DISTRICT HEATING SYSTEM WITH SURPLUS FEED-IN

Description

[0001] The invention relates to a district heating system with a surplus feed-in, as well as a method and a computer program product for controlling the district heating system with surplus feed-in.

[0002] In a district heating system, district heating transfer stations are used to feed district heat from a district heating network into a building. District heating systems consist of a primary side on the supply side and a secondary side on the consumer side. The primary and secondary sides are coupled in a transfer station for heat transfer, for example, via a heat exchanger.

[0003] On the primary and secondary sides, a medium circulates to transport heat through a circuit, each comprising a flow and a return. A hot medium containing district heating is supplied to the primary flow. At the heat exchanger of the district heating transfer station, the district heating can be fed into the secondary flow. The primary return has a correspondingly lower temperature due to the consumer's consumption of district heating. On the secondary side, the heat from the flow is distributed to various heat-dissipating units in the building, for example, a domestic hot water boiler, a series of heating circuits and / or a buffer tank, possibly with a downstream fresh water module, or a domestic hot water storage charging system instead of the domestic hot water boiler. In the secondary return, the medium on the secondary side has a lower temperature than in the secondary flow.Thus, the cold medium from the secondary return at the district heating transfer station can absorb new district heat from the primary circuit for a new circulation of the secondary circuit.

[0004] For the economic efficiency of a district heating network, the largest possible temperature difference between the primary flow and the primary return is desirable. This allows the supplier to ensure that a significant portion of the district heat delivered via the primary circuit is taken up by the consumer and not, as considered superfluous, returned to the combined heat and power plant via the primary return.

[0005] It is known to supply heat to a stratified storage tank in a building using various heat sources, such as solar thermal energy, photovoltaics, a heat pump, and / or gas or wood combustion.

[0006] However, the simple integration of additional heat sources into the secondary side of a district heating system has so far been avoided, as additional heat sources would compete with the supplied district heat and thus negatively impact the efficiency of the district heating network. An increased secondary-side return temperature leads to a higher primary-side return temperature and thus to a reduced energy output, as described above.

[0007] DE 10 2011 103 133A1 relates to a district heating compact station which serves a heating circuit or a drinking water and / or hot water circuit, and for storage purposes a buffer storage tank is provided in the secondary circuit of the district heating compact station.

[0008] DE 10 2013 003 206 A1 and DE 202 14 086 U1 each relate to a heating system with features from the preamble of claim 1.

[0009] The object of the present invention is therefore to provide a district heating system with surplus feed-in as well as a method and a computer program product for controlling such a system, in which the feed-in of additional thermal energy on the secondary side is better integrated into the district heating system.

[0010] This object is achieved by the district heating system, the method and the computer program product having the features of the respective independent claims.

[0011] Accordingly, a district heating system is provided for a building. The district heating system comprises a district heating transfer station, a primary side on the supplier side, and a secondary side, with the secondary side being adapted to receive district heat from a primary side on the supplier side at a district heating transfer station on the building side. The district heating system also comprises a surplus feeder. The surplus feeder comprises a hydraulic connection to the secondary side and is adapted to provide additional thermal energy to at least one heat-dissipating unit on the secondary side.The provided thermal energy can be distributed to a plurality of heat-dissipating units on the secondary side according to a predetermined prioritization sequence, wherein the secondary side comprises a plurality of heat-dissipating units, the heat-dissipating units being arranged in a row, and the first downstream heat-dissipating unit in the row being a heat accumulator. Downstream, a plurality of heat-dissipating units on the secondary side are designed as a heating circuit. The surplus feeder, by means of the hydraulic connection, provides additional thermal energy to the heat accumulator with priority according to the predetermined prioritization sequence. Additionally included is a controller, wherein the controller is adapted to adjust a heating circuit target temperature of a predetermined heating circuit in order to enable forced dissipation of the additional thermal energy provided by the surplus feeder, provided the heat accumulator is fully charged.

[0012] The additional thermal energy differs from district heating in its source and is therefore additional to district heating. The district heating system is characterized by the fact that the surplus feeder is adapted to provide the thermal energy via a hydraulic connection to the secondary side.

[0013] Accordingly, for the first time, the thermal energy from the surplus feeder is not only integrated locally, such as in a single heat storage unit, but holistically into the secondary side. To this end, the thermal energy from the surplus feeder is fed hydraulically into the secondary side, i.e., into a medium on the secondary side. The additional thermal energy is hydraulically integrated into the secondary side via a connection to the main circuit of the secondary side. This means that the additional thermal energy is fed directly into the secondary side, independent of the primary side. In other words, the additional thermal energy from the surplus feeder and the district heating from the district heating transfer station are thus transported through the secondary side and distributed on the secondary side using a common medium.

[0014] This has the advantage that the thermal energy fed in by the surplus feeder can be distributed to heat-dissipating units on the secondary side. This counteracts an increase in the secondary return temperature when the surplus feed-in is active, thus avoiding unnecessary costs for the district heating supplier.

[0015] A heat-dissipating unit is any unit or device in the secondary circuit through which the (common) medium of the secondary side flows and thereby dissipates heat from the (common) medium of the secondary side. Examples of heat-dissipating units include boilers, buffer tanks, and heating circuits.

[0016] In an advantageous embodiment of the invention, the surplus feeder comprises a mixing means. The mixing means is adapted to regulate the temperature of a medium of the surplus feeder to a predetermined flow setpoint, so that the medium contains the additional thermal energy.

[0017] Advantageously, the surplus feeder is adapted to provide at least one heat dissipating unit with the additional thermal energy by means of a pre-pressure pump.

[0018] Providing the thermal energy from the surplus feeder using a booster pump has the advantage that the at least one heat-dissipating unit can receive the thermal heat from the surplus feeder with priority over district heating provided on the secondary side. While the thermal energy from the surplus feeder can be fed directly, i.e. without further technical measures, into the at least one heat-dissipating unit thanks to the booster pressure and hydraulic integration of the surplus feeder, the absorption of district heat from the secondary-side flow requires a negative pressure generated by a charging pump. The output of the charging pump can be regulated such that the district heating supplements the provision of thermal energy to the at least one heat-dissipating unit (if required).

