Device for storing thermal energy from solar sources based on multiple reflections

Abstract

A device (1) for storing and transferring solar-source thermal energy, the device comprising: a containing housing (2) having an illumination opening (10) for allowing incident solar radiation to enter an illumination area (350) defined within the housing (2); a fluidizable granular bed (3) received within the housing (2); and at least one reflecting and / or re-radiating surface (701, 702, 703) disposed within the illumination area (350) and configured to reflect solar radiation entering through the illumination opening (10) directly onto a free space (35) of the fluidizable granular bed (3) or onto another reflecting and / or re-radiating surface of the illumination area (350).

Description

Technical Field

[0001] The present invention relates to an apparatus, device and method for storing and transferring thermal energy from a solar source.

[0002] In particular, the present invention relates to the field of devices for storing thermal energy using a fluidizable bed of particles. Background Art

[0003] Devices for generating electrical energy from the thermal energy associated with concentrated solar radiation are well known. Some of these devices are based on so-called fluidized bed systems that receive solar radiation. These typically include a "beam down" optical system designed to concentrate the solar radiation from above onto a bed of fluidizable solid particles that acts as a thermal energy storage device. This energy can then be used for industrial purposes directly or after conversion into electricity, or even later.

[0004] The above-mentioned optical system associated with this type of equipment comprises one or more fields of heliostats arranged on the ground, transmitting solar radiation on a secondary mirror located at a higher altitude relative to the fluidized bed receiver and reflecting the concentrated radiation inside the receiver itself.

[0005] Some of the biggest issues with the aforementioned device configurations actually relate to the associated optical systems.

[0006] In particular, the secondary mirrors of the aforementioned prior art can operate at a limited maximum temperature (typically up to approximately 200°C). This maximum temperature imposes a significant constraint on the amount of sunlight that can be concentrated onto them, and requires a relatively large reflective surface to maintain a uniform flux. This reflective surface, along with the associated structures for its elevation and support at a high altitude, must be designed to withstand the forces of strong winds, significantly impacting equipment costs. Furthermore, in some locations with particularly strong winds, "beam-down" optical systems are unsuitable.

[0007] Another key point of the known device relates to the energy efficiency of the system for collecting solar radiation. In particular, the reflection efficiency of the secondary mirror can be estimated to be between 80% and 95%, depending on the materials used and the characteristics of the reflective surfaces used.

[0008] Furthermore, the secondary reflectors of prior art "beam-down" optical systems present other practical characteristics that negatively impact the ability to concentrate solar energy within the receiver. Specifically, the secondary reflectors are subject to potential assembly errors; less-than-ideal flatness of the reflective surface (which can locally deform due to thermal distortion); fouling (which requires complex maintenance procedures at greater altitudes); and deformation due to wind thrust and / or climate change. Summary of the Invention

[0009] The technical problem proposed and solved by the present invention is to provide a device, equipment and method for storing and transferring solar thermal energy to overcome the shortcomings of the above-mentioned prior art.

[0010] The present invention provides a device for storing and transferring solar thermal energy, comprising: a containing shell having an illumination opening, the illumination opening being configured to allow incident solar radiation to enter an illumination area defined within the shell; the illumination opening being arranged at a side skirt of the shell; a fluidized granular bed being received within the shell; and a plurality of reflective surfaces being arranged within the illumination area, wherein each of the reflective surfaces is configured to reflect solar radiation entering through the illumination opening directly onto the free space of the fluidized granular bed or onto another reflective surface of the illumination area; the overall configuration enables the incident radiation to be reflected downward multiple times on the reflective surface and illuminate the free space of the fluidized granular bed; wherein the particles of the fluidized granular bed have a higher absorptivity than the reflective surface.

[0011] Optionally, the device further includes heat exchange means, which is thermally connected to the fluidized bed of particles and can be activated to receive thermal energy therefrom, and the overall construction is such that the thermal energy is transferred from the incident solar radiation to the particles of the fluidized bed of particles and simultaneously or later from the particles to the heat exchange means; wherein the heat exchange means includes one or more of the following components: thermoelectric elements, thermionic elements, thermophotovoltaic elements and tube bundles, which are constructed to be passed through by a working fluid in use.

[0012] Optionally, the apparatus comprises means for supplying heated fluidising gas exiting the bed of fluidisable particles to a user.

[0013] Optionally, the illumination opening allows the illumination area of ​​the housing to communicate directly with the external environment without any sealing or shielding means during use.

[0014] Optionally, the illumination opening is arranged close to the upper wall of the housing.

