EP3853533A1

EP3853533A1 - Method and device for obtaining useful energy from geothermal heat

Info

Publication number: EP3853533A1
Application number: EP19755388.6A
Authority: EP
Inventors: Uwe PFÜTZE-RÄMSCH
Original assignee: Climasolutions GmbH
Current assignee: Climasolutions GmbH
Priority date: 2018-08-24
Filing date: 2019-08-21
Publication date: 2021-07-28
Also published as: CN113039398A; US20210325090A1; AU2019323662A1; CA3110280A1; EP3614069A1; WO2020038978A1

Abstract

The invention relates to a method for obtaining useful energy from geothermal heat, in which in a coaxial tube (1) introduced into the earth in a deep bore, having an outer tube (2) and an inner tube (3), in which in an end portion (4) of the coaxial tube (1) countersunk in the deep bore, outer tube (2) and inner tube (3) have a connection to one another, and a heat medium (8), which is liquid under standard conditions, is introduced into the outer tube (2), and flows in the direction of the end portion (4) of the coaxial tube (1) countersunk in the deep bore. The heat medium (8) is heated while absorbing geothermal heat and passes through a phase transition in the region of the end portion (4), and enters the inner tube (3) in gaseous form flowing upwards therein, up to an upper end of the coaxial tube that is located on the surface of the earth, wherein with the flowing, gaseous heat medium (8), a flow generator (14) for generating electrical energy is operated. By means of this method, kinetic energy of a flow of the gaseous heat medium generated by geothermal heat is converted very effectively and with little expenditure to obtain usable energy.

Description

Process and device for obtaining useful energy from geothermal energy

The present invention relates to a method and a device for gaining useful energy from geothermal energy.

The use of geothermal energy to generate energy has been known for a long time. The first geothermal power plant used for the generation of electrical energy was put into operation at the beginning of the 20th century. Currently, not least against the background of a search for climate-neutral and CCh-emission-free forms of energy generation, efforts are being made to make geothermal energy better and more usable in geothermal applications for energy generation.

In particular, there are geothermal facilities and methods for generating heat and / or electrical energy using surface geothermal energy (at depths of up to 400m) or deep geothermal energy (at depths of more than 400m). In the known methods, water is geothermally heated to great depths. The heated water, also called thermal water, is transported to the surface of the earth the geothermal energy absorbed by the water is then used for the production of useful energy.

In deep geothermal energy, a distinction is made between hydrothermal and petrothermal systems. In the hydrothermal systems, water stored in deep layers is tapped and pumped to the surface and its stored heat is used to generate energy. In the petrothermal systems, geothermal energy stored in deep rock is taken up with water that is pumped there and brought into heat exchange with the deep rock, and the water that is heated in this way is pumped to the surface for energy generation there. With hydrothermal systems, open systems are formed in which matter (water) located in the depths is removed and, in exchange, a substitute is usually conducted and deposited there from the earth's surface. The water taken from the depth can also be returned. There is therefore a particular risk of contamination entering the deep water. Petrothermal systems can also be implemented with geothermal probes, in which the water is conducted in a closed circuit, which absorb the geothermal heat stored in the deep rock through a wall of the geothermal probe.

In addition to the problem that there is a problem with hydrothermal systems, namely the possible entry of impurities and contaminants into the deep-lying reservoir of the thermal water, the known systems also have the disadvantage that, in particular for the generation of electrical energy, the efficiency is generally low can be achieved. For the use of the water used in the known systems as a heat medium to drive an electric generator machine, the water must reach the surface at a temperature of at least 80 ° C. The water can only be used directly to drive a steam turbine, for example, if it emerges in vapor form on the surface. This can only be done with very deep Drilled holes can be reached (on average the temperature rises by 3 ° C at a depth of 100 m, so that temperatures of 100 ° C in normal locations can only be found at very great depths) or with holes in the area of special locations, in which even in Shallow depths are particularly high temperatures, for example due to volcanic activity or special anomalies of the earth's magnetism.

Here, the invention is intended to remedy the problem and to specify a method and a device with which geothermal electrical energy can also be generated with or with which even in normal locations and a lower drilling depth.

This task is solved and the set goal is achieved first of all by a method for obtaining useful energy from geothermal energy with the features of claim 1. Advantageous developments of a method according to the invention are specified in claims 2 to 8. With the invention is further proposed as a solution to the above object a device for gaining useful energy from geothermal energy with the features of claim 9. Advantageous developments of a device according to the invention are described in claims 10 to 15.

In the method according to the invention, a coaxial tube is introduced into the earth and inserted into a deep bore. The introduction of the deep hole and the insertion of the coaxial tube into the deep hole can be steps attributed to the method. However, the method can also be carried out without these steps, that is to say in the aftermath and detached from a separately made introduction of the bore and insertion of the coaxial tube. The coaxial tube has an outer tube and an inner tube and is sunk with an end portion in the deep hole, typically extends with this end portion to the bottom of the deep hole. In the area of this end section, the outer tube and the inner tube of the coaxial tube are connected to one another in terms of flow technology, ie a medium guided in the outer tube can be transferred into the inner tube there. to step. When carrying out the method, a liquid medium which is liquid under standard conditions (SATP conditions) is introduced into the outer tube and flows in the direction of the end section of the coaxial tube sunk into the deep bore. The standard conditions are determined by the International Union of Pure and Applied Chemistry (IUPAC) as a temperature of 25 ° C and at the same time a pressure of 1000 mbar. This pressure of 1000 mbar is also referred to in this application as normal pressure.

