Hydronic system and method for transferring thermal energy from a heat pump to at least one thermal energy load

Abstract

The present disclosure is directed to a hydronic system (1) for transferring thermal energy from a heat pump (3) to at least one thermal energy load (5), wherein the hydronic system (1) comprises: - a heat pump feed circuit section (7) for transporting a heat pump flow (qH) downstream of a heat pump circuit pump (11) for driving the heat pump flow (qH) through a heat pump (3); - a load feed circuit section (13) for transporting a load flow (qL) towards at least one thermal energy load (5); - a storage feed circuit section (19) for transporting a storage flow (qS) that goes through a thermal energy storage tank (23), wherein the storage flow (qS) is selectively directable in a charging direction in an operation mode of the hydronic system (1) in which the thermal energy storage tank (23) is charged with thermal energy and in a discharging direction in another operation mode of the hydronic system (1) in which thermal energy is discharged from the thermal energy storage tank (23), wherein the heat pump feed circuit section (7), the load feed circuit section (13) and the storage feed circuit section (19) are connected at a feed connection point (27); - a load flow feed temperature sensor (79) being arranged at the load feed circuit section (13) downstream of the feed connection point (27) for determining a load flow feed temperature (TL) of the load flow (qL); - a load circuit pump (17) for driving the load flow (qL); and - control electronics (20), wherein the control electronics (20) is configured, depending on the operation mode of the hydronic system (1), to control directly or indirectly a speed of the load circuit pump (17) and a speed of the heat pump circuit pump (11) so that a deviation of the load flow feed temperature (TL) from a reference load flow feed temperature is minimised.

Description

[0001] Applicant: GRUNDFOS HOLDING A / STitle: Hydronic system and method for transferring thermalenergy from a heat pump to at least one thermal energy load Our Ref.: GP 3827 WODescription TECHNICAL FIELD

[01] The present disclosure is directed to a hydronic system and amethod for transferring thermal energy from a heat pump to at least 5 one thermal energy load. In particular, the inventive hydronic system may be used in a domestic heating / cooling system with a heat pump as a heat source and radiators and / or underfloor heating as thermal energy loads. Preferably, the inventive hydronic system may also be used as at least part of a domestic hot water, DHW, system for provid-10 ing hot water to a faucet, shower, bathtub or other domestic consum- ers of hot water. The inventive hydronic system is, however, not only ap- plicable for domestic household systems, but also as part of larger heat- ing / cooling systems of larger private or commercial buildings. Most pref- erably, the inventive hydronic system may be implemented as an inte- grated water circuit, IWC, unit connecting a heat pump with at least one thermal energy load. BACKGROUND20

[0002] Heating or cooling systems typically use a hydronic system fortransporting thermal energy from a thermal energy source to one or more thermal energy loads. The hydronic system typically comprises a piping system that contains a thermal energy transporting medium, e.g. water, that is circulated by one or more pumps through the hydronicPatentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025 system. Thermal energy is added to the hydronic system at the thermal energy source, e.g. a boiler, a heat pump, a heat exchanger or an electric coil, and thermal energy leaves the hydronic system at the thermal energy load(s), e.g. radiator(s) or underfloor heating(s). 5

[03] In order to reduce consumption of fossil energy sources, e.g. gas,oil or coal, there is a trend to use electrically driven heat pumps as ther- mal energy source to add thermal energy to the hydronic system for heating or cooling purposes. Heat pumps use electric energy to extract 10 thermal energy from an outside thermal energy reservoir, e.g. outside air or geothermal energy. Heat pumps currently on the market come in two types: a split-type and a mono-block type. In case of a mono- block type heat pump, the full thermodynamic cycle is performed within one unit (mostly an outdoor unit), whereas in case of a split-type heat pump the thermodynamic cycle is split into an evaporator unit (mostly an outdoor unit) and a condenser unit (mostly an indoor unit). Both split-type heat pumps and mono-block type heat pumps typically have an outdoor unit and an indoor unit, wherein the indoor unit is used to distribute the thermal energy to the thermal energy loads and / or to20 integrate a domestic hot water, DHW, system.

[0004] The cost of operating a heat pump depends on the one handon the efficiency of the heat production, sometimes referred to as sea- sonal coefficient of performance (SCOP), and on the other hand on the electricity price. Nowadays, heat pump systems are mostly oper- ated to maximise the SCOP.

[05] However, the operating cost of today’s heat pump systems is stillfully dependent on electricity price fluctuations. If an electricity pro- 30 vider offers a flat electricity price, such a flat electricity price will have electricity price fluctuations factored in, so that a consumer does not benefit from low electricity prices as it would be possible.Patentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025

[0006] There is thus a need for a hydronic system for transferring thermalenergy from a heat pump to at least one thermal energy load, which allows benefitting from low electricity prices and reduces cost when electricity prices are high. There is also a demand for smaller and 5 cheaper hydronic systems that require a smaller buffer tank or no buffer tank at all. The present disclosure is further directed to providing an im-proved indoor unit of a heat pump, wherein a pre-assembled hydronic system in form of an integrated water circuit (IWC) unit can be inte-grated into the indoor unit of the heat pump. 10 SUMMARY

[07] The hydronic system according to the present disclosure and themethod for operating such a hydronic system according to the presentdisclosure provides a solution to this problem.

[08] According to a first aspect of the present disclosure, a hydronicsystem is provided for transferring thermal energy from a heat pump to20 at least one thermal energy load, wherein the hydronic system com-prises: -a heat pump feed circuit section for transporting a heat pump flowdownstream of a heat pump circuit pump for driving the heat pump flow through a heat pump; -a load feed circuit section for transporting a load flow towards atleast one thermal energy load; -a storage feed circuit section for transporting a storage flow thatgoes through a thermal energy storage tank, wherein the storage flow is selectively directable in a charging direction in one opera-30 tion mode of the hydronic system in which the thermal energy stor-age tank is charged with thermal energy and in a discharging di- rection in another operation mode of the hydronic system in which thermal energy is discharged from the thermal energy storage tank,Patentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025 wherein the heat pump feed circuit section, the load feed circuit section and the storage feed circuit section are connected at a feed connection point; -a load flow feed temperature sensor being arranged at the load5 feed circuit section downstream of the feed connection point for determining a load flow feed temperature of the load flow; -a load circuit pump for driving the load flow; and- control electronics,wherein the control electronics is configured, depending on the opera- tion mode of the hydronic system, to control directly or indirectly aspeed of the load circuit pump to obtain a requested load flow and a speed of the heat pump circuit pump so that a deviation of the loadflow feed temperature from a reference load flow feed temperature isminimised.15

[0009] The control electronics may thus be configured to charge in a oneoperation mode the storage tank with thermal energy from the heat pump when the electricity price is low. Analogously, the control electron- ics may thus be configured to discharge, in another operation mode, thermal energy from the storage tank for temporarily substituting or at 20 least partly supporting the heat pump as thermal energy source when the electricity price is high. The information about the electricity price may be derived from online available forecast information that may de- pend on a weather forecast, e.g. outside temperature, wind and / or sun- shine. Alternatively, or in addition, the electricity price may depend on availability of electric power produced by distributed energy sources such as photovoltaic panels, wind-powered generators or battery stor- age.

[10] It should be noted that the thermal energy storage tank is not a30 freshwater tank of a domestic hot water (DHW) system. The thermal en- ergy storage tank is not a hydraulic decoupling buffer tank either. ThePatentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025 thermal energy storage tank may be part of the hydronic system or ar- ranged externally thereof. If the heat pump is a mono-block type heat pump, e.g. as an outdoor unit, it is preferably externally arranged from the hydronic system which may serve as an indoor unit. In case of a 5split-type heat pump, the condenser unit, e.g. as an indoor unit, maybe part of the hydronic system or arranged externally thereof. The ther- mal energy load(s) are connected to the hydronic system.

[11] The inventive hydronic system has the advantage that the refer-ence load flow feed temperature can be precisely established in differ-ent operation modes even without exact knowledge of a current out- put power of the heat pump. The requested load flow may be a conse- quence of an opening degree of one or more load valve(s), e.g. ther- mostatic radiator valve(s) (TRV), regulating the load flow through the at 15 least one thermal energy load.

[12] Optionally, the control electronics may be configured to controlthe speed of the load circuit pump in a feed-forward control, and tocontrol the speed of the heat pump circuit pump in a closed-loop con-20 trol. The feed-forward control of the speed of the load circuit pump isuseful to quickly obtain a requested load flow. However, in order to pro-vide the requested load flow at a certain load flow feed temperatureto provide the needed thermal power for the at least one thermal en- ergy load to consume, it is advantageous to control directly or indi- rectly the speed of the heat pump circuit pump in a closed-loop con- trol so that a deviation of the load flow feed temperature from the ref-erence load flow feed temperature is minimised.

[13] Optionally, the control electronics may be configured, in said an-30 other operating mode of the hydronic system in which thermal energy is discharged from the thermal energy storage tank, to set a speed of the load circuit pump to obtain the requested load flow being largerthan the heat pump flow, and to vary the heat pump flow by varyingPatentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025the speed of the heat pump circuit pump until a deviation of the loadflow feed temperature from the reference load flow feed temperature is minimised.5

[0014] Optionally, the control electronics may be configured, in saidoperating mode of the hydronic system in which the thermal energy storage tank is charged with thermal energy, to control the speed of the load circuit pump to obtain the requested load flow being smaller than the heat pump flow and to vary the heat pump flow by varying 10 the speed of the heat pump circuit pump until a deviation of the load flow feed temperature from the reference load flow feed temperature is minimised.

