Energy storage apparatus

Abstract

The present invention relates to an energy storage apparatus. In particular, the present invention relates to an energy storage apparatus which can be used for high temperature applications such as generators, and a method of reversibly storing and / or extracting energy. In certain embodiments, the energy storage apparatus comprises thermal insulators defining a plurality of thermal zones within a heat storage body in the energy storage apparatus (Figure 5b).

Description

ENERGY STORAGE APPARATUSRelated Application

[0001] The present invention claims priority to Australian Provisional Patent Application No. AU 2023903792, filed 24 November 2023, which is incorporated by reference in its entirety.Field of the Invention

[0002] The present invention relates to an energy storage apparatus. In particular, the present invention relates to an energy storage apparatus which can be used for high temperature applications such as generators, and a method of reversibly storing and / or extracting energy. However, it will be appreciated that the invention is not limited to these particular fields of use.Background of the Invention

[0003] The following discussion of the prior art is provided to place the invention in an appropriate technical context and enable the advantages of it to be more fully understood. It should be appreciated, however, that any discussion of the prior art throughout the specification should not be considered as an express or implied admission that such prior art is widely known or forms part of the common general knowledge in the field.

[0004] Global energy consumption continues to increase year on year to meet demand. While there are many sources of energy such as coal, natural gas, nuclear and oil, coal continues to be one of the major sources for electricity energy production. However, use of coal-fired power stations is highly polluting and releases harmful greenhouse gases. The development of renewable energy technologies has been of particular interest due to environmental concerns (such as reducing pollution and carbon dioxide emissions from coal and other fossil fuels). These renewal energy technologies include hydro, wind, solar, tidal and geothermal heat.

[0005] A particular issue of energy production from renewable energy sources is that they are intermittent sources. For example, wind turbines require strong winds, solar power cannot be generated at night, hydro power generation is reduced severely during drought, and wave power is limited according to weather and sea conditions. As such, renewable technologies ideally require a method of storing the energy for later use.

[0006] One such approach to storing energy is to use battery technology such as lithium- ion batteries so that when on-demand production of electricity from a renewable source is unavailable, the energy demand can readily be met. However, battery technology can still beexpensive for large-scale deployment and the energy capacity stored is limited and may not meet the energy demands when renewable energy production is delayed for long periods (such as when there are consecutive cloudy days for solar energy production, etc.).

[0007] As an alternative to battery technology, sensible heat storage mediums have been used to store thermal energy. For example, graphite energy storage mediums have been used to store electrical energy generated from sources such as renewables in the form of heat. A variant of the above approach is heating a body of graphite induced by eddy currents. The thermal energy stored in a block of graphite can then be recovered for later direct use and / or converted into electrical energy using a fluid such as water / steam.

[0008] The energy storage apparatus disclosed in PCT / AU2022 / 050031 describes a method of and an apparatus for reversibly storing and / or extracting heat energy in a body of graphite. The method comprises heating an inner region of a sensible heat storage body using a removable heating element to input the energy to be stored, and flowing a heat transfer medium having a temperature below that of said sensible heat storage body such that energy is transferred from the sensible heart storage body to the heat transfer medium to extract energy.

[0009] As another alternative to battery technology, latent heat storage mediums have also been used to store thermal energy. For example, molten-salt technologies have been used commercially to store the heat collected by concentrated solar power (e.g., from a heliostat). The heat can then be converted into superheated steam to power conventional steam turbines and generate electricity as needed. The efficacy of various salt mixtures such as calcium nitrate, potassium nitrate and sodium nitrate, has been demonstrated.

[0010] The energy storage apparatus disclosed in PCT / AU2020 / 051304 describes a method of and an apparatus for reversible storing and / or extracting heat energy in an energy storage apparatus comprising a crucible having a phase change material stored in a cavity of the crucible. The method comprises heating the phase change material or the crucible to induce a phase change to store energy, and flowing a heat transfer medium having a temperature below that of the phase change material such that energy is transferred from the phase change material to the heat transfer medium to extract energy.

[0011] When operating an energy storage apparatus, for example an apparatus that includes a sensible heat storage medium and / or a latent heat storage medium as described above, a “hot start” is highly desirable from commercial and efficiency perspectives. It allows an arrangement that multiple units of apparatus can dynamically be switched on and offdepending on the factors including availability of electrical energy, state of charge, consumer demand (for example consumer steam demands).

[0012] However, one issue with the operation of the energy storage apparatus is the thermal gradient that may form across a conduit (for example, a pipe or a tube) in which the heat transfer medium flows. This is especially the case when the apparatus has a “hot start”, during which a cold heat transfer medium flows in an inside surface of the conduit while an outside surface of the conduit is in contact with the hot energy storage medium, thereby creating a substantial thermal gradient and internal stresses (for example, radial and / or longitudinal stress) that limit the effective working life of the conduit and in some cases lead to apparatus failures. This is less of a problem when the heat transfer medium, for example water, substantially changes thermal conductivity, for example after evaporation / phase change. In that case the lower thermal conductivity allows the inside of the conduit to be hotter, reducing the stress in the conduit.

[0013] One option to reduce the internal thermal stress is to reduce the temperature of the heat storage medium. However, this is not commercially viable because reducing the temperature of the heat storage medium would reduce the overall efficiency of the apparatus.

[0014] Another option to reduce the internal thermal stress is to ensure that the heat transfer medium is only ever presented in a low thermal conductivity state, for example steam. However, this is also not commercially viable because a substantially extra external complexity would be involved to manage independent steam generation.

[0015] It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

[0016] Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”.

[0017] Although the invention will be described with reference to specific examples it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.Summary of the Invention

[0018] According to a first aspect of the present invention there is provided an energy storage apparatus comprising:a heat storage body comprising a thermal insulator defining a plurality of thermal zones within the heat storage body; a heat exchanger comprising a conduit adapted to receive a heat transfer medium therein for providing heat extraction from the heat storage body; wherein each thermal zone comprises at least one heating element.

[0019] The inventors of the present invention have surprisingly found that by defining a plurality of thermal zones within the heat storage body using the thermal insulator, the temperature of the heat storage body in different thermal zones may be controlled. This allows control of thermal gradient across the conduit, which avoids or minimises the internal thermal stress that affects the working life of the conduit and the energy storage apparatus. Advantageously, this enables the ability of the energy storage apparatus to stop its output (for example, steam output) while continuing to store energy and therefore provides the “hot start” capability that is commercially desirable. Furthermore, it advantageously allows the heat storage apparatus to operate with a heat storage body at a desirably high temperature and / or with high conductivity heat transfer mediums. Yet further still, it enables the flows of the heat transfer medium to start and / or stop independently of the heat storage body temperature.

[0020] In some embodiments, the energy storage apparatus is thermal energy storage apparatus.Thermal gradient

[0021] In some embodiments, the heating elements are independently controllable. In certain embodiments, a group of heating elements are independently controllable from another group of heating elements. In other embodiments, each heating element is independently controllable from another heating element.

[0022] In some embodiments, the temperature of the heat storage body in thermal zones is independently controllable. In certain embodiments, a group of thermal zones have a temperature of the heat storage body that is independently controllable from another group of thermal zones. In other embodiments, each thermal zone has a temperature of the heat storage body that is independently controllable from another thermal zone.

[0023] Advantageously, independently controllable heating element and / or heat storage body temperature provide flexibility and optimised control in energy storage apparatus operation, because thermal gradient inside the energy storage apparatus can be controlled to thereby minimise or avoid internal thermal stress of the heat exchanger conduit and increase process efficiency.

[0024] In some embodiments, at least one thermal zone comprises the heat exchanger, and wherein, in use, a temperature difference between an inner surface of the conduit and an outer surface of the conduit in each of the at least one thermal zone is less than a predetermined value of between about 50 °C and about 800 °C.

