WO2007002263A1

WO2007002263A1 - Solar stove

Info

Publication number: WO2007002263A1
Application number: PCT/US2006/024268
Authority: WO
Inventors: Byron Hopewell
Original assignee: Byron Hopewell
Priority date: 2005-06-24
Filing date: 2006-06-22
Publication date: 2007-01-04
Also published as: US20060289001A1

Abstract

A solar stove (10) includes a cabinet (14) with a heating area. A hollow reflector (100) including a large opening at one end and a small opening at the other end is positioned below the heating area. A reflector assembly (200) reflects solar energy toward the large opening. The cabinet (14) may also allow solar energy to heat an outer surface of the hollow reflector (100). A cooking vessel (302, 304, 306) used with the solar stove (10) includes a convex bottom (3022, 3042) that extends through the small opening and into an interior of the hollow reflector (100) .

Description

SOLAR STOVE

BACKGROUND

[0001] This invention relates to apparatus for collecting and focusing solar energy. The apparatus may be used for cooking or any other desired purpose.

SUMMARY

[0002] A solar stove according to this invention may include a cabinet including a heating area, and a hollow reflector including a large opening and a small opening. The hollow reflector may be positioned below the heating area such that the large opening faces downward in use of the solar stove.

[0003] A reflector assembly that includes at least one reflector may be provided to reflect solar energy toward the large opening. An adjustment mechanism may be provided to adjust a position of the reflector assembly.

[0004] The solar stove may include casters that facilitate rotation of the solar stove about a vertical axis, for easy positioning of the solar stove to optimize solar collection.

[0005] The cabinet and/or a hood connected to the cabinet may include one or more thermally insulated panels, and may also or alternatively include one or more thermally transmissive panels. In use, the thermally transmissive panels may be positioned facing the sun, to allow absorption of solar energy. The insulated panels restrict heat loss.

[0006] A cooking vessel that includes a convex bottom may be used with the solar stove. The convex bottom may extend through the small opening and into an interior of the hollow reflector. Alternatively, a thermally conductive insert may be provided that includes a convex bottom that extends through the small opening and into an interior of the hollow reflector. The insert may have a flat top surface to accommodate a flat-bottomed cooking vessel.

[0007] The solar stove may conduct solar energy to both inner and outer surfaces of the hollow reflector. For example, a reflector assembly may conduct solar energy to the inner surface, and a transparent window may conduct solar energy to the outer surface.

[0008] These and other objects, advantages and/or features are described in or apparent from the following description of exemplary embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Exemplary embodiments of the invention will be described in detail below with reference to the drawing figures, in which: [0010] Fig. 1 is a front elevation view of a solar stove;

[0011] Fig. 2 illustrates an exemplary embodiment of a reflector support bracket used in the solar stove of Fig. 1;

[0012] Fig. 3 illustrates an exemplary embodiment of another reflector support bracket used in the solar stove of Fig. 1;

[0013] Fig. 4 illustrates a detail of a reflector adjustment mechanism used in the solar stove of Fig. 1;

[0014] Fig. 5 is a perspective view of an exemplary hollow reflector used in the solar stove of Fig. 1;

[0015] Fig. 6 is a perspective view of another exemplary hollow reflector used in the solar stove of Fig. 1;

[0016] Fig. 7 illustrates a cross section along lines 7-7 of Fig. 5;

[0017] Fig. 8 illustrates a detail of a connection between separate parts of the reflector shown in Fig. 5;

[0018] Fig. 9 illustrates an exemplary pot usable with the solar stove of Fig. 1;

[0019] Fig. 10 illustrates another exemplary pot usable with the solar stove of Fig. 1; and

[0020] Fig. 11 illustrates an exemplary pan usable with the solar stove of Fig. 1. DETAILED DESCRIPTION OF EMBODIMENTS

[0021] Fig. 1 illustrates an exemplary solar stove 10 according to this invention. As depicted, the solar stove may include a hood 12, a cabinet 14, and legs 16 and 18. The hood 12 is preferably attached to the cabinet 14 via a hinge (not depicted). The hood 12 preferably includes a handle 128 to facilitate opening and closing of the hood 12.

[0022] hi Fig. 1, a front panel 142 of the cabinet 14 is shown partially cut away so that interior components 100 and 146, described below, can be viewed in cross-section.