[0015] Optionally, in the fluidized state, the free space of the fluidizable particle bed is also arranged below the lower edge of the irradiation opening.

[0016] Optionally, advantageously according to the radiation cavity configuration, the reflective surface is configured to re-radiate heat energy absorbed by solar radiation within the illumination area.

[0017] Optionally, the reflecting surface is realized on an inclined wall contained within said illumination zone, or it is associated with a wall defining said housing, advantageously having a mutual view factor tending to reduce the radiant energy emerging from the illumination opening.

[0018] Optionally, the reflective surface has one of the following schematic reflectivities: specular reflectivity, i.e., the radiation reflection angle is equal to the incident angle; diffuse reflectivity, i.e., reflection in all directions, independent of the radiation incidence plane; and glossy reflectivity, i.e., a mixed behavior between specular reflectivity and diffuse reflectivity.

[0019] Optionally, except for the illumination opening, the housing is made of a heat-insulating material.

[0020] Optionally, the housing is made of high temperature resistant material through a heat recovery and / or loss system.

[0021] Optionally, the apparatus comprises fluidising means configured for introducing a fluidising gas into the bed of fluidisable solid particles.

[0022] Optionally, the apparatus comprises means for selectively varying the flow rate and / or velocity of the fluidising gas.

[0023] Optionally, the device comprises suction means having a hood-like configuration, the suction means being configured to suck the fluidizing gas above the free space of the bed of fluidizable particles.

[0024] Optionally, the apparatus comprises a heat exchange member located between fluidising gas exiting the bed of fluidisable particles and fluidising gas flowing into the bed of fluidisable particles.

[0025] Optionally, the apparatus comprises heating means thermally connected to the fluidised bed of particles, the heating means being configured to transfer thermal energy to the particles.

[0026] Optionally, the apparatus comprises a support structure configured to support the housing at a height above the ground.

[0027] Optionally, the fluidizing gas comprises air.

[0028] The present invention provides an apparatus for generating electrical energy and / or thermal energy, comprising: one or more devices according to the above description, arranged at a relatively high altitude; and collecting means for collecting solar radiation, arranged on the ground and comprising a plurality of heliostats, the configuration being such that the solar radiation is collected by the collecting means and concentrated at an illumination opening of the one or more devices, wherein the collecting means or a subgroup thereof concentrates the solar radiation at a common focus arranged at or near the illumination opening of the devices; the collecting means defining a radiation configuration that causes the solar radiation to converge from the bottom onto the one or more devices.

[0029] The present invention provides a method for generating electrical energy and / or thermal energy from the thermal energy of solar radiation, comprising: - collecting solar radiation at an irradiation opening of a receiver device, the receiver device comprising a fluidized particle bed of a type for storing thermal energy; and - reflecting the solar radiation multiple times onto the fluidized particle bed by means of a plurality of reflecting surfaces arranged below the irradiation opening; the method uses a device according to the above description.

[0030] Optionally, the method comprises a stage of transferring thermal energy through the particles of the fluidizable bed of particles, said stage being selectively activatable simultaneously or later with the stage of storing thermal energy.

[0031] Optionally, the method comprises a stage of using heated fluidising gas exiting the bed of fluidisable particles.

[0032] Optionally, the method comprises a stage of fluidizing the particles of the bed of fluidizable particles, said stage being activated under selected operating conditions.

[0033] Optionally, selective regulation of the flow rate and / or velocity of the fluidizing gas is provided.

[0034] The present invention provides an apparatus, a device and a method based on a fluidizable granular bed which is exposed to solar radiation after being reflected on one or more inner wall portions or surfaces belonging to or contained in an enclosure comprising the fluidizable granular bed itself.

[0035] In particular, solar radiation is concentrated by a field of heliostats positioned on the ground and enters the receiver device through an opening, preferably formed in a side wall portion of the housing. The solar radiation entering through the opening impinges upon one or more inner wall portions, which are positioned in an idle area above the fluidized bed of particles, the idle area being the free space of the fluidized bed of particles. These inner wall portions include reflective and / or re-radiating surfaces configured to receive the incident concentrated solar radiation and reflect it back to the fluidized bed of particles, either directly or indirectly after multiple reflections on other inner surfaces.

[0036] The energy not reflected by the inner wall is partially absorbed by the inner wall. In a preferred embodiment, the wall itself is integrally formed to prevent the transfer of this absorbed energy to the external environment due to the use of materials or insulation. In this way, the reflective surfaces increase their own temperature and re-radiate heat energy to the fluidized bed of particles, either directly or indirectly through re-radiation between other inner surfaces.

