EP3721547A1

EP3721547A1 - Floating photovoltaic module

Info

Publication number: EP3721547A1
Application number: EP18811050.6A
Authority: EP
Inventors: Gilbert EL HAJJE; Matthieu CHIODETTI; Rémi LE BERRE; Frederik VAEL
Original assignee: Electricite de France SA
Current assignee: Electricite de France SA
Priority date: 2017-12-07
Filing date: 2018-12-05
Publication date: 2020-10-14
Also published as: US11245352B2; EP3754842A1; MA51104A; CN111587531A; IL275107A; WO2019110672A1; FR3074985B1; CN112019152A; EP3754842B1; IL275158A; US20200389120A1; IL275107B1; FR3074985A1; IL275107B2

Abstract

The invention relates to a floating module (1) for producing electricity, comprising: - at least one photovoltaic panel (10) and - a floating armature (20), on which the panel (10) is mounted, characterised in that the photovoltaic panel (10) comprises an upper face and a lower face which are capable of generating electricity by the photovoltaic effect, and in that the floating module (1) further comprises a reflective device (40) which is capable of reflecting light rays towards the lower face (11) of the panel, the reflective device (40) comprising a plurality of floating reflective balls (41) and/or a tank (42) which is attached to the armature (20).

Description

FIELD OF THE INVENTION

The invention relates to a floating module for the production of electricity using photovoltaic panels, and a power generation plant comprising several modules.

STATE OF THE ART

Floating photovoltaic systems are known, which comprise one or more photovoltaic panels mounted on a floating armature. These systems are perceived as rather advantageous, especially compared to conventional photovoltaic systems (ie 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 a natural cooling of the panels and thus a gain in efficiency. In addition, a floating photovoltaic system can bring benefits to its environment because, by blocking some of the light from the water, it can limit the undesirable 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 reinforcement comprising cylindrical flotation elements and connection tubes to other identical structures. On this frame are arranged photovoltaic panels comprising a single face provided with photovoltaic cells, this face being oriented towards the sky.

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

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

On the one hand, no cooling system of the panels is described, it can therefore provide a significant increase in the temperature of the panels related to direct light and reflected light, which tends to reduce their effectiveness. On the other hand, to let enough light on the reflective coating, the panels are positioned at a distance from each other, increasing the floor area required by this installation.

PRESENTATION OF THE INVENTION

In view of the foregoing, the object of the invention is to overcome at least in part the disadvantages of the prior art.

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

Another object of the invention is to provide an installation with a small footprint.

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

at least one photovoltaic panel, and

a floating frame on which is mounted the panel,

characterized in that the photovoltaic panel comprises an upper face and a lower face adapted to generate electricity by 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 beads and / or a tarpaulin attached to the frame.

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

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

In one embodiment, the sheet is stretched over the frame so as to extend above the surface of the water when the module is placed on the water. Alternatively, the cover is shaped to receive a water ballast, and the device reflector further comprises a plurality of reflective floating beads contained by edges of the sheet and / or by the floating frame.

Advantageously, but optionally, the floating module may further comprise an azimuth tracking device of the sun, adapted to rotate the module or panel according to the azimuth of the sun.

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

The invention also relates to a photovoltaic power plant, comprising a plurality of floating modules according to the foregoing description.

The floating module according to the invention has a high efficiency. Indeed, the use of two-sided photovoltaic panels and a reflective 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 embodiments, the reflector device comprises reflective floating beads, contained by a tarpaulin or sleepers stiffening the frame. The spherical nature of the beads makes it possible to obtain a diffuse reflection of the incident light, thus a better distribution of the light reflected on the underside of the panels.

In some embodiments, the reflective device includes a tarpaulin attached to the frame, which can be stretched over the water or receive a water ballast. This stabilizes the module, which gives it a good efficiency and a good life.

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

In the case where the floating module further comprises an azimuthal tracking device of the sun, the production of electrical energy in a day is maximized. DESCRIPTION OF THE DRAWINGS

Other features, objects and advantages of the invention will emerge from the description which follows, which is purely illustrative and nonlimiting, 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,

FIGS. 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 azimuth tracking of the sun of a floating module,

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

DETAILED DESCRIPTION OF AT LEAST ONE EMBODIMENT OF THE INVENTION

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

The floating module 1 is adapted to be installed on an aquatic surface. This surface may for example be a lake, natural or artificial, a pond, or the surface of the sea, preferably in a location with little exposure to waves and currents, for example a port, a creek, a lagoon, etc.

The floating module 1 comprises at least one, and preferably several, double-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 adapted to generate electricity from photons by photovoltaic effect. In this case, the surfaces covered with photovoltaic cells are opposed to one another, and comprise a so-called upper face 1 1 which is directed towards the sky to directly receive the light coming from the sun, and a so-called lower face 12 ( referenced in FIG. 2b) which is oriented towards the aquatic surface on which the module is placed, so as to receive photons reflected on this aquatic surface or on other reflecting elements disposed on this surface, as described in more detail hereinafter .

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

The floating module 1 further comprises a floating armature 20, on which are mounted the photovoltaic panel or panels 10. This floating armature advantageously comprises a plurality of tubular elements 21 rectilinear and / or curvilinear adapted to be assembled. To allow the module to float, the floating armature 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. Alternatively, the frame may also comprise, within the frame, one or more cross members 23 delimiting, with the tubular elements forming the frame 22, several closed cells 24 (see Figure 2a).

