Method for providing thermal energy in a thermal network and thermal network

Abstract

The invention relates to a method and a heat network for the modulating provision of heat energy in a heat network to which heat energy is supplied and from which heat energy is extracted independently of the amount of energy supplied. The supplied heat energy is absorbed on the energy supply side by a first heat transfer medium, transferred by means of at least one intermediate heat pump from the first heat transfer medium to a second heat transfer medium flowing hydraulically separately from the first heat transfer medium, and the heat energy is then released from the second heat transfer medium to at least one heat consumer at the same or a higher temperature level. This method is characterized in that the first heat transfer medium flows to an evaporator of a first heat pump and to at least one evaporator of at least a second heat pump.The heat energy absorbed by the first heat transfer medium is at least partially released again at the first heat pump, or at least one second heat pump, or at the first heat pump and at least one second heat pump. Finally, the heat energy released by the first heat transfer medium is transferred by the heat pump(s) receiving the heat energy to a second, output-side heat transfer medium via the condenser.

Description

[0001] The invention relates to a method for the modulating provision of thermal energy in a district heating network, to which thermal energy is supplied in fluctuating proportions and from which thermal energy is withdrawn independently of the amount of energy supplied. The supplied thermal energy is absorbed on the energy supply side by a first heat transfer medium, transferred by means of at least one intermediate heat pump from the first heat transfer medium to a second heat transfer medium flowing hydraulically separately from the first heat transfer medium, and the thermal energy is then released from the second heat transfer medium to at least one heat consumer at the same or a higher temperature level. The invention further relates to a corresponding district heating network.

[0002] A major challenge in the economical use of renewable energy sources lies in combining different energy sources and reconciling their availability with potentially differing energy usage times. Such an approach is pursued in DE 202210106573 A1. According to this patent, higher efficiency in a district heating network is to be achieved by integrating a heat pump into the energy supply-side heat transfer fluid circuit. Both the evaporator and the condenser of the heat pump are connected to this circuit. Furthermore, the condenser is connected to a heat storage tank, which is also connected to the energy supply-side heat transfer fluid circuit. This allows heat energy not drawn from the district heating network to be used to compensate for fluctuations in heat consumption and generation.

[0003] Depending on the amount of heat consumed at any given time, the heat pump of DE 202210106573 A1, located between the energy supply-side and energy output-side heat transfer fluid circuits, does not always operate within its optimal performance range. This can result in, among other things, a lower efficiency, which necessitates a comparatively higher electricity demand for operating the heat pump and thus leads to reduced grid compatibility. Grid compatibility, in particular, is a crucial criterion when electricity supply fluctuates.

[0004] The object of the invention is therefore to further develop a corresponding method and heat network in such a way that heat pumps installed in the heat network operate in an optimized performance range with high efficiency even under loads that vary due to consumption.

[0005] This problem is solved methodically with the features of claim 1 and device-wise with the features of dependent claim 8. Further developments and advantageous embodiments are specified in the respective dependent claims.

[0006] The method for the modulating provision of heat energy in a heat network, to which heat energy is supplied fluctuates and from which heat energy is extracted independently of the amount of energy supplied, wherein the supplied heat energy is absorbed on the energy supply side by a first heat transfer medium, is transferred by means of at least one intermediate heat pump from the first heat transfer medium to a second heat transfer medium flowing hydraulically separately from the first heat transfer medium, and the heat energy is released from the second heat transfer medium at the same or a higher temperature level to at least one heat consumer, is characterized according to the invention in that the first heat transfer medium flows to an evaporator of a first heat pump and to at least one evaporator of at least a second heat pump.that the heat energy absorbed by the first heat transfer medium is at least partially released again at the first heat pump or at the at least one second heat pump or at the first heat pump and at least one second heat pump, that the heat energy released by the first heat transfer medium is transferred by the heat pump or heat pumps receiving the heat energy to a second, output-side heat transfer medium via the condenser.