[15] Optionally, the hydronic system may be an integrated water cir-cuit, IWC, unit, wherein the IWC unit comprises: -a heat pump port for connecting the heat pump feed circuit sec-tion with the heat pump; -a storage port for connecting the storage feed circuit section withthe thermal energy storage tank; and20 - a load port for connecting the load feed circuit section with theat least one thermal energy load.

[16] As already explained above, it is very beneficial to provide thehydronic system in form a pre-assembled IWC unit being at least part of an indoor unit of the heat pump. A minimum number of three ports, i.e. the heat pump port, the storage port and the load port, is needed in the feed line configuration to connect an external heat pump unit, an exter- nal thermal energy storage tank and the thermal energy loads. A return line from the thermal energy loads back to the heat pump and to the 30 thermal energy storage tank may be arranged externally from the IWC unit.Patentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025

[0017] Optionally, the control electronics may be configured to operatethe hydronic system selectively in the following operation modes: a) a first operation mode in which only the heat pump flow providesthe load flow, 5b) a second operation mode in which the heat pump flow and thestorage flow in the discharging direction from the thermal energy storage tank are merged into the load flow, c) a third operation mode in which the heat pump flow splits into theload flow and the storage flow in the charging direction,10 d) a fourth operation mode in which only the storage flow in the dis-charging direction provides the load flow, and e) a fifth operation mode in which the heat pump flow is fully used asthe storage flow in the charging direction.

[18] In the first operation mode, there is no charging or discharging ofthermal energy to or from the thermal energy storage tank. This opera- tion mode may be useful in case the thermal energy storage tank has a low charging level and the electricity price is high. This means that, on the one hand, the thermal energy storage tank cannot be used to sup- 20 port the heat pump, and, on the other hand, it is currently too expensive to charge the thermal energy storage tank. The first operation mode is also useful in case the electricity price is low and the thermal energy stor- age tank has a maximum charging level. This means that the opportunity of charging the thermal energy storage tank at low electricity prices can-not be seized, because the thermal energy storage tank is already fully charged. As the load flow is the same as the heat pump flow in the firstoperation mode, the reference load flow feed temperature may bemaintained by receiving or measuring a heat pump flow return temper- ature and controlling a heat pump flow differential temperature to ob-30 tain a needed heat pump flow feed temperature that corresponds tothe reference load flow feed temperature.Patentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025

[0019] In the second operation mode, thermal energy is withdrawn fromthe thermal energy storage tank to support the heat pump in providingthe load flow. So, both the thermal energy storage tank as well as theheat pump act as a thermal energy source and the storage flow flows in5 the discharging direction through the storage load circuit section. Thesecond operation mode is useful when the thermal energy demand of the load flow is higher than what can be delivered by the heat pump or the thermal energy storage tank alone. Another scenario for applyingthe second operation mode is when the temperature in the thermal en- 10 ergy storage tank and / or downstream in the storage load circuit section in discharging direction of the storage flow is above a required load flow feed temperature, e.g. when the thermal energy load is an underfloor heating that requires relatively low load flow feed temperatures. The heat pump flow at lower temperature may be used to mix the colder heat pump flow into the hotter storage flow to obtain the reference loadflow feed temperature. In the second operation mode, the reference load flow feed temperature may be maintained by receiving or measur- ing a heat pump return flow temperature and then controlling a heat pump differential temperature to obtain a needed heat pump flow feed20 temperature. As the storage flow is mixed into the load flow in the secondoperation mode, the load flow is higher than the heat pump flow,wherein the storage flow is the difference between load flow and the heat pump flow. If no load flow feed temperature measurement is avail- able to directly maintain the load flow feed temperature at the refer- ence load flow feed temperature, a received or measured storage flow feed temperature may be used in addition to the heat pump differential temperature to indirectly maintain the load flow feed temperature at the reference load flow feed temperature. The speed of the load circuitpump and the speed of the heat pump circuit pump is preferably con- 30 trolled to obtain a requested load flow with a needed mixing of heat pump flow and storage flow to obtain the reference load flow feed tem- perature.Patentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025

[0020] In the third operation mode, the heat pump serves as thermal en-ergy source to provide the load flow as well as the storage flow in the charging direction to fill the thermal energy storage tank. This is useful 5 when the electricity prices are low, and the charging level of the thermal energy storage tank is low during a thermal energy demand of the ther- mal energy load(s). The load circuit pump is controlled to provide a load flow that is lower than the heat pump flow, so that the flow difference results in the storage flow in the charging direction. The hydronic system 10 may include the heat pump circuit pump to control the heat pump flow. As an alternative, an external outdoor unit of the heat pump may include the heat pump circuit pump for providing the heat pump flow in the heatpump feed circuit section. In case of an external heat pump circuit pump, the control electronics may be configured to be in communica- tion with the external heat pump for setting a heat pump differential tar- get temperature such that the external heat pump circuit pump providesthe required heat pump flow in the heat pump load circuit section tomaintain a heat pump flow differential temperature at the set heat pump differential target temperature. As the load flow feed temperature20 is the same as the heat pump flow feed temperature in the third opera- tion mode, the reference load flow feed temperature may be main-tained by receiving or measuring a heat pump flow return temperature and controlling a heat pump flow differential temperature to obtain a needed heat pump flow feed temperature that corresponds to the ref-erence load flow feed temperature.

[0021] The control electronics may be configured to adjust the fractionsof storage flow and heat pump flow in the load flow depending on theelectricity price and / or a charging level in the thermal energy storage30 tank. It should be noted that the hydronic system may comprise a tem- perature sensor arranged in the thermal energy storage tank and / or inthe storage load circuit section to measure a storage tank temperatureas an indicator for the charging level in the thermal energy storage tank.Patentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025

[0022] In the fourth operation mode, the heat pump flow in the heatpump load circuit section is zero, so that the storage flow in the discharg- ing direction provides the full load flow alone. This operation mode is use- 5 ful when the electricity price is high, and the thermal energy storage tank is sufficiently charged with thermal energy. A further scenario for apply- ing the fourth operation mode is when the thermal energy demand of the thermal energy load(s) is so low that the required load flow is below aminimum heat pump flow for the heat pump to work. The fourth oper-ation mode is very useful to save a significant number of start / stop cycles of the heat pump, which prolongs the lifetime of the heat pump. The load flow fee temperature is in this case determined by the storage flow fee temperature. If it is not high enough, an electric heater may be used to obtain a higher load flow feed temperature. If it is too high, the hy- 15 dronic system may be switched to the second operation mode to mix colder heat pump flow into the load flow until the reference load flow feed temperature is established.

[0023] In the fifth operation mode, there is no thermal energy demand of20 the thermal energy load(s), and the load flow is zero. In this situation, it is useful to run the hydronic system in the fifth operation mode when the electricity price is low, and the thermal energy storage tank is not fully charged. This is particularly useful during summer months when the ther- mal energy demand is less continuous and comes mainly from a domes- tic hot water (DHW) system. The thermal energy storage tank can be charged during times of no thermal energy demand and discharged, preferably in the fourth operation mode, when the DHW system de- mands thermal energy. This can significantly reduce the number of start / stop cycles of the heat pump, which is advantageous for the life-30 time and efficiency of the heat pump. As the storage flow is the same asthe heat pump flow in the fifth operation mode, a desired storage flowtarget temperature may be maintained by receiving or measuring a heat pump flow return temperature and controlling a heat pump flowPatentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025 differential temperature to obtain a desired heat pump flow target tem- perature that corresponds to the desired storage flow target tempera-ture. 5

[0024] Optionally, the control electronics may be configured to switchbetween the operation modes depending on the electricity price, a thermal energy demand, and a charging level of the thermal energy storage tank.10

[0025] Optionally, the hydronic system may further comprise- a bypass circuit section for transporting a bypass flow as part of theload flow bypassing the at least one thermal energy load, and- a bypass valve arrangement being arranged at a bypass connec-tion point where a load circuit section and the bypass circuit section are connected, wherein the control electronics is configured to control the bypass valvearrangement to obtain a desired heat pump return flow temperature. Itis very beneficial, depending on the operation mode, to establish a de- sired heat pump return flow temperature for reducing the heat pump20 differential temperature the heat pump needs to deliver. Operating the heat pump to deliver a smaller heat pump differential temperature, i.e. a smaller difference between a heat pump flow feed temperature and a heat pump flow return temperature, may be a more efficient operat- ing point of the heat pump. Consequently, it is an efficient way to pro- vide, in the third operation mode, a higher heat pump flow feed temper-ature at the same heat pump operating efficiency for providing a higher the storage flow feed temperature when the heat pump flow chargesthe thermal energy storage tank. If the heat pump flow feed tempera-ture is, in the second operation mode, below the storage flow feed tem-30 perature, the resulting load flow feed temperature is below the storage flow feed temperature, so that the temperature within the storage tank must be kept above the reference load flow feed temperature.Patentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025

[0026] Optionally, the hydronic system may further comprise a domestichot water, DHW, system, wherein the DHW system comprises: -a DHW freshwater circuit section for transporting a freshwater flowcoming from a freshwater supply towards at least one hot water 5consumer, and- a thermal transfer element being arranged to thermally couple thebypass flow with the freshwater flow, wherein the control electronics is configured to control the bypass valvearrangement such that at least a part of the load flow is used as the by-10 pass flow.

