EP4624808A1

EP4624808A1 - System for heating and cooling at least one space and for providing domestic hot water and method for operating the system

Info

Publication number: EP4624808A1
Application number: EP24165975.4A
Authority: EP
Inventors: Dr. Christopher OLKIS; Dr. James FREEMAN
Original assignee: Mitsubishi Electric R&D Centre Europe BV; Mitsubishi Electric Corp; Mitsubishi Electric R&D Centre Europe BV Netherlands
Current assignee: Mitsubishi Electric Corp
Priority date: 2024-03-25
Filing date: 2024-03-25
Publication date: 2025-10-01
Also published as: JP2025148249A

Abstract

The present invention is directed to a system for heating and cooling at least one space and for providing domestic hot water. The system comprises a first thermal energy storage device for providing domestic hot water, at least one emitter for heating and cooling the at least one space, a reconfigurable fluid network for transferring a first heat transfer fluid, a heat exchanger for transferring heat between the first heat transfer fluid and a second heat transfer fluid, and a controller. The reconfigurable fluid network comprises a heat pump unit, at least one valve, and pipes, the heat pump unit comprising a compressor and at least one expansion valve. The reconfigurable fluid network is configurable by the controller in a plurality of specific configurations and the controller is configured such that it can operate the system in a plurality of specific modes. Furthermore, the present invention also applies to a method for operating a system.

Description

The present invention is directed to a system for heating and cooling at least one space and for providing domestic hot water. The system comprises a first thermal energy storage device for providing domestic hot water, at least one emitter for heating and cooling the at least one space, a reconfigurable fluid network for transferring a first heat transfer fluid, a heat exchanger for transferring heat between the first heat transfer fluid and a second heat transfer fluid, and a controller. The reconfigurable fluid network comprises a heat pump unit, at least one valve, and pipes, the heat pump unit comprising a compressor and at least one expansion valve. The reconfigurable fluid network is configurable by the controller in a plurality of specific configurations and the controller is configured such that it can operate the system in a plurality of specific modes. Furthermore, the present invention also applies to a method for operating a system.
Water-to-water heat pumps are increasingly installed in multi-residential apartments. They are installed in individual apartments to deliver hot water and heating and can be connected to a heat network such as a 5th Generation ambient temperature district heat network, which is deployed throughout the building. These water-to-water heat pump systems combine a heat pump refrigerant circuit and a domestic hot water (DHW) thermal energy storage (TES) in the indoor unit, whereas a typical air-to-water heat pump has the heat pump refrigerant circuit in the outdoor unit and the TES in the indoor unit. In water-to-water heat pump systems, the heat pump is often at the bottom of the indoor unit and in the top section is a cylinder for domestic hot water (DHW) provision.
Current water-to-water heat pump systems have many advantages compared to the more established air-to-water systems, e.g. compact design for residential apartments, smaller refrigerant charge, and integration with district heating networks. However, they are not suitable for locations without access to a water-based heat source, e.g. district heating network, especially single-family homes without access to district heating. Furthermore, they cannot be installed with additional heat sources that are free of charge like solar energy or air source.
Water-to-water as well as air-to water heat pumps both have space cooling capabilities, but they are very basic and do not go beyond traditional air-to-air air conditioners (AC). AC will be of increasing importance in the future, when global temperatures are rising and traditional heating markets in central and northern Europe, but also in Asia and the Americas, require cooling as well. Here, heat pumps are advantageous over a combination of gas boilers and AC systems due to their potentially higher degree of energy integration. Current heat pump systems do not exploit their full potential yet.
Starting from this, it was the objective of the present invention to provide an energy efficient system that allows providing domestic hot water, heating at least one space, and cooling the at least one space.
This objective is achieved with respect to a system for heating and cooling at least one space and for providing domestic hot water by the features of claim 1 and with respect to a method for operating such system by the features of claim 15. The dependent claims represent advantageous further developments.
In accordance with the present invention, a system for heating and cooling at least one space and for providing domestic hot water is provided, the system comprising

a first thermal energy storage device for providing domestic hot water,
at least one (heat) emitter for heating and cooling the at least one space, the at least one (heat) emitter being provided within the at least one space,
a reconfigurable fluid network for transferring a first heat transfer fluid (e.g. water-based heat transfer fluid or water), the reconfigurable fluid network comprising a heat pump unit, at least one valve, and pipes, the heat pump unit comprising a compressor and at least one expansion valve, wherein the reconfigurable fluid network is configurable by a controller in a plurality of configurations comprising at least one first configuration in which the reconfigurable fluid network is configured to transfer the first heat transfer fluid from the heat pump unit to the first thermal energy storage device and not to the at least one (heat) emitter, at least one second configuration in which the reconfigurable fluid network is configured to transfer the first heat transfer fluid from the heat pump unit to the at least one (heat) emitter and not to the first thermal energy storage device, and a third configuration in which the reconfigurable fluid network is configured to transfer the first heat transfer fluid from the heat pump unit to the at least one (heat) emitter and from the heat pump unit to the first thermal energy storage device,
a heat exchanger for transferring heat between the first heat transfer fluid and a second heat transfer fluid (e.g. air), the second heat transfer fluid being external to the reconfigurable fluid network, wherein the heat exchanger is external to the heat pump unit, and
the controller, wherein the controller is configured such that it can operate the system in a plurality of modes comprising at least one (first) mode for charging the first thermal energy storage device, in which the reconfigurable fluid network is configured in (a respective configuration of) the (at least one) first configuration (and in which no cooling of the at least one space by the system takes place), at least one (second) mode for heating the at least one space, in which the reconfigurable fluid network is configured in (a respective configuration of) the (at least one) second configuration, and a (third) mode for cooling the at least one space and charging the first thermal energy storage device (wherein the heat removed from the at least one space is used for charging the first thermal energy storage device), in which the reconfigurable fluid network is configured in the third configuration.

