WO2022112661A1

WO2022112661A1 - A hybrid heating arrangement and a method of operating a hybrid heating arrangement

Info

Publication number: WO2022112661A1
Application number: PCT/FI2021/050822
Authority: WO
Inventors: Hannu Helminen
Original assignee: Auris Energiaratkaisut Oy
Priority date: 2020-11-30
Filing date: 2021-11-29
Publication date: 2022-06-02
Also published as: FI20206217A1; FI130059B

Abstract

The invention relates to a hybrid heating arrangement and a method of operating a hybrid heating arrangement connecting a primary energy source (1) and a secondary energy source (2) to a heating circuit (3) for providing thermal energy to the heating circuit (3). The hybrid heating arrangement comprising a heating liquid tank (4) and a hybrid distribution assembly (5) in a heating liquid communication with the heating circuit (3) and with the heating liquid tank (4).

Description

A HYBRID HEATING ARRANGEMENT AND A METHOD OF OPERATING A HYBRID HEATING ARRANGEMENT

FIELD OF THE INVENTION

The present invention relates to a hybrid heating arrangement and more particularly to a hybrid heating arrangement as defined in the preamble of the independent claim 1.

The present invention further relates to a method of operating a hybrid heating arrangement, and more particularly to a method of operating a hybrid heating arrangement as defined in the preamble of the independent claim 10.

The preferred embodiments of the invention are defined in the dependent claims.

BACKGROUND OF THE INVENTION

District heating and air-to-water heat pump are commonly utilized as two separate energy sources in one heating arrangement in connection with a heating network. In the prior art heating arrangements air-to-water heat pump and district heating are utilized as separate energy sources and connected separately to the heating network. The air-to-water heat pump is usually connected to the return side of the heating network. The air-to-water heat is usually operated as a primary energy source and the district heating is utilized as a secondary energy source. Thus, thermal energy is primarily obtained from the air-to-water heat pump and when additional thermal energy is needed it is obtained from the district heating.

One of the problems associated with the prior art is that when an air- to-water heat pump is connected directly to the return side of the heating network, the temperature of the district heating return water rises, which limits the power that can be fed into the heating system. Under certain outdoor temperature and humidity conditions, the outdoor unit of the air-to-water heat pump becomes frozen or in frozen like conditions as a result of which the outdoor unit must be defrosted. During defrosting the heat or thermal energy for the defrosting is taken from the heating network which causes a temperature drop in the heating network.

BRIEF DESCRIPTION OF THE INVENTION

An object of the present invention is to provide a hybrid heating arrangement and a method of operating a hybrid heating arrangement so as to overcome or at least alleviate the prior art disadvantages. The objects of the present invention are achieved by a hybrid heating arrangement which is characterized by what is stated in the independent claim 1. The objects of the present invention are also achieved by a method of operating a hybrid heating arrangement which is characterized by what is mentioned in the independent claim 10. The preferred embodiments of the invention are disclosed in the dependent claims.

The invention is based on the idea of providing a hybrid heating arrangement connecting a primary energy source and a secondary energy source through a heating liquid tank to a heating circuit for providing thermal energy to the heating circuit.

The hybrid heating arrangement comprises at least one primary energy source and at least one secondary energy source which are independently working as separate energy sources. The hybrid heating arrangement also comprises a heating liquid tank for holding heating liquid, the heating liquid tank having an upper tank portion and a lower tank portion in a flow communication with each other. The hybrid heating arrangement further comprises a hybrid distribution assembly in a heating liquid communication with the heating circuit and with the heating liquid tank, the hybrid distribution assembly being arranged to provide thermal energy from the heating liquid tank to the heating circuit, the hybrid distribution assembly further being in a heat exchange communication with the secondary energy source for providing thermal energy from the secondary energy source to the heating liquid tank.

The heating liquid tank is provided with a first upper inlet at the upper tank portion of the heating liquid tank forming a heating liquid connection from the primary energy source to the heating liquid tank for providing thermal energy in a primary supply flow as a heating liquid flow from the primary energy source to the heating liquid tank, and with a first lower outlet at the lower tank portion of the heating liquid tank which the first lower outlet connecting the heating liquid tank to the primary energy source for providing the heating liquid flow as a primary return flow from the heating liquid tank to the primary energy source. The heating liquid tank is further provided with a second upper inlet at the upper tank portion of the heating liquid tank which the second upper inlet connecting the secondary energy source to the heating liquid tank for providing thermal energy as a secondary supply flow from the secondary energy source to the heating liquid tank, with a first lower inlet at the lower tank portion of the heating liquid tank which the first lower inlet connecting the hybrid distribution assembly to the heating liquid tank for providing a heating liquid supply flow from the heating circuit to the heating liquid tank, and with a first upper outlet at the upper tank portion of the heating liquid tank which the first upper outlet connecting the heating liquid tank to the hybrid distribution assembly for providing a heating liquid flow from the heating liquid tank to the heating circuit.

The hybrid heating arrangement of the present invention enables efficient utilization of thermal energy from the separate first and second energy sources in the heating circuit in all situations and without unwanted temperature variations in the heating circuit. The heating liquid tank enables one combined heating liquid source for providing thermal energy to the heating circuit.

In one embodiment, the hybrid distribution assembly comprises a secondary energy source valve forming a connection with a first supply pipe extending between the secondary energy source and the secondary energy source valve, a second supply pipe extending between the secondary energy source valve and the second upper inlet at the upper tank portion of the heating liquid tank, and a third supply pipe extending between the secondary energy source valve and the first lower inlet at the lower tank portion of the heating liquid tank.

The secondary energy source valve is arranged to distribute heating liquid flow from the secondary energy source to the upper tank portion or lower tank portion of the heating liquid tank. Thus, heating liquid flow from the secondary energy source may be supplied to the upper or the lower tank portion based on the operating conditions or operating mode of the hybrid heating arrangement.

In some special embodiments, the secondary energy source valve may also be arranged to distribute the heating liquid flow from the secondary energy source also to both the upper and the lower tank portions.

In one embodiment, the hybrid distribution assembly comprises a distribution valve forming a connection with a fourth supply pipe extending between the heating circuit and the distribution valve, a fifth supply pipe extending between the distribution valve and the first lower inlet at the lower tank portion of the heating liquid tank, and a sixth supply pipe extending between the distribution valve and the secondary energy source.

