Hybrid heating system

Abstract

A hybrid heating system (1) is proposed, comprising a heat generator (5), a heat pump (2), and a heating circuit (8) which are hydraulically connected, wherein the heat pump (2) and the heat generator (5) are configured to heat a heat transfer medium for heating and / or hot water supply, and wherein a first check valve (12) is arranged between a flow connection (24) and a return connection (23) of the heat generator (5) and / or a second check valve (11) is arranged in the flow (7) of the heat generator (5), wherein a flow (4) of the heat pump (2) is connected to a mixing pipe (9), and the flow (7) and return (6) of the heat generator (5) are connected to the mixing pipe (9), and wherein the first check valve (12) is arranged in the mixing pipe (9) between the flow connection (24) and the return connection (23) of the heat generator (5) and / or the second check valve (11) is arranged in the flow (7) of the heat generator (5) to the mixing tube (9)

Description

[0001] The invention relates to a hybrid heating system comprising a heat generator and a heat pump for heating a heat transfer medium.

[0002] Hybrid heating systems for supplying a building with heating and hot water are becoming increasingly common. These systems typically consist of a heat generator, such as a gas boiler, and a heat pump hydraulically connected via a heating circuit, enabling them to generate heat as needed. The heat generator can also be considered an auxiliary heating unit, used when the heat output of the heat pump is insufficient to meet the heating demand. A hybrid heating system offers the advantage that, during periods of high heat demand, the heat generator can contribute heat cumulatively, thus ensuring that all heating requirements are met with a high level of comfort. Such a hybrid heating system is illustrated, for example, in EP 4 253 867 A1. A further advantage of a hybrid heating system is that the heat pump can also operate in a cooling mode by reversing its refrigeration cycle.

[0003] EP 2 806 218 A1 describes such a hybrid heating system including a three-way valve, which is of a complex design.

[0004] DE 100 33 669 A1 also describes a hybrid heating system with a buffer storage tank, which is likewise complex in design.

[0005] A simple heating system with a heat pump and a boiler is shown in DE3049132A1. A disadvantage is that the heat pump and boiler affect each other when operating simultaneously, as the sub-circuits are not hydraulically decoupled.

[0006] DE 10 2022 132 372 A1 also describes a heating system with a combustion unit and a heat pump, although here too, completely independent operation of the heat generators does not appear possible.

[0007] Various configurations of hybrid heating systems are known. Often, the heat generator and the heat pump are connected to a buffer storage tank and can transfer heat into it. A heating circuit can be supplied with heated heat transfer fluid from the buffer storage tank. If necessary, domestic hot water can also be supplied via a heat exchanger in the buffer storage tank. Such hybrid heating systems are often complex in design and require, in particular, sophisticated hydraulic connections and place high demands on the available installation space. Furthermore, in such a hybrid heating system, if the heat pump fails, the heating circuit may no longer be supplied with heat, even though the heat generator is operational.

[0008] Instead of a buffer storage tank, a mixing pipe can also be installed in the flow line of the heat pump, connected to the flow and return lines of the heat generator. This mixing pipe can then act as a hydraulic separator to decouple the parallel operation of the heat pump and heat generator.

[0009] Furthermore, during cooling operation, unfavorable flow conditions can cause cooled heat transfer fluid to flow through the heat generator, leading to condensation. Besides reducing cooling capacity, the condensate in the heat generator can damage it or shorten its service life.

[0010] It is therefore an object of the invention to at least partially alleviate or solve the problems described with reference to the prior art. In particular, a hybrid heating system is to be provided which avoids condensation in the heat generator during cooling operation of the heat pump and which can also continue to be operated using only the heat generator in the event of a heat pump failure.

[0011] Furthermore, the complexity of a hybrid heating system should not be significantly increased, and the invention should also be retrofittable to existing systems.

