WO2017011521A1

WO2017011521A1 - Biofueled power stove

Info

Publication number: WO2017011521A1
Application number: PCT/US2016/042028
Authority: WO
Inventors: Frederick Arlen LEAVITT; Xaio BING
Original assignee: Leavitt Frederick Arlen
Priority date: 2015-07-13
Filing date: 2016-07-13
Publication date: 2017-01-19

Abstract

A power stove that assess heat from the combustion of a fuel to create a temperature differential across a thermoelectric module to generate electricity, and the thermoelectric module is cooled by a heat sink, and the heat sink is cooled by air driven by a fan, and the cooling air after it leaves the heat sink enters one end of an annulus surrounding a combustion chamber, and moves across the surface of the combustion chamber gathering heat lost through the wall of the combustion chamber, and enters the combustion chamber to provide combustion air, and it enters the combustion chamber at a location where radiant heat from the flame is unable to escape the combustion chamber.

Description

BIOFUELED POWER STOVE

Field of the Invention

The present invention relates generally to thermoelectric generator systems that include a thermoelectric module together with a heat source, a heat sink and a low cost method of assembling them. Description of Related Art

Thermoelectric generator systems (TEGs) are well known in the art and are an effective means to reliably convert heat to electricity. For example, FIG. 1 depicts a conventional thermoelectric generator system 100 having thermoelectric modules 101 sandwiched between a heat sink 102 and a heat source 103. The difference in temperature across the module 101 causes it to generate electrical power. The module 101 is kept in close contact to the heat source 103 and the heat sink 102 by bolts 104. It is important to keep the module in intimate contact in order to maintain good heat transfer across the interfaces between the module 101 , the heat sink 102 and the heat source 103.

One of the many potential applications for TEGs is to generate a small amount of electrical power for individuals who live in a areas with an unreliable source of electricity. For example, 75% of the people living in India have cell phones but do not have a reliable means of charging them. Most of these individuals cook their meals on a wood fire so several organizations have created thermoelectric stoves that can be used for cooking and at the same time generate electrical power for charging electronic devices such as cell phones. Some of the many problems commonly associated with these cookstoves are:

• They only generate 2 or 3 watts of power resulting in excessively long charge times for most devices, • They are fed from the top making it inconvenient to fuel the stove while cooking,

• They are inefficient burning more wood than necessary,

• They are expensive.

Accordingly, although great strides have been made in the area of thermoelectric cookstoves, many shortcomings remain.

DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the embodiments of the present application are set forth in the appended claims. However, the embodiments themselves, as well as a preferred mode of use, and further objectives and advantages thereof, will best be understood by reference to the following detailed description when read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a sectioned view of a TEG heated by a heat source and cooled by a heat sink. The heat source, heat sink and thermoelectric module are held in close contact by bolts. FIG. 2 is a cross section of a small cookstove that has an embedded TEG to provide electrical power while being used for cooking. This figure shows the path taken by cooling air being drawn into the stove by the cooling fan.

While the system and method of use of the present application is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular embodiment disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present application as defined by the appended claims. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Illustrative embodiments of the system and method of use of the present application are provided below. It will of course be appreciated that in the development of any actual embodiment, numerous implementation-specific decisions will be made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

The system and method of use in accordance with the present application overcomes one or more of the above-discussed problems commonly associated with conventional cookstoves. Specifically the application describes a method of directing cooling air in such a way that the efficiency of the stove will be improved and the cooling of the stove will be enough to generate 10 or more watts of electrical power from a conventionally sized stove. The system and method of use will be understood, both as to its structure and operation, from the accompanying drawings, taken in conjunction with the accompanying description. Several embodiments of the system are presented herein. It should be understood that various components, parts, and features of the different embodiments may be combined together and/or interchanged with one another, all of which are within the scope of the present application, even though not all variations and particular embodiments are shown in the drawings. It should also be understood that the mixing and matching of features, elements, and/or functions between various embodiments is expressly contemplated herein so that one of ordinary skill in the art would appreciate from this disclosure that the features, elements, and/or functions of one embodiment may be incorporated into another embodiment as appropriate, unless described otherwise.