The distribution valve is arranged to distribute heating liquid flow from the heating circuit to the lower tank portion. Alternatively, the distribution valve is arranged to distribute the heating liquid flow from the heating circuit to the lower tank portion and to the secondary energy source. In a special operating mode, the distribution valve is arranged to distribute heating liquid flow from the heating circuit to the secondary energy source.

In one embodiment, the hybrid distribution assembly comprises a control valve forming a connection with a seventh supply pipe extending between the first upper outlet at the upper tank portion of the heating liquid tank and the control valve, and an eighth supply pipe extending between the control valve and the heating circuit.

The control valve is arranged to control the heating liquid flow from the heating liquid tank to the heating circuit based on the thermal energy demand.

In one embodiment, the hybrid heating arrangement comprises a primary supply pipe extending between the primary energy source and the first upper inlet at the upper tank portion of the heating liquid tank, and a primary return pipe extending between the first lower outlet at the lower tank portion of heating liquid tank and the primary energy source.

This enables circulating the heating liquid between the heating tank and the primary energy source.

In one embodiment, the heating liquid tank comprising a distribution element dividing the heating liquid tank into the upper tank portion and the lower tank portion, the distribution element having at least one aperture through the distribution element providing a flow communication between the upper and lower tank portions.

The distribution element enables separating high temperature heating liquid in the upper tank portion and low or lower temperature heating liquid in the lower tank portion. The distribution element and the at least one aperture thereof further decreases heating liquid flow between the upper tank portion and the lower tank portion. Thus, mixing of the high temperature heating liquid in the upper tank portion and the low temperature heating liquid in the lower tank portion is slowed down.

In one embodiment, the primary energy source is an air-to-water heat pump or a ground-source heat pump or a solar energy source or a wind power energy source or a water energy source or any combination of these.

Thus, the primary energy source may be renewable energy source and/or a local energy source.

In one embodiment, the secondary energy source is a district heating source or an electric energy source or a gas energy source, such as natural or biogas or liquefied petroleum gas, or a light or heavy fuel oil energy source or a solid fuel energy source, such as wood or wood chips or pellets, or any combination of these, and the secondary energy source comprises an interface device such as a heat exchanger or a separator tank. Therefore, the secondary energy source may be a boiler such as an electric boiler, a gas boiler, a gas condensing boiler, an oil boiler or an oil condensing boiler.

In one embodiment, the hybrid heating arrangement further comprises a temperature sensor arranged to detect change in temperature of the heating liquid in the heating liquid tank, and a control unit arranged to control the hybrid distribution assembly to activate the secondary energy source to provide thermal energy to the heating liquid in the heating liquid tank.

Accordingly, the hybrid heating arrangement and the hybrid distribution assembly thereof may be controlled based on the temperature measurement in the heating liquid tank with the temperature sensor.

The present invention further relates to a method of operating a hybrid heating arrangement comprising at least one primary energy source and at least one secondary energy source which are independently working as separate energy sources and separately connected to a heating liquid tank comprising heating liquid for providing thermal energy to the heating circuit. The method comprises operating the primary energy source by providing a primary supply flow heated by the primary energy source as a heating liquid flow from the primary energy source through a first upper inlet of an upper tank portion into the heating liquid tank, providing the heating liquid flow from the heating liquid tank through a first upper inlet of the upper tank portion to the heating circuit for providing thermal energy to the heating circuit, circulating the heating liquid flow as a return flow from the heating circuit through a distribution valve provided in a hybrid distribution assembly and further through a first lower inlet of a lower tank portion into the heating liquid tank, and providing the heating liquid flow as a primary return flow from the heating liquid tank through a first lower outlet of the lower tank portion to the primary energy source for reheating the heating liquid. The method further comprises determining a temperature setpoint for the heating liquid in the heating liquid tank to obtain a predetermined temperature, measuring temperature of the heating liquid in the heating liquid tank to obtain a measured temperature, comparing the measured temperature to the predetermined temperature to obtain a temperature difference, and operating a secondary energy source valve for activating or inactivating the heat exchange communication from the secondary energy source to the heating liquid in the heating liquid tank based on the temperature difference, the secondary energy source valve being arranged in the hybrid distribution assembly and providing the heat exchange communication between the secondary energy source and the heating liquid tank via the heating liquid.

Accordingly, the method enables efficient combined use of the primary and secondary energy sources for providing thermal energy to the heating circuit.

In one embodiment, the step of operating the secondary energy source valve comprises opening the secondary energy source valve for activating the heat exchange communication from the secondary energy source to the heating liquid in the heating liquid tank by allowing a heating liquid communication between the secondary energy source and the second upper inlet of the upper tank portion of the heating liquid tank in response to the temperature difference in which the measured temperature is by a predetermined value below the predetermined temperature, and operating the secondary energy source by providing a second supply flow heated by the secondary energy source as the heating liquid flow from the secondary energy source through the second upper inlet of the upper tank portion into the heating liquid tank.

Thus, thermal energy from the secondary energy source may be added to the heating liquid tank.

In one embodiment, the method further comprises a step of operating a distribution valve provided in a heating liquid communication with the heating circuit and with the first lower inlet of the lower tank portion of the heating liquid tank and further provided in a heat exchange communication with the secondary energy source via the heating liquid, and directing the heating liquid flow from the heating circuit completely through the secondary energy source provided downstream of the distribution valve prior entering through the first lower inlet of the lower tank portion into the heating liquid tank.

In one embodiment, the method further comprises operating a distribution valve provided in a heating liquid communication with the heating circuit and with the first lower inlet of the lower tank portion of the heating liquid tank and further provided in a heat exchange communication with the secondary energy source via the heating liquid, and by distributing the heating liquid flow coming from the heating circuit in the distribution valve, directing part of the heating liquid flow to the secondary energy source, and directing the rest of the heating liquid flow to the first lower inlet. Therefore, part of the heating liquid flow from the heating circuit may be distributed to the secondary energy source and to the lower tank portion of the heating liquid tank.