[0025] In some embodiments, at least one thermal zone comprises the heat exchanger, and wherein, in use, a temperature difference between the heat storage body and the heat transfer medium in each of the at least one thermal zone is less than a predetermined value of between about 50 °C and about 800 °C.

[0026] In some embodiments, the energy storage apparatus comprises a plurality of heat exchangers, wherein each thermal zone comprises at least one heat exchanger, and wherein, in use, a temperature difference between an inner surface of the conduit and an outer surface of the conduit in each thermal zone is less than a predetermined value of between about 50 °C and about 800 °C.

[0027] In some embodiments, the energy storage apparatus comprises a plurality of heat exchangers, wherein each thermal zone comprises at least one heat exchanger, and wherein, in use, a temperature difference between the heat storage body and the heat transfer medium in each thermal zone is less than a predetermined value of between about 50 °C and about 800 °C.

[0028] In some embodiments, the predetermined value is a temperature that avoids or minimises internal thermal stress of the conduit. The skilled person would understand that this temperature may depend on a number of factors including the materials and operating temperature of the conduit, heat transfer medium and heat storage body.

[0029] In some embodiments, the predetermined value is time-varying.

[0030] For example, the predetermined value may be between about 50 °C and about 100°, between about 100 °C and about 200 °C, between about 200 °C and about 300 °C, between about 300 °C and about 400 °C, between about 400 °C and about 500 °C, between about 500 °C and about 600 °C, between about 600 °C and about 700 °C, between about 700 °C and about 800 °C, about 50 °C, about 100 °C, about 150 °C, about 200 °C, about 250 °C, about 300 °C, about 350 °C, about 400 °C, about 450 °C, about 500 °C, about 550 °C, about 600 °C, about 650 °C, about 700 °C, about 750 °C, or about 800 °C.Thermal insulator

[0031] In some embodiments, the thermal insulator has a thermal conductivity lower than the thermal conductivity of the heat storage body. For example, the thermal insulator has athermal conductivity lower than about 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, 1%, 0.5%, 0.1 %, 0.05%, or 0.01 % of the thermal conductivity of the heat storage body. In some embodiments, the thermal insulator has a thermal conductivity lower than about 0.01% to about 1%, about 0.5% to about 5%, about 1% to about 10%, about 5% to about 20%, about 15% to about 35%, about 20% to about 45%, about 35% to about 50%, about 40% to about 60%, about 50% to about 70%, about 60% to about 80%, about 70% to about 90%, or about 75% to about 95% of the thermal conductivity of the heat storage body

[0032] In some embodiments, the thermal insulator has a thermal conductivity lower than about 50% of the thermal conductivity of the heat storage body.

[0033] In some embodiments, the thermal insulator has a thermal conductivity lower than about 10% of the thermal conductivity of the heat storage body.

[0034] In some embodiments, the thermal insulator has a thermal conductivity lower than about 0.1% of the thermal conductivity of the heat storage body.

[0035] In some embodiments, the material of the thermal insulator is selected from the group consisting of ceramic, fibreglass, silica-based wool, inorganic oxide, mineral wool, foams, polymers, vermiculite, perlite, cork, air, gas, aerogel and any combinations thereof.

[0036] In some embodiments, the thermal insulator has a thickness of about 0.1 cm to about 15 cm. For example, the thickness is between about 0.1cm to about 1cm, between about 1cm to about 2 cm, between about 2 cm to about 3 cm, between about 3 cm to about 4 cm, between about 4 cm to about 5 cm, between about 5 cm to about 6 cm, between about 6 cm to about 7 cm, between about 7 cm to about 8 cm, between about 8 cm to about 9 cm, between about 9 cm to about 10 cm, between about 10 cm to about 11 cm, between about 11 cm to about 12 cm, between about 12 cm to about 13 cm, between about 13 cm to about 14 cm, or between about 14 cm to about 15 cm.

[0037] In some embodiments, the thermal insulator has a density of about 0.05 g / cm3to about 50 g / cm3. For example, the density is between about 0.05 g / cm3to about 0.1 g / cm3, between about 0.1 g / cm3to about 1 g / cm3, between about 1 g / cm3to about 5 g / cm3, between about 5 g / cm3to about 10 g / cm3, between about 10 g / cm3to about 15 g / cm3, between about 15 g / cm3to about 20 g / cm3, between about 20 g / cm3to about 25 g / cm3, between about 25 g / cm3to about 30 g / cm3, between about 30 g / cm3to about 35 g / cm3, between about 35 g / cm3to about 40 g / cm3, between about 40 g / cm3to about 45 g / cm3, between about 45 g / cm3to about 50 g / cm3.

[0038] In some embodiments, the thermal insulator has a thermal conductivity of about 0.005 W / mK to about 20 W / mK. For example, the thermal conductivity is between about 0.005 W / mK to about 0.01 W / mK, between about 0.01 W / mK to about 0.05 W / mK, between about 0.05 W / mK to about 0.1 W / mK, between about 0.1 W / mK to about 0.5 W / mK, between about 0.5 W / mK to about 1 W / mK, between about 1 W / mK to about 5 W / mK, between about 5 W / mK to about 10 W / mK, between about 10 W / mK to about 15 W / mK, or between about 15 W / mK to about 20 W / mK.

[0039] In some embodiments, the thermal insulator comprises at least one aperture adapted to receive the heat exchanger. In other embodiments, the heating element and / or the heat exchanger are arranged to circumvent the thermal insulator.

[0040] The skilled person would understand that the energy storage apparatus may comprise any number of thermal insulators defining a plurality of thermal zones within the heat storage body. For example, the energy storage apparatus may comprise 1 , 2, 3, 4, 5, 6, 7, 8,9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 500, or 1000 thermal insulators.

[0041] The skilled person would also understand that thermal insulators may be arranged in any suitable orientations. The number of thermal zones is dependent on the arrangement of the thermal insulators. For example, the heat storage body may comprise 2, 3, 4, 5, 6, 7, 8, 9,10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 500, or 1000 thermal zones.Heat storage body

[0042] In some embodiments, the heat storage body comprises a heat exchanger channel having at least two open ends within the heat storage body.

[0043] In one embodiment, the heat transfer medium is a heat transfer fluid. A heat transfer fluid is a medium (such as a gas, liquid or supercritical gas) which allows passive transfer of energy, typically thermal energy, to another medium or for further conversion to mechanical energy. In this embodiment, the heat transfer fluid is used to extract or transfer heat from the heat storage body and can be used to convert the thermal energy to electrical energy using a generator. The heat transfer fluid can comprise any fluid adapted to transfer heat energy by both conduction and convection, including but not limited to, water, steam and supercritical carbon dioxide (SCO2). In a preferred embodiment, the heat transfer fluid is water.

[0044] In some embodiments, the heat storage body comprises a sensible heat storage body.

[0045] In some embodiments, at least one of the thermal zones comprises the sensible heat storage body.

[0046] In some embodiments, the sensible heat storage body comprises the heat exchanger channel having at least two open ends within the sensible heat storage body, and wherein at least a portion of the heat exchanger is disposed along the heat exchanger channel.

[0047] In some embodiments, the sensible heat storage body comprises a heating element channel adapted to receive the heating element, the heating element channel located internally of the sensible heat storage body.

[0048] In certain embodiments, a portion of the heating element is in contact with an inner region of the sensible heat storage body. Preferably, the heating portion of the heating element is in contact with the inner region of the sensible heat storage body. In these embodiments, the heating portion of the heating element is in thermal contact with the inner region of the sensible heat storage body but not electrical contact.

[0049] In certain embodiments, the heating element comprises an elongated heating portion at one end, a thermally insulated portion at an opposite end, and wherein the thermally insulated portion further comprises an electrical conductor adapted to be in electrical communication with an electrical terminal.

