BE1023389B1 - A heat pump including ground heat exchanger - Google Patents

Abstract

A heat pump (100), located in a building, includes a pipework (110) on the primary side of the heat pump. The pipe network (110) is located in at least a part of the shell (150) of the building (bottom plate and / or basement walls), that portion of the shell (150) being in contact with the ground.

Description

A heat pump including ground heat exchanger. Field of application of the invention

This invention relates generally to heat pumps. The invention relates to an alternative embodiment of a heat pump and a method for controlling it.

BACKGROUND OF THE INVENTION

Heat pumps can be subdivided into different types depending on the way in which they absorb heat from the environment and the way in which they deliver this heat to, for example, a building. Heat pumps can thus be subdivided into air / air heat pumps, air / liquid heat pumps, liquid / liquid heat pumps.

With air / air heat pumps, heat is extracted from the outside air, and this heat is distributed through an air blower in the building. With air / liquid heat pumps, heat is also extracted from the outside air, and this heat is then used to heat a liquid in heating pipes spread through a building. A liquid / liquid heat pump extracts freely available heat from the soil, from groundwater or from surface water, and also uses it to heat a liquid in heating pipes spread through a building. In the latter case, for example, a vertical ground heat exchanger or a horizontal ground heat exchanger is provided.

With a vertical ground heat exchanger or geothermal heat exchanger, pits are drilled into the ground and U-shaped pipes are installed in these pits. The depth of the wells and the number of wells required depend on the surface, volume and insulation of the building to be heated. The wells are usually more than 80 meters deep. The depth of the wells depends on the specifications of the underground soil layers, because sometimes the first running meters are clay layers that are not suitable for heat transfer. Often 20 bores per 1000 m2 of usable interior space are required to meet the heat demand. These bores are, for example, placed at a mutual distance of approximately 6 m, so that it can be stated that approximately 20 to 25 bores can be placed per 100 m2 of ground surface. At a minimum, it can be said that there must be at least as much vacant land area as there is usable space in buildings in the case of vertical probes. The ISSO 73 standard provides a clear package of design-technical quality requirements and implementation guidelines for vertical soil heat exchanger systems.

With a horizontal ground heat exchanger or geothermal heat exchanger, a large pipe network is installed in the ground surface next to the building, usually under the garden. A large surface area (for example, 3 times the surface area of the house to be heated) is required. The size of the surface depends on the extraction capacity of the soil. This extraction capacity is typically greater with a higher soil moisture. Horizontal geothermal heat exchangers are installed by pulling trenches in the ground, the center distance between the trenches often being 50 cm to 1 meter. The tubes used often have a large diameter of 1 inch because of the limited number of tubes that can be laid. These tubes are parallel, which again limits the total length and reduces heat transfer.

Geothermal heat exchangers are the most cost-effective for controlling heat pumps and provide a greater COP "Coefficient of performance" (performance coefficient; ratio between the absolute value of the amount of heat released and the amount of energy used) than the previous air / air based systems or air / water. This is because ground heat is less sensitive to direct changes in the outside temperature. The length or size of the geothermal network will determine how much energy can be extracted from the ground without the ground temperature assuming major differences. A heat pump works best when a bottom temperature of less than 0 ° C is avoided. Positive temperatures do not require antifreeze agents, heat pumps will operate at a maximum COP and cost less electrical energy to move the water through the pumps. There is a demand for more efficient control of the heat pump and more efficient operation thereof.

Summary of the invention

It is an object of embodiments of the present invention to provide a good, for example improved, heat pump. It is also an object of embodiments of the present invention to provide a method for controlling such a heat pump.

In a first aspect, the present invention provides a heat pump placed in a building, the heat pump comprising a pipe network on the primary side of the heat pump, the pipe network being placed in at least a part of the shell of the building, that part of the building peel is in contact with the ground.

