A ground source thermal energy transfer device

Abstract

A ground source thermal energy transfer device comprises a wastewater pipe having an inner surface defining a conduit for carrying a fluid and an outer surface. One or more reinforcement ribs project from and extend around the outer surface of the wastewater pipe. The one or more ribs form one or more channels at the outer surface. At least one ground source thermal transfer pipe is arranged within at least one of the channels to exchange thermal energy with the ground surrounding the conduit and / or with a medium carried within the conduit. The thermal energy transfer device is configured for exchanging thermal energy with the surrounding earth or the fluid medium within the conduit. The thermal transfer may be used for heating and / or cooling via the exchange of thermal energy between the thermal transfer fluid carried by the thermal transfer pipe and the fluid of a heating / cooling system.

Description

A GROUND SOURCE THERMAL ENERGY TRANSFER DEVICEFIELD OF INVENTION

[0001] The present disclosure relates to a ground source thermal energy transfer device and in particular to a conduit having an integrated thermal transfer pipe for a ground source heating / cooling system.BACKGROUND

[0002] Ground source heating utilises a heat pump to transfer heat to or from the ground for the purpose of heating or cooling. A ground source heating system requires a means for recovering heat from the ground, a means to extract the recovered heat, and apparatus for delivering the extracted heat. This disclosure relates to the process of recovering heat from the ground.

[0003] Open loop ground source heating systems recover ground source heat from pumped natural ground water, for example from aquifers. Engineered closed loop ground source heating systems absorb naturally occurring heat directly from the ground via a continuously pumped heat transfer fluid. A closed loop system requires the installation of a sealed network of pipes within the ground. The pipe network can be installed horizontally or vertically. Vertical installation involves drilling of boreholes to depths of around 40 to 120 meters. Drilling vertically taps a more reliable source of heat at depth but is substantially more expensive to install, run and maintain.

[0004] Horizontal ground source heating systems require the installation of a horizontal trench. The trench extends for the length of the ground source heat recovery pipe which is typically hundreds of metres. Heat recovery piping is provided in diameters ranging from 20-60mm (outside diameter) and is normally manufactured from plastic such as High Density Polyethylene (HDPE). The heat recovery pipe network may be laid as straightpipe runs, looped or in a flat coiled arrangement referred to as a slinky configuration. A horizontal installation may cover a land footprint of hundreds of metres squared.

[0005] Heat recovery pipes are installed in an open trench that is then filled in after installation of the pipe run. Trenches are generally formed having a width of 1.5m and a depth of 1.2m. The 1.2m depth is the maximum depth at which workers can safely enter without further protection of the trench. If installed deeper, the provision of trench protection significantly increases the cost of installation and is avoided in nearly all conventional installations because of economic factors. At a depth of 1.2m the soil temperatures are more significantly affected by surface weather patterns and particularly cold extremes. Soil temperatures are cooler in the winter and warmer in the summer. The relatively shallow depth therefore reduces the effectiveness of traditional thermal transfer systems both in terms of heating during the winter and cooling during the summer. In addition, the shallow depth of the pipework leaves the system susceptible to critical failure during extended periods of cold weather when the ground can become frozen in the zone around the pipe. This can render the system inoperable at the vital time of year when heat is needed.

[0006] Therefore, there is a requirement for an improved heat recovery system that addresses the above-described problems and / or provides improvements generally.SUMMARY

[0007] According to the present disclosure there is provided a ground source heating device as described in the accompanying claims.

[0008] In an aspect of the disclosure there is provided a ground source thermal energy transfer device comprising a conduit such as wastewater pipe having an inner surface defining a conduit for carrying a fluid and an outer surface. One or more reinforcement ribs project from and extend around the outer surface of the conduit. The one or more ribs form one or more channels at the outer surface. At least one thermal transfer pipe isarranged within at least one of the one or more channels to exchange thermal energy with a medium surrounding the conduit and / or a medium carried within the conduit. The thermal energy transfer device is configured for exchanging thermal energy with another medium such as the surrounding earth or the fluid medium within the conduit. The transfer may be used for heating and / or cooling via the exchange of thermal energy between the thermal transfer fluid carried by the thermal transfer pipe and the fluid of a heating / cooling system.

[0009] The one or more channels formed by the one or ribs may each have a height and a width and the diameter of the at least one thermal transfer pipe is substantially equal to the width of the one or more channels. As such, the thermal transfer pipe is received and restrained within the channels and therefore protected by the ribs from compression forces when the conduit is buried in use.

