GB2571723A

GB2571723A - Ventilation system including a heat pump

Info

Publication number: GB2571723A
Application number: GB1803526.1A
Authority: GB
Inventors: Lipinski Thomas
Original assignee: VENTIVE Ltd
Current assignee: VENTIVE Ltd
Priority date: 2018-03-05
Filing date: 2018-03-05
Publication date: 2019-09-11
Anticipated expiration: 2038-03-05
Also published as: GB2571723B; GB201803526D0

Abstract

A ventilation system 100 for a building includes incoming flow path 102, outgoing flow path 103 and heat-pump 104 to compress and expand a working fluid in a circuit 105. The incoming flow path includes a first heat exchanger 108 and the outgoing flow path has a second heat exchanger 109. The ventilation system operates in a first passive mode, in which the heat-pump is inactive and at least one of a second active mode, where the incoming air is cooled, and a third active mode where the incoming air is heated. The system may include a reversing valve 110 to reverse the flow of working fluid to switch between the second and third modes. Fans are not used to mechanically move the air, the air being moved by the passive stack effect which may be controlled by the degree of cooling or heating of the incoming air. The air flow may be further modified using a cowl (300 fig.3) attached to the outgoing flow path 103. The heat exchanger may be arranged over a lip (303 fig.3) such that when the system is in the third mode the outgoing cooled air does not return to room 101 by convection.

Description

VENTILATION SYSTEM INCLUDING A HEAT PUMP

The present disclosure relates to a ventilation system that includes a heat pump. In particular, it relates to a ventilation system, such as a non-fanned passive ventilation system, that includes a heat pump to transfer heat between an outgoing flow path of the ventilation system and an incoming flow path of the ventilation system.

As buildings are becoming better insulated and more airtight, the need for adequate ventilation, to maintain a healthy indoor environment, is growing in importance. Ventilation systems with heat recovery are known. These systems comprise an outflow duct and an inflow duct and an air to air heat exchange. A first electrically powered fan is used to move air from inside the building to the outside through the outflow duct, while a second electrically powered fan is used to bring fresh air inside through the inflow duct. The heat exchange comprises a region where the inflow duct and outflow duct are separated by a number of heat exchange plates or a thin membrane that allows heat transfer therethrough. Thus, the warm outgoing air is used to heat the cooler incoming air. These systems have been shown to be able to recover up to 90% of the energy of the outgoing air. These systems can therefore provide ventilation without a significant effect on heating requirement. However, if we take account of the electricity used by the fans, the overall saving in energy usage is very small and they are cumbersome to install.

Passive ventilation systems are known that utilise the buoyancy of warmer air to drive the ventilation of buildings; the so called “passive stack effect”. In some or all examples, a passive or “natural” ventilation system is absent of powered fans to drive air through the system and relies on the buoyancy of air causing a flow through passive stacks, e.g. flow paths or ducts. However, these systems have drawbacks because when the temperature of the air outside a building changes relative to the air inside the building the movement of air through the ventilation system can slow, stop and reverse depending on the relative conditions inside and outside the building. This makes passive ventilation systems ineffective in certain conditions. Some examples of passive ventilation systems use a wind-catching cowl, to use the flow of wind outside the building to drive air through the ventilation system. This has its own drawbacks as during still, warm days the desired ventilation rates may not be achieved.

According to a first aspect of the present disclosure there is provided a ventilation system for a building comprising an incoming flow path configured to receive air from outside the building and deliver it to a room inside the building;

an outgoing flow path configured to receive air from at least an upper half of the room and deliver it to outside the building;

a heat pump configured to compress and expand a working fluid in a heat pump circuit to provide a compressed flow and an expanded flow;

a first heat exchanger configured to be mounted in the incoming flow path and coupled to be part of the heat pump circuit and receive one of the expanded flow for transferring thermal energy from the air in the incoming flow path to the working fluid and the compressed flow for transferring thermal energy from the working fluid to the air in the incoming flow path;

a second heat exchanger configured to be mounted in the outgoing flow path and coupled to be part of the circuit and receive the other of expanded flow for transferring thermal energy from the air in the outgoing flow path to the working fluid and the compressed flow for transferring thermal energy from the working fluid to the air in the outgoing flow path;

the ventilation system configured to operate in at least a first mode and at least one of a second mode and a third mode in which;

the first mode comprises a passive mode in which the heat pump is inactive and ventilation is provided by air flow through the incoming and outgoing flow paths;

in the second mode the heat pump is active and configured to provide the expanded flow to the first heat exchanger and the compressed flow to the second heat exchanger, at least to heat air in the outgoing flow path and thereby increase its buoyancy and thereby promote ventilation; and in the third mode the heat pump is active and configured to provide the expanded flow to the second heat exchanger and the compressed flow to the first heat exchanger.

This is advantageous as the compressed flow provided to the second heat exchanger in the second mode is configured to heat air in the outgoing flow path without the use of one or more fans to blow or draw said air across the second heat exchanger, thereby providing a passive ventilation system. Likewise, the expanded flow provided to the first heat exchanger in the second mode is configured to cool air in the incoming flow path without the use of one or more fans to blow or draw said air across the first heat exchanger, thereby providing a passive ventilation system.

This is advantageous as the expanded flow provided to the second heat exchanger in the third mode is configured to cool air in the outgoing flow path without the use of one or more fans to blow or draw said air across the second heat exchanger, thereby providing a passive ventilation system. Likewise, the compressed flow provided to the first heat exchanger in the third mode is configured to heat air in the incoming flow path without the use of one or more fans to blow or draw said air across the first heat exchanger, thereby providing a passive ventilation system.

This apparatus is advantageous as it is configured to provide passive ventilation (e.g. natural, unpowered) in the first mode as well as in the second and third modes. Further, the use of a heat pump to passively exchange thermal energy between the air in the incoming and outgoing flow paths has been found to be advantageous as the air flow rate through the flow paths may naturally be relatively balanced, due to induced changes in air buoyancy, leading to an efficient ventilation system.

In one or more examples, the ventilation system includes a reversing valve configured to control the flow of the compressed flow and the expanded flow to the first and second heat exchangers, and wherein the ventilation system is configured to selectively operate in at least the first, second and third modes based on control of at least the reversing valve and the heat pump.

In one or more examples, the ventilation system is configured to control a rate at which the heat pump is configured to pump thermal energy by way of the working fluid between the first exchanger and the second heat exchanger based on one or more of:

(i) a measure of the air flow through the outgoing flow path;

(ii) a measure of the air flow through the incoming flow path;

(iii) a measure of the temperature of the air outside the building;

(iv) a measure of the temperature difference between the temperature of the working fluid entering one of the first and second heat exchanger and the temperature of the working fluid leaving the one of the first and second heat exchanger; and (v) a measure of the air temperature within one or both of the incoming and outgoing flow paths.

In one or more examples, said control is used to provide one or both of a desired ventilation rate for the room or building or a desired temperature for the room or building or to ensure the heat pump operates within predetermined operating limits. This is advantageous because the ventilation system is passive and therefore there is no guarantee of air flow over the heat exchangers, the careful control of the heat pump is important to achieve the desired ventilation and/or temperature set-point while ensuring the flow of air over the first and second heat exchangers is sufficient for the heat pump to operate within its predetermined operating limits, such as without overheating.

In one or more examples, the ventilation system comprises an elongate tubular body extending between the room and outside the building, the body including the incoming flow path and the outgoing flow path wherein the incoming flow path and the outgoing flow path each include an opening into the room substantially adjacent one another and configured to be arranged in a ceiling of the room, wherein an opening into the outgoing flow path from the room is configured to be higher than an opening from the incoming flow path into the room.

In one or more examples, the incoming flow path comprises an opening into the room configured for location in a floor or a lower half of a wall of the room and the outgoing flow path comprises an opening into the room configured for location in a ceiling or an upper half of a wall of the room. This configuration may be advantageous as the placement of the openings into the room may be important for effective provision of ventilation over the various modes of operation.

In one or more examples, the incoming flow path is configured to be mounted to deliver air to at least a lower half of the room.

In one or more examples, the ventilation system includes a cowl configured to be coupled to at least the outgoing flow path, the cowl configured to catch a flow of wind outside the building and shaped to create, by way of the flow of wind, a low-pressure region adjacent an opening of the outgoing flow path to draw air from the room, the low pressure region having a lower pressure relative to the air pressure in the outgoing flow path.

In one or more examples, the ventilation system is configured to provide for control of the heat pump to control a rate of air flow through at least one of the incoming and outgoing flow paths to a desired set-point.

In one or more examples, the ventilation system is configured to: (i) provide for control of the heat pump to increase a rate of air flow through at least one of the incoming and outgoing flow paths to a desired set-point; and (ii) monitor a response in the rate of air flow to said control of the heat pump to thereby ensure the heat pump is exchanging thermal energy with the air flow at a sufficient rate to operate within predetermined operating limits, and, if the response is less than a predetermined expected-change value provide for control of the heat pump to reduce its output.

In one or more examples, the ventilation system is configured to: (i) provide for control of the heat pump to one of increase and decrease a temperature of air entering the room from the incoming flow path to a desired set-point; and (ii) monitor a response of the rate of air flow to said control of the heat pump to thereby ensure the heat pump is exchanging thermal energy with the air flow at a sufficient rate to operate within predetermined operating limits, and, if the response is less than a predetermined expected-change value provide for control of the heat pump to reduce its output.

In one or more examples, the building includes at least two rooms and the incoming flow path is configured to receive air from outside the building and deliver it to a first of said at least two rooms inside the building; and the outgoing flow path is configured to receive air from a second of said at least two rooms and deliver it to outside the building, wherein the first room is absent of an outgoing flow path.

In one or more examples, the heat pump of the ventilation system is configured to operate such that thermal energy received from one of:

(i) the air of the outgoing flow path by the second heat exchanger when the expanded flow is provided to the second heat exchanger; and (ii) the air of the incoming flow path by the first heat exchanger when the expanded flow is provided to the first heat exchange;

is configured to be provided to one or more of a hot water store for providing hot water for the building or room, an energy store for storing thermal energy for later use or one or more space heaters for use in providing space heating for the building or room.

