Installation of an underground part of a ground heat exchange system.

Abstract

An underground part of a ground heat exchange system is installed in the following manner. A ground-penetrating device is positioned on a surface of ground with a head section of the ground-penetrating device facing the surface. A push force is exerted on the head section to drive at least a portion of the ground-penetrating device into the ground until the head section has reached a target depth, thereby creating a passage in the ground extending from the surface to the head section. The passage is provided with a heat exchange fluid path adapted to guide a heat exchange fluid downwards from the surface into the ground and then upwards back to the surface. A penetration-assisting fluid is fed from the surface to an inlet on the head section, which is fluidically coupled to an outlet on the head section, so that the penetration-assisting fluid ejects from the outlet into the ground. The penetration-assisting fluid is fed at least some time while exerting the push force on the head section. FIG. 1.

Description

FIELD OF THEINVENTION An aspect ofthe invention relates to amethod ofinstalling an underground part of a ground heat exchange system. Other aspects ofthe invention relate to a head device for use in such a method, and to an assembly for installing an underground part ofa ground heat exchange system. BACKGROUNDART The earth provides a vast reservoir for capturing or storing heat. To bring heat to the surface or discharge it into the ground, a ground heat exchange system with an underground part may be installed. Such system is also referred to as ground heat exchanger (GHE). The actual heat exchange takes place in the underground part. The application ofGHEs reduces power consumption and associated cost and greenhouse gas emissions for heating and cooling homes, ofces, and other buildings. In many areas ofthe world the rst tens to hundreds ofmetres ofthe earths subsurface has a temperature such that the ground can act as a heat or cold reservoir dependent on the local climate and season. Using a GHE, heat exchange uid can be circulated through the GHE such that in the cold season uid entering theGHE that is colder than the ground can be warmed up and in the warm / hot season uid entering theGHE that is warmer can be cooled down. A heatpump installed at the surface may be used to efciently further boost temperature up or down. Using the heat exchange capacity ofthe subsurface in this way results in large savings in power consumption and cost for users. The most widely applied method for installing the underground part ofa GHE comprises, in a rst step, drilling a borehole to form a passage in the ground. In a second step, the passage is provided with a heat exchange uid path adapted to guide a heat exchange uid downwards from the surface into the ground and then upwards back to the surface. In practice, the uid path is implemented by inserting either a tubular or a coaxial GHE into the borehole, which GHEs will be further discussed hereinafter. In a nal step, uid communication between subsurface layers and the surface through space left in the passage is closed offby grouting. Typically, drilled boreholes have a diameter of 10 15 cm and can have a depth up to several hundred meters. A borehole length ofaround 200m can typically accommodate aGHE with sufcient capacity to heat or cool a large home in a moderate climate. In case higher heat transfer capacity is needed boreholes can be drilled more deeply or multiple boreholes are drilled. For a given heat transfer capacity requirement, ground composition, regulations, available space, and access are key parameters that determine the depth per borehole, the number ofboreholes in case ofmultiple boreholes and available equipment. For reasons of cost reduction, reduction or elimination of spillage and grouting, and potential for reducing the equipment footprint, it is advantageous to apply push-based methods as alternative to drilling for installing GHEs. Push-based methods can be used to install both U-tube and coaxial GHEs. However, current methods have as drawback that their installation is limited to soft soil areas, is typically limited to tens of metres ofdepth and to a passage ofaround 5 cm, limiting heat transfer capacity. EP1006322A2 describes a method to install aGHE where, in a rst step, a cylindrical pipe with a conical head is pushed into the ground using pushing equipment standardly used forCPT (Cone Penetration Testing) ground investigation. After completing the pushing, a single U-tube GHE, consisting oftwo tubes connected at the bottom, is installed inside the pipe. The head is connected to the pipe with a bayonet tting such that after reaching target depth and after installation ofthe U-tubeGHE the pipe can be disconnected and retracted. EP0046725A1 describes a method wherein a coaxial GHE, consisting ofan outer pipe and an inner pipe, is installed. A steel outer pipe tted with a conical head is driven into the ground using a small piling installation. A collar with a slightly larger diameter than the pipe is placed between the conical head and the outer pipe to reduce overall friction along the pipe during installation. After installation ofthe outer pipe the subsurface installation ofthe coaxial GHE is completed by inserting the inner pipe in the outer pipe. ITPD20090098A1 describes an alternative method and means to install a steel cylindrical outer pipe of a coaxial GHE tted with a conical head. A vibrator is attached to the pipe at the surface which vibrates as the pipe is pushed into the ground, whereby the vibrations reduce the ground resistance to pushing. In this method it is required that the pushing installation is anchored into the ground in a specied manner. The lattertwo methods have a low footprint compared to that of a typical drilling unit. SIHVIMARYOF THEINVENTION There is need for an improved push-based technique for installing an underground part of a ground heat exchange system. An aspect ofthe invention, which is dened in claim 1, relates to a method ofinstalling an underground part of a ground heat exchange system, the method comprising: - positioning a ground-penetrating device on a surface ofground with a head section ofthe ground-penetrating device facing the surface, - exerting a push force on the head section to drive at least a portion ofthe ground-penetrating device into the ground until the head section has reached a target depth, thereby creating a passage in the ground extending from the surface to the head section, - providing the passage with a heat exchange uid path adapted to guide a heat exchange uid downwards from the surface into the ground and then upwards back to the surface, characterized by: - feeding a penetration-assisting uid from the surface to an inlet on the head section, which is uidically coupled to an outlet on the head section, so that the penetration-assisting uid ejects from the outlet into the ground, the penetration-assisting uid being fed at least some time while exerting the push force on the head section. A further aspect ofthe invention, which is dened in claim 10, relates to a head device for use in a method ofinstalling an underground part of a ground heat exchange system as dened hereinbefore, the head device being adapted to constitute at least partially the head section ofthe ground-penetrating device, whereby the head device comprises the inlet to which the penetration-assisting uid is fed, the outlet from which the penetration-assisting uid ejects into the groundwhen the method is carried out, and at least one conduit uidically coupling the inlet to the outlet. A yet further aspect ofthe invention, which is dened in claim 18, relates to a kit for installing an underground part of a ground heat exchange system. Each ofthese aspects allows a push-basedGHE installation that is deeper or with increased cross-sectional area, or both, compared with conventional push-basedGHE installations. This, in turn, allows achieving greater heat transfer capacity and efciency. What is more, a push-basedGHE installation may become possible in areas where such an installation was hitherto not viable, so that a drilling-basedGHE installation had to be used. Such areas may include, for example, soft soils areas intermingled with stiff clay or soft rock layers. Making a push-basedGHE installation possible in these areas results in cost reduction. These advantages may further stimulate installation ofGHE systems, which represents an advance in greenhouse gas reduction. In an embodiment according to claim 2, a pressure with which the penetration-assisting uid ejects from the outlet on the head section into the ground is varied. In an embodiment according to claim 3, the pressure with which the penetration-assisting uid ejects from the outlet on the head section into the ground is increased when the ground-penetrating device encounters stronger resistance to being driven into the ground and, conversely, the pressure with which the penetration-assisting uid ejects from the outlet is decreasedwhen the ground-penetrating device encounters a weaker resistance to being driven into the ground. In an embodiment according to claim 4, pulse-like pressure variations are induced in the penetration-assisting uid ejecting from the outlet on the head section into the ground. In an embodiment according to claim 5, the