EP4515150A1

EP4515150A1 - Combined heat and power system and exhaust heat exchange module

Info

Publication number: EP4515150A1
Application number: EP23721915.9A
Authority: EP
Inventors: Joseph Cilia; Andrea Brincat; Carmel Ellul; Eryl VELLA; Neville Azzopardi; Redeemer AXISA
Original assignee: Abertax Research and Development Ltd; Universita ta Malta UM
Current assignee: Abertax Research and Development Ltd; Universita ta Malta UM
Priority date: 2022-04-29
Filing date: 2023-04-25
Publication date: 2025-03-05
Also published as: WO2023208888A1; GB202206293D0

Abstract

The disclosure concerns a combined heat and power system for providing heat and power to a building. The system comprises an internal combustion engine; an exhaust line configured to receive an exhaust from the internal combustion engine configured to drive an electrical generator; a storage tank configured to hold a liquid; a conduit system; and a heat exchange system configured to circulate a heat exchange fluid through the conduit system. The conduit system comprises: an exhaust circuit comprising an exhaust circuit pump configured to drive flow of the heat exchange fluid between the storage tank heat exchanger and the exhaust line heat exchanger; and an engine circuit comprising an engine circuit pump configured to drive flow of the heat exchange fluid between the engine heat recovery circuit and a shared conduit forming part of the exhaust circuit and engine circuit.

Description

COMBINED HEAT AND POWER SYSTEM AND EXHAUST HEAT EXCHANGE MODULE

The present invention relates to a combined heat and power system for providing heat and power to a building. The invention also relates to an exhaust heat exchange module for transferring heat to fluid in a circuit.

Combined heat and power (CHP) systems are systems which provide both heat and power in a process also known as cogeneration. Combined heat and power systems may use an engine, or power station, to provide electricity. As the electricity is generated, heat is also generated by the engine or power station. Combined heat and power systems use the engine heat to provide heat for a useful application, rather than the heat energy becoming a wasted by-product of the electricity generation.

Combined heat and power systems may be provided in place of conventional power stations to provided power to a number of buildings, for example in a town or a manufacturing facility. In contrast, micro combined heat and power systems (known as micro CHPs) are smaller scale combined heat and power systems, typically designed for providing heat and power to single buildings or small dwellings, such as apartments. Many micro combined heat and power systems use heat engines, such as internal combustion engines, to generate heat and power.

For example, WO 2012/140591 Al concerns an apparatus for generating electric power for elements for use for example in caravans, bungalows, kiosks, dwelling units and the like which is adapted to heat an enclosed space. WO 2012/140591 Al discloses an arrangement comprising a heat engine and an exhaust pipe, as well as a hydraulic circuit for forced cooling of the engine. The apparatus comprises a heat exchanger to enable heat transfer between the exhaust pipe and the hydraulic circuit and a further heat exchanger to enable heat transfer between the hydraulic circuit and a duct leading to the corresponding element.

Many micro combined heat and power systems are larger than conventional home heating units, such as boilers. Furthermore, in existing micro combined heat and power systems there can be a problem of the systems being bulky and expensive to install. There may also be a problem of inefficient heat transfer between circuits.

It is an object of the disclosure to provide a combined heat and power system that is compact and efficient. It is a further object to provide a micro combined heat and power system which may be suitable for home energy provision. It is a further object to provide an exhaust heat exchange module which aims to efficiently exchange heat between an exhaust and a heat exchange fluid. The exhaust heat exchange module may be arranged such that it may enable more sustainable and lower cost manufacture than existing heat exchange modules.

According to an aspect of the invention, there is provided a combined heat and power system for providing heat and power to a building. The system comprises an internal combustion engine configured to drive an electrical generator; an exhaust line configured to receive an exhaust from the internal combustion engine; a storage tank configured to hold a liquid; a conduit system; and a heat exchange system configured to circulate a heat exchange fluid through the conduit system. The heat exchange system comprises: an engine heat recovery circuit configured to allow transfer of heat from the internal combustion engine to the heat exchange fluid; an exhaust line heat exchanger configured to allow transfer of heat from the exhaust line to the heat exchange fluid; and a storage tank heat exchanger configured to allow transfer of heat from the heat exchange fluid to the liquid in the storage tank. The conduit system comprises: an exhaust circuit comprising an exhaust circuit pump configured to drive flow of the heat exchange fluid between the storage tank heat exchanger and the exhaust line heat exchanger; and an engine circuit comprising an engine circuit pump configured to drive flow of the heat exchange fluid between the engine heat recovery circuit and a shared conduit forming part of the exhaust circuit and engine circuit. In this arrangement, heat exchange fluid is able to flow between the exhaust circuit and the engine circuit to efficiently exchange heat between these circuits.

In an embodiment, the system has a single expansion tank. With this arrangement, the storage tank may be disposed in a readily accessible position to enable maintenance and repair to be performed quickly and effectively. In an embodiment, the system further comprises a power system casing. The internal combustion engine and the exhaust line heat exchanger are disposed within the power system casing, and the single expansion tank is disposed outside the power system casing. With this arrangement, the power system casing may be more compact than in systems having one or more expansion tanks housed within the power system casing.

