NL7908171A - METHOD FOR EXTRACTING NATURAL HEAT AND AN APPARATUS FOR CARRYING OUT THIS METHOD - Google Patents

Description

Method for finning geothermal energy and a device for carrying out this method.

It is known that the temperature in the interior of the Earth is higher than at the surface. The so-called geothermal temperature trend applies, in which the temperature rises every 100 m 3 °. In coal mines, where at a depth of 2,000 m there is thus a temperature of about 60 ° and more, this temperature development only entails disadvantages and makes work underground. However, for today's efforts to tap into new energy sources, this geothermal temperature trend brings great advantages.

Geothermal energy is a new energy source. The engineer is charged with the task of transporting the geothermal heat by means of the simplest possible means and with the least possible energy costs for its transport from the interior of the earth to the earth's surface.

This object is the basis of the present invention. Therefore, the invention contemplates a method and an apparatus with which the heat from the interior of the earth can be used on the earth's surface. Hereby, only known mining technical measures are applied to drill holes in the ground, to pipe them and the like.

The solution for the stated purpose according to the invention is a method according to which a liquid heat transfer agent is introduced cold into a borehole arranged in the ground and is taken from the surrounding soil while absorbing heat, 790 81 71 * / * 2 point of the "borehole, which is inverted by 180 ° and separated from the inserted cold heat transfer agent, is fed upwards into the borehole and is discharged therefrom to take up the absorbed heat. As a heat transfer agent, water Of course, other liquids can also be used if better thermal properties come to the fore and higher costs are justified, but for the sake of simplicity, only water will be used hereinafter.

The present method involves a system of communicating pipes in the borehole. These are interconnected at their bottom ends at the deepest point of the borehole. The cold water is introduced into the top end of one tube. It is believed that due to natural gravity the water sinks down. Here it flows along the wall of the borehole, which is surrounded by the soil, the temperature of which increases as the depth increases. The heat from the ground is transferred to the downflowing water and increases its temperature. At the same tube cross-section, the flow speed thereof also increases. At the deepest point of the borehole, the water enters the other pipe and rises upwards. The system of the two communicating tubes causes the water to flow downwards in one tube and upwards in the other tube without external influence. The larger volume of the hot water leads to a higher flow rate in the latter tube. This creates a suction effect on the water flowing down in one tube. Without an additional pump, a natural cycle is created * The temperature at which the water in this cycle is heated by the soil depends on the depth of the borehole and the size of the heat transfer that can be achieved. At a depth of 790 8 1 71 CS 4 3 1,000 meters, the water is theoretically heated by 30 °. When the water outlet temperature thus obtained is not sufficient for a direct application, for example for heating 5 rooms, a heat pump is used. Likewise, the flow just obtained and caused by natural gravity through the two communicating tubes can be increased by an additional pump.

Some embodiments are possible for carrying out the present method 10. In principle, a device according to the invention is characterized by a hole arranged in the ground and a tube arranged therein, whereby an annular space is formed, wherein in the lower part thereof holes are arranged in the wall thereof, The annular space between the wall of the borehole and the tube forms the downflowing water tube, which absorbs the heat directly from the surrounding soil. At the bottom end of the hole or of the annular space, this heated water 20 enters the tube through the bores and flows upwards.

The borehole is made in a known manner by means of a drill bit, a rod system, etc. Generally, no hard rock, such as granite or primary rock, will be drilled. It means that the drill hole is lined with pipes. A casing pipe which rests against the wall of the borehole and extends to the deepest point of the borehole is thus created. In order for the tube, which forms the tube for the upward flowing water 30, to be concentrically located in this jacket tube and thus favorable flow conditions occur, radial spacers are arranged on the circumference of the tube, which bear against the jacket tube and the tube keep concentric herein * 35 Once the borehole has been brought to the desired depth and the wall of the borehole is lined with pipes, the borehole must be sealed at its lower end. According to the invention, a plug is used for this purpose, which consists of a sealing material, for instance a sealing mortar consisting of plastic, which plug fills in or displaces the bottom end of the casing tube and optionally also the soil beneath it. For this purpose, the sealing material, after the borehole has been lined with pipes and the drill bit has been taken out with the rod system, is introduced into the casing from above. After this, the other tube, which consists of separate parts screwed together, is lowered to this plug.

