EP2356310A1

EP2356310A1 - System for exchanging energy with a ground

Info

Publication number: EP2356310A1
Application number: EP09825052A
Authority: EP
Inventors: Hans Alexandersson
Original assignee: Pemtec AB
Current assignee: Pemtec AB
Priority date: 2008-11-10
Filing date: 2009-06-18
Publication date: 2011-08-17
Also published as: EP2356310A4; WO2010147549A1; US20110265989A1; WO2010053424A1

Abstract

The present invention relates to a system for exchanging energy with a ground. It comprises an elongate ground bore (2), a flexible sealing device (1) for separating sections of said bore (2) and extending inside and generally all along said bore (2) and being closed at its ends, wherein said sealing device (1) in use is filled with a liquid (20) whereby said sealing device (1) is pressed against walls of said bore (1).The system further comprises at least a first duct (5, 6), and heat recovery means, wherein said first duct (5, 6) is operatively connected to said heat recovery means and extending into said sealing device (1). Sealing means (70, 80) are provided at said flexible sealing device (1) at a predefined level along said bore (2), which sealing means (70, 80) are adapted to seal at said level between said sealing device (1) and said bore (2).

Description

SYSTEM FOR EXCHANGING ENERGY WITH A GROUND

Field of the Invention

The present invention relates to a system for exchanging energy with a ground. It comprises an elongate ground bore, a flexible sealing device for separating sections of said bore and extending inside and generally all along said bore and being closed at its ends, wherein said sealing device in use is filled with a liquid whereby said sealing device is pressed against walls of said bore. The system further comprises at least a first duct, and heat recovery means, wherein said first duct extend from said heat recovery means into said sealing device.

Background Art

Such systems for extracting energy from a ground are known. They are used to separate different levels in a borehole in the ground, i.a. in rocky grounds. Different layers at different levels in the ground often have a inferior quality and may comprise not only different types of rock, but also layers of sand or gravel of different fractions which reduces the strength of the walls of the borehole. The borehole may collapse or at least bring unwanted particles into the borehole with the ground water that flows in the ground and especially in these in general more porous layers. If such a borehole is not sealed at least at the levels of lesser quality the borehole may short-circuit the different levels via the hole. This may result in the water in the hole being contaminated or other holes being contaminated via these layers so that undesirable effects occur, such as contamination or pressure drop. For instance, salt deposits at a depth of 100 m can easily contaminate a water well and make the water unfit for human use. An energy well is usually between 100 and 200 m deep. Often the ground water level is a few meters below ground level and above the ground water level the well must be reinforced with usually steel rings around the borehole since there is no pressure from the surrounding water to balance the pressure within the well. A known such system for extracting energy from a ground is disclosed in the applicants own patent application WO2006/126925. Other more used systems comprise the installation of sealing pipes within the borehole at only the position of the layers of lesser quality. In such a system the positions of the layers are mo monitored during drilling of the borehole and thereafter these stiff pipes are installed and sealed against the walls of the borehole at the pipe ends. This latter system requires adjustments for each new well whereas the former system is a more straight forward method not in need of much on-site adjustments.

The bore hole is however still dependent on the quality of the rock around the hole which determines whether the hole will be even and straight or whether, for instance, the hole will be slightly larger than intended since the surface of the hole has poor cohesion and will be rough. In addition, harder or smoother kinds of rock enclosed in an otherwise uniform rock may result in the hole, when being drilled, not extending perfectly straight. Moreover the drill bit is gradually worn away in use and will obtain a smaller diameter. This results in a reduction of the diameter of the hole as well.

Summary of the Invention

The object of the present invention is to further improve the sealing of the energy well and to preferably also reduce the costs for the complete installed energy well as well as preferably also reduce the environmental load of the completed installation.

This object is achieved by a system for exchanging energy with a ground, comprising an elongate ground bore, a flexible sealing device for separating sections of said bore and extending inside and generally all along said bore and being closed at its ends. The sealing device is in use filled with a liquid whereby said sealing device is pressed against walls of said bore. The system further comprises at least a first duct and heat recovery means. The first duct is operatively connected to said heat recovery means and extending into said sealing device. Sealing means are provided at said flexible sealing device at a predefined level along said bore, which sealing means are adapted to seal at said level between said sealing device and said bore. Since the borehole is completely sealed off from the surrounding ground there will be no leakage and the liquid used for extracting the heat energy from the ground comes in much better contact with the surrounding ground since the surface area towards the walls of the borehole is larger than the surface area of the duct against the ground water of the traditional open borehole. The flexible sealing device is in itself advantageous to transport and install into the bore since it may be laid flat and rolled onto a storage and transportation device and also be installed in a generally flat condition and not until after installation filled with liquid. Its inherent flexibility also easily adjusts to the walls of the bore and the often non-straight extension thereof. The sealing means are provided to seal off vertical levels within the bore from one another in order to minimize and preferably fully remove the leakage between different levels which otherwise may contaminate these or other levels. In an embodiment said sealing means comprise a collar which is arranged within said flexible sealing device at said predefined level, which collar is arranged and configured to exert a radial force against said bore. Such a collar is improving the sealing off of different levels along the bore, on the outside of the sealing device, which the internal pressure within the sealing device may not always be able to. This may be needed when the bore is rather uneven or there are levels along the bore of more water permeable material. In an embodiment said collar is rigid and provided with material at its outer periphery which expands in contact with said liquid. The rigidity of the collar is acting against the pressure exerted from the expanding material so that the force is instead directed outwardly towards the sealing device and the bore to effect the intended seal. In an embodiment the outer periphery of said rigid collar has a smaller diameter than the inner diameter of said flexible sealing device in order to certainly be possible to run down the bore.

