OA12555A - Triple glazed solar cooker with four exterior reflectors. - Google Patents

Description

012555 2

DESCRIPTION OF THE INVENTION

The present invention relates to a solar cooker that uses the solar energy as the sole source of energy for cooking food.

There are different philosophies for designing cookstoves. Some use a flat solar collector and a coolant. This is the case of the cooker developed by Rommel et al [1] which is interesting because the coolant (which is oil) circulates in natural convection and the system has an oil storage which ensures that even at night the storage temperature does not drop below 100 ° C. During the day, when the stove receives solar radiation, the temperature can reach 160 ° C. This cooker has two disadvantages. The first is that the absorber is encuivre, and copper foil is very expensive The second drawback is that the absorber is covered with a selective surface, which should therefore be imported in the case of local manufacture. manufacturing cost. There are also "Hot Box" type solar cookers. They are equipped with a single mobile outdoor reflector, use a selective surface and are insulated with glass wool [2]. An Indian model hotbox type, currently marketed ^], [4], which has a double glazing, allows to cook for two to three hours. Its disadvantage is not to allow the food cuirsond beyond 14 h30mn.

Another wide range of solar cookers uses parabolic or spherical reflectors, with focal lengths ranging from 0.5m to just over 2m [5], [6], These devices lead to high temperatures up to 200 ° C and a yield that can approach 60%. A variant of this type of cooker is the tapered cooker [7]. All these devices with parabolic, spherical or conical reflectors have

However, a great disadvantage is that the reflector must be adjusted every 15 or 20 minutes, as the case may be, to follow the direction of the sun, since only the direct component of the solar radiation is concentrated. These adjustments are tedious if they have to be done manually.

The references cited are given below.

[1] Rommel, Stahl, Wittwer. A Solar Cooker based on a fiat platecollector with oil storage, Sun at Work in Europe, 1 (1986) p 3-5 [2] S.M.A. Ibrahim and M.K. Reidy. The performance of a solar cooker inEgypt, Renewable Energy, Vol.5, Part III, pp2441-2447 (1994).

[3] Indian Renewable Energy Development Limited Agency core 4-A, East Court, India Habitat Center Complex, FL Flour, Lodi Road, NewDelhi-110,003 [4] M.K. Ghosh. The design of a Solar Cooker, Proceedings Conference "The Sun in the Service of Mankind", Paper E. 12, Paris, 1973.

[5] Wolfgang Scheffler, Christine Lippold. Our experience with the construction of 3 hybrid solar cookers in India, 9.4-8.12.90 [6] Khalifa AMA, MA Taha, Kgart M. On the prediction of solar cooker performance and cooking in pyrex pots. Solar and Wind Technol 1988; 3 (1): 13-9 [7] Emam Sharaf. A new design of an economy, highly efficient, conical solar cooker. Renewable Energy 27 (2002) 599-619

The solar cooker according to the present invention overcomes at least three disadvantages noted above. Indeed, all the materials that make up the stove, namely the plywood of 15mm, the polystyrene used for the insulation, the aluminum sheets used as reflective surfaces, the stainless steel sheet used as an absorber, the matt black paint that covers Absorber, plaster, 5mm glass, are easily found on site. Furthermore, according to the characteristics of the cooker, in the case of a saucepan containing one liter of water for example, the water can be kept boiling for up to 16h50mn, the total time of keeping the water in boiling can reach 4 hours 15 minutes, for a day wellsoleillée (daily irradiation of the order of 5500Wh / m2). On the other hand, the range according to the invention, comprises four outer reflectors and trois vitres. The triple glazing can significantly reduce the losses before the stove. Polystyrene 80mm thick, with a coefficient of conductivity k = 0.036 W / m. ° C is better thermal insulation than the glass wool often used in earlier "hotbox" ranges. All this makes the range is well insulated, with an overall coefficient of loss U which is 4.8 W / m ° C, and a total efficiency of 0.55. As for the outdoor reflectors, two of them (North and South side ) are fixed at an inclination of 70 ° to the horizontal. The other two reflectors (East and West sides) are mobile with three possible positions for each of them: 35 °, 65 ° and 90 °.

The number of adjustments of the moving reflectors is thus reduced to three hours during the day. The reflectors provide a good concentration of solar radiation, since the geometric concentration of the system is C = 10.

