Heating system, method for operating a heating system and computer program

Abstract

A heating system (1) is proposed, comprising a primary heat exchanger (3) for heat exchange with a heat generator (2). The primary heat exchanger (3) is connected to a heating circuit (4) via a flow (15) and a return (16). A three-way valve (11) is arranged in the return (16) of the heating circuit (4), dividing the heating circuit (4) into a first partial heating circuit (5) and a second partial heating circuit (6). The first partial heating circuit (5) comprises consumers (7) of the heating system (1), and the second partial heating circuit (6) comprises at least one storage heat exchanger (9) configured to transfer heat to at least one hot water storage tank (8). The invention enables the use of the heat stored in a hot water storage tank (8) for heating the heating system (1). Furthermore, a method for operating such a heating system (1) and a computer program are proposed.

Description

[0001] The invention relates to a heating system, a method for operating a heating system and a computer program.

[0002] Heating systems can be configured for combined use in heating and hot water supply. To meet the different heat demands of heating and hot water supply, the modulation range of gas condensing boilers can be increased to a ratio of approximately 1:10, for example, an output range from 3 kilowatts [kW] to 30 kW. The power requirement of a boiler for hot water supply has increased in recent years, while the power requirement for heating has decreased. This decrease in power requirement for heating can be due, for example, to improved insulation of the buildings being heated. A disadvantage can therefore be a heat demand for heating that is around 2 kW, which is below the minimum output of the boiler, resulting in frequent on / off cycling. This can put a strain on the boiler.The increasing energy demand for hot water supply can be attributed to the hot water fixtures used, for example, a rain shower head, which requires 25 liters of water per minute compared to 7 liters per minute for a conventional shower fixture. Providing a hot water flow of 25 liters per minute requires a heating system with a power output significantly exceeding 30 kW. To meet such hot water demands, hot water storage tanks are used, which can at least temporarily satisfy these requirements.

[0003] One disadvantage of using hot water storage tanks is their heat loss, in the form of heat emission to the environment, such as the room where the hot water storage tank is located.

[0004] EP 3 015 786 A1 attempts to address these disadvantages by proposing a thermal energy storage system using a phase change material (PCM). However, this technically complex solution cannot reduce the heat loss from the hot water storage tank.

[0005] EP 2 573 471 A1 describes a method for providing domestic hot water and heating. This method involves a hydraulic circuit divided into a first part for providing heating and a parallel second part for providing domestic hot water, in which a hot water storage tank is located. A heat exchanger is also provided between the first and second parts of the hydraulic circuit, positioned upstream of the hot water storage tank. However, the proposed method cannot sufficiently increase energy efficiency.

[0006] EP 3 594 575 A1 relates to a method for operating a heating system and to a heating system itself. The method comprises a first heating mode in which a heat generator heats a heat transfer fluid to a relatively high temperature and supplies it to a first heat consumer, and a second heating mode in which the heat transfer fluid is heated to a relatively medium temperature and supplied to a second heat consumer. This method is also not sufficiently energy-efficient.

[0007] EP 2 848 870 A1 describes a heating system that is also designed for cooling and has a switchable heat source for this purpose. The heating system has a cooling and heating circuit with an air conditioning branch, whereby a bypass connection between the flow and return is provided in parallel to the air conditioning branch. This system also does not have high energy efficiency.

[0008] EP 3 385 624 B1 discloses a method for operating a heating and domestic hot water system with a power generation unit, a hot water storage tank, and two heat sources for heating the domestic hot water. This system is very complex and expensive.

[0009] DE 20 2022 104 787 U1 describes a control device for a heating system with a central heating unit and a domestic hot water storage tank heated by a climate-dependent energy system, as well as a further heat generator designed to heat the domestic hot water storage tank. This system is also very complex.

[0010] The object of the present invention is to alleviate at least some of the problems described with reference to the prior art and, in particular, to propose a heating system, a method for operating a heating system and a computer program that can improve the energy efficiency of a heating system compared to the prior art.

[0011] Furthermore, the invention should not increase the complexity of a heating system and should be easy to implement.

[0012] These problems are solved by the features of the independent claims. Further advantageous embodiments of the solution proposed here are specified in the independent claims. It should be noted that the features listed in the dependent claims can be combined with one another in any technologically meaningful way and define further embodiments of the invention. Furthermore, the features specified in the claims are further specified and explained in the description, which also presents further preferred embodiments of the invention.

