DE102019111184B4 - Cold heat network with intermediate latent heat storage - Google Patents

Abstract

Cold heat network (1) for controlling the temperature of at least one building (2), comprising a first closed circuit (3) for supplying heat to a heat pump (4) assigned to the respective building (2) or for removing heat from the heat pump (4), and a second circuit (5) which indirectly exchanges thermal energy from a heat source remote from the building with the first closed circuit (3), wherein the heat source remote from the building is a geothermal probe (6), wherein a latent heat accumulator (7) is arranged between the first closed circuit (3) and the second circuit (5), and a first heat transfer fluid flows in the first circuit (3) and a second heat transfer fluid different from the first heat transfer fluid flows in the second circuit (5), characterized in that the first heat transfer fluid is a brine and/or a mixture of water and an antifreeze, and the second heat transfer fluid is water.

Description

The invention relates to a cold heat network for controlling the temperature of at least one building, comprising a first closed circuit for supplying heat to a heat pump associated with the respective building or for removing heat from the heat pump, and a second circuit which indirectly exchanges thermal energy from a heat source remote from the building, preferably a geothermal probe, with the first closed circuit.

Heating systems with geothermal probes are already known from the state of the art. For example, the generic DE 19 727 493 C2 a heating device with a heat pump, the condenser of which is supplied with water from a heating circuit and the evaporator with water or a brine solution from a geothermal probe, the flow and return lines of which can be inserted into a borehole in the ground in such a way that a central pipe with a relatively large internal cross-sectional area is arranged among several pipes with a smaller internal cross-sectional area which are arranged concentrically and symmetrically around its outer circumference and are connected to the central pipe via a distributor head at the base of the central pipe, the central pipe forming the return line of the geothermal probe being provided with thermal insulation and the pipes surrounding the central pipe forming the flow pipes which lead to the evaporator of the heat pump, the sum of the internal cross-sectional areas of the flow pipes corresponding approximately to the internal cross-sectional area of the central pipe.

The generic DE 20 2005 014 597 U1 a cooling/heating system with a heat pump having an evaporator and a condenser, wherein the evaporator is connected to a first circuit and the condenser to a second circuit, wherein at least one geothermal probe, a source pump, and a first switching valve are arranged in the first circuit, a cooling/heating surface and a heating circuit pump are arranged in the second circuit, and the first and second circuits are connected to one another via a heat exchanger such that heat absorbed into the first circuit via the cooling/heating surface can be released to the first circuit via the heat exchanger, and the heat can be released via the at least one geothermal probe, wherein the first switching valve is arranged such that the first circuit can be switched between the evaporator and the heat exchanger, and the heating circuit pump is arranged in the second circuit between the heat exchanger and the condenser. Further examples of the use of latent heat storage devices can be found, inter alia, in DE 10 2010 037 474 A1 , DE 10 2011 120 743 A1 , DE 10 2017 112 407 A1 , DE 30 11 840 A1 , DE 10 2010 037 477 A1 , DE 10 2017 112 409 A1 , DE 10 2011 001 273 A1 , DE 26 19 744 A1 and DE 10 2013 213 823 A1 shown.

However, the state of the art technology usually has the disadvantage that the direct thermal coupling of the heat pump and the geothermal probe results in temperatures below 0°C occurring at the geothermal probe, which leads to freezing and damage to the geothermal probe.

The object of the invention is therefore to avoid or at least mitigate the disadvantages of the prior art. In particular, it is to provide a cold heat network that thermally decouples the geothermal probe from the heat pump.

This object is achieved according to the invention in a generic device in that a latent heat storage device is arranged between the first closed circuit and the second circuit.

This has the advantage that the first circuit and the second circuit are thermally decoupled from each other and can thus be operated in an optimized manner regardless of the ambient conditions and heating or cooling requirements.

Advantageous embodiments are claimed in the subclaims and are explained in more detail below.

In one embodiment of the invention, the second circuit can thermo-fluidically connect the heat source in a closed circuit to a heat transfer element arranged in or on the latent heat storage device. This makes it possible to keep the storage medium (water) in the ice storage device essentially at ≥0°C, so that there is no risk of freezing at the geothermal probe, but as close as possible to the freezing point of the respective medium and, in particular, as constant as possible there.