The concentration of radiation by the reflectors is at a double level. The first level of concentration is done by the outer four-reflectors whose operation is described as follows. Lematin, the stove is opened around 8:30 am. The movable reflector on the west side is fixed at 90 ° and the reflector on the east side at its minimum position of 35 °. During this time, the two north and south fixed reflectors take their orientation of 70 °. °. Solar rays coming from the East will be ignited towards the interior of the stove. From 11 o'clock, the two East and West reflectors are set at 65 °. This position is maintained

012555 5 until 13 h 30mn. At 1:30 pm, we make a new adjustment. The East reflector is fixed at 90 ° and the reflector West at 35 °. This adjustment is maintained until the end of the cooking cycle, ie up to 17 hours. A manual orientation ruler of the moving reflectors has been installed. designed for this purpose. It consists of a rod of "iron 6" which has three teeth. One of the extreme teeth is hung in the middle of the outer surface of the movable reflector support. The second extreme tooth, when it is hooked to the bracket attached to the stove, holds the reflector in the 90 ° position. If the third tooth is hooked at the support fixed to the stove, the movable reflector takes its position of 65 °. The two outer teeth are 338 mm apart. The distance between the tooth 90 ° and 65 ° is 38 mm. As for the fixed reflectors, a metal fastening strip "iron 6" is designed for each of them. Laréglette has two teeth here. One is hung in the middle of the outer surface of the reflector support, while the other is hooked to the stove. These two teeth are 70 mm apart. They are metal lamellas folded in a half circle which is fixed on the stove and in the middle of the external faces of the reflector supports, which allow to hang the strips, for both mobile and fixed reflectors.

The second level of concentration of solar radiation, comes from the fact that the walls of the stove are not vertical. Indeed, its walls East and West are inclined by 35 ° with respect to the horizontal. One of the positions of this inclination is to fight against the effect of shadow which would appear when one is early in the morning or beyond 14 hours. In the same way, the north and south walls are not vertical. They are inclined of 85 ° relative to the This is due to the fact that, not far from the equator, the shadow can be deported either to the north or the south, depending on the season.Thanks to the north and south walls, we fight against this second effect of shadow.

This inclination of the North, South, East and West walls is new compared to classic "hot box" solar cookers that have vertical walls. It provides a second level of concentration, because the dimensions of the aperture, 500mm x 1410mm, are larger than those of the absorber which are 400mm x 500mm. The additional advantage of the invention lies in the fact that it is possible, around 16 hours, to fold down the supports of the four outer reflectors, which allows to close the stove. An additional cover, made of 15mm plywood and 100mm thick polystyrene, applied above the cooker, allows the heat to be kept inside the range up to 18 hours, allowing to heat a dish.

Plate I / IV gives the profile views of the stove. It allows in particular the door of entry of the cooker, practiced on one of the north or south walls but also the rule of manual orientation of the movable external reflectors, the bend on which rests the ruler and the slats folded in half circle which allow to hang the ruler with the support of the external reflector and the elbow.

Plate II / IV shows a section A-A of the stove. It allows to see the two fixed reflectors deployed, the three panes, the absorber, the plasterboard under the absorber, the internal frame made in 15mm plywood, the polystyrene insulation, the outer frame also made against - 15mm plywood, the door, the aluminum interior reflectors, and finally the outer cladding which is a 1mm sheet steel or forged Formica. The manufacturing procedure of the structure is as follows. For the manufacture of the internal reinforcement, the trapezoidal plates indicated on the plate III / IV are cut out in plywood of 15mm. The plate (a) is cut in two examples: these are the internal faces East and West. The plates (b) and (c), which are the north and south faces, are then cut out. On the plate (c) is operated an opening of 200mmx300mm which is the door of entry of the cooker. The four faces are assembled by nailing them to each other. The bottom of the armature is closed by a plate of plywood of 15mm dedimensions 400mmx500mm.

This internal reinforcement must fit into the polystyrene insulation. This is polystyrene 80 mm thick, which is cut into pieces, each piece having a surface equal to that of one of the four walls of the reinforcement internal. Another piece is cut with a surface equal to that of the base of the internal frame. All these pieces are glued with white wood glue. It takes about 3 m2 of 80mm polystyrene to form the insulation. It must be taken to seal all spaces between the polystyrene plates with lacolle and pieces of insulation. When the assembly is dry, the insulation becomes a rigid cage in which one must be able to easily fit the internal armature. For manufacturing on an industrial scale, once the shape of the insulation has been found, the polystyrene manufacturer must be approached to directly mold the insulation in the form provided.