In one or more examples, the heat pump circuit is reconfigurable and the ventilation system is configured to control the flow of at least the compressed flow between one of the first and second heat exchangers and a third heat exchanger provided in a hot water store or for use in providing thermal energy to a space heater, said control based on one or more of (i) user input, (ii) air flow rate in the outgoing flow path; and (iii) air flow rate in the incoming flow path.

In one or more examples:

the second heat exchanger is configured to be located in the outgoing flow path nearer to a second opening to outside than a first opening from the room; and the first heat exchanger is configured to be located in the incoming flow path nearer to a second opening into the room than a first opening from outside.

In one or more examples, the outgoing flow path includes a cowl that comprises a bend between an upwardly extending section configured to be coupled to receive air from the room and a downwardly extending section that includes an opening to outside the building.

in one or more examples, the second heat exchanger is arranged in the downwardly extending section and wherein the opening to outside the building of the cowl is configured to be arranged higher than the opening into the outgoing flow path from the room.

In one or more examples, the second heat exchanger comprises a first-second heat exchanger and the ventilation system includes a second-second heat exchanger, the first-second heat exchanger arranged in the upwardly extending section and secondsecond heat exchanger arranged in the downwardly extending section, wherein the heat pump circuit is configurable such that the first-second heat exchanger and the secondsecond heat exchanger are individually operable to receive the working fluid.

In one or more examples, the ventilation system is configured to selectively operate in a no-ventilation mode in which;

(i) the expanded flow is provided to the second heat exchanger;

(ii) air from outside is mechanically driven across the second heat exchanger;

(iii) the outgoing flow path is at least partially blocked upstream of the second heat exchanger; and (iv) thermal energy of the compressed flow is provided to one or both of an energy store and one or more space heaters configured to provide heating to the room and/or building.

This feature is advantageous as the configuration of the ventilation system allows for operation to exchange thermal energy between the flow paths as well as operation as an air source heat pump. This feature may comprise an aspect of the disclosure.

According to a second aspect of the present disclosure there is provided a ventilation system for a building comprising an incoming flow path configured to receive air from outside the building and deliver it to a room inside the building;

an outgoing flow path configured to receive air from the room and deliver it to outside the building;

the ventilation system configured to operate in at least an exchange mode and at least an air-source-heat-pump mode;

wherein in the exchange mode thermal energy is transferred between air in the outgoing flow path and air in the incoming flow path by the action of the heat pump and the first and second heat exchangers;

wherein in the air-source-heat-pump mode, the expanded flow is provided to the second heat exchanger and the compressed flow is provided to one or more of an energy store, a hot water store for heating water, and one or more space heaters.

In one or more examples, in the exchange mode ventilation of the room by way of the flow of air through the incoming and outgoing flow paths is provided passively, and in the air-source-heat-pump mode the ventilation system is configured to mechanically drive outside air across the second heat exchanger. In one or more examples, the ventilation system is configured to reconfigure the outgoing flow path in the exchange mode and airsource-heat-pump mode, wherein in the air-source-heat-pump mode, the outgoing flow path is at least partially blocked between the room and the second heat exchanger and configured to provide for outside air to flow through at least part of the outgoing flow path across the second heat exchanger, and, in the exchange mode, the flow of outside air through the outgoing flow path is at least partially blocked and the outgoing flow path is configured to provide for flow from the room to outside.

According to a third aspect of the disclosure we provide a kit of parts configured to provide the ventilation system of the first aspect.

According to a fourth aspect we provide a method of operating a ventilation system according to the first aspect comprising controlling the operation of the heat pump to control the buoyancy of air in one or both of the incoming and outgoing flow paths and thereby an air flow rate through the ventilation system.

The figures and Detailed Description that follow also exemplify various example embodiments. Various example embodiments may be more completely understood in consideration of the following Detailed Description in connection with the accompanying Drawings.

One or more embodiments will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 shows a diagram illustrating an example ventilation system comprising a first embodiment in a first state;

Figure 2 shows a diagram illustrating the example ventilation system of the first embodiment in a second state;

Figure 3 shows an example roof cowl for the ventilation apparatus.

Figures 4A-4D show a second embodiment of a ventilation apparatus in four different modes of operation;

Figures 5A-5D show a third embodiment of a ventilation apparatus in four different modes of operation;

Figures 6A-6D show a fourth embodiment of a ventilation apparatus in four different modes of operation;

Figure 7 shows a further embodiment of the ventilation system of figure 1 but with the heat pump circuit including one or both of an optional energy store branch and an optional space heater interface; and

Figure 8 shows a second example roof cowl configured to selectively provide the ventilation system with an air-source heat pump mode.

The examples that follow relate to a ventilation system and, in one or more examples, a passive ventilation system. A passive ventilation system may comprise a ventilation system that is absent of mechanical air-moving means, such as fans, that act to drive air through the ventilation system by physically pushing it with blades and the like. The examples described herein include a heat pump configured to transfer thermal energy from one part of the ventilation system to another. The heat pump is configured to use a working fluid that is pumped through a heat pump circuit, the heat pump circuit including a compressor configured to compress, and thereby heat, the working fluid and an expansion device configured to allow the working fluid to expand, and thereby cool. The heat pump circuit including a first heat exchanger and a second heat exchanger to each receive one of the compressed working fluid flow and the expanded working fluid flow, to provide for heat exchange with the air surrounding the first and second heat exchangers.

Figure 1 shows an example ventilation system 100 for a building for ventilating a room 101 within the building. The diagram shows the ventilation system applied to a single room, although it will be appreciated that the room may be of a plurality of rooms in the building. The room may comprise a room within a domestic dwelling, such as a living room, bedroom or kitchen; a room within a commercial building, such as warehouse space, office or shop floor; a classroom of a school, a garage, a cabin or any other living or occupiable space within a building room.

The ventilation system 100 includes an incoming flow path 102 and an outgoing flow path 103. The incoming flow path is configured to receive air from outside the building and deliver it to the room 101 inside the building. The outgoing flow path 103 is configured to receive air from inside the room and deliver it to outside the building.

In one or more examples, the outgoing flow path 103 is configured to receive air from at least an upper half of the room 101. A passive ventilation system is configured to achieve air throughput without fans and therefore by positioning an opening into outgoing flow path 103 in an upper half of the room, the opening will receive warmer air that is rising in the room relative to cooler air which typically sinks towards the floor. Accordingly, the outgoing flow path may include an opening into the room that is located in the ceiling or close to the ceiling, such as in a wall at a position in an upper half of the walls nearer the ceiling than the floor. In other examples, the outgoing flow path may include a conduit that extends into the room from the ceiling or walls and at a distal end includes said opening that may be located in an upper half of the volume of the room.

The outgoing flow path 103 may comprise a conduit or other elongate tubular structure which includes a first opening into the room 101 and a second opening, such as at an opposite end, that opens to atmosphere at a location outside the building. The tubular structure may have any shaped cross-section.

The incoming flow path 102 may be located at any point in the room. In one or more examples, the incoming flow path may include an opening that is positioned in a lower half of the room, such as in the floor or close to the floor, such as in a wall at a position in a lower half of the walls nearer the floor than the ceiling.

The incoming flow path 102 may comprise a conduit or other elongate tubular structure which includes a first opening that opens to atmosphere at a location outside the building and a second opening, such as at an opposite end, that opens into the room 101. The tubular structure may have any shaped cross-section.

The ventilation system includes a heat pump 104 configured to compress and expand a working fluid in a heat pump circuit 105 to provide a compressed flow in which heat of the working fluid is typically released and an expanded flow in which heat is typically absorbed by the working fluid. The heat pump 104 may include a closed heat pump circuit through which the working fluid is pumped, the circuit including a compressor 106, an expansion device 107, a first heat exchanger 108 and a second heat exchanger 109. The compressor 106 may be configured to compress the working fluid such that it comprises a liquid or a gas in a higher pressure state in a first portion of the heat pump circuit downstream of the compressor 106 and upstream of the expansion device 107. The expansion device 107 may be configured to allow for expansion or expand the working fluid such that it comprises a gas in a lower pressure state in a different, second portion of the heat pump circuit downstream of the expansion device 107 and upstream of the compressor 106. The expansion device 107 may comprise a capillary tube and a thermal expansion valve or any other suitable means known to those skilled in the art of heat pumps. The heat pump 104 may include a pump (not shown) to drive the working fluid through the heat pump circuit 105. The working fluid may be any suitable refrigerant.

The first heat exchanger 108 is configured to be mounted in the incoming flow path 102 and is coupled in part of the heat pump circuit 105 to receive one of the expanded flow and the compressed flow. The second heat exchanger 109 is configured to be mounted in the outgoing flow path 103 and is coupled in part of the heat pump circuit 105 to receive the other of expanded flow and the compressed flow.

Figures 1 and 2 show the same general layout of the ventilation system 100 and heat pump 104, except that a reversing valve 110 is configured to control which of the first and second heat exchangers 108, 109 receives the compressed flow and thereby the other of the first and second heat exchangers 108, 109 receives the expanded flow. In figure 1, the reversing valve is in a first state in which the first heat exchanger 108 receives the compressed flow from the compressor 106 and the second heat exchanger 109 receives the expanded flow from the expansion device 107. in figure 2, the reversing valve 110 is in a second state, in which the direction of flow through the heat pump circuit is effectively reversed. Accordingly, the second heat exchanger 109 receives the compressed flow from the compressor 106 and the first heat exchanger 108 receives the expanded flow from the expansion device 107. The triangular arrows of figures 1 and 2 illustrate the direction of the heat pump working fluid flow with the reversing valve 110 in its two alternate operating states. Accordingly, the reversing valve causes the reversal of flow of the working fluid in at least a part of the heat pump circuit 105.

It will be appreciated that in one or more other embodiments, the reversing valve 110 may not be present and the heat pump circuit 110 may be of a fixed configuration in which the working fluid always passes through the components in the same order. Accordingly, one of the first and second heat exchangers 108, 109 may receive the compressed flow and the other of the first and second heat exchangers 108, 109 may receive the expanded flow. A selected one of the different seasonal modes described below may be provided by such a ventilation system having a heat pump circuit of a fixed configuration.

