US20200166290A1 - A storage device for thermal energy - Google Patents

A storage device for thermal energy Download PDF

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Publication number
US20200166290A1
US20200166290A1 US16/625,083 US201816625083A US2020166290A1 US 20200166290 A1 US20200166290 A1 US 20200166290A1 US 201816625083 A US201816625083 A US 201816625083A US 2020166290 A1 US2020166290 A1 US 2020166290A1
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thermo
thermal
axial
unit
storage
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US16/625,083
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Calogero Gattuso
Fabio Santoro
Gianluca Tumminelli
Gaetano Tuzzolino
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David Srl
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David Srl
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Assigned to DAVID S.R.L. reassignment DAVID S.R.L. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: GATTUSO, Calogero, SANTORO, FABIO, TUMMINELLI, Gianluca, TUZZOLINO, Gaetano
Publication of US20200166290A1 publication Critical patent/US20200166290A1/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D17/00—Regenerative heat-exchange apparatus in which a stationary intermediate heat-transfer medium or body is contacted successively by each heat-exchange medium, e.g. using granular particles
    • F28D17/04—Distributing arrangements for the heat-exchange media
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D20/00—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00
    • F28D20/0056—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00 using solid heat storage material
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D20/00—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00
    • F28D20/0034—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00 using liquid heat storage material
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D20/00—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00
    • F28D2020/0004—Particular heat storage apparatus
    • F28D2020/0021—Particular heat storage apparatus the heat storage material being enclosed in loose or stacked elements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D20/00—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00
    • F28D2020/0004—Particular heat storage apparatus
    • F28D2020/0026—Particular heat storage apparatus the heat storage material being enclosed in mobile containers for transporting thermal energy
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D20/00—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00
    • F28D2020/0065—Details, e.g. particular heat storage tanks, auxiliary members within tanks
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D20/00—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00
    • F28D2020/0065—Details, e.g. particular heat storage tanks, auxiliary members within tanks
    • F28D2020/0078—Heat exchanger arrangements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D20/00—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00
    • F28D2020/0065—Details, e.g. particular heat storage tanks, auxiliary members within tanks
    • F28D2020/0082—Multiple tanks arrangements, e.g. adjacent tanks, tank in tank
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/14—Thermal energy storage

Definitions

  • the present invention regards storage devices for thermal energy, in particular static storage devices for thermal energy.
  • the state of the art offers numerous examples of storage devices for thermal energy that use—as storage material—fluids such as water, diathermic oil or molten salts, and which typically include moving mechanical components for displacing and generally managing storage fluids, which can serve as energy thermovector fluids.
  • storage material fluids such as water, diathermic oil or molten salts
  • a storage device for thermal energy generally comprises a flow duct for an working fluid that is in thermal exchange relationship with a thermo-accumulator unit.
  • thermo-accumulator unit uses fluid storage materials, when the storage material releases the stored thermal energy, it is subjected to the thermal energy quality degradation phenomena alongside the increase of entropy due to the back mixing, which causes the average storage temperature to drop.
  • the result is the degradation of the remainder of the stored thermal energy and generally the quality of the heat transmitted to the working fluid, which is typically a fluid required by an appliance.
  • (static) storage devices for thermal energy in which the storage material is of the solid type include—for example—storage systems based on concrete for thermodynamic plants.
  • the storage material consists in a concrete block provided by casting, embedded in which are the service/process tubes, which pass through the entire block and regard one or more manifolds installed at the ends.
  • thermodynamic performance of the storage material in particular by a low thermal conductivity which leads to low thermal energy transfer speeds (long charge and discharge times) and a—though slow—degradation of the quality of the stored energy due to the thermal continuity between the various regions of the single, large mass of concrete.
  • thermo-vector unit it is not possible, for example, to force the charge times by subjecting a concrete block to high temperatures and/or high charge fluid flow rates, without irreversibly damaging the storage system or extending the discharge times given that—due to the low conductivity of the material—the thermal drop is almost exclusively located in the bulk of the storage material and the actual driving force for the transfer of heat towards the discharge fluid is extremely low (quickly reaching a pseudo-stationary “saturation” condition in a more or less extensive region of storage material surrounding the thermo-vector unit).
  • the object of the present invention is to overcome the aforementioned technical drawbacks.
  • the object of the present invention is to provide a storage device for thermal energy that provides for low maintenance, high energy efficiency both during the charge step and during the discharge step, controllable charge and discharge times, a high exchange power/system mass ratio, a constant flow rate for dispensing to the user at a constant temperature (or, equivalently, a constant thermal power) and that is suitable for series or parallel connections in an extremely flexible manner and generally constitute a modular thermal storage array while minimising the back mixing and entropy increase phenomena.
  • thermal storage device having the features forming the subject of one or more of the claims that follow, which form an integral part of the technical disclosure herein provided regarding the invention.
  • a storage device for thermal energy including:
  • FIG. 1 is a partly exploded perspective view of a storage device for thermal energy according to a first embodiment of the invention
  • FIGS. 2 and 3 each include a portion A and a portion B respectively illustrating an assembled perspective view and an exploded perspective view of a thermo-vector unit for a storage device for thermal energy according to the invention, where FIG. 2 and FIG. 3 illustrate two variants of the thermo-vector unit,
  • FIGS. 4 and 5 are two perspective views—in assembled condition—of storage devices for thermal energy using thermo-vector units respectively according to FIGS. 2 and 3 ,
  • FIG. 6 includes a portion A and a portion B which respectively represent a top and a bottom plan view of an array of storage devices for thermal energy according to the first embodiment of the invention
  • FIG. 7 is a schematic view illustrating the flow paths of the working fluid in the configurations of FIGS. 6A and 6B .
  • FIGS. 8 and 9 each include a portion A and a portion B and they illustrate two variants of a second embodiment of the invention, in which the portions A illustrate an assembled perspective view and the portions B illustrate the same view highlighting the concealed lines for a better intelligibility of the interior structure of the device,
  • FIG. 10 includes a portion A and a portion B which represent a top and bottom plan view of a possible solution of an array connection of devices of FIGS. 8 and 9 , while
  • FIG. 11 represents still a further solution of a possible array connection of devices of FIGS. 8 and 9 .
  • FIG. 12 includes a portion 12 . 1 , a portion 12 . 2 , and a portion 12 . 3 which illustrate operations for the charge, maintenance and discharge respectively of the storage devices according to the invention
  • FIG. 13 includes a portion 13 . 1 and a portion 13 . 2 which show a comparison between the discharge performance of an array of storage devices according to the invention and a fluid storage device of the known type,
  • FIG. 14 illustrates the perspective view of a further embodiment of a storage device for thermal energy according to the invention
  • FIG. 15A is a longitudinal section of the device of FIG. 14
  • FIG. 15B is a cross-section of the same device
  • FIG. 16 is a lateral view of an array of devices according to FIG. 14 .
