CH707577A2 - Apparatus for producing geothermal energy. - Google Patents

Abstract

A device for extracting geothermal heat from a well (1) having a wellhead and a well (2) comprises a conveyor whereby a medium from the wellhead to the well (2) and from the well (2) to the wellhead is recoverable. The device further comprises a filling material (40) introduced into the drilling base (2), with which heat can be transferred to the medium.

Description

Technical area

The invention relates to a device for obtaining geothermal heat from a wellbore having a wellhead and a bottom, comprising a conveyor, whereby a medium from the wellhead to the wellbore and the wellbore to the wellhead is eligible. Furthermore, the invention relates to a method for obtaining geothermal heat.

State of the art

The extraction of energy from geothermal heat has long been known. For this purpose, a heat transfer medium is fed into a bore in order to heat this at the bottom of the elevated temperature in the bottom of the well and then pump it back to the surface, where the heat energy is converted.

In order to optimize the geothermal energy production various developments have been made.

For example, EP 2 189 731 A1 shows such a geothermal probe. The apparatus comprises a downwardly directed conveyor tube which leads into a container in the ground and an upwardly directed conveyor tube, whereby a closed circuit for a medium (for example water) is formed. The device may be operated by natural circulation or alternatively by a pump.

DE 3 029 900 A1 relates to a heat exchanger for use of geothermal energy, with a introduced in a borehole boiler, which is thermostatically controlled by a valve or filled according to the lint principle. The boiler is filled via a downpipe, while the forming steam is discharged upwards via an insulated riser pipe.

The known devices for the production of geothermal energy have the disadvantage that they have a too low efficiency respectively generate too low heat output respectively electrical power.

Presentation of the invention

The object of the invention is to provide a device belonging to the aforementioned technical field for geothermal energy production, whereby a high performance can be generated.

The solution of the problem is defined by the features of claim 1. According to the invention, the device further comprises a filling material introduced into the drilling base, with which heat, preferably via a container, in particular via a vapor pressure vessel, can be transferred to the medium.

In a method for obtaining geothermal heat from a wellbore hole with a wellbore, a medium is conveyed from the wellhead to the wellbore and then from the wellbore to the wellhead with a transport means, heat being transferred from a fill material buried in the wellbore to the medium becomes.

The filler material is preferably a bulk material or a flowable solid. Alternatively, so-called heat pipes or heat pipes can be used for heat transfer to the container. With such a heat exchanger, a high heat flux density is made possible from the environment to the container. The specific embodiment of such heat pipes is well known to the skilled person.

The wellhead refers to the entry of the borehole at the surface of the terrain or the mouth of the borehole.

With the filler, a heat transfer from the environment of the bottom of the well to the medium is improved. For this purpose, the filling material preferably has a high thermal conductivity coefficient and / or a high specific heat capacity. With the high coefficient of thermal conductivity, an efficient heat transfer to the medium, respectively via the vapor pressure vessel to the medium is achieved. Due to the high specific heat capacity, a high heat transfer capacity is achieved. The filler material can also stabilize and support the wellbore, especially during heat recovery operation.

The term "bore" is understood to mean at least one borehole in the soil or rock, which projects into a depth in which there is an elevated temperature relative to the surface. A hole does not necessarily have to be vertical, but can also have an angle of up to 90 ° to the horizontal. The bore diameter can be sized differently and adapted to the circumstances. A diameter may, for example, be between a few centimeters, for example between 10 and 30 cm, up to a meter or more. It is also possible that a bore does not have a single diameter, but several. For example, the bore diameter may continuously decrease from the beginning of the bore to the wellhead, that is, at the lowest point of the bore.

The conveyor ensures the transport of media. On the one hand, the conveyor serves to convey the medium from the wellhead to the bottom of the well, where the medium is warmed or vaporized via the filler. Subsequently, the heated or vaporized medium is transported via the conveyor back to the wellhead, where the heat energy of the medium is used. The usage can be manifold. Depending on the amount of heat can thus be operated a turbine for electricity production. Furthermore, the heat energy can also be used directly, or via a heat exchanger, to heat buildings or to heat water. The person skilled in the art is familiar with further fields of application.

