A ground source heat pump system

Abstract

This invention relates to a ground source heat pump (GSHP) system comprising: a borehole (1, 2) drilled in the earth; a suction pipe (3) mounted in the borehole (1); and a pump (4) mounted in the borehole (2), the pump (4) having a suction opening (5). In the invention the pump (4) has been mounted above the suction pipe (3); a pump housing (7) has been arranged around the pump (4) so that a space remains between the pump (4) and the pump housing (7); the pump (4) has been arranged to suck water from the suction pipe (3) to the space between the pump (4) and the pump housing (7) and further upwards to the suction opening (5) of the pump (4) and via the pump (4) and a pressure side pipe (8) up to the ground level; between the pump housing (7) and the borehole (2) wall, which is bedrock or pipe sunk into the bedrock, a space has been arranged for the downwards flowing water; and that the pump (4) can be lifted from the borehole (2) without the suction pipe (3).

Description

[0001] A GROUND SOURCE HEAT PUMP SYSTEM

[0002] FIELD OF THE INVENTION

[0003] This invention relates to a ground source heat pump (GSHP) system comprising: a borehole drilled in the earth; a suction pipe mounted in the borehole; and a pump mounted in the borehole, the pump having a suction opening.

[0004] BACKGROUND OF THE INVENTION

[0005] In a ground source heat pump (GSHP) system, which is based on ground water circulation, there are known problems in ground water circulation when stand ard circulation pumps are used above the ground or in technical rooms. The level of the ground water is sev eral meters below the ground surface, which means that if the pump is for example 5 m above the ground waster level, thew pressure in the suction side of the pump is max. 0,5 bar, and once the pump is running, the pressure is less, depending on the pressure losses in the riser pipe. This results in a situation in which the suction side of the pump cavitates and the pump cannot keep up the flow of the ground water. Typical ly, this leads to a situation in which the water does not flow at all.

[0006] Instead of using a regular circulation pump above the ground level or in a technical room, a ground water pump, known also as a borehole pump or water well pump can be used. It is common to use such a pump at the bottom of the borehole or close to the bottom of the borehole. In GSHP systems, the wells typically exceed the depth of 300. In more advanced solutions, like in semi-deep boreholes, the targeted depth can be beyond 600 m. Placing a pump at the bot tom of such a deep borehole causes difficulties also, as any technical problem, maintenance or repair of the pump has to be carried out by lifting the whole pipe up and away from the borehole before the pump can be brought to the surface. Further, problems relating to the electricity supply cable length, such as power losses and cable tension in deep boreholes may occur.

[0007] OBJECT OF THE INVENTION

[0008] An object of the invention is to provide a ground source heat pump (GSHP) system in which the wa ter circulation is steady without cavitation of the pump and in which the eventual repair and maintenance of the pump can be carried out without the need to re move the suction pipe from the borehole.

[0009] SUMMARY OF THE INVENTION

[0010] The above object of the invention has been solved with a GSHP system characterized by that the pump has been mounted above the suction pipe; a pump housing has been arranged around the pump so that a space remains between the pump and the pump housing; the pump has been arranged to suck water from the suc tion pipe to the space between the pump and the pump housing and further upwards to the suction opening of the pump and via the pump and a pressure side pipe up to the ground level; between the pump housing and the borehole wall, which is bedrock or pipe sunk into the bedrock, a space has been arranged for the downwards flowing water; and that the pump can be lifted from the borehole without the suction pipe. In one embodiment of the invention the suc tion pipe has been connected to the pump housing via conical shape or the like expansion part. In one embodiment of the invention the suc tion opening of the pump is located at the side of the pump above an electric motor operating the pump.

[0011] In one embodiment of the invention the bore- hole for the pump housing is larger in diameter than the borehole for the suction pipe.

[0012] In one embodiment of the invention the pump housing with a diameter larger than the diameter of the borehole for the suction pipe, is supported on the step between the larger diameter borehole and the smaller diameter borehole.

[0013] In one embodiment of the invention the bore- hole with larger diameter reaches down to 10 m below the ground water level.

[0014] In one embodiment of the invention the sepa ration point separating the pressure side pipe and the suction pipe is located above the pump.

[0015] In one embodiment of the invention the sepa ration point separating the pressure side pipe and the suction pipe is located below the pump.

[0016] In one embodiment of the invention the sur faces touching each other at the separation point are conical in shape to centre the pump and / or pump hous ing when it is lowered into position.

[0017] In one embodiment of the invention the coni cal shapes are arranged so that the part belonging to pressure side pipe is conical so that the top of the cone points downwards.

[0018] In one embodiment of the invention the coni cal shapes are arranged so that the part belonging to pump housing has a cone pointing upwards.