[0023] hi this embodiment, the cabinet 14 includes a top panel 146 supported by supports 147 that are attached to legs 16 and 18 or to panels of the cabinet 14. The top panel 146 includes an opening 148. A high-heat area exists at the opening 148, and a lower-heat area exists at other locations of the top panel 146. In use, for example, one cooking vessel, such as a pot or pan, may be placed at the high-heat area for cooking, and then moved to the lower-heat area for warming.

[0024] A hollow reflector 100 having a large opening at one end and a small opening at the other end is situated below the top panel 146, with the small opening of the hollow reflector 100 being positioned to match the opening 148 of the panel 146. The hollow reflector 100 may be held in place by any suitable support mechanism. Li some embodiments, the ratio of the area of the large opening to the area of the small opening is about 6:1.

[0025] The cabinet 14 is preferably enclosed on all sides so that it can retain heat, but some embodiments may omit one or more panels such that the cabinet 14 is not fully enclosed. A bottom panel (not shown), when present, has an opening corresponding to the large opening of the hollow reflector 100, so that sunlight can pass into the hollow reflector 100. If desired, the large opening of the hollow reflector 100 can be covered by glass or another transparent material that allows sunlight to pass through.

[0026] A panel 144 of the cabinet 14 is preferably made of glass or other transparent material. Sunlight can pass through and heat an outer surface of the hollow reflector 100, providing heat in addition to that provided by the sunlight passing inside the hollow reflector 100. The outer surface of the hollow reflector 100 may be blackened to better absorb the solar energy that passes through the panel 144.

[0027] Preferably at least some panels of the hood 12 and/or some panels of the cabinet 14 are made of or covered by thermally insulating material, to better retain heat generated within the solar stove 10. Preferably the hood 12 and/or the cabinet 14 includes at least one thermally conductive panel that absorbs heat from the sun and transmits it to an interior of the hood 12 and/or the cabinet 14. For example, in this embodiment, panels 122 and 124 of the hood 12 are thermally insulative, and panel 126 of the hood 12 is thermally conductive. The thermally conductive panel 126 may be made of, for example, blackened copper or the like.

[0028] The embodiment shown in Fig. 1 is designed to be positioned with the sunlight coming from the side (upper left in Fig. 1), with the operator standing in front of the solar stove 10. This configuration is advantageous because, with the sunlight coming from the side, instead of from behind the solar stove 10, the sunlight does not shine in the eyes of the operator when the operator is facing the solar stove. If the solar stove 10 were designed so that the front side faces the sun, the operator would block the sunlight when standing in front of the solar stove 10, which would clearly be undesirable.

[0029] The solar stove 10 includes a lower reflector assembly, hereafter referred to as flat reflector assembly 200, that includes at least one, and preferably at least two, reflectors. The flat reflector assembly 200 of this embodiment includes flat reflectors 210, 220 and 230. Although depicted in the drawings and described hereafter as flat reflectors, the reflectors 210, 220 and/or 230 may instead be curved in one or more dimensions to enhance focusing power. At least one of the flat reflectors 210, 220 and 230 is adjustable so that it can be positioned optimally to reflect sunlight into the hollow reflector 100. Preferably, at least two of the flat reflectors 210, 220 and 230 are adjustable. In this embodiment, all three of the flat reflectors 210, 220 and 230 are adjustable. An exemplary adjustment mechanism will be described below, but it will be appreciated that various other adjustment mechanisms are possible and are within the scope of this invention.

[0030] The flat reflector 210 is attached to a reflector support 212 via a pin 214. Fig. 2 illustrates the reflector support 212 in detail. Tabs 2122 of the reflector support 212 are preferably sized to slide over the legs 16.

[0031] The pin 214 may extend through a slot 162 formed in each leg 16 (only the front leg 16 and the front leg 18 are shown in Fig. 1). The pin 214 maybe threaded at both ends, and adjustment knobs 260 with mating threads may be attached to each end of the pin 214 and tightened against the legs 16 to lock the pin 214 in position. Of course, other knob configurations are possible, such as a configuration in which the knobs 260 are attached to a bolt passing through the reflector support 212, instead of to the pin 214.

[0032] The opposite end of the flat reflector 210 may be attached to the reflector 220 by a hinge 242, as shown.

[0033] The flat reflector 220 may be attached to the flat reflector 230 by a hinge connection at a reflector support 244. The reflector support 244, shown in more detail in Fig. 3, may be sized and shaped to be able to slide along support members 20 connected to the legs 16 and 18.

[0034] The flat reflectors 210, 220 and 230 may be conventional mirrors made of silvered glass, or may be made of reflective metal, or any other desired reflective material.