The conveyor does not necessarily have a drive, such as an electric motor or the like, have. It is also conceivable that the transport of the medium is achieved for example by a density difference between the cold medium and the heated medium.

Likewise, the conveyor does not necessarily have a pipe. In one embodiment, for example, only two separate holes may be provided, wherein in the bottom of a filling material is embedded. The medium is then guided into the first borehole and passes, for example in vapor form, back through the second borehole back to the surface.

In a method for producing a device for obtaining geothermal heat, a filling material is placed in a bore, whereby heat from the filler material is transferable to a medium.

The medium may, for example, be in direct contact with the filling material. In this case, the filler is preferably porous or is present as bulk material, so that the largest possible surface is obtained, which allows a correspondingly large heat transfer with the medium. In this case, the medium is preferably water. Water has several advantages, namely the high specific heat capacity, the high heat of vaporization and low viscosity at a relatively high boiling point. Due to its environmental compatibility, water can also be used in open circuits.

Preferably, however, the medium is guided in a closed circuit. Thus, on the one hand contamination of the bottom, but also of the medium can be avoided. Furthermore, a largely free choice of the medium is achieved because the medium does not come into contact with the soil. Thus, oils, such as mineral oils, synthetic oils or biological oils and other media known to those skilled in the art, which are suitable as heat transfer can be used. When using water, it is also possible to add additives such as antifreeze, salts to lower the freezing point, etc.

Preferably, the device comprises a container having a container wall, a medium inlet and a medium outlet, wherein the container wall is in heat-conducting connection with the filling material and the medium inlet and the medium outlet are connected medium leading to the conveyor.

Preferably, a container having a medium inlet and a medium outlet is embedded in heat-conducting contact in the filling material. For this purpose, the container is preferably first placed in the region of the bottom of the well, in order subsequently to introduce the filling material. In variants, the filling material can first be entered in order to then position the container.

About the medium inlet, the medium to be heated is guided into the container. In the container, the medium is heated and then passes through the medium outlet again from the container. By providing a container now a closed medium circulation is made possible. In this case, the filling material does not necessarily have to be porous or have intermediate spaces, but may also be made compact, with which the heat conduction can be further increased. Gaps or pores can also be filled with a, preferably heat-conducting, medium, so that not necessarily a compact filler material must be provided.

Preferably, the medium is conveyed by the wellhead in a container located at the bottom of the well and then conveyed from the container to the wellhead, wherein the heat is transferred from the filler material via a container wall of the container to the medium. Thus, a physical separation of the filling material and the environment of the bottom of the well is achieved by the medium, with which the medium can be chosen freely. As a result, the medium can also be protected against contamination, with which, for example, corrosion of the device or blockages and damage can be avoided.

In variants can be dispensed with the container. It can also be a supply line and a derivative of the medium in the area of the bottom hole U-shaped connected. In this case, the supply line in the region of the bottom of the well can also be spirally guided in order to increase the surface area for the heat exchange and to increase the time of the medium in the warm region of the bore.

Preferably, the conveyor comprises a downcomer and a riser, wherein the downpipe is connected to the medium inlet medium leading and wherein the riser is connected medium leading to the medium outlet, wherein preferably the downpipe and the riser are coaxially guided.

The downpipe can be fed either via a pump with the medium, or only about the weight of the medium itself. Once in the container, the medium can either only be heated or evaporated. In particular, in the latter case, when the medium is evaporated in the container, this has the consequence that the density of the medium drops massively and can be led back to the surface with pressure, so that the hydrostatic pressure through the medium column in the downpipe can be sufficient. Of course, a pump for feeding the downpipe can still be provided to support respectively for better regulation. Also, if necessary, a pump may be provided at the end of the riser, which may favor or regulate the return of the steam or the heated medium. This may optionally be designed as a vapor pump. The riser is preferably thermally insulated, so that a heat loss during the transport of the steam or the heated medium kept as low as possible and the highest possible heat yield can be achieved. Sufficient possibilities are known to the person skilled in the art for isolation, such as, for example, a double jacket, an insulation coating made of a fiber material, a thermal insulation foam such as rock wool, glass wool, polystyrene and / or vacuum, etc. In a preferred embodiment, the downpipe and the riser pipe can be coaxial be guided.