In an embodiment the flexible sealing device comprises a tubular plastic film. This sealing device seals completely off the borehole from the surrounding ground thus limiting the possibility for short circuiting any ground water between different layers at different depths within the borehole. This in turn leads to the possibility to install energy wells in areas where it was not possible earlier. Furthermore, it is no longer necessary to monitor as thoroughly as before where these layers of more penetrable ground materials are located in order to seal them. Also, the sealing system becomes less labour intensive thus cheaper.

In an embodiment is said tubular plastic film composed by at least two film layers. Hereby it is possible to determine the thickness needed in any borehole and to reduce the need for production and storage of several thicknesses of the sealing device. For each energy well the ground water conditions in combination with the type of ground determines the necessary thickness end the number of layers of film is calculated or looked up in an here fore prepared table.

In an embodiment a second duct is operatively connected to said heat recovery means and extending into said sealing device. In an embodiment each first and second duct has a duct end which is open, and in that the first duct end is located vertically below the second duct end. Since the sealing device is completely sealing off the surrounding ground and liquid the ducts may be open in order to improve the contact with the ground to improve the heat transfer. In an embodiment said first duct end is located in a general bottom third of said ground bore, and said second duct end is located in a general top third of said ground bore. The further to the top of the bore and to the bottom of the bore respectively each duct end is positioned, the better the utilisation of the available heat energy of the energy well becomes. In an embodiment said rigid collar is open for vertical flow of liquid in order to allow on open type of duct system to be used.

In one embodiment said first and second ducts are interconnected so as to form a continuous passage. This is a more traditional system, but may be required i.a. when extra security requirements apply. In an embodiment said rigid collar is closed for vertical flow of liquid which makes it even more rigid. An additional advantage with such a collar is that it may carry the weight of the water column vertically above it. Such a situation is i.a. advantageous when the level of ground water surrounding the bore is rather deep into the ground. Under such circumstances the liquid pressure within the sealing device vertically above this ground water lever increases with the same amount of pressure corresponding to the difference in height between the ground water level and the liquid level. When placing a collar according to this embodiment within the sealing device, the collar can carry this additional pressure instead of subjecting the sealing device to this additional pressure.

In an embodiment the sealing device at ground level has a mouth which is enclosed by a rigid tube of plastic material. In traditional systems steel pipes are used which reinforce the ground around the sealing device if positioned in softer material than rock. According to the present invention the steel pipes may be used during drilling and installation of the system, but the steel pipes may be replaced by i.a. plastic tubes in order to reuse the steel tubes in other projects and thereby save costs and the environment by not using as much steel.

In an embodiment the sealing device at ground level has a mouth which is closed by a sealing body. In an embodiment said sealing body is secured between a top of said rigid tube and said mouth of said sealing device.

In an embodiment said sealing body comprises a sealing ring secured to said top of said rigid tube, and a sealing lid, wherein said sealing device is clamped between said sealing ring and sealing lid. In an embodiment said liquid is water which reduces the need for anti-freezing agents as is used in traditional systems which in turn limit the environmental load and if a leak would accidentally happen, then there will only be water flowing into the surrounding ground.

In an embodiment said sealing device is made of non-rigid plastic which makes the sealing device adaptable to the shape of the borehole into which it is installed and any imperfections thereto, and further to make it collapsible in order for it to be able to be rolled only a reel and minimising its transportation size.

In an embodiment said sealing device has a thickness of 0.2-1.5 mm. In an embodiment said sealing device has a diameter which in use corresponds substantially to the diameter of the bore.

In an embodiment said first and a second ducts each is made of non- rigid plastic, and preferably having a thickness of 0.2 - 1.5 mm. This makes also the ducts' transportation size smaller and as such saves costs and improves transportation efficiency.

In an embodiment said sealing means comprise a jacket enclosing said sealing device. This improves the contact between the sealing device and the walls of the bore since the jacket is able to adapt to and to smoothen an uneven wall surface. In an embodiment said jacket is provided generally at the same level as said collar, which improves the seal.

In an embodiment said jacket is made of a material which expands in contact with water. After expansion the jacket may even fill gaps and improve the seal. In an embodiment said jacket is made of a rubber material, preferably between 25 and 45 ⁰Sh. In an embodiment of the invention a system for extracting energy from a ground is disclosed, comprising an elongate ground bore, a flexible sealing device for separating sections of said bore and extending inside and generally all along said bore and being closed at its bottom end, wherein said sealing device in use is filled with a liquid whereby said sealing device is pressed against walls of said bore, said system further comprising a first and a second duct and heat recovery means, wherein said first and second ducts are operatively connected to said heat recovery means and extending into said sealing device, wherein each first and second duct has a duct end which is open, and which first duct end is located vertically below the second duct end. This embodiment may be combined with any one or combinations of the above described embodiments.

Brief Description of the Drawings The invention will now be described in more detail with reference to the accompanying drawings which by way of example illustrate currently preferred embodiments of the present invention.