[0035] Adjustment rods 250 are attached to the flat reflector 220 and the flat reflector 230 by a pin connection, and to the cabinet 14 by rod locking devices 252. hi this embodiment, two adjustment rods 250 are provided, but some embodiments may include only a single adjustment rod 250, or more than two adjustment rods 250. The adjustment rods 250 may be used to adjust and hold the angular position of the flat reflectors 210, 220 and/or 230.

[0036] Casters 30 may be attached to the legs 16 and 18. The casters 30 facilitate transport and positioning of the solar stove 10. Preferably, at least two of the casters 30 are swivel-type casters to facilitate positioning of the solar stove 10 about a vertical axis of the solar stove 10. Using swivel-type casters for all of the casters 30 makes positioning of the solar stove 30 even easier.

[0037] Fig. 4 illustrates details of an exemplary rod locking device 252. As depicted, the rod locking device 252 in this embodiment includes a U-shaped member with holes formed therein to allow passage of the adjustment rod 250. Bent-out tabs of the rod locking device 252 engage a hole 254 formed in the panel 142 of the cabinet 14. The rod locking device 252 is resilient, so that it presses outward toward opposing edge portions of the hole 254. The holes formed in the rod locking device 252 are sized to be just barely larger than the diameter of the adjustment rod 250 so that, when the rod locking device 252 is in the position shown in Fig. 4, the edges of the holes formed in the rod locking device 252 bind against the adjustment rod 250. To perform an adjustment, an operator may squeeze the opposing sides of the rod locking device towards each other to release the bind on the rod 250, and then the adjustment rod 250 may be slid to a desired position. The operator then releases the rod locking device 252, which deflects outward, binding the adjustment rod 250 in the desired position.

[0038] It will be appreciated, of course, that various other rod locking devices are possible.

[0039] The hollow reflector 100 preferably has a parabolic shape, but may have any other shape designed to transmit sunlight toward the small opening of the hollow reflector 100. Some embodiments of the hollow reflector 100 described below have curved surfaces, but some embodiments may include only flat surfaces. For example, a hollow reflector 100 having the shape of a frustum of a pyramid would have only flat surfaces. A curved-surface reflector is generally preferable in terms of collection and reflection efficiency. Roland Winston has described various shapes that are effective in solar collectors, some of which are known in the art as Winston cusp collectors. U.S. Patent No. 3, 923, 381 to Winston, incorporated herein by reference in its entirety, discloses some collector shapes that may be useful for the hollow reflector 100.

[0040] Fig. 5 illustrates an embodiment of the hollow reflector 100 in which the large and small openings are round. Fig. 6 illustrates an embodiment in which the large and small openings are rectangular or square. The embodiment shown in Fig. 5 is optically more efficient, but the embodiment shown in Fig. 6 may offer some advantages in ease of manufacturing because it can be formed by bending sheet metal. The embodiment shown in Fig. 5 may be manufactured by any suitable method. One suitable method is metal spinning, in which a flat sheet of metal is pressed against a rotating body, and gradually assumes the shape of the rotating body. In other embodiments, the hollow reflector 100 may be made of flat sheets of metal that are, for example, hinged together at their edges to form a reflector 100 having the general shape of the hollow reflector 100 of Fig. 5, but with angular openings in the shape of, for example, an octagon or hexagon.

[0041] Fig. 7 shows a cross section along line 7-7 of Fig. 5. hi this embodiment, the hollow reflector 100 is made in two sections 102 and 104. Fig. 8 shows an exemplary detail of a connection between the sections 102 and 104. hi this embodiment, the section 102 overlaps the section 104. The sections 102 and 104 maybe fastened together at the overlap section 1022 by welding, adhesive, screws, rivets or the like.

[0042] An advantage of forming the hollow reflector 100 in two or more sections is that, when metal spinning is employed, it is easier to form shorter sections than longer sections. Another advantage is that the two sections 102 and 104 may be packaged in a more compact manner during shipping.

[0043] Fig. 9 illustrates an exemplary cooking pot 302 usable with the solar stove 10. Preferably, the pot 302 has a convex bottom 3022 that extends slightly into an interior space of the hollow reflector 100. The convex bottom 3022 is preferably shaped so that it reaches a point of maximum concentration of sunlight within the hollow reflector 100. This configuration improves heating efficiency of the pot 302. The pot 302 may be insulated on its side surfaces and top to better retain heat.