In variants can also be dispensed with the downpipe. In this case, the container can be supplied with the medium by flooding the borehole with the medium, so that the medium can penetrate into the container through the hydrostatic pressure via a valve. The riser pipe and the downpipe do not necessarily have to be guided coaxially. In particular, if the downpipe includes a pipe extension, it may be advantageous for structural reasons, if the downpipe and the riser are not guided coaxially.

Preferably, the drop tube comprises a pipe extension located within the container, which comprises a deflection for the distribution of the medium, in particular in the region of a wellhead. Thus, the medium can be guided more targeted in the container. Furthermore, it can be ensured that even in a relatively long container, the medium can absorb heat distributed over the entire container. It should in particular be prevented that the container overheats at a lower end, so that the medium entered evaporates too early and does not reach the lower end of the container. With the diversion, the distribution of the medium in the container can be further optimized. Furthermore, this means that the medium input is separated locally from the medium outlet, so that the residence time of the medium in the container can be increased. The deflection may be formed, for example, as lying transverse to the opening plate on which the medium jet impinges vertically and so can be deflected by an angle of for example about 90 ° or more. This deflection can also be such that the medium is at least partially atomized. But the baffle can also be designed as a simple pipe bend in the end of the pipe extension.

In variants, the deflection can also be dispensed with.

Preferably, the tube extension comprises a pressure reducing valve. Thus, the medium inlet can be regulated in the container. Depending on the length of the container or the tube extension, it may be advantageous to provide several pressure reducing valves. The pressure reducing valve can be set fixed or else be variably controllable. The pressure reducing valve or one of the pressure reducing valves can be arranged at the beginning of the pipe extension respectively at the end of the downpipe in the region of entry into the container. Further, this, or another, pressure reducing valve may also be attached to the end of the pipe extension. Such pressure reducing valves are well known to those skilled in the art.

In variants, it is also possible to dispense with the pressure reducing valve. Instead, the tube extension may have a smaller inner diameter or be equipped with baffles, which reduce the flow rate of the medium.

Preferably, the tube extension comprises a plurality of openings through which the medium in the container can be distributed. These openings are preferably distributed over the length of the tube extension. The opening diameter can be varied so that the most uniform possible entry of the medium in the container is possible. The tube extension can thus be closed in a lower region, so that the medium emerges exclusively through the openings in the tube jacket of the tube extension. The tube extension can also have a taper at the lower end, whereby a backwater for the openings is achieved.

In variants, the openings in the tube extension can also be dispensed with, in particular if the container is not too long.

Preferably, the openings in the edge region on a reinforcement, which includes in particular artificial gems. Even if the tube extension is made of particularly hard stainless steel, edges with erosive damage due to the medium must nevertheless be expected, since the medium is typically introduced into the container at high pressure. Therefore, the openings are preferably reinforced so that they can withstand the medium flow unscathed. Such reinforcement can be achieved by shaping and / or the choice of material. Particularly preferably, the openings are taken with artificial gemstones, since they have a particularly high hardness and yet are relatively inexpensive. Alternatively, other materials, such as specially hardened metal alloys and the like, may be used, with either the tube extension or just the areas around the openings being provided with the material.

Depending on the operating pressure of the medium and / or the material of the tube extension can be dispensed with the gain of the openings.

Preferably, the filler has a thermal conductivity of more than 10 W / m * K, preferably more than 40 W / m * K on. Thus, the heat conduction, for example, against a transmission via an air gap between the medium and the environment, be optimized.

