TECHNICAL FIELD

[001 ] The invention concerns in general the technology of portable combustion devices for generating heat and electricity, such as combined stoves. In partic- ular the invention concerns the way in which both heat and electricity is produced by burning solid material in a stove like device which can be operated as an independent unit in field conditions.

BACKGROUND OF THE INVENTION

[002] Today many military and outdoor devices, such as GPS-, communica- tion, target illumination, night vision, etc. devices are battery operated. The availability of recharging batteries during a military operation or just during a recreational outdoor activity, has become more and more critical aspect of an operation. As soldiers carry more portable electronics, battery weight becomes an issue. According to the US Army Research Laboratory (ARL), on a 72-hour mission in Afghanistan, a US soldier will carry 70 batteries for such devices as night-vision optics, GPS, imaging systems, and communications gear. This adds 20 pounds to a combat load, one-fifth of total weight. The load can contribute to fatigue and affect movement during combat. On the cost side, an infantry battalion spends $150,000 per year on batteries, its second-largest ex- pense after munitions.

[003] In cold environment also heating of portable or movable accommon- dation such as a tent or like is of importance for soldiers, backpackers and hunters staying outdoors overnight. For this purpose there are lightweight but efficient portable stoves capable of warming up a tent. Normally these stoves use chopped firewood as fuel.

[004] In a civil engineering a combined heat and power plant (CHP) is the "standard" configuration for producing heat and electric power for urban areas locating at cold areas. These multimegawatt or terawatt sized plants are technologically very remote from the present invention but still the principle is the same, to produce heat and electric power at the same time. However, this technology is totally different to the present invention intended to be used at temporary accommondations and being easily transported, even portably, to the place of the accommondation need to be changed. [005] From the state of the art it is known document EP 2629007 A2 which discloses a wood pellet using combustion apparatus. In the case where a commercial power source is employed, the motor fails to be driven when power supply stops from the electric company due to a power outage or the like, which disables the fuel conveyor system, making it impossible to supply the wood pellets as fuel to the combustion chamber. As a result, the pellet stove, which is spared the need for electricity as the heat source by using wood pellets as the heat source through the combustion of the wood pellets as fuel, still cannot be used during a power outage because of being incapable of supply- ing fuel. A combustion apparatus according to the EP 2629007A2 includes: a combustion chamber for combusting a fuel material; a thermoelectric power generation module for generating power based on a temperature difference caused by heating with a combustion temperature generated along with the combustion in the combustion chamber and by cooling with an external tem- perature outside the combustion chamber; and an electric drive means which operates using, as a drive force, thermoelectric power generated by the thermoelectric power generation module.

[006] From the state of the art it is also know document WO2008/001276A2 which discloses a solid fuel stove comprising: a combustion chamber for con- taining combustion fuel, which chamber has a lower side portion for accommodating fuel and an upper side portion; a blower assembly configured to provide airflow entering the combustion chamber in operating condition; guiding means to direct the airflow into the combustion chamber; wherein the guiding means direct the airflow from the upper side portion to the lower side portion. Accord- ing to an embodiment, the stove also comprises a rechargeable electrical power source for driving the blower assembly and a thermoelectric element are provided, and wherein the thermoelectric element is configured to provide power to the blower assembly and to the rechargeable power source.

SUMMARY OF THE INVENTION [007] The following presents a simplified summary in order to provide a basic understanding of some aspects of various invention embodiments. The summary is not an extensive overview of the invention. It is neither intended to identify key or critical elements of the invention nor to delineate the scope of the invention. The following summary merely presents some concepts of the invention in a simplified form as a prelude to a more detailed description of exemplifying embodiments of the invention.

[008] As both EP 2629007 A2 (later referred as D1 ) and WO2008/001276A2 (later referred as D2) are intended for fixed installation, the objective of the present invention is to provide a device capable of both to produce heat and electric power and still being portable when the device is not in use i.e. the fuel is not burning. One objective of the present invention is to provide a device without any moving or rotating parts. The state of art documents both D1 and D2 teach the use of blowers to enhance combustion air feeding to improve the combustion and thus to contribute to clean combustion.