It is an advantage of embodiments of the present invention that the pipe network is in the shell of the building. This means that no free ground surface is needed next to the building to install the ground heat exchanger. Indeed, in embodiments of the present invention, the pipe network in the shell of the building serves as a ground heat exchanger. Embodiments of the invention can therefore also be implemented in urban areas, where little ground area is available next to the building, without the need for expensive and / or complex depth drilling. Commercial buildings are usually in ribbon development and generally have a higher V / T (Floor / Terrain Index = floor area of buildings / total area), so there is usually a lack of undeveloped land to draw a vertical or horizontal capture network. It is an advantage of embodiments of the present invention that the placement of geothermal heat exchangers is nevertheless possible regardless of the shortage of undeveloped soil. It is an advantage of embodiments of the present invention that a greater COP (coefficient of performance - performance coefficient) can hereby be obtained than if the heat exchange with the air were to take place instead of with the ground. It is an advantage of embodiments of the present invention that pipes of the pipe network are embedded in the bottom plate of the building. This guarantees good contact, and therefore good heat transfer between the base plate and the pipe network (eg in comparison with a ground heat exchanger where the pipes are laid loose in the ground). It is therefore an advantage that a better efficiency can be achieved than in the case of a ground heat exchanger in which the pipes are laid loose in the ground and in which the contact between the pipes and the ground is less good than the contact between the pipes and the bottom plate . An efficiency improvement of more than 25% or even more than 50% is possible. The skin itself exchanges the heat with the soil with which it is in contact. Due to the large contact surface between the shell and the ground, this transfer is done efficiently. It is an advantage of embodiments of the present invention that the shell is used simultaneously to increase the stability of the building and to exchange heat between the pipe network and the ground. It is an advantage of embodiments of the present invention that the geothermal installation (more specifically, the pipe network) is incorporated into the structural structure. As a result, no separate excavation works or drillings are required next to the building to install the geothermal installation.

The shell of a building can consist of a base plate and side walls. In embodiments of the present invention, the tube network may be in the bottom plate and / or in the side walls, the bottom plate being below the ground level.

It is an advantage of embodiments of the present invention (e.g., in buildings where a basement is present) that the bottom plate is below the ground level. Deeper below the ground, the soil has a more stable temperature that is less dependent on the season. Moreover, the heat exchange between the bottom plate and the ground is better when it is below groundwater level. The more moist the soil is, the better the heat transfer between the bottom plate and the underlying soil.

In a heat pump according to embodiments of the present invention, the pipe network can be attached to reinforcement nets of the bottom plate of the building. It is an advantage of embodiments of the present invention that a simple placement of the pipe network is hereby possible. As a result, an even distribution of the pipes of the pipe network can also be guaranteed, which results in an evenly distributed heat exchange over the entire bottom plate. For ground heat exchangers that are placed in the ground next to the building, this even placement is not guaranteed. It is an advantage of embodiments of the present invention that the reinforcement nets can be used both for placing the pipe network evenly and for increasing the stability of the building.

In a heat pump according to embodiments of the present invention, an insulation layer may be provided between the pipe network and the rest of the building. In this way, heat exchange with the pipe network is mainly done with the underlying ground and not with the rest of the building. In embodiments of the present invention, the insulation layer can also be placed between the basement floor and the rest of the building. It is an advantage of embodiments of the present invention that the basement can serve as a cooling room when the rest of the building needs to be heated.

In a second aspect, the present invention provides for the use of a heat pump according to embodiments of the first aspect of the present invention, wherein the heat pump is controlled so that the temperature of the pipe network does not fall below 0 ° C.

It is an advantage of embodiments of the present invention that peak load of the pipe network is avoided. An even load ensures that the heat is effectively extracted from the ground and not just from the bottom plate. This prevents the bottom plate from freezing. In embodiments of the present invention, the heat pump is controlled so that the temperature of the fluid in the pipe network does not fall below freezing point, or even below 3 ° C or even below 5 ° C. It is an advantage of embodiments of the present invention that the temperature of the liquid in the pipe network does not fall below the freezing temperature. This makes it possible to use water as a liquid in the pipe network instead of, for example, glycol. The COP (coefficient of performance), which is the ratio between the absolute value of the amount of heat released and the amount of energy used, can be maximized by means of the temperature of the fluid in the pipe network. The greatest energy transfer is achieved with the greatest temperature difference between the bottom plate and the liquid in the pipe network. In embodiments of the present invention, it is ensured that the temperature of the liquid in the pipe network does not go below 0 ° C.

