METHOD FOR OPERATING A HEAT GENERATOR

Abstract

A method for operating a heat generator (1, 12) comprises providing a set heat quantity Qsoll in a hydraulic circuit; acquiring a first actual temperature T1 of a heating circuit medium in the circuit; acquiring a second actual temperature T2 at a second time t2, determining a temperature rise ΔT as a difference between the second actual temperature T2 and the first actual temperature T1; acquiring a heat quantity Qzu introduced into the hydraulic circuit; determining a set temperature Tsoll of the heating circuit medium as a function of the set heat quantity Qsoll, the temperature rise ΔT and the introduced heat quantity Qzu; and operating the heat generator (1, 12) as a function of the determined set temperature Tsoll.

Description

The present invention relates to a method for operating a heat generator. In particular, a thermal mass of a hydraulic circuit is to be determined in order to provide a heat quantity required for defrosting a heat pump.

Modern heat pumps are distinguished by their high efficiency and can therefore be used particularly attractively for heating and/or cooling a building from ecological and economic points of view. Heating with environmental heat is climate-friendly on the one hand. On the other hand, many energy suppliers have been offering special heat pump tariffs for some years which are more attractive financially than a normal electricity tariff.

A generic heat pump has a circuit for a refrigerant. The refrigerant absorbs heat from the surroundings at an evaporator. Promoted by low outside temperatures from approximately 7 to 10° C. downward, a frost and/or ice layer can form at the evaporator of the heat pump which can impede the heat transfer at the evaporator and thus impair the efficiency of the heat pump. The ice layer then generally has to be removed by a defrosting process.

The German patent application DE 10 2018 102 670 A1 describes a heat pump 1 with an integrated buffer 3 which is shown schematically in FIG. 1. The heat pump system 10 shown in FIG. 1 consists in a known manner initially of a heat pump 1 and a heat sink 2. A heating circuit 2.1 with a plurality of heating bodies 2.3 and also a hot water store 2.2 are shown by way of example as heat sink 2 in FIG. 1.

In a first operating mode, designated as normal operation or heating operation, ambient heat is transferred from the heat pump 1 to the heat sink 2. In addition, the buffer 3 can be loaded with heat in a second operating mode, designated as buffer charging operation. The buffer 3 stores heat for defrosting the heat pump 1 and is therefore also designated as defrosting buffer. In a third operating mode, designated as defrosting operation, heat is transferred from the buffer 3 to the heat pump 1 for defrosting. In this case, the refrigerant circuit of the heat pump 1 is operated in reverse operation.

The heat pump system 10 has a heat exchanger 6 which operates as a condenser and through which a heating circuit medium flows. An outlet 3.2 of the buffer 3 is connected upstream of an inlet 6.2 of the heat exchanger 6 as viewed in the flow direction of the heating circuit medium. The heating circuit medium flows via a return line RL from the heat sink 2 or from the outlet 3.2 of the buffer 3 in the direction of the heat pump 1, which is indicated in FIG. 1 by an arrow pointing to the left. Correspondingly, the heating circuit medium flows via a feed line VL from the heat pump to the heat sink 2 or to the inlet 3.1 of the buffer 3, which is indicated in FIG. 1 by an arrow pointing to the right.

The heat pump system 10 shown in FIG. 1 consists of two system parts which are connected to one another, of which one is arranged in the building and one is arranged outside the building. Such a configuration is also designated as split heat pump. The two system parts are usually designated as outdoor unit (ODU) and indoor unit (IDU). The refrigerant circulates here between the outdoor unit ODU and the indoor unit IDU. In this embodiment, the buffer 3 is likewise arranged in the indoor unit IDU.

A heating circuit pump 7 for circulating the heating circuit medium is arranged between the inlet 6.2 of the heat exchanger 6 at the return line RL and the buffer 3. Furthermore, a temperature sensor 11 for measuring the return line temperature of the heating circuit medium is arranged in the return line RL.