[009] One aspect of the present invention is to provide a decentralized charging system to charge batteries near the end user, even down to the single, pair or patrol level. Thus to provide an easy way to keep up the batteries charged during the time the user is resting or otherwise not moving. The conventional way has been to use aggregates and similar electricity generating devices in more centralized way, but the objective of the present invention is to reduce this need of centralized battery charging function. Preferably the fuel to be used in the present device is solid fuel such as wood pellet, wood chip, charcoal or like. [010] According to an aspect of the present invention it is provided a portable heat and electricity generating device comprising:

- an enclosure comprising openings for fuel feed, combustion air intake, exhaust gas outlet and an electricity outlet,

- within the enclosure there are provided an intake channel for in- take/combustion air, a combustion chamber and an electricity generating element,

- a heat transfer element extending to the combustion chamber to distribute the heat further from the combustion chamber, when the device is in use,

- a fire grate for fuel material to be located for combustion,

- the fuel feed opening is located above the combustion chamber so that the fuel feed is gravity based,

- the intake channel is located parallel to the combustion chamber and the direction of the air flow in the intake channel is configured opposite to the direction of the combustion/exhaust gas flow,

- a heat sink is provided in the intake channel for pre-heating the in- take/combustion air before combustion,

- the electricity generating element is a thermoelectric element provided between the heat sink and the heat transfer element.

[01 1 ] Thus the device is constructed such that it is portable ie. even a single person, such as a soldier, can carry it for heat and electricity generating purpose. Naturally the device can be up scaled so that more manpower is needed, but the lightest embodiments are easily carried.

[012] The basic construction is an enclosure made of fire proof material like sheet metal and it comprises openings for fuel feed, combustion air intake, ex- haust gas outlet and an electricity outlet. To the fuel feed opening a fuel container can be attached by means of bayonet, thread, friction or like so that the fuel can supplied to the correct place when in use. For combustion exhaust gas outlet a chimney or corresponding tubular element is to be attached to lead the exhaust gas out and also to provide part of the heat radiation to sur- rounding areas. Thus the heating function is carried out partly by the hot surfaces of the enclosure and partly by the chimney attached to the exhaust gas outlet of the enclosure. An electricity outlet is also provided so that the electricity can be taken out of the device. Most preferably it is a socket like outlet.

[013] Within the enclosure there are provided an intake channel for combus- tion air to be led to a combustion chamber. An electricity generating element is provided to generate the electricity. A heat transfer element is extending to the combustion chamber to distribute the heat further from the combustion chamber, when in the device is in use. With the device there is a need to transfer the heat from the place where it is generated, i.e. from the combustion cham- ber. There is also provided a specific element on which the material is put for burning, it is a fire grate for fuel material to be located for combustion. The fuel feed opening is located above the combustion chamber so that the fuel feed is gravity based. It means that there are no need for arrangements like conveyors, manual feeding or like which transport the fuel from a storage place or container to the combustion chamber. Here it is designed so that the gravity does the work, the fuel drops and feeds based on gravity when there is room for fuel in the combustion chamber.

[014] The intake channel is located parallel to the combustion chamber and the direction of the air flow in the intake channel is configured opposite to the direction of the combustion/exhaust gas flow. The purpose of this feature is to be able to provide a small sized unit where it is possible to obtain an effective heat transfer from the combustion chamber to the combustion air by preheating it in an efficient manner. The efficiency is obtained so that a heat sink is provided in the intake channel for pre-heating the intake air before combustion. But to obtain the efficiency in the electricity generating function, the electricity generating element is a thermoelectric element provided between the heat sink and the heat transfer element. Thus the majority of the heat designed to be transferred from the combustion to the combustion air pre-heating is conduct- ed through the thermoelectric element. Thus a great temperature gradient at the thermoelectric element is the desired status when the device is in use. The pre-heated combustion air increases the burning rate and temperature at the combustion and that causes cleaner burning, less pollution and less non- burned volatiles in the exhaust gas. The higher the temperature in the combus- tion chamber, the bigger is the temperature difference over the thermoelectric element which contributes to production of electricity. Further, combustion air preheating, combustion, heat generation, electricity generation forms a self- balancing process wherein the preheating increases both burning temperature and the electricity production. Naturally the combustion and heat transfer reaches at some point a steady state where the temperature is no longer rising.