  • FIG. 17 is a perspective view of an array of storage devices for thermal energy according to still a further embodiment of the invention.
  • FIGS. 17A, 17B are sectional views, respectively, according to lines XVII/A-XVII/A and XVII/B-XVII/B of FIG. 17 ,
  • FIG. 17C illustrates thermal profiles of the array of FIG. 17 during a transient charge of the system
  • FIGS. 18 and 19 respectively illustrate a modular unit and an array of devices according to FIG. 17 , where the modular unit of FIG. 19 can be used for providing the array of FIG. 18 , and
  • FIG. 20 is a support circuit for an electric analogy model of an array of storage devices according to the invention.
  • E wt Specific storable energy (E wt ), as the maximum energy that can be absorbed during charge or, equivalently, that can be transferred during discharge—considering the same operating temperature range—by the mass unit of the storage material from the/to the thermovector fluidthermo-vector fluid and thus available therefor to the user, which includes the energy absorbed/transferred should the thermal storage material be subjected to changes of state (melting/solidification or boiling/liquefaction), or
  • volumetric storable energy (E vol ), as the maximum energy that can be absorbed during charge or, equivalently, that can be transferred during discharge—considering the same operating temperature range—by the volume unit of the storage material from the/to the thermovector fluidthermo-vector fluid and thus available therefor to the user, which includes the energy absorbed/transferred should the thermal storage material be subjected to changes of state (melting/solidification or boiling/condensation).
  • T max Maximum operating temperature
  • a material with high T max value is preferred, so that it can store a better quality energy, given that it is available at a higher temperature, as compared to a material with low T max value, on condition that an energy source, a thermovector fluidthermo-vector fluid and a hydraulic piping system compatible with said high T max value, are available.
  • Thermal diffusivity as ratio between the thermal conductivity ( ⁇ ) of the storage material (if solid, or susceptible to exchange heat exclusively through conductive motions or the equivalent thermal conductivity (as defined herein, if liquid, or susceptible to exchange heat even through convective motions) and the product between specific heat (c p ) and density ( ⁇ ) thereof: this physical quantity is an inherent property of the storage material (function of the temperature thereof) in that it exclusively depends on the property thereof, and it is useful for describing the propagation of a thermal field in non-stationary conditions.
  • a material with high thermal diffusivity ⁇ allows a thermal flow to pass through it more easily if subjected to a temperature gradient and thus guarantees better transmission of the thermal wave as compared to material with low thermal diffusivity ⁇ .
  • ⁇ is a characteristic measurement of the equivalent average distance of thermal exchange between the thermo-vector unit and the thermo-accumulator unit (penetration distance of the thermal wave assessable experimentally);
  • ⁇ acc , ⁇ ace , c p , acc are respectively the thermal capacity, density and specific heat of the storage material (average values in the operating temperature range);
  • n tubi is the number of tubes of the thermo-vector unit;
  • S tubo is the exchange surface between the thermo-vector unit and the thermo-accumulator unit;
  • V acc is the volume of the thermo-accumulator unit.
  • the time constant can instead be expressed as:
  • the equivalent conductivity of the storage liquid is a conductivity increased by a factor equal to Nu, Nusselt number,
  • h is the coefficient of thermal exchange by natural convection
  • L is a characteristic distance of the system
  • ⁇ is the thermal conductivity.
  • the Nusselt number for a given system can be provided from the empirical correlations widely known and available in literature, applicable to systems of various and several geometries and provisions regarding ducts affected by the mass and thermal flows, and as a function of the flow regimes (natural or forced), regarding which reference shall be made to other sources.
  • the equivalent specific heat of the storage liquid can be defined as:
  • ⁇ is the phase change latent heat (melting/boiling, in the charge step, solidification/condensation, in the discharge step);
  • T cf is the temperature at which phase change occurs;
  • T rif is a reference temperature (comparable to the minimum temperature of the operating cycle, during charge step, or the maximum temperature of the operating cycle, during discharge step);
  • c p,acc is the specific heat of the storage material (average between the phase change temperature and the reference temperature).
  • the time constant is useful to establish the duration of the charge and discharge transients of the system: the charge/discharge transient can be deemed completed after a period of time equal to 5 ⁇ .
  • a system with high ⁇ spec values requires a lot of time to store/transfer the thermal energy unit during charge/discharge step and thus offers lower performance with respect to one with low ⁇ spec values, considering the same operating conditions of the operating cycle.
  • E ⁇ is the energy stored after a time ⁇ , equal to 63.2% of the maximum storable energy.
  • thermo-accumulator unit This parameter is useful for comparing storage systems characterised, besides by the materials, by the different geometries of the thermo-accumulator unit and thermo-vector unit alike, from the moment when the exchange surface between the two becomes a factor.
  • a system with high ⁇ ⁇ values requires larger exchange surfaces to transfer the thermal power unit in the charge/discharge step, considering the same achieved charge, or it is consequently more cumbersome and complex due to the high number of tubes required, considering the same amount of total stored energy, as compared to one with low ⁇ ⁇ values.
  • the reference number 1 in FIG. 1 generally indicates a storage device for thermal energy according to a first preferred embodiment of the invention.
  • the storage device 1 includes at least one thermo-vector unit 2 and a thermo-accumulator unit 4 .
  • thermo-vector unit and thermo-accumulator unit 4 are primarily for functional purposes.
  • the distinction in this embodiment the storage device 1 includes two thermo-vector units 2 and a thermo-accumulator unit 4 comprised therebetween.
  • the thermo-vector unit 2 includes a flow duct 6 for the through-flow of an working fluid which—in this embodiment—is provided as a coil duct with parallel loops, which extends into a thermally conductive matrix 8 .
  • the matrix 8 is made of high thermal conductivity material, for example copper, aluminium, and generally any material having a thermal conductivity exceeding 100 ⁇ 200 W ⁇ m ⁇ 1 ⁇ K ⁇ 1 , and which includes a first and a second circular-shaped plate 10 , 12 , each provided with parallel chordial plates 14 (i.e. extending along parallel chords of the geometric circumference of the plate) and with through holes 16 .
  • the shape and the arrangement of the grooves 14 copy the extension of the coil which defines the flow duct 6 so that when the plates 10 and 12 are closed in a pack-like fashion on opposite sides of the coil 6 , the grooves 14 define—when coupling—circular channels in which sections of the loops of the duct 6 are housed.
  • the holes 16 are arranged identically on both plates 10 , 12 so as to be aligned during coupling and so as to consequently direct the bolts or screws (in the latter case on one of two plates of the holes 16 —without prejudice to the fact that the alignment with the holes on the other plate—could be of the non-through type) to keep the assembly closed in a pack-like fashion.