penetration-assisting uid is fed to the outlet with a pressure of at least 4 bar measured at the surface, at least momentarily. In an embodiment according to claim 6, the ground-penetrating device comprises a pipe through which the push force is exerted on the head section. In an embodiment according to claim 7, the penetration-assisting uid is fed from the surface to the inlet on the head section at least partially through the pipe. In an embodiment according to claim 8, the penetration-assisting uid is fed from the surface to the inlet on the head section at least partially through a separate conduit. In an embodiment according to claim 9, providing the passage with a heat exchange uid path comprises: - coupling a heat exchange uid conduit to the head section ofthe ground-penetrating device before the head section is driven into the ground, the heat exchange uid conduit constituting at least partially the heat exchange uid path once the passage has been formed. In an embodiment according to claim 11, the outlet on the head device comprises a nozzle. In an embodiment according to claim 12, the nozzle is one ofthe following types ofnozzles: a rotating nozzle, a vibrating nozzle, and a rotating-and-vibrating nozzle. In an embodiment according to claim 13, the head device comprises multiple outlets, which are uidically coupled to the inlet, the outlet being one ofthe multiple outlets. In an embodiment according to claim 14, the head device comprises at least one valve adapted to prevent aow ofuid from the outlet to the inlet. In an embodiment according to claim 15, the head device is adapted to be releasably coupled to an elongated push member by means ofwhich the push force can be exerted on the head device. In an embodiment according to claim 16, the head device is adapted to be releasably coupled to a separate conduit. In an embodiment according to claim 17, the head device is adapted to be coupled to a heat exchange uid conduit. For the purpose of illustration, some embodiments ofthe invention are described in detail with reference to accompanying drawings. In this description, additional features will be presented, some ofwhich are dened in the dependent claims, and advantages will be apparent. BRIEF DESCRIPTION OF THEDRAWINGS Figure 1 schematically shows a bottom part of a ground-penetrating device for a push-based installation of a pipe. Figure 2 schematically shows an example ofthe bottom part ofthe ground- penetrating device with a head device with a single head device uid conduit running to an outlet placed at its tip. Figure 3 schematically shows an example ofthe bottom part of a ground- penetrating device with a head device with multiple head device uid conduits and outlets. Figure 4 schematically shows an example ofthe bottom part of a ground- penetrating device with a head device with multiple head device uid conduits with nozzles and with an extended shaft holding a valve. Figure 5 schematically shows an example ofthe bottom part of a ground- penetrating device with a head device with an ejection uid conduit coupled to the inlet positioned at the base ofthe head device and further extended with a collar. Figure 6 schematically shows an example ofthe bottom part of a ground- penetrating device with a head device tted with arms to which heat exchange tubes are attached, and with multiple head device uid conduits with nozzles embedded in each arm. Figure 7 shows a horizontal cross section ofthe ground-penetrating device ofFigure 6, showing a tubular ring for connecting the heat exchange tubes and a protective trough for the tubes in the arms. DESCRIPTION OF SOMEEMBODIMENTS The embodiments that will be described hereinafter concern a push-based The embodiments have the following in common. From a surface, a ground-penetrating device having a head section is driven into the ground by exerting a push force on the head section until the head section has reached a target depth. This creates a passage in the ground extending from the surface to the head which is provided with a heat exchange uid path adapted to guide a heat exchange uid downwards from the surface into the ground and then upwards back to the surface. Ground resistance to pushing is reduced by feeding a penetration-assisting uid from the surface to an inlet on the head section uidically coupled to an outlet on the head section so that the penetration-assisting uid ejects from the outlet into the ground. The penetration-assisting uid is fed, at least for some time, while pushing. The penetration-assisting uid may be fed in accordance with a user specied pressure prole. The head sectionmay comprise multiple outlets, the aforementioned outlet being one ofthese. These one or more outlets on the head section may be tted with one or more nozzles, which may be of different types. This further enhances the ability to reduce ground resistance to pushing and adapt to different soil types. SomeGHE aspects are discussed rst for a better understanding ofthe exemplary embodiments that will be described hereinafter. There are two main types of GHE in use, both ofwhich can be installed in a passage in the ground. One type is referred to as U-tube GHE, the other as coaxial GHE. A single U-tubeGHE is comprised oftwo tubes, each being an intermediate section of a heat exchange uid conduit, where the tubes are connected to each other at the bottom, so forming theU shape. TheU connection is placed at the bottom ofthe passage in the ground. One tube is used to transport the heat exchange uid down, and the other is used for the transport back up. In this way a heat exchange uid path is created. Multiple U-tubes may be installed to increase heat transfer capacity. In practice one ortwo U-tubes are installed. In an alternative approach multiple tubes are used for uid ow in one direction. These tubes are connected at the bottom to a single, typically larger diameter tube which is used forow in the other direction. Irrespective of such details, any ofthese types ofGHEs where each up or down going tube is placed in the ground separated from the other tubes (and not within another tube) is generally referred to as a tubular GHE. The other main type ofGHE is a coaxial GHE where the heat exchange uid conduit, in its most simple form, is comprised oftwo intermediate sections, each being a cylindrical pipe. Each pipe has a different diameter so that the narrower pipe can be installed inside the wider pipe leaving a space between the narrower pipe and the surrounding wider pipe. The length axis ofthe pipes will substantially have the same direction, hence use ofthe term coaxial. The outer pipe is closed at the bottom to form the outerbody ofthe coaxial GHE. The inner pipe is open at the bottom and is placed above the bottom ofthe outer pipe. The heat exchange uid path for theGHE is then comprised ofthe space between the pipes and the inside ofthe inner pipe. Heat exchange uid can be circulated down through the part ofthe path between the pipes and up through the part ofthe path formed by the inside ofthe inner pipe or vice versa. When describing coaxial GHEs the word pipe is generally used to describe the cylindrical components. In practice the inner pipe usually is a low-cost plastic tube as it does not need to carry load nor a substantial pressure differential between the uids inside and outside the tube. Dependent on the installation approach, also for the external pipe a plastic tube can be used, be it such a tube will in most cases need to be stronger and stiffer than the inner pipe. The description pipe is often used, with the understanding it can also be a tube dependent on the installation method that is applied. GHE pipes and tubes do not need to be circular in shape. For example, in case of a coaxial GHE, the outer pipe may be shaped to better bear pressure or installation load or improve heat transfer, the inside ofthe outer pipe or the outside ofthe inner pipe may be spirally grooved or otherwise shaped to break or distribute laminar ow. In a tubularGHE the inside ofany ofthe tubes may be shaped for the same reason. The terms pipe and tube should be interpreted broadly, encompassing non-cylindrically shaped pipes, tubes, as well as other hollow elongated objects. The embodiments that will be presented concern a push-based installation of both tubular and coaxial GHEs. This exibility is advantageous and allows selection ofan appropriate method given parameters such as cost, ground conditions, target depth, required heat transfer capacity oftheGHE and available equipment. For example, in one method to install a single U-tube, a pipe is coupled to a cone shaped head section with a bayonet tting that can be decoupled after installation. The pipe with the head section is then pushed down to target depth to create a passage in the ground. A pipe which is used to carry the push force to the head section is referred to as an installation pipe. This is followed by installing the U-tube inside the installation pipe and connecting it to the head section, afterwhich the installation pipe is decoupled and withdrawn. In a second method, the U-tube is attached to the head section such that the head section and U-tube are pushed down together with a rod, afterwhich the rod is decoupled and withdrawn. In a push-based installation of coaxial GHEs, typically the outer pipe is installed rst. A head section is rst connected to the pipe, afterwhich the assembly