[0019] In one embodiment of the invention the sepa ration surfaces of the separation point are equipped with a flexible seal material to seal the water flows upwards and downwards from each other.

[0020] In one embodiment of the invention between the said step and the pump housing there is an ar rangement which allows the water to flow downwards be tween the pump housing and the step.

[0021] In one embodiment of the invention the ar rangement includes for example fins or the like with which the pump housing is supported on the step, but which still allow the water to flow between the fins.

[0022] The invention according to present disclosure offers specific advantages over the prior art. With the invention it is possible to lift the pump from the borehole without the suction pipe. Because the suction pipe may be hundreds of meters long, this makes the repair and maintenance of the pump much easier.

[0023] BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings, which are included to provide a further understanding of the invention and constitute a part of this specification, illus trate embodiments of the invention and together with the description help to explain the principles of the invention. In the drawings: Figure 1 shows one embodiment of the inven- tion; Figure 2 shows another embodiment of the in vention.

[0025] DETAILED DESCRIPTION In this description only the part of the sys tem located in the earth (under the ground level) is explained. It is obvious that in the heat pump systems also the equipment above the earth is needed. However, as it is not part of the actual invention, it is not described further in this connection.

[0026] In Figure 1 the reference number 1 refers to a borehole for a suction pipe 3 in a ground source heat pump (GSHP) system. The borehole 1 for the suc- tion pipe is smaller in diameter than the borehole 2 for a pump 4.

[0027] The pump 4 has a suction opening 5 at the side of the pump 4, right above an electric motor 6. This results in the need to position the pump 4 in a tube-like pump housing 7 enabling the inlet water to flow past the electric motor to the suction opening 5. The pump housing 7 has a larger diameter than the suc tion pipe 3. The suction pipe 3 is connected to the pump housing 7 via a conical shape or the like expan sion part.

[0028] The pump housing 7 must have sufficient space between the inner wall of the pump housing 7 and the pump 4 to allow the water to flow past the pump with out causing too much of pressure loss in the water flowing upwards. There also needs to be sufficient space between the pump housing 7 and the bedrock to enable the water to flow downwards past the pump hous ing. These water flows have been shown by arrows in Figures 1 and 2.

[0029] Due to the required space between the pump housing 7 and the pump 4 as well as the space between the pump housing 7 and the bedrock (can also be a pipe sunk into the bedrock) the diameter of the borehole 2 (or pipe) needs to be larger than the borehole 1 for the suction pipe 3. The pump assembly and a pressure side pipe 8 above it has been positioned in the bore hole 2 with larger diameter than the diameter of the borehole 1 for the suction pipe 3.

[0030] A typical pressure required for the water on the suction side of the pump 4 needs to be approxi mately 1 bar + atmospheric pressure of 1 bar so that the pump 4 does not cavitate. If the ground water lev el is at the depth of 10 m below the ground surface, the 1 bar requirement demands the pump 4 to be at the depth of 20 m below the ground surface. The depth of the larger diameter borehole 2, which is more expen sive to produce, is only a fraction of the depth of the smaller diameter borehole 1, which can be several hundreds of meters deep. The depth of the larger diam eter borehole 2 or pipe can be determined depending on the depth of the ground water. If the ground water level is known to be low, for example at the depth of 30 m below the ground surface, the larger diameter borehole 2 needs to reach the depth of at least 10 m below that depth, i.e. at least 40 m below the ground surface.

[0031] The pump housing 7, which has a larger diame ter than the borehole 1 for the suction pipe 3, can be supported to the step between the larger diameter borehole 2 (or pipe) and the smaller diameter borehole 1. This makes it possible to support the suction pipe so that it hangs in the ground water without the bot tom of the suction pipe 3 contacting the bottom of the borehole 1. This enables the thermal expansion and contraction of the suction pipe 3 as the temperature of the pipe 3 and the ground water varies due to ther mal energy being extracted or deposited in the ground water and bedrock around it. It is obvious that be tween the said step and the pump housing 7 there has to be an arrangement which allows the water to flow downwards between the pump housing 7 and the step. Namely, if the pump housing 7 would be supported di rectly against the step, the water could not flow through the pump housing and the step. The arrangement may include for example fins or the like with which the pump housing 7 is supported on the step, but which still allow the water to flow between the fins.

[0032] In Figure 1 the assembly consisting of the pump 4 and the pressure side pipe 8 can be separated from the suction pipe 3. This solution enables lifting the pump 4 together with the pressure side pipe 8 for repair and maintenance, while most of the pipe height, i.e. the suction pipe 3, can be left in the borehole 1. This is important because the suction pipe 3 can be several hundreds of meters in height. This invention also enables the installation of the suction pipe 3 separately from the pressure side pipe 8 and the pump assembly. The pump assembly means the pump 4 together with the necessary equipment for the pump 4.

