The present invention relates to plants for the utilization, processing and storage of energy from renewable energy sources. In particular the invention relates to a plant that uses an integrated system of renewable sources, and more specifically the irradiation of the sun and the temperature of the ground at an appropriate depth relative to the surface of the ground.

The core of the present invention is a new type of heat exchanger which works buried at an appropriate depth with respect to the surface of the ground, and which allows to recover the heat supplied by an energy source, preferably but not necessarily of a renewable type, transfer said heat to a user device and store at least part of the heat removed from the energy source for later use when said energy source is not available.

With this heat exchanger, the Applicant has found a new way of mutual integration of certain renewable sources by which a considerable daily degree of self-sufficiency of the plant is reached, wherever said plant is geographically located. Such self-sufficiency is achieved in particular thanks to the accumulation of energy when the energy supplied by said sources is overabundant with respect to the needs and to its recovery when that provided by said sources is less than the consumption required. More specifically, the energy alternately accumulated and recovered is thermal energy.

In a first aspect the invention therefore relates to a heat exchanger for use in a geo- thermal plant for the exploitation of renewable energy sources characterized by being itself a heat accumulator for the storage and release of said heat according to the needs.

In a second aspect, the invention also relates to a plant for the production of energy for industrial and/or domestic purposes, characterized in that it comprises a heat exchanger according to the invention, buried with its top surface at a depth not less than 3 meters from the ground.

In any case the present invention may be better understood from the description that follows and with the help of the figures appended hereto, provided solely by way of example and not as a limitation, since other embodiments are possible, however, in respect and within the definition of the exchanger and the plant according to the claims which follow. Said figures illustrate the structure of the exchanger and the operating diagram of the plant according to the invention, highlighting the constituent elements thereof and their mutual connection. However, the constituent elements are not described in detail in their constructive aspects being devices and operations known in the art, or otherwise readily identifiable and definable by every expert in the field. More specifically:

Figure 1 shows a schematic front view, of one of the plates which constitute the constituent elements of the heat exchanger according to the invention,

Figure 2 shows, in perspective view, the pack of plates that defines the heat exchanger according to the invention,

Figure 3 shows in a front view, a possible arrangement of the coils formed in each plate,

Figure 4 shows, in schematic front section, the plant according to the invention, Figure 5 shows, in schematic front section, a different embodiment of the heat exchanger of Figure 1 with entries and exits of the coils arranged in a central position with respect to the plate, Figure 6 shows, in schematic front section, an alternative embodiment of the plate of Figure 3 with the two channelings (one entry and one exit) in a central position but offset with respect to the axis of the plate.

With reference to Figure 1 , the exchanger 1 comprises a pack of plates, of which only the front plate 2 is visible. The plates preferably have a square or rectangular shape, i.e. are delimited by two pairs of opposite sides (3, 4; 5, 6) of equal length and parallel. In a prototype built by the Applicant each plate has dimensions, in millimeters, equal to 1500x750x1.5, i.e. the upper and lower sides, with respect to its vertical position in the plant measure 1500 mm, the lateral sides measure 750 mm while the thickness of the plate is equal to 1.5 mm. Said prototype then comprises ten plates, however those skilled in the art will have no difficulty in deciding the measures and the amount of plates necessary in relation to the desired performance for the plant that is intended to be built.

Each plate is conveniently constructed with the usual technique known as Roll- Bond. This consists of assembling together, by welding, two sided thin metal sheets. The above metal sheets are preferably of aluminum or steel or galvanized metal sheet, i.e. of material chosen in relation to the performance required and to the type and degree of wear to which it will be subjected in operation, in the plant.

On at least one of said sheets, on its surface facing the other sheet, with a material that inhibits bonding between the two sheets, a circuit, is designed, preferably a coil, which reproduces the development of the channeling that will be obtained between the two sheets.

Blowing air under pressure between the two coupled sheets, the wall of at least one of the two sheets, along the track drawn with the bonding inhibitor material, is deformed, because of the minimum thickness of the sheet, expanding outwards and thereby realizing the desired channeling. In the plate according to the invention, preferably, the above channeling comprises (Figure 3) a plurality of coils 7, substantially developed upon the entire surface of the plate, all having the same entry 8 and the same exit 9.

Preferably, the entry 8 and the exit 9 of the said channeling are arranged at the opposite ends of the plate, on the same side 3 although of course other solutions are possible, for example with entries 8 and the exits 9 arranged on the same side of the plate, or in the center of the same, and on the same side 3 (Figures 5 and 6) or on opposite sides 3 and 4.

Preferably, the plates are arranged in the pack so as not to align with each other the entries 8 and the exits 9 of said plates, leaving them alternately offset upon the same surface of the pack, preferably the upper one, and on the same end of said pack; in this way at each end of the pack are available two sided entry rows mutually offset. All entries lying on the same row are conveyed in a single channeling, respectively 10, 1 1, 12, 13.

The connections are established so that the entries of the row 10 correspond to the exits of the row 12 and then the entries of the row 13 correspond to the exits of the row 11. The terms entry and exit used herein identify the circulation direction of the fluid in the plates so that, in the heat exchanger according to the invention two fluids circulating in counter-phase, i.e. in the opposite direction to one another; the first fluid enters the channeling 10 and exits the channeling 12, the second fluid enters the channeling 13 and exits the channeling 1 1.

In a different embodiment of the heat exchanger according to the invention (Figure 6) the plates are inserted in the pack alternately oriented in opposite directions so that the misalignment of the channeling in each plate generates a pack of plates which has four rows of channels, similarly to that shown in Figure 2.

