EP4680911A1

EP4680911A1 - Heat store

Info

Publication number: EP4680911A1
Application number: EP25714191.1A
Authority: EP
Inventors: James Donnelly MACNAGHTEN; Krishan CHANA; William Ranulf Slee; Guy Alexander James WINSTANLEY; Mark Eugene Charles KENWORTH
Original assignee: Energy Systems Management Ltd
Current assignee: Energy Systems Management Ltd
Priority date: 2024-03-05
Filing date: 2025-03-04
Publication date: 2026-01-21
Also published as: GB202403183D0; WO2025186554A8; WO2025186554A1

Abstract

A vacuum-insulated heat store (10) for an energy storage system, comprising: a thermal energy store (17); and a vacuum-insulated cover (15) configured to be placed over the thermal energy store (17) to insulate the thermal energy store, the vacuum-insulated cover (15) comprising an outer shell (20) and an inner shell (30) spaced by a vacuum region (50) extending therebetween, the vacuum-insulated cover (15) including a base (15A) defining an opening (15B) to a chamber (30A) within the inner shell (30), the chamber (30A) being configured to receive the thermal energy store (17) when the vacuum-insulated cover (15) is installed over the thermal energy store (17).

Description

TITLE: HEAT STORE

DESCRIPTION

The present invention relates to a heat store for an energy storage system and particularly but not exclusively to a vacuum-insulated heat store.

Vacuum insulation provides the potential for heat store performance in both domestic and industrial energy storage systems. However, there are practical difficulties in the manufacture and transport of large and heavy vacuum-insulated structures.

The present applicant has identified the need for an improved heat store that overcomes or at least alleviates problems associated with the prior art.

In accordance with a first aspect of the present invention, there is provided a vacuum- insulated heat store for an energy storage system, comprising: a thermal energy store; and a vacuum-insulated cover (e.g. removable vacuum-insulated cover) configured to be placed over the thermal energy store to insulate the thermal energy store, the vacuum-insulated cover comprising an outer shell and an inner shell spaced by a vacuum region extending therebetween.

In this way, a vacuum-insulated heat store is provided in which constituent parts (e.g. thermal energy store and any supporting structure) may be manufactured and transported in sections and assembled on site with the vacuum-insulated cover being provided as a discrete (e.g. prefabricated) component that is installed over the assembled structure.

Typically, the vacuum-insulated cover is configured to be placed over the thermal energy store during installation of the energy storage system (e.g. at the site where the energy storage system is to be operated). In one embodiment, the vacuum-insulated cover is removable after installation (e.g. to allow for maintenance or modular expansion of the thermal energy store).

In one embodiment, the vacuum-insulated cover including a base defining an opening to a chamber within (e.g. located with a volume of) the inner shell, the chamber (e.g. and opening) being configured to receive the thermal energy store when the vacuum-insulated cover is installed over the thermal energy store.

In one embodiment, the vacuum region extends substantially around a full lateral periphery of the thermal energy store (e.g. insulating all lateral sides of the thermal energy store). For example, in one embodiment, the vacuum-insulated cover is configured such that the vacuum region extends substantially around a full lateral periphery of the thermal energy store.

In one embodiment, the vacuum region extends substantially from a base of the thermal energy store to an uppermost region of the thermal energy store (e.g. insulating lateral sides of the thermal energy store along a full height of the thermal energy store).

In one embodiment, the vacuum region extends from below the base of the thermal energy store to an uppermost region of the thermal energy store (e.g. insulating lateral sides of the thermal energy store along a full height of the thermal energy store and overlapping with a region (e.g. thermally insulated region) beneath the thermal energy store). However, typically the vacuum region does not extend beneath the opening in the base (e.g. does not in a region directly below the base of the thermal energy store).

In one embodiment, the vacuum region extends substantially over an upper surface of the thermal energy store (e.g. insulating the upper surface of the thermal energy store).

In one embodiment, the inner and outer shells comprise inner and outer cylindrical sections respectively.

In one embodiment, the inner and outer cylindrical sections are connected by a sealed joining piece.

In one embodiment, the sealed joining piece forms a periphery surrounding the opening to the chamber.

In one embodiment, the sealed joining piece is located at a lower portion of the vacuum- insulated cover.

In one embodiment, the sealed joining piece is a sealed tapered joining piece (e.g. firusto- conical annular joining piece).

Advantageously, a tapered joining piece is both simple to manufacture and highly effective in transmitting structural loads from the inner to the outer shell.

In one embodiment, the sealed joining piece further comprises a peripheral flange (e.g. inwardly projecting peripheral flange).

In one embodiment, the peripheral flange is located at a base of the sealed joining piece.

In one embodiment, the peripheral flange is configured to engage a surface (e.g. upper surface) of a supporting structure.

In one embodiment, the inner and outer shells comprise inner and outer upper domed sections respectively.

In one embodiment, the vacuum-insulated heat store comprises a vacuum pump operative to maintain the vacuum pressure in the vacuum region of the vacuum-insulated cover (e.g. at a vacuum pressure between 0.05mbar and Imbar).

In one embodiment, the vacuum pump connects to a vacuum port provided in the vacuum-insulated cover (e.g. outer shell of the vacuum-insulated cover).

In one embodiment, the vacuum-insulated heat store comprises a sensor operative to measure a parameter at one or more location in the vacuum-insulated heat store and the vacuum pump is configured to operate whenever the sensor indicates that the parameter reaches a predetermined value. This could be directly sensing pressure or a derivative for example temperature or deflection from which pressure can be inferred.

In one embodiment, the vacuum-insulated heat store further comprises a secondary vacuum region (e.g. partial vacuum region) extending between the thermal energy store and the inner shell of the vacuum-insulated cover.

In one embodiment, the secondary vacuum region has a weaker vacuum level than the vacuum region of the vacuum-insulated cover.

Advantageously, the secondary vacuum can reduce the concentration of oxygen in the thermal store (by ensuring that there is no exchange of air with the atmosphere each time the store cycles and the internal gas density varies), reduce the pressure loading on the inner shell of the vacuum-insulated cover and can be used to manage breakdown voltages via Paschen's law.

Further advantageously, the secondary vacuum can also be used to expel moisture or water ingress from the vacuum-insulated heat store (since the vapor pressure of the liquid reduces as the vacuum pressure increases), which can reduce the setup and commissioning time of the electrical system, components and other parts affected by the presence of water.

In one embodiment, the vacuum-insulated heat store comprises a secondary vacuum pump operative to maintain the vacuum pressure in the secondary vacuum region (e.g. at a vacuum pressure between 0.1-0.9bar).

In one embodiment, the vacuum-insulated heat store further comprises a structural base for supporting the thermal energy store.

In one embodiment, the structural base comprises a support platform.

In one embodiment, a lower portion of the vacuum-insulated cover (e.g. sealed joining piece) substantially surrounds at least an upper portion of the support platform when the vacuum-insulated cover is installed over the thermal energy store.

In one embodiment, the support platform (e.g. upper portion) has a tapered profile that increases with cross-sectional area with increased distance from the thermal energy store.

In one embodiment, the support platform comprises a plurality of ribs (e.g. radially extending ribs).

In one embodiment, the plurality of ribs define an outer periphery (e.g. cylindrical outer periphery) of the support platform.

In one embodiment, the plurality of ribs are configured to (e.g. directly) support the thermal energy store.

In one embodiment, the support platform defines a plurality of chambers in fluid communication with the thermal energy store.

In one embodiment, the plurality of chambers are filled with (e.g. air-permeable) thermal insulation (e.g. mineral wool).

In one embodiment, the secondary vacuum extends into the plurality of chambers.

In one embodiment, the plurality of chambers are defined by the radially extending ribs and the outer periphery.

In one embodiment, the plurality of chambers and/or radially extending ribs extend to a base of the support platform (e.g. extend to the floor/ground).

In one embodiment, the outer shell of the vacuum-insulated cover comprises at least one reinforcing rib (e.g. at least one internal reinforcing rib).

In one embodiment, the at least one reinforcing rib is a circumferentially extending reinforcing rib. The at least one reinforcing rib and circumference of the structural base may not be permanently joined but mechanically constrained to manage thermal stresses.