Fig. 1 is a cross-sectional view of an energy well with collector tubes provided with a sealing device and a collar according to the present invention, Fig. 1 b is a cross-sectional view of an energy well with an open system of collector tubes provided with sealing device and two collars according to the present invention,

Fig. 1 c is a plan view of a collar according to the present invention, Figs. 2a-2b are cross-sectional views in sequence of the sealing against the surroundings at the mouth of the borehole,

Fig. 3 is a cross-sectional view of an energy well with collector tubes provided with a multi-layered sealing device according to an alternative embodiment of the present invention,

Fig. 4a is a cross-sectional view of an energy well with a closed system of collector tubes provided with a sealing device and a collar according to the present invention

Fig. 4b is a plan view of a collar according to an alternative embodiment of the present invention,

Fig. 5 is a perspective and sectional view of an alternative embodiment of the present invention. Description of Preferred Embodiments

Fig. 1 a shows a sealing device 1 according to an embodiment of the present invention. The sealing device 1 is used in combination with an open type of energy collecting system. It also illustrates the generally vertical borehole 2 in rock 3. The borehole 2 is used as an energy well for extracting, for instance, heat for heating a house (not shown) or for storing heat in the ground 3. In most cases the borehole 2 is naturally filled with groundwater 4 while being bored. At the upper parts of the borehole 2 the rock 3 has ended and instead soil 3 is lying on top of the rock 3 constituting the ground 3 or land 3. The rock 3 may at some places penetrate the soil 3 and be visible, but it may also be as far down as hundreds of meters. Under normal conditions the rock 3 may be found somewhere between a few up to ten to twenty meters underneath the ground level. The present invention may be used under all of these conditions. The sealing device 1 comprises a thin cylindrical one-layered

"stocking" of non-rigid plastic, preferably a polyeten plastic and of approximately 114 or 138 mm diameter and 0.4 mm thickness. The diameter of the sealing device 1 may be adjusted to the specific project, i.e. each borehole 2. Generally the bore 2 is drilled to a diameter of 114 mm and the diameter of the sealing device 1 is adapted to be lye flat against the wall of the bore 2 and to be flexible enough to follow its contours.

The sealing device 1 is at its bottom end sealed so that no water from the ground may penetrate into the inner parts thereof. The sealing is preferably done by welding a continuous weld 60, but other known methods may be used, such as clamping between rigid plates, possibly together with a material which expands in water 4 such as Hydrotight™, folding or by the use of tape. Below the weld 60 a protective cover (not shown) may be slipped onto and surround the end of the sealing device 1 to protect it from the walls of the bore 2 when lowering it there into. To the protective cover, or if no protective cover is used directly onto the sealing device 1 a weight 50 is connected to facilitate the lowering of the sealing device 1 into the bore 2. Both any protective cover and the weight 50 remains on the sealing device 1 after installation.

The length of the sealing device 1 is adjusted to extend substantially all the way up to the mouth of the bore 2 at the ground level. The reason why it may sometimes be suitable not to let the sealing device 1 open exactly at the level of the mouth of the bore 2 is that it may then be unlawfully manipulated or damaged. In these cases, a suitable level of the opening of the sealing device 1 can be adjacent to the transition between the frost level and the frost-free level, in Sweden about 1-2 m below ground level. That part of the hole which in that case is positioned above the opening of the sealing device 1 but below the mouth of the bore 2 is sealed and can then be covered with, for instance, earth. See below for a detailed description of the sealing of the sealing device 1.It should be noted that normally all arrangements and fittings for a heat exchange system of the type according to the present invention is concealed under ground 3 in order to prohibit manipulation or weather influence. Hence, ducts 5, 6 normally bend at right angle into a horizontal arrangement directly above seal 42.

The length of the sealing device 1 is also adjusted to extend substantially all the way down to the bottom of the bore, in Sweden typically some 100 - 200 meters from ground 3 level in order to utilise the maximum capacity of the well. The bore 2 and consequently the sealing device 1 may be both shorter and longer due to the conditions under which the energy well is to be performing.

Between ground 3 level and the upper surface of the rock 3 possibly another few metres down in the borehole 2, steel pipes or in an embodiment of the invention plastic pipes, referred to as casings 40, are usually installed to shield the earth layers from the borehole 2. The vertically upper end of the casings 40 is sealed with a casing cover 42 or seal 42 to confine any overpressure inside the borehole 2 and to prevent the borehole 2 from being filled with soil and/or surface water. Connections to a heat pump in or connected to the house are then arranged above the borehole 2 and the steel or plastic pipes 40.

As has been discussed above, there is in most cases soil above the rock 3. Due to this soil, casings 40 are normally necessary to stabilise the shape of the bore 2. According to Swedish standards, this casing 40 should extend at least 6 m below the upper edge of the rock to ensure a tight transition. However, this does not always occur. According to the present invention, it is no longer necessary to have casings 40 6 m down in the rock, even if the standards may still stipulate this. The sealing device 1 in itself provides the security against leakage all the way up to the ground 3 level. Hence a casing 40 made of a plastic material which is rigid enough to keep the bore 2 open may replace the traditional steel pipes. During installation it may still be preferable to use a steel pipe casing 40, but this may after installation be removed and be replaced by a plastic casing 40. This way the steel casing 40 may be reused as a casing 40 in another project and a lot of steel material is saved which in turn saves costs and the environment. Often the steel pipes have a diameter of approx. 140 mm whereas the bore 2 and the sealing device have diameters of preferably 114 mm, and consequently the steel pipes are quite easily removed and replaced by a 125 mm plastic pipe.

