TECHNICAL FIELD

5 The present disclosure relates generally to the field of heat pumps. More particularly, it relates to a heat pump with different operating modes as defined in the introductory parts of the independent claims.

BACKGROUND

Nearly all large, developed cities in the world have at least two types of energy grids incorporated in their infrastructures; one grid for providing electrical energy and one grid for providing space heating and hot tap water preparation. Today a common grid used for providing space heating and hot tap water preparation is a gas grid providing a burnable gas, typically a fossil5 fuel gas. The gas provided by the gas grid is locally burned for providing space heating and hot tap water. In order to reduce the carbon dioxide emissions there are plans to replace such gas grid with more “green” energy efficient energy systems.

One such energy efficient energy system is cold thermal grids. Cold0 thermal grids are described in e.g., WO 2017/076866 A1 , and WO 2017/076868 A1 . Cold thermal grids are an evolution of district heating and district cooling systems, where combined district heating and district cooling system with the aid of heat pumps for heating and cooling can provide cooling, heating and tap water preparation to buildings. A cold thermal grid comprising a hot conduit and a cold conduit, may be bidirectional, i.e. , the highest pressure at a particular time instance may be either in the hot conduit or in the cold conduit depending on the heating and/or cooling consumed by the buildings connected to the grid.

Fluid heat pumps are typically designed under the assumption that the0 brine (“cool bearer; hot conduit) has a rather fixed temperature (from 0 to 10 degrees Celsius), which is lower than the desired temperature delivered from the heat pump (from 20 to 30 degrees Celsius for underfloor heating and up to from 60 to 80 degrees Celsius for tap water and radiators in old buildings with little isolation). However, in cold thermal networks the hot conduit may vary from 5 to 40 degrees Celsius, while the cold conduit may vary from 0 to 35 degrees Celsius, depending on the current consumption of heating and/or cooling from the buildings connected to the cold thermal grid.

Inverted heat pumps can be utilized for such cold thermal grids. An inverted heat pump is described in WO 2019/219670 A1 . However, inverted heat pumps are not optimized in terms of size, technical complexity, and electrical energy efficiency. Therefore, there may be a need for a heat pump (arrangement) being smaller, less complex and/or more energy efficient.

SUMMARY

It is an object of some embodiments to solve, mitigate, alleviate, or eliminate at least some of the above or other problems or disadvantages.

According to a first aspect, this is achieved by a method for a heat pump, comprising: measuring a first temperature at a first external inlet of the heat pump; measuring a second temperature at a second external outlet of the heat pump; setting an operating mode of the heat pump based on the first temperature and the second temperature to one of: heat exchange mode, in which the heat pump operates as a heat exchanger; heat pump mode, in which the heat pump operates as a heat pump generating heat; and optionally cooling mode, in which the heat pump operates as a heat pump generating coolness. By selecting the mode based on the measured temperatures, electrical energy efficiency may be increased/improved.

As used herein the term “heat pump” relates to an apparatus which includes a device comprising a heat pump loop in which a working fluid, also termed refrigerant, is configured to circulate through a first heat exchanger, a compressor, a second heat exchanger and optionally through a valve for transferring heat from one of the first and second heat exchangers to the other one of the first and second heat exchangers. The phrasing “includes a heat pump” implies that the term “heat pump”, when used herein, may comprise also further features not necessarily forming a part of the device described above, such as further heat exchangers, piping, control circuitry, valve systems or the like. The term “heat pump” may also be referred to herein as “heat pump system”.

In some embodiments, the operating mode of the heat pump is set to heat exchange mode if the first temperature is between the second temperature minus a first constant and the second temperature plus a second constant, wherein the operating mode of the heat pump is set to heat pump mode if the first temperature is equal to the second temperature minus the first constant or lower, and/or wherein the operating mode of the heat pump is set to cooling mode if the first temperature is equal to the second temperature plus the second constant or higher. By selecting the mode based on different intervals of the difference of the measured temperatures, electrical energy efficiency may be further increased/improved.

According to a second aspect, there is provided a computer program product comprising a non-transitory computer readable medium, having stored thereon a computer program comprising program instructions, the computer program being loadable into a data processing unit and configured to cause execution of the method of the first aspect or any of the herein mentioned embodiments when the computer program is run by the data processing unit.

According to a third aspect, there is provided a heat pump. The heat pump comprises a first external inlet, a first external outlet, a second external inlet, a second external outlet, and controlling circuitry configured to cause: measurement of a first temperature at the first external inlet; measurement of a second temperature at the second external outlet; setting of an operating mode of the heat pump based on the first temperature and the second temperature to one of: heat exchange mode, in which the heat pump operates as a heat exchanger, heat pump mode, in which the heat pump operates as a heat pump generating heat, and optionally cooling mode, in which the heat pump operates as a heat pump generating coolness. By selecting the mode based on the measured temperatures, electrical energy efficiency may be increased/improved.

In some embodiments, the control circuitry comprises a control unit, the heat pump further comprising: a reversible heat pump arrangement comprising a first and a second heat exchanger and a compressor; a third heat exchanger comprising a first inlet, a first outlet, a second inlet and a second outlet; a first valve arrangement comprising a valve inlet, a first valve outlet and a second valve outlet; and the control unit is configured to set the heat pump to one of heat exchange mode, heat pump mode and optionally cooling mode by controlling the reversible heat pump arrangement and/or the first valve arrangement.

In some embodiments, the valve inlet is connected to the first external inlet, such as via the first heat exchanger; the first valve outlet is connected to the second inlet of the third heat exchanger; the second valve outlet is connected to the first external outlet; the first inlet of the third heat exchanger is connected to the second external inlet; the first outlet of the third heat exchanger is connected to the second external outlet, such as via the second heat exchanger; the second outlet of the third heat exchanger is connected to the first external outlet; and the control unit is configured to control a flow through the first valve arrangement to exit through the first valve outlet and to turn the compressor off when setting the operating mode of the heat pump to heat exchange mode and configured to control a flow through the first valve arrangement to exit through the second valve outlet and to turn the compressor on when setting the operating mode of the heat pump to heat pump mode or cooling mode.

In some embodiments, the reversible heat pump arrangement further comprises: a working fluid configured to circulate through the first heat exchanger, the compressor, the second heat exchanger and optionally through a valve; a second valve arrangement comprising: a first four-way valve, and the compressor; and the first heat exchanger comprises: a first inlet connected to the first external inlet, a first outlet connected to the inlet of the first valve arrangement, a second inlet, and a second outlet connected to the first four-way valve; and the second heat exchanger comprises: a first inlet connected to the first outlet of the third heat exchanger; a first outlet connected to the second external outlet; a second inlet connected to the second inlet of the first heat exchanger, such as via a valve; and a second outlet connected to the first four-way valve; and the control unit is configured to control the flow of the working fluid to go from the second outlet of the first heat exchanger to the second outlet of the second heat exchanger and return from the second inlet of the second heat exchanger to the second inlet of the first heat exchanger when setting the operating mode of the heat pump to heat pump mode by controlling the first four-way valve and configured to control the flow of the working fluid to go from the second outlet of the second heat exchanger to the second outlet of the first heat exchanger and return from the second inlet of the first heat exchanger to the second inlet of the second heat exchanger when setting the operating mode of the heat pump to cooling mode, by controlling the first four-way valve.

