An arrangement for heating a building and a method for controlling the same

Abstract

The disclosure relates to an arrangement (100) for heating a building comprising an air-liquid heat pump (130), a buffer tank (140) configured to store a heat buffer liquid in an internal volume thereof, said internal volume having a first portion (140a) and a second portion (140b); and a switchable conduit system (150); wherein, when the arrangement (100) is configured to operate in a heating operational mode, the switchable conduit system (150) is configured to supply buffer liquid heated by the heat pump (130) to the first portion (140a) of the buffer tank (140) and retrieve buffer liquid from the second portion (140b) of the buffer tank (140), and, when the arrangement (100) is configured to operate in a defrosting operational mode, the switchable conduit system (150) is configured to supply buffer liquid cooled by the heat pump (130) to the second portion (140b) of the buffer tank (140) and retrieve buffer liquid from the second portion (140b) of the buffer tank (140). The disclosure further relates to a method for controlling an arrangement (100).

Description

[0001] AN ARRANGEMENT FOR HEATING A BUILDING AND A METHOD FOR CONTROLLING THE SAME

[0002] Technical field

[0003] The present disclosure relates to an arrangement for heating a building. The present disclosure further relates to a method for controlling the same.

[0004] Background art

[0005] Arrangements for heating buildings, such as e.g., arrangements for domestic heating, may work on the principle of a refrigeration cycle. The refrigeration cycle is a conceptual and mathematical model for e.g., heat pump systems. The heat pump is a mechanical system that allows for transmission of thermal energy from one location to another location. One example of such systems is air-liquid heat pump-based systems. Such systems are based on retrieving heat from the outside air via heat exchange to a refrigerant in a heat exchanger, typically termed evaporator.

[0006] When an ambient temperature starts to decline, moisture on exterior components of the heat pump, such as the evaporator coils, may freeze. Increases in relative humidity also affects how quickly exterior parts of the heat pump freezes. In order to solve this problem, the heat pump is typically designed to have a defrost cycle. Once the system detects that the heat pump starts to freeze, the system will switch to the defrost cycle. During this cycle, heat transferred from outside is transferred to the evaporator coils (which will now instead act as condenser coils) in the outside heat pump unit.

[0007] However, defrosting is associated with a number of problems. Defrosting may give rise to thermal shocks in the pipe system which reduces the longevity thereof. Defrosting may also generate unwanted noise from the radiator system. Further, defrosting may cease to function should the heating system be controlled by e.g., a third-party controller. Furthermore, defrosting typically occurs towards a hot accumulator / buffer water tank configured to produce tap water. When defrosting in accordance with conventional methods, the valves in the pipe system are toggled such that water from the bottom of the tank passes through the condenser, which acts as an evaporator during the defrosting cycle, hence cooling off the water. The cooled water is then supplied to the top of the tank, which in turns cools off the hot water. This leads to a poor efficiency and a degraded hot tap water performance.

[0008] Thus, the conventional heating arrangements are associated with several drawbacks. There is thus a need in the art for an improvement in this area.

[0009] It is an object to mitigate, alleviate or eliminate one or more of the above-identified deficiencies in the art and disadvantages singly or in any combination and solve at least the above-mentioned problem.

[0010] It is an object of the disclosure to provide an efficient arrangement for heating a building.

[0011] Another object of the disclosure is to provide a flexible arrangement for heating a building.

[0012] Another object of the disclosure is to provide a durable arrangement for heating a building.

[0013] Another object of the disclosure is to provide a cost-efficient arrangement for heating a building.

[0014] Another object of the disclosure is to provide a reliable arrangement for heating a building.

[0015] It is also an object to provide an efficient, flexible, and cost-efficient method for controlling an arrangement for heating a building.

[0016] According to a first aspect, there is provided an arrangement for heating a building comprising: an air-liquid heat pump; a buffer tank configured to store a heat buffer liquid in an internal volume thereof, said internal volume and having a first portion and a second portion, the first portion and the second portion being spaced from each other and located at opposite ends of the buffer tank; and a switchable conduit system fluidly interconnecting the heat pump with the buffer tank; wherein the arrangement is configured to operate in a heating operational mode in which the heat pump supplies thermal energy to the first portion of the buffer tank, or a defrosting operational mode in which the heat pump retrieves thermal energy from the second portion of the buffer tank; and wherein, when the arrangement is configured to operate in a heating operational mode, the switchable conduit system is configured to supply buffer liquid heated by the heat pump to the first portion of the buffer tank and retrieve buffer liquid from the second portion of the buffer tank to be heated by the heat pump, and, when the arrangement is configured to operate in a defrosting operational mode, the switchable conduit system is configured to supply buffer liquid cooled by the heat pump to the second portion of the buffer tank and retrieve buffer liquid from the second portion of the buffer tank to be cooled by the heat pump.

[0017] The heat pump may be introduced in a housing or a zone, e.g., in a controlled space of a building. The arrangement may be configured to cover, i.e. , being able to heat and / or provide tap water to, an area. The area may be the whole, or a part of, the building. The arrangement may be configured to provide heating and / or tap water to the building, or a part of the building. The heat pump may comprise a refrigerant circulation path which includes a first heat exchanger unit, a compressor, a second heat exchanger unit and an expander which may be connected to one another in a sequence.

[0018] In this context, the arrangement comprises a radiator circuit to which the switchable conduit system is configured to be fluidly connected to while preventing fluid communication with the buffer tank, or to fluidly connect the heat pump to the buffer tank while preventing fluid communication with the radiator circuit. The arrangement may further comprise a tap-water heat exchange circuit configured to be in fluid connection with the buffer tank. The tap water heat exchange circuit may comprise a heat exchanger and a circulation pump, said tap water heat exchange circuit being arranged to retrieve heat buffer liquid from the first portion of the buffer tank to a first side of the heat exchanger and to return the retrieved heat buffer liquid to the second portion of the buffer tank, wherein a second side of the heat exchanger is arranged to be connected to a tap water circuit. Hence, the arrangement is arranged as either a radiator system (for floor heating and / or radiators) or a tap water system depending on if the heat pump is fluidly connected to the radiator circuit or to the buffer tank.

[0019] The temperature of the liquid retrieved from the switchable conduit system to the heat pump (i.e. , the temperature of the liquid entering the heat pump from the switchable circuit system) may depend on the type of heating system, i.e., if the radiator circuit or the tap water circuit that is operating. Thus, the temperature of the liquid retrieved from the switchable conduit system may vary depending on the type of heating system.

[0020] In this context, when the arrangement is configured to operate in the heating operational mode with respect to the buffer tank or in the defrosting operational mode, the switchable conduit system is in fluid connection with the buffer tank while fluid communication with the radiator circuit is prevented. In the heating operational mode, the heat pump supplies thermal energy to the first portion of the buffer tank. During the heating operational mode, the switchable conduit system is configured to supply buffer liquid heated by the heat pump to the first portion of the buffer tank and retrieve buffer liquid from the second portion of the buffer tank to be heated by the heat pump.

[0021] It is implied that the thermal energy being supplied to the first portion of the buffer tank corresponds to an approximate energy difference between buffer liquid heated by the heat pump later supplied to the first portion of the buffer tank and the buffer liquid retrieved from the second portion of the buffer tank to be heated by the heat pump.

[0022] In the defrosting operational mode, the heat pump retrieves thermal energy from the second portion of the buffer tank. During the defrosting operational mode, the switchable conduit system is configured to supply buffer liquid cooled by the heat pump to the second portion of the buffer tank and retrieve buffer liquid from the second portion of the buffer tank to be cooled by the heat pump. It is implied that the thermal energy being retrieved from the second portion of the buffer tank corresponds to an approximate energy difference between the buffer liquid retrieved from the second portion of the buffer tank and the buffer liquid supplied to the second portion of the buffer tank after having been cooled by the heat pump.