[0037] In other words, the idle area or irradiated area defined by the upper surface or free space of the granular fluidized bed and the inner wall portion of the device placed above the surface of the granular fluidized bed behaves as a radiation cavity, wherein the surface reflects and re-radiates incoming solar radiation directly or indirectly towards the granular fluidized bed according to its specific properties.

[0038] Due to the high thermal diffusivity of the fluidized bed, the energy reflected (and possibly re-radiated) by the walls is transferred to the entire mass constituting the fluidized bed, which can then accommodate and store this energy until it is subsequently used.

[0039] In a preferred embodiment, the fluidized bed consists of solid particles which preferably have a higher absorptivity value than the above-mentioned reflecting walls, thereby facilitating a rapid transfer of energy reflected (and possibly re-radiated) by the walls to the fluidized bed itself.

[0040] In an embodiment variant, the fluidized bed can consist of granules made of sand or other granular material.

[0041] In a preferred configuration, the bed particles reach a maximum temperature, preferably greater than or equal to 620°C.

[0042] In a preferred embodiment, the reflective surface has a higher temperature resistance (preferably exceeding 1000°C) and / or a higher reflectivity than the particle fluidized bed (preferably greater than 60% if calculated according to ASTM G173 and ISO 7668).

[0043] The bed of particles is fluidized by a system for supplying and distributing a fluidizing gas, usually air.

[0044] The fluidization may concern a specific working area of ​​the fluidized bed or the entire fluidized bed of particles. Advantageously, the fluidization system may provide a plurality of fluidization units which are activatable independently of one another.

[0045] In a variant embodiment, the device can provide an additional heat supply to the fluidized bed of particles by means of heating elements, such as electrical resistors, heat pumps or dedicated heat exchangers, immersed in particular in the fluidized bed of particles itself. Such dedicated heat exchangers can circulate air or another working fluid in tube bundles or equivalent elements.

[0046] In an embodiment variant, additional heating means (for example electrical resistances) may be provided in order to provide thermal energy to the fluidized bed of particles by heating the fluidizing air entering the fluidized bed itself.

[0047] Advantageously, the heating means and / or the additional heating means may be powered directly or indirectly by an electrical power source which is preferably in excess (ie surplus) to user needs.

[0048] In those embodiments having heating elements, the sources of thermal energy accumulated in the fluidized bed of particles can be twofold: a primary energy source (i.e., solar radiation concentrated by the optical system and absorbed by the fluidized bed itself) and a secondary energy source (i.e., electrical energy converted into thermal energy by the above-mentioned heating elements).

[0049] These embodiments are particularly advantageous when it is necessary to ensure that more thermal energy is available to industrial processes that cannot be interrupted under any meteorological conditions.

[0050] It should be appreciated that the present invention eliminates the need for a "beam-down" optical system by overcoming the key issues discussed in conjunction with the prior art. In particular, the apparatus, device, and method of the present invention are particularly effective in ensuring higher collection efficiency, simplified equipment, and reduced costs.

[0051] The thermal energy accumulated in the fluidized bed of particles can then be converted simultaneously or later into electrical energy, used as thermal energy or even used in a flexible combination of these two forms.

[0052] The apparatus, devices and methods of the present invention can be used to generate electrical energy in a programmable manner for grid regulation and / or as thermal energy for other purposes.

[0053] The device of the present invention can be constructed into expandable modular units according to specific needs to continuously (24 / 365) generate electrical energy and / or thermal energy to serve communities and factories.

[0054] The thermal energy accumulated in the fluidized bed of particles can even be used directly by means of heated fluidizing gas exhausted from the fluidized bed itself.

[0055] Heat exchange means may be provided which are configured to recover and / or dissipate thermal energy from said reflecting and / or re-radiating surfaces in the event that temperatures are reached which would change state or impair their functionality.

[0056] The present invention represents an ecologically compatible, durable, efficient and inexpensive alternative to existing systems for producing thermal or electrical energy from solar sources.

[0057] Other advantages, features and modes of use of the invention will become apparent from the following detailed description of certain embodiments thereof, which are shown by way of illustration and not for the purpose of limitation. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] With reference to the accompanying drawings, in which:

[0059] Figure 1shows, in side view and partial longitudinal section, a schematic assembly of a device for storing and transferring thermal energy according to a first preferred embodiment of the invention, highlighting the interaction between the device itself and the system for collecting the solar radiation associated therewith;

[0060] Figure 2 Shown Figure 1 A top view of the same assembly drawing;

[0061] Figure 3 shows an enlarged view of a device for storing and transferring thermal energy according to a second preferred embodiment of the invention, in side view and partial longitudinal section, highlighting its "glossy" type reflection mode;

[0062] Figure 4 An enlarged view of a device for storing and transferring thermal energy according to a third preferred embodiment of the invention is shown in side view and partial longitudinal section, providing a "diffuse" type reflection mode.

