Description Field of the art

The present invention regards alternative and renewable energy sources, in particular it regards energy transformation plants that use the heat found in the deepest layers of the subsoil as the primary source of energy. More in detail, the present patent prov ides a new and innovative geothermal well adapted to transfer heat from the subsoil to the water that is introduced into the well, resolving the criticalities observed in such kind of plants up to date.

Prior art

Geothermal energy is the energy that comes from geological heat sources and, within relativ ely short operational times, it may be considered an alternativ e and renewable source. It is based on exploiting the geothermal gradient, i .e. the natural heat of the earth, due to the thermal energy released by the natural nuclear decay processes of radioactiv e elements such as uranium, thorium and potassium. Penetrating deep, beneath the earth surface, temperature rises gradually, averagely increasing by about 30°C per km into the earth crust and by about 80°C per km into the mantle. These are mean v alues. As a matter of fact, thermal gradients could ev en be tens of times higher or lower. However, the deposits of thi s energy are at times too deep for them to be exploited. Extracting and using the energy trapped in the Earth requires identifying an area with a positiv e thermal abnormality, where the terrestrial heat is concentrated: these areas are commonly referred to as geothermal reserv oirs or deposits. Hot sources were used for bathing at least since the paleolithic age. In the first century AD, Romans conquered Aquae Sulis, today ^' s Bath, in England and used its hot sources for supplying public baths and floor heating. The fees for entry into these baths represented the first commercial use of geothermal energy. The most ancient geothermal system for a di strict was installed in Chaudes-Aigues, France and began operating in the 14th century. The first industrial exploitation dates back to 1827, when the vapour of a geyser was used for extracting boric acid from a mud volcano, in Larderello, in Tuscany.

In 1892, the first heating system in the United States in Boise (Idaho), was directly supplied by geothermal energy and it was copied in Oregon in 1900. Deep geothermal wells and geysers were used for heating greenhouses in Iceland and Tuscany since 1943.

In the 20th century, electrical energy demand led to considering geothermal power as the primary source for producing electrical energy. Prince Piero Ginori Conti experimented the first geothermal generator on 4 ^th July 1904, in the same Larderello field, where extraction of geothermal energy from acids began. This experiment enabled lighting four lamps. Later, in 1 1 1 , the first commercial geothermal plant ever was built in the same place.

We would like to get deeper into the topic of the current energy application, with reference to a study conducted by the prestigious "MIT" (Massachusetts Institute of Technology). Energy obtained by exploiting the geothermal gradient, currently represents at least 2% of energy demand worldwide. However, according to the aforementioned study, beneath our feet there is an energy potential, generated by the terrestrial heat, amounting to approximately 12,600,000 Z Joules.

Given that the annual energy demand across the Earth amounts to about 0.5 Z Joules and given that modern technology enables us to use just 2,000 Z Joules of said energy, it is clear that utilising geothermal energy alone would be sufficient to meet the energy demand of the entire planet, through green energy, for the next 4,000 years.

Studies aimed at optimising geothermal plants, led to developing binary-cycle plants in which interactions with low boiling coefficient fluids (medium-enthalpy geothermal ) are exploited. In these plants, a mixture of water and ammonia offers good transformation yields. Also the Kafine method, led to a further 3% optimisation yield with respect to a binary cycle plant.

The binary cycle plant was presented for the first time in 1967 in the Soviet Union and it was subsequently introduced in the United States in 1981. This energy enable producing electrical energy from very low temperature sources with respect to the past. Though the energy produced from geothermal heat sources is renewable and thus classifiable as green energy, that has no negative impact on the planet, various criticaliti.es arise due to the existence of the plant itself. Dri lling the earth crust reaching considerable depths that can even exceed 3 km beneath the soi l surface, inevitably irrev ersibly damages the underlying rock layers. Besides this, drilling wells for the introduction of cold water which, deep below, absorbs the heat of the rocks present in the subsoil very often requires breaking hot dry rocks, with the aim of increasing the heat exchange surface. Ruining geological layers may lead to catastrophic consequences for the areas surrounding the well . Constant microseisms may occur, same case applying to the critical subsidence phenomenon, i .e. the sinking of the soi l lev el . The release of hydrogen sul ide into the air i s al so a frequent phenomenon that leaves foul odour over the entire area surrounding the plant. The release of lead, mercury, arsenic, limestone, hypochloric acid, hydrogen sulfide, radon and crumbling elements in general, into the water circulating in the well is equal ly harmful . The presence of these elements requires monitoring the composition of water and taking chemical/physical/mechanical elimination measures, considerably increasing the plant maintenance costs. In addition, the high temperatures present in the subsoil facilitate the formation of crusts in the pipings and in the heat exchangers, threatening the efficiency of the plant over time.