The system according to the present invention comprises a specific reconfigurable fluid network comprising a heat pump unit, wherein the first thermal energy storage device, the at least one emitter for heating and cooling the at least one space, and the heat exchanger for transferring heat between the first heat transfer fluid and the second heat transfer fluid are all connected to the reconfigurable fluid network. The reconfigurable fluid network is configurable by a controller in a plurality of configurations in which the first transfer fluid can be transferred between different components of the system via the pipes of the reconfigurable fluid network. For example, the at least one valve (which is e.g. at least one three-way valve) can be switched by the controller to change the configuration of the reconfigurable fluid network.
The plurality of configurations comprise at least three configurations. In the (at least one) first configuration, the reconfigurable fluid network is configured to transfer the first heat transfer fluid from (a high pressure side of) the heat pump unit to the first thermal energy storage device (and back) but not to the at least one emitter. In the (at least one) second configuration, the reconfigurable fluid network is configured to transfer the first heat transfer fluid from (a high pressure side of) the heat pump unit to the at least one emitter (and back) but not to the first thermal energy storage device. In the third configuration, the reconfigurable fluid network is configured to transfer the first heat transfer fluid from (a low pressure side of) the heat pump unit to the at least one emitter (and back) and also to transfer the first heat transfer fluid from (a high pressure side of) the heat pump unit to the first thermal energy storage device (and back). In order to achieve the third configuration, pipes of the reconfigurable fluid network, which are external to the heat pump unit, can be (or are) connected to both sides of the heat pump unit (i.e. a high pressure side and a low pressure side of the heat pump unit), e.g. to heat pump heat exchangers used as evaporator and condenser or to internal pipes of the heat pump unit on both sides of the heat pump unit.
Since the specific reconfigurable fluid network comprises the heat pump unit and is connected to the first thermal energy storage device, the at least one emitter, and the heat exchanger, which is external to the heat pump unit, a simplified and flexible system is obtained that can be operated in a plurality of specific modes comprising at least one mode for charging the first thermal energy storage device (in which mode no cooling of the at least one space by the system takes place), at least one mode for heating the at least one space, and a mode for both cooling the at least one space and charging the first thermal energy storage device (i.e. a mode in which the at least one space is cooled and the first thermal energy storage device is charged). Since in the mode for cooling the at least one space and charging the first thermal energy storage device, the reconfigurable fluid network is configured in the third configuration in which third configuration the reconfigurable fluid network is configured to transfer the first heat transfer fluid from the heat pump unit to the at least one emitter and from the heat pump unit to the first thermal energy storage device, energy obtained by cooling the at least one space can be used for charging the first thermal energy storage device instead of rejecting the heat to the ambient through an air heat exchanger, which results in an energy efficient charging of the first thermal energy storage device without wasting the heat obtained by space cooling. Thus, the system according to the present invention is an energy efficient system that allows providing domestic hot water, heating at least one space, and cooling the at least one space.
The plurality of modes comprise at least one (first) mode for charging the first thermal energy storage device (in which mode no cooling of the at least one space by the system takes place), at least one (second) mode for heating the at least one space, and a (third) mode for both cooling the at least one space and charging the first thermal energy storage device (i.e. a mode in which the at least one space is cooled and the first thermal energy storage device is charged). In the at least one (first) mode for charging the first thermal energy storage device, the reconfigurable fluid network is configured in (a respective configuration of) the (at least one) first configuration. In the at least one (second) mode for heating the at least one space, the reconfigurable fluid network is configured in (a respective configuration of) the (at least one) second configuration. In the (third) mode for cooling the at least one space and charging the first thermal energy storage device, the reconfigurable fluid network is configured in the third configuration.
Due to the presence of the specific reconfigurable fluid network and the first heat exchanger, which is external to the heat pump unit, in the system according to the present invention, a flexible system is obtained in which a packaged heat pump (i.e. monobloc heat pump) or split-type heat pump can be used and which can be used in several modes.
The system according to the present invention increases the capabilities compared to current water-to-water heat pump systems. It is possible to install additional heat source components (photovoltaic thermal hybrid solar collector and/or solar thermal collector, low temperature phase change material thermal energy storage, high-temperature phase change material thermal energy storage, air-to-water heat exchanger) to improve the system efficiency and/or reduce operation cost. It is further possible to use a second thermal energy storage device that improves the system efficiency and/or reduces operation cost. The second thermal energy storage device can be a heat source for charging the first thermal energy storage device, and/or can be used to preheat mains water, and/or can be used for space cooling/heating.
A simplification of the system according to the present invention can in particular emerge from the connection of pipes of the reconfigurable fluid network, which are external the heat pump unit, to both sides of the heat pump unit (i.e. a high pressure side and a low pressure side of the heat pump unit). Thus, the complexity of the system can be reduced so that, e.g. less valves and pumps need to be used in the reconfigurable fluid network.
The present invention can extend the capabilities and applicability of water-to-water heat pumps from residential apartment buildings to single family homes, where photovoltaic thermal hybrid solar collectors on the roof and/or outdoor space is available. Alternatively, the roof space of an apartment building occupied by a second heat pump can be used for photovoltaic thermal hybrid solar collectors and/or solar thermal collector, and an air-to-water fan assisted heat exchanger.
The heat exchanger for transferring heat between the first heat transfer fluid and a second heat transfer fluid can also be referred to as external heat exchanger.
The heat pump unit can comprise a complete heat pump comprising the compressor, a first heat pump heat exchanger, the at least one expansion valve, and a second heat pump heat exchanger, (and also optionally a four-way reversing valve), or the heat pump unit can be a heat pump subunit comprising only a part of a heat pump (e.g. comprising the compressor and the at least one expansion valve, (and also optionally a four-way reversing valve) but not comprising any heat exchanger). If the heat pump unit is a heat pump subunit that does not comprise any heat exchanger, heat exchangers of the system arranged external of the heat pump unit can act as evaporator and condenser of the heat pump, so that a system similar to a split-type air-conditioning system (i.e. a traditional air-to-air air conditioning system) is provided, where the (e.g. wall mounted) heating and air conditioning unit is supplied with refrigerant from an outdoor unit (of the traditional air-to-air air conditioning system) and can act as evaporator during cooling and condenser during heating mode. Such heat exchangers of the system arranged external of the heat pump unit can be, e.g. the heat exchanger for transferring heat between the first heat transfer fluid and a second heat transfer fluid, the at least one emitter, and/or a heat exchanger of the first thermal energy storage device.
The pipes of the reconfigurable fluid network can comprise pipes that are external to the heat pump unit and pipes that are internal to the heat pump unit. The pipes that are internal to the heat pump unit can also be designated as (internal) pipes of the heat pump unit. The pipes that are external to the heat pump unit can also be designated as distribution circuit.
A preferred embodiment of the system according to the present invention is characterized in that the heat pump unit is a water source heat pump unit.
A further preferred embodiment of the system according to the present invention is characterized in that the first heat transfer fluid comprises or consists of water or a refrigerant different from water.
A further preferred embodiment of the system according to the present invention is characterized in that the heat pump unit is a reversible heat pump unit. This can be achieved e.g. by the heat pump unit comprising a four-way (reversing) valve that is arranged such that the heat pump cycle can be reversed.
A further preferred embodiment of the system according to the present invention is characterized in that the system further comprises a solar heat transfer device, wherein the solar heat transfer device is connected to the reconfigurable fluid network, and wherein preferably the solar heat transfer device comprises at least one solar thermal collector and/or at least one photovoltaic thermal hybrid solar collector.
In a further preferred embodiment of the system according to the present invention, it is also possible to directly use solar thermal energy to provide space heating or domestic hot water without switching on the compressor of the heat pump unit. This reduces electricity consumption. This can be achieved e.g. when the plurality of configurations comprises at least one further configuration in which the reconfigurable fluid network is configured to transfer the first heat transfer fluid from the solar heat transfer device to the first thermal energy storage device or to the at least one emitter but not to the heat pump unit, wherein the plurality of modes comprises at least one further mode for charging the first thermal energy storage device or for heating the at least one space in which mode the reconfigurable fluid network is configured in (one configuration) of the at least one further configuration.
A further preferred embodiment of the system according to the present invention is characterized in that the first thermal energy storage device comprises a phase change material, wherein preferably the melting temperature of the phase change material of the first thermal energy storage device is a temperature in the range from 40 to 100 °C, more preferably from 45 to 65 °C. By using a phase change material, the system has a higher energy storage density, which reduces the system size. Alternatively, the first thermal energy storage device can also be a hot water tank.
A further preferred embodiment of the system according to the present invention is characterized in that the system further comprises a state of charge analyser for determining the state of charge of the first thermal energy storage device, wherein preferably the controller is configured to operate the system in consideration of the state of charge of the first thermal energy storage device determined by the state of charge analyser for determining the state of charge of the first thermal energy storage device.
A further preferred embodiment of the system according to the present invention is characterized in that the system further comprises a second thermal energy storage device, wherein the second thermal energy storage device is connected to the reconfigurable fluid network, and wherein preferably the second thermal energy storage device comprises a phase change material, wherein more preferably the melting temperature of the phase change material of the second thermal energy storage device is