As for said fluids, they are fluids known in the art, chosen in relation to the type of plant and devices for the absorption and dispersion of energy connected with said plant: in particular the fluid used, may be the fluid commonly known as "technical water", or a fluid containing anti-freeze or even a mixture of liquid and gas. According to the invention, in the geo-thermal plant for the exploitation of renewable energy sources, an entry channeling and the corresponding exit channeling on the opposite end of the pack are connected with a device adapted for receiving cold fluid to be heated, the other entry channeling, and the corresponding exit channeling on the opposite end of the pack are connected with a device adapted for receiving hot fluid to be cooled.

As mentioned above, the two fluids travel in opposite directions within the heat exchanger, thus maximizing the yield, since the exchange of heat between the two fluids that intersect each other is favored by the gap in temperature between the two fluids, always maximum in each point of the channeling within the plate. Preferably, according to the invention the plates are embedded in a material with high thermal capacity which is inserted between plate and plate and covers and encompasses the entire pack of plates.

Still more preferably, this material with high thermal capacity comprises a mixture of cement and bentonite, preferably admixed with siliceous sand and/or quartz sand, in order to maximize the thermal conductivity of the mixture.

The mixture selected by the technician can be prepared case by case,from time to time as needed but the technician will find more convenient to use products already pre-mixed and available on the market. The heat exchanger described above has found advantageous application in a geo- thermal type plant, for the production of energy for industrial and/or domestic purposes, in particular through the use of renewable sources.

The plant according to the invention (Figure 4) comprises a first device 14 adapted for receiving cold fluid to be returned at a higher temperature, a second device 15 adapted for receiving hot fluid to be returned at a lower temperature and the heat exchanger 1 already described.

Said device 14 can be a solar thermal panel, or a hybrid photovoltaic panel, adapted to recover heat from solar radiation, or any source of heat that needs to be cooled, such as the radiator of an internal combustion engine or other similar equipment.

The cooling is achieved by circulating in the channeling 10-12, through a pump 16, a fluid Fl . Said fluid, released from the exchanger at exit 12, cold, is sent to the device 14 where it is heated by removing heat from the device, and then cooling it down. The fluid, now at a high temperature, enters into the plates of the exchanger from the entry 10 and during the crossing of the plates yields heat to the second fluid circulating in 13-1 1, in the direction opposite to that of Fl, cooling down, after which is again sent to the device 14.

The second fluid F2, kept in circulation in the system of Figure 4 by way of a pump 19, is used to transfer heat to a third fluid, circulating in the device 15, such as a heat pump, where said third fluid must be heated, or cooled, for a number of possible technical uses, already well known so as not to require for that matter a specific description. See for example, the co-pending patent application N° MI2010A000458 of the same Applicant, filed on March 22, 2010.

In the illustrated case, said third fluid enters, cold, in the device 15 from the entry 17 and exits, hot, from the exit 18.

In this case the second fluid F2, arriving cold from the device 15, enters the heat exchanger 1 from the entry 13 and exits hot from the exit 1 1 to return to the device 15. In fact, during the crossing of the heat exchanger, has subtracted heat to the fluid Fl circulating in counter-phase.

According to the invention, the heat exchanger 1 is used buried, with the top surface 3 of the pack of plates placed at a depth p, with respect to the ground, not less than 3 meters.

At this depth the soil temperature is substantially constant, in the order of 10°C, regardless of the environmental conditions. In this way, the heat coming from the device 14 not only heats the fluid F2 but also the exchanger itself and the surrounding ground, and especially when the circulation of the fluid F2 is reduced or completely absent for any reason. Because of the high thermal capacity of the ground and especially the material in which is embedded the exchanger 1, said heat is maintained unchanged for a considerable time and can thus be recovered from the fluid F2 even when the source of the device 14 is unavailable for any reason.

The invention described provides important qualitative, economic and environmental, benefits in particular adapted to reduce the risks of pollution. In fact, the solution of a heat exchanger at three/four meters below ground is a convenient inexpensive alternative to the extensive network of tubes placed two meters below the ground and a not only cheaper but also safer alternative to the known geothermal probes. These latter may continue on to a hundred meters underground, and to reach this depth the probes must cross at least a water table with the possibility of pollution of the same in the case that, following the breaking of the probe tubes, the fluid circulating therein may be dispersed within the water table.

From the foregoing it will first be clear that the invention has made available a new and original method of mutual integration of different renewable energy sources in order to guarantee the self energy to a plant for exploitation of thermal energy, regardless of the environment temperature. According to the invention said method is characterized in that it accumulates heat, obtained particularly from renewable sources, in the ground during periods of overabundance of said heat, compared to the needs of the plant, to recover it for the use in said plant during periods of lack of said heat.

Thanks to the mutual integration of renewable energy sources, and through the preservation and the subsequent recovery of the accumulated heat, the system may have significant amounts of free and constant thermal energy, so as to guarantee the energetic and economic self-sufficiency of the plant regardless of its particular geographic location, whether in warm weather countries or with temperate or even cold climates, and the course of the seasons. The renewable sources used, the equipment and the method of their use renders the plant emission-less, of harmful emissions in particular, for the atmosphere and for surface and underground water. The construction costs of the plant are limited as technical components already known in the art and therefore with high quality and reliability characteristics are used in a new way.

In conclusion, the construction cost of the plant is recovered in a short time and the management cost makes it particularly convenient.

In the present description all the possible structural and dimensional alternatives to the embodiments of the invention specifically described as usual were not shown: it was not deemed necessary to expand into construction details of the inventive system as each skilled in the art, following the instructions given herein will have no difficulty in designing, selecting appropriate materials and dimensions, and the most advantageous technical solution. These variations, however, are to be considered equally within the scope of protection of this patent, resulting in these alternative embodiments easily derivable from the description here made of the relationship between each embodiment with the result that the invention intends to obtain.