In a range of more than 10 W / m * K, for example, high alloyed austenitic steel with about 15 W / m * K, titanium with 22 W / m * K and certain titanium alloys. This has the advantage that it is resistant to corrosion.

In a range of more than 40 W / m * K, for example, unalloyed or low alloy steel (40-50 W / m * K), iron (80 W / m * K) or carbon (120-160 W / m * K). The person skilled in the art is also familiar with other suitable materials for the filling material. Preferably, they are inert materials, which are inexpensive and environmentally friendly and are characterized by a good thermal conductivity.

In variants, a lower thermal conductivity can be accepted if, for example, an inserted container is sufficiently large, so that the desired performance can still be achieved. In this case, calcium carbonate (calcite) or silica with a thermal conductivity of more than 1 W / m * K (water is just half) can be used.

Preferably, however, the filler material comprises metal, in particular metal balls. The spherical shape is preferred because it can minimize the risk of jamming when entering the wellbore. Metal as the material for the filler is also to be preferred, since it can be filled very compactly between the well and container due to the high density. In addition, metals are characterized by a high thermal conductivity.

In variants, as already mentioned above, other substances can be used as filler. Likewise, the materials can also be entered in other shapes or aggregate states in the spaces between the container and the wellbore.

Preferably, the filler material comprises steel balls, preferably with a diameter between 0.5 and 5 mm, in particular between 1 and 3 mm. Although pure iron has about twice as high thermal conductivity, steel balls, in particular made of low alloy steel, are preferable because they do not rust and yet have a fairly high thermal conductivity. Due to the relatively small diameter of the steel balls, a flowable bulk material is achieved, which is particularly easy to get into the spaces between the container and the borehole. Small balls are particularly preferable, since the heat conduction can be further improved.

Of course, the steel balls may differ in diameter from the above information, in particular, a steel powder with a particle size smaller than 0.5 mm or a mixture of steel balls of different diameters can be used.

Preferably, depending on the bottom of the hole, a hole is made in a depth where a temperature of about 300 ° C prevails. Subsequently, at best, first the container and then the filling material is admitted. The drilling depth depends on the thermal gradient of the drilling ground or the region where drilling is to take place. In the case of a large thermal gradient, that is to say when the temperature per meter of drilling depth increases sharply, the drilling depth can be lower than in the case of a drilling ground in which the temperature per meter of drilling depth increases less sharply.

The temperature at the bottom of the well is preferably between 350 ° C and 500 ° C. Depending on the bottom of the hole, this temperature can be reached even at shallower depths. Depending on the desired performance, the temperature may be lower, for example between 200 ° C and 300 ° C. This depends on the purpose of the geothermal energy. If only a heating, a thermal bath or the like to be fed, even lower temperatures may be sufficient, so that typically the drilling depth can be chosen lower. Preferably, however, an optimal energy yield is sought.

However, it is clear to the person skilled in the art that the device can be operationally suitable even at shallower depths. This depends not least on the desired performance of the device. Thus, a drilling depth of 5 to 7 km or even between 1 and 5 km may be sufficient. If the method, or the device used for example in a volcanic area, the drilling depth can also be much lower. On the other hand, the drilling depth can be greater than 7 km.

From the following detailed description and the totality of the claims, there are further advantageous embodiments and feature combinations of the invention.

Brief description of the drawings

The drawings used to explain the embodiment show: <Tb> FIG. 1 <SEP> is a schematic diagram of a geothermal heat recovery apparatus of a first embodiment; and <Tb> FIG. 2 <SEP> is a schematic representation of a container of a second embodiment.

Basically, the same parts are provided with the same reference numerals in the figures.

Ways to carry out the invention

Fig. 1 shows a schematic representation of a device for recovering geothermal heat of a first embodiment. In a borehole 1 to a container 10 is placed on the well base 2, which is connected via a downcomer 20 and a riser 30 with a device 50 in the region of the wellhead, which comprises a heat exchanger, a steam dryer and a generator, medium leading. The resulting between the bottom 2 and the container 10 gap is presently filled with a filler 40, which is present as steel balls with a diameter from about 0.5 mm. For an optimal heat transfer between the bottom 2 and the container 10 is achieved.