[015] An aspect of the present invention is a method for producing heat and electricity in a portable device, the method comprising steps of:

- providing solid fuel to a combustion chamber,

- providing combustion air to the combustion chamber,

- burning the mixture of fuel and combustion air,

- conducting the heat caused by the combustion via a heat transfer element to a high temperature side of a thermoelectric element,

- cooling a low temperature side of the thermoelectric element with a heat sink located in an intake channel,

- convection of or by the heat sink pre-heat the combustion air in the intake channel before entering to the combustion chamber, the pre-heated combustion air increases the burning temperature and thus causes increasing in the temperature gradient with the thermoelectric element. [016] The exemplary embodiments of the invention presented in this patent application are not to be interpreted to pose limitations to the applicability of the appended claims. The verb "to comprise" is used in this patent application as an open limitation that does not exclude the existence of also unrecited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. In this description terms intake/combustion air (A) is used to describe the air to be participating in combustion. Those terms intake air and combustion air are also used here as synonyms. A term combustion/exhaust gas (E) is used to describe the gas which is burning at that moment/location or no longer burning.

[017] The novel features which are considered as characteristic of the inven- tion are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[018] FIG. 1 illustrates a side view of an embodiment of the device,

FIG. 2 llustrates a front view of the embodiment of FIG. 1 ,

FIG. 3 llustrates a front view of another embodiment of the device,

FIG. 4 llustrates a front view of still another embodiment of the device,

FIG. 5 llustrates a front view of still another embodiment of the device,

FIG. 6 llustrates a front view of still another embodiment of the device.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[019] In FIG. 1 it is presented a portable heat and electricity generating device 1 comprising:

- an enclosure 2 comprising openings for fuel feed 21 , combustion air intake 25, exhaust gas outlet 24 and an electricity outlet 27,

- within the enclosure 2 there are provided an intake channel 3 for combustion air A, a combustion chamber 4 and an electricity generating element 8,

- a heat transfer element 6 extending to the combustion chamber 4 to distrib- ute the heat H further from the combustion chamber 4, when in the device is in use,

- a fire grate 45 for fuel F material to be located for combustion,

- the fuel feed opening 21 is located above the combustion chamber 4 so that the fuel F feed is gravity based, - the intake channel 3 is located parallel to the combustion chamber 4 and the direction of the air A flow in the intake channel is configured opposite to the direction of the combustion/exhaust gas E flow,

- a heat sink 7 is provided in the intake channel 3 for pre-heating the in- take/combustion air A before combustion,

- the electricity generating element 8 is a thermoelectric element 81 provided between the heat sink 7 and the heat transfer element 6.

[020] Thus the process for producing heat and electricity in a portable device 1 in the FIG. 1 is the following: the method comprises steps of:

- providing solid fuel F to a combustion chamber 4,

- providing combustion air A to the combustion chamber 4,

- burning the mixture of fuel F and combustion air A,

- conducting the heat H caused by the combustion via a heat transfer element 6 to a high temperature side of a thermoelectric element 81 ,

- cooling a low temperature side of the thermoelectric element 81 with a heat sink 7 located in an intake channel 3,

- convection by the heat sink 7 pre-heats the combustion air A in the intake channel 3 before entering to the combustion chamber 4, the pre-heated combustion air A increases the burning temperature and thus causes increasing in the temperature gradient with the thermoelectric element 81 .