[0023] Defrosting may typically occur in conjunction with the buffer tank being in fluid connection with the heat pump. One way to defrost the heat pump according to conventional methods, is to configure the switchable conduit system to supply liquid from the second portion of the buffer tank to the heat pump. The liquid is cooled by the second heat exchanger of the heat pump after which the cooled liquid is supplied to the first portion of the buffer tank, hence cooling the buffer liquid of the first portion of the buffer tank. This leads to a poor efficiency and a degraded hot tap water performance in embodiments of the arrangement where tap water is heated by heat exchange with the buffer tank. The disclosed arrangement is advantageous since the liquid, being cooled by the heat pump during the defrosting cycle, is supplied to the same portion, i.e. , the second portion of the buffer tank, from where it was retrieved. Thus, it is avoided that hot water of the first portion of the buffer tank is cooled, which allows for an efficient defrosting as well as a consistent and efficient hot tap water performance.

[0024] In this context, the first and second portions of the buffer tank may be referred to first and second sub-volume of the buffer tank which are spaced from each other. It should be noted that the first and second portions are portions of the same volume of the buffer tank, but the heat buffer liquid comprised in the different portions may have different properties, e.g., different temperature, different density, or the like. It is conceivable that the spaced apart first and second portions are upheld by their mere distance from each other. For example, a buffer tank having a relatively long elongated extension in the horizontal dimension (i.e. a horizontally aligned buffer tank) could have a first portion at the first end of the elongated extension and a second portion at the second end of the elongated extension. However, preferably the first and second portions are upheld by natural layering. For such example embodiments, the buffer tank is typically arranged to extend substantially vertically such that the first portion defines a top portion of the buffer tank and the second portion defines a bottom portion of the buffer tank, as detailed earlier. For such example embodiments, temperature stratification within the tank will ensure that, at equilibrium conditions, the temperature of the buffer liquid in the first portion (i.e. the top portion) will always be larger than the temperature of the buffer liquid in the second portion (i.e. the bottom portion). It should be noted that the smaller the property differences may be, the less distinct may the layering be.

[0025] The first and second portions may extend in a number of different ways in order to allow an efficient defrosting and a consistent hot tap water performance. The buffer tank extends between the two opposite ends, which may be termed the first and second ends, respectively. The first portion is located at the first end. The second portion is located at the second end. The distance between the first and second end defines a main extension of the buffer tank. In example embodiment where the buffer tank is aligned substantially vertically, the first end will be a top end of the buffer tank, and the second end will be a bottom end of the buffer tank.

[0026] By way of example, the second portion may extend from the second end of the buffer tank to 1 / 3 of the distance towards the first end of the buffer tank. Alternatively, the second portion may extend from the second end of the buffer tank to 1 / 4, or 1 / 5, or 1 / 6 of the distance towards the first end of the buffer tank. Alternatively, the second portion may extend from the second end of the buffer tank to 1 / 2 of the distance towards the first end of the buffer tank.

[0027] By way of example, the first portion may extend from the first end of the buffer tank to 1 / 3 of the distance towards the second end of the buffer tank. Alternatively, the first portion may extend from the first end of the buffer tank to 1 / 4, or 1 / 5, or 1 / 6 of the distance towards the second end of the buffer tank. Alternatively, the first portion may extend from the first end of the buffer tank to 1 / 2 of the distance towards the second end of the buffer tank.

[0028] Defrosting is in known arrangements for heating buildings not necessarily limited to occur while a buffer tank is being in fluid connection with the heat pump. Alternatively, defrosting may occur in conjunction with a radiator system, instead of a buffer tank, being in fluid connection with the heat pump. One way to defrost the heat pump according to this method, is to configure the switchable conduit system to retrieve hot water from the radiator system to the heat pump. By way of example, during a heating cycle, the temperature of the liquid in the forward line (i.e. , from the heat pump to the radiator) may be 55 degree Celsius. The temperature of the liquid in the return line (i.e., from the radiator to the heat pump) may be 45 degree Celsius. Upon switching to the defrosting cycle, the compressor is typically configured to reverse the direction of the refrigerant in the heat pump. Thus, during the defrosting cycle, the condenser of the heat pump functions as an evaporator. Analogously, the evaporator functions as a condenser. Since 45 degree Celsius liquid is retrieved from the return line, the condenser of the heat pump will now cool the liquid down to e.g., 25-35 degree Celsius. In other words, 25-35 degree Celsius liquid will exit the heat pump and be supplied to the radiator. However, 55 degree Celsius liquid was just flowing in the forward line just before the switchable conduit system switched to operate in the defrosting cycle. This may give rise to a thermal shock in the pipe system hence reducing the longevity of the pipes. Also, a defrosting cycle as mentioned above typically generates unwanted noise stemming from the radiator system being in connection with the heat pump. The disclosed arrangement is advantageous in that a buffer tank, instead of a radiator system, is in fluid connection with the heat pump during the defrosting cycle. A degraded radiator performance is therefore avoided. Unwanted noise stemming from the radiator system is also avoided. During the defrosting cycle, the disclosed arrangement supplies cooled water from the heat pump to the buffer tank, which buffer tank is merely a container for liquid. On the contrary, a radiator system typically consists of an extensive pipe system which is susceptible to damage due to temperature changes of the liquid. With the disclosed arrangement, it is ensured that liquid with varying temperature is not circulated within such an extensive pipe system hence minimizing the risk of reducing the longevity of the pipe system while, at least partially, preventing unwanted noise stemming from the radiator system.

[0029] A further advantage with the inventive concept as defined in the claims is that, when the arrangement is configured to operate in the defrosting operational mode, the switchable conduit system is configured to supply buffer liquid cooled by the heat pump to the second portion of the buffer tank and retrieve buffer liquid from the second portion of the buffer tank to be cooled by the heat pump. In other words, during defrosting, the first portion of the buffer tank is bypassed and, apart from a minor potential influence from induced turbulence within the buffer tank, the temperature of the buffer liquid in the first portion will not be affected by the defrosting operation, since this is only performed to and from the second portion. The second portion is spaced apart from the first portion. This ensures to keep the influence of any turbulence to a minimum. Needless to say, the effect is increased for increasing distance between the first and second portions. The effect may also be increased for an increasing extension of the buffer tank between the first and second ends.

[0030] By the term “fluidly connect” is herein meant that the switchable conduit system is configured to connect the heat pump to the radiator circuit or to the buffer tank such that a fluid communication between the heat pump and the radiator circuit or the buffer tank is formed. It should be noted that the switchable conduit system may at all times be physically connected to both the radiator circuit and the buffer tank but may only be fluidly connected, i.e. , has fluid communication with, one of the radiator circuit and the buffer tank. Thereby, the heat pump may be arranged to supply heat pump liquid from the heat pump, i.e., liquid exiting the heat pump, to either the radiator circuit or to the buffer tank. Preferably, the arrangement comprises one or more valves arranged to direct the heat pump liquid to either the radiator circuit or the buffer tank. When the heat pump is fluidly connected to the radiator system, the arrangement is arranged to transfer heat to radiator systems within buildings or the like. When the heat pump is fluidly connected to the radiator circuit, liquid exiting the heat pump may be provided to an inlet port of the radiator circuit and liquid entering into the heat pump from the radiator circuit may be retrieved from an outlet port of the radiator circuit. When the heat pump is fluidly connected to the buffer tank, the arrangement is arranged to transfer heat to the buffer tank which in turn may transfer heat to the tap water circuit. Thus, the arrangement is configured to transfer heat to either the radiator circuit or to the tap water circuit. When the heat pump is fluidly connected to the buffer tank, liquid exiting the heat pump is provided to the first portion of the buffer tank and liquid entering into the heat pump from the buffer tank is retrieved from the second portion of the buffer tank. Preferably, the liquid exiting the heat pump into the first portion has different properties than the liquid entering into the heat pump from the second portion because of the arrangement of the buffer tank which comprises the first and second portions as discussed above.