[0050] In certain embodiments, the heating portion of the heating element comprises a resistance wire selected from a material including but not limited to metallic alloys with high electrical resistivity and temperature resistance, surrounded by an electrical insulator and enclosed by a metal or alloy casing. In further embodiments, the heating element can be an electrical resistor. This is used to convert electrical energy to thermal energy to directly heat the sensible heat storage body, representing a direct conversion to and delivery of useful heat energy to the sensible heat storage body.

[0051] In a preferred embodiment, the sensible heat storage body is formed of graphite. In some embodiments, the graphite is crystalline, amorphous or a combination thereof. Graphite also has high thermal stability and electrical and thermal conductivity which makes it suitable for use as a refractory in high-temperature applications. In an embodiment of the invention, the graphite is used between ambient temperature up to 1000 °C and in preferred embodiments of the invention, the operational temperature is between about 120 to 800 °C.

[0052] In preferred embodiments, to provide steam from the energy storage apparatus, heat transfer medium (for example, water) flows through the conduit of the heat exchanger to be heated by the sensible heat storage body having a higher temperature, when disposed along the heat exchanger channels. Heat exchangers of the present invention can take many shapes and sizes depending on the requirements for flowrate of the heat transfer medium, the size, material and conductivity of the sensible heat storage body and the operational requirementsat operating pressures and temperatures. For example, the heat exchanger can be in the shape of a serpentine coil or a helical coil. Heat transfer occurs primarily by conduction from the sensible energy storage body to the heat transfer medium via the heat exchanger. The temperature of the steam at an outlet of the thermal energy storage apparatus depends on any number of factors, for example, relative temperature difference between the sensible storage energy body and the heat transfer medium, the heat transfer medium flow rate, and the heat transfer medium initial temperature.

[0053] Advantageously, the sensible heat storage body can provide higher operating temperatures such as from about 350 °C to about 1500 °C, about 400 °C to about 1000 °C, and even more preferably about 850 °C.

[0054] In some embodiments, the sensible heat storage body has a density between about 1 g / cm3and about 4 g / cm3, between about 1.5 g / cm3and about 3.5 g / cm3, between about 2.0 g / cm3and about 3.5 g / cm3, between about 2.5 g / cm3and about 3.5 g / cm3, preferably between about 1.5 to 2.0 g / cm3.

[0055] The person skilled in the art would appreciate that the sensible heat storage body can be, but is not necessarily required to be, constructed from a single piece of material (a unit body). While in some embodiments, the sensible heat storage body is a unit body, in others it is assembled by component parts.

[0056] Constructing the sensible heat storage body from component parts can provide ease of fabrication and assembly. Each component part of the sensible heat storage body can be fabricated to comprise the requisite heating element channel and / or heat exchanger channel to accommodate the heating element and / or heat exchanger. Advantageously, when the sensible heat storage body is assembled from component parts, costs can be reduced from not having to fabricate the channels from a unit body which adds complexity and can provide increased flexibility and repairability when replacing damaged or components of the energy storage apparatus.

[0057] In some embodiments, the heat storage body comprises a latent heat storage body.

[0058] In some embodiments, at least one of the thermal zones comprises the latent heat storage body.

[0059] In some embodiments, the latent heat storage body comprises a crucible having a cavity and a phase change material stored in the cavity of the crucible.

[0060] In some embodiments, the crucible comprises the heat exchanger channel having at least two open ends within the body of the crucible, and wherein at least a portion of the heat exchanger is encased within the heat exchanger channel.

[0061] In some embodiments, the crucible is adapted to receive the heating element, preferably by providing a heating element channel. In some embodiments, the crucible comprises a heating element disposed within the heating element channel.

[0062] In some embodiments, the crucible comprises one or more channels along an outer surface of the crucible body, and wherein a portion of the heat exchanger is disposed along at least one of the one or more channels.

[0063] In preferred embodiments, the phase change material is disposed between the heat exchanger and the heating element along at least one axis. In this embodiment, the phase change material advantageously provides a thermal barrier between the heating element and the heat exchanger to avoid overheating the heat exchanger and exceeding the heat exchanger materials temperature limit of operation. If a suitable phase change material having a melting temperature close to the maximum operating temperature of the heat exchanger material is chosen, the heat exchanger temperature rise rate can be slowed close to the maximum operating temperature limit making the heat exchanger temperature rise rate easier to control and can ensure that the maximum heat exchanger operating temperature is not exceeded.

[0064] In some embodiments, the phase change material is metallic. Advantageously, the use of a metallic phase change material can provide higher operating temperatures such as from about 350 °C to about 1500 °C, about 400 °C to about 1000 °C, and even more preferably about 850 °C.

[0065] In some embodiments, the crucible comprises an open cavity. Advantageously, the crucible having an open cavity allows for the phase change material to expand in volume when heated and contract in volume when cooled.

[0066] In some embodiments, the crucible comprises a sealed closed cavity. In this configuration, the phase change material is enclosed and sealed gas-tight within the cavity. In other embodiments, the crucible comprises a gas-permeable closed cavity. In this configuration, the cavity is closed but allowing for gas exchange with the external environment. This provides outgassing while allowing inert gas to enter the cavity of the crucible storing the phase change material.

[0067] It should be appreciated by the skilled person that the cavity or cavities can take any geometry or size depending on the amount of phase change material to be stored. The cavity may take any suitable shape and may be for example in the shape of a sphere, cube, cylinder, cone, cuboid, prism, tetrahedron or an irregular shape.

[0068] In some embodiments, the crucible is a unit body. That is, the crucible is a constructed from a single piece of material. In preferred embodiments, the crucible is assembled by component parts.

[0069] In a preferred embodiment, the crucible is formed of graphite. In some embodiments, the graphite is crystalline, amorphous or a combination thereof. Graphite also has high thermal stability and electrical and thermal conductivity which makes it suitable for use as a refractory in high-temperature applications. In preferred embodiments, the graphite is used between ambient temperature up to 1000 °C and in preferred embodiments, the operational temperature is between about 400 to 850 °C. Advantageously, the use of graphite as a crucible material is that it can be self-lubricating and also has dry lubricating properties. This provides improved compatibility with different materials of heat exchangers and can provide versatility due to modular construction.

[0070] In some embodiments, the crucible has a density between about 1 g / cm3and about 4 g / cm3, between about 1.5 g / cm3and about 3.5 g / cm3, between about 2.0 g / cm3and about 3.5 g / cm3, between about 2.5 g / cm3and about 3.5 g / cm3, preferably between about 1.5 to 2.0 g / cm3.

[0071] The phase change material of the present invention can be any suitable material which changes phase (i.e., solid, liquid, gas or plasma) when storing or extracting energy. Preferred phase change materials include any metal, such as aluminium, zinc, lead, tin, magnesium, or an alloy containing any one or more of these metals. Most preferably, the phase change material is aluminium, or an alloy comprising aluminium, or a salt hydrate thereof.

[0072] Advantageously, use of a phase change material provides greater amounts of energy to be stored and extracted making them suitable for efficient energy storage systems which can store energy for extended periods of time. Further, depending on the crucible material and phase change material used, an energy storage apparatus comprising a combination of crucible and phase change material can lower capital costs as less crucible material is required and phase change materials are typically cheaper than the crucible material.

[0073] In other embodiments, the sensible heat storage body may comprise a cavity for receiving a phase change material.

[0074] In some embodiments, the heat storage body comprise both a sensible heat storage body and a latent heat storage body.Heating element

[0075] In some embodiments, the heating element is selected from the group consisting of a heliostat, a furnace, an electrical resistor, a heat transfer fluid, and any combinations thereof.

[0076] In some embodiments, the heating element is removable.

