Hydronic system and method for transferring thermal energy from a heat pump to produce domestic hot water

Abstract

The present disclosure is directed to a hydronic system (1) for transferring thermal energy from a heat pump (3) to produce domestic hot water, DHW, 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 DHW system (49) comprising a thermal transfer element (61) and an electric heater (77), • a load feed circuit section (13) for transporting a load flow (qL) that goes at least partly through the thermal transfer element (61), wherein the thermal transfer element (61) is arranged to thermally couple at least part of the load flow (qB) with a freshwater flow (qFW); • 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), wherein the electric heater (77) is arranged in the load feed circuit section (13) downstream of the feed connection point (27); • a load flow feed temperature sensor (79) for determining a load flow feed temperature (TL) of the load flow (qL), wherein the load flow feed temperature sensor (79) is arranged at the load feed circuit section (13); • a load circuit pump (17) for driving the load flow (qL); and • control electronics (20), wherein the control electronics (20) is configured to control stepwise or gradually a heating power of the electric heater (77) and, depending on the operation mode of the hydronic system (1), to directly or indirectly control a speed of the load circuit pump (17) so that a deviation of the load flow (qL) from a reference load flow (qLref, qLcompref) is minimised, and / or to directly or indirectly control 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 (TLcompref) is minimised.

Description

[0001] Applicant: GRUNDFOS HOLDING A / STitle: Hydronic system and method for transferring thermalenergy from a heat pump to produce domestic hotwater 5Our Ref.: GP 3828 WODescription TECHNICAL FIELD10

[0001] The present disclosure is directed to a hydronic system and amethod for transferring thermal energy from a heat pump to produce domestic hot water. Preferably, 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 providing hot water to a faucet, shower, bathtub or other domestic consumers of hot water. The inventive hydronic system is, however, not only applicable for do- mestic household systems, but also as part of larger heating / cooling 20 systems of larger private or commercial buildings. Most preferably, the inventive hydronic system may be implemented as an integrated water circuit, IWC, unit connecting a heat pump with at least one thermal en- ergy load. BACKGROUND

[02] 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 a30 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 3828 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 3828 WO, 10 / 10 / 2025

[0006] There is thus a need for a hydronic system for transferring thermalenergy from a heat pump to produce domestic hot water, which al-lows benefitting from low electricity prices and reduces cost when elec- tricity prices are high. There is also a demand for smaller and cheaper 5 hydronic systems that require a smaller buffer tank or no buffer tank at all. The present disclosure is further directed to providing an improvedindoor unit of a heat pump, wherein a pre-assembled hydronic system in form of an integrated water circuit (IWC) unit can be integrated 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 to produce domestic hot water, DHW, wherein the hydronic system com-20 prises: -a heat pump feed circuit section transporting a heat pump flowdownstream of a heat pump circuit pump for driving the heat pump flow through a heat pump; -a DHW system comprising a thermal transfer element and an electricheater, -a load feed circuit section for transporting a load flow that goes atleast partly through the thermal transfer element, wherein the thermal transfer element is arranged to thermally couple at least part of the load flow with a freshwater flow;30 - a storage feed circuit section for transporting a storage flow that goesthrough a thermal energy storage tank, wherein the storage flow is selectively directable in a charging direction in an operation mode of the hydronic system in which the thermal energy storage tank isPatentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025 charged with thermal energy and in a discharging direction in an- other operation mode of the hydronic system in which thermal energy is discharged from the thermal energy storage tank, wherein the heat pump feed circuit section, the load feed circuit section and the stor- 5 age feed circuit section are connected at a feed connection point, wherein the electric heater is arranged in the load feed circuit section downstream of the feed connection point; -a load flow feed temperature sensor for determining a load flow feedtemperature of the load flow, wherein the load flow feed temperature sensor is arranged at the load feed circuit section; -a load circuit pump for driving the load flow; and- control electronics,wherein the control electronics is configured to control stepwise or gradually a heating power of the electric heater and, depending on 15 the operation mode of the hydronic system, to directly or indirectly control a speed of the load circuit pump so that a deviation of the load flow from a reference load flow is minimised, and / or to directly or indi- rectly control a speed of the heat pump circuit pump so that a devia- tion of the load flow feed temperature from a reference load flow feed20 temperature is minimised.

[09] 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 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- 30 shine. Alternatively, or in addition, the electricity price may depend on availability of electric power produced by distributed energy sourcesPatentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025 such as photovoltaic panels, wind-powered generators or battery stor- age.

[10] It should be noted that the thermal energy storage tank is not a5 freshwater tank of a domestic hot water (DHW) system. The thermal en- ergy storage tank is not a hydraulic decoupling buffer tank either. Thethermal 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 split-type heat pump, the condenser unit, e.g. as an indoor unit, maybe part of the hydronic system or arranged externally thereof. Further thermal energy load(s) may be connected to the hydronic system.15

[0011] The hydronic system disclosed herein has the advantage thatdomestic hot water can be efficiently provided in different operation modes by the thermal energy storage tank alone with the help of the electric heater, if needed, or in addition with the heat pump flow.20

[0012] Optionally, the control electronics may be configured, depend-ing on the operation mode of the hydronic system, to switch off the heat pump or leave the heat pump switched off and to directly or indi-rectly control the speed of the load circuit pump in a closed-loop con-trol, so that a deviation of the load flow from the reference load flow isminimised, or, to switch on the heat pump or leave the heat pump switched on and to set the speed of the load circuit pump in a feed-forward control to a reference load flow and to directly or indirectly control the speed of the heat pump circuit pump in a closed-loop control so that a devia- 30 tion of the load flow feed temperature from the reference load flow feed temperature is minimised. The first alternative is advantageous ifthe thermal energy storage tank shall be used alone to provide the thermal power for the DHW production, with the help of heating powerPatentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025 of the electric heater if needed. The second alternative is advanta- geous if both the thermal energy storage tank and the heat pump shall be used together to simultaneously provide the thermal power for the DHW production. Also in the second alternative, heating power of the5 electric heater can be added if needed.

[13] Optionally, the control electronics may be configured, in an op-erating mode of the hydronic system in which the heat pump flow and the storage flow in the discharging direction from the thermal energy 10 storage tank are merged into the load flow, to control the speed of the load circuit pump to obtain a reference load flow and to vary the heat pump flow 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. In this operation mode, both thethermal energy storage tank and the heat pump are used together to simultaneously provide the thermal power for the DHW production. Heating power of the electric heater can be added if needed.

