Patent Description:
In particular, the invention refers to a system for storing heat on different stratification levels in a single tank comprising a meatus sequential opening device, integrated within the tank itself.

The invention also refers to the operating method in the context of production processes characterised by cycles of heating and subsequent cooling of containers within which the product is processed.

Production processes in which it is necessary to introduce energy and produce heat are generally known.

Generally, it is proceeded with the heating steps by means of electric or direct or indirect combustion heaters and then a subsequent forced cooling step follows, for example by means of water or oil circulation heat exchangers connected to refrigeration systems capable of dispersing the generated heat.

To limit energy consumption in the heating step, techniques have been developed to store the heat subtracted during the cooling steps inside tanks containing water or oil or in any case liquid carriers, and to then return this heat during the heating steps.

This technique, applied in different areas of current use, as well, in order to be effective, that is in order to obtain a high efficiency, needs to have the lowest thermal jump between the carrier fluid inside the process vessel and the fluid that stores the heat itself.

To do this, it is not only necessary to optimize all the heat exchangers that participate in the process, but it is necessary to fractionate the temperature interval between the ambient temperature and the maximum process temperature into a number of intervals such that within each heating step, i.e. cooling step, the temperature delta of the carrier fluid and the storing fluid is minimum between the initial value and the final value for each stage of the heating process, i.e. of the refrigeration process.

This involves using a large number of distinct volumes in which to store the thermal storage liquid. These volumes can be structurally separated as tanks physically isolated from one another or thermally separated like in the case of a single tank subdivided into volumes by septa that limit or prevent the convective motions and facilitate stratification. A thermal storage system according to the preamble of claim <NUM> is described in document <CIT>.

In any case, for each of the thermal storage volumes, whether they are combined in a single tank or separated into several tanks, it is necessary to have intercepting systems that allow the selective passage of the fluid between the cooling/heating exchanger and the corresponding storage volume characterized by a specific temperature of the process step.

Generally, the thermal processes can operate at temperatures comprised between <NUM> and <NUM> and the liquids that can be used for storage can be water or diathermic oil.

In case water is used, it is clear that these are pressurised plants even at high pressure values, while using oil does not require pressurisation.

In accordance with the current state of the art, plants are being developed consisting of a stratified tank or of several tanks separated from each other, characterized by the use of several disconnecting valves, installed individually for each tank or for each level of the stratification tank.

To this end, <FIG> show the principle diagrams of the current state of the art:
<FIG> shows a known solution with tanks <NUM> and valves <NUM> separated from each other and commanded by electric, pneumatic or hydraulic type motor means <NUM>.

Each valve controls an inlet piping <NUM> or an outlet piping <NUM>. In this case, each tank contains the fluid at an almost homogeneous temperature and the valves are external thereto.

This solution involves the use of a number of tanks and a number of valves corresponding to the number of fractionations desired. This involves high costs in relation also to the operating pressure, high thermal dispersion, risks of losses and leakages, high circuit complexity.

<FIG> shows a further known solution, with a single tank <NUM> provided with separation septa <NUM> and with the external intercepting valves <NUM> controlling the inlet piping <NUM> and the outlet piping <NUM>.

Although this solution is cheaper than the previous one described, it still has high costs deriving from the need to use high-pressure and/or high-temperature valves. In addition, this solution has a thermal dispersion due to the external valves and has risks deriving from losses and leakages.

Ultimately, therefore, being such plants operating at high pressures and/or temperatures, such valves are characterized by a resistance to temperature and to pressure that entails high costs and possible critical failures.

In addition, each of these valves and the fittings connected to it must be insulated with respect to the surrounding environment to limit thermal dispersion and this entails considerable ancillary costs. The multi-valve control system involves considerable software hardware costs based on the number of stages and of transducers used.

It is therefore an object of the present invention to provide a storage system that solves, at least in part, the aforementioned technical drawbacks.

In particular, it is an object of the present invention to provide a storage system that allows to obtain a simplification of the storage and management process with also a higher efficiency and a greater economy in the construction and operation of thermal storage systems.

More particularly, it is an object of the present invention to provide a storage system in which it is not necessary to use intercepting devices, for example valves, adapted to work at high pressure and/or temperature, thereby being able to resort to intercepting devices, for example as said valves, which are more economical while also reducing heat dispersions and leakages.