  • the thermo-accumulator unit 4 includes a casing which provides for one or more concentric jackets 18 .
  • there are provided for three concentric jackets 18 one of which is outer and contains the other two.
  • the three jackets 18 identify an equal number of internal volumes 20 within which there is arranged a thermal storage material, which—according to the invention—is a solid material, or a liquid material, or a two-phase combination of the two (suspension of solids in a liquid) with high thermal conductivity ⁇ , preferably greater than 30 W ⁇ m ⁇ 1 ⁇ K ⁇ 1 , with high specific heat, preferably greater than 400 J/(kg ⁇ K), and with high thermal diffusivity ⁇ , preferably greater than 10 mm 2 /s.
  • a thermal storage material which—according to the invention—is a solid material, or a liquid material, or a two-phase combination of the two (suspension of solids in a liquid) with high thermal conductivity ⁇ , preferably greater than 30 W ⁇ m ⁇ 1 ⁇ K ⁇ 1 , with high specific heat, preferably greater than 400 J/(kg ⁇ K), and with high thermal diffusivity ⁇ , preferably greater than 10 mm 2 /s.
  • a preferred solution according to the invention is to use a solid pulverulent material as is, and more generally with grain size comprised between 0.1 ⁇ m and 150 ⁇ m, so that it can be sufficiently compactable, or a granular solid material, and more generally with grain size comprised between 1 mm and 20 mm, submerged in a second material of the fluid type, to form a two-phase thermal storage material, to adapt the performance parameters thereof to the optimal operating values identified for the purposes of applicability of the present invention.
  • the thermal conductivity values, thermal capacity and thermal diffusivity provided herein regarding the matrix 8 and the thermal storage material are valid for all embodiments described herein, same case applying to the grain size values of the thermal storage material.
  • a coherent solid material i.e. a compact and non-granular or otherwise fractionated structure can obviously be used.
  • Materials that can be used for thermal storage purposes for example include graphite, in monolithic form, fine or micronised pulverulent form, aluminium or its alloys, cast iron, or even composite materials or lastly mixtures of various materials, even containing materials known to be poorly conductive such as sand or basalt serving as a filler, whose performance generally falls within intervals that the inventors indicated to be instrumental towards achieving the technical effect of the present invention.
  • the intervals in question are defined in table 1 attached to this description.
  • the storage material in order to achieve the performance objectives on which the invention is based, the storage material must be selected so as to have both a high volumetric thermal capacity (product between specific heat cp and density ⁇ ), so as to store as much heat as possible without suddenly increasing its temperature—given that this would stop the charging process due to saturation—as well as high thermal conductivity.
  • thermal diffusivity ⁇ which binds the parameters in question, is the distinctive parameter towards achieving the performance objectives on which the invention is based.
  • the thermal diffusivity ⁇ should be greater than a first threshold value, but in the meantime it should avoid exceeding a second threshold value, greater than the first
  • thermal diffusivity intervals are defined:
  • thermo-accumulator unit Storage materials with thermal diffusivity values comprised between the extreme values indicated above allow—irrespective of the final geometry of the thermo-accumulator unit—meeting the performance goals in terms of charge dynamics, discharge dynamics and maintaining the fluid flow rate to the user at a desired temperature for a long time interval, and thus guarantee quick transfer of heat and, in conclusion, a high ratio between exchanged power and storage mass, a high ratio between stored energy and storage mass and a high ratio between storage mass and volume.
  • thermo-vector unit 2 may conveniently be provided with a quadrangular/square geometry ( FIG. 2 ) or circular geometry ( FIG. 3 ).
  • the units 2 with quadrangular geometry are respectively indicated by references 2 S in FIG. 2
  • those with circular geometry are indicated by references 2 C in FIG. 3 .
  • thermo-accumulator unit 4 preferably copies the geometry (sectional) of the thermo-vector units 2 , and in particular when the thermo-vector units 2 are provided quadrangular-shaped even the thermo-accumulator unit 4 is also provided quadrangular-shaped, while when the thermo-vector units 2 are provided circular-shaped even the thermo-accumulator unit 4 is also provided circular-shaped.
  • thermo-vector units of FIGS. 4 and 5 take the same designation adopted for the thermo-vector units 2 , i.e. they are indicated by references 4 S when provided as a prism with quadrangular base coupled to a quadrangular-shaped thermo-vector unit 2 S, and 4 C when provided as a cylinder coupled to a circular-shaped thermo-vector unit 2 S.
  • the jackets 18 take the shape of quadrangular-shaped tubular elements coaxially arranged in the outermost jacket.
  • thermo-vector units 2 S/ 2 C are arranged at opposite ends of a thermo-accumulator unit 4 S/ 4 C, so as to provide substantially two heads of the thermo-accumulator unit 4 S/ 4 C.
  • the lower thermo-vector unit 2 S, 2 C is probably intended to convey a thermovector fluidthermo-vector fluid at low temperature (or—as observable hereinafter—a cold/discharge fluid), while the upper thermo-vector unit 2 is intended to convey a thermovector fluidthermo-vector fluid at high temperature (hot/charge fluid).
  • the numerical references associated to areas or components of the system that manage the cold/discharge fluid are enriched by a symbol “*”, while the numerical references associated to areas or components of the system that manage a hot/charge fluid are enriched by a symbol “!”.
  • the serpentine flow ducts take references 6 ! and 6 *.
  • each coil 6 !/ 6 * can independently form an inlet and an outlet for an working fluid
  • the storage devices 1 are naturally and simply suitable to form an array of devices hydraulically connected to each other.
  • thermo-vector units 1 connected to each other in hydraulic series with a U-shaped arrangement, so that they are two arrays of six parallel devices 1 from a geometric point of view. Due to the arrangement of the thermo-vector units 2 on opposite sides of the thermo-accumulator units 4 , within the array of devices 1 there can be identified an upper array A 1 _T of thermo-vector units 2 , and a lower array A 1 _B of thermo-vector units 2 . Each array shares the general arrangement of the units 1 .
  • a bypass duct BPC! extends manifold like between the two arrays of six thermo-vector units 2 (and just like the six storage devices), and to this end it has three circuit nodes J 1 !, J 2 !, J 3 ! leading into which are branching ducts departing from the further hydraulic nodes located on opposite sides with respect to the channel BPC! and arranged hydraulically between pairs of devices 1 arranged adjacent and in series along the same array.
  • flow regulation valves preferably automated, for example by means of providing the moveable equipment with drive means or by means of pneumatic actuation
  • switchable between an open position and a closed position and—in some embodiments—capable of being split in opening.
