Method of operating a bivalent heating system, control device, and bivalent heating system

Abstract

A method for operating a bivalent heating system (10, fig 1) involving determining 205 a first cost parameter for operating a heat pump (20) of the heating system to provide a predefined comparative heat quantity and a second cost parameter for operating a heat generator (25) of the heating system to provide the predefined comparative heat quantity. A first heat quantity provided by the heat pump over a first predefined time interval for heating a heat transfer medium (65) is determined 210, and a heat pump parameter is determined 225 on the basis of the first heat quantity of the heat pump. The determined heat pump parameter is compared 235 to a predefined first desired value and the first cost parameter of the heat pump is compared to the second cost parameter of the heat generator, wherein if the heat pump parameter undershoots the first desired value and if the first cost parameter is less than the second cost parameter, the heat pump is operated for a predefined second time interval.

Description

Title Method of operating a bivalent heating system, control device, and bivalent heating system The invention relates to a method of operating a bivalent heating system according to claim 1, to a control device according to claim 11, and to a bivalent heating system according to claim 12. Prior art EP 2 655 980 B1 describes a method for optimised adjustment of a heater control of a heating system and / or a water heating system with two series-connected and controllable heat generators for heating a space with a heating circuit. Disclosure of the invention It is the object of the invention to provide an improved method of operating a bivalent heating system, an improved control device, and an improved bivalent heating system. This object is achieved by means of a method according to claim 1, a control device according to claim 11, and a bivalent heating system according to claim 12. Advantageous embodiments are given in the dependent claims. It has been found that an improved method of operating a bivalent heating system with a heat pump and a heat generator can be provided by determining a first cost parameter for operating the heat pump to provide a predefined comparative heat quantity and a second cost parameter for operating the heat generator to provide the predefined comparative heat quantity. Furthermore, a first heat quantity provided by the heat pump over a first predefined time interval for heating a heat transfer medium is determined. A heat pump parameter can be determined on the basis of the first heat quantity. Within the scope of a first comparison, the determined heat pump parameter is compared to a predefined first desired value and the first cost parameter of the heat pump is compared to the second cost parameter of the heat generator. If the heat pump parameter undershoots the first desired value and if the first cost parameter is less than the second cost parameter, the heat pump is operated for a predefined second time interval. This embodiment has the advantage that by determining the first cost parameter and the second cost parameter and taking into account the two cost parameters, an opportunity for the objective technical comparison of the heat generator to the heat pump is provided in order to automatically adjust an operating behaviour of the heating system. In a further embodiment, the first cost parameter is determined on the basis of a first ratio of a first specific cost parameter to a first conversion efficiency of the heat pump. The first conversion efficiency of the heat pump is determined on the basis of at least one source temperature of a further heat transfer medium and a predefined desired supply temperature of the heat transfer medium. For example, the first conversion efficiency of the heat pump may be a coefficient of performance of the heat pump. The second cost parameter is determined on the basis of a second ratio of a second specific cost parameter to a second conversion efficiency of the second heat generator. The second conversion efficiency is determined on the basis of a return flow temperature of the heat transfer medium, at least the desired supply temperature. The second conversion efficiency is, for example, a third ratio of the heat transferred to the heat transfer medium to the supplied chemical energy of the fuel to the heat generator. The heating system can thereby be optimally controlled under the predetermined condition of the first desired value. In a further embodiment, a second heat quantity provided by the heat generator for heating the heat transfer medium over the first predefined time interval is determined. A total heat quantity expended by the heating system for heating the heat transfer medium over the first predefined time interval is determined on the basis of the first heat quantity and the second heat quantity, for example by summing up the first heat quantity and the second heat quantity. The heat pump parameter of the heat pump represents a proportion of the determined first heat quantity in the total heat quantity. This embodiment has the advantage that the first heat quantity corresponds to at least a minimum heat quantity produced by the heat pump so that the heating system has particularly low emissions, especially when the heat pump is operated with electrical power supplied without CO2. In a further embodiment, a first cost quantity of the heat pump for generating the first heat quantity is determined on the basis of the first heat quantity and the first cost parameter. Furthermore, a second heat quantity provided by the heat generator over the first predefined time interval for heating the heat transfer medium is determined. A fictitious cost quantity of the heat generator for generating the first heat quantity by means of the heat generator is determined on the basis of the first heat quantity and the second cost parameter. The heat pump parameter is determined as a fourth ratio of a first sum of the first cost quantity and the second cost quantity to a second sum of the second cost quantity and the fictitious cost quantity. The heat pump parameter represents a reduction of the first cost quantity of the heat pump in comparison to the heat generator. A minimum saving of the heating system in comparison to a mere operation of the heat generator can thereby be determined and maintained. This makes the heating system especially suitable for regions with