NL2028540B1

NL2028540B1 - Hybrid domestic fireplace

Info

Publication number: NL2028540B1
Application number: NL2028540A
Authority: NL
Inventors: Cornelis Christiaan Hund Adriaan
Original assignee: Kal Fire Beheer B V
Priority date: 2021-06-25
Filing date: 2021-06-25
Publication date: 2023-01-02
Also published as: EP4359704A1; AU2022296773A1; WO2022268878A1

Abstract

The present invention relates to a hybrid domestic fireplace, configured to burn a fuel mixture of a first combustible fuel and a second combustible fuel, comprising a combustible 5 long chain hydrocarbon fuel, the fireplace comprising: - a mixing device, configured to mix the first fuel and the second fuel to form the fuel mixture and, - a first fuel supply, configured to supply the first fuel to the mixing device, - a second fuel supply, configured to supply the second fuel to the mixing device, and 10 - a burner, configured to combust the fuel mixture, wherein the mixing device is further configured to heat the second fuel to a mixing temperature, and wherein the mixing device is configured to mix the first fuel with the heated second fuel to form the fuel mixture. 15

Description

P35025NLOO/TRE Title: Hybrid domestic fireplace Field of the invention The present invention relates to a hybrid domestic fireplace and to a method of creating a fire in a hybrid domestic fireplace. State of the art At present, various types of domestic fireplaces are known. Such fireplaces are typically installed in domestic places, such as houses or offices. Generally, these fireplaces have the purpose of displaying flames to contribute to the ambiance in the rooms. Several types of fuels are often used in such domestic fireplaces. A first type of domestic fireplace relies on wooden logs as fuel, which logs are burnt directly. Alternatively, gas hearths are known, which are configured to burn a gas, such as natural gas. Both these types of fireplaces require a flue gas discharge channel and chimney to remove flue gasses out of the room in which the fireplace is located. However, in the absence of a such discharge channels, like in modern apartment buildings, it would be impossible to install one of these types of fireplaces. In an aim to reduce emissions, ethanol fireplaces have been developed, which burn alcohols instead of hydrocarbons. Such alcohols, like ethanol, burn cleaner than wood and natural gas. However, ethanol fireplaces have the drawback that the flames resulting from the combusting of alcohols do not have properties that are desired, i.e. to mimic wood-burning fireplaces. The flames in ethanol fireplaces are typically too vivid, i.e. move too fast, and are coloured relatively bright and transparent, whereas wood flames are more orange.

Object of the invention It is therefore an object of the invention to provide a domestic fireplace that provides flames that mimic flames of wood-burning fireplaces, or at least to provide an alternative domestic fireplace.

Detailed description The present invention provides a hybrid domestic fireplace, configured to burn a fuel mixture of a first combustible fuel and a second combustible fuel, comprising a combustible long chain hydrocarbon fuel, the fireplace comprising: - a mixing device, configured to mix the first fuel and the second fuel to form the fuel mixture and,

2. - a first fuel supply, configured to supply the first fuel to the mixing device, - a second fuel supply, configured to supply the second fuel to the mixing device, and - a burner, configured to combust the fuel mixture, wherein the mixing device is further configured to heat the second fuel to a mixing temperature, and wherein the mixing device is configured to mix the first fuel with the heated second fuel to form the fuel mixture.

The domestic fireplace according to the present invention is a hybrid domestic fireplace, which means that it is configured to burn a mixture of a first fuel and a second fuel. This forms a first difference with existing fireplaces, which generally relied on a single fuel, such as wood, natural gas or ethanol.

The second fuel comprises a long-chain hydrocarbon fuel, which means that the second fuel comprises, but not necessarily exclusively consists of the long-chain hydrocarban fuel. Hence, the second fuel may be a mixture of the long-chain hydrocarbon fuel and, for example, a short-chain hydrocarbon fuel. In an embodiment, however, the second fuel may substantially consist of the long-chain hydrocarbon fuel, possibly only having a slight fraction of impurities.

The long-chain hydrocarbon fuel in the second fuel is defined as a hydrocarbon material of which the hydrocarbon chains have a length of between 16 and 32 carbon atoms. This may include hydrocarbons with elongate, e.g. substantially straight, carbon chains, or possibly entangled, cyclic and/or curved carbon chains.

The mixture that is to be combusted by the fireplace further comprises the first fuel, which may be any type of fuel that is combustible and that can be mixed with the second fuel. Preferably, however, the first fuel comprises an alcohol with a relatively short chain of carbon atoms, for example less than 6 carbon atoms. Alternatively, however, the first fuel may comprise non-hydrocarbons fuels, such as molecular hydrogen.

The mixture of the two fuels provides the present hybrid domestic fireplace with the beneficial properties, since each of the fuels contributes to the appearance of the flames with a certain characteristic. The first fuel, preferably with the short-chain alcohol, may result in fewer emissions, but may be too transparent to mimic wood-burning flames. The second fuel, which is relatively heavy with the long-chain hydrocarbon, may be added, to provide for the orange colour in the flames. By having the fuel mixture, these properties of each of the individual fuels are mixed, to obtain flames that accurately mimic flames of wood-burning fireplaces.

The fractions of the first fuel and the second fuel in the fuel mixture may vary. For example, the ratio between the first fuel and the second fuel may be 50wt% for each of them. Alternatively, for example where the first fuel is in a liquid state at room temperature, such as in particular a first fuel comprising ethanol, and where the second fuel is in a solid state at

-3- room temperature, such as in particular a second fuel comprising paraffin or stearin, the ratio may be in between 98wt®% - 75wt% of first fuel and 2wt% - 25wt% of second fuel, for example 95wt% of ethanol and 5wt% of paraffin.

To obtain these flames, the fireplace comprises the first fuel supply and the second fuel supply, which project into the mixing device, in order to respectively feed the first fuel and the second fuel into the mixing device. The mixing device may comprise an enclosed volume in which the fuels are discharged, but may, alternatively, comprise an open space in the fireplace where both fuels are fed.

The mixing device is configured to mix the first fuel and the second fuel to obtain the fuel mixture. This mixing may involve the mixing of a gaseous first fuel with a gaseous second fuel, of a gaseous first fuel with a liquid second fuel, of a liquid first fuel with a gaseous second fuel or of a liquid first fuel with a liquid second fuel.

The mixing device is connected to a burner, e.g. being fluidly connected to the burner, to guide a flow of the fuel mixture from the mixing device towards the burner. The burner is, in turn, configured to combust the fuel mixture, so that flames are visible in the fireplace. The burner may thereto comprise dedicated ignition means to ignite the fuel mixture supplied to it from the mixing device.

The mixing device is, in addition to the mixing, configured to heat the second fuel. This heating may take place to a mixing temperature, which may be chosen such that the mixing of the fuels is optimized. Instead of mixing the second fuel in the state supplied by the second fuel supply, the mixing device is now configured to mix the first fuel with the heated second fuel to form the fuel mixture.

During heating, the second fuel may undergo a transformation, such as a phase transformation, e.g. vaporizing from a liquid state to an at least partial gaseous state, i.e. into avapor. Such a vaporized second fuel may consist of gaseous second fuel or may comprise only a fraction of gaseous second fuel.

Alternatively or additionally, the second fuel may be nebulized at least partially by the heating, which implies that small droplets of the second fuel become airborne to form a mist of the second fuel in the mixing device. Since the droplets in the mist remain in the liquid phase, no phase transformation will take place. The external surface areas of all droplets combined is significantly larger as compared to when no nebulizing would take place, which increased surface also increases the reactivity of the second fuel.

The mist of second fuel in the mixing device may also be generated when at least part of the vaporized second fuel condenses from the gas phase into the liquid phase, giving rise to a mist of small liquid second fuel droplets.