[0010] The one or ribs may extend helically around the outer surface of the conduit along the length of the conduit. The one or more ribs extends from one end of the conduit to the other about the outer surface in a helical form.

[0011] The one or more channels may be formed between the one or more helically extending ribs and the at least one thermal transfer pipe extends helically around the conduit within the respective one of the one or more channels.

[0012] The one or more reinforcing ribs comprises an outer portion and a reinforcing member contained within the outer portion. The reinforcing member is a rib and is preferably a metal rib and may be a steel rib. The reinforcing member is surrounded and encapsulated by the outer portion of the rib, which is preferably formed of plastic and may be integrally formed with the body of the conduit.

[0013] The conduit may comprise a plastic body and the outer portion of the one or more reinforcing ribs is a plastic portion integrally formed with the body of the conduit.

[0014] A plurality of reinforcement ribs may project radially from the outer surface of the conduit and extend helically around the outer surface of the conduit, the plurality of ribs forming a plurality of helically extending channels. The plurality of channels are separate channels that run parallel and adjacent to each other along the conduit.

[0015] The thermal transfer pipe may comprise an outgoing section and a return section and the outgoing section is located within a first channel and the return section is located within a second channel, with the flow in the outgoing and return pipes being in opposing directions.

[0016] In another aspect there is provided a ground source heating system comprising a pump; a heat exchanger; and a ground source heating device as described above. The thermal transfer pipe is fluidly connected to the pump and the heat exchanger, meaning that fluid from the thermal transfer is able to flow to eth heat exchanger and fluid from the pump flows to the thermal transfer pipe.

[0017] In another aspect there is provided a method of installing a ground source heating system, the method comprising providing a ground source heating system as described above, forming a channel in the ground, installing the ground source heating device within the channel and covering the ground source heating device with a filler material once installed within the channel. The method may further include connecting a heating and / or cooling system to the heat exchanger for thermal energy transfer between the heating cooling system and the thermal transfer pipe.

[0018] The conduit preferably forms part of a conduit network and the method further comprises connecting the conduit to the network.BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present disclosure will now be described by way of example only with reference to the following illustrative figures in which:Figure 1 shows a conduit according to an embodiment of the disclosure;Figure 2 is a cross section of a conduit according to an embodiment of the disclosure;Figure 3 is a cross section of a conduit according to an embodiment of the disclosure with a thermal transfer pipe located within a channel of the conduit;Figure 4 is a view of thermal transfer device according to an embodiment of the disclosure; andFigure 5 is an illustration of a ground source thermal transfer system according an embodiment of the disclosure; andDESCRIPTION OF EMBODIMENTS

[0020] The following description presents exemplary embodiments and, together with the drawings, serves to explain principles of the disclosure. The scope of the disclosure is not intended to be limited to the precise details of the embodiments or exact adherence with all method steps. Variations will be apparent to a skilled person and are deemed also to be covered by the description. Terms for features used herein should be given a broad interpretation that also encompasses equivalent functions and features. In some cases, several alternative terms (synonyms) for structural features have been provided but such terms are not intended to be exhaustive.

[0021] Descriptive terms should also be given the broadest possible interpretation; e.g. the term "comprising" as used in this specification means "consisting at least in part of"such that interpreting each statement in this specification that includes the term "comprising", features other than that or those prefaced by the term may also be present. Related terms such as "comprise" and "comprises" are to be interpreted in the same manner. Directional terms such as "vertical", "horizontal", "up", "down", "upper" and "lower" are relative terms that may be used for convenience of explanation usually with reference to the illustrations and are not intended to be ultimately limiting if an equivalent function can be achieved with an alternative dimension and / or direction.

[0022] The description herein refers to embodiments with particular combinations of configuration steps or features. However, it is envisaged that further combinations and cross-combinations of compatible steps or features between embodiments will be possible. The description of multiple features in relation to any specific embodiment is not an indication that such features are inextricably linked, and isolated features may function independently from other features and not necessarily require implementation as a complete combination.