[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 is achieved using a hybrid heating system comprising at least one heat generator, one heat pump, and one heating circuit, all hydraulically connected. The heat pump and the heat generator are designed to heat a heat transfer fluid, particularly one suitable for (space) heating and / or (domestic) hot water supply. The system includes a first check valve in the heat pump's flow line between a flow and return connection of the heat generator, and / or a second check valve in either the flow or return line of the heat generator.The flow pipe of the heat pump is connected to a mixing pipe, the flow and return pipes of the heat generator are connected to the mixing pipe, and the first check valve is located in the mixing pipe between the flow connection and the return connection of the heat generator and / or the second check valve is located in the flow pipe of the heat generator to the mixing pipe.

[0014] A heat pump can be a familiar type of heat pump that extracts heat from an ambient medium, such as geothermal energy, water, or ambient air, and transfers it to a heat transfer medium for use. The heat pump may include a refrigeration cycle in which a refrigerant circulates and transfers heat through a phase change. In the evaporator of the refrigeration cycle, the refrigerant can evaporate and absorb heat. In a condenser, the refrigerant can be converted into a liquid state, and the resulting heat can be transferred to a heat transfer medium. A compressor and an expansion valve can be located between the evaporator and condenser to control the refrigeration cycle. To switch from heating to cooling mode, the evaporator and condenser can exchange their functions, thus reversing the process.

[0015] The hybrid heating system can operate in heating and cooling modes (switching between them as needed, selectively, or automatically). In heating mode, the heat pump is configured to transfer heat from the ambient medium to a heat transfer fluid. In cooling mode, the heat pump can transfer heat from the heat transfer fluid to the ambient medium, thus absorbing heat via the consumers in the heating circuit and releasing it back into the environment. For cooling mode, the heat pump's refrigeration cycle can be reversed. In this case, the evaporator from heating mode becomes the condenser, and vice versa, thus reversing the direction of heat flow within the heat pump.

[0016] The heat generator can be, in particular, a heating appliance for burning a fuel, such as heating oil, fossil fuels like natural gas, hydrogen, or even wood. Alternatively, the heating appliance can also be an electric heating appliance that heats a heat transfer medium using a flow-through principle. Specifically, the heat generator can be a gas-fired heating appliance.

[0017] The gas-fired heating appliance draws in a mass flow of combustion air via an air intake system. A mass flow of fuel gas, corresponding to a predetermined combustion air ratio (also known as lambda or air-fuel ratio), is then added to this air. The resulting combustion mixture can be fed to a burner via a mixture channel, exit into a combustion chamber, and combusted there. The combustion products can be discharged via an exhaust duct from the gas-fired heating appliance into the building's exhaust system.

[0018] The gas boiler can adjust its burner output to the demand, a process also known as "modulation." Upon detecting a change in heat demand, for example, by considering the flow and return temperatures of a heating circuit connected to the boiler, a control unit adjusts the boiler's fan output and thus the combustion air flow rate to the heat demand. Simultaneously, a control system adjusts the hydrogen flow rate to the changing combustion air flow rate. Modulating operation of the gas boiler enables targeted heat generation, allowing the heat transfer fluid flowing from the heat pump to be heated precisely to a predefined setpoint temperature. The gas boiler can be, in particular, a wall-mounted unit.

[0019] Both the heat pump and the heat generator can include a return line through which the heat transfer fluid to be heated can flow in, and a supply line through which the heated heat transfer fluid can flow out. In particular, the heat generator and the heat pump can be connected in parallel to the heating circuit.