[0019] Advantageously, the district heating system comprises a first check valve, wherein the first check valve is arranged on the secondary side between the district heating transfer station and the surplus feeder.

[0020] The first check valve has the advantage of hydraulically decoupled the district heating transfer station and the surplus feeder on the secondary side. This prevents incorrect circulation on the secondary side, which could negatively impact the district heating transfer station. This means that the additional thermal energy provided by the surplus feeder via the booster pump is completely decoupled from the district heating transfer station and can be fed directly to at least one heat-dissipating unit on the secondary side.

[0021] The predetermined prioritization sequence of the heat-dissipating units according to the invention has the advantage that the additional thermal energy can be distributed specifically to heat-dissipating units on the secondary side—even if the surplus feeder provides more additional thermal energy than required by the secondary side's heat storage. After all, the availability and amount of additional thermal energy from the surplus feeder are usually distributed differently.

[0022] The predetermined prioritization sequence promotes maintaining the largest possible temperature difference between the secondary-side flow and the secondary-side return. This ensures a low temperature in the primary-side return, allowing the district heating supplier's energy balance to remain economical, regardless of whether surplus feed-in to the secondary side is activated.

[0023] It is advantageous if the additional thermal energy is supplied to an upper layer of the heat storage.

[0024] In this way, the loading of the heat storage can be controlled flexibly and precisely while maintaining a significant temperature gradient between the upper layers of the heat storage and the lower layers of the heat storage.

[0025] In contrast to the conventional integration of additional heat sources into a heat storage system—namely, in the middle to lower part of the heat storage system to distribute the additional heat to the largest possible usable volume—temperature layers in the heat storage system are largely maintained. Therefore, a layered system existing in the heat storage system is not disrupted by the heat supply from the surplus feeder.

[0026] This has the advantage that a significant temperature gradient in the heat storage tank, which is necessary for efficient operation, is maintained, whereby the temperature of the medium in the secondary-side return can be kept at the lowest possible level.

[0027] The mixing device can be a heating mixer. Alternatively, the mixing device can be an injection circuit or a controlled pump.

[0028] The forced removal of additional thermal energy from the surplus feeder, which is not required on the secondary side and is therefore considered superfluous, can be adjusted using the controller. This has the advantage that the secondary return flow is not additionally heated.

[0029] Typically, the primary-side flow at the district heating transfer station is also regulated by the controller. This allows the controller to at least partially reduce the district heating supply while additional heat energy from a surplus feeder is coupled into the secondary side. This avoids unused district heating units, which can result in significant cost savings for the district heating supplier, particularly due to the cubic scaling of the pumping capacity for district heating transport.

[0030] In conventional district heating systems, neither the controller nor the supplier is directly aware of additional heat being fed into the secondary circuit, which negatively impacts the supplier's energy balance because unused district heat must be transported away again.

[0031] Through the hydraulic integration of the additional thermal energy provided by the surplus feeder and a corresponding control of the secondary side according to a predetermined prioritization sequence, an essentially constant efficiency of the district heating supply can be achieved.

[0032] The predetermined prioritization sequence depends on the specific design of the secondary side and is explained below with reference to the figures.

[0033] It is advantageous if the heat storage unit is a primary boiler for a hot water circuit. The primary boiler is hydraulically integrated into the secondary side via a first switching valve. The first switching valve is configured to switch the excess feeder between a secondary-side return and a return of the primary boiler.

[0034] The controller is adapted to set the first switching valve to the return of the first boiler when a temperature signal from a first temperature sensor arranged at a lower layer of the first boiler is below a predetermined boiler shutdown value. If the temperature signal from the first temperature sensor exceeds the predetermined boiler shutdown value, the controller is adapted to set the first switching valve to the secondary return to enable the forced dissipation of the additional thermal energy.

[0035] It is also advantageous if, on the secondary side, a second boiler is hydraulically integrated into the secondary side downstream of the first boiler by means of a second switching valve. The second switching valve is adapted to switch the excess feeder between the secondary-side return and a return of the second boiler. The second boiler follows the first boiler in the predetermined priority sequence.

[0036] The controller is adapted to set the second switching valve to the return of the second boiler when a temperature signal from a second temperature sensor arranged at a lower layer of the second boiler is below the predetermined boiler shutdown value and the first switching valve is set to the secondary return. If the temperature signal from the second temperature sensor exceeds the predetermined boiler shutdown value, the controller is adapted to set the first switching valve and the second switching valve to the secondary return to enable the forced dissipation of the additional thermal energy.

[0037] Alternatively, a buffer storage tank can be hydraulically connected downstream of the first boiler on the secondary side, parallel to the first boiler, using a second check valve. The buffer storage tank follows the first boiler in the predetermined priority sequence, meaning that the buffer storage tank is only recharged by the surplus feeder when the first switching valve is set to the secondary return.

[0038] An assignable temperature sensor is located on the buffer tank, preferably on a lower layer of the buffer tank. Typically, several temperature sensors are located on a buffer tank, from which the user can select one. A predetermined buffer fixed value is assigned to the assignable temperature sensor. The buffer fixed value can be variably adjusted to meet the requirements of the heat-dissipating units supplied by the buffer tank.

[0039] The controller is configured to adjust the heating circuit setpoint temperature of a predetermined heating circuit to enable the forced removal of additional thermal energy when the temperature signal from the assignable temperature sensor exceeds the predetermined buffer setpoint by a preconfigured charging hysteresis value. To feed excess heat into a heating circuit, the flow setpoint of the excess heat feeder is adjusted accordingly to the preconfigured heating circuit setpoint.

