Patent Description:
A major limitation for heat pump heating products for single-dwelling homes is a low heat delivery rate (typically <NUM>-<NUM> kW) compared small combination boilers (typically <NUM>-<NUM> kW). This means that heat pumps usually must be installed with a storage cylinder for domestic hot water which can be charged over a longer period of time when convenient. A typical shower uses around <NUM> litres per minute of water at supply temperatures around <NUM>: assuming mains water at <NUM> this leads to heat load of ~<NUM> kW. A single shower uses around <NUM> Litres of water, and <NUM> MJ (<NUM> kWh) of heat.

Phase change materials have been proposed as a more compact alternative to conventional water-based thermal storage for use in domestic heating applications, namely space heating and domestic hot water heating. These two applications have different temperature requirements. For DHW, point-of-use temperature tends to be in the range <NUM>-<NUM>, while for space heating the temperature range can be higher or lower depending on the type of heating system and the basis for sizing that heating system. Older central heating systems designed with fossil-fuel boilers and conventional panel radiators may use water flow temperatures in the range <NUM>-<NUM>, while modern heating systems designed for electric heat pumps use large heat emitter areas for water flow temperatures in the range <NUM>-<NUM>.

Meanwhile, heat pumps are designed to operate all year round, under a range of outdoor conditions. A typical mode for heat pump control in space heating operation is to use a weather compensation curve, for which water flow temperature is increased as outdoor ambient temperature decreases. This means that air-source heat pumps are required to operate over a wide range of "temperature lift" conditions; where the "temperature lift" is the difference between the source temperature and output temperature of a heat pump in heating mode. Thus, air source heat pumps are subject to part-load inefficiencies when designed for higher peak-load conditions in winter, when heat source temperature (outdoor air temperature) is very low and the required heat delivery temperature (water flow temperature) is very high. In other words, the coefficient of performance (COP) of such heat pump systems is low.

One proposed configuration for improving heat pump efficiency and the COP is to separate the heat pumping process into two stages, each with a smaller temperature lift, and to use the ground as a thermal store to store the thermal energy pumped from the air (e.g. at < <NUM>) at an intermediate temperature (e.g. at <NUM>) until it is required, at which point it can be pumped across the second stage to its required delivery temperature (e.g. <NUM> C for space heating). A problem with this approach is that the cost and inconvenience of installing shallow-coil or deep borehole type ground heat exchangers tends to be high, which makes said methods and systems very expensive.

For demand-side flexibility services, attention has focused on increasing thermal storage that can be used for both DHW and space heating. To this extent, many heat pump systems are designed with thermal stores that can be used to off-set the time of heat pump operation from the time of space heating demand. A problem with this approach is that the space requirement inside the building for both a DHW storage tank and thermal store for space heating (which is usually a water storage cylinder) can be excessively large for many single-family dwellings.

<CIT> discloses a system and method in which, when a heat source is insufficient or not matched to consumer-side needs, a backup of heat supply is provided by operating a heat pump by midnight power with the atmosphere as a heat source.

<CIT> discloses a system and method in which a heat storage system includes heat storage tanks that individually store a latent heat accumulating material, a circulating passage that passes through the heat storage tanks in ascending order of the melting point of the latent heat accumulating material in the heat storage tanks, a supply path that supplies a heating medium to an end of the circulating passage and a distribution passage that takes out the heating medium from the other end of the circulating passage.

<NPL>) disclose an operation of a heat pump with an integrated three-media refrigerant/phase change material water heat exchanger (RPW-HEX) in a laboratory under controlled ambient conditions. Two RPW-HEX modules with a total storage capacity of about <NUM> kWh were integrated into an R32 air-source heat pump with a heating power of about <NUM> kW at -<NUM> ambient temperature and a feed water temperature of <NUM>. With RPW-HEX. The system was able to provide a <NUM> higher average feed water temperature for DHW generation compared to the system without RPW-HEX.