The heat medium then flows in the direction of the end section of the coaxial tube, which in particular can be done exclusively by gravity. The heat medium absorbs geothermal energy and is thereby heated. An additional Liche heating can also be done by rubbing the heat medium flowing along a wall of the outer tube. The main heat absorption is accomplished by geothermal energy. In a section of the coaxial pipe located in the last third of the coaxial pipe, a phase transition of the heat medium then takes place, which passes into the gas phase in this area and enters the inner pipe in gaseous form in the area of the end section. The now gaseous heat medium rises in the inner tube and flows upwards. The flowing, gaseous heat medium is then passed to a flow generator which is driven by this gas flow to generate electrical energy.

The heating medium can e.g. Be water. In particular, however, it can also be a different heating medium from water, for example one that has a boiling point that is significantly lower than water at normal pressure. The boiling point of such an alternative heat medium at normal pressure can be in a range between 30 ° C and 60 ° C.

A chimney effect can be used to raise the heat medium in the inner tube. This can be done in particular in that the inner tube has a diameter in the area of an outlet at or in the area of the earth's surface. sererexpansion, by means of which a relaxation and reduction of the temperature of the outflowing gas compared to a temperature of the gaseous heating medium located in the region of the end section, in particular at a lower end of the inner tube, is achieved.

In the method according to the invention, therefore, a thermal energy absorbed and stored in the heat medium is not primarily used, but a kinetic energy of the gas stream used to drive the flow generator when the gaseous heat medium rises in the inner tube is used. With a suitable design of the process parameters, considerable flow velocities, speeds of well over 200 km / h, can be obtained with which appropriately designed flow generators with very small dimensions can be driven. In particular, it is also possible to divide the gas flow into different partial flows in order to drive more than one flow generator in parallel.

The inner tube can have an adhesion-reducing structure on its inner surface, e.g. in the form of a coating, e.g. a structure that shows the so-called lotus effect. In this way, adherence of entrained particles or the like in the gas stream rising in the inner tube is prevented, so that the inner tube remains free in its diameter. This coating can also reduce friction, so that the speed of the gas rising in the inner tube is not reduced. For such a reduction in friction, the inner tube can also have another suitable structure, e.g. in the form of a coating on the inside surface.

For further use of the energy carried by the flowing gaseous heat medium, in particular absorbed by geothermal energy, it can be provided that the heat medium is also passed through a heat exchanger after flowing through the flow generator, and so on gain usable thermal energy. Such a combination increases the overall efficiency of the process.

The heat medium can advantageously be liquefied after flowing through the flow generator (and after a possible flow through the heat exchanger) and brought back in liquid form into the outer tube of the coaxial tube. In this variant, the process is operated with a heat medium that is conducted in a closed circuit, so that new heat medium does not have to be constantly added.

The heat medium in the outer tube can advantageously be guided on a spiral path in the direction of the end section sunk into the deep bore. This can be done, for example, by providing corresponding guide structures in the outer tube, for example in a spiral shape, for example, welded-on guide plates mounted on an outer wall of the inner tube. The guidance of the heat medium in such a spiral shape has various advantages. Thus, in his case, the accelerated heat medium in the direction of the end section is pressed outwards by a spiral path in the outer tube, in the direction of the outer wall, so that it is in particularly good contact with the outer wall there and can effectively absorb the geothermal energy entering it. In addition, such a guide creates friction between the wall of the outer tube and the heat medium, which can lead to additional heating of the heat medium and thus contribute to heat input. Corresponding guide structures, which subdivide the outer tube of the coaxial tube equally into individual height sections, also prevent - at least in the dynamic case in which the heat medium is not in the outer tube, but flows in corresponding compartments or sections without the outer tube being completely filled is - there is a high dynamic pressure in the end section of the coaxial tube, which is also above the boiling point at the temperatures of the heating medium reached by the heat absorbed of the heat medium are at standard conditions, could prevent a phase transition into the gas phase of the heat medium.

Alternatively and also advantageously, the heat medium in the outer tube, but also in at least one section of the outer tube, in particular in a plurality of such sections, can be accumulated by means of barriers introduced into the outer tube, for example tel-type barriers, and via ver contained in the barriers tically deeper section of the outer tube leading nozzle openings are expanded under expansion in the vertically deeper section. This procedure has the advantage that, depending on the amount of the heating medium filled into the outer tube, a water column is created quickly, slowly or constantly on the plate-shaped barrier, for example. This creates a static pressure on the barrier in each section, which can be adjusted via the rate of addition of the heat medium and the opening cross-sections of the nozzle openings, for example to 10 bar. This static pressure prevents a phase transition of the heat medium in this section which is premature for the operation of the method. In a section located vertically below the barrier, the heat medium flowing through the nozzle openings with pressure causes expansion (relaxation), which leads to a cooling of the heat medium and thus to an increase in the temperature difference between the heat medium and the pipe wall. This also cools down the pipe wall, which in turn increases the thermal conductivity of the rock. This results from the entropy theorem of thermodynamics, the second main theorem of thermodynamics. The increase in the thermal conductivity of the rock also results in an increase in the thermal conductivity, which means that thermal energy flows more quickly from a greater distance to the outer tube of the coaxial tube. The cooled heat medium then falls in the section vertically below the nozzle openings at a high speed, which can be, for example, at least 70 m / s, except for a further column of heat medium which is stowed and which is located on the possible additional barrier. The heat medium can thus, despite a temperature of the rock, which is above the phase change point at normal pressure, not evaporate, because the static pressure of the load-bearing column of the heat medium prevents this. It can be at least 5 bar, for example. On a barrier located at the bottom in the outer tube, the nozzle openings are then dimensioned and arranged such that the temperature of the heat medium no longer reaches below the phase change limit with cooling, but the geothermal expansion effect can still be used.