The mixing device may comprise an enclosed chamber into which the first fuel and second fuel are supplied and in which the second fuel is heated prior to mixing with the first

-4- fuel. Alternatively, however, the mixing device may also be open, for example comprising a heated plate onto which the second fuel is supplied to be heated, after which the mixing with the first fuel takes place in the ambient surroundings of the plate, for example above the plate.

The heating of the second fuel in the mixing device may offer a way to improve the flames that are to be generated in the fireplace. Hence, in the prior art, it was only foreseen to combust fuels that were at ambient temperature, e.g. room temperature. However, at room temperature, not all fuels can be mixed to obtain a substantially homogeneous fuel mixture. By heating the second fuel in the mixing device, the mixing of the fuels can be improved.

As a second benefit, the fuels at room temperature may, upon combustion, not yield flames that have desired properties. By heating the second fuel, the properties of the flames may be improved, since the second fuel may combust easier when it is being combusted at higher temperatures.

In an embodiment of the hybrid domestic fireplace, the first fuel supply is configured to supply the first fuel to the mixing device in a liquid state and the mixing device is configured to heat the first fuel to a vaporizing temperature to vaporize the first fuel in the mixing device.

The first fuel may thereby be a liquid at ambient conditions, e.g. at room temperature, but may be heated by the mixing device as well. Upon heating of the first fuel in the mixing device to the vaporizing temperature, the first fuel is vaporized to end up in a gaseous state. In the gaseous state, the mixing of the first fuel with the heated second fuel, i.e. that is vaporized and/or nebulized, may be improved to obtain a more homogeneous fuel mixture. Furthermore, the fuel mixture may effectively become a vapor, so that it can flow towards the burner more easily, as compared to when it were in a liquid state.

In a further embodiment of the hybrid domestic fireplace, the first fuel is in a liquid state at room temperature and/or the second fuel is in a solid state at room temperature.

The heating of the first fuel may thereby effect that the first fuel, i.e. at the vaporizing temperature, is no longer a liquid after leaving the mixing device. Instead, the first fuel may be in a gaseous state, so that its combustibility is improved, compared to when it were to be in a liquid state.

The heating of the second fuel may furthermore effect that the second fuel, i.e. at the mixing temperature, is no longer a salid after leaving the mixing device. It is noted that the fireplace may be configured to preheat the second fuel, so that it is fed into the mixing device as a liquid. Alternatively, however, the second fuel may be supplied into the mixing device as a solid. After heating in the mixing device, the second fuel may be in a liquid, e.g. nebulized,

-5- or gaseous state, so that its combustibility is improved, compared to when it were to be in a solid state.

In an embodiment of the hybrid domestic fireplace, the vaporizing temperature is in the range between 50°C and 130°C, preferably between 70°C and 110°C, for example 90°C.

It was found by the applicant that, for certain first fuels, vaporizing temperatures in these ranges may effectively result in vaporizing of the first fuel.

It is noted here that the above-mentioned temperature ranges represent the temperatures to which the first fuel is subjected in the mixing device.

To obtain these temperatures, the mixing device may comprise one or more first heating elements that are at a higher temperature by themselves, for example at a temperature in the range between 100°C and 400°C, preferably between 200°C and 300°C, for example 250°C.

In an embodiment of the hybrid domestic fireplace, the mixing temperature is in the range between 250°C and 350°C, preferably between 275°C and 325°C, for example 300°C.

It was found by the applicant that, for certain second fuels, mixing temperatures in these ranges may effectively result in vaporizing and/or nebulizing of the second fuel.

Also here, it is noted here that the above-mentioned temperature ranges represent the temperatures to which the second fuel is subjected in the mixing device.

To obtain these temperatures, the mixing device may comprise one or more second heating elements that are at a higher temperature by themselves, for example at a temperature in the range between 400°C and 800°C, preferably between 500°C and 700°C, for example 600°C.

In an embodiment of the hybrid domestic fireplace, the mixing device comprises a first heating element for heating the first fuel and/or a second heating element for heating the second fuel.

These heating elements may be associated with the respective fuel supplies, so that they are each configured to heat the respective fuels independently, i.e. before the first fuel and the second fuel become mixed to form the fuel mixture.

In an embodiment, the hybrid domestic fireplace further comprises a control unit, configured to control the mixing device.

The control unit may thereto be configured to control one or more parameters of the mixing device.

The control unit may thereto comprise a proportional-integral-derivative controller (PID-controller). The control unit may be configured to control the first heating element of the mixing device, in order to set the vaporizing temperature.

This vaporizing temperature is preferably set indirectly by setting a temperature of the first heating element, which will, in turn,

-6- determine the vaporizing temperature. The control unit may comprise a first PID-controller for controlling the first heating element.

Alternatively or additionally, the control unit may be configured to control the second heating element of the mixing device, in order to set the mixing temperature. This mixing temperature is preferably set indirectly by setting a temperature of the second heating element, which will, in turn, determine the mixing temperature. The control unit may comprise a second PID-controller for controlling the second heating element.

The control unit may comprise a first PID-controller and a distinct second PID-controller. Alternatively, however, their functionalities may as well be combined in a single PID- controller, for controlling both the first heating element and the second heating element.

In a further embodiment, the hybrid domestic fireplace further comprises a temperature sensor located in the mixing device, configured to emit a temperature sensor signal representative for the temperature in the mixing device, and the control unit is configured to control the mixing device, e.g. the first heating element and/or the second heating element, on the basis of the temperature signal to set the vaporizing temperature and/or the mixing temperature.

According to this embodiment, the mixing device is controlled on the basis of the temperature in the mixing device, as measured by the temperature sensor. The control unit may be configured to operate in a feedback manner, for which a temperature difference between a desired temperature and the measured temperature forms the basis for a new set temperature for the mixing device.

The mixing device may comprise a first temperature sensor, preferably associated with the first fuel supply and/or the first heating element, which is configured to emit a first temperature sensor signal representing the temperature at which the first fuel is heated, for example representing the temperature of the first heating element. The control unit may be configured to control the first heating element on the basis of the first temperature sensor signal.

The mixing device may comprise a second temperature sensor, preferably associated with the second fuel supply and/or the second heating element, which is configured to emit a second temperature sensor signal representing the temperature at which the second fuel is heated, for example representing the temperature of the second heating element. The control unit may be configured to control the second heating element on the basis of the second temperature sensor signal.

In an embodiment of the hybrid domestic fireplace, the first fuel supply is configured to supply the first fuel to the mixing device in a gaseous state. This embodiment of the fireplace

-7- may lack the first heating element in the mixing device, since the first fuel is already supplied to the mixing device in the gaseous state, which means that no further heating in the mixing device is needed for the first fuel.

This embodiment of the fireplace may comprise a fuel pre-heating element, separate from the mixing device, which is configured to pre-heat the first fuel towards the gaseous state at a location remote from the mixing device.

In an embodiment of the hybrid domestic fireplace, the first fuel supply comprises: - a first fuel storage, configured to store the first fuel, - a first fuel line, extending between the first fuel storage and the mixing device, and - a first fuel pump, configured to pump the first fuel through the first fuel line, i.e. from the first fuel storage to the mixing device.

The first fuel storage and the first fuel pump may be located remotely from the mixing device. The first fuel line thereby extends between the first fuel storage and the mixing device and projects, e.g. indirectly, into the mixing device. This indirect projection may be affected by means of a first nozzle, which is in fluid contact with the first fuel line and which may be able to withstand the heat in the mixing device better than the first fuel line itself would. The first fuel line thereby forms a fluid connection between the first fuel storage and the mixing device for the first fuel, whereas the first pump is configured to actively pump the first fuel from the first fuel storage to the mixing device.

In a further embodiment of the hybrid domestic fireplace, the first fuel storage is configured to store the first fuel in a liquid state. The first fuel storage may thereto be embodied as a liquid tank. For example, the first fuel storage may be an exchangeable bottle containing the first fuel.