[14] Optionally, the hydronic system may be an integrated water cir-20 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 or for connecting a storage return cir-cuit section with a load return circuit section;- a cold freshwater inlet port for connecting the thermal transfer el-ement with a freshwater supply; and -a hot freshwater outlet port for connecting the thermal transferelement with a hot water consumer. 30

[15] It is very beneficial to provide the hydronic system in form a pre-assembled IWC unit being at least part of an indoor unit of the heatPatentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025 pump. A minimum number of four ports, i.e. the heat pump port, the stor- age port and the two freshwater ports, is needed to connect an external heat pump unit, an external thermal energy storage tank, the freshwater supply and the hot water consumer. If the thermal energy storage tank5 and a load return circuit section back to the heat pump and to the ther- mal energy storage tank is integrated into the IWC, the storage port con-nects the storage return circuit section and the load return circuit sectionwith an external heat pump return circuit section. The load return circuitsection from the thermal transfer element may be arranged externally of10 the IWC unit. In that case, another return outlet port may be needed toconnect to the external load return circuit section.

[16] 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, b) 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,20 c) a third operation mode in which the heat pump flow splits into theload flow and the storage flow in the charging direction, 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.

[17] 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 30 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- 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 isPatentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025 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 5charged. 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- tain a needed heat pump flow feed temperature that corresponds to10 the reference load flow feed temperature. The first operation mode isusually not used during a DHW demand.

[18] 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 inthe discharging direction through the storage feed 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 or20 the thermal energy storage tank alone. Another scenario for applyingthe second operation mode is when the temperature in the thermal en- 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. 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 load flow feed temperature. In the second opera-tion mode, the reference load flow feed temperature may be main-tained by receiving or measuring a heat pump return flow temperature and then controlling a heat pump differential temperature to obtain a30 needed heat pump flow feed temperature. As the storage flow is mixedinto the load flow in the second operation mode, the load flow is higherthan the heat pump flow, wherein the storage flow is the difference be- tween load flow and the heat pump flow. The speed of the load circuitPatentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025pump and the speed of the heat pump circuit pump are controlled toobtain a reference load flow with a needed mixing of heat pump flow and storage flow to obtain the reference load flow feed temperature. The second operation mode is a preferred operation mode for produc- 5ing DHW when there is a DHW demand.

[0019] 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 10 when the electricity prices are low, and the charging level of the thermal energy storage tank is low during a thermal energy demand of other thermal energy load(s), e.g. radiators or underfloor heating. The load cir- cuit 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 may include the heat pump cir- cuit pump to control the heat pump flow. As an alternative, an external outdoor unit of the heat pump may include the heat pump circuit pumpfor providing the heat pump flow in the heat pump load circuit section. In case of an external heat pump circuit pump, the control electronics 20 may be configured to be in communication with the external heat pump for setting a heat pump differential target temperature such that the ex-ternal heat pump circuit pump provides the required heat pump flow in the heat pump load circuit section to maintain a heat pump flow differ-ential temperature at the set heat pump differential target temperature. As the load flow feed temperature is the same as the heat pump flow feed temperature in the third operation mode, the reference load flowfeed temperature may be maintained by receiving or measuring a heat pump flow return temperature and controlling a heat pump flow differ- ential temperature to obtain a needed heat pump flow feed tempera-30 ture that corresponds to the reference load flow feed temperature.

[0020] The control electronics may be configured to adjust the fractionsof storage flow and heat pump flow in the load flow depending on thePatentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025electricity price and / or a charging level in the thermal energy storagetank. 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 temperature5 as an indicator for the charging level in the thermal energy storage tank. The third operation mode is usually not used during a DHW demand.

[21] 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-10 ing direction provides the full load flow alone. This operation mode is use- 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 a minimum 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. If the load flow feed temperature is not high enough, the electric heater isused to obtain a higher load flow feed temperature. If it is too high, the 20 hydronic 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. The fourth operation mode is anotherpreferred operation mode for providing DHW when there is a DHW de-mand.

[22] In the fifth operation mode, there is no thermal energy demand,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 30 useful during summer months when the thermal energy demand is less continuous and comes mainly from the DHW system. The thermal energy storage tank can be charged during times of no thermal energy de- mand and discharged, preferably in the fourth operation mode, whenPatentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025 the DHW system demands thermal energy. This can significantly reduce the number of start / stop cycles of the heat pump, which is advanta- geous for the lifetime and efficiency of the heat pump. As the storageflow is the same as the heat pump flow in the fifth operation mode, a 5desired storage flow target temperature may be maintained by receiv-ing or measuring a heat pump flow return temperature and controlling a heat pump flow differential temperature to obtain a desired heat pump flow target temperature that corresponds to the desired storage flow tar-get temperature. The fifth operation mode is usually not used during aDHW demand.

[23] 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 energy15 storage tank.

[24] 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. 20

[25] Optionally, the thermal transfer element may be- a heat exchanger having a primary heat exchanger part transport-ing the bypass flow, which preferably equals the load flow during aDHW demand event, and a secondary heat exchanger part trans-porting the freshwater flow,- a freshwater tank in thermal contact with a coil transporting thebypass flow, and / or- a bypass flow tank in thermal contact with a coil transporting thefreshwater flow. 30Patentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025

[0026] Compared to a freshwater tank, a heat exchanger has the ad-vantage that no freshwater reservoir must be kept above 55°C for reduc- ing the risk of legionella contamination. Furthermore, a heat exchanger consumes less space than a freshwater tank or a bypass flow tank. 5

[27] The electric heater of the hydronic system is arranged at the loadfeed circuit section downstream of the feed connection point and up-stream of the thermal transfer element. The control electronics is config- ured to control gradually or in one or more steps a heating power of the10 electric heater for adding thermal energy to the load flow. The electricheater is particularly beneficial in combination with the DHW system to provide sufficient comfort when a thermal energy demand during a DHW demand event 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 for most of the time. If the thermal output power of the heat pump together with the thermal output power of the thermal energy storage tank is not sufficient to satisfy a high thermal energy demand during a DHW demand event, the electric heater can be switched on 20 and / or turned up to a sufficient degree to add thermal energy to the load flow by increasing the load flow feed temperature. Thus, the electricheater has the advantage of providing a choice between using threedifferent energy sources individually or in combination, in particular dur- ing a DHW demand event. A relatively short DHW demand may be metby running the hydronic system in the fourth operation mode, i.e. the stor-age flow provides the load flow. The electric heater may be switched onin addition, if needed. A longer DHW demand event may require thatthe heat pump circuit pump is switched on and ramped up, so that thehydronic system runs in the second operation mode, i.e. both the heat30 pump flow and the storage flow mix into the load flow. The electricheater may be switched on in addition, but only as much as needed. Ifthe DHW demand is very high, the hydronic system may be run in thesecond operation mode, plus the electric heater if needed.Patentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025

[0028] Optionally, the electric heater may be arranged upstream of thebypass connection point. This is beneficial for the electric heater to in-crease a feed temperature of the bypass flow. 5

[29] Optionally, when the thermal transfer element is a heat ex-changer, the hydronic system may further comprise -a flow sensor being arranged at a freshwater circuit section formeasuring the freshwater flow, and10 - a hot water temperature sensor being arranged at the freshwatercircuit 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 sensor 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. As an alternative to a flow sensor,temperature sensors for measuring the input temperature and the output temperature of the fresh water in the secondary heat exchanger part of 20 the heat exchanger may be used to estimate the freshwater flow if the input temperature and the output temperature of the bypass flow through in the primary heat exchanger part of the heat exchanger andthe bypass flow itself is known. A detected freshwater flow may trigger a DHW demand event.