[0031] The arrangement may further comprise at least one sensor being configured to obtain observed data pertaining to at least one of an ambient temperature and heat pump characteristics, and wherein the arrangement is configured to, when in the heating operational mode, switch the switchable conduit system such that the arrangement starts operating in the defrosting operational mode in response to said observed data meeting a defrosting-on threshold.

[0032] By “heat-pump characteristics” is herein meant operating parameters and / or system health data of the heat pump, such as but not limited to a compressor power, a refrigerant temperature, a refrigerant pressure, a heat pump inlet liquid temperature, an evaporator coil temperature, and ice buildup dimensions.

[0033] By “ambient temperature” is herein meant the temperature of the environment where the arrangement is arranged. Air-liquid heat pumps typically have one outdoor unit and one indoor unit. This implies that the ambient temperature may be an outside temperature or an inside temperature.

[0034] By “defrosting-on threshold” is herein meant a threshold, such as e.g. a threshold temperature value of threshold voltage value, which the observed data may meet.

[0035] By “obtain observed data” is herein meant that the at least one sensor is configured to detect, capture, or measure data which pertains at least to one of the ambient temperature and heat pump characteristics. The heat pump characteristics may include various temperatures within the heat pump, such as a temperature of the liquid entering the heat pump from the radiator circuit, a temperature of the liquid entering the heat pump from the second portion of the buffer tank, or a temperature of the refrigerant. The heat pump characteristics may alternatively be another property of the heat pump, e.g. current compressor operating power, compressor temperature, type of refrigerant, or the like.

[0036] In this context, the at least one sensor may be comprised in the heat pump. This is advantageous as it allows to obtain the observed data pertaining to e.g., the ambient temperature and / or the heat pump characteristics in an easy and accurate way. The at least one sensor should be interpreted broadly to encompass any sensors capable of providing the observed data pertaining to the ambient temperature and / or the heat pump characteristics such as heat pump inlet liquid temperature of the liquid entering the heat pump. For ambient temperature, the at least one sensor may by arranged within an outside module which includes the evaporator and typically a fan. The at least one sensor may be arranged such that incoming air is sucked passed the at least one sensor. It is also conceivable to provide a sensor outside of such an outside module, e.g., mounted separately on an outside wall of the building. The at least one sensor may be in physical contact with the liquid, such as a thermometer, thermocouple, thermistor etc. However, the at least one sensor may alternatively be based on remote sensing, such as e.g., spectrally resolved IR imaging or the like. Other conceivable sensors are cameras and acoustic sensors. Cameras may be used for temperature detection, e.g., using an IR camera, but cameras may also be used to visually detect an onset of ice build-up on the evaporator coil. A camera may be an example of a sensor configured to obtain observed data pertaining to system health data. A direct measurement of ice build-up dimensions may be beneficial for some embodiments where accurate data is required. Other conceivable sensors are acoustic sensors. Irrespective of which technique is chosen, the observed data will relate to the ambient temperature or to the heat pump characteristics such as e.g., the temperature of the heat pump inlet liquid, etc. The at least one sensor may be arranged at an inlet conduit / pipe through which said liquid from the switchable conduit system enters the heat pump. This implies that the observed data may be based on sensor data from only one sensor. The observed data may alternatively be based on sensor data from more than one sensor. For the latter alternative, the sensor data may pertain to more than one temperature, or a combination of a temperature and another property. Upon that is the case, the observed data may comprise a plurality of observed sub data, wherein each observed sub data pertains to a specific property. By providing two or more sensors to provide the observed data, the arrangement may be more redundant. If one of the sensors malfunctions, or starts to deviate from its specified behaviour, it may still be possible to switch the switchable conduit system based on observed data.

[0037] The arrangement may be configured to operate in the defrosting operational mode during a defrosting time period which is based on at least one of a predetermined time, an ambient temperature, and heat pump characteristics. The ambient temperature may be the outdoor temperature. By way of example, the defrosting time period may be based on a temperature of the evaporator coil of the first heat exchanger. This implies that defrosting may be stopped after a certain temperature is reached on the evaporator coil.

[0038] The heat pump characteristics may include data pertaining to one or more from the list of: a compressor power, a refrigerant temperature, a refrigerant pressure, a heat pump inlet liquid temperature, a refrigerant type, and an evaporator coil temperature.

[0039] The arrangement further comprises at least one control unit configured to receive said observed data which pertains to at least one of an ambient temperature and heat pump characteristics, determine if said observed data meets a defrosting-on threshold, and transmit a defrosting-on signal in response to said observed data meeting the defrosting-on threshold.

[0040] The observed data may be transmitted from the respective at least one sensor to a secondary device which may be able to convert the observed data such that the observed data may be usable by the control unit. It is also conceivable that the control unit receives the observed data directly from the sensors and, if a conversion is required, performs the conversion on its own.

[0041] The at least one control unit, when the heat pump is in fluid connection with the buffer tank, may be configured to execute a determination function to determine a data relationship between the observed data and a reference data. The at least one control unit may further be configured to execute a comparison function to compare the data relationship with a comparison criterion and upon the comparison fulfilling the comparison criterion, the observed data may be determined to meet a defrosting-on threshold. By way of example, the data relationship may be a difference between the observed data and the reference data, and the comparison criterion may be a maximum tolerable difference between the observed data and the reference data. This implies that the comparison criterion may be fulfilled if the data relationship exceeds the comparison criterion. Alternatively, the data relationship may be a ratio between the observed data and the reference data, and the comparison criterion may be a minimum (or maximum) tolerable ratio between the observed data and the reference data. This implies that the comparison criterion may be fulfilled if the data relationship exceeds (or falls below) the comparison criterion. As readily appreciated by the person skilled in the art, there are many alternative conceivable data relationships and comparison criterions which may be used within the scope of the claims.

[0042] By the term “control unit” is herein meant any device or unit configured to control an operation of the arrangement. Examples of such device or unit are microprocessors, computers or the like, which are capable of executing computer-implemented instructions based on received input data and output instructions to the arrangement for controlling the same.

[0043] Each control unit may be e.g., a microprocessor or a central processing unit, CPU. The control unit may be configured to control the power and enablement of the arrangement. The control unit may be wired or wirelessly connected to the one or more sensors.

[0044] The control unit may be configured to receive the observed data. The control unit may be configured to store the observed data. The control unit may be configured to receive the comparison criterion. The control unit may be configured to store the comparison criterion. The control unit may be configured to execute a comparison criterion determination function configured to determine the comparison criterion based on current heat pump operation point in terms of e.g., temperatures or pressures in the heat pump. The control unit may be configured to store observed data on a regular basis, i.e. , every second or millisecond, such that the control unit has access to latest data obtained by the sensors of the arrangement.

[0045] The determination function is advantageous as it enables the data relationship between the observed data and the reference data to be determined in a way such that it may be able to be compared with the comparison criterion.

[0046] The comparison function is advantageous as it enables the comparison between the relationship data and the comparison criterion to be performed. In this context, the comparison criterion may pertain to a maximum data tolerance between the observed data and the reference data that may be tolerated by the heat pump.