In normal operation and in buffer charging operation, the refrigerant of the heat pump 1 absorbs ambient heat at a comparatively low temperature level via the outdoor unit ODU (the evaporator 5 with fan 8 is shown schematically in FIG. 1). The refrigerant is then transported via a compressor 9.1 to the heat exchanger 6 which operates as a condenser in order to release the heat there to the heating circuit medium. The refrigerant is then expanded in a known manner via an expansion valve 9.2 before it passes back to the evaporator 5.

In this case, the heating circuit medium first passes from the heat exchanger 6 via the feed line VL to a valve 4 which is designed, for example, as a 4/3-way valve. Depending on requirements, the heating circuit medium is then conducted to the heating circuit 2.1 with the heating bodies 2.3 and/or to the hot water store 2.2. The cooled heating circuit medium passes via the return line RL through the inlet 6.2 back into the heat exchanger 6 in order to close the circuit.

Since the evaporator of the outdoor unit ODU of such a heat pump system 10 tends to icing under corresponding weather conditions, it is occasionally necessary to defrost it. This is done by reversing the heat pump circuit, i.e. the evaporator 5 is now operated as a condenser and the heat exchanger 6 as an evaporator.

In this case, the heat required for the defrosting process is not withdrawn from the heat sink 2, but is provided by the buffer 3 provided for this purpose. The heat for the defrosting process can already be supplied to the buffer 3 during normal operation or alternatively only during buffer charging operation. In defrosting operation, the buffer 3 serves as a heat source for defrosting the evaporator 5 which then operates as a condenser.

In the described embodiment of the heat pump 1 with an outdoor unit ODU and an indoor unit IDU, the buffer 3 can be arranged very close to the heat exchanger 6, so that the amount of heat reserved for the defrosting process depends mainly on the volume of the buffer 3. In the case of a monoblock heat pump, however, the buffer 3 can be arranged comparatively far away from the heat exchanger 6, so that the volume of the lines between the buffer 3 and the heat exchanger 6 and the heat capacity of the lines themselves and of internals, such as, for example, sensors, valves and the like, which are in thermal exchange with the heating circuit medium, are not negligible.

The present invention is therefore based on the object of overcoming the problems known in the prior art and of specifying a method for operating a heat generator which is improved in relation to the prior art. Furthermore, a heating system which is improved in relation to the prior art is intended to be provided.

The object is achieved according to the invention by a method for operating a heat generator according to claim 1 and by a heating system according to claim 9. Preferred refinements of the present invention are the subject matter of the dependent claims, the appended drawings and the following description of exemplary embodiments.

A heating system according to the invention has a heat generator or a plurality of heat generators. A preferred refinement of the heating system comprises a heat pump as heat generator, wherein the heat pump can also be the load at the same time. In particular, the refrigerant circuit of the heat pump can be regarded as a load. The term load generally designates a heat sink. In the example of the heat pump as a load, the latter absorbs heat during a defrosting process and can therefore be operated as a load or heat sink.

In addition to the heat pump, the heating system can have at least one further heat generator. Examples of the further heat generator comprise a gas heating boiler, an oil boiler, a combined heat and power plant, a fuel cell, a solar thermal unit or other devices which can provide heat to the heating circuit medium. The further heat generator can also be designated as external heat generator since it is not a constituent part of the heat pump.

Furthermore, the heat pump can have an electrical heat generator such as, for example, a heating rod as an auxiliary heat generator, for example in the event that the heat pump cannot generate sufficient heat at low outside temperatures. A heat pump with an additional electrical heating element is described, for example, in DE 699 25 389 T2. If the outside temperature lies below a limit value, the additional electrical heating element is activated here in order to heat a feed air of the heat pump. In alternative embodiments, the auxiliary heat generator can directly heat the heating circuit medium and/or the refrigerant.

A heating system according to the invention preferably serves for heating a building. The heating system can have a heating circuit with a plurality of heating bodies and/or a floor heating system and/or a heat store as heat sink.