a temperature in the range from 0 to 50 °C, even more preferably from 15 to 45 °C, and/or
lower than the melting temperature of a phase change material of the first thermal energy storage device.

By using a phase change material in the second thermal energy storage device, the system has a higher energy storage density, which reduces the system size. Alternatively, the second thermal energy storage device can also be a buffer tank.
A further preferred embodiment of the system according to the present invention is characterized in that the system further comprises a state of charge analyser for determining the state of charge of the second thermal energy storage device, wherein preferably the controller is configured to operate the system in consideration of the state of charge of the second thermal energy storage device determined by the state of charge analyser for determining the state of charge of the second thermal energy storage device.
A further preferred embodiment of the system according to the present invention is characterized in that the second thermal energy storage device is connected to the first thermal energy storage device via at least one pipe for transferring water preheated by the second thermal energy storage device to the first thermal energy storage device in which the water is further heated to obtain domestic hot water.
The second thermal energy storage device can be a heat source for charging the first thermal energy storage device, and/or can be used to preheat mains water, and/or can be used for space cooling/heating. When it is used for space cooling/heating, it can be used e.g. as a heat sink for space cooling, as a heat source to provide space heating, or as a combination of both in climates with large temperature variations between day and night, i.e. hot days and cold nights. This can be especially beneficial, when the second thermal energy storage device uses a phase change material for energy storage and the phase change material has a melting temperature that is below the maximum air temperature.
A further preferred embodiment of the system according to the present invention is characterized in that the at least one valve is at least one three-way valve and/or the at least one valve is switchable by the controller (to change the configuration of the reconfigurable fluid network).
A further preferred embodiment of the system according to the present invention is characterized in that the reconfigurable fluid network comprises a least one pump, preferably at least two pumps, and/or the at least one valve comprises at least two valves at least one valve, preferably at least four valves, more preferably at least eight valves. Preferably, the valves are three-way valves and/or are switchable by the controller (to change the configuration of the reconfigurable fluid network).
A further preferred embodiment of the system according to the present invention is characterized in that the second heat transfer fluid is air, preferably ambient air, or water.
A further preferred embodiment of the system according to the present invention is characterized in that the heat pump unit

comprises an internal refrigerant circuit circulating a third heat transfer fluid, the internal refrigerant circuit comprising the compressor, a first heat pump heat exchanger, the at least one expansion valve, and a second heat pump heat exchanger, wherein the first heat pump heat exchanger and the second heat pump heat exchanger are each connected to pipes of the reconfigurable fluid network which are external to the heat pump unit, or
(is a heat pump subunit and) comprises internal pipes for transferring the first heat transfer medium to the compressor and away from the compressor and for transferring the first heat transfer medium to the at least one expansion valve and away from the at least one expansion valve.

If the heat pump is a heat pump subunit, it comprises only a part of a heat pump (e.g. comprises the compressor and the at least one expansion valve but does not comprise any heat exchanger). If the heat pump unit is a heat pump subunit that does not comprise any heat exchanger, heat exchangers of the system arranged external of the heat pump unit can act as evaporator and condenser of the heat pump, so that a system similar to a split-type air-conditioning system (i.e. a traditional air-to-air air conditioning system) is provided, where the wall mounted heating and air conditioning unit is supplied with refrigerant from an outdoor unit (of the traditional air-to-air air conditioning system) and can act as evaporator during cooling and condenser during heating mode. Such heat exchangers of the system arranged external of the heat pump unit can be, e.g. the heat exchanger for transferring heat between the first heat transfer fluid and a second heat transfer fluid, the at least one emitter, and/or a heat exchanger of the first thermal energy storage device.
If the heat pump unit is a heat pump subunit and/or comprises internal pipes for transferring the first heat transfer medium to the compressor and away from the compressor and for transferring the first heat transfer medium to the at least one expansion valve and away from the at least one expansion valve, it is preferred that the first heat transfer fluid is a refrigerant different from water.
If the heat pump unit comprises an internal refrigerant circuit circulating a third heat transfer fluid, it is preferred that the first heat transfer fluid is water and/or the third heat transfer fluid is a refrigerant different from water.
Preferably, the third heat transfer fluid is a refrigerant different from water.
A further preferred embodiment of the system according to the present invention is characterized in that the system further comprises a further heat exchanger connected to the reconfigurable fluid network, wherein the system is connected to a district heating network, preferably a 5^th generation district heating network, via the further heat exchanger. Preferably, the system according to the present invention can be retrofitted to a 5^th generation district heating network in the future, when it becomes available in the city/area.
A further preferred embodiment of the system according to the present invention is characterized in that the at least one (heat) emitter for heating and cooling the at least one space comprises

fan coil units (FCU), and/or
wall-mounted HVAC (Heating, Ventilation and Air Conditioning) units and/or ceiling cassettes, and/or
underfloor heating.