[0047] The control unit may be configured to, upon the comparison not fulfilling the comparison criterion anymore, switch the switchable conduit system such that the arrangement operates in the heating operational mode.

[0048] The determination function may be configured to determine the data relationship based on a ratio between observed data and the reference data.

[0049] This is advantageous as it allows for an alternative way of determining the data relationship compared to determining a difference between the observed and reference data.

[0050] The determination function may be configured to determine the data relationship based on both the difference between the observed and reference data and the ratio between the observed and reference data. This may provide for determining the data relationship in an accurate way.

[0051] It should be understood that the above are examples only, and that any determination function which is capable of providing a data relationship between the observed data and the received data is equally applicable for the arrangement of the present disclosure.

[0052] The at least one control unit may be arranged inside of, or at, at least one of the heat pump and the buffer tank.

[0053] The at least one control unit may be arranged in a remote server and being in wired or wireless communication with parts of the arrangement.

[0054] This is advantageous in that, if one of the control units malfunctions, or starts to deviate from its specified behaviour, it is easily replaceable since it is separable from parts of the arrangement. It is conceivable that it is cumbersome should the control unit be positioned within parts of the arrangement and further malfunction, or start to deviate from its specified behaviour since this may require demounting parts of the arrangement in order to retrieve the control unit. A further advantage may be to allow controlling more than one arrangement using the same at least one control unit. By establishing data communication between the at least one control unit and a plurality of arrangements, e.g. located in a plurality of buildings, a more efficient control of the arrangements may be achieved.

[0055] The buffer tank may further comprise: a first portion inlet arranged to fluidly communicate with the first portion of the buffer tank; a second portion outlet arranged to fluidly communicate with the second portion of the buffer tank; and an auxiliary portion inlet arranged to fluidly communicate with the second portion of the buffer tank; wherein, when the arrangement is operating in the heating operational mode, liquid exiting the heat pump is supplied to the first portion of the buffer tank through the first portion inlet, and liquid entering into the heat pump is retrieved from the second portion of the buffer tank through the second portion outlet, and wherein, when the arrangement is operating in the defrosting operational mode, liquid entering into the heat pump is retrieved from the second portion of the buffer tank through the second portion outlet, and liquid exiting the heat pump is supplied to the second portion of the buffer tank through the auxiliary portion inlet.

[0056] This is advantageous in that the auxiliary portion inlet provides a low complexity solution while allowing for an efficient defrosting and a maintained tap water heat exchange performance. The auxiliary portion inlet may also be retro-fitted to current solutions making it highly convenient. It may be conceivable that the instalment of at least one valve in the switchable conduit system may be necessitated in order for the auxiliary portion inlet to function properly. Furthermore, the instalment of the auxiliary portion inlet is simple since a high amount of material is not needed. Thus, this solution is also cost-efficient.

[0057] The second portion of the buffer tank may consist of a first sub-portion and a second sub-portion, and wherein the second portion outlet is arranged to fluidly communicate with the first sub portion, and the auxiliary portion inlet is arranged to fluidly communicate with the second sub-portion, wherein the first and second sub-portions of the second portion of the buffer tank are separated from each other, and wherein the second sub-portion is arranged between the first portion and the first sub portion within the buffer tank.

[0058] Analogously to what was previously disclosed for the first and second portions, the first and second sub-portions of the second portion may be referred to first and second sub-volumes defined by the second portion of the buffer tank, which sub-volumes are separated from each other. It should be noted that the first and second sub-portions are portions of the same volume of the buffer tank, namely the volume defined by the second portion, but the heat buffer fluid comprised in the different sub-portions may have different properties, e.g., different temperature, different density, or the like.

[0059] The skilled person realizes that the temperature of the heat buffer liquid in a buffer tank is typically graded due to heat exchange between the heat pump and the buffer liquid. It may alternatively be expressed that buffer liquid in the first portion of the buffer tank is typically warmer than that in the second portion of the buffer tank. By the second sub-portion being arranged between the first portion and the first sub-portion within the buffer tank, when the arrangement is operating in the defrosting operational mode, cooled buffer liquid that exits the heat pump is supplied to the second sub-portion of the buffer tank, instead of being supplied to the first portion where hot buffer liquid is arranged. This is advantageous as it may ensure that the warmer heat buffer liquid, provided in the first portion, will be supplied to the heat exchanger of the tap water heat exchanger circuit (which is connected to the first portion) and that the cooler heat buffer liquid, provided in the second portion, will be supplied to the heat pump (which may be connected to the second portion). This is also advantageous in that the efficient defrosting is allowed while a good tap water heat exchange performance is maintained.

[0060] Furthermore, by allowing buffer liquid to be retrieved from a different sub-portion than the sub-portion to which the same liquid is subsequently been supplied to, the risk of circulating essentially the same liquid several times may be reduced. The buffer liquid retrieved from the first sub-portion of the second portion may for example be retrieved from the very bottom of the tank, whereas the buffer liquid supplied to the second sub-portion of the second portion may be supplied at a certain distance away from the very bottom of the tank, thus avoiding recirculating the same liquid.

[0061] By way of example, the first sub-portion may have a volume being 1 / 2, or 1 / 3, or 1 / 4, or 1 / 6 of the total volume of the second portion.

[0062] The buffer tank may, when in use, be arranged to extend substantially vertically such that the first portion defines a top portion of the buffer tank and the second portion defines a bottom portion of the buffer tank.

[0063] This may be advantageous as it allows to further uphold a temperature gradient within the buffer tank by means of temperature stratification within the tank. Such temperature stratification will ensure that, at equilibrium conditions, the temperature of the buffer liquid in the first portion (i.e. the top portion) will always be larger than the temperature of the buffer liquid in the second portion (i.e. the bottom portion). This arrangement may depend on the properties as introduced and discussed above. If the arrangement is configured to operate in the heating operational mode, the heat buffer liquid within the first portion may have a temperature between 55-75 degree Celsius and the heat buffer liquid within the second portion may have a temperature between 10-50 degree Celsius. Since the liquid density varies with temperature (water is typically used as a buffer liquid), a natural layering will occur in the vertical direction of the buffer tank. By providing the high- temperature liquid at the upper part (i.e. , providing the first portion at the top portion of the tank) and providing the low-temperature liquid to the lower part (i.e. providing the second portion at the bottom portion of the tank) the natural layering will strive to maintain the separation between the first and second portions also over time. This is advantageous as it may ensure that the warmer heat buffer liquid, provided in the first portion, will be supplied to the heat exchanger of the tap water heat exchanger circuit (which is connected to the first portion) and that the cooler heat buffer liquid, provided in the second portion, will be supplied to the heat pump (which may be connected to the second portion). This is also advantageous in that the efficient defrosting is allowed while a good tap water heat exchange performance is maintained. It is conceivable that the temperature of the buffer liquid in the substantially vertically extending buffer tank is maintained by at least one of the heat exchange occurring between the heat pump and the buffer liquid, and the natural layering due to the vertical direction of the buffer tank. The substantially vertical extension of the buffer tank is hence advantageous in that the natural layering aids in maintaining a graded temperature within the buffer tank and thus allows for efficient defrosting and a high tap water heat exchange performance.

