ITRE20110096A1 - METHOD AND PLANT FOR THE RENOVATION OF RENEWABLE ENERGY - Google Patents

Description

DESCRIPTION

â € œMETHOD AND PLANT FOR THE EXPLOITATION OF RENEWABLE ENERGYâ €

FIELD OF TECHNIQUE

The present invention relates to a method and a plant for the exploitation of renewable energy.

STATE OF THE ART

As is well known, the term â € œrenewable energyâ € generally refers to a form of energy generated by a source which, due to its intrinsic characteristic, is naturally regenerated or is exhausted in a technically very long time.

Various types of energy are commonly considered renewable energy, including in particular solar energy and geothermal energy.

From a technical point of view, solar energy is commonly exploited through the use of so-called thermal solar panels, more properly called thermal solar collectors, and photovoltaic solar panels, more properly called photovoltaic modules.

A solar thermal collector is a device suitable for converting solar radiation into thermal energy, which usually comprises a panel of conductive material which is heated by solar radiation and which transfers the heat thus collected to a heat transfer fluid, usually mixed water. antifreeze, which is circulated inside a dense network of channels associated with the panel itself. The heat transferred to the heat transfer fluid can subsequently be used in various different ways, the most widespread of which is the production of hot water for sanitary purposes inside the buildings.

A photovoltaic module, on the other hand, is a device capable of converting solar energy directly into electricity due to the photovoltaic effect. The basic elements of a photovoltaic module are the so-called photovoltaic cells. The most common version of a photovoltaic cell is essentially made up of a sheet of semiconductor material such as silicon. When a luminous flux strikes a photovoltaic cell, a certain number of electrons that are in the valence band of the semiconductor material pass, due to the photovoltaic effect, to the conduction band, thus making charge carriers available that can be used to generate a current. electric. The performance of a photovoltaic module is influenced by numerous factors, one of which is the operating temperature of the photovoltaic cells. In particular, the efficiency of a photovoltaic module is higher when the photovoltaic cells work at low temperatures, for example in the winter months, when however there is low irradiation. For this reason, it was decided to combine some photovoltaic modules with a system that allows the photovoltaic cells to be cooled, increasing their performance even in the summer months.

Based on this concept, the so-called hybrid photovoltaic modules have been proposed, commonly called PVT (PhotoVoltaic and Thermal), which are devices that allow the conversion of the energy radiated by the sun into both electrical and thermal energy. A PVT generally consists of a photovoltaic module which is associated with a heat exchanger in which a heat transfer fluid circulates. In this way, the heat transfer fluid cools the photovoltaic cells and is simultaneously heated by the part of solar radiation not converted into electrical energy. Compared to traditional solar thermal collectors, PVTs are able to heat the heat transfer fluid at a lower temperature, up to a maximum of about 40 ° C. The heat of the heat transfer fluid heated by the PVTs is currently used only for the production of domestic hot water, especially in the very hot months, or at most to heat swimming pools, but with the problem in any case of disposing of the excess heat.

The techniques for exploiting geothermal energy are studied by geothermal energy, which generally deals with the possibility of exploiting the heat present in the deeper layers of the earth's crust as a source of thermal energy. However, there is also another form of geothermal, called low-enthalpy geothermal, which allows to exploit the heat of the ground at low depths. Low enthalpy geothermal energy is based on the characteristic of the soil of having a mass of great thermal capacity, and of maintaining, already a few meters deep from the surface, an almost constant temperature of about 10 ° C for the whole year (the € ™ effect of the fluctuations in the surface temperature of the soil is in fact exhausted at contained depths). Taking advantage of this feature, low enthalpy geothermal is generally used for heating buildings, by means of systems that schematically include a heat pump connected to a geothermal heat exchanger. The geothermal heat exchanger is a closed circuit piping system that is buried in the ground surrounding the building to be heated, and inside which flows a heat transfer fluid which exchanges heat with the ground itself. The pipes are generally made of polyethylene and have a rather small diameter (a few centimeters). The geothermal heat exchanger can have a vertical configuration, including one or more U-shaped tubes (called geothermal probes) that go deep into the ground (up to 50-150 meters), or a configuration horizontal or superficial, ie comprising one or more coils or spirals of pipes that are buried over a larger area but at a lower depth (up to a maximum of about 15 meters). The heat transfer fluid circulating in the geothermal exchanger can be simple water, with the drawback of not being able to drop below 4 ° C to avoid freezing, or a mixture of water and antifreeze (for example ethylene or propylene glycol), which it can be circulated even at temperatures below 0 ° C.

The heat pump absorbs the thermal energy of the heat transfer fluid, which acts as a low temperature heat source, and uses it to heat a warmer fluid, typically water, which circulates in a heating system located inside the € ™ building, typically a radiant panel heating system. To perform the aforementioned heat transfer, the heat pump consumes a certain amount of mechanical energy, the value of which is directly proportional to the difference in temperature between the heat transfer liquid coming from the geothermal heat exchanger and the water in the system. of heating. The yield of a geothermal heat pump is therefore expressed by the so-called Coefficient of Performance (COP), ie the ratio between the thermal energy transferred to the water in the heating system and the mechanical energy spent to perform this transfer.

