IT201800021301A1 - FLUIDIZED BED DEVICE, SYSTEM AND RELATIVE METHOD FOR ENERGY ACCUMULATION - Google Patents

Description

FLUIDIZED BED DEVICE, PLANT AND RELATIVE METHOD FOR

ACCUMULATION OF ENERGY

DESCRIPTION

Technical field of the invention

The present invention refers to a device, a plant and a method for the production of energy, in particular electricity, based on the exploitation of thermal energy. In particular, the invention relates to the field of thermal energy storage devices that use a bed of fluidizable particles.

State of the art

Plants for the production of low-cost electricity from renewable sources, in particular of the photovoltaic and wind power type, are known.

One of the major problems of this type of systems is the impossibility of producing electricity continuously, as they are dependent, respectively, on the presence of sun and wind. Therefore - particularly in so-called "off-grid" applications, in which the energy produced is not immediately supplied to the distribution grid - electrochemical storage systems (batteries) are required, which, in fact, store the electrical energy produced and make it also available in the absence of solar radiation or wind. These electrochemical storage systems are the most critical element of the whole system, especially due to their short useful life, the high investment cost compared to performance, the need for disposal at the end of the year and the limited capacity to accumulate the quantity of electricity necessary to ensure continuity of supply in all environmental conditions.

Summary of the invention

The technical problem posed and solved by the present invention is therefore that of overcoming the aforementioned drawbacks with reference to the prior art, by providing a particularly effective thermal energy storage and transfer device, above all to ensure continuity of operation in the supply. of electrical or thermal energy to an end user.

The aforesaid technical problem is solved by a device according to claim 1 and a method according to claim 14.

Preferred features of the invention are the subject of the dependent claims.

The invention provides a device that allows an accumulation of thermal energy in a bed of fluidizable particles and a simultaneous or subsequent transfer and / or conversion of it into electrical energy, for flexible use according to the needs of the end user. Thermal energy is produced, due to the Joule effect, by electrical resistors or resistors immersed in, or lapped by, the bed of particles. The resistors, in turn, can be effectively powered by photovoltaic or wind systems, by the same production plant in which the storage device is inserted or by other sources.

The particle bed can be made of sand or other suitable material with high specific heat and is preferably fluidized by means of a system for the supply and distribution of a fluidization gas, typically air.

The fluidization can affect a specific operating region of the bed, for example a section directly in contact with the electrical resistances, or the entire bed of particles. Advantageously, the fluidization system can provide multiple fluidization units that can be activated independently of each other.

As mentioned, the resistors are preferably powered by photovoltaic and / or wind systems - inserted in the same system or in a remote location - or by any other source of electricity, for example from the same system that includes the storage device when this energy electricity is available in excess of the user's needs.

Advantageously, the electrical resistances are immersed in the bed of particles, for example connected to a base or to the side walls of an enclosure of the device, and preferably protected by suitable layers, or screens, of material resistant to high temperatures, for example ceramic or refractory media. .

In preferred configurations, the bed particles reach storage temperatures ≥ 600 ° C and more preferably in a range of about 700-1000 ° C.

The energy accumulated in the device can then be transformed, simultaneously or deferred, into electrical energy, used as thermal energy or even allow a combined and flexible use of these two forms. The final energy thus obtained can then be used for the programmable production of electricity, for example for the regulation of electrical networks, and / or as thermal energy, for example in desalinators or other users.

The storage device is therefore configured to transfer, as mentioned in a simultaneous or deferred way, the thermal energy to another component and / or plant for the production and supply of electricity and / or thermal energy. For this purpose, the storage device can include, or be associated with, one or more of the following heat exchange components:

- elements of the thermoelectric and / or thermoionic and / or thermo-photovoltaic type, or even of a different type, capable of converting the accumulated thermal energy into electrical energy;

- heat exchangers - housed within the storage device and immersed or lapped by the bed of particles - in which an operating fluid flows to feed a thermodynamic cycle for the production of electricity; - heat exchangers that operate, in general, to heat a fluid, typically steam, for the direct and efficient use of thermal energy for civil, agricultural or industrial uses.

Preferably, these heat exchange components - when immersed in the bed of particles or lapped by it - are protected by suitable layers, or screens, of material resistant to high temperatures, for example ceramic or refractory media.

Preferably, said heat exchange components can be selectively activated, for example by means of electrical switches and / or valves, independently of each other, so as to intervene or be deactivated according to the actual demand for electrical and / or thermal energy of the 'user.

According to preferred embodiments, two configurations of the accumulation device are provided, as illustrated below.

A first embodiment is based on a configuration, which we will call "closed", in which the bed of particles is housed within a casing that has no openings to the external environment. Therefore, in this configuration the thermal energy accumulated by the bed of particles is produced exclusively by the electrical resistances positioned in it.