Taken together, the systems and methods of the prior art suffer at least the following disadvantages. Firstly, if a single-stage heat pump system is used, it must operate across a large temperature difference between an outdoor air heat source and a required delivery temperature for domestic hot water, which does not allow an efficient operation, i.e. does not allow an operation at a high coefficient of performance (COP). Secondly, if two-stage heat pump systems or two compressors are used, the complexity of said systems and thus the costs for providing said systems is high. Thirdly, if a thermal storage device like a water storage cylinder is used, a large space is occupied by said thermal storage device leaving less space for other purposes in a room, which is particularly relevant in an indoor room.

Starting therefrom, it was the object of the present application to provide a system and a method for providing domestic hot water and space heating in a building, which does not have the disadvantages of prior art systems and methods. Specifically, it should be possible with the system and method to provide domestic hot water and/or space heating in a building in a more efficient manner and at a minimum of space needed by the system and for implementing the method. Preferably, it should also be possible to provide the system method for providing domestic hot water and space heating in a building, and carry out the respective method, at low costs.

The object is solved by the device having the features of claim <NUM> and the method having the features of claim <NUM>. The dependent claims illustrate advantageous embodiments of the invention.

According to the invention, a system for providing domestic hot water and/or space heating within a building is presented, comprising.

The system has the advantage that it can provide domestic hot water and space heating in a building in a more efficient manner. The higher efficiency and coefficient of performance (COP) is achieved by having the first storage device and second storage device in the described arrangement, wherein both the first storage device and the second storage device contain a phase change material. The two storage devices allow to separate the heat pumping process into two stages with an intermediate storage temperature condition, i.e. allows a first heat-pumping stage between a low temperature and an intermediate temperature and allows a second heat-pumping stage between an intermediate temperature and a high temperature. A higher efficiency and coefficient of performance is also achieved by the control of the system based on at least a state of charge of the first storage device and a state of charge of the second storage device, because the system can reliable select a proper operation mode based on the respective state of charge. For example, if the state of charge of the first storage device is high (e.g. at or above a set lower limit), the controller can select an operation mode in which heat for heating a space or for charging the second storage device is provided directly by the first storage device instead of being provided directly by outside air (which can be inefficient especially at low outside air temperatures). Furthermore, if the state of charge of the second storage device is low (e.g. below a set lower limit), the controller can select an operation mode in which heat is conveyed only to the second storage device to charge the second storage device and to render it capable to efficiently provide large volumes of domestic hot water.

The system also has the advantage that it can provide domestic hot water and space heating in a building with a minimum of space needed by the system. Since the system uses two storage devices containing a phase change material and phase change materials have a relatively high heat storage capability, the overall volume of the two storage devices can be smaller than if e.g. a water storage tank without a phase change material (e.g. a typical domestic hot water storage cylinder) for storing heat energy is employed in the system. It is preferred that the system does not comprise a water storage tank lacking a phase change material.

According to the invention, the state of charge of a storage device (i.e. of the first and second storage device, respectively) is the amount of heat energy stored in the storage device. In other words, the state of charge of a storage device represent the amount of heat energy that can be provided by the storage device. The state of charge of a storage device also indicates the amount of heat energy that is required to charge the storage device.

The detector for determining the state of charge (i.e. the first and second detector for determining the state of charge, respectively) of the storage device (i.e. of the first and second storage device, respectively) can comprise at least one temperature sensor (optionally more than one temperature sensor) suitable for detecting a temperature inside the storage device. Said at least one temperature sensor (optionally all temperature sensors) can be suitable to detect a temperature of an outer surface of the storage device (e.g. by being placed on or at an outer surface of the storage device). The at least one temperature sensor (optionally all temperature sensors), or at least one further temperature sensor in addition to the at least one temperature sensor, can be suitable to detect a temperature of a content inside the storage device (e.g. by being placed in an inner volume of the storage device, like an interior of the storage device or an interior of a phase change material heat exchanger within the storage device). In this regard, the state of charge of the storage device can e.g. be determined as described in EP patent application <CIT>. It is also possible that the detector for determining the state of charge comprises at least one temperature sensor and at least one electrical resistance sensor (e.g. as separate sensors or as a combined temperature-and-electrical-resistance sensor), wherein at least the electrical resistance sensor is suitable to detect an electrical resistance of a content (specifically: a fluid comprising or consisting of a PCM) inside the storage device (e.g. by being placed in an inner volume of the storage device and by contacting the inner content). In this regard, the state of charge of the storage device can e.g. be determined as described in the EP patent application<CIT>.