In some embodiments, the heat pump further comprises a second and a third four-way valve, each of the second and third four-way valves comprising first, second, third and fourth access points, the first, second, third and fourth access points of the second four-way valve being connected to the first external inlet, the first inlet of the first heat exchanger, the first outlet of the first heat exchanger, and the valve inlet, the first, second, third and fourth access points of the third four-way valve being connected to the second external outlet, the first inlet of the second heat exchanger, the first outlet of the second heat exchanger, and the first outlet of the third heat exchanger and the control unit is configured to control the flow of a first added fluid inside the first heat exchanger to go from the first inlet to the first outlet and control the flow of the first added fluid inside the second heat exchanger to go from the first inlet to the first outlet when in heat pump mode and configured to control the flow of the first added fluid inside the first heat exchanger to go from the first outlet to the first inlet and control the flow of the first added fluid inside the second heat exchanger to go from the first outlet to the first inlet when in cooling mode.

In some embodiments, the first external inlet is connectable to a hot conduit of a cold thermal grid system and the first external outlet is connectable to a cold conduit of the cold thermal grid system.

In some embodiments, the heat pump further comprises first and second valve arrangements and the control unit is further configured to control the first and second valve arrangements, the first valve arrangement being connectable to a hot conduit and the second valve arrangement being connectable to a cold conduit, and the control of each of the first and second valve arrangements is based on the operating mode of the heat pump.

The disclosed inventive concept may be expressed in an alternative way which will now be described with reference to the fourth, fifth, and sixth aspects, respectively.

According to a fourth aspect, there is provided a heat pump system comprising a first external inlet for receiving a first added fluid, a first external outlet for outputting the first added fluid, a second external inlet for receiving a second added fluid, and a second external outlet for outputting the second added fluid, wherein the heat pump system further comprises: a reversible heat pump arrangement comprising a first heat exchanger, a second heat exchanger, and a compressor and optionally a valve which are connected to each other to form a heat pump loop in which a working fluid is configured to circulate for moving heat between the first and second heat exchangers; a third heat exchanger comprising a first inlet fluidly connecting to a first outlet, and a second inlet fluidly connecting to a second outlet; a first valve arrangement comprising a valve inlet, a first valve outlet and a second valve outlet, wherein the first valve outlet is connected to the second inlet of the third heat exchanger and the second valve outlet is directly connected to the first external outlet thereby bypassing the third heat exchanger; and controlling circuitry configured to: cause measurement of a first temperature of the first added fluid at the first external inlet; cause measurement of a second temperature of the second added fluid at the second external outlet; and control the reversible heat pump arrangement and/or the first valve arrangement so as to set, based on the first temperature and the second temperature, an operating mode of the heat pump system to one of:

(a) a heat exchange mode, in which a flow through the first valve arrangement exits through the first valve outlet to allow the first added fluid to pass through the third heat exchanger and in which the compressor is turned off so as to allow the heat pump system to operate as a heat exchanger by exchanging heat between the first and second added fluid in the third heat exchanger,

(b) a heat pump mode, in which the valve inlet is connected to the first external inlet via the first heat exchanger, in which the first outlet of the third heat exchanger is connected to the second external outlet via the second heat exchanger, in which a flow through the first valve arrangement exits through the second valve outlet to allow the first added fluid to bypass the third heat exchanger, and in which the compressor is turned on, so as to allow the heat pump system to operate as a heat pump generating heat by transferring heat from the first heat exchanger to the second heat exchanger by means of the heat pump loop so as to allow heating the second added fluid which passes through the heat pump system, and

(c) optionally a cooling mode, in which the valve inlet is connected to the first external inlet via the first heat exchanger, in which the first outlet of the third heat exchanger is connected to the second external outlet via the second heat exchanger, in which a flow through the first valve arrangement exits through the second valve outlet to allow the first added fluid to bypass the third heat exchanger, and in which the compressor is turned on, so as to allow the heat pump system to operate as a heat pump generating coolness by transferring heat from the second heat exchanger to the first heat exchanger by means of the heat pump loop so as to allow cooling the second added fluid which passes through the heat pump system.

In some embodiments of the heat pump system according to the fourth aspect, the reversible heat pump arrangement further comprises: a second valve arrangement comprising: a first four-way valve, and the compressor; and wherein the first heat exchanger comprises: a first inlet connected to the first external inlet, a first outlet connected to the inlet of the first valve arrangement, a second inlet and a second outlet connected to the first four-way valve; and wherein the second heat exchanger comprises: a first inlet connected to the first outlet of the third heat exchanger; a first outlet connected to the second external outlet; a second inlet connected to the second inlet of the first heat exchanger, such as via a valve; and a second outlet connected to the first four-way valve; and wherein the control unit is configured to control the flow of the working fluid to go from the second outlet of the first heat exchanger to the second outlet of the second heat exchanger and return from the second inlet of the second heat exchanger to the second inlet of the first heat exchanger when setting the operating mode of the heat pump to heat pump mode by controlling the first four-way valve and configured to control the flow of the working fluid to go from the second outlet of the second heat exchanger to the second outlet of the first heat exchanger and return from the second inlet of the first heat exchanger to the second inlet of the second heat exchanger when setting the operating mode of the heat pump to cooling mode, by controlling the first four-way valve.

In some embodiments of the heat pump system according to the fourth aspect, the heat pump system further comprises a second and a third fourway valve, each of the second and third four-way valves comprising first, second, third and fourth access points, the first, second, third and fourth access points of the second four-way valve being connected to the first external inlet, the first inlet of the first heat exchanger, the first outlet of the first heat exchanger, and the valve inlet, the first, second, third and fourth access points of the third four-way valve being connected to the second external outlet, the first inlet of the second heat exchanger, the first outlet of the second heat exchanger, and the first outlet of the third heat exchanger and wherein the control unit is configured to control the flow of a first added fluid inside the first heat exchanger to go from the first inlet to the first outlet and control the flow of the first added fluid inside the second heat exchanger to go from the first inlet to the first outlet when in heat pump mode and configured to control the flow of the first added fluid inside the first heat exchanger to go from the first outlet to the first inlet and control the flow of the first added fluid inside the second heat exchanger to go from the first outlet to the first inlet when in cooling mode.

In some embodiments of the heat pump system according to the fourth aspect, the first external inlet is connectable to a hot conduit of a cold thermal grid system and the first external outlet is connectable to a cold conduit of the cold thermal grid system.

In some embodiments of the heat pump system according to the fourth aspect, the heat pump system further comprises first and second valve arrangements and wherein the control unit is further configured to control the first and second valve arrangements, the first valve arrangement being connectable to a hot conduit and the second valve arrangement being connectable to a cold conduit, and wherein the control of each of the first and second valve arrangements is based on the operating mode of the heat pump.

According to a fifth aspect there is provided a method for a heat pump system according the fourth aspect, said method comprising: measuring a first temperature of a first added fluid at a first external inlet of the heat pump system; measuring a second temperature of a second added fluid at a second external outlet of the heat pump system; setting, based on the first temperature and the second temperature, an operational mode of the heat pump system to one of:

(a) the heat exchange mode in which the heat pump operates as a heat exchanger;

(b) the heat pump mode in which the heat pump operates as a heat pump generating heat; and

(c) optionally, the cooling mode in which the heat pump operates as a heat pump generating coolness.

In some embodiments of the method according to the fifth aspect, the step of setting the heat pump system to an operational mode of the heat pump system comprises: setting the heat pump system to the heat exchange mode in response to the first temperature being between the second temperature minus a first constant and the second temperature plus a second constant; setting the heat pump system to the heat pump mode in response to the first temperature being equal to the second temperature minus the first constant or lower; and optionally, setting the heat pump system to the cooling mode in response to the first temperature being equal to the second temperature plus the second constant or higher.