In an embodiment, the system further comprises an electrical generator comprising a generator fan; and a power system casing comprising a partition wall separating a first compartment and a second compartment. The first compartment houses the internal combustion engine and the exhaust line heat exchanger. The first compartment comprises an engine air inlet configured to allow air to enter the internal combustion engine, and an engine air outlet configured to output exhaust gas from the exhaust line heat exchanger to the outside of the power system casing. The second compartment houses the electrical generator and comprises an air inlet and an air outlet. The second compartment is configured to provide an air flow path from the air inlet to the air outlet and the generator fan is configured to circulate air through the air flow path. In an embodiment, the system further comprises a battery disposed in the air flow path between the air inlet and the electrical generator. These arrangements help achieve stable operating temperatures, supporting increased reliability and/or reduced susceptibility to damage, and advantageously provides heating to the room.

In an embodiment, the partition wall comprises a sound insulating material. In this way the power system casing may be disposed such that the air inlet and/or the air outlet of the second compartment are in an area or room, such as a kitchen, in a dwelling, without causing significant sound disruption to the occupants of the dwelling, for example due to noise from the internal combustion engine.

According to an aspect of the invention, there is provided an exhaust heat exchange module for transferring heat to fluid in a circuit. The exhaust heat exchange module comprises: a first stage heat exchanger configured to reduce a temperature of exhaust gas from a first exhaust temperature to a second exhaust temperature. The first stage heat exchanger comprises a catalyser configured to catalyse the exhaust gas, a catalyser casing housing the catalyser and comprising a fluid inlet and a fluid outlet, and one or more ridges. The one or more ridges are provided between the catalyser and an inside surface of the catalyser casing to define a fluid flow channel between the fluid inlet and the fluid outlet, wherein the one or more ridges are configured such that fluid flowing from the fluid inlet to the fluid outlet follow an indirect fluid flow path. This arrangement may provide the advantage that forming a fluid flow channel from ridges reduces manufacturing cost compared to the more common method of forming a fluid flow channel from pipes.

In an embodiment, the catalyser comprises an outer surface, wherein the outer surface is a surface of the fluid flow channel, and the outer surface is configured to transfer heat from the catalyser to fluid in the fluid flow channel. In an embodiment, the one or more ridges are configured such that the fluid flow path between the fluid inlet and the fluid outlet is a helix. In an embodiment, the fluid inlet and the fluid outlet are at different longitudinal positions along a longitudinal direction of the catalyser. Preferably the fluid inlet and the fluid outlet are at or near opposite ends of the catalyser in the longitudinal direction of the catalyser. This may have the benefit of allowing effective heat transfer from the catalyser to the fluid in the fluid flow path.

In an embodiment, the first exhaust temperature is between 500 °C and 750 °C, and the second exhaust temperature is between 250 °C and 350 °C. In an embodiment, the module further comprises a second stage heat exchanger configured to reduce a temperature of exhaust gas from a third exhaust temperature to a fourth exhaust temperature. With these arrangements, the catalyser may be maintained at a temperature which enables it to operate effectively. Furthermore, the temperature of the exhaust gas leaving the second stage heat exchanger may be relatively low. This may lower the cost of installation and maintenance compared to arrangements having a higher exhaust gas output temperature and requiring the use of expensive metal pipework.

The present invention will now be described with reference to exemplary embodiments and the accompanying figures, in which:

Figure 1 illustrates an example of a combined heat and power system according to the prior art;

Figure 2 illustrates an example of a combined heat and power system according to an embodiment of the present disclosure;

Figure 3 illustrates an example of a power system casing;

Figure 4A illustrates a front view of an example of an exhaust heat exchange module; and

Figure 4B illustrates a cross-sectional view of the exhaust heat exchange module of Figure 4A.

An example combined heat and power system according to the prior art is illustrated in Figure 1. The combined heat and power system of Figure 1 comprises an internal combustion engine 10; an exhaust line 20 configured to receive an exhaust from the internal combustion engine 10; a storage tank 30 configured to hold a liquid; a primary conduit system 40; a primary heat exchange system configured to circulate a heat exchange fluid through the primary conduit system 40; an engine conduit system; and an engine heat exchange system configured to circulate a heat exchange fluid through the engine conduit system.

The internal combustion engine can be used to generate electrical power. Furthermore, heat from the exhaust of the internal combustion engine may be used to heat the liquid in the storage tank. This heated liquid may then be used for a desired application, such as central heating in a dwelling. The primary heat exchange system is configured to transfer heat from the exhaust to the liquid in the storage tank. The engine heat exchange system is configured to regulate the temperature of the internal combustion engine by enabling heat transfer between the heat exchange fluid in the primary conduit system and heat exchange fluid in the engine conduit system.

In particular, the primary heat exchange system comprises: an exhaust line heat exchanger 44 configured to allow transfer of heat from the exhaust line 20 to the heat exchange fluid in the primary conduit system 40; a storage tank heat exchanger 45 configured to allow transfer of heat from the heat exchange fluid in the primary conduit system 40 to the liquid in the storage tank 30; and a primary-engine heat exchanger 46 configured to allow transfer of heat from the heat exchange fluid in the primary conduit system 40 to the heat exchange fluid in the engine conduit system.

