CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application claims priority to US Provisional Patent Application No. 63/283,816, filed November 29, 2021, which is incorporated by reference herein.

BACKGROUND

[0002] The present disclosure provides three-dimensional (3-D or 3D) printed cookstoves and methods for making the same.

[0003] According to the World Health Program (WHO), more than 3 billion of the world’s population do not have access to clean cooking facilities and still rely on solid fuels (wood, animal dung, charcoal, crop wastes and coal) for cooking and heating. The fuels are burned in extremely inefficient and highly polluting stoves. One of the world’s greatest environmental health risk factors is exposure to emissions from these cooking stoves.

[0004] Cooking related household air pollution in general leads to 4.9 million premature deaths annually, which is more than the mortality rate of HIV/AIDS, malaria and tuberculosis combined. Household air pollution accounts for 12% of ambient air pollution globally - 84% of which is from households in developing countries. Indoor smoke contains a range of healthdamaging pollutants, such as small particles and carbon monoxide. Sometimes, particulate pollution levels in these areas are 20 times higher than accepted guideline values. Indoor air pollution is responsible for 2.7% of the global burden of disease. For example, 50% of pneumonia deaths in children under 5 are due to household air pollution.

[0005] Women are the most affected segment of the society being exposed to these circumstances. Women in developing countries spend on average five hours per day in cooking, most often with their children around.

[0006] Parallel to the health problems from air, the widespread use of cooking with solid biomass fuel contributes to climate change through increased emissions of carbon dioxide and black carbon particulates that strongly absorb solar radiation (25% of global black carbon is produced from cooking). Biomass-burning stoves generate over 1 billion tons of CO2 annually, and much of this CO2 is from wood that is harvested un-sustainably and therefore will not be removed again from the atmosphere.

[0007] Increasing access to clean, efficient cookstoves not only saves lives and dramatically improves health by reducing the burden of disease associated with cooking, but also empowers women, who are the large majority of the world’s cooks, and protects the environment. Clean cookstoves and fuels will also play a substantial part in achieving adopted climate goals.

[0008] Cookstove projects have been trying to address these issues for upwards of 40 years. Their failure has rarely been due to technology, but instead an issue of behavior change and lack of sustainable supply chain systems..

SUMMARY

[0009] The systems and methods according to the present embodiments provide ceramic 3D printed smoke reduction wood burner stoves, and methods of making the same.

[0010] According to an embodiment, a ceramic 3-D printed stove is provided that includes a double-walled clay structure forming at least one burning chamber along a center axis therein, and a plurality of pores formed in the double-walled structure proximal a lower portion of the double-walled structure to enable air to be provided or injected into the at least one burning chamber. In certain aspects, the double-walled structure includes at least two portions or segments, each of the at least two portions comprising a sealed outer chamber between the double walls of said portion. In certain aspects, the double-walled structure includes three or more portions or segments or segmented units. In certain aspects, the stove further includes a second plurality of pores formed in an inner wall of the double-walled structure proximal an upper portion of the double-walled structure to enable air to be provided or injected into an inner chamber defined between the inner wall and an outer wall of the double-walled structure.

[0011] According to an embodiment, a method of fabricating a 3-D printed stove is provided. The method includes providing a digital model representing a configuration of a stove, sourcing local clay material, and printing the stove with the local clay material using a 3D printer according to the digital model. In certain aspects, the method further includes providing the 3-D printer, e.g., providing the printer to a user. In certain aspects, printing includes printing the stove as a single unit. In certain aspects, printing includes printing the stove as two or more segmented units, and combining the two or more segmented units to form the stove. [0012] In certain aspects, the digital model defines a double-walled clay structure including at least one burning chamber along a center axis therein. In certain aspects, the digital model defines a plurality of pores formed in the double-walled structure proximal a lower portion and/or upper portion of the double-walled structure. In certain aspects, the digital model includes an STL file or similar printer file format readable by a processor, e.g., a processor of the 3-D printer.