The ventilation system 100 is configured to operate in at least a first mode and at least one of a second mode and a third mode, in one or more examples, all of the modes provide passive ventilation flow wherein the movement of air through the incoming flow path 102 and outgoing flow path 103 is provided by air buoyancy and, optionally and additionally, by outside wind flow using a wind catching cowl. Thus, the ventilation system 100 may be absent of fans to move air through the ventilation system. The ventilation system 100 may be absent of fans, in particular, to move air over both the first and second heat exchanger 108, 109.

The first mode comprises a passive mode in which the heat pump 104 is inactive, in an inactive state, the compressor 106 may be unpowered and/or the working fluid may not be circulated through the heat pump circuit 105. in the passive mode, the movement of air through the flow paths of the ventilation system may be provided exclusively by air buoyancy, also known as passive stack effect ventilation, and optionally assisted by a wind catching cowl that creates pressure gradients in the ventilation system flow paths by a venturi effect using the flow of wind.

In one or more examples, one of the second and third modes may be provided. The second and third modes may comprise active modes in which the heat pump 104 is active such that heat from the air in one of the flow paths 102, 103 is absorbed by the working fluid and transferred to the air in the other of the flow paths 103, 102 by way of the working fluid being pumped and therefore circulating around the heat pump circuit 105. Thus, the ventilation system 100 may be switchable between the first mode and the second mode or the first mode and the third mode depending on when the heat pump 104 is active and inactive. Such a two-mode system may be provided in examples absent of the reversing valve 110. In one or more other examples, both of the second and third modes may be provided in addition to the first mode. Thus, the ventilation system may be switchable between the first mode, the second mode and the third mode depending on when the heat pump 104 is active and inactive and the state of the reversing valve 110 when the heat pump is active.

The second mode may comprise a “summer cooling” mode. The second mode is intended for use in the summer wherein the air temperature inside the room of the building is greater than that desired. It will be appreciated that it may be used in other seasons. Accordingly, it is desirable for the ventilation system 100 to deliver air having a temperature that is cooler than the air outside and inside the building into the room 101. The heat pump 104 is configured to provide the expanded flow to the first heat exchanger 108 in the incoming flow path 102 and the compressed flow to the second heat exchanger 109 to at least heat air in the outgoing flow path 103. This configuration is shown in figure 2. The heat pump 104 is therefore configured to provide the “cold” expanded working fluid to the first heat exchanger 108 and thereby remove heat from the air in the incoming flow path 102. Further, the heat pump 104 is therefore configured to provide the “hot” compressed working fluid to the second heat exchanger 109 and thereby heat the air in the outgoing flow path 103.

The heating of the outgoing air increases its buoyancy in the outgoing flow path. The outgoing flow path, in this and other embodiments, extends upwardly (from its opening into the room to its opening to atmosphere) and therefore the heating of the outgoing air by the heat pump 104 promotes ventilation by causing the air in the outgoing air path 103 to rise more quickly and draw in more air from the room 101 into its first opening. The air entering the room 101 will be cooler by the action of the heat pump 104, thereby providing an incoming flow of cooler air into the room 101. If the room is reasonably sealed, the increased rate of air in the outgoing flow path 103 due to the heating of the air therein may cause more air to be drawn in through the incoming flow path 102. In one or more examples, the incoming flow path 102 is configured to extend downwardly from its opening to atmosphere through to its opening into the room. Accordingly, air that is cooled by the action of the heat pump will become denser and sink along the incoming flow path 102 and therefore into the room 101. In one or more examples the incoming flow path and the outgoing flow path may include one-way valve to restrict outgoing flow in the incoming flow path and restrict incoming flow in the outgoing flow path.

The third mode may comprise a “winter heating” mode. The third mode is intended for use in the winter wherein the air temperature inside the room of the building is less than that desired. It will be appreciated that it may be used in other seasons. Accordingly, it is desirable for the ventilation system 100 to deliver air having a temperature that is warmer than the air outside of the building and, in some cases, the air inside the building into the room 101. The heat pump 104 is configured to provide the expanded flow to the second heat exchanger 109 in the outgoing flow path 103 and the compressed flow to the first heat exchanger 108 to at least heat air in the incoming flow path 102. This configuration is shown in figure 1. The heat pump 104 is therefore configured to provide the “hot” compressed working fluid to the first heat exchanger 108 and thereby heat the air in the incoming flow path 102. Further, the heat pump 104 is configured to provide the “cool” expanded working fluid to the first heat exchanger 108 and thereby cool the air in the outgoing flow path 103.

The cooling of the air in the outgoing flow path decreases its buoyancy in the outgoing flow path 103. The cooling of air in the outgoing flow path may need to be carefully controlled to ensure that the passive stack effect is maintained, and that the air exits to atmosphere via the outgoing flow path. Further, the cooling of the air in the outgoing flow path 103 may be controlled to prevent reverse flow into the room 101 from the outgoing flow path 103. The air temperature inside the room will typically be warm given that the heat pump 104 is heating air that is entering via the incoming flow path 102. The air temperature outside the building will typically be cold given this mode is used in winter time. Therefore, the ventilation system 100 may be configured to control or limit the operation or power to heat pump 104 to control the amount of cooling applied to the outgoing air flow to maintain the buoyancy of the air leaving via the outgoing flow path 103. Thus, the operation and/or power of the heat pump may be controlled based on one or more of the outside air temperature, the air temperature in the room 101 and the air flow rate through the outgoing flow path 103 to maintain a non-zero, positive outgoing flow of air in the outgoing flow path 103.

In one or more examples, as exemplified in figure 3, the outgoing flow path 103 may be configured to include a cowl 300 at its opening to atmosphere, wherein the cowl 300 provides an extension to the outgoing flow path 103 and includes a bend 301 between an upwardly extending section 302 and a downwardly extending section 303 that includes the (e.g. only) opening 304 to atmosphere at its end. The second heat exchanger 109 may be positioned in the downwardly extending section 303. Accordingly, air cooled by the second heat exchanger 109 (with its increased density) may therefore sink down along the downwardly extending section 303 to atmosphere. The outgoing flow path cowl 300 may advantageously include a scoop 305 positioned directly below (and/or downstream and below) the second heat exchanger 109 to catch cooled air that sinks following interaction with the second heat exchanger 109 and that acts to prevent said cooled air from sinking back into the upwardly extending section 302 and therefore into the room 101 and instead directs it out of the cowl and therefore the outgoing flow path. Further, the sinking of cooled air in the downwardly extending section 303 may lead to a low-pressure region in the bend 301, which may act to promote air flow through the outgoing flow path by drawing air up from the room 101, through the outgoing flow path and the upwardly extending section 302. in one or more examples, the cowl is insulated (e.g. over all surfaces) so that the temperature of the air therein can be carefully controlled. Thus, the cooling of air in the outgoing flow path with the cowl of figure 3 (i.e. having a downwardly inclined section to house the heat exchanger) may promote ventilation.

In one or more examples, the second heat exchanger 109 may be used to heat the air in the cowl. The hot air will rise and collect in the bend 301, but will also escape out of the open end 304. Thus, provided the opening 304 is higher than the inlet from the room 101 into the outgoing flow path 109, air flow through the outgoing flow path may be promoted by the action of the heat pump, in any of the examples described herein or in other examples, at least two second heat exchangers 109 may be provided in the outgoing flow path at different positions therein, wherein the heat pump can selectively provide working fluid to the two second heat exchangers. One of the heat exchangers may be located in the downwardly extending section 303 and the other in the upwardly inclined section 302. The second heat exchanger in the upwardly extending section may be configured to receive working fluid and not the other when the compressed flow is provided to the second heat exchangers while the second heat exchanger in the downwardly extending section may be configured to receive working fluid and not the other when the expanded flow is provided to the second heat exchangers.

In one or more examples (not shown), the cowl is provided with two openings to outside 103 in a bifurcated arrangement: a first outgoing opening extending upwardly from a divergent point within the outgoing flow path 103 and a second outgoing opening extending downwardly from the divergent point with the outgoing flow path 103. The second heat exchanger 109 may be arranged at the divergent point. Accordingly, in the second mode, air heated by the second heat exchanger 109 will rise out of the outgoing flow path by way of the first outgoing opening and not (or less so) by the second outgoing opening and in the third mode air cooled by the second heat exchanger will sink out of the outgoing flow path by way of the second outgoing opening and not (or less so) by the first outgoing opening. This bifurcated opening may include an opening blocking means to selectively block one of the first and second outgoing openings and wherein the ventilation system is configured to control the flap based on the provision of the second or third modes of operation. It will be appreciated that the opening blocking means may comprise one or more of a valve(s), a flap(s) and a louver(s), among other means for example.

The air entering the room 101 will be heated by the action of the heat pump 104 thereby providing an incoming flow of heated air into the room 101. In one or more examples, the incoming flow path 102 is configured to extend upwardly from its opening to atmosphere through to its opening into the room 101. Accordingly, air that is heated by the action of the heat pump 104 will become less dense and rise along the incoming flow path 102 and therefore into the room 101. The rising air in the incoming flow path may assist in drawing more air into the incoming flow path. In one or more examples, the incoming flow path may be reconfigurable, such as automatically reconfigurable, such that the incoming flow path 102 may extend upwardly or downwardly based on the ventilation system 100 being in the second or third modes. One or more flaps may be provided in the incoming flow path to achieve this.

In one or more examples, the ventilation system includes a plurality of outgoing flow paths, such as arranged in different rooms of a building. In one or more examples, the ventilation system includes a greater number of outgoing flow paths than incoming flow paths. In one or more examples, the one or more incoming flow paths are configured to be located in different rooms of the building to the greater number of outgoing flow paths. This may be advantageous as a building having a plurality of rooms may be effectively ventilated by providing a net air flow from the room having the incoming flow path through to the room having the outgoing flow path, provided said rooms provide for air flow therebetween by, for example, being adjacent to one another and not air sealed from one another. In one or more examples, the incoming flow path 102 may be provided in a hall way, which provides access to a plurality of other rooms. In one or more examples, two or more of the plurality of other rooms are provided with the outgoing flow path. Accordingly, we may provide a method of installation of the ventilation system based on this principal.