These and other purposes are therefore achieved by the present thermal energy storage system comprising:.

In accordance with this solution, all the purposes of the invention are now easily achieved.

Thanks to the fact that the intercepting devices (for example, as said, the valves) are arranged directly inside the tank, they will work in a certain pressurised environment and at a certain temperature.

The thermal dispersion between the intercepting devices and the external environment is cancelled, as they are immersed directly in the fluid contained in the tank.

In addition, the pressure jump will be reduced compared to cases of external valves that suffer from a greater pressure jump due to the difference between the pressure of the environment and those of the fluid circulating in them. In this way, the possible leakages do not entail dispersion of the fluid to the outside as they are immersed in the tank itself.

In a nutshell, therefore, the invention consists in the integration of the storage fluid intercepting device(s) inside the tank itself so that there is not a high pressure delta between the fluid and the environment in which said intercepting device is inserted in order to be able to use intercepting devices (for example valve elements, such as valves) that are technologically simpler and economically advantageous.

Advantageously, therefore, the septa are placed at a certain distance from each other.

In this way, advantageously, two consecutive septa form a chamber or even a septum and the apex of the tank or its bottom form a further chamber.

Advantageously, in a preferred form of invention, actuation means for activating said one or more intercepting devices are comprised.

According to the invention, said actuation means are arranged inside the tank.

This solution is advantageous in that it makes it possible to considerably simplify the system for managing the opening and closing of the intercepting devices, the whole being reduced to a simple position control for example of a linear or rotary actuator that can be used as actuation means.

However, in this invention, a solution of control in opening/closing (or activation/deactivation) of said intercepting devices is also not excluded, even with singular actuation means that can be arranged externally at a distance from the tank and therefore not necessarily arranged inside the same.

In all the configurations described, advantageously, said actuation means can be configured to activate said intercepting devices sequentially, i.e. in succession.

According to a preferred solution, advantageously said actuation means can provide a single mechanical means and, as mentioned, at least partly arranged in the tank.

According to the invention, said actuation means comprise a rod that is inserted into said tank at least in part, in such a way as to intercept said intercepting devices.

According to the invention, said rod has an actuation motion to activate said intercepting devices.

Advantageously, such actuation motion can for example provide a sliding motion along the insertion seat of said rod in the tank or a rotation motion around its longitudinal axis.

In all embodiments of the invention, advantageously said intercepting device may be in the form of a valve.

The valve is well known in the sector and there are multiple valves that can be used commercially and could be used for the present invention.

The valve, as is well known, is operable between an opening position, in which it allows the passage of a fluid through it (thereby creating a fluidic passage) and a closing position in which a shutter is activated to close said passage.

The valve is therefore interposed in a fluidic passage path while being activated in order to selectively open this path to the passage of a fluid or obstruct and therefore interrupt said path.

As mentioned, they are well known and not specific subject-matter of the present invention.

The person skilled in the art will be able to evaluate which type of valve is most suitable for his purposes.

Advantageously there are a delivery conduit (<NUM>) for leading the fluid in the tank (<NUM>) and an outlet conduit (<NUM>) for expelling the fluid out of the conduit.

Advantageously, the delivery conduit and the outlet conduit pass through all the septa in such a way as to penetrate into the relative chambers generated by said septa.

Advantageously, for each chamber, there are an intercepting device, for example a valve, connected to said delivery conduit for filling the relative chamber with said fluid and a further intercepting device, for example a valve, connected to the outlet conduit for expelling the fluid from the relative chamber.

Advantageously, for all the configurations described, there is at least one intercepting device (e.g. one valve) for each chamber of the tank (preferably two intercepting devices, e.g. two valves, for each chamber).

Advantageously, in all the configurations described, the intercepting devices may also not be exclusively valves but, more generally, valve elements.

Valve elements are therefore more generically understood to be a selective passage element for a fluid (for example gas or liquid) operable between an open position, in which it allows the passage of the fluid, and a closed position in which it prevents said passage.

Advantageously, a plant comprising an autoclave and a system in accordance with one or more of the above characteristics is also an object of the present invention.

