CA3055880C - Hydro-photovoltaic mat - Google Patents

Abstract

A solar mat for installation on a mountain lake, comprising a plurality of floating elements, each of the floating elements being configured to support loads while floating on the surface of the lake and resisting forces coming from at least another of the floating elements or from environmental influence; one or more photovoltaic panels mounted on each of the elements of the plurality of floating elements, by means respectively of a support structure configured to separate the photovoltaic panels from the surface of the water at a predetermined height, chosen to avoid contact with the water and so that any snow that may come in contact with a photovoltaic panel can easily fall from the panel for removal without accumulating in front of the panels; an inverter and a transformer; a floating structure defined to support the inverter and the transformer; articulated connection means connecting the elements of the plurality of floating elements and the floating structure defined between them in a matrix to constitute the solar mat. The articulated connection means are furthermore configured so that the floating elements are placed on the ground at the bottom of the lake by conforming to the topography of the lake when the lake is substantially empty of water.

Description

Hydro-photovoltaic mat Technical field of the invention PCT/IB2018/051559 The invention is in the field of solar power plants obtained by surfaces of photovoltaic cells arranged on top of a water surface.

Prior art The deployment of an array of floating photovoltaic elements in an aquatic environment is known.

This type of deployment particularly makes it possible to overcome a lack of land with a sufficient area and in particular the cost of this land.

EP 2 535 259 Bl describes such an array, in which floating photovoltaic elements are connected to each other by means of at least one cable, each floating element comprising a buoy and a photovoltaic surface fixed on top.

The photovoltaic surfaces pivot about a non-vertical axis and the floating photovoltaic elements can be placed on fixed mooring elements installed on the bottom of a basin.

The array includes elements for adjusting the length of the cables.

Large-scale floating solar arrays already exist in Japan, Great Britain, France, Malaysia, etc., but only in regions with a mild climate.

At the beginning of2017, no fewer than 63 MWp (megawatt peak) of floating solar power had been installed worldwide.

The finalization of a solar project in an alpine environment promises improved performance compared with regions with a mild climate.

The present invention proposes an alternative embodiment that enables simplified installation of the array on a mountain lake, together with an embodiment that is more economical overall.

Summary of the invention In a first aspect, the invention proposes a solar mat for installation on a mountain lake, comprising a plurality of floating elements, each of the floating elements being configured to support loads while floating on the surface of the lake and withstand forces originating at least from another of the floating elements or from an environmental influence; one or more photovoltaic panels mounted on each of the elements of the plurality of floating elements, by means respectively of a support structure configured to separate the photovoltaic panels from the surface of the water by a predetermined height, selected to avoid contact with the water and so that any snow that might come into contact with a photovoltaic panel can easily fall off the panel for removal without accumulating in front of the panels; an inverter and a transformer; a defined floating structure to support the inverter and the transformer; articulated connection means connecting the elements of the plurality of floating elements and the defined floating structure together in a matrix in order to form the solar mat.

The articulated connection means are also configured so that the floating elements are placed on the ground at the bottom of the lake following the topography thereof when the lake is substantially empty of water.

In a preferred embodiment, the support structure comprises a loadbearing upper frame configured to remain out of the water of the lake at all times, and to receive and bear the photovoltaic panel(s).

In another preferred embodiment, the articulated connection means are configured to connect the floating elements by fastenings on the upper frames, thus making it possible to avoid any trapping in ice in the event that the lake water freezes.

In another preferred embodiment, the upper frame is configured to hold the solar panel(s) at least 1.5 m above the floating element.

In another preferred embodiment, the upper frame comprises an aluminum structure.

In another preferred embodiment, the connection means comprise main cables, secondary cables and intermediate buoys, the secondary cables being configured to hold the floating elements and the defined floating structure in their relative positions, the main cables being 2 configured to support the secondary cables and fix the solar mat to anchoring means situated substantially on the edge of the lake, the intermediate buoys being configured to support the main cables and hold them above the surface of the water.