According to a sixth aspect there is provided a computer program product comprising a non-transitory computer readable medium, having stored thereon a computer program comprising program instructions, the computer program being loadable into a data processing unit and configured to cause execution of the method according to the fifth aspect when the computer program is run by the data processing unit.

The disclosed inventive concept may be expressed in yet another alternative way which will now be described with reference to the seventh, eighth, and ninth aspects, respectively.

According to a seventh aspect there is provided a heat pump system for transferring heat between a first and a second added fluid caused to separately pass therethrough, said heat pump system comprising: a reversible heat pump arrangement comprising a first heat exchanger, a second heat exchanger, and a compressor and optionally a valve which are connected to each other to form a heat pump loop in which a working fluid is configured to circulate for moving heat between the first and second heat exchangers; a third heat exchanger, and controlling circuitry configured to: cause measurement of a first temperature of the first added fluid at a position where the first added fluid is input to the heat pump system; cause measurement of a second temperature of the second added fluid at a position where the second added fluid is being output from the heat pump system; and control the heat pump system so as to set, based on the first temperature and the second temperature, an operating mode of the heat pump system being one of:

(a) a heat exchange mode in which the compressor is turned off and in which the first added fluid and the second added fluid are caused to, separated from each other, pass through the third heat exchanger so as to allow heat exchange between the first and the second added fluids by means of the third heat exchanger;

(b) a heat pump mode in which the compressor is turned on, in which the first added fluid is caused to pass through the first heat exchanger but not through the third heat exchanger, in which the second added fluid is caused to pass through the second heat exchanger, and in which the reversible heat pump arrangement is caused to transfer heat from the first heat exchanger to the second heat exchanger by means of the heat pump loop so as to allow heating the second added fluid by means of the reversible heat pump arrangement, and

(c) optionally, a cooling mode in which the compressor is turned on, in which the first added fluid is caused to pass through the first heat exchanger but not through the third heat exchanger, in which the second added fluid is caused to pass through the second heat exchanger, and in which the reversible heat pump arrangement is caused to transfer heat from the second heat exchanger to the first heat exchanger by means of the heat pump loop so as to allow cooling the second added fluid by means of the reversible heat pump arrangement.

In some embodiments of the heat pump system according to the seventh aspect, the heat pump system further comprises a first valve arrangement for guiding the first added fluid passing therethrough, said first valve arrangement comprising a valve inlet, a first valve outlet and a second valve outlet, wherein the first valve outlet is connected to the third heat exchanger and the second valve outlet is directly connected to a first external outlet of the heat pump system thereby bypassing the third heat exchanger.

In some embodiments of the heat pump system according to the seventh aspect, the heat pump system further comprises a second valve arrangement comprising: a first four-way valve, and the compressor; and wherein the first four-way valve is connected to the heat pump loop in such a manner that a flow direction of the working fluid in the heat pump loop can be controlled.

In some embodiments of the heat pump system according to the seventh aspect, the heat pump system further comprises a second four-way valve connected to the second heat exchanger in such a manner as to allow switching between a cocurrent and a countercurrent flow of the first added fluid inside the second heat exchanger.

In some embodiments of the heat pump system according to the seventh aspect, the heat pump system further comprises a third four-way valve connected to the first heat exchanger in such a manner as to allow switching between a cocurrent and a countercurrent flow of the second added fluid inside the second heat exchanger.

In some embodiments of the heat pump system according to the seventh aspect, the heat pump system further comprises a first external inlet for receiving the first added fluid and a first external outlet for outputting the first added fluid, and wherein the first external inlet is connectable to a hot conduit of a cold thermal grid system and the first external outlet is connectable to a cold conduit of the cold thermal grid system.

According to an eighth aspect there is provided a method for a heat pump system configured to transfer heat between a first and a second added fluid passing therethrough, said method comprising: measuring a first temperature of a first added fluid at a position where the first added fluid is input to the heat pump system; measuring a second temperature of a second added fluid at a position where the second added fluid is being output from the heat pump system; setting, based on the first temperature and the second temperature, an operational mode of the heat pump system to one of:

(a) a heat exchange mode in which the compressor is turned off and in which the first added fluid and the second added fluid are caused to, separated from each other, pass through the third heat exchanger so as to allow heat exchange between the first and the second added fluids by means of the third heat exchanger;

(b) a heat pump mode in which the compressor is turned on, in which the first added fluid is caused to pass through the first heat exchanger but not through the third heat exchanger, in which the second added fluid is caused to pass through the second heat exchanger, and in which the reversible heat pump arrangement is caused to transfer heat from the first heat exchanger to the second heat exchanger by means of the heat pump loop so as to allow heating the second added fluid by means of the reversible heat pump arrangement, and

(c) optionally, a cooling mode in which the compressor is turned on, in which the first added fluid is caused to pass through the first heat exchanger but not through the third heat exchanger, in which the second added fluid is caused to pass through the second heat exchanger, and in which the reversible heat pump arrangement is caused to transfer heat from the second heat exchanger to the first heat exchanger by means of the heat pump loop so as to allow cooling the second added fluid by means of the reversible heat pump arrangement.

In some embodiments of the method according to the eighth aspect, the step of setting the heat pump system to an operational mode of the heat pump system comprises: setting the heat pump system to the heat exchange mode in response to the first temperature being between the second temperature minus a first constant and the second temperature plus a second constant; setting the heat pump system to the heat pump mode in response to the first temperature being equal to the second temperature minus the first constant or lower; and optionally, setting the heat pump system to the cooling mode in response to the first temperature being equal to the second temperature plus the second constant or higher.

According to a ninth aspect there is provided a computer program product comprising a non-transitory computer readable medium, having stored thereon a computer program comprising program instructions, the computer program being loadable into a data processing unit and configured to cause execution of the method according to the eighth aspect when the computer program is run by the data processing unit.

Effects and features of the second and third aspects are to a substantial extent analogous to those described above in connection with the first aspect and vice versa. Embodiments mentioned in relation to the first aspect are fully or largely compatible with the second and third aspects and vice versa.

Effects and features of the fourth, fifth and sixth aspects are to a substantial extent analogous to those described above in connection with the first, second and third aspects and vice versa.

Effects and features of the seventh, eighth and ninth aspects are to a substantial extent analogous to those described above in connection with the first, second and third aspects and vice versa.

An advantage of some of the embodiments is that electrical energy efficiency is increased/improved.

Another advantage of some of the embodiments is that power is saved.

Yet another advantage of some of the embodiments is that switching between cocurrent and countercurrent flow inside heat exchangers is enabled. Thus, a more efficient transfer of coolness and/or an increase in efficiency (when in cooling mode) is provided.

A further advantage of some of the embodiments is that the efficiency is increased in the heat pump mode and/or the cooling mode.

Yet a further advantage of some of the embodiments is that the transition from a gas grid system to a green thermal grid system is facilitated and/or speeded up, thereby enabling a faster reduction of carbon dioxide emissions.

BRIEF DESCRIPTION OF THE DRAWINGS

Further objects, features and advantages will appear from the following detailed description of embodiments, with reference being made to the accompanying drawings. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the example embodiments.

Figure 1A is a flowchart illustrating method steps implemented in a heat pump apparatus according to some embodiments;

Figure 1 B is a schematic drawing illustrating a heat pump according to some embodiments;

Figure 2 is a flow chart illustrating a method for a heat pump;

Figure 3 is a schematic drawing illustrating connections for a heat pump according to some embodiments;

Figure 4 is a schematic drawing illustrating connections for a heat pump according to some embodiments;

Figure 5 is a schematic drawing illustrating valve arrangements for a heat pump according to some embodiments;

Figure 6 is a schematic drawing illustrating details of a first four-way valve;

Figure 7 is a schematic drawing illustrating a computer readable medium according to some embodiments;

Figure 8A is a schematic drawing illustrating a heat pump according to some embodiments;

Figure 8B is a schematic drawing illustrating details of a second fourway valve; and

Figure 8C is a schematic drawing illustrating details of a third four-way valve.