More particularly, advantageously, the object of the present invention is a plant comprising:.

Advantageously, in a preferred solution, the heat exchanger can be placed directly inside the apparatus.

Advantageously, the apparatus can for example be an autoclave usable in various production processes, for example pneumatic ones or any other sector.

Advantageously, the use of a system, in accordance with one or more of the above characteristics, for the recovery of the process heat is also an object of the present invention.

A thermal energy recovery method is also an object of the present invention, the method comprising the following steps:.

In this way, the heat stored in the tank through the stratification of the temperatures in it can be advantageously exploited to raise the apparatus to a certain operating temperature, therefore with considerable energy savings.

Advantageously, said sending in succession of layers of fluid at different temperatures takes place through a sequential activation of the intercepting devices present in each chamber of the tank.

Advantageously, the reverse process can be activated to withdraw heat from the apparatus and store it in the fluid in a stratified manner in the tank.

In this way, the heat subtracted from the apparatus that in a certain working process thereof is in a forced cooling step can be transferred back, through the exchanger (<NUM>), to the tank with which it is in communication. In this way, the tank stores in stratified manner a fluid with different temperatures for each layer (each chamber has a different temperature compared to the next layer).

The operation in this case is exactly the reverse, so that from the highest temperature generated by the apparatus, temperature is released to the tank in a decreasing manner until the maximum cooling of the apparatus.

The invention, in one or more of its embodiments, will be detailed below in accordance with the following drawings:.

As discussed in more detail below, the invention can be realized in various ways. Each technique described represents an example of a possible non-exclusive and non-exhaustive embodiment.

The essence of the invention, as better highlighted in the claims and in the continuation of the present description, consists in the transfer of intercepting devices <NUM> from the outside of the storage tanks to the inside of the same in order to reduce the costs and optimize efficiency.

Referring to the figures, we can see the circuit diagram of the proposed innovation (<FIG>), in relation to an equivalent example of the state of the art (<FIG>).

The object of the present invention is therefore a thermal energy storage system comprising:.

In particular, for each chamber there is at least one intercepting device to allow the fluid to be sent from the outside of the tank into the relative tank chamber and/or said fluid to be sent from the chamber to the outside of the tank. All the intercepting devices are therefore arranged within the tank.

In accordance with the invention, an intercepting system (<NUM>, <NUM>, <NUM>) is therefore present.

The intercepting system comprises one or more intercepting devices <NUM> as introduced above, for example in the form of valves or valve elements in general, and actuation means (<NUM>, <NUM>) to activate the opening or closing said intercepting devices <NUM>.

In accordance with the invention, at least said intercepting devices <NUM> used for filling or emptying the tank <NUM> are placed inside the tank itself.

Thanks to this solution, special sealing measures are no longer required, since the pressure delta between the fluid intercepted by the (internal) device and the fluid in which the intercepting device is immersed is very small.

Similar considerations can be made between the pressure upstream and downstream of these devices, which pressure is limited only by the pressure losses of the pipings. In addition, any losses and leakages of the sealing devices does not affect the operation of the system.

In an advantageous form of the invention also the actuation means (<NUM>, <NUM>) are at least partly arranged within said tank.

The command (<NUM>, <NUM>) (i.e. said actuation means) for activating the intercepting devices <NUM> inserted inside the tank can be realized for example by a command element <NUM> which can have a rotary or linear motion, as better highlighted in the embodiments immediately below.

This command element, being activated by a single motor (M) for all the intercepting devices, represents an important economic advantage compared to the conventional systems in which each valve has its own electrical or pneumatic command.

For the aforementioned reasons, the intercepting devices <NUM> have a much lower cost than the conventional solution, since they do not present sealing problems and have a zero thermal dispersion since they are a unique ensemble with the tank itself.

<FIG> shows the schematic diagram of the principle in accordance with the invention, in which the tank <NUM> can be seen inside which the intercepting devices <NUM>, for example the normal valves <NUM>, are positioned.

The tank <NUM> is subdivided horizontally by means of a plurality of septa <NUM>.

These septa are intended to limit the convective motions and allow the thermal stratification of the fluid.

These septa <NUM>, as immediately described below, can be made of metal or other material.