In another preferred embodiment, the intermediate buoys are situated in a peripheral zone of the solar mat.

In another preferred embodiment, each of the floating elements comprises a structure made from at least one of the materials in the list comprising steel, polyethylene, and aluminum.

In another preferred embodiment, each of the floating elements comprises a hollow structure, this hollow structure being empty.

In another preferred embodiment, the hollow structure is filled with foam arranged to prevent the floating element from filling with water in the event that the hollow structure is breached.

In another preferred embodiment, each floating element comprises a float made in one piece or from a plurality of pieces, and describing a shape with an octagonal circumference.

In another preferred embodiment, the solar mat also comprises anchoring means configured to attach one or more floating elements to the edge of the lake.

In another preferred embodiment, at least one of the connection means includes a chain, the chain having a defined mass.

In a second aspect, the invention proposes a method for installing a solar mat on a mountain lake according to one of the embodiments described above.

The process comprises placing at least one base for anchoring the solar mat to the ground in a location corresponding to the edge of the lake when the lake is filled to 2/3 of the maximum level; assembling, for each anchoring base, a cable attached at one of its ends to the anchoring base and the opposite end of which is intended for attaching to a floating element of the solar mat, the cable having a length configured to at least ensure that the solar mat is held in a first defined position when the water level in the lake is at a minimum, and to ensure 3 that the solar mat is held in a second defined position when the water level in the lake is at a maximum, the cable then being extended; and for each cable, when the water level in the lake is substantially higher than the minimum level, attaching a floating element to the cable.

In another preferred embodiment, prior to the placement step, the ground of the lake is dried up or drained.

Brief description of the figures The invention will be more clearly understood on reading the detailed description of preferred embodiments of the invention and with reference to the drawings, in which figure 1 contains an assembly of three mats of 81 floats arranged on a natural site according to a preferred embodiment of the invention; figures 2A to 2D respectively diagrammatically illustrate floats or floating elements according to several preferred embodiments of the invention; figure 3 shows two examples of planes of float mats: example A extends without the effect of the wind, example B with the effect of the wind; figure 4 illustrates the position of a float mat depending on the water level of a lake on which the mat is arranged; figure 5 illustrates a float buoy in two flotation scenarios; figure 6 illustrates an embodiment of the solar mat with connection means comprising main cables, secondary cables and intermediate buoys according to the invention; 4 figure 7 illustrates an example of a floating element bearing photovoltaic panels; and figure 8 illustrates an example of a floating structure defined to support an inverter and a transformer in a solar mat according to the invention.

The references used to denote structures in the figures will be the same from one figure to another if the structure in question is the same or of the same type.

Detailed description of preferred embodiments of the invention The invention relates to a floating solar mat for installation on a mountain lake, and to a method for installing such a floating solar mat on the mountain lake.

The floating mat is designed to withstand the stresses of a mountain lake in an alpine environment - wind, snow, layer of ice on the surface of the lake in winter in particular, large fluctuations in the water level if the lake is dammed, large temperature fluctuations, etc.

The solar mat comprises a number of floating elements that can be placed on the ground when the lake is empty.

Introduction Photovoltaic power is set to contribute to the electricity and heat production objectives set out in energy strategies that aim to increase the proportion of renewable power production.

In addition, photovoltaic power contributes to reducing annual CO2 em1ss1ons: the production of one kilowatt hour of solar electricity in Switzerland typically emits 42 g of CO2 equivalents.

These figures take into account the manufacture and disposal of the entire photovoltaic system; WO 2018/163121 PCT/1B2018/051559 by way of comparison, a gas-fired power plant has emissions of almost 452 g, while a lignite-fired power plant generates as much as 1,347 g.

The European electrical mix emits 552 g of CO2 equivalents per kilowatt hour (Source: ESU Services 2013: Life Cycle Inventories of Electrical Mixes and Grid (PDF)); - solar electricity therefore generates almost 13 times less greenhouse gas emission than the European electrical mix and makes a significant contribution to climate protection.