[0063] The illustrations in the above-described figures are merely schematic, and components and distances are not necessarily shown to scale. DETAILED DESCRIPTION

[0064] Hereinafter, embodiments and modifications of the present invention will be described with reference to the above-mentioned drawings.

[0065] The same reference numbers are used throughout the several drawings to denote similar components.

[0066] In the detailed description that follows, only those aspects of the embodiments and variants which differ from what has already been described will be described in relation to the embodiments and variants already mentioned in the description itself.

[0067] Furthermore, where compatible, several embodiments and modifications described below may be used in combination.

[0068] See also Figure 1 , according to a first preferred embodiment of the present invention, a device or receiver for storing and exchanging thermal energy of a solar source is indicated as a whole by 1.

[0069] The device 1 according to the present embodiment is intended to be inserted into an installation for energy production, possibly comprising a plurality of devices such as the one envisaged here.

[0070] Likewise Figure 2As shown, the device 1 is advantageously associated with an optical system for collecting solar radiation (indicated as a whole by 500), which is configured to concentrate the incident solar radiation on the device 1 (or on a plurality of devices similar to the one envisaged here). In particular, the optical system 500 may comprise a plurality of heliostats 501 or equivalent optical reflection means, which are arranged on the ground and are suitable for collecting the incident solar radiation in order to direct / concentrate it on the device 1 and, in particular, in the present example, on a common focus F.

[0071] Heliostats 501 may be deployed in sub-fields, for example, arranged according to cardinal directions.

[0072] In the configuration shown, the device 1 is located above the plane of the heliostat 501 so as to receive the solar radiation concentrated thereby according to a "beam-up" configuration. The device 1 is therefore supported at a relatively high level by a structure (for example a metal structure) schematically shown and indicated by 800.

[0073] Now see Figure 3 , illustrating some components of the apparatus, which are common to the several embodiments described herein. The apparatus shown here (still designated 1) first includes a containment housing 2 having or defining an interior compartment 20 adapted to contain a bed 3 of fluidizable particles, as described below. Housing 2 can have a polygonal (e.g., a cube or parallelepiped) or cylindrical geometry. In this example, housing 2 has an upper wall portion 21 (or roof), sidewall portions (or side skirt portions 22), and a lower wall portion 23 (or base).

[0074] The housing 2 is realized so as to thermally insulate the compartment 20 from the outside.

[0075] The housing 2 may have a multi-layer structure.

[0076] The geometry of the device 1 (in particular the geometry of its housing 2 ) allows for defining a longitudinal direction L (vertical in this example) and a transverse direction T in a plane perpendicular to the longitudinal direction L (horizontal in this example).

[0077] Housing 2 has an illumination opening 10. In this embodiment, the aforementioned reflector focuses the incident solar radiation that actually enters this illumination opening 10, at or near it. Advantageously, as described above, the radiation is focused at a single focal point F. The relative positioning of receiver assembly 1 and field heliostats, such that focal point F corresponds to illumination opening 10, minimizes the size of the opening itself, thereby reducing both radiation losses and losses due to natural convection passing therethrough.

[0078] Generally speaking, the configuration is such that radiation is transmitted within the compartment 20 .

[0079] In this embodiment, the illumination opening 10 provides direct communication between the inner compartment 20, and thus the fluidized bed of particles 3 contained therein, and the external environment. In particular, during use, the illumination opening 10 lacks any closure or shielding means, such as a transparent window. In other words, the device 1 is configured to operate without any closure or shielding means. During periods of inactivity, the opening can be reclosed by removable and appropriately insulating means to protect the system and prevent or reduce the dissipation of thermal energy to the external environment.

[0080] Without interfering with the concentrated radiation entering the device itself, components (e.g., baffles or screens) may be placed near the illumination opening 10 to limit airflow or wind from the external environment from entering the device. Furthermore, additional optical equipment, such as a CPC (Compound Parabolic Concentrator) known in the art, may be provided around the illumination opening 10 to recover all or part of the concentrated solar radiation that would otherwise leak outside the illumination opening 10 itself.

[0081] It is also possible to provide an embodiment in which the illumination opening 10 can be shielded even during operation by a transparent window or other equivalent means.

[0082] In this example, the illumination opening 10 is shown as being provided at the side skirt 22 of the housing 2 , close to the upper wall 21 . However, this description is for illustrative purposes only. The opening is limited by a lower edge 230 .