The bottom of the hole 2 is below 5 km below the surface of the earth, wherein at the bottom of the well an elevated temperature of over 300 ° C prevails. The present embodiment comprises a container 10 having a length of 200 m or more with a diameter of over 15 cm. The container 10 is thus formed substantially as a tube with an enlarged inner diameter.

As the heat carrier water is used in the present embodiment. The water passes through the hydrostatic pressure independently, that is without additional drive by pumps or the like, via the provided with an insulation 21 downpipe 20 in the downcomer immediately subsequent downcomer extension 26, which is already within the container 10 and therefore is not isolated , At the end of the drop tube 20 is a pressure reducing valve 22, whereby the water supply in the container 10 is controllable. In the present case, it is a valve with a constant setting. This is pre-set depending on the drilling depth and the downpipe diameter.

Finally, the water passes into the container 10 via the pressure-reducing valve 22. The heat of the bottom 2 of the drilling is now transferred via the filling material 40, that is to say via the steel balls, to the container wall. From the container wall, the heat is conducted to the medium, in this case water. The water is thus vaporized and passes through the riser pipe 30, which is insulated with an insulating layer 31 against heat loss, upwards. The hot steam finally passes into the heat exchanger 50, where with the heat energy, for example via a steam turbine, a power generator can be operated. Before the steam reaches the steam turbine, it is passed through a superheater or steam dryer. Thus, the efficiency of the steam turbine can be increased. However, this steam dryer can also be dispensed with if the steam temperature at the wellhead is above 374 ° C., since wet steam only exists between 100 ° C. and 374 ° C. (based on normal pressure), whereas at a temperature of more than 374 ° C. the steam already present as dry steam.

After the condensed steam, the residual heat has been withdrawn, the now cooled water can be passed through the downpipe 20 into the container, whereby the cycle begins again.

Fig. 2 shows a schematic representation of a device for obtaining geothermal heat of a second embodiment. As in the first embodiment, the container 10.1 is embedded in the well bottom (not shown) in a filler material 40 made of steel balls. In contrast to FIG. 1, the drop tube 20.1 and the riser 30.1 are coaxially guided until they enter the container 10.1. In order to locally separate the outlet from the downpipe 20.1 and the inlet of the riser pipe 30.1, the riser pipe in the present case opens inside the container 10.1 in an upper region, ie when it enters the container 10.1, laterally from the downpipe 20.1. For this purpose, the downpipe 20.1 has an opening there. However, other modifications of the same principle are also known to the person skilled in the art (the outlet can also be formed just above the container 10.1).

Both the drop tube 20.1 and the riser 30.1 are presently thermally insulated (not shown). The downpipe 20.1, that is, the outer of the two coaxial tubes, immediately before entry into the container 10.1, a pressure reducing valve 22.1, which controls the entry of the water or the heat transfer medium. The skilled person is aware of the design of such annular valves, for example, the pressure reducing valve 22.1 may be formed only as a taper of the downpipe.

Alternatively, the entrance of the riser 30.1 also outside, that is, formed above the container, so that the pressure reducing valve 22.1 can be arranged between the inlet and the container. The entry of the riser 30.1 would be easily connected by a piece of pipe to the container, so that even a simple design, in particular controllable pressure reducing valve 22.1 can be provided.

The downcomer extension 20.1 has in the present case laterally openings 23, which are reinforced on the edge with artificial gemstones and thus protected against erosion. Through these openings, the water flows at high pressure and is uniformly sprayed in the container 10.1. In this embodiment, located at the distal end of the downcomer extension 26.1, ie at the outlet of the downcomer extension 26.1, a nozzle 25, which is directed downwards, in the direction of the downpipe 20.1. Below the nozzle 25, a curved deflecting plate 24 is connected to the downcomer extension 26.1 in such a way that water exiting from the nozzle 25 strikes the concave side of the deflecting plate 24 and is sprayed on the circumference, laterally.