The distance between the barriers and / or the opening cross section of the nozzle openings are determined depending on which geothermal conditions are to be found at the place of use of the coaxial tube. It is particularly desirable to set these values so that the expansion achieved by means of the barriers and nozzle openings results in a temperature difference between the temperature of the surrounding earth layers (of the rock) in the respective depth, and the temperature of the tube wall of the outer tube between 20 K and Is 25 K.

Basically, it is also conceivable to change the opening cross sections of the nozzle openings during operation for the control of the system.

This can e.g. by means of remotely adjustable nozzle openings (in the manner of an aperture) or also by inserting inserts which reduce the opening cross sections into the nozzle openings (or removing such inserts from the nozzle openings), which e.g. with the help of small robots arranged in the outer tube and controllable by means of a control.

The depth of the deep hole is in particular at least 1000 m, advantageously at least 1300, in particular at least 1500, can furthermore in particular be at a maximum depth of 6000 m, depending on the temperature required for the process, which also depends on the selected heating medium , but also a maximum of 2500 m, in particular a maximum of 2000 m. In accordance There is a depth of around 48 ° C to 78 ° C (at depths up to 2500 m) at normal geological locations if the rule of thumb is 3 ° C per 100 m and 6 ° C for the first 100 m ). If depths of up to 6000 m are selected, temperatures of over 130 ° C can be obtained there. As mentioned at the beginning, temperatures from 48 ° C to 78 ° C are not yet sufficient to operate an electrical generator with the water used in conventional processes. With a suitable heat medium that has a boiling temperature in the range between 30 ° C and 60 ° C under standard conditions, the effect described above can be achieved and the method described above can also be operated with less deeply driven holes. In particular, dodecafluoro-2-methylpentane-3-1 can be used as a heat medium used as an alternative to water. This is a colorless and odorless liquid under standard conditions, which is offered, for example, by 3M under the trade name Novec ^® , for example as Novec ^® 649. However, as already mentioned, water can also be used as a heating medium find, where then higher temperatures, thus deeply sunk holes are required.

Even if a maximum depth of the deep hole is mentioned above and, for example, is specified as 6000 m, it is easily conceivable to deep hole the deep hole, e.g. to advance up to 10,000 m and to insert a coaxial pipe according to the invention into a correspondingly deep deep hole. However, since the costs of deep drilling with a greater depth increase significantly and in particular also not linearly, shallower depths of the deep drilling are preferred - provided suitable geothermal conditions are found in the drilled layers for the process.

A device according to the invention for extracting energy from geothermal energy has the following elements: • a coaxial tube inserted in a deep bore. This coaxial tube has an outer tube and an inner tube, the outer tube and inner tube having a connection to one another in an end section of the coaxial tube that is countersunk in the deep bore. The coaxial tube is typically guided with the end section to a bottom of the deep bore.

• Arranged in the outer tube, the cross-section of which is through guide structures, in particular spiral guide plates or through which there are nozzle openings, for example plate-shaped barriers;

• a with an inlet opening of the outer tube, which is provided at an end section axially opposite the end of the coaxial tube, connected lead;

A gas flow channel connected to an outlet opening of the inner tube, which is provided at the end of the coaxial tube;

A flow generator arranged in the gas flow channel for generating electrical energy. The flow generator is arranged in such a way in the gas flow channel that a rotor of the generator is moved by inflowing gas to drive the generator;

A heat medium arranged to flow through the coaxial tube, which is liquid under standard conditions and a boiling point at normal pressure (i.e. 1000 mbar) of between 30 ° C and 120 ° C, e.g. of between 30 ° C and 60 ° C.

With this device according to the invention, a method as described above can be carried out. The two examples of guide structures, i.e. spiral guide plates on the one hand or barriers provided with nozzle openings, such as plate-like barriers, which are also used as expansion plate can be called, give the advantages described above in connection with the method.

In the device, in particular a section of the inner tube arranged at the end of the coaxial tube can have a diameter widening. There, a diameter of the inner tube is then expanded starting from a first diameter, which the inner tube has along its extent to the end section, to a second diameter, which the outlet opening has. By this measure, a desired effect of the chimney during operation of the device is reinforced in the inner tube, by which there is an upward flow of gaseous heating medium, which is drawn in the direction of the end of the coaxial tube on the surface of the earth.

The chimney effect can be influenced, in particular for starting up the system or the device, but also during operation, by setting a temperature difference in order to support the control of the system. For this purpose, a device for controlled heating and / or cooling of the wall of the inner tube can be seen, in particular in the upper end portion of the inner tube.

The device according to the invention may also have a flow line with a diameter extension behind the flow generator in the flow direction. This can act as a diffuser and achieve a reduction in the flow rate of the heating medium.

The device can also additionally have a heat exchanger which is arranged on the other side of the flow generator, that is to say on the side which is opposite the flow channel connecting the outlet opening to the flow generator. Usable thermal energy can then be obtained with such a heat exchanger. If, as mentioned above, a flow line seen in the flow direction behind the flow generator is provided with a diameter extension, this is advantageously in front of the inflow opening of the heat exchanger, so that the heat medium flows through the heat exchanger at a reduced speed.