[27] The DHW system is preferably integrated into the hydronic systemin form of an integrated water circuit, IWC, being implemented into an indoor unit of the heat pump. In that case, the IWC requires at least two more ports, i.e. a cold freshwater inlet port and a hot freshwater outlet port. In the feed line configuration of the hydronic system, a bypass re-turn outlet port may also be needed.

[28] Optionally, the thermal transfer element may be20 - a heat exchanger having a primary heat exchanger part transport-ing the DHW flow and a secondary heat exchanger part transport-ing the freshwater flow,- a freshwater tank in thermal contact with a coil transporting theDHW flow, and / or -a DHW flow tank in thermal contact with a coil transporting thefreshwater flow.

[29] Compared to a freshwater tank, a heat exchanger has the ad-vantage that no freshwater reservoir must be kept above 55°C for reduc- 30 ing the risk of legionella contamination. Furthermore, a heat exchanger consumes less space than a freshwater tank or a DHW flow tank.Patentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025

[0030] Optionally, the hydronic system may further comprise an electricheater being arranged at the load circuit section, wherein the control electronics is further configured to control gradually or in one or more steps a power of the electric heater for adding thermal energy to the 5load flow. The electric heater is particularly beneficial in combinationwith a DHW system to provide sufficient comfort when a thermal energy demand is very high. It may be more efficient to cover short periods of high thermal energy demand with the electric heater rather than sizing the heat pump and / or the thermal energy storage tank to be oversized 10 for most of the time. If the thermal power of the heat pump together with the thermal energy storage tank is not sufficient to satisfy a high thermal energy demand, the electric heater can be switched on and / or turned up to a sufficient degree to add thermal energy to the load flow by in- creasing the load flow feed temperature. Thus, the electric heater hasthe advantage of providing a choice between using three different en-ergy sources individually or in combination, in particular during a hotfreshwater demand. A relatively low hot freshwater demand may be metby running the hydronic system in the first or third operation mode, i.e. the heat pump flow provides the load flow. The electric heat may be 20 switch on in addition, if needed. The reason for this choice could be low electricity prices. At times of high electricity prices, the heat pump maybe stopped and the hydronic system run in the fourth operation mode,i.e. the storage flow from the thermal energy storage tank provides the load flow. The electric heat may be switch on in addition, but only as much as needed. If the hot freshwater demand is very high, the hydronicsystem may be run in the second operation mode, plus the electric heater if needed. In this situation, the heat pump flow feed temperature may be established to be equal to the storage flow feed temperature.30

[0031] Optionally, the electric heater may be arranged upstream of theDHW connection point. This is beneficial for the electric heater to in-crease a feed temperature of the DHW flow.Patentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025

[0032] Optionally, when the thermal transfer element is a heat ex-changer, the hydronic system may further comprise -a flow sensor being arranged at the DHW freshwater circuit section5 for measuring the freshwater flow, and -a hot water temperature sensor being arranged at the DHW fresh-water circuit section downstream of the heat exchanger, wherein the control electronics is configured to determine a hot waterthermal energy demand based on measured values of the flow sensor10 and the hot water temperature sensor. This is a very convenient embod-iment to save a freshwater tank, which consumes a lot of space and re- quires a minimum temperature of 55°C in the freshwater tank to reduce the risk of legionella contamination.

[33] Optionally, when the thermal transfer element is a freshwater tankor a bypass flow tank, the hydronic system may further comprise- a DHW temperature sensor being arranged at the thermal transferelement for measuring a DHW temperature, wherein the control electronics is configured to control the bypass valve20 arrangement such that the DHW temperature is kept above a settable minimum DHW temperature. This is useful to ensure a minimum tempera-ture in the freshwater tank to reduce the risk of legionella contamination. In case of a bypass flow tank, this is beneficial to provide sufficient com- fort for extracting thermal energy from the bypass flow tank into the fresh- water flow whenever it is needed.

[34] Optionally, when the thermal transfer element is a heat ex-changer, the control electronics may be configured to determine a hotwater thermal energy demand based on at least two pre-determined30 hot water consumption profiles. A first hot water consumption profile ofthe at least two pre-determined hot water consumption profiles may bea “showering” profile indicated by a relatively high freshwater flow, e.g. at or above 7 l / min, wherein a first target hot water temperature is setPatentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025relatively low, e.g. 42 °C. This is useful to reduce the need for mixing coldwater into the hot freshwater flow to obtain a desired showering temper- ature. A second hot water consumption profile of the at least two pre-determined hot water consumption profiles may be a “kitchen” profile5 indicated by a relatively low freshwater flow, e.g. below 7 l / min, wherein a second target hot water temperature is set relatively high, e.g. 55 °C. This is useful to provide sufficiently hot water for a kitchen sink, for exam- ple. Each of the at least two pre-determined hot water consumption pro- files may be time dependent based on experienced usage behaviour.10 As the hot water consumption profiles are usually similar on the samedays of the week, e.g. working days and weekend days, it is useful to have the thermal energy storage tank charged well before a hot water thermal energy demand can be expected according to the at least twopre-determined hot water consumption profiles.

[35] Optionally, the hydronic system may further comprise a storageflow feed temperature sensor being arranged in a storage feed circuitsection for measuring a storage flow feed temperature in the discharg-ing direction into the load flow. 20

[36] Optionally, the hydronic system may further comprise a storagetank temperature sensor being arranged within the thermal energy stor- age tank, wherein the control electronics is configured to determine acharging level of the thermal energy storage tank based on a measuredvalue of the storage tank temperature sensor.

[0037] Optionally, the thermal energy storage tank may be integratedinto the hydronic system being an integrated water circuit, IWC, unit.30

[0038] Optionally, the bypass valve arrangement may be a mixing valvein form of a three-way valve.

[39] Optionally, the hydronic system may further comprise a heatpump circuit pump being arranged at the heat pump circuit section forPatentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025driving the heat pump flow. Alternatively, or in addition, the heat pumpcircuit pump may be part of an outdoor unit of the heat pump.

[0040] Optionally, the hydronic system may further comprise a load flow5 feed temperature sensor being arranged at a load feed circuit section upstream of the at least one thermal energy load, wherein the control electronics is configured to control a heating power of an electric heaterbased on measured values of the load flow feed temperature sensor and based on a load flow measured by a load flow sensor or estimated10 on the basis of operating values of the load circuit pump, wherein theelectric heater is arranged at the load feed circuit section upstream of the at least one thermal energy load.

[41] Optionally, the control electronics may comprise a communica-tion interface for communication with a heat pump control, wherein the communication interface is configured to -receive a heat pump flow value,- send a start / stop command to the heat pump,- receive a heat pump flow feed temperature and a heat pump flow20 return temperature, and / or -send a reference control value to the heat pump for setting theheat pump flow feed temperature and / or a difference betweenthe heat pump flow feed temperature and the heat pump flow re-turn temperature.

[42] Optionally, e.g. if the load flow return temperature is not availablefrom a communication with a heat pump control, the hydronic system may further comprise: -a load return circuit section for transporting the load flow returning30 from the at least one thermal energy load, and -a load return temperature sensor for measuring a load flow returntemperature,Patentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025wherein the control electronics is configured to control the bypass valvearrangement further based on the load flow return temperature. The by-pass valve arrangement can be used to establish the load flow return temperature by mixing a part of the load feed flow directly into the load 5 return flow, i.e. that part of the load flow is not fed through the at least one thermal energy load. This may be beneficial especially in the first operation mode, e.g. when the thermal energy storage tank is fully charged, and electricity prices are low. The bypass valve arrangementcan thereby be used to establish the reference load flow return temper-10 ature independent of any hot water demand. It is also beneficial to in-crease the load flow return temperature by increasing the bypass flow in the second operation mode in order to reduce the heat pump differen- tial temperature when a high heat pump flow feed temperature is needed to meet the storage flow feed temperature when the heat pump flow is mixed with the storage flow at the feed connection point.

[43] Optionally, e.g. if a heat pump circuit pressure is not availablefrom a communication with a heat pump control, the hydronic system may further comprise a pressure sensor being arranged in the heat pump20 feed circuit section, wherein the control electronics is configured to con-trol the speed of the load circuit pump based on measured values of the pressure sensor. For example, when the heat pump circuit pressure ex-ceeds a predetermined pressure threshold, the control electronics mayenable a storage flow in the charging direction, i.e. the hydronic systemmay be switched to the third or fifth operation mode.

[44] Optionally, the hydronic system may further comprise:- a heat pump,- a thermal energy storage tank, and / or30 - at least one thermal energy load.Patentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025

[0045] According to another aspect of the present disclosure, a methodis provided for operating a hydronic system as described above, whereinthe method comprises the following steps: -planning an operation schedule that defines in which operation5 mode the hydronic system is going to be operated during different daytimes of one or more hours in the future based on forecast in- formation including an electricity price at said daytimes; and- operating the hydronic system according to the operation sched-ule. 10

[46] Optionally, the forecast information may be a weather forecast,and / or an electricity price determined on the basis of accessible onlineinformation. The forecast information may comprise an estimation of atime-dependent future building heat loss, wherein said building heat lossis based on a weather forecast and a heat loss model of the building.Alternatively, or in addition, the forecast information may comprise a cost optimization for future operation hours, wherein a heat pump en-ergy consumption model is used in combination with expected electric- ity prices, a weather forecast, and a modelled future building heat loss,20 for establishing an operation schedule for the operation of hydronic sys-tem.

