Balloon comprising photovoltaic means and a solar concentration device

Abstract

A balloon equipped with photovoltaic means exhibiting an active face intended to receive solar rays and comprising an envelope, characterized in that the envelope comprises at least: a first zone transparent to solar rays; a second reflecting zone for said solar rays; a third zone comprising said photovoltaic means, the active face of which is directed toward the inside of said envelope; the second and third zones being positioned and cooperating in such a way as to reflect the solar rays in the direction of said third zone.

Claims

1. A balloon comprising photovoltaic means exhibiting an active face configured to receive solar rays and comprising: an envelope having a first skin and a second skin, wherein: the first skin has a first zone transparent to solar rays, the second skin has a second zone reflecting said solar rays, and the first skin further has a third zone transparent to solar rays and positioned off-center of the first skin, the third zone supporting said photovoltaic means placed on an outside of the envelope, the active face of which is directed toward an inside of said envelope, and wherein: a shape of the first skin of the envelope and a shape of the second skin of the envelope having the second zone are different, the second and the third zones are positioned and cooperate to reflect and transmit the solar rays in a direction of the photovoltaic means, and the first zone, the second zone, and the third zone are disposed on outer walls of the balloon, the balloon being a buoyant body configured to float in an atmosphere.

2. The balloon according to claim 1, wherein the photovoltaic means are photovoltaic panels.

3. The balloon according to claim 1, further comprising: a first reflecting zone and a second reflecting zone, said first reflecting zone reflecting the solar rays in a direction of said second reflecting zone, said second reflecting zone and said third zone are positioned to cooperate to reflect the solar rays in the direction of said third zone.

4. The balloon according to claim 1, further comprising a sub-envelope comprising a third skin located interior of said third zone, the sub-envelope configured to protect the third skin from a concentrated reflected radiation of solar rays.

5. The balloon according to claim 1, wherein the second zone exhibits a parabolic surface.

6. The balloon according to claim 1, wherein the shape of the first skin of the envelope is optimized for lift and the shape of the second skin of the envelope is optimized for concentrating solar rays.

7. The balloon according to claim 1, wherein a volume of the balloon is 50,000 m.sup.3.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be better understood and other advantages will become apparent on reading the following description given in a non-limiting way and with reference to the accompanying drawings in which: FIG. 1 illustrates a diagram of a stratospheric balloon according to the prior art; FIG. 2 schematically shows a balloon according to the present invention; FIG. 3 illustrates a sub-envelope according to the present invention.

DETAILED DESCRIPTION

(2) The present invention will be described hereafter in the context of a stratospheric balloon, but it could also be applied to any type of balloon. Generally, a stratospheric balloon comprises a pressurized envelope inflated with helium. In the context of the invention, said envelope comprises at least a first transparent zone to let the solar rays pass, a second reflecting zone to reflect the rays toward a third zone comprising means formed by photovoltaic cells oriented in such a way that their active detection faces are directed toward the inside of the balloon.

(3) The shape of the reflecting surface can be adapted so as to concentrate the solar rays onto said photovoltaic cells.

(4) FIG. 2 thus schematically shows the balloon of the invention which exhibits an envelope. The envelope comprises a first zone ZT transparent to solar rays R, a second reflecting zone ZR for said solar rays and a third zone ZC comprising said photovoltaic cells, the active face Fa of which is directed toward the inside of said envelope. The second and third zones are positioned such that they cooperate to reflect the solar rays in the direction of said third zone. Moreover, the shape of the envelope also conditions the angle of flux of the reflected beam of solar rays R.sub.R in order to concentrate it onto the active surface of the photovoltaic cells.

(5) The envelope can advantageously be made of reinforced complex polyurethane. To this end, there exist polyurethanes that are transparent to solar rays. Regarding the reflecting zone, provision can be made for a fabric coated with a reflecting coating and placed against said polyurethane envelope.