[0023] Referring to Figure 1, a ground source thermal transfer device comprises a wastewater conduit 1. The conduit 1 is a cylindrical pipe having an axial length L and a diameter D. It will be appreciated that while the conduit is described as a wastewater conduit the disclosure is not limited to wastewater conduits and the conduit may for example be a utility tunnel, power cabling conduit, air vent or other types of shafts, or any other conduit or similar structure suitable to be submerges in the ground. The conduit 1 has a wall 2 with an inner surface 4 that defines a channel for carrying wastewater, and an outer surface 6. The conduit 1 has a first axial end 8 and a second axial end 10. A plurality of axially spaced helical ribs 14 extend around the outer surface 6 of the conduit 1.

[0024] The conduit 1 is formed from an elongate composite strip comprising an elongate plastic strip and an elongate metal reinforcing rib embedded withing the plastic strip. The composite has a width of approximately 112mm that is helically wound to form the conduit 1 having a diameter between 600mm and 2250mm. The conduits 1 areformed in standard pipe section lengths 3.0m and 2.6m. Such dimensions are representative of illustrative embodiments and are not intended to limit the disclosure. The elongate metal reinforcing strip is at least partially embedded within the plastic strip.

[0025] Referring to Figure 2, the wall 2 of the conduit 1 includes a body section 16 with the plurality of upstanding composite ribs 14 extending radially outwards away from the body section 16 relative to the circular cross section of the body section 16 and perpendicular to the longitudinal axis of the conduit 1. The body section extends axially along the conduit and comprises the inner and outer surfaces 4,6. Each rib 14 includes an internal reinforcing rib 18 formed of steel. The body section 16 and ribs 14 are integrally formed of HDPE, although it will be appreciated that other suitable materials may be used. The reinforcing elements 18 formed of metal strip are arranged within the ribs 14 in a parallel relationship with the ribs 14, extending radially away from the body and perpendicular to the longitudinal axial of the conduit 1. The reinforcing elements or 'ribs' 18 are fully embedded within the plastic ribs 14, with the ribs 14 forming an outer shell around the reinforcing ribs 18 to form a composite rib. Each rib 14 comprises a pair of parallel walls 20 and 22 arranged on opposing sides of the respective reinforcing rib 18 and an outer wall 24 that covers the distal end of the reinforcing rib 18. By embedding the reinforcing ribs 18 within the outer shell formed by the plastic rib 14, the reinforcing ribs 18 are protected from corrosion.

[0026] The ribs 14 a-c are axially spaced along the body section 16 of the conduit 1. Slots 26 and T1 are defined between the ribs 14a and 14b and between 14b and 14c respectively. Each slot 26,27 has a width w2 and a height h2 corresponding to the height of the ribs 14. Each composite strip from which the conduit is formed comprises three ribs 14 a-c as shown in Figure 2. The ribs 14 a-c are each part of separate continuous helically wound ribs formed around the conduit 1. As the composite strip is wound the first slot 26 forms a first continuous channel 28 and the second slot T1 forms a second continuous channel 30, the channels 28,30 being separated from each other by the central intermediate rib 14b. A third channel 32 is defined between the first rib 14a andthe third rib 14c of the adjacent composite strip. A such, three parallel helical channels28,30,32 extend along the outer surface of the conduit 1.

[0027] The composite ribs 14 provide structural integrity to the conduit 1, both in terms of resisting compression when the conduit 1 is buried and improving the pressure rating of the conduit 1. The conduit 1 is configured to manage, store and transport, drainage, stormwater, wastewater or sewage. Such conduits are required to meet statutory requirements for the management of drainage, stormwater, wastewater or sewage. The required depth for conduits of this type is typically around 4m. Although submerging pipes to this depth is more costly, the installation is a requirement of legislation and therefore unavoidable.

[0028] The heat recovery device takes advantage of the compulsory installation of wastewater conduits by integrating one of more thermal transfer pipes with the wastewater conduit 1. The heat recovery device provides one or more thermal transfer pipes within the channels defined by the reinforced composite ribs 14.

[0029] As shown in Figure 3, a thermal transfer pipe 34 is provided in the first channel 28 defined between ribs 14a and 14b. The thermal transfer pipe 34 has a diameter d2 corresponding to the width w2 of the channel 28. Preferably the diameter of the thermal transfer pipe 34 is selected such that thermal transfer pipe 34 is received within the channel 28 with a close tolerance push fit. The thermal transfer pipe 34 is constrained and supported within the channel 28 in engagement with the ribs 14a and 14b. Spot welds are applied along the length of the thermal transfer pipe 34 to weld the thermal transfer pipe 34 to the ribs 14a, 14b to secure the thermal transfer pipe 34 within the channel 28. It will be appreciated that the pipe 34 may be secured within the channel 28 by other suitable means such as adhesive bonding, mechanical fixings or frictional fit. The thermal transfer pipe 34 is applied to the conduit 1 after the conduit 1 has been formed. Applying the thermal transfer pipe 34 as a separate component in this manner significantly simplifies manufacture as compared to attempting to integrally mould the pipe as part of the composite strip. Also, it enables the thermal transfer pipe 34 to bemodified and upgraded over time, for example as pipe technology improves, by replacing the type of pipe used, without having to modify manufacture of the conduit.