The next module is the external reinforcement, in which the insulation (polystyrene) comes to fit. For the construction of the external reinforcement, the procedure is the same as that of the internal reinforcement. The dimensions of the plates are shown on Plate III / IV. The plate (d) is cut in two copies which constitute the outer faces East and West. The plates (e) and (f) are the North and South faces. On the plate (f), the door of dimensions 200mmx300mm is cut. On these plates (e) and (f), sections are made according to TC and T'C '(Plate III / IV), so that the final shape of the North and South faces is the polygon TCSS'C'T'. The four faces are then assembled and the bottom of the external armature is closed by a plate of plywood of 15mm of 012555 8 dimensions 606mmx530mm. A second plate of the same size is applied to the first which thus doubles the bottom of the outer armature.

The two internal and external frames also serve as thermal insulators for the stove.

As for the three 5mm panes, they have the following dimensions. Glass 3 (the innermost): 467mmx 1083mm; window 2 (that of the middle): 475mmxl 185mm; vitrel (the outermost): 478mmxl292mm .these dimensions are chosen so as to leave the windows a margin of dilation without which they can crack under the effect of heat.These are wooden rods which serve as a support for these windows. , proceed as indicated on the plate II / IV. The edge of the door and the window 3 are 60mm apart; the distance between the window 3 and the window 2 is 40 mm; the window 2 is distant from the window 1 of 40mm. These distances are measured along the north or south wall where the door is made. Slots are made in the internal and external reinforcements and in the polystyrene, in the wall which includes the door, to slide the three panes.

It remains to specify the fixing of the external reflectors. When the internal frame is assembled, a door with two equal leaves serves him closing at its upper part. Each leaf, which is in 15mm plywood, is fixed to the internal frame by three regularly spaced hinges. These leaves are 1453mm long and 265mm wide. The hinges are fixed in the direction of the length. These two wings are such that when they are open, they come to rest on their supports in order to make an angle of 70 ° relative to the horizontal. The support of each leaf is nothing more than a plywood board that splits the polystyrene between the two frames, along the upper part of the north and south faces. It is on the inside of each of the two wings that a 0.5mm thick reflective foil is applied as a reflector.

With regard to the East and West movable reflectors, they are installed in the following manner. At the east and west ends, in the upper part of the stove, a plywood board is attached to hide the polystyrene between the two frames. Then, at 38mm from the end of the stove, a wooden rod, dimensions 678mmx20mmxl9mm is nailed to the plywood board, east duct and west side. On each of these rods, two hinges are fixed, to which a flapper in plywood of 15mm come to hang. The dimensions of the two flaps, one on the East side, the other on the West side, are identical and equal to 662mmx755mm. When the two leaves are folded, they completely close the stove, which thus constitute a second closing. A reflective aluminum foil is applied to the inner face of each of the two West Estet flaps, thus becoming the other two outer reflectors. The stove has a double closing system, consisting of one side by the two wings North and South, and the other by the two wings East and West, when folded. They thus provide additional thermal insulation of the cooker when, from 17 hours, it is desired to keep heat inside the system to maintain a hot plate. Note that when the four flaps are folded, the two East and West seats must not rest directly on the North and South leaves. This double-closing system also serves as a glazing protection for the cooker when it is not in operation. It should be stated that before fixing the aluminum foil on their counter-plated supports, the internal faces of these are coated with putty and painted with aluminum paint. The inner walls of the internal 012555 sontο frame are similarly induced from putty and painted with aluminum paint. - Concerning the inside of the internal frame, after the aluminum painting has been done, it is applied on all four sides, reflective aluminum sheets of thickness 0.5mm. The dimensions of the aluminum foils are as follows:

For the East and West walls: a trapezium with a large base = 455mm; base debit = 400mm; side = 380mm

For the North and South walls: a trapezium of large base = 1050mm; base debit = 500mm; side = 380mm. On one of these two platesNorth - South, the door of dimensions 200mmx300mm is practiced.

These aluminum sheets are screwed on the internal walls of the internal armature. It is necessary to choose short screws to prevent them from preserving thermal bridges. It is best to simply glue these aluminum foils. But for that, it is necessary to have a glue which holds at temperatures of 120 ° to 140 ° C.