[0013] This system includes a heating system, comprising at least a primary heat exchanger for heat exchange with a heat generator. The primary heat exchanger is connected to a heating circuit via a flow and a return line. A three-way valve is located in either the return or the flow line, dividing the heating circuit into a first and a second sub-circuit. The first sub-circuit includes consumers of the heating system, and the second sub-circuit includes at least one storage heat exchanger designed to transfer heat to at least one domestic hot water storage tank. The heating system includes a control unit configured to set a target flow temperature for the heating circuit by adjusting the mixing position of the three-way valve when heating is required and the heat generator is switched off.

[0014] The heat generator can be a heating appliance, for example, designed to burn a fuel such as oil or gas. The combustion gas can be a fossil gas like natural gas or hydrogen, possibly produced from sustainable energy sources. In particular, the heat generator can be a condensing gas boiler, which allows a modulation ratio—that is, the ratio of lowest to highest possible heat output—of 1:10 or more. Condensing technology, in addition to utilizing the waste heat from combustion, also allows the utilization of the condensation heat of the resulting water vapor by cooling the exhaust gas stream below a condensation temperature.

[0015] A gas-fired heating appliance, acting as a heat generator, draws in a mass flow of combustion air via a conveying device. A gas control device, such as a gas valve, adds a mass flow of fuel gas corresponding to a predetermined combustion air ratio (also known as lambda or air ratio). The resulting combustion mixture of air and fuel gas can be fed via a mixture channel to a burner located in a combustion chamber, where it is combusted. The combustion products can be discharged into the open air via an exhaust pipe from the heating appliance and a downstream exhaust system.

[0016] Furthermore, a primary heat exchanger is provided for heat exchange, connected to a flow and a return line of the heating circuit. The primary heat exchanger can have several heat exchanger sections or compartments, for example, a first section designed to absorb the heat of combustion and a second section designed to absorb the heat of condensation from the exhaust gas.

[0017] The heat generator can also be a heat pump, a (wall-mounted) electrically operated heating device or an instantaneous water heater.

[0018] A three-way valve and, correspondingly, a branch can be installed in the flow or return of the heating circuit, dividing it into a first and a second sub-circuit. To clarify, the three-way valve can be located in the flow and the branch in the return, or vice versa. In this sense, the first and second sub-circuits can be understood as parallel sub-circuits (or parallel sections of the heating circuit) to which a mass flow of heat transfer fluid, flowing through the primary heat exchanger, is divided according to a mixing position or predefined setting of the three-way valve. The first sub-circuit can (exclusively) connect one or more consumers, such as radiators or underfloor heating systems.

[0019] A second heating circuit comprises at least one hot water storage tank, which stores hot water specifically for use as potable or domestic hot water. This hot water storage tank has at least one heat exchanger for heat exchange with the second heating circuit. This heat exchanger can transfer heat from the heat transfer medium of the second heating circuit to the domestic hot water contained in the storage tank and vice versa. For this purpose, the hot water storage tank has a cold water inlet, which can be connected to a water supply, such as a public water network or a well, and typically terminates in a lower geodetic region of the storage tank. A draw-off connection, which is connected to one or more taps such as showers or faucets, can be located in a higher geodetic region of the storage tank due to temperature stratification.The storage heat exchanger can be designed, for example, as a spirally arranged pipe inside the hot water storage tank. Several hot water storage tanks can be connected in parallel or (preferably) in series.

[0020] The return lines from the first and second heating circuits can be combined in the return line of the heating circuit (primary heat exchanger) by means of the three-way valve. This allows the three-way valve to supply the primary heat exchanger with a mass flow of heat transfer fluid that, depending on the valve's position, is mixed from the return lines of the first and second heating circuits. The second heating circuit primarily serves for heat exchange with the domestic hot water storage tank and therefore can only comprise one or more storage heat exchangers for one or more domestic hot water storage tanks. This exclusion applies to any further heat exchangers or devices for heat extraction and / or supply.

[0021] The three-way valve can be a three-way valve suitable for heating circuits. It may include an actuator, such as a stepper motor, which can set a mixing position of the three-way valve. The mixing position can be set by means of electronic control, for example by a control unit of the heating system.

[0022] Furthermore, the heating system can include several temperature sensors. These can be located, in particular, in the flow and return lines of the first and second heating circuits and / or in the hot water storage tank. Within the hot water storage tank, multiple temperature sensors can be positioned at different geodetic heights, enabling the detection and / or incorporation of developing temperature stratification into the determination of the thermal energy stored in the hot water storage tank.