The first fuel storage may comprise a first fuel level sensor, which is configured to emit a first fluid level sensor signal representative for the fluid level in the first fuel storage. The first fuel level sensor may be a floating sensor, configured to float on a surface level of the first fuel in the first fuel storage. The sensor signal of such a floating sensor may, for example, be determined by whether the sensor floats freely on the fluid surface, or whether the sensor contacts a bottom surface of the first fuel storage.

In a further embodiment of the hybrid domestic fireplace, the control unit is further configured to emit a fuel level warning signal when the amount of first fuel remaining in the first fuel storage is below a desired threshold amount, e.g. a threshold fuel level of first fuel.

The control unit may thereby detect when the first fluid level signal is below a threshold first fluid level signal. Accordingly, a user can be warned if the amount of first fuel remaining

-8- in the first fuel storage is too low. The warning signal may comprise a visible and/or audible alarm that is presented to the user.

Furthermore, in case the user may not replenish the first fuel in time, the control unit may be configured to shut down the fireplace, e.g. to stop the first fuel pump, the second fuel pump, the air pump, the first heating element and/or the second heating element.

In an additional or alternative embodiment of the hybrid domestic fireplace, the first fuel pump is a peristaltic pump. The peristaltic pump may be provided at the first fuel line, i.e. in between the first fuel storage and the mixing device. Such a peristaltic pump not necessarily needs to be provided in or near the first fuel storage, but may for example be provided halfway the first fuel line.

The peristaltic pump may be configured to pump the first fuel in a pulsed manner, e.g. by means of consecutive pulses for a certain first pulse duration. The pulsed pumping of first fuel may effect that the flow of first fuel to the mixing device, and therefore also the flow of fuel mixture towards the burner, varies over time. Accordingly, the intensity of the flames may vary over time, so that the flames more accurately mimic the flames in a wood-burning fireplace.

Additionally or alternatively, the pumping of the first fuel may be carried out cyclically, i.e. to vary over time. In this way, the normal burning behaviour of wooden logs can be simulated. Hence, at the onset of burning a log, the intensity of the flames may be relatively low. At this stage, the first fuel pump may be configured to supply a relatively small flow of first fuel as well.

Next, for example over a time span of 5 minutes, the first fuel pump may be controlled to increase the flow of first fuel, to mimic a wooden log that becomes combusted to a larger extent. Finally, for example after 20 minutes, the first fuel pump may be controlled to decrease the flow of first fuel again, for example gradually over a time span of 5 minutes, to mimic extinction of the wooden log.

In an embodiment of the hybrid domestic fireplace, the second fuel supply comprises: - a second fuel storage, configured to store the second fuel, - a second fuel line, extending between the second fuel storage and the mixing device, and - a second fuel pump, configured to pump the second fuel through the second fuel line, i.e. from the second fuel storage to the mixing device.

The second fuel storage and the second fuel pump may be located remotely from the mixing device. The second fuel line thereby extends between the second fuel storage and the

-9.- mixing device and projects, e.g. indirectly, into the mixing device. This indirect projection may be affected by means of a second nozzle, which is in fluid contact with the second fuel line and which may be able to withstand the heat in the mixing device better than the second fuel line itself would. The second fuel line thereby forms a fluid connection between the second fuel storage and the mixing device for the second fuel, whereas the second pump is configured to actively pump the second fuel from the second fuel storage to the mixing device.

In a further embodiment of the hybrid domestic fireplace, the second fuel storage is, at least during use of the fireplace, configured to store the second fuel in a liquid state, i.e. at an elevated storage temperature, compared to the temperature of the surroundings of the fireplace.

This storage of the second fuel at the elevated storage temperature may be beneficial in case the second fuel is in a solid state at room temperature. Such a solid cannot be pumped by the second fuel pump, so the second solid fuel must be heated to end up being in liquid state in order to allow for pumping.

The heating of the second fuel may, but not necessarily, be carried out continuously, to hold the second fuel in the liquid state continuously. Alternatively, the heating of the second fuel may only be carried out temporarily, for example only when the fireplace is activated.

Preferably, the heating of the second fuel is activated prior to activating the fireplace, since the pumping of the second fuel can only be carried out when the second fuel is in liquid state and since it will generally take some time to melt all the second fuel in the second fuel storage.

In a further embodiment of the hybrid domestic fireplace, the second fuel storage comprises a storage heating device, configured to heat the second fuel in the second fuel storage to the elevated storage temperature, and to keep the second fuel in the second fuel storage in the liquid state.

The storage heating device may be arranged inside the second fuel storage to heat the second fuel arranged therein and may be an electric storage heating device. The storage heating device may be a resistive storage heating device that is, e.g. under influence of an electric current through it, configured to undergo an increase in temperature, thereby heating the second fuel in the second fuel storage.

The elevated storage temperature is for example in the range between 60°C and 100°C, preferably between 70°C and 90°C, for example 80°C. This temperature range may be beneficial to, on the one hand, allow the second fuel to be pumped and to, on the other hand, prevent overheating and fuming of the second fuel, to prevent unwanted scents. For

-10- example when the second fuel were to be wax, like paraffin or stearin, such smells could occur if the elevated storage temperature were to be set too high.

In an embodiment of the hybrid domestic fireplace, the second fuel line comprises a line heating device, configured to heat the second fuel in the second fuel line to an elevated fuel line temperature and to keep the second fuel in the second fuel line in the liquid state.

The line heating device may be arranged inside a wall of the second fuel line and is configured to prevent solidifying of the second fuel inside the second fuel line. Hence, in the absence of such a line heating device, the second fuel would be subject to the ambient conditions, e.g. room temperature, in the second fuel line.

The elevated fuel line temperature is for example in the range between 50°C and 90°C, preferably between 60°C and 80°C, for example 70°C. At these temperatures, the viscosity of the liquid second fuel may be such that it can be pumped by the second fuel pump.

In a further embodiment of the hybrid domestic fireplace, the fuel line heating device is a resistive fuel line heating device, extending over substantially the entire length of the second fuel line. The resistive fuel line heating device may, e.g. under influence of an electric current through it, undergo an increase in temperature, thereby heating the second fuel in the second fuel line. With the fuel line heating device extending over the entire length of the second fuel line, the heating of the second fuel inside the second fuel line may be affected over the entire length of the second fuel line.

In an embodiment, the storage heating device and the fuel line heating device may be combined, e.g. being formed by a single heating device, so that the heating of the second fuel inside the second fuel storage and the heating of the second fuel inside the second fuel line is carried out by a single heating device, preferably a single resistive heating device.

According to this embodiment, it may be safeguarded that the heating of the second fuel storage is carried out to prevent over-heating of the second fuel, in order to prevent fuming thereof in the second fuel storage, whilst still keeping the second fuel in fluid form in the second fuel line. This may be done by only heating activating the single heating device periodically.

In an embodiment of the hybrid domestic fireplace, the second fuel pump is a pulse pump, preferably located in the second fuel storage. The pulse pump may comprise a movable diaphragm, which is configured to be actuated to take in the second fuel at one side and to discharge the second fuel at an opposed side.

-11- A pulse pump has the benefit that it can be placed inside the second fuel storage, both when the second fuel is in its solid state, i.e. at room temperature, and in its liquid state. However, the second fuel must be at the elevated storage temperature in the liquid state to be able to pump it, since pumping with a pulse pump may not be possible when the second fuel is in the solid state.

The pulse pump may be configured to pump the second fuel in a pulsed manner, e.g. by means of consecutive pulses for a certain second pulse duration. The pulsed pumping of second fuel may effect that the flow of second fuel to the mixing device, and therefore also the flow of fuel mixture towards the burner, varies over time. Accordingly, the intensity of the flames may vary over time, so that the flames more accurately mimic the flames in a wood- burning fireplace.