In a further embodiment according to the invention, the second circuit can connect the heat source directly to the latent heat storage device in an open circuit. Preferably, a first heat transfer fluid can flow in the first circuit, and a second heat transfer fluid, different from the first heat transfer fluid, can flow in the second circuit. It is advantageous if the first heat transfer fluid is a brine and/or a mixture of water and an antifreeze, in particular glycol, and the second heat transfer fluid is water. In particular, the first circuit can be connected by a pipeline. system can be designed with double-walled pipes and the second circuit can be designed by a piping system with single-walled pipes, which enables a cost-effective rehabilitation of damaged and/or outdated geothermal probes by using a non-critical medium, such as pure water, in the second circuit.

According to an advantageous further development, the latent heat storage device can be designed as an ice storage device.

• 1 eine schematische Anordnung eines Kaltnahwärmenetzes gemäß einem ersten Ausführungsbeispiel.
• 2 eine schematische Anordnung eines Kaltnahwärmenetzes gemäß einem zweiten Ausführungsbeispiel.

The invention is explained below with the aid of drawings. They show:

• 1 a schematic arrangement of a cold local heating network according to a first embodiment.
• 2 a schematic arrangement of a cold local heating network according to a second embodiment.

The figures are merely schematic in nature and serve solely to facilitate understanding of the invention. The same elements are provided with the same reference numerals. The features of the individual embodiments can be interchanged.

1 shows a schematic arrangement of a cold local heating network 1 according to a first embodiment. The cold local heating network 1 as an example of a cold heating network according to the invention is designed to heat or cool at least one building 2. A first closed circuit 3 of the cold local heating network 1 supplies heat to or from a heat pump 4 assigned to the building 2, depending on the operating mode. Furthermore, the cold local heating network 1 has a second circuit 5, which indirectly exchanges thermal energy from a geothermal probe 6 with the first closed circuit 3. As in 1 As shown, an ice storage tank 7 is arranged between the first circuit 3 and the second circuit 5. In other words, the first circuit 3 is thermally decoupled from the second circuit 5 by the ice storage tank 7. Here, the geothermal probe 6 is an example of a "heat source remote from the building" and the ice storage tank 7 is an example of a "latent heat storage device."

The first circuit 3 comprises a building supply line 8 and a building return line 9, in which a first heat transfer fluid circulates between the heat pump 4 and an extraction heat transfer element 10 arranged in the ice storage 7. The flow directions of the first heat transfer fluid within the building supply line 8 and the building return line 9 are shown in 1 shown as an example by the arrows A and B.

In the first embodiment, the second circuit 5 is designed as a closed circuit, which thermo-fluidically connects the geothermal probe 6 via a geothermal probe supply line 11 and a geothermal probe return line 12 to a geothermal probe heat transfer element 13 arranged in or on the ice storage tank, so that in the second circuit 5, a second heat transfer fluid can circulate between the geothermal probe 6 and the geothermal probe heat transfer element 13. The flow directions of the second heat transfer fluid within the geothermal probe supply line 11 and the geothermal probe return line 12 are in 1 shown as an example by the arrows C and D.

Furthermore, in the first embodiment, the first heat transfer fluid and the second heat transfer fluid differ from each other. A glycol-water mixture is used for both the first heat transfer fluid, and water is used for the second heat transfer fluid. Due to legal regulations regarding groundwater protection, the pipes used underground with glycol-water mixtures must be double-walled or meet additional requirements. Therefore, in the first embodiment, the (horizontal) pipes of the first circuit 3 are double-walled, and the pipes of the second circuit 5 are single-walled.

When a heat demand exists in building 2, the first circuit 3 extracts thermal energy from the ice storage tank 7 through heat exchange between the first heat transfer fluid and a storage medium stored in the ice storage tank 7 via the extraction heat transfer element 10 and supplies this energy to the heat pump 4, where the thermal energy is used to heat the building 2. Water serves as the storage medium in the ice storage tank 7.

