WO2012055431A1

WO2012055431A1 - Sunoven and method for constructing such a sunoven

Info

Publication number: WO2012055431A1
Application number: PCT/EP2010/066188
Authority: WO
Inventors: Roland De Vicq
Original assignee: Roland De Vicq
Priority date: 2010-10-26
Filing date: 2010-10-26
Publication date: 2012-05-03

Abstract

Sunoven (1) for heating food products, comprising a parabolic reflector (2) for focusing sunlight, substantially incoming along an optical axis (4), into a focal point (5) lying at a focus distance from the vertex (6) of the parabolic reflector, the optical axis (4) interconnecting the vertex (6) and the focal point (5), characterized in that at least part (13) of the parabolic reflector (2) extends substantially beyond an imaginary plane extending perpendicular through the focal point (5) with respect to the optical axis (4).

Description

Sunoven and method for constructing such a sunoven

The current invention relates to a sunoven according to the preamble of the first claim. The current invention also relates to a method for constructing such a sunoven.

Such sunovens are already known to the person skilled in the art, for example from DE10238632. The sunoven described in DE10238632 comprises a parabolic reflector for focusing sunlight, substantially incoming along an optical axis, into a focal point lying at a focus distance from the vertex of the parabolic reflector. The optical axis interconnects the vertex and the focal point.

However, it has been found that the temperature reached with such sunovens is insufficient.

Therefore, it is an object of the current invention to provide a sunoven in which higher temperatures can be reached.

This is achieved according to a sunover having the technical features according to characterizing part of the first claim.

Thereto, the at least part of the parabolic reflector extends substantially beyond an imaginary plane extending perpendicular through the focal point with respect to the optical axis.

It has been found that such a parabolic reflector allows to reflect more sunlight to the focal point leading to an increased amount of energy which is concentrated into the focal point and therefore leading to increased temperatures which can be reached by the sunoven.

Without wanting to be bound to any theory it is believed that existing sunovens did not substantially extend beyond the imaginary plane as sunlight being reflected by this part is no longer being reflected from below in an upwards direction but instead from above in a downward direction. When using a heating plate on which, for example, a receptacle was placed with food products in it, it was considered that only sunlight reflect towards a bottom surface of the heating plate facing the vertex of the parabolic reflector could be used as an upper surface of the heating plate opposing the bottom surface would be covered with the receptable and therefore would be unsuitable for receiving reflected sunlight. However, the inventor has found that this prejudice is incorrect and that sunlight can very well be collected by the upper surface of the heating plate and can therefore increase the temperature reached on the heating plate.

Moreover, the inventor has found that with such a parabolic reflector, the parabolic reflector is less susceptible to the position of the sun. Therefore, it has been found that the sunoven is less susceptible to repositioning with respect to the sun.

Moreover, the inventor has found that since the parabolic reflector extends beyond the imaginary plane, the focal point is now less accessible so that the sunoven is less accident-prone.

In preferred embodiments of the sunoven according to the present invention, the sunoven comprises a support frame supporting a heating plate for supporting the food products, wherein the assembly of the support frame and the heating plate are arranged such that reflected sunlight is directed by the parabolic reflector onto the heating plate. It has been found that although the heating plate occludes part of the parabolic reflector from sunlight, the part of the parabolic reflector extending beyond the imaginary plane makes up for the occlusion of the heating plate and even allows to increase the heating with respect to state of the art sunovens, as according to the invention, sunlight is now received on the upper surface of the heating plate. Preferably, the area of the part of the parabolic reflector extending beyond the imaginary plane is larger, preferably substantially larger, than the area of the part of the parabolic reflector occluded by the heating plate, preferably by the heating plate in combination with the receptacle. It has been found that in such a configuration, the decrease in heating caused by the presence of the heating plate is compensated by the increase in heating caused by the part of the parabolic reflector extending above the imaginary plane.

According to more preferred embodiments of the sunoven according to the present invention, a receptacle in which a food product is contained being positioned on top of the heating plate, the heating plate is arranged such that a substantial part of the sunlight reflected onto an upper surface of the heating plate turned away from the vertex is reflected on an area of the upper surface which is not covered by the receptacle. This allows to hat the heating plate, and therefore to heat the receptacle, with increased intensity as more sunlight can be reflected onto the heating plate.