  • a bypass duct BPC* extends manifold like between the two arrays of six thermo-vector units 2 (and just like the six storage devices) and to this end it has three circuit nodes J 1 *, J 2 *, J 3 * leading into which are branching ducts departing from the further hydraulic nodes located on opposite sides with respect to the channel BPC! and arranged hydraulically between pairs of devices 1 arranged adjacent and in series along the same array.
  • flow regulation valves preferably automated, for example by means of providing the moveable equipment with drive means or by means of pneumatic actuation
  • switchable between an open position and a closed position and—in some embodiments—capable of being split in opening.
  • the array A 1 _T includes three operating ports, in particular:
  • the array A 1 _B similarly includes three operating ports, in particular:
  • the flow path for the working fluid when all units 1 are active corresponds to the sum of the sections 6 ! For the hot fluid, and 6 * for the cold fluid.
  • FIG. 7 The global arrangement of the inlet and outlet ports of the working fluid is schematically illustrated in FIG. 7 .
  • the storage device 1 operates as follows. The description shall apply both considering the device 1 independently and considering the device 1 operating in an array.
  • the storage device 1 operates as a thermal cell which is charged and discharged by means of thermo-vector units 2 .
  • the element that is materially subject of energy charge and discharge is the thermo-accumulator unit 4 .
  • thermo-vector units 2 in which a high temperature working fluid (if arranged like in FIG. 6 is a thermo-vector unit of the array A 1 _T) flows, provides the charging of the thermo-accumulator unit 4 and the storage of thermal energy in the system due to the thermal exchange between the working fluid which flows in the thermo-vector unit and the storage material which occupies the thermo-accumulator unit 4 .
  • thermo-vector unit 2 When the working fluid flows in the flow duct 6 of the thermo-vector unit 2 , only the flow duct is configured to bear the pressure of the working fluid, while the matrix 8 is not required to perform any structural function, given that it has the sole function of conveying the thermal flow towards the thermal storage material in the thermo-accumulator unit 4 , whose material is at contact with the matrix 8 .
  • the jackets 18 of the thermo-vector unit 4 serve as heat conductor fins so as to maximise the transfer of energy from the matrix 8 to the thermal storage material.
  • thermo-accumulator unit When the thermo-accumulator unit is fully “charged”, i.e. upon reaching the maximum charge temperature possible as a function of the temperature of the working fluid (i.e. substantially the thermal balance between the working fluid and the temperature of the thermal storage material in the thermo-accumulator unit 4 ), the storage device 1 is maintained in the charged conditions due to the insulation that covers it externally (not illustrated in the figures for the sake of simplicity), thus preventing loss of thermal energy towards the external upon completing the charge process.
  • the thermo-accumulator unit When the thermo-accumulator unit is fully “charged”, i.e. upon reaching the maximum charge temperature possible as a function of the temperature of the working fluid (i.e. substantially the thermal balance between the working fluid and the temperature of the thermal storage material in the thermo-accumulator unit 4 ), the storage device 1 is maintained in the charged conditions due to the insulation that covers it externally (not illustrated in the figures for the sake of simplicity), thus preventing loss of thermal energy towards the external upon completing the charge process.
  • the charge may also be maintained by circulating a minimum flow rate of the high temperature working fluid to restore any energy losses.
  • thermo-vector unit 2 When using the thermal energy stored in the thermo-accumulator unit 4 , it is sufficient to introduce the low temperature working fluid into the thermo-vector unit 2 at the opposite end with respect to the unit 2 associated to the hot working fluid (it is a thermo-vector unit of the array A 1 _B if arranged according to FIG. 6 ).
  • thermo-vector unit 2 (port *OUT) has a higher temperature with respect to the inlet one (on the port *IN).
  • the device 1 is free of back-mixing phenomena which affect fluid thermal storage devices, and it is thus capable of maintaining—for a more extended time interval and without substantial internal loss—a desired flow rate of the working fluid (discharge) through the thermo-vector unit 2 at a desired temperature, thus allowing to meet the demands of several appliances and/or various applications that receive the fluid heated by the energy stored in the device 1 .
  • the unit 1 is totally insulated externally and thus thermally insulated from the surrounding environment and it is capable of charging and/or discharging even in several different and separate time sessions: if the device 1 is installed in series, for example, to a solar concentrator in which the working fluid is diathermic oil or heated vapour, then the charging step is suspended in the absence of solar radiation, with the simultaneous stop of circulation of the working fluid. The stored energy is maintained in the thermo-accumulator unit 4 until solar radiation is available again, thus allowing to resume charging. An efficient insulation can allow to limit the thermal dispersions and maintain the storage temperatures even for several days.
  • the high temperature working fluid (charge fluid) during the charge process flows in through the inlet !IN of the array A 1 _T and flows through a series of flow ducts 6 ! whose extension is defined by the opening and closing pattern of the flow regulation valves. Discharging part of the hot fluid rate into the duct BPC! whenever required also allows reducing the charge processes. In any case, except for the working fluid which is discharged through the bypass duct BPC!, the remaining amount of cooled high temperature working fluid flows out from the outlet port ! OUT.
  • the low temperature working fluid (discharge fluid) during the discharge process flows in through the inlet *IN of the array A 1 _B and flows through a series of flow ducts 6 * whose extension is defined by the opening and closing pattern of the flow regulation valves (generally separate and independent from that of the valves of the array A 1 _B).
  • Discharge of part of the hot fluid flow rate into the duct BPC* whenever required also allows reducing the discharge processes of the system, for example should there be a surplus flow rate with respect to the temporary needs of the user or for preventing the thermochemical degradation (irreversible) phenomena regarding the discharge thermovector fluidthermo-vector fluid upon exceeding the maximum temperature admissible by the thermovector fluidthermo-vector fluid (wall and bulk limit temperatures).
  • the remaining amount of cooled high temperature working fluid flows out from the outlet port *OUT.
  • valves on the hydraulic nodes of the system allow excluding one or more storage devices 1 so as to use, for example in the discharge step, only some of the consecutive devices 1 (arranged immediately adjacent and hydraulically in series) and strictly required to bring the discharge working fluid to the desired temperature without the risk of overheating, or exceeding the wall temperature thereof.
  • This solution also opens up to the possibility of using two different working fluids for the charge and discharge step, respectively.
  • high pressure water vapour produced, for example, in a solar concentrator
  • a diathermic oil in the discharge step, which—being affected by the limits in terms of maximum admissible bulk and wall temperatures—must bypass the subsequent devices 1 possibly still charged upon reaching a limit temperature.
  • bypass systems valve units on circuit nodes
  • a 1 _T and A 1 _B for the hot and cold fluids discharge and discharge lines, respectively
  • the bypass systems are totally independent so as to have an exceptional flexibility of use, with the possibility of simultaneous flow of the two fluids, even in different parts of the circuit, and thus perform the two charge and discharge steps simultaneously.