The method steps described below can preferably be carried out by a control device of the heating system which, in particular, controls the heat generator and/or other constituent parts of the heating system, for example one or more valves. Functions of the control device can be carried out completely or partially by a geographically remote device, for example a cloud or a server. For this purpose, a local control device of the heating system can be connected to a network, for example the Internet, via a suitable interface.

The at least one heat generator heats the fluid heating circuit medium which circulates in a hydraulic circuit. In particular, water can be used as heating circuit medium. The hydraulic circuit comprises lines for the heating circuit medium and connects a load, a buffer and the heat generator. The heating circuit medium can preferably also be supplied to the heating circuit via a valve.

Hydraulic lines which belong to the heat sink of the heating system are preferably not a constituent part of the hydraulic circuit under consideration. The heating circuit medium in the hydraulic circuit and the associated lines and thermal losses, etc. form a total thermal mass of the hydraulic circuit. This total thermal mass of the circuit can be determined by the present method, so that a predefined set heat quantity Qsoll can be introduced into the hydraulic circuit as efficiently as possible.

According to a preferred embodiment, the set heat quantity Qsoll can serve in particular to free an evaporator of a heat pump from tyres or ice during a defrosting operation. The set heat quantity Qsoll can be dependent in particular on the type and magnitude of the load of the heat pump and on an external temperature.

In order to determine the total thermal mass of the hydraulic circuit, firstly a temperature rise ΔT is determined as a difference between a first actual temperature T1 of the heating circuit medium at a first time t1 and a second actual temperature T2 of the heating circuit medium at a second time t2 which lies after the first time t1 by a predefined time period Δt. The temperature rise ΔT therefore results from the following equation:

$\begin{array}{cc}\Delta T=T2-T1& \left(1\right)\end{array}$

Furthermore, the heat quantity Qzu introduced into the hydraulic circuit by the heat generator during the time period Δt is acquired. This can take place, for example, by integrating the applied heating power over the time period Δt. In this case, it should be noted that more than one heat generator can be used to introduce heat into the hydraulic circuit. In this case, the sum of the integrated heating powers is used as introduced heat quantity Qzu in the following.

The sought total thermal mass of the hydraulic circuit results as a quotient of the introduced heat quantity Qzu and the temperature rise ΔT:

$\begin{array}{cc}{\left(m·c\right)}_{tot}=\mathrm{Qzu}/\Delta T& \left(2\right)\end{array}$

In this case, m denotes the total mass of the hydraulic circuit including heating circuit medium, lines and internals. Furthermore, c denotes the total heat capacity. The product (m·c)_tot denotes the total thermal mass of the hydraulic circuit.

So that the introduced heat quantity Qzu relates only to the hydraulic circuit, a heating circuit is separated from the supply with the heating circuit medium before carrying out the method. For this purpose, a controllable valve can be arranged in the heating system.

In the case of the heat pump system according to the prior art described at the outset, which is shown in FIG. 1, lines, containers and the like can be neglected when calculating the total thermal mass, since in this case substantially only the volume of the buffer 3 is decisive. In the case of comparatively long lines between the buffer 3 and the heat exchanger 6, however, the volume of the heating circuit medium contained therein and the heat capacity of the lines themselves also has to be taken into consideration. Since it is in particular difficult to determine the contribution of lines, internals and the like analytically, a relatively accurate measurement of the total thermal mass can be carried out by determining the temperature rise ΔT and comparing with the introduced heat quantity Qzu without having accurate knowledge of the system configuration. The total thermal mass of the entire circuit under consideration can therefore be determined by the method described here by measuring the temperature of the heating circuit medium.

Using the magnitudes determined above, a set temperature Tsoll of the heating circuit medium can be calculated as a function of the set heat quantity Qsoll on the basis of the following equation:

$\begin{array}{cc}\mathrm{Tsoll}=\mathrm{Qsoll}/{\left(m·c\right)}_{tot}+\mathrm{Tmin}& \left(3\right)\end{array}$

In this case, Tmin represents a predefined minimum temperature of the heating circuit medium.