[0020] In particular, the heat pump's return line can be connected to a return line of the heating circuit, so that the heat transfer fluid is heated by the heat pump first. The heat pump's flow line can be connected to the heating circuit's flow line. Specifically, the heat pump's flow line can be connected to a buffer tank or a mixing tube. The heat pump's return line can (also) be connected to the buffer tank. The heat generator's flow and return lines can be connected to the mixing tube or buffer tank at a flow connection and a return connection, respectively, whereby, with respect to a normal flow direction of the heat transfer fluid, the return connection can be located upstream of the flow connection on the mixing tube. For example, the return connection can be located at the beginning of the mixing tube, and the flow connection at the end of the mixing tube.The initial and final sections refer to the flow direction of the heat transfer fluid. The described arrangement allows the hybrid heating system to operate in three modes. In the first mode, only the heat pump can operate and heat the heat transfer fluid to a predetermined setpoint temperature. In a second mode, the heat pump and heat generator can operate simultaneously. The heat pump initially heats the heat transfer fluid to a temperature below the predetermined setpoint temperature, and the heat generator, through which the heat transfer fluid flows after the heat pump, then further heats the heat transfer fluid to the predetermined setpoint temperature. In this respect, the heat pump and heat generator can be considered to be connected in series in the second mode. In a third mode, only the heat generator can operate.The third operating mode can occur, for example, in the event of a heat pump malfunction and / or very low outside temperatures and a correspondingly high heating demand. The first operating mode can occur when the heat pump's output is sufficient to meet the heating demand. The second operating mode may be necessary when the heat pump cannot meet the heating demand and additional heating output from the heat generator is required. This heating demand can relate to space heating, hot water production, and / or charging a storage tank, such as a hot water storage tank or buffer tank.

[0021] Both the heat pump and the heat generator can include a circulation pump that moves the heat transfer fluid. The circulation pump can, in particular, be a controlled pump.

[0022] A heating circuit can contain heat consumers such as radiators, heating elements, or underfloor heating systems (room heating such as wall or floor heating) and act as a heat sink. The heating circuit can also comprise several sub-circuits. These sub-circuits can be assigned to different rooms or residential units within the building. They can be high-temperature circuits for supplying radiators or heating elements, or low-temperature circuits for supplying underfloor heating systems. The sub-circuits can be connected to a primary heating circuit, which may include the heat generator, heat pump, and, if applicable, a buffer tank and / or hot water storage tank.

[0023] The mixing pipe can be a section of pipe in which a partial flow of the heat transfer fluid, heated by the heat generator, is mixed with a partial flow of the heat transfer fluid flowing directly from the heat pump to the heating circuit. The mixing pipe has, in particular, a hydraulic connection for at least one of the following components: the heat pump's flow, a flow and return from the heat generator, and a flow from the heating circuit (i.e., the heat sink). The flow rates of the heat generator and the heat pump are largely hydraulically decoupled by the use of the mixing pipe.

[0024] The mixing tube advantageously allows the heat generator to operate independently of the heat pump. This means that the heat generator can use a smaller, the same, or a larger flow rate of heat transfer fluid without affecting the flow rate exiting the at least one heating circuit. According to one embodiment, the mixing tube can be dimensioned such that the following heat transfer fluid flow rates can be adjusted independently of each other in the hybrid heating system: a volume flow rate in the heat pump of 400 - 5000 I / h, preferably of 500 - 2500 I / h, and a volume flow rate in the heat generator of 400 - 2500 I / h, preferably of 500 - 1500 I / h.

[0025] The volume flow rate in the mixing tube is the difference between the volume flow rate of the heat pump and the volume flow rate of the heat generator and is 0–5000 l / h, preferably 0–2500 l / h. The resulting volume flow rate supplied to the heating circuit can be in the range of 400–5000 l / h, preferably 500–2500 l / h.

[0026] According to one embodiment, the ratio of the inner diameter of a pipe in the flow of the heat pump, the return of the heat pump, or the heating circuit (especially the flow and return of the heating circuit connected to the hybrid heating system) to the inner diameter of the mixing pipe can be equal to 1, particularly greater than ½, or particularly greater than 1 / 5. It is noted that the pipes have a circular cross-section and thus also a circular internal flow cross-section. This embodiment can contribute to the hydraulic decoupling of the heat generator and the heat pump by means of the mixing pipe.

[0027] The hybrid heating system can include a control unit that regulates and controls its operation. For this purpose, the control unit can be connected electronically to at least the heat generator, the heat pump, and several sensors, such as temperature sensors in the flow and return lines of the heat pump and / or the heat generator, temperature sensors to measure the temperature of the contents of a hot water storage tank and / or a buffer tank, and / or a temperature sensor to measure the temperature of the ambient medium used by the heat pump.