particularly restrictive emission regulations. In a further embodiment, the heat pump heats the heat transfer medium to a first supply temperature. The first supply temperature of the heat transfer medium is determined on the outlet side of the heat pump. The first supply temperature is compared to the desired supply temperature in a second comparison. If the desired supply temperature is undershot by a predefined second desired value, the heat generator is connected to the heat pump to heat the heat transfer medium to the desired supply temperature. This ensures that the building is heated at the desired supply temperature and maintains a familiar level of comfort for the user of the heating system. In a further embodiment, if the heat pump parameter exceeds the first desired value and if the first cost parameter is greater than the second cost parameter in the first comparison, the heat generator is operated for a predefined third time interval. Preferably, the heat pump is deactivated. This avoids unfavourable operating conditions, in which, for example, the heat pump has a particularly low coefficient of performance and / or is not able to heat the heat transfer medium to the desired supply temperature. In a further embodiment, prior to performing the first comparison, it is checked whether the heat pump is operating or deactivated, the first comparison being performed only if the heat pump is operating. It is particularly advantageous if a third comparison is performed when the heat pump is deactivated. Within the scope of the third comparison, the determined heat pump parameter is compared to the predefined first desired value and the first cost parameter of the heat pump is compared to the second cost parameter. If the heat pump parameter undershoots the first desired value in the third comparison or if the first cost parameter is less than or equal to the second cost parameter in the third comparison, the heat pump is operated for the predefined second time interval. In a further embodiment, if the heat pump parameter exceeds the first desired value in the third comparison or if the first cost parameter is greater than the second cost parameter, the second heat generator is operated for a predefined third time interval. In a further embodiment, prior to the expiration of the first time interval and after the expiration of the second time interval, the first heat quantity is determined again. Furthermore, the heat pump parameter is re-determined on the basis of the re-determined first heat quantity. The heat pump parameter is thereby always determined in an automated manner on the basis of the current first heat quantity and / or cost quantity and the current total heat quantity and / or total cost quantity. An improved control device for a bivalent heating system having a heat pump and a heat generator can be provided by the control device comprising a control unit, a data memory connected to the control unit in terms of data technology, and a data interface connected to the control unit in terms of data technology. The data interface can be connected to the heat pump and the heat generator in terms of data technology. A predefined first desired value is stored in the data memory. The control unit is designed to determine a first cost parameter for operating the heat pump to provide a predefined comparative heat quantity and a second cost parameter for operating the heat generator to provide the predefined comparative heat quantity. The control unit is also designed to determine a first heat quantity provided by the heat pump within a first predefined time interval for heating the heat transfer medium. The control unit is furthermore designed to determine a heat pump parameter on the basis of the first heat quantity, wherein the control unit is designed to provide a first control signal at the interface for operating the heat pump for a predefined second time interval if the heat pump parameter undershoots the first desired value and if the first cost parameter is less than the second cost parameter. The control unit can thereby optimally control the heating system. An improved bivalent heating system may be provided by the heating system comprising a control device described above, a heat pump and a heat generator for heating a heat transfer medium to a predefined desired supply temperature, wherein the data interface is connected to the heat pump and the heat generator in terms of data technology, wherein the control unit is designed to use the first control signal provided at the interface to operate the heat pump for a predefined second time interval. As a result, the heating system has particularly low CO2 emissions. The operating costs for the heating system are also particularly low. The invention is explained in more detail below with reference to figures. The figures show: Fig. 1 a schematic illustration of a bivalent heating system; Fig. 2 a flow chart of a method according to a first embodiment for operating the bivalent heating system shown in Fig. 1; Fig. 3 a two-dimensional map of a first cost parameter AP1; and Fig. 4 a two-dimensional map of a second cost parameter AP2. Fig. 1 show a schematic illustration of a bivalent heating system 10. The bivalent heating system 10 comprises a control device 15, a heat pump 20, a heat generator 25, at least a first heat exchanger 30, a circuit 35, and a feed pump 60. Additionally, the heating system 10 may comprise a second heat exchanger 40. The circuit 35 may also be referred to as a heating circuit. The heat pump 20, the heat generator 25, a first primary side 50 of the first heat exchanger 30, preferably a second primary side 55 of the second heat exchanger 40, and the feed pump 60 are incorporated into the circuit 35 and thereby fluidly connected to one another by means of a heat transfer medium 65 circulating in the circuit 35. For example, the heat transfer medium 65 may be water and may be conveyed by means of the feed pump 60 of the heating system 10 in the circuit 35. For example, the heat pump 20 and the heat generator 25 are fluidly connected in series in relation to a conveyance direction of the heat transfer medium 65, wherein, by way of example, the heat pump 20 in Fig. 1 is connected upstream of the heat generator 25 in relation to the conveyance direction of the heat transfer medium 65. Fluidly, the first primary side 50 of the first heat exchanger 30 and preferably the second primary side 55 of the second heat exchanger are connected downstream of the heat