The minimum temperature Tmin can be predefined in particular as a function of the operating mode. By way of example, the minimum temperature Tmin in the heating operation can be approximately 5° C. An increased minimum temperature Tmin of, for example, approximately 35° C. can be predefined for the defrosting operation. The minimum temperature Tmin for the defrosting operation can ensure in particular that the heat exchanger which operates as an evaporator in the defrosting operation does not freeze. In equation (3), the minimum temperature Tmin additionally serves as a zero level for determining the set temperature Tsoll of the heating circuit medium.

If the heat quantity required for defrosting is determined sufficiently exactly and then output during defrosting operation, precisely the zero level of the minimum temperature Tmin can be achieved in the most energy-efficient case after defrosting. The minimum temperature Tmin can be in particular a predefined value which is provided by the heat pump.

According to the method, the heat generator is operated as a function of the determined set temperature Tsoll. This can mean, for example, that the heat generator is operated with maximum heating power until the actual temperature of the heating circuit medium is equal to or greater than the set temperature Tsoll.

The actual temperature of the heating circuit medium is preferably measured between the buffer and the load. In other words, the temperature sensor is preferably arranged between the buffer and the load, that is to say in the return line. In the case of such an arrangement, the measured temperature is also designated as return line temperature.

According to a preferred embodiment, the load is a refrigerant circuit of a heat pump. This corresponds to the case described at the outset according to the prior art from FIG. 1, wherein the heat exchanger of the heat pump functions as an evaporator in reverse operation. In this case, the heat flows from the buffer via the return line to the heat pump. The heat from the heating circuit medium is released to the refrigerant via the condenser of the refrigerant circuit which is operated as an evaporator and can then heat the evaporator of the heat pump which is operated as a condenser during defrosting, with the result that ice or frost formed thereon defrosts.

In the case of a preferred defrosting method, the buffer is charged until a current actual temperature of the heating circuit medium is equal to or greater than the set temperature Tsoll. Since the actual temperature is preferably measured downstream of the buffer, that is to say in the return line, the stored temperature of the buffer can be inferred from the measured actual temperature. In preferred embodiments, at least one additional temperature sensor which measures the stored temperature can be arranged in the buffer.

A predefined state of charge of the buffer can be reached, for example, when the buffer or the heating circuit medium has reached the set temperature Tsoll at the temperature sensor.

As soon as the set temperature Tsoll is reached in the heating circuit medium, the circuit has the predefined set heat quantity Qsoll. Correspondingly, a defrosting operation for defrosting the evaporator of the heat pump can then be carried out.

The predefined set heat quantity Qsoll can preferably be determined as a function of an external temperature and a device type of the heat pump. The external temperature can be measured, for example, by an external temperature sensor or can be received by the control device of the heating system.

According to a preferred embodiment, the heat generator is operated with maximum heating power during the charging of the buffer until the actual temperature of the heating circuit medium is equal to or greater than the set temperature Tsoll. In this case, a heating power required to reach the set temperature Tsoll can preferably be determined in advance. If the required heating power is greater than the maximum heating power of the heat generator, a second heat generator for heating the heating circuit medium can additionally be operated.

The control device can preferably have an interface. An interface of the control device for outputting messages to a user or operator of the heating system can generally be understood to be a human-machine interface (HMI) via which the user or operator can preferably also make inputs. In a preferred embodiment, the HMI can be an application (“app”) on the mobile terminal of the user or operator. The cloud or the server can also be used as an interface. In particular, access to data in the cloud or on the server can thus be made possible via an Internet browser, wherein control interventions can also be made possible as a result.