The primary conduit system 40 comprises: an exhaust circuit 41 comprising an exhaust circuit pump 42 configured to drive flow of the heat exchange fluid between the storage tank heat exchanger 45, the primary-engine heat exchanger, and the exhaust line heat exchanger 44.

The engine heat exchange system comprises: an engine heat recovery circuit configured to allow transfer of heat from the internal combustion engine to the heat exchange fluid in the engine conduit system.

The engine conduit system comprises: an engine circuit comprising an engine circuit pump configured to drive flow of the heat exchange fluid between the engine heat recovery circuit and the primary-engine heat exchanger.

With this arrangement, the primary conduit system and the engine conduit system are not in fluid communication. In particular, the heat exchange fluid in the engine circuit is not able to enter the exhaust circuit and the heat exchange fluid in the exhaust circuit is not able to enter the engine circuit. Instead, heat is transferred between the engine circuit and the exhaust circuit via the primary-engine heat exchanger. Some heat from the engine circuit may therefore not be effectively transferred to the exhaust circuit due to any inefficiency in the primary-engine heat exchanger. Thermal losses in the arrangement of Figure 2 may be lower than in the arrangement of the prior art as shown in Figure 1.

The system shown in Figure 1 comprises two expansion tanks 13, 43 configured to contain heat exchange fluid. The engine conduit system comprises an engine circuit expansion tank 13 configured to regulate pressure in the engine circuit 11. The primary conduit system comprises a primary expansion tank 43 configured to regulate pressure in the exhaust circuit 41.

The system comprises a power system casing 80, as shown for example in Figure 1. The internal combustion engine 10, the exhaust line heat exchanger 44, and the engine circuit expansion tank 13 are disposed within the power system casing. Thus, there is at least one expansion tank housed within the power system casing 80 of the system arranged as shown in Figure 1. Thus, the size of the power system casing 80 must be sufficiently large to house an expansion tank. The exhaust circuit expansion tank 43 may also be disposed within the power system casing 80, as shown in Figure 1. In addition to providing a means to transfer heat from the exhaust to the heat exchange fluid in the primary conduit system, the exhaust line heat exchanger 44 may comprise a catalyser. The catalyser may be configured to catalyse the exhaust gas from the internal combustion engine. Typical catalysers function most effectively at a minimum temperature of approximately 300 °C. Thus, for proper operation of the catalyser, the exhaust line heat exchanger 44 may be configured to cool the exhaust gas from a first exhaust temperature, of between 500 °C and 750 °C, to a second exhaust temperature of between 250 °C and 350 °C. However, this presents the problem that a significant amount of heat from the exhaust has not been transferred to the heat exchange fluid in the exhaust circuit, and thus is not being used in a useful application by heating the fluid in the storage tank. A further problem is that there is a need to safely channel the exhaust gas at the second temperature out of the power system casing. This requires the combined heat and power system to include an exhaust outlet channel 21 made of a material, such as a metal, which can withstand temperatures in excess of 250 °C. As a consequence, the exhaust outlet channel 21 of the arrangement shown in Figure 1 cannot be made of plastic materials which would be at risk of damage due to the high temperatures of the output exhaust. This increases the cost of manufacture and installation of the combined heat and power unit.

In a system according to some embodiments of the present disclosure, for example as shown in Figure 2, there is a shared conduit 56 forming part of the exhaust circuit 51 and engine circuit 61. In this way, heat exchange fluid is able to flow between the exhaust circuit 51 and the engine circuit 61. Thus, the arrangement of Figure 2 does not comprise a primaryengine heat exchanger as shown in the arrangement of Figure 1. As such, any loss of heat due to inefficiency in the primary-engine heat exchanger is avoided in the arrangement of Figure 2.

The system may comprise an engine thermostat configured to control the flow of fluid from the exhaust circuit 51 to the engine circuit 61. In particular, the engine thermostat is desirably configured to open to allow fluid to flow into the engine circuit 61 and to close to block the flow of fluid into the engine circuit 61. During start-up of the internal combustion engine 10, the engine thermostat is desirably configured to open when the engine reaches a predetermined temperature. The predetermined temperature may be a desired operating temperature of the engine. For example, the predetermined temperature is desirably between 70 °C and 100 °C, more desirably between 80 °C and 90 °C.

The engine circuit 61 may desirably be compact and have a relatively small fluid capacity. For example, the engine circuit 61, for example as shown in Figure 2, optionally does not comprise the engine circuit expansion tank 13 or the primary-engine heat exchanger the engine circuit 61 may contain less fluid due to having fewer components in which to circulate fluid. The fluid in the engine circuit 61 may desirably heat up relatively quickly on engine start up due to a small amount of fluid being provided in a compact space. The internal combustion engine may therefore reach its operating temperature quickly on start up.