generator 25. In this case, the feed pump 60 can be arranged on the outlet side of the heat generator 25 in relation to the conveyance direction of the heat transfer medium 65 in the circuit 35. The feed pump 60 is designed to convey the heat transfer medium 65 from the heat generator 25 to the first primary side 50. For example, the first heat exchanger 30 may be arranged as a radiator in a room of a building. The second heat exchanger 40 may be arranged in a further room of the building and may likewise be designed as a radiator, for example. For example, the heat pump 20 may be designed as an air-to-water heat pump. It is also conceivable for the heat pump to be a brine-water heat pump. For example, the heat generator 25 may be designed as a condensing gas boiler or a condensing oil boiler. It is noted that the heating system 10 shown in Fig. 1 has an exemplary design. By way of example, the heating system in Fig. 1 is simplified in comparison to domestic heating systems so that a method of operating the bivalent heating system 10 illustrated in Fig. 2 can be illustrated clearly and simply. The heating system 10 may also be designed differently than shown in Fig. 1. Of course, the bivalent heating system 10 may comprise further components, such as a household water reservoir, or a different number of heat exchangers 30, 40. A different fluidic connection of the components, especially the heat exchangers 30, 40 and / or the heat pump 20 to the heat generator 25, is also possible. For example, the first and second heat exchangers 30, 40 may also be fluidly connected to one another in parallel. The control device 15 comprises a control unit 85, a data memory 90, and a data interface 95. The data interface 95 is connected to the heat pump 20 in terms of data technology by means of a first data link 100. Via a second data link 105, the data interface 95 is connected to the heat generator 25 in terms of data technology. Additionally, a first temperature sensor 110 of the bivalent heating system 10 may be arranged on the outlet side of the heat pump 20 in relation to the conveyance direction of the heat pump medium 65. The first temperature sensor 110 is connected to the data interface 95 in terms of data technology by means of a third data link 115. Furthermore, a second temperature sensor 120 of the bivalent heating system 10 may be arranged on the outlet side of the second heat generator 25 in relation to the conveyance direction of the heat transfer medium 65 and connected to the data interface 95 in terms of data technology by means of a fourth data link 125. For example, a fifth data link 130 may connect the data interface 95 to an input device 135. The input device 135 may, for example, comprise a touch-sensitive monitor and / or control panel. The input device 135 may also comprise a central computer or be designed as a central computer. Furthermore, the bivalent heating system 10 may comprise a source temperature sensor 136 that is connected to the data interface 95 in terms of data technology by means of a sixth data link 137. For example, the source temperature sensor 136 may be designed as an outside temperature sensor. Additionally, a return flow temperature sensor 140 may be arranged on the inlet side of the heat pump 20, wherein the return flow temperature sensor 140 is connected to the data interface 95 in terms of data technology via a seventh data link 145. Additionally, the heating system 10 may comprise further sensors (not shown) that are connected in terms of data technology to the data interface 95. Fig. 2 shows a flow chart of a method of operating the heating system 10 shown in Fig. 1. Fig. 2 symbolically illustrates the fulfilment of a condition by means of a check mark and the non-fulfilment of a condition by means of a check mark. The condition is shown in Fig. 2 by means of a diamond. The method, explained below, of operating the bivalent heating system 10 shown in Fig. 1 may, for example, be stored as a computer program in the data memory 90 of the control device 15. Furthermore, a first desired value, a first specific cost parameter, a first conversion efficiency, a second specific cost parameter, a second conversion efficiency, and a second desired value are stored in the data memory 90. The first conversion efficiency and / or the second conversion efficiency may be designed as an algorithm and / or a computer program and / or a tabular mapping and / or a map. Furthermore, the desired supply temperature Ts of the heat transfer medium 65 may be stored in the data memory 90. The first specific cost parameter, the second specific cost parameter, and / or the desired supply temperature Ts may, for example, be stored in the data memory 90 by input via the input device 135 by a user of the heating system 10. When performing the first method step 205, the control unit 85 can advantageously retrieve the first and / or second specific cost parameters from the master computer via the data interface 95 and the fifth data link 130. In a first method step 205, the source temperature Ta is determined. In the embodiment, the source temperature sensor 136, by way of example, measures the source temperature Ta of a heat source medium supplied to the heat pump 20. For example, the heat source medium may be an outside air in the case of an air-to-water heat pump or brine in the case of a brine-water heat pump. The source temperature sensor 136 provides a source temperature signal corresponding to the source temperature Ta to the data interface 95, which provides the source temperature signal to the control unit 85. Furthermore, a return flow temperature Tr of the heat transfer medium 65 at which the heat transfer medium 65 flows back after flowing through the primary side 50, 55 of the heat exchangers 30, 40 is determined. In the embodiment, the return flow temperature sensor 140 on the inlet side of the heat pump 20, by way of example, measures the return flow temperature Tr and provides a return flow temperature signal corresponding to the return flow temperature Tr to the data interface 95, which provides the return flow temperature signal to the control unit 85. Moreover, a first supply temperature Tai of the heat transfer medium 65 is determined on the outlet side of the heat pump 20. The determination may be made, for example, by the first temperature sensor 110 measuring the first supply temperature Tai on the outlet side of the heat pump 20. The first temperature sensor 110 provides a first temperature signal