is pushed down. This creates the passage. In one method the pipe and head section are coupled in a sealing manner and are left in the ground to form the outerbody ofthe coaxial GHE. As an alternative, it is also feasible to pull down the outer pipe by connecting it to a head section and exerting the push force with a separate pipe or rod running inside the outer pipe, which is decoupled and retracted after target depth is reached. The crux to using a coaxial GHE is to install the outer body, as once this is accomplished, the ground heat exchange uid path is readily completed by inserting the inner pipe. It also possible to install a tubularGHE or coaxial GHE within a pipe after it is installed, irrespective ofwhether the pipe used for the installation is removed or not. When using the term target depth for push-based methods, it indicates either a predened depth or the depth that can be reached given the ground-penetrating device, pushing method and means and push force. In a push-based installation, the head part ofthe head section may be a cone or be conically shaped. The terms cone and conical should be interpreted broadly, encompassing shapes that support smooth coupling to non-cylindrically shaped pipes and tubes and encompasses shapes to further enhance heads, for example with a curved tip rather than sharp tip, curved surfaces in general, ns, teeth, and blades. There are different means by which a push force from the surface can be exerted on the head section, for example by a rod, a pipe, which may be perforated, or a sufciently strong and stifftube that can be installed from a reel. In this description, when reference is made to a pipe that is used to transmit a push force, it is understood it can also be substituted with a sufciently stiffand strong tube. Given their elongated shape, such a pipe, rod, tube, or other component is in this description is generally referred to as elongated push member. Additional components and extensions may be added to the elongated push member. For example, different coupling mechanisms whereby an elongated push member can be coupled to the head section may be added, with the choice dependent on ifthe coupling is permanent or if decoupling is required. A further example is the use oftrusses to distribute the push force over the head section. When referring to any elongated push member, this includes reference to such additions and extensions. The head section comprises a head, typically cone shaped, and, as needed, will also comprise one or more couplers to couple an elongated push member andGHE or other components. The assembly ofthe head section and elongated push member and any further component that is pushed into the ground is referred to as a ground-penetrating device. The ground-penetrating device can be congured and applied in several different ways to support differentways ofinstalling the underground part ofboth tubular and coaxial ground heat exchange systems. As discussed hereinbefore, there are multiple ways to install both tubular and coaxial GHEs. The embodiments that will be presented, as well as other embodiments, concern an improved push-basedGHE installation. An improvement consists in, when needed, feeding uid from the surface to and through the head section and ejecting it into the ground in front of and, as needed, around the head section. This reduces the ground resistance to pushing thereby facilitating the penetration ofthe ground-penetrating device into the ground. This, in turn, allows installing a GHE, which may be tubular or coaxial, more deeply, or with larger cross-sectional area, or both, for a given push force and technique. In the alternative, for aGHE that can be installed with current push-based methods and equipment to a certain depth, the same can be achieved with less push force thanks to the aforementioned improvement. This implies less heavy equipment with a smaller footprint can be used. Additionally, in case a pipe is used for the installation that also become part ofthe GHE, such pipe can be oflower strength and hence lower cost. Further, thanks to the improvement, a push-basedGHE installation may be possible in areas where soft soil is intermingled with, for example, stiff clays and soft rocks. It is noted that the improvement can also be utilised to install subsurface sensors in areas where the subsurface mostly consists of soft soils, even ifintermingled with stiffer and harder material. In case an installation pipe is used, it can be left in place or withdrawn. In all cases the installation is efcient and less costly and does not suffer from the spillage disadvantages ofthe drilling alternative. Compared to using currently available push-based methods, the improvement allows installing sensors more deeply or installing larger sensors to the same depth. The improvementmay also be utilized to install water wells in soft soil areas, also where intermingled with stiffer and harder materials, at substantially lower cost compared to the drilling alternative or more deeply or with larger capacity when using a push-based technique that includes the improvement. The rst example, illustrated in Figure 1, shows how the outerbody of a coaxial GHE may be installed with a current push-based method. Figure 1 focusses on the bottom part ofthe ground-penetrating device. A head section (11) is attached to an elongated push member consisting of a cylindrical installation pipe (12), where the bottom part ofthe head section has a head with a conical shape (13) ending in a tip. As illustrated in Figure 1, one way to couple the head section to the pipe is by extending the head with a shaft (14) with a thread (15) so that it can be screwed onto the inside ofthe bottom ofthe pipe tted with the counter thread (also at 15). With sufcient thread length the coupling will be sealing. The pipe extends to the surface to complete the ground-penetrating device. The ground-penetrating device is installed in the ground to target depth to create a passage in the ground by applying a downward push force (16) on the pipe at the surface that is transmitted through the pipe and head section and applied to the ground in front ofthe head. This force pushes the ground away and is also applied to overcome the frictional resistance to pushing between the ground and head and pipe. The coaxial GHE is completed by inserting an inner pipe inside the outer pipe. In the example ofFigure 1 the installation pipe is used as the outer pipe of a coaxial GHE. The installation pipe may also be used to install a tubular or coaxial GHE inside it, which can be comprised oflow-cost materials, leaving the installation pipe in the ground. This may be advantageous in case, for example, a low-cost metal installation pipe is used with risk ofcorrosion or other deterioration or ifthere is a risk ofleakage caused by the push method in combination with the ground conditions. A further option is to make use of a coupling ofthe installation pipe to the head section that can be decoupled after installation. Under this option, a tubular or coaxial GHE is installed inside the pipe after target depth is reached after which the installation pipe is decoupled from the head section and retracted to the surface leaving theGHE in the ground. In case a screw coupling has been used, it can be decoupled by unscrewing, as long as the head section has sufcient rotational resistance. For purposes of efciently decoupling a thread-based rotational coupling mechanism, a coupling can be used that couples and decouples with a limited number ofturns or evenjust a partial turn. One way to implement this is to use a compressible O-ring or gasket tted around the shaft and placed between the head and the end ofthe pipe (Figure 1, 17). This may be used together with a thread with a pitch such that the O-ring or gasket is compressedwhen the head section is screwed on with limited turns or a partial turn. As a result, the head section will be clamped to the pipe while also sealing the coupling. The pipe can be decoupled from the head section after target depth is reached by making the reverse turn afterwhich it can be retracted. A further alternative is to use a bayonet type tting to also mitigate the risk ofan unintended decoupling. In all approaches, part ofthe head section can be tted with ns to provide sufcient rotational resistance to achieve the decoupling with the reverse turn. Another example ofan option to apply a push-based method is where either type ofGHE is attached to the head section in part or in whole and where a pipe or rod is used to transmit the push force. For a coaxial GHE the outer pipe will typically be attached to the head section, and the elongated push member will be run inside. Pushing down the head section will pull along the attached GHE. After target depth is reached, the push member will in most cases be decoupled and retracted to the surface. A U-tubeGHE can be installed in this way in a single step. For a coaxial GHE the inner tube will still need to be inserted. The ground resistance to pushing down a ground-penetrating device on average increases with depth or the cross-sectional area ofthe ground-penetrating device. For any ofthe push-based methods available today to install both coaxial and tubular GHEs with any ofthe options described above, the ground resistance to pushing can be reduced by ejecting uid fed into head section into the ground through one or more