The invention relates to a stove for solid fuels, comprising: a combustion chamber for holding solid fuel defined by a housing, wherein a lower part of the housing is configured to carry solid fuel and an upper side of the housing takes a substantially open form. The invention also relates to a housing of a combustion chamber for use in a stove according to the invention.

It is estimated that about 2.5 billion people use wood to cook. The known stoves are usually inefficient and burn the wood only incompletely, resulting in considerable generation of smoke which is not only toxic to humans but also contributes toward global warming. An estimated four million people die annually from poisoning due to generation of smoke. When wood does not burn completely, incomplete combustion of volatile substances from the wood particularly occurs. These volatile substances will already escape from the wood at low temperatures, but escape significantly more quickly at increased temperatures (> 250°C). From about 600°C the released volatile substances will combust and be converted to less harmful components. In many stoves however this high combustion temperature is not reached and/or insufficient oxygen is available, whereby the volatile substances are not combusted, or hardly so, which results in generation of toxic smoke.

An object of the invention is to provide an improved stove with which a relatively clean combustion can be realized. The invention provides for this purpose a stove of the type stated in the preamble, comprising: a combustion chamber for holding solid fuel defined by a housing, wherein a lower part of the housing is configured to carry solid fuel and an upper side of the housing takes a substantially open form, and wherein a side wall of the housing is provided with a plurality of air inlet openings, at least one fan for generating an airflow, and at least one guide structure for guiding the airflow generated by the fan via the air inlet openings into the combustion chamber, wherein the housing of the combustion chamber comprises a support frame and a plurality of refractory tiles coupled to the support frame, wherein the tiles form at least a part of the side wall of the housing. The stove according to the invention is configured to realize a relatively clean (complete) combustion process of solid fuels, wherein the emission of harmful substances, such as carbon monoxide and condensed volatile substances, can be considerably limited. The solid fuels are preferably formed here by biomass such as wood, plant debris, animal remains or coal, although it is also possible to envisage burning other types of solid fuel in the stove according to the invention. This improved combustion is caused by two aspects. A first aspect which contributes toward an improved combustion is the forced air circulation which is applied in the stove, wherein an airflow is generated by means of the at least one fan and guided via the guide structure and the air inlet openings into the combustion chamber. The combustion chamber is hereby provided in forced manner with additional oxygen, which enhances the combustion process. A second aspect which contributes toward realizing an improved combustion is the application of the refractory tiles as wall of the combustion chamber. The tiles define at least a part of a side wall enclosing the combustion chamber and are therefore in direct contact with the solid fuels to be combusted. The tiles are generally manufactured from a material comprising clay (mineral), such as chamotte and vermiculite. The tiles are characterized by a relatively high heat capacity, whereby they can retain heat occurring in the combustion chamber for a relatively long time, whereby the combustion chamber can be kept at high temperature for a relatively long time, this enhancing (the efficiency of) the combustion of, among others, the released volatile substances, whereby fewer harmful substances will be present in the produced flue gases. The stove preferably takes a portable form and is more preferably provided with one or more handles to enable displacing of the stove. This makes it possible to displace and install the relatively clean stove according to the invention in relatively simple manner. The guide structure connects to the at least one fan as well as to the air inlet openings. Since the air inlet openings are arranged particularly in a side wall of the housing of the combustion chamber, it is advantageous for the housing to be partially or even wholly enclosed by the guide structure. Tt is advantageous for the housing to be received releasably in the guide structure, whereby the housing can be taken out of the guide structure. This modular construction of the stove makes replacing of (parts of) the housing relatively simple. The guide structure will generally function here as basket for the - also basket-like - housing of the combustion chamber. It is advantageous here for an annular air column to be formed between an outer wall of the guide structure and an outer wall of the housing of the combustion chamber. The air column is used to guide the airflow from the fan via the air inlet opening into the combustion chamber. The air guided via this air column is moreover already preheated, whereby the preheated air supplied to the combustion chamber will not cause an appreciable decrease in the temperature in the combustion chamber. In addition, the air column acts as a kind of insulating intermediate layer, whereby the temperature of an outer side of the outer wall of the guide structure can remain considerably lower than the temperature in the combustion chamber, this reducing the chance of injuries due to the stove. The housing of the combustion chamber is generally supported by the guide structure. The guide structure is more preferably configured to hold the combustion chamber at a distance relative to the fan, whereby overheating of the fan can be prevented.