[0040] According to one aspect of the invention, the first downstream heat storage unit is a buffer storage unit. Downstream of the buffer storage unit, a boiler is hydraulically integrated into the secondary side. The buffer storage unit is positioned ahead of the boiler in the predetermined priority sequence. The boiler can be charged with thermal energy from the buffer storage unit by means of a boiler charging pump.

[0041] An assignable temperature sensor is located on the buffer tank, preferably on a lower layer of the buffer tank. A predetermined buffer fixed value is assigned to the assignable temperature sensor.

[0042] The controller is adapted to activate the boiler charging pump and to adjust the flow setpoint of the surplus feeder to the boiler setpoint in order to enable the forced removal of the additional thermal energy when the temperature signal of the assignable temperature sensor exceeds the predetermined buffer fixed value by a preconfigured charging hysteresis value.

[0043] As soon as the boiler is fully charged (temperature signal of the second temperature sensor exceeds the boiler switch-off temperature) and the temperature signal of the assignable temperature sensor of the buffer storage continues to exceed the predetermined buffer fixed value by the preconfigured charging hysteresis value, the forced discharge of the heating circuits begins.

[0044] According to an advantageous aspect of the invention, the surplus feeder is adapted to heat the medium by means of a heat source powered by solar energy.

[0045] The surplus feeder can be designed as an electric heating cartridge or electric cartridge.

[0046] Accordingly, a method for controlling a district heating system according to the invention is also provided. The method comprises activating the pre-pressure pump of the surplus feeder. The method further comprises controlling the mixing medium of the surplus feeder. The mixing medium regulates the temperature of the medium of the surplus feeder to the predetermined flow setpoint. In addition, the method comprises charging a heat accumulator. For charging the heat accumulator, the surplus feeder is hydraulically preferred over the district heating transfer station. In this case, the controller limits the charging of the heat accumulator by the district heating transfer station to a predetermined minimum temperature value of the heat accumulator. The predetermined minimum temperature value can include a hysteresis value, e.g., 2 K. Furthermore, the method comprises forced removal of the thermal energy provided by the surplus feeder.To do this, the controller adjusts the heating circuit setpoint temperature of the predefined heating circuit. Specifically, the controller increases the heating circuit setpoint temperature of the predefined heating circuit. This allows the thermal energy provided by the surplus feeder to be fed to the predefined heating circuit, provided that a heat storage unit with priority according to the prioritization sequence is fully charged.

[0047] On the secondary side, a hydraulic balance is established between the flow rate requested by the heat storage tank's charging pump and the flow rate provided by the pre-pressure pump of the surplus feeder. The heat storage tank is charged with the sum of the two flow rates. By hydraulically prioritizing the provided flow rate over the requested flow rate, the output of the district heating transfer station can be reduced without actively controlling a flow setpoint assigned to the district heating transfer station.

[0048] Limiting the charging of the heat storage by the district heating transfer station means that more additional energy can be fed into the heat storage by the surplus feeder.

[0049] Advantageously, the heat storage unit is a first boiler, wherein the controller sets the first switching valve to the return of the first boiler to charge the first boiler using the thermal energy provided by the surplus feeder. The method further comprises switching the first switching valve from the return of the first boiler to the secondary return, provided the first boiler is fully charged, in order to continue switching according to the predetermined prioritization sequence.

[0050] Furthermore, an alternative operating mode is provided, according to which the controller is adapted to close a primary-side valve, thereby significantly reducing the district heating flow and thus the delivery of district heating, while maintaining a frost protection function of the district heating system.

[0051] Furthermore, a computer program product is provided which is adapted to carry out the method according to the invention in the controller of the district heating system according to the invention.

[0052] The invention is described in more detail below with reference to exemplary embodiments and the drawings. The drawings show: Fig. 1 shows a district heating system with a surplus feed into a first boiler as a heat storage device according to an embodiment of the invention; Fig. 2 shows a district heating system with a surplus feed into both a first boiler and a second boiler according to an embodiment of the invention; Fig. 3 shows a district heating system with a surplus feed into a first boiler and a buffer storage device as a heat storage device according to an embodiment of the invention; and Fig. 4 shows a district heating system with a surplus feed into a buffer storage device and a boiler according to an embodiment of the invention.

[0053] For all embodiments of the invention and figures, regardless of the specific design, a district heating transfer station 10, a surplus feeder 30 and a controller 50 are present on the secondary side.

[0054] The district heating transfer station 10, hereinafter also referred to as transfer station 10, couples the primary circuit 11 with the secondary circuit 12 in a district heating system 1, for example, by means of a heat exchanger. Thus, district heating can be coupled from a supplier-side primary circuit 11 into a consumer-side secondary circuit 12 on the secondary side. Both the primary circuit 11 and the secondary circuit 12 have a flow and a return. On the secondary side, a secondary-side medium flows through the flow and return. The secondary-side medium typically has a significantly higher temperature in the flow than in the return.

[0055] The secondary-side medium can be water, especially water treated for heating systems. Alternatively, a hot medium in the supply line can also be steam. Condensate then forms in the secondary-side return line, which can absorb district heating at the transfer station.

[0056] Furthermore, according to the invention, the district heating system 1 comprises a surplus feeder 30. The surplus feeder 30 is hydraulically integrated into the secondary side by means of a mixing medium 33 and provides additional thermal energy or heat energy. In particular, the surplus feeder 30 is hydraulically integrated into the secondary circuit 12 of the secondary side. The additional heat energy from the surplus feeder 30 can be transferred under pre-pressure into the secondary-side supply line. This means that the secondary-side medium, i.e., the medium that distributes the district heat on the secondary side, also transports (and distributes) the additional thermal energy.

[0057] Through the hydraulic integration, the surplus feeder 30 becomes part of the secondary-side circuit 12. This means that the secondary-side medium in the surplus feeder 30 can absorb the provided heat energy and direct it downstream into or through the secondary side.

[0058] The excess feeder 30 also includes a heat source 31 and a vessel 32. By regulating the mixing agent 33 and the pre-pressure, a circuit for excess feed, referred to as a surplus circuit for short, can be created. The pre-pressure can be generated, for example, by means of a pre-pressure pump 34.