[0077] The heating element used in the present invention can be any suitable power density. In certain embodiments, the power density per heating element is between about 5 W / in2to about 50 W / in2, between about 5 W / in2to about 40 W / in2, between about 5 W / in2to about 30 W / in2, between about 5 W / in2to about 30 W / in2, between about 10 W / in2to about 30 W / in2, between about 15 W / in2to about 30 W / in2. In preferred embodiments, the power density per heating element is between about 5 W / in2to about 15 W / in2.

[0078] The heating element used in the present invention can be any suitable power. In certain embodiments, the power per heating element is between about 1 to 50 kW, between about 5 to 50 kW, between about 5 to 40 kW, between about 5 to 30 kW, between about 5 to 20 kW, between about 10 to 20 kW, more preferably about 15.4 kW.

[0079] In some embodiments, the thermal zone may comprise a plurality of heating elements. For example, each thermal zone can comprise 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100 heating elements.Heat exchanger

[0080] Heat exchangers of the present invention can take many shapes and sizes depending on the requirements for flow rate of the heat transfer medium, the size, material and conductivity of the heat storage body and the operational requirements at operating pressures and temperatures.

[0081] In one embodiment, the heat exchanger is in the shape of a serpentine coil or a helical coil. Coiling structures of enclosed conduits comprise the heat exchanger in order to maximise the number of passes the heat exchanger makes while disposed along the heat exchanger channels. In preferred embodiments, the heat exchanger is in the shape of a serpentine coil. Advantageously, a serpentine coil heat exchanger provides a more uniform temperature profile across the heat storage body during energy / heat extraction because whenthe heat transfer fluid flows through the heat exchanger, the heat in the heat storage body transfers throughout the body. Each pass of the heat exchanger is typically adequately offset in order to maximise the bulk volume of the storage body material that the heat exchanger is in thermal communication with, in order to make the heat transfer as uniform as possible. In some embodiments, multiple parallel passes of the enclosed conduit disposed in a perpendicular direction relative to the overall direction of flow for the heat transfer medium. For example, the parallel passes are in fluid communication with each other by about 180 degree turns which over their length rise by a set distance to offset the otherwise overlapping passes. This rise of the serpentine coil allows the passes to be offset from each other and brings the heat exchanger into thermal communication with a larger bulk volume of the heat storage body.

[0082] In certain embodiments, each turn of the serpentine coil can be either in the same plane or in alternating planes. The former would result in the parallel passes of embedded heat exchanger to be arranged in along a single plane, while the latter can result in the parallel passes arranged in at least two planes, preferably at least two parallel planes, between which the embedded heat exchanger rises in alternating fashion similar to a stairwell. As a result of the rises, each sequential alternating parallel pass of the latter design are offset along two axes.

[0083] In one embodiment, the material of the heat exchanger is an alloy, titanium or a ceramic. In some embodiments, the material of the heat exchanger is a superalloy or high temperature ceramic such as a refractory ceramic. Preferably, the material of the heat exchanger is resistant to oxidation or degradation at operating temperatures. In one embodiment, the material of the heat exchanger is selected from the group consisting of borides, carbides, nitrides, oxides of transition metals and combinations thereof. In one embodiment, the oxides of transition metals are selected from the group consisting of hafnium diboride, zirconium diboride, hafnium nitride, zirconium nitride, titanium carbide, titanium nitride, thorium dioxide, tantalum carbide and combinations thereof.

[0084] In certain embodiments, the material of the heat exchanger is a superalloy selected from the group consisting of a nickel-based superalloy, cobalt-based superalloy, iron-based superalloy, chromium-based superalloy and combinations thereof.

[0085] In some embodiments, the heat exchanger is shell and tube type, a tube-in-tube type, or a plate type.Process Control

[0086] In preferred embodiments, the energy storage apparatus comprises at least one process control system. Examples of the system include, but are not limited to a process controlsystem that controls the temperature of each thermal zone through the heating element, based on the flowrate of heat transfer medium, temperature of the heat transfer medium, temperature of the heat storage body, measured by at least one temperature and flowrate transducer. Preferably, the process control system employs a feedback control algorithm. For example, the algorithm can be proportional integral derivative control or model predicative control.Steam

[0087] In preferred embodiments, the heat transfer medium is water, and the energy storage apparatus provides steam to a user. The steam provided by the energy storage apparatus has a temperature of from about 120 °C to about 700 °C. For example, the temperature is between about 120 °C and 150 °C, or about 150 °C and 200 °C, or about 200 °C and 250 °C, or about 250 °C and 300 °C, or about 300 °C and 350 °C, or about 350 °C and 400 °C, or about 400 °C and 450 °C, or about 450 °C and 500 °C, or about 500 °C and 550 °C, or about 550 °C and 600 °C, or about 600 °C and 650 °C, or about 650 °C and 700 °C.

[0088] In some embodiments, the steam provided by the energy storage apparatus has a pressure of from about 100 kPaG to about 4000 kPaG. For example, the pressure is between about 500 kPaG and about 1000 kPaG, or about 1000 kPaG and about 1500 kPaG, or about 1500 kPaG and about 2000 kPaG, or about 2000 kPaG and about 2500 kPaG, or about 2500 kPaG and about 3000 kPaG, or about 3000 kPaG and about 3500 kPaG, or about 3500 kPaG to 4000 kPaG.

[0089] In some embodiments, the steam provided by the thermal energy storage apparatus has a variable flowrate. In preferred embodiments, the flowrate is from about 50 kg / h to about 2000 kg / h. For example, the flowrate is between about 50 kg / h and about 100 kg / h, or about 100 kg / h and about 150 kg / h, or about 150 kg / h and about 200 kg / h, or about 200 kg / h and about 250 kg / h, or about 250 kg / h and about 300 kg / h, or about 300 kg / h and about 350 kg / h, or about 350 kg / h and about 400 kg / h, or about 400 kg / h and about 450 kg / h, or about 450 kg / h and about 500 kg / h, or about 500 kg / h and about 550 kg / h, or about 550 kg / h and about 600 kg / h, or about 600 kg / h and about 650 kg / h, or about 650 kg / h and about 700 kg / h, or about 700 kg / h and about 750 kg / h, or about 750 kg / h and about 800 kg / h, or about 800 kg / h and about 850 kg / h, or about 850 kg / h and about 900 kg / h, or about 900 kg / h and about 950 kg / h, or about 950 kg / h and about 1000 kg / h, or about 1000 kg / h and about 1200 kg / h, or about 1200 kg / h and about 1400 kg / h, or about 1400 kg / h and about 1600 kg / h, or about 1600 kg / h and about 1800 kg / h, or about 1800 kg / h and about 2000 kg / h.

[0090] According to a second aspect of the present invention there is provided an energy storge array comprising a plurality of energy storage apparatus according to the first aspect of the present invention.

[0091] In some embodiments, the plurality of energy storage apparatus is in thermal and / or electrical communication. In certain embodiments, the energy storage array further comprises a conduit disposed between an outlet of the heat exchanger of one energy storage array and an inlet of the heat exchanger of another energy storage array.

[0092] According to a third aspect of the present invention there is provided a method of reversibly storing and / or extracting energy, comprising the steps of providing an energy storage apparatus comprising a heat storage body comprising: a thermal insulator defining a plurality of thermal zones within the heat storage body; a heat exchanger comprising a conduit adapted to receive a heat transfer medium therein for providing heat extraction from the heat storage body; wherein each thermal zone comprises at least one heating element; heating the heat storage body using the heating element to thereby store energy; extracting energy by flowing a heat transfer medium having a temperature below that of the heat storage body through the conduit of the heat exchanger such that energy is transferred from the heat storage body to the heat transfer medium, thereby providing reversible energy storage and extraction.