In the device, the outlet opening and the inlet opening are advantageously connected to one another in a closed line system, so that an overall closed circuit is obtained in which the heat medium can circulate. In such a closed circuit, in particular, a degassing and storage container can be arranged, into which the heat medium flowing through the flow generator flows after liquefaction, which can take place by expansion and cooling, can degas there and return to the liquefied heat medium Directed to the inlet opening of the outer tube and can be reintroduced into the circuit.

Advantageously, one or more valve (s) can also be provided in the device, which can be arranged in particular in the feed line and / or the gas flow channel for the targeted opening and / or closing of the feed line and / or the gas flow channel and which can be controlled are connected to the automatic actuation of the at least one valve. Via such valves, which can also be flow control valves for the targeted setting of a flow rate, the device can be controlled before. It is essential for the operation of the device that the heat medium flows through the coaxial tube in a dynamic process. In particular, only as much liquid heat medium has to be added as evaporates in the end section of the coaxial tube and rises through the inner tube. If too much heat medium is added here, there is a risk that the entire outer tube will be filled with (still liquid) heat medium and the resulting hydrostatic pressure will prevent the phase transition process in the end section of the coaxial tube, causing the system to come to a standstill. Accordingly, one must Control system to ensure that the dynamic process is maintained. In order to monitor and control this process, responsive sensors can also be provided, which record characteristic values of the process, such as pressure and temperature of the outflowing gaseous heating medium or a volume flow of the heating medium, and are available as input variables for the process control of the control put.

The heating medium used in the device measured in the invention can in particular dodecafluoro-2-methylpentane-3-1, but can also e.g. Be water.

Further advantages and features of the invention result from the following description of an exemplary embodiment with reference to the attached figures. Show:

1 shows a schematic sketch of a device according to the invention and illustrates the method according to the invention in a first possible embodiment;

2 shows a schematic sketch of a device according to the invention and illustrates the method according to the invention in a second possible embodiment;

Fig. 3 is an enlarged, schematic sectional view of the coaxial tube of the embodiment shown in Fig. 2 and

Fig. 4 schematically shows a top view of a nozzle opening

Expansion plate of the configuration according to FIG. 2.

FIG. 1 shows - very schematically - a sketch of a first possible embodiment of the invention, which also schematically explains the method according to the invention in a first embodiment variant. A coaxial tube 1 is introduced into a borehole of a deep bore (not shown in more detail here). This is closed at one end inserted into the borehole and consists of an outer tube 2 and an inner tube 3. The inner tube 3 is shorter than the outer tube 2, so that in an end section 4 the outer tube 2 is connected to the inner tube 3.

The depth of the bore into which the coaxial tube 1 is inserted, and thus also the length of the coaxial tube 1, can be in particular between 1000 m and a maximum of 6000 m, for example also a maximum of 2500 m, in the exemplary embodiment shown is approximately 1600 in particular m.

The outer tube 2 can be thermally insulated from the inner tube 3 to a depth of approximately 1000 m. On the inner tube 2 baffles 5 (which can be shaped as a continuous baffle) are fixed, which extend into the passage of the outer tube 2 and up to its outer wall and spiral or spiral in the direction of the end portion 4.

The inner tube 3 opens out at the end opposite the end of the coaxial tube 1, which is lowered into the borehole, with an expansion 6.

A heating medium 8, which is liquid under standard conditions, is stored in a degassing and storage container 7. It is in the degassing and before storage container 7 in the liquid phase. Liquid heat medium 8 is continuously introduced into the outer tube through a line 9 by means of a pump 10 and via an inlet 11. In the heat medium can be eg., Be dodecafluoro-2-methyl pentane-3-1, for example, from the 3M Company under the trademark Novec ^® 649 displaced fluid. This heating medium has, for example, a boiling point under standard conditions of 49 ° C. But it can also What water or another fluid can be used as a heating medium. In the line 9, a valve 11 is provided, with which the line 9 is closed and with which the flow rate of the heating medium 8 through the line 9 can be controlled.

Through the turns of the baffles 5, which on the outer wall of the inner tube 3 e.g. can be welded, the heat medium 8 flows in a rotating movement in the outer tube 2 down towards the end section 4. Due to the increasing speed at which the heat medium 8 flows downwards and through the acting central force, the heat medium 8, the further it is in the Depth reaches, pressed with greater force to the outer wall of the outer tube 2. The heat medium 8 absorbs geothermal heat energy, this being done particularly effectively by pressing the heat medium 8 against the outer wall of the outer tube 2. In addition, further heat is generated by the friction of the heat medium 8 on the inside of the outer wall of the outer tube 2, which causes the temperature of the heat medium 8 to increase additionally.

The guide plates 5 guided in spiral turns are provided up to a point at which a phase transition threshold begins. This is a point in the depth of the hole at which the heat medium 8 has warmed up to the boiling point by the absorption of heat described above and is now gaseous. The lowest section of the inner tube 3, e.g. the last 100 m, is not thermally insulated from the outer tube 2, so that the baffles 5 in this area also represent additional heat transfer surfaces. Since the hot gaseous heat medium 8 rises in the inner tube 3, the inner tube 3 and the baffles 5 also heat up, and can thus also emit thermal energy.

