wherein the term "essentially" encompasses cross-sections regionally deviating from the mentioned cross-sections. The essentially triangular cross-section has the advantage that the thermal energy storage device can comprise more containers than with the essentially rectangular cross-section for a given size of the thermal energy storage device, which can be beneficial if the containers contain a different phase change material and a very compact size is desired. The essentially rectangular cross-section has the advantage that a higher amount of phase change material can be contained in each container and, if the containers also contain a gas (e.g. at 10 vol.-%), the thermal transfer to fluid is improved because, overall, a smaller total surface of each container under which gas is located is decreased compared to the essentially triangular cross-section.
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In addition, the first and/or second container, optionally each container of the thermal energy storage device, can have a wall comprising or consisting of a material selected from the group consisting of metal, plastic, ceramic, glass and combinations thereof. Preferably, the obverse wall and/or the reverse wall, optionally also the first side wall of the container, comprise or consist of a material selected from the group consisting of metal, plastic, ceramic, glass and combinations thereof.
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Furthermore, the first and/or second container, optionally each container of the thermal energy storage device, can have a wall having a maximum thickness of 9 mm, preferably 8 mm, more preferably 7 mm, even more preferably 6 mm, particular preferably 5 mm, optionally 4 mm, wherein the wall especially has a thickness in the range of 0.04 to 3 mm. The smaller the thickness of the wall, the better the thermal transfer efficiency between the phase change material in the internal space of each container and the fluid flowing in the flow path.
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The internal space of the first container and/or second container, optionally of each container of the thermal energy storage device, can comprise fins which are configured to improve a heat transfer within the internal space. The presence of fins has the advantage that heat is more efficiently transferred from the internal space of each container to fluid in the flow path and vice versa.
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The fins can comprise or consist of metal and/or graphite. These materials have the advantage of having a high thermal conductivity.
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Moreover, the fins can comprise at least one hole, preferably a plurality of holes. This has the advantage that a surface area of the fins is increased which further enhances heat transfer efficiency.
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Furthermore, the fins can have a porous structure, preferably a mesh structure or foam structure. The advantage is that a surface area of the fins is increased which further enhances heat transfer efficiency.
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Optionally, the fins are attached to the wall of the container or are not attached to the wall of the container.
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The internal space of the first container and/or second container, optionally of each container of the thermal energy storage device, can contain a gas.
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Preferably, the gas has a higher thermal conductivity than air, wherein the gas is more preferably selected from the group consisting of helium, hydrogen, methane, neon and combinations thereof, wherein the gas even more preferably comprises of consists of helium. The advantage is that heat transfer efficiency is improved compared to containers which internal space contains air.
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Moreover, the gas can be present in the internal space of the container at a gas pressure of 0.1 to 20 bar, preferably 0.5 to 10 bar, more preferably 1 to 6 bar, absolute pressure. The higher the pressure, the higher the thermal conductivity of the gas.
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Furthermore, the gas can be present in the internal space of the container in an amount of 5 to 15 vol.-%, preferably 8 to 12 vol.-%, especially 10 vol.-%, relative to the complete volume of the internal space of the container. The lower the volume, the higher the thermal storage capacity of each container. However, for avoiding damage to the container in case of mechanically rigid container walls or a deformation of the container walls in case of mechanically flexible container walls, the gas volume should not be too low to allow for a volume expansion of the phase change material during solidification thereof.
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In a preferred embodiment, the internal space of both the first container and the second container, optionally the internal space of each container of the thermal energy storage device, contains a phase change material.
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The phase change material in the internal space of each container can comprise an organic phase change material or consists thereof.
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Moreover, the phase change material in the internal space of each container can comprise an inorganic phase change material or consists thereof.
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Furthermore, the phase change material in the internal space of each container have a melting temperature in the range of 25 °C to 200 °C, preferably in the range of 30 °C to 90 °C, more preferably in the range of 35 °C to 80 °C, even more preferably in the range of 40 °C to 70 °C, optionally in the range of 40 °C to 60 °C.