In one embodiment, the method comprises directing 70-95% of the heating liquid flow to the secondary energy source and the rest to the first lower inlet, and preferably directing 80-90% of the heating liquid flow to the secondary energy source and the rest to the first lower inlet. Therefore, majority of the heating liquid flow from the heating circuit is directed to the secondary energy source.

In one embodiment, the step of operating the secondary energy source valve comprises closing the secondary energy source valve for inactivating the heat exchange communication from the secondary energy source to the heating liquid in the heating liquid tank by preventing a heating liquid communication between the secondary energy source and the second upper inlet of the upper tank portion of the heating liquid tank in response to the temperature difference in which the measured temperature is the predetermined temperature or above the predetermined temperature.

In one embodiment, the step of circulating the heating liquid flow as a return flow from the heating circuit comprises circulating the return flow downstream of the distribution valve through the secondary energy source in a passive state before providing the return flow through the first lower inlet of the lower tank portion into the heating liquid tank.

In one embodiment, the method further comprises a temporary defrosting procedure which comprises operating the secondary energy source by providing the second supply flow heated by the secondary energy source as the heating liquid flow from the secondary energy source through the second upper inlet of the upper tank portion into the heating liquid tank, providing the heating liquid flow from the heating liquid tank through the first lower outlet of the lower tank portion to the primary energy source for defrosting an outdoor unit of the primary energy source, and circulating the heating liquid flow from the primary energy source through the first upper inlet on the upper tank portion into the heating liquid tank for mixing with the heating liquid flow heated by the secondary energy source.

This enables providing the thermal energy for the heating circuit and for the defrosting from the secondary energy source.

The hybrid heating arrangement according to the invention preferably provides 60-90 percent of the heating energy needs by the primary energy source such as a heat pump. The rest of the heating energy need is provided by the secondary energy source such as district heating, electricity, boiler. The primary energy source can be for example a medium deep heat well or an air-to-water heat pump which transfers heat energy from the outside air to the circulating heating of a heating circuit. A heating circuit refers to the piping system that carries heating liquid from the energy source to radiators or underfloor heating and back. This is also commonly called a heating zone.

The present invention provides a hybrid heating arrangement and method in which the temperature of the district heating return water is not heated. Furthermore, the power of the primary energy source, such as air-to-water heat pump, is restricted. Additionally, the defrosting energy may be compensated with thermal energy from the secondary energy source, such as district heating. Thus, temperature variations in the circuit may be minimized and the primary energy source may be utilized rapidly for heating after defrosting.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in detail by means of specific embodiments with reference to the enclosed drawing, in which

Figure 1 shows the hybrid heating arrangement according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 shows the hybrid heating arrangement according to the invention in which a heating liquid tank 4 has separate connections with a primary energy source 1 and a secondary energy source 2. The primary energy source 1 is preferably a renewable energy source such as an air-to-water heat pump or a ground-source heat pump or a solar energy source or a wind power energy source or a water energy source or any combination of these. The secondary energy source 2 is a district heating source or an electric energy source or a fossil energy source or any combination of these. The secondary energy source 2 may comprise an interface device such as a heat exchanger or a separator tank through which the heating liquid flows and is heated by the actual energy source. The primary and secondary energy sources are independent energy sources which means that they work independently and separately from each other. Only connection between the primary and secondary energy sources is the heating liquid which is supplied from the heating liquid tank 4 to both energy sources. As the secondary energy source 2 may comprise the interface device, the heating liquid is therefore flowing through the secondary energy source 2. In this case, for example, when the district heating has its own liquid which is separate from the heating liquid but since the interface device such as a heat exchanger is considered part of the secondary energy source and the heating liquid flows through the heat exchanger then the heating liquid flows through the secondary energy source.

The heating liquid tank 4 is further in a flow communication with the heating circuit 3 which may also be called a heating zone providing heating to multiple locations. The hybrid heating arrangement further comprises a hybrid distribution assembly 5 providing heating liquid communication between the various parts of the hybrid heating arrangement. The primary energy source 1 is directly connected to the heating liquid tank 4 without a connection to the hybrid distribution assembly 5 whereas the secondary energy source 2 and the heating circuit 3 are preferably connected to the heating liquid tank 4 through the hybrid distribution assembly 5. The hybrid distribution assembly 5 is provided in a heating liquid communication with the heating circuit 3 and with the heating liquid tank 4 which means that the heating liquid supplied from the heating liquid tank 4 to the heating circuit 3 is flown through the hybrid distribution assembly 5 and the return flow from the heating circuit 3 to the heating liquid tank 4 is provided through the hybrid distribution assembly 5 providing the flow communication between the heating liquid tank 4 and the heating circuit 3. The hybrid distribution assembly 5 is therefore arranged to provide thermal energy from the heating liquid tank 4 to the heating circuit 3. The hybrid distribution assembly 5 is further provided in a heat exchange communication with the secondary energy source 2 for providing thermal energy from the secondary energy source 2 to the heating liquid tank 4. The heat exchange communication is preferably provided through the interface device providing heating from the secondary energy source to the heating liquid.

The heating liquid tank 4 is divided into an upper tank portion 4a and a lower tank portion 4b which are in a flow communication with each other. The division of the heating liquid tank 4 is provided by a distribution element 40 having at least one aperture 4c through the distribution element 40 allowing the flow communication between the tank portions 4a, 4b. The distribution element 40 helps to keep the warm heating liquid in the upper tank portion 4a of the heating liquid tank 4 to which the heating liquid heated by the primary energy source 1 or by the secondary energy source 2 or both energy sources flows, because the upper tank portion 4a comprises the inlets for the heated heating liquid. The upper tank portion 4a is preferably at least ^l/i- of the total volume of the heating liquid tank 4 or V4 of the total volume of the heating liquid tank 4, or ¹/s of the total volume of the heating liquid tank 4.