[0030] During installation, the conduit 1 (including the thermal transfer pipe 34) is installed in a pre-formed trench. As the conduit 1 is a wastewater pipe the trench is formed to a depth significantly greater than 1.2m, which is advantageous for improved thermal transfer. The thermal transfer pipe 34 is pre-installed during manufacture but it is contemplated that it could be installed in situ. When the conduit 1 is in position within the trench, the trench is then backfilled with earth to cover the conduit. When the conduit 1 is covered, the thermal transfer pipe 34 is in thermal contact with the surrounding earth. The rigid reinforced ribs 14 create a rigid support structure about the thermal transfer pipe 34 that mechanically protects the thermal transfer pipe 34 contained within the channel 28 between the ribs 14a and 14b. Without this mechanical protection, the weight of the conduit 1 acting on the pipe 34 at the lower side of the conduit 1 and the static load arising from the compacted bedding material above the thermal transfer pipe 34, would crush the thermal transfer pipe 34 and prevent or at least inhibit fluid flow through the thermal transfer pipe 34 and potentially compromise the thermal transfer pipe 34 leading to leakage. The reinforcing ribs 14 also prevent damage to the thermal transfer pipe 34 during transport, site handling and installation. The width of the channel 28 and the diameter of the thermal transfer pipe 34 is such that sufficient thermal contact is created between the thermal transfer pipe 34 and the surrounding earth / bedding material despite the thermal transfer pipe 34 being contained within the channel 28.

[0031] The ribs 14 also improve the thermal transfer between the thermal transfer pipe 34 and the surrounding earth. The ribs 14 improve thermal transfer by modifying the otherwise regular distribution of temperature along the length of the composite carrier pipe by providing a thermal barrier between adjacent sections of the coiled thermal transfer pipe 34. The ribs 14 create concentrated zones of thermal gradient in and around the spirally wrapped thermal transfer pipe 34 and reduce the likelihood of a uniform thermal layer developing across the whole integrated ground source heating and coolingpipework, which would inhibit thermal transfer. This aids the energy transfer between the mediums inside and outside of the carrier pipe and mitigates against thermal blocking at the surface of the thermal capture pipework.

[0032] In another embodiment additional system components such as thermal sensors, monitoring devices etc may be installed in one or more of the channels 28,30,32 without requiring alteration or modification to the ground source heating system to accommodate such components.

[0033] Referring to Figure 4, a thermal transfer pipe 34 extends helically around the outer surface 6 of the conduit 1 within the channel 28 defined by the first and second ribs 14a and 14b. The thermal transfer pipe 34 is an outgoing pipe carrying thermal transfer fluid such as propylene glycol or ethylene glycol. The thermal transfer pipe 34 is connected at a first end to a ground source heating pump. The thermal transfer fluid is pumped along the helically wound thermal transfer pipe 34. Heat from the surrounding earth is absorbed by the thermal transfer fluid, which is then returned to a heat exchanger to extract the heat from the thermal transfer fluid.

[0034] The thermal transfer pipe 34 is formed as a loop having an outgoing section and a return section. In one embodiment the return section of the thermal transfer pipe 34 may be channelled within the conduit 1 such that the outgoing section is located at the outer surface of the conduit and the return section is located at the inner surface within the conduit. In another embodiment, the outgoing section of the thermal transfer pipe 34 may be located within a first channel 28 and run along the length of the conduit 1 in a first direction. The return section of the thermal transfer pipe 34 is located in a second channel 30 and runs along the length of the conduit in the opposing direction. As such, the outgoing and return sections are able to be housed on the same conduit.