In the examples described above, the first heat exchanger 108 and the second heat exchanger 109 are described as being mounted within a conduit that comprises the incoming and outgoing flow paths. The positioning of the heat exchanger 108, 109 in the conduit may affect the performance of the ventilation system. For example, in one or more examples it may be advantageous to position the heat exchanger 108, 109 in a central section of the conduit spaced from the first and second openings. Placement of the heat exchanger in this way may provide the most benefit in the promotion of the passive stack effect. In one or more other examples, it may be advantageous to position the heat exchanger 108, 109 adjacent the first and second openings and therefore towards one end of the flow path 102, 103, such as shown in figure 3. in one or more preferred examples, the second heat exchanger 109 is located in the outgoing flow path nearer to the second opening than the first opening (and preferably adjacent the second opening) and the first heat exchanger 108 is located in the incoming flow path nearer to the second opening into the room than the first opening (and preferably adjacent the second opening into the room). In one or more preferred examples, the outgoing flow path is provided with dampers (of shut-off or modulating type, for example) located in a central section of the flow path. In one or more examples the incoming flow path is provided with dampers (shut-off or modulating) located nearer to the first opening from atmosphere. This configuration has been found to be advantageous to help prevent temperature induced ‘blowbacks’ or backdraught. In one or more examples, the dampers comprise at least one of a valve, one or more moveable louvres or a moveable flap configured to regulate air flow through the respective flow path. The damper may thus provide a variable restriction in the flow path. The damper may be configured to provide a fully open position or a fully closed position (e.g. blocking the flow path) or one or more intermediate positions. In one or more examples, the ventilation system may be configured to control the dampers in response to one or more of a user-request, a desired temperature set-point or a desired ventilation rate set-point. For example, it may be necessary to slightly restrict the airflow in the incoming flow path so that it is resident therein for longer to increase its temperature (or reduce droughts) in periods of really cold weather when the ventilation system is operating in the third mode. It will be appreciated that when providing a passive ventilation system, the control of the air flow is important due to the lack of mechanical air driving means, such as fans, to guarantee or control the flow rate. Accordingly, the control of a damper may be advantageous in such passive ventilation systems.

In summary, the ventilation system 100 may provide at least one incoming flow path 102 to introduce fresh air to the room 101 and at least one outgoing flow path 103 to vent stale air from the room 101, the system 100 including a heat pump 104 having a heat pump circuit for the pumping of a working fluid therethrough via at least one compressor and at least one expansion device 107, the heat pump circuit configured to extend (e.g. exclusively) between one or more heat exchangers located in each of the incoming flow path(s) 102 and the outgoing flow path(s) 103.

Heat pumps 104, also known as air conditioning units, are typically operated with fans that blow air over at least one of their heat exchangers. Accordingly, a heat pump as conventionally used has a known or guaranteed quantity of air flowing over the heat exchangers and can be operated accordingly. In the implementation of the present disclosure, there are no fans to guarantee a particular air flow. In fact, the temperature of the working fluid in heat exchangers 108, 109, or the amount of thermal energy they transfer to the air around them within the incoming and outgoing flow paths 102, 103 may be used to control the rate of air flow over them (in addition to any naturally occurring passive stack effects based on the room air temperature and outside air temperature). Accordingly, the heat pump 104, when used in a passive ventilation system may need to be controlled differently.

In one or more examples, the operation of the heat pump 104 may be controlled to realise a desired ventilation flow rate set-point. In one or more examples, the desired ventilation flow rate set-point may be determined based on one or more sensors that determine one or more of room temperature, room humidity and carbon dioxide concentrations in the room 101. The set-point may be user-set or set at the time of installation of the ventilation system or any other time. A current ventilation flow rate may be measured based on the air flow through one or both of the outgoing flow path and the incoming flow path. Accordingly, the ventilation system 100 may include one or more air flow rate sensors to provide a measure of a current ventilation flow rate provided by the system 100. The ventilation system 100 may therefore be configured, based on the current ventilation flow rate, to control the heat pump 104 to increase or decrease the current ventilation flow rate to meet the desired set-point. The control of the heat pump may be achieved by one or more of (i) control of the output of the compressor 106, (ii) control of the flow rate of the working fluid provided by the pump that circulates the working fluid in the heat pump circuit, and (iii) time modulation of the heat pump between active and inactive modes. Thus, to increase the ventilation flow rate, the heat pump may be controlled to increase its output to increase the heating (or cooling depending on the configuration of the outgoing flow path or the desired internal temperature) of the air in the outgoing flow path and promote the stack effect therein. To decrease the flow rate, the output of the heat pump may be decreased at least in the second, summer, mode. In the third, winter, mode the output of the heat pump 104 may be increased to cause a decrease in the ventilation flow rate (depending on the configuration of the cowl 103 and whether or not cold air sinking out of the cowl 300 draws air out of the outgoing flow path 103 from the room 101).

In other examples, a measure of the amount of heat transferred to the air by one or both of the heat exchanger may be used to control the heat pump 104. Thus, in one or more examples, the ventilation system 100 may include temperature sensors configured to measure the temperature of the working fluid entering the heat exchanger 108, 109 and the temperature of the working fluid leaving the same heat exchanger 108, 109 and the system may be configured to control the heat pump 104 based on a difference between the temperatures. As this temperature difference may be related to the air flow across the heat exchanger, the temperature difference may be used in addition to or as an alternative to the above-mentioned air flow rate sensor(s). In one or more examples, a measure of the temperature of the air in one or both of the incoming and outgoing flow paths may be used to control the heat pump. In one or more examples, the temperature of the air in one or both of the incoming and outgoing flow paths relative to a measure of the air in one or both of the room or outside may be used to control the heat pump, as this difference may provide an indication of relative buoyancy of the air and therefore the flow rate (as well as the performance of the heat pump).

Regardless of how the air flow over the heat exchanger is determined, the output of the heat pump may be controlled based on the degree to which he heat exchangers 108, 109 can transfer heat to/from the air flow in the incoming and outgoing flow paths. Accordingly, in one or more examples, the heat pump 104 adjusts to the airflow not the other way around. This may be achievable because the flow rate of the outgoing air is more less proportional to the flow rate of the incoming air (the heat pump exchanges thermal energy between the two). Accordingly, in one or more examples, because the ventilation system uses heat exchangers in both incoming and outgoing flow paths of the passive system, any increase in flow rate on one side is likely replicated at the other side making the system almost self-balancing. Thus, in a passive ventilation system, rather than the rate of heat exchange or compressor duty being designed for a set air flow, the air flow is the variable factor while heat pump either switches on/off intermittently or modulates to match it.

In summary, the air flow across the heat exchangers 108, 109 is not guaranteed because temperature changes in the rooms or wind from outside may stop any passive stack effect airflow. Further, as mentioned above, the temperature of the heat exchangers relative to the air surrounding them in the flow paths also contributes to air flow over the heat exchangers 108, 109.

Thus, the ventilation system may be configured to: (i) provide for control of the heat pump to increase (or decrease) a rate of airflow through at least one of the incoming and outgoing flow paths to a desired set-point; while (ii) monitoring a response, i.e. a change, in the rate of air flow following said control of the heat pump to ensure the heat pump is exchanging thermal energy with the air flow at a sufficient rate to operate within predetermined operating limits. As an example, it may be desirable to increase the ventilation rate for the room (e.g. the amount of stale air in the room replaced with fresh air from outside by the ventilation system per unit time) and accordingly, the operating time/power to the heat pump may be increased, for example, to heat the air in the outgoing flow path 103. The air in the outgoing flow path may respond by rising more quickly due to it being heated and more buoyant thereby increasing the flow rate and thus the ventilation of the room. The power level to the heat pump may therefore be maintained until the desired set-point flow rate is achieved. However, if a strong external wind or other factor hindered the escape of air from the outgoing flow path, the heated air in the outgoing flow path may not be able to flow and thus there may be a less than expected response in flow rate (such as a response below a predetermined expectedchange threshold value). This may lead to the heat pump overheating or operating outside one or more operating limits. Accordingly, the power or duty of the heat pump may need to be at least temporarily reduced for at least predetermined pause-timeperiod. A similar approach may be taken when operating the ventilation system to obtain a desired incoming air temperature. Thus, the ventilation system may be configured to:

(i) provide for control of the heat pump to decrease (or increase) the temperature of air entering the room from the incoming flow path to a desired set-point; while (ii) monitoring a response of the rate of air fiow to said control of the heat pump to ensure the heat pump is exchanging thermal energy with the air flow at a sufficient rate to operate within predetermined operating limits. As above, if the response is less than an expected change in flow rate (such as a response below a predetermined expected-change threshold value) the power or duty of the heat pump may need to be at least temporarily reduced for at least predetermined pause-time-period.

In one or more examples, different control schemes may be required depending on the mode of operation. For example, in the second “summer cooling” mode, the heating of air in the outgoing flow path acts to increase air flow therethrough by increasing the buoyancy of the air in the outgoing flow path which can travel up the upwardly inclined flow path. While a passive ventilation system may further assist flow by a venturi effect caused by the flow of wind across a cowl, there are no fans to ensure a flow rate across the heat exchanger. In response to an increase in the cooling demand for the incoming air (e.g. based on a user input or one or more room-based sensors for humidity, temperature and carbon dioxide levels, for example), the ventilation system may be configured to increase the output of the heat pump 104 but the level of increase may be based on a measure of the flow rate through the outgoing flow path to ensure the fiow rate therethrough is sufficient to remove a desired amount of thermal energy from the working fluid. This may prevent the heat pump 104 over heating or operating outside acceptable limits.