[30] 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,30 wherein the control electronics is configured to control, outside of a DHWdemand event, the bypass valve arrangement such that the DHW tem-perature is kept above a settable minimum DHW temperature. This is use-ful to ensure a minimum temperature in the freshwater tank to reducePatentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025 the risk of legionella contamination. In case of a bypass flow tank, this is beneficial to provide sufficient comfort for extracting thermal energy from the bypass flow tank into the freshwater flow whenever it is needed. 5

[0031] Optionally, when the thermal transfer element is a heat ex-changer, the control electronics may be configured to determine a DHWdemand based on at least two pre-determined hot water consumption profiles. A first hot water consumption profile of the at least two pre-de-termined hot water consumption profiles may be a “showering” profile10 indicated by a relatively high freshwater flow, e.g. at or above 7 l / min, wherein a first target hot water temperature is set relatively low, e.g. 42 °C. This is useful to reduce the need for mixing cold water into the hotfreshwater flow to obtain a desired showering temperature. A second hot water consumption profile of the at least two pre-determined hotwater consumption profiles may be a “kitchen” profile indicated by arelatively low freshwater flow, e.g. below 7 l / min, wherein a second tar- get hot water temperature is set relatively high, e.g.55 °C. This is useful to provide sufficiently hot water for a kitchen sink, for example. Each of the at least two pre-determined hot water consumption profiles may be time20 dependent based on experienced usage behaviour. As the hot waterconsumption profiles are usually similar on the same days of the week,e.g. working days and weekend days, it is useful to have the thermal en- ergy storage tank charged well before a hot water thermal energy de- mand can be expected according to the at least two pre-determinedhot water consumption profiles.

[32] 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-30 ing direction into the load flow.Patentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025

[0033] 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 measured5 value of the storage tank temperature sensor.

[0034] Optionally, the thermal energy storage tank may be integratedinto the hydronic system being an integrated water circuit, IWC, unit.

[0035] Optionally, the bypass valve arrangement may be a mixing valvein form of a three-way valve.

[36] Optionally, the hydronic system may further comprise the heatpump circuit pump being arranged at the heat pump circuit section for15 driving the heat pump flow. Alternatively, or in addition, the heat pumpcircuit pump may be external of the hydronic system, e.g. part of an out-door unit of the heat pump.

[37] Optionally, the control electronics may comprise a communica-20 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 flowreturn 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. 30

[38] 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 pumpPatentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025feed 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 may5 enable a storage flow in the charging direction, i.e. the hydronic systemmay be switched to the third or fifth operation mode.

[39] Optionally, the hydronic system may further comprise:- the heat pump,10 - the thermal energy storage tank, and / or- at least one thermal energy load, e.g. radiator(s) or underfloorheating(s).

[40] 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 operationmode the hydronic system is going to be operated during different daytimes of one or more hours in the future based on forecast in-20 formation including an electricity price at said daytimes; and- operating the hydronic system according to the operation sched-ule.

[41] 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 a30 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,Patentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025for establishing an operation schedule for the operation of hydronic sys-tem.

[42] According to another aspect of the present disclosure, a method5 is provided for transferring thermal energy from a heat pump to produce domestic hot water, DHW, wherein the method comprises:- transporting a heat pump flow that comes from a heat pump via aheat pump feed circuit section, wherein the heat pump flow is drivenby a heat pump circuit pump;10 - transporting, via a load feed circuit section, a load flow that goes atleast partly through a thermal transfer element of a DHW system, wherein the thermal transfer element thermally couples at least part of the load flow with a freshwater flow; -transporting a storage flow that goes through a thermal energy stor-age tank via a storage feed circuit section, wherein the storage flowis selectively directable in a charging direction in an operation mode in which the thermal energy storage tank is charged with thermal en-ergy and in a discharging direction in another operation mode in which thermal energy is discharged from the thermal energy storage 20 tank, 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, wherein an electric heater of the DHW system is ar- ranged in the load feed circuit section downstream of the feed con- nection point; -determining a load flow feed temperature of the load flow by a loadflow feed temperature sensor, wherein the load flow feed tempera- ture sensor is arranged at the load feed circuit section; -controlling stepwise or gradually a heating power of the electricheater; and30 - directly or indirectly controlling, depending on the operation mode ofthe hydronic system, a speed of the load circuit pump so that a devi- ation of the load flow from a reference load flow is minimised, and / or a speed of the heat pump circuit pump so that a deviation of the loadPatentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025 flow feed temperature from a reference load flow feed temperature is minimised.

[43] Optionally, depending on the operation mode of the hydronic5 system, the heat pump is switched off and the speed of the load circuit pump is directly or indirectly controlled in a closed-loop control so that a deviation of the load flow from the reference load flow is minimised, or the heat pump is switched on and the speed of the load circuit pump isset in a feed-forward control to a reference load flow and the speed of10 the heat pump circuit pump is directly or indirectly controlled in a closed- loop control so that a deviation of the load flow feed temperature from the reference load flow feed temperature is minimised.

[44] Optionally, in an operating mode of the hydronic system in whichthe heat pump flow and the storage flow in the discharging direction from the thermal energy storage tank are merged into the load flow, the speed of the load circuit pump is controlled to obtain the reference loadflow and to vary the heat pump flow by varying the speed of the heat pump circuit pump until a deviation of the load flow feed temperature20 from the reference load flow feed temperature is minimised.

[0045] 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- 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.30

[0046] The present invention may be a system, a method, and / or a com-puter program product at any possible technical detail level of integra- tion. The computer program product may include a computer readablePatentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025 storage medium (or media) having computer readable program instruc- tions thereon for causing a processor to carry out aspects of the present invention. 5

[0047] 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- age device, an optical storage device, an electromagnetic storage de- 10 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 portable 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 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. A20 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 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.