corresponding to the first supply temperature Tai via the third data link 115 of the data interface 95, which passes the third data signal to the control unit 85. Fig. 3 shows a two-dimensional map of a first conversion efficiency for calculating the first cost parameter AP1, plotted over the source temperature Ta. A first cost parameter AP1 of the heat pump 20 for providing a predefined comparative heat quantity, for example 1 MJ, is substantially dependent on the source temperature Ta, the desired supply temperature Ts, and a speed of a compressor of the heat pump 20. The exemplary first curve of the first conversion efficiency for calculating the first cost parameter AP1 is shown in Fig. 3 and plotted over the source temperature Ta. In the first method step 205, the control unit 85 determines the first conversion efficiency of the heat pump 20 on the basis of the determined source temperature Ta, the predefined desired feed temperature Ts, the compressor speed, for example. The first cost parameter AP1 is a first ratio of the first specific cost parameter to the first conversion efficiency of the heat pump 20. The first specific cost parameter for determining the first cost parameter AP1 represents a technical effort and / or an environmental impact and / or a CO2 emission of the heat pump 20 as a result of the electrical energy required for operating the heat pump to provide the predefined comparative heat quantity. For example, the first specific cost parameter may, for example, have the unit “mass CO2 / kWh”. In the first method step 205, on the basis of the predefined first specific cost parameter and the first conversion efficiency, the control unit 85 determines the first cost parameter AP1 for providing the predefined comparative heat quantity. Furthermore, several graphs marked with different lines are shown, by way of example, in Fig. 3 and correspond to a respective associated desired supply temperature Ts. When determining the first conversion efficiency, the control unit 85 preferably assumes that the compressor is operated at an optimal speed associated with the desired supply temperature Ts and the source temperature Ta. Furthermore, a second supply temperature Ta2 of the heat transfer medium 65 is determined on the outlet side of the heat generator 25. This may be done, for example, by measuring by means of the second temperature sensor 120, which provides a second supply temperature signal corresponding to the second supply temperature Ta2 via the fourth data link 125 to the data interface 95, which passes it to the control unit 85. Fig. 4 shows a two-dimensional map of a second conversion efficiency for determining the cost parameter AP2, plotted over the return flow temperature Tai and the desired supply temperature Ts. The second conversion efficiency of the heat generator 25 for providing the predefined comparative heat quantity is dependent on the return flow temperature Tai and the desired supply temperature Ts. The second cost parameter AP2 is a second ratio of a second specific cost parameter to the second conversion efficiency of the heat generator 25. In the first method step 205, the control unit 85 determines the second conversion efficiency on the basis of the determined desired supply temperature Ts, the first supply temperature Tai. The second specific cost parameter thus represents a technical effort and / or an environmental impact and / or a CO2 emission of the heat generator 25 as a result of the electrical energy and primary energy required for operating the heat generator 25 to provide the predefined comparative heat quantity. In doing so, for example, necessary technical resources for being able to operate the heat generator 25 to provide the predefined comparative heat quantity and for being able to connect it in the building to a supply network, for example, can be taken into account when determining the second specific cost parameter. For example, the second specific cost parameter may, for example, have the unit “mass CO2 / kWh”. In the first method step 205, on the basis of the predefined second specific cost parameter and the second conversion efficiency, the control unit 85 determines the second cost parameter AP2 for providing the predefined comparative heat quantity. Furthermore, several graphs marked with different lines are shown, by way of example, in Fig. 4 and correspond to a respective associated desired supply temperature Ts. When determining the second conversion efficiency, the control unit 85 assumes that a fan of the heat generator 25 is operated at the optimal speed associated with the desired supply temperature Ts and the second temperature difference between the desired supply temperature Ts and the return flow temperature Tr. During activated operation of the heat pump 20 and the feed pump 60, the heat transfer medium 65 flows through the heat pump 20. In doing so, the heat transfer medium 65 is heated to a first supply temperature Tai from the return flow temperature Tr at which the heat transfer medium 65 enters the heat pump 20. For example, a second temperature difference between the return flow temperature Tr and the first supply temperature Tai may be 10 to 30°C. When the heat pump 20 is deactivated and the feed pump 60 is activated, the first supply temperature Tai corresponds to the return flow temperature Tr. In a second method step 210, the control unit 85 determines a first heat quantity that the heat pump 20 has provided over an unexpired predefined first time interval, for example an hour, to heat the heat transfer medium 65. For example, the first heat quantity may be determined on the basis of an integration of the first temperature difference between the first supply temperature Tai on the outlet side of the heat pump 20 and the return flow temperature Tr, a delivery rate over the first time interval of the feed pump 60, and a heat capacity of the heat transfer medium 65. In a third method step 215 following the second method step 210, a second heat quantity of the heat generator 25 for heating the heat transfer medium 65 from the first supply temperature Tai, which, when the heat pump 20 is deactivated, corresponds to the return flow temperature Tr, to a second supply temperature Ta2 over the first time interval is determined. For example, the second heat quantity may be determined on the basis of an integration of the second temperature difference between the second supply temperature Ta2 and the first supply temperature Tai, the delivery rate over the