The casing preferably consists of separate metal tube sections. These have the necessary strength and furthermore form a good heat transfer from the soil to the downflowing water. The concentric. The pipe lying in the jacket pipe preferably consists of separate pipe sections of plastic, on which the spacers can be arranged. A plastic with a low thermal conductivity is preferably used. As a result, the hot water flowing upwards maintains its temperature and is not cooled excessively by the cold water flowing down. As has already been said, the water flowing upwards has a higher speed at the same cross section of the two tubes than the water flowing downwards. This shortens the residence time of the upflowing water in the pipe into which it is led. Thus also less time is available during which the water can give off its heat to the cold water flowing down. As a result, the present device operates with a high thermal efficiency.

The embodiment just described is used with a non-hard bottom. The casing tube forms a formwork and at the same time the tube or lead tube 790 8 171

* A

5 for the water flowing down. Its large surface area ensures good heat transfer from the soil to the flowing water without any action. With hard rock, such as granite or undisturbed primary rock, the casing tube forms an extra cost factor and can be omitted. For such a solid rock, a second embodiment is used, which also has a bore arranged in the rock and is characterized by at least one pipe-line consisting of parts of pipes running in the bore going down to the deepest point of the borehole, since reversing direction and then leading upwards again, and a heat-conducting filler filling the void between the wall of the borehole or rock on the one hand and the pipeline on the other.

Thus, in this embodiment, the downwardly conducting tubes and the downwardly conducting parts of the tubes are identical to the upwardly extending tubes and the upwardly extending parts of the tubes. Thus, the thermal efficiency is lower than in the first embodiment. However, since the soil remains and the borehole remains open, casing the hole is unnecessary and the cost of drilling the borehole is also lower. Multiple boreholes can thus be made at the same cost. As a result, the same thermal efficiency is again obtained at constant costs.

When the water on entering the down-draining pipes has a lower temperature than the surrounding soil, and only then does the desired heat release from the soil occur, it is preferable that the down-draining pipes have a larger diameter than the upward running tubes. The larger cross-section can herein be formed by a larger diameter 35 as well as by several tubes.

790 8 1 71! 6

According to the invention, in order to obtain the greatest possible surface area for the transfer of heat from the soil to the water in a borehole, two or more drilling lines, each with downwardly and upwardly extending parts of pipes, are arranged in a borehole.

The heat transfer from the ground to the water mainly depends on a good filling of the hollow space. For backfilling, the heat conducting material is poured into the borehole 10 after insertion of the tubes. It must be ensured that the filling material falls down to the deepest point of the borehole and from there is evenly built upwards. When the pipes run eccentrically or not straight in the borehole, there is a risk that the filler material on the wall of the borehole will drag along or not fall down, forming air pockets. This prevents good heat transfer. According to the invention, horizontal spacing ribs running horizontally therebetween are arranged for accurate positioning of the pipe sections. These keep the pipe sections at the desired mutual distance and ensure their centric location in the borehole. In such a location of the pipe sections, the filler material poured from above falls to the deepest point of the borehole. Hence the filling material is built upwards and hereby falls and slides radially downwards between the pipe sections and fills the borehole without damaging the wall thereof. In accordance with the invention, the pipe sections are composed of pipe sections and the spacer ribs extending therebetween are at least 2.5 times the grain size of the filler material. This ensures that the filler material poured between the pipe sections falls radially outwardly and slips and fills the entire hollow space of the borehole.