[0083] Preferably, the free space 35 of the bed of fluidizable particles 3 is below the lower edge 230 both under static conditions and under fluidized conditions during operation.

[0084] Preferably, the irradiation opening 10 is provided in a free area or empty space of the compartment 20, which is defined on the lower side by the free space 35 of the fluidizable granular bed, on the sides by the upper parts of the side skirts 22, and on the top by the upper wall 21. This area may be defined as the irradiation area 350.

[0085] The fluidizable particle bed 3 is of granular type and is formed of solid particles.

[0086] The preferred type of granular material for the fluidizable granular bed of apparatus 1 is one that has the thermal properties of high heat capacity and high thermal diffusivity. An example of a preferred granular material is river sand, which, in addition to having the aforementioned thermal properties, has a naturally rounded shape of the particles, thereby minimizing the phenomenon of inter-particle abrasion.

[0087] Even when fluidized, the inner wall portions of the housing 2 located above the bed of fluidizable particles 3 are directly or indirectly affected by the solar radiation concentrated by the heliostats 501. These wall portions of the irradiated area 350 have reflective surfaces exposed within the compartment 20, which are made of materials and / or processes that can have different types of reflective properties, as described below.

[0088] - Specular reflection: A surface reflects light in one direction. The direction of the outgoing radiation is in the plane of incidence, and the angle of reflection is equal to the angle of incidence.

[0089] - Diffuse reflection: The surface reflects light evenly in all directions, the light reflection is independent of the direction and the plane of entry / incident.

[0090] - Glossy reflections: The surface has a mix of specular and diffuse reflection properties.

[0091] exist Figure 1 In a first embodiment, an inclined inner wall portion 701 is provided, which directly receives the concentrated solar radiation and has a reflective and / or re-radiating surface (also designated 701) operating in a specular reflection mode. This arrangement allows the incident solar radiation to be reflected almost entirely at the free space 35 of the fluidizable particle bed 3, depending on the reflective area corresponding to the cross section of the housing 2.

[0092] exist Figure 3 In the second embodiment, the wall portion, illustrated by the inclined baffles 702, has a "glossy" type optical behavior.

[0093] exist Figure 4 In the third embodiment of the invention, the "diffuse" behavior is provided by a reflecting and / or re-radiating surface 703 belonging to the curved wall 24 connected between the side skirt 22 and the upper wall 21 of the housing 2. Figure 4 In the configuration of , an additional inclined wall portion or baffle 25 is provided having an auxiliary reflecting and / or re-radiating surface opposite the surface.

[0094] Still see Figure 4 , shows a schematic diagram of a system 101 for closing the illumination opening 10, the system being in the form of a hinged shutter and in an open position associated with the concentrated radiation collection phase. The system 101 can be closed when energy collection is not required but rather conserved.

[0095] In other preferred configurations, the inner wall portion of the housing 2 (in particular, the portion of the side skirt 22 defining the irradiation area 350 and / or the upper wall portion 21 and / or the connecting portion still between the latter) also has one or more reflective surfaces, or only the inner wall portion of the housing 2 has one or more reflective surfaces.

[0096] The surface of the inner wall portion of the housing 2 may be flat or have a selected profile so as to minimize the total flux of radiation emerging from the illumination opening 10 and maximize the total flux into the fluidized bed, even due to mutual view factors.

[0097] Said reflecting and / or re-radiating surfaces consist of a material that can withstand the high temperatures caused by the high heat fluxes to which they are subjected, such as preferably ceramic tiles, refractory cement and / or similar materials.

[0098] In the above configuration, the electromagnetic energy emitted by the inner surface as a whole (the sum of the radiation emitted by the surfaces 701-703 through the mutual viewing coefficient and the radiation reflected) is absorbed by the fluidized bed of particles 3, which is advantageously chosen to have a higher absorption coefficient than all surfaces exposed to the concentrated solar radiation.

[0099] In particular, solar radiation reflected by the inner surfaces of the illumination area 350 impinges on the fluidizable granular bed 3 directly or after multiple downward reflections, depending on the mutual view coefficient. Furthermore, the inner surfaces absorb the unreflected energy portion, which causes the temperature of these surfaces to increase, depending on the mutual view coefficient. The inner surfaces then reradiate the solar energy to the fluidizable granular bed directly and indirectly via reradiation between the inner surfaces, depending on the mutual view coefficient.