Thus, monitoring the plant is becoming increasingly crucial thanks to the current avai lability of modern technologies of software and control systems. The recently filed United States patent n° US 201601 1 570 describes a geothermal plant optimisation process, based on controlling the parameters of the ci cuit water through a plurality of sensors and detectors. However, a geothermal well capable of avoiding the occurrence of the aforementioned drawbacks instead of monitoring them, does not seem to hav e been designed yet. Most phenomena arising from detrimental drilling of the soil, can be overcome by a let's say "concentric ^" wel l, i .e. a plant in which the w ell for introducing cold water and the one for extracting hot water, are inside each other and sealed in-depth so as to form a circuit. Actually, up to date the dril ling operations requi ed for installing a geothermal w ell hav e always been at least two, one or more for the inflow piping and one or more for the outflow piping. This entails doubling production costs as ell as the environmental problems described above.

Thus, an object of the present inv ention is to provide a geothermal el 1 capable of overcoming the env ironmental criticalities and requiring low maintenance, guaranteeing an operational duration of about 35 years. Furthermore, the operation of the well in question is supported by a dedicated software that guarantees the maintenance of the conditions required for proper and safe use of the plant.

Description of the invention

According to the present inv ention, a geothermal w ell with communicating vessels is prov ided whose main purpose is to reduce the geothermal plant production costs as well as av ert the environmental problems related to the presence of the well in the subsoil .

More in detail , the w el 1 of the present inv ention requires drilling only once instead of twice as requi ed by the geothermal wel ls in use up to date. Furthermore, the geothermal w el 1 in question effectiv ely eliminates problems related to the subsidence and microseisms phenomena that have nev er been solv ed up to date.

Just like the common wells in use up to date, such geothermal well exploits the endogenous heat typical of the deepest rock layers of the Earth's subsoil . With the aim of extracting and making it exploitable, a fluid, commonly represented by water, is introduced into a piping vertical ly extending beneath the soi l lev el . Descending, the fluid absorbs part of the Earth's heat and it is subsequently once again conv eyed to the surface, through an extraction piping, which conveys the fluid to a heat user device, i.e. any device adapted to exploit said heat as primary source of energy.

Advantageously, the geothermal well in question, is made up of an internal piping 20 and an external piping 10 arranged coaxially and adapted to serve, respectively, as a piping for introducing the inflowing cold fluid 4 1 and a piping for remov ing the outflowing hot fluid 51. More in detai l, said internal piping 20 is adapted to transfer an inflow 41, from an inlet pump 40 up to the level determined by the depth of the well. Such level beneath the soil level depends on the depth of interception of the geothermal coefficient and the operating temperature of the plant. Said external piping 10, instead, is suitably sized to enable the ascent of the fluid in form of an outflow 51 which, from the di stal end of the well, is conveyed upward until it reaches any heat user device.

Advantageously, in order to guarantee the maintenance of the mutually coaxial position between the internal piping 20 and the external piping 10, the internal surface of each modular element I 1 forming said external piping 10 is prov ided with a plurality of spacers 14, preferably three, which converge, fol lowing a straight path, in a circular col lar 15. Such collar 1 5, is constituted by a circular metal element, coaxial to said external piping 10, w ithin which the corresponding modular element 2 1 of said internal piping 20 is inserted during assembly. Advantageously, said corresponding modular element 2 1 of said internal piping 20, is in turn provided - on the external surface thereof - with a circular metal flange 24, adapted to be engaged with said collar 1 5 with the aim of locking the position of said modular element 2 1 of said internal piping 20, with respect to said collar 1 5.

These solutions also help av oiding the excessiv e mutual oscillations between said internal piping 20 and said external piping 10.

It should be observed that the sizing of said collar 1 5 with respect to said modular element 21 of said internal piping 20, is such to enable the thermal expansions both in the linear direction and in the cubic direction of said modular element 2 1 , said thermal expansions inev itably being caused by the high operating temperatures of the plant and the high pressure exerted by the circulating fluid.