According to further preferred embodiments of the sunoven according to the present invention, the heating plate is provided through the optical axis at a heating position outside off the interval between the vertex and the focal point. It has been found that in such a position sunlight reflected onto the upper surface of the heating plate is not centered in the middle of the heating plate, where usually the receptacle is located, but instead is reflected around the middle of the heating plate, whereas the sunlight reflected onto the bottom surface is centered around the middle of the heating plate, usually directly below the position of the receptacle. As a heating plate is made of heat conducting material such as for example copper, aluminium and/or iron, both types of reflected sunlight will increase the temperature. Moreover, since in such an application the heating plate is not heated by concentrating the reflected sunlight into a single point at the focal point lying on or very near the heating plate, it has been found that although a sufficient temperature can be reached at the heating plate for heating food products or ironing, there is no longer a single very hot point on the hating plate. This has been found to reduce the risk for accidents and has been found to reduce damage to the heating plate or receptacles put on top of the heating plate.

According to further preferred embodiments of the sunoven according to the present invention the receptacle is at least partly filled with water and comprises a condensing element for condensing water evaporated from the receptacle connected to a receiving volume such that water condensed on the condensing element is guided to and received in the receiving volume. It has been found that this way desalinized water can be obtained. As it has been found that the temperature of obtained by the sunlight can be increased by the parabolic reflector according to the invention, it has been found that the number of bacteria in the condensed water decreases significantly and that even potable water, can be obtained.

In preferred embodiments of the sunoven according to the present invention, the condensing element is dome-shaped with an open base covering the receptacle. It has been found that such a condensing element allows an easy condensation of water.

In preferred embodiments of the sunoven according to the present invention the condensing element has a channel running along the open base for collecting condensed water. It has been found that such a channel allows an easy collection of the condensed water.

In preferred embodiments of the sunoven according to the present invention, the condensing element comprises a cylinder positioned on top of the dome with the longitudinal axis of the cylinder in a substantial upright direction for casting a shadow over at least part of the dome. It has been found that such a cylinder allows creating shadow over at least part of the dome such that the dome is at least partly cooled and the condensation of evaporated water can be increased, increasing the effectiveness of the condensing element.

According to preferred embodiments of the sunoven according to the invention, the condensing element comprises a propeller which has an upright axis of rotation and is put on top of the dome. It has been found that such a propeller allows to create a flow of air over the surface of the dome such that the dome is cooled and thus the effectiveness of the condensing element is further increased.

According to preferred embodiments of the sunoven according to the present invention, the axis of rotation of the propeller and the longitudinal axis of the cylinder are substantially the same. It has been found that in such a configuration, the effect of the propeller is further increased, as it is now placed in the cylinder, next to the existing effects created by the shadow cast over the dome.

According to preferred embodiments of the sunoven of the current invention the bottom of the cylinder comprises at least one opening near the dome such that the flow of air can more easily enter the cylinder and can further enhance the cooling of the dome.

According to preferred embodiments of the sunoven according to the present invention, the support frame comprises two intersecting linear supporting elements. It has been found that this type of support element occludes the parabolic reflector to a minimal extent such that the supporting elements interfere less with incoming sunlight. Preferably, the elements are cables suspended in the parabolic reflector as such type of cables are easy to transport as they take up little room when, for example, rolled up.

In preferred embodiments of the sunoven according to the present invention, the parabolic reflector comprises at least two substantially bended longitudinal segments, longitudinal first end regions of the segments being connected to each other and second longitudinal end regions, opposing the first longitudinal end regions, being connected to each other such that at least part of a parabolic shape is obtained, the parabolic shape being covered with a reflective layer facing the focal point. Such parabolic reflectors have been found sufficiently accurate for sufficiently heating the food products or, when present, the heating plate, while being easy to produce.

In further preferred embodiments of the sunoven according to the present invention, the parabolic reflector comprises at least two first segments, first and second longitudinal end regions being respectively rotationally connected to each other such that adjacent surfaces of the first segments can be slid over each other. It has been found that such a sunoven can be compacted by sliding the segments over each other, such that it can be transported more easily.