A common drawback of many renewable energies is that they have a seasonal nature, that is to say that they have different yields in the various periods of the year. For example, in temperate latitudes, the availability of solar energy is maximum in the sunny summer months, minimum in the cold winter months and highly variable in the transition months. For this reason, the PVT described above are capable of producing peaks in electricity and hot water especially in the summer months, when the electricity demand is actually high due to the operation of the electrical air cooling devices (air conditioners). ), but when the demand for thermal energy is normally low and in any case much lower than in the winter months. Therefore, most of the heat absorbed by the heat transfer fluid in the PVT is currently dissipated, sometimes with an additional energy expense due to the need to install a heat exchanger specifically configured to cool the carrier fluid before returning it to the PVTs.

As for solar thermal collectors, even the most efficient solar thermal collectors in temperate latitudes produce little energy especially in the winter months, for example between November and January.

Low enthalpy geothermal energy, especially when carried out with a horizontal configuration geothermal exchanger, is affected by a certain seasonality. In fact, the operation of the heat pump removes heat from the ground especially in the cold winter months, when the demand for hot water for heating is greater. The heat removed from the ground is then regenerated by the rain and the sun, especially in the hot summer months. This results in an annual thermal balance which, however, does not always reach perfect parity, with the risk of having a slightly colder soil every winter than the previous year, progressively lowering the COP of the heat pump. To solve this problem, it is currently necessary to significantly increase the area of land occupied by the geothermal heat exchanger, in order to increase its exposure to the sun and rain. By way of example, a surface geothermal system currently requires an area of land of at least 150 m <2>, possibly south-facing and unshaded, for every 100 m <2> of internal surface of the building to be heated. In current homes it is very difficult to find such an area of land available, if not considering single-family villas with large land area.

SUMMARY OF THE INVENTION

In light of the foregoing, an aim of the present invention is to solve the aforementioned drawbacks of the prior art, providing a system for the joint and coordinated exploitation of solar energy and low enthalpy geothermal energy, which allows better overall yields. compared to the systems currently used.

A further aim is to achieve the aforementioned objective in the context of a simple, rational and low cost solution.

These objects are achieved by the characteristics of the invention reported in the independent claims. The dependent claims outline preferred and / or particularly advantageous aspects of the invention.

In particular, the invention makes available a method for the exploitation of renewable energy comprising the operating phases of:

- heat a heat transfer fluid by means of one or more hybrid photovoltaic modules,

- use the heat transfer fluid heated by the hybrid photovoltaic modules to heat a ground,

- use said ground to heat a heat transfer fluid, and - use the heat transfer fluid heated by the ground in a heat pump.

The first two operational phases of the method can be carried out in the hot periods and periods of greater insolation, typically in the hot summer months, for example from May to September. In this way, the low temperature of the ground guarantees the heat transfer fluid to remove a lot of heat from the hybrid photovoltaic modules, whose electrical productivity can increase by up to 20%. At the same time, the heat coming from the hybrid photovoltaic modules is accumulated in the ground, which can thus reach a temperature of about 20-25 ° C at the end of the hot season.

In this way, it is advantageously avoided that the ground is heated to excessively high temperatures, which would only contribute to increasing the losses due to entropy and to create â € œsufferingâ € in the ground itself, since the maximum temperature of the heat transfer fluid exiting the hybrid photovoltaic modules It is around 40 ° C.

The large thermal capacity of the soil means that the accumulated heat is then stored in the soil for a certain time.

The last two operational phases of the method can therefore be carried out in the cold periods and with minimal sunshine, typically in the winter months, for example from November to January. In this way, the heat previously stored in the ground can be advantageously exploited by the heat pump to operate with a higher Coefficient of Performance (COP) and therefore with a better yield.

In other words, the invention makes it possible to exploit the solar thermal energy collected by the hybrid photovoltaic modules in certain periods of the year, typically the hot ones and the maximum insolation, to increase the COP of the heat pump in other periods of the year. € ™ year, typically in the cold ones and with minimal sunshine.

In this way, a higher energy efficiency is obtained both of the hybrid photovoltaic modules and of the geothermal system, which allows to obtain very high energy classes (also class A) and to have (where required by law) economic incentives due to their use. rational energy. Furthermore, with the same thermal energy to be produced, the increase in COP of the geothermal heat pump allows the adoption of smaller geothermal heat exchangers, which also require a smaller ground surface, with the consequent possibility of being installed in gardens or relatively small areas.

A preferred aspect of the invention provides that the method includes the further operational step of:

- use the heat pump to heat water.