In a second embodiment there is a configuration, which we will call "open", in which the device has a casing with an opening towards the external environment. Through this opening, the solar radiation concentrated by a special optical system is transferred to the bed of particles.

Such use of the thermal potential of solar energy, possibly concentrated by heliostats, for the production of electrical energy is known in the art. In particular, devices for the accumulation and transfer of said thermal energy based on a bed of fluidizable solid particles exposed, directly or indirectly, to solar radiation are disclosed, for example in WO2013 / 150347A1 and WO2017 / 021832A1 of the same Applicant.

In this second embodiment, therefore, the thermal energy accumulated in the fluid bed can come from two contributions: a primary energy contribution such as solar radiation concentrated by the optical system and absorbed by the fluid bed and a secondary energy contribution, such as '' electrical energy converted into thermal thanks to the electrical resistances positioned in the same fluidizable bed.

The proposed storage device, as mentioned, stores thermal energy, preferably from renewable sources, to flexibly produce electrical and / or thermal energy. It can constitute a module that can be multiplied as desired to produce 24/365 electrical and thermal energy for the service of communities and industrial plants and represents a "green" alternative, as well as durable and economical, to the current electrochemical storage systems, as well as to fossil fuel power generation systems.

Further advantages, characteristics and methods of use of the present invention will become evident from the following detailed description of some of its embodiments, presented by way of non-limiting example.

Brief description of the figures

Reference will be made to the figures of the attached drawings, in which:

- Figure 1 refers to a first preferred embodiment of a thermal energy storage and transfer device according to the invention, in a closed configuration and equipped with thermionic, thermoelectric and / or thermo-photovoltaic components for direct energy transformation thermal in electrical energy, showing a schematic representation in longitudinal section;

- Figure 2 refers to a preferred embodiment variant of the thermal energy storage and transfer device according to the invention, in which heat exchangers immersed in the bed of particles have been added to the configuration of Figure 1, showing a schematic representation in longitudinal section;

- Figure 3 refers to a second preferred embodiment of the thermal energy storage and transfer device according to the invention, in an open configuration and equipped with thermionic, thermoelectric and / or thermo-photovoltaic components for the direct transformation of the thermal energy in electrical energy, showing a schematic representation in longitudinal section; And

- Figure 4 refers to a further preferred embodiment variant of the thermal energy storage and transfer device according to the invention, in which heat exchangers immersed in the bed of particles have been added in the configuration of Figure 3, showing a schematic representation in longitudinal section.

The dimensions shown in the figures introduced above are intended as purely illustrative and are not necessarily represented in proportion.

Detailed description of preferred embodiments of the invention Following will be described embodiments and variants of the invention, and this with reference to the figures introduced above.

Similar components are denoted in the various figures with the same numerical reference.

In the following detailed description, further embodiments and variants with respect to embodiments and variants already dealt with in the same description will be illustrated limitedly to the differences with what has already been disclosed.

Furthermore, the different embodiments and variants described below are capable of being used in combination, where compatible.

With reference to Figure 1, a thermal energy storage and transfer device according to a first preferred embodiment of the invention is generally denoted with 1.

The device 1 first of all comprises a containment casing 2, which defines an internal compartment 20, the latter configured to host a bed 3 of fluidizable particles.

The envelope 2 can have polygonal geometry, for example cubic or parallelepiped, or cylindrical. In the present example, the casing 2 has an upper wall 21, a side skirt 23 and a lower wall or base 24.

With respect to the geometry of the device 1, we can define a longitudinal direction L, in the present example vertical, and a transversal direction T, orthogonal to the longitudinal direction L and in this example, therefore, horizontal. The device 1 is here configured in closed form, ie it has no openings towards the external environment and is preferably thermally insulated with respect to it. The fluidizable particle bed 3 is of the granular type, ie formed by solid particles.

The type of granular material preferred for the bed of particles of the device 1 has characteristics of high capacity, conductivity and thermal diffusivity.

The bed 3 occupies the internal compartment 20 so as to leave, even in use, a vacant space 22, or freeboard, above its own free surface 35. In particular, the space 22 is delimited below by the free surface 35, above from the wall 21 of the casing 2 and laterally from the casing 23 of the casing itself.

The bed of particles 3 is set in motion by means of fluidization means, generally denoted by 4 and configured to supply and distribute a fluidization gas, in particular air, through the same bed of particles 3. In the present embodiment, the means 4 they comprise a plurality of elements for the supply or inlet of fluidization air, arranged at the lower base 24 of the envelope 2 or of the bed of particles 3.

The path of the fluidization air within the bed of particles 3 is therefore from bottom to top, in particular vertical or substantially vertical. In more general terms, the introduction of the fluidization gas takes place in the longitudinal direction L. The fluidization gas coming from the bed of particles 3 collects within the free zone, or freeboard 22, and is captured by means of suitable suction hoods (not illustrated), placed on the upper wall 21.