[48] 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 external30 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 comprise copper transmission cables, optical transmission fibres, wireless transmission, routers, firewalls, switches, gateway computers and / or edgePatentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025 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- 5 spective computing / processing device. SUMMARY OF THE DRAWINGS

[49] Embodiments of the present disclosure will now be described by10 way of example with reference to the following figures of which: 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 systemdisclosed herein in the feed line configuration;Fig. 3 shows schematically another embodiment of the hydronic systemdisclosed herein in the feed line configuration; 20 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;Fig. 6 shows schematically another embodiment of the hydronic systemdisclosed herein in the return line configuration;30 Fig. 7 shows schematically another embodiment of the hydronic systemdisclosed herein in the return line configuration;Patentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025Fig. 8 shows schematically another embodiment of the hydronic systemdisclosed herein in the feed line configuration with a freshwater tank asa thermal energy transfer element; 5Fig. 9 shows schematically another embodiment of the hydronic systemdisclosed herein in the return line configuration with a freshwater tankas a thermal energy transfer element; Fig. 10 a flow chart of an embodiment of the inventive DHW production 10 method when the hydronic system is operated in the fourth operation mode; and Fig. 11 a flow chart of an embodiment of the inventive DHW production method when the hydronic system is operated in the second operation mode. DETAILED DESCRIPTION

[50] Fig. 1 shows an embodiment of a hydronic system 1 for transferring20 thermal energy from a heat pump 3 to at least one thermal energy load 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. 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 30 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 transportingPatentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025 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 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 5 pump feed circuit section 7 or in the heat pump return circuit section 9, or within the heat pump 3.

[51] 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-10 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 circuit 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 circuit section 15 is arranged downstream of the at least one thermal energy load 5.

[52] The hydronic system 1 further comprises a storage circuit section19, 21 for transporting a storage flow qS that goes through a thermal en-20 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 isconnected to an upper, hotter part of the thermal energy storage tank30 23 and the storage return circuit section 21 is connected to a lower,cooler part of the thermal energy storage tank 23.Patentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025

[0053] The hydronic system 1 further comprises a storage valve arrange-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- 5 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- 10 tion 9, the load return circuit section 15 and the storage return circuit section 21 are connected in a return line configuration. It should benoted that the valve arrangement 25 is an optional feature and the op- eration modes of the hydronic system 1 may be established by a speed control of the load circuit pump 17 and the heat pump circuit pump 11 alone. However, a controlled storage valve arrangement 25 is preferred.

[54] 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-20 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 intothe 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.

[0055] The hydronic system 1 further comprises control electronics 20 (see30 Fig. 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.Patentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025

[0056] 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 5 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 510 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 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 differentcombinations of configurations of the load circuit pump 17 and the stor-age valve arrangement 25.

[57] It is preferred that the hydronic system 1 is an integrated watercircuit, 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 3720 comprises 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.

[58] In the return line configuration (see Figs. 5 and 6), the heat pumpport 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 30 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 heat pump feed port 43b for connecting the heat pump feed circuitPatentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025 section 7 with the heat pump 3 without a need for a heat pump return port 43a.

[59] The storage port 45 of the IWC unit 37 may be a storage return5 port 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- 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 port 45b nor the storage feed port 45b, because the thermal energy storage tank 43 is there fully integrated in the return line configuration. 15

[60] The load port 47 of the IWC unit 37 is in all shown embodiments aload 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 20 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-mestic hot water, DHW, system 49 as described below.

[61] All embodiments of the hydronic system 1 shown in the figurescomprise a domestic hot water, DHW, system 49. The DHW system 49 isvery beneficial to use the hydronic system 1 for providing hot water to a hot water consumer 51, e.g. a faucet, shower or bathtub. The DHW sys- tem 49 comprises a DHW freshwater circuit section 53, 55 for transportinga freshwater flow qFW coming from a fresh water supply towards the at30 least one hot water consumer 51. The DHW system 49 further comprises a bypass circuit section 57, 59 for transporting a bypass flow qB as at least part of the load flow qL. Furthermore, the DWH system 49 comprises athermal transfer element 61 (in Figs. 1 to 7 shown as a heat exchanger)Patentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025being arranged to thermally couple the bypass flow qB with the freshwa-ter flow qFW. Finally, the DHW system 49 comprises a bypass valve ar-rangement 63 being arranged at a bypass connection point 65, 67, where the load circuit section 13, 15 and the bypass circuit section 57, 59 5are connected. It should be noted that, independent of the configura-tion 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 connection point 65 where the load feedcircuit section 13 and the bypass feed circuit section 57 are connected, 10 or in a return line configuration at the bypass return connection point 67 where the load return circuit section 15 and the bypass return circuit sec- tion 59 are connected. It should be noted that the bypass valve arrange-ment 63 is not used to control the bypass flow qB during a DHW demand event, because the load flow qL is preferably fully directed as bypass flow qB through the bypass circuit section 57, 59 during a DHW demand event.

[0062] The control electronics 20 is further configured to control, outsideof a DHW demand event, the bypass valve arrangement 63 such that atleast part of the load flow is used as the bypass flow qB. The embodiments20 of the hydronic system 1 shown 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 qB and a secondary heat exchanger part transporting the freshwater flow qFW. The embodiments of Figs. 8 and 9show the thermal transfer element 61 as a freshwater tank being in ther- mal contact with a coil 69 transporting the bypass flow qB. Yet anotheroption for an embodiment for the thermal transfer element 61 is a bypass flow tank (not shown) in thermal contact with a coil transporting the freshwater flow qFW.30

[0063] 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 aPatentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025 hot water temperature sensor 73 being arranged at the DHW freshwater circuit section 55 downstream of the heat exchanger 61. The control electronics 20 is configured to detect a DHW demand event based onmeasured values of the flow sensor 71 and the hot water temperature 5 sensor 73. In case the thermal transfer element 61 is a freshwater tank (as shown in Figs. 8 and 9) or a bypass flow tank, the hydronic system 1 mayfurther comprise a DHW temperature sensor 75 being arranged at the thermal transfer element 61 for measuring a DHW temperature. The con- trol electronics 20 may then be configured to control, outside of a DHW10 demand event, the bypass valve arrangement 63 such that the DWHtemperature 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 for reducing the risk of legionella contamination.

[64] A further feature of all embodiments of the hydronic system 1shown in the figures is an electric heater 77 being arranged at the load feed circuit section 13 downstream of the feed connection point 27 and upstream of the bypass feed connection point 65. The control electronics 20 is further configured to control gradually or in one or more steps the20 power of the electric heater 77 for adding thermal energy PBUH to theload flow qL in the load feed circuit section 13. The hydronic system 1 may further comprise a load flow feed temperature sensor 79 being ar-ranged at the load feed circuit section 13 upstream of the bypass feed connection point 65 and preferably upstream of the electric heater 77. The control electronics 20 is configured to control stepwise or graduallya heating power PBUH of the electric heater 77 based on measured values of the load flow feed temperature sensor 79 and based on a load flowqL measured by a load flow sensor (not shown) or estimated on the basisof operating values of the load circuit pump 17. The estimation is pre-30 ferred to save a load flow sensor. The electric heater 77 is useful to pro-vide 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 peakPatentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025times 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 feedtemperature TL of the at least one thermal energy load 5 during times of5 no DHW demand. In case of an underfloor heating as the at least one thermal energy load 5, such load flow feed temperature TLcan 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 10 during times of DHW demand.

