FIELD OF THE INVENTION

The invention relates to a floating module for producing electricity using photovoltaic panels, and to a power station for producing electricity comprising several modules.

STATE OF THE ART

Floating photovoltaic systems are known, which comprise one or more photovoltaic panels mounted on a floating frame. These systems are seen as rather advantageous, especially compared to conventional photovoltaic systems (that is to say installed on the ground or on buildings), for several reasons.

On the one hand, the presence of water in the immediate environment of the photovoltaic system allows natural cooling of the panels and therefore increases in efficiency. In addition, a floating photovoltaic system can bring benefits to its environment because, by blocking some of the light coming from the water, it can limit the unwanted growth of algae or evaporation, for example in a lake.

By way of example, document US2006 / 0090789 discloses a floating photovoltaic module, which comprises a tubular frame comprising cylindrical flotation elements and tubes for connection to other identical structures. Photovoltaic panels are arranged on this frame comprising a single face provided with photovoltaic cells, this face being oriented towards the sky.

This type of structure has limited efficiency, which cannot be increased by the use of two-sided panels, because the water reflection coefficient, of the order of 7%, is too low to justify the additional cost associated with such panels.

Document US2009 / 0120486 is also known, which describes two-sided photovoltaic panels which are arranged parallel to the surface of the ground, on which a reflecting coating is placed. This structure is also limited from the point of view of efficiency for several reasons.

On the one hand, no cooling system for the panels is described, so it is possible to provide for a significant rise in the temperature of the panels linked to direct light and to reflected light, which tends to reduce their efficiency.

On the other hand, to allow sufficient light to pass on the reflective coating, the panels are positioned at a distance from each other, which increases the floor area required by this installation.

PRESENTATION OF THE INVENTION

In view of the above, the aim of the invention is to remedy at least in part the drawbacks of the prior art.

In particular, the object of the invention is to propose a photovoltaic installation exhibiting increased efficiency compared to the prior art.

Another object of the invention is to provide an installation having a reduced size.

In this regard, the invention proposes a floating module for producing electricity, comprising:

at least one photovoltaic panel, and

a floating frame on which the panel is mounted,

characterized in that the photovoltaic panel has an upper face and a lower face adapted to generate electricity by the photovoltaic effect, and in that the floating module further comprises a reflector device, adapted to reflect light rays towards the lower face of the panel, the reflector device comprising a plurality of floating reflective balls and / or a tarpaulin fixed to the frame.

The floating frame of the floating module can comprise a plurality of tubular elements connected to each other so as to define at least one closed cell in which the floating reflecting balls are then arranged, the frame being furthermore adapted to retain said balls. in the cell.

In embodiments where the reflective device comprises at least one tarpaulin attached to the frame, the tarpaulin is preferably reflective.

In one embodiment, the tarp is stretched over the frame so as to extend above the surface of the water when the module is laid on the water. As a variant, the tarpaulin is shaped to receive a water ballast, and the reflector device further comprises a plurality of reflective floating balls contained by the edges of the tarpaulin and / or by the floating frame.

Advantageously, but optionally, the floating module can further comprise a device for azimuth tracking of the sun, adapted to rotate the module or the panel as a function of the azimuth of the sun.

Preferably, each photovoltaic panel extends at an angle of between 0 and 40 ° with respect to the horizontal, and preferably at an angle of between 25 and 35 ° with respect to the horizontal.

The subject of the invention is also a photovoltaic power plant, comprising a plurality of floating modules according to the above description.

The floating module according to the invention has a high efficiency. Indeed, the use of two-sided photovoltaic panels and of a reflector device on a floating module makes it possible to preserve the advantages associated with a floating module (natural cooling, limitation of evaporation, etc.) while increasing the efficiency of '' a conventional photovoltaic barge.

In some embodiments, the reflector device comprises reflective floating balls, contained by a tarpaulin or cross members stiffening the frame. The spherical nature of the balls makes it possible to obtain a diffuse reflection of the incident light, therefore a better distribution of the light reflected on the underside of the panels.

In certain embodiments, the reflector device comprises a tarpaulin fixed to the frame, this tarpaulin being able to be stretched above the water or to receive a water ballast. This makes it possible to stabilize the module, which gives it good efficiency and a good service life.

In the case where the sheet is reflective, the functions of mechanical stabilization and optical reflection are performed simultaneously without generating additional costs.