[0100] When the radiation cavity is equipped with an opening toward the outside of which the dimensions are reduced relative to the average dimensions of the radiation cavity itself, this configuration results in a device behavior similar to that of a radiation cavity or a black body. Under these conditions, the concentrated solar radiation incident on the opening is almost entirely repeatedly reflected, absorbed, and re-radiated within the radiation cavity, so that only a minimal portion of it escapes, and the solar energy thus captured accumulates in the bed of fluidizable particles.

[0101] In the configuration of the aforementioned figures, the fluidized bed of particles 3 is moved by fluidizing means 4, which are configured to supply and distribute a fluidizing gas (particularly air) within the compartment 20. In this embodiment, the fluidizing means 4 comprises a plurality of elements for supplying or inputting fluidizing air 41, which are arranged at the lower wall 23 of the housing 2, which forms the base of the fluidized bed of particles 3. The fluidizing air is directed from bottom to top within the fluidized bed of particles 3, and is particularly vertical or substantially vertical. More generally, the fluidizing gas is supplied in a longitudinal direction L.

[0102] In the present example, a uniform or substantially uniform fluidization of the bed 3 of fluidizable particles is provided.

[0103] The fluid dynamics of the fluidized bed 3 of particles allow for efficient heat exchange between particles in different portions thereof. This is aided by the continuous exchange and recirculation to which the bed particles are subjected. In use, particles disposed on or near the free space 35 absorb heat energy from reflected or re-radiated solar radiation and transfer it to other bed particles.

[0104] The convection motion determined by the fluidization state is beneficial to the heat exchange between particles.

[0105] Embodiment variants may provide different fluidization in different regions or parts of the bed of fluidizable particles 3. The velocity (and where possible the rate) of the fluidizing air stream entering the bed of fluidizable particles 3 may be different for the fluidization (or the fluidization mode that may be selected therefor) of the various bed regions or parts.

[0106] The fluidizing elements may be arranged uniformly at the base of the bed 3 of fluidizable particles, such as in the present example, or may be positioned in a different manner.

[0107] It is also possible to provide fluidizing elements that are structurally similar to one another and which are possibly controlled differently, for example with respect to their speed and / or velocity.

[0108] The fluidization may even be of the boiling type and / or in a manner that generally favours convective movement of the particles in the bed 3 of fluidisable particles or in regions or parts thereof.

[0109] In some embodiment variants, the fluidization method selected for the entire bed of fluidizable particles or for regions or parts thereof can even be of the so-called "spout" type, for example, similar to jets, fountains or pulses. Spout-type fluidized beds generally have a fluid dynamics regime characterized by a central jet of fluidizing gas at the base of the same fluidized bed, which, due to the large velocity difference between the particles directly exposed to this jet and the surrounding particles, generates a practically fountain-like effect in the central part of the solid supply entrained by the sides of the jet, generating a motion entrained by the bed columns adhering to the jet itself and the (cylindrical) area above.

[0110] Heat exchange elements, in particular tube bundles, are housed in the fluidizable particle bed 3. Such exchangers can be traversed by a working fluid (for example steam or CO2) under continuous or selected operating conditions.

[0111] In particular, during the heat exchange phase (i.e., the phase utilizing the thermal energy accumulated in the fluidized particle bed 3), the working fluid can be caused to flow in the tube bundle 5 and receive heat from the bed particles. Conversely, during the storage phase, the tube bundle 5 can be inactive, i.e., the working fluid is not circulated.

[0112] The storage phase is activated in the presence of sunlight. Preferably, the heat exchange phase (ie the transfer of heat energy to the working fluid) can be activated even in the absence of sunlight.

[0113] The working fluid exiting the device 1 at the designed temperature and pressure conditions can be expanded in a turbine coupled to a generator to generate electrical energy, or it can be used for other industrial purposes (e.g., to produce a fluid carrier for use in industrial processes), particularly when thermal energy is continuously required at even very high temperatures. In other words, in this example, the tube bundle 5 is connected to additional components of the apparatus (e.g., one or more turbines, a condenser, a heat exchanger, a pump, etc.), each of which is known per se.

[0114] The device 1 further comprises suction means 6 for sucking in the fluidizing air which has completed its journey within the bed 3 of fluidizable particles and which emerges therefrom at the irradiation zone 350. Such suction means 6 are then configured to suck in the air above the free space 35 of the bed 3 of fluidizable particles within the housing 2. In the present example, the suction means 6 comprise elements 61, for example in the form of a hood, for collecting air from the free space, which are arranged on the upper wall 21 of the housing 2.

[0115] Preferably, the suction means 6 is even designed to prevent the fluidizing air and / or the particles entrained thereby from being discharged or discharged in large quantities into the external environment through the irradiation opening 10 .