An example of a floating mat project is under way in Switzerland, at the Les Toules Dam, with a target power of 420 kWp (capacity to install 1,400 PV panels with dimensions of 1,600 mm x 1,000 mm).

The dam is located in an alpine environment, which brings the following advantages in particular to the project: Increased power production and therefore profitability of the project.

The tests carried out on site over four years using a pilot installation have shown that bifacial photovoltaic technology enables 50% greater production compared to the production of a monofacial PV panel in the lowlands.

With bifacial technology, the solar production capacity at Lac des Toules is close to that of southern Spain or northern Morocco with non-bifacial photovoltaic technology.

At altitude, photovoltaic production is greater than in the lowlands, due to the following phenomena: the UV index is higher; the Albedo effects (reflection of the sun on a surface) of snow, ice and water are greater than those of a rooftop or grass; and the temperatures are colder.

Continuous, significant production throughout the year.

Winter production (October to March inclusive) reaches or even exceeds 40% of annual production for bi facial photovoltaic technology.

It 6 WO 2018/163121 PCT /1B2018/051559 is also important to note that monthly production is almost unchanging from March to September inclusive.

This is mainly due to the reflection from snow during the months when the days are shorter.

Limitation of the impacts on the environment.

This is the case in particular for Lac des Toules, due to the artificial nature of this dammed lake, and may also be true for other dammed lakes: the fluctuations in water level do not permit the development of significant marginal vegetation or the establishment of particular wildlife or plant species; the turbidity and low temperature of the lake naturally slow down the development of zoo- and phytoplankton, resulting in a limited impact on the fish fauna; the landscaping of the site is not natural; the site facilities and electrical connections can be installed without any particular impact on the environment; and the installation is placed on the ground for an average of six months per year (between January and June).

Ease of distribution of the power produced by taking advantage of the existing installations relating to the dam.

Territorial coherence with the activities already present on the site.

The lake already plays a hydroelectric role and with the solar mat becomes a single multi-energy production center (hydroelectric and photovoltaic), with advantages in terms of: complementarity of renewable energies; environmental impacts concentrated in one area; and synergy in terms of connection to the power grid. 7 For any solar mat to be placed on a dammed lake, the floating system can be connected to the existing distribution system for the dam.

An example of the environmental conditions to which a floating mat for a mountain lake might be subjected is given by the parameters of Lac des Toules: temperatures: -25°C to +30°C~ snow depth on the PV panels before removal: 50 cm maximum thickness of ice on the lake: approx. 60 cm wind speed: gusts ofup to 120 km/h fluctuation in the level of the lake: a maximum of 62 m over the last 10 years.

General description The basic principle of the invention is to have, for a mountain lake, a multitude of floating elements bearing photovoltaic panels that will be connected to each other in order to create a solar mat.

In an embodiment similar to that of Lac des Toules mentioned above, each float element receives 40 photovoltaic panels with an area of I .6 m2 each.

In addition to the environmental conditions already mentioned, a mountain lake is generally characterized by a bottom with a fairly uneven topography possibly including rocks and/or holes.

The bottom can also be made up of two mountain slopes that at the same time form the edges of the mountain lake.

If applicable, it can be necessary to adjust the bottom of the lake by making it flatter, which could be done by work preferably when the lake is drained.

The fairly flat nature of the bottom would make it possible to facilitate the floating elements being placed on it without overturning when the water empties out of the lake.

The flat nature of the bottom does not in any way imply that the bottom has no gradient. 8 WO 2018/163121 PCT /1B2018/051559 Another specific aspect of the invention is that at least one element of the floating mat is designed to floatably support one or more inverters and one or more transformers to perform initial handling of the current produced by the photovoltaic panels.

In view of the weight and specific density of the load to be floated, this requires a defined floating structure that can differ from the aforementioned floating elements.