[0093] According to a fourth aspect of the present invention there is provided a method of reversibly storing and / or extracting energy, comprising the steps of providing an energy storage apparatus according to the first aspect of the present invention; heating the heat storage body using the heating element to thereby store energy; extracting energy by flowing a heat transfer medium having a temperature below that of the heat storage body through the conduit of the heat exchanger such that energy is transferred from the heat storage body to the heat transfer medium, thereby providing reversible energy storage and extraction.

[0094] In some embodiments, the method comprises the steps of: heating an inner region of the sensible heat storage body using the heating element thereby storing energy, wherein a portion of the heating element is in contact with the inner region of the sensible heat storage body;extracting energy by flowing the heat transfer medium having a temperature below that of said sensible heat storage body through the conduit of the heat exchanger such that energy is transferred from the sensible heat storage body to heat transfer medium, thereby providing reversible energy storage and extraction.

[0095] In some embodiments, the method comprises steps of: heating the phase change material using the heating element to induce a phase change thereby storing energy; and extracting energy by flowing the heat transfer medium having a temperature below a temperature of the phase change material through the conduit of the heat exchanger such that the energy is transferred from the phase change material to the heat transfer medium, thereby providing reversible energy storage and extraction.

[0096] In some embodiments, the method comprises the steps of: heating the crucible comprising the phase change material using the heating element to induce a phase change thereby storing energy; and extracting energy by flowing the heat transfer medium along the crucible having a temperature below a temperature of the phase change material though the conduit of the heat exchanger such that the energy is transferred from the phase change material to the heat transfer medium, thereby providing reversible energy storage and extraction.

[0097] Other aspects of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention.Definitions

[0098] In describing and claiming the present invention, the following terminology will be used in accordance with the definitions set out below. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments of the invention only and is not intended to be limiting. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one having ordinary skill in the art to which the invention pertains.

[0099] Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”.

[0100] As used herein, the phrase “consisting of’ excludes any element, step, or ingredient not specified in the claim. When the phrase “consists of” (or variations thereof) appears in a clause of the body of a claim, rather than immediately following the preamble, it limits only the element set forth in that clause; other elements are not excluded from the claim as a whole. As used herein, the phrase “consisting essentially of” limits the scope of a claim to the specified elements or method steps, plus those that do not materially affect the basis and novel characteristic(s) of the claimed subject matter.

[0101] With respect to the terms “comprising”, “consisting of’, and “consisting essentially of”, where one of these three terms is used herein, the presently disclosed and claimed subject matter may include the use of either of the other two terms. Thus, in some embodiments not otherwise explicitly recited, any instance of “comprising” may be replaced by “consisting of” or, alternatively, by “consisting essentially of”.

[0102] Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients or reaction conditions used herein are to be understood as modified in all instances by the term “about”. The examples are not intended to limit the scope of the invention. In what follows, or where otherwise indicated, “%” will mean “weight %”, “ratio” will mean “weight ratio” and “parts” will mean “weight parts”.

[0103] The term ‘substantially’ as used herein shall mean comprising more than 50% by weight, where relevant, unless otherwise indicated.

[0104] The recitation of a numerical range using endpoints includes all numbers subsumed within that range (e.g., 1 to 5 includes 1 , 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

[0105] Further, unless expressly stated to the contrary, “or” refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

[0106] The terms “preferred” and “preferably” refer to embodiments of the invention that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one ormore preferred embodiments does not imply that other embodiments are not useful and is not intended to exclude other embodiments from the scope of the invention.

[0107] It must also be noted that, as used in the specification and the appended claims, the singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise.

[0108] As used herein, with reference to numbers in a range of numerals, the terms “about,” “approximately” and “substantially” are understood to refer to the range of -10% to +10% of the referenced number, preferably -5% to +5% of the referenced number, more preferably -1 % to +1 % of the referenced number, most preferably -0.1 % to +0.1 % of the referenced number. Moreover, with reference to numerical ranges, these terms should be construed as providing support for a claim directed to any number or subset of numbers in that range. For example, a disclosure of from 1 to 10 should be construed as supporting a range of from 1 to 8, from 3 to 7, from 1 to 9, from 3.6 to 4.6, from 3.5 to 9.9, from 8 to 10, and so forth.

[0109] The prior art referred to herein is fully incorporated herein by reference.

[0110] The term “internal stress” refers to a mechanical stress created by changes in temperature of a material. These stresses can lead to fracturing or plastic deformation depending on the other variables of heating, which include material types and constraints. When a material is rapidly heated or cooled, the surface and internal temperature will have a difference in temperature which causes thermal expansion or contraction respectively, this localised movement of material causes thermal stresses.

[0111] The term “predetermined” refers to a value that is determined or decided in advance. The value may be time-varying. For example, a predetermined value may be a series of values at different time points, or a trajectory of values.

[0112] The term “sensible heat storage body” refers to a heat storage body that includes heat storage mediums that do not experience a phase change when temperature of the storage body changes.

[0113] The term “latent heat storage body” refers to a heat storage body that includes heat storage mediums that experience phase changes when temperature of the storage body changes.

[0114] The term “hot start” refers to a scenario where an energy storage apparatus is initially started and has enough energy to provide steam or steam at required temperature. In some cases, the energy storage medium of the apparatus is hot enough to heat a cold fluid to provide steam or steam at required temperature.

[0115] Although exemplary embodiments of the disclosed technology are explained in detail herein, it is to be understood that other embodiments are contemplated. Accordingly, it is not intended that the disclosed technology be limited in its scope to the details of construction and arrangement of components set forth in the following description or illustrated in the drawings. The disclosed technology is capable of other embodiments and of being practiced or carried out in various ways.Brief Description of the Drawings

[0116] Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0117] Figure 1 shows a side perspective view of an embodiment of the energy storage apparatus of the present invention, the energy storage apparatus comprising a sensible heat storage body.

[0118] Figure 2 shows a side perspective view of an embodiment of the energy storage apparatus of the present invention, the energy storage apparatus comprising a latent heat storage body.

[0119] Figure 3 shows a cross-sectional view of a conduit in a heat exchanger in contact with a heat storage body.

[0120] Figure 4 shows a schematic diagram of an embodiment of the energy storage apparatus comprising three thermal insulators defining four thermal zones within the heat storage body.

[0121] Figure 5a shows a schematic diagram of an embodiment of the energy storage apparatus comprising one thermal insulator defining two thermal zones within the heat storage body.

[0122] Figure 5b shows the thermal insulator configuration from Figure 5a applied to the energy storage apparatus shown in Figure 2.

[0123] Figures 6a-c show schematic views of embodiments of the energy storage apparatus comprising different configurations of thermal insulators defining different number of thermals zones within the heat storage body.Detailed Description of the Invention

[0124] The skilled addressee will understand that the invention comprises the embodiments and features disclosed herein as well as all combinations and / or permutations of the disclosed embodiments and features.Example 1 - Energy storage apparatus comprising a sensible heat storage body

[0125] Referring to Figure 1 , there is shown a sensible heat storage body 102 for use as an energy storage apparatus 100. The sensible heat storage body 102 has a heating element channel 104 for receiving a removable heating element (not shown). The sensible heat storage body 102 also has a heat exchanger channel 108 for receiving the heat exchanger 110. The sensible heat storage body 102 is assembled by component parts and can be milled, machined or the like to provide the heating element channel 104 and heat exchanger channel 108 having at least two open ends within the sensible heat storage body. The sensible heat storage body 102 is in the form of a graphite panel comprised of component ‘slabs’ of graphite machined to snugly receive a heat exchanger 110 as well as a heating element 106.

[0126] The sensible heat storage body 102 comprises at least one thermal insulators (not shown) defining the body 102 into a plurality of thermal zones.