  • thermo-accumulator units 4 behaves, for thermal exchange purposes, like an insulated section of a heat exchanger separated—by means of thermal interruptions—from the adjacent sections, similarly to what is described in the patent application number 102016000009566 dated 29 Jan. 2016.
  • the thermal interruptions are arranged transverse to the flow direction of the working fluid, whether hot or cold.
  • thermo-accumulator units which are obviously provided between subsequent thermo-accumulator units connected in series, allow to physically segregate—in space—thermal storage material portions susceptible to generally have a temperature even very different from each other.
  • thermo-accumulator units 4 would create a heat flow in the storage material which would extend by conduction along the longitudinal direction of the system, i.e. along the flow direction of the thermovector fluidthermo-vector fluid. This would—in sufficiently long times—level and homogenise the temperature, thus causing a degradation of the stored heat, or a loss of “quality” of the heat, which would become less “valuable” and more scarcely usable (due to the increase of entropy by mixing).
  • FIG. 8 and FIG. 9 illustrate two further embodiments of a storage device for thermal energy according to the invention
  • the reference number 100 designates a second embodiment of the storage device for thermal energy according to the invention.
  • the device 100 includes a thermo-vector unit 102 and a thermo-accumulator unit 104 .
  • the thermo-vector unit 102 includes a first and a second flow duct 106 ! and 106 * for an working fluid respectively at high and low temperature which are both housed in a matrix 108 provided for closing—in a pack-like fashion—on the ducts 106 *, 106 ! of a first and a second plate 110 , 112 .
  • thermo-vector unit 102 is embedded in the thermo-accumulator unit 104 , in particular the entire thermo-vector unit 102 is surrounded by the solid thermal storage material of the thermo-vector unit 104 .
  • thermoinsulating casing IL which allows preventing substantial thermal dispersion towards the external, acting as a passive thermal charge preserver.
  • reference number 200 designates a storage unit for thermal energy according to a third embodiment of the invention.
  • thermo-accumulator unit forms the matrix of the thermo-vector unit.
  • the storage device for thermal energy 200 includes a thermo-vector unit 202 comprising a plurality of flow ducts 206 which are embedded in a matrix 204 forming the thermo-accumulator unit.
  • the matrix 204 includes a first and a second half-matrix 204 A, 204 B made of preferably solid thermal storage material with coherent (i.e. non-granular) structure, which is processed by providing grooves capable of accommodating the flow ducts 206 .
  • the whole of the above is enclosed by a thermal insulating casing IL similar to the casing IL of the device 100 .
  • the flow ducts 206 can be intended—according to an association that can vary as a function of the needs—for hot fluid and cold fluid.
  • thermo-accumulator unit in order to be able to guarantee the final user a constant discharge thermovector fluidthermo-vector fluid temperature (as long as it is lower or at most equal to the maximum operating temperature of the storage cycle), similarly to what is described in the patent application no 102016000009566 dated 29 Jan. 2016, it is preferable to provide thermal interruptions even in the thermo-accumulator unit, for canceling or at least limiting the heat flow along the main direction of flow of the thermovector fluid.
  • the need for this provision increases proportionally to the increase of conductivity of the storage material used, depending on the extension of the thermo-accumulator unit along the direction of flow of the thermovector fluid.
  • thermal storage material is of the liquid type, and even more if the liquid is undergoing phase change (boiling liquid).
  • the thermal level of even extensively vast regions of the storage array would become uniform, reducing over time, with respect to what would be witnessed in would occur if the regions that can be at a different temperature were to maintain such condition due to the spatial segregation provided using the aforementioned thermal interruptions.
  • thermo-accumulator unit i.e. in the storage material
  • thermal interruptions transverse to the flow direction of the working fluid is ranked, in terms of importance towards providing the technical objectives of the present invention, immediately after the thermal diffusivity interval indicated above.
  • thermo-accumulator unit 104 , 204 The provision of thermal interruptions is neither strictly necessary in a single thermo-accumulator unit 104 , 204 nor practical in case of the thermo-accumulator unit 4 which is even physically segregated with respect to the thermo-vector unit 2 , but it is in any case practically provided when connecting the various units 1 , 100 , 200 as an array, and—if provided in units 104 , 204 —it allows to boost the performance of the respective storage device as indicated above.
  • a storage device for thermal energy according to the invention having a storage material capable of meeting the thermal diffusivity requirements and which preferably also has thermal interruptions (required in case of thermal storage material of the fluid type) amplifies the results and advantages of the invention.
  • thermo-accumulator unit also meets requirements regarding the FOMs corresponding to ⁇ spec , and even more preferably to ⁇ ⁇ .
  • the storage devices for thermal energy 100 e 200 are suitable for connection as an array similarly to the storage devices for thermal energy 1 .
  • the top ( FIG. 10A ) and bottom ( FIG. 10B ) plan views are illustrated in FIG. 10 .
  • the arrays of devices 100 , 200 there may not be provided two heads within which high temperature and low temperature working fluids flow respectively (as the arrays A 1 _T and A 1 _B instead are), given that the devices 100 , 200 include a single thermo-vector unit.
  • the flow ducts thereof are partly intended for the circulation of high temperature (charge) working fluid, partly intended for the circulation of low temperature (discharge) working fluid.
  • the flow ducts are—for the sake of illustration simplicity—two, one ( 106 !, 206 ! intended for the circulation of high temperature working fluid ( FIG. 10A ), the other ( 106 *, 206 *) intended for the circulation of low temperature working fluid.
  • welve storage devices 100 , 200 in which there are provided two separate circuits (hot/cold) each providing a hydraulic series connection with a U-shaped arrangement so that—from a geometric point of view—they are two parallel arrays of devices 100 , 200 .
  • a bypass duct BPC! extends manifold-like between the two arrays of six storage devices and—to this end—it has three circuit nodes J 1 !, J 2 !, J 3 ! leading into which are branching ducts departing from the further hydraulic nodes located on opposite sides with respect to the channel BPC! and arranged hydraulically between pairs of devices 100 , 200 arranged adjacent and in series along the same array.
  • a bypass duct BPC* extends manifold-like between the two arrays of six storage devices and—to this end—it has three circuit nodes J 1 *, J 2 *, J 3 * leading into which are branching ducts departing from the further hydraulic nodes located on opposite sides with respect to the channel BPC* and arranged hydraulically between pairs of devices 100 , 200 arranged adjacent and in series along the same array.
  • the array of devices 100 , 200 includes three operating ports, in particular:
  • the array of devices 100 , 200 includes three operating ports, in particular:
  • the arrangement of the flow ducts intended for the circulation of the high and low temperature working fluids is substantially horizontal (coplanar).
  • the flow ducts and the bypass ducts BPC! and BPC* can for example be arranged on opposite sides of the array, with discharge ends opposite thereto.