In the case where the floating module further comprises a device for azimuth tracking of the sun, the production of electric energy in a day is maximized.

DESCRIPTION OF THE DRAWINGS

Other characteristics, aims and advantages of the invention will emerge from the following description, which is purely illustrative and non-limiting, and which should be read with reference to the appended drawings in which:

FIG. 1 represents an example of a floating module according to a first embodiment of the invention,

Figures 2a and 2b show an example of a floating module according to a second embodiment of the invention,

FIG. 3 represents an example of a floating module according to a third embodiment of the invention,

FIG. 4 represents an example of azimuthal tracking of the sun of a floating module,

FIGS. 5a and 5b represent the relative gains in monthly and annual electrical energy production respectively of a floating photovoltaic plant according to an exemplary embodiment of the invention compared to a terrestrial photovoltaic plant provided with single-sided panels.

DETAILED DESCRIPTION OF AT LEAST ONE EMBODIMENT OF THE INVENTION

With reference to FIGS. 1 to 3, a description will now be given of a floating module 1 for producing electricity according to various embodiments of the invention.

The floating module 1 is suitable for being installed on an aquatic surface. This surface can for example be a lake, natural or artificial, a pond, or even the surface of the sea, preferably in a place weakly exposed to waves and currents, for example a port, a cove, a lagoon, etc.

The floating module 1 comprises at least one, and preferably several two-sided photovoltaic panels 10, for example up to ten two-sided photovoltaic panels 10. By “two-sided photovoltaic panel” is meant a panel covered on two surfaces of photovoltaic cells suitable for generating electricity from photons by photovoltaic effect. In this case the surfaces covered with photovoltaic cells are opposite to each other, and include a so-called upper face 1 1 which is oriented towards the sky to directly receive the light from the sun, and a so-called lower face 12 ( referenced in Figure 2b) which is oriented towards the aquatic surface on which the module is placed,

Advantageously, each photovoltaic panel 10 extends along a plane which forms an angle of between 0 and 40 ° with respect to the plane of the aquatic surface. Preferably, this angle is between 25 and 35 ° for better photovoltaic conversion efficiency. In fact, below 25 °, this angle is preferably 30 °, which corresponds to the position of maximum photovoltaic conversion efficiency.

The floating module 1 further comprises a floating frame 20, on which the photovoltaic panel (s) 10 are mounted. This floating frame advantageously comprises a plurality of rectilinear and / or curvilinear tubular elements 21 adapted to be assembled. To allow the module to float, the floating frame is preferably made of a light material such as, but not limited to, polyethylene.

According to a preferred embodiment, the tubular elements connected to each other define at least one closed cell. For example, the frame can define a square or rectangular frame 22. As a variant, the frame can also comprise, within the frame, one or more cross members 23 delimiting, with the tubular elements forming the frame 22, several closed cells 24 (cf. FIG. 2a).

This structure comprising a number of closed cells confers good stability on the module 1. To further increase this stability, the photovoltaic panels 10 carried by the frame do not advantageously extend beyond the cell or cells delimited by the frame 10. , that is to say that they are contained in a volume whose side edges are defined by the frame, as is the case in Figures 1 to 3.

As a variant, other forms of reinforcement can be produced by assembling the tubular elements, such as for example a cross.

Advantageously, but optionally, the floating module 1 can also comprise a platform 30 for access to the panels 10, this platform being

mounted on the frame 20. Such a platform is shown for example in Figure 3. To preserve the buoyancy of the module, the platform 30 is preferably made of a slatted floor, that is to say in the form of trellis or grid. This platform is advantageously removable, so as to be installed only in the context of maintenance and repair operations.

The floating module 1 further comprises a reflector device 40, this device being adapted to increase the albedo of the aquatic surface on which the module is positioned.

In this way, the quantity of incident light reflected towards the underside of the photovoltaic panels is greater than in the absence of the reflector device.

Figures 1 to 3 illustrate different embodiments of this reflector device.