Additionally or alternatively, the pumping of the second fuel may be carried out cyclically, i.e. to vary over time. In this way, the normal burning behaviour of wooden logs can be simulated. Hence, at the onset of burning a log, the intensity of the flames may be relatively low. At this stage, the second fuel pump may be configured to supply a relatively small flow of second fuel as well.

Next, for example over a time span of 5 minutes, the second fuel pump may be controlled to increase the flow of second fuel, to mimic a wooden log that becomes combusted to a larger extent. Finally, for example after 20 minutes, the second fuel pump may be controlled to decrease the flow of second fuel again, for example gradually over a time span of 5 minutes, to mimic extinction of the wooden log.

In an embodiment of the hybrid domestic fireplace, the second fuel storage comprises a second fuel level sensor, configured to emit a second fuel level sensor signal representative for the amount, e.g. fuel level, of second fuel remaining in the second fuel storage.

The second fuel level sensor may comprise an elongate temperature sensor, which may be aligned in a substantial vertical direction. This temperature sensor may be configured to measure temperatures over its length in the vertical direction, e.g. at various measuring points over its height. Accordingly, the temperature sensor may be configured to determine a temperature difference between adjacent measuring points.

During use of the fireplace, the second fuel may be stored at the elevated storage temperature, i.e. above the ambient, e.g. room temperature. As such, all measuring points of the temperature sensor in contact with the second fuel are configured to emit a sensor signal representative for the elevated storage temperature, whereas all other measuring points, i.e. above the fluid level of the second fuel, are configured to emit a sensor signal representative for the ambient temperature. The fluid level in the second fuel storage may be determined by

-12- determining the number of measuring points of the temperature sensor being in contact with the second fuel at the elevated storage temperature. Additionally, this second fluid level sensor, i.e. embodied as a temperature sensor, may be used to detect whether the second fuel in the second fuel storage is in the liquid state already and whether it is ready to be pumped. Hence, if the measuring points of the temperature sensor in contact with the second fuel would emit a sensor signal representative for a temperature lower than the elevated storage temperature, the control unit may determine that further heating, e.g. by the storage heating element, may be needed to heat the second fuel towards the elevated storage temperature.

In a further embodiment of the hybrid domestic fireplace, the control unit is further configured to emit a fuel level warning signal when the amount of second fuel remaining in the second fuel storage is below a desired threshold amount, e.g. a threshold fuel level of second fuel.

The control unit may thereby detect when the second fluid level signal is below a threshold second fluid level signal. Accordingly, a user can be warned if the amount of second fuel remaining in the second fuel storage is too low. The warning signal may comprise a visible and/or audible alarm that is presented to the user.

Furthermore, in case the user may not replenish the second fuel in time, the control unit may be configured to shut down the fireplace, e.g. to stop the first fuel pump, the second fuel pump, the air pump, the first heating element and/or the second heating element.

In an embodiment of the hybrid domestic fireplace, the second fuel storage comprises a fuel capsule holder, which is configured to receive a fuel capsule containing the second fuel.

According to this embodiment, the second fuel storage may not be a reservoir to hold the second fuel, but instead comprises the holder, which for example includes the second fuel pump and the fuel storage heating device and in which individual capsule are to be received.

The fuel capsules may be recharge capsules, which may be commercialized separately from the fireplace. In case the fireplace of a user runs out of second fuel, the user may provide a new fuel capsule filled with second fuel. Instead of having to fill a reservoir, either with solid or liquid second fuel, the user may now simply remove the empty fuel capsule and may place the new fuel capsule in the holder. This improves the convenience for a user of operating the fireplace.

In a further embodiment of the hybrid domestic fireplace, the threshold fluid level represents that the fuel capsule in the fuel capsule holder is empty, and the fluid level warning

-13- signal comprises a user notification that the empty fuel capsule needs to be replaced with a new fuel capsule. In an embodiment, the hybrid domestic fireplace further comprises an air supply, projecting into the mixing device and configured to provide a flow of air through the mixing device, wherein the mixing device is further configured to mix the fuel mixture with the air supplied by the air supply.

The flow of air through the mixing device may act as a carrier for the vaporized first fuel and/or the heated second fuel, so that these fuels are drawn through the mixing device by the air, instead of having to be pumped at high pressures by the first fuel supply and the second fuel supply. The flow of air induced by the air supply may flow along the first fuel supply and the second fuel supply to pick up the first fuel and the second fuel directly. Preferably, the flow of air is guided along the first heating element, to pick up vaporized first fuel, and/or along the second heating element, to pick up heated, e.g. vaporized and/or nebulized, second fuel.

The flow of air in the mixing device may further give rise to turbulences in the mixing device, which turbulences may contribute to the mixing of the first fuel and the second fuel, i.e. with each other and with the air in the flow of air, in order to provide for a more homogeneous fuel mixture.

Furthermore, with the air being mixed with the fuel mixture, primary combustion air may already be present in the mixture that is fed from the mixing device towards the burner. This primary combustion air may contribute in reducing the formation of CO upon combusting the fuel mixture.

In a further embodiment of the hybrid domestic fireplace, the air supply comprises an air pump and an air hose, extending between the air pump and the mixing device, wherein the air pump is configured to pump the air through the air hose, i.e. towards the mixing device.

The air pump may be located remotely from the mixing device. The air hose may thereby extend between the ambient air at an air inlet and the mixing device and projects, e.g.

indirectly, into the mixing device. This indirect projection may be affected by means of an air nozzle, which is in fluid contact with the air hose and which may be able to withstand the heat in the mixing device better than the air hose itself would.

The air pump may be provided at the air inlet or at any intermediate location along the air hose. The air hose thereby forms a fluid connection between the ambient air, i.e. at the air inlet, and the mixing device for the flow of air, whereas the air pump is configured to actively pump the air from the ambient, i.e. outside the fireplace, to the mixing device.

-14 - In an embodiment of the hybrid domestic fireplace, the air supply forms part of the first fuel supply, configured to supply a gas mixture to the mixing device, which gas mixture comprises the flow of air and the gaseous first fuel.

According to this embodiment, the functionalities of the first fuel supply and of the air supply are combined. The gaseous first fuel is thereby mixed with the flow of air before entering the mixing device. The mixing device may thereto lack a first heating element for heating the first fuel, but may, instead, comprise only a single second heating element for heating the second fuel. The gas mixture, containing the flow of air and the first fuel, may be supplied into the mixing device at a location at or near the second fuel supply and/or the second heating element.

In an embodiment of the hybrid domestic fireplace, the control unit is further configured to control the first fuel pump, the second fuel pump and/or the air pump, for example configured to set a flow rate thereof.

The control unit may comprise a respective own PID-controller for the first fuel pump, the second fuel pump and/or the air pump. Alternatively, however, their functionalities may as well be combined in a single PID-controller, i.e. for controlling all pumps.

The control unit may be configured to control the flow rate, i.e. the volume of fluid pumped per unit of time, for the first fuel pump, the second fuel pump and/or the air pump.

Alternatively or additionally, the control unit may determine a pumping duration for each of the pumps and/or a pumping pressure.

The control unit may be configured to control the first fuel pump, the second fuel pump and/or the air pump to pump in a pulsed manner, e.g. by means of consecutive pulses for a certain air pulse duration. The pulsed pumping may effect that the flow of fluids to the mixing device, and therefore also the flow of fuel mixture towards the burner, varies over time. Accordingly, the intensity of the flames may vary over time, so that the flames more accurately mimic the flames in a wood-burning fireplace.

In an embodiment of the hybrid domestic fireplace, the control unit is further configured to control the storage heating device and/or the fuel line heating device, for example configured to set the elevated storage temperature and/or the elevated fuel line temperature.