For example, in the third “winter heating” mode, the heating of air in the incoming flow path by the heat pump 104 results in a cooling of air in the outgoing flow path thereby decreasing the buoyancy of the air in the outgoing flow path 103 and potentially decreasing the ventilation of the room. While a passive ventilation system may further assist flow by a venturi effect caused by the flow of wind across a cowl, there are no fans to blow the cooled, and therefore less buoyant, air out of the outgoing flow path, in response to an increase in the heating demand for the incoming air (e.g. based on a user input or one or more room-based sensors for humidity, temperature and carbon dioxide levels, for example), the ventilation system may be configured to increase the output of the heat pump 104 but the level of increase may be based on a measure of the flow rate through the outgoing flow path and/or of the outside air temperature. This may prevent the heat pump 104 operating at too high a level that prevents the flow of air for ventilation by stopping the passive stack effect occurring in the outgoing flow path. In other examples, in which the outgoing flow path includes a bend, the cooling of the air in the outgoing flow path at a location in the downwardly inclined section may assist passive ventilation due the cooler air “sinking out” of the outgoing flow path (i.e. gravity driven) and drawing further air from the room up into the outgoing flow path. In this instance, in response to an increase in the heating demand for the incoming air (e.g. based on a user input or one or more room-based sensors for humidity, temperature and carbon dioxide levels, for example), the ventilation system may be configured to increase (or decrease) the output of the heat pump 104 but the level of increase (or decrease) may be based on a measure of the flow rate through the outgoing flow path to ensure the flow rate therethrough is sufficient to remove a desired amount of thermal energy from the working fluid. This may prevent the heat pump 104 over heating or operating outside acceptable limits.

Thus, to summarise, in one or more examples, the ventilation system 100 is configured to control a rate at which the heat pump is configured to pump thermal energy between the first exchanger and the second heat exchanger based on one or more of:

(i) a measure of the air flow through the outgoing flow path;

(ii) a measure of the air flow through the incoming flow path;

(iii) a measure of the temperature of air outside the building;

(iv) a measure of the temperature difference between the temperature of the working fluid entering one of the first and second heat exchanger and the temperature of the working fluid leaving the one of the first and second heat exchanger;

(v) a measure of the air temperature within one or both of the incoming and outgoing flow paths.

This control of the heat pump may be used to effectively maintain the desired buoyancy of air in the outgoing or incoming flow paths and/or or a desired ventilation rate and/or a desired temperature in the room and/or ensure the heat pump operates within its operating limits.

In a passive ventilation system controlling the buoyancy of the air at various locations within the incoming and/or outgoing flow paths 102, 103 may be critical to its performance. In one or more examples, one or both of the incoming and outgoing flow paths may be insulated. In one or more examples, in relation to one or both of the incoming and outgoing flow paths, one end of the flow path may be insulated by a first amount and an opposite end of the flow path may be insulated by a second amount different to the first amount. Accordingly, the difference in insulation may help to control how the air in the flow paths cools or is heated as it flows through to maintain a desired level of buoyancy in a range of different atmospheric/room temperature conditions.

In one or more examples, the heat pump circuit may extend into one or both of the incoming flow path and the outgoing flow path through one of the first and second openings i.e. the open ends of the flow paths. In other examples, the heat pump circuit extends through a wall of the flow paths in order to connect to the respective heat exchanger therein.

Figures 4 to 6 illustrate different embodiments of the ventilation system 100. In particular, the embodiments show different arrangements of the incoming and outgoing flow paths. The sub-figures 4A-D, 5A-D and 6A-D show how the particular arrangement may operate in different seasons, which represent different heating/cooling needs and different indoor and outdoor temperature differences. It will be appreciated that the different seasons/times of day described below in relation to the sub-figures 4A-D, 5A-D and 6A-D are to aid understanding but non-limiting. Accordingly, the configuration of the ventilation system described may be applied in other seasons/times of day as required by the ventilation needs, temperature needs and indoor and outdoor temperature differences at the time. The same reference numerals as used in figures 1 and 2 are used in these figures for the like parts. In figures 4 to 6, various arrows are shown to illustrate the typical flow of air in these embodiments. The black arrows illustrate warm or heated air. The dashed lines illustrate cool or chilled air. The grey arrows illustrate tempered air.

Looking first at figures 4A-4D, a room 101 is shown including the ventilation system 100, which is embodied as a ceiling mounted unit having an elongate tubular body 400. The body 400 may be of square, circular, oval, rectangular, regular or irregular cross-section when viewed along its axis. The cross-section may vary from one end to the other. The body 400 is configured to extend between the room 101 and outside the building 103. The body 400 is configured to include the incoming flow path 102 and the outgoing flow path 103 wherein the incoming flow path and the outgoing flow path each include an opening 401, 402 respectively into the room 101 substantially adjacent one another and configured to be arranged in a ceiling 403 of the room 101. In one or more examples, the opening 402 into the outgoing flow path 103 from the room 101 is configured to be higher than the opening 401 from the incoming flow path 102 into the room 101. The heat pump 104 with its associated heat pump circuit, compressor, expansion device and pump are mounted in the body 400 and are therefore not visible in figure 4. The first and second heat exchangers 108, 109 of the heat pump are mounted within the incoming and outgoing flow paths 102, 103 as before, but are not shown in figure 4 for reasons of clarity.

Figure 4A illustrates the ventilation system 100 in a winter scene and therefore the outside air temperature is typically low at around 0°C and the temperature inside the room is desired to be around 21°C. In figure 4A, the ventilation system 100 may be configured to operate in the third mode, as described above. Accordingly, the heat pump is active and configured to provide the compressed flow of the working fluid to the first heat exchanger 108 located in the incoming flow path 102. Accordingly, thermal energy obtained by the working fluid from the air in the outgoing flow path 103 is used to heat the incoming air. The warmed air is thus provided into the room as shown by arrow 404. This incoming air 404 may be urged into the room by a combination of one or more of the cooler outside air sinking into incoming flow path 102, the wind speed of the outside air driving a flow into the body 400, a pressure difference caused by air leaving the room via the outgoing flow path and the incoming air being less buoyant than the air currently in the room 101 (which may be heated by other means, such as radiators or underfloor heating).

Stale air within the room 101 may be circulated by naturally occurring air currents and/or heated and may thus rise towards the body 400 as shown by arrows 405. The stale air may enter the opening 402 and thus the outgoing flow path 103. The heat pump, in the third mode, is configured to heat the incoming air and it will therefore cool the outgoing air. Cooling the outgoing air may reduce its buoyancy and reduce the flow rate out through the outgoing flow path 103. Thus, the ventilation system 100 may be configured to measure the flow rate through the outgoing flow path 103 (or other parameter indicative thereof) and limit the amount of cooling provided by the heat pump to the outgoing air to ensure that there is an above-zero flow rate in the outgoing direction.

Figure 4B illustrates the ventilation system 100 in a spring or autumn/fall season scene and therefore the outside air temperature may be typically around 12°C and the temperature inside the room is desired to be around 21°C. In these conditions the ventilation system 100 may be configured to operate in the first mode. In the first mode, the heat pump is inactive, and the ventilation system 100 provides ventilation through the same incoming and outgoing flow paths 102, 103 passively (absent of the mechanical movement of air by fans, for example, and reliant on passive stack effect).

In one or more examples, the body 400 may include an air-to-air heat exchange to exchange heat between the air flowing in one of the incoming flow path and the outgoing flow path and air flowing in the other of the incoming flow path and the outgoing flow path.

Accordingly, cooler outside air is received by the body 400 and enters the incoming flow path 102. Stale air heated by internal thermal gains such as occupants and equipment in the room or sunlight through the window or a heating system of the room rises as shown by arrows 406. The air-to-air heat exchanger may be configured to exchange thermal energy from the outgoing heated air to the incoming cooler air and thereby provide tempered air (shown by arrow 407) to the room 101 by way of the incoming flow path 102.

Figure 4C shows a night-time scene during the summer season. The temperature outside the building may be around 15°C while the temperature inside, after being in heated in the sunshine all day or due to internal gains may be warmer than 15°C, such as 20-30°C. In this instance, the ventilation system 100 may be configured to operate in a fourth mode, which may be considered a night-time-cooling mode. In this mode the heat pump is inactive. Hot air in the room 101 may rise as shown by arrows 408 and leave the room by the outgoing flow path 103. Cooler air 409 from outside may be drawn into the room 101 from a vent 410. In this fourth mode, the incoming flow path may temporarily act as an additional outgoing flow path since it is now located above the air inlet 410 or the ventilation system may be configured to close the incoming flow path in the body 400 by way of a movable barrier (not shown) (for example during periods of high wind). The barrier may be automatically closed or manually closed by a user in the fourth mode. A barrier in the vent 410 may be automatically opened in the fourth mode. In one more examples, the barrier in the vent 410 may be automatically closed when operating in other modes.

Figure 4D illustrates the ventilation system 100 in a summer scene and therefore the outside air temperature is typically high at around 25-30°C and the temperature inside the room is desired to be around 18-21°C. In figure 4D, the ventilation system 100 may be configured to operate in the second mode, as described above. Accordingly, the heat pump is active and configured to provide the compressed flow of the working fluid to the second heat exchanger 109 located in the outgoing flow path 103. Accordingly, thermal energy obtained from the air in the incoming flow path 102 is used to heat the outgoing air thereby increasing its buoyancy. The cooled incoming air is thus provided into the room as shown by arrow 411. This cooled air may be at around 18°C. This incoming air 411 is typically cooler than the air already in the room and therefore it may move into the room by a combination of one or more of its reduced buoyancy relative to air already in the room, the wind speed of the outside air driving a flow into the body 400 and a pressure difference caused by air leaving the room via the outgoing flow path.

Hot, stale air within the room 101 may rise towards the body 400 as shown by arrows 412. The stale air may enter the opening 402 and thus the outgoing flow path 103. The heat pump, in the second mode, is configured to cool the incoming air and it will therefore heat the outgoing air. Heating the outgoing air may increase its buoyancy and increase the flow rate out through the outgoing flow path 103. Thus, the ventilation system 100 may be configured to measure the flow rate through the outgoing flow path 103 and limit the amount of cooling provided by the heat pump to the incoming air to ensure that the heat pump is operating at a level where the air flow through the outgoing flow path is sufficient to remove the thermal energy and prevent the heat pump from exceeding any operating conditions.