[0059] The excess feeder 30 is adapted to raise the temperature of the medium in the secondary return flow in the vessel 32 by means of the heat source 31 and the mixing medium 33. This allows the excess feeder 30 to provide a medium with a temperature regulated to a flow setpoint. When the excess circuit is activated, additional heat energy can be hydraulically introduced or coupled into the secondary side using the hot medium.

[0060] The heat source 31 of the surplus feeder 30 can be designed as an electric heating cartridge or electric cartridge.

[0061] The heat source 31 can be supplied, for example, by solar energy, such as solar thermal energy or photovoltaics.

[0062] Furthermore, the excess feeder 30 can have a temperature sensor TF. The temperature of the medium in the vessel 32 is detected by the temperature sensor TF. Thus, the increase in the temperature of the secondary return, referred to as the return increase, can be monitored by the excess feeder 30. Advantageously, the temperature sensor TF is therefore arranged such that the temperature of the medium can be detected near the heat source 31.

[0063] Vessel 32 of the excess feeder is so small that the cold medium of the secondary return is essentially heated in one pass through the excess feeder. Vessel 32 is not intended as an intermediate storage for the hot medium.

[0064] By means of the mixing means 33, the return flow increase by the surplus feeder 30 can be regulated to the flow setpoint. The flow setpoint corresponds to the setpoint temperature of a selected heat-dissipating unit. The flow setpoint can be adjusted to a heat storage charging setpoint or a heating circuit setpoint, or can be a preconfigured fixed value. The predetermined flow setpoint can further include a predetermined hysteresis difference value, for example, 10 K.

[0065] Typically, the first heat-dissipating unit on the secondary side is a heat storage unit, such as a domestic hot water boiler, a domestic hot water storage charging system, or a buffer tank, possibly with a downstream fresh water module. Other heat-dissipating units arranged downstream include heating circuits. Details regarding temperature control will be explained in relation to the specific embodiments of the invention.

[0066] For control purposes, the district heating system 1 includes a controller 50 (not shown). In practice, the controller 50 can be provided by the district heating supplier. The controller is adapted to regulate the distribution of the heat energy supplied to the secondary side via the hydraulic integration of the surplus feeder 30. For this purpose, the controller 50 can activate the surplus circuit, for example, by activating the pre-pressure pump 34. In particular, the controller is also adapted to regulate the mixing medium 33.

[0067] The mixing means 33 can be a heating mixer. Furthermore, the mixing means can be a mixing valve or a three-way valve. The mixing means 33 can also be configured as an injection circuit (not shown).

[0068] Mixing the hot medium provided by the surplus feeder 30 with the secondary return in the surplus circuit can also be achieved by means of an additional pump in the secondary return (not shown). Thus, the mixing control can be adjusted to speed control of the additional pump.

[0069] Furthermore, controller 50 typically controls a primary-side valve. The primary-side valve regulates the flow of the primary-side supply line, thus controlling the district heating supply. This allows the controller to adjust, in particular reduce, the output of the transfer station when excess feed-in is active.

[0070] According to one aspect of the invention, a predetermined prioritization sequence or prioritization control is provided, based on which the additional heat energy provided by the surplus feeder 30 is distributed on the secondary side. The predetermined prioritization sequence is implemented by the controller and depends on the specific design of the secondary side.

[0071] Fig. 1 shows an embodiment of a district heating system with surplus feed-in according to the invention.

[0072] The Fig. 1 The illustrated embodiment of the district heating system 1 comprises a heat storage unit 20 on the secondary side, here configured as a first boiler 21a. The first boiler 21a serves to provide hot domestic water (DHW) on the consumer side. For this purpose, the domestic water in the boiler 21a can be heated or charged via a flow line using district heating and / or thermal energy from the surplus feeder 30.

[0073] The first boiler 21a is hydraulically integrated into the secondary side by means of a first changeover valve 60a and a first boiler charging pump.

[0074] The first boiler 21a has a first temperature sensor TU1, which is arranged on a lower layer of the first boiler. A predetermined boiler shutdown value is assigned to the first temperature sensor.

[0075] Furthermore, the first boiler 21a has a temperature sensor TO1 arranged on an upper layer of the first boiler. A predetermined boiler setpoint and a predetermined boiler minimum value are assigned to the temperature sensor TO1.

[0076] The surplus circuit is activated by the controller 50, i.e., the surplus feeder 30 feeds heat energy into the heat storage tank 20 when the temperature signal received by the temperature sensor TF of the surplus feeder 30 is above the flow setpoint. For this purpose, a circuit through the surplus feeder 30 is activated by the pre-pressure pump 34. In the surplus feeder 30, the cold medium of the secondary-side return is continuously heated to the temperature of the predetermined flow setpoint by means of the heat source 31 and the mixing medium 33 and is hydraulically fed into the secondary side, in particular into the secondary-side flow.

[0077] In this embodiment, the predetermined flow setpoint of the surplus feeder 30, e.g., 65 °C, corresponds to the predetermined boiler setpoint, e.g., 55 °C. The predetermined flow setpoint may include a hysteresis difference value, e.g., 10 °C.

[0078] According to one aspect of the invention, the surplus circuit remains active for a predefined minimum running time after its activation. The controller 50 can deactivate the surplus circuit again after the predefined minimum running time has elapsed, provided the temperature signal from the temperature sensor TF of the surplus feeder 30 has fallen below the flow setpoint.

[0079] According to one aspect of the invention, the heat supply from the surplus feeder 30 has priority over the district heating supply from the district heating transfer station 10. This priority results from the hydraulic integration of the surplus feeder into the secondary side with pre-pressure. Thus, the heat energy provided by the surplus feeder can be absorbed directly by a heat storage unit, i.e., even without an activated first boiler charging pump. The district heat absorbed by means of negative pressure from the secondary-side flow line supplements the heat energy provided by the surplus feeder.