When using a heat pump in accordance with embodiments of the present invention, the pipe network can be used both to extract heat from the ground and to transfer heat to the ground. It is an advantage of embodiments of the present invention that heat can be extracted from the ground during the summer months, and that heat is released to the ground during the winter months. This minimizes the load on geothermal energy.

Specific and preferred aspects of the invention are included in the appended independent and dependent claims. Features of the dependent claims can be combined with features of the independent claims and with features of other dependent claims as appropriate and not merely as explicitly stated in the claims.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment (s) described below.

BRIEF DESCRIPTION OF THE FIGURES FIG. 1 is a schematic representation of a heat pump including pipe network in accordance with embodiments of the present invention. The figure shows a cross section of the system. FIG. 2 is a schematic representation of a heat pump including pipe network in accordance with embodiments of the present invention. The figure shows a top view of the system. FIG. 3 is a block diagram of the various elements of a heat pump in accordance with embodiments of the present invention. FIG. 4 illustrates the power supplied and power consumption over the one-year period of a heat pump in accordance with an embodiment of the present invention.

The figures are only schematic and non-limiting. In the figures, the dimensions of some parts may be exaggerated and not represented to scale for illustrative purposes.

Reference numbers in the claims may not be interpreted to limit the scope of protection. In the various figures, the same reference numbers refer to the same or similar elements.

Detailed description of illustrative embodiments

The present invention will be described with reference to particular embodiments and with reference to certain drawings; however, the invention is not limited thereto but is only limited by the claims. The described drawings are only schematic and are not limitative. In the drawings, the dimensions of some elements may be increased for illustrative purposes and not drawn to scale. The dimensions and the relative dimensions sometimes do not correspond to the current practical embodiment of the invention.

It is to be noted that the term "comprises", as used in the claims, is not to be interpreted as being limited to the means described thereafter; this term does not exclude other elements or steps. It can therefore be interpreted as specifying the presence of the listed features, values, steps or components referred to, but does not exclude the presence or addition of one or more other features, values, steps or components, or groups thereof. Thus, the scope of the expression "a device comprising means A and B" should not be limited to devices that consist only of components A and B. It means that with regard to the present invention, A and B are the only relevant components of the device.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a specific feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the occurrence of the expressions "in one embodiment" or "in an embodiment" at various places throughout this specification need not necessarily refer to the same embodiment in each case, but it can do so. Furthermore, the specific features, structures, or characteristics may be combined in any suitable manner, as would be apparent to those skilled in the art based on this disclosure, in one or more embodiments.

Similarly, it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together into a single embodiment, figure, or description thereof for the purpose of streamlining disclosure and assisting in understanding one or several of the various inventive aspects. This method of disclosure should not be interpreted in any way as a reflection of an intention that the invention requires more features than explicitly mentioned in any claim. Rather, as the following claims reflect, inventive aspects lie in less than all the features of a single prior disclosed embodiment. Thus, the claims following the detailed description are hereby explicitly included in this detailed description, with each independent claim as a separate embodiment of the present invention.

Furthermore, while some embodiments described herein include some, but not other, features included in other embodiments, combinations of features of different embodiments are intended to be within the scope of the invention, and constitute different embodiments, as would be understood by those skilled in the art . For example, in the following claims, any of the described embodiments can be used in any combination.

Numerous specific details are set forth in the description provided here. It is, however, understood that embodiments of the invention can be practiced without these specific details. In other cases, well-known methods, structures and techniques have not been shown in detail to keep this description clear.

Where in embodiments of the present invention the term "the shell" of a building to be heated or cooled is referred to, the outside of the building is meant to be in contact with the ground on which the building stands. The shell consists of the base plate, and in the case of a basement, the outer walls under the ground also form part of the shell of the building.

Where in embodiments of the present invention the term "the primary side of the heat pump" is used, this is meant that is in contact with the environment from which energy is extracted (this may be heat or cold).

Where "radiators" are used in embodiments of the present invention, heating / cooling elements are meant. This can be, for example, convection systems, pipes in accumulable concrete slabs (floors, ceilings), air ventilation systems. In the case of accumulable concrete slabs, they are preferably 30 cm thick or even thicker. Preferably about 15% of the building volume consists of accumulated concrete slabs. Accumulable concrete slabs are used in buildings that are heated / cooled by concrete core activation. With concrete core activation, the mass of the building is used to heat the building. For this, pipes are installed in the floor slabs (and ceilings) and possibly also in the walls of the building. This results in the accumulable concrete plates. The water in the tubes of the accumulable concrete slabs is, depending on the requirements, cooled or heated. As a result, the space surrounded by the accumulable concrete plates can be cooled or heated respectively.