This operational phase can be carried out especially in cold periods, to produce the large quantities of hot water normally required.

According to another aspect of the invention, the method can also include the operational phase of:

- directly use the heat transfer fluid heated by the hybrid photovoltaic modules to heat water.

This operational phase can be carried out especially in hot periods, for example alternating it with the heating phase of the ground. In this way, the heat produced by the hybrid photovoltaic modules is also effectively used to produce hot water, avoiding having to use the heat pump.

We would like to specify here that by â € œdirect useâ € we mean that the heat is transferred between the two fluids without passing from the accumulation in the ground, and preferably without the interposition of any other heat transfer fluid, for example inside of a heat exchanger which is lapped on each side by one of the two fluids.

A further aspect of the invention provides that the method may also include the operational steps of:

- heat a heat transfer fluid by means of one or more solar thermal collectors, e

- directly use the heat transfer fluid heated by the solar thermal collectors to heat water.

These phases can be performed especially in hot periods, in order to produce sufficient hot water even when the hybrid photovoltaic modules are used to heat the ground, without having to activate the heat pump.

The hot water heated by the heat pump and / or directly by the hybrid photovoltaic modules and / or by the solar thermal collectors, can be advantageously used for multiple functions inside the building.

In particular, an aspect of the invention provides that hot water can be used to heat other water to be delivered to one or more consumption users present in the building, such as faucets in sinks, showers or other sanitary ware, and / or to hot water outlets for household appliances. This use of hot water is clearly foreseen throughout the year with consequent significant savings in electricity.

Hot water can also be used to heat one or more internal rooms of the building, for example by circulating it in a heating system, preferably a radiant panel heating system, for example underfloor, ceiling or wall. Clearly, this use of hot water is especially foreseen in the cold periods of the year.

To effectively carry out the method outlined above, the invention also makes available a plant for the exploitation of renewable energy which essentially comprises:

- one or more hybrid photovoltaic modules,

- a first hydraulic circuit adapted to connect said hybrid photovoltaic modules with a geothermal heat exchanger buried in a ground, so as to allow a heat transfer between the hybrid photovoltaic module and the ground, by means of a heat transfer fluid able to circulate in the first circuit plumber, - a heat pump, ed

- a second hydraulic circuit adapted to connect said heat pump with a geothermal heat exchanger buried in said ground, so as to allow a transfer of heat between said ground and the heat pump, by means of a heat transfer fluid able to circulate in the second circuit hydraulic.

In principle, the first hydraulic circuit and the second hydraulic circuit could each be connected to a respective geothermal heat exchanger, as long as both of these heat exchangers are buried in the same ground.

However, a preferred aspect of the invention provides that said first hydraulic circuit and second hydraulic circuit are connected to the same geothermal heat exchanger.

In this way, the installation costs of the system are advantageously reduced and it is possible to use a single heat transfer fluid both to cool the hybrid photovoltaic modules (in the hot summer periods) and to operate the heat pump (in the cold winter periods. ).

The heat pump can use a different operating fluid than the heat transfer fluid flowing in the geothermal heat exchanger. This operating fluid circulates in a closed hydraulic circuit passing in series through an evaporator, in which it is evaporated and brought to the state of vapor, a compressor, in which the vapor is compressed by increasing its temperature, a condenser, in which the vapor condenses back in the liquid state, and finally an expansion valve, in which the pressure of the operating fluid is lowered before returning to the evaporator. The heat necessary for the evaporation of the operating fluid is supplied by the heat transfer fluid that circulates in the geothermal exchanger, while the heat produced by condensation can be exploited in various ways, including those described above.

Alternatively, the heat pump could be direct expansion, i.e. the operating fluid that circulates in the heat pump could be the same heat carrier fluid that also circulates in the geothermal heat exchanger. In this case, the heat transfer fluid evaporates in the geothermal heat exchanger and then enters directly into the heat pump compressor to continue the thermodynamic cycle outlined above.

The geothermal heat exchanger can comprise one or more pipe systems, for example configured as coils or coils. Preferably, said pipe systems are arranged by overlapping layers inside the ground, for example up to a depth not exceeding about 10 meters, in such a way as not to require large excavations, reducing costs and avoiding as much as possible problems of hydrogeological instability.

According to an aspect of the invention, the heat pump is connected to an accumulation tank designed to contain water, so as to allow a transfer of heat between a fluid operating in the heat pump and the water contained in the storage tank. accumulation.

This solution has the advantage of allowing the heat pump to heat water, which can then be used in the ways explained above.

Another aspect of the invention provides that the first hydraulic circuit can be further adapted to connect at least one hybrid photovoltaic module with an accumulation tank suitable for containing water, by means of heat exchange to allow a transfer of heat between the heat-carrying fluid to circulate in the first hydraulic circuit and the water contained in the storage tank itself. In this case, valve means are provided for conveying the heat-carrying fluid that passes through said hybrid photovoltaic modules selectively into said storage tank or into the geothermal heat exchanger.