[0080] When the boiler is loaded in parallel by the district heating transfer station and the surplus feeder, the controller 50 is further adapted to reduce the temperature value to which the district heating transfer station should load the boiler (boiler setpoint for the district heating transfer station). For example, the loading of the boiler by the district heating transfer station can be set to a temperature value just above the preconfigured boiler minimum value. This can delay reloading by district heating or reduce the amount of district heating charging the boiler, allowing more additional energy to be introduced into the boiler by the surplus feeder. When surplus feed is active, the district heating only maintains the temperature in an upper layer of the first boiler 21a around the boiler minimum value. As a result, the loading of the boiler by the district heating transfer station is completed earlier than conventionally.

[0081] For example, the boiler setpoint can be configured to 55 °C and the boiler minimum value to 45 °C. When surplus feed-in is active, the controller 50 automatically adjusts the (storage) setpoint temperature for the boiler temperature sensor TO1 to the boiler minimum value and a small hysteresis difference, i.e., approximately 47 °C. Recharging of the first boiler 21a by the district heating transfer station only starts when the temperature signal from the temperature sensor TO1 falls below the boiler minimum value. If, however, the temperature signal from the temperature sensor TO1 exceeds the boiler minimum value again, recharging by the district heating transfer station is terminated, whereby the charging setpoint, i.e., the secondary-side setpoint temperature of the district heating transfer station, remains unchanged. To do this, the controller shuts off the first boiler charging pump. Accordingly, when the surplus feeder is active, recharging by the district heating transfer station begins later and ends earlier.Thus, the primary-side district heating flow, which is required due to recharging, is reduced due to a significantly shorter charging time. The remaining recharging, ideally down to the boiler setpoint of 55°C, is carried out via surplus feeder 30. The temperature signal from temperature sensor TO1 can also exceed the boiler setpoint of 55°C when surplus feed is active, since full charging, i.e., a fully charged boiler or heat storage tank, is detected by the temperature signal from temperature sensor TU1 exceeding the preconfigured boiler shutdown value.

[0082] A first check valve 40a is provided in the secondary flow between the surplus feeder 30 and the district heating transfer station 10. This prevents heat from the surplus feeder 30 from being conducted to the district heating transfer station 10.

[0083] The additional heat from the surplus feeder 30 can be conducted directly into an upper layer of the heat storage tank 20 by means of a hot medium through the secondary-side flow. This has the advantage that mixing of layers in the heat storage tank 20 is kept as low as possible, thus maintaining the most significant temperature gradient possible between the lower layers of the heat storage tank 20 and the upper layers of the heat storage tank 20.

[0084] According to one aspect of the invention, a predetermined prioritization sequence of the heat dissipating units of the secondary side is provided. In the specific embodiment of the secondary circuit according to Fig. 1 The predetermined prioritization sequence provides that, when the surplus circuit is active, the first boiler 21a is charged first until it is fully charged. The first boiler is considered fully charged when the temperature signal from the first temperature sensor TU1 exceeds the predetermined boiler switch-off value. Subsequently, provided the surplus circuit remains active, the heat from the surplus feeder 30 is forcibly dissipated by a predetermined heating circuit 70a. The user specifies which heating circuits are permitted to dissipate heat and which are not. Underfloor heating circuits are particularly suitable for the forced dissipation of heat energy from the surplus feeder. If all heating circuits considered have been activated and excess heat energy can still be provided by the surplus feeder 30, the temperature of the medium provided by the surplus feeder 30 increases.As soon as the temperature of the medium provided by the surplus feeder 30 rises to a maximum value set in the surplus feeder 30, the surplus feeder 30 deactivates automatically, ie without intervention of the controller 50, in order to avoid damage to the surplus feeder.

[0085] For the forced removal of excess heat to heating circuits 70a, in the embodiment of the district heating system according to the invention, the Fig. 1 A first switching valve 60a is provided. The first switching valve 60a has two inlets, A and B, and a common outlet AB, allowing switching between the inlets A and B. In this exemplary embodiment, inlet A represents the secondary return, and inlet B represents the return of the first boiler 21a.

[0086] In the AB-B position of the first switching valve 60a, the boiler 21a can be recharged or charged from the surplus feeder 30 in parallel with the transfer station 10. Boiler recharging by the district heating transfer station occurs up to a predetermined boiler minimum value at the upper temperature sensor TO1. Boiler recharging by the district heating is considered complete when the temperature signal from the upper temperature sensor TO1 exceeds the boiler minimum value by a hysteresis value, e.g., 2K.

[0087] If the temperature sensor TU1 has exceeded the defined switch-off point, and the surplus feeder 30 remains active, the first changeover valve 60a is to be set to the AB-A position, i.e. to the secondary return, in accordance with the predetermined prioritization sequence.

[0088] In the AB-A position of the first switching valve 60a, the additional heat energy from the surplus feeder 30 can be bypassed by the heat accumulator 20 or the boiler 21a on the secondary side. In this case, one aspect of the invention provides for the forced activation of a predetermined heating circuit 70a in order to consume the excess heat. The heating circuit 70a is thus forced activated if it is not already active. The controller 50 regulates the flow setpoint temperature of the heating circuit, or heating circuit setpoint for short, of the selected heating circuit 70a to a freely adjustable fixed value. The fixed value is typically selected to be lower than a heating circuit setpoint at colder outside temperatures. The non-selected heating circuits 70b remain inactive.

[0089] For the forced surplus discharge, the controller 50 also adjusts the flow setpoint temperature of the surplus feeder to the heating circuit setpoint, if necessary with a small hysteresis contribution.

[0090] The compulsory surplus discharge creates a decisive advantage in the event of an oversupply of additional heat from the surplus feeder 30: If the surplus feeder 30 supplies more heat than required to recharge one or more heat storage units 20, the surplus heat is not indirectly returned to the supplier's combined heat and power plant due to an increased return temperature, but is consumed locally, i.e. on the secondary side.