[0023] A circulation pump can be positioned in the heating circuit to allow heat transfer fluid to circulate through both the first and second sub-circuits. Specifically, the circulation pump can be located between the three-way valve and the primary heat exchanger, and / or in the flow line of the heating circuit between the branch point of the first and second sub-circuits and the primary heat exchanger. For the sake of completeness, it should be noted that multiple circulation pumps are also possible. Furthermore, the circulation pump can be positioned elsewhere in the flow or return line, particularly in the undivided section, i.e., the section from the heat generator to the three-way valve or the branch point.

[0024] The heat transfer medium circulating in the heating circuit (i.e., in the first sub-heating circuit and the second sub-heating circuit) can be, for example, heating water.

[0025] In this method for operating a heating system, a target flow temperature for the heating circuit is set by adjusting the mixing position of the three-way valve when heating is required and the heat generator is switched off. This mixes the heat transfer fluid to the target flow temperature via the three-way valve, and the resulting mixture is then distributed proportionally, according to the valve's mixing position, to the first and second heating circuits, and thus to the consumers and the storage heat exchanger. The invention therefore enables the use of heat stored in the hot water storage tank for heating. The target flow temperature can be determined, or has been determined, according to a heating curve. The required mixing position of the three-way valve can be specified or calculated based on the temperature of the hot water storage tank and / or the return temperature of the first heating circuit.Alternatively, a mixed temperature measured by the flow or return temperature sensor of the heating unit can also be controlled. Finally, an expected mixed temperature can also be calculated based on a volume flow analysis by assigning a position of the three-way valve to a distribution of the volume flows and a storage temperature.

[0026] Furthermore, a control system or control loop can be provided to regulate the target flow temperature based on the mixing position of the three-way valve. This system can utilize the aforementioned methods for determining the mixing temperature, for example, by controlling a mixing temperature (detected by a flow or return temperature sensor of the heating appliance) using the mixing position of the three-way valve as the actuator. Alternatively, the temperatures in the return lines of the first and / or second heating circuit can be the input variables for the control system, which specifies the control variable for the mixing position of the three-way valve and the target flow temperature as the setpoint. For this purpose, the resulting mixing temperature (in the return line downstream of the three-way valve or in the flow line of the heating circuit) can also be detected and, if necessary, taken into account.

[0027] The process can be implemented, in particular, by means of a control unit for the heating system or the heat generator. For this purpose, the control unit can be electrically connected to the three-way valve, the heat generator, the circulation pump, and the temperature sensors.

[0028] The proposed method, in conjunction with the proposed heating system, enables the consumers of the first heating circuit to utilize the thermal energy stored in the hot water storage tank. The mass flow of heat transfer fluid, supplied to the primary heat exchanger at the target flow temperature set by the three-way valve, is fed via the primary heat exchanger to the flow of the first heating circuit and there distributed between the first and second heating circuits according to the set mixing position of the three-way valve. When the heat generator is switched off, i.e., without heating the heat transfer fluid in the primary heat exchanger, a target flow temperature can be set in either the return or flow line using the three-way valve. This is possible because the flow and return temperatures are the same when the heat generator is switched off.

[0029] If the temperature in the hot water storage tank falls below a preset limit, the tank can be charged. For this purpose, the heat generator can be activated, and heat transfer fluid heated by the primary heat generator can be directed to the storage tank's heat exchanger, transferring thermal energy into the hot water storage tank. The three-way valve can then assume a mixing position, directing the entire mass flow of heat transfer fluid heated by the primary heat exchanger to the hot water storage tank. Alternatively, a portion of the mass flow of heat transfer fluid heated by the primary heat exchanger can also be directed to the first heating circuit to maintain heating operation. The limit temperature can be set by the user according to their comfort requirements. It can also be adjusted according to the time of day and / or predefined usage scenarios.

[0030] According to one implementation of the method, the limit temperature can be determined based on recorded user behavior. This user behavior can relate in particular to hot water usage and withdrawal. Specifically, user behavior, especially hot water withdrawals, can also be recorded and analyzed by artificial intelligence. During periods in which there is regularly no or only very low hot water withdrawal, the limit temperature for charging the hot water storage tank can be lowered, thereby reducing the heat loss from the hot water storage tank.

[0031] Two operating states of the heating system can therefore be identified. The first operating state ensures heating operation and allows for the (simultaneous) withdrawal of hot water even when the heat generator is switched off. In the second operating state, the heat generator is in operation and can supply heat energy to both the hot water storage tank for charging and to consumers in the second heating circuit for heating operation. Hot water withdrawal is also possible in the second operating state.

