Cold heat network with intermediate latent heat storage

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 tempering at least one building, having a first closed circuit, in order to supply heat to a heat pump assigned to the respective building or to remove it from the heat pump, and having a second circuit, which indirectly exchanges thermal energy of a heat source remote from the building, preferably a soil probe, with the first closed circuit.Heating systems with earth probes are already known from the prior art. Thus, for example, the generic DE 19 727 493 C2 discloses a heating device with a heat pump, the condenser of which is acted upon by water of a heating circuit and the evaporator of which is acted upon by water or a brine solution of an earth probe, wherein the supply and return lines thereof can be inserted into an earth bore in such a way that a central pipe having a relatively large internal cross-sectional area of a plurality of pipes, arranged symmetrically around its outer periphery, having a smaller internal cross-sectional area, are arranged, which pipes are connected to the central pipe via a distributor head at the foot of the central pipe, wherein the central pipe forming the return line of the earth probe is provided with a thermal insulation and the pipes surrounding the central pipe form the supply pipes which lead to the evaporator of the heat pump, wherein the sum of the internal cross-sectional areas of the supply pipes corresponds approximately to the internal cross-sectional area of the central pipe.The generic DE 20 2005 014 597 U1 also discloses a cooling / heating system having a heat pump which has an evaporator and a condenser, wherein the evaporator is connected to a first circuit and the condenser is connected to a second circuit, wherein at least one earth probe, a source pump and a first changeover 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 in such a way that heat absorbed into the first circuit via the cooling / heating surface can be discharged to the first circuit via the heat exchanger and the heat can be discharged via the at least one earth probe, wherein the first changeover valve is arranged in such a way 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 accumulators are shown, 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.However, the prior art usually has the disadvantage that due to the direct thermal coupling of the heat pump and the earth probe to the earth probe, temperatures below 0° C. occur, which lead to freezing and damage to the earth probe.It is therefore the object of the invention to avoid or at least alleviate the disadvantages from the prior art. In particular, a cold heat network is to be provided, which thermally decouples the earth probe from the heat pump.This object is achieved according to the invention in a device of the generic type in that a latent heat store 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 one another and can thus be operated in an optimized manner independently of the ambient conditions and heat or cold requirements.Advantageous embodiments are claimed in the dependent claims and are explained in more detail below.In one configuration according to 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 store. This makes it possible to keep the storage medium (water) in the ice storage medium substantially ≥0° C., so that there is no risk of freezing at the earth 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 configuration according to the invention, the second circuit can connect the heat source directly to the latent heat store in an open circuit. In this case, a first heat transfer fluid can preferably 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 agent, in particular glycol, and the second heat transfer fluid is water. In particular, the first circuit can be configured according to the invention by a pipeline system with double-walled pipes and the second circuit can be configured by a pipeline system with single-walled pipes, which enables cost-effective repair of damaged and / or old soil probes by virtue of the fact that non-critical medium, such as pure water, can be used in the second circuit.According to an advantageous development, the latent heat store can be designed as an ice store.The invention is explained below with the aid of drawings. The following are shown: FIG. 1 shows a schematic arrangement of a cold local heat network according to a first exemplary embodiment. FIG. 2 shows a schematic arrangement of a cold local heat network according to a second exemplary embodiment.The figures are merely schematic in nature and serve exclusively for understanding the invention. The same elements are provided with the same reference numerals. The features of the individual exemplary embodiments can be interchanged.FIG. 1 shows a schematic arrangement of a cold waste heat network 1 according to a first exemplary embodiment. The cold local heat grid 1 as an example of a cold heat grid according to the invention is configured to heat or cool at least one building 2. Depending on the operating mode of a heat pump 4 assigned to the building 2, a first closed circuit 3 of the cold local heat network 1 feeds heat to or from the heat pump 4. Furthermore, the cold local heat network 1 has a second circuit 5, which indirectly exchanges thermal energy of a soil probe 6 with the first closed circuit 3. As shown in FIG. 1, an ice storage 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 7. Here, the earth probe 6 is an example of a "building remote heat source" and the ice storage 7 is an example of a "latent heat storage".The first circuit 3 has a building inlet line 8 and a building return line 9, in which a first heat transfer fluid circulates between the heat pump 4 and a extraction heat transfer element 10 arranged in the ice store 7. The flow directions of the first heat transfer fluid within the building inlet line 8 or the building return line 9 are