In further preferred embodiments of the sunoven according to the present invention, the parabolic reflector comprises at least two second segments, sides of adjacent second longitudinal segments being connected to each other, preferably at their center, along longitudinal direction. Such a constructed parabolic reflector has been found to be more easily produced materials which are easy to obtain and to transport. In preferred embodiments of the sunoven according to the present invention the segments are bendable pieces of aluminum foil which are easy to obtain and can be easily transported.

In preferred embodiments of the sunoven according to the present invention, the sunoven is positioned on a positioning basis being provided to rotate and tilt the sunoven with respect to the position of the sun. Although the sunoven according to the present invention is less dependent on the position of the sun with respect to the sunoven, such a basis however allows some positioning of the sunoven with respect to the sun to increase the amount of sunlight collected by it and ultimately increase the temperature reached by it.

In preferred embodiments of the sunoven according to the present invention, the heating plate comprises a heat conducting material covered with an anti-reflective coating. It has been found that such a heating plate allows to increase the amount of the sunlight providing heat to the food products as less sunlight is allowed to reflect on the surface of the heating plate.

The invention also relates to a method for constructing a sunoven according to the invention. Preferably in such a method, longitudinal segments are connected to each other with their respective first and second end regions such that at least part of a parabolic shape is obtained, the parabolic shape being covered with a reflective layer facing the focal point such as to obtain the parabolic reflector. It has been found that such a method for constructing the sunoven according to the present invention can be easily performed, for example in a less industrial environment such as for example regions which are less economically developed and which, in particular, have no or less access to usual heating means such as electricity, gas, etc. Moreover, these regions usually are situated in geographical regions having a large amount of solar energy per square meter.

The present invention is further illustrated in the accompanied figure and description of the figure.

Figure 1 shows an overview of a sunoven according to the present invention.

Figure 2 shows an overview of areceptacle covered with a condensing element according to the invention.

The sunoven 1 according to figure 1 is provided for heating food products. The sunoven 1 , however, can also be used for other applications. For example, it can also be used for heating an iron after which it can be used for ironing clothes.

The sunoven 1 comprises a parabolic reflector 2 for focusing sunlight. The sunlight substantially comes in along an optical axis 4 into a focal point 5 lying at a focus distance from the vertex 6 of the parabolic reflector 2. The optical axis 4 interconnects the vertex 6 and the focal point 5. At least part 13 of the parabolic reflector 2 extends substantially beyond an imaginary plane extending perpendicular through the focal point 5 with respect to the optical axis 4.

Preferably, the parabolic reflector is substantially a circular paraboloid.

The part 13 extending substantially beyond the imaginary plane shown in figure 1 comprises a part 13 substantially protruding from along a circumference of the parabolic reflector 2 parallel to the imaginary plane of the parabolic reflector 2. This is however not critical for the invention and the part 13 can also, for example, protrude from along the entire circumference of the parabolic reflector 2 parallel to the imaginary plane of the parabolic reflector 2. Although the part 13 shown in figure 1 is made as a segment mounted along the said circumference of the parabolic reflector 2, this is not critical for the present invention and the part could be provided in one piece with the rest of the parabolic reflector 2.

The sunoven 1 preferably comprises a support frame 7 supporting a heating plate 8 for supporting the food products. The hating plate 8 and the support 7 are arranged such that reflected sunlight is directed by the parabolic reflector onto the heating plate 8. The heating plate 8 is for example shown in figure 1 . Such a heating plate 8 can have any shape and dimension deemed appropriate by the person skilled in the art. Preferably, the heating plate 8 comprises a heat conducting material such that heat generated by sunlight being reflected on the heating plate 8 is distributed over the heating plate 8. Although the material of the heating plate 8 is not critical for the current invention, the material can for example be aluminium, copper, iron, etc. and/or alloys of one or more of the materials.

Preferably, the heating plate 8 is covered with an anti- reflective coating to avoid that sunlight reflected by the parabolic reflector 2 is again reflected away from the heating plate 8, decreasing the heating of the heating plate 8. Such coatings can be in the form of known dark, or even black coatings, which are preferably resistant to the heat generated by the sunlight reflected onto the heating plate 8 by the parabolic reflector 2.