[0064] According to a second aspect of the disclosure, these and other objects are also achieved in full or at least in part, by a method for controlling an arrangement which comprises: an air-liquid heat pump; a buffer tank configured to store a heat buffer liquid in an internal volume thereof, said internal volume having a first portion and a second portion, the first portion and the second portion being spaced from each other and located at opposite ends of the buffer tank; and a switchable conduit system fluidly interconnecting the heat pump with the buffer tank; the method comprising: in response to a defrosting-on signal: switching the switchable conduit system so as to configure the arrangement to operate in a defrosting operational mode in which the switchable conduit system supplies buffer liquid cooled by the heat pump to the second portion of the buffer tank and retrieves buffer liquid from the second portion of the buffer tank to be cooled by the heat pump, and in response to a defrosting-off signal: switching the switchable conduit system so at to configure the arrangement to operate in a heating operational mode in which the switchable conduit system supplies buffer liquid heated by the heat pump to the first portion of the buffer tank and retrieves buffer liquid from the second portion of the buffer tank to be heated by the heat pump.

[0065] The method may further comprise: receiving sensor data pertaining to at least one of an ambient temperature and heat pump characteristics; determining, when the arrangement is operating in the heating operational mode, if said observed data meets a defrosting-on threshold; and upon said observed data meeting the defrosting-on threshold: switching the switchable conduit system such that the arrangement operates in the defrosting operational mode.

[0066] The method may further comprise: in response to the defrosting-on signal:

[0067] (a) supplying buffer liquid cooled by the heat pump to the second portion of the buffer tank through an auxiliary portion inlet arranged to fluidly communicate with the second portion of the buffer tank, and

[0068] (b) retrieving buffer liquid from the second portion of the buffer tank to be cooled by the heat pump through a second portion outlet arranged to fluidly communicate with the second portion of the buffer tank such that the heat pump retrieves thermal energy from the second portion of the buffer tank, and in response to the defrosting-off signal: (c) supplying buffer liquid heated by the heat pump to the first portion of the buffer tank through a first portion inlet arranged to fluidly communicate with the first portion of the buffer tank, and

[0069] (d) retrieving buffer liquid from the second portion of the buffer tank to be heated by the heat pump through the second portion outlet.

[0070] The method may further comprise: in response to the defrosting-on signal: supplying buffer liquid cooled by the heat pump to a second subportion of the second portion of the buffer tank through the auxiliary portion inlet, and retrieving buffer liquid from a first sub-portion of the second portion of the buffer tank to be cooled by the heat pump through the second portion outlet, and wherein the first and second sub-portions of the second portion of the buffer tank are separated from each other, and wherein the second subportion is arranged between the first portion and the first sub-portion within the buffer tank.

[0071] Effects and features of the second aspect are largely analogous to those described above in connection with the first aspect. Embodiments mentioned in relation to the first aspect are largely compatible with the second aspect. It is further noted that the inventive concepts relate to all possible combinations of features unless explicitly stated otherwise. A further scope of applicability of the present invention will become apparent from the detailed description given below. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the scope of the invention will become apparent to those skilled in the art from this detailed description.

[0072] Hence, it is to be understood that this invention is not limited to the particular component parts of the device described or steps of the methods described as such device and method may vary. It is also to be understood that the terminology used herein is for purpose of describing particular embodiments only and is not intended to be limiting. It must be noted that, as used in the specification and the appended claim, the articles "a", "an", "the", and "said" are intended to mean that there are one or more of the elements unless the context clearly dictates otherwise. Thus, for example, reference to "a unit" or "the unit" may include several devices, and the like. Furthermore, the words "comprising", "including", "containing" and similar wordings does not exclude other elements or steps.

[0073] The disclosure may also in short be said to relate to an arrangement for heating a building comprising an air-liquid heat pump, a buffer tank configured to store a heat buffer liquid in an internal volume thereof, said internal volume having a first portion and a second portion; and a switchable conduit system; wherein, when the arrangement is configured to operate in a heating operational mode, the switchable conduit system is configured to supply buffer liquid heated by the heat pump to the first portion of the buffer tank and retrieve buffer liquid from the second portion of the buffer tank, and, when the arrangement is configured to operate in a defrosting operational mode, the switchable conduit system is configured to supply buffer liquid cooled by the heat pump to the second portion of the buffer tank and retrieve buffer liquid from the second portion of the buffer tank. The disclosure may further in short be said to relate to a method for controlling an arrangement.

[0074] Brief description of the drawings

[0075] The disclosure will by way of example be described in more detail with reference to the appended schematic drawings, which shows a presently preferred embodiment of the invention.

[0076] Figure 1 illustrates an arrangement for heating a building according to an example embodiment of the disclosure.

[0077] Figure 2A illustrates an arrangement for heating a building according to an example embodiment of the disclosure when the arrangement operates in a heating operational mode.

[0078] Figure 2B illustrates an arrangement for heating a building according to an example embodiment of the disclosure when the arrangement operates in a defrosting operational mode. Figure 3 is a flow chart of a method for controlling an arrangement according to an example embodiment of the present disclosure.

[0079] Detailed description

[0080] The present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the disclosure are shown. This disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and fully convey the scope of the disclosure to the skilled person.

[0081] With reference to figure 1 , an arrangement 100 for heating a building is illustrated by way of example. The arrangement 100 comprises a heat pump 130, a buffer tank 140, a switchable conduit system 150 and a tap water heat exchanger circuit 170. The arrangement 100 is configured to transfer heat to a radiator circuit 160 or to a tap water circuit 180. The arrangement 100 is using the same heat pump 130 for the radiator circuit 160 (i.e. , floor heating / radiator systems) and for generating hot tap water to the tap water circuit 180. The heat pump 130 may be an air-liquid heat pump. The air-liquid heat pump 130 exchanges heat with air on the cold side, typically outside of a building, and transfers the heat to the hot side, typically inside of a building.

[0082] The heat pump 130 comprises a first heat exchanger unit 135 configured for heat exchange with air. The first heat exchanger unit 135 is during heating usually termed the evaporator and is typically located in a separate module disposed outside of the building, e.g., on the ground or an outside wall of the building. Heat exchange with air is achieved by providing air to the first heat exchanger unit 135 by means of a fan 131 and heat is transferred to a first heat exchanger coil 132.

[0083] The heat pump 130 further comprises a second heat exchanger unit 137 configured for exchanging heat with a liquid which is circulated to the heat pump 130 in a hot side grid 112. The second heat exchanger unit 137 exchanges heat via second heat exchanger coil 139. The heat pump 130 further comprises a refrigerant circulation loop 134.

[0084] The refrigerant recirculation loop 134 comprises the first heat exchanger coil 132 of the first heat exchanger unit 135 and the second heat exchanger coil 139 of the second heat exchanger unit 137 as well as a compressor 136 and an expander 138. The second heat exchanger unit 137 is fluidly connected to the hot side grid 112. The refrigerant circulation loop 134 preferably circulates a refrigerant through the first heat exchanger unit 135, the compressor 136, the second heat exchanger unit 137 and the expander 138. The refrigerant and the air are configured to exchange thermal energy between each other in the first heat exchanger unit 135 such that a temperature of the refrigerant increases. The refrigerant is circulated from the first heat exchanger unit 135 to the compressor 136 which is configured to increase the temperature and pressure of the refrigerant even further before supplying the refrigerant to the second heat exchanger unit 137. The refrigerant and the hot liquid are configured to exchange thermal energy between each other in the second heat exchanger unit 137 such that a temperature of the refrigerant decreases and a temperature of the hot liquid increases. The hot liquid is supplied to the radiator circuit 160 or to the buffer tank 140. The refrigerant is circulated from the second heat exchanger unit 137 to the expander 138 which is configured to control an amount of refrigerant released into the first heat exchanger unit 135. The hot side grid 112 may comprise the switchable conduit system 150. The heat pump 130 is physically connected to the radiator circuit 160 and the buffer tank 140 via the hot side grid 112. The switchable conduit system 150 is configured to fluidly connect the heat pump 130 to the radiator circuit 160 or to fluidly connect the heat pump 130 to the buffer tank 140 (as illustrated in figure 1 ). Thus, it should be noted that the heat pump 130 is physically connected to the radiator circuit 160 and the buffer tank 140 at the same time. It should however be noted that the heat pump 130 is fluidly connected to either the radiator circuit 160 or the buffer tank 140. When the heat pump 130 is fluidly connected to the radiator circuit 160, it is preventing fluid communication with the buffer tank 140. When the heat pump 130 is fluidly connected to the buffer tank 140, it is preventing fluid communication with the radiator circuit 160. The hot side grid 112 is configured to supply a hot liquid from the heat pump 130 to the radiator circuit 160 or the buffer tank 140. The hot side grid 112 is further configured to return the hot liquid from the radiator circuit 160 or the buffer tank 140 to the heat pump 130. The hot liquid being returned from the radiator circuit 160 or the buffer tank 140 is entering the heat pump 130 via the switchable conduit system 150. The hot liquid is herein after referred to as “liquid”.