DETAILED DESCRIPTION

It should be emphasized that the term "comprises/comprising" (replaceable by "includes/including") when used in this specification is taken to specify the presence of stated features, integers, steps, or components, but does not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

Embodiments of the present disclosure will be described and exemplified more fully hereinafter with reference to the accompanying drawings. The solutions disclosed herein can, however, be realized in many different forms and should not be construed as being limited to the embodiments set forth herein.

Terminology

The term “working fluid” utilized below refers to a fluid circulating in the heat pump loop. The Heat pump loop is defined as the loop, in which the working fluid is configured to circulate through a first heat exchanger 120, a compressor 144, a second heat exchanger 160 and optionally through a valve 180 (shown in figure 1 B). The working fluid may also be referred to as a refrigerant.

The term “first added fluid” utilized below refers to a fluid added from a first external inlet 102 (shown in figure 1 B).

The term “second added fluid” utilized below refers to a fluid added from a second external inlet 106 (shown in figure 1 B).

Below is referred to a “heat pump generating coolness”. Such a heat pump may also be referred to as a cool pump.

Below reference is made to the term “cocurrent”. A cocurrent flow involves flow of fluids (e.g., a hot fluid and a cold fluid) in the same direction.

Below reference is made to the term “countercurrent”. A countercurrent flow is when two different fluids, such as a hot fluid and a cold fluid, flows in opposite directions.

Figure 1A illustrates method steps implemented in a heat pump/apparatus 100 according to some embodiments and Figure 1 B illustrates the heat pump 100 according to some embodiments. As shown in figure 1 B, the heat pump 100 comprises a first external inlet 102, a first external outlet 104, a second external inlet 106, and a second external outlet 108. In some embodiments, the heat pump comprises a first and a second pump 190, 192 for circulating first and second added fluids. Furthermore, the heat pump 100 comprises controlling circuitry. In some embodiments, the control circuitry comprises or consists of a control unit 110. The controlling circuitry is configured to cause (a first) measurement 10 of a first temperature T1 at the first external inlet 102. To this end, the control circuitry may be associated with (e.g., operatively connectable, or connected to) a first temperature sensor 103 at the first external inlet 102. Furthermore, the controlling circuitry is configured to cause (a second) measurement 20 of a second temperature T2 at the second external outlet 108. To this end, the control circuitry 160 may be associated with (e.g., operatively connectable, or connected to) a second temperature sensor 109 at the second external outlet 108. Moreover, the controlling circuitry is configured to cause setting 30 of an operating mode of the heat pump 100 based on the first temperature T1 and the second temperature T2. To this end, the control circuitry 160 may be associated with (e.g., operatively connectable, or connected to) a setting unit (setting circuitry or a setter). The operating mode is set to one of: heat exchange mode, in which the heat pump 100 operates as a heat exchanger; heat pump mode, in which the heat pump 100 operates as a heat pump generating heat, and optionally cooling mode, in which the heat pump 100 operates as a heat pump generating coolness. By selecting/setting the mode based on the measured temperatures, electrical energy efficiency for the heat pump may be increased/improved.

Optionally, the controlling circuitry is configured to cause a comparison 25 of the first temperature T1 to the second temperature T2. To this end, the control circuitry 160 may be associated with (e.g., operatively connectable, or connected to) a first comparing unit (first comparing circuitry or first comparator). Alternatively, the comparison may be performed by the control unit 110. Furthermore, the controlling circuitry, e.g., the control unit 110, is optionally configured to cause calculation of a difference (AT) between T1 and T2, configured to cause a comparison of the difference (AT) to first and second constants K1 , K2, and configured to cause a determination as to which mode the heat pump 100 should be set to, based on the comparison to the first and second constants K1 , K2. To this end, the control circuitry may be associated with (e.g., operatively connectable, or connected to) a calculating unit, a second comparing unit and a determining unit (calculating circuitry or calculator; second comparing circuitry or second comparator; determining circuitry or determinator). In some embodiments, the setting of operating mode is further dependent on a set-point temperature Tsp (e.g., from a thermostat, heating/cooling control unit, a remote control, an app) and an actual temperature, such as an actual temperature of a floor, an actual air temperature of a room or an actual temperature of tap water (at a tap water heating unit).

In some embodiments, the operating mode of the heat pump 100 is set to heat exchange mode if the first temperature T1 is between the second temperature T2 minus the first constant K1 and the second temperature T2 plus the second constant K2, i.e. , if (T2-K1 ) < T1 < (T2+K2). In some embodiments, the operating mode of the heat pump 100 is set to heat pump mode if the first temperature T1 is equal to the second temperature T2 minus the first constant K1 or lower, i.e., if T1 < (T2-K1 ). In some embodiments, the operating mode of the heat pump 100 is set to cooling mode if the first temperature T1 is equal to the second temperature T2 plus the second constant K2 or higher, i.e., if T1 > (T2+K2). By selecting/setting the mode based on different intervals of the difference of the measured temperatures, electrical energy efficiency may be further increased/improved. The first and second constants K1 , K2 are adjustable or user settable. Furthermore, in some embodiments the first constant K1 has a value of 2 or higher, preferably 5 or higher, more preferably 10 or higher, such as 10. However, the first constant K1 may have any suitable value. Moreover, in some embodiments the second constant K2 has a value of 2 or higher, preferably 5 or higher, more preferably 10 or higher, such as 10. However, the second constant K2 may have any suitable value. In some embodiments, the first constant K1 is equal to the second constant K2, i.e., K1=K2.

In some embodiments, the heat pump 100 comprises a reversible heat pump arrangement 150. The reversible heat pump arrangement 150 comprises a first and a second heat exchanger 120, 160 and a compressor 144. Furthermore, the heat pump 100 comprises a third heat exchanger 170. The third heat exchanger 170 comprises a first inlet 172, a first outlet 174, a second inlet 176 and a second outlet 178. Moreover, the heat pump 100 comprises a first valve arrangement 130. The first valve arrangement 130 comprises a valve inlet 132, a first valve outlet 134 and a second valve outlet 136. The control unit 110 is configured to set the heat pump 100 to one of heat exchange mode, heat pump mode and optionally cooling mode by controlling the reversible heat pump arrangement 150 and/or by controlling the first valve arrangement 130.

In some embodiments, the valve inlet 132 is connected to the first external inlet 102, directly or via the first heat exchanger 120. The first valve outlet 134 is connected to the second inlet 176 of the third heat exchanger 170. Furthermore, the second valve outlet 136 is connected to the first external outlet 104. Thus, when the first added fluid (entering the heat pump 100 at the first external inlet 102) exits the first valve arrangement 130 through the second valve outlet 136, the third heat exchanger 170 is bypassed. Moreover, the first inlet 172 of the third heat exchanger 170 is connected to the second external inlet 106 directly or via pump 192. The first outlet 174 of the third heat exchanger 170 is connected to the second external outlet 108, directly or via the second heat exchanger 160. Furthermore, the second outlet 178 of the third heat exchanger 170 is connected to the first external outlet 104. The control unit 110 is configured to control a flow through the first valve arrangement 130 to exit through the first valve outlet 134 and to turn the compressor 144 off (OFF) when setting the operating mode of the heat pump 100 to heat exchange mode. Furthermore, the control unit 110 is configured to control a flow through the first valve arrangement 130 to exit through the second valve outlet 136 and to turn the compressor 144 on (ON) when setting the operating mode of the heat pump 100 to heat pump mode or cooling mode. Thus, by controlling the first valve arrangement 130 and turning the compressor off and on, the control unit 110 controls whether the operating mode of the heat pump 100 is heat pump mode/cooling mode or heat exchange mode. By turning the compressor off and on, power/energy may be saved.