[0013] In certain aspects, the local clay is sourced from a region proximal the 3-D printer, e.g. within 40 or 50 miles, or within 10 or 20 miles, or within a mile or so of the 3-D printer. [0014] Reference to the remaining portions of the specification, including the drawings and claims, will realize other features and advantages of the present invention. Further features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, are described in detail below with respect to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Embodiments will be described in conjunction with the appended drawings to illustrate and not to limit the embodiments, and in which:

[0016] FIG. 1 illustrates an example of a digitally fabricated and scripted 3D printed clay cookstove according to an embodiment; the stove is designed in Rhinoceros and the toolpath created using Grasshopper in this specific example.

[0017] FIGS. 2-4 show fabrication, using a ceramic 3D printer, of 3D printed ceramic cook stove components, according to an embodiment.

[0018] FIG. 5 and FIG. 6 illustrate field testing of the printed double-walled stove, according to an embodiment.

[0019] FIGS. 7-9 illustrate examples of the gasification and recirculation mechanisms, where lower air intake and upper outlets are highlighted, according to embodiments.

[0020] FIG. 10 and FIG. 11 illustrate an example of a bore system according to an embodiment. [0021] FIGS. 12-14 illustrate examples of fabricating stove segments, according to embodiments.

[0022] FIGS. 15-18 illustrate chimney effects and choke points in a stove according to an embodiment.

[0023] FIG. 19 illustrates various 3D cookstove configurations and components fabricated according to embodiments.

[0024] FIG. 20 illustrates various 3D cookstove configurations and components fabricated according to embodiments.

DETAILED DESCRIPTION

[0025] The systems and methods according to the present embodiments provide ceramic 3D printed smoke reduction wood burner stoves, and methods of making the same.

[0026] The embodiments advantageously address household air pollution in developing countries, especially where biomass is the prime fuel for cooking and heating. The present embodiments weave together a dynamic relationship between the creative practice of additive manufacturing technology , e.g., a process by which digital 3D design data is used to build up an object in layers by depositing material, and enable adoption by localizing production, material sourcing, and supply chains.

[0027] In certain embodiments, a cookstove includes a double-walled design fabricated (e.g., 3D printed) using clay, preferably locally sourced clay, as the print material.

[0028] Clay 3D printer systems and designs are provided to efficiently produce a new type of customized ceramic smoke reduction wood burning stove. By leveraging additive manufacturing technology, this stove adopts a simple and efficient process of onsite manufacturing and distribution. Before 3D printing, it was extremely labor-intensive, if not impossible, to manufacture the necessary delicate system elements for such a high-efficiency low smoke stove in clay either by hand or through casting processes. The 3D printing process advantageously bypasses several of the steps involved in traditional production, which include molding, form making, extraction, casting, making it possible to go directly from file to fabrication and greatly reducing the costs associated with these materials and making it a much more environmentally friendly method of manufacture. [0029] Previous research reveals that introducing turbulence via air injection (normally with a fan) into the gas-phase combustion zone promotes better gaseous fuel-air mixing, leading to maximized combustion, and increased residence time of soot in the flame, promoting oxidation of soot and reducing the total mass of particulate matter (PM). In certain embodiments, a 3D printed clay cook stove utilizes a passive (no fans) recirculating air injection mechanism to reduce smoke and ultrafine particle emissions and to enhance combustion, leading to clean and efficient performance.

[0030] In an embodiment, a 3D printed clay cookstove may be digitally fabricated and scripted, e.g., using the Rhinoceros modeling program with the Grasshopper plug in as shown in FIG. 1. For example, this pairing of software programs allows one to produce the tool path instructions for the 3D printer. In order to 3D print an object the model must be first designed and prototyped, then translated into a toolpath using a “slicer” program which provides the machine with a toolpath for creating the model. Within the slicer program, in this case Grasshopper, the movement speed, extrusion speed, printer layer height, and toolpath variables are all defined for use with a variety of 3D printers including one or multiple print nozzles.

[0031] FIGS. 2-4 show fabrication, using a ceramic 3D printer, of 3D printed ceramic cook stove components which have been designed to be uniquely simple, according to an embodiment. The double walls of the stove, which may be relatively thin (e.g., 4- 10mm or greater), are well insulated by comparison and therefore better retain heat and direct heat towards the cooking pot while costing very little to produce.

[0032] FIG. 5 and FIG. 6 illustrate field testing of the printed stove, according to an embodiment.