The sealing device 1 is suitably sealed at the mouth of the bore 2 in the following way, see Figs 2a-2b. The seal 42 consists of two rigid steel sheets 42a and 42c between which a thick rubber plate 42b is mounted. The opening of the sealing device 1 is inserted between two metal rings 41a and 41 b which are assembled with a screw 41 c. The metal rings 41 a and 41 b have the same outer and inner diameter as the casing 40 and can therefore be placed loosely on the upper edge of the casing 41. The casing 40 may be the traditional steel pipes or the plastic pipes according to the present invention. When the metal rings 41 a and 41 b together with the sealing device 1 are placed on the casing 40, the seal 42 can be placed on top of the metal rings 41 a and 41 b. In this position, parts of the rubber plate 42b and the lower steel sheet 42c extend down into the casing 40 and the sealing device 1. Through the entire seal 42 extend 4 through bolts 42d which are now tightened so that the lower steel sheet 42c is pulled towards the upper steel sheet 42a, thus squeezing the rubber plate 42b. The rubber plate 42b is now pressed towards the walls of the casing 40 and presses the sealing device 1 against the same so as to form a tight closure. As an alternative to the illustrated embodiment the upper metal plate 42a may not protrude beyond the inner diameter of the casing 40 or even all the way out to the outer diameter of the casing 40. The pressure with which the bolts 42d make the rubber plate 42b expand to the sides to the casing 40 is enough to keep the seal 42 intact also without this "upper lid" 42a. The upper and lower plates 42a and 42c respectively do not have to be made of metal, but any suitably rigid material or a suitable material in combination with a rigid design.

In order to extract heat energy from the energy well normally two collector tubes 5, 6 are installed in the borehole 2, see Fig. 1 a. These collector tubes 5, 6 are one example of the first and second ducts 5, 6 according to the claims. One tube supplies, in this case tube 5, and the other tube returns, in this case tube 6, the cooling medium liquid 20 with which the tubes 5, 6 are filled. The supply tube 5 has an open tube end which is positioned close to the bottom of the sealing device 1. The return tube 6 has an open tube end which is positioned either at the seal 42 or penetrates down into the bore 2 only just a short distance. In order to extract the maximum available heat energy from the borehole 2 the supply tube end should be positioned as far down the bore 2 as possible and the return tube end as far up the bore 2 as possible in order to maximise the distance there between. It is however reasonable to at least install the tube ends such that the return tube end is positioned above the supply tube end to have the liquid 20 circulating. The collector tubes 5, 6 are then connected to the heat pump system in or in close proximity of the house. The tubes 5, 6 are preferably made of a rigid plastic material.

In order to extract energy from the well the liquid 20 may also be driven in the reversed direction in comparison to the manner described in the preceding paragraph if the energy removed from the ground 3 in such a case is increased. The system may also be utilised to store heat in the ground or to cool the liquid 20 in a cooling system for buildings or other applications. In these applications the liquid 20 may also be driven either by supplying energy through the tube 5 ending at the general bottom of the bore 2 and extracting at the general top of the bore 2, or in a reversed direction. Different ground 3 conditions may affect which is the best operational mode.

Returning to the embodiment of Fig. 1 a, when the heat pump circulates the liquid 20 in the system, the liquid 20 is entering into the well through the supply tube 5 at the bottom of the well and the over pressure produced by the heat pump forces the liquid 20 up through the well and into the return tube 6 which returns the liquid to the heat pump where the heat energy that the liquid 20 has absorbed within the energy well is extracted and transferred to the heating system of the house. Since the sealing device 1 is completely sealed off from the surrounding ground 3 there is no leakage of liquid 20 and the system is closed off. However, within the system the collector tubes 5, 6 are open ended in contrast to the traditional closed circuit the system according to the present invention may be defined as an "open" system.

The cooling medium liquid 20 consists traditionally of water and an anti-freezing agent, but according to the present invention it is possible to use only water without the anti-freezing agent. This way no anti-freezing agent is needed and thus a reduced environmental loading is achieved and a cut in costs results here from. It is important for the liquid 20 of the collector tubes 5, 6 to make good contact with the surrounding to function in a satisfactory manner and be able extract energy to, for instance, the heat pump. The inventive idea of the present invention is to make direct contact with the surrounding ground 3 with the liquid 20 instead of as in the traditional systems first have the liquid 20 (comprising water and anti-freezing agent) circulating in the closed collector tubes and extracting energy from the open bore 2 in which the ground water circulates freely. According to the present invention the liquid 20 comes in better contact with the surrounding and consequently the well may be more efficiently utilised and more energy may be extracted or smaller well and system may be necessary for a specific need. Both may naturally be achieved simultaneously.

In Fig. 1a the collector tube 5 is also provided with a collar 70 which encircles the tube 5. The collar is made of a polyethene material and is quite rigid. The vertical height of the collar 70 is preferably approx. 5 - 15 cm high. The diameter of the outer periphery of the collar is slightly smaller than the bore 2 since the bore 2 not always is completely circular and may have walls that may sink in slightly due to less rigid material at certain levels and the collar 70 should be possible to insert into the bore 2. On the outer periphery of the collar 70 a continuous strip 71 of Hydrotight™ is applied, which is a material that expands in contact with water. The vertical height of the strip 71 is preferably approx. 1 - 4 cm. Other materials having the same technical effect may be used as alternative. The expansion of the strip 71 induces a force to be applied to the walls of the bore 2 in the range of up to 90 kg/cm². This presses the sealing device 1 towards the wall and very effectively closes off any passage of water surrounding the sealing device 1 within the bore 2 from penetrating from one vertical level within the bore 2 to another vertical level at the other side of the collar 70. Due to the strong force applied by the expansion of the strip 71 it is important that the collar is strong and rigid enough to also counteract against the force in order not to collapse. The strip 71 need not be continuous along the periphery of the collar 70 if the material is such that the expansion is directed so as to fill also the gaps between strip 71 parts or at least to make sure that the seal is tight. This type of seal may be needed when a level of a bore 2 has a porous structure which may contaminate another level and thus make i.a. a water well useless due to salt leakage or other contaminants. At the same level as the collar 70 on the outer periphery of the sealing device 1 it may be advantageous to even further improve the vertical seal by installing another strip 80 of a similar material as for strip 71. Naturally also here other materials than Hydrotight™ may be used. When the sealing device 1 and collector tubes 5, 6 have been installed the strips 71 and 80 will expand and together form a tight seal against vertical leakage. The strip 80 is one embodiment of a sealing means 80 according to the claims.