[47] According to another aspect of the present disclosure, a methodis provided for transferring thermal energy from a heat pump to at leastone thermal energy load, wherein the method comprises the followingsteps: -transporting a heat pump flow that comes from a heat pump via aheat pump feed circuit section, wherein the heat pump flow isdriven by a heat pump circuit pump;30 - transporting a load flow towards at least one thermal energy loadvia a load feed circuit section;Patentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025- transporting a storage flow that goes through a thermal energy stor-age tank via a storage feed circuit section, wherein the storageflow is selectively directable in a charging direction in an operation mode in which the thermal energy storage tank is charged with5 thermal energy and in a discharging direction in another operation mode in which thermal energy is discharged from the thermal en-ergy storage tank, wherein the heat pump feed circuit section, theload feed circuit section and the storage feed circuit section are connected at a feed connection point;10 - determining a load flow feed temperature of the load flow by aload flow feed temperature sensor being arranged at the load feed circuit section downstream of the feed connection point; and -directly or indirectly controlling, depending on the operation mode,a speed of the load circuit pump to obtain a requested load flow and a speed of the heat pump circuit pump so that a deviation ofthe load flow feed temperature from a reference load flow feed temperature is minimised.

[48] Optionally, the speed of the load circuit pump may be controlled20 in a feed-forward control, and the speed of the heat pump circuit pump may be controlled in a closed-loop control.

[0049] Optionally, in said another operating mode in which thermal en-ergy is discharged from the thermal energy storage tank, the speed ofthe load circuit pump may be set to obtain the requested load flow be-ing larger than the heat pump flow, and the heat pump flow may be varied by varying the speed of the heat pump circuit pump until a devi-ation of the load flow feed temperature from the reference load flow feed temperature is minimised. 30

[50] Optionally, in said operating mode of the hydronic system (1) inwhich the thermal energy storage tank is charged with thermal energy, the speed of the load circuit pump may be set to obtain the requestedPatentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025 load flow being smaller than the heat pump flow and the heat pump flow may be varied by varying the speed of the heat pump circuit pump until a deviation of the load flow feed temperature from the reference load flow feed temperature is minimised. 5

[51] Optionally, a bypass valve arrangement, being arranged at abypass connection point where a load circuit section and a bypass cir- cuit section for transporting a bypass flow as part of the load flow by-passing the at least one thermal energy load are connected, may becontrolled to obtain a desired heat pump return flow temperature.

[52] The method disclosed herein may be implemented in form ofcompiled or uncompiled software code that is stored on a computer readable medium with instructions for executing the method. Alterna-15 tively, or in addition, the method may be executed by software in acloud-based system and / or a building management system (BMS), e.g. in control electronics disclosed herein.

[53] The present invention may be a system, a method, and / or a com-20 puter program product at any possible technical detail level of integra- tion. The computer program product may include a computer readable storage medium (or media) having computer readable program instruc- tions thereon for causing a processor to carry out aspects of the present invention.

[54] The computer readable storage medium can be a tangible de-vice that can retain and store instructions for use by an instruction execu- tion device. The computer readable storage medium may be, for exam- ple, but is not limited to, an electronic storage device, a magnetic stor-30 age device, an optical storage device, an electromagnetic storage de- vice, a semiconductor storage device, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of the computer readable storage medium includes the following: a portablePatentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025 computer diskette, a hard disk, a random access memory (RAM), a read- only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile 5 disk (DVD), a memory stick, a floppy disk, a mechanically encoded de- vice such as punch-cards or raised structures in a groove having instruc- tions recorded thereon, and any suitable combination of the foregoing. A computer readable storage medium, as used herein, is not to be con- strued as being transitory signals per se, such as radio waves or other 10 freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fibre-optic cable), or electrical signals transmit- ted through a wire.

[55] Computer readable program instructions described herein can bedownloaded to respective computing / processing devices from a com-puter readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area net- work, a wide area network and / or a wireless network. The network may 20 comprise copper transmission cables, optical transmission fibres, wireless transmission, routers, firewalls, switches, gateway computers and / or edge servers. A network adapter card or network interface in each compu- ting / processing device receives computer readable program instructions from the network and forwards the computer readable program instruc- tions for storage in a computer readable storage medium within the re- spective computing / processing device. SUMMARY OF THE DRAWINGS30

[0056] Embodiments of the present disclosure will now be described byway of example with reference to the following figures of which:Patentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025 Fig. 1 shows schematically an embodiment of the hydronic system dis- closed herein in the feed line configuration; Fig. 2 shows schematically another embodiment of the hydronic system5 disclosed herein in the feed line configuration;Fig. 3 shows schematically another embodiment of the hydronic systemdisclosed herein in the feed line configuration; Fig. 4 shows schematically another embodiment of the hydronic systemdisclosed herein in the feed line configuration;Fig. 5 shows schematically another embodiment of the hydronic systemdisclosed herein in the return line configuration;15 Fig. 6 shows schematically another embodiment of the hydronic systemdisclosed herein in the return line configuration;Fig. 7 shows schematically another embodiment of the hydronic systemdisclosed herein in the return line configuration;Fig. 8 shows schematically another embodiment of the hydronic systemdisclosed herein in the feed line configuration with a freshwater tank asa thermal energy transfer element; and 25 Fig. 9 shows schematically another embodiment of the hydronic systemdisclosed herein in the return line configuration with a freshwater tankas a thermal energy transfer element.Patentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025 DETAILED DESCRIPTION

[57] Fig. 1 shows an embodiment of a hydronic system 1 for transferringthermal energy from a heat pump 3 to at least one thermal energy load 5 5. All figures show embodiments of the hydronic system 1 as part of a domestic heating system with the heat pump 3 as a heat source and radiators and / or underfloor heating as thermal energy loads 5. A skilled reader will readily understand that the hydronic system 1 may be used in analogy as a cooling system, for example as part of an HVAC-System. 10 The hydronic system 1 comprises a heat pump circuit section 7, 9 for transporting a heat pump flow qH that goes through the heat pump 3. The heat pump circuit section 7, 9 comprises a heat pump feed circuit section 7 arranged downstream of the heat pump 3 for providing the heat pump flow qH within the hydronic system 1. Furthermore, the heat pump circuit section 7, 9 comprises a heat pump return circuit section 9for returning the heat pump flow qH from the hydronic system 1 back to the heat pump 3. The temperature TH of the thermal energy transporting medium, e.g. water, is higher in the heat pump feed circuit section 7 than in the heat pump return circuit section 9 when the heat pump 3 is used 20 as a heat source in a heating system. The heat pump flow qH is driven by a heat pump circuit pump 11 that may be installed upstream of the heat pump feed circuit section 7 or in the heat pump return circuit section 9, or within the heat pump 3.

[58] The hydronic system 1 further comprises a load circuit section 13,15 for transporting a load flow qL that goes through the at least one ther- mal energy load 5. The load flow qL is driven by a load circuit pump 17being arranged at the load circuit section 13, 15. The load circuit section 13, 15 comprises a load feed circuit section 13 and a load return circuit30 section 15, wherein the load feed circuit section 13 is arranged down- stream of the heat pump feed circuit section 7 and the load return circuitPatentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025 section 15 is arranged downstream of the at least one thermal energy load 5.

[59] The hydronic system 1 further comprises a storage circuit section5 19, 21 for transporting a storage flow qS that goes through a thermal en- ergy storage tank 23. It should be noted that the storage flow qS in thestorage circuit section 19, 21 is bidirectional and the flow direction of thestorage flow qS depends on the operation mode of the hydronic system1. The storage flow qS is selectively directable in a charging directionwhen the thermal energy storage tank 23 is charged with a thermal en- ergy and in a discharging direction when the thermal energy is dis- charged from the thermal energy storage tank 23. The storage circuit section 19, 21 comprises a storage feed circuit section 19 and a storagereturn circuit section 21, wherein the storage feed circuit section 19 is15 connected to an upper, hotter part of the thermal energy storage tank23 and the storage return circuit section 21 is connected to a lower,cooler part of the thermal energy storage tank 23.

[0060] The hydronic system 1 further comprises a storage valve arrange-20 ment 25 being arranged at a connection point 27, 29, where the heatpump circuit section 7, 9, the load circuit section 13, 15, and the storagecircuit section 19, 21 are connected. It should be noted that the connec- tion point 27, 29 may be a feed connection point 27 in a feed line con- figuration as shown in Figs. 1 to 4, where the heat pump feed circuit sec-tion 7, the load feed circuit section 13 and the storage feed circuit sec-tion 19 are connected. Alternatively, the connection point 27, 29, may be a return connection point 29, where the heat pump return circuit sec- tion 9, the load return circuit section 15 and the storage return circuit section 21 are connected in a return line configuration. It should be30 noted that the valve arrangement 25 is an optional feature and the op- eration modes of the hydronic system 1 may be established by a speedcontrol of the load circuit pump 17 and the heat pump circuit pump 11 alone. However, a controlled storage valve arrangement 25 is preferred.Patentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025

[0061] In the feed line configuration of the storage valve arrangement25, as shown in Fig. 1, the storage valve arrangement 25 is arranged atthe feed connection point 27, e.g. in form of a motor-controlled three-5 way valve, comprising a storage valve inlet 31, a storage valve storageport 33 and a storage valve outlet 35. The storage valve inlet 31 is con-nected to the heat pump feed circuit section 7 and receives the heat pump flow qH from the heat pump 3. The storage valve outlet 35 is con- nected to the load feed circuit section 13 to guide the load flow qL into10 the load feed circuit section 13. Depending on the operation mode ofthe hydronic system 1, the storage valve storage port 33 serves as an inletor outlet to or from the storage feed circuit section 19.