In some embodiments, the reversible heat pump arrangement 150 comprises a working fluid configured to circulate through the first heat exchanger 120, the compressor 144, and the second heat exchanger 160. Furthermore, if the heat pump 100 comprises a valve 180, the working fluid is configured to circulate through the valve 180. Moreover, the reversible heat pump arrangement 150 comprises a second valve arrangement 140. The second valve arrangement 140 comprises a first four-way valve 142, and the compressor 144. Thus, the working fluid is configured to circulate through the first four-way valve. The first heat exchanger 120 comprises a first inlet 122. The first inlet 122 of the first heat exchanger 120 is connected to the first external inlet 102, directly or via pump 190. Furthermore, the first heat exchanger 120 comprises a first outlet 124. The first outlet 124 of the first heat exchanger 120 is connected to the inlet 132 of the first valve arrangement 130. Moreover, the first heat exchanger 120 comprises a second inlet 126 and a second outlet 128. The second outlet 128 of the first heat exchanger 120 is connected to the first four-way valve 142. In these embodiments, the second heat exchanger 160 comprises a first inlet 162. The first inlet 162 of the second heat exchanger 160 is connected to the first outlet 174 of the third heat exchanger 170. Furthermore, the second heat exchanger 160 comprises a first outlet 164. The first outlet 164 of the second heat exchanger 160 is connected to the second external outlet 108. Moreover, the second heat exchanger 160 comprises a second inlet 166. The second inlet 166 of the second heat exchanger 160 is connected to the second inlet 126 of the first heat exchanger 120, directly or via the valve 180. The second heat exchanger 160 comprises a second outlet 168. The second outlet 168 of the second heat exchanger 160 is connected to the first four-way valve 142. The control unit 110 is configured to control the flow of the working fluid to go from the second outlet 128 of the first heat exchanger 120 to the second outlet 168 of the second heat exchanger 160 (via the first four-way valve 142 and the compressor 144) and return from the second inlet 166 of the second heat exchanger 160 to the second inlet 126 of the first heat exchanger 120 (optionally via the valve 180) when setting the operating mode of the heat pump 100 to heat pump mode (and while the heat pump 100 is in the heat pump mode) by controlling the first four-way valve 142, e.g., by setting the first four-way valve 142 to a first flow position or to cause the first four-way valve 142 to switch from a second flow position to the first flow position, by sending a control signal, such as a negative (electric) control signal or a low signal, to the first four-way valve 142. Furthermore, the control unit 110 is configured to control the flow of the working fluid to go from the second outlet 168 of the second heat exchanger 160 to the second outlet 128 of the first heat exchanger 120 (via the first four-way valve 142 and the compressor 144) and return from the second inlet 126 of the first heat exchanger 120 to the second inlet 166 of the second heat exchanger 160 (optionally via the valve 180) when setting the operating mode of the heat pump 100 to cooling mode (and while the heat pump 100 is in the cooling mode), by controlling the first four-way valve 142, e.g., by setting the first four-way valve 142 to the second flow position or to cause the first four-way valve 142 to switch from the first flow position to the second flow position, by sending a control signal, such as a positive (electric) control signal or a high signal, to the first four-way valve 142.

Figure 2 illustrates a method 200 for a heat pump 100. The method 200 comprises measuring 210 a first temperature T1 at a first external inlet 102 of the heat pump 100. Furthermore, the method 200 comprises measuring 220 a second temperature T2 at the second external outlet 108. Moreover, the method 200 comprises setting 230 an operating mode of the heat pump 100 based on the first temperature T1 and the second temperature Tsp. The operating mode is set to one of: heat exchange mode, in which the heat pump 100 operates as a heat exchanger; heat pump mode, in which the heat pump 100 operates as a heat pump generating heat, and optionally cooling mode, in which the heat pump 100 operates as a heat pump generating coolness. In some embodiments, the operating mode of the heat pump 100 is set to heat exchange mode if the first temperature T1 is between the second temperature T2 minus a first constant K1 and the second temperature T2 plus a second constant K2, i.e., if (T2-K1 ) <T1 <(T2+K2). In some embodiments, the operating mode of the heat pump 100 is set to heat pump mode if the first temperature T1 is equal to the second temperature T2 minus the first constant K1 or lower, i.e., if T1<(T2-K1 ). In some embodiments, the operating mode of the heat pump 100 is set to cooling mode if the first temperature T1 is equal to the second temperature T2 plus the second constant K2 or higher, i.e., if T1>(T2+K2). Optionally, the method 200 comprises comparing 225 the first temperature T1 to the second temperature T2. This comparison may be performed by a control unit 110. In these embodiments, the control unit 110 may calculate a difference (AT) between T1 and T2 and then compare the difference (AT) to the first and second constants K1 , K2 in order to decide which mode the heat pump 100 should be set to. In some embodiments, the setting of operating mode is further dependent on a set-point temperature Tsp (e.g., from a thermostat, heating/cooling control unit, a remote control, an app) and an actual temperature, such as an actual temperature of a floor, an actual air temperature of a room or an actual temperature of tap water (at a tap water heating unit).

Figure 3 illustrates some possible connections for the heat pump 100. In some embodiments, the first external inlet 102 is connectable or connected to a hot conduit 310 of a cold thermal grid system 300, e.g., via a third pump 340 or via a second valve 350. In some embodiments, the heat pump 100 comprises the third pump 340 and/or the second valve 350. The control unit 110 may then be configured to select or switch between utilizing the third pump 340 or the second valve 350 based on a differential pressure between the cold conduit 320 and the hot conduit 310. Furthermore, the first external outlet 104 is connectable or connected to a cold conduit 320 of the cold thermal grid system 300. Moreover, the second external inlet 106 and the second external outlet 108 are connectable or connected to a heating and/or cooling system 330, e.g., such that the second added fluid enters the second external inlet 106 from the heating and/or cooling system 330 and returns from the second external outlet 108 to heating and/or cooling system 330. The heating and/or cooling system 330 relates to/provides space heating and/or cooling. Alternatively, or additionally, the heating and/or cooling system 330 is a tap water heating unit.

As another alternative, shown in figure 4, the first external inlet 102 is connectable or connected to a conduit 410 of an ambient loop system 400. An ambient loop system 400 circulates low-grade heat to all the apartments in a development. Within each apartment, a water-to-water heat pump draws water from the ambient loop 400 and upgrades this to a usable temperature for space heating and/or cooling and/or for heating water. As shown in figure 4, the first external inlet 102 is connectable or connected to a (hot) conduit 410 of an ambient loop system 400, e.g., via a third valve 450. In some embodiments, the heat pump 100 comprises the third valve 450. The control unit 110 may then be configured to control the third valve 450. Furthermore, the first external outlet 104 is connectable or connected to the same (hot) conduit 410 of the ambient loop system 400, downstream/downflow of the connection for the first external inlet 102. Moreover, the second external inlet 106 and the second external outlet 108 are connectable or connected to a heating and/or cooling system 430, e.g., such that the second added fluid enters the second external inlet 106 from the heating and/or cooling system 430 and returns from the second external outlet 108 to heating and/or cooling system 430. The heating and/or cooling system 430 relates to/provides space heating and/or cooling. Alternatively, or additionally, the heating and/or cooling system 430 is a tap water heating unit.