When the heat medium 8 reaches the thermal temperature range or the phase transition threshold, the heat medium 8 begins to evaporate, as mentioned. Due to the constant feeding of heat medium 8 into the outer tube 2 of the coaxial tube 1, more and more heat medium 8 realizes the phase change. Sieren. As a result, the heat medium 8 then present in gaseous form in the end section 4 cannot rise upwards in the outer tube 2. The baffles also do not allow the gaseous heat medium 8 to rise. The gas-shaped heat medium 8 therefore rises in the inner tube 3, driven in particular by a negative pressure which arises as a result of a chimney effect, on upwards in the direction of the upper end of the coaxial tube 1. There it is relaxed and cooled in the area of expansion. For the temperature reduction of the heat medium 8, therefore, no technical aids and no use of energy are required, as a result of which the overall efficiency of the method would otherwise deteriorate.

By widening the tube diameter, the temperature difference between the sunk in the borehole lower end of the coaxial tube 1 and the highest point of the inner tube 3, in which the gaseous heating medium 8 flows, is greater. This once again increases the chimney effect, which drives an accelerated rise of the gaseous heat medium 8 inside the inner tube 3. As a result, the gaseous heat medium 8 flowing rapidly upwards receives a high kinetic energy. The relaxation and temperature reduction of the gaseous heat medium 8 in the expansion is - by appropriate design of the geometric conditions - advantageously limited to 5K above the boiling point of the heat medium 8, so that this is still gaseous even after the Ent and no phase change back in the liquid phase takes place until the kinetic energy of the heating medium 8 has been used.

The flow rate at which the gaseous heat medium 8 flows upwards, and thus its kinetic energy (mass x speed), of the gaseous heat medium 8, is dependent on the depth of the bore, the temperature of the gaseous heat medium 8, its density and the temperature difference between the lower end of the coaxial tube 1 and the highest point of the inner tube 3, in which the gaseous heating medium 8 flows. The gaseous heat medium 8 is in the area of expansion in an outlet from the inner tube 3 transferred into a line 13 and through this upper table to a flow generator 14, which works similar to a wind turbine. The flow generator 14 is composed of a flow turbine 1 5, which is flown by the gaseous heat medium 8 and is set in rotation, and a generator 16 directly coupled to and driven by the flow turbine 15 for generating electrical energy.

A valve 17 in line 13 can be used to block and selectively open line 13 and, if necessary, also to set a flow rate through line 13. For starting the system, the valve 17 is closed, so that by the constantly refilled and evaporating heat medium by 8, which rises in the inner tube 3, the pressure and the temperature within the coaxial tube 1 steadily increase except for the continuous operation of the A direction required value. If the required temperature and the pressure has been reached, a control opens valve 17 automatically. The temperature and the pressure are maintained by the constant tracking of the liquid heat medium 8 by means of the pump 10, since the tracked heat medium 8 constantly pulls the phase change in the area of the phase transition threshold and thus supplies gaseous heat medium 8. This process is comparable to the way a steam boiler works with continuously flowing feed water.

After flowing through the flow turbine 15, it is passed further in line 18 to an optionally available heat exchanger 19, where the gaseous heat medium 8 can be extracted from the thermal energy still present. This thermal energy can then be used, for example, for district heating or for production heat supply. The cooled, still gaseous heat medium 8 flows back into the degassing and storage container 7 via a further line 20, where it carries out the phase change from gas mig too fluid. The degassing and storage container 7 can be cooled with outside air, for example. It serves to change the phase of the heat medium 8 and at the same time serves as a storage container for supplying the heat medium 8 into the outer tube 2 of the coaxial tube 1. The cycle is closed.

If no electrical energy is to be generated, the flow turbine 15 and thus the flow generator 14 can already be avoided via a dashed line and switchable short-circuit line 21 with valves not shown. In a similar manner, a short-circuit line 22, also shown in dashed lines, can be activated by means of valves, not shown, if no thermal energy is desired. Then the heat medium 8 is passed to the heat exchanger 18 directly from the flow turbine 15 in the degassing and reservoir 8.

With 23 an installation building is indicated, in which the technical facilities are included.

FIGS. 2 to 4 show, very schematically, a sketch of a second possible embodiment of the invention, which also explains the method according to the invention in a second embodiment. The basic principle of the device for utilizing geothermal energy in the variant shown in FIGS. 2 to 4 is the same as that shown in FIG. 1 and described above. To this extent, the same reference numerals are used in FIGS. 2 to 4 to denote the same or functionally identical elements.

The device shown in FIGS. 2 to 4 also contains, as a core piece, a coaxial tube 1 sunk into a deep bore. In this embodiment, too, the coaxial tube 1 is closed at one end inserted into the borehole and consists of an outer tube 2 and an inner tube 3. The inner tube 3 is also shorter than the outer tube 2 here, so that the outer tube 2 is connected to the inner tube 3 in an end section 4.

The depth of the bore is dimensioned in this embodiment as described before using the first embodiment and is in the same dimensions. It also depends on which temperatures are required for a phase transition of the heat medium to be obtained.

The outer tube 2 can also in this over a first vertical section, e.g. 2/3 of the total length of the outer tube 2 can be insulated from the inner tube 3.

In the embodiment shown in Figures 2 to 4 are not on the inner tube 2 as in the previous example spiral or screw-shaped in the direction of the end portion 4 baffles 5 fixed, but, in particular at regular intervals, barriers in the form of So-called. Learn expansion plates 25. These expansion plates 25 complete the entire cross-section of the outer tube 2, but have passage nozzles 26, ie nozzle-shaped openings that penetrate the expansion plates 25. These passage nozzles 26 may in particular be conically tapered in a vertically downward direction. The expansion plate 25 thus divide the outer tube 2 into a plurality of vertically superimposed sections which are connected in terms of flow technology via the passage nozzles 25.