[0062] The hydronic system 1 further comprises control electronics 20 (seeFig. 2) that is preferably configured to control the storage valve arrange-ment 25 and the load circuit pump 17 such that the storage flow in the storage circuit section 19, 21 is selectively directed in the charging direc- tion or in the discharging direction.20

[0063] It should be noted that the configuration of the hydronic system 1in the feed line configuration or in the return line configuration dependson whether the storage valve arrangement 25 is arranged in a feed line configuration, i.e. at the feed connection point 27, or in a return line con- figuration, i.e. at the return connection point 29. Irrespective of the con-figuration of the storage valve arrangement 25, the load circuit pump 17may be arranged in a feed line configuration, in which the load circuit pump 17 is arranged upstream of the at least one thermal energy load 5 at the load feed circuit section 13 (as shown in Figs. 1-6, 8 and 9), or in areturn line configuration, in which the load circuit pump 17 is arranged 30 downstream of the at least one thermal energy load 5 in the load return circuit section 15 (as shown in Fig. 7). It is possible to combine differentPatentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025combinations of configurations of the load circuit pump 17 and the stor-age valve arrangement 25.

[64] It is preferred that the hydronic system 1 is an integrated water5 circuit, IWC, unit 37 as a part of an indoor unit 39. The IWC unit 37 maybe arranged within a housing 41 of the indoor unit 39. The IWC unit 37comprises at least three ports 43, 45, 47, i.e. a heat pump port 43 for con- necting the heat pump circuit section 7, 9 with the heat pump 3, a stor-age port 45 for connecting the storage circuit section 19, 21 with thethermal energy storage tank 23, and a load port 47 for connecting the load feed circuit section 13, 15 with the at least one thermal energy load5.

[65] In the return line configuration (see Figs. 5 and 6), the heat pump15 port 43 of the IWC unit 37 may be a heat pump return port 43a for con- necting the heat pump return circuit section 9 with the heat pump 3. An additional heat pump feed port 43b may then be needed to connect the heat pump feed circuit section 7 with the heat pump 3. In the feed line configuration (see Figs. 2 to 4), the heat pump port 43 may be the 20 heat pump feed port 43b for connecting the heat pump feed circuit section 7 with the heat pump 3 without a need for a heat pump return port 43a.

[66] The storage port 45 of the IWC unit 37 may be a storage returnport 45a for connecting the storage return circuit section 21 with the ther- mal energy storage tank 23 (see Figs.4 and 5). If the thermal energy stor- age tank 23 is not entirely integrated into the IWC unit 37 (as shown in Figs. 2, 3 and 5), the storage port may be a storage feed port 45b toconnect the storage feed circuit section 19 with the thermal energy stor- 30 age tank 23. The embodiment shown in Fig.5 comprises both the storage return port 45b and the storage feed port 45b. The embodiment shown in Fig.6 comprises no storage port 45, i.e. neither the storage return portPatentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025 45b nor the storage feed port 45b, because the thermal energy storage tank 43 is there fully integrated in the return line configuration.

[67] The load port 47 of the IWC unit 37 is in all shown embodiments a5 load feed port 47b for connecting the load feed circuit section 13 with the at least one thermal energy load 5. In the return line configuration as shown in Figs.5 and 6, an additional load return port 43a may be needed to connect the load return circuit section 15 with the at least one thermal energy load 5. The IWC unit 47 needs further ports if it comprises a do-10 mestic hot water, DHW, system 49 as described below.

[68] All embodiments of the hydronic system 1 shown in the figurescomprise a domestic hot water, DHW, system 49. However, the DHW sys-tem 49 is an optional feature and very beneficial to use the hydronic sys-tem 1 for providing hot water to a hot water consumer 51, e.g. a faucet, shower or bathtub. The DHW system 49 comprises a DHW freshwater cir-cuit section 53, 55 for transporting a freshwater flow qFW coming from afresh water supply towards the at least one hot water consumer 51. The DHW system 49 further comprises a bypass circuit section 57, 59 for trans-20 porting a bypass flow qB as at least part of the load flow qL. Furthermore,the DWH system 49 comprises a thermal transfer element 61 (in Figs. 1 to7 shown as a heat exchanger) being arranged to thermally couple thebypass flow qB with the freshwater flow qFW. Finally, the DHW system 49comprises a bypass valve arrangement 63 being arranged at a bypass connection point 65, 67, where the load circuit section 13, 15 and thebyapss circuit section 57, 59 are connected. It should be noted that, in-dependent of the configuration of the storage valve arrangement 25 and / or the load circuit pump 17, the bypass valve arrangement 63 may be arranged in a feed line configuration at a bypass feed connection30 point 65 where the load feed circuit section 13 and the bypass feed cir-cuit section 57 are connected, or in a return line configuration at the by- pass return connection point 67 where the load return circuit section 15 and the bypass return circuit section 59 are connected.Patentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025

[0069] The control electronics 20 is further configured to control the by-pass valve arrangement 63 such that at least part of the load flow is used as the bypass flow qB. The embodiments of the hydronic system 1 shown5 in Figs. 1 to 7 show the thermal transfer element 61 as a heat exchanger having a primary heat exchanger part transporting the bypass flow and asecondary heat exchanger part transporting the freshwater flow qFW.The embodiments of Figs. 8 and 9 show the thermal transfer element 61 as a freshwater tank being in thermal contact with a coil 69 transporting10 the bypass flow qB. Yet another option for an embodiment for the ther-mal transfer element 61 is a bypass flow tank (not shown) in thermal con- tact with a coil transporting the freshwater flow qFW.

[0070] In case of the thermal transfer element 61 is a heat exchanger,the hydronic system 1 preferably comprises a flow sensor 71 being ar- ranged in the DHW freshwater circuit section 53, 55 for measuring the freshwater flow qFW. Additionally, the hydronic system 1 may comprise ahot water temperature sensor 73 being arranged at the DWH freshwater circuit section 55 downstream of the heat exchanger 61. The control20 electronics 20 is configured to determine a hot water thermal energy de-mand based on measured values of the flow sensor 71 and the hot water temperature sensor 73. In case the thermal transfer element 61 is a fresh- water tank (as shown in Figs.8 and 9) or a bypass flow tank, the hydronicsystem 1 may further comprise a DHW temperature sensor 75 being ar- ranged at the thermal transfer element 61 for measuring a DHW temper- ature. The control electronics 20 may then be configured to control thebypass valve arrangement 63 such that the DWH temperature is kept above a settable minimum DHW temperature. For example, in case of a freshwater tank 61, the DHW temperature should be kept above 55°C for30 reducing the risk of legionella contamination.

[71] A further optional feature of all embodiments of the hydronic sys-tem 1 shown in the figures is an electric heater 77 being arranged at thePatentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025 load feed circuit section 13 upstream of the bypass feed connection point 65. The control electronics 20 is further configured to control grad-ually or in one or more steps the power of the electric heater 77 for add- ing thermal energy PBUH to the load flow qL in the load feed circuit section5 13. The hydronic system 1 may further comprise a load flow feed temper-ature sensor 79 being arranged at the load feed circuit section 13 up- stream of the bypass feed connection point 65 and preferably upstream of the electric heater 77. The control electronics 20 is configured to con-trol a heating power PBUH of the electric heater 77 based on measured10 values of the load flow feed temperature sensor 79 and based on a loadflow qL measured by a load flow sensor (not shown) or estimated on thebasis of operating values of the load circuit pump 17. The estimation ispreferred to save a load flow sensor. The electric heater 77 is useful toprovide sufficient comfort at peak times of high thermal energy demandand to avoid dimensioning of the heat pump 3 and the thermal storagetank 23 that would be oversized for most of the time outside such peak times of high thermal energy demand. The electric heater 77 may alsoallow a setup of the hydronic system 1, in which the temperature Ts in the thermal energy tank storage tank 23 can be kept at the load flow feed20 temperature TL of the at least one thermal energy load 5 during times ofno DHW demand. In case of an underfloor heating as the at least one thermal energy load 5, such load flow feed temperature TL can be rela- tively low. In this manner, a significant dissipation power loss from the ther- mal energy storage tank 23 can be avoided. The electric heater 77 ispreferably only need to provide a higher load flow feed temperature TL during times of DHW demand.

[72] Preferably, the control electronics 20 receives a heat pump circuitpressure value via the communication interface 88 from the heat pump30 3. However, if this is not available, the hydronic system 1 may further com- prise a pressure sensor 80 being arranged in the heat pump feed circuit section 7. The control electronics 20 may preferably be configured toPatentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025control the storage valve arrangement 25 and the load circuit pump 17based on measured values of the pressure sensor 80.