The conveying means for circulating water through the heat medium heat exchanger can be a pump.

In a preferred embodiment, the system according to the invention does not comprise a two stage-compressor and/or does not comprise a further (i.e. at least a second) compressor. By using only one single compressor to pump heat across the first stage and the second stage, a smaller degree of complexity is achieved and the system can be provided at lower costs. Furthermore, since heat can be pumped across smaller temperature differences in two stages by the same single compressor, a smaller temperature lift across the heat pump and a higher COP is achieved.

In a further preferred embodiment, the first storage device is located outdoors, preferably within a heat pump outdoor unit comprising the compressor, the first expansion valve, the second expansion valve, the first three-way valve, the second three-way valve, the four-way switching valve, the outdoor heat exchanger and the heat medium heat exchanger. The advantage of this embodiment is that the system only needs a minimum of space in a room inside of a building and that the system can perform a more efficient operation. Furthermore, locating the first storage device outdoors is not connected to high thermal losses because the first storage device contains a phase change material with a lower phase change temperature than the second storage device. Hence, the temperature inside the first storage device can be kept lower so that a temperature gradient to an outdoor environment can be lower than if the second storage device was located outdoors.

Hence, in a further preferred embodiment, the second storage device (containing the phase change material with the higher phase change temperature) is preferably located indoors (i.e. inside a building). Since a significant fraction of the total required heat storage can be provided by the low-temperature phase change material in the first storage device, the size of the second storage device can be smaller than the size of the first storage device, which provides more free space in a room in which the second storage device is located. This is especially relevant if the room is inside of a building.

The first phase change material can have a phase transition temperature which is half way between an outdoor ambient air temperature in winter in a location where the system is located, and the phase change temperature of the second phase change material. For example, the first phase change material can have a phase transition temperature in the range of <NUM> to <NUM>, preferably <NUM> to <NUM>.

The second phase change material can have a phase transition temperature in the range of <NUM> to <NUM>, preferably <NUM> to <NUM>.

The controller can be configured to control an operation of the system which is further based on a requirement of a defrosting operation (of the outdoor heat exchanger). To this end, the outdoor heat exchanger can comprise a temperature sensor which is suitable to communicate with the controller or the system can comprise a temperature sensor for detecting a refrigerant temperature which is suitable to communicate with the controller. In this embodiment, the outdoor heat exchanger can comprise an outdoor heat exchanger temperature sensor and the controller can be configured to select a defrosting operation mode based on a temperature information communicated by said temperature sensor. This configuration has the advantage that in a case in which a defrosting operation is needed, the controller can switch to a defrosting operation mode. In said defrosting operation mode, the outdoor heat exchanger can be defrosted which allows a more efficient operation of the outdoor heat exchanger after the defrosting operation.

The controller can be configured to control an operation of the system which is further based on a demand for space heating within a building. In this embodiment, the system can comprise an indoor air temperature sensor in an indoor space to be heated and the controller can be configured to select a space heating operation mode based on a temperature information communicated by said temperature sensor. This configuration of the controller has the advantage that, if there is a demand of space heating, the system can switch to a space heating only operation mode. For example, in said heating mode, no heating energy is used for charging the first storage device and/or for charging the second storage device (with heat energy) and/or for providing domestic hot water. This is beneficial because heating a space to be heated becomes more efficient. If there is no demand for space heating, the system can switch to operation modes in which no heat is used to provide space heating. For example, in said operation modes, heat is used for charging the first storage device and/or second storage device (with heat energy) and/or for providing domestic hot water.