The heat pump can preferably be operated in a first operating state as a heat generator for heating the building. The first operating state corresponds to a normal operation or heating operation of the heat pump. A user or operator can preferably put the heat pump into the first operating state via the interface. The heat pump can furthermore preferably be operated in a second operating state for defrosting the heat pump. The methods described here are carried out in particular when the heat pump is operated in the second operating state for defrosting the heat pump.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantageous refinements are described in more detail below on the basis of an exemplary embodiment which is illustrated in the drawings but to which the invention is not restricted.

In the drawings:

FIG. 1 illustrates a generic heat pump system.

FIG. 2 illustrates a heat pump system according to a first exemplary embodiment of the present invention.

FIG. 3 illustrates a heat pump system according to a second exemplary embodiment of the present invention.

FIG. 4 shows a diagram which describes a dependence of the defrost energy on the external temperature.

DETAILED DESCRIPTION OF THE INVENTION ON THE BASIS OF EXEMPLARY EMBODIMENTS

In the following description of a preferred embodiment of the present invention, identical reference signs denote identical or comparable components.

FIG. 2 illustrates an exemplary embodiment of a heating system 10 according to the invention for a building. The heating system 10 according to the invention is constructed in a similar manner to the known heat pump system 10 of FIG. 1. Identical reference signs denote identical or similar constituent parts here.

The heating system 10 of FIG. 2 comprises a heat pump 1 which is designed as a monoblock heat pump. The individual components of the heat pump 1 such as, for example, the evaporator 5, the refrigerant circuit and the heat exchanger 6 are arranged in the outdoor unit ODU of the heat pump 1 and are not shown in FIG. 2.

In contrast to the heat pump 1 of FIG. 1, in which the heat exchanger 6 is arranged in the indoor unit IDU, this component is located in the outdoor unit ODU in the case of the heat pump 1 of FIG. 2. Otherwise, the construction of the heating system 10 in FIG. 2 is substantially identical to FIG. 1.

The heating system 10 can be operated in particular in one of three operating modes. A first operating mode is the normal operation or heating operation, in which the heat pump 1 provides heat for the heat sink 2. A second operating mode is the buffer charging operation, in which the heat pump 1 provides heat for loading the buffer 3. A third operating mode is the defrosting operation, in which the heat pump 1 is operated in reverse operation for defrosting and absorbs the heat stored in the buffer 3.

According to a preferred embodiment, the charging of the buffer 3 can also be carried out in parallel with the heating operation. This can also be interpreted as a fourth operating mode, in which the heat pump 1 is preferably operated with maximum heating power.

In the case of typical arrangements of monoblock heat pumps outside buildings, the length of the feed line VL and the return line RL between the buffer 3 and the heat pump 1 can be approximately 2 meters to 25 meters, preferably approximately 6 meters to approximately 20 meters. It should be noted that the length of the lines is not shown true to scale in FIG. 2.

The capacity of the buffer 3, which preferably serves exclusively for storing heat for the defrosting process, is approximately 10 liters to approximately 20 liters. As a result of the total length of the lines between the buffer 3 and the heat exchanger 6 of the heat pump 1 of approximately 4 meters to approximately 50 meters, preferably of approximately 12 meters to approximately 40 meters, the thermal mass of the heating circuit medium located in the lines and the thermal mass of the lines and the internals themselves cannot be neglected compared with the volume of the buffer 3. In addition, the total thermal mass of the hydraulic circuit can also comprise heat losses which cannot be quantified precisely a priori.

In order to be able to carry out a defrosting process of the heat pump 1 as efficiently as possible, it is advantageous to know the set heat quantity Qsoll required for this purpose as precisely as possible. In addition, it is desirable to adjust the heat quantity introduced into the hydraulic circuit as precisely as possible to the set heat quantity Qsoll.

If the heating system 10 is operated in an operating state for defrosting the heat pump 1, firstly the hydraulic circuit including buffer 3 is loaded with the required set heat quantity Qsoll. For this purpose, in a first step, the heat sink 2 with the heating circuit 2.1 and the hot water store 2.2 can be separated from the hydraulic circuit via the valve 4.