This solution has the advantage of allowing the system to use the heat transfer fluid from the hybrid photovoltaic modules directly to heat water, according to the methods and for the purposes previously explained in relation to the method.

According to a further aspect of the invention, the plant can also include:

- one or more solar thermal collectors, ed

- a third hydraulic circuit adapted to connect said solar thermal collector with an accumulation tank adapted to contain water, by means of heat exchange to allow a transfer of heat between the solar thermal collectors and water contained in the heat exchanger itself, by means of a heat transfer fluid suitable for circulating in the third hydraulic circuit.

This solution has the advantage of allowing the system to heat water, according to the methods and for the purposes previously explained in relation to the method.

According to one aspect of the invention, the hybrid photovoltaic modules, the solar thermal collectors and the heat pump can all be connected to the same storage tank, which can be for example a boiler.

According to another aspect of the invention, the storage tank can be connected to a hydraulic heating circuit, which is installed in a building in order to allow a heat exchange between the hot water coming from the storage tank. and at least one room inside the building.

This solution has the advantage of allowing the use of hot water for heating one or more internal rooms of the building.

Preferably, the hydraulic heating circuit comprises one or more radiant panels, for example on the floor, ceiling or wall, which can effectively operate with hot water at a lower temperature than other known systems.

According to one aspect of the invention, the system can also include a hydraulic water supply network to at least one consumer, such as one or more sinks, showers or other sanitary taps, or water outlets. hot for household appliances. In this case, said supply network is connected to said storage tank by means of heat exchange to allow a transfer of heat between the water contained in the storage tank and the water in the supply network.

In this way, it is advantageously possible to produce instant domestic hot water without the losses that are obtained when a condensing boiler is switched on, with consequent savings in electricity.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the invention will become evident by reading the following description provided by way of non-limiting example, with the aid of the figure illustrated in the attached table.

Figure 1 is a diagram of a plant for the exploitation of renewable energy according to the present invention.

DETAILED DESCRIPTION

The figure illustrates a plant 200 for the exploitation of renewable energies, in particular for the coordinated and joint exploitation of solar energy and low enthalpy geothermal energy, for a building 100.

The system 200 includes a plurality of hybrid photovoltaic modules 205, commonly called PVT (PhotoVoltaic and Thermal), which can be placed outside the building 100 so as to be exposed to solar radiation. Each PVT 205 essentially comprises a photovoltaic collector capable of converting solar radiation into electrical energy, which is combined with a heat exchanger configured to exchange heat with the photovoltaic cells. The heat exchangers of the PVTs 205 are connected to each other in parallel by a closed hydraulic circuit 210 containing a suitable heat transfer fluid, typically a mixture of water and antifreeze (for example ethylene or propylene glycol). The heat transfer fluid can be made to circulate inside the hydraulic circuit 210 by means of a pump 215, for example a pump driven by an electric motor. In this way, the heat transfer fluid that flows in the heat exchangers of the PVT 205 is heated by the part of solar radiation not converted into electrical energy and simultaneously cools the photovoltaic cells, advantageously increasing the electrical conversion efficiency of the PVT 205. Energy electricity produced by the PVT 205 is capable of being fed into the electricity distribution network of building 100 and / or being fed (sold) into the public electricity distribution network. In the example illustrated, the PVT 205 are divided into a plurality of groups 220, in this case into four groups of five PVTs, in which the PVT 205 of each group 220 can be dedicated to the production of electricity for a single housing unit of the € ™ building 100. For this reason, each group 220 of PVT 205 is electrically connected to a respective photovoltaic inverter 225, which is designed to convert the direct electric current produced by the PVT 205 of the respective group 220 into alternating current to be fed directly into the electricity distribution network of the housing unit to which it is dedicated. Since each photovoltaic inverter 225 works on the individual housing units, and not on the centralized electrical system of building 100, it is possible to use the electricity more contemporaneously than the production phase and / or in any case receive the maximum economic incentive that some countries provide for the production of electricity from renewable sources, which is generally higher the smaller the size of the plant.

The system 200 also comprises a device for the production of hot water for building 1. In the example shown, said device first of all comprises an accumulation tank 230 suitable for containing the water to be heated. The storage tank 230 must be large enough to at least compensate for the daily fluctuations in hot water consumption in building 100.

The storage tank 230 is operationally connected with the PVT 205. More in detail, the storage tank 230 contains a first system of pipes, in this case a first coil 235, which is placed in a position of heat exchange with the Water contained in the tank 230. The first coil 235 is inserted in the hydraulic circuit 210, so as to be hydraulically connected to the heat exchangers of the PVT 205. In other words, the first coil 235 has an inlet in communication with the output of the PVT 205 and an output in communication with the input of the PVT 205. In this way, the first coil 235 can be crossed by the heat transfer fluid that has been heated by the PVT 205, which in turn heats directly the water in the storage tank 230, cooling down before returning to the PVT 205.

