Heat source or heat sink unit with thermal ground coupling

Abstract

The invention relates to a heat source or a heat sink unit with thermal ground coupling, comprising at least one ground probe arranged in the earth, whereby each earth probe is a probe tube made from several pile tube segments. An open dip tube or a U-shaped tube loop is arranged in the probe tube at the open lower end thereof. Said unit is characterized in that each pile tub segment is made from ductile cast iron, the pile tube segments re embodied such as to plug into each other at the ends thereof and each pile tube segment comprises, at the one end thereof, a conical outer circumference and, at the other end thereof, a sleeve embodied with a shoulder stop having a matching conical internal circumference, whereby the diameter thereof and the cone angle are such that on driving in the pile tube segments a positive and sealed connection between the pile tube segments is generated.

Description

BACKGROUND OF THE INVENTION [0001] The present invention relates to a heat source or heat sink system with thermal ground coupling for near-surface recovery of thermal energy from the ground or for near-surface discharge of thermal energy into the ground, wherein the system comprises at least one ground probe arranged in the ground, wherein thermal energy can either be withdrawn from or discharged into the ground by means of a heat transfer fluid supplied through the ground probe, wherein each ground probe comprises a metallic probe shaft that is tight against the surrounding ground and consists of several drive-pipe segments driven into the ground, and wherein either an immersion pipe that is open at its lower end or a U-shaped pipe loop is arranged in the probe shaft for supplying or removing the heat transfer fluid. [0002] Systems for the aforementioned types of intended use are known from practice in various executive forms. In essence, these known solutions can be grouped in th...

AI Technical Summary

Benefits of technology

[0009] Initially, it is provided according to the invention that each drive-pipe segment is formed of ductile cast iron. In essence, ductile cast iron differs from traditional gray cast iron in that the graphite is contained in ductile cast iron in the form of nodular graphite, so that the mechanical properties are changing; in particular, the strength and tenacity are increased. As compared with gray cast iron, the chemical properties of ductile cast iron are also improved, in particular the corrosion resistance against pitting. The drive-pipe segments can, for example, be produced according to the centrifugal casting method, wherein it is practically possible to use 100-percent recycling material, i.e. steel scrap, this being both to economical and ecological advantage. Since they are subjected to a special post-casting process, the drive-pipe segments of ductile cast iron have such a mechanical resistance that they can be driven into the ground with considerable impact forces without suffering any damage. To further facilitate the formation of the probe shafts, the invention provides that the drive-pipe segments are designed such that they can be fitted into each other at their ends. Large-scale screwed, soldered or welded connections which can be established and tested on the construction site only under the greatest difficulties are not required between the successive drive-pipe segments. This also facilitates the mechanical treatment of the ends of the drive-pipe segments during their production and also reduces the amount of work and the risk of faults on the construction site at the place where the drive-pipe segments are driven into the ground. Therein, it is, furthermore, provided according to the invention that each drive-pipe segment comprises a tapered outer perimeter at one of its ends and, at its other end, a sleeve having a mating tapered inner perimeter, wherein their taper angles are dimensioned such that the drive-pipe segments, solely by being driven in, can be connected to each other in a force-closed and tight manner. This embodiment of the drive-pipe segments ensures that the desired tightness and force-closed connection of the various drive-pipe segments to each other is obtained solely by the drive-in process. Special sealants are not required. Each sleeve is provided with a shoulder and, as regards the fitted part of the respectively other segment, is designed such that, after the sleeve has been expanded by a defined amount, the fitted segment comes to rest on this shoulder and then transfers the drive pulses, therein preventing the sleeve from being subjected to the stress of a further expansion to an impermissible extent. If the pulses or drive blows for driving in the drive-pipe segments are sufficiently strong, a friction weld ensuring the desired tightness and force-locking connection for very long operating times of the probe shaft is obtained in the region where two drive-pipe segments are connected to each other. Since it is not necessary to ensure that the individual drive-pipe segments are, at a later point, disconnected from each other without being destroyed, this non-detachable friction-welded connection is not of any technical disadvantage whatsoever.

[0030] A further contribution to avoiding corrosion damages consists in using pipes for the piping of the remaining system and for its connection with a heating or cooling device, which are oxygen-diffusion-tight. By this, an introduction of oxygen into the heat transfer fluid, which might promote corrosion of the drive-pipe segments, is prevented.

Problems solved by technology

Such panel collectors require extensive earthworks, thus causing expensive installation; in addition, they can often not be used owing to local conditions.

It is also obvious that the establishment of such a system is very complicated and, thus, expensive.

In addition, such systems require official approval, so that additional cost and time expenditures are caused by the appropriate application for and processing of the approvals.

What is more and as practical observations have shown, the responsible authorities often treat such applications in a restrictive manner and with exaggerated care as regards the potential contamination of groundwater in case of leakages.

This is to disadvantage in that the screwed connections between the segments are sensitive while the driving-in procedure is in progress, and have a tendency to tears and leaks associated therewith; this also applies to the welded or soldered connections that are known from practice.

The cutting of threads, the welding or the soldering are to disadvantage in that all of these processes result in local changes in the structure and hardness of the material of the probe shaft segments and, thus, in potential weak spots which may, sooner or later, be the starting point of cracks or breakages.

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