This is beneficial because heating domestic hot water and/or charging the first and/or second storage device becomes more efficient.

The controller can be configured to control an operation of the system which is further based on an outdoor ambient air temperature. In this embodiment, the system can comprise an outdoor air temperature sensor in an outdoor space and the controller can be configured to select an operation mode of the system based on a temperature information communicated by said temperature sensor. This configuration of the controller has the advantage that an outdoor ambient air temperature can be used to decide whether the second storage device is charged with heat from outdoor air (if outdoor ambient air temperature is at or above a set lower limit) or charged with heat from the first storage device (if outdoor ambient air temperature is below a set lower limit). This allows a more efficient charging of the second storage device because heat is pumped over a shallower temperature gradient into the second storage device. Furthermore, an outdoor air temperature can be used to decide whether space heating is performed with heat from outdoor air (if outdoor ambient air temperature is at or above a set lower limit) or performed with heat from the first storage device (if outdoor ambient air temperature is below a set lower limit). This allows a more efficient space heating because heat is pumped over a shallower temperature gradient to the space to be heated.

The first three-way valve is preferably located in a fluid line connecting the compressor with the first phase change material heat exchanger and the heat medium heat exchanger.

Moreover, the second three-way valve is preferably located in a fluid line connecting the compressor with the first phase change material heat exchanger and the outdoor heat exchanger.

The refrigeration circuit of the system can comprise a receiver (accumulator). The receiver can be located in a fluid line between the first expansion valve and the second expansion valve in the refrigeration circuit.

The first expansion valve of the refrigeration circuit of the system can be located in a fluid line between the outdoor heat exchanger and a receiver of the refrigerant circuit.

The second expansion valve of the refrigeration circuit can be located in a fluid line between a receiver of the refrigerant circuit and a fluid line branching to the first phase change material heat exchanger and to the heat medium heat exchanger.

The controller of the system can be configured to.

This configuration of the controller has the advantage that heat stored in the second storage device can be used to defrost the outdoor heat exchanger in cold-ambient conditions, without compromising comfort conditions in the internal living space or supply temperature of the domestic hot water output.

The controller of the system can be configured to,.

This configuration of the controller has the advantage that the second storage device can be charged with heat energy from outside air.

This configuration of the controller has the advantage that the second storage device can be charged with heat energy from the first storage device.

This configuration of the controller has the advantage that heat energy from outside air can be (directly) transported to at least one space in a building. Hence, heat can be directly pumped from the outdoor air to a heat emitter circuit of a building.

This configuration of the controller has the advantage that heat energy from the first storage device can be (directly) transported to at least one space in a building. Hence, heat can be directly pumped from the first storage device (containing phase change material at lower temperature) to a heat emitter circuit of a building.

This configuration of the controller has the advantage that the first storage device can be charged with heat energy from outside air.

The heat medium circuit of the system can comprise a further heat exchanger suitable for exchanging heat between water (flowing in the heat medium circuit) and mains water (flowing in domestic hot water circuit). The further heat exchanger has the advantage that heat can be provided to mains water beside the second phase change material heat exchanger of the second storage device. For example, the further heat exchanger can be located upstream of the second phase change material heat exchanger of the second storage device. This location allows the further heat exchanger to preheat mains water before it enters into the second phase change material heat exchanger of the second storage device. Alternatively, the further heat exchanger may be located downstream of the second phase change material heat exchanger of the second storage device. This location allows the further heat exchanger to postheat mains water exiting the second phase change material heat exchanger of the second storage device. In this embodiment, the heat medium circuit preferably comprises a further three-way valve which is suitable to switch a flow of water to the second phase change material heat exchanger of the second storage device via the further heat exchanger or directly to the second phase change material heat exchanger of the second storage device by bypassing the further heat exchanger.