[021 ] Further in the FIG. 1 it is shown that the fire crate 45 is configured such that the fuel F is prevented from falling in to the air intake channel 3. It can be a mesh structure, the fire crate can be bent in a suitable way or inclined to a direction preventing the fuel to go wrong place. The solid fuel is provided in a fuel container (not shown) which is attachable to the fuel feed opening 21 . According to an embodiment the fuel container is designed to contain an amount of fuel of a predetermined burning time. The fuel container can also be an open top funnel like container, where the user can increase fuel when needed. It is also preferable, that the container has at least some ventilation to pass some replacement air through the container to ensure the proper function of gravity based fuel feed.

[022] In FIG. 2 it is presented a front view of the embodiment of FIG. 1 . Thus within the enclosure 2 there are provided an intake channel 3 for combustion air A, a combustion chamber 4 and an electricity generating element 8, 81 - a heat transfer element 6 extending to the combustion chamber 4 to distrib- ute the heat H further from the combustion chamber 4, when in the device is in use. In the embodiment of FIG. 2 the heat transfer element is the wall of the enclosure 2. Thus the combustion heats the wall of the enclosure 2, which conducts the heat H downwards to electricity generating element 8 such as the thermoelectric element 81 . In general, the heat transfer element 6 is configured to conduct heat H from combustion chamber 4 to the thermoelectric element 81 . The heat transfer element 6 can have also various other forms as will be shown in other figures. There is also provided an insulation layer 5 between the combustion chamber 4 and the intake channel 3 to reduce the heat trans- fer via other routes than through the thermoelectric element 81 . This has a positive effect on efficiency of the electricity production. The temperature difference is bigger between the intake channel 3 and the combustion chamber when heat transfer thorough other routes is prevented by an insulation layer 5. It also improves significantly the electricity production efficiency.

[023] In FIG. 2 it is shown that there is provided a fire grate 45 for fuel F material to be located for combustion and that the fuel feed opening 21 is located above the combustion chamber 4 and the fire crate so that the fuel F feed is gravity based. For illustrative purposes there are only few fuel F pellets shown in figures. Preferably the fire crate 45 is inclined so that the fuel F flows to an accumulation area for effective combustion. As the combustion is effective when the distance between the burning fuel particles is small in relation to each other and the combustion air feed is effective, the inclined fire crate by nature collects all the fuel particles, such as wood pellet, wood chip, charcoal or like, together for effective combustion. According to tests the angle of inclination is preferably within a range of 15° to 60°, wherein 45° is especially suitable. The accumulation area here refers to an area where the potential energy of a fuel pellet 4 in the combustion chamber 4 is its local minimum. Also according to an aspect the fire grate 45 for fuel material to be located for burning is inclined so that the burning material flows toward the heat transfer element 6 for optimal combustion and heat transfer to the heat transfer element 6.

[024] In FIG. 2 is illustrated a location for the thermoelectric element 81 which is configured to generate electricity from the temperature difference between the heat transfer element 6 and the heat sink 7 in the intake channel 3. The heat sink is preferably a construction comprising multiple parallel plates at- tached together via a base plate. It may be of steel, cast iron, extruded aluminium or like. [025] The thermoelectric element is a Seebeck element or similar where a thermal gradient formed between two dissimilar conductors produces a voltage. At the heart of the thermoelectric effect is the fact that a temperature gradient in a conducting material results in heat flow; this results in the diffusion of charge carriers. The flow of charge carriers between the hot and cold regions in turn creates a voltage difference. This topic is under intensive scientific studies, research and development so in near future it can be expected to have better materials and improvements in efficiency compared to present thermoelectric elements. Further the thermoelectric element is connectable to an elec- trie unit comprising a transformer for converting the voltage of the thermoelectric element to a charge voltage, such as 5 or 14 Volts. As a user interface, the enclosure is provided with electricity outlet 27, such as a socket for connecting the electric unit to the device 1 .