[65] Preferably, the control electronics 20 receives a heat pump circuitpressure value via the communication interface 88 from the heat pump 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 tocontrol the storage valve arrangement 25 and the load circuit pump 17based on measured values of the pressure sensor 80.20

[0066] The hydronic system 1 may further comprise a safety valve 81 atthe 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- 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 a30 charging 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 1Patentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025(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.

[0067] Preferably, the control electronics 20 comprises a communication5 interface 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 10 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- 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 pump 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-20 cation interface 88 may be configured to send a reference control value to the heat pump 3 for setting the heat pump flow feed temperature TH and / or a difference TH-THR between the heat pump flow feed tempera- ture TH and the heat pump flow return temperature THR.

[0068] The control electronics 20 is preferably configured to control thestorage 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 provides30 the 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,Patentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025c) a third operation mode in which the heat pump flow splits into theload flow and the storage flow in the charging direction, d) a fourth operation mode, in which only the storage flow in the dis-charging direction provides the load flow, and 5e) a fifth operation mode in which are the heat pump flow is fully usedas the storage flow in the charging direction

[69] In the first operation mode, there is no charging or discharging ofthermal energy to or from the thermal energy storage tank 23, because10 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 storagetank 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 tank 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 in20 the 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. The first operation mode is usually not usedduring a DHW demand.

[70] 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 heat30 pump 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 whatPatentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025 can be delivered by the heat pump 3 or the thermal energy storage tank 23 alone. Another scenario for applying the second operation mode iswhen the temperature in the thermal energy storage tank 23 and / ordownstream in the storage load circuit section 19 in discharging direc- 5tion 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-10 erence load flow feed temperature in the load feed circuit section 13.The second operation mode is a preferred operation mode for produc- ing DHW when there is a DHW demand.

[71] In the third operation mode, the heat pump 3 serves as a thermalenergy 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 storageflow 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 useful20 when the electricity prices are low, and the charging level of the thermalenergy storage tank 23 is low during a moderate thermal energy de- mand 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-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 30 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-Patentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025trol 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 5 circuit pump 11. The control electronics 20 preferably sets a heat pump flow differential reference temperature for the heat pump 3 to achieve.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. The third operation mode is usually not used during a DHW10 demand.

[72] 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 price 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 theheat pump. Therefore, it is a further scenario for applying the fourth op- eration mode when the thermal energy demand of the thermal energy 20 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 mode 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. The fourth operation mode is a preferred operationmode for producing DHW when there is a DHW demand.

[73] In the fifth operation mode, there is no thermal energy demand ofthe 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 30 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 chargedPatentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025 during 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 advantageous 5for the lifetime and efficiency of the heat pump 3. The fifth operationmode is usually not used during a DHW demand.

[74] The control electronics 20 is further configured to check in the firstfour operation modes whether the load flow feed temperature in the10 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. 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 electricity price, the thermal energy demand and the charging level of the thermal20 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- nents and allows the most economic operation of the hydronic system 1. Preferably, the electric heater 77 is only used in the second and fourth operation mode during during a DHW demand.

[75] 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-30 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.Patentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025

[0076] 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 heat5 pump feed circuit section 7 with the heat pump 3 and the storage portfor connecting the storage feed circuit section 19 with the thermal en- 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 circuit10 section 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. The bypass return outlet port 92 is used to connect the bypass return cir-cuit section 59 with the load return circuit section 15.20

[0077] 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 pump return circuit section 9 are connected.

[78] 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- 30 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,Patentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 202547a,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.

[79] As shown in Fig. 6, the two ports 43a,b to the thermal energy stor-5 age tank 23 can be saved if the thermal energy storage tank 23 is fullyintegrated 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 2510 and / 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.

[80] 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 guided 20 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 withinthe 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- trol electronics 20 may thus be configured to control, outside of a DHW30 demand event, the bypass valve arrangement 63 such that the DHWtemperature is at least kept above a settable minimum DHW tempera- ture, e.g. above 55°C for reducing the risk of legionella contamination.Fig. 9 shows the DHW system 49 with a freshwater tank 61 in combinationPatentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025 with a hydronic system 1 having the storage valve arrangement 25 and the bypass valve arrangement 63 in the return line configuration.

[81] The control electronics 20 is preferably integrated into the IWC unit5 37 as part of the indoor unit 39. Preferably, at least parts of electronicsalready 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 system15 (BMS) external of the IWC unit 37.

[82] The control to establish a reference load flow feed temperature isnow explained with reference to Fig. 1 in more detail. However, it shouldbe noted that the control to establish the reference load flow feed tem-20 perature applies to all embodiments of Figs.1 to 9.

[83] The following situation may apply. There is no DHW demand andthe 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 power 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 feed30temperature TH. The following equations apply in this situation: Patentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025wherein ^ 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- 5vide alone the load flow qL that equals the heat pump flow qH. Thecontrol electronics 20 directly controls the speed of the heat pump cir-cuit pump 11 to obtain a load flow qL requested by the at least one thermal energy load 5. Alternatively, the control electronics 20 may seta heat pump differential TH-THR so that the heat pump 3 sets the speed of the heat pump circuit pump 11 accordingly to provide the re- quested heat pump differential TH-THR. thereby, the control electronics20 indirectly controls the speed of the heat pump circuit pump 11. Theopening degree of the bypass valve arrangement 65 is, outside of a DHW demand event, controlled to obtain a desired bypass flow qB for15 establishing a desired heat pump flow return temperature THR that is de- termined by the following equation: 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 flow20 feed temperature TL from the reference load flow feed temperature isminimised.

[84] Another situation may apply as follows. There is no DHW demandand 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- ergy consumption PL of the at least one thermal energy load 5 then30 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. ThePatentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025 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: 5 This means that the needed heat pump flow qH can be found to establish the reference load flow feed temperature. In the first, second and fourthoperation mode, i.e. when the storage flow is zero or in discharging di- rection, TBLR is equal to the known heat pump flow return temperature10 THR.