[0007] The heat energy required on the consumption side can thus be supplied to the heat transfer medium of the district heating network by at least two independently operating heat pumps. The individual heat pumps can therefore operate within an optimal performance range with high efficiency, even with varying heat demand and the resulting different loads in the district heating network. Large fluctuations in heat demand are compensated for by individually switching the heat pumps on or off and regulating their operation.

[0008] According to a further development of the invention, the heat pumps have different capacities and are switched on depending on the amount of heat supplied to and extracted from the heating network, in particular depending on the amount of heat currently supplied to and simultaneously extracted from the heating network. The more powerful of the two heat pumps can, for example, be designed to handle the expected base load, while the at least one second heat pump is only operated additionally during peak loads.

[0009] By designing the heat pumps for different output levels, it is easily ensured that their efficiency ranges complement each other and only overlap minimally. This prevents the heat pumps from operating in a partial load range where their efficiency would drop significantly.

[0010] Typically, the efficiency drops significantly, especially at partial loads below 50% of a heat pump's maximum output. Therefore, in further developments, the heat pumps are designed with carefully matched outputs to ensure they operate at at least 50% of their maximum capacity.

[0011] To utilize supplied heat energy even when demand on the supply side is lower, a further development plan envisions feeding excess heat energy into a thermal storage system. During periods when the heat demand in the district heating network exceeds the available heat energy on the supply side, the heat energy temporarily stored in the network, and specifically in the thermal storage system, can then be supplied to the heat transfer medium on the supply side. Storing this heat energy thus achieves greater independence between the heat generator / energy supply side of the district heating network on the one hand, and the heat consumer / energy supply side of the district heating network on the other.

[0012] In a further embodiment of the invention, the thermal energy supplied by at least one second heat pump acts indirectly on the heat transfer medium on the output side. Thermal energy is first transferred to another heat transfer medium and then transferred from this second heat transfer medium back to the heat transfer medium on the output side. This allows thermal energy to be stored easily and independently of the heat transfer medium on the output side. The second heat transfer medium can be supplied to a thermal storage unit for this purpose. While thermal energy is being stored in the thermal storage unit with the second heat transfer medium, thermal energy can also be transferred simultaneously to the heat transfer medium on the output side via the first heat pump.

[0013] In a simple manner, the evaporators of the heat pumps are sequentially traversed in the direction of heat transfer fluid flow, following a further development process. The heat energy carried along with the heat transfer fluid flowing on the energy supply side can thus be used particularly efficiently in the district heating network. Depending on the operating mode of the district heating network, heat energy is then extracted again from the heat transfer fluid, from which heat energy has already been transferred at the first heat pump. This ensures that, throughout its entire energy supply-side cycle – i.e., after passing through all evaporators of the district heating network – the heat transfer fluid exhibits the largest possible temperature difference to a connected heat source, allowing it to absorb a particularly large amount of heat at the heat source.

[0014] In the same way, the heat transfer fluid flows through the condensers or condenser of the first heat pump and a heat exchanger of an indirectly connected second heat pump in succession, in order to absorb a larger amount of heat and be able to deliver it to a consumer.

[0015] The invention further relates to a heat network comprising an energy supply side and an energy output side connected to the energy supply side in a heat-transferring manner, and at least one heat pump arranged between the energy supply side and the energy output side, wherein hydraulically separate heat transfer circuits are assigned to the energy supply side and the energy output side.This is characterized by the fact that at least one energy supply-side heat transfer circuit and at least one energy output-side heat transfer circuit are connected by means of a first heat pump and at least one second heat pump for heat transfer, that the first heat pump and the at least one second heat pump are each connected to the energy supply-side heat transfer circuit via their evaporator, and that the first heat pump and the at least one second heat pump are connected to the energy output-side heat transfer circuit via their condenser for heat transfer.

[0016] The inventive design, in which each heat pump is connected to both the energy supply and energy output sides via heat transfer, makes it easy to operate the heat pumps independently of one another. The heat pumps are then switched on according to the heat demand on the output side in order to provide the required amount of heat.