For systems featuring at least two heating spaces and/or heating-only applications underfloor heating can also be advantageous. Underfloor heating is one of the most efficient heat emitter systems, but it can be uncomfortably cold for the feet to use underfloor heating for space cooling. Thus, if at least two heating spaces are present, at least one space can be fitted with FCU for heating and cooling, while the at least one other space can be fitted with underfloor heating for space heating at high efficiency and low fan noise.
A further preferred embodiment of the system according to the present invention is characterized in that the system is connected to an electricity grid, preferably using a time-of-use (ToU) variable electricity tariff.
A further preferred embodiment of the system according to the present invention is characterized in that the controller which operates the system with either or a combination of the following objectives:

Cost savings by optimal use of solar energy and/or heat pump operation avoiding peak ToU tariff periods and/or heat integration between components.
Maximisation of self-sufficiency by minimising electricity imports from the grid.
Minimisation of CO₂ emissions, which can be achieved through optimal use of solar energy and/or maximisation of heat pump COP during operation and/or heat integration between components.

A further preferred embodiment of the system according to the present invention is characterized in that the system further comprises at least one renewable electric energy source, which is preferably the photovoltaic thermal hybrid solar collector acting as a heat source, but can also comprise a photovoltaic solar collector, and/or a wind energy collector.
A further preferred embodiment of the system according to the present invention is characterized in that the system further comprises at least one electric energy storage system (EES). For example, the EES can be comprised of a home battery and/or an electric vehicle. The EES of the electric vehicle is preferably featuring vehicle-to-grid charging and discharging capabilities. The at least one EES can be charged from the electricity grid and/or panels of the photovoltaic thermal hybrid solar collector. The EES can be linked to a state-of-charge analyser and/or to the controller.
The present invention also relates to a method for operating the system according to the present invention, in which method the controller operates the system at least in at least one mode for charging the first thermal energy storage device, in at least one mode for heating the at least one space, and/or in a mode for cooling the at least one space and charging the first thermal energy storage device.
The preferred embodiments of the system described above also correspondingly apply to the method according to the present invention.
The present invention will be explained in more detail with reference to the following figures and examples without restricting it to the specific embodiments and parameters shown here.

Example 1

Fig. 1 shows a schematic view of a first example (Example 1) of the system according to the present invention. The system comprises a first thermal energy storage device 13 for providing domestic hot water (DHW-TES), fan coil units 14 (FCU) as (heat) emitters for heating and cooling at least one space, a reconfigurable fluid network for transferring a first heat transfer fluid, a heat exchanger 10, a solar heat transfer device, a second thermal energy storage device 12 (LT-TES), and a controller (not shown in Fig. 1). In this example, the first heat transfer fluid is water.
The reconfigurable fluid network comprises a heat pump unit 1, two pumps 8, 9, ten three-way valves, and pipes. The heat pump unit 1 is a water-to-water heat pump unit comprising a (complete) water-to-water heat pump. The heat pump unit 1 comprises an internal refrigerant circuit circulating a third heat transfer fluid, the internal refrigerant circuit comprising a first heat pump heat exchanger 2, two expansion valves 3a, 3b, a refrigerant receiver 4, a second heat pump heat exchanger 5, a four-way valve 6, and a compressor 7, wherein the first heat pump heat exchanger 2 and the second heat pump heat exchanger 5 are each connected to pipes of the reconfigurable fluid network which are external to the heat pump unit 1. The third heat transfer fluid is a refrigerant different from water.
The expansion valves are e.g. linear expansion valves. The compressor is preferably a hermetic scroll or reciprocating type. The first and second heat pump heat exchangers 2, 5 are preferably plate heat exchangers due to their high efficiencies and compactness.
The heat exchanger 10 is a heat exchanger for transferring heat between the first heat transfer fluid and a second heat transfer fluid, the second heat transfer fluid being external to the reconfigurable fluid network, wherein the heat exchanger 10 is external to the heat pump unit 1. In this example, the heat exchanger 10 is an-assisted air-to-water heat exchanger (ATW-HEX) and the second heat transfer fluid is air.
The solar heat transfer 11 device comprises a photovoltaic thermal hybrid solar collector (PVT) in this example.
The first thermal energy storage device 13 preferably comprises a phase change material (PCM) as energy storage means. If PCM is used, the melting temperature should be between 40 to 100 °C, preferably 45 to 65 °C, to supply at domestic hot water of at least 40°C according to EN16147. The first thermal energy storage device 13 is linked to a state-of-charge (SOC) analyser (not shown in Fig. 1) that is configured to determine the state of charge of the first thermal energy storage device (SOC DHW-TES).
The second thermal energy storage device 12 is a low temperature thermal energy storage device that preferably comprises a phase change material (PCM) as energy storage means. If PCM is used, the melting temperature should be between 0 to 50 °C, preferably 15 to 45°C, and preferably below the melting temperature of the PCM of the first thermal energy storage device 13. The second thermal energy storage device 12 is linked to the same or a second state-of-charge (SOC) analyser (not shown in Fig. 1) that is configured to determine the state of charge of the second thermal energy storage device (SOC LT-TES).
The system requires high flowrates ṁ_HTF in the water-based distribution circuit: Evaporation and condensation of the refrigerant occur in heat exchangers 2 and 5. The phase change of the refrigerant in the heat exchanger leads to high heat flow. The refrigerant's latent heat ΔH_r is absorbed by the sensible heat c_p,HTF of the heat transfer fluid (HTF), i.e. water, in the distribution circuit according to: ${\dot{m}}_{r} {ΔH}_{r} = {\dot{m}}_{HTF} c_{p, HTF} (T_{HEX, out} - T_{HEX, in})$
The high flowrate reduces the temperature difference ΔT = (T_HEX,out - T_HEX,in ) between inlet and outlet of components 10, 11, 12, 13, and/or 14, e.g. a 5 kW heat pump system requires a flow rate of at least 15 L/min to maintain ΔT below 5K. Pumps, pipes and/or heat exchangers need to be sized accordingly.
The controller is configured such that it can operate the system in a plurality of modes (operating modes), wherein the reconfigurable fluid network is configurable by the controller in a plurality of configurations. The ten three-way valves are switchable by the controller to change the configuration of the reconfigurable fluid network.
In these operating modes, the first thermal energy storage device 13 can be charged and the second thermal energy storage device 12 can be charged and discharged in the following ways:

The first thermal energy storage device 13 can be charged:
- By the heat pump unit 1 using as heat source either or a combination of:
  - ∘ the solar heat transfer device 11
  - ∘ the heat exchanger 10
  - ∘ the fan coil units 14 during space cooling
- By the solar heat transfer device / photovoltaic thermal hybrid solar collector directly
The second thermal energy storage device 12 can be discharged:
- To preheat mains water
- As a heat source for the heat pump unit 1 to charge for the first thermal energy storage device 13
- As a heat source for the heat pump unit 1 to provide space heating
- By the heat exchanger 10 to the ambient environment. This can be beneficial at night, when the second thermal energy storage device 12 has been used as heat sink for space cooling during the day.
The second thermal energy storage device 12 can be charged:
- By the heat pump unit 1
- By the solar heat transfer device 11
- As a heat sink, while the heat pump unit 1 provides space cooling.

The specific operating modes of the system according to Example 1 are summarized in the following table:

Table 1: Operating modes of the system according to Example 1

Modes	Purpose	Heat source	Heat sink	HPU	Evap	Cond
M1	DHW-TES charging	PVT + ATW-HEX	DHW-TES	On	5	2
M2	DHW-TES charging	PVT + LT-TES	DHW-TES	On	5	2
M3	DHW-TES charging	PVT	DHW-TES	On	5	2
M4	DHW-TES charging	PVT	DHW-TES	Off	-	-
M5	LT-TES charging	PVT + ATW-HEX	LT-TES	On	2	5
M6	LT-TES charging	PVT	LT-TES	Off	-	-
M7a	Space heating	PVT + ATW-HEX	FCU	On	5	2
M7b	Space cooling	FCU	ATW-HEX (+ PVT)	On	2	5
M8a	Space heating	LT-TES	FCU	On	5	2
M8b	Space cooling	FCU	LT-TES	On	2	5
M9	Space heating	LT-TES	FCU	Off	-	-
M10	Space heating	PVT	FCU	Off	-	-
M11	Space heating	LT-TES + PVT	FCU	Off	-	-
M12	DHW-TES charging + Space cooling	FCU	DHW-TES	On	5	2
M13	LT-TES charging	LT-TES	ATW-HEX	Off	-	-