Advantageously, the pressure of the circulating fluid, is regulated by an inlet pump 40, arranged at the entrance of said internal piping 20.

The safety of the entire plant regarding the geothermal well is advantageously guaranteed by a common dedicated software. The latter monitors the circulation of the fluid within the well and receiv es data relative to the osci llations of the pipings coming from special detection sensors 60. More precisely, said detection sensors 60 will be at least two and, even more in detail, one will regard recording the oscillations of said internal piping 20 and the other will be dedicated to the external piping 10. Possibly, said detection sensors 60, may also be adapted to transmit to said dedicated software the information regarding the chemical- physical characteristics of the circulating fluid and the internal pressure of the well.

Advantageously, said dedicated software is programmed to operate on the inlet pump 40, on a driven regulation valve 7 1 and on a plurality of actuators, with the aim of bringing the oscillations back to ithin pre-establi shed threshold values, thus eliminating the potential occurrence of microseisms. Said actuators can be constituted by common motors and/or synchronous motors and/or flow regulation valves.

Advantageously, said well is also provided ith an automatic safety valve 70, arranged, for safety reasons regarding potential overpressures, at the proximal end of said external piping 10. The entirety contributing to the purpose of the invention regarding eliminating impacts on the surrounding environment, due to the presence of an operating geothermal well .

Advantageously, the configuration of the well with communicating vessel s already enables, due its nature, a considerable damping of the oscillations. As a matter of fact, the descent and ascent flow, mutually nullify most of the vibrations due to the opposite direction of the motion thereof. Adv antageously, the total damping occurs subsequently due to the action of the software on the due actuators and valves.

A further advantage of the present invention, lies in the modularity of the pipings that the well is made up of. Actual ly, similarly to the internal pipings 20, said external piping 10 is made up of a plurality of modular elements 1 1 , 21 , each one of which is constituted by a common cylindrical and hollow Mannesmann pipe provided with a pair of threaded sections 1 2- 1 2 ^' , 22-22 ^" arranged at the upper and lower end of said modular element 1 1, 21.

Said threaded sections 1 2- 12 ^" , 22-22 ^" are advantageously adapted to enable the stable but reversible screwing and fixing, of each modular element 1 1 , 2 1 with the subsequent one, up to obtaining the desired depth for both pipings 10, 20.

Contrary to the other modular elements 1 1 , the terminal element of the external piping 10 is adv antageously constituted by a cylinder prov ided with a threaded section 1 2 at the upper end and with a closure cap 13 at the lower distal end. This, so as to prevent the outflow of the fluid from said external piping 10 and the ensuing dispersion thereof into the ground. Said internal piping 20, instead has a terminal element prov ided with a threaded section 22 at the upper end and with a free end 23 at the lower end. Thi s to enable the outflow of the fluid from the internal piping 20 to the external piping 10.

Advantageously, in order to guarantee the sealing of the joinings between the various modular elements 1 1 , 2 1 both of the external piping 10 and the internal piping 20, a Teflon layer seals the joining from the internal and the external .

One of the further advantages offered by the geothe mal well in question, lies in the fact that it does not extract water from the subsoil, modifying the hygrometric conditions of the ground. As a matter of fact, after being exploited as a source of energy by a special heat user device, said outflow 51 is re-introduced into the circuit as a cooled return fluid, forming the new inflow 4 1 .

Advantageously, said heat user dev ice may be a common heat exchanger or a common vapour generator.

Description of the figures

The invention will be described hereinafter in at least one preferred embodiment, prov ided by way of non-limiting example, with reference to the attached figures, wherein:

- FIGURE 1 shows an ov erall operating diagram of the geothermal well of the present inv ention which shows the external piping 10 and the internal piping 20 arranged in a concentric fashion. On the left of the drawing, the flow of the inflowing water 4 1 is i llustrated which, passing through the inlet pump 40, is conv eyed under high pressure in the internal pipings 20. As the water descends deeper, it gets hotter and hotter, thanks to the heat gradient present in the depth of the Earth. Upon reaching the bottom of the internal piping, the water flow, which is represented by increasingly darker arrows representing the temperature increase, ascends upwards into the space found between the external surface of the internal piping 20 and the internal surface of the external piping 10. The outflow 51 , represented by the black arrow, is conveyed towards the heat exchanger and the vapour generators or any other instrument for utili sing the plant. In addition, two detection sensors 60, the automatic safety valve 70 and the driven regulation valve 71 , which monitor the safety and efficiency of the well through a dedicated software, are shown.