Also in this embodiment, a heating medium 8 is stored in a degassing and storage container 7, which is liquid under standard conditions. This heat medium can in turn be water or, for example, dodecafluoro-2-methylpentane-3-1. It is in the degassing and storage container 7 in the liquid phase. Through a line 9, liquid heat medium 8 is continuously introduced into the outer tube 2 by means of a pump 10. In the exemplary embodiment from FIGS. 2 to 4, line 9 can also be used (not here shown) valve can be provided with which the line 9 is closed and with which the flow rate of the heating medium 8 through the line 9 can be controlled.

The heat medium 8 filled into the outer tube 2 now falls free of a section until it hits the first expansion plate 25. The heat medium 8 builds up there, since the flow rate through the passage valves 26 is comparatively low. Due to the accumulation of the inflowing thermal medium around 8, a standing column of the thermal medium 8 forms on the expansion plate 25, in which a static pressure builds up.

When passing through the passage nozzles 26 there is a relaxation (expansion) of the heat medium 8, which then leads to cooling. This means that the heat medium 8 can in turn absorb heat from the environment better.

This accumulation and relaxation of the heat medium 8 learn at the Expansionstel 25, or when passing through the passage nozzles 26 is now repeated in the lower area of each section or when passing into the next lower section. The static pressure of the column of the heat medium 8 which is respectively loaded on the expansion plate 25 also prevents it from going through a phase transition into the gaseous phase at an early stage. Also, the cooling effect obtained by the expansion when the heat medium 8 passes through the passage nozzles 26 prevents a premature phase transition.

After passing through the passage nozzles 26 of the expansion plate 25 arranged at the bottom in the outer tube 2, the heat medium then reaches a phase transition threshold. Thus, by absorbing heat in the end section as described above, heat medium 8 is finally reached up to the boiling point also given the conditions (pressure, temperature) prevailing there. warms and is now gaseous. Here, too, the lowermost section of the inner tube 3, for example the last third or even the last 100 m, cannot be thermally insulated from the outer tube 2, so that the expansion plates 25 can additionally represent heat transfer surfaces in this area. Since the hot gaseous heat medium 8 rises in the inner tube 3, the inner tube 3 and the expansion plate 5 also heat up, and can thus also emit thermal energy.

The setting of the pressures required for continuous operation of the system of the columns of the heat medium 8 standing on the expansion plates 25 can be achieved by designing the number and opening cross sections of the nozzle openings 26, which can be selected differently for the expansion plates 25 at different levels, and above the feed rate of the heat medium 8 fed into the outer tube 2.

If the heat medium 8 reaches the thermal temperature range or the phase transition threshold, the heat medium 8 also begins to evaporate in this design variant. Due to the constant supply of heat medium 8 in the outer tube 2 of the coaxial tube 1 on the one hand and through the barriers in the form of only the passage nozzles as a fluid connection leaving Expansionstel ler, an increase in the gaseous heat medium 8 in the outer tube 2 is prevented ver. Instead, more and more heat medium 8 will also implement the phase change here. The gaseous heating medium 8 in turn rises in the inner tube 3, driven in particular by a negative effect resulting from a chimney effect, upwards in the direction of the upper end of the coaxial tube 1. There it is relaxed and cooled in the area of a diffuser 28, which is formed by an expansion in the pipeline. For the temperature reduction of the heat medium 8, no technical aids are required and no energy is required, so that the overall efficiency of the method does not deteriorate here either. The temperature difference between the lower end of the coaxial tube 1, which is sunk in the borehole, and the highest point of the inner tube 3, in which the gaseous heat medium 8 flows, increases again due to the diffuser 28 and the cooling of the heat medium thereby achieved. Here again, this increases the chimney effect, which drives an accelerated rise of the gaseous heat medium 8 inside the inner tube 3. As a result, the gaseous heat medium 8 flowing rapidly upwards also receives high kinetic energy in this configuration variant. The relaxation and tempera ture reduction of the gaseous heat medium 8 in the diffuser 28 is - by appropriate design of the geometric conditions - advantageously limited to 5K above the boiling point of the heat medium 8, so that this is still gaseous after the relaxation and no phase change back into the liquid phase until the kinetic energy of the heating medium 8 has been used.

The flow rate at which the gaseous heating medium 8 flows upward, and thus its kinetic energy (mass x speed), of the gaseous heating medium 8, is also dependent on the depth of the bore and the temperature of the gaseous heating medium 8 in this variant Density and the temperature difference between the lower end of the coaxial tube 1 and the highest point of the inner tube 3, in which the gaseous heating medium 8 flows.

The gaseous heat medium 8 flowing out of the diffuser 28 flows onto a flow turbine 15 which is set in rotation and drives a generator 16 for generating electrical energy. This electrical energy is transformed by means of a transformer 31, which is controlled by a control 30, to a voltage and, with a frequency converter which may be present, is adapted to the network frequency of the power network, so that the electrical energy can then be fed into the power network. After flowing through the flow turbine 15, the heat medium is passed to an optionally available heat exchanger 19. There the thermal energy still contained can be extracted from the gaseous heat medium 8. This thermal energy can then be used, for example, for district heating or local heating supply 33. The cooled, still gaseous heat medium 8 then flows back here into the degassing and storage container 7. There it completes the phase change from gaseous to liquid. The degassing and storage container 7 can be cooled with outside air, for example. It serves the Pha senwechsel of the heat medium 8 and also serves as a reservoir for the supply of the heat medium 8 in the outer tube 2 of the coaxial tube. 1 The cycle is closed.