[0028] A first check valve must be installed between the flow and return connections of the heat generator. Alternatively or additionally, a second check valve can be installed in the flow or return line of the heat generator. A check valve is a component that allows flow in a normal direction while preventing flow in the opposite direction, thus closing the flow path. The normal flow direction can, in particular, correspond to the normal flow direction of the hybrid heating system, or the heat pump and heat generator, from the return to the flow. The check valve can be designed as a flap valve. The first check valve advantageously allows, for example, the operation of the heat generator in the event of a heat pump failure or during maintenance work on the heat pump.

[0029] The first check valve ensures the flow direction of the heat transfer fluid from the heat pump to the heat sink, or heating circuit, and prevents any side flows. If the flow rate of the heat generator is greater than that of the heat pump, the check valve prevents the supply fluid from flowing back into the return line of the heat generator. The check valve in the mixing pipe also prevents the heat transfer fluid from flowing back to the heat pump and enables or supports the independent operation of the heat generator and heat pump. When only the heat pump is operating, it can supply the heating circuit via the check valve, independent of the heat generator. If only the heat generator is operating, it can operate independently of the heat pump. If only the circulation pump of the heat generator is running, the heat transfer fluid can be transported to the heating circuit by the heat pump and the heat generator.

[0030] The second check valve can prevent flow through the heat generator in or against the normal flow direction. This can occur, for example, during cooling operation of the heat pump, where unfavorable flow conditions can cause the heat transfer fluid to flow from the heat generator's supply line into its return line. The second check valve can be designed so that an opening pressure is required to allow flow. This opening pressure should be selected to be greater than the pressure differences between the supply and return lines of the heat generator caused by unintended flow effects. This effectively prevents unintended flow effects and their consequences to a large extent.

[0031] According to one embodiment, the check valve can be configured to open at an opening pressure greater than the differential pressure generated by the heat pump during operation. Furthermore, as described above, the opening pressure should also be higher due to pressure differences arising from unintended flow effects. This embodiment applies particularly to the second check valve and ensures that the check valve cannot be opened by the operation of the heat pump and only opens when the circulation pump of the heat generator is started.

[0032] According to one embodiment, the hybrid heating system can include a buffer storage tank for the heat transfer fluid, which can be arranged as a mixing pipe. Alternatively or cumulatively, a buffer storage tank can also be arranged in the return line of the heating circuit.

[0033] In one embodiment, the hybrid heating system can include a hot water storage tank for storing heated potable or domestic hot water from a hot water supply. This tank can be connected to a supply network, a water network, or a well to replace hot water drawn from the storage tank. The hot water storage tank can have a heat exchanger through which a heat transfer fluid flows to heat the water contained within. The hot water storage tank can be integrated into the heating circuit via a three-way valve. Depending on the heat demand, the three-way valve can control whether the heat transfer fluid flows through the heating circuit or, alternatively, through the hot water storage tank to heat it.

[0034] According to one embodiment, the mixing tube and the first check valve and / or the second check valve can be arranged or housed in a (common) component. In particular, the component can comprise exactly one (single) housing containing the mixing tube and the first check valve and / or the second check valve. The component can be part of a kit for constructing a hybrid heating system. Thus, the component can include at least one connection each for the flow and return of the heat generator, for a flow of the heat pump, and for the flow of the heating circuit.

[0035] Arranging a first check valve and a second check valve in a hybrid heating system can advantageously allow the use of synergistic effects of the two check valves depending on their installation position.

[0036] 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.

[0037] This document describes a hybrid heating system that at least partially solves the problems outlined with reference to the state of the art. In particular, the hybrid heating system can ensure efficient heat transfer and prevent bypass flow. Furthermore, it completely avoids condensation in the heat generator, thus preventing damage to the generator and extending its service life. The non-return valves are advantageously inexpensive and easy to install. Therefore, the invention is also suitable for retrofitting existing hybrid heating systems.