In Fig. 1 b a similar embodiment as in Fig. 1 a is illustrated, but it can also be seen that a porous level within the bore 2 is closed or sealed off by the installation of two collars 70, one below and one above the level in question. The upper collar 70 makes sure that no leakage from an even higher vertical level is contaminating the level in question, or the other way around, and the lower collar 70 is in the same manner prohibiting the contamination of the level in question or any lower porous level. A difference between the present embodiment and the one illustrated in Fig. 1 a is that the sealing means 80 on the periphery of the sealing device 1 in the present case is not made of a material which expands in contact with water, but with an elastic material which adapts to the rather rough surface of the bore 2 walls so that the sealing device 1 seals off the vertical level from surrounding levels. Such an elastic jacket 80 may be made of a rubber material having a shore value of approx. 25 - 45 ⁰Sh. The jacket 80 may also be much higher in the vertical direction in comparison to the strip 80 of the Fig. l a-embodiment. Preferably in the range of 0.5 - 1 m in the vertical direction, but other lengths may apply. One reason for such a wide sealing means 80 is that the tolerance level with which the collector tubes 5, 6 later are installed with may be much less. The thickness in the horizontal direction may be in the range of approx. 0.5 to 3 cm. The sealing means 80 in both this embodiment and the earlier one is installed on the sealing device 1 above ground and then lowered into the bore 2 together with the sealing device 1. It should be noted that any number of collars 70, with or without any embodiment of strips or jackets 80, may be installed according to the needs of the specific bore 2 and ground 3 properties. It should also be noted that not only a one-layered sealing device 1 may be utilised, but several, if there is a need for instance due to security requirements. In Fig. 1 c a collar or sealing means 70 according to one embodiment of the present invention is illustrated. There is an outer ring intended to provide the stability and rigidity of the collar 70 which is the main part. In order to be able to fasten the collar 70 to the collector tubes 5, 6 a generally centhcally positioned ring 73 is provided and arms 74 for carrying the outer ring on the inner ring 73. Since the present invention is an open type of energy well in which the two collector tubes 5, 6 communicate via the sealing device 1 and the ends of said tubes 5, 6 most likely are positioned one on each side of the collar 70, the collar 70 need to provide for a vertical flow of liquid 20 and hence vertical through holes 72 are provided, in this case four. The strip 71 is fastened by a glue or by using press-fit, for instance by the aid of an O-ring or a expanding material which is arranged around the duct 5, 6, on the outer ring of the collar 70 in an enclosure which is best seen in Fig. 1 a and 1 b. Also other manners of fastening of the strip 71 may be utilised.

Fig. 3 discloses a further embodiment of the present invention in which the sealing device 1 comprises 3 concentrically positioned, i.e. one within the other, flexible sealing devices 1. The aim is to improve the security of the system as a whole. If for instance the bore 2 is reaching a level where the wall of the bore 2 is made up of gravel and smaller loose stones instead of the hard rock 2, the bore 2 wall may be less stiff and the diameter of the bore 2 may be slightly increased. At that level the wall of the bore 2 will not be an efficient wall against which the sealing device 1 may rest, but instead the sealing device 1 may need to be self supportive. Unless the wall of the sealing device 1 is strong enough in itself the sealing device 1 may rupture and the sealing effect is lost and the system and the surrounding environment are adversely affected.

Another reason for installing several layers to build up the sealing device 1 is that if the ground water level is rather deep into the ground the seal 42 is generally still installed at ground level or slightly below that, which means above ground water level. However, this introduces a higher internal pressure within the sealing device 1 towards its bottom, and a further risk is introduced if the walls of the bore 2 are not strong enough to withstand this internal pressure.

The reason for not producing and installing a thicker sealing device 1 rather than installing several layers is amongst other things that it is simpler and cheaper to only produce one thickness rather than several. Furthermore, the effect of collapsing the sealing device 2 and rolling it onto a reel for transportation purposes is less pronounced or even lost.

A suitable thickness of the sealing device 1 may vary between 0.5 and 1.5 mm, but deviations may be necessary due to the circumstances, both to smaller and greater thicknesses. The sealing device 1 may be manufactured and delivered as a continuous "stocking" with a certain diameter, which is cut by the fitter to a suitable length when the borehole 2 is completed. Alternatively the sealing device can be completed in the factory. The diameter of the sealing device 1 is suitably selected to substantially correspond to the diameter of the borehole 2, thus fitting tightly against the same. When installing several concentrically positioned layers of the sealing device 1 the inner layers may be produced with a diameter corresponding to the inner diameter of the surrounding layer. In this embodiment a collar 70 is installed having a strip 71 to seal off the different levels within the bore 2. However in this embodiment it has been determined that no strip 80 on the outer surface or periphery of the sealing device 1 has been necessary.

The sealing device 1 is installed in the borehole 2 by first sealing the end by applying a preferably continuous weld 60 and either fold the end as is disclosed in Fig. 1 a and described below, or by fastening the protective cover or some other suitable protection, to which the weight 50 is then connected. The sealing device 1 may be closed at its end facing the bottom of the bore 2, Fig. 1a II, by first having its open end being folded along the entire width of the sealing device 1 , thus forming a triangular tab at an angle of 45° to its longitudinal extent. Subsequently the now folded edge is folded once in the opposite direction, Fig. 1 a III, thus forming a triangular tab at an angle of 45° to the longitudinal extent of the sealing device 1 , the tip of the triangular tab being formed along the centre line of the sealing device 1 seen in its longitudinal extent, Fig. 1 a IV. A small through hole is made through this triangular tab and provided with a reinforcing ring in the form of a staple, Fig. 1 a V. A cotter pin can then be passed through this staple, thus holding the sealing device 1 attached to its weight 50. Finally one or more lines 60 are welded across the sealing device 1 just above the just formed fold lines, said welds 60 ensuring that the sealing device 1 is perfectly sealed at this end.