The solar mat is anchored to the edges of the lake, at 2/3 of the maximum level of the water in the lake, and not to the bottom of the lake, unlike certain systems of the prior art.

Solar mat The invention proposes for example a solar mat 100 for installation on a mountain lake such as the one illustrated in figure 1.

The solar mat 100 comprises a plurality of floating elements 101 and one or more photovoltaic panels (not explicitly illustrated in figure 1) mounted on each of the plurality of floating elements 101.

The solar mat 100 also comprises an inverter and a transformer (not explicitly illustrated in figure 1) mounted on a defined floating structure 102.

The floating elements 101 of the plurality of floating elements and the defined floating structure 102 are connected together in at least one matrix 104 by articulated connection means 103.

In the example illustrated in figure 1, four matrices 104 are fully or partially visible.

The number of matrices 104 can be adjusted depending for example on the size of the lake.

The organization into restricted matrices 104 of floating elements 101 also meets the objective of improved wind resistance, and easier maintenance due to improved access to the floating elements once they have been installed.

The wind resistance effect is illustrated in figure 3, which shows two examples of planes of float mats, in which example A extends without the effect of the wind, example B with the effect of the wind.

It is clearly visible that in example B, despite the deformation of the matrices I 04 from a rectangle in example A to a shape 9 WO 2018/163121 PCT /IB2018/051559 with curved edges in example B, the floating elements 101 remam positioned in a matrix, and are clearly separated from one element to another.

The articulated connection means 103 are configured so that the floating elements IO 1 are placed on the ground at the bottom of the lake following the topography thereof (not shown in figure 1) when the lake is substantially empty of water.

This obviously also applies to the defined floating structure 102, and will be discussed during the explanation of figure 4 later in the description.

Each of the floating elements 101 is configured to support loads while floating on the surface of the lake (not shown in figure 1) and withstand forces (not shown in figure 1) originating at least from another of the floating elements or from an environmental influence (not shown in figure 1 ).

The resistance is provided by the intrinsic construction of the floating elements 101, and also by the articulated connection means 103, which make it possible to hold both the floating elements 101 and the defined floating structure 102 at minimum distances when the wind or the gradient of the lake bottom (not shown in figure 1) cause relative movements between them.

Figure 2A illustrates an example of a floating element 101 configured to support loads while floating.

Each floating element 101 is sized to support one or more photovoltaic panels 700 mounted in it, as illustrated in the example in figure 7.

The photovoltaic panels 700 are mounted on the floating element 101 by means of a support structure 200 configured to separate the photovoltaic panels 700 from the surface of the water (not shown in figure 7 or figure 2A) by a predetermined height when the floating element is floating on the water.

This predetermined height is selected to avoid contact with the water and so that any snow that might come into contact with a photovoltaic panel during a period of precipitation for example can easily fall off the panel for removal without accumulating WO 2018/163121 PCT /IB2018/051559 in front of the panels and obscuring them. A person skilled in the art will easily understand that this height must be appropriate to the snow cover conditions of the location.

The support structure 200 illustrated in figure 2A includes a number of bars assembled together in a known manner.

Other support structures with suitable geometries can be envisaged.

Returning to figure 1 and figure 8, the solar mat also comprises the inverter and the transformer already mentioned above and shown in figure 8 with reference signs 800 and 801 respectively.

These are supported by the defined floating structure 102, an embodiment of which is illustrated in figure 8.

Support structure In a preferred embodiment of the solar mat according to the invention, the support structure 200 comprises a load-bearing upper frame 201 configured to remain out of the water of the lake at all times, and to receive and bear the photovoltaic panel(s) (not illustrated in figures 2A and 2B).

Such an upper frame 201 is illustrated for example in figure 2A or figure 2B, and also in figure 7 with photovoltaic panels mounted on the frame.

The upper frame is a structure of bars fixed together to obtain a light, sturdy frame that is sufficiently tall so that the top of the upper frame is always out of the water of the lake.