[0116] Advantageously, the suction means 6 are provided with control means (preferably a rate sensor) (not shown) which, in cooperation with additional control means (not shown) associated with the fluidizing means 4, determine whether the air flow rate extracted from the device 1 is equal to or higher than the fluidizing air flow rate entering the fluidized particle bed 3.

[0117] Advantageously, the apparatus 1 provides for heat exchange between the (heated) fluidizing air exiting the fluidized bed 3 at the free space 35 thereof and drawn in by the suction means 6, and the fluidizing air entering the fluidized bed 3 via the fluidizing means 4. In other words, heat regeneration is achieved by the heat exchange means. This is schematically illustrated in the drawing by heat exchange means 512, means 513 for removing dust from the fluidizing air, means 514 for drawing fluidizing air from the external environment, and means 515 for introducing air into the fluidizing system of the fluidizing means 4.

[0118] In one embodiment variant, the device 1 has a quiescent chamber above the free space 35 of the bed of fluidizable particles 3. This quiescent chamber is a region of low or zero velocity of the bed particles and, in the example, is defined by the empty space.

[0119] Even a static chamber helps to avoid leakage or substantial leakage of air and / or particles through the illumination opening 10 .

[0120] An exemplary configuration of a plant similar to that contemplated above, including a 350 ton bed of particles, may be achieved with one or more of the following size parameters:

[0121] -Reflective surface is about 10000m 2 Field heliostats;

[0122] - Minimum focal length is 60m and maximum focal length is 200m, where focal length is defined as the distance between the center of the heliostat and the point where the parallel sunlight striking it focuses;

[0123] - Positioning the entrance of the device at a height of about 40 m relative to the field of heliostats on the ground;

[0124] The ratio of the dimensions of the total extension of the internal reflecting surface and the entrance surface of the device is approximately equal to 15 to 20.

[0125] The device of the invention is of a modular nature, that is to say that it is very suitable for connection to one or more similar devices connected in series or in parallel with the heat exchanger.

[0126] Furthermore, the device types according to the various forms and embodiment variants described can advantageously be combined for greater production and / or operating flexibility of industrial plants.

[0127] Furthermore, in a preferred configuration, an apparatus based on one or more devices of the present invention can advantageously be associated with a photovoltaic system for providing daily electrical energy production. In this configuration, these storage and transfer devices can be managed in such a way that they store solar thermal energy during periods of high sunlight and begin transferring thermal energy at dusk.

[0128] Furthermore, in the same configuration, this plant can be linked to a desalination plant or other system for exploiting solar thermal energy. In this case, by dedicating the associated thermal energy transfer to the plant's continuous operation (e.g., desalination), these devices can be managed in a hybrid manner to achieve storage, nighttime electricity production, and daily real-time transfer.

[0129] The device of the present invention can be integrated with equipment based on other renewable energy sources (e.g., photovoltaic, wind, and geothermal) or non-renewable energy to ensure the continuity of energy production, with the aim of reducing or eliminating the production of energy generated by non-renewable energy sources.

[0130] The present invention also provides a method for storing and exchanging thermal energy of solar origin based on the functions already described above in connection with the apparatus and device of the present invention.

[0131] So far, the objects of the present invention have been described in conjunction with the preferred embodiments of the present invention. This means that there may be other embodiments belonging to the same inventive core, all of which are within the scope of protection of the following claims.

Claims

1. A device for storing and transferring solar thermal energy (1), comprising: A housing (2) having an illumination opening (10) configured to allow incident solar radiation to enter an illumination area (350) defined within the housing (2); the illumination opening (10) being disposed at a side skirt (22) of the housing (2); a fluidizable bed of particles (3) received within the housing (2); as well as a plurality of reflective surfaces (701, 702, 703) disposed within the illumination area (350), wherein each of the reflective surfaces is configured to reflect solar radiation entering through the illumination opening (10) directly onto the free space (35) of the fluidizable particle bed (3) or onto another reflective surface in the illumination area (350); The overall configuration is such that the incident radiation impinges on the free space (35) of the fluidizable particle bed (3) by being reflected downward multiple times on the reflecting surfaces (701, 702, 703); The particles of the fluidizable particle bed (3) have a higher absorptivity than the reflective surface (701, 702, 703).

2. The device (1) according to claim 1 further comprises heat exchange means, which is thermally connected to the fluidized granular bed (3) and can be activated to receive thermal energy therefrom, and the overall construction is such that the thermal energy is transferred from the incident solar radiation to the particles of the fluidized granular bed (3) and simultaneously or later from the particles to the heat exchange means; wherein the heat exchange means comprises one or more of the following components: thermoelectric elements, thermionic elements, thermophotovoltaic elements and a tube bundle (5), which is constructed to be passed through by a working fluid in use.