Obviously, the metal or the material generally selected must meet the required temperature and pressure resistance requirements that may be generated inside the tank.

Preferably, these septa must not be sealed in order to be able to allow the passage of any air present towards the upper part of the tank.

Each septum, as thus clearly highlighted in <FIG>, creates a chamber in the tank.

More septa overlapped on each other at a certain distance result in the formation of more chambers stacked together along the height of the tank.

The intercepting devices <NUM>, for example valves or valve elements in general, are arranged inside the chamber (preferably in all chambers).

At each volume delimited by two consecutive septa (i.e. in a chamber) there are therefore two intercepting devices <NUM>, for example two valves or valve elements in general.

By way of non-limiting example, in fact, <FIG> shows the presence of four septa that subdivide the internal volume of the tank <NUM> into five mutually overlapped chambers. In each of these chambers there are two intercepting devices <NUM> (in particular two valves) and of which, as clarified below, one is connected to an inlet manifold <NUM> while the other is connected to an outlet manifold <NUM>.

As introduced above, in fact, each individual intercepting device, for example a valve as mentioned, is connected to a common tube (<NUM>, <NUM>) defined as a manifold and through which the fluid is sent and collected. The manifolds are connected to the inlet and outlet fittings <NUM> and <NUM>.

The inlet manifold <NUM> can therefore simply be a duct through which the fluid enters into the tank in a specific chamber delimited by the aforementioned septa and then exits from the outlet manifold <NUM>.

In essence, again with reference to <FIG>, an inlet manifold <NUM> and an outlet manifold <NUM> are therefore provided.

Joint actuation means, are used to operate the intercepting devices <NUM> in a sequential manner.

The preferred solution provides for the aforementioned command element <NUM>, for example in the form of a rod, which acts on all the intercepting devices <NUM> by opening them in sequence as a function of the position assumed by it. The opening of the individual valves <NUM> is in relation to the linear or rotary position of the command element in question. By travelling all the excursion or the rotation of the command element <NUM>, all the valves are opened sequentially.

In summary, the fluid is sent through the inlet manifold <NUM> at the predetermined volume delimited by two septa and withdrawn from it as a function of the position of the command element <NUM> while all the intercepting devices relating to the other levels of the tank are closed.

<FIG> depicts the circuit diagram of the invention inserted in an autoclave system for the heat treatment of a generic product.

This diagram has been summarized to the maximum and only the components useful for describing the function of the invention are highlighted.

This diagram represents only a possible use of the present invention and other applications are possible in areas where thermal energy storage is required.

With reference to <FIG> we can see the thermal tank <NUM> with its elements as described in <FIG>. The tank is connected to a pump <NUM> and to a mixing valve <NUM> commanded by the motor <NUM>. The mixing valve <NUM> is connected to the exchanger <NUM> (e.g. liquid/gas such as water/air or oil/air), which transfers heat inside the autoclave <NUM>. Downstream of the exchanger there are the electrical resistors <NUM> that are necessary to bring the plant to the maximum temperature required by the ongoing process. The air inside the autoclave is moved by the fan <NUM> keyed to an electric motor <NUM>.

<FIG>, <FIG>, <FIG>, <FIG> represent non-limiting examples of how the invention can be technically realized.

<FIG> shows the overall plan view of the possible embodiment <NUM> while <FIG> shows the same construction example in sectioned axonometric view and consisting of a metal tank <NUM> of adequate thickness to withstand the operating pressure.

Inside the tank at regular intervals the dividing septa <NUM> are positioned, for example made of metallic, or ceramic, or plastic or other material that hinder the mixing of the fluid and facilitate stratification.

At the top of the tank, at a removable flange, the fittings of the inlet and outlet pipings <NUM> are positioned. These fittings are connected to two pipings <NUM> (for example of square or rectangular section) that convey the incoming fluid to the individual intercepting devices (39A, 39B) and convey the outgoing fluid from the intercepting devices (39A, 39B) to the corresponding outlet flange.

The opening of the intercepting devices (39A, 39B) is commanded via the command element <NUM>.