[0127] In use, the removable heating element heats the inner region of the sensible heat storage body 102 and the heat exchanger 110 is encased within the heat exchanger channel 108 of the sensible heat storage body 102 such that a heat transfer medium can flow from an inlet to an outlet of the heat exchanger 110 through the body 102.Example 2 - Energy storage apparatus comprising a latent heat storage body

[0128] Referring to Figure 2, the energy storage apparatus 200 comprises a latent heat storage body comprising a crucible 202, where the crucible is assembled by component parts preferably made of graphite having a cavity 208 to store the phase change material 210, a channel 204 to receive a heat exchanger (not shown) and a heating element channel 216 to receive a heating element (not shown). A series of heating element channels may be provided to receive a plurality of heating elements. The heating element is internal to the energy storage apparatus 200 and more particularly within the crucible 202. The heating element is in heating communication with the crucible 202 in order to heat the crucible 202 and phase change material 210. The heating element is in the form of electrical resistors which can be inserted into the heating element channel 216 and optionally the heating element can mechanically engage with the heating element channel to lock the heating element in the energy storage apparatus.

[0129] The phase change material 210 is located within the crucible 202 such that when the crucible 202 is heated by the internal heating elements, the thermal energy is transferred to the phase change material 210 to store energy. The heat exchanger is encased within the crucible 202 so that it can extract the thermal energy from the phase change material 210 when required. The heat exchanger can be a high pressure pipe network which facilitates storing and / or extraction of the thermal energy from the phase change material 210 and converting said thermal energy to electricity. The heat exchanger has an inlet and an outlet. The inlet of the heat exchanger is generally connected to a high pressure pump (not shown) and the outlet will generally be connected to a turbine (not shown). In this regard, the heat exchanger has an inlet where a heat transfer medium can be added if desired or required.

[0130] The latent heat storage body comprises at least one thermal insulators (not shown) defining the body into a plurality of thermal zones.Example 3 - Thermal gradient across a heat exchanger conduit

[0131] Referring to Figure 3, a conduit 302 in a heat exchanger receives a heat transfer medium 303, for example water. A heat storage body 301 transfers thermal energy to the heat transfer medium 303 flowing in the conduit 302.

[0132] Internal thermal stress across the conduit 304 develops when there is a thermal gradient or temperature difference between an inner surface 305 and an outer surface 304 of the conduit 302, particularly when the heat transfer medium 303 has substantially lower temperature than that of the heat storage body 301 and / or when the heat transfer medium 303 has high thermal conductivity.Example 4 - Energy storage apparatus comprising thermal insulators

[0133] Referring to Figure 4, an energy storage apparatus 400 comprises three thermal insulators 402, 403 and 404 defining the heat storage body into four thermal zones 406, 407, 408 and 409. Each thermal zone comprises at least one heating element (not shown). Heat transfer medium 401 , for example water, flows through a conduit of a heat exchanger (not shown) to receive thermal energy from the heat storage body. The water 401 enters the apparatus at 25 °C and exits the apparatus at 600 °C as steam 405.

[0134] The heating element and / or the temperature of heat storage body in each thermal zone are independently controllable. As such, the temperature profile of the energy storage apparatus can be controlled according to Table 1. In this example, the predetermined value is 100 °C. However, the skilled person would appreciate that the predetermined value may be different for different thermal zones, and that the predetermined value for the storage body - heat transfer medium temperature difference may be different from inner surface - outer surface of conduit temperature difference.

[0135] Table 1 : An example of a temperature profile of the energy storage apparatusExample 5 - Energy storage apparatus comprising different thermal insulator configurations

[0136] The skilled person would appreciate that different thermal insulator configurations may be used to suit different operation reguirements. For example, a relatively smaller thermal gradient across the conduit, that is, the temperature difference between an inner surface and an outer surface of the conduit, may be maintained in part of the energy storage apparatus where conduits susceptible to internal thermal stress are used.

[0137] Figure 5a shows an energy storage apparatus comprising one thermal insulator 501 defining two thermal zones 504 and 505, each thermal zone comprises a plurality of heating elements in heating element channels 503. The apparatus comprises heat exchangers 502 for extracting energy from heat storage body.

[0138] Figure 5b shows the thermal insulator configuration from Figure 5a applied to the energy storage apparatus shown in Figure 2. The energy storage apparatus comprising one thermal insulator 50T defining two thermal zones 504’ and 505’, each thermal zone comprises a plurality of heating elements in heating element channels 503’. The apparatus comprises heat exchangers 502’ for extracting energy from heat storage body.

[0139] Figures 6a-c show energy storage apparatus comprising different configurations of thermal insulators 601 defining different number of thermal zones.

[0140] Although the invention will be described with reference to specific examples it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