Here too, the system technology is largely accommodated in an installation building 23, in which there is also a control center 32 from which the system can be controlled and operated.

The inventor has calculated that for both embodiments only about 25 m ^{2 of} floor space of the installation building 23 are required to accommodate the technical equipment required for the installation in order to implement a system with a nominal output of about 2.5 MW. Another part lies in the comparatively high density with which the systems according to the invention can be implemented in the area. The inventor calculated here that - again for systems of both design variants - a density of 4 systems per km ^{2 is} possible. This is significantly more than in the case of conventional ge othermie systems, which have a wider catchment area to the sides.

Particular features and advantages of the method according to the invention and a device implementing this method are:

A coaxial tube is inserted deep. • In an outer tube, the coaxial tube, a liquid heat medium is introduced (e.g. pumped into it), which heat medium - at normal pressure of 1000 mbar - at a temperature between 40 ° C and 120 ° C (especially at a low temperature, e.g. between 40 ° C and 60 ° C) evaporated. With a heat medium that evaporates at low temperature, for example between 40 ° C and 60 ° C at normal pressure, the phase transition occurs at a comparatively shallow depth, for example from a depth of 1 300 to 1400 m, in the coaxial tube.

On an outer wall of an inner tube of the coaxial tube can lead to the depth at which the phase transition occurs (phase transition threshold), e.g. spiral baffles or with nozzle openings through set barriers, e.g. Expansion plate, fixed, in particular be welded on (comparable to a vertical tubular screw). In the case of spiral baffles, the steepness of the turns influences the time until the heat medium reaches the phase transition threshold. In the case of barriers interspersed with nozzle openings, the opening cross sections of the nozzle openings and the distance between adjacent barriers determine this duration, among other things.

• If baffles are provided, a central force (centrifugal force) acts on the liquid heat medium, so that the heat medium is pressed against an inside of the outer tube as it flows downwards, generating frictional heat.

• The inner tube can be thermally insulated from the outer tube in order to prevent heat transfer from the gaseous heat medium guided in the inner tube to the liquid heat medium flowing in the outer tube, in any case to reduce it. This insulation can be omitted in a lowermost section of the coaxial tube, for example in the lowermost 100 m, so that the thermal energy from the depth to the win- fertilize the baffles is transferred and these turns represent an additional che heat transfer surface.

• The liquid heat medium reaches the phase transition threshold at the boiling temperature that is available due to the geothermal energy at a certain drilling depth.

• The heating medium becomes gaseous and, due to the lower density, wants to rise in the outer tube. However, this is prevented due to the constant tracking of the liquid heat medium and the turns of the guide plates.

• The continuous feeding of the liquid heat medium into the outer tube constantly creates new gaseous heat medium in the area of the end section. The gaseous heat medium fills the space between the area in which the phase transition threshold lies and a bottom end of the coaxial tube in the outer tube and up to the shut-off unit of the inner tube.

• After a certain period of time that can be controlled (e.g. via the filling quantity of the heating medium), the pressure and the temperature in the coaxial tube rise. A technical aid, such as a compressor or a compressor, which would minimize the economic yield, is not necessary for the temperature and pressure increase.

• If a shut-off unit of the coaxial pipe is now opened, the gaseous heat medium rises through the chimney effect in the inner pipe. The Ka effect of this arises from a temperature difference between the temperature of the gaseous heat medium in the end section of the coaxial tube and at the highest point of the inner tube in which the gaseous heat medium flows. So the gaseous heat medium flows upwards in the inner tube at a high speed.

• For a higher temperature difference and thus an increase in the chimney effect, an expansion of the pipe diameter on the inner pipe on upper end (the head) of the coaxial tube can be used. Also in an uppermost section, for example the uppermost 50m, of the inner tube ge not given thermal insulation can contribute by there the still cold liquid heat medium can help to cool down the gaseous heat medium flowing there.

• The high kinetic energy of the gaseous heat medium is converted into rotational energy in a flow turbine (which may be similar to a wind turbine, for example) and used to drive an electrical generator. Due to the high kinetic energy of the gaseous heat medium, this turbine can be built smaller and more compact than would be possible with a steam turbine or an updraft turbine and would make economic sense.

• The thermal energy in the gaseous heat medium can also be used for heat supply or as production heat by means of heat exchangers.

• In this new process, geothermal heat energy is only used to trigger a phase change in a heating medium.

• For energy generation (electrical and / or thermal energy), the high kinetic energy of the gaseous heat medium, which is generated by the frictional heat, the geothermal energy, the phase change with the heat of vaporization, the temperature and pressure increase and the chimney effect, is used.

• The new process is preferably carried out in a closed cycle so that no heat medium has to be introduced into the ground and that there is no danger to the environment or groundwater.

• If a heating medium with a low boiling point is used, low thermal temperatures corresponding to the low boiling point of the heating medium, which can be achieved using known geothermal processes, are sufficient. which can still be used directly for heat energy supply for electrical energy production.

• The density of the heating medium and the height difference between the lowest point of the coaxial pipe and the highest point of the pipeline in which the gaseous heating medium flows also have a significant influence.

• A selectable low boiling point of the heating medium leads to lower drilling depths. This also makes the use of the process economically very interesting in many areas where geothermal energy was previously uneconomical due to the required drilling depths.

• By implementing the new process, it is possible, for example, to operate electrical charging stations for trucks, buses, cars, ships, excursion boats, ferries with the electrical energy obtained on land and at sea, thus making a significant contribution to reducing the To make CO ₂ emissions.