[0035] Figure 5 is an illustrative schematic of a ground source heating system utilising the present invention. The ground source heating system 40 comprises a heating / cooling system including a network of underfloor heating pipes 42, and one or more radiators 44. The underfloor heating system 42 and the radiators 44 are fluidly connected to a heatpump system 46. The wastewater conduit 1 is submerged below ground to channel wastewater. The thermal transfer pipe 34 can be seen coiled around the conduit 1. The length of the thermal transfer pipe 34 coiled around the conduit 1 forms a ground collector. The heat pump system 46 is connected to a first end of the thermal transfer pipe 34 by outgoing pipe 48. The heat pump system 46 pumps thermal transfer fluid to the thermal transfer pipe 34 via the outgoing pipe 48. As the fluid flows through the coiled section of the thermal transfer pipe 34 surrounding the conduit 1, the thermal transfer fluid within the thermal transfer pipe 34 absorbs thermal energy from the ground. The thermal transfer fluid returns to the heat pump system 46 via return pipe 50. Thermal energy is transferred between the thermal transfer fluid and the fluid of the heating / cooling system via a heat exchanger of heat pump system 46 and the thermal transfer fluid, at an altered thermal energy level, is pumped back to the thermal transfer pipe 34 to repeat the process.

[0036] Integrating the wastewater conduit 1 and the thermal transfer pipe 34 advantageously enables a ground source heat recovery system to be installed as part of the installation process of the wastewater pipe, the installation of which is specifically required by legislation. The requirement to separately form a horizontal trench or create vertical boreholes is therefore avoided. Instead, the cost of the installing the pipe network of ground source heating system is solely dependent on the incremental costs of thermal energy recovery components and their associated installation. The provision of reinforcing ribs on the outer surface of the conduit protects the thermal transfer pipe 34 when installed. Furthermore, as the installation depth of wastewater conduits is significantly deeper than the 1.2m trench depth of a traditional horizontal ground source heating system, the thermal performance of the ground source heating system is significantly improved and the thermal transfer pipes 34 are protected from fluctuating environmental conditions experienced at shallower depths. The ground source heating device of this disclosure therefore provides significant economic and technical advantages.

Claims

CLAIMS1. A ground source thermal energy transfer device comprising: a conduit having an inner surface and an outer surface; one or more reinforcement ribs projecting from and extending around the outer surface of the conduit, the one or more ribs forming one or more channels on the outer surface of the conduit; and at least one thermal transfer pipe arranged within at least one of the one or more channels to exchange thermal energy with a medium surrounding the conduit and / or a medium carried within the conduit.

2. A ground source thermal energy transfer device according to claim 1 wherein the one or more channels formed by the one or ribs has a width corresponding to the diameter of the at least one thermal transfer pipe.

3. A ground source thermal transfer device according to claim 1 or 2 wherein the one or ribs extends helically around the outer surface of the conduit along the length of the conduit.

4. A ground source thermal transfer device according to claim 3 wherein the one or more channels are formed between the one or more helically extending ribs and the at least one thermal transfer pipe extends helically around the conduit within the respective one of the one or more channels.

5. A ground source thermal energy transfer device according to any preceding claim wherein the one or more reinforcing ribs comprises an outer wall and a reinforcing member contained within the outer wall.

6. A ground source thermal energy transfer device according to claim 5 wherein the conduit comprises a plastic body and the outer wall of the one or more reinforcing ribs is a plastic portion integrally formed with the body of the conduit.

7. A ground source thermal energy transfer device according to claim 6 wherein the thermal transfer pipe is wound around the conduit in a series of loops and the reinforcing ribs are configured and arranged to create a thermal barrier between adjacent looped sections of the thermal transfer pipe.

8. A ground source thermal energy transfer device according to claim comprising a plurality of reinforcement ribs projecting radially from the outer surface of the conduit and extending helically around the outer surface of the conduit, the plurality of ribs forming a plurality of helically extending channels.

9. A ground source thermal energy transfer device according to claim 7 wherein the thermal transfer pipe comprises an outgoing section and a return section and the outgoing section is located within a first channel and the return section is located within a second channel.

10. A ground source thermal energy transfer system comprising: a pump; a heat exchanger; and a ground source thermal transfer device according to any preceding claim, wherein the thermal transfer pipe is fluidly connected to the pump and the heat exchanger.

11. A method of installing a ground source thermal energy transfer system, the method comprising providing a ground source thermal energy transfer system according to claim 10, forming a channel in the ground, installing the ground source thermal energy transfer device within the channel and covering the ground source thermal energy transfer device with a filler material once installed within the channel.

12. A method according to claim 10 wherein the conduit forms part of a conduit network and the method further comprises connecting the conduit to the network.

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