The upper tank portion 4a comprises a first upper inlet 11 and a second upper inlet 21 and a first upper outlet 32 whereas the lower tank portion 4b comprises a first lower outlet 12 and a first lower inlet 31. The terms inlet and outlet describe the direction of the heating liquid relative to the tank such that the heating liquid is supplied through the inlet into the heating liquid tank 4 and the heating liquid is supplied through the outlet out from the heating liquid tank 4. The first upper inlet 11 connects the primary energy source 1 to the heating liquid tank 4 through a primary supply pipe 109 extending between the primary energy source 1 and the first upper inlet 11 for supplying the heating liquid from the primary energy source 1 to the upper tank portion 4a of the heating liquid tank 4. The first lower outlet 12 further connects the primary energy source 1 to the heating liquid tank 4 through a primary return pipe 110 extending between the first lower outlet 12 and the primary energy source 1 such that the flow direction of the heating liquid is from the heating liquid tank 4 through the first lower outlet 12 to the primary energy source 1. The figure shows the primary energy source 1 as an indoor unit comprises an outdoor unit la which is separated by a wall W from the indoor unit.

The second upper inlet 21 connects the secondary energy source 2 to the heating liquid tank 4 through the hybrid distribution assembly 5 for providing thermal energy as a secondary supply flow from the secondary energy source 2 to the heating liquid tank 4. The hybrid distribution assembly 5 comprises a secondary energy source valve 200 connecting the second upper inlet 21 and the secondary energy source 2 by a first supply pipe 101 extending between the secondary energy source 2 and the secondary energy source valve 200 and by a second supply pipe 102 extending between the secondary energy source 2 and the second upper inlet 21. The secondary energy source valve 200 further providing a connection to the first lower inlet 31 of the heating liquid tank 4 by a third supply pipe 103 extending between the secondary energy source valve 200 and the first lower inlet 31 at the lower tank portion 4b of the heating liquid tank 4.

The first lower inlet 31 further connects the hybrid distribution assembly 5 to the heating liquid tank 4 for providing a heating liquid supply flow from the heating circuit 3 to the heating liquid tank 4. The hybrid distribution assembly 5 further comprises a distribution valve 300 connecting the heating circuit 3 to the heating liquid tank 4 by a fourth supply pipe 104 extending between the heating circuit 3 and the distribution valve 300 in the hybrid distribution assembly 5 and by a fifth supply pipe 105 extending between the distribution valve 5 and the first lower inlet 31 at the lower tank portion 4b of the heating liquid tank 4 for providing a heating liquid supply flow from the heating circuit 3 to the heating liquid tank 4. The distribution valve 300 further providing a connection to the secondary energy source 2 by a sixth supply pipe 106 extending between the distribution valve 300 and the secondary energy source 2. The secondary energy source 2 is therefore connected through the secondary energy source valve 200 to the upper tank portion 4a of the heating liquid tank 4 and through the distribution valve 300 to the lower tank portion 4b of the heating liquid tank 4. The first lower inlet 31 may comprise two separate inlets or the third supply pipe 103 and the fifth supply pipe 105 may be connected together through a valve prior the first lower inlet 31 or at the first lower inlet 31.

The first upper outlet 32 connects the heating liquid tank to the hybrid distribution assembly 5 for providing a heating liquid flow from the heating liquid tank 4 to the heating circuit 3. The hybrid distribution assembly 5 comprises a control valve 400 connecting the first upper outlet 32 of the heating liquid tank 4 to the heating circuit 3 by a seventh supply pipe 107 extending between the first upper outlet 32 and the control valve 400 and by an eighth supply pipe 108 extending between the control valve 400 and the heating circuit 3.

In special circumstances when there is a need to operate only with the secondary energy source 2 the hybrid heating arrangement may comprise a direct heating valve 500 connecting the secondary energy source 2 to the heating circuit 3 without being in a liquid communication with the heating liquid tank 4. The direct heating valve 500 can be used to control the heating liquid flow from the secondary energy source 2 to the heating circuit 3 in part or in full. With the direct heating valve 500 the primary energy source 1 can be bypassed completely wo that the primary energy source 1 only provides thermal energy to the heating liquid tank 4 or is temporarily complete switched off. The direct heating valve 500 is provided preferably in connection with the second supply pipe 102 and the seventh supply pipe 107 or such that there is a connecting pipe extending between the second supply pipe 102 and the seventh supply pipe 107. The direct heating valve 500 provides a heating liquid connection from the second energy source 2 via the first supply pipe 101 and the second supply pipe 102 to the eighth supply pipe 108 extending to the heating circuit 3 but the piping between the second supply pipe 102 and the eighth supply pipe 108 can be implemented in various alternative ways. The direct heating valve 500 is illustrated in the figure with a dashed circle since it does apply to normal routines of the hybrid heating arrangement and the position of the direct heating valve 500 may vary. The direct heating valve 500 is controlled according to a predetermined temperature in the heating circuit 3 and if the predetermined temperature in the heating circuit 3 drops or does not reach its setpoint, the direct heating valve 500 is opened for supplying thermal energy from the secondary energy source 2 directly to the heating circuit 3. When the predetermined temperature is reached, the direct heating valve 500 will be closed.

In the method of operating a hybrid heating arrangement the hybrid heating arrangement is arranged to heat a heating circuit providing heat to multiple places. In a normal heating mode, the hybrid heating arrangement is operated by the primary energy source 1 providing a heating liquid flow heated by the primary energy source 1 from the primary energy source 1 to the heating liquid tank 4. The secondary energy source 2 is in a stand-by mode which means that the secondary energy source 2 is ready to be operated when a temperature drop down occurs in the heating liquid tank 4 or an outdoor unit of the primary energy source 1 freezes or is fogged. In the event of temperature drop down of the heating liquid in the heating liquid tank 4, the secondary energy source 2 is operated together with the primary energy source 1 for providing thermal energy to the heating liquid. In the event of defrosting the outdoor unit of the primary energy source 1 the secondary energy source 2 provides thermal energy to the heating liquid in the heating liquid tank 4 and the primary energy source 1 uses the heating liquid heated by the secondary energy source 2 for defrosting. The decrease in the temperature of the heating liquid in the heating liquid tank 4 is due to the inadequacy of the primary energy source 1 alone to heat the heating liquid sufficiently. Therefore, the secondary energy source 2 is operated together with the primary energy source 1 as long as needed to reach the predetermined temperature for the heating liquid which is adequate for the heating circuit 3 to operate normally. The adequate temperature is presented in a heating curve presenting the heating needs of a property.