outlets in the head section. Ejection is achieved by applying pressure on the uid inside the head section that is higher than the uid pressure in the ground surrounding the head section. The pressure differential is referred to as ejection pressure or the pressure with which the uid ejects into the ground. The uid can be constituted in differentways to enhance penetration and hence is referred to as penetration-assisting uid. The conduit from the surface to the head section is referred to as uid conduit or ejection uid conduit to distinguish it from other uid conduits. In the further description, a key component to enable uid ejection is the head device. It is adapted to constitute at least partially the head section ofthe ground- penetrating device, whereby the head device comprises the inlet for the penetration- assisting uid, the outlet and at least one uid conduit connecting the inlet to the outlet for, when needed, ejecting the penetration-assisting uid into the ground. It further comprises one or more couplings dependent onhow the elongated push member, the ejection uid conduit, and any part of a coaxial GHE are combined. Subsequent explanatory drawings illustrating different methods show the bottom part ofthe ground-penetrating device with the head device, elongated push member and any further attached components ofthe GHE. In the drawings the orientation is vertical. This does not imply a limit to vertical installation only. Non-vertical installations can be made ifthe ground-penetrating device is pushed down at a non-vertical angle to the surface. One ofmany ways to eject uid into the ground, is illustrated in Figure 2. It is the same as illustrated in Figure 1, except that it shows a head device to support ejection ofthe penetration-assisting uid into the ground in front ofand around the head. In this example the head device is coupled to an installation pipe (21) with a screw coupling. The pipe also serves as uid conduit for the penetration-assisting uid (22) that is fed from the surface through the pipe to the inlet (23) on the base (24) ofthe head device (25), through the uid conduit within (26), referred to as head device uid conduit, and through the outlet (27) at the tip into the ground in front ofthe tip. The head device with its uid conduit, the installation pipe, and the connection means ofthe head device to the pipe forms the bottom part (28) ofthe ground-penetrating device. Figure 2 illustrates an example ofhow penetration-assisting uid can be fed into the head device and ejected into the ground at the tip. This uid ejection softens or can even liquify the ground ahead ofand around the tip. This reduces ground resistance to pushing. As the head device moves down, the softened or liquied ground will be pushed aside and form a layer along the head device and the installation pipe with more uid relative to not using uid ejection. This further reduces the resistance to pushing by reducing the friction to motion ofthe ground-penetrating device with the ground. Hence, for a given pushing method and push force, the ground-penetrating device will be pushed into the ground to a deeper level when using uid ejection relative towhen uid ejection is not used. Alternatively, a ground-penetrating device with a larger cross-section can be pushed to the same depth. A head device can be tted with more outlets and head device uid conduits. For example, with the head device shown in Figure 3, uid can be ejected into the ground through multiple outlets each with a uid conduit (30) internal to the head device (25). One way to feed the penetration-assisting uid to these conduits is to letthem branch out from a main head device uid conduit (31). Figure 3 shows multiple head device outlets and head device uid conduits in a single vertical cross-section. In practice, uid conduits and outlets can be similarly mounted to cover any direction. Using multiple outlets, penetration-assisting uid can be ejected into a largervolume ofground than with a single outlet. This softens more ground to further reduce ground resistance to pushing relative to using a head device with a single outlet. In Figures 2 and 3, the outlet or outlets into the ground are straight, thin head device uid conduits. Ifthe sum ofthe cross-sectional areas ofthe outlets is lower than that ofthe main head device ejection uid conduit, the uid ow rate into the ground is accelerated relative to the uid ow rate within the main ejection uid conduit. In other words, the outlets act as nozzles, in this case so called straight nozzles. With sufcient pressure, and when nozzles are sized to leverage the available pressure andow rate, strong jets can be formed. Using nozzles in this manner allows the penetration-assisting uid to be ejected more deeply into the ground. By shaping a nozzle, the effectiveness ofuid ejection into ground can yet be further enhanced. For example, as shown in Figure 4, head device uid conduits (41) can be used with a nozzle shape that narrows towards the outlets which have a small opening through which the penetration-assisting uid is ejected into the ground. Such a shaped nozzle can, for example, be used to spread the ejected uid upon exit from the outlet so that a larger swathe ofground is impacted ahead ofthe tip. Head uid conduits with shaped nozzles can be realised by shaping the head device uid conduits themselves, as illustrated in Figure 4. An alternative is to place nozzle components in the head device uid conduits. Such nozzle components are widely used in various industrial elds for spraying and jetting, for example for cleaning surfaces and the inside ofpipes, declogging pipes, sewer cleaning and for cutting many kinds of materials. Awide selection ofnozzle components is available offthe shelfto meet a wide range ofrequirements in terms of shape, pressure, and ow. Nozzle components can be purchased at the single nozzle level or combined into larger units comprised ofmultiple nozzles with different functionality. In industry, a unit comprised ofmultiple nozzles is also referred to in the singular as a nozzle. This convention is also used in this description. In addition, the term nozzle is further used both for a nozzle comprised of a shaped head uid conduit or implemented with a separate nozzle component. As a further example ofshaped nozzles, nozzles with a attened opening at their tip are widely available and can be used to advantage. They can be placed as outlet in the face ofthe head ofthe head device and oriented horizontally. Ajet formed through such a nozzle will be ejected into a swathe ofground more deeply than when a comparable round nozzle is used. Additional examples of standard available nozzles are, among others, vortex inducing nozzles to achieve deeper penetration with a given uid ow and rotating nozzles to sweep a larger area. Such a rotating nozzle can readily be used to form the head or part ofthe head ofthe head device. A rotating nozzle can have multiple outlets each at a different height from the tip, or in other congurations. Various rotating nozzles can be acquired offthe shelf or custom ordered as required. A rotating nozzle can also be used to induce vibrations, for example by asymmetrically positioning nozzles. This can be advantageous in reducing ground resistance to pushing due to vibration induced liquecation. Further, the outside of a rotating nozzle can be tted with, for example, grooves, blades, or teeth to enhance penetration into the ground. In this description use ofthe word nozzle encompasses straight and shaped nozzles, head device uid conduits that are shaped to form a nozzle, and more specialized nozzles such as vortex inducing, rotating, vibrating, and rotating-and-vibrating nozzles. A head device with xed nozzles, dependent on soil conditions, may require a signicant number ofnozzles to effectively eject uid to cover the ground around the head as it is pushed down. One alternative approach to using many outlets to cover multiple directions is to use fewer outlets and, when needed, to combine ejection with rotating the ground-penetrating device. Another approach is to use a rotating nozzle to achieve the same effectwhereby the ground around the head is swept as the nozzle rotates. Either approach can be combined in an approach where the ground-penetrating device is moved up and down, which is away to reduce the number ofvertically spaced nozzles that is required. Any ofthese and similar approaches typically reduces the number ofnozzles required, which will also result in a reduction in the volume ofpenetration-assisting uid that needs to be ejected. To eject penetration-assisting uid into the ground through the head device positive overpressure, i.e. the difference between the uid pressure in the head device and the uid pressure in the ground at the depth ofthe head device, is required. To achieve such overpressure, the pressure at the surface must exceed the static pressure ofthe ground column, which is at least 1 bar per 10 meters ofground, andow resistance. One source of uid pressure at the surface is the household water supply. Typical pressure at the household level is 2 to 4 bar, though in some cases can reach 5 or 6 bar. With such surface level pressure only limited ejection in the rst ten or few tens ofmeters ofground can be achieved. In most cases it is desirable to use pumping to increase the pressure on the penetration-assisting uid in the head and