METHOD AND AGRIVOLTAIC DEVICE FOR PROTECTING A PLANT FROM FROST

Description

FIELD OF THE INVENTION

[0001] The present invention relates to the field of agrivoltaics.

[0002] The invention relates more specifically to a device and a method for protecting a plant against frost. STATE OF THE ART

[0003] Climate change is increasingly affecting crops, particularly through alternating warm periods in spring, which are favorable for buds and flowers to emerge, followed by cold periods leading to frost. If the temperature drops below 0°C when the buds have emerged, they can freeze and lead to a drastic reduction in the quantity of crops (grapes, fruit, etc.) for the current year.

[0004] By definition, a photovoltaic cell is an electronic component whose function is to produce electricity when exposed to light.

[0005] It has been proposed to arrange panels containing photovoltaic cells performing this function above crops. Thanks to this arrangement, the panels not only produce electricity but also protect crops from bad weather.

[0006] Such panels are particularly effective against frost damage to crops as long as the ambient temperature is around 0°C. However, at lower temperatures, these panels are no longer effective enough to prevent frost damage to buds or flowers.

[0007] EP 2 965 618 A1 illustrates a state of the prior art. STATEMENT OF THE INVENTION

[0008] An object of the invention is to remedy the situation set out above.

[0009] For this purpose, according to a first aspect, there is provided a device for protecting a plant against frost, according to claim 1, the device comprising: a panel suitable for being positioned above the plant, the panel comprising a photovoltaic cell, at least one source capable of supplying the panel with an electric current so that the panel heats by the Joule effect while the photovoltaic cell is not exposed to light.

[0010] The panel comprises a conductive and non-photovoltaic part, such as a metal frame surrounding the photovoltaic cell, the electric current being supplied to said part.

[0011] Thanks to the electrical power source, the panel (especially the metal frame) can be powered even in cloudy weather or at night, which are weather conditions particularly conducive to plant frost. During this power supply, the panel heats up by the Joule effect, and therefore emits heat nearby. This emitted heat warms the plant located below the photovoltaic cell, and therefore improves its resistance to frost.

[0012] The device according to the first aspect takes advantage of the fact that the panel comprising the photovoltaic cell is an element already installed near the plant for the purpose of generating electricity and protecting the plant against certain bad weather, and which is capable of serving as a heating element for the plant. This is clever, because it saves the need for a dedicated heating element, in addition to the panel; the proposed device is thus less bulky and more economical than a device which would include such a dedicated heating element.

[0013] The device according to the first aspect may also comprise the following optional features, taken alone or in combination whenever technically possible.

[0014] Preferably, the electric current is supplied to the photovoltaic cell.

[0015] Preferably, the source is a battery configured to be charged by the photovoltaic cell, when the photovoltaic cell is exposed to light.

[0016] Preferably, the device comprises an interface configured to obtain at least one meteorological parameter indicative of weather conditions experienced by the plant, wherein the source is configured to control the supply of the panel with electrical current based on the obtained meteorological parameter.

[0017] Preferably, the meteorological parameter includes a temperature.

[0018] Preferably, the source is configured to not supply the panel with electrical current until the weather parameter has crossed a predefined threshold.

[0019] Preferably, the electric current has a first intensity when the meteorological parameter has a first value indicative of first meteorological conditions experienced by the plant, and a second intensity greater than the first intensity, when the meteorological parameter has a second value indicative of second meteorological conditions more conducive to freezing of the plant than the first meteorological conditions.

[0020] Preferably, the source is configured to control the supply of electrical current to the panel based on the current time in a day.

[0021] Preferably, the panel comprises a wall arranged between the photovoltaic cell and the exterior of the panel, the wall being made of a polymer material.

[0022] Preferably, the device comprises a control unit configured to move the panel relative to the structure in a displacement that increases an amount of heat transmitted by the panel to the plant.

[0023] Also provided in a second aspect is a method of protecting a plant against frost comprising the use of a device according to one of claims 1-10. DESCRIPTION OF FIGURES

[0024] Other characteristics, aims and advantages of the invention will emerge from the following description, which is purely illustrative and non-limiting, and which must be read in conjunction with the appended drawings in which: THE Figure 1 and 2 schematically illustrate a device according to a first embodiment of the invention. The figure 3 schematically illustrates a device according to a second embodiment of the invention.

[0025] Throughout the figures, similar elements have identical references. DETAILED DESCRIPTION OF THE INVENTION

[0026] In reference to the figure 1 , a device 1 for protecting a plant against frost comprises a structure 2 suitable for being fixed to the ground, and a panel 4 movable relative to the structure.

[0027] The structure 2 comprises one or more masts intended to extend vertically relative to the ground, for example two or more masts. The structure 2 further comprises a crosspiece intended to extend horizontally relative to the ground.

[0028] The panel 4 is mounted movably on the structure 2, so as to overhang the ground and in particular a plant growing from this ground. The panel 4 is for example mounted on the crosspiece. The panel 4 is for example mounted to rotate on the structure 2 on one or two axes of rotation, but other types of mounting can be envisaged, for example in translation in a vertical direction relative to the ground.