Figure 5 illustrates valve arrangements for a heat pump 100 according to some embodiments. In some embodiments, the heat pump 100 comprises a heating and/or cooling system 330, a third pump 340, a second valve 350 and first and second valve arrangements 560, 570. Each of the first and second valve arrangements 560, 570 comprises first and second inlets and an outlet. The first and second inlets of the first valve arrangement 560 are connectable or connected to a hot conduit 510 and a cold conduit 520 of a cold thermal grid system 500. The outlet of the first valve arrangement 560 is connectable or connected to the first external outlet 104 of the heat pump 100. Furthermore, the first and second inlets of the second valve arrangement 570 are connectable or connected to the hot conduit 510 and the cold conduit 520 of the cold thermal grid system 500. The outlet of the second valve arrangement 570 is connectable or connected to the first external inlet 102 of the heat pump 100 (via the third pump 340 or the second valve 350). The cold thermal grid system 500 may be identical or similar to the cold thermal grid system 300. The control unit 110 is configured to control the first and second valve arrangements 560, 570. Furthermore, the control of each of the first and second valve arrangements 560, 570 is based on the operating mode of the heat pump 100. E.g., if the operating mode is heat pump mode, the control unit 110 controls the second valve arrangement 570 to provide fluid from the hot conduit 510 of the cold thermal grid system 500 to the first external inlet

102 and controls the first valve arrangement 560 to return the fluid from the first external outlet 104 to the cold conduit 520 of the cold thermal grid system 500, i.e. , the control unit 110 controls the first valve arrangement 560 to open the second inlet and close the first inlet and controls the second valve arrangement 570 to open the first inlet and close the second inlet.

Alternatively, or additionally, if the operating mode is cooling mode, the control unit 110 controls the first valve arrangement 560 to provide fluid from the cool conduit 520 of the cold thermal grid system 500 to the first external inlet 102 and the second valve arrangement 570 to return the fluid from the first external outlet 104 to the hot conduit 510 of the cold thermal grid system 500, i.e., the control unit 110 controls the second valve arrangement 570 to open the second inlet and close the first inlet and controls the first valve arrangement 560 to open the first inlet and close the second inlet. This may be advantageous as it may increase the efficiency of the heat pump 100 (especially when in the cooling mode). Moreover, the second external inlet 106 and the second external outlet 108 are connectable or connected to a heating and/or cooling system 530, e.g., such that the second added fluid enters the second external inlet 106 from the heating and/or cooling system 530 and returns from the second external outlet 108 to heating and/or cooling system 530. The heating and/or cooling system 530 relates to/provides space heating and/or cooling. Alternatively, or additionally, the heating and/or cooling system 530 is a tap water heating unit.

Figure 6 illustrates details of a first four-way valve 142. The first fourway valve 142 comprises a first access point 642, a second access point 644, a third access point 646 and a fourth access point 648. As mentioned above in connection with figure 1 , in some embodiments the control unit 110 is configured to control the first four-way valve 142 when setting the operating mode, e.g., to heat pump mode or cooling mode. The first four-way valve 142 may be controlled to take on a first flow position or to take on a second flow position, i.e., the first four-way valve 142 may be set (e.g., by the control unit 110) to a first flow position or a second flow position. In the first flow position the first access point 642 is connected to the second access point 644 so that a working fluid can flow between the first and second access points 642, 644, and the third access point 646 is connected to the fourth access point 648 so that the working fluid can flow between the third and fourth access points 646, 648. Thus, when the first four-way valve 142 is in the first flow position, the compressor 144 will (if turned on) circulate the working fluid from the second outlet 128 of the first heat exchanger 120, via the first four-way valve 142 and the compressor 144 to the second outlet 168 of the second heat exchanger 160. Furthermore, in the second flow position the first access point 642 is connected to the third access point 646 so that the working fluid can flow between the first and third access points 642, 646, and the second access point 644 is connected to the fourth access point 648 so that the working fluid can flow between the second and fourth access points 644, 648. Thus, when the first four-way valve 142 is in the second flow position, the compressor 144 will (if turned on) circulate the working fluid from the second outlet 168 of the second heat exchanger 160, via the first four-way valve 142 and the compressor 144 to the second outlet 128 of the first heat exchanger 120.

Figure 7 is a schematic drawing illustrating an example computer readable medium in the form of a compact disc (CD) ROM 700. Alternatively, the computer readable medium is a universal serial bus, USB, flash drive or other flash memory. The computer readable medium has stored thereon a computer program comprising program instructions. The computer program is loadable into a data processing unit (PROC) 720, which may be a processor/control circuitry, the control unit 110 or another processing unit comprised in or otherwise associated with the heat pump 100. When loaded into the data processing unit, the computer program may be stored in a memory (MEM) 730 associated with (connectable or connected to) or comprised in the data processing unit. The memory may be data storage unit. According to some embodiments, the computer program may, when loaded into and run by the data processing unit, cause execution of method steps according to, for example, any of the methods illustrated in Figure 2 or otherwise (e.g., in claims 1-2) described herein.

Figure 8A illustrates a heat pump according to some embodiments, figure 8B illustrates details of a second four-way valve, and figure 8C illustrates details of a third four-way valve. In some embodiments, the heat pump 100 comprises a second and a third four-way valve 820, 860. The second four-way valve 820 comprises first, second, third and fourth access points 822, 824, 826, 828. Furthermore, the third four-way valve 860 comprises first, second, third and fourth access points 862, 864, 866, 868. The first, second, third and fourth access points 822, 824, 826, 828 of the second four-way valve 820 are connected to the first external inlet 102 (via pump 190), the first inlet 122 of the first heat exchanger 120, the first outlet 124 of the first heat exchanger 120, and the valve inlet 132, i.e. , the first access point 822 is connected to the first external inlet 102, the second access point 824 is connected to the first inlet 122 of the first heat exchanger 120, the third access point 826 is connected to the first outlet 124 of the first heat exchanger 120 and the fourth access point 828 is connected to the valve inlet 132. The first, second, third and fourth access points 862, 864, 866, 868 of the third four-way valve 860 are connected to the second external outlet 108, the first inlet 162 of the second heat exchanger 160, the first outlet 164 of the second heat exchanger 160, and the first outlet 174 of the third heat exchanger 170, i.e., the first access point 862 is connected to the second external outlet 108, the second access point 864 is connected to the first inlet 162 of the second heat exchanger 160, the third access point 866 is connected to the first outlet 164 of the second heat exchanger 160 and the fourth access point 868 is connected to the first outlet 174 of the third heat exchanger 170. The control unit 110 is configured to control the flow of a first added fluid inside the first heat exchanger 120 to go from the first inlet 122 to the first outlet 124 and control the flow of a second added fluid inside the second heat exchanger 160 to go from the first inlet 162 to the first outlet 164 when in heat pump mode. Furthermore, the control unit 110 is configured to control the flow of the first added fluid inside the first heat exchanger 120 to go from the first outlet 124 to the first inlet 122 and control the flow of the second added fluid inside the second heat exchanger 160 to go from the first outlet 164 to the first inlet 162 when in cooling mode. The control is performed in the same or a similar manner as explained above (in connection with figures 1 and 6) for the first four-way valve 142, wherein each of the second and third four-way valves 820, 860 are set in either a first or a second flow position. This embodiment may be advantageous as switching between cocurrent and countercurrent flow inside heat exchangers is enabled, thereby providing a more efficient transfer of coolness/increasing the efficiency of the heat pump 100 (especially when in cooling mode).

Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and/or is implied from the context in which it is used. Reference has been made herein to various embodiments. However, a person skilled in the art would recognize numerous variations to the described embodiments that would still fall within the scope of the claims. For example, the method embodiments described herein discloses example methods through steps being performed in a certain order. However, it is recognized that these sequences of events may take place in another order without departing from the scope of the claims. Furthermore, some method steps may be performed in parallel even though they have been described as being performed in sequence. Thus, the steps of any methods disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and/or where it is implicit that a step must follow or precede another step. In the same manner, it should be noted that in the description of embodiments, the partition of functional blocks into particular units is by no means intended as limiting. Contrarily, these partitions are merely examples. Functional blocks described herein as one unit may be split into two or more units. Furthermore, functional blocks described herein as being implemented as two or more units may be merged into fewer e.g., a single) unit. Any feature of any of the embodiments/aspects disclosed herein may be applied to any other embodiment/aspect, wherever suitable. Likewise, any advantage of any of the embodiments may apply to any other embodiments, and vice versa. Hence, it should be understood that the details of the described embodiments are merely examples brought forward for illustrative purposes, and that all variations that fall within the scope of the claims are intended to be embraced therein.

LIST OM EMBODIMENTS

Embodiment 1 . A method (200) for a heat pump (100), comprising: measuring (210) a first temperature (T1 ) at a first external inlet (102) of the heat pump (100); measuring (220) a second temperature (T2) at a second external outlet (108) of the heat pump (100); setting (230) an operating mode of the heat pump (100) based on the first temperature (T1 ) and the second temperature (T2) to one of: heat exchange mode, in which the heat pump (100) operates as a heat exchanger; heat pump mode, in which the heat pump (100) operates as a heat pump generating heat; and optionally cooling mode, in which the heat pump (100) operates as a heat pump generating coolness.

Embodiment 2. The method of Embodiment 1 , wherein the operating mode of the heat pump (100) is set to heat exchange mode if the first temperature (T1 ) is between the second temperature (T2) minus a first constant (K1 ) and the second temperature (T2) plus a second constant (K2), wherein the operating mode of the heat pump (100) is set to heat pump mode if the first temperature (T1) is equal to the second temperature (T2) minus the first constant (K1) or lower, and/or wherein the operating mode of the heat pump (100) is set to cooling mode if the first temperature (T1 ) is equal to the second temperature (T2) plus the second constant (K2) or higher.

Embodiment 3. A computer program product comprising a non- transitory computer readable medium (700), having stored thereon a computer program comprising program instructions, the computer program being loadable into a data processing unit (720) and configured to cause execution of the method of any of Embodiments 1 -2 when the computer program is run by the data processing unit.

Embodiment 4. A heat pump (100) comprising a first external inlet (102), a first external outlet (104), a second external inlet (106), and a second external outlet (108), and controlling circuitry configured to cause: measurement (10) of a first temperature (T1 ) at the first external inlet (102); measurement (20) of a second temperature (T2) at the second external outlet (108); setting (30) of an operating mode of the heat pump (100) based on the first temperature (T1 ) and the second temperature (T2) to one of: heat exchange mode, in which the heat pump (100) operates as a heat exchanger, heat pump mode, in which the heat pump (100) operates as a heat pump generating heat, and optionally cooling mode, in which the heat pump (100) operates as a heat pump generating coolness.

Embodiment 5. The heat pump (100) of Embodiment 4, wherein the control circuitry comprises a control unit (110), the heat pump (100) further comprising: a reversible heat pump arrangement (150) comprising a first and a second heat exchanger (120, 160) and a compressor (144); a third heat exchanger (170) comprising a first inlet (172), a first outlet (174), a second inlet (176) and a second outlet (178); a first valve arrangement (130) comprising a valve inlet (132), a first valve outlet (134) and a second valve outlet (136); and wherein the control unit (110) is configured to set the heat pump (100) to one of heat exchange mode, heat pump mode and optionally cooling mode by controlling the reversible heat pump arrangement (150) and/or the first valve arrangement (130).

Embodiment 6. The heat pump (100) of Embodiment 5, wherein the valve inlet (132) is connected to the first external inlet (102), such as via the first heat exchanger (120), wherein the first valve outlet (134) is connected to the second inlet (176) of the third heat exchanger (170), wherein the second valve outlet (136) is connected to the first external outlet (104), wherein the first inlet (172) of the third heat exchanger (170) is connected to the second external inlet (106), wherein the first outlet (174) of the third heat exchanger (170) is connected to the second external outlet (108), such as via the second heat exchanger (160), wherein the second outlet (178) of the third heat exchanger (170) is connected to the first external outlet (104) and wherein the control unit (110) is configured to control a flow through the first valve arrangement (130) to exit through the first valve outlet (134) and to turn the compressor (144) off when setting the operating mode of the heat pump (100) to heat exchange mode and configured to control a flow through the first valve arrangement (130) to exit through the second valve outlet (136) and to turn the compressor (144) on when setting the operating mode of the heat pump (100) to heat pump mode or cooling mode.

Embodiment 7. The heat pump (100) of Embodiment 6, wherein the reversible heat pump arrangement (150) further comprises: a working fluid configured to circulate through the first heat exchanger (120), the compressor (144), the second heat exchanger (160) and optionally through a valve (180); a second valve arrangement (140) comprising: a first four-way valve (142), and the compressor (144); and wherein the first heat exchanger (120) comprises: a first inlet (122) connected to the first external inlet (102), a first outlet (124) connected to the inlet (132) of the first valve arrangement (130), a second inlet (126) and a second outlet (128) connected to the first four-way valve (142); and wherein the second heat exchanger (160) comprises: a first inlet (162) connected to the first outlet (174) of the third heat exchanger (170); a first outlet (164) connected to the second external outlet (108); a second inlet (166) connected to the second inlet (126) of the first heat exchanger (120), such as via a valve (180); and a second outlet (168) connected to the first four-way valve (142); and wherein the control unit (110) is configured to control the flow of the working fluid to go from the second outlet (128) of the first heat exchanger (120) to the second outlet (168) of the second heat exchanger (160) and return from the second inlet (166) of the second heat exchanger (160) to the second inlet (126) of the first heat exchanger (120) when setting the operating mode of the heat pump (100) to heat pump mode by controlling the first fourway valve (142) and configured to control the flow of the working fluid to go from the second outlet (168) of the second heat exchanger (160) to the second outlet (128) of the first heat exchanger (120) and return from the second inlet (126) of the first heat exchanger (120) to the second inlet (166) of the second heat exchanger (160) when setting the operating mode of the heat pump (100) to cooling mode, by controlling the first four-way valve (142).

Embodiment 8. The heat pump (100) of any of Embodiments 5-7, further comprising a second and a third four-way valve (820, 860), each of the second and third four-way valves (820, 860) comprising first, second, third and fourth access points (822, 824, 826, 828, 862, 864, 866, 868), the first, second, third and fourth access points (822, 824, 826, 828) of the second four-way valve (820) being connected to the first external inlet (102), the first inlet (122) of the first heat exchanger (120), the first outlet (124) of the first heat exchanger (120), and the valve inlet (132), the first, second, third and fourth access points (862, 864, 866, 868) of the third four-way valve (860) being connected to the second external outlet (108), the first inlet (162) of the second heat exchanger (160), the first outlet (164) of the second heat exchanger (160), and the first outlet (174) of the third heat exchanger (170) and wherein the control unit (110) is configured to control the flow of a first added fluid inside the first heat exchanger (120) to go from the first inlet (122) to the first outlet (124) and control the flow of the first added fluid inside the second heat exchanger (160) to go from the first inlet (162) to the first outlet (164) when in heat pump mode and configured to control the flow of the first added fluid inside the first heat exchanger (120) to go from the first outlet (124) to the first inlet (122) and control the flow of the first added fluid inside the second heat exchanger (160) to go from the first outlet (164) to the first inlet (162) when in cooling mode.