The geothermal probe 6 in turn extracts thermal energy from the ground and thus heats the second heat transfer fluid, which flows via the geothermal probe return line 12 to the geothermal probe heat transfer element 13 and transfers its thermal energy to the ice storage 7 before flowing back to the geothermal probe 6 via the geothermal probe supply line 11.

Due to the thermal decoupling of the first circuit 3 and the second circuit 5, the water around the heat exchanger 13 in the ice storage 7 can be kept at a constant temperature of ≥ 0°C (crystallization phase), ie as close to the freezing point as possible but ice-free. It is ensured that the second heat transfer fluid in the geothermal probe inlet line 11 always flows in liquid form with a temperature greater than or equal to 0°C, so that the risk of freezing at the geothermal probe 6 and thus damage to the geothermal probe 6 can be reduced.

2 shows a cold district heating network 1 according to a second exemplary embodiment. The functionality and the majority of the components do not differ from the first exemplary embodiment, which is why the focus below is on the differences between the two exemplary embodiments.

In the cold district heating network 1 according to the second exemplary embodiment, a second circuit 5 between the geothermal probe 6 and the ice storage tank 7 is designed as an open circuit with a geothermal probe supply line 11 and a geothermal probe return line 12. This means that liquid water from the ice storage tank 7 flows through the geothermal probe supply line 11 to the geothermal probe 6, where it absorbs thermal energy from the ground and then flows back through the geothermal probe return line 12. In the ice storage tank 7, the water does not exchange its thermal energy via a heat transfer element, but rather mixes with the water present in the ice storage tank 7 and leads to the defrosting of the ice present in the ice storage tank 7.

In the second embodiment, the second circuit 5 is located below the frost line G, so that the use of pure water as the second heat transfer fluid in the second circuit 5 does not lead to freezing within the geothermal probe supply line 11. Furthermore, the use of pure water as the second heat transfer fluid allows the pipes of the geothermal probe supply line 11 and the geothermal probe return line 12 to be constructed with single walls and, through the then permitted use of water, to repair damaged (leaky) geothermal probes cost-effectively.

In order to compensate for possible water loss, a water connection 14 is additionally provided on the ice storage tank 7 so that water escaping via a damaged geothermal probe can be compensated through the water connection 14.

List of reference symbols

1

Cold district heating network

2

Building

3

first cycle

4

heat pump

5

second circuit

6

Geothermal probe

7

Ice storage

8

Building supply line

9

Building return line

10

Extraction heat transfer element

11

Geothermal probe inlet line

12

Geothermal probe return line

13

Geothermal probe heat transfer element

14

Water connection

AWAY

Flow directions in the first circuit

C, D

Flow directions in the second circuit

G

Frost line

Claims (5)

Cold heat network (1) for controlling the temperature of at least one building (2), comprising a first closed circuit (3) for supplying heat to a heat pump (4) assigned to the respective building (2) or for removing heat from the heat pump (4), and a second circuit (5) which indirectly exchanges thermal energy from a heat source remote from the building with the first closed circuit (3), wherein the heat source remote from the building is a geothermal probe (6), wherein a latent heat accumulator (7) is arranged between the first closed circuit (3) and the second circuit (5), and a first heat transfer fluid flows in the first circuit (3) and a second heat transfer fluid, different from the first heat transfer fluid, flows in the second circuit (5), characterized in that the first heat transfer fluid is a brine and/or a mixture of water and an antifreeze, and the second heat transfer fluid is water. Cold heat network (1) to Claim 1 , characterized in that the second circuit (5) thermo-fluidically connects the geothermal probe (6) in a closed circuit with a heat transfer element (13) arranged in or on the latent heat accumulator (7). Cold heat network (1) to Claim 1 , characterized in that the second circuit (1) connects the geothermal probe (6) directly to the latent heat storage device (7) in an open circuit. Cold heat network (1) according to one of the Claims 1 until 3 , characterized in that the first circuit (3) is designed by a piping system with double-walled pipes and the second Circuit (5) is designed by a piping system with single-walled pipes. Cold heat network (1) according to one of the Claims 1 until 4 , characterized in that the latent heat storage device (7) is designed as an ice storage device.