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Besides, the phase change material in the internal space of the first container can be different to the phase change material in the internal space of the second container (e.g. have a different melting temperature).
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The first container and/or second container, optionally each container of the thermal energy storage device, can comprises at least one protrusion on its obverse wall and/or reverse wall, preferably a plurality of protrusions, wherein the at least one protrusion, optionally the plurality of protrusions, is/are configured to extend a flow length of a liquid heat transfer fluid along the flow path and/or increase a surface area of the obverse wall and/or reverse wall. The advantage is that the thermal energy transfer between the phase change material and the fluid flowing in the flow path of the thermal energy storage device is improved.
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In a preferred embodiment, the first container and/or second container, optionally each container of the thermal energy storage device, has no pipe in the internal space of the container. This embodiment is advantageous because it allows a less cost-intensive and easier provision of the containers and also of the thermal energy storage device.
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The first container and second container, optionally all containers of the thermal energy storage device, can occupy a volume the range of 50% to 95%, preferably in the range of 60% to 95%, more preferably in the range of 70% to 95%, especially in the range of 80 to 95%, optionally in the range of 85% to 90%, of the total volume of the internal space of the thermal energy storage device. The larger the occupation volume, the higher the energy density of the thermal energy storage device.
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According to the invention, a system is provided, comprising
- a) a first thermal energy storage device according to one of the preceding claims;
- b) a second thermal energy storage device according to one of the preceding claims;
- c) a heat pump; and
- d) a controller.
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In the system, the controller is preferably configured to control the heat pump to charge the first thermal storage device and to control the second thermal storage device to provide domestic hot water and/or space heating.
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Moreover, in the system, the first thermal energy storage device is preferably connected to the second thermal energy storage device in a thermally conductive manner.
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With reference to the following figures, the subject-matter of the invention is intended to be explained in more detail without wishing to restrict said subject-matter to the specific embodiments shown here.
- Figure 1 schematically shows a container 1 according to the invention in a cross section side view (Figure 1a) and a front view (Figure 1b). In this embodiment, the container 1 is assembled within a frame 12. As can be seen in Figure 1a, the container 1 is attached to the frame 12 at its second side wall 5, wherein the first side wall 4 of the container 1 remains unattached the frame 12 and allows for a heat medium 8 to pass. In Figure 1b, it can also be seen that the container 1 is attached to the frame 12 at its third side wall 6 and at its fourth side wall 7.
- Figure 2 schematically shows a thermal energy storage device according to the present invention which comprises a first container 1 having at least an obverse wall 3, a reverse wall 3', first side wall 4 connecting the obverse wall 3 and reverse wall 3', and an internal space, wherein the obverse wall 3 and reverse wall 3' both have a substantially planar surface, and which comprises a second container 2 having at least an obverse wall, a reverse wall, first side wall 4 connecting the obverse wall and reverse wall, and an internal space, wherein the obverse wall and reverse wall both have a substantially planar surface. The internal space of the first container 1 and/or the internal space of the second container 2 contains a phase change material. The first container 1, second container 2 and 14 further containers according to the invention are stacked to define a flow path 8 for a fluid in an internal space of the thermal energy storage device. The flow path 8 allows a fluid to flow in a serpentine manner from an inflow port of the thermal energy storage device over the complete reverse wall 3' of the first container 1, over the first side wall 4 of the first container 1, over the complete obverse wall 3 of the second container 2, over the first side wall 4 of the second container 2 and then over the complete reverse wall 3' of the second container. The containers are stacked in horizontal direction 9, i.e. perpendicular to gravitational force vectors.
- Figure 3 schematically shows a further container according to the invention, wherein the container is identical to the container shown in Figure 1 except that its internal space comprises fins 13.
- Figure 4 schematically shows a thermal energy storage device according to the invention which is identical to the thermal energy storage device shown in Figure 2 except that it comprises, instead of 16 containers according to the invention, 31 containers according to the invention and one first end-plate 16 attached to a first side and a second end plate 17 attached to the second, opposing side. Like in Figure 2, the containers are stacked in horizontal direction 9, i.e. perpendicular to gravitational force vectors.