Advantageously, means can be provided for selectively varying the speed and / or flow rate of the fluidizing gas.

Inside the bed of particles 3 are positioned, and preferably completely immersed in it, one or more electrical resistors 7. In the present embodiment, they are introduced, by way of example, from the base of the particle bed. in the longitudinal direction L.

Said electric resistances 7 are powered by means of production of electric energy, for example of the photovoltaic and / or wind power type, and are preferably protected by high temperature resistant screens (not shown), such as for example layers of ceramic material.

In the free area, or freeboard 22, and connected to the wall 21 of the envelope 2, one or more heat exchange components 8 are housed, thermally connected to the bed of particles 3 and activated by systems such as electrical switches (not shown). In the present example, the components 8 are advantageously of the thermoelectric, thermionic, thermo-photovoltaic type or a combination of these. Components 8 are configured for a direct transformation of thermal energy into electrical energy.

The components 8 can also be housed inside the bed of fluidized particles 3, thus being immersed in or lapped by the fluidized particles.

The components 8 are also preferably protected by shields resistant to high temperatures and abrasion (not shown), such as layers of ceramic material.

Figure 2 refers to a variant of the device according to the invention, denoted here with 1 '. The device 1 'differs from that of the first embodiment described above in that it has further heat exchange elements housed within the bed 3, in particular tube bundles 5. These tube bundles 5 can be traversed by an operating fluid, for example for example water in the liquid and / or vapor state, and receiving heat from the particles of the bed 3.

In particular, in the configuration of Figure 2, the operating fluid leaving the device 1 'through the tube bundles 5, under the design temperature and pressure conditions, can be made to expand in a turbine 510 coupled to a generator for the production of energy. electric or it can be used for other industrial purposes, for example for the production of hot water, in air conditioning systems or in desalination plants. In other words, the tube bundles 5 are connected to further components of the system in which the device 1 'is inserted, for example one or more turbines 510, condensers 521, refrigerators 530, intermediate heat exchangers 511, pumps 520 and so on. , each known in itself.

Variants of construction can provide, as the only components or heat exchange elements, the tube bundles 5.

Figure 3 refers to a second preferred embodiment of the device of the invention, denoted here by 100. With respect to the device described with reference to Figure 1, the device 100 has an irradiation opening 10 in correspondence with the upper wall 21 of the casing 2. An optical system (not shown), associated with the device 100, concentrates the incident solar radiation right at the entrance to this opening 10 and within the compartment 20. In this way, the particles of the bed 3 absorb primary thermal energy, of origin solar. In the present example, the opening 10 is shown as arranged in correspondence with the upper wall 21 of the envelope 2 and preferably centered longitudinally with respect to it. Variants of construction may provide for a different location. Likewise, the opening 10 can be, in operating conditions, completely open to the outside, without means of screen or cover, or have a protective window transparent to incident solar radiation.

The configuration considered here allows to accumulate thermal energy from the power supply of the electric resistances 7 already mentioned and from solar radiation concentrated through the irradiation aperture 10.

Figure 3 also shows a shaped confinement structure 80, or invitation, of the device 100, arranged at the mouth of the irradiation opening 10. The confinement structure 80 can develop completely or mainly outside the device 100, i.e. or not partially protrude into the vacant space 22.

The confinement structure 80 has a through opening, that is, it has a tubular construction, in such a way as to maintain direct communication between the interior and exterior of the envelope 2 by means of the irradiation opening 10.

In a variant embodiment, the confinement structure 80 defines a calm chamber which assists the freeboard 22 in avoiding or reducing air and / or particle leaks towards the outside.

In the present variant embodiment, the confinement structure 80 has a tapered conformation, in particular conical, with a decreasing section towards the inside of the envelope 2. This section of the confinement structure allows not to interfere with the direction of the solar radiation concentrated by the dedicated optical system.

Furthermore, in the present variant embodiment the device 100 comprises an auxiliary device 9, arranged in correspondence with the confinement structure 80 or, in general terms, with the irradiation opening 10. The auxiliary device 9 consists of thermoelectric and / or thermionic panels and / or photovoltaic and is configured to be directly exposed to the incident solar radiation for the generation of electrical energy. Alternatively, the device 9 consists of a heat exchanger adapted to directly absorb the heat of the solar radiation by means of its own carrier fluid.

With reference to Figure 4, it schematically illustrates a variant embodiment of the device of the invention, here denoted with 100 '. Similarly to the configuration of Figure 2, the device 100 'differs from that described with reference to Figure 3 in that it has further heat exchange elements housed within the bed 3, in particular tube bundles 5. The configuration of said tube bundles and further system components associated with them is the same as already described above with reference precisely to Figure 2.