The weight 50 helps the sealing device 1 to be dragged down to its end position. If further layers of the sealing device 1 should be installed, the same procedure to seal and install them is followed until a suitable number of layers are installed. The total length of the bore 2 must be adapted to the number or layers of the sealing device 1 , since each layer normally is provided with its on set of weld 60, protective cover and weight 50 which adds to the total length of installed sealing device 1.

When the sealing device 1 is installed it is filled with water 20, either from above or, as shown in Fig. 3, using a tube 30 inside the sealing device 1. After that the collector tubes 5, 6 are let down into the bore 2 each to its own position inside the sealing device 1 , and the seal 42 is connected to the mouth.

As a rule of thumb there are two types of boreholes 2: those naturally filled with water and those not filled and thus being empty. The holes 2 which from the beginning are filled with water can apply a water pressure to the installed collector tubes 5, 6 and the sealing device 1 so that a water pressure inside the sealing device 1 may have to be built up to expand the sealing device 1 against the borehole 2 wall. This is conveniently done by passing, together with the collector tubes 5, 6 and the sealing device 1 while being installed, a water tube down in the bore 2, see Fig. 3. The water tube 30 is arranged beside the collector tubes 5, 6 and inside the sealing device 1. The water tube 30 has one opening adjacent to the tight-fitting connection of the sealing device 1 to or under the collector tubes 5, 6 and its other opening above the ground to be connected to a suitable pump system. With these parts installed in the borehole 2, water 20 is pumped down in the sealing device 1 through the water tube 30, this water 20 thus pressing away any other water in the bore 2, so that the sealing device 1 places itself along the side of the borehole 2 wall. In this way, different levels in the borehole 2 are sealed, thus preventing groundwater from one level in the hole from reaching another level. Also no special sealing is required of that part (in most cases the upper part) of the hole 2 that does not consist of rock but of earth and/or clay, which otherwise would normally have been sealed by means of, for instance steel rings, referred to as casings 40. Thus this sealing device 1 makes it possible to utilise the entire borehole 2 for energy withdrawal all the way from its bottom to its opening at the ground level. Another advantage is that no surface water from the ground surface can flow down in the borehole 2 since the sealing device 1 is suitably sealed against the environment at the ground level. After installation and filling the sealing device 1 with water 20, the system is ready to be connected to a suitable heat pump in a house and thereafter the energy well is ready for use. It is possible for the water tube to remain in the borehole 2 since further filling with water may be required at a later stage. This water tube can also be used if it appears necessary to maintain a certain overpressure inside the sealing device 1. By mounting a pressure-sensitive transducer on the water tube and connecting the transducer to a reading system, it will be possible to continuously read the condition of the borehole 2. This information can be sent in prior-art manner either wirelessly or by appropriate wiring to a reading position, for instance, in connection with the installation for withdrawal of energy from the energy well. In a borehole 2 which is empty from the beginning, or if the water pressure in the borehole is so low that it does not prevent the sealing device 1 from being filled with water 20 without overpressure, it is possible to fill the sealing device 1 without water pressure from inside. Thus in this case it is not necessary, but still possible, to use a water tube 30 according to the above method. Instead collector tubes 5, 6 and a sealing device 1 can be inserted and installed in the hole 2 as described above, after which water 20 can be supplied through the opening of the sealing device 1 at the ground level. Even if a water tube 30 has not been used in this case for supplying water 20, a pressure-sensitive transducer can still be inserted into the upper part of the borehole to monitor its condition. It should be noted that the open type of system according to the above described embodiments may well be used without the use of collars 70 or jacket 80 if the ground 3 and bore 2 so allows. This may be the case when the bore 2 has appropriately even walls and/or the internal pressure of liquid 20 within the sealing device 1 is enough to seal against the bore 2 walls between different levels therein.

Yet another embodiment of the present invention is illustrated in Fig. 4a. In this embodiment a closed type of system is used in which the two collector tubes 5, 6 are interconnected at the bottom of the sealing device 1. The forward end of the collector tubes 5, 6 is then preferably provided with its own weight 51 connected via a connector 53 to a protective cover 52 which are useful during installation. The collar 70 with strip 71 may in this case also be used to better seal off vertical levels outside of the sealing device 1. Also a jacket 80 may be used of any kind as already discussed. Such a jacket 80 is however not used in the embodiment as illustrated. In Fig. 4b a collar 70 is illustrated which is provided with two holes 73' and 73" to connect to both ducts 5, 6. In this embodiment the collar 70 is not open, i.e. having a closed wall 74, for vertical flow of liquid 20 which is possible when the collector tubes 5, 6 are a closed system. Also an open collar 70 with openings 72 may be used.

In a further embodiment of the present invention which is illustrated in Fig. 5 a sealing device 1 is used which is provided with a collar 70 and strip 71 (and possibly a jacket 80), but in which the sealing device 1 is not extending all the way down the bore 2. In this embodiment a sealing means is used to seal off the sealing device 1 at its bottom end from the rest of the bore 2. Other embodiments having one or several longer or shorter sealing devices 1 along all or parts of the bore 2 may also be contemplated due to the particulars of each bore 2.