The cooker has an entrance door which is constructed in the following way. It is cut into plywood from two 170mmx270mm dimension plates. 80mm polystyrene is cut into a plate of the same dimensions. Using the wood glue, glue the two plywood sheets to the sides of the polystyrene, so as to obtain a single block. A 15mm plywood frame with exterior dimensions 200mmx300mm is also produced. The block in which the confection has just been described is simply embedded in this frame. Wood glue is used to maintain the rigidity of the whole. The door thus made is fixed to the opening of the stove, using two hinges. It should be noted that the opening of the stove shows the polystyrene between the two internal and external armatures. This polystyrene is hidden with another 012555 11 15mm plywood frame, internal dimensions 200mmx300mm and 80mm deep. This frame is glued on the polystyrene using wood glue. The two frames we have just discussed must be made in such a way that they respect the inclination of the north and south walls. As regards the door, its internal face and its perimeter are masticated and painted with aluminum paint. A 0.5 mm thick reflective aluminum plate is then attached to the inside of the door.

Regarding the three windows, it has already been specified that they are introduced by three slots in the north or south wall of the stove, the one precisely where the door is made. This provision is adopted so that if one of the windows accidentally breaks, its replacement can be done easily. These three slots are visible on the wall of the stove. They are hidden with a trapezoidal 15mm plywood plate, which has the following dimensions: large base = 1420mm; small base = 1123mm; side = 220mm. This plate is simply screwed on the wall to hide the slots.

The stove also has an absorber which is its heating plate. The absorber is made of 1mm thick stainless steel. It is a cuvedont the dimensions are as follows: length = 500mm; width = 400mm; height = 20mm. This absorber is based on a slab plaster of dimensions 400mmx500mm and thickness 20mm. It takes about 4kg of plaster to make the slab. This plaster slab, which serves as an additional insulation, rests on the bottom of the internal part of the internal armature.

Plate IV / IV shows a top view of the solar cooker.

Claims (1)