In one embodiment, the structural base further comprises a lower base section (e.g. configured to support (e.g. and couple with) the support platform).

In one embodiment, the lower base section is configured to support (e.g. and couple with) the vacuum-insulated cover (e.g. the peripheral flange of the sealed joining piece).

In one embodiment, the lower base section comprises an upper plate and an outer support wall (e.g. outer cylindrical support wall).

In one embodiment, the upper plate defines a support surface configured to engage a base of the support platform.

In another embodiment, the upper plate defines an aperture (e.g. annular upper plate) configured to receive the support platform.

In one embodiment, the lower base section comprises at least one service connection (e.g. electrical connection, mechanical connection (e.g. fluid path connection for working fluid) or vacuum port for the secondary vacuum pump).

In one embodiment, the lower base section comprises a plurality of radially extending base ribs.

In one embodiment, the structural base comprises a cooling arrangement configured to cool the at least one service connection.

In one embodiment, the cooling arrangement comprises airflow apertures provided in the outer support wall and/or radially extending base ribs.

In one embodiment, the vacuum-insulated heat store comprises a sensor (e.g. further sensor) operative to measure a parameter at one or more location in the vacuum-insulated heat store and the secondary vacuum pump is configured to operate whenever the sensor indicates that the parameter reaches a predetermined value. This could be directly sensing pressure or a derivative for example temperature or deflection from which pressure can be inferred.

In one embodiment, the vacuum pump and/or secondary vacuum pump is located on or adjacent an outer wall of the structural base.

In one embodiment, the vacuum-insulated heat store further comprises thermal insulation provided within the vacuum region.

In one embodiment, the thermal insulation comprises n layers of multilayer insulation, each layer of multilayer insulation comprises a reflective layer and a spacer layer, wherein n >50.

In one embodiment, n is approximately 200.

In one embodiment the vacuum-insulated cover further comprises an internal cage structure provided inside the vacuum region, the internal cage structure being configured to hold the thermal insulation in position (e.g. relative to the inner and outer shell walls).

In this way, the thermal insulation may be maintained in a predetermined position within the vacuum region during thermal cycling of the system.

In one embodiment, the thermal insulation is provided within the cage structure (e.g. with the cage structure enclosing the thermal insulation).

In one embodiment, the cage structure comprises a wire mesh.

In one embodiment, the cage structure comprises an inner cage part and an outer cage part (with the thermal insulation provided between the inner and outer cage parts).

In one embodiment, the vacuum-insulated heat store further comprises a vertically- extending support extending through the thermal energy store.

In one embodiment, the vertically-extending support is a central vertically-extending support.

In one embodiment, the vertically-extending support extends through the structural base (e.g. through the support platform and/or the lower base section thereof).

In one embodiment, at least one of the vacuum-insulated cover and the vertically- extending support are configured (e.g. sized and shaped) to allow lateral expansion of the thermal energy store.

In one embodiment, the vacuum-insulated heat store comprises: at least one electrical heating element operative to act as a heat input to the thermal energy store; and/or at least one heat exchanger element operative to receive a heat transfer fluid.

In one embodiment, the vacuum-insulated heat store comprises at least one temperature monitoring sensor (e.g. for measuring temperature of the heat store to calculate the thermal energy stored).

In one embodiment, the thermal energy store is a solid store and the at least one electrical heating element and/or at least one heat exchanger element are embedded within the solid store.

In one embodiment, the thermal energy store comprises a solid body comprising a solid thermally conductive matrix with a solid thermal filler material embedded therein, the solid thermally conductive matrix forming a thermally conductive pathway to the solid thermal filler material distributed within the solid thermally conductive matrix.

In one embodiment, the vacuum-insulated heat store is configured to heat the thermal energy store to a temperature greater than 300°C.

In one embodiment, the thermal energy store is a modular thermal energy store as defined in accordance with the second aspect of the present invention (e.g. in accordance with any embodiment of the second aspect of the present invention). In accordance with a second aspect of the present invention, there is provided a modular thermal energy store comprising: a first thermal storage layer comprising a first modular thermal storage block arrangement; and a second thermal storage layer supported by the first thermal storage layer, the second thermal storage layer comprising a second modular thermal storage block arrangement.

In one embodiment the first modular thermal storage block arrangement comprises a first plurality of thermal storage blocks.

In one embodiment the second modular thermal storage block arrangement comprises a second plurality of thermal storage blocks.

In one embodiment, the first modular thermal storage block arrangement comprises a first plurality of n thermal storage blocks (e.g. n laterally spaced thermal storage blocks).

In one embodiment, the first plurality of n thermal storage blocks are circumferentially spaced relative to a vertical axis (e.g. central vertical axis) of the modular thermal energy store.

In one embodiment, each thermal storage block forms a part (e.g. sector) of a p- sided polygonal shape (e.g. low p polygonal shape or a substantially circular or elliptical polygonal shape) centred around the central vertical axis.

In one embodiment, p = n.

In one embodiment, n > 5 (e.g. n > 6).

In one embodiment, the second modular thermal storage block arrangement comprises a second plurality of m thermal storage blocks (e.g. m circumferentially spaced thermal storage blocks).

In one embodiment, the second plurality of m thermal storage blocks are circumferentially spaced relative to a vertical axis (e.g. central vertical axis) of the modular thermal energy store.

In one embodiment, each thermal storage block forms a part (e.g. sector) of a t/-sided polygonal shape (e.g. low q polygonal shape or a substantially circular or elliptical polygonal shape) centred around the central vertical axis.

In one embodiment, q = m.

In one embodiment, m > 5 (e.g. m> 6).

In one embodiment, n = m.

In one embodiment, the n thermal storage blocks are identical to (e.g. interchangeable with) the m thermal storage blocks. For modular thermal energy stores intended for use with a three-phase electrical supply, n = m = 6 or l 2 may be optimal (with n = m = 6 being ideal).

In one embodiment, the thermal energy store comprises at least one vertically- extending support extending through the first and second thermal storage layers.

Advantageously, the use of a vertically-extending support provides lateral support for the thermal storage blocks. A central support allows for different thermal expansion rates of the various modular parts during thermal cycling of the modular thermal energy store.

In one embodiment, the first and second modular thermal storage block arrangements each define a recess (e.g. central recess) for receiving the at least one vertically-extending support.

In one embodiment, the recess is configured (e.g. sized and/or shaped) to allow lateral (e.g. laterally inward) expansion of first and second modular thermal storage block arrangements.

In one embodiment, the first thermal storage layer is supported by a base (e.g. structural base).

In one embodiment, the second thermal storage layer is supported by a plate (e.g. plate formed by multiple interlocking sections).

In one embodiment, each of the first plurality of n thermal storage blocks and/or each of the second plurality of m thermal storage blocks interlock with the plate (e.g. to control lateral (e.g. radial and/or circumferential) movement of the thermal storage blocks relative to the plate). For example, in one embodiment a surface (e.g. upper surface in the case of blocks supported by the plate or lower surface in the case of a plate supported by the blocks) of the plate and a surface of each block (e.g. lower surface or upper surface respectively) comprises interengaging profiles (e.g. interengaging male and female profiles). In one example each block comprises an aperture and the surface of the plate comprises a plurality of circumferentially spaced protuberances configured to slidably engage a respective aperture of the block (e.g. during installation of the modular thermal energy store). This feature also provides a target location for a thermal storage block to be position on the plate during installation which aids construction of the vacuum-insulated thermal store.

In one embodiment, the plate defines an aperture (e.g. central aperture) for receiving the at least one vertically-extending support.

In one embodiment, the plate is supported by the first thermal storage layer. In one embodiment, the plate comprises a retaining feature (e.g. outer lip) operative to permit limited laterally outward (e.g. radially outward) expansion of the first and/or second thermal storage layer relative to the plate (e.g. permit limited laterally outward (e.g. radially outward) expansion of the n thermal storage blocks and/or m thermal storage blocks relative to the plate).

In one embodiment, the modular thermal energy store further comprises a cap piece supported by the second modular thermal storage block arrangement.

In one embodiment, the at least one vertically-extending support is expandable by adding a further vertically-extending support section.

In one embodiment, the modular thermal energy store further comprises at least one further thermal storage layer (e.g. installed at the same time as the first and second thermal storage layers are installed or subsequently installed in order to expand the modular thermal energy store).