Fig. 2 shows a schematic view of mode M1 of the system according to Example 1. In mode M1, the first thermal energy storage device 13 (DHW-TES) is charged using the fan assisted air-to-water heat exchanger 10 (ATW-HEX) and/or the solar heat transfer device 11, e.g. photovoltaic thermal hybrid solar collector (PVT), as thermal input to the evaporator of the water-to-water heat pump. This mode can be beneficial as default for charging the first thermal energy storage device 13.
Fig. 3 shows a schematic view of mode M2 of the system according to Example 1. In mode M2, the first thermal energy storage device 13 (DHW-TES) is charged using a combination or either of the second thermal energy storage device 12 (LT-TES) and/or solar heat transfer device 11, e.g. photovoltaic thermal hybrid solar collector (PVT), as heat source. The LT-TES 12 and the solar heat transfer device 11 can either be in series or parallel. This mode can be beneficial if enough solar irradiance is present to top-up the temperature supplied by the LT-TES 12.
Fig. 4 shows a schematic view of mode M3 of the system according to Example 1. In mode M3, the first thermal energy storage device 13 (DHW-TES) is charged using the solar heat transfer device 11, e.g. photovoltaic thermal hybrid solar collector (PVT), as sole heat source to the evaporator, i.e. the second heat pump heat exchanger 5. This mode can be beneficial, when it is more efficient to operate the solar heat transfer device 11 at a low temperature and/or excess photovoltaic electricity is available and/or the ToU tariff is favorable at a given time.
Fig. 5 shows a schematic view of mode M4 of the system according to Example 1. In mode M4, the first thermal energy storage device 13 (DHW-TES) is directly charged from the solar heat transfer device 11, e.g. photovoltaic thermal hybrid solar collector (PVT), without using the heat pump. This mode can be beneficial on days with high solar irradiance and/or electricity demand from other devices than the heat pump and/or simultaneous charging of an EES using photovoltaics.
Fig. 6 shows a schematic view of mode M5 of the system according to Example 1. In mode M5, the second thermal energy storage device 12 (LT-TES) is charged using the water-to-water heat pump and either or a combination of the heat exchanger 10 (ATW-HEX) and/or the solar heat transfer device 11, e.g. photovoltaic thermal hybrid solar collector (PVT), as heat source. This mode can be beneficial, when the state of charge of the LT-TES 12 drops below a threshold and/or in winter when the LT-TES 12 can act as a heat source for space heating. Here, the LT-TES 12 can be charged during the day, when ambient temperatures are high, and discharged for space heating at night.
Fig. 7 shows a schematic view of mode M6 of the system according to Example 1. In mode M6, the second thermal energy storage device 12 (LT-TES) is charged directly from the solar heat transfer device 11, e.g. photovoltaic thermal hybrid solar collector (PVT), without using the heat pump unit 1. This mode can be beneficial on days with high solar irradiance, and/or electricity demand from other devices than the heat pump unit, and/or simultaneous charging of an EES using photovoltaics, and/or on sunny days in the intermediate seasons, when solar irradiance is high during the day, but space heating is required at night.
Fig. 8 shows a schematic view of modes M7a and M7b of the system according to Example 1. In mode M7a, space heating of the at least one space is provided via the fan coil units 14 (FCU) using the heat pump unit 1 and either or a combination of the heat exchanger 10 (ATW-HEX) and/or the solar heat transfer device 11, e.g. photovoltaic thermal hybrid solar collector (PVT), as heat source. In mode M7b, space cooling of the at least one space can be provided via the FCUs 14 by reversing the entire cycle. Here it can be beneficial to only use the ATW-HEX 10 as heat sink as the solar thermal collector of the solar heat transfer device 11 may increase the condenser temperature in the second heat pump heat exchanger 5, which would decrease the heat pump COP. This mode can be beneficial as default mode for space heating.
Fig. 9 shows a schematic view of modes M8a and M8b of the system according to Example 1. In mode M8a, space heating of the at least one space is provided via the fan coil units 14 (FCU) by discharging the second thermal energy storage device 12 (LT-TES). In mode 8b, space cooling of the at least one space is provided via the FCUs 14 by charging the LT-TES 12. In both cases, the heat pump unit 1 is used. If the PCM melting temperature of the LT-TES 12 is sufficiently high, mode M9 is preferable over mode M8a for space heating. This mode can be beneficial in the intermediate seasons or in climatic zones with hot days and cold nights, e.g. space cooling and charging the LT-TES 12 during the day. Space heating and discharging the LT-TES 12 at night.
Fig. 10 shows a schematic view of mode M9 of the system according to Example 1. In mode M9, space heating of the at least one space is provided via the fan coil units 14 (FCU) directly from the second thermal energy storage device 12 (LT-TES) bypassing the heat pump unit 1. This mode can be beneficial, when SOC of the LT-TES 12 is above a threshold and/or the LT-TES 12 has previously been charged from the solar heat transfer device 11, e.g. photovoltaic thermal hybrid solar collector (PVT), which avoids heat pump electricity consumption. Here, it is advantageous when the PCM melting temperature of LT-TES 12 is sufficiently high for efficient FCU operation. In systems, which do not require space cooling or feature two heating zone, underfloor heating can also be beneficial here. For space cooling applications, the PCM melting temperature of the LT-TES 12 is selected below ambient temperature, preferably in the range between 0 - 20 °C.
Fig. 11 shows a schematic view of mode M10 of the system according to Example 1. In mode M10, space heating of the at least one space is provided space heating of the at least one space is provided via the fan coil units 14 (FCU) directly from the solar heat transfer device 11, e.g. photovoltaic thermal hybrid solar collector (PVT), bypassing the heat pump unit 1. This mode can be beneficial on sunny, cold days to provide space heating and conserve electricity.
Fig. 12 shows a schematic view of mode M11 of the system according to Example 1. In mode M11, space heating of the at least one space is provided via the fan coil units 14 (FCU) directly from the solar heat transfer device 11, e.g. photovoltaic thermal hybrid solar collector (PVT), and the second thermal energy storage device 12 (LT-TES) bypassing the heat pump unit 1. A parallel configuration of solar heat transfer device 11 and LT-TES 12 as shown in mode M2 is also possible here. The parallel configuration may be beneficial to reduce pressure drop in the system, while this mode can be beneficial on sunny, cold days to provide space heating and conserve electricity. The LT-TES 12 can be used to compensate for insufficient solar irradiance intensity to meet the space heating demand. This could be the case in the early morning after sunrise and/or evening before sunset and/or during the day in winter.
Fig. 13 shows a schematic view of mode M12 of the system according to Example 1. In mode M12, space cooling of the at least one space is provided via the fan coil units 14 (FCU) by charging the first thermal energy storage device 13 (DHW-TES) using the heat pump unit 1. This mode can be beneficial as it approximately doubles the heat pump efficiency by rejecting heat from space cooling into the DHW-TES instead of rejecting this heat into the ambient. The heat pump performs two beneficial tasks simultaneously. This reduces energy consumption, cost, and time.
Fig. 14 shows a schematic view of mode M13 of the system according to Example 1. In mode M13, the second thermal energy storage device 12 (LT-TES) is discharged to the ambient by the heat exchanger 10 (ATW-HEX) without using the heat pump unit 1. This mode can be beneficial in climates with hot days and mild nights, where space cooling is required during the day. When the ambient air temperature is higher than the PCM melting temperature of the LT-TES 12, the heat pump unit 1 provides space cooling and uses the LT-TES 12 as a heat sink (see M8), which charges the LT-TES 12. If the heat from the LT-TES 12 is not needed elsewhere in the system, e.g. for charging the first thermal energy storage device 13 (DHW-TES), the LT-TES 12 can be discharged in M13 at night. This enables space cooling in mode M8 during the day.
Fig. 15 shows a schematic view of an exemplary simple control strategy to apply the control modes M1 to M13. In the schematic view shown in Fig. 15, "Y" means "Yes" and "N" means "No". In the simplest embodiment, the control strategy comprises a single SOC-threshold applied to both the first thermal energy storage device 13 (DHW-TES) and the second thermal energy storage device 12 (LT-TES), which could be in the range 20 - 80 %, but is preferably 40 - 60 %. An alternative strategy may include a different SOC-threshold for each occurrence in the diagram. The thresholds can be constants or variable. The control strategy shown here assumes a PCM melting temperature, e.g. 40 ± 5 °C, of the LT-TES 12 suitable for direct space heating from the LT-TES 12 (mode M9) and therefore it does not use mode M8a (space heating from LT-TES 12 using the heat pump unit 1).
The aim of the control strategy shown in the decision tree in Fig. 15 is the use of the solar heat transfer device 11, e.g. photovoltaic thermal hybrid solar collector (PVT), as much as possible as sole heat source to charge the thermal energy storage devices and/or provide space heating. The heat pump supplements the solar heat transfer device 11, whenever needed. The decision tree only outlines the thermal management to meet thermal comfort. However, a EES may be connected to the system. The control strategy for the at least one EES connected to the system could be the following, running simultaneously with the decision tree shown here, with the aim to reduce cost, maximise self-sufficiency, and/or minimise CO₂ emissions:

Charging EES with all available excess electricity from any available renewable energy source, e.g. solar PVT, solar PV, wind.
Discharging for use of any electric appliance including the heat pump, whenever the EES-SOC > EES-SOC-threshold, which can be constant and/or variable

The following Table 2 shows properties, thresholds, and setpoints used in the exemplary control strategy shown in Fig. 15.

Table 2: Properties, thresholds, and setpoints used in the exemplary control strategy shown in Fig. 15. Some thresholds are described as multiples of the heat pump thermal output. Properties of range "n/a" are measured values, which are used as input and basis for control decisions.