ejection volume. As overpressure and / or ejectionvolume is increased, jets will become increasingly powerful resulting in increased softening or even liquecation ofthe ground in front ofand around the head. This reduces the ground resistance to pushing and supplies more uid to reduce the frictional resistance to pushing. Required pressure and volume levels for an installation depend on various parameters, among others soil composition, target depth, cross sectional area ofthe ground-penetrating device and available pushing equipment. For soft soil areas, pressure of 10 to 100 bar in combination with a 10 40 litre per minuteow rate covers a wide range ofparameters. In case of stiffer and harder soil, pressure can readily be extended upwards. For example, with appropriate nozzles and overpressure ofaround 150 bar soft stone can be cut, whereby, for example, a steel pipe can be used as ejection uid conduit and push member. Pumping equipment achieving a pressure of several hundred bar and ows of several tens of litres per minute and appropriate nozzles and pipes are widely available. In the examples shown, the head uid conduits have an ejection direction more or less orthogonal to the face ofthe cone. This is just for illustration, in practice uid may be ejected in any direction, and direction can be used as a parameter to strike a balance between the number ofnozzles placed in a head device and the effectiveness ofthe reduction ofground resistance to pushing. Choices in the length and shape ofthe head device; in the number, position, and ejection direction ofthe nozzles in the head device outlets; and in the use ofnozzles and their shape and design allows wide exibility in the design ofthe head device. This exibility supports the use ofhead devices that are tailored to parameters such as the soil composition, cross-sectional area ofthe ground-penetrating device, specications ofthe available pumps and pushing equipment, installation speed and overall installation cost. Such head devices all fall within the scope ofthis disclosure as is the use of a head device with application ofoverpressure tojust achieve fluid ejection to reduce friction or, at higher levels, to achieve jetting sufcient to soften or liquefy the ground around the head device, including ground consisting of stiffmaterials or soft rock. The static pressure ofuid in the ground around the head will generally be higher than the static pressure ofthe uid column from the surface to the level ofthe head device. As a result, in case the connection from the ground through any head device uid conduit and ejection uid conduit is open during installation, ground uid may ow back into the head device and the ejection uid conduit unless during the installation sufcient over pressure is maintained. Such backow is undesirable as it will bring ground water into the head device and attached uid conduit, potentially with undesirable chemicals and pollutants and soil particles. An alternative to maintaining sufcient overpressure to preventbackow is to install one or more check valves in the head device that close in case ofinsufcient overpressure. For example, standard ball, poppet, orwing check valves can be used. In practice, check valves are often spring loaded to ensure they are closed unless the overpressure at the level such valve exceeds a preset level. Such check valves are also widely available. Oneway to place one or more check valves is illustrated in Figure 4, where a shaft (14) forming part ofthe head device (25) and used to connect the head device to the pipe is lengthened to hold a valve chamber with a valve (42) placed in the main head device uid conduit (31). Such a valve chamber holding one or more valves is easily created in a rst section ofthe lengthened shaft afterwhich a second section is mounted on top to close offthe valve chamber. A further benet ofusing check valves to preventbackow is in case, after target depth is reached, at least part of a heat exchange uid conduit is installed inside the installation pipe afterwhich the installation pipe is withdrawn. With a check valve in place, should there be any uid in the installation pipe, it can be partially or fully pumped out to facilitate the heat exchange uid conduit installation. In case the installation pipe is left in the ground and used as outerbody ofa coaxial GHE, it typically must be closed off at the bottom. In case ofdoubt about the integrity ofthe seal between the head device and the pipe and / or valve or valves ifused, a plug may be installed. Oneway to achieve this is by using a seat positioned in the pipe above the top ofthe head device, whereby the plug is installed by mounting it on a rod or tube that is pushed down. The installation can be facilitated by using a guide that is part of the seat. An alternative or addition to using a plug is to create a seal with swelling material placed at the bottom ofthe pipe and that is impermeable. One possible method to install aGHE is where the installation pipe is also used as penetration-assisting uid conduit. When a method is selected where the installation pipe is left in the ground either to serve as the outerbody of a coaxial GHE or to hold aGHE inside it, it is desirable to be able to use a pipe made of material such as plastic, which is both low cost and durable. This poses limitations in terms ofpush force load and ejection uid overpressure that can be applied. One way to avoid using the installation pipe as ejection uid conduit is to use a separate hose or pipe as conduit. Using a separate uid conduit facilitates ejection of the penetration-assisting uid with high overpressure. The terms low pressure and high pressure are used to distinguish between the pressure levels that can be sustained in low-cost pipes such as made from plastic from pressure levels that can be sustained in pipes made from stronger materials such as steel. The low pressure threshold lies in the 10 20 bar range for typical plastic pipes. High pressure ejection can be achieved using a separate high-pressure hose or pipe as a conduit. In most cases it will be desirable to recover such a conduit after target depth is reached. Figure 5 presents one example ofone ofthe ways to use an installation pipe in combination with a separate ejection uid conduit, which in this example is taken to be a high-pressure hose. Here the head device is extended with a coupling means (51), referred to as the head device connector, which, for example, is one side of a so called quick connect coupler (in practice also referred to as quick connect tting). When the bottom ofthe ejection uid conduit (52) is tted with the corresponding counter coupler (53) the coupling can be made by pushing it onto the head device connector. The penetration-assisting uid can now be ejected from the surface through the ejection uid conduit and head device into the ground. The ejection uid conduit can be built up at the surface from segments as the installation proceeds. This facilitates combined use ofthe installation pipe and the ejection uid conduit as the head device is pushed into the ground. Once target depth is reached the ejection uid conduit will in most applications need to be disconnected and retracted. The disconnect can be achieved with a push-pull coupling mechanism, whereby the coupling is made by pushing and disengaged by pulling. One means to achieve this is to use a so-called breakaway coupling whereby the ejection uid conduit releases when it is pulled up and a preset force is exceeded. Such coupling can be integrated into the head device connector or can be placed above it. Another push-pull coupling mechanism forwhen a hose is used as ejection uid conduit comprises using a male quick connect part at the top ofthe head device connector which can be coupled with its female counterpart on the ejection uid conduit and where its release ring has a xed coupling to the bottom of a section ofpipe, stifftube, or other stiff member. Higher up, this section is xed to the hose, which is typically somewhat elastic. Then, when the ejection uid conduit is pulled up with sufcient force, the section between the release ring and xed coupling above will lengthen. Release is achieved once the length corresponds to the distance required to release the quick connect. As needed, this effect can be amplied by winding the section between its coupling to the release ring and xed connection point above it and / or using a section ofhose that is more elastic than the further hose running to the surface. In this option a pipe can also be used instead ofthe further hose. Quick connect couplers are widely available as are hoses and pipes and hose and pipe segments pre-tted with quick connect or threaded couplers. Further, high- pressure coupler parts and corresponding pre-tted high-pressure hoses and pipes that can handle several hundred bars or more are widely available. When a high-pressure pipe is used as ejection uid conduit a rotational coupling to the head device can be used as described earlier so that the pipe can be disconnected after target depth is reached. In this approach the pipe can also be used as elongated push member. In the description the terms releasably coupled and releasable couplings are used to generically describe couplings to hoses or pipes that can be connected and disconnected using a push-pull, rotational or other method. In case quick connect couplers are used, they