3. Apparatus (1) according to claim 1 or 2, comprising means for supplying heated fluidising gas exiting the bed of fluidisable particles (3) to a user.

4. The device (1) according to claim 2, wherein the illumination opening (10) allows the illumination area (350) of the housing (2) to communicate directly with the external environment without sealing or shielding means in use.

5. The device (1) according to claim 2, wherein the illumination opening (10) is arranged close to an upper wall portion (21) of the housing.

6. The device (1) according to claim 2, wherein in the fluidized state the free space (35) of the fluidizable particle bed (3) is also arranged below the lower edge (230) of the illumination opening (10).

7. The device (1) according to claim 2, wherein the reflective surfaces (701, 702, 703) are configured to re-radiate heat energy absorbed by solar radiation within the illumination area (350), advantageously according to a radiation cavity configuration.

8. Device (1) according to claim 2, wherein the reflecting surface (701, 702, 703) is realized on an inclined wall contained in the illumination area (350), or it is associated with a wall defining the housing (2), advantageously having a mutual view factor that tends to reduce the radiant energy emerging from the illumination opening (10).

9. The device (1) according to claim 2, wherein the reflective surface (701, 702, 703) has one of the following exemplary reflectivities: specular reflectivity, i.e., the radiation reflection angle is equal to the angle of incidence; diffuse reflectivity, i.e., reflection in all directions, independent of the radiation incidence plane; and glossy reflectivity, i.e., a mixed behavior between specular reflectivity and diffuse reflectivity.

10. The device (1) according to claim 2, wherein the housing (2) is made of a heat-insulating material except for the illumination opening (10).

11. The device (1) according to claim 2, wherein the housing (2) is made of a high temperature resistant material through a heat recovery and / or loss system.

12. The device (1) according to claim 2, comprising fluidizing means (4) configured for introducing a fluidizing gas into the bed (3) of fluidizable particles.

13. Apparatus (1) according to claim 12, comprising means for selectively varying the flow rate and / or velocity of the fluidising gas.

14. The device (1) according to claim 2, comprising suction means (6) having a hood-like configuration (61), said suction means being configured to suck fluidizing gas above the free space (35) of the bed (3) of fluidizable particles.

15. The apparatus (1) according to claim 12, comprising a heat exchange member (512) located between the fluidizing gas exiting the bed (3) of fluidizable particles and the fluidizing gas flowing into the bed (3) of fluidizable particles.

16. Apparatus (1) according to claim 2, comprising heating means thermally connected to the bed of fluidizable particles (3), said heating means being configured to transfer thermal energy to the particles.

17. The apparatus (1) of claim 2, comprising a support structure (800) configured to support the housing (2) at a height above the ground.

18. The apparatus (1) according to claim 12, wherein the fluidizing gas comprises air.

19. An apparatus for generating electrical energy and / or thermal energy, comprising: One or more devices (1) according to any one of the preceding claims, arranged at a higher altitude; as well as Collection means for collecting solar radiation, arranged on the ground and comprising a plurality of heliostats (501), The configuration is such that the solar radiation is collected by the collecting means and concentrated at the illumination opening (10) of one or more devices (1), wherein the collecting means or a subgroup thereof concentrates the solar radiation at a common focus (F) disposed at or near the illumination opening (10) of the device (1); The collecting means define a radiation configuration that concentrates solar radiation from the bottom onto the one or more devices (1).

20. A method for generating electrical energy and / or thermal energy from thermal energy of solar radiation, comprising: - Concentrating solar radiation at an illumination opening (10) of a receiver device (1) comprising a bed (3) of fluidizable particles of the type used to store thermal energy; as well as - multiple reflection of solar radiation onto the bed of fluidizable particles by means of a plurality of reflective surfaces (701-703) arranged below the illumination opening (10); The method uses the device according to any one of claims 1-18.

21. The method according to claim 20, comprising: A phase of heat energy transfer by the particles of the fluidizable particle bed (3), which phase can be selectively activated simultaneously or later with the heat energy storage phase.

22. The method according to claim 20, comprising: A stage using heated fluidizing gas exiting the fluidizable particle bed (3).

23. The method according to claim 20, comprising: A stage for fluidizing the particles of the bed of fluidizable particles (3), said stage being activated under selected operating conditions.

24. A method according to claim 23, providing for selective adjustment of the flow rate and / or velocity of the fluidising gas.

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