According to one embodiment shown in FIG. 3, the reflector device 40 comprises floating reflecting balls 41. The balls are arranged on the aquatic surface within each cell defined by the floating frame 20, and the frame 20 is advantageously shaped. to contain the beads in the cells. For example, when the module 1 is positioned on the aquatic surface, the emerged part of the tubular elements defining the frame 22 and the cross members 23 must have a height, relative to the water level, at least equal to one third, and of preferably at least equal to half the height of a log. For example, the balls may have a diameter of between 20 and 40 cm, and the emerged part of the tubular elements and cross members may have a height greater than 10 cm,

The balls are preferably spherical to ensure better diffuse reflection of the incident light. They are preferably white in color or coated with a reflective material such as Mylar ™. As a variant, they can also be coated with white paint, or have a silver or gold surface, obtained by a coating or directly by the material of the balls, for example metallic.

In this embodiment, and as visible in FIG. 3, the floating frame 20 preferably comprises a frame 22 and a plurality of cross members 23, making it possible to define several cells where the balls are positioned, while stiffening the frame 20. Good stability is then obtained for the module.

This embodiment is economically very interesting since it makes it possible to obtain good photovoltaic conversion efficiency by limiting the number of components of the module.

As a variant, the reflector device 40 is itself suitable for stabilizing the floating module 1. In this regard, the reflector device 40 may comprise a cover 42 fixed to the frame 20.

The tarpaulin 42 is preferably highly reflective. For example, the tarpaulin can be white, either by being woven with white thread, or by being painted white; or be made of a highly reflective material, for example Mylar ™.

Preferably, the reflecting beads and / or the tarpaulin (s) are made or coated with a non-polluting material. For example, the use of materials containing titanium oxide TiO will be avoided.

According to a first embodiment, the cover 42 is stretched over the floating frame so as to extend above the aquatic surface when the module 1 is placed thereon.

As in the example shown in FIG. 1, the floating reinforcement may comprise several cells delimited by the frame formed by the tubular elements and additional cross members (not visible in the figure). In this case, the reflector device 40 can comprise several tarpaulins 42, each tarpaulin being dimensioned so as to cover a respective cell, and being stretched over this cell.

Stretching a reflective sheet over the frame makes it possible both to significantly increase the reflection of light rays towards the underside of the photovoltaic modules, but also to stiffen the frame and therefore to stabilize the module.

According to an alternative embodiment shown in Figures 2a and 2b, the cover 41 (not visible in Figure 2a) is dimensioned and fixed to the frame.

floating 20 so as to be able to receive a water ballast B which makes it possible to stabilize the module. In this case, the tarpaulin is dimensioned so that it can be stretched once a water ballast with a thickness of preferably between 5 and 15 cm, for example between 10 and 15 cm, is positioned on the tarpaulin. This makes it possible to stabilize the module while limiting the loss of the reflective properties (albedo) of the water-bound cover.

Nevertheless, to compensate for the loss of albedo of the tarpaulin linked to the presence of the ballast, the reflector device 40 very advantageously comprises floating reflecting balls 42, arranged on the water ballast and contained by the edges of the tarpaulin 30, and optionally by the edges and / or cross members of the floating frame 10. For example the floating balls 42 can be contained by the edges of the cover 30 on two opposite sides and by the edges or cross members of the floating frame 10 on the other two sides.

In this embodiment, the rate of reflection of the light rays on the underside of the panels is increased by the tarpaulin and by the reflecting balls, and the module 1 is stabilized by the water ballast received on the tarpaulin.

The choice of one among the embodiments described above results from a compromise between the mechanical stability obtained (which is optimal in the cases where a tarpaulin is used), the amplification of the reflection (which is optimal when using spherical balls), and the economic criterion, the solution combining tarpaulin and balls being the most advantageous from the point of view of the preceding criteria but also the most expensive.

Referring to Figures 4a and 4b, the module 1 advantageously comprises a device 50 for azimuth tracking of the sun. This device 50 makes it possible to rotate the module 1 during the day so that the upper face of the panels is always oriented towards the sun, in order to maximize the production of electrical energy from the panels.

Thus, as visible in FIG. 4a, the azimuth tracking device of the sun makes it possible to position the module so as to orient the panels towards the east in the morning, towards the south at noon, and towards the west in the evening.

Azimuth tracking devices 50 are well known to those skilled in the art, and marketed by companies such as, for example, Upsolar, Mecasolar, Jsolar, etc.

Depending on the quantity of electricity that is to be produced, several modules can be grouped together to form a photovoltaic plant (not shown). In this case the modules can be physically connected to each other by fixing means, possibly removable, and can be connected to a common conversion device, suitable for converting the direct current produced by the photovoltaic panels into alternating current suitable for being injected into the network.