In some embodiments of the present disclosure, the combined heat and power system is configured to be suitable for providing heat and power to a building. As shown, for example, in Figure 2, and similarly to the system depicted in Figure 1, in some embodiments the system comprises an internal combustion engine 10; an exhaust line 20 configured to receive an exhaust from the internal combustion engine 10; and a storage tank 30 configured to hold a liquid. The system further comprises a conduit system 50; and a heat exchange system configured to circulate a heat exchange fluid through the conduit system 50.

Similarly to the arrangement of Figure 1, in the arrangement of Figure 2 the internal combustion engine can be used to generate electrical power. Furthermore, heat from the exhaust of the internal combustion engine may be used to heat the liquid in the storage tank. This heated liquid may then be used for a desired application, such as central heating in a dwelling. The heat exchange system is configured to transfer heat from the exhaust to the liquid in the storage tank. The heat exchange system also aids in regulating the temperature of the internal combustion engine by enabling heat transfer between the internal combustion engine and the heat exchange fluid in the conduit system.

In an embodiment, the heat exchange system comprises: an engine heat recovery circuit 64, an exhaust line heat exchanger 54, and a storage tank heat exchanger 55. The engine heat recovery circuit 64 is configured to allow transfer of heat from the engine 10 to the heat exchange fluid. The exhaust line heat exchanger 54 is configured to allow transfer of heat from the exhaust line 20 to the heat exchange fluid. The storage tank heat exchanger 55 is configured to allow transfer of heat from the heat exchange fluid to the liquid in the storage tank 30.

In an embodiment, the conduit system comprises a fluid flow channel through which the heat exchange fluid flows. In particular, the fluid flow channel provides a fluid flow path between and through the engine heat recovery circuit 64, the exhaust line heat exchanger 54, and the storage tank heat exchanger 55. In an embodiment, the fluid flow channel provides a fluid flow path from the exhaust line heat exchanger 54 to the storage tank heat exchanger 55, from the storage tank heat exchanger 55 to the engine heat recovery circuit 64, and from the engine heat recovery circuit 64 to the exhaust line heat exchanger 54. In an embodiment, the conduit system 50 comprises: an exhaust circuit 51 comprising an exhaust circuit pump 52 configured to drive flow of the heat exchange fluid between the storage tank heat exchanger 55 and the exhaust line heat exchanger 54. The conduit system 50 further comprises an engine circuit 61 comprising an engine circuit pump 62 configured to drive flow of the heat exchange fluid between the engine heat recovery circuit 64 and a shared conduit 56 forming part of the exhaust circuit 51 and engine circuit 61. The exhaust circuit pump 52 may be disposed at any position along the conduits of the exhaust circuit. It is desirable that the exhaust circuit pump is not disposed at the highest temperature portion of the circuit. The exhaust circuit pump 52 is preferably disposed between the storage tank heat exchanger 55 and the exhaust line heat exchanger 54, more preferably the exhaust circuit pump 52 is disposed between the storage tank heat exchanger 55 and the shared conduit 56. The engine circuit 61 desirably further comprises the engine thermostat configured to control the flow of heat exchange fluid into the engine circuit 61.

The shared conduit 56 desirably comprises an engine flow inlet 561 configured to allow heat exchange fluid from the exhaust circuit 51 to enter the engine circuit 61. The shared conduit 56 may comprise an engine flow outlet 562 configured to allow heat exchange fluid from the engine circuit 61 to enter the exhaust circuit 51. The engine thermostat may be configured to open to enable fluid to flow from the exhaust circuit 51 to enter the engine circuit 61. The conduit system is preferably configured such that the heat exchange fluid flows from the storage tank heat exchanger 55 to the shared conduit 56. The conduit system is desirably configured such that the heat exchange fluid flows into the shared conduit 56, through the engine flow inlet to the engine heat recovery circuit 64, and from the engine heat recovery circuit 64 through the engine flow outlet 562 into the shared conduit 56. The shared conduit 56 is desirably configured such that the heat exchange fluid can flow from the shared circuit 56 to the exhaust line heat exchanger 54.

The system desirably has a single expansion tank 53. The exhaust circuit 51 comprises the single expansion tank 53 in the arrangement shown in Figure 2. The single expansion tank 53 is desirably disposed adjacent to the storage tank 30. In particular, it is desirable that the single expansion tank 53 is connected to the storage tank heat exchanger 55 via the conduit such that the heat exchange fluid is directed from the single expansion tank 53 to the storage tank heat exchanger 55. More desirably, as shown in Figure 2, the single expansion tank 53 is connected to the storage tank heat exchanger 55 via the conduit such that the heat exchange fluid is directed from the storage tank heat exchanger 55 to the single expansion tank 53. Yet more desirably, the expansion tank 53 is disposed along the exhaust circuit 51 such that the heat exchange fluid flows directly between the storage tank heat exchanger 55 and the expansion tank 53. With this arrangement both the storage tank and the expansion tank may be disposed in a readily accessible position to enable maintenance and repair to be performed quickly and effectively.