  • the storage devices 100 , 200 operate substantially identically to the devices 1 , except for the fact that the charge and discharge fluids flow (separately or simultaneously), as a function of the needs.
  • the action on the valves which are arranged at the hydraulic nodes J 1 !, J 2 !, J 3 ! and the relative branching nodes allow to provide different flow paths and charge/discharge patterns of the array of storage devices for thermal energy 100 , 200 .
  • the extension and development of the flow path can be established based on criteria identical to those described above as concerns the array of devices 1 .
  • FIG. 12 illustrates—in portions 12 . 1 , 12 . 2 , 12 . 3 —three qualitative examples of thermal profiles of an array of devices 100 , 200 during the charge ( FIG. 12.1 ), maintenance ( FIG. 12.2 ), and discharge ( FIG. 12.3 ) operations.
  • Each of the diagram representations of FIG. 12 illustrates three isochrone curves A, B, C, associated to three subsequent general time instants (the representation shall be deemed purely for qualitative purposes).
  • the isochrone curves coexist in the diagrams essentially due to the fact that they underlie a time development parameter t, whose increase direction is indicated in figures (A ⁇ B ⁇ C).
  • Each of the curves illustrated in the shapes of the single modules 100 , 200 represents the quality trend of the temperature of the solid storage device with respect to the position in the module along the horizontal axis (the temperature shall be deemed as the average on the surface orthogonal to the horizontal axis).
  • the temperature shall be deemed as the average on the surface orthogonal to the horizontal axis.
  • the high temperature working fluid which impinges the array through the port !IN transfers thermal energy to the storage material of each of the thermo-accumulator units of the devices 100 , 200 (directly in the latter case, without the thermal flow passing through any further matrix), which increase the respective temperatures as a function of the amount of energy received.
  • T MAX maximum temperature of the operating cycle
  • the temperature of the system evolves more slowly, given that the working fluid has already lost an amount of energy in the interaction with the first device 100 , 200 of the array.
  • approximately 40% of the storage material in the thermo-accumulator unit 104 , 204 will have a reached the charge temperature T MAX .
  • the last device 100 , 200 on the working fluid path is substantially still in conditions of substantial discharge, given that by now the working fluid will have lost most of its thermal energy in the interaction with the storage devices previously encountered along the path.
  • thermovector fluid to the user at the temperature (maximum) required even under partial charge conditions of the entire storage volume, as long as there remains at least one module (or fraction thereof) of the array of modules at an average temperature greater than the one required by the user.
  • FIG. 12.3 illustrates the discharge step of the array of storage devices 100 , 200 .
  • the cold fluid flow that impinges the array through the port *IN reduces—in a relatively quick manner—the temperature of the storage material in the first device 100 , 200 with which the fluid interacts along the flow path.
  • the second device With which the working fluid interacts already at a higher temperature with respect to the system inflow temperature, transfers a lower amount of thermal energy remaining for a substantial part (more than 60% approximately) still at the charge temperature.
  • the phenomenon is further amplified in the last device 100 , 200 of the array, which remains charged in an almost integral manner, given that the fluid has already been heated at an even higher temperature (as a function of the user's demand).
  • FIGS. 13.1 and 13.2 once again illustrate the discharge steps of storage devices for thermal energy, but while FIG. 13.1 illustrates a array of devices according to the invention (the connection methods are those of FIG. 10 ), FIG. 13.2 illustrates three iso-temperature profiles A, B, C parametrised with respect to the time evolution with reference to a conventional oil or molten salts thermal storage device (IN and OUT are the working fluid inlet and outlet ports).
  • connection in series and/or parallel of the storage devices 1 , 100 , 200 according to the invention substantially provides a system of concentrated thermal exchanges due to the fact that the subsequent thermo-vector units are separated from each other by a thermal interruption corresponding to the inter-device section (between two subsequent devices). This strongly limits, if not entirely cancels, parasitic thermal exchanges in the axial direction (in particular between adjacent thermo-accumulator units), concentrating thermal exchanges in the direction transverse to the flow, maximising the efficiency thereof.
  • thermo-vector units 102 , 202 behaves, for thermal exchange purposes, like an insulated section of a heat exchanger separated by means of thermal interruptions from the adjacent sections, similarly to what is described in the patent application number 102016000009566 dated 29 Jan. 2016.
  • thermal interruptions which are obviously provided between a storage device for thermal energy 100 , 200 and the subsequent one allow to physically segregate—in the spaces—thermal storage material portions susceptible to generally have temperatures that could even be very different from each other.
  • thermo-accumulator units 4 would create a heat flow in the storage material which extends by conduction along the longitudinal direction of the system. This would, in sufficiently long times, level and homogenise the temperature, thus causing a degradation of the stored heat, or a loss of “quality” of the heat, which would become less “valuable” and more scarcely usable.
  • the constancy of the temperature and the flow rate dispensed to the user can be guaranteed for a period of duration that extends depending on how low the temperature is and/or the flow rate required by the user.
  • both specifications are provided by sending only one predetermined portion of the working fluid flow rate in the storage system. This will heat up to the maximum available temperature instant by instant (depending on the residual charge of the single modules that form the thermal cell), and it will be mixed with a predetermined thermo-vector fluid flow rate sent to the bypass conduits instead.
  • the bypass flow rate is progressively reduced while the flow rate sent to the module is increased progressively, so that the resulting cumulative flow rate sent to the user is always constant, same case applying to the temperature thereof.
  • the constant temperature and flow rate specifications of the user can be maintained only due to the thermal interruptions and for a very short period of time, i.e. as long as there is at least one storage element having a temperature equal to the maximum.
  • the thermal cell will be totally discharged (to meet the user's requests) when the bypass flow rate becomes null: at that instant, the temperature and flow rate of the fluid flowing out from the thermo-vector unit are exactly those required by the user and, if the flow rate is still maintained constant, the temperature to the appliance will inevitably drop below the specification.
  • the system thus conceived operates perfectly similarly to a common rechargeable electric cell, which is capable of dispensing a constant current and a constant voltage, until sufficiently charged.
  • the device 300 is still of the type wherein the segregation between the thermo-vector unit and the thermo-accumulator unit is only functional, the former being embedded in the latter, but it is characterised in that it has a charge side and a discharge side that are segregated and asymmetric.
  • the geometry of the charge side is different from that of the discharge side so as to allow the optimised management of two different types of fluids, for the charge and discharge respectively.
  • the storage device 300 includes a thermo-vector unit 302 embedded in a thermo-accumulator unit 304 .
  • the thermo-accumulator unit 304 is a matrix of solid thermal storage material (with coherent or compacted granular structure) within which there are housed a first tube bundle 306 ! configured for the circulation of the charge fluid (hot fluid, preferably water vapour), and a second tube bundle 306 * configured for the circulation of a discharge fluid (cold fluid, preferably diathermic oil).