The first storage device of the system can comprise a renewable energy heat exchanger suitable for exchanging heat between the first phase change material and a fluid which receives heat energy from a renewable energy source. This embodiment has the advantage that heat energy from a renewable energy source can be transferred to the first storage device and stored by the first phase change material inside the first storage device. The renewable energy source can be a solar thermal array. In this case, water can flow through the solar thermal array, absorb heat energy from the sun and transfer the absorbed heat energy to the first storage device by the renewable energy heat exchanger. In a particularly preferred embodiment, the renewable energy source is a solar photovoltaic-thermal array. In this case, water can flow through the solar photovoltaic thermal array, absorb heat energy from the sun and transfer the absorbed heat energy to the first storage device by the renewable energy heat exchanger and additionally, electric energy generated by the solar photovoltaic thermal array can be used to provide electricity to the system, i.e. can be used to operate the complete system or at least parts thereof (e.g. parts relating to the heat pump). In this embodiment, the system can further comprise an inverter to convert a DC voltage to an AC voltage.

According to the invention, a method for providing domestic hot water (DHW) and/or space heating (SH) within a building is provided, comprising.

The method has at least the advantages that it can provide domestic hot water and space heating in a building in a more efficient manner and with a minimum of space needed.

The first storage device of the system used in the method can be placed outdoors, preferably within a heat pump outdoor unit comprising the compressor, the first expansion valve, the second expansion valve, the first three-way valve, the second three-way valve, the four-way switching valve, the outdoor heat exchanger and the heat medium heat exchanger. The advantage is that carrying out the method requires less indoor space and results in a more efficient operation.

The method can be characterized in that, if a defrosting of the outdoor heat exchanger is required,.

This method has the advantage that heat stored in the second storage device can be used to defrost the outdoor heat exchanger in cold-ambient conditions, without compromising comfort conditions in the internal living space or supply temperature of the domestic hot water output.

The method can be characterized in that,.

This method has the advantage that the second storage device can be charged with heat energy from outside air.

This method has the advantage that the second storage device can be charged with heat energy from the first storage device.

This method has the advantage that heat energy from outside air can be (directly) transported to at least one space in a building. Hence, heat can be directly pumped from the outdoor air to a heat emitter circuit of a building.

This method has the advantage that heat energy from the first storage device can be (directly) transported to at least one space in a building. Hence, heat can be directly pumped from the first storage device (containing phase change material at lower temperature) to a heat emitter circuit of a building.

This method has the advantage that the first storage device can be charged with heat energy from outside air.

In the method, a system according to the invention can be provided and used, i.e. the method can be conducted with a system according to the invention. The controller of the system can be configured to control steps of the method, e.g. control the settings of parts of the system.

With reference to the following figures and examples, the subject according to the invention is intended to be explained in more detail without wishing to restrict said subject to the specific embodiments shown here.

In this operating mode, the heat pump is used to pump heat from the outdoor air <NUM> to the first storage device <NUM> via the first phase change material heat exchanger <NUM> embedded in the first storage device <NUM>. The refrigerant circuit flow configuration is set according to <FIG>.

The four-way switching valve <NUM> is set to its normal "heating" position. The three-way valve <NUM> is set to direct superheated refrigerant vapour from the compressor <NUM> discharge to the first storage device store heat exchanger <NUM>, where it condenses, releasing heat to melt the first phase change material. The three-way valve <NUM> is set to direct <NUM>-phase refrigerant leaving the linear expansion valve <NUM> to the outdoor heat exchanger <NUM>, where it evaporates, absorbing heat from the air stream. The orifice of the first linear expansion valve <NUM> is adjusted to control the superheat temperature at the evaporator outlet, while the second linear expansion valve <NUM>' is set fully open.

In this operating mode, the heat pump is used to pump heat from the first storage device <NUM> to the second storage device <NUM>, which allows an efficient provision of domestic hot water by the second storage device. This mode is used when outdoor air temperature is sufficiently low that using the heat stored in the first storage device <NUM> as the heat source offers a significant improvement to the COP of the heat pump compared to using outdoor air <NUM>. The refrigerant circuit flow configuration is set according to <FIG>.