In one embodiment, the at least one further thermal storage layer comprises a third thermal storage layer comprising a third modular block arrangement supported by the second thermal storage layer.

In one embodiment, the third thermal storage layer (or alternatively the cap piece) is supported by a further plate (e.g. with the plate being as previously defined).

In one embodiment, the at least one vertically-extending support comprises a plurality of sections (upper and lower sections corresponding to the position of the first and second thermal storage layers respectively).

In one embodiment, at least one of the first and second modular thermal storage bock arrangements defines a peripheral channel (e.g. conductor connector channel).

In one embodiment, the peripheral channel is a vertically-extending peripheral channel.

In one embodiment, at least one (e.g. each) thermal storage block defines at least a portion of the peripheral channel (e.g. defines a partial (e.g. half) channel portion that combines with the partial channel portion of an adjacent thermal storage block to form the (complete) peripheral channel).

In one embodiment, the at least one (e.g. each) thermal storage block defines a pair of circumferentially spaced vertically-extending peripheral channels (e.g. located at circumferentially opposed points of an outer periphery of the thermal storage block). In one embodiment, the at least one (e.g. each) thermal storage block defines a single vertically-extending peripherals channel (e.g. located at a leading or trailing point of an outer periphery of the thermal storage block).

In one embodiment, at least one of the first and second modular thermal storage block arrangements (e.g. at least one of the first plurality of n thermal storage blocks or second plurality of m thermal storage blocks) comprises: a solid body; and at least one thermal transfer element embedded therein.

In one embodiment, the solid body comprises a solid thermally conductive matrix with a solid thermal filler material embedded therein, the solid thermally conductive matrix forming a thermally conductive pathway to the solid thermal filler material distributed within the solid thermally conductive matrix.

In one embodiment, the thermal transfer element comprises one or more of an electrical heating element (e.g. electrical heating coil means); and a heat exchanger element operative to transfer thermal energy between the solid body and a heat transfer fluid.

Typically, each thermal storage block will include an (e.g. embedded) electrical heating element. All or a subset of the thermal storage blocks will include a (e.g. embedded) heat exchanger element.

In one embodiment, the modular thermal energy store is configured to be heated using a three-phase electrical supply.

In one embodiment, each of the first and second thermal storage block arrangements are divided into three phase groups.

In one embodiment, each thermal storage block comprises at least one electrical connector (e.g. at least one exposed electrical connector wire extending from an outer wall of the thermal storage block).

In one embodiment, the modular thermal energy store further comprises at least one electrical distribution bus (e.g. electrically conductive bus bar or rod) electrically connecting the first thermal storage layer to the second thermal storage layer.

In one embodiment, the modular thermal energy store comprises at one electrical distribution bus (e.g. bus bar or rod) for each phase of the electrical supply.

In one embodiment, the at least one electrical connector (e.g. at least one exposed electrical connector wire) is located adjacent a lateral side of the thermal storage block (e.g. in close proximity to the electrical distribution bus).

Keeping the electrical connectors short is advantageous since it allows the use of uninsulated bare metal connectors. Accordingly, having the output of the electrical element near the edge of each block in close proximity to the electrical conductor bars minimises the length.

In one embodiment, each thermal storage block is associated with a respective electrical distribution bus (e.g. all or at least a subset of the plurality of thermal storage blocks arranged in a vertical column are connected to a common electrical distribution bus).

In one embodiment, each thermal storage block comprises a support operative to support the electrical distribution bus.

In one embodiment, the support comprises a post projecting from a surface of the thermal storage block and a rigid conductor link extending laterally from the post.

In one embodiment, the rigid conductor link is configured to support an electrical distribution bar.

In one embodiment, the post is electrically conductive (e.g. and electrically isolated from the thermal storage block).

In one embodiment, the at least one exposed electrical connector wire is connected to the post.

In one embodiment, the at least one electrical distribution bus is located within the at least one central vertically-extending support.

In one embodiment, the embedded heat exchanger element of each thermal storage block has a working fluid input and/or working fluid output located on an outer periphery of the thermal storage block.

In one embodiment, the working fluid input and/or working fluid output of the embedded heat exchanger element of a plurality of the (e.g. each) thermal storage blocks in the first thermal storage layer are connected by a circumferentially extending working fluid connection (e.g. pipe connection).

In one embodiment, the working fluid input and/or working fluid output is located within the vertically-extending peripheral channel defined by the thermal storage block (e.g. single vertically-extending peripheral channel).

In one embodiment, the thermal transfer element comprises a heat exchanger element operative: during a charging phase of the thermal energy store to act as a heat input; and during a discharging phase of the thermal energy store to transfer thermal energy from the solid body to the heat transfer fluid.

In one embodiment, the thermal transfer element comprises: an electrical heating element operative during a charging phase of the thermal energy store to act as a heat input; and a heat exchanger element operative during a discharging phase of the thermal energy store to transfer thermal energy from the solid body to the heat transfer fluid.

In one embodiment, the modular thermal energy store is a sensible (i.e. non-phase change) thermal energy store.

In one embodiment, the solid thermal filler material has a melting point that is higher than the melting point of the solid thermally conductive matrix.

In one embodiment, the solid thermally conductive matrix comprises a solid metal matrix.

In one embodiment, the solid metal matrix comprises a solid aluminium matrix.

In one embodiment, the solid thermally conductive matrix material has a substantially higher thermal conductivity than the solid thermal filler material.

In one embodiment, the solid thermal filler material comprises a plurality of discrete elements (e.g. particles) interspersed within the solid thermally conductive matrix.

In accordance with a third aspect of the present invention, there is provided a vacuum- insulated heat store for an energy storage system, the vacuum-insulated heat store comprising: a modular thermal energy store according to the second aspect of the present invention (e.g. according to any embodiment of the second aspect of the present invention); and a vacuum- insulated cover configured to be placed over the modular thermal energy store to insulate the modular thermal energy store, the vacuum-insulated cover comprising an outer shell and an inner shell spaced by a vacuum region extending therebetween.

In one embodiment, the vacuum-insulated heat store is as defined in any embodiment of the first aspect of the present invention.

In one embodiment, the vacuum-insulated cover is configured to constrain movement of the first and second modular thermal storage block arrangements (e.g. constrain movement of the first and second plurality of thermal storage blocks).

In accordance with a fourth aspect of the present invention, there is provided a method of constructing a vacuum-insulated heat store for an energy storage system, comprising: providing a thermal energy store; providing a vacuum-insulated cover configured to be placed over the thermal energy store to insulate the thermal energy store, the vacuum-insulated cover comprising an outer shell and an inner shell spaced by a vacuum region extending therebetween, the vacuum-insulated cover including a base defining an opening to a chamber within the inner shell, the chamber being configured to receive the thermal energy store when the vacuum- insulated cover is installed over the thermal energy store; and lowering the vacuum-insulated cover over the thermal energy store.

In one embodiment, the step of providing a thermal energy store comprises: installing a first thermal storage layer comprising a first modular thermal storage block arrangement on a thermally insulated base; and installing a second thermal storage layer on top of the first thermal storage layer, the second thermal storage layer comprising a second modular thermal storage block arrangement and being supported by the first thermal storage layer.

In one embodiment, the step of installing a first thermal storage layer comprises installing (e.g. block by block) a first plurality of n thermal storage blocks circumferentially spaced relative to a central vertical axis of the modular thermal energy store; and the step of installing a second thermal storage layer comprises installing (e.g. block by block) a second plurality of m thermal storage blocks circumferentially spaced relative to the central vertical axis of the modular thermal energy store.

In one embodiment, the vacuum-insulated cover is supported by the thermally insulated base.

In one embodiment, the vacuum-insulated heat store is as defined in any embodiment of the first aspect of the invention and/or the thermal energy store is a modular thermal energy store according to any embodiment of the second aspect of the invention.

The present invention discloses an insulated thermal store designed for efficient energy storage. The design is fully scalable, suitable for small-scale (0-10 MWh) as well as large-scale (100MWh+) applications. The system comprises a structural base upon which layers of thermal storage blocks are assembled. A number of these blocks collectively form a flat ring when arranged in a layer, and steel plates are positioned between each layer for structural integrity. The modular nature of the system allows for the assembly of multiple layers, including the incremental addition of layers after installation.