can also be used to place one or more check valves including spring loaded check valves. Quick connect couplers including a check valve can be acquired offthe shelf. A breakaway connector, ifused, typically also includes a check valve. Check valves directly connected to the head device connector can be an alternative or addition to a separately placed check valve or valves in the main head device uid conduit. Reference to the head device connector, dependent on the conguration, includes the option to use one or more check valves. The head assembly ofFigure 5 additionally shows use of a collar (54) mounted on the head device (25). This serves several purposes. First, as the head is pushed down and as the collar has a larger diameter than the installation pipe, it pushes out the soil more than is needed for the installation pipe. Together with the ejection uid, this creates a larger uid layer to reduce friction between the installation pipe (21) and the ground during pushing. Second, the collar protects the coupling point (55) from ground contact and against lateral forces as these are distributed over the overlapping section ofpipe and collar. The collar can also be used to add weight to the head device which is advantageous for maintaining verticality for the installation of a vertical GHE. In the examples the head uid conduits are channels in the head. In an alternative conguration, a head device can be formed comprised ofpipe or hose segments that connect the nozzles to a pipe segment or chamber that connects to the ejection uid conduit. In case an ejection uid conduit is used that runs inside an installation pipe, this coupling can again be made through a head device connector. In the methods illustrated in gures 2 to 5, the pipe transmits the push force. An alternative is to use a separate elongated push member. One option is to rst attach the pipe to the head device, typically at the edge ofthe head device or slightly within to form a collar, and then position the push member inside the pipe and couple it to the head device. The push member will typically be centred with the ejection uid conduit placed next to it. In case there is no need for pulling up the ground-penetrating device during installation, it sufces to connect to the base ofthe head device without coupling. In case a releasably coupled pipe is used as elongated push member, such pipe may also be used as ejection uid conduit or a separate ejection uid conduitmay be run within it. With any ofthese approaches, the outer pipe, which is attached to the head device, is pulled down as the head device is pushed down. Once the elongated push member is decoupled and withdrawn, the pipe is in place in the same way as if it had itself been used as elongated push member. In case the approach illustrated in gure 5 is applied for high pressure ejection in conjunction with the use of a separate elongated push member, both the pressure and load specications for the outer pipe can be low, facilitating the use oflow cost, typically plastic material for the pipe. Rather than eject the penetration-assisting uid under a certain constant pressure, it will generally be benecial to vary the pressure according to a user dened ejection uid pressure prole. Generally, the pressure with which the uid ejects from the outlet or outlets on the head device into the ground is increased when the ground- penetrating device encounters stronger resistance to being driven into the ground and, conversely, the pressure with which the penetration-assisting uid ejects from the outlet is decreased, even to zero, when the ground-penetrating device encounters a weaker resistance to being driven into the ground. Typically, the objective ofapplying an ejection uid pressure prole is to strike a balance between the time required to achieve target depth and the volume ofpenetration-assisting uid that is ejected. Further, the ability to reduce the need for ejection by using a pressure prole can help to eliminate or at least reduce the need for any grouting. Use of a pressure prole includes a pulsed ejection mode whereby the penetration-assisting uid is ejected with pulse-like pressure variations, varying anywhere between the highest available pressure and the low or noow pressure. Pulsed ejection may induce vibrations which may help to break down stiff or hard layers. Additionally, vibrations may enhance or induce ground liquecation along the head device and attached pipes which further reduces ground resistance to pushing. To handle a wide range of situations, it is advantageous to be able to choose from several ejection pressure modes and mode parameters, for example including: duration and pressure of a constant pressure mode which includes zero or noow pressure; pressure ramp up and ramp down mode with ramp rate, base pressure and high pressure and duration ofbase and high pressure intervals as parameters; and pulse mode with pulse duration, rate, base pressure, and high pressure as parameters. In practice, a uid ejection pressure prole can combine sections where different modes with different parameters are applied, dependent on ground conditions and to achieve a certain installation speed while minimising the volume of ejection uid used. In addition, maxima on pressure can be set, among others to ensure safety and to maintain integrity oftheGHE and installation components subjected to pressure. The purpose of ejecting penetration-assisting uid into the ground in front ofand around the head device is to assist penetration ofthe ground-penetrating device, hence its description which points to its main purpose. The starting point for the penetration-assisting uid generally will be a base uid, typically water. The composition ofthe base uid can be changed to enhance its penetration. One example is to use additives that reduce friction between the ground, also when softened or liqueed, and the ground- penetrating device. A further example, in case the need is to penetrate through stiffer or harder layers, is to add abrasives to cut into such layers to better soften or liquefy them to reduce ground resistance to pushing. Additives can also be used to create uid grout that can be ejected if it is advantageous or required to seal certain layers from each other or even the complete passage. The uid composition can also be changed to improve its heat conductivity. One way to achieve this is to add small, even down to nano-size, particles ofhigh conductivity materials to the uid. An additive that improves heat conductivity can also be selected to at the same time support friction reduction or abrasiveness. Dependent on the objectives, additives can be combined. When considering installation alternatives in conjunction with using penetration-assisting uid ofvarying composition, an additional aspect ofthe use of a separate ejection uid conduit should be considered. It has as advantage that it will typically have a signicantly smaller diameter than an installation pipe alternative. As a result, substantially less uid will need to be pumped down for a uid composition change to enter into the ground. In summary, the methods and devices illustrated by means gures 2 5 and further variations all support the push-based installation of a pipe in the ground, where the methods are characterised by ejecting a penetration-assisting uid fed from the surface through the head device into the ground to reduce the ground resistance to pushing. As discussed, there are multiple ways to use such a pipe in placing the GHE. First, the pipe can be used as the outer pipe of a coaxial GHE. A second option is to install a coaxial or tubularGHE inside the pipe after target depth is reached, afterwhich the installation pipe is decoupled and withdrawn. A yet further option is, after placement oftheGHE inside the pipe, to leave the installation pipe in place. This optionality is advantageous for selecting the most suitable method and most appropriateGHE conguration given such parameters as soil conditions, regulations, available equipment, and cost. With respect to cost, it is noted that the methods and devices support options for installing low cost GHEs fabricated from plastic or similar material. One method and its variations described above to install a coaxial GHE is whereby the outerbody is pulled down as the head device is pushed into the ground. Such method can also be used to pull down a tubular GHE, where its bottom can be attached to the base ofthe head device next to any elongated push member and ejection uid conduit, which, in case a pipe is used as push member, can be combined. The ground-penetrating device formed in this manner is then pushed down to target depth and the installation of theGHE is completed by decoupling and withdrawing the elongated push member and any ejection uid conduit. In most cases it is preferable to use a conical shape for the head device and symmetrically position the tubes of a tubularGHE to support maintaining direction while pushing. To achieve this an assembly comprised ofthe head device and a tubular ring attached to the base ofthe head device can be used where the ring has ports to connect the vertical tubes. In case ofjusttwo tubes, like for a single U-tube, a heat exchange uid path is created by selecting one tube for the descending heat exchange uid, using the ring to pass the heat exchange uid to the other tube and using that tube for the upgoing uid. More