[0091] According to one aspect of the invention, the forced surplus discharge through heating circuits 70a can be deactivated when the affected heating circuits change to a regular operating status according to the heating curve, e.g. daytime operation or night-time reduction.

[0092] Furthermore, the forced surplus discharge can be deactivated by controller 50 if the temperature signal from the temperature sensor TF of the surplus feeder 30 falls below the flow target temperature and / or a boiler recharge is requested. Boiler recharge is prioritized according to the predetermined prioritization sequence. To recharge the boiler 21a, the first switching valve 60a is set back to the AB-B position.

[0093] Fig. 2 shows a district heating system with a surplus feed into both a first boiler and a second boiler according to an embodiment of the invention.

[0094] In contrast to the embodiment of the Fig. 1 includes the design of the Fig. 2 two heat storage units 20, wherein the two heat storage units 20 are configured as a first boiler 21a and a second boiler 21b. The first boiler 21a and the second boiler 21b are hydraulically connected in series, so that the second boiler 21b is located downstream of the first boiler 21a. This allows the first boiler 21a to be recharged before the second boiler 21b in the event of excess heat being fed in. Forced removal of excess heat is only provided when both boilers 21a; 21b are fully charged.

[0095] The second boiler 21b is hydraulically connected to the secondary side by means of a second switching valve 60b and a second boiler charging pump. The second switching valve 60b can switch the excess feeder 30 between the secondary-side return flow and the return flow of the second boiler 21b. Analogous to the first boiler 21a, the second boiler 21b also has a temperature sensor TO2 located on an upper layer of the second boiler 21b and a second temperature sensor TU2 located on a lower layer of the second boiler 21b.

[0096] The selection of the boiler 21a; 21b to be loaded is controlled by the controller 50 through corresponding positions of the first switching valve 60a and the second switching valve 60b.

[0097] To regulate the surplus feed-in in the design of the Fig. 2 is referred to the above description for Fig. 1 referred to.

[0098] Fig. 3 shows a district heating system with a surplus feed into a first boiler, and a buffer storage as heat storage according to an embodiment of the invention.

[0099] Compared to the embodiment of the invention in Fig. 1 The design of the district heating system according to the invention comprises Fig. 3 additionally a buffer storage tank 22, which is hydraulically integrated between the heating circuits 70a; 70b; 70c; 70d.

[0100] The buffer tank 22 is typically designed as a stratified storage tank. This allows a significant temperature gradient for economical operation to be created between the uppermost layers, into which hot medium is added from the secondary-side flow, and the lowermost layers, from which cold medium is withdrawn.

[0101] In the concrete design of the secondary side according to Fig. 3 The predetermined priority control provides that, when the surplus circuit is active, the first boiler 21a is charged first until it is fully charged. Subsequently, provided the surplus circuit remains active, the buffer storage 22 is charged until it is fully charged. The buffer storage 22 is considered fully charged when the temperature signal of an assignable temperature sensor TU3, for example, at a lower layer of the buffer storage, exceeds a predetermined buffer fixed value. Only then is the heat from the surplus feeder 30 forcibly dissipated by the predetermined heating circuits 70a and 70c. If all considered heating circuits have been activated and additional thermal energy can still be provided by the surplus feeder, the temperature of the medium provided by the surplus feeder 30 increases.As soon as the temperature of the medium provided by the surplus feeder 30 rises to a maximum value set in the surplus feeder 30, the surplus feeder 30 deactivates itself automatically.

[0102] The buffer storage 22 includes a temperature sensor TO3 located on an upper layer of the buffer storage. A predetermined buffer setpoint is assigned to the temperature sensor TO3 of the buffer storage. For charging the buffer storage, the flow setpoint of the surplus feeder can be adjusted to the buffer setpoint increased by a charging hysteresis.

[0103] Buffer storage 22 requests recharging from the district heating transfer station when a temperature signal from temperature sensor TO3 falls below the predetermined buffer setpoint, including a charging hysteresis. To this end, controller 50 activates the buffer charging pump and the buffer charging valve.

[0104] To charge the buffer tank 22 via the surplus feeder 30, the mixing device 33 regulates the temperature of the hot medium provided by the surplus feeder 30 to the predetermined buffer setpoint. For this purpose, the flow setpoint of the surplus feeder 30 is adjusted to the buffer setpoint.

[0105] To implement the prioritization sequence, an assignable temperature sensor TU3 and the predetermined buffer fixed value assigned to this temperature sensor TU3 are provided on the buffer storage. The assignable temperature sensor TU3 can be selected from a plurality of temperature sensors arranged at different layers of the buffer storage. Typically, a temperature sensor arranged at a lower layer of the buffer storage is selected. If only a lower loading of the buffer storage 22 is desired, a temperature sensor at a middle or upper layer of the buffer storage can also be configured as the assignable temperature sensor TU3. As soon as the temperature value of the assignable temperature sensor rises above the buffer fixed value, the buffer storage 22 is fully charged.

[0106] If the buffer storage 22 reaches the fully charged state with active surplus feed-in, according to one aspect of the invention, the thermal energy hydraulically fed in by the surplus feed-in is forcibly discharged via the predetermined heating circuits 70a; 70c.

[0107] To enable the buffer storage 22 to be charged via the pre-pressure of the surplus circuit, a second check valve 40b is provided according to one aspect of the invention. The second check valve 40b is arranged parallel to the buffer charging pump and the charging valve of the buffer storage 22. The second check valve 40b enables a secondary-side return flow from the buffer storage 22 during recharging of the buffer storage by the surplus feeder 30.

[0108] In parallel with charging by the surplus feeder 30, the buffer storage 22 can be recharged by the district heating transfer station 10 as described above, particularly if a sufficient energy supply to downstream (heating) circuits can no longer be guaranteed. In contrast to conventional charging behavior, charging by district heating is terminated when the temperature signal from temperature sensor TO3 exceeds the buffer setpoint, particularly by a hysteresis value of 2 K. In this case, the charging pump is deactivated and the charging valve is closed.