first time interval of the feed pump 60, and the heat capacity of the heat transfer medium 65. In a fourth method step 220 following the third method step 215, a total heat quantity is determined by the control unit 85. By way of example, the total heat quantity is a sum of the first heat quantity (determined in the second method step 210) and the second heat quantity (determined in the third method step 215). The total heat quantity reflects the heat expended by the heating system 10 over the first time interval to heat the heat transfer medium 65 from the return flow temperature Tr to the second supply temperature Ta2. In a fifth method step 225 following the fourth method step 220, the control unit 85 determines a heat pump parameter. The heat pump parameter is a proportion of the first heat quantity in the total heat quantity. In other words, the heat pump parameter is a quotient of the first heat quantity in the numerator and the total heat quantity in the denominator. For example, the heat pump parameter may have values between 0 and 1. In a sixth method step 230 following the fifth method step 225, the control unit 85 checks whether the heat pump 20 is activated. If this is the case, the control unit 85 continues with a seventh method step 235. The heat generator 25 may be activated or deactivated. If the heat pump 20 is deactivated, the control unit 85 continues with an eighth method step 240. When the heat pump 20 is deactivated, the heat transfer medium 65 in Fig. 1 flows through the heat pump 20, wherein the return flow temperature Tr substantially corresponds to the first supply temperature Tai. In the seventh method step 235, as part of a first comparison, the control unit 85 compares the determined heat pump parameter to the first desired value stored in the data memory 90. For example, the first desired value may have a value from 0 exclusive to 1 exclusive, for example from 0.4 inclusive to 0.8 inclusive. The first desired value may also be predefined. In addition, the control unit 85 compares the first cost parameter AP1 to the second cost parameter AP2 within the scope of the first comparison. The control unit 85 continues with a ninth method step 245 if the heat pump parameter is greater than or equal to the first desired value and, additionally, the first cost parameter AP1 is greater than or equal to the second cost parameter AP2. If either the heat pump parameter is less than the first desired value or the first cost parameter AP1 is less than the second cost parameter AP2, the control unit 85 continues with a tenth method step 250. In the ninth method step 245, by means of a first control signal provided to the data interface 95, the control unit 85 deactivates the heat pump 20 and in turn activates, for a third time interval, the heat generator 25 by means of a second control signal provided to the data interface 95. The third time interval may be 5 minutes to 20 minutes. In the ninth method step 245, the heating of the heat transfer medium 65 is thus switched from the heat pump 20 to the heat generator 25. In the ninth method step 245, the heating of the heat transfer medium 65 is carried out exclusively via the heat generator 25. At the heat exchanger 30, 40, the heat transfer medium 65 transfers at least a portion of the heat to the secondary side 70, 80, wherein the secondary side 70, 80 in the embodiment respectively heats the space of the building. Cooled, the heat transfer medium 65 is recirculated from the second heat exchanger 40 to the heat pump 20. There, the cooled heat transfer medium 65 enters the heat pump 20 again at the return flow temperature Tr. In the ninth method step 245, the control unit 85 uses the second temperature signal of the second supply temperature Ta2 provided by the second temperature sensor 120 and the determined return flow temperature Tr to control the heat generator 25 in the closed loop and to heat the heat transfer medium 65 to the desired supply temperature Ts. In the eighth method step 240, the control unit 85 performs a second comparison. The control unit 85 compares the heat pump parameter (determined in the fifth method step 225) to the first desired value. Furthermore, in the eighth method step 240, the control unit 85 compares the first cost parameter AP1 to the second cost parameter AP2 (determined in the first method step 205). If the heat pump parameter is less than the first desired value or if the first cost parameter AP1 is less than the second cost parameter AP2, the control unit 85 continues with the tenth method step 250. If the heat pump parameter is greater than or equal to the first desired value or if the first cost parameter AP1 is greater than or equal to the second cost parameter AP2, the control unit 85 continues with an eleventh method step 255. In the tenth method step 250, by means of the first control signal, the control unit 85 activates or keeps the heat pump 20 in operation for a predefined second time interval. The heat pump 20 heats the heat transfer medium 65 flowing at the return flow temperature Tr to the first supply temperature Tai. The second time interval may, for example, be five minutes to twenty minutes. The operation of the heat pump 20 for at least the second time interval ensures that a brief alternating operation between the heat pump 20 and the heat generator 25 with fast switching between the heat pump 20 and the heat generator 25 is avoided. In the eleventh method step 255, the control unit 85 determines how long the heat generator 25 has been in operation and compares this to the predefined third time interval. The control unit 85 leaves the heat generator 25 in operation until the third time interval has expired. In a twelfth method step 260 following the tenth method step 250, the first supply temperature Tai of the heat transfer medium 65 is determined again. In a thirteenth method step 265 following the twelfth method step 260, the control unit 85 compares the determined first supply temperature Tai to the predefined desired supply temperature Ts. If the determined first supply temperature Tai undershoots the predefined desired supply temperature Ts by the predefined second desired value (for example 3°C), the control unit 85 continues with a fourteenth method step 270. If the first supply temperature Tai deviates by less than the second desired value from the predefined desired supply temperature Ts, the control unit 85 continues with a fifteenth method step 275. In the fifteenth method step 275, the heat pump 20 