tubes can be connected, also of different diameter. The installer can select which tubes are for the descending heat exchange uid and which for the upgoing, with the ring providing the connection. Below, an example ofthe use of such a ring is illustrated in more detail. An installation pipe can be coupled to the head device through the ring. One option is to use the pipe both for transmitting the push force and as ejection uid conduit. Alternatively, a separate ejection uid conduit can be run inside the installation pipe or placed eccentrically by appropriately shaping the heat exchange uid ring connector to leave space for the connector on the base ofthe head device. In the latter case the installation pipe can also be replaced with just a push rod. In the described cases for pulling down a tubular GHE, the coupling ofthe push member and any ejection uid conduit to the head device will typically be decouplable, so that after target depth is reached, the installation pipe and any ejection uid conduit can be decoupled and retracted to the surface. This leaves the head device and the attached tubularGHE in place, completing the installation ofthe underground part of a ground heat exchange system. This method ofinstalling a tubularGHE is attractive. It is efcient, as the GHE is installed in a single run. Further, tubes are exible and at the surface can be deployed straight from a reel and they run separate from the elongated push member and, if applied, a separate ejection uid conduit. In addition, there is no need to close off a pipe after installation. The method is also cost effective from a materials point ofview as the tubes typically used in tubularGHEs are made oflow-cost plastic. These benets will often outweigh the disadvantages that, compared to a coaxial GHE installed in the same ground passage, it has less heat capacity because ofthe space taken up by the elongated push member and ejection uid conduit and space between the tubes, and that in certain cases it may be advisable or even required to grout given the space left between the tubes. In case oftubular GHEs, the separation between the tubes is mainly determined by the geometry ofthe largest cross section ofthe head device. For example, it is attractive ifthe tubes of a tubularGHE are spread out so that a largervolume of earth can be accessed by theGHE for heat exchange. This can be achieved by extending the head device with arms. An example ofthis approach is shown for a tubularGHE with four tubes in Figures 6 (vertical section through the centre and two arms) and 7 (horizontal section) at level (60). The vertical tubes (61) are connected to each other through horizontal sections ofvertically stretched tube (62) that connect to aGHE tubular ring connector (70). The vertical and horizontal tubes and ring constitute the heat exchange uid path ofthe GHE. The horizontal tubes are vertically stretched to reduce the horizontal cross-sectional area ofthe head device whereby the vertical cross-sectional area remains close to that ofthe connectedGHE tubes or is larger to not create an unnecessaryow bottleneck. The tube assembly is mounted with any convenient mounting means on the base ofthe head device consisting of a central cone (63) extended with four arms (64). The GHE tubes are not used to transmit the push force, and as result low-cost tubes can be used. The tube assembly may be protected from damage during pushing by placing it within a trough (65) in each arm ofthe head device as shown at (65) in Figure 6, whereby the side ofthe trough may form a full perimeter at the base ofthe head device as shown (65) in Figure 7. The installation pipe (21) is run through the ring and coupled to the head device such that it can be decoupled after target depth is reached and retracted. As in the example presented in Figure 5, a separate ejection uid conduit (52) running inside the installation pipe is coupled to the head device, which can also be decoupled and retracted after target depth is reached. The penetration-assisting uid can be ejected into the ground through head device uid conduits (66 to 69) placed in the arms (64) and the tip ofthe head to reduce the ground resistance to pushing down the ground-penetrating device, the bottom part of which comprises the components indicated with the bar (28). The four head device uid conduits (69) positioned underneath the centre ofthe vertical GHE tubes (61) point downwards and will typically have a straight or round nozzle so that at the end ofeach arm and its attachedGHE tube a circular channel is created with softened or liqueed ground which has less resistance to pulling down the tubes than the surrounding soil. As a result, as the head assembly is pushed down, theGHE tubes will tend to stay in their channels and so maintain full spacing. The central nozzle (66) will typically also be straight or round. The nozzles (67) placed in the side ofthe cone can, for example, be horizontally shaped to reduce ground resistance to pushing down the central cone and need not be placed in the same directions as the arms. The nozzles (68) positioned in between the conical nozzles and the outer conduit can, for example, be close to straight shaped as the arm is narrow and only a narrow strip ofground ahead ofthe arm is then softened or liqueed. The head device in this example shows four arms. Another number ofarms can be chosen as required. The head device is similar to the head devices described in Figures 2 5, except for the arm extension to increase the spread oftheGHE tubes of a tubular GHE. Hence, the variation ofcomponents and functionality ofthe head device, use ofan ejection pressure prole, varying the composition ofthe penetration-assisting uid and many ofthe earlier described variations in the application methods all apply. Additional variations can readily be made. In one example ofan alternate set-up, cut-outs are made in the push pipe (21) which are large enough to accommodate the tubes (62) sitting on the top ofthe arms. These tubes can then be run through these cut-outs and connected to a tubular ring sitting within the installation pipe. In the example ofFigure 6 the head device shaft then also needs a cut-out to accommodate the ring. In this way the diameter ofthe central cone ofthe head device can be signicantly reduced which reduces the ground resistance to pushing down the head device. To install the underground part of a ground heat exchange system many of the pushing methods and supporting equipment available in elds such as geotechnical ground investigation, GHE installation and piling can be applied. Pushing methods from these elds include, among others, pushing by weight, constant rate pushing as used for CPT ground investigation, impact hammering and vibratory pushing, and combinations of these methods. From the equipment perspective, equipment from the drilling industry may also be useful. Further, pumping equipment and supporting components such as hoses, pipes, connectors, and nozzles for utilising pressures up to several hundred bar are, among others, widely available from the elds of spraying, cleaning including pipe and sewer cleaning, and drilling. Equipment for even higher pressures to around a thousand bar is also standard available. Field units to carry out theGHE installation are therefore readily assembled. Additional components for the head devices can be cast, machined, 3D printed or otherwise manufactured. Hence, embodiments may be readily elded for application. Various methods and devices are disclosed with which an underground part of a broad range ofcongurations ofground heat exchange systems can be installed with push-based methods characterised by feeding a penetration-assisting uid from the surface into the ground to reduce the ground resistance to pushing. The uid can be ejected over a wide pressure range according to a user dened ejection prole. Further, the uid composition can be varied to reduce ground resistance to pushing, improve heat transfer and for grouting ifrequired. Using standard available equipment, the embodiments that have been presented, as well as other embodiments, can readily and economically be applied in soft soil areas and areas where soft soils are intermingled with such ground materials as stiff clays and soft rock. For special cases higher pressure can be considered. The disclosed methods and devices offer several benets compared to applying push-based methods without the benet ofuid ejection. One key benet is that the underground part of a ground heat exchange system can be installed more deeply, with a larger cross-sectional area, or both. In the alternative, a given ground-penetrating device can be pushed to the same depth with less push force. As a result, less heavy, lower cost and lower footprint equipment can be used. A further benet is that various options are supported to install both coaxial and tubularGHEs built from low-cost plastic materials. Yet another benet is that the geographic areas and depth to which a push-based technique can be applied is substantially widened. Numerous modications and variations can be made to the methods and devices disclosed in the description to achieve the benets. In addition, means, components and materials that are described can be replaced with others having a similar function. All such modications, variations and replacements fall within the scope ofthe invention as dened in the claims.