Thus, when cooling the incoming air, the heat pump acts to increase the buoyancy of the air in the outgoing flow path and reduce the buoyancy of the air in the incoming flow path which act together to improve the ventilation rate through the room 101. However, as the temperature in the room decreases, the difference in buoyancy between the air entering the room relative to that air already in the room decreases. Thus, the heat pump may be controlled to reduce the power or duty of the heat pump to account for the reduced rate of flow over the heat exchangers in the incoming and outgoing flow paths based on any of the above-mentioned sensors.

Figures 5A to 5D show the same operating conditions as corresponding figures 4A to 4D, although in the figures 5A-5D the arrangement of the ventilation system is different.

In this example and other examples, the incoming flow path 102 may be configured to be mounted to deliver air into at least a lower half of the room 101. In this example, the incoming flow path 102 is mounted in a wall 500 in a lower half of the room 101.

In this example and other examples, the outgoing flow path 103 may be configured to be mounted to receive air from an upper half of the room 101, such as near ceiling. In this example, the outgoing flow path 103 is mounted in a wall 500 in an upper half of the room 101. In an alternative example, the outgoing flow path 103 may be mounted in the ceiling. This mounting arrangement of the incoming and outgoing flow paths may be suitable for rooms, schools, universities, hospitals, offices, and apartments or flats where there may not be access to a roof through the ceiling, although it will be appreciated the mounting arrangement is not limited to such a setting and may be used in other buildings and/or for other rooms.

As in the other examples, the heat pump and, in particular, the heat pump circuit 105 extends between the incoming flow path 102 and the outgoing flow path 103 by virtue of the first and second heat exchangers 108, 109 being located therein. In this example, the heat pump circuit may include conduits, such as insulated conduits that transfer the heat transfer fluid through or adjacent the wall 500 between the heat exchangers 108, 109 in the flow paths (and the compressor, pump, expansion valve and the like that comprise the heat pump).

In one or more examples, the incoming and outgoing flow paths 102, 103 include nonreturn valves to provide for a one-way flow therein.

In the winter conditions shown in figure 5A, the outside air temperature is typically low at around 0°C and the temperature inside the room is desired to be around 21 °C. In figure 5A, the ventilation system 100 may be configured to operate in the third mode, as described above. Accordingly, the heat pump is active and configured to provide the compressed flow of the working fluid to the first heat exchanger 108 located in the incoming flow path 102. Accordingly, thermal energy obtained from the air in the outgoing flow path 103 is used to heat the incoming air. The warmed air is thus provided into the room 101 as shown by arrow 501. This incoming air 501 may be urged into the room by a combination of one or more of the wind speed of the outside air driving a flow into the incoming flow path 102, a pressure difference caused by air leaving the room via the outgoing flow path 103 and the incoming air being heated by other means, such as radiators or underfloor heating, and rising away from the second opening of the incoming flow path.

Stale air within the room 101 may be circulated by naturally occurring air currents and/or heated and may thus rise and circulate back towards the outgoing flow path 103 as shown by arrow 502. The stale air may enter the outgoing flow path 103. The heat pump, in the third mode, is configured to heat the incoming air and it will therefore cool the outgoing air. Cooling the outgoing air may reduce its buoyancy. Cooling of the outgoing air and configuration of the outgoing flow path such that it perhaps extends downwardly may provide for the cooled air to sink out of the outgoing flow path 103 to atmosphere. The ventilation system 100 may be configured to measure the flow rate through the outgoing flow path 103 and limit the amount of cooling provided by the heat pump to the outgoing air to ensure that there is an above-zero flow rate in the outgoing direction.

Figure 5B illustrates the ventilation system 100 in a spring or autumn/fall season scene and therefore the outside air temperature is typically around 12°C and the temperature inside the room is desired to be around 21 °C. In these conditions the ventilation system 100 may be configured to operate in the first mode or intermittently between first and second modes, in the first mode, the heat pump is inactive, and the ventilation system 100 provides ventilation through the same incoming and outgoing flow paths 102, 103 passively (absent of the mechanical movement of air by fans, for example, and reliant on passive stack effect).

In this or the other examples, the heat pump may be active but to a lesser degree than in the third mode. Accordingly, cooler outside air is received by the incoming flow path 102 and heated by the compressed fiow being provided to the first heat exchanger 108 and enters the room 101 shown by arrow 503. Stale air heated by internal heat gains (due to occupants or heat generating equipment in the room) and sunlight through the window or by a heating system of the room rises as show by arrow 504. The warmed stale air may thus circulate through the room towards the outgoing flow path 103 and thereby leave the room 101 as shown by arrow 505. The outgoing air is cooled by the heat pump by virtue of the expanded flow being provided to the second heat exchanger.

Figure 5C shows a night-time scene during the summer season. The temperature outside the building may be around 15°C while the temperature inside, after being in the heated in the sunshine and internal heat gains during the day may be warmer than 15°C, such as 20-30°C. In this instance, the ventilation system 100 may be configured to operate in a first mode, which, in this context, may be considered a night-time-cooling mode. In this mode the heat pump is inactive. Hot air in the room 101 may leave the room by the outgoing flow path 103 as shown by arrow 506. Cooier air 507 from outside may be drawn into the room 101 through the incoming flow path 102 and into the room as shown by arrow 508. Thus, the buoyancy of air rising within the room 101 may drive the ventilation of the room in this instance. This operation may cool the room (e.g. overnight or at any other time of day this mode may be appropriate) in the first, passive mode.

Figure 5D illustrates the ventilation system 100 in a summer scene and therefore the outside air temperature is typically high at around 25-30°C and the temperature inside the room is desired to be around 18-21 °C. In figure 5D, the ventilation system 100 may be configured to operate in the second mode, as described above. Accordingly, the heat pump is active and configured to provide the compressed flow of the working fluid to the second heat exchanger 109 located in the outgoing flow path 103. Accordingly, thermal energy obtained from the air in the incoming flow path 102 is used to heat the outgoing air thereby increasing its buoyancy. The cooled incoming air is thus provided into the room as shown by arrow 510. This cooled air may be at around 18°C. This incoming air 510 is typically cooler than the air outside as well as the air already in the room.

Hot, stale air within the room 101 may rise towards the outgoing flow path 103 as shown by arrows 511 and 512. The stale air may enter the outgoing flow path 103. The heat pump, in the second mode, is configured to cool the incoming air and it will therefore heat the outgoing air. Heating the outgoing air may increase its buoyancy and increase the flow rate out through the outgoing flow path 103. The ventilation system 100 may be configured to measure the flow rate through the outgoing flow path 103 and limit the amount of cooling provided by the heat pump to the incoming air to ensure that the heat pump is operating at a level where the air flow through the outgoing flow path is sufficient to remove the thermal energy and prevent the heat pump from exceeding any operating conditions. Thus, when cooling the incoming air, the heat pump acts to increase the buoyancy of the air in the outgoing flow path and reduce the buoyancy of the air in the incoming flow path which act together to improve the ventilation rate through the room 101. However, as the temperature in the room decreases, the difference in buoyancy between the air entering the room relative to that air already in the room decreases. Thus, the heat pump may be controlled to reduce the power or duty of the heat pump to account for the reduced rate of flow over the heat exchangers in the incoming and outgoing flow paths based on any of the above-mentioned sensors.

Figures 6A to 6D show the same operating conditions as corresponding figures 5A to 5D and 4A to 4D, although in the figures 6A-6D the arrangement of the ventilation system is different.

Figures 6A to 6D show a building 600 having a plurality of rooms 601,602, 603 and 604.

In this exampie and in one or more other examples, the ventilation system comprises a first number of incoming flow paths 102 and a second number, greater than the first number, of the outgoing flow paths. In this example, the incoming flow path 102 may be provided in a hall way 601, which provides access to the plurality of other rooms 602, 603, 604. In one or more examples, two or more of the plurality of other rooms are provided with an outgoing flow path 103A, 103B, 103C. The outgoing flow paths 103A, 103B, 103C in this example are connected to a common cowl 605, although in other examples, separate cowls may be provided for each flow path or groups of outgoing flow path.

Further, in this example, the ventilation system includes a heat pump. The second heat exchanger (not visible in figures 6A-6D) may be located in the cowl 605 and, by virtue of the outgoing flow paths 103A, 103B, 103C meeting at the cowl 605, each of the outgoing flow path 103A, 103B, 103C may be considered to include the second heat exchanger. The first heat exchanger is located in the incoming flow path 102. Conduits 607 may convey the air to the cowl 605.

Thus, a plurality of the rooms may be ventilated by the fresh air entering the building in a first room without its own outgoing flow path, and the outgoing flow paths 103A, 103B, 103C being located in rooms adjacent to the first room. The first room is typically a hall way or atrium from which the other rooms are accessible.

In this example and optionally in other examples, the ventilation system may include a cowl 605 that is configured to catch a flow of wind outside the building and shaped to create, by way of the flow of wind, a low-pressure region adjacent an opening of the outgoing flow path to draw air from the room, the low pressure region having a lower pressure relative to the air pressure in the outgoing flow path.

In this example and other examples, the incoming flow path 102 may be configured to be mounted to deliver air into at least a lower half of the room 101. In this example, the incoming flow path 102 is mounted in a wall 606 in a lower half of the room 601.

In this example and other examples, the plurality of outgoing flow paths 103A, 103B, 103C may be configured to be mounted to receive air from an upper half of each of the rooms 602, 603, 604, such as near a ceiling thereof.

As in the other examples, the heat pump and, in particular, the heat pump circuit 105 extends between the incoming flow path 102 and the outgoing flow path 103 in the cowl 605 by virtue of the first and second heat exchangers 108, 109 being located therein. In this example, the heat pump circuit may include conduits, such as insulated conduits that transfer the heat transfer fluid through the building between the heat exchangers in the flow paths (and the compressor, pump, expansion valve and the like that comprise the heat pump).