The storage tank 230 is also operationally connected to a plurality of solar thermal collectors 280, which can be placed outside the building 100 so as to be exposed to solar radiation. Solar thermal collectors can be glazed or vacuum tubes or heat pipes. Each solar thermal collector 280 generally comprises a panel of conductive material which is heated by solar radiation. A dense network of channels is associated with the panel of conductive material that define a sort of heat exchanger. The heat exchangers of the solar thermal collectors 280 are connected to each other in parallel by a closed hydraulic circuit 285 containing a suitable heat transfer fluid, typically a mixture of water and antifreeze (for example ethylene or propylene glycol). The heat transfer fluid can be made to circulate inside the hydraulic circuit 285 by means of a pump 290, for example a pump driven by an electric motor. In this way, the heat transfer fluid flowing into the heat exchanger of the solar thermal collectors 280 is heated by the heat collected by the panel of conductive material. The storage tank 230 contains a second system of pipes, in this case a second coil 295, which is placed in a position of heat exchange with the water contained in the storage tank 230. The second coil 295 is inserted in the circuit 285, so as to be hydraulically connected to the heat exchangers of the solar thermal collectors 280. In this way, the second coil 295 can be crossed by the heat transfer fluid which has been heated by the solar thermal collectors 280, which in turn heats the water contained in the storage tank 230 directly, cooling down before returning to the solar thermal collectors 280.

Note the higher position of this second coil 295, because the solar thermal panels 280 work at a higher temperature than the PVT 205 and therefore create a stratification in the storage tank 230.

The storage tank 230 is also operationally connected to a heat pump 300. The heat pump 300 is a machine designed to subject an operating fluid to a thermodynamic cycle (Carnot cycle) which allows the transfer of heat from a thermal source. at low temperature to a higher temperature heat source. The heat pump 300 essentially comprises a closed circuit 305 containing the operating fluid, typically water. An evaporator 310 is inserted in series along the circuit 305, in which the operating fluid is evaporated by subtracting heat from the low-temperature thermal source, a compressor 315, in which the vapor is compressed by increasing its temperature, a condenser 320, in which the superheated vapor is brought back to the liquid state by giving heat to the high temperature source, and finally a lamination valve 325, in which the pressure of the operating fluid is lowered before returning to the evaporator 310. The operation of the compressor 315 consumes a certain amount of mechanical energy that can be supplied by an electric drive motor. The ratio between the heat transferred between the two heat sources and the mechanical energy expended by the compressor 315 is called the Coefficient of Performance (COP) of the heat pump 300, and is proportional to the temperature difference between the heat source. low temperature and high temperature heat source. A smaller temperature difference corresponds to a higher COP and therefore to a higher efficiency of the heat pump 300.

In the case in question, the condenser 320 of the heat pump 300 is defined by a heat exchanger, which can comprise a tank 321 suitable for containing the operating fluid and a system of pipes, in this case a coil 322, which is It is contained inside the tank 321 in a heat exchange position with the operating fluid contained therein. The coil 322 is provided with an inlet and an outlet communicating directly with the storage tank 230. A pump 323, for example a pump driven by an electric motor, is located along the pipe that connects the storage tank 230 with the inlet of the coil 322, so that the water contained in the storage tank 230 can be made to circulate in the coil 322. In this way, the water contained in the storage tank 230 can act as a heat source at high temperature which heats up by subtracting heat from the operating fluid in the condenser 320 of the heat pump 300.

On the other hand, the evaporator 310 is defined by a further heat exchanger, which can comprise a tank 311 able to contain the operating fluid and a system of pipes, in this case a coil 312, which is contained inside the tank 311 in a heat exchange position with the operating fluid contained therein.

The coil 312 is inserted in a hydraulic circuit 345 containing a heat transfer fluid, typically a mixture of water and antifreeze (for example ethylene or propylene glycol). The heat transfer fluid can be made to circulate in the hydraulic circuit 345 by means of a pump 313, for example a pump driven by an electric motor. In this way, the heat transfer fluid flowing through the coil 312 can act as a low temperature heat source which cools by giving heat to the operating fluid in the evaporator 310.

More in detail, the hydraulic circuit 345 is able to connect the coil 312 of the evaporator 310 with a geothermal heat exchanger, globally indicated with 355. The geothermal heat exchanger 355 is generally a closed circuit piping system which is buried in a ground T surrounding building 100. In this way, the heat transfer fluid that comes out cooled by the evaporator 310 can flow through the geothermal heat exchanger 355 where it can be heated (by a few degrees) by the ground T , before returning to evaporator 310.