The first key feature of the invention is the utilisation of a vacuum-insulated cover that can be lowered over the entire thermal store. This may securely seat on the structural base or directly onto the ground. This decouples the part of the invention used for thermal storage and insulation and therefore has a number of major advantages. The vacuum- insulated cover is removable to provide access to the thermal store as needed. As well as to provide insulation, the lightweight vacuum-cover structure acts to weatherproof the thermal store.

The second key feature of this design enables the construction of a thermal store comprised of factory-built modular components, facilitating rapid on-site assembly. This permits additional structure within the internal space, regular servicing and maintenance. The third key feature of the design is that the vacuum cover can be fabricated and transported vertically as well as horizontally, allowing efficient assembly into a vertical orientation at any point. This ensures ease of transportation and installation.

A fourth key feature are the thermal storage blocks constructed in modules which may be wedge-shaped and arranged in layers. These modular blocks divide the total weight of storage into manageable sizes which can be easily transported and installed.

Another key feature is the co-location of thermal storage with the heat input mechanism and heat output mechanism. The modular approach allows high levels of heat transfer to be achieved for these two mechanisms. It also allows the rate of heat addition and heat rejection to be customised spatially throughout the thermal store and temporally to manage the performance of the thermal store.

A further key feature is a structural base which supports the weight of the thermal store independently and resists lateral loading from e.g. wind and seismic loads. The base can be adapted to seal the thermal store volume and therefore a separate vacuum is permissible. This environment can be advantageous at much higher temperatures.

The insulated thermal store therefore addresses the challenges associated with transportation and on-site construction, offering a cost-effective and scalable solution for large-scale thermal energy storage.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:

Figure la is a schematic cross-sectional view of a vacuum-insulated heat store in accordance with a first embodiment of the present invention;

Figure lb is a schematic sectional view of the vacuum-insulated heat store of Figure la taken along line A- A of Figure la;

Figure 1c is a schematic cross-sectional view of a vacuum-insulated heat store in accordance with a second embodiment of the present invention;

Figure Id is a schematic cross-sectional view of a vacuum-insulated heat store in accordance with a third embodiment of the present invention;

Figure le is a schematic cross-sectional view of a vacuum-insulated heat store in accordance with a fourth embodiment of the present invention;

Figure If is a schematic sectional view of the vacuum-insulated heat store of Figure le taken along line A’ -A’ of Figure le;

Figure 2 is a schematic cross-sectional view of an alternative embodiment of a vacuum-insulated cover for use in the vacuum-insulated heat stores of any of Figures la ,1b or Id;

Figure 3a is a schematic cross-sectional view of a modular thermal energy store in accordance with an embodiment of the present invention;

Figure 3b is a schematic sectional view of the modular thermal energy store of Figure

3 a;

Figure 3c is a schematic sectional view of a modular thermal energy store in accordance with a further embodiment of the present invention;

Figure 3d is a schematic sectional view of a modular thermal energy store in accordance with yet a further embodiment of the present invention;

Figure 3e is a schematic sectional view of a modular thermal energy store in accordance with yet a further embodiment of the present invention;

Figure 3f is a schematic cross-sectional view of a modular thermal energy store in accordance with yet a further embodiment of the present invention;

Figure 4a is a top view of a heat block component of the modular thermal energy store of Figure 3 a illustrating a lifting feature;

Figure 4b is a bottom view of a heat block component of the modular thermal energy store of Figure 3 a illustrating an optional interlocking feature;

Figure 5a is a perspective view of a heat block component of the modular thermal energy store of Figure 3a showing a possible arrangement of the electric elements located within the block;

Figure 5b is a plan view of the heat block component of Figure 5a;

Figure 5c is a rear view of the heat block component of Figure 5a;

Figure 5d is a perspective view of a heat block component of the modular thermal energy store of Figure 3a showing a further possible arrangement of the electric elements located within the block;

Figure 5e is a plan view of the heat block component of Figure 5d;

Figure 5f is a rear view of the heat block component of Figure 5d;

Figure 6a is a plan view of a steel plate component of the modular thermal energy store of Figure 3a that is placed on top of the heat block components;

Figure 6b is a plan view of an alternative embodiment of a steel plate for use in the modular thermal energy store of Figure 3a;

Figure 6c is a plan view of a further alternative embodiment of a steel plate for use in the modular thermal energy store of Figure 3a;

Figure 6d is a plan view of a yet further alternative embodiment of a steel plate for use in the modular thermal energy store of Figure 3a in conjunction with the heat block component of Figure 4b;

Figure 7a is a cross-sectional view of an alternative embodiment of central tubular column for use in the modular thermal energy store of Figure 3a;

Figure 7b is a cross-sectional view of a further alternative embodiment of central tubular column for use in the modular thermal energy store of Figure 3 a.

Figure 8a is a schematic sectional view of a modular thermal energy store in accordance with yet a further embodiment of the present invention;

Figure 8b is a schematic sectional view of a modular thermal energy store in accordance with yet a further embodiment of the present invention;

Figure 8c is a schematic cross-sectional view of a vacuum-insulated heat store comprising a modular thermal energy store in accordance with yet a further embodiment of the present invention showing the key stages of on-site assembly; and

Figure 8d is a schematic cross-sectional view of a modular thermal energy store in accordance with an embodiment of the present invention.

Figure la shows a vacuum-insulated heat store 10 comprising a (e.g. removable) vacuum-insulated cover 15, structural base 16 and thermal store 17.

Vacuum-insulated cover 15 comprises an outer shell 20 and an inner shell 30. The inner and outer shells 20, 30 each comprise a cylindrical section 22, 32 and an upper domed section 21, 31. The inner shell 20 has a smaller diameter and can be inserted into the outer shell 30. The vacuum-insulated cover 15 is created when the outer shell 20 is joined to the inner shell 30, by a frusto-conical joining piece 33 forming a sealed volume between the two shells that can be evacuated. This arrangement of inner and outer shells allows any commonly manufactured dome shape to be used. A flange 34 is located below the frusto-conical joining piece 33. The space between the inner shell 30 and outer shell 20 is evacuated via a vacuum port 35 to form a vacuum region 50 with a pressure below lOmbar, preferably below 0. Imbar.

As illustrated, vacuum-insulated cover 15 includes a base 15A defining an opening 15B leading to a chamber 30A located within the volume of inner shell 30. Chamber 30A and opening 15B are each configured to receive thermal store 17 when the vacuum-insulated cover 15 is installed over the thermal store 17 during on-site installation.

In addition to the main vacuum region 50, the space between inner shell 30 and thermal store 17 may be evacuated via an internal vacuum port 82 to form a secondary (e.g. weaker) vacuum region with a pressure below lOOOmbar, preferably below 800mbar.

The outer cylindrical section 22 may further comprise optional reinforcing ribs 23. These reinforcing ribs 23 may be external or internal to parallel cylindrical section 22. They are preferably internal as they do not require continuous welding when inserted internally. The design of the ribs 23 (shape, thickness, spacing and material) may be selected to optimise the volume of the vacuum region 50 and to ease fabrication. Frusto-conical joining piece 33, may further comprise optional reinforcing ribs 23.

Vacuum region 50 is filled with an insulation barrier 40 comprising an outer cage 42, optional inner cage 43 and insulation material 41 such as Multi-Layer Insulation (MLI) or ceramic insulation blankets.

Outer cage 42 and inner cage 43 are optional structural elements that constrain and/or support the insulation material 41. The outer and inner cages 42, 43 may comprise a material that is flexible and resistant to changes in temperature, such as wire mesh. Alternatively, the insulation material 41 may be applied to the inner shell 30 with only an outer cage 42 applied. The insulation barrier 40 may be applied/attached to the inner shell 30 such that the outer shell 20 can be lowered over both the inner shell 30 and insulation barrier 40 before the outer and inner shells 20, 30 are joined. Alternatively, the insulation barrier 40 may be freestanding such that either the inner or outer cage 42, 43 provide structural support. This support allows the insulation barrier to be assembled separately and located between the inner shell 30 and the outer shell 20.