remains activated and heats the heat transfer medium 65 to the predefined desired supply temperature Ts. In this state, the control unit 85 deactivates the heat generator 25. The heat transfer medium 65 flows through the heat generator 25 and reaches the first and / or second primary side 50, 55 of the heat exchangers 30, 40 at the desired supply temperature in the warm state. In the embodiment, in a closed loop method, the control unit 85 controls the heating of the heat transfer medium 65, taking into account the return flow temperature Tr at which the heat transfer medium 65 flows back from the second heat exchanger 40, and the first supply temperature Tai. In the fourteenth method step 270, in addition to the heat pump 20, the control unit 85 activates the heat generator 25 by means of the second control signal, which is transmitted from the control unit 85 to the heat generator 25 via the data interface 95 and the second data link 105. Activation of the heat generator 25 is preferably carried out for the third time interval, wherein the second time interval and the third time interval are preferably selected to be of identical lengths and may end simultaneously. The third time interval may also be shorter or longer than the second time interval. The heat transfer medium 65 heated to the first supply temperature Tai flows into the heat generator 25 at the first supply temperature Tai. In the activated state, the heat generator 25 heats the heat transfer medium 65 from the first supply temperature Tai to the desired supply temperature Ts. In doing so, the control unit 85 may use the first temperature sensor 110 and the second temperature sensor 120 to control the heat generator 25 and the heat pump 20 in a closed loop. As already described above, the feed pump 60 then conveys the heat transfer medium 65 heated to the desired supply temperature Ts to the heat exchanger 30, 40 so that the heat transfer medium 65 also flows in the circuit 35 in the fourteenth method step 270. After the ninth and eleventh method steps 245, 255 as well as the fourteenth and fifteenth method steps 270, 275, the control unit 85 continues with the first method step 205. In repeating the second method step 210, the first heat quantity provided by the heat pump 20 to heat the heat transfer medium 65 is re-determined. The further method steps 215 to 275 are performed on the basis of the re-determined first heat quantity. In repeating the third method step 215, the second heat quantity provided by the heat generator 25 as a whole within the first predefined time interval is recalculated and the further method steps 220 to 275 are repeated on the basis of the second heat quantity. The bivalent heating system 10 is especially suitable for the flexible use of the heat pump 20 and of the heat generator 25. The bivalent heating system 10 furthermore has the advantage that two different energy carriers are available for supplying the primary energy for the heat pump 20 and the heat generator 25. By means of the method described above, an optimisation in the operating mode can thus be carried out as a function of the properties of the energy carrier in order to cause minimum cost quantities, for example of CO2. Especially, unfavourable conversion efficiency ranges of the heat pump 20 or of the heat generator 25 may, for example, be avoided by the method described above. The control behaviour of the control device can especially be easily influenced by the corresponding determination of the first and / or second specific cost parameters. A second embodiment of a method of operating the heating system 10 shown in Fig. 1 is designed substantially identical to the method illustrated in Fig. 2. In the following, only the differences of the method described in Fig. 2 are discussed. In the second embodiment, in the third method step 215, the control unit 85 determines a first cost quantity for generating the first heat quantity on the basis of the predefined first cost parameter AP1 and the determined first heat quantity. Furthermore, in the third method step 215, the control unit 85 determines a second cost quantity for generating the second heat quantity on the basis of the predefined second cost parameter AP2 and the determined second heat quantity. The first and / or second cost quantities may correspond to a primary energy requirement and / or a CO2 emission of the heat pump 20 and / or of the heat generator 25 on the basis of the primary energy requirement. In the fourth method step 220, the control unit 85 determines a fictitious cost quantity of the heat generator 25 for generating the first heat quantity by the heat generator 25 on the basis of the determined first heat quantity and the predefined second cost parameter AP2. In other words, the fictitious cost quantity corresponds to the consumption of the second cost quantity that would have been necessary to generate the first heat quantity by means of the heat generator 25. By means of the second specific cost parameter, especially an operating behaviour of the heat generator 25 for generating the first heat quantity is represented. In the fifth method step 225, the control unit 85 determines the heat pump parameter as a fourth ratio of a first sum of the first cost quantity and the second cost quantity to a second sum of the second cost quantity and the fictitious cost quantity (in mathematical notation: heat pump parameter = (first cost quantity + second cost quantity) I (second cost quantity + fictitious cost quantity)). For example, the heat pump parameter reflects a saving of, for example, CO2 by operating the bivalent heating system 10 in operation in comparison to the sole operation of the second heat generator 25. The first desired value may be selected such that the first desired value represents a desired target reduction, for example a CO2 reduction, of the bivalent heating system 10 in comparison to a mere operation of the heat generator 25. The further method steps are carried out as described above. The alternative embodiment ensures that on the one hand, a reduction goal (for example, a predefined CO2 saving) is ensured by means of the heating system 10. On the one hand, this ensures cost-efficient operation and, on the other hand, possible requirements that the user desires can be met in a particularly simple and automated manner. In addition, the control unit 85 can be designed as a model-predictive controller in order to enable optimal use of the primary energies within the first time interval.