  • the first tube bundle 306 ! includes an array of coplanar and adjacent tubes (six in this embodiment) hydraulically connected to an inlet manifold 308 (port !IN) and an outlet manifold 310 (port !OUT), both provided as a tubular body with an end connection for connecting to the vapour circulation hydraulic system.
  • the second tube bundle 306 * instead includes one or more tubes (two in this embodiment) which—at the inlet port *IN—is connected to a regulation valve V 300 (preferably automated, for example by providing the moveable equipment with drive means or by means of pneumatic actuation) with one inlet and two outlets, in which the inlet is configured to receive a flow rate of a cold fluid (diathermic oil); a first outlet functionally provides the port *IN, and a second outlet terminates in a bypass channel (cold) BP*.
  • V 300 preferably automated, for example by providing the moveable equipment with drive means or by means of pneumatic actuation
  • V 300 preferably automated, for example by providing the moveable equipment with drive means or by means of pneumatic actuation
  • a first outlet functionally provides the port *IN
  • a second outlet terminates in a bypass channel (cold) BP*.
  • bypass channel BP! is connected to the outlet *OUT of the tube bundle 306 * connecting the two flow paths at a single connection flange.
  • thermo-accumulator unit 304 is provided as a matrix made of solid material within which the tube bundles 306 ! and 306 * are embedded, and—furthermore—it is in turn enclosed in a jacket made of insulating material IL, by means of which there is provided the function of passive maintenance of the charge of the system (besides that of limiting thermal energy dispersion towards the external).
  • thermo-accumulator unit 304 when the storage material is of the coherent solid type, the matrix substituting the thermo-accumulator unit 304 is conveniently provided in three sections 304 A (upper), 304 B (intermediate), 304 C (lower), wherein the sections 304 A and C close the section 304 B in a pack-like fashion and define channels for inserting tube bundles 306 * and 306 ! at the respective interfaces with the section 304 B.
  • FIG. 14 and the section of FIG. 15A correspond to a modular unit of an array of storage devices for thermal energy 300 .
  • this due to the considerable flexibility of the storage device on which the invention is based, there are even possible two different options for providing an array of devices, in particular:
  • each modular unit is associated to a respective valve V 300 so as to provide for an independent control of the bypass.
  • the matrix of the unit 304 is inserted in a jacket made of insulating material IL preferably providing for an interspace at the opposite axial ends of the matrix.
  • Each interspace serves as a thermal interruption which—at the time of assembly of the devices 300 as an array—actually serves as a single thermal cell in which the complex of matrices 304 is equivalent to a single matrix with thermal interruptions provided for by the interspaces.
  • thermo-accumulator unit 304 In terms of features of the thermal storage material of the thermo-accumulator unit 304 and operation, all the observations outlined above shall apply.
  • FIGS. 17 to 19 still a further embodiment of a storage device for thermal energy according to the invention is indicated with reference number 400 .
  • the device 400 is once again of the type wherein the segregation between the thermo-vector unit and the thermo-accumulator unit is only functional, the former being embedded in the latter, and it is characterised in that it has a charge side and a discharge side that are segregated and symmetric.
  • the geometry of the charge side is identical to that of the discharge side, but the respective tube bundles are arranged on opposite sides of the device 400 .
  • the storage device 400 includes a thermo-vector unit 402 embedded in a thermo-accumulator unit 404 .
  • the thermo-vector unit 304 is a matrix of solid thermal storage material (with coherent or compacted granular structure) within which there are housed a first tube bundle 406 ! configured for the circulation of the charge fluid (hot fluid, preferably water vapour), and a second tube bundle 406 * configured for the circulation of a discharge fluid (cold fluid, preferably diathermic oil).
  • the first tube bundle 406 ! includes a pair of tubes that are parallel, coplanar and adjacent, and same case applying to the second tube bundle 406 *, whose two tubes are parallel to each other and parallel to the tubes of the bundle 406 !
  • thermo-accumulator unit 404 is provided as a matrix of solid material within which the tube bundles 406 ! and 406 * are embedded. Obviously, the entirety can be covered by a jacket made of thermal insulating material.
  • the figures do not illustrate a thermal insulating coating 400 , but rather a jacket IL which wraps an array 5400 of four devices 400 , by means of which there is provided the function of passive maintenance of the charge of the system besides that of limiting dispersion of thermal energy towards the external).
  • thermo-accumulator unit 404 when the storage material is of the coherent solid type, the matrix substituting the thermo-accumulator unit 404 is conveniently provided in three sections 404 A (upper), 404 B (intermediate), 404 C (lower), wherein the sections 404 A and C close the section 404 B in a pack-like fashion and define channels for inserting tube bundles 406 * and 406 ! at the respective interfaces with the section 404 B.
  • connection ducts When the devices 400 are connected as an array as observable in FIGS. 17A to 17C , the tube bundles 406 ! and 406 * are hydraulically connected by means of substantially U-shaped connection ducts.
  • the path of the charge and discharge circuits respectively coils along the extension of the array due to the conformation of the connection ducts.
  • the inlets and outlets of the hot and cold circuits are indicated with references !IN, !OUT and *IN, *OUT respectively (according to the established convention).
  • connection ducts actually provides thermal interruptions in the global thermo-accumulator unit of the array 5400 , even though this does not rule out the fact that the single thermo-accumulator units 404 can be provided including thermal interruptions in the matrix of each one of them.
  • FIG. 17C illustrates a temperature distribution in the array 5400 during a general charge transient instant.
  • FIG. 18 illustrates the complete array
  • FIG. 19 illustrates the modular unit of the array, indicated with reference M 400 and from which the description that follows starts.
  • the unit M 400 includes a single storage device for thermal energy 400 preferably enclosed in a jacket made of insulating material and mounted on a support frame F 400 .
  • the inlet and outlet ports of the cold and hot circuits are indicated with references !IN, !OUT and *IN, *OUT respectively (according to the established convention).
  • the following description is provided by designating the position of the inlets and outlets according to a counter-current operating flow pattern for the hot and cold flows. Obviously, the man skilled in the art can adapt the following description also to various arrangements of the ports, given that the arrangement of the connections follows consequently.
  • a first and a second shut-off valve V*and V! preferably automated, for example by providing the moveable equipment with drive means or by means of pneumatic actuation.
  • upstream is herein used without necessarily referring to the direction of flow of the fluid in the circuit, but by simply taking the core of the figure (i.e. the device 400 ) as the “downstream” position.
  • valves V* and V! When in open position, the valves V* and V! enable the flow rate to flow through from and towards the device 400 . When in closed position, they shut off the through-flow of the flow rate from and towards the device 400 .