The system may comprise a power system casing 80. The single expansion tank is desirably disposed outside the power system casing, for example as shown in Figure 2. With this configuration, the power system casing of Figure 2 may be more compact than that of Figure 1. This is because, with the arrangement of Figure 1, there will be at least one expansion tank housed within the casing, as the engine expansion tank 13 is required and is most conveniently disposed adjacent to the internal combustion engine 10. It is difficult for the expansion tank to function effectively if it is disposed further from internal combustion engine 10. Furthermore, to dispose the engine expansion tank 13 further from the internal combustion engine 10 would require the engine circuit 10 to be larger, with the conduit channels extending further from the internal combustion engine. This would increase the complexity of the system, making it more bulky and taking more time for the engine to heat up to the ideal temperature when started, therefore increasing the installation and maintenance costs as well as the likelihood of malfunctions.

The system as shown in Figure 2 may have the advantage of being more compact and easier to install and maintain than systems of the type depicted in Figure 1. This is because, with the arrangement of Figure 2, only one expansion tank is included in the system. Furthermore, due to the shared conduit 56, the single expansion tank 53 is in fluid communication with the whole conduit system, and not only the engine circuit. There is no restriction on where in the conduit system 50 the single expansion tank 53 is disposed. In particular, it is not necessary to dispose the single expansion tank 53 in proximity to the internal combustion engine 10.

The single expansion tank is desirably disposed outside of the power system casing 80. If the single expansion tank 53 is disposed outside of the power system casing 80, the expansion tank may be more easily installed and accessed for maintenance. Furthermore, as discussed above, it is desirable that the single expansion tank 53 is disposed adjacent to the storage tank 30. As shown, for example, in Figure 2, the storage tank 30 is desirably disposed outside the power system casing 80. The storage tank 30 may therefore be large to store a large volume of liquid without increasing the size of the power system casing 80. In particular, the power system casing may be disposed inside a building, such as a domestic dwelling, for example in the kitchen, while the storage tank and/or the expansion tank may be disposed outside or in a separate area where space is less limited and the units are not in the way of occupants of the building. The storage tank can in principle have any size. For example, have a capacity of less than or equal to 300 litres, desirably less than or equal to 200 litres, optionally less than or equal to 100 litres.

The internal combustion engine 10 and the exhaust line heat exchanger 54 are desirably disposed within the power system casing 80. The engine heat recovery circuit 64 is desirably disposed in the power system casing 80 such that the engine heat recovery circuit 64 is configured to transfer heat from the engine to the heat exchange fluid. The exhaust circuit pump 52 and the engine circuit pump 62 are optionally disposed within the power system casing 80. The mixing conduit 56 and the engine conduit 61 are desirably disposed within the power system casing 80, as shown for example in Figure 2.

The power system casing may comprise a sound insulating material. In particular, an outer wall of the power system casing may be configured to absorb sound waves. Desirably, the power system casing is configured to reduce sound transfer from the internal combustion engine which is transferred to the outside of the power system casing. In this way the power system casing may be disposed in an area, such as a kitchen, in a dwelling without causing disruption to the occupants of the dwelling.

Optionally, the power system casing may comprise a heat insulating material. Desirably, the power system casing is configured to reduce heat transfer from the exhaust to the outside. In this way thermal loss to the surroundings may be reduced such that more heat is provided to the liquid in the storage tank.

The system optionally further comprises a reservoir 90 configured to collect condensate from the exhaust line heat exchanger 54. The system may further comprise a drain 91 providing a channel between the reservoir 90 and an outlet. The outlet may lead to the outside of the power system casing 80. Optionally, the drain may lead to the outside of a building in which the power system casing is disposed. The system may comprise a nonreturn valve 92 configured to allow condensate from the reservoir 90 to enter the drain 91. Alternatively, instead of being connected to a drain with an outlet, the reservoir may comprise a removable container to collect condensate. The removable container may be configured such that a user can access and remove the container to dispose of the condensate. For example, a liquid level sensor may be provided in the removable container and to alert the user when the liquid level in the container is at a predetermined threshold, such that the user can empty the container before it becomes full.

The power system casing optionally also houses an electrical generator, and may further house a battery. The power system casing is desirably suitable for use in a dwelling. For example, the power system casing may be approximately the same size as a typical household appliance, such as a dishwasher. The power system casing is preferably less than 1 m³ in volume. The power system casing may be less than 1 m long by 65 cm wide by 65 cm deep. Desirably the power system casing is less than 85 cm long by 65 cm wide by 60 cm deep.

The system is desirably configured to output up to 2 kW of electrical power, more desirably up to 2.5 kW, yet more desirably up to 3 kW. The system is desirably configured to recover up to 5 kW of power from heat, more desirably up to 6 kW, yet more desirably up to 7 kW. The combined heat and power system may be a micro combined heat and power system. The system may be configured to provide electricity and heat to a domestic dwelling. The system may be configured to provide electricity and heat to a house or an apartment, or to more than one apartment.

The heat exchange fluid desirably comprises a glycol. For example, the heat exchange fluid may comprise propylene glycol or ethylene glycol.

In addition to the heat transfer using a heat exchange fluid in a conduit system, as described above with reference to Figure 2, the system may also be configured to transfer heat by the flow of air through the system.