Figure 2C illustrates a cross-section of a floating element resting on the surface of the water.

The reference sign "Top Structure" corresponds to the upper frame 201 already introduced above.

In another preferred embodiment of the solar mat according to the invention, the articulated connection means are configured to connect the floating elements by fastenings on the upper frames, thus making it possible to avoid any trapping in ice in the event that the lake water freezes.

In concrete terms, and with reference to figure 2C, these fastenings would be positioned on the edges of the Top Structure.

Figure 2D illustrates a cross-section of the floating element in figure 2C, except 11 WO 2018/163121 PCT /1B2018/051559 that here the floating element is resting on the ice.

It is clearly shown that the floats have risen to the surface of the ice instead of being trapped in the ice.

At the same time, it will be understood that any articulated means attached to the top structure by fastenings positioned on the edges of the Top Structure (fastenings and connection means not illustrated in figures 2C and 2D) would likewise not be trapped in the ice precisely because of the raised position relative to the ice.

In another preferred embodiment of the solar mat according to the invention, the upper frame is configured to hold the solar panel(s) at least 1.5 m above the floating element.

In another preferred embodiment of the solar mat according to the invention, the upper frame comprises an aluminum structure.

This metal provides a good compromise in terms of rigidity and weight. A person skilled in the art could also envisage and select other materials not named here.

Connection means In a preferred embodiment illustrated in figure 6, the connection means 103 comprise main cables 600, secondary cables 601, and intermediate buoys 602.

The secondary cables 601 are configured to hold the floating elements 101 and the defined floating structure 102 in their relative positions.

The main cables 600 are configured to support the secondary cables 601 and fix the solar mat 104 to anchoring means 603 situated substantially on the edge of the lake ( edge and lake not shown in figure 6). 12 The intermediate buoys 602 are configured to support the main cables 600 and hold them above the surface of the water (surface of the water not shown in figure 6).

As a result, the solar mat 104 is connected by cables to the intermediate buoys 602, which in tum are anchored to the edges of the basin using the main cables 600.

In a preferred embodiment, the main cables 600 have a mass that is manifested as illustrated in figure 4, in which the situation of the solar mat is shown for three water levels of the mountain lake.

Preferably, the anchoring points 603 on the edges of the lake are situated substantially at two-thirds of the maximum height of the lake in the position of the anchorage.

In figure 4, it is clearly visible that whatever the filling level of the lake, i.e. completely full for the top illustration, two-thirds full for the middle illustration, and empty for the bottom illustration, the main cables 600 hold the solar mat I 04 in place relative to the ground.

This is particularly due to the mass of the cables, which in this case is equivalent on the left and right of the mat to maintain a constant force towards the edge of the lake on both sides of the mat.

Preferably, the intermediate buoys 602 are situated in a peripheral zone of the solar mat.

Aside from the embodiment in figure 4, in another embodiment the weight of the cable plays no part in the positioning of the solar mat - the positioning is carried out instead by selecting a suitable length of the cables.

Floating elements Figures 2A and 2B illustrate two embodiments of floating elements: in figure 2A an octagonal buoy 203 forms a flotation element whereas in figure 2B it is shown to have eight cylindrical flotation elements 204 arranged in the shape of an octagon.

The embodiment in figure 2B has the advantage that manufacturing separate cylindrical elements is easier 13 WO 2018/163121 PCT /1B2018/051559 than manufacturing an octagonal element.

In addition, cylindrical elements are easier to transport than the octagonal element.

The individual cylindrical shapes can be assembled underneath the support structure on the site of the water surface and ultimately produce a comparable flotation effect to that obtained with the one-piece octagonal element.

In a preferred embodiment, each of the floating elements, cylindrical or octagonal, comprises a hollow structure, this hollow structure being empty.

In a further embodiment, the hollow structure is filled with foam arranged to prevent the floating element from filling with water in the event that the hollow structure is breached.