This command element consists of a rod <NUM> (for example metallic and/or for example of rectangular section) provided with laterally protruding cams <NUM> (see <FIG>) which contrast with a wheel <NUM> integral with the shutter of said intercepting device, thereby allowing it to be opened.

The closing of the intercepting devices (39A 39B) is carried out by the force of a spring <NUM> which is antagonist to the thrust of the cam.

In the details of <FIG> and <FIG>, an intercepting device is highlighted in the closed position (39A) and one in the open condition (39B).

In fact, precisely in the detail of <FIG>, the rod <NUM> is highlighted, which has been translated into a position such that a cam <NUM> of the rod <NUM> intercepts the valve (39B), thereby pushing the shutter of said valve into the open position, while the other cam <NUM> is placed out of contact by the shutter of the valve (39A), thereby with the valve remaining in the closed position.

The relative distance of the cams <NUM> along the command element <NUM> and the relative position of the valves along the conduit <NUM> is such as to cause a total opening of only one valve at a time, therefore with a sequential opening in succession.

Except for only one possible moment of transition in which two adjacent devices can be partially open.

This technique allows to have no pressure peaks or water hammers during switching.

The command element <NUM> is moved vertically by means of a motor means <NUM> placed outside the tank itself.

It preferably consists of a linear actuator, for example a trapezoidal or recirculating screw, provided with an appropriate position transducer that allows the correct control of the system.

A temperature sensor for measuring the temperature of each stage will be positioned outside the tank at each volume delimited by the septa.

In addition, at each stage an electrical resistor can be advantageously inserted for preheating the system, i.e. for maintaining it at a temperature in the interval between two subsequent cycles.

Since, as can be observed from the diagrams of <FIG>, the final cooling step of the autoclave requires that the temperature of the last stage of the storage tank has a sufficiently low temperature to reach the door opening condition of the autoclave itself, it is necessary to have an exchanger <NUM> advantageously inserted inside the tank itself and connected to a dissipation system such as an evaporative tower or chiller.

<FIG> shows the overall plan view of a second possible embodiment, while <FIG> highlights the same construction example in sectioned axonometric view.

Also in this case there is always the usual metallic tank <NUM> of adequate thickness to withstand the operating pressure.

Inside the tank, at regular intervals, there are always positioned the dividing septa <NUM>, for example in metallic, or ceramic, or plastic or other material that hinder the mixing of the fluid and facilitate stratification.

At the top of the tank, at a removable flange, the fittings of the inlet and outlet pipings <NUM> are positioned. These fittings are connected to two pipings <NUM>, for example of circular section, provided with lateral perforations <NUM> and which convey the incoming fluid to the individual intercepting devices <NUM>.

This part is therefore identical, de facto, to the first configuration already described.

In accordance with this solution, the intercepting devices now consist of cylindrical rings that are free to rotate, also provided with a similar perforation <NUM>.

The relative position of the intercepting device <NUM> with respect to the central tube <NUM> causes the two holes <NUM> and <NUM> to be aligned, allowing the passage of the fluid from the inlet piping towards the tank and in the opposite direction from the tank towards the outlet tube.

Since this embodiment of the invention is perfectly specular, there is no difference between the two inlet and outlet pipings, which can therefore be reversible.

The rotation of all the outer rings <NUM> constituting the intercepting devices is commanded by the command element <NUM> consisting of a tube with protruding toothing that couples with the corresponding toothing on the intercepting devices.

The relative position of the individual circular rings <NUM>, suitably mounted by offsetting the toothing thereof, entails that for a single couple of rings the perforation between the inner tube <NUM> and the outer tube <NUM> coincide whereas for all the other rings the perforations are not coincident.

In this way the passage of the fluid takes place only at the desired volume delimited between two septa <NUM>, as described for the other configuration.

In summary, the piping through which the fluid arrives is connected to a single volume comprised between two septa and, vice versa, this volume is connected to the outlet piping.

During the switching step it is possible that the openings of two adjacent levels are partially open at the same time, thus making the switching smoother and more progressive, avoiding overpressures and water hammers.

In the details of <FIG> and <FIG>, an intercepting device is highlighted lower down in the open position while all the others are closed.

The command element <NUM> is rotated by means of a motor means <NUM> placed outside the tank itself.