In a first aspect, the present invention provides a heat pump 100 in a building, wherein the heat pump 100 comprises a pipe network 110 disposed in the shell 150 of the building. In embodiments of the present invention, the tube network 110 is placed in the bottom plate 152 of the building and / or in the basement walls 154 of the building and / or in the foundations of the building. When the heat pump 100 is operational, the pipe network 110 acts as a ground heat exchanger for the heat pump 100. In embodiments of the present invention, the heat pump 100 is used to heat / cool a building and / or an infrastructure in the building. The infrastructure can for example be a swimming pool.

In embodiments of the present invention, the tube network 110 consists of tubes with a diameter between 8 and 30 mm, preferably between 16 and 20 mm, preferably 16 mm. Due to the limited diameter, it is an advantage of embodiments that the pipe network consists of pipes that are easily pliable and can be placed. In embodiments of the present invention, the tube network in the base plate has a coverage of 5 to 15 meters of tube per square meter of shell surface, preferably 10 meters of tube per square meter of base plate 152. This allows a gradual heat transfer between the tube network 110 and the base plate 152. to become. The tubes can be made of any suitable material to allow heat transfer, for example from PVC (polyvinyl chloride) or PE (Polyethylene).

In embodiments of the present invention, the heat transfer occurs by circulating water in the tube network 110. A smaller pipe diameter is more cost-effective than a larger one because in larger pipe diameters the water in the center of the pipe has no contact surface to exchange energy with the surrounding soil. Since vertical and horizontal capture networks are placed at large center-to-center distances, pipe diameters of 1 inch are generally used, which are therefore less cost-effective than the standard diameters of 16 or 20 mm PVC pipes that can be used for the pipe network 110, for example. In embodiments of the present invention, the tube diameter is less than 21 mm (e.g., 20 mm or less) or more preferably, less than 17 mm (e.g., 16 mm or less) to optimize heat transfer and thus minimize the required ground area. After all, a better heat transfer between the pipe network 110 and the environment results in a smaller ground surface area that is required to realize the transfer. So the more contact surface there is between the tube network 110 and the environment, the better the energy transfer will take place.

When the tube network 110 is located in the bottom plate 152, it is preferably placed as close to the substrate as possible to optimize heat transfer between the substrate and the tube network 110. In addition, the bottom plate 152 can also accumulate heat from the substrate and later transfer it to the pipe network 110 or the heat pump 100. FIG. 1 and FIG. 2 show a schematic overview, in side view and top view, respectively, of a heat pump 100 according to embodiments of the present invention. FIG. 1 shows a cross-section of this heat pump 100. This figure shows a pipe network 110 that is embedded in a bottom plate 152. This bottom plate 152 is below ground level 160 (e.g. 3 m below ground level, or 6 m below ground level, or deeper, depending on the number of basements). It is an advantage that a better heat transfer can be realized when the bottom plate 152 is below the groundwater level. This is for example the case when the bottom plate 152 is at a depth of approximately 3 m. It is an advantage of embodiments of the present invention that the bottom plate 152 of a building is often below the groundwater level and that the pipe network 110 installed therein can thereby exchange heat with the ground in optimum conditions. This is an advantage over existing horizontal capture networks that are not that deep because the excavation works for placing a horizontal capture network are not carried out so deeply because of the cost price. The deeper the bottom plate is, the more stable the temperature of the subsurface (eg colder in summer), so that a better heat pump efficiency can be achieved at deeper locations. When the pipe network is located in the basement walls, the same applies that a better efficiency of the heat pump can be achieved when a better heat transfer is possible (eg because the basement wall is below groundwater level), and when the temperature of the substrate is more stable (eg colder in the summer). The thickness of the bottom plate 152 is more than 10 cm, or more preferably, more than 20 cm, or more preferably, more than 30 cm. A larger volume of the bottom plate 152 (or of the parts of the shell 150) allows the tube network 110 to initially extract heat from the bottom plate 152 (and / or basement walls 154), after which heat exchange between the bottom plate 152 (and / or basement walls 154) and the underlying and / or adjacent ground can happen. More heat can be extracted from a bottom plate 152 with a larger volume than from a bottom plate 152 with a smaller volume. A thicker bottom plate 152 thus allows to accommodate larger fluctuations in a heat demand. The ends of the pipe network 110 are attached to a compressor 120 of the heat pump 100.