[0085] The buffer tank 140 is configured to store a heat buffer liquid. The buffer tank 140 comprises a first portion 140a and a second portion 140b, wherein the first and second portions 140a, 140b are spaced from each other within the tank 140. The first portion 140a is defined in an uppermost part of the buffer tank 140 extending from a top end 144a, and the second portion 140b is defined in a lowermost part of the buffer tank 140 extending from a bottom end 144b. As further depicted in Fig. 1 , the first and second portions 140a, 140b are spaced from each other by a third portion 140c. Although not illustrated, the buffer tank 140 may comprise further portions arranged between the first and second portions 140a, 140b. The second portion 140b of the buffer tank may comprise a first sub-portion 140b1 and a second subportion 140b2. The first 140b1 and second 140b2 sub-portions are separated from each other. The second sub-portion 140b2 is arranged between the first portion 140a and the first sub-portion 140b1 within the buffer tank 140.

[0086] As depicted in figure 1 , the switchable conduit system 150 comprises two valves 151a, 151 b arranged to fluidly connect the heat pump 130 to either the radiator circuit 160 or to the buffer tank 140. The valves 151a, 151 b are arranged for controlling the liquid flow retrieved from the heat pump 130 to the switchable conduit system 150 and for controlling the liquid flow entering the heat pump 130 from the switchable conduit system 150. The switchable conduit system 150 further comprises a third valve 151c arranged to fluidly connect the heat pump 130 to the second sub-portion 140b2.

[0087] The valve 151a is arranged for directing the fluid flow entering the heat pump 130 from either the radiator circuit 160 or the buffer tank 140.

[0088] The valve 151 b is arranged for directing the fluid flow retrieved from the heat pump 130 to either the radiator circuit 160 or to the buffer tank 140. The valve 151c is arranged for directing fluid retrieved from the heat pump 130 to the second sub-portion 140b2 of buffer tank 140. It may be noted that while fluid communication has been established between the heat pump 130 and the second sub-portion 140b2 of buffer tank 140, fluid connection is prevented between the first portion 140a and the heat pump 130. Further, while fluid communication has been established between the heat pump 130 and the first portion 140a, fluid connection is prevented between the first second sub-portion 140b2 and the heat pump 130.

[0089] With reference to figures 2A-B, when the arrangement 100 is in fluid connection with the buffer tank 140, the arrangement 100 is configured to operate either in a heating operational mode (figure 2A) or a defrosting operational mode (figure 2B).

[0090] In the following, the heat operational mode will be described in detail. With reference to figure 2A, the buffer tank 140 comprises a first portion inlet 141a configured to receive heated liquid exiting the heat pump 130 and being supplied to the buffer tank 140. Thus, liquid exiting the heat pump 130 is provided to the first portion 140a of the buffer tank 140 via the first portion inlet 141a. The buffer tank 140 comprises a second portion outlet 142b configured to return liquid to be heated by the heat pump 130 from the buffer tank 140 to the heat pump 130. Thus, when the arrangement 100 is operating in the heating operational mode, liquid entering the heat pump 130 is retrieved from the second portion 140b of the buffer tank 140 via the second portion outlet 142b. As readily appreciated by the person skilled in the art of air-liquid heat pumps, the heat pump 130 will during the heating operational mode operate as indicated in figure 2A, i.e. by transferring heat from the outside air via the first heat exchanger unit 135 to the hot side grid via the second heat exchanger unit 137. This is indicated by the refrigerant cycle 134 being clockwise in figure 2A.

[0091] The valve 151a directs the liquid flow entering the heat pump 130 from the second portion 140b of the buffer tank 140 via the second portion inlet 142b.

[0092] The valve 151 b directs the liquid flow retrieved from the heat pump 130 to first portion 140a the buffer tank 140 via the first portion inlet 141a. Since fluid communication has been established between the heat pump 130 and the first portion 140a, fluid connection is prevented between the first second sub-portion 140b2 and the heat pump 130.

[0093] In the following, the defrosting operational mode will be described in detail with reference to figure 2B. During the defrosting operational mode, the heat pump 130 is operated in reverse so as to transfer heat from the second heat exchanger 137 to the first heat exchanger 135. This is performed in order to supply heat to the first heat exchanger in order to defrost ice which has a tendency to be formed on the evaporator coils therein. The reverse operation is achieved by reversing the refrigerant cycle 134 as indicated by the arrows in figures 2A and B respectively. The general principle of reversing the a refrigerant cycle 134 of a heat pumps and to defrost of air-liquid heat pump by reversing the refrigerant cycle 134 are well-known in the technical field of air-liquid heat pumps and is therefore not further discussed herein.

[0094] During the defrosting operational mode, the second heat exchanger unit 137 is hence configured to cool down the liquid, as opposed to heating it as is done during the heating operational mode. The liquid is received from the second portion 140b of the buffer tank 140. The second sub-portion 140b2 of the second portion 140b is configured to receive cooled liquid exiting the heat pump 130 and being supplied to the buffer tank 140. Liquid exiting the heat pump 130 is provided to the second portion 140b of the buffer tank 140 via an auxiliary portion inlet 143. The first sub-portion 140b1 of the second portion outlet 140b is configured to return liquid to be cooled by the heat pump 130 from the buffer tank 140 to the heat pump 130. Thus, when the arrangement is operating in the defrosting operational mode, liquid entering the heat pump 130 is retrieved from the first sub-portion 140b1 of the second portion 140b of the buffer tank 140 via the second portion outlet 140b.

[0095] The valve 151a directs the fluid flow entering the heat pump 130 from the second portion 140b of the buffer tank 140 via the second portion inlet 142b.

[0096] The valve 151c directs the liquid retrieved from the heat pump 130 to the second sub-portion 140b2 of buffer tank 140 via the auxiliary portion inlet 143. Since fluid communication has been established between the heat pump 130 and the second sub-portion 140b2, fluid connection is prevented between the first portion 140a and the heat pump 130.