[0038] 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 intended to be 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 hybrid heating system, Fig. 2: an alternative design of the hybrid heating system, and Fig. 3: a hybrid heating system with hot water supply.

[0039] Fig. 1 Figure 1 shows an exemplary and schematic representation of a proposed hybrid heating system 1. This system comprises a heat pump 2 with a flow 4 and a return 3, and a heat generator 5 with a flow 7 and a return 6. The heat generator 2 can be, in particular, a gas-fired boiler. The heat pump 2 and the heat generator 5 supply heat to a heating circuit 8, which acts as a heat sink. The heating circuit 8 has a flow 10 and a return 17. The return 17 of the heating circuit 8 can be connected to the return 3 of the heat pump 2. An optional buffer storage tank 16 can be arranged between the return 17 of the heating circuit 8 and the return 3 of the heat pump 2. The heat pump 2, the heat generator 5, a mixing tube 9, and the heating circuit 8 have a flow direction 21 in which the heat transfer fluid flows through them.

[0040] The flow pipe 4 of the heat pump 2 can be connected to the mixing pipe 9, the other end of which can be connected to the flow pipe 10 of the heating circuit 8. The return pipe 6 of the heat generator 5 can be connected to a return connection 23 in an initial section of the mixing pipe 9 (relative to the flow direction 21), and the flow pipe 7 can be connected to an end section of the mixing pipe 9 (relative to the flow direction 21) via a flow connection 24. In this way, the heat generator 5 draws a volume of heat transfer fluid from the mixing pipe 9 via the return connection 23, heats this volume, and returns it to the mixing pipe 9 via the flow connection 24. A temperature sensor 22 can also be arranged in the end section of the mixing pipe 9. This sensor can be connected to a control unit (not shown here) of the hybrid heating system 1 and measures the flow temperature of the heating circuit 8.

[0041] A first check valve 12 can be arranged in the mixing tube 9 and a second check valve 11 can be arranged in the flow line of the heat generator. Fig. 1 It is shown that both the first check valve 12 are located in the mixing tube 9 and the second check valve 11 are located in the flow line 7 of the heat generator 5. It is explicitly noted that according to the invention (unlike in Fig. 1 (as shown) only the first check valve 12 can be present in the mixing tube 9. Furthermore, (unlike in Fig. 1 (as shown) only the second check valve 11 is present in the flow line 7 of the heat generator 5.

[0042] The first check valve 12 is thus arranged in the mixing pipe 9 between the return connection 23 and the supply connection 24 of the heat generator 5 on the mixing pipe 9 and can prevent flow in the mixing pipe 9 against its flow direction 21, thereby ensuring that the heat generator 5 can be operated and supply the heating circuit 8 with heat even when the heat pump 2 is switched off. The second check valve 11 is arranged in the supply line 7 of the heat generator 5 and prevents flow through the heat generator 5 in a direction opposite to its flow direction 21. In an alternative embodiment not shown here, the second check valve 11 can also be arranged in the return line 8 of the heat generator 5.

[0043] The mixing tube 9 and the first and second check valves 12, 11 can be arranged in a component 13, in particular together within a housing of the component 13. The component 13 can be part of a kit for the hybrid heating system 1 and significantly simplify assembly.

[0044] Fig. 2 It also shows, by way of example and schematically, the hybrid heating system 1. Fig. 1 with a bypass valve 20, which can be arranged between the mixing pipe 9 and the return 17 of the heating circuit 8 or the return 3 of the heat pump 2. The bypass valve 20 can enable defrosting of an evaporator of the heat pump 22 and ensure a minimum circulation rate when the consumers of the heating circuit 8 are closed. The reference numerals and their respective explanations from or to Fig. 1 can also be used in or for Fig. 2 be applied.

[0045] In Fig. 2 It is shown that both the first check valve 12 are located in the mixing tube 9 and the second check valve 11 are located in the flow line 7 of the heat generator 5. It is explicitly noted that according to the invention (unlike in Fig. 2 (as shown) only the first check valve 12 may be present in the mixing tube 9. Likewise, (unlike in Fig. 2 (as shown) only the second check valve 11 is present in the flow line 7 of the heat generator 5.