In the winter conditions shown in figure 6A, the outside air temperature is typically low at around 0°C and the temperature inside the room is desired to be around 21°C. In figure 6A, the ventilation system 100 may be configured to operate in the third mode, as described above. Accordingly, the heat pump is active and configured to provide the compressed flow of the working fluid to the first heat exchanger (not shown) located in the incoming flow path 102. Accordingly, thermal energy obtained from the air in the outgoing flow path 103 is used to heat the incoming air. The warmed air is thus provided into the room 601 as shown by arrow 608. This incoming air 608 may be urged into the room by a combination of one or more of the wind speed of the outside air driving a flow into the incoming flow path 102, a pressure difference caused by air leaving the room via the outgoing flow paths 103A, 103B, 103C and the incoming air being heated by other means, such as radiators or underfloor heating, and rising away from the second opening (the opening that opens into the room) of the incoming flow path 102.

The stale air within each of the rooms 601,602, 603, 604 may rise towards the outgoing flow paths 103A, 103B, 103C as shown by arrows 609. The stale air may enter the outgoing flow paths 103A, 103B, 103C. The heat pump, in the third mode, is configured to heat the incoming air and it will therefore cool the outgoing air. Cooling the outgoing air may reduce its buoyancy. Cooling of the outgoing air and the configuration of the outgoing flow path in the cowl, as exemplified in figure 3, such that it perhaps extends downward may provide for the cooled air to sink out of the outgoing flow paths 103A, 103B, 103C to atmosphere. The ventilation system 100 may be configured to measure the flow rate through the outgoing flow paths 103A, 103B, 103C and limit the amount of cooling provided by the heat pump to the outgoing air to ensure that there is an abovezero flow rate in the outgoing direction.

Figure 6B illustrates the ventilation system 100 in a spring or autumn/fall season scene and therefore the outside air temperature may be typically around 12°C and the temperature inside the room is desired to be around 21 °C. In these conditions the ventilation system 100 may be configured to operate in the first mode. In the first mode, the heat pump is inactive, and the ventilation system 100 provides ventilation through the same incoming and outgoing flow paths 102, 103 passively (absent of the mechanical movement of air by fans, for example, and reliant on passive stack effect). Thus, air rising into the outgoing flow path along with any venturi effect provided by the cowl 605 may act to extract stale air from the rooms 601-604.

In one or more other examples, the heat pump may be active but to a lesser degree than in the third mode. Accordingly, cooler outside air 610 is received by the incoming flow path 102 and heated by the compressed flow being provided to the first heat exchanger 108 and enters the room 101 shown by arrow 611. Stale air heated by internal heat gains such as occupants or equipment as well as solar gains or by a heating system of the building/each room rises as show by arrow 612. The warmed stale air may thus circulate through the room towards the outgoing flow paths 103A, 103B, 103C and thereby leave the rooms 602, 603, 604. The outgoing air is cooled by the heat pump in the cowl 605 by virtue of the expanded flow being provided to the second heat exchanger. Cooling of the outgoing air in the cowl 605 may cause it to sink out of the outgoing flow paths 103A, 103B, 103C to atmosphere. In this and other examples, such as those where the outgoing flow path does not include a bend, the ventilation system 100 may be configured to measure the flow rate through the outgoing flow paths 103A, 103B, 103C and limit the amount of cooling provided by the heat pump to the outgoing air to ensure that there is an above-zero flow rate in the outgoing direction.

Figure 6C shows a night-time scene during a summer season. The temperature outside the building may be around 15°C while the temperature inside, after gaining heat during the day may be warmer than 15°C, such as 20-30°C. In this instance, the ventilation system 100 may be configured to operate in the first mode. In this mode the heat pump is inactive. Hot air in the room 101 may leave the room by the outgoing flow path 103 as shown by arrows 613. Cooler air 614 from outside may be drawn into the rooms 601, 602, 603, 604 through the incoming flow path 102 and into the room as shown by arrow 508. Thus, the buoyancy of air rising within the rooms 601-604 may drive the ventilation of the room in this instance.

Figure 6D illustrates the ventilation system 100 operating in a summer scene and therefore the outside air temperature is typically high at around 25-30°C and the temperature inside the room is desired to be around 18-21 °C. In figure 6D, the ventilation system 100 may be configured to operate in the second mode, as described above. Accordingly, the heat pump is active and configured to provide the compressed flow of the working fluid to the second heat exchanger 109 located in the outgoing flow path 103. Accordingly, thermal energy obtained from the air in the incoming flow path 102 is used to heat the outgoing air thereby increasing its buoyancy. The cooled incoming air is thus provided into the hall way room as shown by arrow 615. This cooled air may be at around 18°C. This incoming air 615 is typically cooler than the air outside as well as the air already in the room.

Warm, stale air within the rooms 601, 602, 603, 604 may rise towards the respective outgoing flow paths 103A, 103B, 103C as shown by arrows 616. The outgoing flow paths 103 are configured to receive this warm, rising stale air. The heat pump, in the second mode, is configured to cool the incoming air and it will therefore heat the outgoing air. Heating the outgoing air may increase its buoyancy and increase the flow rate out through the outgoing flow paths 103A-C by virtue of heating the air within the cowl 605. If the cowl 605 is of a design with a bend, as exemplified in figure 3, the rising hot air may accumulate at the top-most part of the cowl, but as it has no other exhaust route it will leave via the opening 304. The ventilation system 100 may be configured to measure the flow rate through the outgoing flow path 103 and limit the amount of cooling provided by the heat pump to the incoming air to ensure that the heat pump is operating at a level where the air flow through the outgoing flow path is sufficient to remove the thermal energy and prevent the heat pump from exceeding any operating conditions. Thus, when cooling the incoming air, the heat pump acts to increase the buoyancy of the air in the outgoing flow path and reduce the buoyancy of the air in the incoming flow path which act together to improve the ventilation rate through the room 101. However, as the temperature in the room decreases, the difference in buoyancy between the air entering the room relative to that air already in the room decreases. Thus, the heat pump may be controlled to reduce the power or duty of the heat pump to account for the reduced rate of flow over the heat exchangers in the incoming and outgoing flow paths based on any of the above-mentioned sensors.

Thus, as exemplified above, the ventilation system 100 may be installed in a building or room in a plurality of different ways. The way the heat pump is controlled may vary between implementations. For example, a different control scheme may be required when a cowl having a bend such as shown in Figure 3 is used compared to when it is not used.

In one or more examples, and with reference to figures 6A-6D and figure 7, the ventilation system may additionally include an energy store 700, which may comprise a domestic or commercial hot water cylinder, and a space heater 701. The hot water cylinder may thus serve a dual purpose of storing energy and providing a source of hot water for the building. In other examples, the energy store 700 is solely provided for storing energy and may or may not use water as its energy storage medium.

The heat pump circuit 105 may include an energy store branch 702 comprising flow-to 703 and return conduits 704 to the energy store 700 and a third heat exchanger 705 in the energy store to exchange thermal energy between heat transfer fluid flowing through the third heat exchanger and the energy store. The energy store branch 702 may be selectively active in the heat pump circuit 105 based on the position of control valves 706. Thus, with the valves 706 in an on-state, the working fluid may flow through the energy store 700 while in an off-state the working fluid may bypass the energy store branch 702 as it circulates. In one or more examples, the energy store branch may include a second working fluid (or heat transfer fluid) and the energy store branch 702 may be configured to exchange thermal energy with the working fluid in the heat pump circuit 105. Accordingly, the energy store branch may include a circuit separate to the heat pump circuit 105 and thermal energy may be exchanged therebetween.

The heat pump circuit 105 may include a space heater interface 710 with a space heater circuit 715 through which a space heater working fluid flows. The space heater circuit may comprise flow-to 711 and return conduits 712 to the one or more space heaters 713 which forms the space heater circuit 715 with a heat exchanger 716, which is configured to exchange thermal energy between the working fluid of the heat pump circuit 105 and the space heater working fluid. The space heaters 713 are configured to exchange thermal energy from the space heater working fluid flowing through the space heaters 713 with the air in the room. It will be appreciated that the space heater(s) may be of radiant heater type, convective heater type, underfloor heater type or any other type of space heater. The space heater circuit 715 may include a pump 714 to assist in pumping the working fluid through the space heater circuit 715. The space heater branch 710 may be selectively active in the heat pump circuit 105 by way of control of a pump 714.

In one or more examples, the part of the heat pump circuit 105 that delivers the working fluid to the second heat exchanger 109 in the outgoing flow path may comprise a “HEX” branch 720 which may be selectively active in the heat pump circuit 105 by control valve 721. Thus, in an on-state, the working fluid may flow through the second heat exchanger 109 while in an off-state the working fluid may bypass the “HEX” branch 720 and therefore the second heat exchanger 109 as it circulates. Thus, rather than provide hot, compressed working fluid to the second heat exchanger 109, it may be provided to one or both of the energy store branch 702 and the space heater interface 710. Accordingly, the ventilation system 100 may be configured to control the branch valves 706 or pump 714 of the branch/interface such that when the HEX branch 720 is inactive at least one of the energy store branch 702 and space heater branch 710 are active. In one or more examples, the part of the heat pump circuit 105 that delivers the working fluid to the first heat exchanger 108 in the incoming flow path 102 may comprise a second “HEX” branch 722 which may be selectively active in the heat pump circuit 105 by control valves 723. Accordingly, the hot, compressed working fluid may be provided to one or both of the energy store branch 702 and the space heater interface 710, as required.

In one or more examples, based on a measure of an air flow rate through one or both of the incoming or outgoing flow paths being above a threshold level, the ventilation system may be configured to provide the compressed flow to one or both of the energy store branch 702 for heating hot water, for example, and the space heater interface 710 for providing space heating in the room. Thus, provided that a threshold level of ventilation is provided, the ventilation system 100 may be used to heat the energy store, which may comprise a domestic hot water supply, and/or a space heater. In one or more examples, if the air flow rate through one or both of the incoming or outgoing flow paths is below the threshold level, then the compressed flow may not be provided to one or both of the energy store branch 702 and space heater interface 710.