[0029] The panel 4 comprises at least one photovoltaic cell 6. In accordance with the definition given in the introduction, the photovoltaic cell 6 is a known electronic component, the function of which is to produce electricity when it is exposed to light.

[0030] The panel 4 may comprise several photovoltaic cells 6. In the embodiment shown in figure 1 , panel 4 comprises 24 photovoltaic cells arranged in a checkerboard pattern of dimensions 4x6.

[0031] Panel 4 has a first face, and a second face opposite the first face.

[0032] Panel 4 also includes other parts that are not photovoltaic cells (in the sense that these parts do not produce electricity when exposed to light).

[0033] In particular, the panel 4 comprises a first wall extending between the first face and each photovoltaic cell 6, and a second wall extending between the second face and each photovoltaic cell 6. In other words, each photovoltaic cell 6 is arranged between the first wall and the second wall.

[0034] The first wall is transparent. Thus, each photovoltaic cell 6 is arranged to receive light having entered the panel through the first face.

[0035] The second wall may be transparent, in which case each photovoltaic cell 6 is capable of receiving light that has entered the panel through the second face (this is then referred to as a “bi-face” panel). Alternatively, the second wall is opaque (this is then referred to as a “mono-face” panel).

[0036] The first wall and / or the second wall may be made of glass or a polymer material. A polymer material has the advantage of generally promoting heat dissipation by the Joule effect towards the outside of the panel 4.

[0037] The panel 4 may also comprise a metal frame 8 surrounding the or each photovoltaic cell 6, and where appropriate the first wall and / or the second wall mentioned above.

[0038] The 8-frame is typically made of aluminum, which is a very good thermal conductor. Alternatively, the 8-frame can be made of a more resistive metal or alloy (steel, nickel / chromium, etc.).

[0039] The device 1 further comprises an electric current source 10 capable of supplying the panel 4 with an electric current so that the panel heats by the Joule effect.

[0040] The electric current source 10 has the particularity of being capable of supplying the panel 4 with such an electric current not only when the panel 4 is exposed to light, but also when the panel 4 is not exposed to light. Thus, the electric current source 10 is not in itself a photovoltaic cell 6.

[0041] Different parts of the panel 4 can be supplied with electric current by the electric current source 10: the metal frame 8, and optionally at least one of its photovoltaic cells 6 and / or other conductive parts of the panel 4.

[0042] The electric current source 10 is external to the panel 4.

[0043] The electric current source 10 is a battery, for example of the lithium-ion type.

[0044] The battery is for example arranged in a mast of structure 2.

[0045] Of course, the device 1 may include additional panels having the same characteristics as the panel 4 (the embodiment illustrated in figure 1 comprises four panels). In this case, the different panels can be rotatably mounted on the structure 2, their respective axes of rotation being parallel. Furthermore, the different panels 4 and the electric current source 10 are mounted in series.

[0046] Preferably, the battery is configured to be charged by at least one photovoltaic cell 6 when it is exposed to light. Thus, the battery can store part of the energy produced by a panel of the device, before returning this energy in a delayed manner to the panel 4, at a time when the device 1 is in the dark or at least when the device 1 is no longer exposed to light in sufficient quantity to produce electricity from light (in overcast weather or at night for example).

[0047] The device 1 may also comprise an inverter 12 when the source is a direct current source. The inverter has the function of converting the direct electric current generated by the source into an alternating electric current, and of supplying the panel 4 with this alternating current. Furthermore, when the source 10 is a battery, the inverter converts the alternating electric current generated by the panel 4 exposed to light into direct current, and charges the battery with this direct current.

[0048] The device 1 may further comprise at least the following additional components, electrically powered by the source 10 or another source: a heating element (cord, cable or panel for example) positioned or wrapped around the mat or around a vermiculite-based refractory brick which itself can be positioned at the base of the plant. a fan or rotating element for mixing the ambient air, installed on the mat of the panels or at the base of the plant. a heating lamp installed on the mat or at the base of the plant, such as those used in incubators or terrariums. A low-consumption ceramic or infrared heating lamp, emitting very little light and with a good lifespan, can be used advantageously.

[0049] These additional components constitute means improving the performance of protection of the plant against frost by the device 1.

[0050] A method of using the device 1 is as follows: the source 10 is activated, so as to generate an electric current. This electric current is supplied to the panel 4, which heats by the Joule effect. The heat generated by this day effect dissipates outside the panel 4, as shown in figure 2 . In particular, this heat heats the environment near panel 4, and in particular the environment near the plant which is located below panel 4. This heating improves the protection of the plant against frost.

[0051] Preferably, device 1 is used in this way at night, because it is at night that the risk of freezing is greatest.

[0052] In order to further improve the protection of the plant against frost, it may be provided to move the panel 4 relative to the structure, so that more heat dissipated by the panel reaches the plant. This movement may in particular consist of bringing the panel 4 closer to the plant by lowering it, when the panel is mounted in vertical translation on the structure. When the panel 4 is mounted in rotation, this movement may be a rotation towards an orientation in which a face of the panel which dissipates the most heat is located opposite the plant (downwards). The device 1 may comprise a control unit for the panels 4 configured to move the panel 4 in this way. This movement may be carried out before the source 10 supplies the panel with electrical current, or during this supply.