Claims

1. Method of operating a bivalent heating system (10) having a heat pump (20) and a heat generator (25),wherein a first cost parameter (AP1) for operating the heat pump (20) to provide a predefined comparative heat quantity and a second cost parameter (AP2) for operating the heat generator (25) to provide the predefined comparative heat quantity are determined, wherein a first heat quantity provided by the heat pump (20) over a first predefined time interval for heating a heat transfer medium (65) is determined, wherein a heat pump parameter is determined on the basis of the first heat quantity of the heat pump (20), wherein, within the scope of a first comparison, the determined heat pump parameter is compared to a predefined first desired value and the first cost parameter (AP1) of the heat pump is compared to the second cost parameter (AP2) of the heat generator (25), wherein if the heat pump parameter undershoots the first desired value and if the first cost parameter (AP1) is less than the second cost parameter (AP2), the heat pump (20) is operated for a predefined second time interval,wherein a first cost quantity of the heat pump (20) for generating the first heat quantity is determined on the basis of the first heat quantity and the first cost parameter (AP1), wherein a second heat quantity provided by the heat generator (25) over the first predefined time interval for heating the heat transfer medium (65) is determined, wherein a fictitious cost quantity of the heat generator (25) for generating the first heat quantity by the heat generator (25) is determined on the basis of the first heat quantity and the second cost parameter (AP2), wherein the heat pump parameter is determined as a fourth ratio of a first sum of the first cost quantity and the second cost quantity to a second sum of the second cost quantity and the fictitious cost quantity, wherein the heat pump parameter represents a reduction of the first cost quantity of the heat pump (20) in comparison to the heat generator (25).

2. Method according to Claim 1, wherein the first cost parameter (AP1) is determined on the basis of a first ratio of a first specific cost parameter to a first conversion efficiency of the heat pump (20), wherein the first conversion parameter is determined on the basis of at least one source temperature (Ta) and a predefined desired supply temperature (Ts) of the heat transfer medium (65),12 09 24wherein the second cost parameter (AP2) is determined on the basis of a second ratio of a second specific cost parameter to a second conversion efficiency of the heat generator (25), wherein the second conversion efficiency is determined on the basis of at least one return flow temperature (Tr) and at least the desired supply temperature (Ts).