[0141] Other embodiments of the present invention as described herein are defined in the following paragraphs:An energy storage apparatus comprising: a heat storage body comprising a thermal insulator defining a plurality of thermal zones within the heat storage body; a heat exchanger comprising a conduit adapted to receive a heat transfer medium therein for providing heat extraction from the heat storage body; wherein each thermal zone comprises at least one heating element. The energy storage apparatus according to paragraph 1 , wherein the heating elements are independently controllable. The energy storage apparatus according to any one or more of the preceding paragraphs, wherein the temperature of the heat storage body in thermal zones is independently controllable. The energy storage apparatus according to any one or more of the preceding paragraphs, wherein at least one thermal zone comprises the heat exchanger, and wherein, in use, a temperature difference between an inner surface of the conduit and an outer surface of the conduit in each of the at least one thermal zone is less than a predetermined value of between about 50 °C and about 800 °C. The energy storage apparatus according to any one or more of the preceding paragraphs, wherein at least one thermal zone comprises the heat exchanger, and wherein, in use, a temperature difference between the heat storage body and the heat transfer medium in each of the at least one thermal zone is less than a predetermined value of between about 50 °C and about 800 °C. The energy storage apparatus according to any one or more of the preceding paragraphs,, comprising a plurality of heat exchangers, wherein each thermal zone comprises at least one heat exchanger, and wherein, in use, a temperature difference between an inner surface of the conduit and an outer surface of the conduit in each thermal zone is less than a predetermined value of between about 50 °C and about 800 °C. The energy storage apparatus according to any one or more of the preceding paragraphs, comprising a plurality of heat exchangers, wherein each thermal zone comprises at least one heat exchanger, and wherein, in use, a temperature difference between the heat storage body and the heat transfer medium in each thermal zone is less than a predetermined value of between about 50 °C and about 800 °C. The energy storage apparatus according to any one or more of the preceding paragraphs, wherein the predetermined value is time-varying.The energy storage apparatus according to any one or more of the preceding paragraphs, wherein the thermal insulator has a thermal conductivity lower than the thermal conductivity of the heat storage body. The energy storage apparatus according to any one or more of the preceding paragraphs, wherein the thermal insulator has a thermal conductivity lower than about 50% of the thermal conductivity of the heat storage body. The energy storage apparatus according to any one or more of the preceding paragraphs,, wherein the thermal insulator has a thermal conductivity lower than about 10% of the thermal conductivity of the heat storage body. The energy storage apparatus according to any one or more of the preceding paragraphs, wherein the thermal insulator has a thermal conductivity lower than about 0.1 % of the thermal conductivity of the heat storage body. The energy storage apparatus according to any one or more of the preceding paragraphs, wherein the material of the thermal insulator is selected from the group consisting of ceramic, fibreglass, silica-based wool, inorganic oxide, mineral wool, foams, polymers, vermiculite, perlite, cork, air, gas, aerogel and any combinations thereof. The energy storage apparatus according to any one or more of the preceding paragraphs, wherein the thermal insulator has a thickness of about 0.1 cm to about 15 cm. The energy storge apparatus according to any one or more of the preceding paragraphs, wherein the thermal insulator has a density of about 0.05 g / cm3to about 50 g / cm3. The energy storage apparatus according to any one or more of the preceding paragraphs, wherein the thermal insulator comprises at least one aperture adapted to receive the heat exchanger. The energy storage apparatus according to any one or more of the preceding paragraphs, wherein the heat storage body comprises a heat exchanger channel having at least two open ends within the heat storage body. The energy storage apparatus according to any one or more of the preceding paragraphs, wherein the heat storage body comprises a sensible heat storage body. The energy storage apparatus according to any one or more of the preceding paragraphs, wherein at least one of the thermal zones comprises the sensible heat storage body.The energy storage apparatus according to any one or more of the preceding paragraphs, wherein the sensible heat storage body comprises the heat exchanger channel having at least two open ends within the sensible heat storage body, and wherein at least a portion of the heat exchanger is disposed along the heat exchanger channel. The energy storage apparatus according to any one or more of the preceding paragraphs, wherein the sensible heat storage body comprises a heating element channel adapted to receive the heating element, the heating element channel located internally of the sensible heat storage body. The energy storage apparatus according to any one or more of the preceding paragraphs, wherein the heat storage body comprises a latent heat storage body. The energy storage apparatus according to any one or more of the preceding paragraphs, wherein at least one of the thermal zones comprises the latent heat storage body. The energy storage apparatus according to any one or more of the preceding paragraphs, wherein the latent heat storage body comprises a crucible having a cavity and a phase change material stored in the cavity of the crucible. The energy storage apparatus according to any one or more of the preceding paragraphs, wherein the crucible comprises the heat exchanger channel having at least two open ends within the body of the crucible, and wherein at least a portion of the heat exchanger is encased within the heat exchanger channel. The energy storage apparatus according to any one or more of the preceding paragraphs, wherein the crucible comprises one or more channels along an outer surface of the crucible body, and wherein a portion of the heat exchanger is disposed along at least one of the one or more channels. The energy storage apparatus according to any one or more of the preceding paragraphs, wherein the heating element is selected from the group consisting of a heliostat, a furnace, an electrical resistor, a heat transfer fluid, and any combinations thereof. The energy storage apparatus according to any one or more of the preceding paragraphs, wherein the heat exchanger is shell and tube type, a tube-in-tube type, or a plate type. An energy storge array comprising a plurality of energy storage apparatus according to any one or more of the preceding paragraphs.The energy storage array according to any one or more of the preceding paragraphs, wherein the plurality of energy storage apparatus is in thermal and / or electrical communication. A method of reversibly storing and / or extracting energy, comprising the steps of providing an energy storage apparatus comprising a heat storage body comprising: a thermal insulator defining a plurality of thermal zones within the heat storage body; a heat exchanger comprising a conduit adapted to receive a heat transfer medium therein for providing heat extraction from the heat storage body; wherein each thermal zone comprises at least one heating element; heating the heat storage body using the heating element to thereby store energy; extracting energy by flowing a heat transfer medium having a temperature below that of the heat storage body through the conduit of the heat exchanger such that energy is transferred from the heat storage body to the heat transfer medium, thereby providing reversible energy storage and extraction. The method according to paragraph 31 , wherein the heating elements are independently controllable. The method according to any one or more of the preceding paragraphs, wherein the temperature of the heat storage body in thermal zones is independently controllable. The method according to any one or more of the preceding paragraphs, wherein at least one thermal zone comprises the heat exchanger, and wherein a temperature difference between an inner surface of the conduit and an outer surface of the conduit in each of the at least one thermal zone is less than a predetermined value of between about 50 °C and about 800 °C. The method according to any one or more of the preceding paragraphs, wherein at least one thermal zone comprises the heat exchanger, and wherein a temperature difference between the heat storage body and the heat transfer medium in each of the at least one thermal zone is less than a predetermined value of between about 50 °C and about 800 °C. The method according to any one or more of the preceding paragraphs, comprising a plurality of heat exchangers, wherein each thermal zone comprises at least one heat exchanger, and wherein a temperature difference between an inner surface of the conduit and an outer surface of the conduit in each thermal zone is less than a predetermined value of between about 50 °C and about 800 °C.The method according to any one or more of the preceding paragraphs, comprising a plurality of heat exchangers, wherein each thermal zone comprises at least one heat exchanger, and wherein a temperature difference between the heat storage body and the heat transfer medium in each thermal zone is less than a predetermined value of between about 50 °C and about 800 °C. The method according to any one or more of the preceding paragraphs, wherein the predetermined value is time-varying. The method according to any one or more of the preceding paragraphs, wherein the thermal insulator has a thermal conductivity lower than the thermal conductivity of the heat storage body. The method according to any one or more of the preceding paragraphs, wherein the thermal insulator has a thermal conductivity lower than about 50% of the thermal conductivity of the heat storage body. The method according to any one or more of the preceding paragraphs, wherein the thermal insulator has a thermal conductivity lower than about 10% of the thermal conductivity of the heat storage body. The method according to any one or more of the preceding paragraphs, wherein the thermal insulator has a thermal conductivity lower than about 0.1% of the thermal conductivity of the heat storage body. The method according to any one or more of the preceding paragraphs, wherein the material of the thermal insulator is selected from the group consisting of ceramic, fibreglass, silica-based wool, inorganic oxide, mineral wool, foams, polymers, vermiculite, perlite, cork, air, gas, aerogel and any combinations thereof. The method according to any one or more of the preceding paragraphs, wherein the thermal insulator has a thickness of about 0.1 cm to about 15 cm. The method according to any one or more of the preceding paragraphs, wherein the thermal insulator has a density of about 0.05 g / cm3to about 50 g / cm3. The method according to any one or more of the preceding paragraphs, wherein the thermal insulator comprises at least one aperture adapted to receive the heat exchanger. The method according to any one or more of the preceding paragraphs, wherein the heat storage body comprises a heat exchanger channel having at least two open ends within the heat storage body. The method according to any one or more of the preceding paragraphs, wherein the heat storage body comprises a sensible heat storage body.The method according to any one or more of the preceding paragraphs, wherein at least one of the thermal zones comprises the sensible heat storage body. The method according to any one or more of the preceding paragraphs, wherein the sensible heat storage body comprises the heat exchanger channel having at least two open ends within the sensible heat storage body, and wherein at least a portion of the heat exchanger is disposed along the heat exchanger channel. The method according to any one or more of the preceding paragraphs, wherein the sensible heat storage body comprises a heating element channel adapted to receive the heating element, the heating element channel located internally of the sensible heat storage body. The method according to any one or more of the preceding paragraphs, comprising the steps of:- heating an inner region of the sensible heat storage body using the heating element thereby storing energy, wherein a portion of the heating element is in contact with the inner region of the sensible heat storage body;- extracting energy by flowing the heat transfer medium having a temperature below that of said sensible heat storage body through the conduit of the heat exchanger such that energy is transferred from the sensible heat storage body to heat transfer medium, thereby providing reversible energy storage and extraction. The method according to any one or more of the preceding paragraphs, wherein the heat storage body comprises a latent heat storage body. The method according to any one or more of the preceding paragraphs, wherein at least one of the thermal zones comprises the latent heat storage body. The method according to any one or more of the preceding paragraphs, wherein the latent heat storage body comprises a crucible having a cavity and a phase change material stored in the cavity of the crucible. The method according to any one or more of the preceding paragraphs, wherein the crucible comprises the heat exchanger channel having at least two open ends within the body of the crucible, and wherein at least a portion of the heat exchanger is encased within the heat exchanger channel. The method according to any one or more of the preceding paragraphs, wherein the crucible comprises one or more channels along an outer surface of the crucible body, and wherein a portion of the heat exchanger is disposed along at least one of the one or more channels.The method according to any one or more of the preceding paragraphs, comprising the steps of:- heating the phase change material using the heating element to induce a phase change thereby storing energy; and- extracting energy by flowing the heat transfer medium having a temperature below a temperature of the phase change material through the conduit of the heat exchanger such that the energy is transferred from the phase change material to the heat transfer medium, thereby providing reversible energy storage and extraction. The method according to any one or more of the preceding paragraphs, comprising the steps of:- heating the crucible comprising the phase change material using the heating element to induce a phase change thereby storing energy; and- extracting energy by flowing the heat transfer medium along the crucible having a temperature below a temperature of the phase change material though the conduit of the heat exchanger such that the energy is transferred from the phase change material to the heat transfer medium, thereby providing reversible energy storage and extraction. The method according to any one or more of the preceding paragraphs, wherein the heating element is selected from the group consisting of a heliostat, a furnace, an electrical resistor, a heat transfer fluid, and any combinations thereof. The method according to any one or more of the preceding paragraphs, wherein the heat exchanger is shell and tube type, a tube-in-tube type, or a plate type.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:-1. An energy storage apparatus comprising: a heat storage body comprising a thermal insulator defining a plurality of thermal zones within the heat storage body; a heat exchanger comprising a conduit adapted to receive a heat transfer medium therein for providing heat extraction from the heat storage body; wherein each thermal zone comprises at least one heating element.