- FIGURE 2 A shows a front view of a modular element 21 of the internal piping 20 and a modular element 1 1 of the external piping 10. In particular, the threaded sections 1 2 and 12' are shown at the two ends of the modular element 1 1 of the external piping 10, whi le other two threaded sections 22 and 22' are shown at the two ends of the modular element 2 1 of the internal piping 20. Such sections are designated for the stable engagement with the previous and subsequent modular element 1 1, 21, so as to form the pipings that descend deep into the ground.

- FIGURE 2B il lustrates the same front view of the preceding figure but, in thi s case, regarding the terminal modular elements 1 1 , 2 1 of the internal piping 20 and the external piping 10. The corresponding threaded section 22, 1 2 which enables connection with the overlying modular element 1 1, 2 1 is shown at the upper end of each modular element 1 1, 2 1 . The lower end of the modular element 1 I of the external piping 10 is prov ided with a closure cap 13. The lower end of the modular element 2 1 of the internal piping 20 is a free end 23 instead.

- FIGURE 2C shows a top view of the well, in which the external circumference representing the profile of the external piping 10, the internal circumference representing the profi le of the internal piping 20 with the collar 1 5 on the external and three spokes present in the circular crown comprised between said internal piping 20 and said external piping 10, are shown. The three spokes represent the spacers 14, better visible and understandable with the help of the subsequent figure. - FIGURE 3, as previously mentioned, shows a three-dimensional view of the deep structure of the wel l in which, besides the external piping 10 and the internal piping 20, there are the shown spacers 14 which, starting from the external piping 10, converge on the collar 15. It should be obser ed that the image is represented with a bottom to top view, i .e. from the bottom of the ell towards the surface. As a matter of fact, at the top part of the col lar 15, the engagement of the flange 24 is seen relative to the modular element 2 1 of the internal piping 20.

Detailed description of the invention

Now, the present invention will be i llustrated purely by way of non-limiting example, with reference to the figures i llustrating some embodiments regarding the present inventive concept.

With reference to FIG. 1, an operating diagram of the geothermal well of the present invention is shown. For a better understanding of the deeply innov ativ e aspect of the present inv ention, it should be observ ed that wells used up to date requi e two dril lings and a piping arranged deep horizontally connecting the water inflow piping to the outflow piping. Thanks to the present inv ention, the outflow piping contains the piping for the inflow of water, the fluid more general ly. Thus, the external piping 10 and the internal piping 20 are coaxial and the internal piping 20 is sufficiently large to guarantee a slower ascent of the outflow 5 1 which occurs in the circular crown comprised between the external surface of the internal piping 20 and the internal surface of the external piping 10. This so as to enable a longer period in which the fluid is at contact with the external wall of the well and thus absorbs the thermal energy thereof.

Thus, when creating the wel l, only one dri lling w il l be required instead of two.

For the understanding of the invention, we would like to emphasi se on the great difference that a vertical circuit has w ith respect to a well of the type used up to date, i .e. hav ing a fluid path in the horizontal direction between the well , in inflow and outflow . Giv en that the thermal gradient increases proportional ly to the increase of depth, a vertically extending system enables regulating the flow rate to the thermal power demand.

Stil l with reference to FIG. 1 , the arrows show the fluid path. The first white arrow on the left shows the inflow 41 which - through the inlet pump 40 - is conveyed into the internal piping 20 at the desired pressure. Descending deeper, the fluid absorbs the endogenous heat transmitted by the deepest rock layers. We would like to point out that the depth of the well depends on the type of rocks encountered through core sampling carried out during the preliminary study of the site. The depth thereof will be established at the planning stage as a function of the temperature detected deep down.

Increasingly hotter, the fluid reaches the di stal end of the well and, given that the internal piping 20 is open, said fluid is made to flow into the external piping 10. The ascent, represented by the black arrows w hich constitute the outflow 51 , begins from here. The latter is conveyed towards at least one special heat user device which may be both a common heat exchanger and a common vapour generator. At thi s point, the fluid has been cooled and it is reintroduced into circulation as a cooled return fluid, constituting a new inflow 4 1 .

The reintroduction of the circulating fluid, eliminates the possibility of occurrence of the subsidence phenomenon, i .e. the sinking of the soil due to the extraction of the aquifer.