[0073] The hydronic system 1 may further comprise a safety valve 81 at5 the load feed circuit section 13, an expansion vessel 82 at the heat pumpfeed circuit section 7, and / or an air powered purge 83 at the load feedcircuit section 13 as shown in Fig. 2. The hydronic system 1 further com-prises a storage flow feed temperature sensor 85 being arranged in the storage feed circuit section 19 for measuring the storage flow feed tem-10 perature TS in the discharging direction into the load flow qL. It may befurther beneficial for the hydronic system 1 to comprise a storage tank temperature sensor 87 being arranged within the thermal energy storage tank 23, wherein the control electronics 20 is configured to determine acharging level of the thermal energy storage tank 23 based on meas-ured value of the storage tank temperature sensor 87. The thermal en-ergy storage tank 23 may be arranged outside of the hydronic system 1 (as shown in Fig. 3) or integrated into the hydronic system 1 as part of theintegrated water circuit, IWC, unit 37 as shown in Fig. 4.20

[0074] Preferably, the control electronics 20 comprises a communicationinterface 88 for a communication 90 with a heat pump control of theheat pump 3. The communication interface 88 may be configured toreceive a heat pump flow value qH that is measured by means of a heatpump flow sensor (not shown) or estimated on the basis of operating val-ues of the heat pump circuit pump 11. The communication interface 88 may be further configured to send a start / stop command to the heat pump 3, and / or to receive a heat pump flow feed temperature TH meas-ured by a heat pump flow feed temperature sensor 89 and a heat pump flow return temperature THR measured by a heat pump return flow tem- 30 perature sensor 91. The heat pump flow feed temperature sensor 89 may be integrated into the heat pump 3 or arranged at the heat pump feed circuit section 7 of the hydronic system 1. Analogously, the heat pumpPatentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025 flow return temperature sensor 91 may be integrated into the heat pump 3 or arranged at the heat pump return circuit section 9 that may be in- ternal or external to the hydronic system 1. Furthermore, the communi- cation interface 88 may be configured to send a reference control value 5 to the heat pump 3 for setting the heat pump flow feed temperature TH and / or a difference TH-THRbetween the heat pump flow feed tempera- ture TH and the heat pump flow return temperature THR.

[0075] The control electronics 20 is preferably configured to control the10 storage valve arrangement 25 and / or both the load circuit pump 17 andthe heat pump circuit pump 11 to operate the hydronic system 1 selec- tively in the following operation modes: a) a first operation mode in which only the heat pump flow providesthe load flow, b) a second operation mode ion which the heat pump flow and thestorage flow in the discharging direction from the thermal energy storage tank 23 are merged into the load flow,c) a third operation mode in which the heat pump flow splits into theload flow and the storage flow in the charging direction,20 d) a fourth operation mode, in which only the storage flow in the dis-charging direction provides the load flow, and e) a fifth operation mode in which are the heat pump flow is fully usedas the storage flow in the charging direction

[76] In the first operation mode, there is no charging or discharging ofthermal energy to or from the thermal energy storage tank 23, because there is no storage flow in the storage circuit section 19, 21 and prefera-bly the storage valve storage port 33 of the valve arrangement 25 is closed. This first operation mode is useful if the thermal energy storage30 tank 23 has a low charging level and the electricity price is high. There-fore, it is currently too expensive to charge the thermal energy storagetank 23. Due to the low charging level of the thermal energy storage tankPatentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025 23, it cannot be used to support the heat pump 3 in providing a required load flow. The first operation mode is also useful if the electricity price is low and the thermal energy storage tank 23 has a maximum charging level. It may therefore be more economic to save the thermal energy in 5the thermal energy storage tank 23 for times of higher electricity prices.As the thermal energy storage tank 23 is already fully charged, the op- portunity of charging the thermal energy storage tank 23 at low electric-ity prices cannot be seized.10

[0077] In the second operation mode, thermal energy is withdrawn fromthe thermal energy storage tank 23 to support the heat pump 3 in provid- ing the load flow. In this situation, the storage flow in the storage feedcircuit section 19 is in the discharging direction to merge into the heatpump flow at the feed connection point 25. Both, the thermal energystorage tank 23 as well the heat pump 3 act as a thermal energy source in the second operation mode. The second operation mode is useful when the thermal energy demand of the load flow is higher than whatcan be delivered by the heat pump 3 or the thermal energy storage tank 23 alone. Another scenario for applying the second operation mode is20 when the temperature in the thermal energy storage tank 23 and / ordownstream in the storage load circuit section 19 in discharging direc- tion of the storage flow is above a required load flow feed temperature.This may, for example, be the case if the thermal energy load 5 is an underfloor heating that requires relatively low loaf flow feed tempera- tures. The heat pump flow at a lower temperature may be used to mix the colder heat pump flow into the hotter storage flow to obtain the ref- erence load flow feed temperature in the load feed circuit section 13.

[0078] In the third operation mode, the heat pump 3 serves as a thermal30 energy source to provide the load flow as well as the storage flow in the charging direction to fill the thermal energy storage tank 23. The heat flow is therefore split up at the feed connection point 25 into the storagePatentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025 flow and the load flow. The storage flow is in this situation directed into the charging direction in the storage feed circuit section 19. This is usefulwhen the electricity prices are low, and the charging level of the thermalenergy storage tank 23 is low during a moderate thermal energy de- 5mand of the thermal energy loads 5. In this situation, it is economic toseize the opportunity of low electricity prices and to run the heat pump3 at a higher power than needed by the thermal energy load(s) 5 andto charge the thermal energy storage tank 23 with thermal energy. The control electronics 20 commands the load circuit pump 17 in this situa-10 tion to provide a load flow that is lower than the heat pump flow pro- vided by the heat pump circuit pump 11 so that the flow difference re-sults in the storage flow in the charging direction. Irrespective of whether the heat pump circuit pump 11 is arranged in an outdoor unit of the heat pump 3 or integrated into the IWC unit 37 as part of the indoor unit 39,the control electronics 20 may be configured to directly or indirectly con-trol the speed of the heat pump circuit pump 11. However, a direct con-trol of the heat pump circuit pump 11 is not preferred if the heat pumpcircuit pump 11 is integrated in the external heat pump 3. Preferably, itthen the heat pump 3 that controls directly the speed of the heat pump 20 circuit pump 11. The control electronics 20 preferably sets a heat pump flow differential reference temperature for the heat pump 3 to obtain.Thereby, the control electronics 20 is able to indirectly control the speedof the heat pump circuit pump 11 and thus to indirectly control the heat pump flow.

[79] In the fourth operation mode, the heat pump flow in the heatpump circuit section 7, 9 is zero, so that the storage flow in the discharg- ing direction in the storage feed circuit section 19 provides the full loadflow alone. The fourth operation mode is useful when the electricity price30 is high and the thermal energy storage tank 23 is sufficiently charged with thermal energy. It is useful to save one or more start / stop cycles of thePatentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025 heat pump. Therefore, it is a further scenario for applying the fourth op- eration mode when the thermal energy demand of the thermal energy loads 5 is so low that the required load flow is below a minimum heat pump flow for the heat pump 3 to properly work. The fourth operation 5mode is therefore very useful to save a significant number of start / stopcycles of the heat pump 3, which prolongs the lifetime and efficiency of the heat pump 3.

[80] In the fifth operation mode, there is no thermal energy demand of10 the thermal energy loads 5, so that the load flow is zero. In the situation, it is useful to run the hydronic system 1 in the fifth operation mode when the electricity price is low, and the thermal energy storage tank 23 is not fully charged. This is particularly useful during summer months when the thermal energy demand is less continuous and comes mainly from the DHW system 49. The thermal energy storage tank 23 can be chargedduring times of no thermal energy demand and discharged, preferably in the fourth operation mode, when the DHW system 49 demands ther-mal energy. This can significantly reduce the number of start / stop cycles of the heat pump 3 during the summer months, which is advantageous20 for the lifetime and efficiency of the heat pump 3.

[81] The control electronics 20 is further configured to check in the firstfour operation modes whether the load flow feed temperature in the load feed circuit section 13 as measured by the load flow feed temper- ature sensor 70 is sufficient to satisfy the thermal energy demand of the thermal energy load(s) 5 and / or the DHW system 49. If this is not the case,the control electronics 20 is configured to switch on and or turn up, grad-ually and / or in steps, the power of the electric heater 77 to obtain theneeded load flow feed temperature in the load feed circuit section 13.30 The control electronics 20 may be configured to balance the fractions ofthermal energy coming from the heat pump 3, from the thermal energy storage tank 23 and the electric heater 77 depending on the electricityPatentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025 price, the thermal energy demand and the charging level of the thermal energy storage tank 23. The flexibility of mixing the thermal energy con- tributions of the heat pump 3, the thermal energy storage tank 23 and the electric heater 77 allows a smaller dimensioning of all three compo- 5 nents and allows the most economic operation of the hydronic system 1.

[82] The above-mentioned operation modes are applicable for all em-bodiments shown in the figures. Fig. 1 shows the hydronic system 1 in thefeed line configuration, wherein the storage valve arrangement 25 is ar-10 ranged at the feed connection point 25, the load circuit pump 17 is ar- ranged at the load feed circuit section 13 and the bypass valve arrange- ment 63 is arranged at the bypass feed connection point 65.

[83] Fig. 2 and 3 show the embodiment of Fig. 1 in form of an inte-grated water circuit, IWC, unit 37 as part of an indoor unit 39, wherein thehydronic system 1 is arranged within the housing 41 of the indoor unit 39.The IWC unit 37 comprises the heat pump port 43 for connecting the heatpump feed circuit section 7 with the heat pump 3 and the storage portfor connecting the storage feed circuit section 19 with the thermal en- 20 ergy storage tank 23. In the feed line configuration, the heat pump port 43 may be a heat pump feed port 44b. The load port 47, here a load feed port 47b, of the IWC unit 37 is used to connect the load feed circuitsection 13 with the at least one thermal energy load 5. The DHW system 49 requires in the feed line configuration of Figs. 1 to 4 three additionalports 86, 84, 92, namely a cold freshwater inlet port 86, a hot freshwateroutlet port 84 and a bypass return outlet port 92. The cold freshwater inletport 86 is used to connect the DHW freshwater circuit section 53 with a freshwater supply. The hot freshwater outlet port 84 is used to connectthe DHW freshwater circuit section 55 with the hot water consumer 51.30 The bypass return outlet port 92 is used to connect the bypass return cir-cuit section 59 with the load return circuit section 15.Patentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025

[0084] In Fig. 4, the thermal energy storage tank 23 is integrated into theIWC circuit 37, so that the storage port 45, here a storage return port 45a,is used to connect the storage return circuit section 21 with the return connection point 29 where the load return circuit section 15 and the heat 5 pump return circuit section 9 are connected.