2. The energy storage apparatus according to claim 1 , wherein the heating elements are independently controllable.

3. The energy storage apparatus according to claim 1 or claim 2, wherein the temperature of the heat storage body in thermal zones is independently controllable.

4. The energy storage apparatus according any one of claims 1 to 3, wherein at least one thermal zone comprises the heat exchanger, and wherein, in use, a temperature difference between an inner surface of the conduit and an outer surface of the conduit and / or a temperature difference between the heat storage body and the heat transfer medium in each of the at least one thermal zone is less than a predetermined value of between about 50 °C and about 800 °C.

5. The energy storage apparatus according to any one of claims 1 to 4, comprising a plurality of heat exchangers, wherein each thermal zone comprises at least one heat exchanger, and wherein, in use, a temperature difference between an inner surface of the conduit and an outer surface of the conduit and / or a temperature difference between the heat storage body and the heat transfer medium in each thermal zone is less than a predetermined value of between about 50 °C and about 800 °C.

6. The energy storage apparatus according to any one of claims 1 to 5, wherein the heat storage body comprises a heat exchanger channel having at least two open ends within the heat storage body.

7. The energy storage apparatus according to claim 6, wherein the heat storage body comprises a sensible heat storage body.

8. The energy storage apparatus according to claim 7, wherein the sensible heat storage body comprises the heat exchanger channel having at least two open ends within the sensible heat storage body, and wherein at least a portion of the heat exchanger is disposed along the heat exchanger channel.

9. The energy storage apparatus according to claim 7 or claim 8, wherein the sensible heat storage body comprises a heating element channel adapted to receive the heating element, the heating element channel located internally of the sensible heat storage body.

10. The energy storage apparatus according to any one of claims 6 to 9, wherein the heat storage body comprises a latent heat storage body.11 . The energy storage apparatus according to claim 10, wherein the latent heat storage body comprises a crucible having a cavity and a phase change material stored in the cavity of the crucible.

12. The energy storage apparatus according to claim 11 , wherein the crucible comprises the heat exchanger channel having at least two open ends within the body of the crucible, and wherein at least a portion of the heat exchanger is encased within the heat exchanger channel.

13. The energy storage apparatus according to claim 11 or claim 12, wherein the crucible comprises one or more channels along an outer surface of the crucible body, and wherein a portion of the heat exchanger is disposed along at least one of the one or more channels.

14. An energy storge array comprising a plurality of energy storage apparatus according to any one of claims 1 to 13.

15. A method of reversibly storing and / or extracting energy, comprising the steps of providing an energy storage apparatus comprising a heat storage body comprising:a thermal insulator defining a plurality of thermal zones within the heat storage body; a heat exchanger comprising a conduit adapted to receive a heat transfer medium therein for providing heat extraction from the heat storage body; wherein each thermal zone comprises at least one heating element; heating the heat storage body using the heating element to thereby store energy; extracting energy by flowing a heat transfer medium having a temperature below that of the heat storage body through the conduit of the heat exchanger such that energy is transferred from the heat storage body to the heat transfer medium, thereby providing reversible energy storage and extraction.

16. The method according to claim 15, wherein the heating elements are independently controllable.

17. The method according to claim 15 or claim 16, wherein the temperature of the heat storage body in thermal zones is independently controllable.

18. The method according to any one of claims 15 to 17, wherein at least one thermal zone comprises the heat exchanger, and wherein a temperature difference between an inner surface of the conduit and an outer surface of the conduit and / or a temperature difference between the heat storage body and the heat transfer medium in each of the at least one thermal zone is less than a predetermined value of between about 50 °C and about 800 °C.

19. The method according to any one of claims 15 to 18, comprising a plurality of heat exchangers, wherein each thermal zone comprises at least one heat exchanger, and wherein a temperature difference between an inner surface of the conduit and an outer surface of the conduit and / or a temperature difference between the heat storage body and the heat transfer medium in each thermal zone is less than a predetermined value of between about 50 °C and about 800 °C.

20. The method according to any one of claims 15 to 19, wherein the heat storage body comprises a heat exchanger channel having at least two open ends within the heat storage body.

21. The method according to claim 20, wherein the heat storage body comprises a sensible heat storage body.

22. The method according to claim 21 , wherein the sensible heat storage body comprises the heat exchanger channel having at least two open ends within the sensible heat storage body, and wherein at least a portion of the heat exchanger is disposed along the heat exchanger channel.

23. The method according to claim 21 or claim 22, wherein the sensible heat storage body comprises a heating element channel adapted to receive the heating element, the heating element channel located internally of the sensible heat storage body.

24. The method according to any one of claims 21 to 23, comprising the steps of:- heating an inner region of the sensible heat storage body using the heating element thereby storing energy, wherein a portion of the heating element is in contact with the inner region of the sensible heat storage body;- extracting energy by flowing the heat transfer medium having a temperature below that of said sensible heat storage body through the conduit of the heat exchanger such that energy is transferred from the sensible heat storage body to heat transfer medium, thereby providing reversible energy storage and extraction.

25. The method according to any one of claims 20 to 24, wherein the heat storage body comprises a latent heat storage body.

26. The method according to claim 25, wherein the latent heat storage body comprises a crucible having a cavity and a phase change material stored in the cavity of the crucible.

27. The method according to claim 26, wherein the crucible comprises the heat exchanger channel having at least two open ends within the body of the crucible, and wherein at least a portion of the heat exchanger is encased within the heat exchanger channel.

28. The method according to claim 26 or claim 27, wherein the crucible comprises one or more channels along an outer surface of the crucible body, and wherein a portion of the heat exchanger is disposed along at least one of the one or more channels.

29. The method according to any one of claims 26 to 28, comprising the steps of:- heating the phase change material using the heating element to induce a phase change thereby storing energy; and- extracting energy by flowing the heat transfer medium having a temperature below a temperature of the phase change material through the conduit of the heat exchanger such that the energy is transferred from the phase change material to the heat transfer medium, thereby providing reversible energy storage and extraction.

30. The method according to any one of claims 26 to 28, comprising the steps of:- heating the crucible comprising the phase change material using the heating element to induce a phase change thereby storing energy; and- extracting energy by flowing the heat transfer medium along the crucible having a temperature below a temperature of the phase change material though the conduit of the heat exchanger such that the energy is transferred from the phase change material to the heat transfer medium, thereby providing reversible energy storage and extraction.

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