[85] 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: 20 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.25

[0086] Embodiments of the inventive DHW production are explained withreference to Figs.10 and 11 in combination with Fig.1. However, it should be noted that the inventive DHW production is applicable for all embod-iments of Figs. 1 to 9.Patentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025

[0087] Fig. 10 shows an example of the inventive method of transferringthermal energy from the heat pump 3 to produce DHW, wherein the hydronic system 1 is operated in the fourth operation mode in whichthe heat pump flow is zero and the storage flow provides the full load 5 flow. The following operating variables are known, measured or esti- mated: a storage flow feed temperature TSwhich may be determined by the storage flow feed temperature sensor 85 and / or the storage tank temperature sensor 87; a freshwater flow qFW which may be deter-mined by the flow sensor 71 or deduced from the bypass flow qB and 10 temperature differentials across the primary and secondary parts of the heat exchanger 61; a hot water temperature TDHW of the freshwaterflow as measured by the hot water temperature sensor 73; and load flow qL as measured by a load flow sensor or preferably estimated based on the current speed and power consumption of the load flow circuit pump 17. It should be noted that, during a DHW demand event,the load flow qL is preferably directed fully into the bypass flow qB, so that the bypass flow qB through the primary part of the heat exchanger 61 equals the load flow qL. The flow through other thermal energyload(s) 5 is then zero during a DHW demand event. 20

[88] In step 1001, it is checked if the freshwater flow qFW exceeds a startthreshold value qstart for triggering a DHW demand event. It is also checked in step 1001 if the freshwater flow has dropped below a stop threshold value qstop for ending a DHW demand event. The threshold val-ues qstart and qstop may be identical or differ from each other. If the fresh- water flow is below the threshold(s) qstart or qstop for having a DHW de-mand event, the DHW production stops at step 1003 by stopping the electric heater 77 (and the load circuit pump if there is currently no other thermal energy load 5 demanding a load flow qL). 30

[89] If, however, there is a DHW demand event ongoing, the methodproceeds to step 1005 in which a reference temperature differentialPatentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025^THEXref between the primary part and the secondary part of the heat ex-changer 61, a reference hot water temperature TDHWref, and a referenceload flow qLref is determined. The reference load flow qLref depends on the freshwater flow qFW and a desirable thermal transfer element ratio 5RHEX for operating the heat exchanger 61 efficiently. A heat exchangerratio RHEXabout one is usually most efficient. The heat exchanger ratio RHEX may be a pre-defined constant or a pre-defined function of temper- atures and / or flows. Anyway, the reference load flow qLref is fully defined by the known freshwater flow qFW. 10

[90] The reference hot water temperature TDHWref is defined by the fol-lowing equation: ^^^^^^^ = −^^^ ∙ ^^^ + ^^^15 wherein ^^^and ^^^are pre-determined parameters of a linear rela- tionship between the reference hot water temperature TDHWref and thefreshwater flow qFW. The rationale is here to have a lower reference hotwater temperature TDHWref when a high freshwater flow qFW is detected.The aim is here to extend the maximum duration of a DHW demand20 event for a given charging level of the thermal energy storage tank 23 when the freshwater flow qFW is high. A high freshwater flow qFW is mostlikely requested by an open shower tap or a bathtub tap. However, asshowers and bathtubs nowadays use a thermostat to mix cold waterwith hot water, there will is no need for very hot water during a DHW de-mand event of a shower or bathtub. The lower the reference hot watertemperature TDHWref is, the longer the DHW demand event can be with- out the help of the heat pump flow. The relationship between refer- ence hot water temperature TDHWref and the freshwater flow qFW couldalso be given by a lookup table, wherein a fixed low reference hot wa-30 ter temperature TDHWref could be used for high freshwater flows qFW, e.g.at or above 66% of a maximum freshwater flow qFW, and another fixedhigher reference hot water temperature TDHWref could be used for low freshwater flows qFW, e.g. below 66% of the maximum freshwater flowqFW.Patentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025

[0091] The reference temperature differential ^THEXref between the pri-mary part and the secondary part of the heat exchanger 61 is definedby the following equation: 5∆^^^^^^^ = −^∆^^^^ ∙ ^^^ + ^∆^^^^wherein ^∆^^^^and ^∆^^^^are pre-determined parameters of a linear relationship between the reference temperature differential ^THEXref andthe freshwater flow qFW. The rationale is here is to make a best guess forthe required temperature lift ^THEXref that the heat exchanger 61 must pro-10 vide. The heat exchanger 61 has a flow-dependent specific temperaturelift, because the efficiency of the heat transfer from the primary part tothe secondary part of the heat exchanger 61 is dependent on the flowspassing through both the primary and secondary parts of the heat ex-changer 61. A high flow passing through the heat exchanger 61 is moreturbulent than a low flow and turbulent flow provides a higher efficiencyof the heat transfer. Therefore, a lower hex temperature lift is needed for high freshwater flows. It follows that the bypass flow qB in the bypass feedcircuit section 57 must be at a reference temperature THEXref that is the reference hot water temperature TDHWref plus the reference temperature20 differential ^THEXref.

[0092] In step 1007, a heating power PBUH of the electric heater 77 is de-termined. If the known storage flow feed temperature TS is below THEXref, the electric heater 77 is needed to heat up the load flow qL. A reference heating power PBUHref of the electric heater 77 can be determined by: The electric heater 77 may have only three discrete heating power steps to choose, in which one, two or three power phases of the electric heater 77 may be activated. In order to select the needed number of activated 30 power phases, the smallest whole-numbered multiple of a third of the maximum heating power PBUHmax may be selected to run the electric heater 77 with a certain heating power PBUH, i.e.:Patentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025 The electric heater 77 is activated in step 1009 accordingly to providethe heating power PBUH. 5

[0093] The reference load flow qLref is then used as an input into a feed-forward control of the speed of the load circuit pump 17. However, the reference load flow qLref is compensated using a PI controller in a closed-loop control in step 1011. In step 1011, a PI reference load flow qLPIrefis determined to minimise a deviation of the hot water temperature TDHW 10 from the reference hot water temperature TDHWref. The PI reference load flow qLPIref is added to the feed-forward reference load flow qLref to yielda compensated reference load flow qLcompref that is used in step 1013 as a reference for controlling the speed of the load circuit pump 17 to ob- tain a load flow qL that equals the compensated reference load flow qLcompref. Thereby, the hydronic system 1 is most efficiently operated toproduce DHW using the storage flow alone as the load flow.

[94] Fig. 11 shows an example of the inventive method of transferringthermal energy from the heat pump 3 to produce DHW, wherein the hy- 20 dronic system 1 is operated in the second operation mode in which the heat pump flow and the storage flow mix to provide together simultane- ously the load flow. The DHW production method is very similar to thesituation described in Fig. 10. The feed-forward control part of the speed of the load circuit pump 17 is the same, but the closed-loop control part is different. There is also another operating variable of the hydronic sys- tem 1 needed, namely the load flow feed temperature TL.

[95] In step 1101, it is checked if the freshwater flow qFW exceeds a startthreshold value qstart for triggering a DHW demand event. It is also 30 checked in step 1101 if the freshwater flow has dropped below a stop threshold value qstop for ending a DHW demand event. The threshold val-Patentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025 ues qstart and qstop may be identical or differ from each other. If the fresh- water flow is below the threshold(s) qstart or qstop for having a DHW de-mand event, the DHW production stops at step 1103 by stopping the electric heater 77 (and the load circuit pump if there is currently no other 5 thermal energy load 5 demanding a load flow qL).