[0053] The supply of electric current to the panel 4 from the source 10 can be controlled automatically, and in different ways.

[0054] In one embodiment, the device 1 comprises or is connected to a clock determining the current time in a day. This current time is for example expressed to the nearest hour, to the nearest minute or to the nearest second. The electric current supply to the panel 4 is then controlled according to the current time determined by the clock. It is thus possible to define different time ranges during the day associated with different current supply parameters. For example, the electric current supplied by the source 10 may have: a first intensity during a first time slot in a day, and a second intensity higher than the first intensity during a second time slot of the day

[0055] The first time slot can be a daytime slot and the second time slot can be a nighttime slot.

[0056] It can be considered that the first intensity is zero. In this case, the electric current source only causes heat dissipation by Joule effect within the panel for part of the day. Alternatively, the first intensity is not zero.

[0057] In another embodiment, the device 1 comprises an interface configured to obtain at least one meteorological parameter indicative of weather conditions experienced by the plant. The electrical current source 10 is then configured to control the power supply to the panel 4 as a function of the or each meteorological parameter obtained.

[0058] The interface may be a communication interface with a remote server providing the or each meteorological parameter. Alternatively, the interface is a sensor that locally measures the or each parameter considered. This sensor may be positioned at the foot of the plant.

[0059] The electrical power source 10 may not supply the panel with electrical power until the weather parameter has crossed a predefined threshold. In other words, the source 10 only supplies the panel with electrical power once this parameter has crossed this threshold.

[0060] A particularly advantageous meteorological parameter for controlling the power supply of the panel from the source is a temperature measured near the plant. Indeed, this parameter is very relevant for assessing the risk of freezing of the plant.

[0061] Thus, source 10 can supply the panel with electrical current only when the temperature is below a certain temperature threshold, for example 0 degrees Celsius.

[0062] Alternatively, the electrical current supplied by the source can be adjusted to: a first intensity when a meteorological parameter obtained has a first value indicative of first meteorological conditions experienced by the plant, and a second intensity greater than the first intensity, when the meteorological parameter obtained has a second value indicative of second meteorological conditions more conducive to freezing of the plant than the first meteorological conditions.

[0063] In this variant, the current intensity can be modulated. When temperature is used as a meteorological parameter, the source can be arranged to supply an electric current to the panel, the intensity of which increases as the temperature decreases.

[0064] Parameters other than temperature may be used to control the supply of electrical current to the panel from source 10, such as the ambient humidity near the plant.

[0065] In the above, a device 1 has been described in which a single source of electric current 10 is capable of supplying different parts of the panel 6 with electric current. However, it is conceivable to provide several sources of electric current supplying different parts of the panel, for example a first source 10 which supplies the photovoltaic cells 6, and a second source 11, which supplies the frame 8, as shown in figure 3 .

Claims

1. A device (1) for protecting a plant against frost, the device (1) comprising: - a panel (4) suitable for positioning above the plant, the panel comprising a photovoltaic cell (6) and a metal frame (8) surrounding the photovoltaic cell, the metal frame (8) being a conductive and non-photovoltaic part, - at least one source (10) capable of supplying the metal frame (8) with an electric current while the photovoltaic cell is not exposed to light, so that the metal frame (8) heats by Joule effect .

2. Device (1) according to claim 1, in which the electric current is supplied to the photovoltaic cell (6).

3. A device (1) according to one of claims 1 and 2, wherein the source (10) is a battery configured to be charged by the photovoltaic cell (6), when the photovoltaic cell (6) is exposed to light.

4. A device (1) according to any one of claims 1 to 3, comprising an interface configured to obtain at least one meteorological parameter indicative of weather conditions experienced by the plant, wherein the source is configured to control the supply of electric current to the panel as a function of the obtained meteorological parameter.

5. Device (1) according to claim 4, wherein the meteorological parameter comprises a temperature.

6. Device (1) according to one of claims 4 and 5, in which the source (10) is configured not to supply the panel (4) with electric current until the meteorological parameter has exceeded a predefined threshold.

7. A device (1) according to one of claims 4 to 6, wherein the electric current has - a first intensity when the meteorological parameter has a first value indicative of first weather conditions experienced by the plant, and - a second intensity higher than the first intensity, when the meteorological parameter has a second value indicative of second weather conditions more conducive to plant freezing than the first weather conditions.

8. A device (1) according to one of claims 1 to 7, comprising a clock configured to determine a current time in a day, wherein the source (10) is configured to control the supply of the panel (4) with electric current in dependence on the current time in the day.

9. Device (1) according to one of claims 1 to 8, wherein the panel (4) comprises a wall arranged between the photovoltaic cell and the outside of the panel (4), the wall being made of a polymer material.

10. Device (1) according to one of claims 1 to 9, further comprising a control unit configured to move the panel relative to the structure according to a displacement which increases an amount of heat transmitted by the panel (4) to the plant.

11. A method of protecting a plant against frost comprising the use of a device according to one of the preceding claims.