Vacuum-insulated cover 15 may also comprise a structural support 44 to provide resistance to the vacuum-insulated cover 15, between inner shell 20 and outer shell 30, during lateral load conditions (e.g. horizontal transport, seismic loading, etc.). Structural support 44 may comprise a pin and socket arrangement for example.

As illustrated, the vacuum-insulated cover 15 may be used in a substantially vertical orientation and it may be located on structural base 16.

The structural base 16 comprises a support platform 16a, a lower base section 16b and a central tubular column 62. The structural base 16 is made of steel or similar material and supports the mass of the thermal store 17 that is enclosed within the vacuum-insulated cover 15. Lower base section 16b comprises an outer cylindrical support 64 configured to engage the ground/floor and a flat plate 61 configured to support the support platform 16a. Flat plate 61 includes a central aperture for receiving central tubular column 62. Support platform 16a comprises a plurality of radially extending ribs 60 extending radially from the central tubular column 62, with adjacent pairs of radially extending ribs 60 together defining a plurality of open-topped cells 60a.

Supporting ribs 60 are welded to the top of the flat plate 61 to stiffen and support the flat plate 61. Insulation (not shown) can be placed in cells 60a between the supporting ribs 60 to reduce heat flows from the thermal store 17 to the flat plate 61. Supporting ribs 60 may have optional features to further reduce heat flow, e.g. locally thinned walls and castellations.

Outer cylindrical support 64 and central tubular column 62 are each welded to flat plate 61. Outer cylindrical support 64 may be further welded to the radially outer-most edge of supporting ribs 60. Central tubular column 62 may be further welded to the radially innermost edge of supporting ribs 60. Outer cylindrical support 64 is also welded to a lower flange 63, which can be bolted (bolts not shown) to a suitable foundation such as concrete. The bolts allow any lateral loads on the structure to be supported without the structure becoming unstable. Central tubular column 62 may extend above the supporting ribs 60 to provide lateral support to the thermal store 17 above.

The outer portion of the flat plate 61 is designed to receive flange 34 of the vacuum- insulated cover 15.

A number of restraining fittings 65 (e.g. at least two) are attached to the vacuum- insulated cover 15 and the structural base 16 and allow the vacuum-insulated cover 15 to be mechanically coupled to the structural base. These restraining fittings 65 may allow vacuum- insulated cover 15 to lift vertically by a pre-determined distance. For example, the vacuum- insulated cover 15 may lift by l-5cm. This allows rapid pressure relief that may be required from the volume containing the thermal store 17. For example, if an internal pipe ruptures releasing steam or other gas, this must be safely vented to minimise internal pressure in thermal store 17. In one embodiment, the internal pressure is designed to increase to a minimal level required to lift the weight of vacuum-insulated cover 15 which in turn allows gas to be released. In another embodiment, the gas leakage path may be routed through structural base 16. The restraining fittings 65 may be wire strops connected to both the vacuum-insulated cover 15 and the structural base 16 or alternatively any restraint/guide which allows vertical movement. The structural base 16 may comprise electrical fittings 80 to carry electrical power into the structure via a wire and/or mechanical fittings 81 to allow fluids to enter/leave via one or more pipes. There may be multiple fittings of both electrical and mechanical nature.

Thermal Store 17 may be made from a solid material such as steel or concrete or from a combination of rock and aluminium as covered in granted U.K. patent GB2597006. The thermal store 17 may be similar to the one disclosed in granted U.K. patent GB2577579 where the rock/aluminium matrix may store heat. In addition, further media may be added to the composition of thermal store 17 to achieve improved thermal performance. In one embodiment, cast iron may be added to improve thermal capacity per unit volume and bulk thermal conductivity. Thermal store 17 may contain electrical heating elements (not shown) to generate heat that can be stored within the thermal storage material and embedded pipes (not shown) that can carry a fluid that is heated while passing through the pipes to extract the stored heat.

Figure lb illustrates a section taken along line A- A of Figure la showing the position of supporting ribs 60 within structural base 16. Supporting ribs 60 extend radially from central tubular column 62.

Figure 1c shows an alternative embodiment of a vacuum-insulated heat store 10’ based on vacuum-insulated heat store 10 (features in common are labelled accordingly) comprising additional thermal material 18 which may be a capstone for example.

Figure Id shows a further alternative embodiment of a vacuum-insulated heat store 10” based on vacuum-insulated heat store 10 (features in common are labelled accordingly) in which flat plate 61 of lower base section 16b” is removed and alternative supporting ribs 60” are provided which extend from the base of thermal store 17” to the ground. Electrical fittings 80” and mechanical fittings 81” may be located on external face of cylindrical support 64”. Internal vacuum port 82 may be removed in this case.

Figure le shows a further alternative embodiment of a vacuum-insulated heat store 10”’ based on vacuum-insulated heat store 10 (features in common are labelled accordingly) in which the structural base 16’” comprises an inner cylinder 300 and an outer cylinder 302 which are joined by radially extending ribs 307.

The lower part of structural base 16b’” comprises a plurality of holes (e.g. circular holes) 310 in outer cylinder 302 to enable air to flow in and out of this space. Radially extending ribs 307 also comprise holes (e.g. circular holes) 305 to promote air flow in and out of this space. This acts to increase heat loss from the lower portion of the structural base 16”’ and to reduce conduction to the ground and the temperature of the lower portion of the structural base 16’”. Radially extending ribs 307 extend radially beyond the outer cylinder 302 and upwards to support an annular flange 311 which in turn supports flange 34” ’of the vacuum-insulated cover 15’”.

The reduction of temperature in this region is beneficial to enable reliable electrical connections to external wires and cables (not shown) in this space.

Insulation such as mineral wool or fibre-based polymers may be used in the upper portions of the structural base 16’” in the regions not open to the atmosphere to reduce heat loss further. Insulation material 306 (mineral wool or fibre polymer based) is shown in the centre of inner cylinder 300, insulation material 301 is shown in between outer cylinder 302 and inner cylinder 300. Removable steel plate 304 may be used to support further insulation material 308 as well as provide a separation or containment of services. For example, fluid and gas services (not shown) may be connected above steel plate 304 and electrical connections are made below steel plate 304. Steel plate 309 can be used to support insulation 301 in the region between outer cylinder 302 and inner cylinder 300.

Figure If illustrates a section taken along line A’ -A’ of Figure le showing the position of outer cylinder 302, inner cylinder 300 and radially extending ribs 307.

Figure 2 shows an alternative embodiment of the vacuum-insulated cover 15”” based on the vacuum-insulated cover 15 (features in common are labelled according) where the external frusto-conical joining piece 33”” is inverted so the inner cylindrical section 32”” extends below the outer cylindrical section 22””. The flange 34”” may optionally be located facing outwards as shown. Frusto-conical joining piece 33”” may further comprise optional reinforcing ribs 23””. This arrangement may be used to maximise the widest diameter of the vacuum-insulated cover 15”” relative to the widest diameter of the structural base 16””.

Figures 3a and 3b show a modular thermal energy store 100 for use in any of the vacuum-insulated heat stores 10, 10’, 10”, 10’” or any other heat store application. The modular thermal energy store 100 comprises a plurality (in this case three) of modular thermal storage block layers 101A-C, a structural base 216 supporting the plurality of thermal storage block layers 101A-C and a central tubular column 262 extending along a central longitudinal axis of the modular thermal energy store 100 through the plurality of modular thermal storage block layers 101 A-C and the structural base 216. As shown in Figure 3b, each of the plurality of modular thermal storage block layers 101 A-C comprising six blocks 101 arranged around central tubular column 262 and forming a hexagonal outer profile. With reference to Figure 3a, a steel plate 120 with retaining feature 121 is located between each layer.

Each block 101 may be made from a combination of aluminium and rock or steel as described in granted U.K. patent GB2597006. As illustrated each block 101 includes one or more electric heating elements 110 to add heat to the storage block 101 and (optionally) a heat exchanger 102 that can be used to extract heat from the block 101. Electric heating elements 110 may be configured into a V shape and cast within the block 101. Electric heating elements 110 are connected to a conductor 104 by wire 111 at one junction and connected to conductor 106 by wire 112 at the other junction. While not shown, each block 101 may contain just electric elements 110, just a heat exchanger 102, both electric elements 110 and heat exchanger 102 or neither. For example, alternate blocks could contain heat exchangers

102 or alternate layers of the store could contain electric elements 110. Each block 101 may comprise just a thermal store 17 or a thermal store provided within a containment housing.