The system may comprise an electrical generator 70 configured to generate electrical power. The electrical generator 70 preferably comprises a generator fan 71. The electrical generator 70 desirably comprising a brushless motor. As shown, for example, in Figure 3, the system may comprise a power system casing 80 having a partition wall 85 separating a first compartment and a second compartment. The first compartment houses the internal combustion engine 10. The first compartment may also house the exhaust line heat exchanger 54. Preferably, the first compartment houses the engine heat recovery circuit 64, the exhaust circuit pump 52 and the engine circuit pump 62. The mixing conduit 56 and the engine conduit 61 are desirably disposed within first compartment.

The first compartment comprises an engine air inlet 81 configured to allow air to enter first compartment. Desirably, the system may be configured such that air entering the first compartment via the engine air inlet 81 is directed into the internal combustion engine 10. The first compartment further comprises an engine air outlet 82 configured to output exhaust gas from the exhaust line heat exchanger to the outside of the power system casing 80. In this way the air entering the first compartment via the engine air inlet 81 may be compressed by the internal combustion engine 10. Furthermore, the engine air outlet 82 is preferably connected to an outside such that catalysed exhaust gas is outlet to an outside area, rather than inside a building. This is a preferable configuration because it enables the power system casing to be disposed inside a building without having an adverse effect on occupants. The second compartment desirably houses the electrical generator 70. The second compartment desirably also houses a battery 72, and additionally or alternatively houses electronics used to control the system. The second compartment comprises an air inlet 83 and an air outlet 84. The second compartment is configured to provide an air flow path from the air inlet 83 to the air outlet 84. The generator fan 71 is configured to circulate air through the air flow path. The battery 72 and/or the control electronics are preferably disposed in the air flow path between the air inlet 83 and the electrical generator 70, as shown for example in Figure 3. Air travelling through the air flow path may therefore absorb heat from the battery and/or the electrical generator. As a result, the air may be heated and the battery and electrical generator may be cooled. This reduces the risk of the battery and/or electrical generator being damaged by overheating. This arrangement may therefore provide a system which operates at a more stable temperature aiding in making the system more reliable and less susceptible to damage. This might have the beneficial effect of reducing downtime and maintenance costs, and may advantageously provide heating to the room.

The power system casing may be disposed such that the air inlet 83 and/or the air outlet 84 of the second compartment are in an area or room, such as a kitchen, in a dwelling. The air which enters the second compartment via the air inlet 83 will be at an ambient temperature of the area/room. During use, the air which exits the second compartment via the air outlet 84 is warmer, due to the heat imparted to the air from the battery and/or electrical generator, and thus can contribute to heating the dwelling. Thus, this arrangement desirably makes efficient use of the heat generated by the electrical generator and/or battery. Furthermore, some heat from the internal combustion engine 10 may also be transferred to the second compartment and may contribute to heating the room. The power system casing may be compact such that it is readily situated in a room of a dwelling.

The partition wall 85 is preferably configured to seal the first compartment and/or the second compartment such that gas, such as exhaust gas, from the first compartment is not able to enter the second compartment. In this way the power system casing may be disposed such that the air inlet 83 and/or the air outlet 84 of the second compartment are in an area or room, such as a kitchen, in a dwelling, without causing harmful or unpleasant smelling gas, such as exhaust from the internal combustion engine, to adversely affect occupants of the dwelling.

The partition wall 85 may comprise a sound insulating material. In particular, the partition wall 85 may be configured to absorb sound waves. Desirably, the power system casing is configured to reduce sound transfer from the first compartment to the second compartment. In this way the power system casing may be disposed such that the air inlet 83 and/or the air outlet 84 of the second compartment are in an area or room, such as a kitchen, in a dwelling, without causing sound disruption to the occupants of the dwelling, for example due to noise from the internal combustion engine.

An exhaust heat exchange module may be configured to transfer heat to fluid in a circuit, in particular to transfer heat from an exhaust to a heat exchange fluid. In the combined heat and power system, as described above with reference to Figures 2 and 3, the exhaust line heat exchanger 54 may comprise an exhaust heat exchange module, or the exhaust line heat exchanger 54 may be an exhaust heat exchange module.

The exhaust heat exchange module may comprises a first stage heat exchanger 541, as shown for example in Figure 4A. The first stage heat exchanger 541 may comprise an exhaust gas inlet 23 configured to enable exhaust to enter the first stage heat exchanger 541, and an exhaust gas outlet 24 configured to enable exhaust, which has been catalysed, to exit the first stage heat exchanger 541.

The first stage heat exchanger 541 is configured to reduce a temperature of exhaust gas from a first exhaust temperature to a second exhaust temperature. The exhaust gas may have the first exhaust temperature at the exhaust gas inlet 23 and the exhaust has may have the second exhaust temperature at the exhaust gas outlet 24. The first stage heat exchanger 541 comprises a catalyser 1, as shown in Figure 4B which illustrates a cross-sectional view through section A-A of the first stage heat exchanger 541 shown in Figure 4 A. The catalyser 1 is configured to catalyse exhaust, such as the exhaust from an internal combustion engine.