The preferred embodiment herein described is not intended to be exhaustive or to limit the invention to the precise form disclosed. It is chosen and described to explain the principles of the invention and its application and practical use to enable others skilled in the art to follow its teachings. Referring now to the drawings wherein like reference characters identify corresponding or similar elements throughout the several views,

The system of the present application consists of a cylindrical combustion chamber 201 with a mouth 202 located near the bottom of the combustion chamber through which fuel 203 can be fed into the combustion chamber 201 . The presence of the mouth 202 is highly desired in India since it allows branches and twigs to be used as fuel without the need to chop or cut the fuel 203 into smaller pieces. In most of Africa the fuel of choice is charcoal in which case the mouth 203 may not be included.

In the combustion chamber 201 the fuel is burned to generate a flame 204. Heat from the flame radiates onto a heat exchanger 205 heating it to above 250 °C. The heat exchanger 205 may or may not include one or more fins (not shown) to collect conducted heat as well as radiated heat. The heat collected by heat exchanger 205 is then used to heat the hot side of thermoelectric module 206 to about 250 °C. the cold side of module 206 is kept cool by heat sink 207. Heat sink 207 include an extended surface 208 which in the example described are fins. Fan 209 blows ambient air over fins 208 to remove the heat that is being rejected by module 206. The cooling air from the fan is forced into the fins 208 and some of the air will be diverted up 210 and out of the fins and some of the air 21 1 will be diverted down and out of the fins. As the cooling air leaves the fins it enters a plenum 212 that surrounds the combustion chamber 201 .

Surrounding the combustion chamber is a small annulus 213 that separates the combustion chamber 201 from the plenum 212. Cooling air 210 entering the plenum 212 from heat sink 208 can leave the plenum 212 and enter the annulus through openings 214 near the top of the annulus. Alternatively, air can leave the plenum through vents 215 in the base of the plenum. The amount of air entering the annulus can be adjusted by opening or closing vent holes 215.

Air from the annulus then enters the combustion chamber through injection ports 216 that are located just above the mouth 202 of the stove. Alternatively the ports 216 can be located near the bottom of the stove. As air moves from the top 214 of the annulus to the injection ports 216 it picks up thermal energy from the wall of the combustion chamber carrying heat that would have been otherwise lost back into the combustion chamber. In this way the efficiency of the stove is improved. To further improve the efficiency of the stove a layer of thermal insulation 217 is added to the outside wall of the annulus to reduce the heat from being carried from the annulus to the plenum. In addition to further improving the efficiency of the stove this also keeps the outside wall of the stove cooler making the stove safer for the stove user.

If the air injection ports feed air into the combustion chamber near the bottom of the stove the combustion air will encourage a bright and intense flame in that location. While this will result in efficient combustion, much of the energy produced will be lost out the mouth 202 of the stove as radiant heat and will be unavailable for cooking or for generating electrical power. By locating the injection ports above the mouth 202 of the stove unburned carbon particles will be oxidized at that location where the energy produced will be trapped in the combustion chamber and remain available for cooking or power production.

The particular embodiments disclosed above are illustrative only, as the embodiments may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. It is therefore evident that the particular embodiments disclosed above may be altered or modified, and all such variations are considered within the scope and spirit of the application. Accordingly, the protection sought herein is as set forth in the description. Although the present embodiments are shown above, they are not limited to just these embodiments, but are amenable to various changes and modifications without departing from the spirit thereof.

Claims

What is claimed is:

1 ) A power stove that ;

Uses heat from the combustion of a fuel to create a temperature differential across a thermoelectric module to generate electricity, and the thermoelectric module is cooled by a heat sink, and the heat sink is cooled by air driven by a fan, and the cooling air after it leaves the heat sink enters one end of an annulus surrounding a combustion chamber, and moves across the surface of the combustion chamber gathering heat lost through the wall of the combustion chamber, and enters the combustion chamber to provide combustion air, and it enters the combustion chamber at a location where radiant heat from the flame is unable to escape the combustion chamber.

2) Claim 1 but where the fuel is fed through a mouth in the stove wall.

3) As claim 1 but where no mouth exists and the fuel is fed through the top of the stove.

4) As claim 1 but where the fuel is plant matter or other biologically derived material.

5) As claim 1 but where the fuel is charcoal.

6) As claim 1 but where the fuel is coal.

7) As claim 1 but where the thermoelectric module is based on bismuth telluride alloys.

8) As claim 1 but where the thermoelectric module is based on tetrahedrite alloys.