While six is an optimum number of blocks 101 per layer for three phase electricity, the number of blocks 101 per layer can be higher or lower (e.g. depending upon the number of phases).

The outer edges of each block 101 may be recessed to form channels 101a that allow pipes and electrical conductor bus bars to route up and down modular thermal energy store 100. In addition, inner profiles of each block 101 are recessed to form a central recess 101b configured to accommodate central structural elements including central tubular column 262 as shown and to allow for thermal expansion of the blocks relative to the central tubular column 262.

When configured for three phase electricity, conductors 103,104 and 105 could all be live conductors with a common neutral conductor 106. It should be understood by one skilled in the art that there are multiple configurations of conductor, wiring and polarity that are possible. For example if DC electricity was used then conductors 103,104, and 105 could all be positive and the three conductors 106 would be negative (e.g. circuit conductors 103,104, and 105 would have positive electrical polarity and the conductors 106 would have negative electrical polarity). The use of a V shape element 110 minimises the length of wiring 112 and 111.

Wiring 112 may be designed as a “sacrificial” fuse link to clear short-circuit faults without requiring circuit breakers or manual intervention. Figure 3c shows a cross section of an alternative embodiment of a modular thermal energy store 100’ based on modular thermal energy store 100 (features in common are labelled accordingly) in which there is a different arrangement configured for three-phase electricity. Electricity flows from live conductor 103’, through electric heating element 110’, and then neighbouring electric heating element 110’ via conductor 108.

Figure 3d shows a cross section of an alternative embodiment of a modular thermal energy store 100” based on modular thermal energy store 100 (features in common are labelled accordingly) wherein any of or a subset of conductors 103”, 104”, 105”, 107”, 108’ and 109’ are fabricated from a number of strips or individual rods of conductive elements to reduce skin effect if AC power is used. Alternatively, a laminate structure of conductive and insulating elements could be used. These may be supported at regular intervals (not shown) to provide additional structure at high temperatures. The conductive material used for the conductors will typically operate at high temperatures which rules out aluminium and makes copper difficult to use due to oxidation, high temperature embrittlement and the difficulty forming suitable joins that will survive at high temperatures. The conductors can be made from a metal with lower conductivity such as stainless steel, carbon steel or an alloy steel that is structurally stable at high temperatures and can resist oxidation. These materials would not normally be used for conductors, but a significant advantage is that aU joins can be formed by welding so that they will perform reliably for long periods of time.

Figure 3e shows a cross section of an alternative embodiment of a modular thermal energy store 100’” based on modular thermal energy store 100 (features in common are labelled accordingly) wherein a W shaped electric heating element 110’” is included in each block 101’”. In general, any shape of element may be used to optimise the diffusion of heat into the thermal block for a particular application. In the case of ‘direct-energy-usage’ as an example where there is simultaneous heat addition through heating element 110’” and heat rejection through heat exchanger 102’”, it is advantageous to co-locate heating element 110’” and heat transfer coil 102’” in the plan view to minimise the conductive path length.

If fabricated from strips or individual elements, all or a subset of conductors 103’”, 104’”, 105’”, 107’”, 108’” and 109” may contain both positive conductor 117 and negative conductor 118.

Figure 3f shows a side view of structural base 16”” where conductor 103”” is shown to be contained within electrical containment 200 and be terminated onto conductor 204 at junction 202. Conductor 204 may be a flexible conductor (as illustrated) or a solid conductor. Conductor 204 in turn passes through bulkhead 203 which is sealed from water ingress by rubber gromets or other means and connects to electrical isolation cabinet 205. External connections are then made to isolation cabinet 205 by any standard termination means for example electrical lug or other fastening. The junction 202 is passively cooled by air which flows through port 201. This allows standard electrical connections to be made for example a brazed or bolted joint. In additional conductor 204 may be made of a suitable material such as copper or aluminium with a lower resistivity value and thus small cross-sectional area compared to the conductor 103”” it is connected to. Air can naturally circulate through the structural base 16”” in an unrestricted manner as previously mentioned. Electrical insulator 206 is made of a material with very high electrical resistivity and acts to support and space conductor 103”” which is fabricated from a number of strips or individual rods. In the illustration conductor 103”” only is shown. It should be understood by one skilled in the art that that any one of the conductors 103””, 104””, 105””, 107””, 108”’ and 109”’ is applicable.

Conductor 204 may provide the ability to electrically isolate each electrical circuit which provides power to each thermal block 101 via a plurality of individual conductors 103”” each associated with a respective thermal block 101. This allows individual thermal blocks 101 to be individually charged which is beneficial for stepping power up and down to heat thermal store 100 in a variable manner.

Figure 4a shows a top view of block 101 comprising a lifting feature 115 on the top face to allow for easy handling and installation. Lifting feature 115 may be located on any face of block 101. There may be multiple instances of lifting feature 115 on one block 101.

Figure 4b shows a bottom view of block 101 comprising an interlocking feature 124 which engages securely with interlocking feature 123 in steel plate 120. In one case, interlocking feature 124 could be a recess in thermal block 110 and interlocking feature 123 could be a pedestal in steel plate 120.

Figure 5a shows a three-dimensional view of block 101 and a possible arrangement of the electric heating elements 110 located within wherein only one connection 113 to a live conductor 103, 104 or 105 and only one connection 116 to a neutral conductor 106 is required per block. This reduces electrostriction effect in the block as current flowing in consecutive electric elements 110 carries reversing direction. To manage heat transfer (W/cm²) it may be advantageous to increase the heater length whilst avoiding horizontal non-heating conductors external to the block 101. It should be understood by one skilled in the art that there are multiple configurations of electric element 110 and wiring 113, 116 that are possible.

Figure 5b shows the top face of block 101 with an internal arrangement of electric elements 110 as seen in Figure 5 a.

Figure 5c shows the back face of block 101 with an internal arrangement of electric elements 110 as seen in Figure 5 a.

Figure 5d shows a three-dimensional view of block 101”” where connection 113’ is terminated onto conductor post 500 which is electrically isolated from block 101”” but structurally attached to block 101”” such that it can sustain a nominal structural load. Rigid conductor link 501 in turn connects the conductor post 500 to live conductor 103, 104 or 105 (not shown). The mass of live conductor 103, 104 or 105 (not shown) may be supported by conductor post 500 only which is advantageous to manage thermal expansion and electrical insulation of live conductors. Conductor post 502 and rigid conductor link 503 are used to make connections to the neutral conductors in the same manner.

Figure 5e shows the top face of block 101”” with the arrangement of conductor post 500 and rigid conductor link 501 as seen in Figure 5d.

Figure 5f shows the back face of block 101”” with the arrangement of conductor post 500 and rigid conductor link 501 as seen in Figure 5d.

Figure 6a shows steel plate 120 that is placed on top of the six blocks 101 around central tubular column 262. Steel plate 120 may have retaining features 121 located at the edge of the plate. For example, this may be a pin or a lip feature on the plate 120, which may or may not engage with a feature in block 101. The purpose of the retaining feature 121 is to stop the block 101 from moving out of position when thermally cycled. It may also be advantageous during construction of the constructed thermal store.

Figure 6b shows an alternative embodiment of steel plate 120’ wherein central tubular column 262’ has a male key feature 269 that minimises movement of the steel plate 120’ which comprises a corresponding female key feature.

Figure 6c shows a further alternative embodiment of steel plate 120” which comprises multiple interlocking sections 122 to facilitate manufacture, handling and transport of steel plate 120” and which do not need mechanical joining. This reduces electrostriction effect induced in the plate 120” and therefore the aggregate effect in the constructed thermal store. An insulating strip (not shown) may be fitted between interlocking sections 122.

Figure 6d shows a further alternative embodiment of steel plate 120’” based on steel plate 120” with an interlocking feature 123 designed to engage with the counterpart interlocking feature 124 in thermal block 110 illustrated in Figure 4b. As discussed above, in one example interlocking feature 124 could be a recess in thermal block 110 and interlocking feature 123 could be a pedestal in steel plate 120.