Property	Description	Range	Preferable
Is sunny?	Minimum Q-PVT to provide any useful heat to the system	0 - 0.5 x Q-HP	0.1 x Q-HP
Q-HP	Nominal thermal heat pump output	1 - 20 kW	5 -8 kW
Q-min	Minimum value for Q-PVT to provide heat without switching on the heat pump unit	0.1 - 1 x Q-HP	0.5 x Q-HP
Q-PVT	Current heat flow from PVT	n/a	n/a
SOC-threshold	Threshold of TES	20 - 80 %	40 - 60 %
T-amb	Ambient temperature	n/a	n/a
T-LT-PCM-melt	Melting point of PCM used in LT-TES	0 - 50 °C	35-45 °C here
T-PCM-melt	Melting point of PCM used in DHW-TES	40 - 100 °C	45 - 65 °C
T-PVT	Temperature at outlet of PVT	n/a	n/a
T-room	Current room temperature	n/a	n/a
T-setpoint	Thermostat setpoint by user	10-40 °C	17-25 °C

Example 2

Fig. 16 shows a schematic view of a second example (Example 2) of the system according to the present invention. A part of the system is present in form of a compact indoor unit. The components can be set in many different arrangements to form the overall system. In this advantageous example, the system comprises a first thermal energy storage (DHW-TES) for providing domestic hot water and a second thermal energy storage device (LT-TES) that are placed next to each other. The DHW-TES, the LT-TES, and the reconfigurable fluid network (and thus also the heat pump unit) are comprised in the compact indoor unit.

Example 3

Fig. 17 shows a schematic view of a third example (Example 3) of the system according to the present invention. A part of the system is present in form of a tall indoor unit with larger thermal energy storage capacities. In this beneficial example, the system comprises a first thermal energy storage device (DHW-TES) for providing domestic hot water and a second thermal energy storage device (LT-TES), wherein the components are arranged such that the heat pump unit is located at the bottom of the indoor unit together with the distribution circuit and that the DHW-TES and the LT-TES are stacked at the top of the indoor unit. This configuration may improve the systems footprint in terms of floor area that is occupied by the system.

Example 4

Fig. 18 shows a schematic view of a fourth example (Example 4) of the system according to the present invention that is very similar to the system according to Example 1. In contrast to the system according to Example 1, the system according to Example 4 comprises a further heat exchanger 15 connected to the reconfigurable fluid network instead of a second thermal energy storage device, wherein the system is connected to a 5^th generation district heating network 16 via the further heat exchanger 15. The 5^th generation district heating network 16 can be used as a heat source in the winter and a heat sink in the summer. In this case, the heat exchanger 10 and the solar heat transfer device 11, e.g. photovoltaic thermal hybrid solar collector, are optional, e.g. in residential apartments.

Example 5

Fig. 19 shows a schematic view of a fifth example (Example 5) of the system according to the present invention that is also similar to the system according to Example 1. In contrast to the system according to Example 1, the second thermal energy storage device 12 of the system according to Example 5 can also be used to preheat mains water from cold inlet to an intermediate temperature before heating it further in the first thermal energy storage device 13. This configuration can be beneficial as it improves heat pump efficiency and increases the DHW discharge volume. The size of the first thermal energy storage device 13 can be reduced to allow the same domestic hot water discharge volume that would have been achieved without preheating.

Example 6

Fig. 20 shows a schematic view of a sixth example (Example 6) of the system according to the present invention that is very similar to the system according to Example 5. In contrast to the system according to Example 5, an additional three-way valve 17 is connected to the supply branch of the distribution circuit to connect a further heat exchanger 15, which is preferably a plate heat exchanger. The further heat exchanger 15 can be used to interface the system to an additional heat source like a 5th generation district heating network 16. This embodiment can be adapted in residential apartment buildings. In this embodiment, the integration of the heat exchanger 10 and/or the solar heat transfer device 11, e.g. photovoltaic thermal hybrid solar collector, are optional, but advantageous for energy savings. In case, the heat exchanger 10 and/or the solar thermal heat transfer device 11, e.g. photovoltaic thermal hybrid solar collector, are omitted from the installation, the further heat exchanger 15 can be installed in either of their place and the simpler system with the additional three-way valve 17 can be selected for the installation.

Example 7

Fig. 21 shows a schematic view of a seventh example (Example 7) of the system according to the present invention that is very similar to the system according to Example 1. In contrast to the system according to Example 1, the heat pump unit 1 of the system according to Example 7 does not comprise a complete heat pump but is a heat pump subunit comprising only a part of a heat pump. In detail, the heat pump unit 1 in the system of Example 7 does not comprise the first and second heat pump heat exchanger 2 and 5 that separate the refrigerant and water circuits in the system of Example 1. Instead the entire system is using refrigerant as (first) heat transfer fluid. The heat pump unit 1 of Example 7 comprises internal pipes for transferring the first heat transfer medium to the compressor 7 and away from the compressor 7 and for transferring the first heat transfer medium to the expansion valves 3a, 3b and away from the expansion valves 3a, 3b. Since the system of Example 7 does not feature heat pump heat exchangers, heat exchangers of the system (components) arranged external of the heat pump unit can act as evaporator and condenser of the heat pump, so that a system similar to a split-type air-conditioning system (i.e. a traditional air-to-air air conditioning system) is provided, in which the wall mounted heating and air conditioning unit is supplied with refrigerant from an outdoor unit (of the traditional air-to-air air conditioning system) and can act as evaporator during cooling and condenser during heating mode. Such heat exchangers of the system arranged external of the heat pump unit can be, e.g. components 10, 11, 12, 13, and/or 14 or heat exchangers comprised in these components.
This specific arrangement is beneficial for the following reasons:

Firstly, removing the two heat pump heat exchangers improves heat transfer, which would otherwise be reduced by the heat exchanger effectiveness.
Secondly, the refrigerant's latent heat of evaporation is utilised in the evaporation and condensation steps inside the components 10, 11, 12, 13, and 14. In the water circuit case, sensible heat transfer occurs in components 10, 11, 12, 13, and 14 while phase change for evaporation and/or condensation takes place in the heat pump heat exchangers 2 and 5.
Thirdly, the system may not require the pumps 8, 9 of the system according to Example 1. Therefore, the system can operate more efficiently at lower flow rates in the components.
Wall-mounted HVAC (Heating, Ventilation and Air Conditioning) units and/or ceiling cassettes 18 can be used for efficient heating and cooling. Compared to FCU, Wall-mounted HVAC (Heating, Ventilation and Air Conditioning) units and/or ceiling cassettes 18 transfer heat directly from or to the refrigerant requiring one less heat transfer step by omitting transfer of heat from refrigerant to water first.

The system according to Example 7 would require larger quantities of refrigerant that are needed to supply the additional pipes and components with heat transfer fluid. Here, the selection of a non-flammable and/or nontoxic refrigerant with low global-warming-potential can be particularly beneficial.