Claims

1. Procedure for installing an underground part of a ground heat exchange system, where the method includes: - positioning a ground-penetrating device on a ground surface with a head section of the ground-penetrating device that is aimed at the ground area; - applying a pushing force to the head section to at least a to drive part of the soil-penetrating device into the ground until the head section a has reached the desired depth, creating a passage in the ground that extends from the surface to the head section, - providing the passage with a heat exchange fluid pad that is adapted for a heat exchange fluid from the surface down into the ground to guide and then back up to the surface, characterized by: - supplying a penetration-supporting fluid from the surface to an inlet on the head section, which is connected in a fluid-permeable manner to an outlet on the cylinder head, so that the penetration-supporting fluid exits the outlet injects into the ground, whereby the penetration-supporting fluids for at least some time is applied while the thrust force is exerted on the head section.

2. Procedure for installing an underground part of a ground heat exchange system in accordance with claim l, comprising: - varying the pressure with which the penetration-supporting fluid is expelled the exhaust on the front section sprays into the ground.

3. Procedure for installing an underground part of a ground heat exchange system according to claim 2, where the pressure with which the penetration-supporting fluid sprays into the ground from the outlet on the head section is increased when the ground-penetrating device has a stronger resistance experiences against driving into the ground and, conversely, the pressure with which the penetration The supporting fluid from the outlet spray is reduced when it is ground-penetrating. device encounters weaker resistance against driving into the ground.

4. Procedure for installing an underground part of a ground heat exchange system in accordance with one of conclusions 2 and 3, whereby pulse-like pressure variations are induced in the pressure with which the penetration- sprays supporting fluid into the ground from the outlet on the front section.

5. Procedure for installing an underground part of a in-ground ground heat exchange system in accordance with one of conclusions 1 through 4, whereby the penetration-supporting fluids are directed to the outlet, at least temporarily. inflated with a pressure of at least 4 bar, measured at the surface.

6. Procedure for installing an underground part of a ground heat exchange system according to one of conclusions 1 to 5, where the ground-penetrating device comprises a pipe through which the thrust force on the head section is exercised.

7. Procedure for installing an underground part of a ground heat exchange system according to claim 6, where the penetration- supporting fluids at least partially via the pipe from the surface to the The intake is routed to the head section.

8. Procedure for installing an underground part of a ground heat exchange system in accordance with one of conclusions 1 through 6, where the penetration-supporting fluids at least partially via a separate pipe is fed from the surface to the inlet on the head section.

9. Procedure for installing an underground part of a ground heat exchange system according to one of conclusions 1 to 5, where the equipped with the passage with a heat exchange fluid pad, includes the following: - connecting a heat exchange fluid piping system to the head section of the soil-penetrating device before the head section is inserted into the ground driven, whereby the heat exchange fluid piping system at least partially the heat exchange fluid path forms after the passage has been formed.

10. Head device for use in a procedure for installing a underground part of a soil heat exchange system according to one of 1 to 9, where the head device is adapted to at least partially the to form the head section of the soil-penetrating device, whereby the head device the The inlet comprises where the penetration-supporting fluid is supplied, the outlet from which the penetration-supporting fluid is injected into the soil when the procedure is carried out, and at least one pipe connecting the fluid-permeable inlet to the exhaust.

11. Head apparatus within the meaning of claim 10, where the outlet comprises a nozzle.

12. Head apparatus according to claim 11, where the mouthpiece is one of the the following types of mouthpieces are: a rotating mouthpiece, a vibrating mouthpiece, and a rotating and vibrating mouthpiece.

13. Head apparatus according to one of claims 10 through 12, which multiple comprises outlets, which are connected to the inlet in a fluid-permeable manner, where the outlet a of the multiple exhausts is.

14. Header device according to one of claims 10 to 13, which at least comprises a valve that is adapted to a fluid flow from the outlet to the inlet prevent.

15. Head apparatus according to one of claims 10 to 14, whereby the The head device has been modified to be detached and coupled to an elongated push element by means of which the pushing force on the head device can be exercised.

16. Head device pursuant to one of claims 10 to 15, for use in a procedure for installing an underground part of a ground heat exchange system in accordance with claim 8, where the header device has been modified to be disconnectably connected to the separate pipe.

17. Head device pursuant to one of claims 10 to 16, for use in a procedure for installing an underground part of a ground heat exchange system in accordance with claim 9, where the header device has been modified to be connected to the heat exchange fluid piping system.

18. Kit for installing an underground part of a ground heat exchange system, where the kit is a header device according to one of the comprises conclusions 10 through 17. 1 / 4

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