Device and method for estimating the soiling of photovoltaic panels

Abstract

Title: Device and Method for Estimating Soiling of Photovoltaic Panels. A device for estimating soiling of photovoltaic panels, comprising first and second units (2, 3), each unit (2, 3) comprising at least two zones (Z1 to Z8) for receiving solar radiation, and an electronic control unit (21) configured to calculate, for each zone (Z1 to Z4) of the first unit (2), a parameter relating to a current transmission loss rate from a ratio between a current supplied by said at least one photovoltaic module (4 to 7) in zone (Z1 to Z4) of the first unit (2) and a current supplied by said at least one photovoltaic module (8 to 11) in a zone (Z5 to Z8) of the second unit (3), and to determine a soiling distribution on the first unit (2) from at least one comparison between two current transmission loss rates. Figure for the abstract: Fig. 2

Description

Title of the invention: Device and method for estimating the soiling of photovoltaic panels technical field

[0001] The present invention relates to the estimation of soiling of photovoltaic panels, in particular photovoltaic cell panels, and more particularly to the estimation of the impact of soiling on photovoltaic energy production from such panels. STATE OF THE ART

[0002] Currently, panels equipped with photovoltaic modules are used to produce electrical energy by converting a portion of solar radiation using photovoltaic cells. These panels are located outdoors to receive maximum solar radiation and are susceptible to soiling due to snow, dirt, dust, and other particles, such as bird droppings, which can coat the surface of the photovoltaic modules. This soiling can lead to energy production losses, known as soiling loss.

[0003] Photovoltaic panels are subject to varying degrees of soiling depending on several parameters, particularly their geographical location and installation methods, notably their tilt. This soiling affects the efficiency of the panels, which directly impacts energy production.

[0004] The soiling of photovoltaic panels can be estimated using soiling kits. For example, patent documents US 10720882, WO2020 / 144618, US10337201, WO2014 / 061967, US10554171, and CN110266269 disclose the use of such soiling kits. Such a kit comprises a first panel, referred to as soiled, and a second panel, referred to as clean, and the current output of the two panels can be compared to estimate the impact of the soiling on the soiled panel. In particular, the currents supplied by the short-circuited panels are measured, the measured current being proportional to the incident photon radiation captured by the photovoltaic panel cells. For example, some systems use one clean panel that is periodically cleaned while the other panel gradually gets dirty.Furthermore, an electronic device measures the currents supplied by the photovoltaic panels, and a ratio between the two measured currents is calculated. This ratio quantifies the soiling rate, also known as the "soiling ratio." In addition, others... Some systems use a cover to protect the clean panel, opening it only briefly to take the necessary current measurements. Other systems protect the clean panel with a drawer that houses it and is placed beneath the soiled panel exposed to radiation. The drawer opens, exposing the clean panel to its side during measurement. However, these systems do not allow for estimating the distribution of soiling on photovoltaic panels, particularly whether the soiling is evenly distributed or dispersed across one or more areas of the panel. A lack of knowledge about soiling distribution can lead to serious errors in diagnosing and assessing the impact of soiling on energy production, especially when soiling is concentrated in certain areas, such as bird droppings or muddy rain residue.Furthermore, the clean and soiled panels of the soiling measurement assemblies are identical to the panels intended to produce electricity in a power plant, making them heavy and bulky and resulting in significant manufacturing and maintenance costs.

[0005] One example is Indian patent IN201941047730, which discloses a method for optimizing module cleaning by providing an estimate of losses induced by soiling. The method uses a system for acquiring and controlling data provided by the panels, a remote operations center, a weather station, and a knowledge engineering system. However, such a method is complex to implement.

[0006] We can also cite international application WO2019 / 158982, which discloses a soiling detection device based on the relative evolution of an electrical signal over time. However, the device does not allow for the identification of a soiling distribution on a photovoltaic panel.

[0007] One example is Korean patent KR10-2262361, which discloses a device comprising four sensors for measuring the amount of incident sunlight (called soiling measurement units). The sensors are located at the top, bottom, left, and right of a photovoltaic panel. Each sensor is similar to a module of the panel. The device includes a unit for calculating a soiling level by comparing the sensor measurements with a reference value stored in a database. The device can calculate four soiling levels for four distinct locations on the photovoltaic panel. However, the device is not sufficiently precise because it does not take into account the soiling of the photovoltaic panel itself.

[0008] One object of the invention is to overcome these drawbacks, and more particularly to provide means of estimating energy production that are simple to implement and to implement, and which are sufficiently precise. SUMMARY

[0009] To achieve this objective, a device for estimating the soiling of photovoltaic panels is proposed, comprising first and second units, each unit comprising at least two zones for receiving solar radiation, each zone comprising at least one photovoltaic module, the device comprising a movable protection system between a protection position in which the protection system is configured to mask said at least two zones of the second unit and a measurement position in which said at least two zones of the second unit are exposed to solar radiation, and an electronic control unit configured to receive a current supplied by each photovoltaic module.

[0010] The units have the same number of receiving zones, the photovoltaic modules of the first unit have identical characteristics, in particular in terms of size and number of photovoltaic cells, to those of the photovoltaic modules of the second unit, the electronic control unit is configured to calculate, for each zone of the first unit, a parameter relating to a current transmission loss rate from a ratio between the current supplied by said at least one photovoltaic module of the zone of the first unit and the current supplied by said at least one photovoltaic module of a zone of the second unit, and the electronic control unit is configured to determine at least one parameter relating to a distribution of soiling on the first unit from at least one comparison between two current transmission loss rates.