In embodiments of the present invention, the tube network 110 forms the primary circuit of the compressor 120 and starts the secondary circuit at the supply and discharge pipes 130, 140. Optionally, the heat pump 100 is used for both heating and cooling of the building. In that case, on the secondary side there are supply and discharge pipes 130, 140 for hot water, and supply and discharge pipes 318, 320 (see also FIG. 3) for cold water. The heat taken up from the ground through the pipe network 110 can be delivered to the building via a circuit (not illustrated in FIG. 1) connected to the hot water supply pipe 130 and to the hot water discharge pipe 140. In embodiments of the present invention, multiple supply pipes 130 and multiple discharge pipes 140, as well as multiple pipe networks 110, are possible.

It is an advantage that with embodiments of the present invention in which the tube network 110 is embedded in the bottom plate 152, a minimum transfer of 30 W per m2, or even 70 W per m2 can be realized. FIG. 2 shows a top view of the same heat pump. In this figure the reinforcement network 210 can be seen, to which the pipe network 110 of the heat pump 100 is attached. Due to the even distribution of the bars 212 of the reinforcement mesh 210, the tubes of the tube network, which are attached to the wires of the reinforcement mesh 210, are also uniformly distributed. Thus, in embodiments of the present invention, coverage is obtained from 5 to 15 meters, preferably about 10 meters, of tube per square meter of bottom plate 152. In embodiments of the present invention, multiple tube networks 110 can be arranged one above the other in bottom plate 152. These pipe networks can then lie one above the other. For example, if the bottom plate 152 is thicker than 30 cm and contains a double reinforcement mesh, it is possible to attach a first tube network to the first reinforcement mesh and attach a second tube network to the second reinforcement mesh.

For example, heat pumps according to embodiments of the present invention can be used to heat buildings that are well insulated. The insulation in the walls can for example be made of polyurethane and have a thickness of 15 cm or more. The glass sections may, for example, consist of triple glass and / or glass whose U value is 0.8 or less. These buildings, for example, have accumulated a consumption that is lower than 100 Kwh per m2 per year, cooling and heating. The insulation has, for example, a calculated EPC value of 50 Kwh / m2 or less.