[0097] The buffer tank 140 further comprises a first portion outlet 141 b and a second portion inlet 142a, both being connected to the tap water heat exchange circuit 170. The tap water heat exchange circuit 170 comprises a heat exchanger 171 and a circulation pump 172. The tap water heat exchange circuit 170 is arranged to retrieve heat buffer liquid from the first portion 140a of the buffer tank 140, via the first side outlet 141 b, to a first side 171 a of the heat exchanger 171. The tap water heat exchanger circuit 170 is further configured to return the retrieved heat buffer liquid from the first side 171 a of the heat exchanger 171 to the second portion 140b of the buffer tank 140, via the second portion inlet 142a. As depicted in figure 1 , the tap water heat exchanger circuit 170 is configured to return the retrieved heat buffer liquid from the first side 171a of the heat exchanger 171 to the buffer tank 140 via the circulation pump 172. A second side 171 b of the heat exchanger 171 is connected to the tap water circuit 180. The tap water circuit 180 is connected to the second side 171 b of the heat exchanger 171 via a domestic hot water supply line DHW and a cold water supply line CW. The domestic hot water supply line DHW is arranged for supply hot tap water from the tap water heat exchange circuit 170 to the tap water circuit 180. The cold water supply line CW is arranged for return tap water from the tap water circuit 180 to the tap water heat exchange circuit 170. A hot water circulation supply line HWC is connected to the cold water supply line CW. The hot water circulation supply line HWC is arranged for maintaining a constantly circulating base flow of hot tap water from the tap water circuit such that hot tap water is always available once the tap water circuit is activated.

[0098] As said, the switchable conduit system 150 is configured to fluidly connect the heat pump 130 to the radiator circuit 160 or to fluidly connect the heat pump 130 to the buffer tank 140.

[0099] Continuing with figure 1 , the arrangement 100 further comprises at least one sensor 210, 220, 230, 240, 250, 260. As depicted in figure 1 , three of these sensors 240, 250, 260 may be arranged in the heat pump 130. The sensor 240 is arranged in an inlet supply line 133 of the heat pump 130 and is configured to obtain observed data which pertains to an inlet temperature of the liquid entering the heat pump to be heated (or cooled). Thus, the sensor 240 is configured to obtain an observed data which pertains at a heat pump characteristic. The sensor 250 is arranged inside the first heat exchanger unit 135 in the air intake at the fan 131 and is configured to obtain observed data which pertains to an outside air temperature. The sensor 260 is arranged on the first heat exchanger coil 132 and is configured to obtain observed data which pertains to the temperature of the first heat exchanger coil 132. As depicted in figure 1 , the sensor 210 is disposed inside the buffer tank 140 and is configured to obtain data which pertains at least to a heat buffer liquid temperature of heat buffer liquid within the second portion 140b of the buffer tank 140. As further depicted in figure 1 , the sensor 220 is arranged at the tap water heat exchanger circuit 170 downstream the heat exchanger 171 and is arranged to determine a temperature of heat buffer liquid leaving the first side 171 a of the heat exchanger 171 . As yet further depicted in figure 1 , the sensor 230 is arranged downstream the second side 171 b of the heat exchanger 171 . The sensor 230 is configured to determine observed data which pertains to an outgoing hot tap water temperature of tap water leaving the second side 171 b of the heat exchanger 171 to the tap water circuit 180.

[0100] The arrangement 100 may further comprise at least one control unit 190. The control unit 190 may be arranged anywhere within the arrangement 100. For example, at least one control unit 190 may be arranged inside of, or at, at least one of the heat pump and the buffer tank. The control unit 190 is configured to control an operation of the arrangement 100. The control unit 190 may be wired, or wireless connected to the at least one sensor 210, 220, 230, 240, 250, 260. The control unit 190 may be wired, or wirelessly connected to any of the components comprised in the arrangement 100. The control unit 190 may be arranged in a remote server.

[0101] The at least one control unit 190 may be configured to receive observed data which pertains to at least one of an ambient temperature and heat pump characteristics, determine if said observed data meets a defrosting-on threshold, and transmit a defrosting-on signal in response to said observed data meeting the defrosting-on threshold.

[0102] The control unit 190 may be configured to determine a data relationship between the observed data and the reference data. The control unit 190 may be configured to determine the data relationship by executing a determination function when the heat pump 130 is fluidly connected to the radiator circuit 160 or when the heat pump 130 is fluidly connected to the buffer tank 140.

[0103] The control unit 190 may be configured to compare the data relationship with a comparison criterion. The control unit 190 may be configured to compare the data relationship with the comparison criterion by executing a comparison function when the heat pump 130 is fluidly connected to the radiator circuit 160 or when the heat pump 130 is fluidly connected to the buffer tank 140.

[0104] Even though illustrated and described in a certain order, other orders may also be used.

[0105] A method for controlling an arrangement, such as the previously described arrangement 100, will now be described with reference to figure 3. The method comprises the following steps:

[0106] First, a control signal is received S502. The control signal may be transmitted from a control unit 190, which has determined the control signal by analysing sensor data, as previously described herein. The control signal may be a defrosting-on signal transmitted in order to instruct the arrangement 100 to operate in a defrosting operational mode, or a defrosting-off signal transmitted in order to instruct the arrangement 100 to operate in a heating operational mode.

[0107] In case the control signal is a defrosting-on signal, a determination is made as to which operational mode the arrangement 100 is currently operated. If the arrangement 100 is operated in the defrosting operational mode, no further action is taken. If instead the arrangement 100 is operated in the heating operational mode, the following steps are initiated:

[0108] The refrigerant cycle 134 of the heat pump is reversed S504 to a defrosting operational mode. This means that the refrigerant cycle 134 is operated in the manner described with reference to Fig. 2B at which heat is transferred from the second heat exchanger 137 to the first heat exchanger 135 to heat the first heat exchanger coil 132 and defrost the same.

[0109] The switchable conduit system 150 is switched S504 the so as to configure the arrangement 100 to operate in a defrosting operational mode. In this mode, the switchable conduit system 150 supplies buffer liquid cooled by the heat pump 130 to the second portion 140b of the buffer tank 140 and retrieves buffer liquid from the second portion 140b of the buffer tank 140 to be cooled by the heat pump 130. This is achieved by the following steps:

[0110] Buffer liquid cooled by the heat pump 130 is supplied S508 to the second portion 140b of the buffer tank 140 through an auxiliary portion inlet 143 arranged to fluidly communicate with the second portion 140b of the buffer tank 140.

[0111] Buffer liquid is retrieved S510 from the second portion 140b of the buffer tank 140 to be cooled by the heat pump 130 through a second portion outlet 142b arranged to fluidly communicate with the second portion 140b of the buffer tank 140.

[0112] In case the control signal is instead a defrosting-off signal, a verification is made as to which operational mode the arrangement 100 is currently operated. If the arrangement 100 is operated in the heating operational mode, no further action is taken. If instead the arrangement 100 is operated in the defrosting operational mode, the following steps are initiated:

[0113] The refrigerant cycle 134 of the heat pump is reversed S512 to a heating operational mode. This means that the refrigerant cycle 134 is operated in the manner described with reference to Fig. 2A at which heat is transferred from the first heat exchanger 135 to the second heat exchanger 137.

[0114] The switchable conduit system 150 is switched S514 so as to configure the arrangement 100 to operate in a heating operational mode. In this mode, the switchable conduit system 150 supplies buffer liquid heated by the heat pump 130 to the first portion 140a of the buffer tank 140 and retrieves buffer liquid from the second portion 140b of the buffer tank 140 to be heated by the heat pump 130. This is achieved by the following steps: Buffer liquid heated by the heat pump 130 is supplied S516 to the first portion 140a of the buffer tank 140 through a first portion inlet 141a arranged to fluidly communicate with the first portion 140a of the buffer tank 140.

[0115] Buffer liquid is then retrieved S518 from the second portion 140b of the buffer tank 140 through the second portion outlet 142b to be heated by the heat pump 130.