• The locations can be selected very flexibly, since the method according to the invention does not impose any special location requirements, such as the presence of thermal springs, water-carrying or permeable layers / rocks or high temperatures at low depth.

reference numeral

1 coaxial tube

2 outer tube

3 inner tube

4 end section

5 baffle

6 expansion

7 degassing and storage tank

8 heating medium

9 line

10 pump

1 1 inlet

12 valve

13 line

14 flow generator

15 flow turbine

16 generator

17 valve

18 management Heat transfer

management

Short-circuit line

installation building

expansion plate

injection nozzle

arrow

diffuser

control

transformer

control station

District / local heating supply

Claims

Expectations

1 . Method for the production of useful energy from geothermal energy, wherein in a deep hole in the earth, an outer tube (2) and an inner tube (3) having coaxial tube (3), in which in an end section sunk in the deep hole tion (4) of the coaxial tube (1) outer tube (2) and inner tube (3) have a connection to one another, a liquid heating medium (8) is introduced into the outer tube (2) under standard conditions and in the direction of the recessed end section (4) of the coaxial tube (1) flows, the heat medium (8) being heated while absorbing geothermal heat and undergoing a phase transition in the region of the end section (4) and passing in gaseous form into the inner tube (3) and therein up to an upper end of the surface located on the earth Koaxi alrohrs flows upwards, and with the flowing, gaseous heat medium (8) a flow generator (14) is operated to generate electrical energy.

2. The method according to claim 1, characterized in that the Wärmeme medium (8) after flowing through the flow generator (14) by egg NEN heat exchanger (18) is performed to obtain usable heat me energy.

3. The method according to any one of the preceding claims, characterized

is characterized in that the heat medium (8) is liquefied after flowing through the flow generator (14) and is again introduced in liquid form into the outer tube (2) of the coaxial tube (3).

4. The method according to any one of the preceding claims, characterized

shows that the heat medium (8) in the outer tube (2) is guided on a spiral path in the direction of the end portion sunk in the deep bore.

5. The method according to any one of claims 1 to 4, characterized in that the heat medium (8) in the outer tube (2) in at least one section of the outer tube (2), in particular in several such sections, by introduced into the outer tube (2) Barriers (25), e.g. plate-like barriers, pent up and transferred into the vertically lower section via uninterrupted expansion via nozzle openings (26) formed in the barriers (25) and leading to a vertically lower section of the outer tube (2).

6. The method according to any one of the preceding claims, characterized

shows that it also involves driving a deep hole into the earth and inserting the coaxial tube (1) into the deep hole.

7. The method according to claim 5, characterized in that the deep drilling is made to a depth of at least 1000 m.

8. The method according to any one of claims 5 or 6, characterized in that the deep drilling is made to a depth of at most 2500 m.

9. The method according to any one of the preceding claims, characterized

records that dodecafluoro-2-methylpentane-3-1 is used as the heating medium (8).

10. Device for the production of useful energy from geothermal energy

• a coaxial tube (1) introduced into a deep bore, the coaxial tube (1) having an outer tube (2) and an inner tube (3) and wherein in an end section (4) of the coaxial tube (1) recessed in the deep bore, outer tube (2) and inner tube (3) have a connection with each other;

• arranged in the outer tube (2), the cross-section of which extends through guide structures (5), in particular spiral guide plates or with nozzle openings (26), for example plate-shaped barriers (25); • an inlet pipe (9) connected to an inlet opening (1 1) of the outer pipe (2) provided at an end of the coaxial pipe (1) axially opposite the end section;

• With a gas flow channel (13) connected to an end opening of the inner tube (3) provided at the end of the coaxial tube (1);

• In the gas flow channel (13) arranged flow generator (14) for generating electrical energy; and

• a heat medium (8) arranged to flow through the coaxial tube (1), which is liquid under standard conditions and has a boiling point at normal pressure of between 30 ° C and 120 ° C.

1 1. Device according to claim 10, characterized in that the heat medium (8) has a boiling point at normal pressure of between 30 ° C and 60 ° C.

12. Device according to one of claims 10 or 1 1, characterized by a at the end of the coaxial tube (1) arranged section (6; 28) of the inner tube (3), in which a diameter of the inner tube (3) starting from a first Diameter, which the inner tube (3) along its extension up to the end section (4), is expanded to a second diameter, which has the outlet opening.

13. Device according to one of claims 10 to 12, characterized in that seen in the flow direction behind a flow turbine (15) of the flow generator (14), a flow line with a diameter extension (29) is arranged.

14. Device according to one of claims 10 to 13, characterized by an on one of the outlet opening with the flow generator (14) connecting gas flow channel (13) opposite side of the flow generator (14) arranged and with the flow generator (14) with a flow line (18) connected heat exchanger (19) for the recovery of usable thermal energy.

15. Device according to one of claims 10 to 14, characterized in that the outlet opening and the inlet opening (1 1) are connected to one another in a closed line system.

16. The device according to claim 15, characterized by one in the ge

closed line system arranged degassing and storage container (7).

17. Device according to one of claims 10 to 16, characterized by one or more valves (10, 17) in the feed line (9) and / or the gas flow duct (13) for the targeted opening and / or closing of the feed line (9) and / or the gas flow channel (13) and by a control, in particular with sensors for determining parameters of the heat medium (8) located in the feed line (9) and / or the gas flow channel (1 3), for automatic actuation of the at least one valve ,

18. Device according to one of claims 10 to 17, characterized by dodecafluoro-2-methylpentane-3-1 as a heating medium (8).