  • valves V* and V! there are arranged a first and a second branching which are connected to the cold (BP*) and hot (BP!) bypass conduits, on which the respective bypass valves BPV* for the cold circuit and the bypass valves BPV! for the hot circuit are fitted (once again, preferably automated, for example by providing the moveable equipment with drive means or by means of pneumatic actuation).
  • the bypass valves BPV* and BPV! regulate the fluid through-flow along the respective bypass ducts, which terminate on the opposite end with a corresponding connection flange BPCON* (cold) and BPCON! (hot).
  • first and second branching connection BPR* (cold), BPR! (hot) which serve as a connection point for the flanges BPCON* (cold) and BPCON! (hot) of the modular unit M 400 adjacent in the series when assembling the array.
  • VCON* (cold) and VCON! (hot) preferably automated, for example by providing the moveable equipment with drive means or by means of pneumatic actuation—upstream of which there are in turn arranged connection ports *CON (cold) and !CON (hot), the latter designated for connection with the ports *IN and !OUT of the modular unit M 400 adjacent in the series when assembling the array.
  • shut-off valves VCON* (cold) and VCON! (hot) allow to completely exclude the unit M 400 from the series, including the corresponding bypass ducts BP* and BP! (this not being achievable by the valves V* and V!).
  • thermo-vector unit defined by the series of the single thermo-vector units of each device 400 is intervalled by thermal interruptions transverse to the flow direction of the hot/cold working fluid (parallel herein) identically to what has been described above regarding the devices 100 , 200 , 300 , 400 , with the same beneficial effects detailed previously.
  • ⁇ being the electrical resistivity
  • ⁇ the electrical conductivity
  • Lc a characteristic dimension of the conductor along a reference direction (for example a length of the conductor)
  • A the cross-section of the conductor
  • R term L c /( ⁇ A )
  • ⁇ is the thermal conductivity
  • Lc and A maintain the physical meaning of characteristic dimension of the conductor—thermal—along a reference direction, and cross-section.
  • thermal system schematised in FIG. 20 comprising two thermal storage devices 100 , 200 , 300 , 400 connected as an array (the geometric shape may not necessarily represent the actual shape: this is just a case of schematisation) and separated by a thermal interruption, an axial and a radial thermal resistance can particularly be identified.
  • the references in FIG. 20 respectively designate
  • L the characteristic dimension in the transverse/radial direction of the thermo-accumulator unit; purely by way of example, a diameter ( FIG. 20 ) or a radius for cylindrical or spherical geometries—or even prismatic geometries, or a side of the section in case of parallelepiped-shaped geometries)
  • thermo-accumulator unit L axial : length in the axial/longitudinal direction of the thermo-accumulator unit
  • L int length in the axial/longitudinal direction of the thermal interruption between two adjacent thermo-accumulator units.
  • the thermal resistance in the axial/longitudinal direction can be expressed according to the following correlations (which does not provide exact dependence, but should be deemed as a proportionality correlation or simply as an operative definition):
  • R t,axial N ⁇ [ L axial /( ⁇ mat ⁇ L 2 )]+( N ⁇ 1) ⁇ [ L int /( ⁇ int ⁇ L 2 )]
  • N is the number of thermal storage devices (deemed with a thermo-accumulator unit without internal thermal interruptions, hence N coincides with the number of thermo-accumulator units),
  • ⁇ mat is the thermal conductivity of the material of the thermo-accumulator unit
  • L is the characteristic dimension in the transverse/radial direction of the thermo-accumulator unit
  • ⁇ int is the thermal conductivity of the material forming the thermal interruption (e.g. air or insulating material).
  • the thermal resistance in the radial direction can instead be expressed as follows (once again the correlation does not provide exact dependence, but should be deemed as a proportionality correlation or simply as an operative definition):
  • S scambio is the exchange surface between flow ducts for the working fluid and the thermo-accumulator unit (as previously described), and it thus indicates the “through-flow section” of the heat in the radial direction.
  • the other symbols maintain the meaning adopted previously.
  • the N number of storage devices (thus of the thermo-vector units), and hence the N ⁇ 1 number of the thermal interruptions can be established, as a function of the characteristics of the storage devices 100 , 200 , 300 , 400 , supposing that the ratio between the thermal resistance in the radial direction R t,radial and the thermal resistance in the axial/longitudinal direction R t,axial as defined above is less than 20%, or more preferably less than 10%, or even more preferably less than 2%, with the aim of limiting thermal dispersions as much as possible by means of suitable spatial segregation of the stored heat.
  • N 1 storage devices (unitary array, no thermal interruption), there can be provided
  • L axial relatively “long” (L axial ) storage device 100 , 200 , 300 , 400 and/or with relatively “small” radial extension (L), thus with a high slenderness ratio L axial /L, and with a ratio between the thermal exchange surface and characteristic cross-section L 2 /S scambio as high as possible.
  • thermal interruptions has the purpose of reducing the thermal exchange in the longitudinal direction as much as possible, facilitating thermal exchange in radial direction.
  • this enables to guarantee a discharge process of the single storage device 100 , 200 , 300 , 400 and an array thereof maintaining a fluid flow rate dispensing to the appliance at a constant temperature for the entire discharge process.
  • thermo-accumulator unit extend scarcely in the axial/longitudinal direction, i.e. in the direction in which the charge fluid and discharge fluid flow—though with opposite directions (the arrays of devices 100 , 200 , 300 , 400 operate in a counter-current manner)—the choice of the thermal diffusivity alone is not sufficient to reduce the thermal exchange in the longitudinal/axial direction (actually, the reduced length in the direction is per se an incentive for uniforming the thermal exchange temperature, especially if with high thermal diffusivity material).
  • the thermal interruptions block such unwanted thermal exchange, hence—as clear from the description above—the number of thermal interruptions increase as the c value reduces, and as the slenderness ratio reduces.
  • the thermal interruptions enable to recover, even in a low slenderness ratio body, the distribution curves of the average temperature subject of FIG. 13.1 (which are naturally provided as a slender body). Such curves can be actually approximated by a series of horizontal linear sections which are as many as the storage units, each at its average operating temperature.
  • the thermal interruptions allow to create an anisotropy of the thermal diffusivity between the radial direction and the axial/longitudinal direction, allowing to provide the desired performance even when the geometry of a single storage unit of an equivalent mass would not allow it.
  • thermovector fluidthermo-vector fluids flow, which constitute a marginal fraction of the total volume of the storage system

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US10739083B1 (en) * 2018-08-22 2020-08-11 Walter B. Freeman System and method for storing thermal energy in a heated liquid in a pressurized vessel
US20200377279A1 (en) * 2019-06-03 2020-12-03 Sonoco Development, Inc. Heat Pipe Cooled Pallet Shipper
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