In a third, not shown variant can also be dispensed with the baffle in the embodiment according to FIG. Likewise, the embodiment according to FIG. 2 can also be equipped with a side by side parallel, ie not coaxially guided, downpipe and riser pipe. In a fourth variant, not shown, the embodiment according to FIG. 1 may comprise such a deflection plate at the bottom of the downcomer extension 26. In a fifth embodiment, not shown, the embodiment according to FIG. 1 may have openings according to the embodiment of FIG. 2.

The steel balls may also have other diameters. In addition, other materials for the heat transfer between bottom 2 and container 10 may be provided. Thus, the gap could also be filled with a cementitious material or poured, which has a sufficiently good thermal conductivity. In addition, the stability of the borehole could be further improved.

As a heat carrier, in particular in the preferred closed circuit of the heat carrier, an oil or other liquids may be provided. The pressure reducing valve 22 may also be mounted at the end of the downcomer extension 26.

Instead of leading the water vapor through a heat exchanger, it is also possible to directly operate a steam turbine or the like (for example for power generation).

Although the bore is shown vertically in FIG. 1, it is clear to the person skilled in the art that such bores can also have a certain angle of inclination. This can for example be between an angle of 1 ° to 10 ° to the vertical or be greater.

In summary, it should be noted that, according to the invention, a particularly efficient apparatus for obtaining geothermal energy is provided.

Claims (12)

A device for obtaining geothermal heat from a bore (1) having a wellhead and a bottom (2), comprising a conveyor, whereby a medium from the wellhead to the well (2) and from the well (2) is conveyed to the wellhead, characterized in that the device further comprises a filling material (40) introduced into the drilling base (2), with which heat can be transferred to the medium. 2. Device according to claim 1, characterized in that it comprises a container (10) having a container wall, a medium inlet and a medium outlet, wherein the container wall is in heat-conducting connection with the filling material (40) and the medium inlet and the medium outlet leading to the medium Conveyor are connected. 3. A device according to claim 2, characterized in that the conveying device comprises a downpipe (20) and a riser (30), wherein the downpipe (20) is connected to the medium inlet medium leading and wherein the riser pipe (30) connected medium leading to the medium outlet is, wherein preferably the downpipe (20) and the riser pipe (30) are guided coaxially. 4. The device according to claim 3, characterized in that the downpipe (20) within the container (10) lying tubular extension (26), which in particular in the region of a wellhead of the tubular extension (26) comprises a deflection for the distribution of the medium. 5. Apparatus according to claim 4, characterized in that the tube extension (26) comprises a pressure reducing valve (22). 6. Apparatus according to claim 4 or 5, characterized in that the tube extension (26) comprises a plurality of openings (23) through which the medium in the container (10) can be distributed. 7. The device according to claim 6, characterized in that the openings (23) have a reinforcement in the edge region, which comprises in particular artificial gems. 8. Device according to one of claims 1 to 7, characterized in that the filling material (40) has a thermal conductivity of more than 10 W / m * K, preferably more than 40 W / m * K. 9. Device according to one of claims 1 to 8, characterized in that the filling material (40) comprises metal, in particular metal balls. 10. The device according to claim 9, characterized in that the filling material (40) comprises steel balls, preferably with a diameter between 0.4 and 5 mm, in particular between 0.5 and 3 mm. 11. A method for obtaining geothermal heat from a wellbore having a wellhead and a wellbore (2), wherein a medium is conveyed from the wellhead to the wellbore (2) and then from the wellbore (2) to the wellhead by a transport means, characterized in that heat is transferred from a in the bottom (2) embedded filling material (40) to the medium. 12. The method according to claim 11, characterized in that the medium is conveyed from the wellhead into a located on the bottom (2) container (10) and is subsequently conveyed from the container (10) to the wellhead, wherein the heat from the filler (40) is transmitted to the medium via a container wall of the container (10).