[96] If, however, there is a DHW demand event ongoing, the methodproceeds to step 1105 in which a reference temperature differential ^THEXref between the primary part and the secondary part of the heat ex- changer 61, a reference hot water temperature TDHWref, and a reference load flow qLref is determined. The reference load flow qLref depends on the freshwater flow qFW and a desirable thermal transfer element ratio RHEX for operating the heat exchanger 61 efficiently. A heat exchanger ratio RHEX about one is usually most efficient. The heat exchanger ratio15 RHEX may be a pre-defined constant or a pre-defined function of temper- atures and / or flows. Anyway, the reference load flow qLref is fully defined by the known freshwater flow qFW.

[97] The reference hot water temperature TDHWref is defined by the fol-20 lowing equation: ^^^^^^^ = −^^^ ∙ ^^^ + ^^^wherein ^^^and ^^^are pre-determined parameters of a linear rela- tionship between the reference hot water temperature TDHWref and thefreshwater flow qFW. The rationale is here to have a lower reference hotwater temperature TDHWref when a high freshwater flow qFW is detected.The aim is here to extend the maximum duration of a DHW demandevent for a given charging level of the thermal energy storage tank 23 when the freshwater flow qFW is high. A high freshwater flow qFW is mostlikely requested by an open shower tap or a bathtub tap. However, as30 showers and bathtubs nowadays use a thermostat to mix cold waterwith hot water, there will is no need for very hot water during a DHW de-mand event of a shower or bathtub. The lower the reference hot waterPatentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025 temperature TDHWref is, the longer the DHW demand event can be with- out the help of the heat pump flow. The relationship between refer- ence hot water temperature TDHWref and the freshwater flow qFW couldalso be given by a lookup table, wherein a fixed low reference hot wa-5 ter temperature TDHWref could be used for high freshwater flows qFW, e.g.at or above 66% of a maximum freshwater flow qFW, and another fixedhigher reference hot water temperature TDHWref could be used for low freshwater flows qFW, e.g. below 66% of the maximum freshwater flowqFW. 10

[98] The reference temperature differential ^THEXref between the pri-mary part and the secondary part of the heat exchanger 61 is definedby the following equation: ∆^^^^^^^ = −^∆^^^^ ∙ ^^^ + ^∆^^^^wherein ^∆^^^^and ^∆^^^^are pre-determined parameters of a linear relationship between the reference temperature differential ^THEXref andthe freshwater flow qFW. The rationale is here is to make a best guess forthe required temperature lift ^THEXref that the heat exchanger 61 must pro-vide. The heat exchanger 61 has a flow-dependent specific temperature20 lift, because the efficiency of the heat transfer from the primary part tothe secondary part of the heat exchanger 61 is dependent on the flowspassing through both the primary and secondary parts of the heat ex-changer 61. A high flow passing through the heat exchanger 61 is moreturbulent than a low flow and turbulent flow provides a higher efficiencyof the heat transfer. Therefore, a lower hex temperature lift is needed for high freshwater flows. It follows that the bypass flow qB in the bypass feedcircuit section 57 must be at a reference temperature THEXref that is the reference hot water temperature TDHWref plus the reference temperaturedifferential ^THEXref. 30

[99] In step 1107, a heating power PBUH of the electric heater 77 is de-termined. If the known storage flow feed temperature TS is below THEXref,Patentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025 the electric heater 77 is needed to heat up the load flow qL. A reference heating power PBUHref of the electric heater 77 can be determined by: The electric heater 77 may have only three discrete heating power steps 5 to choose, in which one, two or three power phases of the electric heater 77 may be activated. In order to select the needed number of activated power phases, the smallest whole-numbered multiple of a third of the maximum heating power PBUHmax may be selected to run the electric heater 77 with a certain heating power PBUH, i.e.: The electric heater 77 is activated in step 1109 accordingly to provide the heating power PBUH.

[100] The reference load flow qLref is then used as an input into a feed-forward control of the speed of the load circuit pump 17. The reference load flow qLref is used in step 1113 as a reference for controlling the speed of the load circuit pump 17 to obtain a load flow qL that equals the ref- erence load flow qLref.20

[0101] In step 1115, a reference load flow feed temperature TLref is deter-mined by:

[102] In step 1117, a PI reference load flow feed temperature TLPIref is de-termined in a closed-loop control by a PI controller that minimises a de- viation of the hot water temperature TDHW from the reference hot water temperature TDHWref. That PI reference load flow feed temperature TLPIref is added to the reference load flow feed temperature TLref to yield a com-pensated reference load flow feed temperature TLcompref that is used in30 step 1119 as a reference for controlling the speed of the heat pump cir-cuit pump 11 to obtain a load flow feed temperature TL that equals thecompensated reference load flow feed temperature TLcompref. Thereby,Patentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025 the hydronic system 1 is most efficiently operated to produce DHW using the storage flow and the heat pump flow mixed together as the load flow 5

[0103] Where, in the foregoing description, integers or elements are men-tioned which have known, obvious or foreseeable equivalents, then such 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 such10 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.

[104] The above embodiments are to be understood as illustrative ex-amples of the disclosure. It is to be understood that any feature de-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,20 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.

[105] In addition, "comprising" does not exclude other elements or steps,and "a" or "one" does not exclude a plural number. Furthermore, charac-30 teristics or steps which have been described with reference to one of the above exemplary embodiments may also be used in combination with other characteristics or steps of other exemplary embodiments de- scribed above. Method steps may be applied in any order or in parallelPatentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025 or 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. 5 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.

[106] List of reference numerals:10 1hydronic system3 heat pump5 thermal energy loads7 heat pump feed circuit section9 heat pump return circuit section11 heat pump circuit pump13 load feed circuit section15 load return circuit section17 load circuit pump20 19 storage feed circuit section20 control electronics21 storage return circuit section23 thermal energy storage tank25 storage valve arrangement27 feed connection point29 return connection point31 storage valve inlet33 storage valve storage port35 storage valve outlet30 37 integrated water circuit, IWC 39 indoor unit41 housing of indoor unit43 heat pump portPatentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 202543a heat pump return port43b heat pump feed port45 storage port45a storage return port5 45b storage feed port47 load port47a load return port47b load feed port49 DHW system10 51 hot water consumer53 cold DHW freshwater circuit section55 hot DHW freshwater circuit section57 bypass feed circuit section59 bypass return circuit section61 thermal transfer element63 bypass valve arrangement65 bypass feed connection point67 bypass return connection point69 coil20 71 flow sensor73 hot water temperature sensor75 DHW temperature sensor77 electric heater79 load flow feed temperature sensor80 pressure sensor81 safety valve82 expansion vessel83 air purge84 hot freshwater outlet port30 85 storage flow feed temperature sensor86 cold freshwater inlet port87 storage tank temperature sensor88 communication interfacePatentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 202589 heat pump flow feed temperature sensor90 communication91 heat pump return temperature sensor92 bypass return outlet port5 93 electronic hardware components of the indoor unitPSthermal 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 heating power of the electric heater qS storage flow qH heat pump flow qL load flow 15 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 TBLR load flow return temperature after mixing with the bypass flow TDHW hot water temperature of the freshwater flow 25Patentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025