Preferably, the support frame 7 is positioned such that the heating plate 8 can simply rest on top of the support frame 7 without requiring further fastening means, such as for example bolts, to attach the heating plate 8 to the frame 7. It has been found that the friction between the frame 7 and the heating plate 8 can be sufficient to position the heating plate 8 on top of the frame 7, at least when the frame 7 is substantially perpendicular to the gravitational pull. This is however not critical for the invention and the heating plate 8 can also be attached to the frame 7, for example by nuts, bolts, staples, etc.

The frame 7 preferably is positioned substantially perpendicular to the gravitational pull as such a positioning allows a more easy installation of the heating plate 8. This is however not critical for the invention and the frame 7 can be positioned in every position deemed appropriate by the person skilled in the art.

The heating plate 8 can be substantially flat. This is however not critical for the invention and the heating plate 8 can have every shape deemed appropriate by the person skilled in the art. For example, the heating plate 8 can comprise a first flat part 14 and a second part 15 extending from the first part 14 in an upright direction for hooking over at least part of the frame 7 for securing the position of the heating plate 8 with respect to the frame 7 in a plane substantially parallel to the frame 7. Such a second part 15 is for example shown in figure 1 and hooks over part of the frame 7 and is especially usefull when used in combination with a T-shaped frame 7 as discussed below.

Preferably, the position of the heating plate 8 in the parabolic reflector 2 can be changed, for example by changing the position of the frame 7 inside the parabolic reflector 8.

Preferably, the support frame 7 comprises two intersecting linear supporting elements 9, 10. However, this is not critical for the invention and other supporting elements 9, 10 can be used such as for example a net-like supporting element or a supporting element which is transparent for the sunlight, at least that part of the sunlight spectrum which is responsible for heating the heating plate 8. Preferably, the linear supporting elements 9, 10 are positioned with respect to each other in a T-shape (as shown in figure 1 ) or an X-shape which is then positioned inside the parabolic reflector 2 resting on the reflective surface of the parabolic reflector 2. Although not shown these linear elements can also be interconnected with a substantially circular element surrounding the elements 9, 10 for improving their positioning inside the parabolic reflector 2. Moreover, such a circular element allows to position the elements 9, 10 inside parabolic reflector 2 without having to use fastening means such as bolts, nuts, nails, staples, etc. It has moreover been found that the circular element avoids damaging the parabolic reflector 2.

The linear supporting elements 9, 10 preferably are cables 9, 10 suspended in the parabolic reflector 2. When not mounted to the parabolic reflector 2, the cables 9, 10 can then be, for example, rolled up and take up less space. When using cables for the positioning elements 9, 10, the cables 9, 10 are preferably fastened to the parabolic reflector using known cable tensioning means.

Although not shown in the figure, the sunoven 1 according to the invention is provided with a receptacle in which a food product is contained. Any type of receptacle can be used deemed appropriate by the person skilled in the art. By way of example a receptacle is shown in figure 2. The receptacle is positioned on top of the heating plate 8. the receptacle preferably just rests on top of the heating plate 8 without having to use further fastening means. Thereto, the heating plate 8 is preferably substantially perpendicular to the gravitational pull. The heating plate 8 is preferably arranged such that a substantial part of the sunlight reflected onto an upper surface 1 1 of the heating plate 8 turned away from the vertex 6 is reflected on an area of the upper surface which is not covered by the receptacle. Instead of a receptacle containing a food product also an iron for ironing can be put on top of the heating plate 8. Preferably, thereto the heating plate 8 is provided through the optical axis 4 at a heating position outside off the interval between the vertex 6 and the focal point 5.

When the receptacle is at least partly filled with water, preferably is filled with water, and is put on the heating plate 8 heated by sunlight, the temperature of the water will rise. It has been found that the water in the receptacle can be pasteurised this way if heated above 65°C. The water heated this way can, for example, also be used to cook, for example rice. If the water is heated to 65°C, preferably for at least a quarter of an hour, it is for example possible to make the water potable.