In a next step, a first return line temperature T1 of the heating circuit medium is acquired at a first time t1. After a predefined time period Δt, a second return line temperature T2 of the heating circuit medium is acquired at a second time t2. The predefined time period Δt can be, for example, 60 to 600 seconds, preferably 60 to 180 seconds. Further preferably, the predefined time period Δt is approximately 120 seconds.

In order to acquire the return line temperatures, a return line temperature sensor 11 is arranged in the return line RL between the buffer 3 and the heat pump 1. In addition, further temperature sensors can be arranged in the heating system 10 (not shown), for example in the buffer 3 and/or in the feed line VL.

Subsequently, a temperature rise ΔT is calculated as a difference between the second return line temperature T2 and the first return line temperature T1 via equation (1). A set temperature Tsoll of the heating circuit medium can then be calculated via equations (2) and (3).

Since the losses and the total volume of heating circuit medium in the hydraulic circuit can change, the set temperature Tsoll is preferably determined again before each defrosting operation or at the beginning of each loading operation of the buffer 3. In particular, the heat losses of the hydraulic circuit can change, for example, as a function of the external temperature, with the result that the total thermal mass can therefore also change.

As the only heat generator, the heating system 10 of FIG. 2 comprises the heat pump 1 itself. That is to say that the heat pump 1 generates the heat during the charging of the buffer 3. In the defrosting operation, by contrast, the heat pump 1 is the load to which the heat is transferred from the buffer 3 or from the entire hydraulic circuit. Therefore, the heat pump 1 initially generates the heat during the charging of the buffer 3, which heat is used later for defrosting the heat pump 1.

In preferred embodiments, the heat pump 1 can have an additional auxiliary heat generator, for example an internal electrical heating rod (not shown), which can likewise be arranged in the outdoor unit ODU.

The operation of charging the buffer 3 is completed when the measured return line temperature is equal to or greater than the calculated set temperature Tsoll. For safety purposes, a limit value which lies above the set temperature Tsoll by 1 or 2 K can additionally be defined. As soon as the limit value is reached, the defrosting operation can be started.

FIG. 3 shows a second exemplary embodiment of a heating system 10 according to the invention. The heating system 10 of the second exemplary embodiment comprises, in addition to the heat pump 1, at least one second heat generator 12. The second heat generator 12 can be, for example, an external peak-load boiler which is operated with gas as fuel. Alternative examples of the second heat generator 12 comprise a gas heating boiler, an oil boiler, a combined heat and power plant, a fuel cell, a solar thermal unit or other devices which can provide heat to the heating medium. The further heat generator can also be designated as external heat generator since it is not an internal constituent part of the heat pump.

According to a preferred embodiment, the second heat generator 12 can be an electrical heat generator such as, for example, a heating rod or the like. In preferred embodiments, two additional heat generators 12 can also be provided in the heating system 10.

The second heat generator 12 can be used during the charging of the buffer 3 for providing additional heat in the event that the heat pump 1 alone cannot provide sufficient heat to reach the predefined set temperature Tsoll. During the defrosting operation, the second heat generator 12 can therefore support the charging of the buffer 3 with heat.

If, for example, the limit value or the set temperature Tsoll is not reached during the charging of the buffer 3, the second heat generator 12 can be actuated in order to provide additional heat. In this case, the second heat generator 12 can be operated, for example, with a predefined heating power, preferably with maximum heating power. According to a preferred embodiment, the heating power of the second heat generator 12 can be calculated or predefined as a function of a predefined charging duration of the buffer 3.

The second heat generator 12 is preferably operated with a minimum required heating power. In order to determine this heating power, a gradient of a temperature development of the buffer 3 can be predefined. The actually occurring gradient of the temperature can be measured during the charging of the buffer 3 and can be compared with the set gradient. If the measured gradient is lower than the predefined gradient, the second heat generator 12 can be correspondingly switched on.