Figure 7a shows a cross section of an alternative embodiment of central tubular column 262” wherein central tubular column 262” is fabricated from multiple sections 267 for easier handling and installation. Sections 267 may be joined by a connecting sleeve for example. The number of sections 267 required to fabricate central tubular column 262”may be two or more.

Figure 7b shows a cross section of a further alternative embodiment of central tubular column 262”’ wherein central tubular column 262”’ comprises additional thermal storage 268 within. This alternative embodiment also allows heat exchange fluid and instrumentation to pass in and out of modular thermal energy store 100 via central tubular column 262’”. This has additional benefits should modular thermal energy store 100 be subject to thermal convection including buoyancy effects wherein central tubular column 262’” takes advantage of this.

Figure 8a shows a modular thermal energy store 100’”” based on modular thermal energy store 100 (features in common are labelled accordingly) for use in any of the vacuum- insulated heat stores 10, 10’, 10”, 10’” or any other heat store application. In this embodiment inner cylindrical section 30’”” ofvacuum cover 15’”” can be used to constrain the movement of blocks 101’””. This aids the control and management of design tolerances and assembly of modular thermal energy store 100’””. Heating elements 110’”” are connected to electrical conductors 600 in the centre of blocks 101’””. In this case central tubular column 262’”” is made up of sections allowing the connections between heating elements 110’”” and electrical conductors 600 to be made safely and reliably during the construction of modular thermal energy store 100’””. The use of a central column for conductors has a number of advantages. It isolates and protects the electrical conductors so they cannot be accessed or damaged during installation of the vacuum cover. It is necessary to provide suitable electrical insulation, i.e. the correct clearance and creepage distances between live conductors and the main structure. This distance can have an impact on how much space is used when the conductors are located close to the cover. By combining all conductors within the same central circular space, the amount of store volume used for insulation purposes is greatly reduced. As shown in Figure 8b this allows a significantly greater proportion of the volume under the vacuum cover to be used.

Figure 8b shows a further embodiment of modular thermal energy store 100””” based on modular thermal energy store 100””’ (features in common are labelled accordingly) with a petal shaped electric heating element 110”’ and wherein thermal blocks 101””” extend radially outward toward inner cylindrical section 30””” of vacuum cover 15”””. This increases the storage capacity per unit area in the plan view of modular thermal energy store 100”””. In addition, the minimum distance between inner cylindrical section 30””” and blocks 101””” is reduced, further constraining the movement of blocks 101”””. In this embodiment, the inlet and outlet of heat exchanger 102””” in block 101””” are connected to a combined inlet header pipe 602 and outlet header pipe 601 respectively. These connections are made within the inner cylindrical section 30””” of vacuum cover 15””” such that for the construction and maintenance of modular thermal energy store 100”””, access to the piping assembly is only required by personnel and equipment from one side. This approach of access from a single side requires a complete layer of 6 blocks 101””” to be assembled into one ‘component’ and installed a layer at a time as shown in Figure 8c.

Figure 8c illustrates a method of assembling heat store 10””. First structural base 16’”” is positioned onto the ground. Preassembled thermal layers 700 of modular thermal energy store 100’””” are then lifted onto structural base 16’””. Lifting point 701 is designed such that thermal layer 700 can be lifted as a single assembly and engage with the previous thermal layer via engagement points 702. In this way modular thermal energy store 100’””” is built up to a determined height. In the case shown 6 layers 700 are shown. Vacuum insulated cover 15’””” is then lowered onto thermal energy store 100’””” and is supported by structural base 16’”” once seated. Once in position, vacuum insulated cover 15’””” may be releasably coupled to the structural base 16’”” for ease of access. Alternatively it is feasible that the secondary vacuum region extending between the thermal energy store and the inner shell of the vacuum-insulated cover itself is adequate to retain vacuum insulated cover 15’””” in place under vacuum loading alone.

Figure 8d describes the packing density advantage that can be achieved where access to modular thermal energy store 10””” is only required from one side. Required access annulus 800 can be reduced to the access area 801 and in turn this reduces the overall footprint of a per metre basis of an assembly of a number of vacuum-insulated heat stores 10”””. In this case an array of six vacuum-insulated heat stores 10””” are shown. The length and width of the array can be reduced to around 63% of the equivalent area required should a vacuum-insulated heat store 10””’ require access all round. This is equivalent to a footprint area which is 40% that of a vacuum-insulated heat store 10””’ which requires access all round.

Claims

Claims:

1. A vacuum-insulated heat store for an energy storage system, comprising: a thermal energy store; and a vacuum-insulated cover configured to be placed over the thermal energy store to insulate the thermal energy store, the vacuum-insulated cover comprising an outer shell and an inner shell spaced by a vacuum region extending therebetween, the vacuum-insulated cover including a base defining an opening to a chamber within the inner shell, the chamber being configured to receive the thermal energy store when the vacuum-insulated cover is installed over the thermal energy store.

2. A vacuum-insulated heat store according to claim 1, wherein the vacuum-insulated cover is configured such that the vacuum region extends substantially from a base of the thermal energy store to an uppermost region of the thermal energy store.

3. A vacuum-insulated heat store according to claim 2, wherein the vacuum region extends from below the base of the thermal energy store to an uppermost region of the thermal energy store.

4. A vacuum-insulated heat store according to any of the preceding claims, wherein the inner and outer shells comprise inner and outer cylindrical sections respectively connected by a sealed joining piece located at a lower portion of the vacuum-insulated cover.

5. A vacuum-insulated heat store according to claim 4, wherein the sealed joining piece forms a periphery surrounding the opening to the chamber.

6. A vacuum-insulated heat store according to claim 4 or claim 5, wherein the sealed joining piece is a sealed tapered joining piece.

7. A vacuum-insulated heat store according to any of claims 4-6, wherein the sealed j oining piece further comprises a peripheral flange located at a base of the sealed joining piece and configured to engage a surface of a supporting structure.

8. A vacuum-insulated heat store according to any of the preceding claims, wherein the vacuum-insulated heat store further comprises a secondary vacuum region extending between the thermal energy store and the inner shell of the vacuum-insulated cover.

9. A vacuum-insulated heat store according to claim 8, wherein the secondary vacuum region has a weaker vacuum level than the vacuum region of the vacuum-insulated cover.

10. A vacuum-insulated heat store according to any of the preceding claims, wherein the vacuum-insulated heat store further comprises a structural base for supporting the thermal energy store.

11. A vacuum-insulated heat store according to claim 10, wherein the structural base comprises a support platform.

12. A vacuum-insulated heat store according to claim 11, wherein a lower portion of the vacuum-insulated cover substantially surrounds at least an upper portion of the support platform when the vacuum-insulated cover is installed over the thermal energy store.

13. A vacuum-insulated heat store according to claim 11 or claim 12, wherein the support platform has a tapered profile that increases with cross-sectional area with increased distance from the thermal energy store.

14. A vacuum-insulated heat store according to any of claims 11-13, wherein the support platform comprises a plurality of radially extending ribs configured to support the thermal energy store.

15. A vacuum-insulated heat store according to any of claims 11-14, wherein the support platform defines a plurality of chambers in fluid communication with the thermal energy store.

16. A vacuum-insulated heat store according to claim 15, wherein the plurality of chambers are filled with thermal insulation.

17. A vacuum-insulated heat store according to claim 15 or claim 16 (when dependent upon claim 7), wherein the secondary vacuum extends into the plurality of chambers.

18. A vacuum-insulated heat store according to any of claims 10-17, wherein the structural base further comprises a lower base section.

19. A vacuum-insulated heat store according to claim 18, wherein the lower base section is configured to support the vacuum-insulated cover.

20. A vacuum-insulated heat store according to claim 18 or claim 19, wherein the lower base section comprises an upper plate and an outer support wall.

21. A vacuum-insulated heat store according to any of claims 18-20, wherein the lower base section comprises at least one service connection.

22. A vacuum-insulated heat store according to any of claims 18-21, wherein the lower base section comprises a plurality of radially extending base ribs.

23. A vacuum-insulated heat store according to any of claims 18-21, where the structural base comprises a cooling arrangement configured to cool the at least one service connection.