The stove preferably comprises a base, which base is configured to support the guide structure and wherein the fan is connected to the base. It is advantageous for the stove to comprise at least one rechargeable power source, such as a rechargeable battery or accumulator, for the purpose of driving the fan. This makes it possible to apply the portable stove at locations where no mains electricity is available. The autonomously functioning portable stove according to the invention can be applied particularly advantageously in developing countries. Charging of the power source can take place by means of an electrical connection, via which the power source can be (temporarily) connected to the mains electricity. It is also possible to envisage coupling the power source to a solar panel, via which the power source can be charged. The solar panel can also be directly coupled to the fan. The solar panel can be connected non-releasably to a part of the stove, although it is also possible to envisage the solar panel being coupled as a module to the stove.

Since at least a part of the inner side of the housing, preferably the whole inner side of the housing, is formed by the refractory tiles, it is advantageous for one or more tiles to be provided with a plurality of air inlet openings. The airflow will hereby be guided via the tiles into the combustion chamber. It is advantageous here for an upper part of the tile to be provided with more air inlet openings than a lower part of the tile, wherein the upper air inlet openings are more preferably configured to guide the airflow in the direction of a lower part of the combustion chamber. The air inlet openings are for this purpose optionally oriented at an angle (relative to a horizontal). The airflow according to the above stated embodiment of the stove generates a kind of turbulent air mixture which is highly advantageous in being able to achieve complete combustion. The explanation for this lies in the fact, among others, that the flammable gases are held in the combustion chamber for longer and therefore have more time to completely combust before eventually leaving the combustion chamber. The optimal positioning and angle of the air inlet openings is greatly dependent on the design and dimensioning of the stove, and on the fuel arranged in the stove.

The housing of the combustion chamber is a type of basket in which the solid fuels can be arranged. A lower part of the housing, configured to carry the solid fuels, is preferably formed by a part of the support frame, in particular a substantially closed bottom element thereof. A support plate for the solid fuels can optionally also be clamped by the tiles. This support plate will then preferably be situated above and at a distance from a bottom element of the housing of the combustion chamber. This closed bottom element or optional support plate thereabove is generally formed by a (metal) plate, which plate may have a flat or non-flat, such as for instance a conical, geometry. Giving the bottom element (or support plate) a substantially closed form can prevent the possibility of ash or other waste falling onto a fan generally positioned under the bottom element. The support frame preferably comprises a plurality of standing, more preferably substantially vertical, bars. Applying the bars creates a cage enabling the refractory tiles to be held fixedly. It is advantageous here for each bar to be configured to cover a substantially vertical join between two connecting tiles. Since the tiles usually take a substantially flat form and connect at an angle to each other, it is advantageous for at least a number of bars to have a substantially V-shaped cross- section so that the bars can lie closely against the connecting tiles. An upper side of the housing is preferably formed by a top element, more preferably an annular element, to which the bars are coupled. The bars are also coupled to the bottom element. In a preferred embodiment at least a number of bars is connected displaceably to the bottom element and/or the top element, and each bar is coupled to a forcing element, such as a compression spring or draw spring, which forcing element is also coupled to the bottom element and/or the top element for the purpose of forcing the bottom element and the top element toward each other. This forcing action of the support frame provides for an active clamping of the tiles in longitudinal direction (vertical direction) of the housing of the combustion chamber. The relative displaceability, generally bounded by the forcing elements, of the top element and the bottom element of the support frame moreover ensures that this allows a thermal action (expansion and contraction) of the tiles and the support frame, whereby the material stresses in the tiles and the support frame can be limited and which enhances the durability of the housing of the combustion chamber. An additional advantage of the (somewhat) deformable support frame is that the tiles can in this way be placed and removed in simplified manner without disassembly of the support frame being required for the purpose. The maximum relative displacement of the bottom element and the top element is preferably limited to a distance of 1-5 millimetres. This displacement is generally substantially linear, and preferably extends in a substantially vertical direction and/or a direction substantially parallel to one of the longitudinal sides and/or longitudinal axis of the tiles. It is also possible to envisage coupling at least a number of bars via a forcing element to the bottom element and coupling them via another forcing element to the top element. In an alternative embodiment variant at least a number of bars take a resilient form such that these bars are themselves configured to force the bottom element and the top element toward each other, whereby no separate forcing elements would be required.