As shown in figure 2, it is also possible to provide the receptacle 17 with a condensing element 22 for condensing water evaporated from the receptacle 17 connected to a receiving volume 23 such that water condensed on the condensing element 22 is guided to and received in the receiving volume 23. Although any type of condensing element 22 can be used, preferably a dome-shaped, more in particular a cone-shaped, condensing element 22 similar to the condensing element described in WO03040040 is used and put with its open base 16 on top of the receptacle 17. The reservoir 23 in such a dome-shaped element, in particular a cone- shaped element, is for example a channel 18 at the open base 16 of the dome. Preferably, the channel 18 is provided with an outlet opening 24 to which a tube can be connected through which condensed water can be collected.

The condensing element 22 preferably is cooled to increase the amount of collected water in the receiving volume 23. Thereto, it has been found that the condensing element 22 can be cooled using a shadow-casting element for casting a shadow on the condensing element, preferably in the form of cylinder 19 positioned on top of the dome with the longitudinal axis of the cylinder 19 in a substantial upright direction. Such a cylinder is for example shown in figure 2.

Moreover it has been found that the condensing element 22 can be cooled by a propeller 20 creating an airflow over the condensing element 22. The propeller 20 can for example be driven by the heat of the condensing element. In such case the propeller 20 has an upright axis of rotation and is put on top of the dome.

Preferably, the shadow casting element, preferably the cylinder 19, and the propeller 20 are combined. In such a configuration, the axis of rotation of the propeller 20 and the axis of the cylinder 19 are the same. More preferably, one or more openings 21 are provided at the bottom of the cylinder 19 near or preferably adjacent to the dome to allow air to flow over the dome towards the propeller 20.

As shown in figure 1 , the parabolic reflector 2 preferably comprises at least two substantially bended longitudinal segments 12. Preferably, the segments 12 are connected to each other along their longitudinal sides, for example with a snap-fit connection or using nuts and bolts.

This is however not critical for the invention and longitudinal first end regions of the segments and second longitudinal end regions, opposing the first longitudinal end regions, can also be respectively connected to each other such that at least part of a parabolic shape is obtained. The parabolic shape is covered with a reflective layer facing the focal point 5. In such an embodiment, the parabolic reflector 2 for comprises at least two first segments. The first and second longitudinal end regions are respectively rotationally connected to each other such that adjacent surfaces of the first segments can be slid over each other. For example, the part 13, can be provided as such a first segment. In such an embodiment, the parabolic reflector can also comprise at least two second segments, sides of adjacent second longitudinal segments being connected to each other, preferably at their center, along longitudinal direction.

The segments preferably are bended pieces of aluminum foil. However, other materials are also possible such as for example: such as for example steel, preferably covered with a reflective layer, for example an aluminum coating.

Preferably, the sunoven 1 is positioned on a positioning basis being provided to rotate and tilt the sunoven 1 with respect to te position of the sun. The positioning basis is however not shown in the figure. Any type of basis can be used deemed appropriate by the person skilled in the art. For example a hinging foot can be used or a cylindrical base into which the parabolic reflector can be positioned. Preferably, the angle between the imaginary plane and the vertical is about 60° for an optimal collection of sunlight on .

The invention also relates to a method for constructing the sunoven 1 according to the invention. The longitudinal segments are in such a method connected to each other such as to obtain the sunoven. Preferably, the previously discussed segments are used and their respective first and second end regions are connected to each other such that at least part of a parabolic shape is obtained, the parabolic shape being covered with a reflective layer facing the focal point such as to obtain the parabolic reflector 2.

The reflective layer can be provided after the segments have been connected to each other, for example by spraying, painting or gluing the reflective layer on top of the joined segments. However, the reflective layer can also be provided on the segments before connecting them to each other into the parabolic reflector. The segments could, for example, be reflective due to the material used for the segments, for example when aluminum segments are used, or the segments could be provided with a reflective layer by spraying, painting or gluing the reflective layer.

Claims

CLAIMS:

1 . Sunoven (1 ) for heating food products, comprising a parabolic reflector (2) for focusing sunlight, substantially incoming along an optical axis (4), into a focal point (5) lying at a focus distance from the vertex (6) of the parabolic reflector, the optical axis (4) interconnecting the vertex (6) and the focal point (5), characterized in that at least part (13) of the parabolic reflector (2) extends substantially beyond an imaginary plane extending perpendicular through the focal point (5) with respect to the optical axis (4).