The reaching of the limit value or of the set temperature Tsoll can be checked, for example, after the expiry of a predefined time period. Alternatively, the heating power required to reach the limit value or the set temperature Tsoll can be calculated in advance, so that this heating power can be applied for a calculated time period.

The heat quantity Qzu introduced during the time interval Δt can be determined by integrating the heating power. The applied heating power dQzu/dt can be known, for example, as a predefined value of the heat pump 1 and/or of the second heat generator 12. In this case, knowledge of the fluid used as heating circuit medium is not necessary.

Alternatively, the applied heating power dQzu/dt can be calculated on the basis of the mass of the heating circuit medium. For this purpose, the thermodynamic properties, such as, for example, the density and the heat capacity of the fluid used as heating circuit medium, have to be known. According to a preferred embodiment, water is used as heating circuit medium. The heating power can then be expressed by the following formula:

$\begin{array}{cc}d\mathrm{Qzu}/\mathrm{dt}=\epsilon \left(c·\mathrm{dm}/\mathrm{dt}·\Delta T^{*}\right)& \left(4\right)\end{array}$

The mass flow dm/dt can be determined with the aid of a flowmeter 13 which is arranged upstream of the second heat generator 12 in the feed line. The temperature difference ΔT* is determined as a difference between the return line temperature measured by the temperature sensor 11 and a temperature measured by a second temperature sensor 11 which is arranged upstream of the valve 4.

The heat power dQzu/dt introduced into the heating circuit medium can be calculated with respect to the total thermal mass on the basis of equation (4) via the heat capacity c and the measured mass flow dm/dt and the measured temperature difference ΔT* and an empirically determined coefficient ε.

FIG. 4 shows a diagram which describes a dependence of the defrost energy on the external temperature. The defrost energy is the heat quantity required for defrosting the evaporator 5 and corresponds to the setpoint heat quantity Qsoll. It can be seen on the basis of FIG. 4 that the defrost energy Qsoll required for defrosting becomes higher as the external temperature falls. For example, at an external temperature T1 a defrost energy Q1 is required which is higher than the defrost energy Q2 at an external temperature T2>T1.

FIG. 4 is merely an example of how the heat quantity can depend on the external temperature. The heat quantity can also be dependent, for example, on the air humidity, the installation location of the ODU, the wind speed etc. The functional relationship can therefore also be different from that in FIG. 4 and in particular does not have to be a straight line.

In general, the set heat quantity Qsoll can be dependent on the device type of the heat pump 1. In particular, the defrost energy or set heat quantity Qsoll can be dependent on the dimensions of the components of the heat pump, in particular of the evaporator 5, of the heat exchanger 6 and/or of the refrigerant circuit and the like. Furthermore, the set heat quantity Qsoll can be dependent on the heat capacity or on the total thermal mass of the refrigerant or of the refrigerant circuit.

The order of magnitude of the set heat quantity Qsoll can be in the range of a few megajoules, for example.

The features disclosed in the preceding description, the claims and the drawings can be significant both individually and in any desired combination for the realization of the invention in its various refinements.

Claims

1. A method for operating a heating system for heating and/or cooling a building with a heat pump which heats a fluid heating circuit medium which circulates in a hydraulic circuit, wherein the circuit has a load, a buffer and the heat pump which are connected to one another via lines, wherein the method comprises the following steps: providing a set heat quantity Qsoll in the hydraulic circuit;acquiring a first actual temperature T1 of the heating circuit medium at a first time t1;acquiring a second actual temperature T2 of the heating circuit medium at a second time t2 which lies after the first time t1 by a predefined time period Δt;determining a temperature rise ΔT as a difference between the second actual temperature T2 and the first actual temperature T1;acquiring a heat quantity Qzu introduced into the hydraulic circuit by the heat pump during the time period Δt;determining a set temperature Tsoll of the heating circuit medium as a function of the set heat quantity Qsoll, the temperature rise ΔT and the introduced heat quantity Qzu; andoperating the heat pump as a function of the determined set temperature Tsoll.