The operation of the secondary energy source 2 is controlled according to a heating curve of the heating needs of a property in question. The heating curve represents the temperatures according to certain conditions in the property. A temperature sensor is provided at the upper tank portion 4a of the heating liquid tank 4. The secondary energy source 2 is operated when the primary energy source is unable to produce the required heating energy. This is detected by the temperature sensor in the heating liquid tank 4 which measures the temperature of the heating liquid. The secondary energy source 2 is activated by a control unit which co-operates with the temperature sensor and controls the hybrid distribution assembly 5 in which a secondary energy source valve 200 is provided. In response to a temperature drop of the heating liquid in the heating liquid tank 4, the secondary energy source valve 200 is opened for activating the heat exchange communication from the secondary energy source 2 to the heating liquid in the heating liquid tank 4 for providing thermal energy to the heating liquid and increasing the temperature of the heating liquid. The activation of the secondary energy source 2 is performed when the measured temperature of the heating liquid is by a predetermined value below the predetermined temperature of the heating liquid provided in the heating liquid tank 4. The predetermined value is for example 2 or 3 °C below the predetermined temperature.

The hybrid heating arrangement comprises at least one primary energy source 1 and at least one secondary energy source 2 which are independently working as separate energy sources and separately connected to a heating liquid tank 4 comprising heating liquid for providing thermal energy to the heating circuit 3. The method of operating the hybrid heating arrangement comprises a step of operating the primary energy source 1 by providing a primary supply flow which is heated by the primary energy source 1 from the primary energy source 1 into the heating liquid tank 4. The primary supply flow is the heating liquid flow which circulates in the hybrid heating arrangement. In other words, the heating liquid tank 4 hold the heating liquid which is circulated through the primary energy source 1 and through the heating circuit 3 and through the secondary energy source 2, although the secondary energy source 2 heating the heating liquid preferably through an interface device such that the secondary energy source 2 comprises a separate heating liquid than the heating liquid of the hybrid heating arrangement. The heating liquid supplied from the primary energy source 1 enters through a first upper inlet 11 of an upper tank portion 4a into the heating liquid tank 4 as a heating liquid flow. In the hybrid heating arrangement, the heated heating liquid is supplied all the time into the upper tank portion 4a of the heating liquid tank 4 and the distribution element 40 dividing the heating liquid tank 4 into the upper tank portion 4a and the lower tank portion 4b contributes maintaining the warmest heating liquid in the upper tank portion 4a wherefrom the heating liquid is supplied out from the heating liquid tank 4 to the heating circuit 3. Therefore, the method further comprises a step of providing the heating liquid flow from the heating liquid tank 4 through a first upper outlet 32 of the upper tank portion 4a to the heating circuit 3 for providing thermal energy to the heating circuit 3. The hybrid heating arrangement comprise a hybrid distribution assembly 5 which is provided to the hybrid heating arrangement such that the connection between the heating liquid tank 4 and the heating circuit 3 is provided through the hybrid distribution assembly 5. Therefore, the first upper outlet 32 of the upper tank portion 4a is connected to the heating circuit 3 through a seventh supply pipe 107 extending between the heating liquid tank 4 and the hybrid distribution assembly 5 and through an eighth supply pipe 108 extending between the hybrid distribution assembly 5 and the heating circuit 3. The hybrid distribution assembly 5 preferably comprises a control valve 400 connecting the seventh and eighth supply pipes 107, 108 together. The method further comprises a step of circulating the heating liquid flow as a return flow from the heating circuit 3 through a distribution valve 300 provided in the hybrid distribution assembly 5 and further through a first lower inlet 31 of a lower tank portion 4b into the heating liquid tank 4. The heating circuit 3 is connected to the hybrid distribution assembly 5 through a fourth supply pipe 104 extending between the heating circuit 3 and the distribution valve 300 and the first lower inlet 31 of a lower tank portion 4b is connected to the hybrid distribution assembly 5 through a fifth supply pipe 105 extending between the distribution valve 300 and the heating liquid tank 4. The heating liquid provided as the return flow from the heating circuit 3 to the heating liquid tank 4 is cooler than the heating liquid flow supplied from the primary energy source 1 and heated by the primary energy source 1. This cooler heating liquid needs to be heated again in the primary energy source 1 and therefore the method comprises a further step of providing the heating liquid flow as a primary return flow from the heating liquid tank 4 through a first lower outlet 12 of the lower tank portion 4b to the primary energy source 1 for reheating the heating liquid.

The temperature of the heating liquid in the heating liquid tank 4 has to be maintained warm enough for the heating circuit and the temperature of the heating liquid has to be monitored. The temperature of the heating liquid in the heating liquid tank has a certain predetermined temperature in which the heating liquid provides enough thermal energy for the heating circuit 3. The hybrid heating arrangement further comprises a predetermined value for the temperature drop which shows that the primary energy source 1 does not provide sufficient thermal energy for the heating liquid. Therefore, the method further comprises the steps of determining a temperature setpoint for the heating liquid in the heating liquid tank 4 to obtain a predetermined temperature, measuring the temperature of the heating liquid in the heating liquid tank 4 to obtain a measured temperature and comparing the measured temperature to the predetermined temperature to obtain a temperature difference. If the temperature difference is negative, i.e. the measured temperature is below the predetermined temperature, then the secondary energy source 2 has to be operated together with the primary energy source 1 and if the temperature difference is positive, i.e. the measured temperature is above the predetermined temperature, or there is no temperature difference, then the secondary energy source 2 remains passive and the hybrid heating arrangement is operated only with the primary energy source 1. Therefore, the method further comprises a step of operating a secondary energy source valve 200 for activating or inactivating the heat exchange communication from the secondary energy source 2 to the heating liquid in the heating liquid tank 4 based on the temperature difference. The secondary energy source valve 200 is arranged in the hybrid distribution assembly 5 and providing the heat exchange communication between the secondary energy source and the heating liquid tank 4 via the heating liquid. In other words, operating the secondary energy source valve 200 for activating the heat exchange communication between the secondary energy source 2 and the heating liquid allows the use of the secondary energy source 2 into the heating and operating the secondary energy source valve 200 for inactivating the heat exchange communication between the secondary energy source 2 and the heating liquid excludes the secondary energy source 2 from the heating.