The pipes of the 355 geothermal heat exchanger are generally made of polyethylene and have a rather small diameter (a few centimeters). The geothermal heat exchanger 355 preferably has a horizontal or surface configuration, i.e. comprising a plurality of pipe systems 360, for example coils or coils, which are connected together in series and which are buried by overlapping layers over an extended area but at a reduced depth (up to a maximum of about 15 meters). In this way, the excavation costs for the installation of the geothermal heat exchanger 355 are reduced and the risk of causing hydrogeological instability is reduced. In the specific example, only three 360 pipe systems are shown for convenience. However, the 355 geothermal heat exchanger can comprise eight to twelve overlapping 360 pipe systems with a pitch of, for example, between 70cm and 80cm, up to a maximum depth of about 10m.

The more superficial 360 pipe system of the geothermal heat exchanger 355 is connected to the outlet of the coil 312 of the evaporator 310, whose inlet is instead connected to the 360 pipe system which is located deeper .

The geothermal heat exchanger 355 is also connected to the heat exchangers of the PVT 205, via the hydraulic circuit 210. In particular, the most superficial pipe system 360 of the geothermal heat exchanger 355 is connected to the inlet of the PVT 205, the outlet of which is connected to the deeper pipe system 360, by means of a diverter valve 365. The diverter valve 365 includes an inlet in communication with the output of the PVT 205, a first outlet in communication with the PVT 205. ™ inlet of the first coil 235 of the storage tank 230, and a second outlet in communication with the pipe system 360 placed at a greater depth. In this way, the diverter valve 365 is configured in such a way as to convey the heat transfer fluid that exits from the PVT 205 selectively into the first coil 235 of the storage tank 230 for the production of hot water, or inside the geothermal heat exchanger 355 for seasonal accumulation. From this plant structure it clearly follows that the heat transfer fluid flowing inside the PVT 205 will be the same as it will also flow inside the evaporator 310 of the heat pump 300.

The storage tank 230 is connected to a closed hydraulic circuit 255 for heating the internal rooms of the building 100 or of the single dwelling unit. Said heating circuit 255 is designed to convey the hot water coming out of the storage tank 230 towards one or more thermal diffusers (not shown), which are installed inside the building 100 in the heat exchange position with the rooms to be heated, and subsequently to return it to the storage tank 230. The thermal diffusers can be usual radiators or, more preferably, radiant floor, ceiling or wall panels. The radiant panels essentially comprise a system of pipes generally arranged in a spiral, serpentine or grid, which are placed behind the surfaces of the room to be heated, typically under the floor, on the ceiling or in the walls. In this way, the hot water circulating in the pipes heats the surfaces in which they are embedded, which in turn heat the environment by radiation and convection. The use of radiant panels is preferable because their operation normally requires hot water at a lower temperature than usual radiators, normally between 30 ° C and 40 ° C. A meter 260 of the quantity of hot water passing through it can be applied to the heating circuit 255, in order to measure the heat used for heating.

The storage tank 230 also contains a third system of pipes, in this case a third coil 330, placed in a position of heat exchange with the water contained in the tank 230. The third coil 330 is equipped with an inlet 331 of the cold water, which is capable of being connected with an attack on the public aqueduct. In this way, the water flowing in the third coil 330 is heated by the water present inside the storage tank 230. The water in the third coil 330 can also be heated directly by the first and second coil 235 and 295, which are partially wound on the third coil 330 itself. The third coil 330 is then equipped with a hot water outlet 332, which is suitable for being connected to an open hydraulic network 265 for conveying and supplying hot water to a plurality of of consumption users 270 of the building 100 or of the single housing unit. These consumer utilities 270 may include, for example, the taps of sinks, showers or other sanitary fixtures, and may also include hot water outlets for household appliances, such as washing machines or dishwashers. To each consumption user 270, or to each group of consumption user 270, a meter 271 of the hot water it supplies can be associated.

The system 200 also includes a series of further hydraulic devices (not shown), such as valves and fittings, designed to regulate the flow of hot water that circulates in the heating circuit 255 and in the distribution network 265.

Finally, the system 200 comprises an electronic control unit 400, which is connected to various sensors and various actuator devices of the system, and is programmed to control its operation as described below.

Especially during hot periods and periods of greater insolation, for example in the summer months from May to September, the heating circuit 255 of building 100 is closed or bypassed, so the demand for hot water is relatively low. For this reason, the control unit 400 can deactivate the heat pump 300 and with it the pump 313 of the hydraulic circuit 345.

At the same time, the control unit 400 uses the PVT 205 for the production of electricity. Due to the high temperatures, the control unit 400 activates the pump 215 of the hydraulic circuit 210, so that the heat transfer fluid flows inside the heat exchangers of the PVT 205, cooling the photovoltaic cells and thus significantly increasing the efficiency of the electricity generation. Passing through the PVT 205, the heat transfer fluid also collects the solar thermal energy which is not transformed into electricity, thus heating up.