In embodiments of the present invention, the area of the bottom plate 152 in which the tube network 110 is arranged is a minimum of 50% of the total utilizable area. Where in embodiments of the present invention reference is made to the usable area of a building, the total area to be heated / cooled is meant. FIG. 3 shows a block diagram of the components of a heat pump 100 in accordance with embodiments of the present invention. The figure shows a compressor 120 which is coupled on the primary side to pipe network 110 (in the shell of the building) via supply pipe 310 and discharge pipe 312. Optionally, an additional heat exchanger 370 is possible on the primary side that can extract additional heat from additional heat. systems, for example from rain pits filled with rainwater. The coupling between this additional heat exchanger 370 and the compressor 120 is represented in this figure by means of the supply pipe 380 and discharge pipe 390. On the secondary side, the heat pump is coupled to a conversion module 330 which is connected to the radiators 360 via supply pipes 340 and discharge pipes. 350. The coupling between the compressor 120 and the conversion module 330 occurs in FIG. 3 with supply pipe 130 and discharge pipe 140 for the hot water and with supply pipe 318 and discharge pipe 320 for the cold water. A direct coupling between the tube network 110 and the conversion module 330 via supply pipe 314 and discharge pipe 316 is also possible. This can be used, for example, when the subsurface has not yet been heated but the building must already be cooled. The cold can be taken directly from the ground at that time without the presence of a compressor 120. In embodiments of the present invention, the radiators 360 to which the heat pump is coupled are accumulated concrete plates with a minimum thickness of 20 cm or more preferably 30 cm . In embodiments of the present invention, between 10% and 20% of the building volume, e.g., 15% of the building volume consists of accumulated concrete slabs. The conversion module 330 takes care of the transport of the water (or possibly another liquid) to the radiators 360. For this purpose the conversion module has one or more pumps, one or more collectors, and possibly taps to switch off certain radiators or not. . In embodiments of the present invention, the conversion module 330 includes a buffer tank to increase the volume of water, and thus guarantee a more stable operation of the heat pump. Due to the presence of a buffer tank, the heat pump can continue to run for longer periods and give up for longer periods, resulting in an efficiency improvement. FIG. 4 shows an example of the energy consumption and the power supplied from a heat pump 100 with pipe network 110 in the bottom plate 152 of a building according to an embodiment of the present invention. The power supplied in summer and in winter, as well as the electrical consumption, are shown in this figure. The electrical consumption is indicated by the curve 410. On the horizontal axis times are indicated (January 1, April 1, July 1, October 1) and the vertical axis is expressed in kWh. In zone A heat is delivered to the building, in zone B the building is actively cooled and in zone C the building is directly cooled whereby cold is extracted from the ground by means of the pipe network 110 without the use of the compressor 120 In this example, during the winter (zone A), the heat pump 100 supplies a total power of 158,910 kWh for a usable area of 4,500 m2 (water at 45 ° C in supply pipe 130). During the summer (zone B), a total capacity of 163,210 kWh is supplied (water at 7 ° C in supply pipe 318). In the intermediate period (zone C), a power of 17,400 kWh is supplied to "free cooling" (no compressor required). "Free cooling" means that the water is cooled by flowing through the pipe network. The only consumption then comes from the pumps needed to circulate the water through the building and through the pipe network 110. The temperature in the supply pipe 314 is then usually between 5 ° C and 21 ° C.

In a second aspect, the invention provides a method for controlling a heat pump 100 so that the temperature of the pipe network 110 does not fall below 0 ° C. This can be achieved by spreading peak loads over time, for example by installing a buffer vessel as part of the conversion module 330. This buffer vessel makes it possible for the compressor 120 to continue to run for longer periods and to dispense for longer periods. This is also possible by keeping the radiators 360 (e.g., accumulable concrete plates) at a constant temperature as much as possible. This temperature can be lower in the summer months (to cool the building) than in the winter months (to heat the building). This temperature can for example be between 18 ° C and 23 ° C or even between 21.5 ° C and 22.5 ° C. For example, in the summer months the radiators 360 can be kept at 18 ° C. By keeping the radiators 360 and consequently the building at a constant temperature, peak loads of the pipe network 110 are avoided. In this way a measured maximum possible energy demand of 152 W / m2 or even 100 W / m2 can be achieved.

In embodiments of the present invention, heat is extracted from the ground during the winter months to heat the building. During the summer months, cold is removed from the ground to cool the building. In this way, the soil is reheated during the summer months and the geothermal energy is minimized.

The various aspects can be easily combined with each other, and the combinations thus also correspond to embodiments according to the present invention.

Claims (6)

Conclusions A heat pump (100) located in a building, the heat pump comprising a pipe network (110) on the primary side of the heat pump, the pipe network (110) being placed in at least a portion of the shell (150) of the building wherein that portion of the shell (150) is in contact with the ground and wherein the pipe network is positioned so that it can serve as a ground heat exchanger. A heat pump (100) according to claim 1, wherein the shell (150) consists of a bottom plate (152) and side walls (154) and wherein the pipe network (110) is located in the bottom plate (152) and / or in the side walls (154) and the bottom plate (152) being below the ground level (160). A heat pump (100) according to any of the preceding claims, wherein the pipe network (110) is attached to reinforcement nets (210) of the base plate (150) of the building. A heat pump (100) according to any one of the preceding claims, wherein an insulating layer is provided between the pipe network (110) and the rest of the building. The use of a heat pump (100), the heat pump (100) according to one of the preceding claims, wherein the heat pump (100) is controlled so that the temperature of the pipe network (110) does not fall below 0 ° C. The use of a heat pump (100) according to claim 5, wherein the pipe network (110) is used both to extract heat from the ground and to transfer heat to the ground.