[0033] The separation point 9 separating the pres sure side pipe 8 and the pump 4 from the suction pipe 3 can be either above the pump 4 (Figure 1) or below the pump 4 (Figure 2). The surfaces touching each oth er at the separation point 9 need to be for example conical in shape to centre the pump assembly when it is lowered into the position. The conical shapes cab be, as shown in Figure 1, arranged so that the part belonging to the pressure side pipe 8 is conical with the point of the cone pointing downwards. It could as well be conical so that the part belonging to the pump housing 4 has a cone pointing upwards. The latter con figuration may be better, because it directs the de bris, the sand or small pieces of rock away from the pump 4.

[0034] The separation surfaces of the separation point 9 are equipped with a flexible seal material to seal the water flows upwards and downwards from each other.

[0035] As shown in Figure 2, the separation point 9 can also be below the pump 4. In that case, when the pump 4 needs to be lifted, also the pump housing 7 is lifted. Only the suction pipe 3 remains in the bore hole 1. Further, in this embodiment the conical shapes must have suitable openings so that the water flowing downwards does not meet too much of a pressure loss.

[0036] Further, it is possible to equip the pump 4 with an inverter control to optimize the water flow to a heat exchanger of a heat pump.

[0037] It is obvious to a person skilled in the art that with the advancement of technology, the basic idea of the invention may be implemented in various ways. The invention and its embodiments are thus not limited to the examples described above, instead they may vary within the scope of the claims.

Claims

CLAIMS1. A ground source heat pump (GSHP) system comprising: a borehole (1, 2) drilled into the earth; a suction pipe (3) mounted in the borehole(1); and a pump (4) mounted in the borehole (2), the pump (4) having a suction opening (5), characterized in that: the pump (4) has been mounted above the suc tion pipe (3); a pump housing (7) has been arranged around the pump (4) so that a space remains between the pump (4) and the pump housing (7); the pump (4) has been arranged to suck water from the suction pipe (3) to the space between the pump (4) and the pump housing (7) and further upwards to the suction opening (5) of the pump (4) and via the pump (4) and a pressure side (8) pipe up to the ground level; between the pump housing (7) and the borehole(2) wall, which is bedrock or pipe sunk into the bed rock, a space has been arranged for the downwards flowing water; and that the pump (4) can be lifted from the borehole (2) without the suction pipe (3).

2. A GSHP system according to claim 1, characterized in that the suction pipe (3) has been con nected to the pump housing (7) via conical shape or the like expansion part.

3. A GSHP system according to claim 1 or 2, characterized in that the suction opening (5) of the pump (4) is located at the side of the pump (4) above an electric motor (6) operating the pump (4).

4. A GSHP system according to any of claims 1-3, characterized in that the borehole (2) for the pump housing (7) is larger in diameter than the bore hole (1) for the suction pipe (3).

5. A GSHP system according to claim 4, characterized in that the pump housing (7) with a diameter larger than the diameter of the borehole (1) for the suction pipe (3), is supported on the step between the larger diameter borehole (2) and the smaller diameter borehole (1).

6. A GSHP system according to claim 4 or 5, characterized in that the borehole (2) with larger di ameter reaches down to at least 10 m below the ground water level.

7. A GSHP system according to any of claims 1-6, characterized in that the separation point (9) separating the pressure side pipe (8) and the suction pipe (3) is located above the pump (4).

8. A GSHP system according to any of claims 1-6, characterized in that the separation point (9) separating the pressure side pipe (8) and the suction pipe (3) is located below the pump (4).

9. A GSHP system according to claims 7 or 8, characterized in that the surfaces touching each other at the separation point (9) are conical in shape to centre the pump (4) and / or pump housing (7) when low ered into position.

10. A GSHP system according to claim 9, characterized in that the conical shapes are arranged so that the part belonging to pressure side pipe (8) is conical so that the top of the cone points downwards.

11. A GSHP system according to claim 9, characterized in that the conical shapes are arranged so that the part belonging to pump housing (7) has a cone pointing upwards.

12. A GSHP system according to any of claims 7-11, characterized in that the separation surfaces of the separation point (9) are equipped with a flexible seal material to seal the water flows upwards and downwards from each other.

13. A GSHP system according to any of claims5-12, characterized in that between the said step and the pump housing (7) there is an arrangement which al- lows the water to flow downwards between the pump housing (7) and the step.

14. A GSHP system according to claim 13, characterized in that the arrangement includes for ex- ample fins or the like with which the pump housing (7) is supported on the step, but which still allow the water to flow between the fins.

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