The controlling of the storage heating device may provide the advantage that the temperature of the second fuel in the second fuel storage can be optimally set to, on the one hand, allow the second fuel to be pumped and to, on the other hand, prevent overheating and fuming of the second fuel, to prevent unwanted scents. For example when the second fuel were to be wax, like paraffin or stearin, such smells could occur if the elevated storage temperature were to be set too high by the control unit.

-15- In an embodiment of the hybrid domestic fireplace, the first fuel is in a liquid state at room temperature, comprising an alcohol, such as ethanol, or a spirit, for example comprising alcohol and up to 50wt% of water.

According to this embodiment, the first fuel comprises an alcohol, which means that the first fuel comprises, but not necessarily exclusively consists of the alcohol. Hence, the first fuel may be a mixture of the alcohol and, for example, water.

The alcohol in the first fuel may be defined as an alcohol with a relatively short chain of carbon atoms, for example less than 6 carbon atoms, such as methanol, ethanol, propanol or butanol.

An example of a mixture comprising alcohol is a spirit, which may typically contain ethanol with about 15wt% water in it. The water may have a positive contribution in the vaporizing of the first fuel in the mixing device and in the combusting of the fuel mixture in the burner, for example contributing to flames that more accurately mimic flames in wood-burning fireplaces. In other examples, the amount of water in the first fuel may be up to 50wt%.

In another example, the first fuel may substantially consist of the alcohol, possibly only having a slight fraction of impurities. An example thereof would be bioethanol, which mainly consists of ethanol.

Alternatively, however, the first fuel may comprise non-hydrocarbons fuels, such as molecular hydrogen.

In an embodiment of the hybrid domestic fireplace, the second fuel is in a solid state at room temperature, comprising a wax, such as paraffine, stearin and/or candle wax.

The second fuel comprises a long-chain hydrocarbon fuel, which is defined as a hydrocarbon material of which the hydrocarbon chains have a length of between 16 and 32 carbon atoms. This may include hydrocarbons with elongate, e.g. substantially straight, carbon chains, or possibly entangled, cyclic and/or curved carbon chains.

Examples of such a long-chain hydrocarbon fuel are paraffine, stearin, candle wax or other types of synthetic or natural waxes, which are in a solid state at room temperature.

Hereinafter, wax is used to refer to all these materials.

The second fuel comprises, but not necessarily exclusively consists of a wax that is solid at room temperature. Hence, the second fuel may be a mixture of the wax and, for example, a short-chain hydrocarbon fuel. In an embodiment, however, the second fuel may substantially consist of the wax, possibly only having a slight fraction of impurities, like it is the case with tealight, e.g. remains thereof, or other candles.

- 16 - The second fuel cannot be mixed in the mixing chamber when it is a solid at room temperature. However, by heating the second fuel in the mixing device and/or by preheating the second fuel outside the mixing device, the mixing of the fuels can be facilitated.

In an alternative embodiment of the hybrid domestic fireplace, the second fuel is in a liquid state at room temperature, for example comprising lamp oil and/or paraffine oil.

Also in this embodiment, the second fuel comprises a long-chain hydrocarbon fuel, such as paraffine, stearin, or other types of synthetic or natural hydrocarbons. The second fuel further comprises other ingredients, such as liquid hydrocarbon fuels, which are mixed with the long-chain hydrocarbon fuel, e.g. the solid ingredient. This mixture is liquid at room temperature, which implies that no storage heating device may be needed in the second fuel storage and/or that no line heating device may be needed in the second fuel line, because the liquid second fuel can already be pumped at room temperature.

An example of a liquid second fuel is lamp oil or paraffine oil, which may be a mixture of paraffine or stearin and a liquid hydrocarbon, such as kerosene.

According to a second aspect, the present invention provides a method of creating a fire in a hybrid domestic fireplace, comprising the steps of: - supplying a first combustible fuel to a mixing device of the fireplace, - supplying a second combustible fuel, comprising a combustible long chain hydrocarbon fuel, to the mixing device, - heating, in the mixing device, for example with a second heating element, the second fuel to a mixing temperature, - mixing, in the mixing device, the first fuel with the heated second fuel to form a fuel mixture, and - combusting the fuel mixture with a burner of the fireplace to create the fire.

The method according to the present invention is carried out in a hybrid domestic fireplace, which means that it relies on the combusting of a mixture of a first fuel and a second fuel. This forms a first difference with existing methods, which generally relied on a single fuel, such as wood, natural gas or ethanol.

The second fuel comprises a long-chain hydrocarbon fuel, which means that the fuel comprises, but not necessarily exclusively consists of the long-chain hydrocarbon fuel. Hence, the second fuel may be a mixture of the long-chain hydrocarbon fuel and, for example, a short-chain hydrocarbon fuel. In an embodiment, however, the second fuel may substantially consist of the long-chain hydrocarbon fuel, possibly only having a slight fraction of impurities.

-17 - The long-chain hydrocarbon fuel in the second fuel is defined as a hydrocarbon material of which the hydrocarbon chains have a length of between 16 and 32 carbon atoms. This may include hydrocarbons with elongate, e.g. substantially straight, carbon chains, or possibly entangled, cyclic and/or curved carbon chains.

The mixture of the two fuels provides the present method with the beneficial properties, since each of the fuels contributes to the appearance of the flames with a certain characteristic. The first fuel, preferably with the short-chain alcohol, may result in fewer emissions, but may be too transparent to mimic wood-burning flames. The second fuel, which is relatively heavy with the long-chain hydrocarbon, may be added, to provide for the orange colour in the flames. By having the fuel mixture, these properties of each of the individual fuels are mixed, to obtain flames that accurately mimic flames of wood-burning fireplaces.

The fractions of the first fuel and the second fuel in the fuel mixture may vary. For example, the ratio between the first fuel and the second fuel may be 50wt% for each of them. Alternatively, for example where the first fuel is in a liquid state at room temperature, such as in particular a first fuel comprising ethanol, and where the second fuel is in a solid state at room temperature, such as in particular a second fuel comprising paraffin or stearin, the ratio may be in between 98wt% - 75wt% of first fuel and 2wt% - 25wt% of second fuel, for example 95wt% of ethanol and 5wt% of paraffin.

To obtain these flames, the first fuel and the second fuel are fed into the mixing device.

The mixing device may comprise an enclosed volume in which the fuels are discharged, but may, alternatively, comprise an open space in the fireplace where both fuels are fed.

The mixing device is connected to the burner, e.g. being fluidly connected to the burner, to guide a flow of the fuel mixture from the mixing device towards the burner. The burner is, in turn, configured to combust the fuel mixture, so that flames are visible in the fireplace. The burner may thereto comprise dedicated ignition means to ignite the fuel mixture supplied to it from the mixing device.

The second fuel is heated in the mixing device, in addition to the mixing taking place therein. This heating may take place to a mixing temperature, which may be chosen such that

-18- the mixing of the fuels is optimized.

Instead of mixing the second fuel in the state supplied by the second fuel supply, the mixing device is now configured to mix the first fuel with the heated second fuel to form the fuel mixture.

During heating, the second fuel may undergo a transformation, such as a phase transformation, e.g. vaporizing from a liquid state to an at least partial gaseous state, i.e. into a vapor.

Such a vaporized second fuel may consist of gaseous second fuel or may comprise only a fraction of gaseous second fuel.

Alternatively or additionally, the second fuel may be nebulized at least partially by the heating, which implies that small droplets of the second fuel become airborne to form a mist of the second fuel in the mixing device.

Since the droplets in the mist remain in the liquid phase, no phase transformation will take place.

The external surface areas of all droplets combined is significantly larger as compared to when no nebulizing would take place, which increased surface also increases the reactivity of the second fuel.