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

Alternatively, other forms of reinforcement can be achieved by assembling the tubular elements, such as a cross.

Advantageously, but optionally, the floating module 1 may also include 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 grating, that is to say in the form of lattice or grid. This platform is advantageously removable, to be installed only as part 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 amount 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 an embodiment shown in FIG. 3, the reflector device 40 comprises floating reflective balls 41. The balls are disposed on the aquatic surface within each cell defined by the floating armature 20, and the armature 20 is advantageously shaped. to contain the beads in the cells. For example, when the module 1 is positioned on the aquatic surface, the emergent part of the tubular elements defining the frame 22 and sleepers 23 must have a height, relative to the water level, at least equal to one-third, and preferably at least half the height of a ball. For example, the balls may have a diameter of between 20 and 40 cm, and the raised portion of the tubular elements and sleepers may have a height greater than 10 cm, preferably greater than 15 cm.

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

In this embodiment, and as visible in FIG. 3, the floating armature 20 preferably comprises a frame 22 and a plurality of crosspieces 23, allowing 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 very interesting economically since it allows to obtain a good photovoltaic conversion efficiency by limiting the number of components of the module.

As a variant, the reflector device 40 is itself adapted to stabilize the floating module 1. In this respect, the reflector device 40 may comprise a tarpaulin 42 fixed to the armature 20.

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

Preferably, the reflective 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 sheet 42 is stretched on the floating armature so as to extend above the aquatic surface when the module 1 is placed thereon.

As in the example shown in Figure 1, the floating armature may comprise several cells delimited by the frame formed by the tubular elements and additional sleepers (not visible in the figure). In this case, the reflector device 40 may comprise several tarpaulins 42, each tarpaulin being sized so as to cover a respective cell, and being stretched on this cell.

The fact of stretching a reflective cover on the frame makes it possible at the same time to significantly increase the reflection of the light rays towards the lower face of the photovoltaic modules, but also to stiffen the frame and thus 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 receive a water ballast B which stabilizes the module. In this case, the sheet is dimensioned so that it can be tensioned once a water ballast of a thickness preferably between 5 and 15 cm, for example between 10 and 15 cm, is positioned on the sheet. This makes it possible to stabilize the module while limiting the loss of the reflective properties (the albedo) of the tarpaulin bound to the water.

Nevertheless, to compensate for the albedo loss of the tarpaulin related to the presence of the ballast, the reflector device 40 very advantageously comprises floating reflective balls 42, disposed on the water ballast and contained by the edges of the sheet 30, and if necessary by the edges and / or the cross members of the floating armature 10. For example, the floating balls 42 may be contained by the edges of the sheet 30 on two opposite sides and by the edges or cross members of the floating armature 10 on the other two sides.

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

The choice of one of the embodiments described above results from a compromise between the mechanical stability obtained (which is optimal in 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 beads being the most advantageous from the point of view of the above criteria but also the most expensive.

With reference to FIGS. 4a and 4b, the module 1 advantageously comprises a device 50 for monitoring the azimuth 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 electrical energy production of the panels.

Thus, as shown in Figure 4a, the azimuth tracking device of the sun allows to position the module so as to orient the panels east in the morning, south at noon, and west at night. Azimuthal 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 amount of electricity that one wishes to produce, one can group several modules to form a photovoltaic power 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, adapted to convert the direct current produced by photovoltaic panels into alternating current adapted to be injected into the network.

Referring to Figure 5a, there is shown the theoretical efficiency gain between a photovoltaic power plant made from floating modules according to one embodiment of the invention and a terrestrial power station of equivalent power comprising single-sided panels.

This efficiency gain has been modeled for an installed electrical power of 1 megawatt peak. The plant comprises 175 chains each comprising 18 double-sided crystalline silicon photovoltaic panels, each with 350 Watts peak power. The 18 panels of a chain are distributed over 4 floating modules, for example two modules carrying 4 panels and two modules carrying 5 panels.

The floating plant is modeled for the following parameters:

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

The module comprises a reflective cover stretched over the frame in accordance with the example of FIG.

The tarpaulin has a 60% albedo,

The photovoltaic panels are inclined by 30 ° with respect to the surface of the water,

The panels are spaced 2.85 meters apart,

Modules include an azimuthal sun tracking device.

The earth station used for the comparison is of the same power and includes the same number of chains and panels. It is considered that the air temperature is one degree higher than the lake temperature. In addition, the properties of the plant are as follows:

The panels are single-sided,

The panels are inclined 15 ° to the ground surface,

- The albedo of the soil is 20%,

The panels are spaced 2.5 meters apart

The plant 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 coating of the tarpaulin or reflective beads.

In FIG. 5b, the gain provided by the use of the floating module according to the invention has been decomposed as a function of the various parameters of the module. We note in particular the importance of the biface aspect of the panels coupled to the use of the reflector device since it is responsible for a gain of 10.84% efficiency.

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

The sun's azimuthal tracking device allows a 5.72% gain over the ground 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 power generation.

Claims

A floating module (1) for generating electricity, comprising:

at least one photovoltaic panel (10), and

a floating armature (20) on which the panel (10) is mounted, characterized in that the photovoltaic panel (10) has 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).

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

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

Floating module (1) according to claim 5, wherein the cover (42) is stretched over the armature (20) so as to extend above the surface of the water when the module (1) is lying on the water.

Floating module (1) according to one of claims 1 to 3, wherein the cover (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 edges of the sheet 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) according to the azimuth of 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 ° to the horizontal.

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