The auxiliary device 9 can be independent of the heat exchange elements 5 immersed in the bed of particles or be connected to them.

In "open" configurations such as those just described with reference to Figures 3 and 4, the storage and transfer device can include thermionic and / or thermoelectric and / or thermo-photovoltaic components, arranged outside the casing 2, to example around the irradiation opening 10, of the same type as the components 8 mentioned with reference to Figures 1 and 2 and configured to supply the resistors 7.

The invention also provides a method of accumulation and transfer of thermal energy, based on the functions already described above in relation to the device and system of the invention.

The object of the present invention has been described up to now with reference to its preferred embodiments. It is to be understood that other embodiments may exist which pertain to the same inventive core, all falling within the protection scope of the claims set out below.

Claims (17)

CLAIMS 1. Device (1; 1 '; 100; 100') configured for the accumulation and transfer of thermal energy, which device (1) includes: - a containment envelope (2); - a bed (3) of fluidizable solid particles received within said envelope (2); - electric resistor means (7) arranged inside said casing (2) and thermally connected with said bed of particles (3), which electric resistor means (7) are configured to generate thermal energy by Joule effect and transmit it to said particles; And - heat exchange means (8; 5), also thermally connected with said bed of particles (3) and selectively activatable to receive thermal energy from it, the overall configuration being such that said thermal energy is transferred by the electrical resistor means ( 7) to the fluidizable solid particles of said bed (3) and, in a contextual or deferred way, from said fluidizable solid particles to said heat exchange means (8; 5). Device (1; 1 '; 100; 100') according to claim 1, wherein said electrical resistor means (7) are arranged, at least in part, immersed in, or so as to be lapped by, said bed of particles (3). 3. Device (1; 1 '; 100; 100') according to any one of the preceding claims, wherein said electrical resistor means (7) comprise one or more elongated elements extending longitudinally in a direction substantially orthogonal to a free surface (35) of said bed of particles (3). 4. Device (1; 1 '; 100; 100') according to any of the preceding claims, in which said heat exchange means comprise one or more of the following components: thermoelectric elements (8); thermionic elements (8); thermo-photovoltaic elements (8); tube bundles (5) configured to be crossed, in use, by an operating fluid. 5. Device (1; 1 '; 100; 100') according to any one of the preceding claims, wherein said electrical resistor means (7) and / or said heat exchange means (8; 5) have layers, or screens, of material resistant to high temperatures, for example ceramic or refractory media. Device (1; 1 ') according to any one of the preceding claims, wherein said casing (2) has an irradiation aperture (10) configured to allow incident solar radiation to enter, so that said bed particles (3) receives thermal energy from the latter. Device (1; 1 ') according to the preceding claim, wherein said irradiation opening (10) puts in direct communication an internal compartment (20) of said casing (2) with the external environment, being free, in use , of closing or shielding means. Device (1; 1 ') according to claim 6 or 7, wherein said irradiation aperture (10) is arranged in correspondence with an upper wall (21) of said enclosure (2), so that said bed ( 3) of fluidizable solid particles, or a part of it, is directly exposed, in use, to incident solar radiation. 9. Device (100; 100 ') according to any one of claims 1 to 5, in which said casing (2) is closed from the outside, preferably thermally insulated with respect to it. Device (1; 1 '; 100; 100') according to any one of the preceding claims, comprising fluidization means (4) configured for introducing a fluidizing gas, preferably air, into said bed (3) of solid particles fluidizable. 11. Device (1; 1 '; 100; 100') according to the previous claim, comprising means for selectively varying the speed and / or flow rate of the fluidizing gas. 12. Electricity and / or thermal energy production plant, comprising one or more devices (1; 1 '; 100; 100') according to any of the preceding claims and means of transformation of energy output from said or each device. 13. Plant according to the preceding claim, comprising means for capturing the solar radiation which define, together with said device (s) (1; 1 '; 100; 100'), an irradiation configuration which causes the solar radiation to converge from the tall. 14. Method for the production of electrical and / or thermal energy, which method comprises a step of producing thermal energy by Joule effect by means of electrical resistor means (7) arranged in thermal connection with a bed of fluidizable solid particles (3), a phase of accumulation of the thermal energy in said bed of fluidizable solid particles (3) and a phase, subsequent or contextual, of transferring the thermal energy accumulated to heat exchange means (8; 5) which transform the thermal energy of said solid particles that can be fluidized into electrical energy and / or transfer said thermal energy to the outside. Method according to the preceding claim, comprising a fluidization step of said fluidizable solid particles of said bed (3) which is activated under selected operating conditions. Method according to the preceding claim, which provides for a selective adjustment of the speed and / or flow rate of a fluidizing gas. Method according to any one of claims 14 to 16, employing a device or implant according to any of claims 1 to 13.