Reference signs

1: Heat pump unit
2: First heat pump heat exchanger
3a, 3b: Expansion valve
4: Refrigerant receiver
5: Second heat pump heat exchanger
6: Four-way valve
7: Compressor
8,9: Pump
10: Heat exchanger
11: Solar heat transfer device, e.g. photovoltaic thermal hybrid solar collector
12: Second thermal energy storage device
13: First thermal energy storage device
14: Fan coil units
15: Further heat exchanger
16: 5^th Generation district heating network
17: Additional three-way valve
18: Wall-mounted HVAC units and/or ceiling cassettes

Claims

System for heating and cooling at least one space and for providing domestic hot water, comprising
a first thermal energy storage device (13) for providing domestic hot water,

at least one emitter (14, 18) for heating and cooling the at least one space, the at least one emitter being provided within the at least one space,

a reconfigurable fluid network for transferring a first heat transfer fluid, the reconfigurable fluid network comprising a heat pump unit (1), at least one valve, and pipes, the heat pump unit (1) comprising a compressor (7) and at least one expansion valve (3a, 3b), wherein the reconfigurable fluid network is configurable by a controller in a plurality of configurations comprising at least one first configuration in which the reconfigurable fluid network is configured to transfer the first heat transfer fluid from the heat pump unit (1) to the first thermal energy storage device (13) and not to the at least one emitter (14, 18), at least one second configuration in which the reconfigurable fluid network is configured to transfer the first heat transfer fluid from the heat pump unit (1) to the at least one emitter (14, 18) and not to the first thermal energy storage device (13), and a third configuration in which the reconfigurable fluid network is configured to transfer the first heat transfer fluid from the heat pump unit (1) to the at least one emitter (14, 18) and from the heat pump unit (1) to the first thermal energy storage device (13),

a heat exchanger (10) for transferring heat between the first heat transfer fluid and a second heat transfer fluid, the second heat transfer fluid being external to the reconfigurable fluid network, wherein the heat exchanger (10) is external to the heat pump unit (1), and

the controller, wherein the controller is configured such that it can operate the system in a plurality of modes comprising at least one mode (M1, M2, M3) for charging the first thermal energy storage device, in which the reconfigurable fluid network is configured in the first configuration, at least one mode (M7a, M8a) for heating the at least one space, in which the reconfigurable fluid network is configured in the second configuration, and a mode (M12) for cooling the at least one space and charging the first thermal energy storage device, in which the reconfigurable fluid network is configured in the third configuration.
System according to claim 1, characterized in that the heat pump unit (1) is a water source heat pump unit.
System according to any one of the preceding claims, characterized in that the first heat transfer fluid comprises or consists of water or a refrigerant different from water.
System according to any one of the preceding claims, characterized in that the heat pump unit (1) is a reversible heat pump unit.
System according to any one of the preceding claims, characterized in that the system further comprises a solar heat transfer device, wherein the solar heat transfer device is connected to the reconfigurable fluid network, and wherein preferably the solar heat transfer device comprises at least one solar thermal collector and/or at least one photovoltaic thermal hybrid solar collector (11).
System according to any one of the preceding claims, characterized in that the first thermal energy storage device (13) comprises a phase change material, wherein preferably the melting temperature of the phase change material of the first thermal energy storage device (13) is a temperature in the range from 40 to 100 °C, more preferably from 45 to 65 °C.
System according to any one of the preceding claims, characterized in that the system further comprises a state of charge analyser for determining the state of charge of the first thermal energy storage device (13), wherein preferably the controller is configured to operate the system in consideration of the state of charge of the first thermal energy storage device (13) determined by the state of charge analyser for determining the state of charge of the first thermal energy storage device (13).
System according to any one of the preceding claims, characterized in that the system further comprises a second thermal energy storage device (12), wherein the second thermal energy storage device (12) is connected to the reconfigurable fluid network, and wherein preferably the second thermal energy storage device (12) comprises a phase change material, wherein more preferably the melting temperature of the phase change material of the second thermal energy storage (12) device is
- a temperature in the range from 0 to 50 °C, even more preferably from 15 to 45 °C, and/or

- lower than the melting temperature of a phase change material of the first thermal energy storage device (13).
System according to claim 8, characterized in that the system further comprises a state of charge analyser for determining the state of charge of the second thermal energy storage device (12), wherein preferably the controller is configured to operate the system in consideration of the state of charge of the second thermal energy storage device (12) determined by the state of charge analyser for determining the state of charge of the second thermal energy storage device (12).
System according to claim 8 or 9, characterized in that the second thermal energy storage device (12) is connected to the first thermal energy storage device (13) via at least one pipe for transferring water preheated by the second thermal energy storage device (12) to the first thermal energy storage device (13) in which the water is further heated to obtain domestic hot water.
System according to any one of the preceding claims, characterized in that the reconfigurable fluid network comprises a least one pump (8, 9), preferably at least two pumps (8, 9), and/or the at least one valve comprises at least two valves, preferably at least four valves, more preferably at least eight valves.
System according to any one of the preceding claims, characterized in that the second heat transfer fluid is air, preferably ambient air, or water.
System according to any one of the preceding claims, characterized in that the heat pump unit (1)
- comprises an internal refrigerant circuit circulating a third heat transfer fluid, the internal refrigerant circuit comprising the compressor (7), a first heat pump heat exchanger (2), the at least one expansion valve (3a, 3b), and a second heat pump heat exchanger (5), wherein the first heat pump heat exchanger (2) and the second heat pump heat exchanger (5) are each connected to pipes of the reconfigurable fluid network which are external to the heat pump unit (1), or

- comprises internal pipes for transferring the first heat transfer medium to the compressor (7) and away from the compressor (7) and for transferring the first heat transfer medium to the at least one expansion valve (3a, 3b) and away from the at least one expansion valve (3a, 3b).
System according to any one of the preceding claims, characterized in that the system further comprises a further heat exchanger (15) connected to the reconfigurable fluid network, wherein the system is connected to a district heating network, preferably a 5^th generation district heating network (16), via the further heat exchanger (15).
Method for operating a system according to any one of the preceding claims, in which the controller operates the system at least in at least one mode (M1, M2, M3) for charging the first thermal energy storage device (13), in at least one mode (M7a, M8a) for heating the at least one space, and/or in a mode (M12) for cooling the at least one space and charging the first thermal energy storage device (13).