In a further embodiment of the present invention the jacket 80 may be designed as a carrier 80 e.g. in the form of a plastic or rubber thin sheet which is e.g. glued or taped to the outer periphery of the sealing device 1 at a predefined level before installation. In this embodiment the jacket 80 could be used with or without a collar or sealing means 70 within the sealing device 1. The outer diameter of this carrier is larger than the diameter of the bore 2 so that the carrier 80 after installation becomes at least slightly cup-shaped and bears against the bore 2 walls. After installation of the sealing device 1 a sealing material e.g. montmorillonite or other clay material is poured into the bore 2 on the outside of the sealing device 1. The sealing material falls down and is caught up by the carrier 80 and a layer of sealing material is built up. The amount of sealing material is adapted to each specific bore 2 so that a vertical seal of the bore 2 is achieved, at least when liquid 20 is expanding the sealing device 1. This type of sealing means 80 or jacket 80 may also be utilised all the way from the bottom of the bore 2 up to a desired level. Then there is no need for a carrier, since the bore 2 bottom carries the weight of the clay material. If needed, a carrier 80 and clay material may be installed vertically above this desired level so that there is no jacket 80 along a part of the bore 2. Any number of sealing means 70, 80 may be installed along the bore 2, of any combination of embodiments herein according to the needs of the specific bore 2.

The above disclosed embodiments of the present invention represent merely a minor range of contemplated embodiments. There are a wide variety of embodiments within the scope of the claims that may be utilised to adapt the system to the current conditions. Some embodiments may i.a. be: The sealing means 70 as discussed in the more general sense may also be e.g. a flat and rather thick rubber plate which is forced onto the duct or ducts 5, 6 and which has an outer diameter which is slightly larger than the diameter of the bore so that the inherent elasticity of the rubber material is exerting a force outwardly against the bore 2 walls and hence provides for a seal between the bore 2 and the sealing device 1. This type of sealing means 70 is also closed for vertical flow of liquid 20 within the sealing device 1 and will consequently also carry the weight of the liquid 20 vertically above the collar 70 or sealing means 70. Another contemplated embodiment of this type is a more thin plate of plastic or otherwise flexible material which also has an outer diameter larger than the bore 2, but which is utilising the inherent flexibility of the total design to exert the outwardly directed force by flexing or bending the plate outer periphery into a cup-shape after installation.

Sealing means 70 of the type described in the previous paragraph may be used, at least in combination with a closed loop duct system, in combination with a clay material, cement material or other suitable material in order to withstand any compressive forces from the surrounding ground 3 if the bore 2 walls are not rigid enough to keep them selves intact, or if the liquid 20 pressure within the sealing device 1 is not sufficient to withstand such forces. The sealing means 70 is then installed at the appropriate level and such material is poured on top. Several such sealing means 70 with such material may be used in one bore 2. Such material may also be used in order to close the end of the sealing device 1 at the general bottom of the bore 2, or as described above, to keep the bore 2 intact at this level. This embodiment may naturally also be used with or without a jacket 80.

The bore 2 needs not be circular, but may have any shape. This also applies to the shape of the ducts 5, 6 and the collar 70. However, in that case the sealing device 1 may need to be adjusted in shape to the intended use. If either the hole 2 or the ducts 5, 6 or the collar 70 is in the shape of a polygon, for instance a hexagon, a circular sealing device 1 may yet function, provided that either the material of the sealing device 1 is sufficiently weak ("non-rigid") or the construction of the sealing device 1 is sufficiently flexible.

The multi-layered sealing device 1 may be delivered to the installation site not merely as a long circular but flattened plastic film which is cut to length and installed one layer after the other, but the sealing device 1 may already at the production plant be assembled in the multi-layer build up, and the sealing weld 60 and the protective cover 52 and weight 50 may also be connected in advance. The volume between two concentric sealing films in such a multi-layer device 1 may be utilised as one of the ducts 5, 6 for removing or inserting energy from the ground 3. In this case the inner film is smaller in diameter than the outer film in order to provide such duct 5, 6 space.

The sealing device 1 may not only be a "hose" of flat sheet plastic, but may be built up by small capillary stems or pipes along the outer periphery, either alone or in combination with a flat sheet. These capillary stems or pipes may be utilised as one of the ducts 5, 6 for extracting or inserting energy from the ground 3.

The system may according to an embodiment of the invention utilise more than one borehole 2 and have several boreholes 2 interconnected in order to extract more energy with the same heat pump. Naturally the borehole 2 may have a different diameter and length, in particular when installing several interconnected ones. Also an elongate bore 2, i.e. which has an extension both in the vertical and in the horizontal direction, may be utilised having several loops of ducts 5, 6. Also, the collar 70 may then be adapted to the cross-section of the bore 2 and extend in a similar manner along the bore 2. Under any circumstances the collar 70 may also be utilised as carrier for the ducts 5, 6 in order to keep them in place at appropriate distances.

The collector tubes 5, 6 may as well as the sealing device 1 be made of a flexible material in order to enable the same positive effect of rolling on a reel during transportation in order to minimise the transported volume. Such an embodiment may be of rather thin thickness, in the same range as for the sealing device 1.

The metal rings 41 a and 41 b of the seal 42 may naturally be of another suitably rigid and durable material such as a plastic.

The energy well may not only be located in rocky grounds 3, but also in other types of grounds 3 such as sand or clay. The borehole 2 is then generally achieved by producing a so called "standing hole" by pressing away the ground material and reinforcing it with e.g. montmorillonite or other clay material. The function of the bore 2 after reinforcement becomes the same as in rocky grounds and hence the system and the sealing device 1 are installed in a similar manner. Another ground 3 type comprises one or several aquifers. The system according to any one of the embodiments of this application may be utilised also if a bore 2 passes such aquifers since the liquid 20 pressure within the sealing device 1 is keeping the system expanded also in water and the sealing device 1 possibly in combination with any sealing means 70, 80 is ensuring the integrity of the system. Such an aquifer could be utilised as a storage facility for ground energy by installing two bore holes 2, one at either side of the aquifer. In each bore 2 a system according to the invention is installed and in one of the systems energy is inserted into the water of the aquifer, and in the other energy is extracted. In this way a heat exchanger is created.