[85] In Fig. 5, the hydronic system 1 is in a return line configuration, be-cause the storage valve arrangement 25 is arranged at the return con-nection point 29. The bypass valve arrangement 63 is here also arranged in the return line configuration, because it is arranged at the bypass re- turn connection point 67. The load circuit pump 17 is here in the feed line configuration, because it is arranged at the load feed circuit section 13. In this embodiment, the load return circuit section 15 is fully integrated into the IWC unit 37. The IWC unit 37 then needs two ports 43a,b, 45a,b,15 47a,b, 86, 84 each for the thermal energy storage tank 23, for the heatpump 3, for the thermal energy load(s) 5, and for the DHW system 49.

[86] As shown in Fig. 6, the two ports 43a,b to the thermal energy stor-age tank 23 can be saved if the thermal energy storage tank 23 is fully20 integrated into the IWC unit 37. Fig. 7 shows that the load circuit pump17 may be arranged, in a return line configuration, at the load return cir-cuit section 15. If the load return circuit section 15 is fully integrated intothe IWC unit 37, for example when the storage valve arrangement 25and / or the bypass valve arrangement 63 are in the return line configura- tion, the return line configuration of the load circuit pump 17 may be beneficial, because the return temperature in the load return circuit sec-tion 15 is lower than the load flow feed temperature in the load feed circuit section 13.30

[0087] The embodiment shown in Fig. 8 is a feed line configuration for allthe storage valve arrangement 25, the load circuit pump 17, and thebypass valve arrangement 63, wherein the thermal transfer element 61 of the DHW system 49 is a freshwater tank. The DHW flow is guidedPatentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025 through the coil 69 arranged within the freshwater tank 61 in order to heat up the fresh water within the freshwater tank 61 to a desired DHWtemperature. The flow sensor 71 may measure a freshwater flow qFW, butthis is not needed. The DHW temperature senor 75 being arranged within5 the freshwater tank 61 may be used to measure the DHW temperature to indicate a hot water demand. The freshwater tank 61 is heated up as soon as the DHW temperature falls below a pre-determined lower thresh- old. The heating up of the freshwater tank 61 is stopped as soon as the DHW temperature reaches a pre-determined upper threshold. The con-10 trol electronics 20 may thus be configured to control the bypass valvearrangement 63 such that the DHW temperature is at least kept above asettable minimum DHW temperature, e.g. above 55°C for reducing therisk of legionella contamination. Fig. 9 shows the DHW system 49 with afreshwater tank 61 in combination with a hydronic system 1 having the storage valve arrangement 25 and the bypass valve arrangement 63 in the return line configuration.

[88] The control electronics 20 is preferably integrated into the IWC unit37 as part of the indoor unit 39. Preferably, at least parts of electronics20 already available in the indoor unit 39 may be programmed or updatedto be used to function as the control electronics 20 of the IWC unit 37.The control electronics 20 may alternatively be arranged on extra hard-ware components arranged within the housing 41 of the indoor unit 39. Such extra hardware components may be in communication connec-tion with other electronic hardware components 93 of the indoor unit 39,such as a human machine interface and / or a display of the indoor unit39. As an alternative, or in addition, the control electronics 20 may bepart of a cloud-based system and / or a building management system (BMS) external of the IWC unit 37. 30

[89] The inventive control to establish a reference the load flow feedtemperature is now explained with reference to Fig. 1 in more detail.However, it should be noted that the inventive control to establish thePatentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025 reference load flow feed temperature applies to all embodiments of Figs. 1 to 9.

[90] The following situation may apply. There is no DHW demand and5 the hydronic system 1 is operated in the first operation mode in which only the heat pump 3 provides thermal power PH to the at least one ther- mal energy load 5. In this situation, the output power of the thermal en- ergy storage tank PS is zero and the thermal energy consumption PL of the at least one thermal energy load 5 equals the thermal output power10 PH of the heat pump 3. The heat pump flow qH equals the load flow qL and the load flow feed temperature TL equals the heat pump flow feed temperature TH. The following equations apply in this situation: wherein ^ ist the density of the thermal energy transferring medium, e.g.water, and cp is the specific heat capacity of the thermal energy trans- ferring medium, e.g. water. The load circuit pump 17 may be switched off in this situation, because the heat pump circuit pump 11 may pro- vide alone the load flow qL that equals the heat pump flow qH. Thecontrol electronics 20 directly controls the speed of the heat pump cir-20 cuit pump 11 to obtain a requested load flow qL. Alternatively, the con-trol electronics 20 may set a heat pump differential TH-THR so that the heat pump 3 sets the speed of the heat pump circuit pump 11 accord- ingly to provide the requested heat pump differential TH-THR. thereby,the control electronics 20 indirectly controls the speed of the heatpump circuit pump 11. The opening degree of the bypass valve ar-rangement 65 is controlled to obtain a desired bypass flow qB for estab- lishing a desired heat pump flow return temperature THR that is deter- mined by the following equation: 30 wherein TLR is the load flow return temperature. The speed of the heat pump circuit pump 11 is then varied until a deviation of the load flowPatentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025feed temperature TL from the reference load flow feed temperature isminimised.

[91] Another situation may apply as follows. There is no DHW demand5 and the hydronic system 1 is operated in the second operation mode in which both the heat pump 3 and the thermal energy storage tank 23simultaneously provide thermal power to the at least one thermal energy load 5. In this situation, the output power of the thermal energy storage tank PS adds to the output power of the heat pump PH. The thermal en- 10 ergy consumption PL of the at least one thermal energy load 5 then equals the sum of the output power of the thermal energy storage tankPS and the thermal output power PH of the heat pump 3. The speed ofthe load circuit pump 17 is set to provide a requested load flow qL. The speed of the heat pump circuit pump 11 is varied until a deviation of the load flow feed temperature TL from the reference load flow feed tem-perature is minimised. The following equations apply in this situation: This means that the needed heat pump flow qH can be found to establish20 the reference load flow feed temperature.

[0092] In another situation, the hydronic system 1 may be operated in thethird operation mode in which the heat pump 3 supplies thermal energy simultaneously to both the thermal energy storage tank 23 and to the at least one thermal energy load 5. The following equations apply in this situation: 30 Patentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025 wherein TBLR is a load flow return temperature after mixing with the bypass flow qB. This means that the needed heat pump flow qH can be found toestablish the reference load flow feed temperature. In the first, secondand fourth operation mode, i.e. when the storage flow is zero or in dis- 5 charging direction, TBLR is equal to the known heat pump flow return tem- perature THR.

[0093] Where, in the foregoing description, integers or elements are men-tioned which have known, obvious or foreseeable equivalents, then such10 equivalents are herein incorporated as if individually set forth. Referenceshould be made to the claims for determining the true scope of the pre- sent disclosure, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or fea-tures of the disclosure that are described as optional, preferable, advan- tageous, convenient or the like are optional and do not limit the scope of the independent claims.

[94] The above embodiments are to be understood as illustrative ex-amples of the disclosure. It is to be understood that any feature de-20 scribed in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. While at least oneexemplary embodiment has been shown and described, it should be un- derstood that other modifications, substitutions and alternatives are ap- parent to one of ordinary skill in the art and may be changed without departing from the scope of the subject matter described herein, and this application is intended to cover any adaptations or variations of the specific embodiments discussed herein. 30Patentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025

[0095] In addition, "comprising" does not exclude other elements or steps,and "a" or "one" does not exclude a plural number. Furthermore, charac-teristics or steps which have been described with reference to one of the above exemplary embodiments may also be used in combination with 5 other characteristics or steps of other exemplary embodiments de- scribed above. Method steps may be applied in any order or in parallelor may constitute a part or a more detailed version of another method step. It should be understood that there should be embodied within thescope of the patent warranted hereon all such modifications as reason- ably and properly come within the scope of the contribution to the art. Such modifications, substitutions and alternatives can be made without departing from the spirit and scope of the disclosure, which should be determined from the appended claims and their legal equivalents.15

[0096] List of reference numerals:1 hydronic system3 heat pump5 thermal energy loads20 7 heat pump feed circuit section9 heat pump return circuit section11 heat pump circuit pump13 load feed circuit section15 load return circuit section17 load circuit pump19 storage feed circuit section20 control electronics21 storage return circuit section23 thermal energy storage tank30 25 storage valve arrangement27 feed connection point29 return connection point31 storage valve inletPatentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 202533 storage valve storage port35 storage valve outlet37 integrated water circuit, IWC 39 indoor unit5 41 housing of indoor unit43 heat pump port43a heat pump return port43b heat pump feed port45 storage port10 45a storage return port45b storage feed port47 load port47a load return port47b load feed port49 DHW system51 hot water consumer53 cold DHW freshwater circuit section55 hot DHW freshwater circuit section57 bypass feed circuit section20 59 bypass return circuit section61 thermal transfer element63 bypass valve arrangement65 bypass feed connection point67 bypass return connection point69 coil71 flow sensor73 hot water temperature sensor75 DHW temperature sensor77 electric heater30 79 load flow feed temperature sensor80 pressure sensor81 safety valvePatentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 202582 expansion vessel83 air purge84 hot freshwater outlet port85 storage flow feed temperature sensor5 86 cold freshwater inlet port87 storage tank temperature sensor88 communication interface89 heat pump flow feed temperature sensor90 communication10 91 heat pump return temperature sensor92 bypass return outlet port93 electronic hardware components of the indoor unitPS thermal output power of the storage tank PH thermal output power of the heat pump PL thermal power consumption of the at least one thermal energy load PDHW thermal power consumption of the thermal transfer element PBUH thermal output power of the electric heater qS storage flow 20 qH heat pump flow qL load flow qB bypass flow qFW freshwater flow TS storage flow feed temperature TSR storage flow return temperature TL load flow feed temperature TLR load flow return temperature TH heat pump flow feed temperature THR heat pump flow return temperature 30 TBLR load flow return temperature after mixing with the bypass flowPatentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025