3. Method according to Claim 1 or 2, wherein a second heat quantity provided by the heat generator (25) over the first predefined time interval for heating the heat transfer medium (65) is determined, wherein a total heat quantity expended by the heating system (10) over the first predefined time interval for heating the heat transfer medium (65) is determined on the basis of the first heat quantity and the second heat quantity, wherein the heat pump parameter of the heat pump (20) represents a proportion of the determined first heat quantity in the total heat quantity.

4. Method according to one of the preceding claims, wherein the heat pump (20) heats the heat transfer medium (65) to a first supply temperature (Tai), wherein the first supply temperature (Tai) of the heat transfer medium (65) is determined on the outlet side of the heat pump (20), wherein the first supply temperature (Tai) is compared to the desired supply temperature (Ts) in a second comparison, wherein if the desired supply temperature (Ts) is undershot by a predefined second desired value, the heat generator (25) is connected to the heat pump (20) in order to heat the heat transfer medium (65) to the desired supply temperature (Ts).

5. Method according to one of the preceding claims, wherein if the heat pump parameter exceeds the first desired value and if the first cost parameter (AP1) is greater than the second cost parameter (AP2) in the first comparison, the heat generator (25) is operated for a predefined third time interval and the heat pump (20) is preferably deactivated.

6. Method according to one of the preceding claims, wherein prior to performing the first comparison, it is checked whether the heat pump (20) is operating or deactivated, the first comparison being performed only if the heat pump (20) is operating.12 09 247. Method according to Claim 6,wherein a third comparison is performed when the heat pump (20) is deactivated, wherein, within the scope of the third comparison, the determined heat pump parameter is compared to the predefined first desired value and the first cost parameter (AP1) of the heat pump (20) is compared to the second cost parameter (AP2), wherein if the heat pump parameter undershoots the first desired value in the third comparison or if the first cost parameter (AP1) in the third comparison is less than or equal to the second cost parameter (AP2), the heat pump (20) is operated for the predefined second time interval.

8. Method according to Claim 7, wherein if the heat pump parameter exceeds the first desired value in the third comparison or if the first cost parameter (AP1) is greater than the second cost parameter (AP2), the heat generator (25) is operated for a predefined third time interval.

9. Method according to one of the preceding claims, wherein prior to the expiration of the first time interval and after the expiration of the second time interval, the first heat quantity is determined again and the heat pump parameter is determined again on the basis of the re-determined first heat quantity.

10. Control device (15) for a bivalent heating system (10) having a heat pump (20) and a heat generator (25), wherein the control device (15) comprises a control unit (85), a data memory (90) connected to the control unit (85) in terms of data technology, and a data interface (95) connected to the control unit (85) in terms of data technology, wherein the data interface (95) can be connected to the heat pump (20) and the heat generator (25) in terms of data technology, wherein at least a first desired value is stored in the data memory (90), wherein the control unit (85) is designed to determine a first cost parameter (AP1) for operating the heat pump (20) to provide a predefined comparative heat quantity and a second cost parameter (AP2) for operating the heat generator (25) to provide the predefined comparative heat quantity, wherein the control unit (85) is designed to determine a first heat quantity provided by the heat pump (20) within a first predefined time interval for heating the heat transfer medium (65), wherein the control unit (85) is designed to determine a heat pump parameter on the basis of the first heat quantity, wherein the control unit (85) is designed to provide a first control signal to the data interface (95) for operating the heat pump (20) for a predefined second time interval if the heat pump parameter undershoots12 09 24the first desired value and if the first cost parameter (AP1) is less than the second cost parameter (AP2), wherein the control unit is designed to determine a first cost quantity of the heat pump (20) for generating the first heat quantity on the basis of the first heat quantity and the first cost parameter (AP1) and to determine a second heat quantity provided by the heat generator (25) over the first predefined time interval for heating the heat transfer medium (65), wherein the control unit is designed to determine a fictitious cost quantity of the heat generator (25) for generating the first heat quantity by the heat generator (25) on the basis of the first heat quantity and the second cost parameter (AP2), wherein the control unit is designed to determine the heat pump parameter as a fourth ratio of a first sum of the first cost quantity and the second cost quantity to a second sum of the second cost quantity and the fictitious cost quantity, wherein the heat pump parameter represents a reduction of the first cost quantity of the heat pump (20) in comparison to the heat generator (25).

11. Bivalent heating system (10) having a control device (15), a heat pump (20) and a heat generator (25) for heating a heat transfer medium (65) to a predefined desired supply temperature (Ts), wherein the control device (15) is designed according to claim 10, wherein the data interface (95) is connected in terms of data technology to the heat pump (20) and the heat generator (25), wherein the control unit (85) is designed to operate the heat pump (20) for a predefined second time interval by means of the first control signal provided to the data interface (95).

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