[0017] To operate the heat pumps as efficiently as possible and to cover large fluctuations in the heat demand on the supply side, further training stipulates that the first heat pump must be designed with a capacity at least 80% greater than that of at least one second heat pump. Specifically, the first heat pump must be designed for at least twice the capacity of at least one second heat pump. The combined heat pumps can then always be operated at at least 50% of their maximum capacity and will not enter a partial load range with significantly decreasing efficiency.

[0018] In a further configuration, at least one second heat pump can be connected to the heat transfer circuit on the energy output side via an intermediate distribution heat circuit and a heat exchanger on the condenser side. The heating network and its components can thus be easily adapted to a specific installation location, as the two heat pumps and the heat transfer circuits connected to them can be arranged more flexibly relative to each other.

[0019] Furthermore, a heat storage unit can be integrated into the distribution heating circuit. This heat storage unit expands the possible operating modes of the device, enabling it to compensate for fluctuations in energy supply and to utilize inexpensive or surplus electrical energy for heat storage. The heating network thus exhibits improved grid compatibility.

[0020] In a further embodiment, the heat storage unit is connected to the distribution heat circuit via a storage supply line leading from a heat exchanger supply line section of the distribution heat circuit and a storage return line leading into a condenser supply line section of the distribution heat circuit. When filling the heat storage unit, the heat transfer fluid advantageously circulates only between the condenser of the second heat pump and the heat storage unit, without reaching the heat exchanger. A separate bypass of the distribution heat circuit at the heat exchanger is therefore unnecessary.

[0021] According to a further development, the energy-supply-side heat transfer circuit at the evaporator of the second heat pump is equipped with a bypass that bypasses the evaporator. The bypass, or rather the amount of heat transfer fluid flowing through it, can be used to regulate whether and how much heat transfer fluid from the supply-side circuit is supplied to the evaporator of at least one second heat pump. Similarly, a bypass can also be assigned to the evaporator side of the first heat storage unit.

[0022] To utilize and transfer available thermal energy as effectively as possible, the evaporators in the energy-supply-side heat transfer fluid circuit are advantageously connected in series in the direction of flow of the heat transfer fluid in the energy-supply-side circuit. In the at least one subsequent evaporator, the heat from the heat transfer fluid not extracted in the at least one preceding evaporator is then utilized, further cooling the heat transfer fluid. The heat transfer fluid, thus cooled, can then absorb a larger usable amount of heat from an energy-supply-side heat source.

[0023] Similarly, and with a corresponding effect, in a further embodiment the condensers or condenser of the first heat pump and the heat exchanger of the distribution heat circuit are connected in series in the energy-distribution-side heat transfer fluid circuit in the direction of flow of a heat transfer fluid flowing in the energy-distribution-side heat transfer fluid circuit. The heat transfer fluid flowing on the energy-distribution side then absorbs a larger amount of heat, which can be used by at least one heat consumer.

[0024] An embodiment of the invention, from which further essential features of the invention may emerge, is shown in the drawing.

[0025] The single figure in the drawing shows a process diagram of the device according to the invention, comprising a first heat pump 1 and a second heat pump 2, as well as an energy-supply-side heat transfer circuit 3 and an energy-discharge-side heat transfer circuit 4. A heat source 5 is associated with the energy-supply-side heat transfer circuit 3, from which thermal energy is supplied to the energy-supply-side heat transfer circuit 3. A heat consumer 6 is associated with the energy-discharge-side heat transfer circuit 4, to which thermal energy is drawn from the district heating network. The two heat transfer circuits 3, 4 are connected to each other via the two heat pumps 1, 2, with the evaporators 1a, 2a of the heat pumps 1, 2 each being connected to the energy-supply-side heat transfer circuit 3 and the condensers 1b, 2b of the heat pumps 1, 2 each being connected to the energy-discharge-side heat transfer circuit 4.

[0026] Both the evaporators 1a, 2a connected to the energy-supply side heat transfer circuit 3 and the condensers 1b, 2b connected to the energy-discharge side heat transfer circuit 4 are connected in series in their respective heat transfer circuits 3, 4. The evaporator 1a or condenser 1b that is closest to the flow direction of the heat transfer fluid in the heat transfer circuits 3, 4 is assigned to the larger first heat pump 1. This first heat pump 1 has twice the output of the second heat pump 2.