(6) According to one variant of the invention, the photovoltaic cells are placed on the inside of the balloon and receive the concentrated solar rays directly. They can in this case be bonded onto the envelope. This configuration exhibits the benefit of ensuring a very good yield and provides for preventing a premature wear of the transparent envelope portion since the latter is not heated by the solar rays reflected and concentrated at this level of the envelope. According to this variant, provision can be made for cooling means coupled to said photovoltaic cells.

(7) According to one variant of the invention, the photovoltaic cells are placed on the envelope on the outside of the balloon, the concentrated solar energy then passing through a transparent portion of the envelope other than the first zone dedicated to capturing solar rays. This arrangement favours the cooling of said cells since the heating of the photovoltaic cells takes place outside and thus benefits from natural ventilation. In this case, provision can advantageously be made for a second skin to protect the envelope insofar as the latter receives a concentrated beam of solar rays. Particular polyurethane films can be used for this purpose. The balloon may further include a sub-envelope 2 located at the third zone ZC, enabling the third zone ZC to be protected from the concentrated reflected radiation of solar rays, as illustrated in FIG. 3.

(8) According to one variant of the invention, the photovoltaic cells are integrated with the envelope of the balloon. To this end, an opening is made in the envelope in which said photovoltaic cells are integrated. A joint is in this case used to provide the seal between the portion of the envelope formed by the photovoltaic cells and the other portions of the envelope.

(9) Regardless of the variant used, the reflecting zone ZR of the envelope can take the shape of the envelope: in this case, the shape of the envelope is chosen so as to optimize both the lift of the balloon and the optical convergence of the solar rays toward the photovoltaic cells.

(10) According to one variant of the invention, the envelope can comprise a first skin and a second skin comprising the reflecting zone ZR, so as to be able to have a shape that is different from that of the envelope. In this case, the shape of the envelope and that of the reflecting surface can be chosen independently. The shape of the envelope can be adapted to optimize lift, the shape of the reflecting surface being chosen for optical reasons only. In this case and advantageously, the reflecting zone can be deformable, so as to optimize its shape, also taking into account the angle of incidence of the solar rays. This angle can vary according to the time of day, season, altitude and geographic position of the balloon.

(11) Generally, the shape of the envelope is preferably one of revolution. An ellipsoid shape for the envelope is suitable to provide satisfactory lift and optical performance, in particular if the reflecting surface is the same as that of the envelope. Alternatively, the envelope can be of parabolic shape.

(12) The usual shapes of balloons, which can be spherical as well as parabolic, can be used, in particular if the shape of the reflecting zone is independent of the shape of the envelope.

(13) The shape of the reflecting zone is preferably parabolic.

(14) Generally, the configuration of the envelope leads to imparting to the reflecting zone which forms a part of it a capability of concentrating solar rays in the direction of the photovoltaic cells. The concentration factor can be adjustable; typically it can be greater than 1 and less than 5, varying with the time of day, since the angle of the solar rays varies with the time of day.

(15) The geometric concentration of the sunshine thus provides for significantly reducing the surface area of photovoltaic cells and therefore the associated weight.

(16) According to one variant, the stratospheric balloon can also comprise more than one reflecting zone, the various reflecting zones cooperating with each other and the active surface of the photovoltaic panels.

(17) Example Stratospheric Balloon:

(18) Taking into account the weight to load on board a stratospheric balloon for a given mission, a necessary volume of the envelope to be inflated with helium is defined for example, and the lift calculations condition the shape and therefore the appropriate surface of the balloon. The balloon exhibits a volume in the order of 50000 m.sup.3 and a borne weight in the order of 4 tonnes; it comprises a parabolic shape envelope; a first part of the envelope is formed by complex polyurethane transparent to solar rays; a second part of the envelope, also of parabolic shape, comprises a reflecting coating; the third part of the envelope comprises a group of photovoltaic cells bonded on said envelope.