2. The method according to claim 1, wherein the actual temperature of the heating circuit medium is measured between the buffer and the load.

3. The method according to claim 1, wherein: the load is a refrigerant circuit of a heat pump; andthe heating circuit medium flows through a heat exchanger of the heat pump in order to transfer heat to the refrigerant.

4. The method according to claim 3, further comprising: carrying out a charging operation of the buffer until a current actual temperature of the heating circuit medium is equal to or greater than the set temperature Tsoll; andcarrying out a defrosting operation for defrosting an evaporator of the heat pump.

5. The method according to claim 3, wherein the predefined set heat quantity Qsoll is determined as a function of an external temperature and a device type of the heat pump.

6. The method according to claim 1, wherein the heat pump is operated with maximum heating power until the actual temperature of the heating circuit medium is equal to or greater than the set temperature Tsoll.

7. The method according to claim 6, further comprising: determining a heating power required to reach the set temperature Tsoll; andif the required heating power is greater than the maximum heating power of the heat pump, operating an additional heat generator for heating the heating circuit medium.

8. The method according to claim 1, further comprising: providing a minimum temperature Tmin for the heating circuit medium; anddetermining the set temperature Tsoll of the heating circuit medium as a function of the minimum temperature Tmin.

9. A heating system for heating and/or cooling a building, comprising: a hydraulic circuit with a load and a buffer which are connected to one another via lines, wherein a fluid heating circuit medium circulates in the hydraulic circuit;a heat pump which is arranged in the circuit and is configured to heat the heating circuit medium;a temperature sensor which is arranged in the hydraulic circuit and is configured to acquire an actual temperature of the heating circuit medium; anda control device for controlling the heat pump, wherein the control device is configured to: provide a set heat quantity Qsoll in the hydraulic circuit;acquire a first actual temperature T1 of the heating circuit medium at a first time t1;acquire a second actual temperature T2 of the heating circuit medium at a second time t2 which lies after the first time t1 by a predefined time period Δt;determine a temperature rise ΔT as a difference between the second actual temperature T2 and the first actual temperature T1;acquire a heat quantity Qzu introduced into the hydraulic circuit by the heat pump during the time period Δt;determine a set temperature Tsoll of the heating circuit medium as a function of the set heat quantity Qsoll, the temperature rise ΔT and the introduced heat quantity Qzu; andoperate the heat pump as a function of the determined set temperature Tsoll.

10. The heating system according to claim 9, wherein the temperature sensor is arranged between the buffer and the load.

11. The heating system according to claim 9, wherein: the load is a refrigerant circuit of a heat pump in the heating system; andthe heating circuit medium flows through a heat exchanger of the heat pump in order to transfer heat to the refrigerant.

12. The heating system according to claim 11, wherein the control device is further configured to: carry out a charging operation of the buffer until a current actual temperature of the heating circuit medium is equal to or greater than the set temperature Tsoll; andcarry out a defrosting operation for defrosting an evaporator of the heat pump.

13. The heating system according to claim 11, further comprising an external temperature sensor for measuring an external temperature, wherein the control device is configured to determine the predefined set heat quantity Qsoll as a function of the external temperature and a device type of the heat pump.

14. The heating system according to claim 9, wherein the control device is configured to operate the heat pump with maximum heating power until the actual temperature of the heating circuit medium is equal to or greater than the set temperature Tsoll.

15. The heating system according to claim 14, further comprising: an additional heat generator for heating the heating circuit medium, wherein the control device is further configured to:determine a heating power required to reach the set temperature Tsoll; andif the required heating power is greater than the maximum heating power of the heat pump, operate the additional heat generator for heating the heating circuit medium.

16. The heating system according to claim 9, wherein the control device is further configured to: provide a minimum temperature Tmin for the heating circuit medium; anddetermine the set temperature Tsoll of the heating circuit medium as a function of the minimum temperature Tmin.