Claims

Claims 1. A hydronic system (1) for transferring thermal energy from a heatpump (3) to produce domestic hot water, DHW, 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 DHW system (49) comprising a thermal transfer element (61)and an electric heater (77),10 - a load feed circuit section (13) for transporting a load flow (qL)that goes at least partly through the thermal transfer element(61), wherein the thermal transfer element (61) is arranged to thermally couple at least part of the load flow (qB) with a fresh- water flow (qFW); -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-20 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 at a feed connection point (27), wherein the electric heater (77) is arranged in the load feed circuit section (13) downstream of the feed connection point (27); -a load flow feed temperature sensor (79) for determining a loadflow feed temperature (TL) of the load flow (qL), wherein the30 load flow feed temperature sensor (79) is arranged at the loadfeed circuit section (13); -a load circuit pump (17) for driving the load flow (qL); andatentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025- control electronics (20),wherein the control electronics (20) is configured to control step-wise or gradually a heating power of the electric heater (77) and,depending on the operation mode of the hydronic system (1), to5 directly or indirectly control a speed of the load circuit pump (17)so that a deviation of the load flow (qL) from a reference load flow (qLref, qLcompref) is minimised, and / or to directly or indirectly control a speed of the heat pump circuit pump (11) so that a deviation ofthe load flow feed temperature (TL) from a reference load flow feed10 temperature (TLcompref) is minimised.

2. The hydronic system (1) of claim 1, wherein the control electronicsis configured, depending on the operation mode of the hydronic system (1), to directly or indirectly control the speed of the load cir-cuit pump (17) in a closed-loop control when the heat pump circuitpump (11) is switched off, so that a deviation of the load flow (qL)from the reference load flow (qLcompref) is minimised, orto set the speed of the load circuit pump (17) in a feed-forwardcontrol to a reference load flow (qLref) and to directly or indirectly20 control the speed of the heat pump circuit pump (11) in a closed-loop control so that a deviation of the load flow feed temperature (TL) from the reference load flow feed temperature (TLcompref) is min-imised.

3. The hydronic system (1) of any of the preceding claims, wherein thecontrol electronics is configured, in an operating mode of the hy-dronic system (1) in which the heat pump flow (qH) and the storage flow (qS) in the discharging direction from the thermal energy stor- age tank (23) are merged into the load flow (qL), to control the30 speed of the load circuit pump (17) to obtain a reference load flow(qLref) and to vary the heat pump flow (qH) by varying the speed ofthe heat pump circuit pump (11) until a deviation of the load flowatentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025feed temperature (TL) from the reference load flow feed tempera- ture (TLcompref) is minimised.

4. The hydronic system (1) of any of the preceding claims, wherein the5 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);- a storage port (45) for connecting the storage feed circuit sec-10 tion (19) with the thermal energy storage tank (23) or for con-necting a storage return circuit section (21) with a load returncircuit section (15); -a cold freshwater inlet port (86) for connecting the thermaltransfer element (61) with a freshwater supply; and -a hot freshwater outlet port (84) for connecting the thermaltransfer element (61) with a hot water consumer (51).

5. The hydronic system (1) of any of the preceding claims, wherein thecontrol electronics (20) is configured to operate the hydronic sys-20 tem (1) selectively in the following operation modes:a) a first operation mode in which only the heat pump flow (qH)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,30 d) a fourth operation mode in which only the storage flow (qS) inthe discharging direction provides the load flow (qL), ande) a fifth operation mode in which the heat pump flow (qH) is fullyused as the storage flow (qS) in the charging direction.atentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 20256. The hydronic system (1) of any of the preceding claims, furthercomprising a storage tank temperature sensor (87) being arranged5 within the thermal energy storage tank (23), wherein the controlelectronics (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 7. 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),- 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 difference20 between the heat pump flow feed temperature (TH) and theheat pump flow return temperature (THR).

8. A method of transferring thermal energy from a heat pump (3) toproduce domestic hot water, DHW, wherein the method comprises:- 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); -transporting, via a load feed circuit section (13), a load flow (qL)that goes at least partly through a thermal transfer element (61)30 of a DHW system (49), wherein the thermal transfer element (61) thermally couples at least part of the load flow (qB) with a fresh- water flow (qFW);atentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025- 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 5storage 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 circuit section (13) and the storage feed circuit section (19) are 10 connected at a feed connection point (27), wherein an electric heater (77) of the DHW system (49) is arranged in the load feed circuit section (13) downstream of the feed connection point (27); -determining a load flow feed temperature (TL) of the load flow(qL) by a load flow feed temperature sensor (79), wherein the load flow feed temperature sensor (79) is arranged at the load feed circuit section (13); -controlling stepwise or gradually a heating power of the electricheater (77); and20 - directly or indirectly controlling, depending on the operationmode of the hydronic system (1), a speed of the load circuit pump (17) so that a deviation of the load flow (qL) from a refer- ence load flow (qLref, qLcompref) is minimised, and / or 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 tem- perature (TLcompref) is minimised.

9. The method of claim 8, wherein, depending on the operationmode of the hydronic system (1), the heat pump circuit pump (11) 30 is switched off and the speed of the load circuit pump (17) is directly or indirectly controlled in a closed-loop control so that a deviation of the load flow (qL) from the reference load flow (qLcompref) is mini-mised, oratentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025the speed of the load circuit pump (17) is set in a feed-forward con-trol to a reference load flow (qLref) and the speed of the heat pumpcircuit pump (11) is directly or indirectly controlled in a closed-loop control so that a deviation of the load flow feed temperature (TL) 5from the reference load flow feed temperature (TLcompref) is mini-mised.

10. The method of claim 8 or 9, wherein, in an operating mode of thehydronic system (1) in which the heat pump flow (qH) and the stor- 10 age flow (qS) in the discharging direction from the thermal energy storage tank (23) are merged into the load flow (qL), the speed of the load circuit pump (17) is controlled to obtain the reference load flow (qLref) and to vary the heat pump flow (qH) by varying the speed of the heat pump circuit pump (11) until a deviation of the 15 load flow feed temperature (TL) from the reference load flow feed temperature (TLcompref) is minimised.atentanwälte Hemmer Lindfeld Frese GP 3828 WO, 10 / 10 / 2025

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