790 8 1 71 7

An embodiment of the invention will now be further explained by way of the description and accompanying drawings, in which:

Fig. a side view, partially in section 5, of a first embodiment, wherein a casing tube is placed in the borehole and an inner tube has not yet been fitted; Fig. 2 is a side view of the same embodiment, partly in section, after the inner tube has been put on; Fig. 3 is a sectional view taken on the line III-III in Fig. 2; Fig. k is a sectional view taken on the line IV-IV in Fig. 2; Fig. 5 is a side view, partly in section, of a second embodiment without casing pipe with internal pipelines already partially lowered; Fig. 6 is a side view, partly in cross-sections 20 of the same embodiment in the final state with fully lowered internal pipelines and an infill inserted; Fig. 7 is a sectional view taken on the line VII-VII in Fig. 5;

Fig. 8 is a section along line VIII-VIII

in fig. 6; FIG. 9 is a top plan view of the embodiment of FIGS. V and VI with a larger cross section of the downwardly extending pipes of the pipelines; Fig. 10 is a plan view of the same embodiment with a total of three pipelines disposed.

Figures 1 and 2 indicate the soil or rock with 12. A bore hole 1¾ is provided in this.

The borehole 1 ^ is lined with a jacket pipe 16. This 790 8 1 71 8 consists of a few metal pipe sections screwed together. These are shown in fig.

2 not shown separately. In the casing tube 16, the middle tube 18 is lowered to form the annular space 20. On the tube 18 there are radial spacers 22. At the lower end of the borehole 1U, respectively of the casing tube 16, there is a plug 2k of sealing material. This closes the deepest point of the borehole, indicated by 26. The inner tube 18 has the bores 28 on its underside.

To obtain this embodiment of the present arrangement shown in Figs. 1 and 2 and the associated cross-sections 3 and 4, a borehole is drilled in a known manner. This hole is hereby lined with metal pipe sections. These remain in place and form the drilling jacket 16. After drilling, a sealing material is poured into the borehole. This forms the plug 2 ^. Then, the inner tube 18 is lowered to the deepest point 26 of the borehole. This tube also consists of a few parts screwed together.

The lower parts have the bores 28.

In operation, cold water, for example, the cold water flowing from a heater, is introduced into the annular space 20. The two arrows indicated above in Fig. 2 indicate this. The cold water falls down in the annular space 20. In doing so, it absorbs the heat which is released by the rock 12 via the metal jacket pipe 16. The temperature of this rises. In the lower part of the borehole 1¼, the now hot water enters through the bores 28 into the inner tube 18. The arrows indicated in the lower part of fig. 2 and the arrows in fig. 4 indicate this transition. The hot water flows upwards in the inner tube 18 and is drawn off at the top end thereof. The described embodiment is used with soil which would crumble in the borehole, so that the borehole must be lined with a casing 16.

The embodiment of Figures 5 to 10 to be described below, on the other hand, is applied to solid rock. In the embodiment shown in Figs. 5 to 10, the casing of the borehole I is not provided with pipes, because these are solid rock 12.

Fig. 5 shows the borehole 1k whose deepest point 26 of the borehole is not closed with a plug 2k, but remains open. Fig. 5 shows the embodiment in which pipelines 30 are already partially loaded downwards. As in particular the cross-section in Fig. 7 indicates, these are two pipelines 30, each with a downwardly extending tube 32 and an upwardly extending tube 3k. The ribs 36 running between the 15 tubes keep them at an accurate distance from each other. After completely lowering the pipelines 30, they assume the position shown in Fig. 6. The material which forms the filling 38 is now introduced. This is a mortar with 20 good heat conducting properties. This is inserted into the borehole between and laterally of the pipe sections.

After the mortar has reached the deepest point 26 of the borehole, it is built up. Finally, rising from below, the mortar fills the entire hollow space in the borehole 1k. This creates an intimate heat-conducting connection between the rock 12 and the pipe sections.

As the arrows in Fig. 6 indicate, the cold water is introduced into the downwardly extending pipe sections 32.

In this it flows downwards, taking up the heat which is released by the rock 12. At the deepest point 26 of the borehole, the water enters the upwardly extending pipe sections 3k. There too, the water will absorb heat further, as long as its temperature is below that of the rock 12, 35. Finally, the water is taken off as warm water at the top end of the tube 31 *.