In one or more examples, in at least one mode of operation, the compressed flow may be provided exclusively to one of the first and second heat exchangers or exclusively to the third heat exchanger. In other examples, the compressed flow may be provided to both in varying proportions based on the airflow rate through one or both of the incoming or outgoing flow paths, for example.

The heating of hot water or, more generally, the energy store 700 (or space heater 701) may be provided in the second or third modes of operation. Thus, in one or more examples, the ventilation system is configured to operate such that thermal energy received from one of:

is configured to be selectively provided to a hot water store and/or a space heater for use in providing hot water or space heating for the building/room.

This arrangement may be advantageous as there may be instances where the room and/or building may require heating or hot water, but operating the heat pump at such a (high) level may lead to an over ventilation of the room by way of the over-promotion of air flow in the incoming and/or outgoing flow paths. Therefore, selectively providing thermal energy of the working fluid to the energy store and/or space heater branches may act to control the ventilation rate.

Figure 8 provides a further feature of the ventilation system that may act to prevent over ventilation. Figure 8 shows the cowl of figure 3 and the same reference numerals have been used. In figure 8, the cowl 300 or, more generally, the outgoing flow path 103, includes a moveable flap 800 and a fan 801. The flap 800 acts to block the outgoing flow path 103 thereby shutting off ventilation provided by the ventilation system 100. The flap 800 further opens an aperture in the cowl 300 such that the fan 801 may act to blow air from outside across the second heat exchanger 109, as shown by arrow 803.

Accordingly, in one or more examples, the ventilation system 100 may be configured to operate in a no-ventilation mode (in addition to any one or more other modes described herein) in which:

(i) the expanded flow is provided to the second heat exchanger 109;

(ii) air from outside is mechanically driven (e.g. by a fan or the like) across the second heat exchanger 109;

(iii) the outgoing flow path is selectively blocked upstream of the second heat exchanger; and (iv) the compressed flow is provided to one or both of an energy store 700 and one or more space heaters 713 configured to provide heating to the room and/or building.

Thus, while in the other modes no fans are used to provide ventilation, in the noventilation mode, the ventilation system may be configured to operate as an air source heat pump to heat water, the energy store or provide space heating without ventilating the room or building. This control of the configuration of the outgoing flow path 103 is advantageous as the second heat exchanger 109 can act effectively in passive modes of operation to promote passive ventilation and can also act in the no-ventilation mode or “air-source heat pump mode”.

The ventilation system may be configured such that the operation of various modes may be based on signalling from an electricity grid that provides the heat pump with electrical power, wherein the signalling indication may be indicative of a need to address an imbalance in the demand and supply of the electricity grid. Accordingly, the ventilation system, when installed in a sufficient number of buildings, may be useful in managing frequency response issues and supply/demand issue in an electricity grid. It will be appreciated that the price of electricity may fluctuate with differing levels of supply and demand and the ventilation system may be configured to react to said fluctuations by use of various operation modes such as water or space heating or cooling mode.

Considering now a further modification to the cowl, in one or more examples, the cowl 300, which may be with or without the flap 800 and fan 801, may include two second heat exchangers. The second heat exchanger 109 may comprise a first-second heat exchanger and the ventilation system 100 and heat pump circuit 105 may include a second-second heat exchanger. The first-second heat exchanger (not shown) may be arranged in the upwardly extending section 302 and second-second heat exchanger (not shown) arranged in the downwardly extending section 303, wherein the heat pump circuit 105 is configurable such that the first-second heat exchanger and the second-second heat exchanger are individually operable to receive the working fluid. This may be advantageous depending on which mode the ventilation system is operating. For example, if the second mode is active, the compressed flow may be provided to the firstsecond heat exchanger. For example, if the third mode is active, the expanded flow may be provided to the second-second heat exchanger. This configuration may provide effective airflow in each of the second and third modes of operation.

In one example, one or more instructions or steps discussed herein are automated. The terms automated or automatically (and like variations thereof) mean controlled operation of an apparatus, system, and/or process using computers and/or mechanical/electrical devices without the necessity of human intervention, observation, effort and/or decision.

It will be appreciated that any components said to be coupled may be coupled or connected either directly or indirectly. In the case of indirect coupling, additional components may be located between the two components that are said to be coupled.

In this specification, example embodiments have been presented in terms of a selected set of details. However, a person of ordinary skill in the art would understand that many other example embodiments may be practiced which include a different selected set of these details. It is intended that the following claims cover all possible example 10 embodiments.

Claims

1. A ventilation system for a building comprising an incoming flow path configured to receive air from outside the building and deliver it to a room inside the building;

a second heat exchanger configured to be mounted in the outgoing flow path and coupled to be part of the heat pump circuit and receive the other of expanded flow for transferring thermal energy from the air in the outgoing flow path to the working fluid and the compressed flow for transferring thermal energy from the working fluid to the air in the outgoing flow path;

2. The ventilation system of claim 1, wherein the ventilation system includes a reversing valve configured to control the flow of the compressed flow and the expanded flow to the first and second heat exchangers, and wherein the ventilation system is configured to selectively operate in at least the first, second and third modes based on control of at least the reversing valve and the heat pump.

3. The ventilation system of claim 1 or claim 2, wherein the ventilation system is configured to control a rate at which the heat pump is configured to pump thermal energy by way of the working fluid between the first exchanger and the second heat exchanger based on one or more of:

(i) a measure of the air flow through the outgoing flow path;

(ii) a measure of the air flow through the incoming flow path;

(iii) a measure of the temperature of the air outside the building;

4. The ventilation system of any of claims 1 to 3, comprising an elongate tubular body extending between the room and outside the building, the body including the incoming flow path and the outgoing flow path wherein the incoming flow path and the outgoing flow path each include an opening into the room substantially adjacent one another and configured to be arranged in a ceiling of the room, wherein an opening into the outgoing flow path from the room is configured to be higher than an opening from the incoming flow path into the room.

5. The ventilation system of any of claims 1 to 3, wherein the incoming flow path comprises an opening into the room configured for location in a floor or a lower half of a wall of the room and the outgoing flow path comprises an opening into the room configured for location in a ceiling or an upper half of a wall of the room.

6. The ventilation system of any of claims 1 to 3, wherein the incoming flow path is configured to be mounted to deliver air to at least a lower half of the room.

7. The ventilation system of any of claims 1 to 3, wherein the ventilation system includes a cowl configured to be coupled to at least the outgoing flow path, the cowl configured to catch a flow of wind outside the building and shaped to create, by way of the flow of wind, a low-pressure region adjacent an opening of the outgoing flow path to draw air from the room, the low pressure region having a lower pressure relative to the air pressure in the outgoing flow path.

8. The ventilation system of any preceding claim, wherein the ventilation system is configured to: (i) provide for control of the heat pump to increase a rate of air flow through at least one of the incoming and outgoing flow paths to a desired set-point; and (ii) monitor a response in the rate of air flow to said control of the heat pump to thereby ensure the heat pump is exchanging thermal energy with the air flow at a sufficient rate to operate within predetermined operating limits, and, if the response is less than a predetermined expected-change value provide for controi of the heat pump to reduce its output.

9. The ventilation system of any preceding ciaim, wherein the ventilation system is configured to: (i) provide for control of the heat pump to one of increase and decrease a temperature of air entering the room from the incoming flow path to a desired set-point; and (ii) monitor a response of the rate of air flow to said controi of the heat pump to thereby ensure the heat pump is exchanging thermal energy with the air flow at a sufficient rate to operate within predetermined operating limits, and, if the response is less than a predetermined expected-change value provide for controi of the heat pump to reduce its output.

10. The ventilation system of any preceding claim, wherein the building includes at least two rooms and the incoming flow path is configured to receive air from outside the building and deliver it to a first of said at least two rooms inside the building; and the outgoing fiow path is configured to receive air from a second of said at least two rooms and deliver it to outside the building, wherein the first room is absent of an outgoing flow path.

11. The ventilation system of any preceding ciaim, wherein the ventilation system is configured to operate in a further mode in which the heat pump of the ventilation system is configured to operate such that thermal energy received from one of:

12. The ventilation system of any preceding claim, wherein the heat pump circuit is reconfigurable and the ventilation system is configured to control the flow of at least the compressed flow between one of the first and second heat exchangers and a third heat exchanger provided in a hot water store or energy store or for use in providing thermal energy to a space heater, said control based on one or more of (i) user input, (ii) air flow rate in the outgoing flow path; and (iii) air flow rate in the incoming flow path.

13. The ventilation system of any preceding claim, wherein the second heat exchanger is configured to be located in the outgoing flow path nearer to a second opening to outside than a first opening from the room; and the first heat exchanger is configured to be located in the incoming flow path nearer to a second opening into the room than a first opening from outside.

14. The ventilation system of any preceding claim, wherein the outgoing flow path includes a cowl that comprises a bend between an upwardly extending section configured to be coupled to receive air from the room and a downwardly extending section that includes an opening to outside the building.

15. The ventilation system of claim 14, wherein the second heat exchanger is arranged in the downwardly extending section and wherein the opening to outside the building of the cowl is configured to be arranged higher than the opening into the outgoing flow path from the room.

16. The ventilation system of claim 14, wherein the second heat exchanger comprises a first-second heat exchanger and the ventilation system includes a secondsecond heat exchanger, the first-second heat exchanger arranged in the upwardly extending section and second-second heat exchanger arranged in the downwardly extending section, wherein the heat pump circuit is configurable such that the firstsecond heat exchanger and the second-second heat exchanger are individually operable to receive the working fluid.

17. The ventilation system of any preceding claim, wherein the ventilation system is configured to selectively operate in a no-ventilation mode in which:

(i) the expanded flow is provided to the second heat exchanger;

(ii) air from outside is mechanically driven across the second heat exchanger;

(iii) the outgoing flow path is at least partially blocked upstream of the second heat exchanger; and (iv) thermal energy of the compressed flow is provided to one or more of an energy store, hot water store and one or more space heaters configured to provide heating to the room and/or building.

5

18. A kit of parts configured to provide the ventilation system of any preceding claim.