The four-way switching valve <NUM> is set to its normal "heating" position. The three-way valve <NUM> is set to direct superheated refrigerant vapour from the compressor <NUM> discharge to the heat medium heat exchanger <NUM>, where it condenses, releasing heat to primary circulating fluid. The three-way valve <NUM> is set to direct <NUM>-phase refrigerant leaving linear expansion valve <NUM> to the first storage device <NUM>, where it evaporates, absorbing heat from the first phase change material which changes phase from liquid to solid. The orifice of the first linear expansion valve <NUM> is adjusted to control the superheat temperature at the evaporator outlet, while the second linear expansion valve <NUM>' is set fully open.

The three-way valve <NUM> (shown in <FIG>) is set to direct water of the heat medium circuit <NUM> to the second storage device <NUM> and not to the heat emitter(s) <NUM>.

In this operating mode, the heat pump is used to pump heat from the first storage device <NUM> to at least one heat emitter <NUM>, which allows an efficient heating of at least one inside room in which the heat emitter is located. This mode is used when outdoor air temperature is sufficiently low and heat demand is sufficiently high that using the heat stored in the first storage device <NUM> as the heat source offers a significant improvement to the heat pump COP compared to using outdoor air <NUM>. The refrigerant circuit flow configuration is set according to <FIG>.

The three-way valve <NUM> (shown in <FIG>) is set to direct water of the heat medium circuit <NUM> to the heat emitter(s) <NUM> and not to the second storage device <NUM>.

In this operating mode, the heat pump is used to pump heat from the outdoor air <NUM> to the second storage device <NUM>. This mode is used when there is an immediate demand for domestic hot water (DHW), but there is not sufficient thermal energy stored in the first storage device <NUM>, or when outdoor air <NUM> temperature is sufficiently high that using the heat stored in the first storage device <NUM> as the heat source offers no significant improvement to the heat pump COP compared to using the outdoor air <NUM>. The refrigerant circuit flow configuration is set according to <FIG>.

The four-way switching valve <NUM> is set to its normal "heating" position. The three-way valve <NUM> is set to direct superheated refrigerant vapour from the compressor <NUM> discharge to the heat medium heat exchanger <NUM>, where it condenses, releasing heat to primary circulating fluid. The three-way valve <NUM> is set to direct <NUM>-phase refrigerant leaving linear expansion valve <NUM> to the outdoor heat exchanger <NUM>, where it evaporates, absorbing heat from the air stream. The orifice of the first linear expansion valve <NUM> is adjusted to control the superheat temperature at the evaporator outlet, while the second linear expansion valve <NUM>' is set fully open.

In this operating mode, the heat pump is used to pump heat from the outdoor air <NUM> to the heat emitter(s) <NUM>. This mode is used when outdoor air <NUM> temperature is sufficiently high and heat demand is sufficiently low that using the heat stored in the first storage device <NUM> as heat source offers no significant improvement to the heat pump COP compared to using the outdoor air <NUM>. The refrigerant circuit flow configuration is set according to <FIG>.

The three-way valve <NUM> (shown in <FIG>) is set to direct water of the heat medium circuit to the heat emitter(s) <NUM> and not to the second storage device <NUM>.

In this operating mode, the heat pump is used to pump heat from the first storage device <NUM> to (periodically) defrost the outdoor heat exchanger <NUM> during cold outdoor temperatures. The refrigerant circuit flow configuration is set according to <FIG>.