Embodiment 9. The heat pump (100) of any of Embodiments 4-8, wherein the first external inlet (102) is connectable to a hot conduit (310) of a cold thermal grid system (300) and the first external outlet (104) is connectable to a cold conduit (320) of the cold thermal grid system (300).

Embodiment 10. The heat pump (100) of any of Embodiments 4-9, further comprising first and second valve arrangements (560, 570) and wherein the control unit (110) is further configured to control the first and second valve arrangements (560, 570), the first valve arrangement (560) being connectable to a hot conduit (510) and the second valve arrangement (570) being connectable to a cold conduit (520), and wherein the control of each of the first and second valve arrangements (560, 570) is based on the operating mode of the heat pump (100).

Embodiment 11 . A heat pump system (100) for transferring heat between a first and a a second added fluid caused to separately pass therethrough, said heat pump system comprising: a reversible heat pump arrangement (150) comprising a first heat exchanger (120), a second heat exchanger (160), and a compressor (144) and optionally a valve (180) which are connected to each other to form a heat pump loop in which a working fluid is configured to circulate for moving heat between the first (120) and second (160) heat exchangers; a third heat exchanger (170), and controlling circuitry configured to: cause measurement (10) of a first temperature (T1) of the first added fluid at a position where the first added fluid is input to the heat pump system; cause measurement (20) of a second temperature (T2) of the second added fluid at a position where the second added fluid is being output from the heat pump system; and control the heat pump system so as to set, based on the first temperature (T1 ) and the second temperature (T2), an operating mode of the heat pump system (100) to one of:

(a) a heat exchange mode in which the compressor is turned off and in which the first added fluid and the second added fluid are caused to, separated from each other, pass through the third heat exchanger (170) so as to allow heat exchange between the first and the second added fluids by means of the third heat exchanger (170);

(b) a heat pump mode in which the compressor (144) is turned on, in which the first added fluid is caused to pass through the first heat exchanger (120) but not through the third heat exchanger (170), in which the second added fluid is caused to pass through the second heat exchanger (160), and in which the reversible heat pump arrangement (150) is caused to transfer heat from the first heat exchanger (120) to the second heat exchanger (160) by means of the heat pump loop so as to allow heating the second added fluid by means of the reversible heat pump arrangement (150), and

(c) optionally, a cooling mode in which the compressor is turned on, in which the first added fluid is caused to pass through the first heat exchanger but not through the third heat exchanger, in which the second added fluid is caused to pass through the second heat exchanger, and in which the reversible heat pump arrangement (150) is caused to transfer heat from the second heat exchanger (160) to the first heat exchanger (120) by means of the heat pump loop so as to allow cooling the second added fluid by means of the reversible heat pump arrangement (150).

Embodiment 12. The heat pump system (100) according to Embodiment 11 , further comprising a first valve arrangement (130) for guiding the first added fluid passing therethrough, said first valve arrangement (130) comprising a valve inlet (132), a first valve outlet (134) and a second valve outlet (136), wherein the first valve outlet (134) is connected to the third heat exchanger (170) and the second valve outlet (136) is directly connected to a first external outlet (104) of the heat pump system thereby bypassing the third heat exchanger (170).

Embodiment 13. The heat pump system (100) according to Embodiment 11 or 12, further comprising a second valve arrangement (140) comprising: a first four-way valve (142), and the compressor (144); and wherein the first four-way valve (142) is connected to the heat pump loop in such a manner that a flow direction of the working fluid in the heat pump loop can be controlled.

Embodiment 14. The heat pump system (100) according to any one of Embodiments 11 to 13, further comprising a second four-way valve (820) connected to the second heat exchanger (120) in such a manner as to allow switching between a cocurrent and a countercurrent flow of the first added fluid inside the second heat exchanger (120).

Embodiment 15. The heat pump system (100) according to any one of Embodiments 11 to 14, further comprising a third four-way valve (860) connected to the first heat exchanger (160) in such a manner as to allow switching between a cocurrent and a countercurrent flow of the second added fluid inside the second heat exchanger (160).

Embodiment 16. The heat pump (100) according to any one of Embodiments 11 to 15, wherein the heat pump system (100) further comprises a first external inlet (102) for receiving the first added fluid and a first external outlet (104) for outputting the first added fluid, and wherein the first external inlet (102) is connectable to a hot conduit (310) of a cold thermal grid system (300) and the first external outlet (104) is connectable to a cold conduit (320) of the cold thermal grid system (300).

Embodiment 17. A method (200) for a heat pump system (100) configured to transfer heat between a first and a second added fluid passing therethrough, said method comprising: measuring (210) a first temperature (T1) of a first added fluid at a position where the first added fluid is input to the heat pump system (100); measuring (220) a second temperature (T2) of a second added fluid at a position where the second added fluid is being output from the heat pump system (100); setting (230), based on the first temperature (T1 ) and the second temperature (T2), an operational mode of the heat pump system (100) to one of:

(a) a heat exchange mode in which the compressor (144) is turned off and in which the first added fluid and the second added fluid are caused to, separated from each other, pass through the third heat exchanger (170) so as to allow heat exchange between the first and the second added fluids by means of the third heat exchanger (170);

(b) a heat pump mode in which the compressor is turned on, in which the first added fluid is caused to pass through the first heat exchanger (120) but not through the third heat exchanger (170), in which the second added fluid is caused to pass through the second heat exchanger (160), and in which the reversible heat pump arrangement (150) is caused to transfer heat from the first heat exchanger (120) to the second heat exchanger (160) by means of the heat pump loop so as to allow heating the second added fluid by means of the reversible heat pump arrangement (150), and

(c) optionally, a cooling mode in which the compressor (144) is turned on, in which the first added fluid is caused to pass through the first heat exchanger (120) but not through the third heat exchanger (170) , in which the second added fluid is caused to pass through the second heat exchanger (160) , and in which the reversible heat pump arrangement (150) is caused to transfer heat from the second heat exchanger (160) to the first heat exchanger (120) by means of the heat pump loop so as to allow cooling the second added fluid by means of the reversible heat pump arrangement (150).

Embodiment 18. The method (200) according to Embodiment 17, wherein the step of setting (230) the heat pump system (100) to an operational mode of the heat pump system (100) comprises: setting the heat pump system (100) to the heat exchange mode in response to the first temperature (T1 ) being between the second temperature

(T2) minus a first constant (K1 ) and the second temperature (T2) plus a second constant (K2); setting the heat pump system (100) to the heat pump mode in response to the first temperature (T1 ) being equal to the second temperature (T2) minus the first constant (K1 ) or lower; and optionally, setting the heat pump system (100) to the cooling mode in response to the first temperature (T1) being equal to the second temperature (T2) plus the second constant (K2) or higher. Embodiment 19. A computer program product comprising a non- transitory computer readable medium (700), having stored thereon a computer program comprising program instructions, the computer program being loadable into a data processing unit (720) and configured to cause execution of the method according to Embodiment 17 or 18 when the computer program is run by the data processing unit.