The mixing device may comprise an enclosed chamber into which the first fuel and second fuel are supplied and in which the second fuel is heated prior to mixing with the first fuel.

Alternatively, however, the mixing device may also be open, for example comprising a heated plate onto which the second fuel is supplied to be heated, after which the mixing with the first fuel takes place in the ambient surroundings of the plate, for example above the plate.

The heating of the second fuel in the mixing device may offer a way to improve the flames that are to be generated in the fireplace.

Hence, in the prior art, it was only foreseen to combust fuels that were at ambient temperature, e.g. room temperature.

However, at room temperature, not all fuels can be mixed to obtain a substantially homogeneous fuel mixture.

By heating the second fuel in the mixing device, the mixing of the fuels can be improved.

As a second benefit, the fuels at room temperature may, upon combustion, not yield flames that have desired properties.

By heating the second fuel, the properties of the flames may be improved, since the second fuel may combust easier when it is being combusted at higher temperatures.

In an embodiment, the method further comprises the step of: - heating, in the mixing device, for example with a first heating element, the first fuel to a vaporizing temperature to vaporize the first fuel.

According to this embodiment, the first fuel may be heated by the mixing device as well.

Upon heating of the first fuel in the mixing device to the vaporizing temperature, the first fuel

-19- is vaporized to end up in a gaseous state. In the gaseous state, the mixing of the first fuel with the heated second fuel, i.e. that is vaporized and/or nebulized, may be improved to obtain a more homogeneous fuel mixture. Furthermore, the fuel mixture may effectively become a vapor, so that it can flow towards the burner more easily, as compared to when it were in a liquid state.

In an embodiment, the method further comprises the steps of - measuring, with a temperature sensor, the temperature of the mixing device, e.g. of the first heating element and/or the second heating element, and - controlling, with a control unit, the heating of the first fuel and/or the second fuel on the basis of the measured temperature to set the vaporizing temperature and/or the mixing temperature.

The mixing device may comprise a first temperature sensor, preferably associated with the first fuel supply and/or the first heating element, which emits a first temperature sensor signal representing the temperature at which the first fuel is heated. The control unit may be configured to control the first heating element on the basis of the first temperature sensor signal.

The mixing device may comprise a second temperature sensor, preferably associated with the second fuel supply and/or the second heating element, which emits a second temperature sensor signal representing the temperature at which the second fuel is heated. The control unit may be configured to control the second heating element on the basis of the second temperature sensor signal.

In an embodiment of the method, the first fuel is in a liquid state at room temperature, for example comprising an alcohol, such as ethanol, or a spirit, for example comprising alcohol and up to 50wt% of water.

-20- An example of a mixture comprising alcohol is a spirit, which may typically contain ethanol with about 15wt% water in it. The water may have a positive contribution in the vaporizing of the first fuel in the mixing device and in the combusting of the fuel mixture in the burner, for example contributing to flames that more accurately mimic flames in wood-burning fireplaces. In other examples, the amount of water in the first fuel may be up to 50wt%.

In an embodiment of the method, the second fuel is in a solid state at room temperature, for example comprising a wax, such as paraffine, stearin and/or candle wax.

Hereinafter, wax is used to refer to all these materials.

The second fuel cannot be mixed in the mixing chamber when it is a solid at room temperature. However, by heating the second fuel in the mixing device and/or by preheating the second fuel outside the mixing device, the mixing of the fuels can be facilitated.

In an alternative embodiment of the method, the second fuel is in a liquid state at room temperature, for example comprising lamp oil and/or paraffine oil.

Also in this embodiment, the second fuel comprises a long-chain hydrocarbon fuel, such as paraffine, stearin or other types of synthetic or natural hydrocarbons. The second fuel further comprises other ingredients, such as liquid hydrocarbon fuels, which are mixed with the long-chain hydrocarbon fuel, e.g. the solid ingredient. This mixture is liquid at room temperature, which implies that no storage heating device may be needed in the second fuel

-21- storage and/or that no line heating device may be needed in the second fuel line, because the liquid second fuel can already be pumped at room temperature. An example of a liquid second fuel is lamp oil or paraffine oil, which may be a mixture of paraffine or stearin and a liquid hydrocarbon, such as kerosene.

Brief description of drawings Further characteristics of the invention will be explained below, with reference to embodiments, which are displayed in the appended drawings, in which: Figure 1 schematically depicts an embodiment of the hybrid domestic fireplace according to the present invention, Figure 2 schematically depicts a close-up on the mixing device and burner of the fireplace of figure 1, and Figure 3 shows a diagram with the components of the fireplace of figure 1.

Throughout the figures, the same reference numerals are used to refer to corresponding components or to components that have a corresponding function. Detailed description of embodiments Figure 1 schematically depicts an embodiment of the hybrid domestic fireplace according to the present invention, to which is referred with reference numeral 1. The fireplace 1 comprises a mixing device 10, which is configured to mix a first fuel F1 and a second fuel F2 to form a fuel mixture 101. The first fuel F1 is in a liquid state at room temperature, comprising an alcohol. In particular, the first fuel F1 is a mixture comprising a spirit, which contains ethanol with about 15wt% water in it. The second fuel F2 is in a solid state at room temperature, comprising a wax. In particular, the second fuel F2 contains paraffin or stearin. The fireplace 1 further comprises a first fuel supply 20, which projects into the mixing device 10 and which is configured to supply the first fuel F1 to the mixing device 10, and a second fuel supply 30, which projects into the mixing device 10 as well, being configured to supply the second fuel F2 to the mixing device 10. The mixing device 10 comprises an enclosed volume in which the fuels F1, F2 are discharged. The mixing device 10 is configured to mix the first fuel F1 and the second fuel F2 to obtain the fuel mixture 101. Furthermore, the fireplace 1 comprises a burner 40, which is fluidly connected to the mixing device 10 by means of a burner channel 41 to guide a flow of the fuel mixture 101 from the mixing device 10 towards the burner 40. The burner 40 is, in turn, configured to

22. combust the fuel mixture 101, so that flames 102 are visible in the fireplace 1. The burner 40 comprises dedicated ignition means to ignite the fuel mixture 101 supplied to it from the mixing device 10. The mixing device 10 is further configured to heat the first fuel F1 by means of a first heating element 11, which is embodied as an infrared heating element. The mixing device 10 is configured to heat the first fuel F1 to a vaporizing temperature to vaporize the first fuel F1 in the mixing device 10. In the present embodiment, the vaporizing temperature is set at 90°C. To obtain this temperature, the first heating element 11 itself is controlled to reach a temperature of 250°C.

The mixing device 10 is further configured to heat the second fuel F2 by means of a second heating element 12, which is embodied as a resistive heating element. The mixing device 10 is configured to heat the second fuel F2 to a mixing temperature to heat the second fuel F2 in the mixing device 10, to vaporize and/or to nebulize the second fuel F2. In the present embodiment, the mixing temperature is set at 300°C. To obtain this temperature, the second heating element 12 itself is controlled to reach a temperature of 600°C.

After heating the fuels, the mixing is configured to take place in the enclosed chamber of the mixing device 10, in order to obtain the fuel mixture 101 in the burner channel 41.

The mixing device 10 comprises a first temperature sensor 13, which is arranged adjacent the first heating element 11. The first temperature sensor 13 is configured to emit a first temperature sensor signal representing the temperature at which the first fuel F1 is heated.

The mixing device 10 further comprises a second temperature sensor 14, which is arranged adjacent the second heating element 12. The second temperature sensor 14 is configured to emit a second temperature sensor signal representing the temperature at which the second fuel F2 is heated.