Said motor means <NUM> may for example be constituted by a gearmotor whose shaft is connected to the gear wheel <NUM>.

The gear wheel <NUM>, in turn, engages with the corresponding wheel <NUM> placed at the upper end of the chain constituted by the sectioning rings of each tube.

As in the previous embodiment example, a temperature sensor for measuring the temperature of each stage will be positioned outside the tank at each volume delimited by the septa.

<FIG> depict the time diagrams of the cooling and heating steps of a plant conceptually similar to that described in <FIG> but having a number of fractionings equal to three in the first diagram (<FIG>) and equal to eight in the second diagram (<FIG>).

Both diagrams provide a maximum process temperature of <NUM>, an ambient temperature of <NUM> and an end-of-cycle temperature corresponding to the opening step of the door of the autoclave of <NUM>.

The marked solid line represents the internal temperature of the autoclave.

The left part represents the cooling step starting from the temperature of <NUM> to <NUM>, the ascending part on the right represents the heating step starting from <NUM> to reach the process temperature.

The part represented by the continuous ascending line highlights the heating of the autoclave and of the product contained therein due to the release of heat of the fluid stored in the tank subject-matter of the invention and described above, while the final dashed part represents the last heating step obtained by means of external heat supply presumably by means of electric heating or with diathermic oil.

The initial temperatures of the various stages of the tank are reported on the left, the initial and final temperatures of the individual steps are reported on the right.

The values contained in the diagrams, while being influenced by other factors such as the volume of the tanks and the dimensions of the autoclave, the efficiency of the exchangers, etc. still represent reference values to evaluate the efficiency of the proposed method.

Referring to <FIG>, which represents the three-stage system, it can be observed that the temperature reached by the system for the sole contribution of the stored fluid is <NUM>° with a temperature increase of <NUM> with respect to the initial temperature (difference between said temperature of <NUM>° and <NUM>°). Since the total increase required is <NUM> (from <NUM>° degrees on the right-hand scale it is necessary to reach <NUM>° again on the right-hand scale), we can affirm that the efficiency of the process understood as the ratio between the total energy and the contribution of the storage system described is <NUM>/<NUM> = <NUM>%.

While referring to <FIG> which represents the eight-stage system, it can be observed that the temperature reached by the system for the sole contribution of the stored fluid is <NUM>° with a temperature increase of <NUM> (<NUM>° minus the initial <NUM> always shown on the right) compared to the initial temperature. Since the total increase required is <NUM> (<NUM>° minus the initial <NUM>°), we can affirm that the efficiency of the process understood as the ratio between the total energy and the contribution of the storage system is <NUM>/<NUM> = <NUM>%.

This suggests that the greater the number of the stages, that is, of the temperature intervals with which the process is fractionated, the greater the efficiency becomes with the other factors that contribute to the final result being equal.

It can be demonstrated that as the maximum temperature decreases, the efficiency decreases considerably.

Furthermore, this analysis did not take into account either the dispersions of the accumulator between the heating and cooling steps or the dispersions of the system for maintaining the temperature of the autoclave.

Despite these approximations, the statement that the greater the number of stages is, the greater the efficiency remains true. But referring to <FIG> it can be understood that the cost of the known plants increases considerably with the increase of the tanks and of the valves necessary for fragmentation.

Once the diagrams have been introduced, with reference to the example diagram of <FIG>, the operation is as follows.

Thanks to the described storage system comprising the stratified tank <NUM> with the valves (i.e. the intercepting devices according to the various configurations described) placed internally, it is possible to store the process heat and then progressively return it, according to needs, as per example diagrams of <FIG>.

The number of stages therefore depends on the number of septa present and more stages are carried out with smaller thermal release intervals between them and the greater the efficiency will be (in fact, compare the case of three stages in <FIG> with the case of eight stages in <FIG>).

To correctly describe the working cycle, we must assume that it is fully operational, i.e. that it has already run a few cycles and has therefore already stored a quantity of heat inside the tank itself, or that it has brought the tank itself to operating temperature by means of electrical resistors or another technique.

The tank, therefore, already contains the stratified fluid in the various chambers with increasing temperatures from a lower chamber to the upper one (see for example <FIG> to this end). It is not essential that all the chambers are filled so that starting from the lower chamber, in succession one or more chambers can contain the stratified fluid with increasing temperatures.