[0109] The heating circuits 70a; 70b in the secondary circuit upstream of the buffer storage 22 direct their energy request to the transfer station 10 or the surplus feeder 30. The heating circuits 70c; 70d in the secondary circuit downstream of the buffer storage 22 direct their energy request to the buffer storage 22. For the forced removal of excess heat when the buffer storage 22 is fully charged, the controller can in principle activate any heating circuit 70a; 70b; 70c; 70d, whereby in practice, as described above, only heating circuits specified by the user are activated.

[0110] Fig. 4 shows a district heating system with surplus feed into a buffer storage tank and a boiler according to an embodiment of the invention.

[0111] In contrast to the embodiments of the invention described above, Fig. 4 an embodiment according to which the excess feed is not directly fed into a boiler 21a; 21b, but directly into a buffer storage 22. The hydraulic integration of a buffer storage 22 does not require a switching valve, since excess heat from the buffer storage would be passed on in the secondary-side flow and thus is not fed directly into the secondary-side return.

[0112] In the concrete design of the secondary circuit according to Fig. 4 The predetermined priority control provides that, when the surplus circuit is active, the buffer storage tank 22 is charged first until it is fully charged. Subsequently, or already in parallel, if the surplus circuit is still active, the boiler 21 is charged via the buffer storage tank 22 until the boiler 21c is fully charged. Only then is further heat fed in from the surplus feeder 30 forcibly dissipated by a predetermined heating circuit 70a. If all heating circuits considered have been activated and excess heat energy can still be provided by the surplus feeder 30, the temperature of the medium provided by the surplus feeder 30 increases. As soon as the temperature of the medium provided by the surplus feeder 30 rises to a maximum value specified in the surplus feeder 30, the surplus feeder 30 deactivates itself automatically, as described above.

[0113] In contrast to the hydraulic integration of the boilers 21a; 21b in the Fig. 1 bis 3 the boiler 21 in the embodiment of the Fig. 4 without a changeover valve connected in parallel to the heating circuit.

[0114] To recharge the boiler 21 via the buffer tank 22, the controller 50 can activate the boiler charging pump.

[0115] In all of the illustrated embodiments, the temperature of the secondary-side return flow at the district heating transfer station can be kept as low as possible by operating in the forced heat surplus removal mode. This allows a relatively large difference between the secondary-side flow temperature and the secondary-side return temperature to be achieved. Through the hydraulic integration of the surplus feeder 30 into the secondary side, the heat it provides can be individually distributed on the secondary side and locally dissipated in selected heating circuits 70a. This ensures that, even with active surplus feed-in, the efficiency of the district heating supply deteriorates only very slightly, if at all.

[0116] Furthermore, regardless of the specific design of the secondary side, a main operating mode "surplus only" can be provided. In this main operating mode, heat storage units 20, such as boilers 21a; 21b and / or buffer storage units 22, can only be charged by the surplus feeder 30. The district heating contribution can be significantly reduced by the controller 50 in this main operating mode or deactivated, with the exception of the frost protection function. List of reference symbols

[0117] 1 District heating system 10 District heating transfer station 11 Primary circuit 12 Secondary circuit 20 Heat storage tank 21 Boiler 21a; 21b First or second boiler 22 Buffer tank 30 Excess feeder 31 Heat source 32 Vessel 33 Mixing medium 34 Pre-pressure pump 40a First check valve 40b Second check valve 50 Controller 60 Switching valve 70a; 70c Selected heating circuits for forced surplus discharge 70b; 70d Heating circuits not selected for surplus discharge TU1; TU2 First or second temperature sensor, located on a lower layer of the first boiler 21a or second boiler 21b TO1; TO2Temperature sensor, arranged on an upper layer of the first boiler 21a or second boiler 21b. TO3; TU3Temperature sensors of the buffer tank 22. TFTemperature sensor of the surplus feeder 30.

Claims

1. District heating system (1) for a building, comprising a district heating transfer station, a supplier-side primary side, a secondary side, wherein the secondary side is suitable for receiving district heating from the supplier-side primary side at the district heating transfer station (10) on the building side, a surplus feeder (30), wherein the surplus feeder (30) is suitable for providing additional thermal energy to at least one heat-dissipating unit of the secondary side, wherein the additional thermal energy has an origin different from the district heating, the surplus feeder (30) comprises a hydraulic integration into the secondary side and the surplus feeder (30) is suitable for providing the additional thermal energy by means of the hydraulic integration into the secondary side, characterized in that the additional thermal energy can be distributed to a plurality of heat-dissipating units of the secondary side according to a predetermined prioritization sequence, wherein the secondary side comprises a plurality of heat-dissipating units, wherein the heat-dissipating units are arranged in a row and the first downstream heat-dissipating unit of the row is a heat accumulator (20, 21a, 22), wherein a plurality of downstream heat-dissipating units are designed as a heating circuit, and wherein the surplus feeder (30) provides additional thermal energy to the heat accumulator (20, 21a, 22) as a priority according to the predetermined prioritization sequence by means of the hydraulic integration, additionally comprising a controller (50), wherein the controller (50) is suitable for adjusting a heating circuit target temperature of a predetermined heating circuit (70a; 70c) in order to enable a forced removal of the additional thermal energy provided by the surplus feeder (30) if the heat accumulator (20, 21a, 22) is fully loaded.

2. District heating system according to claim 1, wherein the surplus feeder (30) comprises a mixing means (33), wherein the mixing means (33) is suitable for controlling the temperature of a medium of the surplus feeder (30) to a predetermined flow setpoint so that the medium comprises the additional thermal energy.

3. District heating system according to any one of the preceding claims, wherein the surplus feeder (30) is suitable for providing the additional thermal energy to the at least one heat-dissipating unit by means of a pre-pressure pump (34), and wherein the district heating system (1) further comprises a check valve (40a), wherein the check valve (40a) is arranged on the secondary side between the district heating transfer station (10) and the surplus feeder (30) in order to hydraulically decouple the district heating transfer station (10) and the surplus feeder (30).