With the aim of also eliminating the microseisms that currently occur in common geothermal well s, the plant of the present invention is provided with numerous precautions for damping the oscil lations generated in the internal piping 20. More precisely, the configuration of concentric flows of the well, already guarantees a given level of damping of the oscil lations in that, flowing in the opposite direction, the vibrations generated by the inflow 4 1 at least partly nullify the vibrations generated by the ascending flow. Furthermore, a circular flange 24 is arranged outside said internal piping 20 so as to support such damping of the oscillations, ensure the maintenance of coaxial ity between the two pipings and simultaneously enable the inevitable thermal expansions. Said flange 24 is adapted to be engaged - at the upper part - with a circular collar 1 5 - belonging to the external piping 10 and connected - at the internal surface thereof - through a plurality (preferably three) of spacers 14, constituted by common bars or plates made of any metal or metal alloy, adapted to provide structural support, between the two pipings.

FIG 3 exhaustively shows the mutual engagement between the components described above. It should be observed that the fluid is introduced into the internal piping 20 at a very high pressure, amounting to about 200 bars, thus the oscillations may be rather considerable. More in detail, said collar 15 will be suitably dimensioned to enable possible thermal expansions, both in linear and cubic direction, due to the high operating temperatures. Even more in detail, said collars 15 with the relative spacers 14, are arranged at regular interval s, in particular, in case of pipings constituted by modular elements 1 1 , 21, there il l be a col lar 15 with spacers 14 for each modular element 1 1 of the external piping 10 and a flange 24 for each modular element 2 1 of the internal piping 20.

The stiffening mechanical systems, are supported by an electronic control system through a dedicated software adapted to prevent the aforementioned microsei sms.

In particular, the well is prov ided w ith at least one detection sensor 60 at the external piping 10 and a detection sensor at the internal piping 20. The latter are adapted to transfer to said dedicated software, the information regarding the osci llations of the pipings 10, 20 deriv ing from the pressure of the circulating fluid. Possibly and preferably, said detection sensors 60 may also be adapted to communicate to said software the information regarding the chemical-physical composition of the circulating fluid and regarding the circulating pressure thereof.

Upon collecting thi s information, said dedicated software is capable of damping oscil lations should the return flow vibrations not be sufficient to bring them back within the pre-set threshold. In particular, said software operates through the following means: a driven regulation valv e 71 , the inlet pump 40 and a plurality of actuators, constituted by common motors and/or synchronous motors and/or flow regulation valves, suitable to dampen the osci llations and prevent potential microseisms.

Said well i s also provided with an automatic safety valve 70, adapted to automatically operate in case of detection of an ov erpressure of the circulating fluid. Also the constmction characteristics of the well of the present invention reveal innovative advantages. Both the external piping 10 and the internal piping 20, are constituted by a plurality of modular elements 1 1, 21 mutually coupled one after the other, up to reaching the project depth . Said modular elements 1 1 , 2 1 , are constituted by common cylindrical and hollow Mannesmann pipes (i .e. without welding), prov ided with a pair of threaded sections 1 2- 12 ^" , 22-22' arranged at the upper and lower end of said modular element 1 1, 2 1 . Said threaded sections 1 2- 1 2 ^' , 22-22' are adapted to enable the stable but reversible screwing and fixing of each modular element 1 1 , 2 1 with the subsequent one, up to obtaining the desired depth. Each joining between one modular element 1 1 , 21 and the other is sealed by means of a Teflon layer arranged inside and outside the joining.

The only elements representing an exception with respect to the abov e, are the terminal elements of both pipings 10, 20, as exhaustiv ely represented in FIG. 2B. In particular, the terminal element of the external piping 10, which represents the distal end thereof, is represented by a cylindrical and hollow body, prov ided with a threaded section 12, like the one described prev iously, which enable the screwing thereof with respect to the ov erlying modular element 1 1. The opposite end is instead prov ided w ith a closure cap 13 adapted to prev ent the outflow of the fluid from said external piping 10 and the ensuing dispersion thereof into the ground.

The terminal element of the internal piping 20, is instead constituted by a cylindrical and hollow element provided with a threaded section 22 at the upper end, for screwing thereof to the ov erlying modular element 2 1 , and w ith a free end 23 at the lower end. This to enable outflow of the fluid from the internal piping 20 to the external piping 10.

Lastly, it is clear that the invention described up to now may be subjected to modifications, additions or variants obv ious to a man skilled in the art, without departing from the scope of protection outlined by the attached claims.