Figure 5 illustrates an example of a float in a cross-sectional view in two flotation situations.

This figure demonstrates the normal draft of the floating structure when it is floating in the lake.

The maximum permissible draft is also shown.

This must never be exceeded or there is a risk that the floating structure will sink or be trapped in the ice.

The external stresses and loads have been taken into account so that this does not occur.

Installation and assembly The process described below should be followed for the installation and assembly of a floating solar mat structure. 1.

Civil engineering work necessary: a.

Flattening of the bottom of the lake in which the floating structure will be installed; b.

Creation of two logistics areas: The first for unloading elements coming by truck from the factory and the final assembly of each floating element.

The second will be used for launching each floating element; c.

An access road between these two logistics areas will also be created (if possible, by consolidating an existing road); 14 WO 2018/163121 PCT/1B2018/051559 d.

Small temporary site areas will also be created near the anchor blocks; e.

Creation of the anchorages; f.

Earth works necessary for the electrical connection to the grid.

All of this civil engineering work must be carried out as a priority.

Points a and e must be carried out when the level of the lake is low. 2.

Assembly of each floating element on land with all of the photovoltaic panels as well; 3.

Installation of the external buoys and pulling through of the cables between the anchorages and the buoys in order to "weave the external web", to be done when the water level reaches the level of the anchorages; 4.

Transportation of the floating elements one by one between the two logistics areas; 5.

Progressive launching of all of these floating elements when the water level is high, by crane; 6.

Formation of all of these floating elements into a "mat"; 7.

Launching of the floating structure with the inverter and the transformer and incorporation thereof into the mat; 8.

Electrical connection between the floating elements, up to the inverter; 9.

Electrical connection between the inverter and the transformer, then connection to the power grid; 10.

Reinstatement of the temporary logistics areas created.

Thus, according to another aspect, the invention proposes a method for installing a solar mat on a mountain lake.

This method envisages placing at least one base for anchoring the solar mat to the ground, in a WO 2018/163121 PCT /1B2018/051559 location corresponding to the edge of the lake when the lake is substantially filled to two thirds of the maximum level.

It then envisages assembling, for each anchoring base, a cable attached at one of its ends to the anchoring base and the opposite end of which is intended for attaching to a floating element of the solar mat.

The cable has a length configured to at least ensure that the solar mat is held in a first defined position when the water level in the lake is at a minimum, and to ensure that the solar mat is held in a second defined position when the water level in the lake is at a maximum, the cable then being extended.

For each cable, when the water level in the lake is substantially higher than the minimum level, provision is made for attaching a floating element to the cable.

Preferably, prior to the placement step, the ground of the lake is dried up or drained.

Advantages Of the numerous advantages inherent in the invention, the following advantages are highlighted.

The solar mat according to the invention makes it possible to avoid any mooring system involving one or more attachment elements at the bottom of the mountain lake or means of lashing the floating elements to the attachment elements at the bottom of the lake, and is therefore notably simpler and more economical to put in place on the mountain lake.

In addition, the solar mat according to the invention also avoids any adjustment system such as members for adjusting the length of the cable, which makes the system less subject to failure, and also more economical to produce. 16

Claims (19)