illustrated in FIG. 1 by way of example by the arrows A and B, respectively.In the first exemplary embodiment, the second circuit 5 is designed as a closed circuit which connects the geothermal probe 6 thermo-fluidically via an geothermal probe feed line 11 and an geothermal probe return line 12 to an geothermal probe heat transfer element 13 arranged in or on the ice store, such that a second heat transfer fluid can circulate between the geothermal probe 6 and the geothermal probe heat transfer element 13 in the second circuit 5. The flow directions of the second heat transfer fluid within the geothermal probe inlet line 11 or the geothermal probe return line 12 are illustrated in FIG. 1 by way of example by the arrows C and D.Furthermore, in the first embodiment, the first heat transfer fluid and the second heat transfer fluid are different from each other. Both a glycol-water mixture is used for the first heat transfer fluid and water is used for the second heat transfer fluid. On account of legal regulations for groundwater protection, when glycol-water mixtures are used underground, the pipes must be of double-walled design or must meet additional measures, which is why in the first exemplary embodiment the (horizontal) pipelines of the first circuit 3 are double-walled and the pipelines of the second circuit 5 are of single-walled design.If a heat demand is now present in the building 2, the first circuit 3 extracts thermal energy from the ice storage 7 by heat exchange between the first heat transfer fluid and a storage medium stored in the ice storage 7 via the extraction heat transfer element 10 and feeds this to the heat pump 4, where the thermal energy is used for heating the building 2. Water is present as storage medium in the ice storage 7.The geothermal probe 6 in turn extracts thermal energy from the soil 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 here emits its thermal energy to the ice storage device 7, before it flows back to the geothermal probe 6 via the geothermal probe inlet line 11.By thermally decoupling the first circuit 3 and the second circuit 5, the water can be kept in the ice storage 7 around the heat exchanger 13 at a constant temperature of ≥0° C. (crystallization phase), i.e. as close as possible to the freezing point but free of ice. This ensures that the second heat transfer fluid in the geothermal probe inlet line 11 always flows in liquid form at 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.FIG. 2 shows a cold local heat network 1 according to a second exemplary embodiment. The mode of operation and the majority of the components do not differ from the first exemplary embodiment, which is why the focus lies subsequently on the differences between the two exemplary embodiments.In the cold local heat network 1 according to the second exemplary embodiment, a second circuit 5 between the geothermal probe 6 and the ice storage 7 is designed as an open circuit having an geothermal probe inlet line 11 and an geothermal probe return line 12. That is, liquid water from the ice storage 7 flows through the geothermal probe inlet line 11 to the geothermal probe 6, where it absorbs thermal energy of the soil and then flows back through the geothermal probe return line 12. In the ice storage 7, the water now does not exchange its thermal energy via a heat transfer element, but rather mixes with the water present in the ice storage 7 or leads to defrosting of the ice present in the ice storage 7.In the second exemplary embodiment, the second circuit 5 is situated below the frost limit G, so that the use of pure water as the second heat transfer fluid in the second circuit 5 does not lead to freezings within the geothermal probe feed line 11. Furthermore, the use of pure water as the second heat transfer fluid allows the pipes of the geothermal probe feed line 11 and the geothermal probe return line 12 to be single-walled and to be repaired cost-effectively by the then allowed use of water of damaged (leaking) geothermal probes.In order to compensate for possible water loss, a water connection 14 is additionally provided on the ice storage 7, so that water emerging via a damaged earth probe can be compensated by the water connection 14.List of reference characters1 Cold local heat network 2 Building 3 First circuit 4 Heat pump 5 Second circuit 6 Geothermal probe 7 Ice storage 8 Building inlet 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 A, B Flow directions in the first circuit C, D Flow directions in the second circuit G Frost boundary

Claims

Cold heat network (1) for controlling the temperature of at least one building (2), having a first closed circuit (3) in order to supply heat to a heat pump (4) assigned to the respective building (2) or to remove it from the heat pump (4), and having a second circuit (5) which indirectly exchanges thermal energy of a heat source remote from the building with the first closed circuit (3), wherein the heat source remote from the building is an earth probe (6), wherein a latent heat store (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 agent and the second heat transfer fluid is water.Cold heat network (1) according to Claim 1, characterized in that the second circuit (5) thermo-fluidically connects the earth probe (6) in a closed circuit to a heat transfer element (13) arranged in or on the latent heat store (7).Cold heat network (1) according to Claim 1, characterized in that the second circuit (1) connects the earth probe (6) directly to the latent heat store (7) in an open circuit.Cold heat network (1) according to one of claims 1 to 3, characterised in that the first circuit (3) is configured by a pipe system with double-walled pipes and the second circuit (5) is configured by a pipe system with single-walled pipes.Cold heat network (1) according to one of Claims 1 to 4, characterized in that the latent heat store (7) is designed as an ice store.

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