The support frame preferably substantially encloses the tiles. The tiles hereby form a housing defining a (standing) inner wall of the combustion chamber. It is moreover advantageous for an outer side of the tiles to be left at least partially uncovered by the support frame. This on the one hand facilitates guiding of air into the combustion chamber. The support frame can in this way moreover be manufactured with a limited amount of material, which considerably reduces the weight of the housing, this being practical during transportation of the portable stove. Although the tiles can take a curved form and can together form a cylinder, the refractory tiles usually take a substantially flat form for reasons of cost. In order to allow relatively efficient connection of the (end surfaces of the) substantially flat tiles to each other it is advantageous for each tile to have a substantially trapezoidal cross-sectional form.

The invention also relates to a housing of a combustion chamber according to the invention. Advantages and embodiment variants of the housing have already been described at length in the foregoing.

The invention will be elucidated on the basis of non-limitative exemplary embodiments shown in the following figures. Herein: figure 1 is a perspective view of a portable stove according to the invention, figure 2 is a perspective cross-section of the stove according to figure 1,

figure 3 is a perspective view of a housing of a combustion chamber as applied in a stove according to figure 1 , and

figure 4 is a perspective detail view of an underside of the housing according to figure 3.

Figure 1 is a perspective view of a portable stove 1 according to the invention. Stove 1 comprises a metal base 2 provided with a fan 3 (see figure 2), a rechargeable power source 4 and an electrical connection 5, such as a USB connection or mains connection, for charging power source 4. Base 2 is also provided with a switch (not shown) to enable fan 3 to be switched on and off, and with an indicator light 6 which shows whether fan 3 is switched on or off. An upper side 2a of base 2 takes an open form such that an airflow generated by fan 3 is guided via upper side 2a out of base 2 and into a preheating space 7 which is bounded by upper side 2a of base 2, a guide structure 8 mounted on base 2 and, arranged in guide structure 8, a housing 9 for a combustion chamber 10 for solid fuels such as biomass, in particular wood. Figure 2 shows that a bottom element 11 of housing 9 is positioned at a distance from base 2, whereby a thermal separation is present between base 2 and housing 9, which enhances the lifespan of the electronics, in particular fan 3, accommodated in base 2. Guide structure 8 has a substantially cylindrical form and comprises a substantially closed outer wall 12 to which two handles 13 are attached by means of pop rivets 14. An annular upper wall 15 of guide structure 8 also takes a closed form and is configured to support a pan support 16. As shown in figure 2, upper wall 15 of guide structure 8 connects to an inner wall 17 lying a distance from outer wall 12. Guide structure 8, and particularly inner wall 17 thereof, substantially encloses housing 9 which is received releasably in guide structure 8. Housing 9 comprises a support frame 18, which support frame comprises bottom element 1 1 , a top element 19 and substantially vertical uprights 20, 21 connected to bottom element 11 and top element 19. Support frame 18 is configured to hold and enclose a plurality of elongate refractory tiles 22. Tiles 22 have a trapezoidal cross-sectional form (see figures 1 and 3) and fit closely together on the longitudinal sides, thereby forming combustion chamber 10. Each tile 22 is provided with a plurality of air inlet openings 23, wherein an upper part of each tile 22 is provided with more air inlet openings 23 than the lower part of said tile 22, as shown in figures 2 and 3. Air blown by fan 3 into preheating space 7 is guided via air inlet openings 23 into combustion chamber 10, this contributing toward a cleaner combustion of the solid fuel. The air inlet openings 23 arranged in the upper part of tiles 22 preferably have an inclining orientation such that air is blown in downward direction into combustion chamber 10, this also contributing toward an improved combustion, as already elucidated in the foregoing. Combustion chamber 10 is moreover held at temperature relatively well by applying tiles 22, which further increases the efficiency of the combustion process. Housing 9 comprises two types of upright 20, 21. A first upright 20 has a V-shaped cross-section and is positioned such that a join 22a formed between connecting tiles 22 is substantially sealed. A second type of upright 21 is formed by a bar 21 which on an upper side is attached to top element 19 and on an underside protrudes through bottom element 11 and is connected via a compression spring 24 to bottom element 11 (see also figure 4). By applying compression springs 24 the top element 1 and bottom element 11 are forced toward each other, which on the one hand locks tiles 22 in support frame 18 and on the other can compensate thermal action on support frame 18 and tiles 22, which considerably increases the durability of housing 9. A support plate 25 is optionally clamped between tiles 22 for the purpose of carrying the solid fuel, whereby the underlying bottom element will remain relatively clean. This support plate 25 can for instance be manufactured from metal or a material comprising clay, such as for instance chamotte.

It will be apparent that the invention is not limited to the exemplary embodiments shown and described here, but that within the scope of the appended claims numerous variants are possible which will be self-evident to the skilled person in the field.