Therefore, starting from the condition of autoclave at ambient temperature with the product to be treated also cold, the heating cycle will begin with sending the fluid to the exchanger <NUM> through the pump <NUM> withdrawn in the lowest temperature zone of the tank <NUM> with the opening of the valves <NUM> (in any case of the intercepting device generally used) placed lower down inside the tank itself.

The temperature inside the autoclave will increase while the temperature of the low level of the tank will decrease by a value given by the ratio of the thermal masses between the autoclave and the tank itself.

In this step, therefore, the fluid is withdrawn through the opening of the relative valve and sent along the outlet conduit to pass into the exchanger and be reintroduced into the same chamber through the opening of the other valve through the inlet conduit. Obviously the re-entering fluid will be colder because it has released heat in the passage through the exchanger <NUM>.

Once a fluid temperature value has been reached that is now insufficient to release further heat to the autoclave, the command system, by acting on the command motor M of the actuators, will switch the closing of the lower valves and the opening of the upper valves (i.e. those relating to the immediately following chamber with higher temperature fluid) allowing the liquid contained in the corresponding volume delimited by the septa to provide sufficient heat to further raise the temperature of the autoclave, according to the process already described.

This sequence is repeated for a number of times equal to the number of stages that characterize the system until the maximum temperature allowed by the system is reached, i.e. those temperatures at which the fluid in the tank no longer has a temperature delta sufficient to release heat to the autoclave. The number of stages therefore corresponds to the number of chambers containing the liquid.

Once the heating step deriving from the energy recovery through the tank, to bring the autoclave to the operating temperature necessary for the ongoing process, has been ended, an auxiliary heating device <NUM> will be activated consisting of electrical resistors or of water or diathermic oil exchangers not covered by this study.

Once the operating temperature has been reached, the autoclave will be kept at temperature for the time necessary for the ongoing process by means of the auxiliary heater <NUM>.

At the end of the maintenance step, the cooling step begins, which will be obtained by circulating through the pump <NUM> inside the tube bundle exchanger <NUM> the liquid contained in the highest level of the tank itself, which is at a lower temperature than that of the autoclave as a result of the heat release that occurred during heating.

At this stage the temperature of the autoclave decreases and that of the corresponding septum of the tank increases. Upon reaching the temperature value whose delta is no longer able to subtract heat from the process, the command motor M of the valves will cause the top valve to close so as to allow the opening of the valves of the lower chamber and allow further cooling.

By repeating the sequence for the number of chambers that characterize the system, we reach the lower limit temperature that allows the opening of the door and the process to end.

Once this cooling step is ended, the tank is characterised by reaching the temperatures that allow restarting a subsequent heating step.

It is useful to highlight that if the temperatures inside the tank are lower than the optimal ones, the cycle works the same, obviously reducing the recovery efficiency and therefore entrusting the auxiliary heater with the task of bringing the temperature to the process value, but it is clear that in the subsequent cooling step of the autoclave the temperature values inside the tank will increase until reaching after a few cycles the optimal values.

To make the management independently of the transitional condition given by the first use or by a use after a long time, an auxiliary heating system of the tank has been provided, not indicated in the tables, which allows to bring or maintain the individual sectors of the tank at the optimal temperature value.

Claim 1:
A thermal energy storage system comprising:
- At least one tank (<NUM>) comprising on its inside at least one or a plurality of septa (<NUM>) overlapped on each other along the height of the tank in such a way as to define two or more chambers overlapped on each other that allow to obtain, in use, a stratification of the fluid inside said tank;
- One or more fluid intercepting devices (<NUM>, 38A, 39B, <NUM>, <NUM>) to allow fluid to be sent from the outside of the tank into each chamber of the tank and/or said fluid to be sent from each chamber to the outside of the tank;
- Said one or more fluid intercepting devices being arranged inside the tank;
- And wherein actuation means for activating said one or more fluid intercepting devices are comprised;
- Characterized in that:
- Said actuation means comprise a rod that fits into said tank, said rod having an actuation motion so as to activate said fluid intercepting devices.