With reference to FIG. 5a, there is shown the theoretical gain in efficiency between a photovoltaic power station produced from floating modules according to one embodiment of the invention and a land power station of equivalent power comprising single-sided panels.

This efficiency gain was modeled for an installed electrical power of 1 megawatt peak. The power station comprises 175 chains each comprising 18 photovoltaic panels in bifacial crystalline silicon, each having 350 Watts peak power. The 18 panels of a chain are distributed over 4 floating modules, for example in two modules carrying 4 panels and two modules carrying 5 panels.

The floating plant is modeled for the following parameters:

The plant is located on a lake with a water temperature of 16 ° C,

The module includes a reflective tarpaulin stretched over the frame in accordance with the example of Figure 1,

The tarpaulin has an albedo of 60%,

The photovoltaic panels are inclined at 30 ° relative to the surface of the water,

The panels are spaced 2.85 meters apart,

The modules include an azimuthal sun tracking device.

The land plant used for the comparison is of the same power and includes the same number of chains and panels. We consider that the

air temperature is one degree higher than lake temperature. In addition, the properties of the plant are as follows:

The panels are single-sided,

The panels are inclined at 15 ° from the ground surface,

- The albedo of the soil is 20%,

The panels are spaced 2.5 meters apart,

The control unit does not include an azimuthal sun tracking device.

In Figure 5a, there is an efficiency gain of between 27% for the month of February, and 35% for the month of June, for an annual average of 31.2%.

It is important to note that these figures are obtained for a tarpaulin albedo of 60%, but this albedo can be even higher depending on the choice of material and / or the covering of the tarpaulin or the reflective beads.

In FIG. 5b, the gain obtained by the use of the floating module according to the invention has been broken down as a function of the various parameters of the module. We note in particular the importance of the two-sided aspect of the panels coupled with the use of the reflector device since it is responsible for a gain of 10.84% ​​in efficiency.

The inclination of the panels at 30 ° also allows an efficiency improvement of 10.98%.

The azimuth tracking device of the sun allows a gain of 5.72% compared to the earth station.

Finally, we note that the productivity gain is not the sum of the gains resulting from the different parameters, but is greater than this sum, so that we can deduce the existence of a synergy between factors affecting the total gain of photovoltaic energy production

CLAIMS

1. Floating module (1) for electricity production, comprising:

at least one photovoltaic panel (10), and

a floating frame (20) on which the panel (10) is mounted, characterized in that the photovoltaic panel (10) comprises an upper face (11) and a lower face (12) adapted to generate electricity by photovoltaic effect , and in that the floating module (1) further comprises a reflector device (40), adapted to reflect light rays towards the underside (1 1) of the panel, the reflector device (40) comprising a plurality of balls ( 41) floating reflective and / or a tarpaulin (42) attached to the frame (20).

2. Floating module (1) according to claim 1, wherein the reflector device comprises a plurality of floating reflecting balls (41), the floating frame (20) comprises a plurality of tubular elements (21) connected to each other. so as to define at least one closed cell (24) in which the floating reflecting balls (41) are arranged, the frame being further adapted to retain said balls in the cell.

3. A floating module (1) according to claim 1, wherein the reflector device comprises a tarpaulin (42) fixed to the frame, and the tarpaulin (42) is reflective.

4. Floating module (1) according to claim 5, wherein the tarpaulin (42) is stretched over the frame (20) so as to extend above the surface of the water when the module (1) is placed on the water.

5. Floating module (1) according to one of claims 1 to 3, wherein the tarpaulin (42) is shaped to receive a water ballast (B), and the reflector device (40) further comprises a plurality of reflective floating balls (41) contained by the edges of the tarpaulin and / or by the floating frame.

6. Floating module (1) according to one of the preceding claims, further comprising an azimuth tracking device (50) of the sun, adapted to rotate the module (1) or the panel (10) as a function of the azimuth. from the sun.

7. Floating module (1) according to one of the preceding claims, wherein each photovoltaic panel (10) extends at an angle between 0 and 40 ° relative to the horizontal, and preferably at an angle between 25 and 35 ° from the horizontal.

8. Photovoltaic plant, comprising a plurality of floating modules (1) according to one of the preceding claims.