[0027] While the condenser 1b of the first heat pump 1 is directly connected to the energy-discharge-side heat transfer circuit 4, the condenser 2b of the second heat pump 2 acts on the energy-discharge-side heat transfer circuit 4 via an intermediate distribution heat circuit 7. The intermediate distribution heat circuit 7 and the energy-discharge-side heat transfer circuit 4 are connected to each other via a heat exchanger 8.

[0028] A heat storage tank 9 is connected to the distribution heat circuit 7. For this purpose, a storage tank feed line 11 extends from a heat exchanger supply line section 7a of the distribution heat circuit 7 at a three-way valve 10. Heat transfer fluid to be drawn from the heat storage tank 9 flows via a storage tank return line 12 into a condenser supply line section 7b of the distribution heat circuit 7.

[0029] The energy supply-side heat transfer circuit 3 also has a bypass 13 leading around the evaporator 2a of the second heat pump 2, which is controlled via another three-way valve 14.

[0030] With the two heat pumps 1 and 2, different operating modes are now possible. In the first operating mode, only the first, larger heat pump 1 is switched on and provides a sufficient amount of heat that corresponds to the amount of heat required by the heat consumer 6.

[0031] If the amount of heat used or required by the heat consumer 6 exceeds the amount of heat supplied by the first heat pump 1, the second heat pump 2 is activated according to a second operating mode. The additional heat required is transferred to the energy-distribution-side heat transfer circuit 4 via the distribution heat circuit 7 and the heat exchanger 8, so that more heat energy can be supplied to the energy-distribution-side heat transfer circuit 4 and made available to the heat consumer 6. The outputs of the two heat pumps 1 and 2 are coordinated so that each operates at at least 50% of its installed capacity.

[0032] If the heat consumer 6 requires an amount of heat that is less than 50% of the installed capacity of only the first heat pump 1, the heat network can also be operated according to a third operating mode using only the second heat pump 2, which then alone provides the heat energy required by the heat consumer 6.

[0033] According to a fourth operating mode, the heat energy required by the heat consumer 6 is supplied by the first heat pump 1. Since the second heat pump 2 only indirectly affects the energy-discharge-side heat transfer circuit 4 via the distribution heat circuit 7, it can, after the heat transfer fluid in the energy-supply-side heat transfer circuit 3 has flowed through the evaporator 1a of the first heat pump 1, extract any remaining heat energy from the heat transfer fluid using its evaporator 2a. The heat energy thus obtained is then transferred via the condenser 2b to the distribution heat circuit 7 and, instead of the heat exchanger 8, is fed to the heat storage tank 9 and stored there. This operating mode is particularly beneficial to the electricity grid, as electrical energy can be used when it is available in surplus and at a low cost.

[0034] The three-way valves 10, 14 can also be used to split partial flows of the heat carriers of the energy supply-side heat carrier circuit 3 and the distribution heat circuit 7, so that heat energy is supplied, for example, to both the heat storage 9 and the heat exchanger 8.

[0035] In a fifth operating mode, unlike the first four operating modes, insufficient thermal energy is available at heat source 5 to supply heat consumer 6. Depending on the amount of thermal energy available at heat source 5, either both heat pumps 1 and 2, or only one of them, are switched on. Additionally, thermal energy is extracted from the thermal storage tank 9 and transferred via the distribution circuit 7 and the heat exchanger 8 to the heat transfer circuit 4, which is then used by heat consumer 6. This may be necessary, in particular, for heat sources 5 with fluctuating thermal energy availability.