24. A vacuum-insulated heat store according to claim 23, wherein the cooling arrangement comprises airflow apertures provided in the outer support wall and/or radially extending base ribs.

25. A vacuum-insulated heat store according to any of the preceding claims, wherein the vacuum-insulated heat store further comprises thermal insulation provided within the vacuum region.

26. A vacuum-insulated heat store according to claim 25, wherein the vacuum-insulated cover further comprises an internal cage structure provided inside the vacuum region, the internal cage structure being configured to hold the thermal insulation in position.

27. A vacuum-insulated heat store according to any of the preceding claims, wherein the vacuum-insulated heat store further comprises a central vertically-extending support extending through the thermal energy store.

28. A vacuum-insulated heat store according to any of the preceding claims, wherein the vacuum-insulated heat store comprises: at least one electrical heating element operative to act as a heat input to the thermal energy store; and/or at least one heat exchanger element operative to receive a heat transfer fluid.

29. A modular thermal energy store comprising: a first thermal storage layer comprising a first modular thermal storage block arrangement; and a second thermal storage layer supported by the first thermal storage layer, the second thermal storage layer comprising a second modular thermal storage block arrangement.

30. A modular thermal energy store according to claim 29, wherein: the first modular thermal storage block arrangement comprises a first plurality of n thermal storage blocks circumferentially spaced relative to a central vertical axis of the modular thermal energy store; and the second modular thermal storage block arrangement comprises a second plurality of m thermal storage blocks circumferentially spaced relative to the central vertical axis of the modular thermal energy store.

31. A modular thermal energy store according to claim 29 or claim 30, the thermal energy store comprises at least one central vertically-extending support extending through the first and second thermal storage layers.

32. A modular thermal energy store according to claim 31, wherein the first and second modular thermal storage block arrangements each define a central recess for receiving the at least one central vertically-extending support.

33. A modular thermal energy store according to claim 32, wherein the central recess is configured to allow lateral expansion of first and second modular thermal storage block arrangements.

34. A modular thermal energy store according to any of claims 29-33, wherein the first thermal storage layer is supported by a base.

35. A modular thermal energy store according to any of claims 29-34, wherein the second thermal storage layer is supported by a plate that is supported by the first thermal storage layer.

36. A modular thermal energy store according to claim 35, wherein the plate comprises a retaining feature operative to permit limited laterally outward expansion of the first and/or second thermal storage layer relative to the plate.

37. A modular thermal energy store according to any of claims 29-36, wherein the modular thermal energy store further comprises a cap piece supported by the second modular thermal storage block arrangement.

38. A modular thermal energy store according to any of claims 29-37 (when dependent upon claim 31), wherein the at least one central vertically-extending support is expandable by adding a further vertical support section.

39. A modular thermal energy store according to claim 38, wherein the modular thermal energy store further comprises at least one further thermal storage layer.

40. A modular thermal energy store according to any of claims29-39, wherein at least one of the first and second modular thermal storage bock arrangements defines a vertically- extending peripheral channel.

41. A modular thermal energy store according to claim 40 (when dependent upon claim 30), wherein at least one thermal storage block defines at least a portion of the vertically-extending peripheral channel.

42. A modular thermal energy store according to claim 41, wherein the at least one thermal storage block defines a pair of circumferentially spaced vertically-extending peripheral channels.

43. A modular thermal energy store according to claim 41, wherein the at least one thermal storage block defines a single vertically-extending peripherals channel.

44. A modular thermal energy store according to any of claims 29-43, wherein at least one of the first and second modular thermal storage block arrangements comprises: a solid body; and at least one thermal transfer element embedded therein.

45. A modular thermal energy store according to claim 44 (when dependent upon claim 30), wherein each thermal storage block includes an embedded electrical heating element.

46. A modular thermal energy store according to claim 44 (when dependent upon claim 30), wherein all or a subset of the thermal storage blocks include an embedded heat exchanger element.

47. A modular thermal energy store according to any of claims 29-46, wherein: the modular thermal energy store is configured to be heated using a three-phase electrical supply; and each of the first and second thermal storage block arrangements are divided into three phase groups.

48. A modular thermal energy store according to any of claims 29-47, wherein each thermal storage block comprises at least one exposed electrical connector wire extending from an outer wall of the thermal storage block.

49. A modular thermal energy store according to any of claims 29-48, wherein the modular thermal energy store further comprises at least one electrical distribution bus electrically connecting the first thermal storage layer to the second thermal storage layer.

50. A modular thermal energy store according to claim 49, wherein the at least one exposed electrical connector wire is located adjacent a lateral side of the thermal storage block in close proximity to the electrical distribution bus.

51. A modular thermal energy store according to claim 49 or claim 50, wherein each thermal storage block is associated with a respective electrical distribution bus.

52. A modular thermal energy store according to any of claims 49-51, wherein each thermal storage block comprises a support operative to support the electrical distribution bus.

53. A modular thermal energy store according to claim 52, wherein the support comprises a post projecting from a surface of the thermal storage block and a rigid conductor link extending laterally from the post.

54. A modular thermal energy store according to claim 53, wherein the rigid conductor link is configured to support an electrical distribution bar.

55. A modular thermal energy store according to claim 53 and 54, wherein the post is electrically conductive.

56. A modular thermal energy store according to claim 55 (when dependent upon claim 48), wherein the at least one exposed electrical connector wire is connected to the post.

57. A modular thermal energy store according to any of claims 49-56, wherein the at least one electrical distribution bus is located within the at least one central vertically-extending support.

58. A modular thermal energy store according to any of claims 29-57 (when dependent upon claim 46), wherein the embedded heat exchanger element of each thermal storage block has a working fluid input and/or working fluid output located on an outer periphery of the thermal storage block.

59. A modular thermal energy store according to claim 58, wherein the working fluid input and/or working fluid output of the embedded heat exchanger element of a plurality of the thermal storage blocks in the first thermal storage layer are connected by a circumferentially extending working fluid connection.

60. A modular thermal energy store according to claim 58 or claim 59, wherein the working fluid input and/or working fluid output is located within the vertically-extending peripheral channel defined by the thermal storage block.

61. A vacuum-insulated heat store for an energy storage system, the vacuum-insulated heat store comprising: a modular thermal energy store according to any of claims 29-60; and a vacuum-insulated cover configured to be placed over the modular thermal energy store to insulate the modular thermal energy store, the vacuum-insulated cover comprising an outer shell and an inner shell spaced by a vacuum region extending therebetween.

62. A vacuum-insulated heat store according to claim 61, wherein the vacuum-insulated heat store is as defined in any of claims 1-28.

63. A vacuum-insulated heat store according to claim 61 or 62, wherein the vacuum- insulated cover is configured to constrain movement of the first and second modular thermal storage block arrangements.

64. A method of constructing a vacuum-insulated heat store for an energy storage system, comprising: providing a thermal energy store; providing a vacuum-insulated cover configured to be placed over the thermal energy store to insulate the thermal energy store, the vacuum-insulated cover comprising an outer shell and an inner shell spaced by a vacuum region extending therebetween, the vacuum-insulated cover including a base defining an opening to a chamber within the inner shell, the chamber being configured to receive the thermal energy store when the vacuum-insulated cover is installed over the thermal energy store; and lowering the vacuum-insulated cover over the thermal energy store.

65. The method of claim 64, wherein the step of providing a thermal energy store comprises: installing a first thermal storage layer comprising a first modular thermal storage block arrangement on a thermally insulated base; and installing a second thermal storage layer on top of the first thermal storage layer, the second thermal storage layer comprising a second modular thermal storage block arrangement and being supported by the first thermal storage layer.

66. The method of claim 65, wherein: the step of installing a first thermal storage layer comprises installing a first plurality of n thermal storage blocks circumferentially spaced relative to a central vertical axis of the modular thermal energy store; and the step of installing a second thermal storage layer comprises installing a second plurality of m thermal storage blocks circumferentially spaced relative to the central vertical axis of the modular thermal energy store.

67. The method of any of claims 64-66, wherein the vacuum-insulated heat store is as defined in any of claims 1-28 and the thermal energy store is a modular thermal energy store according to any of claims 29-60.