A solar cooker for cooking food using the solar energy as sole energy source characterized in that it is provided with three panes of thickness 5 mm (1), (2), (3), through which the solar radiation enters the range, it is also provided with four 0.8mm thick aluminum outer reflectors (4), (5), (6), (7) applied to 15mm plywood plates, it also includes an internal frame in plywood of 15mm (8) whose inner face is made reflective by a sheet of aluminum thickness of 0.5mm and an outer frame also counter-plated of 15mm (9) which reinforcements serve of insulators and frame the 80mm polystyrene insulation (10), which also includes a 1mm thick stainless steel absorber (11) for heating plate of dimensions 400mm x 500mm with a height of 20mm, which absorber (11) is separated from u bottom of the internal frame (8) by a gypsum slab (12) serving as an insulator, and that it finally comprises a door (13) of dimensions 200mmx300mm by which the breakers are introduced. 2 / solar cooker according to claim 1, characterized in that the three windows (1), (2), (3) slide inside the stove by three lateral slits (14) and rest on wooden rods ( 15) nailed to the four faces of the internal frame, the dimensions of these windows being 467mmx1083mm for the window (3), 475mmx1185mm for the window (2), and 478mmx 1292m m for the window (1). 3 / solar cooker according to claim 1 or claim 2characteriser in that the pane (3) is 60mm from the upper edge of the door (13), the pane (2) being 40mm from the window (3) and the pane (1) at 40mm from the window (2), the distances being measured Parallel to the face of the internal frame (8) in which the door (13) is machined. 4 / solar cooker according to claim 1 characterized in that the port (13) is itself insulator and consists of a polystyrene plate of 80mm (10) framed by two plywood plates of 15mm, all being embedded in a plywood frame of 15mm, external dimensions 200mmx300mm. 5 / solar cooker according to claim 1 or claim 4characterized in that the lower edge of the door (13) is 140mm from the bottom of the range, the distance being measured parallel to the wall in which the door (13) is practiced. 6 / solar cooker according to claim 1 characterized in that the internal armature (8) consists of two East-West walls, two north-south walls and a bottom, fits perfectly in the polystyrene insulation (10), which insulation (10) in turn perfectly fits into the outer frame (9) which also has two East - West walls, two North - South walls and a bottom, at the bottom of which a 15mm plywood plate of dimensions 530x606mm is nailed. 7 / solar cooker according to claim 1 or claim 6characteriser in that the East and West walls of the inner frame (8). are angled 35 ° to the horizontal, the north and south walls of the same internal frame (8) are inclined 85 ° relative to the horizontal, so that the opening of the range has dimensions 500mmxl410mm. 8 / solar cooker according to claim 1 or one of the two preceding claims characterized in that the east and west faces of the internal armature (8) are trapezes whose dimensions are .grandebase = 500mm, small base = 400mm, side = 605mm, the North and South walls of the same internal frame (8) are trapezes whose 012555 14 dimensions are: large base = 1410mm, small base = 500mm, side = 605mm, the door (13) of dimensions 200mmx300mm being practiced in one of the two faces North or South. 9 / solar cooker according to claim 1 characterized in that theupports of the two North and South fixed reflectors (6) and (7) consisting of two flappers equal plywood of 15mm of dimensions265mmx 1453mm are each fixed by three regularly spaced hinges, which Casements perfectly close the internal frame when they are folded, while they keep a fixed orientation that is at an angle of 70 ° to the horizontal when they are open and let them rest on their supports. 10 / solar cooker according to claim 1 characterized in that theupports of the two east-west movable reflectors (4) and (5), consisting of two flappers equal plywood of 15mm of dimensions662mmx755mm are each fixed by two hinges, which hinges are fixed to a wooden rod (16), that these two leaves are a second closing of the range when folded, and that a manual orientation bar (18) allows each leaf, when open, d occupy two possible orientations, one of which is at an angle of 65 °, while the other is at an angle of 90 ° with respect to the horizontal, the orientation of 35 ° being that which each leaf takes when it is based on a wooden elbow (17) attached to the end of the stove. 11 / solar cooker according to claim 1 or claim 10characterized in that the manual orientation strips (18) of the two movablereflectors (4) and (5) are formed with "iron 6", that these slides (18) are provided with three teeth (20), (21), (22), that the fixing of a tooth on the elbow (17) or in the middle of the outer face of the support of one of the two reflectors (4) or (5), is done by pressing the tooth into the space delimited by a semicircular folded metal strip (19) or (20), that by fixing the tooth (20) on the elbow (17) via the semi-circular alumina (23) and the tooth (22) on the support of the mobile reflector (4) or (5), the movable reflector takes its orientation of 90 °, that by fixing the tooth (21) on the elbow (17) and the tooth (22) on the movable hard reflector support (4) or (5), the movable reflector takes its orientation of 65 °, the distances (20) - (22) and (20) - (21) being 338mm and 38mm. 12 / -Cuisinièr Solar wind according to claim 1 or claim 9, characterized in that the supports of the two fixed reflectors (6) and (7) consisting of two equal flaps made of plywood with a thickness of 15mm and a thickness of 265mm × 1450mm are fixed by three regularly spaced hinges, which hinges are fixed on the upper edges of the inner frame (8), these two flaps are a first closure of the range when folded, and aeglette manual fastener (24) allows each leaf, whenopened and rests on its support, to be maintained in the fixed orientation of 70 ° relative to the horizontal. 13 / solar cooker according to claim 1 or one of the two claims 9 or 12 characterized in that the fastening strips (24) of the fixed reflectors (6) and (7) are constructed with "iron 6", that these rglettes fasteners (24) are provided with two teeth spaced 70mm apart, that one of the teeth is fixed on the body of the cooker, the fastening being effected via a semicircular lamella (26), while laseconde tooth is fixed in the middle of the outer face of the durflector support (6) or (7), the fixing being done via a semicircular array (25). 14 /-solar cooker according to claim 1 characterized in that the outer reflectors (4), (5), (6) and (7) applied to their counter-plated supports 15mm, are reflective aluminum thickness 012555 16 0 , 5mm, that the dimensions of these external reflectors are the same as those of their supports, that the inner part of the inner frame (8), located under the pane (3) is covered with reflective aluminum, each of the four faces Is , West North and South thus constituting an interior reflector, that the East-West interior reflectors are destrapezes with the following dimensions: large base = 455mm, small base = 400mm, that the North-South interior reflectors are also destrapezes with the following dimensions: large base = 1050mm, small base = 500mm, a door is made in one of the two North or South reflectors, dimensions 200mmx300mm. 15 / solar cooker according to claim 1 characterized in that it comprises an absorber (11) serving as a heating plate where the solar radiation comes to focus, dimensions of 400mmx500mm with a height of 20mm, cut in a stainless steel sheet of 1mm thickness, and in that the interior of the absorber is painted with ordinary matte black paint. 16 / solar cooker according to claim 1 characterized in that it comprises a gypsum slab (12) of dimensions 400mmx500mm, 20mm thick, which placed between the absorber (11) and the bottom of the internal armature (8). ) serves as insulation. 17 / solar cooker according to claim 1 or claim 2characteriser in that the three lateral slots (14) through which the three panes (1), (2) and (3) flow, are closed by a counter-plated plate of 15mm Trapezoidal shape whose dimensions are: large base = 1420mm; small base = 1123mm; side = 220mm.