Claims

1. Method for the modulating provision of heat energy in a heat network to which heat energy is supplied fluctuates and from which heat energy is withdrawn independently of the amount of energy supplied, wherein the supplied heat energy is absorbed on the energy supply side by a first heat transfer medium, is transferred by means of at least one intermediate heat pump (1, 2) from the first heat transfer medium to a second heat transfer medium which flows hydraulically separately from the first heat transfer medium and the heat energy is released from the second heat transfer medium at the same or a higher temperature level to at least one heat consumer (6), characterized by that the first heat transfer medium flows to an evaporator (1a) of a first heat pump (1) and to at least one evaporator (2a) of at least a second heat pump (2), thatthe heat energy absorbed by the first heat transfer medium is at least partially released again at the first heat pump (1) or at the at least one second heat pump (2) or at the first heat pump (1) and at the at least one second heat pump (2), that The heat energy emitted by the first heat transfer medium is transferred from the heat energy absorbing heat pump (1, 2) or heat energy absorbing heat pumps (1, 2) to a second, output-side heat transfer medium on the condenser side.

2. Method according to claim 1, characterized by the fact that the heat pumps (1, 2) have different power outputs and are switched on depending on the amount of heat supplied to the heat network and the amount of heat extracted from the heat network.

3. Method according to one of claims 1 or 2, characterized by the fact thatthe heat pumps (1, 2) have such coordinated outputs that they are operated at at least 50% of their maximum output.

4. Method according to any one of claims 1 to 3, characterized by the fact that excess heat energy is fed into a heat storage device (9).

5. Method according to any one of claims 1 to 4, characterized by the fact that The heat energy temporarily stored in the heat network can be supplied to the heat transfer medium on the supply side.

6. Method according to any one of claims 1 to 5, characterized by the fact that The heat energy provided by at least one second heat pump (2) is indirectly transferred to the heat transfer medium on the output side.

7. Method according to any one of claims 1 to 6, characterized by the fact that The evaporators (1a, 2a) of the heat pumps are flowed through in series one after the other in the direction of flow of the heat transfer medium.

8. Heat network comprising an energy supply side and an energy output side connected to the energy supply side in a heat-transferring manner and at least one heat pump (1, 2) arranged between the energy supply side and the energy output side, wherein hydraulically separate heat transfer circuits (3, 4) are assigned to the energy supply side and the energy output side, characterized by that at least one energy supply-side heat transfer circuit (3) and at least one energy output-side heat transfer circuit (4) are connected by means of a first heat pump (1) and by means of at least one second heat pump (2) for heat transfer, thatthe first heat pump (1) and the at least one second heat pump (2) are each connected to the energy supply side heat transfer circuit (3) via their evaporators (1a, 2a) and that the first heat pump (1) and the at least one second heat pump (2) are connected to the energy output side heat transfer circuit (4) via their condensers (1b, 2b) in a heat transfer manner.

9. Heat network according to claim 8, characterized by the fact that the first heat pump (1) is designed to have a capacity at least 80% greater than that of the at least one second heat pump (2), in particular the first heat pump (1) is designed for at least twice the capacity of the at least one second heat pump (2).

10. Heat network according to one of claims 8 or 9, characterized by the fact thatwhich at least one second heat pump (2) is connected on the condenser side via a distribution heat circuit (7) and a heat exchanger (8) to the energy output side heat transfer circuit (4).

11. Heat network according to claim 10, characterized by the fact that a heat storage unit (9) is integrated into the distribution heat circuit (7).

12. Heat network according to one of claims 10 or 11, characterized by the fact that a storage supply line (11) branches off from a heat exchanger supply line section (7a) of the distribution heat circuit (7) and a storage return line (12) leads into a condenser supply line section (7b) of the Z distribution heat circuit (7).

13. Heat network according to one of claims 8 to 12, characterized by the fact that a bypass (13) bypassing the evaporator (2a) is assigned to the energy supply-side heat transfer circuit (3) at the evaporator (2a) of the second heat pump (2).

14. Heat network according to one of claims 8 to 13, characterized by the fact thatthe evaporators (1a, 2a) are connected in series in the energy supply-side heat transfer circuit (3) in the direction of flow of a heat transfer fluid flowing in the energy supply-side heat transfer circuit (3).

15. Heat network according to one of claims 8 to 14, characterized by the fact that the condensers or the condenser (1a) of the first heat pump (1) and the heat exchanger (8) of the distribution heat circuit (7) are connected in series in the energy-supply side heat transfer circuit (4) in the direction of flow of a heat transfer fluid flowing in the energy-supply side heat transfer circuit (4).

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