The exhaust heat exchange module may comprises a catalyser casing 2 housing the catalyser 1. The catalyser casing 2, as shown for example in Figure 2, comprises fluid inlet 41 and a fluid outlet 42. The catalyser casing 2 further comprises one or more ridges 3. The one or more ridges 3 may act as baffles to direct the flow of fluid from the fluid inlet 41 to the fluid outlet 42. In other words, the one or more ridges 3 define a fluid flow channel 4 between the fluid inlet 41 and the fluid outlet 42. The one or more ridges 3 are configured such that fluid flowing from the fluid inlet 41 to the fluid outlet 42 follow an indirect fluid flow path. The one or more ridges 3 are preferably provided between the catalyser 1 and an inside surface of the catalyser casing 2. The arrangement may provide the advantage that forming a fluid flow channel from ridges reduces manufacturing cost compared to the more common method of forming a fluid flow channel from pipes.

With the arrangement of Figure 4A and 4B, the fluid flowing between the fluid inlet 41 and the fluid outlet 42 is contained by a fluid flow channel 4 around the outside of the catalyser. This may desirably enable fluid in the fluid flow channel 4 to absorb noise of the catalyser as well as absorbing heat. The catalyser 1 may comprises an outer surface. The outer surface of the catalyser 1 may be a surface of the fluid flow channel 4. The outer surface of the catalyser 1 is desirably configured to transfer heat from the catalyser 1 to fluid in the fluid flow channel 4.

The one or more ridges 3 are desirably configured such that the fluid flow path between the fluid inlet 41 and the fluid outlet 42 is a helix. The helix defined by the fluid flow path may have a constant diameter. Alternatively, the diameter of the helix may vary in a longitudinal direction of the catalyser. For example, the diameter at the fluid inlet 41 may be greater than the diameter at the fluid outlet 42, or the diameter at the fluid inlet 41 may be smaller than the diameter at the fluid outlet 42. The ink flow path does not need to be exactly helical, for example the pitch of the helix may vary.

Alternatively, the one or more ridges may be configured such that the fluid flow path between the fluid inlet 41 and the fluid outlet 42 is a meander. With a meander, the fluid flow path follows a winding course, preferably wherein the fluid flow path goes around the circumference of the outside of the catalyser in a first direction, re-directs to a longitudinal direction of the catalyser, then re-directs to a second direction. Preferably, the first direction is a first circumferential direction of the catalyser and the second direction is an opposing circumferential direction of the catalyser.

The fluid inlet 41 and the fluid outlet 42 are desirably at different longitudinal positions along a longitudinal direction of the catalyser. Preferably, the fluid inlet 41 and the fluid outlet 42 are at or near opposite ends of the catalyser in the longitudinal direction of the catalyser. In particular, the distance in a longitudinal direction of the catalyser between the fluid inlet 41 and the fluid outlet is preferably over 50% of the total length of the catalyser, more preferably over 65 %, yet more preferably over 75 %. With this arrangement, the fluid flow path between the fluid inlet and the fluid outlet may be longer than with alternative arrangements. This may desirably result in the fluid flowing through the fluid flow path having longer to absorb heat from the catalyser.

The first exhaust temperature is desirably between 450 °C and 800 °C, more desirably between 500 °C and 750 °C, yet more desirably between 550 °C and 700 °C. The second exhaust temperature is desirably between 200 °C and 400 °C, more desirably between 250 °C and 350 °C, yet more desirably between 275 °C and 325 °C. These temperature ranges are preferable because the catalyser may operate most effectively at these temperatures. For this reason, it is desirable that the second exhaust temperature is not less than 250 °C.

As shown, for example, in Figure 2, the exhaust heat exchange module may comprise a second stage heat exchanger 542. The second stage heat exchanger 542 is configured to reduce a temperature of exhaust gas from a third exhaust temperature to a fourth exhaust temperature. The exhaust gas outlet 24 of the first stage heat exchanger 541 may be connected directly to an exhaust gas inlet of the second stage heat exchanger 542. The third exhaust temperature may, in this arrangement, be equal to the second exhaust temperature. The third exhaust temperature may be within 50 °C of the second exhaust temperature, desirably within 25 °C, more desirably within 10 °C.

The third exhaust temperature is desirably between 200 °C and 400 °C, more desirably between 250 °C and 350 °C, yet more desirably between 275 °C and 325 °C. The fourth exhaust temperature is desirably between 30 °C and 100 °C, more desirably between 50 °C and 80 °C, yet more desirably between 60 °C and 70 °C. With this arrangement, the exhaust gas is catalysed such that it is not harmful and can directed via an exhaust outlet channel 21 to the outside. Furthermore, the temperature of the exhaust gas leaving the second stage heat exchanger 542 may be sufficiently low that exhaust outlet channel 21 can be made of a material, such as a plastic, which is not resistant to hot temperatures. This may lower the cost of installation and maintenance compared to arrangements having a high exhaust gas output temperature and requiring metal pipes to direct the exhaust away from the system.