Claims

Claims 1. A hydronic system (1) for transferring thermal energy from a heatpump (3) to at least one thermal energy load (5), wherein the hy-dronic system (1) comprises:5 - a heat pump feed circuit section (7) for transporting a heatpump flow (qH) downstream of a heat pump circuit pump (11) for driving the heat pump flow (qH)through a heat pump (3); -a load feed circuit section (13) for transporting a load flow (qL)towards at least one thermal energy load (5);10 - a storage feed circuit section (19) for transporting a storage flow(qS) that goes through a thermal energy storage tank (23),wherein the storage flow (qS) is selectively directable in a charg-ing direction in an operation mode of the hydronic system (1) inwhich the thermal energy storage tank (23) is charged with ther-mal energy and in a discharging direction in another operation mode of the hydronic system (1) in which thermal energy is dis-charged from the thermal energy storage tank (23), wherein theheat pump feed circuit section (7), the load feed circuit section (13) and the storage feed circuit section (19) are connected at20 a feed connection point (27); -a load flow feed temperature sensor (79) being arranged at theload feed circuit section (13) downstream of the feed connec- tion point (27) for determining a load flow feed temperature (TL) of the load flow (qL);- a load circuit pump (17) for driving the load flow (qL); and- control electronics (20),wherein the control electronics (20) is configured, depending on the operation mode of the hydronic system (1), to directly or indi-rectly control a speed of the load circuit pump (17) to obtain a re-30 quested load flow and a speed of the heat pump circuit pump (11)atentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025so that a deviation of the load flow feed temperature (TL) from a reference load flow feed temperature is minimised.

2. The hydronic system (1) of claim 1, wherein the control electronics5 is configured to control the speed of the load circuit pump (17) ina feed-forward control, and to control the speed of the heat pumpcircuit pump (11) in a closed-loop control.

3. The hydronic system (1) of any of the preceding claims, wherein thecontrol electronics is configured, in said another operating modeof the hydronic system (1) in which thermal energy is discharged from the thermal energy storage tank (23), to control the speed ofthe load circuit pump (17) to obtain the requested load flow (qL)being larger than the heat pump flow (qH) and to vary the heat15 pump flow (qH) by varying the speed of the heat pump circuitpump (11) until a deviation of the load flow feed temperature (TL)from the reference load flow feed temperature is minimised.

4. The hydronic system (1) of any of the preceding claims, wherein the20 control electronics is configured, in said operating mode of the hy-dronic system (1) in which the thermal energy storage tank (23) is charged with thermal energy, to control the speed of the load cir- cuit pump (17) to obtain the requested load flow (qL) being smaller than the heat pump flow (qH) and to vary the heat pump flow (qH) by varying the speed of the heat pump circuit pump (11) until a deviation of the load flow feed temperature (TL) from the reference load flow feed temperature is minimised.

5. The hydronic system (1) of any of the preceding claims, wherein the30 hydronic system (1) is an integrated water circuit, IWC, unit (37),wherein the IWC unit (37) comprises: -a heat pump port (43) for connecting the heat pump feed cir-cuit section (7) with the heat pump (3);atentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025- a storage port (45) for connecting the storage feed circuit sec-tion (19) with the thermal energy storage tank (23); and- a load port (47) for connecting the load feed circuit section (13)with the at least one thermal energy load (5).5 6. The hydronic system (1) of any of the preceding claims, wherein thecontrol electronics (20) is configured to operate the hydronic sys-tem (1) selectively in the following operation modes:a) a first operation mode in which only the heat pump flow (qH)10 provides the load flow (qL),b) a second operation mode in which the heat pump flow (qH)and the storage flow (qS) in the discharging direction from thethermal energy storage tank (23) are merged into the load flow(qL), c) a third operation mode in which the heat pump flow (qH) splitsinto the load flow (qL) and the storage flow (qS) in the chargingdirection, d) a fourth operation mode in which only the storage flow (qS) inthe discharging direction provides the load flow (qL), and20 e) a fifth operation mode in which the heat pump flow (qH) is fullyused as the storage flow (qS) in the charging direction.

7. The hydronic system (1) of any of the preceding claims, furthercomprising -a bypass circuit section (57, 59) for transporting a bypass flow(qB) as part of the load flow (qL) bypassing the at least one ther- mal energy load (5), and- a bypass valve arrangement (63) being arranged at a bypassconnection point (65, 67) where a load circuit section (13, 15)30 and the bypass circuit section (57, 59) are connected,atentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025wherein the control electronics (20) is configured to control the by- pass valve arrangement (63) to obtain a desired heat pump returnflow temperature (THR).5 8. The hydronic system (1) of claim 7, further comprising a domestichot water, DHW, system (49), wherein the DHW system (49) com-prises: -a DHW freshwater circuit section (53, 55) for transporting a fresh-water flow (qFW) coming from a freshwater supply towards at10 least one hot water consumer (51), and- a thermal transfer element (61) being arranged to thermallycouple the bypass flow (qB) with the freshwater flow (qFW),wherein the control electronics (20) is configured to control the by-pass valve arrangement (63) such that at least a part of the loadflow (qL) is used as the bypass flow (qB).

9. The hydronic system (1) of any of the preceding claims, furthercomprising a storage tank temperature sensor (87) being arrangedwithin the thermal energy storage tank (23), wherein the control20 electronics (20) is configured to determine a charging level of thethermal energy storage tank (23) based on a measured value ofthe storage tank temperature sensor (87).

10. The hydronic system (1) of any of the preceding claims, wherein thecontrol electronics (20) comprises a communication interface (88) for communication with a heat pump control, wherein the commu- nication interface (88) is configured to- receive a heat pump flow value (qH),- send a start / stop command to the heat pump (3),30 - receive a heat pump flow feed temperature (TH) and a heatpump flow return temperature (THR), and / or- send a reference control value to the heat pump (3) for settingthe heat pump flow feed temperature (TH) and / or a differenceatentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025between the heat pump flow feed temperature (TH) and theheat pump flow return temperature (THR).

11. A method of transferring thermal energy from a heat pump (3) to5 at least one thermal energy load (5), wherein the method com-prises: -transporting a heat pump flow (qH) that comes from a heatpump (3) via a heat pump feed circuit section (7), wherein theheat pump flow (qH) is driven by a heat pump circuit pump (11);10 - transporting a load flow (qL) towards at least one thermal en-ergy load (5) via a load feed circuit section (13);- transporting a storage flow (qS) that goes through a thermal en-ergy storage tank (23) via a storage feed circuit section (19),wherein the storage flow (qS) is selectively directable in a charg-ing direction in an operation mode in which the thermal energy storage tank (23) is charged with thermal energy and in a dis-charging direction in another operation mode in which thermal energy is discharged from the thermal energy storage tank (23),wherein the heat pump feed circuit section (7), the load feed 20 circuit section (13) and the storage feed circuit section (19) are connected at a feed connection point (27); -determining a load flow feed temperature (TL) of the load flow(qL) by a load flow feed temperature sensor (79) being ar- ranged at the load feed circuit section (13) downstream of the feed connection point (27); and -directly or indirectly controlling, depending on the operationmode, a speed of the load circuit pump (17) to obtain a re- quested load flow and a speed of the heat pump circuit pump (11) so that a deviation of the load flow feed temperature (TL)30 from a reference load flow feed temperature is minimised.

12. The method of claim 11, wherein the speed of the load circuitpump (17) is controlled in a feed-forward control, and the speed ofatentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025the heat pump circuit pump (11) is controlled in a closed-loop con-trol.

13. The method of claim 11 or 12, wherein, in said another operating5 mode in which thermal energy is discharged from the thermal en- ergy storage tank (23), the speed of the load circuit pump (17) isset to obtain the requested load flow (qL) being larger than theheat pump flow (qH) and the heat pump flow (qH) is varied by var- ying the speed of the heat pump circuit pump (11) until a deviationof the load flow feed temperature (TL) from the reference load flow feed temperature is minimised.

14. The method of any of the claims 11 to 13, wherein, in said operatingmode of the hydronic system (1) in which the thermal energy stor- 15 age tank (23) is charged with thermal energy, the speed of the load circuit pump (17) is set to obtain the requested load flow (qL) being smaller than the heat pump flow (qH) and the heat pump flow (qH) is varied by varying the speed of the heat pump circuit pump (11) until a deviation of the load flow feed temperature (TL) from the reference load flow feed temperature is minimised.

15. The method of any of the claims 11 to 14, wherein a bypass valvearrangement (63), being arranged at a bypass connection point(65, 67) where a load circuit section (13, 15) and a bypass circuit25 section (57, 59) for transporting a bypass flow (qB) as part of the loadflow (qL) bypassing the at least one thermal energy load (5) are connected, is controlled to obtain a desired heat pump return flowtemperature (THR).atentanwälte Hemmer Lindfeld Frese GP 3827 WO, 10 / 10 / 2025

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