For activating the heat exchange communication between the secondary energy source 2 and the heating liquid flowing through the secondary energy source 2 to the heating liquid tank 4, the step of operating the secondary energy source valve 200 comprises steps of opening the secondary energy source valve 200 for activating the heat exchange communication from the secondary energy source 2 to the heating liquid in the heating liquid tank 4 by allowing a heating liquid communication between the secondary energy source 2 and the second upper inlet 21 of the upper tank portion 4a of the heating liquid tank 4 in response to the temperature difference in which the measured temperature is by a predetermined value below the predetermined temperature; and operating the secondary energy source 2 by providing a second supply flow heated by the secondary energy source 2 as the heating liquid flow from the secondary energy source 2 through the second upper inlet 21 of the upper tank portion 4a into the heating liquid tank 4. The temperature difference between the predetermined temperature and the measured temperature may be defined to have a certain operational value such that when the difference is very small, for example 1°C, the heat exchange communication will not be activated but when the measured temperature is by a predetermined value below the predetermined temperature, then the heat exchange communication from the secondary energy source 2 will be activated.

For inactivating the heat exchange communication between the secondary energy source 2 and the heating liquid flowing through the secondary energy source 2 to the heating liquid tank 4, the step of operating the secondary energy source valve 200 comprises steps of closing the secondary energy source valve 200 for inactivating the heat exchange communication from the secondary energy source 2 to the heating liquid in the heating liquid tank 4 by preventing a heating liquid communication between the secondary energy source 2 and the second upper inlet 21 of the upper tank portion 4a of the heating liquid tank 4 in response to the temperature difference in which the measured temperature is the predetermined temperature or above the predetermined temperature. However, this does not mean that the heating liquid will not flow through the secondary energy source 2 comprising an interface device such as a heat exchanger, but this means that the secondary energy source 2 will not produce thermal energy for the heating liquid flowing through the secondary energy source 2. However, when the secondary energy source 2 is not in the heat exchange communication with the heating liquid, i.e. the secondary energy source 2 will not provide heat for the heating liquid, then the communication from the secondary energy source 2 to the second upper inlet 21 is not open. The secondary energy source 2 is connected to the second upper inlet 21 through the first supply pipe 101 extending between the secondary energy source 2 and the secondary energy source valve 200 in the hybrid distribution assembly 5 and through a second supply pipe 102 extending between the secondary energy source valve 200 and the second upper inlet 21. The connection between the secondary energy source valve 200 and the second upper inlet 21 is only open when the secondary energy source 2 provides thermal energy for the heating liquid.

The hybrid heating assembly 5 comprises a distribution valve 300 connected to the first lower inlet 31 of the lower tank portion 4b of the heating liquid tank 4 through a fifth supply pipe 105, and to the secondary energy source 2 through a sixth supply pipe 106, and to the heating circuit 3 through a fourth supply pipe 104. The method comprises a step of operating the distribution valve 300 and directing the heating liquid flow from the heating circuit 3 completely through the secondary energy source 2 provided downstream of the distribution valve 300 prior entering through the first lower inlet 31 of the lower tank portion 4b into the heating liquid tank 4. However, the return flow from the secondary energy source 2 is provided through a first supply pipe 101 extending between the secondary energy source 2 and the secondary energy source valve 200 and through a third supply pipe 103 extending from the secondary energy source valve 200 to the first lower inlet 31. The first lower inlet 31 may comprise two inlets: one connecting with the third supply pipe 103 extending from the secondary energy source valve 200 to the first lower inlet 31 and another connecting with the fifth supply pipe 105 extending from the distribution valve 300 to the first lower inlet 31 or the third supply pipe 103 and the fifth supply pipe 105 may connect together prior the single connection to the first lower inlet 31. Although the heating liquid from the heating circuit 3 is completely directed through the secondary energy source 2 prior directing it to the first lower inlet 31, the secondary energy source 2 will not provide thermal energy to the heating liquid since the heating liquid heated by the secondary energy source 2 will always be supplied to the upper tank portion 4a of the heating liquid tank 4, whereas the first lower inlet 31 is provided to the lower tank portion 4b of the heating liquid tank 4. Therefore, in this method step only the primary energy source 1 is operated and the secondary energy source 2 remains passive. This means that in the step of circulating the heating liquid flow as a return flow from the heating circuit 3 comprises circulating the return flow downstream of the distribution valve 300 through the secondary energy source 2 in a passive state before providing the return flow through the first lower inlet 31 of the lower tank portion 4b into the heating liquid tank 4.

Alternatively, the method comprises a step of operating the distribution valve 300 by distributing the heating liquid flow coming from the heating circuit 3 in the distribution valve 300 directing part of the heating liquid flow to the secondary energy source 2 and directing the rest of the heating liquid flow to the first lower inlet 31. In this embodiment of the method, the secondary energy source 2 is active such that the part of the heating liquid flow directed from the distribution valve 300 to the secondary energy source 2 is heated by the secondary energy source 2 and thereafter directed to the second upper inlet 21 as a heated heating liquid. Therefore, only part of the heating liquid flow coming from the heating circuit is heated by the secondary energy source 2 and the rest of the heating liquid is directed to the first lower inlet 31 to the lower tank portion 4b wherefrom the heating liquid is supplied through the first lower outlet 12 as a primary return flow to the primary energy source 1 for reheating the heating liquid by the primary energy source 1. Therefore, in this method step both the primary energy source 1 and the secondary energy source 2 are used for heating the heating liquid.

In a preferable embodiment the step of operating the distribution valve 300 comprises directing 70-95% of the heating liquid flow to the secondary energy source 2 and the rest to the first lower inlet 31, and preferably directing 80-90% of the heating liquid flow to the secondary energy source 2 and the rest to the first lower inlet 31. Therefore, not all the heating liquid flow coming from the heating circuit 3 is heated by the secondary energy source 2 which is more costly or less environmental.