The four-way switching valve <NUM> is set to its reverse "defrost" position. Low-pressure <NUM>-phase refrigerant enters the first phase change material heat exchanger <NUM> where it is evaporated, absorbing latent heat released by the first phase change material. The three-way valve <NUM> is set to direct the low-pressure vapour leaving the first phase change material heat exchanger <NUM> to the compressor <NUM> intake. The three-way valve <NUM> directs the high pressure superheated vapour leaving the compressor <NUM> discharge to the outdoor heat exchanger <NUM> where it condenses, releasing heat to defrost the ice build-up on the external surface of outdoor heat exchanger <NUM>. The orifice of the second linear expansion valve <NUM>' is adjusted to control the superheat temperature at the outlet of the first phase change material heat exchanger <NUM>, while the first linear expansion valve <NUM> is set fully open.

<FIG> shows a possible implementation by which mains water can be preheated using the heat pump (either with air as heat source or the first storage device <NUM> as heat source) and a further heat exchanger (e.g. a plate type heat exchanger) and a further <NUM>-way valve <NUM> in the heat medium circuit.

Such an arrangement is particularly beneficial during longer DHW draw-off events (e.g. bath or shower), allowing the fraction of the DHW heating load extracted from the second storage device <NUM> to be reduced by as much as <NUM>-<NUM>% (depending on the nominal capacity of the heat pump). Thus a larger volume of DHW can be supplied before it is necessary to charge the second storage device <NUM> or, when the aim is to provide a comparable volume of DHW, the second storage device <NUM> can be sized smaller which allows for less indoor room to be occupied by the second storage device <NUM>.

By incorporating a dual heat exchanger design for the first storage device <NUM>, a secondary renewable heat source, such as a solar thermal collector array can be used to provide thermal input to the system. This has a particular advantage in this arrangement because the solar thermal collector array can achieve a higher-efficiency operation at the low melting temperature of the first storage device <NUM> compared to a conventional arrangement where solar thermal collectors are required to heat DHW to higher storage temperatures of approx. This means that lower-cost solar collector designs (e.g. unglazed flat-plat collectors) could be used, for which there is usually a more pronounced reduction in efficiency at higher operating temperatures than for higher-cost designs (e.g. evacuated-tube collectors).

Claim 1:
System for providing domestic hot water (DHW) and/or space heating (SH) within a building, comprising
a) a refrigeration circuit comprising
a refrigerant as heat medium,
a compressor (<NUM>),
a first expansion valve (<NUM>) and a second expansion valve (<NUM>'),
a first three-way valve (<NUM>) and a second three-way valve (<NUM>),
a four-way switching valve (<NUM>), and
an outdoor heat exchanger (<NUM>) suitable for exchanging heat between the refrigerant and air,
a first storage device (<NUM>) containing a first phase change material, wherein the first storage device (<NUM>) comprises a first detector for determining the state of charge (SOC<NUM>) of the first storage device (<NUM>) and comprises a first phase change material heat exchanger (<NUM>) suitable for exchanging heat between the refrigerant and the first phase change material;
b) a heat medium circuit comprising
water as heat medium,
a second storage device (<NUM>) arranged for being thermally connected to a domestic hot water circuit and containing a second phase change material, wherein the phase change temperature of the second phase change material is higher than the phase change temperature of the first phase change material, wherein the second storage device (<NUM>) comprises a second detector for determining the state of charge (SOC<NUM>) of the second storage device (<NUM>) and comprises a second phase change material heat exchanger (<NUM>) suitable for exchanging heat between water of the heat medium circuit and the second phase change material;
a third three-way valve (<NUM>) suitable for switching a flow of water to either at least one heat emitter for space heating within a building or to the second phase change material heat exchanger (<NUM>);
at least one conveying means (<NUM>) for circulating water through the heat medium heat exchanger;
c) a heat medium heat exchanger (<NUM>) comprised by both the refrigeration circuit and the heat medium circuit, and being suitable for transferring heat between the refrigerant and water; and
d) a controller (<NUM>) configured to control an operation of the system based on at least a state of charge (SOC<NUM>) of the first storage device (<NUM>) determined by information obtained from the first detector and a state of charge (SOC<NUM>) of the second storage device (<NUM>) determined by information obtained from the second detector.