1. Claims 1. A solar mat for installation on a lake, the solar mat comprising: a plurality of floating elements, each of the floating elements being configured to support loads while floating on a surface of the lake and withstand forces originating at least from another of the floating elements or from an environmental influence; one or more photovoltaic panels mounted on each of the elements of the plurality of floating elements, by means respectively of a support structure configured to separate the one or more photovoltaic panels from the surface of the lake by a predetermined height, selected to avoid contact with water of the lake and so that any snow that might come into contact with a given said photovoltaic panels can easily fall off the given said panel for removal without accumulating in front of the one or more photovoltaic panels; an inverter and a transformer; a floating structure defined to support the inverter and the transformer; 18 articulated connection means connecting elements of the plurality of floating elements and the floating structure together in a matrix in order to form the solar mat, and the articulated connection means being configured so that the floating elements are placed on the ground at a bottom of the lake following a topography thereof when the lake is substantially empty of water; wherein the articulated connection means comprise main cables, secondary cables and intermediate buoys, the secondary cables being configured to hold the floating elements and the floating structure in their relative positions, the main cables being configured to support the secondary cables and fix the solar mat to anchoring means situated substantially on an edge of the lake, the intermediate buoys being configured to support the main cables and hold the main cables above the surface of the water; and wherein the solar mat is connected to the intermediate buoys by the secondary cable, with the intermediate buoys being connected to the anchoring means by the main cables.
2. 2. The solar mat as claimed in claim 1, wherein the support structure comprises a load-bearing upper frame configured to remain out of the water of the lake at all times, and to receive and bear the one or more photovoltaic panels. 19
3. 3. The solar mat as claimed in claim 2, wherein the articulated connection means are configured to connect the floating elements by fastenings on the load-bearing upper frames, thus making it possible to avoid any trapping in ice in the event that the water of the lake freezes.
4. 4. The solar mat as claimed in claim 2, wherein the load-bearing upper frame is configured to hold the one or more photovoltaic panels at least 1.5 m above the one or more floating elements.
5. 5. The solar mat as claimed in claim 2, wherein the load-bearing upper frame comprises an aluminum structure.
6. 6. The solar mat as claimed in claim 1, wherein the intermediate buoys are situated in a peripheral zone of the solar mat.
7. 7. The solar mat as claimed in any one of claims 1 to 6, wherein each of the floating elements comprises a structure made from at least one of the materials in the list comprising steel, polyethylene, and aluminum.
8. 8. The solar mat as claimed in any one of claims 1 to 6, wherein each of the floating elements comprises a structure made of steel.
9. 9. The solar mat as claimed in any one of claims 1 to 6, wherein each of the floating elements comprises a structure made of polyethylene
10. 10. The solar mat as claimed in any one of claims 1 to 6, wherein each of the floating elements comprises a structure made of aluminum.
11. 11. The solar mat as claimed in any one of claims 1 to 10, wherein each of the floating elements comprises a hollow structure, with said hollow structure being empty.
12. 12. The solar mat as claimed in claim 11, wherein the hollow structure is filled with foam arranged to prevent the one or more floating elements from filling with water in the event that the hollow structure is breached.
13. 13. The solar mat as claimed in one of claims 1, 11, and 12, wherein each of the floating elements comprises a float made in one piece or from a plurality of pieces, and describing a shape with an octagonal circumference.
14. 14. The solar mat as claimed in any one of claims 1 to 13, comprising said anchoring means configured to attach one or more floating elements to the edge of the lake.
15. 15. The solar mat as claimed in any one of claims 1 to 14, wherein at least one of the connection means includes a chain, the chain having a defined mass. 21
16. 16. The solar mat as claimed in any one of claims 1 to 15, wherein the lake is a mountain lake.
17. 17. A method for installing a solar mat on a lake as claimed in one of claims 1 to 16, comprising: placing at least one anchoring base for anchoring the solar mat to the ground, in a location corresponding to an edge of the lake when the lake is substantially filled to 2/3 of a maximum level thereof; assembling, for each said anchoring base, a cable attached at one end thereof to the anchoring base and the opposite end of which is intended for attaching to a floating element of the solar mat, the cable having a length configured to at least ensure that the solar mat is held in a first defined position when a water level in the lake is at a minimum, and to ensure that the solar mat is held in a second defined position when the water level in the lake is at a maximum, the cable then being extended; for each said cable, when the water level in the lake is substantially higher than the minimum level, attaching a floating element to the chain. 22
18. 18. The installation method as claimed in claim 17, wherein, prior to the placement step, the lake is dried up or drained.
19. 19. The installation method as claimed in any one of claims 17 to 18, wherein the lake is a mountain lake.