The method according to the invention further comprises a temporary defrosting procedure. In the defrosting procedure the secondary energy source 2 is used for defrosting the outdoor unit of the primary energy source 1. The outdoor unit la is shown in figure 1 as separated by the wall W from the rest of the primary energy source 1. The secondary energy source 2 is then operated for heating the heating liquid which is supplied from the secondary energy source 2 to the second upper inlet 21 for providing heated heating liquid into the heating liquid tank 4. The secondary energy source 2 is operated so that the heating liquid tank 4 will comprise heating liquid which is warm enough also in the lower tank portion 4b such that the heating liquid flow from the first lower outlet 12 to the primary energy source 1 is warm and will defrost the outdoor unit la of the primary energy source 1. The steps of the defrosting procedure comprise therefore operating the secondary energy source 2 by providing the second supply flow heated by the secondary energy source 2 as the heating liquid flow from the secondary energy source 2 through the second upper inlet 21 of the upper tank portion 4a into the heating liquid tank 4; providing the heating liquid flow from the heating liquid tank 4 through the first lower outlet 12 of the lower tank portion 4b to the primary energy source 1 for defrosting an outdoor unit la of the primary energy source 1; and circulating the heating liquid flow from the primary energy source 1 through the first upper inlet 11 on the upper tank portion 4a into the heating liquid tank 4 for mixing with the heating liquid flow heated by the secondary energy source 2.

The invention has been described above with reference to the examples shown in the figures. However, the invention is in no way restricted to the above examples but may vary within the scope of the claims.

Claims

1. A hybrid heating arrangement connecting a primary energy source (1) and a secondary energy source (2) to a heating circuit (3) for providing thermal energy to the heating circuit (3), c h a r a c t e r i z e d in that the hybrid heating arrangement comprises: at least one primary energy source (1) and at least one secondary energy source (2) which are independently working as separate energy sources; a heating liquid tank (4) for holding heating liquid, the heating liquid tank (4) having an upper tank portion (4a) and a lower tank portion (4b) in a flow communication with each other; and a hybrid distribution assembly (5) in a heating liquid communication with the heating circuit (3) and with the heating liquid tank (4), the hybrid distribution assembly (5) being arranged to provide thermal energy from the heating liquid tank (4) to the heating circuit (3), the hybrid distribution assembly (5) further being in a heat exchange communication with the secondary energy source (2) for providing thermal energy from the secondary energy source (2) to the heating liquid tank (4); the heating liquid tank (4) further having: a first upper inlet (11) at the upper tank portion (4a) of the heating liquid tank (4) forming a heating liquid connection from the primary energy source (1) to the heating liquid tank (4) for providing thermal energy in a primary supply flow as a heating liquid flow from the primary energy source (1) to the heating liquid tank (4); a first lower outlet (12) at the lower tank portion (4b) of the heating liquid tank (4) which the first lower outlet (12) connecting the heating liquid tank (4) to the primary energy source (1) for providing the heating liquid flow as a primary return flow from the heating liquid tank (4) to the primary energy source

(i); a second upper inlet (21) at the upper tank portion (4a) of the heating liquid tank (4) which the second upper inlet (21) connecting the secondary energy source (2) to the heating liquid tank (4) for providing thermal energy as a secondary supply flow from the secondary energy source (2) to the heating liquid tank (4); a first lower inlet (31) at the lower tank portion (4b) of the heating liquid tank (4) which the first lower inlet (31) connecting the hybrid distribution assembly (5) to the heating liquid tank (4) for providing a heating liquid supply flow from the heating circuit (3) to the heating liquid tank (4); and a first upper outlet (32) at the upper tank portion (4a) of the heating liquid tank (4) which the first upper outlet (32) connecting the heating liquid tank (4) to the hybrid distribution assembly (5) for providing a heating liquid flow from the heating liquid tank (4) to the heating circuit (3).

2. A hybrid heating arrangement according to claim 1, c h a r a c t e r i z e d in that the hybrid distribution assembly (5) comprising a secondary energy source valve (200) forming a connection with a first supply pipe (101) extending between the secondary energy source (2) and the secondary energy source valve (200); a second supply pipe (102) extending between the secondary energy source valve (200) and the second upper inlet (21) at the upper tank portion (4a) of the heating liquid tank (4); a third supply pipe (103) extending between the secondary energy source valve (200) and the first lower inlet (31) at the lower tank portion (4b) of the heating liquid tank (4).

3. A hybrid heating arrangement according to claim 1 or 2, c h a r a c t e r i z e d in that the hybrid distribution assembly (5) comprising a distribution valve (300) forming a connection with a fourth supply pipe (104) extending between the heating circuit (3) and the distribution valve (300); a fifth supply pipe (105) extending between the distribution valve (300) and the first lower inlet (31) at the lower tank portion (4b) of the heating liquid tank (4); and a sixth supply pipe (106) extending between the distribution valve (300) and the secondary energy source (2).

4. A hybrid heating arrangement according to any previous claim, c h a r a c t e r i z e d in that the hybrid distribution assembly (5) comprising a control valve (400) forming a connection with a seventh supply pipe (107) extending between the first upper outlet (32) at the upper tank portion (4a) of the heating liquid tank (4) and the control valve (400); and an eighth supply pipe (108) extending between the control valve (400) and the heating circuit (3).

5. A hybrid heating arrangement according to any previous claim, characterized in that the hybrid heating arrangement comprising: a primary supply pipe (109) extending between the primary energy source (1) and the first upper inlet (11) at the upper tank portion (4a) of the heating liquid tank (4); and a primary return pipe (110) extending between the first lower outlet (12) at the lower tank portion (4b) of heating liquid tank (4) and the primary energy source (1).

6. A hybrid heating arrangement according to any previous claim, characterized in that the heating liquid tank (4) comprising a distribution element (40) dividing the heating liquid tank (4) into the upper tank portion (4a) and the lower tank portion (4b), the distribution element (40) having at least one aperture (4c) through the distribution element (40) providing a flow communication between the upper and lower tank portions (4a, 4b).

7. A hybrid heating arrangement according to any previous claim, characterized in that the primary energy source (1) is an air-to-water heat pump or a ground-source heat pump or a solar energy source or a wind power energy source or a water energy source or any combination of these.

8. A hybrid heating arrangement according to any previous claim, characterized in that the secondary energy source (2) is a district heating source or an electric energy source or a gas energy source or a fuel oil energy source or a solid fuel energy source or any combination of these, and the secondary energy source (2) comprises an interface device such as a heat exchanger or a separator tank.