[0116] The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. Additionally, variations to the disclosed embodiments may be understood and effected by the skilled person in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

Claims

CLAIMS1. An arrangement (100) for heating a building comprising: an air-liquid heat pump (130); a buffer tank (140) configured to store a heat buffer liquid in an internal volume thereof, said internal volume having a first portion (140a) and a second portion (140b), the first portion (140a) and the second portion (140b) being spaced from each other and located at opposite ends of the buffer tank (140); and a switchable conduit system (150) fluidly interconnecting the heat pump (130) with the buffer tank (140); wherein, when the arrangement (100) is configured to operate in a heating operational mode, the switchable conduit system (150) is configured to supply buffer liquid heated by the heat pump (130) to the first portion (140a) of the buffer tank (140) and retrieve buffer liquid from the second portion (140b) of the buffer tank (140) to be heated by the heat pump (130), and, when the arrangement (100) is configured to operate in a defrosting operational mode, the switchable conduit system (150) is configured to supply buffer liquid cooled by the heat pump (130) to the second portion (140b) of the buffer tank (140) and retrieve buffer liquid from the second portion (140b) of the buffer tank (140) to be cooled by the heat pump (130).

2. The arrangement (100) according to claim 1 , wherein the arrangement (100) further comprises at least one sensor (240, 250, 260) being configured to obtain observed data pertaining to at least one of an ambient temperature and heat pump (130) characteristics, and wherein the arrangement (100) is configured to, when in the heating operational mode, switch the switchable conduit system (150) such that the arrangement (100) starts operating in the defrosting operational mode in response to said observed data meeting a defrosting-on threshold.

3. The arrangement (100) according to claim 1 or 2, wherein the arrangement (100) is configured to operate in the defrosting operational modeduring a defrosting time period which is based on at least one of a predetermined time, an ambient temperature, and heat pump characteristics.

4. The arrangement (100) according to claim 2 or 3, wherein the heat pump characteristics include data pertaining to one or more from the list of: a compressor power, a refrigerant temperature, a refrigerant pressure, a heat pump inlet liquid temperature, a refrigerant type, and an evaporator coil temperature.

5. The arrangement (100) according to any one of claims 2 to 4, wherein the arrangement (100) further comprises at least one control unit (190) configured to receive said observed data which pertains to at least one of an ambient temperature and heat pump characteristics, determine if said observed data meets a defrosting-on threshold, and transmit a defrosting-on signal in response to said observed data meeting the defrosting-on threshold.

6. The arrangement (100) according to claim 5, wherein the at least one control unit (190) is arranged inside of, or at, at least one of the heat pump (130) and the buffer tank (140).

7. The arrangement (100) according to claim 5, wherein the at least one control unit (190) is arranged in a remote server and being in wired or wireless communication with parts of the arrangement (100).

8. The arrangement (100) according to any one of the preceding claims, wherein the buffer tank (140) further comprises: a first portion inlet (141a) arranged to fluidly communicate with the first portion (140a) of the buffer tank (140); a second portion outlet (142b) arranged to fluidly communicate with the second portion (140b) of the buffer tank (140); and an auxiliary portion inlet (143) arranged to fluidly communicate with the second portion (140b) of the buffer tank (140);wherein, when the arrangement (100) is operating in the heating operational mode, liquid exiting the heat pump (130) is supplied to the first portion (140a) of the buffer tank (140) through the first portion inlet (141a), and liquid entering into the heat pump (130) is retrieved from the second portion (140b) of the buffer tank (140) through the second portion outlet (142b), and wherein, when the arrangement (100) is operating in the defrosting operational mode, liquid entering into the heat pump (130) is retrieved from the second portion (140b) of the buffer tank (140) through the second portion outlet (142b), and liquid exiting the heat pump (130) is supplied to the second portion (140b) of the buffer tank (140) through the auxiliary portion inlet (143).

9. The arrangement (100) according to claim 8, wherein the second portion (140b) of the buffer tank (140) consists of a first sub-portion (140b1 ) and a second sub-portion (140b2), and wherein the second portion outlet (142b) is arranged to fluidly communicate with the first sub-portion (140b1 ), and the auxiliary portion inlet (143) is arranged to fluidly communicate with the second sub-portion (140b2), wherein the first and second sub-portions (140b1 , 140b2) of the second portion (140b) of the buffer tank (140) are separated from each other, and wherein the second sub-portion (140b2) is arranged between the first portion (140a) and the first sub-portion (140b1 ) within the buffer tank (140).

10. The arrangement (100) according any one of the preceding claims, wherein the buffer tank (140), when in use, is arranged to extend substantially vertically such that the first portion (140a) defines a top portion of the buffer tank (140) and the second portion (140b) defines a bottom portion of the buffer tank (140).11 . A method for controlling an arrangement (100) which comprises: an air-liquid heat pump (130); a buffer tank (140) configured to store a heat buffer liquid in an internal volume thereof, said internal volume having a first portion (140a) and asecond portion (140b), the first portion (140a) and the second portion (140b) being spaced from each other and located at opposite ends of the buffer tank (140); and a switchable conduit system (150) fluidly interconnecting the heat pump (130) with the buffer tank (140); the method comprising: in response to a defrosting-on signal: switching (S504) the switchable conduit system (150) so as to configure the arrangement (100) to operate in a defrosting operational mode in which the switchable conduit system (150) supplies buffer liquid cooled by the heat pump (130) to the second portion (140b) of the buffer tank (140) and retrieves buffer liquid from the second portion (140b) of the buffer tank (140) to be cooled by the heat pump (130), and in response to a defrosting-off signal: switching (S514) the switchable conduit system (150) so at to configure the arrangement (100) to operate in a heating operational mode in which the switchable conduit system (150) supplies buffer liquid heated by the heat pump (130) to the first portion (140a) of the buffer tank (140) and retrieves buffer liquid from the second portion (140b) of the buffer tank (140) to be heated by the heat pump (130).

12. The method according to claim 11 , further comprising: receiving sensor data pertaining to at least one of an ambient temperature and heat pump characteristics; determining, when the arrangement (100) is operating in the heating operational mode, if said observed data meets a defrosting-on threshold; and upon said observed data meeting the defrosting-on threshold: switching the switchable conduit system (150) such that the arrangement (100) operates in the defrosting operational mode.

13. The method according to claim 11 or 12, wherein the method further comprises: in response to the defrosting-on signal:(a) supplying (S508) buffer liquid cooled by the heat pump (130) to the second portion (140b) of the buffer tank (140) through an auxiliary portion inlet (143) arranged to fluidly communicate with the second portion (140b) of the buffer tank (140), and(b) retrieving (S510) buffer liquid from the second portion (140b) of the buffer tank (140) to be cooled by the heat pump (130) through a second portion outlet (142b) arranged to fluidly communicate with the second portion (140b) of the buffer tank (140) such that the heat pump (130) retrieves thermal energy from the second portion (140b) of the buffer tank (140), and in response to the defrosting-off signal:(c) supplying (S516) buffer liquid heated by the heat pump (130) to the first portion (140a) of the buffer tank (140) through a first portion inlet arranged to fluidly communicate with the first portion (140a) of the buffer tank (140), and(d) retrieving (S518) buffer liquid from the second portion (140b) of the buffer tank (140) to be heated by the heat pump (130) through the second portion outlet (142b).

14. The method according to claim 13, further comprising: in response to the defrosting-on signal: supplying buffer liquid cooled by the heat pump (130) to a second sub-portion (140b2) of the second portion (140b) of the buffer tank (140) through the auxiliary portion inlet (143), and retrieving buffer liquid from a first sub-portion (140b1 ) of the second portion (140b) of the buffer tank (140) to be cooled by the heat pump (130) through the second portion outlet (142b), and wherein the first and second sub-portions of the second portion (140b) of the buffer tank (140) are separated from each other, and wherein the second sub-portion (140b2) is arranged between the first portion (140a) and the first sub-portion (140b1 ) within the buffer tank (140).

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