If the temperature of the heat transfer fluid leaving the PVT 205 is higher than a certain threshold temperature, for example 27 ° C, the control unit 400 commands the diverter valve 365 to convey the heat transfer fluid inside the geothermal heat exchanger 355, in which it flows from the deepest 360 pipe system to the shallowest 360 pipe system before returning to the PVT 205. In this way, the soil T surrounding the heat exchanger 355 extracts heat from the heat transfer fluid, in order to cool it properly so that it can continue to cool the photovoltaic cells of the PVT 205. At the same time, the ground T heats up, storing the heat removed from the heat transfer fluid.

If the temperature of the heat transfer fluid at the outlet of the PVT 205 does not exceed the aforementioned threshold value, the control unit 400 commands the diverter valve 365 to convey the heat transfer fluid inside the first coil 235 of the storage tank 230, preheating directly the water inside.

At the same time, the control unit 400 can also activate the pump 290 of the hydraulic circuit 285 headed by the solar thermal collectors 280. In this way, the heat transfer fluid that circulates in the hydraulic circuit 285 is heated by the solar thermal collectors 280, and then passes through the Inside the second coil 295 of the storage tank 230, directly heating the water contained in it and cooling it before returning to the solar thermal collectors 280.

Thanks to this solution, it is possible to produce sufficient hot water without activating the heat pump 300 and without using all the thermal energy collected by the PVT 205. In hot periods of great insolation, the hot water is in fact used essentially to heat the water in the third coil 330 which is then supplied to consumer users 270 through the supply network 265.

Thanks to the operation outlined above, at the end of the hot season, the ground T where the geothermal heat exchanger 355 is buried can have stored heat from the PVT 205 until it reaches a temperature between 20 ° C and 25 ° C. This heat remains stored in the soil T with minimal losses at least for at least half of the cold winter period, for example from November to January, thanks to the great thermal inertia typical of the soil T itself. In fact, it is known that in temperate latitudes, the months of February and March can still be cold but there is some irradiation, thus giving the possibility to the surface soil to regenerate well with the sun and the melting of snow and / or with the rain.

Especially during the cold periods, that is when the outside temperature is low, for example in the winter months, the hot water produced in the storage tank 230 must be able to be used both to heat the water directed to the consumers 270 through the supply network 265, both for heating the internal areas of the building 100 through the heating circuit 255. The temperature of the water in the storage tank 230 must therefore generally be between 30 ° C and 40 ° C. To reach these temperature levels, the water can continue to be heated by means of the solar thermal collectors 280 and the PVT 205 as described above. However, if the heat supplied is not sufficient, for example due to poor insolation, the control unit 400 can activate the heat pump 300, as well as obviously the pump 323 and pump 313 of the hydraulic circuit 345. In this way, the heat transfer fluid circulating in the hydraulic circuit 345 cools in the evaporator 310, transferring heat to the heat pump 300 which transfers it to the water contained in the storage tank 230, heating it up to the desired temperature, for example up to 40 ° C . At the outlet of evaporator 310, the heat transfer fluid passes through the geothermal heat exchanger 355, where it heats up by subtracting heat from the surrounding ground T. In this phase of heat absorption from the ground T, the geothermal heat exchanger 355 is traversed by the heat-carrying fluid in the opposite direction with respect to the phase of transfer of heat to the ground T described above. Thanks to the heat stored by the ground T during hot periods, the temperature difference between the heat transfer fluid in the evaporator 310 and the water in the storage tank 230 is significantly lower than in a conventional low enthalpy geothermal system, so that © the heat pump 300 can effectively operate at very high COP, especially when combined with a heating circuit 255 with radiant panels.

It should be noted here that, alternatively, the heat pump 300 could be of the direct expansion type, that is, it could use the heat transfer fluid which circulates in the geothermal heat exchanger 355 directly as operating fluid. In other words, the hydraulic circuit 345 and the circuit 305 of the heat pump 300 could be made as a single circuit, configured and sized so that the heat transfer fluid evaporates inside the geothermal heat exchanger 355, and then passes directly as vapor inside the compressor 315, and from there into the condenser 320 and the lamination valve 325, before returning to liquid form inside the geothermal heat exchanger 355.

Thanks to the plant 200 described above, therefore, a more effective global exploitation of solar energy and low enthalpy geothermal energy is obtained during the year, obtaining not only significant benefits in terms of energy balance but also in terms of installation. By way of example, it has in fact been calculated that by applying the 200 system to a building 100 in class C, it may be sufficient to use a quantity of land equal to 1 m <3> / month for each m <2> of living space. to be heated. This means that if an area of 300m <2> is to be heated, an amount of land of 900m <3> destined for heat storage guarantees three months of optimum COP for the heat pump 300. An amount of land equal to 900m < 3> It can be obtained, for example, with an excavation having plan dimensions of 10m by 10m, and a depth of 9m. This excavation therefore provides much smaller surfaces than the excavations required for conventional low enthalpy geothermal plants, which entails benefits in terms of cost, hydrogeological stability and environmental impact. Furthermore, this solution makes it possible to apply low-enthalpy geothermal energy also to houses having land T not perfectly south or not sufficiently large for a classic surface geothermal system.