[0046] Fig. 3 Figure 1 shows a hybrid heating system 1 with a hot water supply, which may include a hot water storage tank 15 with a flow 14 and a return 18. An alternative flow through the hot water storage tank 15 with heat transfer fluid can be initiated via a motor-driven three-way valve 19. For this purpose, the three-way valve 19 can be connected to a control unit of the hybrid heating system 1. The reference symbols and their respective explanations are from or relating to... Fig. 1 can also be used in or for Fig. 3 be applied.

[0047] Furthermore, the hybrid heating system 1 has a buffer storage tank 16, which can hold heated heat transfer fluid. For this purpose, the buffer storage tank 16 is connected to the return line 17 of the heating circuit 8 and the return line 3 of the heat pump 2, so that heat transfer fluid from the return line 17 of the heating circuit 8 can flow through the buffer storage tank 16.

[0048] In Fig. 3 It is shown that both the first check valve 12 are located in the mixing tube 9 and the second check valve 11 are located in the flow line 7 of the heat generator 5. It is explicitly noted that according to the invention (unlike in Fig. 3 (as shown) only the first check valve 12 may be present in the mixing tube 9. Likewise, (unlike in Fig. 3 (as shown) only the second check valve 11 is present in the flow line 7 of the heat generator 5. Reference symbol list

[0049] 1 Hybrid heating system 2 Heat pump 3 Heat pump return 4 Heat pump flow 5 Heat generator 6 Heat generator return 7 Heat generator flow 8 Heating circuit 9 Mixing pipe 10 Heating circuit flow 11 Second check valve 12 First check valve 13 Component housing 14 Hot water storage tank flow 15 Hot water storage tank 16 Buffer tank 17 Heating circuit return 18 Hot water storage tank return 19 Three-way valve 20 Bypass valve 21 Flow direction 22 Temperature sensor 23 Return connection 24 Flow connection

Claims

1. Hybrid heating system (1) comprising a heat generator (5), a heat pump (2) and a heating circuit (8) hydraulically connected to each other, wherein the heat pump (2) and the heat generator (5) are configured to heat a heat transfer medium, wherein at least a first check valve (12) is arranged between a flow connection (24) and a return connection (23) of the heat generator (5) or a second check valve (11) is arranged in a flow (7) or a return (8) of the heat generator (5), wherein a flow (4) of the heat pump (2) is connected to a mixing pipe (9), the flow (7) and the return (6) of the heat generator (5) are connected to the mixing pipe (9), and wherein the first check valve (12) is arranged in the mixing pipe (9) between the flow connection (24) and the return connection (23) of the heat generator (5) and / or the The second check valve (11) is located in the flow line (7) of the heat generator (5) to the mixing tube (9).

2. Hybrid heating system (1) according to claim 1, wherein the ratio between an inner diameter of a flow line (4) and an inner diameter of the mixing tube (9), between an inner diameter of a return line (3) of the heat pump (2) and the inner diameter of the mixing tube (9) or between the inner diameter of a heating circuit line (8) and the inner diameter of the mixing tube (9) is greater than 0.

5.

3. Hybrid heating system (1) according to one of the preceding claims, wherein the second check valve (11) is configured to open at an opening pressure that is greater than the differential pressure built up by the heat pump (2) during operation.

4. Hybrid heating system (1) according to claim 2 or 3, wherein the mixing tube (8) and at least the first check valve (12) or the second check valve (11) are arranged in exactly one component (13).

5. Hybrid heating system (1) according to one of the preceding claims, wherein the heating circuit (8) comprises a buffer storage tank (16) which is arranged in the return line (3) of the heat pump (2).

6. Hybrid heating system (1) according to one of the preceding claims, wherein a hot water storage tank (15) is integrated into the heating circuit (8) via a three-way valve (19).

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