[026] In FIGs 3, 4, 5 and 6 there are shown various configurations of the pre- sent device 1 , shown all from the front view. It is shown that the intake channel 3 located parallel to the combustion chamber 4 is below, above or beside the combustion chamber 4. The heat transfer element 6 is configured to conduct heat H from combustion chamber 4 to the thermoelectric element 81 and there are many possibilities to arrange the same function but in a different configura- tion.

[027] In FIG. 3 it is presented a front view of an embodiment of a flat layout. Within the enclosure 2 there are provided an intake channel 3 for combustion air A, a combustion chamber 4 and an electricity generating element 8, the thermoelectric element 81 . The intake channels are provided on both sides of the combustion chamber 4. A heat transfer element 6 extending to the combustion chamber 4 to distribute the heat H further from the combustion chamber 4, when in the device is in use, is here the wall of the combustion chamber 4. Thus the combustion heats the wall of the combustion chamber, which conducts the heat H directly through to electricity generating element such as the thermoelectric element 81 . In this embodiment there are not provided an insulation layer 5, however it could be for example on the bottom of the enclosure 2 to reduce the heat transfer downwards. This layout has a positive effect on efficiency of the electricity production since the heat transfer distance is the shortest possible. However it may restrict the selection of suitable thermoelec- trie elements since the temperature at that location is reasonable high. [028] In FIG. 4 it is presented a front view of an embodiment of a layout. Within the enclosure 2 there are provided an intake channel 3 for combustion air A, a combustion chamber 4 and an electricity generating element 8, the thermoelectric element 81 . The intake channels are provided below the combustion chamber 4. A heat transfer element 6 is extending to the combustion chamber 4 to distribute the heat H further from the combustion chamber 4, when in the device is in use, is here a wall like element provided in the middle of the enclosure 2. Thus the combustion heats the wall like heat transfer element in or at the combustion chamber, which conducts the heat H to electricity generating element such as the thermoelectric element 81 . In this embodiment there is provided an insulation layer 5. This layout may be modified also so that the inclined fire crate is inclined towards the heat transfer element.

[029] In FIG. 5 it is presented a front view of another embodiment of a flat layout. Within the enclosure 2 there are provided an intake channel 3 for combus- tion air A, a combustion chamber 4 and an electricity generating element 8, the thermoelectric element 81 . The intake channels are provided on both sides of the combustion chamber 4. A heat transfer element 6 extending to the combustion chamber 4 to distribute the heat H further from the combustion chamber 4, when in the device is in use, is here the roof of the combustion chamber 4. Thus the combustion heats the roof of the combustion chamber, which conducts the heat H through to electricity generating element such as the thermoelectric element 81 . In this embodiment there are not provided an insulation layer 5, however it could be for example on the bottom of the enclosure 2 to reduce the heat transfer downwards. [030] In FIG. 6 it is presented a front view of another embodiment of a flat layout. Within the enclosure 2 there are provided an intake channel 3 for combustion air A, a combustion chamber 4 and an electricity generating element 8, the thermoelectric element 81 . The intake channels are provided on both sides of the combustion chamber 4. A heat transfer element 6 extending to the com- bustion chamber 4 to distribute the heat H further from the combustion chamber 4, when in the device is in use, is here a separate element within of the combustion chamber 4. Thus the combustion heats the heat transfer element in the combustion chamber, which conducts the heat H through to electricity generating element such as the thermoelectric element 81 . In this embodiment there are not shown an insulation layer 5, however it could be for example on the bottom of the enclosure 2 to reduce the heat transfer downwards. [031 ] Variations and modifications to the embodiments described above are possible without departing from the scope of the amended claims. For example, instead of heat sink, the heat can be transferred to the intake channel by means of other conductive or convective device.

REFERENCE SIGNS USED IN FIGURES

[032] 1 device

2 enclosure

21 fuel feed opening

24 exhaust gas outlet

25 combustion air intake

27 electricity outlet

3 intake channel for combustion air

4 combustion chamber

45 fire crate

5 insulation layer

6 heat transfer element

7 heat sink

8 electricity generating element

81 thermoelectric element

A intake/combustion air

E combustion/exhaust gas

F fuel

H heat