[0032] In addition, a computer program is proposed that is designed to (at least partially) execute a procedure presented here. In other words, this specifically concerns a computer program (product) comprising commands that, when executed by the heating device, the heating system proposed here, or a control unit of the heating device or heating system, cause the heating system to execute a procedure proposed here. The heating system can have at least one or more temperature sensors to which a computer executing the procedure can be electrically connected. Furthermore, the computer executing the procedure can be electrically connected to the electrically controlled actuator of the three-way valve.Furthermore, parameters necessary for the execution of a process, such as a heating curve or a limit temperature, can be stored on the memory of the computer carrying out the process.

[0033] The explanations regarding the heating system can also be used to further characterize the process and / or the computer program, and vice versa.

[0034] It should be noted as a precaution that the numerical terms used here ("first", "second", etc.) primarily serve (only) to distinguish between several similar objects, quantities, or processes, and thus do not necessarily dictate any dependency and / or sequence between these objects, quantities, or processes. Should a dependency and / or sequence be required, this is explicitly stated here, or it will be obvious to a person skilled in the art upon studying the specific configuration described. Where a component can occur multiple times ("at least one"), the description of one of these components may apply equally to all or some of the multiple components, but this is not mandatory.

[0035] This document describes a heating system, a method for operating a heating system, and a computer program that at least partially solve the problems described with reference to the state of the art. In particular, the heating system and the method contribute to increasing the energy efficiency of the heating system by utilizing the thermal energy stored in a hot water storage tank to meet the heating demand. This allows the temperature in the hot water storage tank, and thus the temperature difference to the ambient environment, to decrease, thereby reducing heat loss. A further positive effect is a reduction in the cycling of the heating unit, thus reducing wear and tear and increasing its service life.

[0036] The invention also makes it possible to reduce the requirements for the modulation range of a heating appliance, since low heating demands can be met by utilizing the thermal energy of the hot water storage tank. For example, using the hot water storage tank for heating can cover heat demands of less than 5 kW, thus making it necessary to activate the heat generator only when heat demands exceed 5 kW. This could also be understood as an increase in the modulation range of the overall system. Therefore, the invention can also be used to modify older heating appliances with a lower modulation ratio so that they can operate in a heating system with a high power differential.

[0037] The invention and its technical context are explained in more detail below with reference to the accompanying figures. It should be noted that the invention is not limited by the exemplary embodiments shown. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the situations described in the figures and combine them with other components and findings from the present description. It should be emphasized that the figures, and especially the depicted dimensions, are only schematic. They show: Fig. 1: a heating system proposed here. Fig. 1 Figure 1 shows an exemplary and schematic representation of a heating system 1 proposed here. This system comprises a heat generator 2 and a primary heat exchanger 3 for transferring heat from the heat generator 2 to a heating circuit 4. The heating circuit 4 has a flow 15 and a return 16. A three-way valve 11 can be arranged in the return 16, which divides the heating circuit 4 into a first sub-circuit 5 with a return 22 and a second sub-circuit 6 with a return 21. The flow 15 of the heating circuit 4 can be split at a junction 18 into a flow 20 of the first sub-circuit 5 and a flow 19 of the second sub-circuit 6. It is noted that alternatively, the The three-way valve 11 can be located in the supply line 15 and the branch 18 in the return line 16.

[0038] In the first sub-circuit 5, consumers 7, such as underfloor heating systems or radiators, can be integrated. In the second sub-circuit 6, a hot water storage tank 8 can be used to receive and supply heated domestic hot water, and a storage heat exchanger 9 can be used to exchange heat between the hot water storage tank 8 and the heat transfer fluid circulating in the second sub-heating circuit 6. The heat transfer fluid in heating circuit 4, or in the first and second sub-heating circuits 5 and 6, is circulated by a circulation pump 10 in a circulation direction 17.

[0039] A first temperature sensor 13 can be installed in the return line 22 of the first partial heating circuit 5, and a second temperature sensor 14 can be installed in the return line 21 of the second partial heating circuit 6 to measure the temperature of the heat transfer fluid. A control unit 12 of the heating system 1 can be electrically connected to the three-way valve 11, the circulation pump 10, and the first and second temperature sensors 13 and 14. It should be noted that additional temperature sensors can be used, in particular a temperature sensor downstream of the three-way valve 11 in the direction of circulation 17 to measure the temperature set by the mixing position of the three-way valve 11. For this purpose, a (usually already present) flow or return temperature sensor of the heating appliance / heating system 1 can also be used, which would make the first and second temperature sensors 13 and 14 unnecessary.Alternatively, this temperature can also be set by a control system using the mixing position of the three-way valve as an actuator.