4. District heating system according to any one of the preceding claims, wherein the additional thermal energy is supplied to an upper layer of the heat accumulator (20).

5. District heating system according to any one of the preceding claims, wherein the heat accumulator (20) is a first boiler (21a) for a hot water circuit, wherein the first boiler (21a) is hydraulically integrated into the secondary side by means of a first switching valve (60a), wherein the first switching valve (60a) is suitable for switching the surplus feeder (30) between a secondary-side return flow and a return flow of the first boiler (21a), wherein the controller (50) is suitable for setting the first switching valve (60a) to the return flow of the first boiler (21a) when a temperature signal from a first temperature sensor (TU1) arranged on a lower layer of the first boiler (21a) is below a predetermined boiler switch-off value, and to set the first switching valve (60a) to the secondary-side return flow to enable the forced removal of the additional thermal energy when the temperature signal from the first temperature sensor (TU1) exceeds the predetermined boiler switch-off value.

6. District heating system according to the preceding claim, wherein on the secondary side a second boiler (21b) is hydraulically integrated into the secondary side downstream of the first boiler (21a) by means of a second switching valve (60b), wherein the second switching valve (60b) is suitable for switching the surplus feeder (30) between the secondary-side return flow and a return flow of the second boiler (21b), wherein the second boiler (21b) follows the first boiler (21a) in the predetermined prioritization sequence, wherein the controller (50) is suitable for setting the second switching valve (60b) to the return flow of the second boiler (21a) when a temperature signal from a second temperature sensor (TU2) arranged on a lower layer of the second boiler (21b) is below the predetermined boiler switch-off value and the first switching valve (60a) is set to the secondary-side return flow, and for setting the first switching valve (60a) and the second switching valve (60b) to the secondary-side return flow to enable the forced removal of the additional thermal energy when the temperature signal from the second temperature sensor (TU2) exceeds the predetermined boiler switch-off value.

7. District heating system according to claim 6, wherein on the secondary side a buffer tank (22) is hydraulically integrated in parallel downstream of the first boiler (21a) by means of a check valve, wherein the buffer tank (22) follows the first boiler (21a) in the predetermined prioritization sequence, wherein an assignable temperature sensor (TU3) is arranged on the buffer tank (22), preferably on a lower layer of the buffer tank, wherein a predetermined buffer fixed value is associated with the assignable temperature sensor (TU3), wherein the controller is suitable for adapting the heating circuit target temperature of a predetermined heating circuit (70a; 70c) in order to enable the forced removal of the additional thermal energy when the temperature signal from the assignable temperature sensor (TU3) exceeds the predetermined buffer fixed value.

8. District heating system according to any one of claims 2 to 7, wherein the heat accumulator (20) is a buffer tank (22) and a boiler (21c) is hydraulically integrated into the secondary side downstream of the buffer tank (22), wherein the buffer tank (22) is ahead of the boiler (21c) in the predetermined prioritization sequence, and the boiler (21c) can be loaded with thermal energy from the buffer tank (22) by means of a boiler loading pump, wherein an assignable temperature sensor (TU3) is arranged on the buffer tank (22), preferably on a lower layer of the buffer tank, wherein a predetermined buffer fixed value is associated with the assignable temperature sensor (TU3), wherein the controller is suitable for activating the boiler loading pump in order to enable the forced removal of the additional thermal energy when the temperature signal from the assignable temperature sensor (TU3) exceeds the predetermined buffer fixed value.

9. District heating system according to any one of claims 2 to 8, wherein the surplus feeder (30) is suitable for heating the medium by means of a heat source (31) powered by solar energy.

10. Method for controlling a district heating system (1) according to any one of claims 1 to 9, the method comprising activation of the pre-pressure pump (34) of the surplus feeder (30), control of the mixing means (33) of the surplus feeder (30), wherein the mixing means (33) controls the temperature of the medium of the surplus feeder (30) to the predetermined flow setpoint, loading of the heat accumulator (20), wherein, for the loading of the heat accumulator, the surplus feeder via the pre-pressure pump is hydraulically preferred over the district heating transfer station, and the controller (50) limits the loading of the heat accumulator (20) by the district heating transfer station to a predetermined minimum temperature value of the heat accumulator (20), forced removal of the thermal energy provided by the surplus feeder (30), wherein the controller (50) adjusts the heating circuit target temperature of the predetermined heating circuit (70a; 70c), in particular increases it, in order to supply the thermal energy provided by the surplus feeder (30) to the predetermined heating circuit (70a; 70c), provided that a heat accumulator (20) having priority according to the predetermined prioritization sequence is fully loaded, wherein the surplus feeder (30) provides the additional thermal energy by means of the hydraulic integration into the secondary side, wherein the additional thermal energy is distributed to a plurality of heat-dissipating units of the secondary side according to a predetermined prioritization sequence, and wherein the surplus feeder (30) provides additional thermal energy as a priority to the heat accumulator (20) by means of the hydraulic integration according to the predetermined prioritization sequence.

11. Method according to claim 10, wherein the heat accumulator (20) is a first boiler (21a), wherein the controller (50) sets the first switching valve (60a) to the return flow of the first boiler (21a) in order to load the first boiler (21a) by means of the thermal energy provided by the surplus feeder (30), wherein the method further comprises: switching the first switching valve (60a) from the return flow of the first boiler to the secondary-side return flow, if the first boiler (21a) is fully loaded, in order to make further switches according to the predetermined prioritization sequence.

12. Method according to claim 10, comprising a predetermined operating mode, wherein the controller is suitable for closing a primary-side valve in the predetermined operating mode, so that a delivery of the district heating is significantly reduced.

13. Computer program product suitable for carrying out the method according to any one of claims 10 to 12 in the controller (50) of the district heating system (1) according to any one of claims 1 to 9.