The fireplace 1 further comprises a control unit 50, which is embodied as a proportional-integral-derivative (PID) controller and which is configured to control the mixing device 10 and to operate in a feedback manner. The control unit 50 is electrically connected to the first heating element 11 and to the second heating element 12, for providing electricity towards the respective heating elements 11, 12, and is electrically connected to the first temperature sensor 13 and to the second temperature sensor 14, for transmitting the sensor signals from the respective temperature sensors 13, 14 to the control unit 50.

The control unit 50 is configured to control the first heating element 11 on the basis of the first temperature sensor signal, in order to set the vaporizing temperature, and is configured to control the second heating element 12 on the basis of the second temperature sensor signal, in order to set the mixing temperature.

- 23.

The fireplace 1 further comprises an air supply 60, projecting into the mixing device 10 and configured to provide a flow of air through the mixing device 10, to act as a carrier for the vaporized first fuel F1 and the heated second fuel F2. The mixing device 10 is further configured to mix the fuel mixture 101 with the air supplied by the air supply 60. Inside the mixing device 10, the flow of air is guided along the first heating element 11, to pick up vaporized first fuel F1, and along the second heating element 12, to pick up heated second fuel F2.

The air supply 60 comprises an air pump 61 and an air hose 62, extending between the ambient air at an air inlet 63, i.e. outside the fireplace 1, and the mixing device 10. The air pump 61 is located remotely from the mixing device 10 and is configured to pump the air through the air hose 62 and towards the mixing device 10.

The control unit 50 is electrically connected to the air pump 61 for providing electricity towards the air pump 81. The control unit 50 is further configured to control the air pump 61, in particular to control an air flow rate for the air pump 81.

The first fuel supply 20 comprises a first fuel storage 21, configured to store the first fuel F1, a first fuel line 22, extending between the first fuel storage 21 and the mixing device 10, and a first fuel pump 23, configured to pump the first fuel F1 through the first fuel line 22, i.e. from the first fuel storage 21 to the mixing device 10. The first fuel storage 21 and the first fuel pump 23 are located remotely from the mixing device 10, being connected to each other via the first fuel line 22.The first fuel pump 23 is a peristaltic pump that is provided in the first fuel line 22, i.e. in between the first fuel storage 21 and the mixing device 20.

The control unit 50 is electrically connected to the first fuel pump 23 for providing electricity towards the first fuel pump 23. The control unit 50 is further configured to control the first fuel pump 23, in particular to control a flow rate for the first fuel pump 23.

The control unit 50 is configured to control the first fuel pump 23 in a pulsed manner, e.g. by means of consecutive pulses for a certain first pulse duration. The pulsed pumping may effect that the flow of first fuel F1 to the mixing device 10, and therefore also the flow of fuel mixture 101 towards the burner 40, varies over time.

The first fuel storage 21 comprises a first fuel level sensor 24, which is configured to emit a first fluid level sensor signal representative for the fluid level in the first fuel storage 21. The first fuel level sensor 24 is a floating sensor, configured to float on the surface level of the first fuel F1 in the first fuel storage 21. The control unit 50 is electrically connected to the first fluid level sensor 24, for transmitting the first fluid level sensor signal from the first fluid level sensor 24 to the control unit 50.

The control unit 50 is further configured to control the first fuel pump 23 on the basis of the first fluid level sensor signal, in order to stop pumping of the first fuel pump 23 when the

-24 - fluid level in the first fuel storage 21 is below a threshold level and to emit a visible and audible warning signal from the fireplace 1.

The second fuel supply 30 comprises a second fuel storage 31, configured to store the second fuel F2, a second fuel line 32, extending between the second fuel storage 31 and the mixing device 10, and a second fuel pump 33, configured to pump the second fuel F2 through the second fuel line 32, i.e. from the second fuel storage 31 to the mixing device 10.

The second fuel storage 31 and the second fuel pump 33 are located remotely from the mixing device 10, being connected to each other via the second fuel line 32. The second fuel pump 33 is a pulse pump that is submerged in the second fuel F2 in the second fuel storage

31.

The control unit 50 is electrically connected to the second fuel pump 33 for providing electricity towards the second fuel pump 33. The control unit 50 is further configured to control the second fuel pump 33, in particular to control a flow rate for the second fuel pump

33.

The control unit 50 is configured to control the second fuel pump 33 in a pulsed manner, e.g. by means of consecutive pulses for a certain second pulse duration. The pulsed pumping may effect that the flow of second fuel F2 to the mixing device 10, and therefore also the flow of fuel mixture 101 towards the burner 40, varies over time.

The second fuel storage 31 comprises a second fuel level sensor 34, which is configured to emit a second fluid level sensor signal representative for the fluid level in the second fuel storage 31. The second fuel level sensor 34 is an elongate temperature sensor, which is aligned in a substantial vertical direction and which is configured to measure temperatures at various measuring points over its height. The control unit 50 is electrically connected to the second fluid level sensor 34, for transmitting the second fluid level sensor signal from the second fluid level sensor 34 to the control unit 50.

The control unit 50 is configured to determine the fluid level in the second fuel storage 31 by determining the number of measuring points of the temperature sensor 34 being in contact with the second fuel F2 at an elevated storage temperature and the number of measuring points of the temperature sensor 34 being in contact with the ambient air in the second fuel storage 31 at an ambient temperature.

The control unit 50 is further configured to control the second fuel pump 33 on the basis of the second fluid level sensor signal, in order to stop pumping of the second fuel pump 33 when the fluid level in the second fuel storage 31 is below a threshold level and to emit a visible and audible warning signal from the fireplace 1.

The second fuel storage 31 is configured to store the second fuel F2 in a liquid state, i.e. at an elevated storage temperature, compared to the temperature of the surroundings of the fireplace 1. To this effect, the second fuel storage 31 comprises a storage heating device

- 25. 35, configured to heat the second fuel F2 in the second fuel storage 31 to an elevated storage temperature, and to keep the second fuel F2 in the second fuel storage 31 in the liquid state.

The storage heating device 35 is a resistive storage heating device, which is electrically connected to the control unit 50 and which is arranged inside the second fuel storage 31 and submerged in the second fuel F2. The storage heating device 35 is configured to heat the second fuel F2 in the second fuel storage 31 to the elevated storage temperature, which is set at 80°C in the present embodiment. The control unit 50 is thereby further configured to control the storage heating device 35, i.e. to set the elevated storage temperature.

The control unit 50 is, upon activation of the fireplace 1, further configured to detect, on the basis of the second fluid level sensor signal, whether the second fuel F2 in the second fuel storage 31 is in the liquid state already or whether it may be needed to further heat the second fuel F2 towards the elevated storage temperature.

The second fuel line 32 comprises a line heating device 36, configured to heat the second fuel F2 in the second fuel line 32, to keep the second fuel F2 in the second fuel line 32 in the liquid state.

The line heating device 36 is a resistive line heating device, which is arranged in a wall of the second fuel line 32, extending spirally in the wall over substantially the entire length of the second fuel line 32, to prevent solidifying of the second fuel F2 inside the second fuel line

32. The line heating device 36 is configured to heat the second fuel F2 in the second fuel line 32 to an elevated temperature, compared to an ambient temperature of the fireplace 1, which elevated temperature is set at 70°C in the present embodiment. The line heating device 36 is electrically connected to the control unit 50. The control unit 50 is thereby further configured to control the line heating device 36, i.e. to set the elevated temperature.

Claims

-26- CONCLUSIONS

A domestic hybrid fireplace arranged to burn a fuel mixture of a first combustible fuel and a second combustible fuel comprising a combustible long chain hydrocarbon fuel, the fireplace comprising: - a mixing device arranged to mix the first fuel and the second fuel to form the fuel mixture and, - a first fuel supply, arranged to deliver the first fuel into the mixing device, - a second fuel supply, arranged to deliver the second fuel into the mixing device, and - a burner, arranged to deliver the fuel mixture to burn, wherein the mixing device is further configured to heat the second fuel to a mixing temperature, and wherein the mixing device is configured to mix the first fuel with the heated second fuel to form the fuel mixture.