Obviously, a person skilled in the art can make numerous modifications of a technical-applicative nature to the plant 200 described above, without thereby departing from the scope of the invention as claimed below.

REFERENCES

100 building

200 plant

205 hybrid photovoltaic module / PVT 210 hydraulic circuit

215 pump

220 PVT group

225 photovoltaic inverter

230 storage tank

235 first serpentine

255 heating circuit

260 counter

265 distribution network

270 consumer accounts

271 counter

280 solar thermal collectors

285 hydraulic circuit

290 pump

295 second serpentine

300 heat pump

305 closed circuit

310 evaporator

311 tank

312 serpentine

313 pump

315 compressor

320 capacitor

321 tank

322 serpentine

323 pump

325 lamination valve

330 third serpentine

331 cold water inlet

332 hot water outlet

345 hydraulic circuit

355 geothermal heat exchanger 360 pipe system

365 diverter valve

400 control unit

T ground

Claims (13)

CLAIMS 1. A method for the exploitation of renewable energy comprising the operational steps of: - heating a heat transfer fluid by means of at least one hybrid photovoltaic module (205), - use the heat transfer fluid heated by the hybrid photovoltaic module (205) to heat a ground (T), - use said ground (T) to heat a heat transfer fluid, - use the heat transfer fluid heated by the ground (T) in a heat pump (300). 2. A method according to claim 1, characterized in that it provides for the operating step of: - use the heat pump (300) to heat water. 3. A method according to any one of the preceding claims, characterized in that it provides for the operating step of: - directly use the heat transfer fluid heated by the hybrid photovoltaic module (205) to heat water. 4. A method according to any one of the preceding claims, characterized in that it provides: - heating a heat transfer fluid by means of at least one solar thermal collector (280), e - directly use the heat transfer fluid heated by the solar thermal collector (280) to heat water. 5. A method according to any one of claims 2 to 4, characterized in that it provides: - use heated water to heat at least one room inside a building (100). 6. A method according to any one of claims 2 to 5, characterized in that it provides: - use the heated water to heat water to be delivered to at least one consumer user (270). 7. A plant (200) for the exploitation of renewable energy comprising: - at least one hybrid photovoltaic module (205), - a first hydraulic circuit (210) adapted to connect said hybrid photovoltaic module (205) with a geothermal heat exchanger (355) buried in a ground (T), so as to allow heat transfer between the hybrid photovoltaic module (205 ) and the ground (T), by means of a heat transfer fluid able to circulate in the first hydraulic circuit (210), - a heat pump (300), e - a second hydraulic circuit (345) adapted to connect said heat pump (300) with a geothermal heat exchanger (355) buried in said ground (T), so as to allow heat transfer between said ground (T) and the heat pump (300), by means of a heat transfer fluid able to circulate in the second hydraulic circuit (345). A plant (200) according to claim 7, characterized in that said first hydraulic circuit (210) and second hydraulic circuit (345) are connected to the same geothermal heat exchanger (355). 9. A plant (200) according to claim 7 or 8, characterized in that said heat pump (300) is connected to an accumulation tank (230) suitable for containing water, so as to allow heat transfer between a fluid operating in the heat pump (300) and the water contained in the storage tank (230). 10. A system (200) according to any one of claims 7 to 9, characterized in that the first hydraulic circuit is further adapted to connect said at least one hybrid photovoltaic module (205) with an accumulation tank (230) adapted to contain water, by means of heat exchange means to allow a heat transfer between the heat transfer fluid able to circulate in the first hydraulic circuit (210) and the water contained in the storage tank (230) itself, valve means (365) being provided to convey the heat carrier fluid which passes through said at least one hybrid photovoltaic module (205) selectively into the storage tank (230) or into the geothermal heat exchanger (355). A plant (200) according to any one of claims 7 to 10, characterized in that it comprises: - at least one solar thermal collector (280), e - a third hydraulic circuit (285) able to connect said solar thermal collector (280) with storage tank (230) able to contain water, by means of heat exchange to allow a transfer of heat between the solar thermal collector (280) and the water contained in the storage tank (230) itself, by means of a heat transfer fluid able to circulate in the third hydraulic circuit (285). A system (200) according to any one of claims 9 to 11, characterized in that said storage tank (230) is connected to a hydraulic heating circuit (155), which is installed in a building ( 100), so as to allow a heat exchange between the hot water coming from the storage tank (230) and at least one room inside the building (100). 13. A plant (200) according to any one of claims 9 to 12, characterized in that it comprises a hydraulic water supply network (265) to at least one consumption user (270), which is connected to said storage tank (230) by means of heat exchange to allow a heat transfer between the water contained in the storage tank (230) and the water in the supply network (265).