9. A hybrid heating arrangement according to any previous claim, characterized in that the hybrid heating arrangement further comprising a temperature sensor arranged to detect change in temperature of the heating liquid in the heating liquid tank (4); and a control unit arranged to control the hybrid distribution assembly (5) to activate the secondary energy source (2) to provide thermal energy to the heating liquid in the heating liquid tank (4).

10. A method of operating a hybrid heating arrangement comprising at least one primary energy source (1) and at least one secondary energy source (2) which are independently working as separate energy sources and separately connected to a heating liquid tank (4) comprising heating liquid for providing thermal energy to the heating circuit (3), c h a r a c t e r i z e d in that the method comprises steps of: operating the primary energy source (1) by providing a primary supply flow heated by the primary energy source (1) as a heating liquid flow from the primary energy source (1) through a first upper inlet (11) of an upper tank portion (4a) into the heating liquid tank (4); providing the heating liquid flow from the heating liquid tank (4) through a first upper outlet (32) of the upper tank portion (4a) to the heating circuit (3) for providing thermal energy to the heating circuit (3); circulating the heating liquid flow as a return flow from the heating circuit (3) through a distribution valve (300) provided in a hybrid distribution assembly (5) and further through a first lower inlet (31) of a lower tank portion (4b) into the heating liquid tank (4); providing the heating liquid flow as a primary return flow from the heating liquid tank (4) through a first lower outlet (12) of the lower tank portion (4b) to the primary energy source (1) for reheating the heating liquid; determining a temperature setpoint for the heating liquid in the heating liquid tank (4) to obtain a predetermined temperature; measuring temperature of the heating liquid in the heating liquid tank (4) to obtain a measured temperature; comparing the measured temperature to the predetermined temperature to obtain a temperature difference; and operating a secondary energy source valve (200) for activating or inactivating the heat exchange communication from the secondary energy source (2) to the heating liquid in the heating liquid tank (4) based on the temperature difference, the secondary energy source valve (200) being arranged in the hybrid distribution assembly (5) and providing the heat exchange communication between the secondary energy source (2) and the heating liquid tank (4) via the heating liquid.

11. A method of operating a hybrid heating arrangement according to claim 10, c h a r a c t e r i z e d in that the step of operating the secondary energy source valve (200) comprises: opening the secondary energy source valve (200) for activating the heat exchange communication from the secondary energy source (2) to the heating liquid in the heating liquid tank (4) by allowing a heating liquid communication between the secondary energy source (2) and the second upper inlet (21) of the upper tank portion (4a) of the heating liquid tank (4) in response to the temperature difference in which the measured temperature is by a predetermined value below the predetermined temperature; and operating the secondary energy source (2) by providing a second supply flow heated by the secondary energy source (2) as the heating liquid flow from the secondary energy source (2) through the second upper inlet (21) of the upper tank portion (4a) into the heating liquid tank (4).

12. A method of operating a hybrid heating arrangement according to claim 10 or 11, c h a r a c t e r i z e d in that the method further comprises a step of: operating a distribution valve (300) provided in a heating liquid communication with the heating circuit (3) and with the first lower inlet (31) of the lower tank portion (4b) of the heating liquid tank (4) and further provided in a heat exchange communication with the secondary energy source (2) via the heating liquid, and directing the heating liquid flow from the heating circuit (3) completely through the secondary energy source (2) provided downstream of the distribution valve (300) prior entering through the first lower inlet (31) of the lower tank portion (4b) into the heating liquid tank (4).

13. A method of operating a hybrid heating arrangement according to claim 10 or 11, c h a r a c t e r i z e d in that the method further comprises a step of: operating a distribution valve (300) provided in a heating liquid communication with the heating circuit (3) and with the first lower inlet (31) of the lower tank portion (4b) of the heating liquid tank (4) and further provided in a heat exchange communication with the secondary energy source (2) via the heating liquid, and by distributing the heating liquid flow coming from the heating circuit (3) in the distribution valve (300) directing part of the heating liquid flow to the secondary energy source

(2); and directing the rest of the heating liquid flow to the first lower inlet (31).

14. A method of operating a hybrid heating arrangement according to claim 13, c h a r a c t e r i z e d in that directing 70-95% of the heating liquid flow to the secondary energy source (2) and the rest to the first lower inlet (31), and preferably directing 80-90% of the heating liquid flow to the secondary energy source (2) and the rest to the first lower inlet (31).

15. A method of operating a hybrid heating arrangement according to any of claims 10-14, c h a r a c t e r i z e d in that the step of operating the secondary energy source valve (200) comprises: closing the secondary energy source valve (200) for inactivating the heat exchange communication from the secondary energy source (2) to the heating liquid in the heating liquid tank (4) by preventing a heating liquid communication between the secondary energy source (2) and the second upper inlet (21) of the upper tank portion (4a) of the heating liquid tank (4) in response to the temperature difference in which the measured temperature is the predetermined temperature or above the predetermined temperature.

16. A method of operating a hybrid heating arrangement according to any of claims 10-15, c h a r a c t e r i z e d in that the step of circulating the heating liquid flow as a return flow from the heating circuit (3) comprises: circulating the return flow downstream of the distribution valve (300) through the secondary energy source (2) in a passive state before providing the return flow through the first lower inlet (31) of the lower tank portion (4b) into the heating liquid tank (4).

17. A method of operating a hybrid heating arrangement according to any of claims 10-16, c h a r a c t e r i z e d in that the method further comprises a temporary defrosting procedure which comprises steps of: operating the secondary energy source (2) by providing the second supply flow heated by the secondary energy source (2) as the heating liquid flow from the secondary energy source (2) through the second upper inlet (21) of the upper tank portion (4a) into the heating liquid tank (4); providing the heating liquid flow from the heating liquid tank (4) through the first lower outlet (12) of the lower tank portion (4b) to the primary energy source (1) for defrosting an outdoor unit (la) of the primary energy source (1); and circulating the heating liquid flow from the primary energy source (1) through the first upper inlet (11) on the upper tank portion (4a) into the heating liquid tank (4) for mixing with the heating liquid flow heated by the secondary energy source (2).