The system may be utilised in a slanted manner or in a curved manner, and even installed into a first bore 2 in connection with a second bore 2 such that said sealing device 1 interconnects said two bores 2 and forms one continuous system for energy exchange.

Claims

1. A system for exchanging energy with a ground, comprising an elongate ground bore (2), a flexible sealing device (1 ) for separating sections of said bore (2) and extending inside and generally all along said bore (2) and being closed at its ends, wherein said sealing device (1 ) in use is filled with a liquid (20) whereby said sealing device (1 ) is pressed against walls of said bore (1 ), said system further comprising at least a first duct (5, 6) and heat recovery means, wherein said first duct (5, 6) is operatively connected to said heat recovery means and extending into said sealing device (1 ), c h a r a c t e r i s e d i n t h a t sealing means (70, 80) are provided at said flexible sealing device (1 ) at a predefined level along said bore (2), which sealing means (70, 80) are adapted to seal at said level between said sealing device (1 ) and said bore (2).

2. A system for extracting energy according to claim 1 , wherein said sealing means (70, 80) comprise a collar (70) which is arranged within said flexible sealing device (1 ) at said predefined level, which collar (70) is arranged and configured to exert a radial force against said bore (2).

3.A system for extracting energy according to claim 2, wherein said collar (70) is rigid and provided with material (71 ) at its outer periphery which expands in contact with said liquid (20).

4.A system for extracting energy according to claim 3, wherein the outer periphery of said rigid collar (70) has a smaller diameter than the inner diameter of said flexible sealing device (1 ).

5.A system for extracting energy according to any one of the preceding claims, wherein said flexible sealing device (1 ) comprises a tubular plastic film

(1 )-

6. A system for extracting energy according to claim 5, wherein said tubular plastic film (1 ) is composed of at least two film layers (1 ).

7.A system for extracting energy according to any one of the preceding claims, further comprising a second duct (5, 6) operatively connected to said heat recovery means and extending into said sealing device (1 ).

8.A system for extracting energy according to any one of the preceding claims, wherein each first and second duct (5, 6) has a duct end which is open, and in that the first duct end is located vertically below the second duct end.

9. A system for extracting energy according to claim 8, wherein said first duct end is located in a general bottom third of said ground bore (2), and said second duct end is located in a general top third of said ground bore (2).

10. A system for extracting energy according to claim 8 or 9, wherein said rigid collar (70) is open for vertical flow of liquid (20).

11. A system for extracting energy according to any one of claims 1 to 6, wherein said first and second ducts (5, 6) are interconnected so as to form a continuous passage.

12. A system for extracting energy according to claim 11 , wherein said rigid collar (70) is closed for vertical flow of liquid (20).

13. A system for extracting energy according to any one of the preceding claims, wherein the sealing device (1 ) at ground level has a mouth which is enclosed by a rigid tube (40) of plastic material.

14. A system for extracting energy according to any one of the preceding claims, wherein the sealing device (1 ) at ground level has a mouth which is closed by a sealing body (42).

15. A system for extracting energy according to claim 14 in combination with claim 12, wherein said sealing body is secured between a top of said rigid tube (40) and said mouth of said sealing device (1 ).

16. A system for extracting energy according to claim 15, wherein said sealing body comprises a sealing ring (41 ) secured to said top of said rigid tube (40), and a sealing lid (42), wherein said sealing device (1 ) is clamped between said sealing ring (41 ) and sealing lid (42).

17. A system for extracting energy according to any one of the preceding claims, wherein said liquid (20) is water.

18. A system for extracting energy according to any one of the preceding claims, wherein said sealing device (1 ) is made of non-rigid plastic.

19. A system for extracting energy according to any one of the preceding claims, wherein said sealing device (1 ) has a thickness of 0.2 - 1.5 mm.

20. A system for extracting energy according to any one of the preceding claims, wherein said sealing device (1 ) has a diameter which in use corresponds substantially to the diameter of the bore (2).

21. A system for extracting energy according to any one of the preceding claims, wherein said first and a second ducts (5, 6) each is made of non-rigid plastic, and preferably having a thickness of 0.2 - 1.5 mm.

22. A system for extracting energy according to any one of the preceding claims, wherein said sealing means (70, 80) comprise a jacket (80) enclosing said sealing device (1 ).

23. A system for extracting energy according to claim 22 in combination with claim 2 or 3, wherein said jacket (80) is provided generally at the same level as said collar (70).

24. A system for extracting energy according to claim 22 or 23, wherein said jacket (80) is made of a material which expands in contact with water.

25. A system for extracting energy according to claim 22 or 23, wherein said jacket (80) is made of a rubber material, preferably between 25 and 45 ⁰Sh.

26. A system for extracting energy from a ground is disclosed, comprising an elongate ground bore (2), a flexible sealing device (1 ) for separating sections of said bore (2) and extending inside and generally all along said bore (2) and being closed at its bottom end, wherein said sealing device (1 ) in use is filled with a liquid (20) whereby said sealing device (1 ) is pressed against walls of said bore (2), said system further comprising a first and a second duct (5, 6) and heat recovery means, wherein said first and second ducts (5, 6) are operatively connected to said heat recovery means and extending into said sealing device (1 ), wherein each first and second duct (5, 6) has a duct end which is open, and which first duct end is located vertically below the second duct end.