[0040] According to a method proposed here, a target flow temperature, determined, for example, based on the heat demand and the heating curve, can be set using a mixing position of the three-way valve 11. Based on the measurement signals from the first temperature sensor 13 in the return line 22 of the first sub-heating circuit 5 and the second temperature sensor 14 in the return line 21 of the second sub-heating circuit 6, a mixing position of the three-way valve 11 can be determined to set the target flow temperature. By actuating the three-way valve 11, it can be set to the determined mixing position. Heat transfer fluid at the target flow temperature is then supplied to the first and second heating circuits according to the determined and set mixing position of the three-way valve 11. The heat transfer fluid in the first sub-heating circuit 5 is cooled by the consumers, while the heat transfer fluid in the second sub-heating circuit 6 is heated in the storage heat exchanger 9.

[0041] Alternatively, a target flow temperature can be specified. This can be continuously compared to the return temperature (16) or the flow temperature (15) (these are the same when heat generator 2 is switched off). If there is a deviation, the 3-way valve is adjusted so that the specified target flow temperature is maintained.

[0042] The hot water storage tank 8 can be charged by starting up the heat generator 2. In addition, the three-way valve 11 can be set to a mixing position, in which the mass flow from the primary heat generator 3 is almost entirely directed to the storage heat exchanger 9. For this purpose, the heat generator 2 can be operated at high or nominal output to enable rapid heating of the hot water storage tank 8. Reference symbol list

[0043] 1 Heating system 2 Heat generator 3 Primary heat exchanger 4 Heating circuit 5 First sub-heating circuit 6 Second sub-heating circuit 7 Consumer 8 Hot water storage tank 9 Storage tank heat exchanger 10 Circulating pump 11 Three-way valve 12 Control unit 13 First temperature sensor 14 Second temperature sensor 15 Flow heating circuit 16 Return heating circuit 17 Circulation direction 18 Branch 19 Flow second sub-heating circuit 20 Flow first sub-heating circuit 21 Return second sub-heating circuit 22 Return first sub-heating circuit

Claims

1. Method for operating a heating system (1), comprising a primary heat exchanger (3) for heat exchange with a heat generator (2), wherein the primary heat exchanger (3) is connected to a heating circuit (4) via a flow pipe (15) and a return pipe (16), and a three-way valve (11) is arranged in the flow pipe (15) or return pipe (16) of the heating circuit (4), which divides the heating circuit (4) into a first partial heating circuit (5) and a second partial heating circuit (6), wherein the first partial heating circuit (5) comprises consumers (7) of the heating system (1) and the second partial heating circuit (6) comprises at least one storage heat exchanger (9), wherein, according to the method, when a heating request is made with the heat generator (2) switched off, a flow setpoint temperature of the heating circuit (4) is set by a mixing position of the three-way valve (11).

2. Method according to claim 1, wherein, when a temperature in the hot water storage tank (8) and / or in the return flow (21) of the second partial heating circuit (6) is detected to be below a limit temperature, the three-way valve (11) is moved to a charging position in which, when the heat generator (2) is switched on, the heat transfer medium heated in the primary heat exchanger (3) is fed to the hot water storage tank (8).

3. Method according to claim 2, wherein the limit temperature is determined on the basis of detected user behaviour.

4. Heating system (1) comprising a primary heat exchanger (3) for heat exchange with a heat generator (2), wherein the primary heat exchanger (3) is connected to a heating circuit (4) via a flow pipe (15) and a return pipe (16), and a three-way valve (11) is arranged in the flow pipe (15) or return pipe (16) of the heating circuit (4), which divides the heating circuit (4) into a first partial heating circuit (5) and a second partial heating circuit (6), wherein the first partial heating circuit (5) comprises consumers (7) of the heating system (1) and the second partial heating circuit (6) comprises at least one storage heat exchanger (9), and a regulating and control device (12) designed to carry out a method according to one of claims 1 to 3.

5. Heating system (1) according to claim 4, wherein the heat generator (2) is a gas condensing heating appliance.

6. Heating system (1) according to one of claims 4 or 5, wherein in the flow (15) and / or in the return (16) of the heating circuit (4) between the three-way valve (11) and the primary heat exchanger (3) and / or between a branch (18) of the first partial heating circuit (5) and the second partial heating circuit (6) and the primary heat exchanger (3).

7. Heating system (1) according to one of claims 4 to 6, wherein the second partial heating circuit (6) is designed exclusively for heat exchange with a hot water storage tank (8).

8. Computer programme comprising commands that cause a heating system (1) according to claim 4 to execute a method according to claim 1.

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