The hybrid fireplace of claim 1, wherein the first fuel supply is arranged to deliver the first fuel in a liquid state into the mixing device and the mixing device is arranged to heat the first fuel to a vaporization temperature to vaporize the first fuel in the mixing device.

The hybrid fireplace according to claim 2, wherein the first fuel is in a liquid state at room temperature and/or wherein the second fuel is in a solid state at room temperature.

4. Hybrid fireplace according to one of claims 2 or 3, wherein the evaporation temperature is in the range between 50°C and 130°C, preferably between 70°C and 110°C, for example 90°C.

5. Hybrid fireplace according to one of the preceding claims, wherein the mixing temperature is in the range between 250°C and 350°C, preferably between 275°C and 325°C, for example 300°C.

6. Hybrid fireplace according to one of the preceding claims, wherein the mixing device comprises a first heating element for heating the first fuel.

27 - and/or comprises a second heating element for heating the second fuel.

7. Hybrid fireplace as claimed in any of the foregoing claims, further comprising a control device adapted to control the mixing device, for instance the first heating element and/or the second heating element, in order to set the evaporation temperature and/or the mixing temperature.

8. Hybrid fireplace as claimed in claim 7, further comprising a temperature sensor located in the mixing device arranged to provide a temperature sensor signal representative of the temperature in the mixing device, the control device being arranged to control the mixing device, for example the first heating element and/or the second heating element, to set the evaporation temperature and/or the mixing temperature on the basis of the temperature signal.

The hybrid fireplace of claim 1, wherein the first fuel supply is arranged to deliver the first fuel in a gaseous state into the mixing device.

10. Hybrid fireplace according to one of the preceding claims, wherein the first fuel supply comprises: - a first fuel storage, adapted to store the first fuel, - a first fuel line, extending between the first fuel storage and the mixing device, and - a first fuel pump arranged to pump the first fuel through the first fuel line, i.e. from the first fuel storage to the mixing device.

The hybrid fireplace of claim 10, wherein the first fuel storage is configured to store the first fuel in a liquid state.

12. Hybrid fireplace according to claim 10 or 11, wherein the first fuel pump is a hose pump.

13. Hybrid fireplace according to one of the preceding claims, wherein the second fuel supply comprises: - a second fuel storage, adapted to store the second fuel, - a second fuel line, which extends between the second fuel storage

-28- and the mixing device, and - a second fuel pump arranged to pump the second fuel through the second fuel line, i.e. from the second fuel storage to the mixing device.

14. Hybrid fireplace according to claim 13, wherein the second fuel storage, at least during use of the fireplace, is arranged to store the second fuel in a liquid state, i.e. at an elevated storage temperature relative to the ambient temperature of the fireplace.

The hybrid fireplace of claim 14, wherein the second fuel storage comprises a storage heater arranged to heat the second fuel in the second fuel storage to the elevated storage temperature, and to maintain the second fuel in the second fuel storage in the liquid state, the elevated storage temperature, for example, is in the range between 60°C and 100°C, preferably between 70°C and 90°C, for example 80°C.

The hybrid fireplace of claim 14 or 15, wherein the second fuel line includes a line heater arranged to heat the second fuel in the second fuel line to an elevated fuel line temperature and maintain the second fuel in the liquid state in the second fuel line, wherein the elevated fuel line temperature is for example in the range between 50°C and 90°C, preferably between 60°C and 80°C, for example 70°C.

The hybrid fireplace of claim 18, wherein the fuel line heater is a resistance fuel line heater extending substantially the entire length of the first fuel line.

18. Hybrid fireplace according to one of claims 13 - 17, in which the second fuel pump is a pulse pump, which is preferably located in the second fuel storage.

A hybrid fireplace according to any of claims 13-18, wherein the second fuel storage comprises a second fuel level sensor arranged to transmit a second fuel level sensor signal representative of the amount, e.g. fuel level, of the second fuel remaining in the second fuel storage .

-29-

A hybrid domestic fireplace according to claim 7 and claim 19, wherein the control device is further adapted to issue a warning signal for the fuel level when the amount of second fuel remaining in the second fuel storage is below a desired threshold value, for example a threshold fuel level of the second fuel. .

A hybrid fireplace according to any one of claims 13 to 20, wherein the second fuel storage comprises a fuel capsule holder adapted to receive a fuel capsule containing the second fuel.

The hybrid fireplace of claim 20 and claim 21, wherein the threshold fuel level indicates that the fuel capsule in the fuel capsule holder is empty, and wherein the fuel level warning signal includes a user notification to replace the empty fuel capsule with a new fuel capsule.

A hybrid domestic fireplace according to any one of the preceding claims, further comprising an air supply which opens into the mixing device and is adapted to provide an air flow through the mixing device, the mixing device being further adapted to mix the fuel mixture with the fuel supplied by the air supply. sky.

A hybrid fireplace according to claim 23, wherein the air supply comprises an air pump and an air hose extending between the air pump and the mixing device, the air pump being adapted to pump the air through the air hose, i.e. to the mixing device.

25. Hybrid fireplace as claimed in claim 9 and claim 23 or 24, wherein the air supply forms part of the first fuel supply, adapted to deliver a gas mixture into the mixing device, which gas mixture comprises the air stream and the gaseous first fuel.

26. Hybrid fireplace as claimed in claim 7 and one of claims 10 - 25, wherein the control device is further arranged to control the first fuel pump, the second fuel pump and/or the air pump, for instance arranged to set a flow rate thereof.

-30-

A hybrid fireplace according to claim 7 or claim 26, wherein the control device is further adapted to control the storage heating device and/or the fuel line heating device, for instance arranged to set the increased storage temperature and/or the increased fuel line temperature.

A hybrid fireplace according to any one of the preceding claims, wherein the first fuel is in a liquid state at room temperature, comprising an alcohol, such as ethanol, or spirits, e.g. comprising alcohol and up to 50% water by weight.

A hybrid fireplace according to any one of the preceding claims, wherein the second fuel is in a solid state at room temperature, comprising a wax, such as paraffin, stearin and/or candle wax.

30. Hybrid fireplace according to one of claims 1 - 28, wherein the second fuel is in a liquid state at room temperature, for instance comprising lamp oil and/or paraffin oil.

31. Method of creating fire in a hybrid fireplace, comprising the steps of: supplying a first combustible fuel to a mixing device of the fireplace, supplying a second combustible fuel comprising a combustible long chain hydrocarbon fuel to the mixing device - heating, in the mixing device, for example with a second heating element, the second fuel to a mixing temperature, - mixing, in the mixing device, the first fuel with the heated second fuel to form a fuel mixture, and - burning of the fuel mixture with a fireplace burner to create the fire.

A method according to claim 31, further comprising the step of: - heating, in the mixing device, for example with a first heating element, the first fuel to a vaporization temperature to vaporize the first fuel.

33. Method as claimed in claim 31 or 32, further comprising the steps of: - measuring, with a temperature sensor, the temperature of the mixing device, for instance of the first heating element and/or of the second

-31- heating element, and - controlling the heating of the first fuel and/or of the second fuel with a control device on the basis of the measured temperature in order to set the evaporation temperature and/or the mixing temperature.

A method according to any one of claims 31 to 33, wherein the first fuel is in a liquid state at room temperature, for example comprising an alcohol, such as ethanol, or spirit, for example comprising alcohol and up to 50 wt.% water.

A method according to any one of claims 31 to 34, wherein the second fuel is in a solid state at room temperature, for example comprising a wax, such as paraffin, stearin and/or candle wax.

A method according to any one of claims 31 - 34, wherein the second fuel is in a liquid state at room temperature, for instance comprising lamp oil and/or paraffin oil.