2. Sunoven (1 ) for heating food products according to claim 1 , characterized in that the sunoven (1 ) comprises a support frame (7) supporting a heating plate (8) for supporting the food products, wherein the assembly of the support frame (7) and the heating plate (8) are arranged such that reflected sunlight is directed by the parabolic reflector (2) onto the heating plate (8).

3. Sunoven (1 ) for heating food products according to claim 2, characterized in that the support frame (7) comprises two intersecting linear supporting elements (9, 10).

4. Sunoven (1 ) for heating food products according to claim 3, characterized in that the elements (9, 10) are cables (9, 10) suspended in the parabolic reflector (2).

5. Sunoven (1 ) for heating food products according to any one of claims 2 - 4 provided with a receptacle in which a food product is contained, the receptacle being positioned on top of the heating plate (8), characterized in that the heating plate (8) is arranged such that a substantial part of the sunlight reflected onto an upper surface (1 1 ) of the heating plate (8) turned away from the vertex (6) is reflected on an area of the upper surface which is not covered by the receptacle.

6. Sunoven (1 ) for heating food products provided with a receptacle according to claim 5, characterized in that the receptacle is provided through the optical axis (4) at a heating position outside off the interval between the vertex (6) and the focal point (5).

7. Sunoven (1 ) for heating food products provided with a receptacle according to claim 5 or 6, characterized in that the receptacle is at least partly filled with water and comprises a condensing element (22) for condensing water evaporated from the receptacle (17) connected to a receiving volume (23) such that water condensed on the condensing element (22) is guided to and received in the receiving volume (23).

8. Sunoven (1 ) according to claim 7, characterized in that the condensing element is dome-shaped with an open base (16) covering the receptacle (17).

9. Sunover (1 ) according to claim 8, characterized in that the condensing element has a channel (18) running along the open base (16) for collecting condensed water.

10. Sunoven (1 ) according to claim 8 or 9, characterized in that the condensing element comprises a cylinder (19) positioned on top of the dome with the longitudinal axis of the cylinder in a substantial upright direction for casting a shadow over at least part of the dome.

1 1 . Sunoven (1 ) according to any one of claims 8 - 10, characterized in that the condensing element comprises a propeller (20) which has an upright axis of rotation and is put on top of the dome.

12. Sunoven (1 ) according to claim 1 1 in combination with claim 10, characterized in that the axis of rotation of the propeller (20) and the longitudinal axis of the cylinder (19) are substantially the same.

13. Sunoven (1 ) according to claim 12, characterized in that the bottom of the cylinder comprises at least one opening (21 ) near the dome.

14. Sunoven (1 ) according to any one of the preceding claims, characterized in that the parabolic reflector (2) comprises at least two substantially bended longitudinal segments, longitudinal first end regions of the segments being connected to each other and second longitudinal end regions, opposing the first longitudinal end regions, being connected to each other such that at least part of a parabolic shape is obtained, the parabolic shape being covered with a reflective layer facing the focal point (5).

15. Sunoven (1 ) according to claim 14, characterized in that the parabolic reflector comprises at least two first segments, first and second longitudinal end regions being respectively rotationally connected to each other such that adjacent surfaces of the first segments can be slid over each other.

16. Sunoven (1 ) according to claim 14 or 15, characterized in that the parabolic reflector comprises at least two second segments, sides of adjacent second longitudinal segments being connected to each other, preferably at their center, along longitudinal direction.

17. Sunoven (1 ) according to any one of claim 14 - 16, characterized in that the segments are bended pieces of aluminum foil.

18. Sunoven (1 ) according to any one of the preceding claims, characterized in that the sunoven (1 ) is positioned on a positioning basis being provided to rotate and tilt the sunoven (1 ) with respect to the position of the sun.

19. Sunoven (1 ) according to any one of claims 2 - 18, characterized in that the heating plate (8) comprises a heat conducting material covered with an anti-reflective coating.

20. Method for constructing a sunoven (1 ) according to any one of the preceding claims.

21 . Method for constructing a sunoven (1 ) according to claim 20 in combination with any one of claims 14 - 17, characterized in that longitudinal segments are connected to each other with their respective first and second end regions such that at least part of a parabolic shape is obtained, the parabolic shape being covered with a reflective layer facing the focal point such as to obtain the parabolic reflector (2).