[0044] Fig. 10 shows another exemplary pot 304 usable with the solar stove 10. Like the pot 302 of Fig. 9, the pot 304 has a convex bottom 3042. The pot 304 also has legs 3044 that extend at least as far as the convex bottom 3042. The legs 3044 allow the pot 304 to be placed on a flat surface without rolling. Like the pot 302, the pot 304 may have insulated sides and/or lid. Additionally, as depicted in Fig. 10, the top panel 146 of the solar stove 10 may be shaped to accommodate the legs 3044.

[0045] Fig. 11 illustrates a pan 306 that may be used with the solar stove 10. The pan 306 has a flat bottom, and may be placed on top of an insert 400 that is placed in the opening of the panel 146. The insert 400 is preferably made of conductive metal such as copper, and preferably has a convex bottom as depicted. The convex bottom of the insert 400, like the convex bottom of the pots 302 and 304, increases heating efficiency. Like the pots 302 and 304, the pan 306 may have insulated sides and/or top. [0046] In some embodiments of the solar stove 10, the insert 400 may be permanently attached to the panel 146, or to the hollow reflector 100. The permanent attachment may be accomplished by, for example, integrally molding the panel 146 or the hollow reflector 100 with a portion that acts as the insert 400, or by forming the parts separately and then attaching them together by welding, adhesive, screws, rivets or the like, hi some embodiments, the panel 146 may be a solid panel without an opening, and may absorb solar energy from the hollow reflector 100 and transmit the energy to the cooking surface by thermal conduction.

[0047] Any of the cooking vessels shown in Figs. 9-11 may be pressure vessels. Specifically, a mechanism may be provided to hold the lid against the pot or pan so that, during heating, higher pressure is developed within the pot or pan, as compared to the ambient atmospheric pressure. This can increase heating efficiency. The mechanism that holds the lid against the pot may include interlocking tabs provided respectively on the lid and on the vessel, as in a conventional pressure-cooking vessel, or any other known or later- developed mechanism.

[0048] In some embodiments, the solar stove 10 may be constructed in such a manner that few or no tools and/or hardware are required to assemble the solar stove 10. For example, the panels of the cabinet 14 may be made of sheet material and include portions that are bent into shapes that mate with the other panels and/or the legs.

[0049] hi addition to cooking, the solar stove 10 may be used for other purposes, such as drying crops or other items, distilling water, sterilizing medical instruments, generating electricity, and so forth.

[0050] While the invention has been described with reference to specific embodiments, these embodiments are illustrative and not limiting. Various changes, substitutes, improvements or the like may be made without departing from the spirit and scope of the invention.

Claims

WHAT IS CLAIMED IS:

1. A solar stove, comprising: a cabinet including a heating area; and a hollow reflector including a large opening and a small end, the hollow reflector being positioned below the heating area such that the large opening faces downward in use.

2. The solar stove of claim 1, further comprising a reflector assembly that includes at least one reflector that reflects solar energy toward the large opening.

3. The solar stove of claim 2, further comprising an adjustment mechanism that adjusts a position of the reflector assembly.

4. The solar stove of claim 1, further comprising a plurality of casters, at least two of the casters being swivel casters that facilitate rotation of the solar stove about a vertical axis.

5. The solar stove of claim 1, further comprising a hood that covers the heating area.

6. The solar stove of claim 5, wherein the cabinet and/or the hood comprises at least one thermally insulated panel, and at least one thermally transmissive panel.

7. The solar stove of claim 1, wherein the hollow reflector includes at least one curved surface.

8. The solar stove of claim 7, wherein the curved surface is a parabolic surface.

9. The solar stove of claim 1, wherein the heating area includes a high-heat area and a lower-heat area.

10. A combination, comprising: the solar stove of claim 1, wherein the small end of the hollow reflector has a small opening, and a cooking vessel that includes a convex bottom that extends through the small opening and into an interior of the hollow reflector.

11. A combination, comprising: the solar stove of claim 1, wherein the small end of the hollow reflector has a small opening, and a thermally conductive insert that includes a convex bottom that extends through the small opening and into an interior of the hollow reflector.

12. The combination of claim 8, wherein a top surface of the insert is flat.

13. A solar stove, comprising : a hollow reflector including an inner surface and an outer surface; a first device that conducts solar energy to the inner surface; and a second device that conducts solar energy to the outer surface.

14. The solar stove of claim 13, wherein the first device comprises a reflector assembly.

15. The solar stove of claim 13, wherein the second device comprises a transparent window.

16. A solar stove, comprising: a hollow reflector including a large opening and a small end, and a reflector assembly that includes at least one reflector that reflects solar energy toward the large opening.