The cross sections in Figs. 7 and 8 show the embodiment shown in Figs. 5 and 6, wherein the down and up running tubes have the same cross section. Fig. 9 shows an embodiment in which the downwardly extending tubes 32 have a larger diameter than that of the upwardly extending tubes 31. Among other things, this measure ensures that the hot water in the tubes 31 * assumes a greater speed. Thus, the time is shortened during which the water in the parts in which its temperature is above that of the rock 12 can give off heat to it. This improves the thermal efficiency. In Fig. 10 a further embodiment is shown, in which two three pipelines with a downward and upwardly extending tube 32 and 3U respectively are used instead of 15.

The borehole depths applicable in the invention are theoretically not limited. In practice, however, a bottom borehole depth of perhaps 1,000 m 20 and an upper borehole depth of perhaps 2,000 m exist. At a borehole depth of less than about 1,000 m, the temperature is too low and at borehole depths above 2,000 m, costs become too high. The diameter of the borehole and of the pipes will generally fall in the range of from 100 to 00 mm. The pumps that are additionally used under certain circumstances, which support the heat flow, have only a very small power. The upward pressure created by the lower specific gravity of the heated water is generally sufficient to circulate the water.

Thus, a pump is only needed to correct the flow losses. Accordingly, the power of this will be small.

790 8 171

Claims (12)

1 1 1 «Method of extracting geothermal heat, characterized in that a flowing heat transfer agent is introduced cold into a borehole, which is arranged in the ground, and is taken from the surrounding ground with absorption of heat, to the deepest point from the borehole, since it is turned through 180 ° and separated from the introduced cold heat transfer agent is fed upwards into the borehole and discharged therefrom to take off the absorbed heat. Method according to claim 1, characterized in that. that is used as a heat transfer agent water. Method according to claim 1, characterized in that. that the natural gravity flow of the heat transfer agent is supported by a pump. 1 *. Device for carrying out the method according to claims 1-3, characterized by a borehole (1M) arranged in the ground (12) and a tube (18) placed therein, whereby an annular space (20) 20 is formed, wherein in the lower part part of the wall of this tube (18) have bores (28). Device according to claim U, characterized by a casing (16) arranged in the borehole (1U), which abuts against the wall of the borehole and extends to the deepest point of the borehole. 6. Device according to claims t and 5, characterized by radially running spacers (22) arranged on the circumference of the tube (18), which abut against the casing (16) and hold the tube (18) concentrically in the casing (16) . Device according to claim k-6, characterized in that a plug (2 ^) consisting of a sealing material fills in the lower end of the casing (16) and optionally also the soil below it, respectively displaces 790 8 1 71 . Device according to claim U-7, characterized in that the jacket pipe (16) consists of metal pipe parts. Device according to claim U-8, characterized in that the pipe (18) consists of plastic pipe parts and that the spacer (22 ·) is arranged thereon. 10. Device for carrying out the method according to claims 1-3, characterized by a borehole (1H) arranged in the ground (12), at least one pipeline arranged in the borehole (1 ^), consisting of a deepest point (26) descending from the borehole, reversing it and then again ascending tube (32, 3 ^) and a heat-conducting filling (38), which fill the cavity between the borehole wall and the piping. Device according to claim 10, characterized in that the downwardly extending tube (32) has a larger diameter than the upwardly extending tube (3 * 0). Device according to claim 10, characterized in that. That two or more pipelines (30) are each provided with a downward and upwardly extending tube (32, 3M). Device according to claims 10-12, characterized by spaced ribs (36, 1U) running horizontally at vertical distances between the tubes (32, 3M) Device according to claims 10-13, characterized in that the tubes (32, 3 * 0 consist of separate tube sections and that the spacer ribs (36) have a length at least 2.5 times the grain size of the material forming the filling (38). Device substantially as described in the description and / or shown in the drawings 790 8 1 71