Aspects of the present disclosure have been described with particular reference to the examples illustrated. While specific examples are shown in the drawings and are herein described in detail, it should be understood, however, that the drawings and detailed description are not intended to limit the invention to the particular form disclosed. It will be appreciated that variations and modifications may be made to the examples described within the scope of the present invention, as defined by the claims.

Claims

1. A combined heat and power system for providing heat and power to a building, the system comprising an internal combustion engine configured to drive an electrical generator; an exhaust line configured to receive an exhaust from the internal combustion engine; a storage tank configured to hold a liquid; a conduit system; and a heat exchange system configured to circulate a heat exchange fluid through the conduit system, wherein the heat exchange system comprises: an engine heat recovery circuit configured to allow transfer of heat from the internal combustion engine to the heat exchange fluid; an exhaust line heat exchanger configured to allow transfer of heat from the exhaust line to the heat exchange fluid; a storage tank heat exchanger configured to allow transfer of heat from the heat exchange fluid to the liquid in the storage tank; wherein the conduit system comprises: an exhaust circuit comprising an exhaust circuit pump configured to drive flow of the heat exchange fluid between the storage tank heat exchanger and the exhaust line heat exchanger; and an engine circuit comprising an engine circuit pump configured to drive flow of the heat exchange fluid between the engine heat recovery circuit and a shared conduit forming part of the exhaust circuit and engine circuit.

2. The system of claim 1, wherein the shared conduit comprises an engine flow inlet configured to allow heat exchange fluid from the exhaust circuit to enter the engine circuit.

3. The system of claim 1 or 2, wherein the shared conduit comprises an engine flow outlet configured to allow heat exchange fluid from the engine circuit to enter the exhaust circuit.

4. The system of any one of claims 1 to 3, wherein the system has a single expansion tank.

5. The system of claim 4, wherein the single expansion tank is disposed adjacent to the storage tank.

6. The system of either of claims 4 and 5, further comprising a power system casing, wherein the internal combustion engine and the exhaust line heat exchanger are disposed within the power system casing, and the single expansion tank is disposed outside the power system casing.

7. The system of any one of claims 1 to 6, further comprising a reservoir configured to collect condensate from the exhaust line heat exchanger; a drain providing a channel between the reservoir and an outlet; and a non-retum valve configured to allow condensate from the reservoir to enter the drain.

8. The system of any one of claims 1 to 7, further comprising an electrical generator comprising a generator fan; and a power system casing comprising a partition wall separating a first compartment and a second compartment; wherein the first compartment houses the internal combustion engine and the exhaust line heat exchanger, the first compartment comprises an engine air inlet configured to allow air to enter the internal combustion engine, and an engine air outlet configured to output exhaust gas from the exhaust line heat exchanger to the outside of the power system casing, and the second compartment houses the electrical generator, control electronics and a battery and comprises an air inlet and an air outlet, wherein the second compartment is configured to provide an air flow path from the air inlet to the air outlet and the generator fan is configured to circulate air through the air flow path for heating the room.

9. The system of claim 8, wherein the battery and control electronics are positioned in the air flow path between the air inlet and the electrical generator.

10. The system of any one of claims 1 to 9, wherein the partition wall comprises a sound insulating material.

11. An exhaust heat exchange module for transferring heat to fluid in a circuit, the exhaust heat exchange module comprising: a first stage heat exchanger configured to reduce a temperature of exhaust gas from a first exhaust temperature to a second exhaust temperature, the first stage heat exchanger comprising a catalyser configured to catalyse the exhaust gas, a catalyser casing housing the catalyser and comprising a fluid inlet and a fluid outlet, and one or more ridges provided between the catalyser and an inside surface of the catalyser casing to define a fluid flow channel between the fluid inlet and the fluid outlet, wherein the one or more ridges are configured such that fluid flowing from the fluid inlet to the fluid outlet follow an indirect fluid flow path.

12. The module of claim 11, wherein the catalyser comprises an outer surface, wherein the outer surface is a surface of the fluid flow channel, and the outer surface is configured to transfer heat from the catalyser to fluid in the fluid flow channel.

13. The module of claim 11 or 12, wherein the one or more ridges are configured such that the fluid flow path between the fluid inlet and the fluid outlet is a helix.

14. The module of any one of claims 11 to 13, wherein the fluid inlet and the fluid outlet are at different longitudinal positions along a longitudinal direction of the catalyser, preferably at or near opposite ends of the catalyser in the longitudinal direction of the catalyser.

15. The module of any one of claims 11 to 14, wherein the first exhaust temperature is between 500 °C and 750 °C, and the second exhaust temperature is between 250 °C and 350

16. The module of any one of claims 11 to 15, further comprising a second stage heat exchanger configured to reduce a temperature of exhaust gas from a third exhaust temperature to a fourth exhaust temperature.

17. The module of claim 16, wherein the third exhaust temperature is between 250 °C and 350 °C, and the fourth exhaust temperature is between 50 °C and 80 °C.

18. The module of claim 16 or 17, wherein the third exhaust temperature is within 10 °C of the second exhaust temperature.

19. The system of any one of claims 1 to 10, wherein the exhaust line heat exchanger is an exhaust heat exchange module according to any one of claims 11 to 18.