[0033] Advantageous innovations found in the various stove embodiments include:

[0034] Localized material sourcing: stove production takes advantage of novel, inexpensive and locally sourced material. For example, clay is low cost and widely available. In addition to its minimal environmental impact, and compared to a metal stove, a clay stove helps keep food warm longer when it is left in the cooking platform. Thanks to the thermal property of clay as a heat sink as well as the double wall structure design which improves heat retention.

[0035] Additive manufacturing: utilizing additive manufacturing technologies for the production of the stove minimizes waste. In traditional manufacturing as much as 10-15% of the materials used may be wasted and go to landfill or require further operations to be recycled. In the fabrication of stoves, material must oftentimes be cut, milled or otherwise subtracted from. 3D printing greatly reduces the amount of mold material traditionally used in casting. Because 3D printing uses only the material it needs, there is no waste. No toxic materials are used in the manufacture of the stoves.

[0036] Localized supply chain system: antithetical to the common supply chain systems of delivering masses of stoves to people in need, in an embodiment, solar-powered clay 3D printers are supplied, which enable fabricating the stoves on-site with locally sourced clay. The paradigm is similar to giving people a shovel to make their own bricks rather than transporting the bricks to them. In addition to the huge cost offset and logistical merit of this model, locally made products by locals will be better welcomed by users and do not require behavior change - a huge factor that may have compromised many innovative clean stove projects.

[0037] More technical features: because the present embodiments include aspects about the method of production, which leverage additive manufacturing technology, various stove embodiments may take advantage of different configurations to accommodate different cooking styles and ultimately reduce smoke and particulate matters.

[0038] Bore system

[0039] In an embodiment, the stove production method via additive manufacturing introduces bore systems in forms of multiple pores or amplitudes that allow air to be recirculated and injected into burning chambers. FIGS. 7-9 illustrate examples of the gasification and recirculation mechanisms, where lower air intake and upper outlets are highlighted (in green), according to embodiments. FIG. 10 and FIG. 11 illustrate an example of a bore system according to an embodiment. In an embodiment, a plurality of bores are formed in the bottom portion of the cookstove and provide an airflow pathway for air to enter the inner burning chamber of the cookstove via pores. As shown in FIG. 11, for example, in an embodiment, the bore system include a plurality of pores spaced around the bottom portion of the cookstove, wherein air enters the pores proximal the exterior of the cookstove and flows through the double walled structure to the inner burning chamber. In an embodiment, a plurality of pores are also located on an upper portion of the inner wall to allow airflow/circulation from the inner burning chamber through upper pores into the outer chamber defined by the double-walled structure and down to the pores in the lower bore system.

[0040] Segmentation [0041] In an embodiment, the body of the stove (burning chamber) may be digitally modeled and additively manufactured as a single unit, or in multiple segments (or segmented units) to allow thermal expansion. This segmentation is applied perpendicular to the grain of the toolpath layers in an embodiment. Each sealed (e.g., sealed, double-walled) segment thermally expands and shrinks independently. This strategy is meant to reduce the probability of ceramic cracking due to exposure to sudden change in temperature. If any segment of the burning chamber cracks or malfunctions, it will be replaced without junking the stove. FIGS. 12-14 illustrate examples of fabricating stove segments, according to embodiments. Additionally, segmentation renders practical merits in production, packing and shipping. In an embodiment, each segmented unit includes a bore system as described herein.

[0042] In embodiments, the stove may introduce different pores or amplitudes in form of choking points to amplify turbulence. FIGS. 15-18 illustrate chimney effects and choke points. [0043] FIG. 19 and FIG. 20 illustrate various 3D cookstove configurations and components fabricated according to embodiments.

[0044] All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. [0045] The use of the terms “a” and “an” and “the” and “at least one” and similar referents in the context of describing the disclosed subject matter (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The use of the term “at least one” followed by a list of one or more items (for example, “at least one of A and B”) is to be construed to mean one item selected from the listed items (A or B) or any combination of two or more of the listed items (A and B), unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or example language (e.g., “such as”) provided herein, is intended merely to better illuminate the disclosed subject matter and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0046] Certain embodiments are described herein. Variations of those embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the embodiments to be practiced otherwise than as specifically described herein. Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.