- Figure 5 schematically shows a thermal energy storage device according to the invention (in isometric view on the left-hand side and in front view on the right-hand side) which is identical to the thermal energy storage device shown in Figure 4 except that it only comprises 7 containers according to the invention. Here, the first manifold 14 of the first inflow port 10 and the second manifold 14' of the outflow port 11 are shown.
- Figure 6 schematically shows a system according to the invention. The system comprises a first thermal energy storage device A according to the invention and a second thermal energy storage device B according to the invention (in isometric view on the left-hand side and in front view on the right-hand side). The system further comprises a heat pump (not shown) and a controller (not shown). Here, the first thermal energy storage device A is connected to the second thermal energy storage device B in a thermally conductive manner. The combination of the two thermal energy storage devices A, B in the system allows for a simultaneous charging and discharging. For example, the first thermal energy storage device can be charged by the heat pump of the system while the second thermal energy storage device can provide domestic hot water and/or space heating. The system allows a semi-continuous operation. Front view is shown as wireframe and skeletal drawing that allows perspective on internals of the system. An alternative to this embodiment would be to compartmentalize, i.e. to split flow path into half to allow essentially two flow paths within one (larger) system that can also be charged and discharged simultaneously by using each flow path respectively. As a further alternative, both flow paths could be used simultaneously for the same operation (discharge/charging).
- Figure 7 shows a velocity profile from CFD simulations. The velocity profile is shown for the (vertical) flow channel which is formed between the reverse wall of the first container of the invention and the obverse wall of the second container of the invention, wherein said two walls are set apart at a distance of 3 mm. Flow velocity is slow towards the walls but has a uniform distribution outside of the wall area. Thus, almost all of the surface shows a uniform, laminar flow. The manifold at the inlet of the thermal energy storage device helps to establish the uniform flow distribution. No baffles or protrusions are needed to establish the uniform flow, but optionally they could be present.
- Figure 8 schematically shows several different views of a specific structure of a manifold 14, 14' which can be comprised by the thermal storage device of the invention. The manifold 14, 14' can distribute a fluid flow from the inlet uniformly along the length of the surfaces of the containers.
- Figure 9 schematically shows four thermal energy storage devices according to the invention. The first one (see top left) is similar to the one shown in Figure 2, but the first side wall of each container does not have a substantially convex shape in a cross-sectional plane perpendicular to the obverse wall and/or reverse wall of the first container, but rather a straight line shape. The second one (see top right) is similar to the one shown in Figure 2, but comprises only 14 containers, there is a baffle located between each of two containers, and the first side wall of each container faces in the same direction (i.e. faces in top direction). The third one (see bottom left) is similar to the one shown in Figure 2, but comprises 38 containers and the containers have an essentially triangular cross-section (in a plane which is parallel to the flow path). The fourth one (see bottom right) is very similar to the one shown in Figure 2, but comprises 18 containers instead of 16 containers. In each thermal energy storage device, the containers are stacked in horizontal direction 9, i.e. perpendicular to gravitational force vectors.
List of reference signs
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- 1:
- first container;
- 2:
- second container;
- 3:
- obverse wall of each container;
- 3':
- reverse wall of each container;
- 4:
- first side wall of each container;
- 5:
- second side wall of each container;
- 6:
- third side wall of each container;
- 7:
- fourth side wall of each container;
- 8:
- heat medium (e.g. water) or (part of) flow path;
- 9:
- horizontal direction;
- 10:
- inflow port;
- 11:
- outflow port;
- 12:
- frame;
- 13:
- fin(s);
- 14:
- first manifold;
- 14':
- second manifold;
- 15:
- baffle;
- 16:
- first end plate;
- 17:
- second end plate;
- A:
- first thermal energy storage device;
- B:
- second thermal energy storage device.