[0011] Thus, a device is provided for estimating the impact of soiling on photovoltaic panels, in particular by providing a sufficiently precise estimate. Specifically, the device differentiates between a homogeneous and a localized distribution of soiling. Furthermore, the device allows for estimating the absence of soiling. The device determines the distribution of soiling on a soiled panel in order to estimate the soiling distribution of a so-called energy production panel in a power plant within a specific environment.

[0012] According to another aspect, a photovoltaic energy production estimation system is proposed, comprising the photovoltaic panel soiling estimation device as defined above, in which the electronic control unit of the estimation device is configured to calculate a current loss of the first unit from said at least one parameter relating to a soiling distribution on the first unit.

[0013] Thus, it is possible to estimate photovoltaic energy production in an improved way taking into account the impact of dirt.

[0014] According to another aspect, a photovoltaic power plant is proposed comprising a plurality of production panels, each production panel comprising at least one photovoltaic module, called a production module, intended to produce electricity, the photovoltaic power plant comprising at least one estimation device as defined above.

[0015] According to another aspect, a method for estimating the soiling of photovoltaic panels is proposed using an estimation device as defined above.

[0016] The method includes an initial step in which the protection system is in the measurement position, a step of measuring the currents supplied by each photovoltaic module of the first and second units, a step of calculating, for each zone of the first unit, a parameter relating to a current transmission loss rate from a ratio between the current supplied by said at least one photovoltaic module of the zone of the first unit and the current supplied by said at least one photovoltaic module of a zone of the second unit, and a step of determining at least one parameter relating to a distribution of soiling on the first unit from at least one comparison between two current transmission loss rates.

[0017] According to another aspect, a method for estimating photovoltaic energy production is proposed, comprising an estimation of the soiling of photovoltaic panels according to the method as defined above, and a calculation of a current loss of the first unit from said at least one parameter relating to a distribution of soiling on the first unit.

[0018] According to yet another aspect, a computer program product is proposed comprising instructions which, when executed by an electronic control unit, enable the electronic control unit to perform the steps of the process for estimating the soiling of photovoltaic panels as defined above. BRIEF DESCRIPTION OF THE FIGURES

[0019] The aims, objects, features and advantages of the invention will become clearer from the detailed description of embodiments and implementations thereof, illustrated by the following accompanying drawings in which:

[0020] [Fig.1] [Fig.1] schematically illustrates an embodiment of a photovoltaic energy production estimation device;

[0021] [Fig.2] [Fig.2] schematically illustrates another embodiment of a photovoltaic energy production estimation device;

[0022] [Fig.3] The [Fig.3] schematically illustrates an eigenstate of the first unit of a photovoltaic energy production estimation device;

[0023] [Fig.4] the [Fig.4], schematically illustrates a homogeneous distribution of soiling;

[0024] [Fig.5]

[0025] [Fig.6]

[0026] [Fig.7] Figures 5 to 7 schematically illustrate different localized distributions of soiling

[0027] [Fig.8] [Fig.8] schematically illustrates a preferred localized distribution of soiling; and

[0028] [Fig.9] The [Fig.9] schematically illustrates the main steps of a method of implementing a photovoltaic energy production estimation process.

[0029] The drawings are given by way of example and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate understanding of the invention and are not necessarily to scale with practical applications. DETAILED DESCRIPTION

[0030] Before beginning a detailed review of embodiments of the invention, optional features which may possibly be used in association or alternatively are stated below.

[0031] According to one example, - the electronic control unit is further configured to calculate an average of the current transmission loss rates, and to determine a homogeneous distribution of soiling when the average is strictly greater than a main threshold, called the main soiling threshold, and a clean state of the first unit, free of soiling, when the average is less than or equal to the main soiling threshold. - The electronic control unit is configured to calculate at least one rate deviation, each rate deviation corresponding to a difference between two current transmission loss rates of said at least two zones of the first unit, the electronic control unit being further configured to determine a localized distribution of soiling when at least one rate deviation is strictly greater than a second threshold, called the second soiling threshold. - Each unit includes a first zone called upper and second and third zones called lower, the electronic control unit is further configured to determine a preferred localized distribution on the lower zones of the first unit when the rate difference between the two lower zones is less than or equal to a third threshold, called the third soiling threshold. - Each unit includes a fourth zone, called intermediate, located between the first zone and the second and third zones. - The photovoltaic modules of the estimation device units are smaller than or equal to the sizes of the power plant's production photovoltaic modules. - The calculation step includes calculating an average of the current transmission loss rates, and the determination step includes identifying a homogeneous distribution of soiling when the average is strictly greater than a main threshold, called the main soiling threshold, and a clean state of the first unit, free of soiling, when the average is less than or equal to the main soiling threshold. - The calculation step includes a calculation of at least one rate deviation, each rate deviation corresponding to a difference between two current transmission loss rates of said at least two zones of the first unit, and the determination step includes an identification of a localized distribution of soiling when at least one rate deviation is strictly greater than a second threshold, called the second soiling threshold. - Each unit of the estimation device includes a first zone called upper and second and third zones called lower, and the determination step includes an identification of a preferred localized distribution on the lower zones of the first unit when the rate difference between the two lower zones is less than or equal to a third threshold, called the third soiling threshold.

[0032] Figures 1 and 2 show a device 1 for estimating photovoltaic energy production. Device 1 is designed to estimate the quality of energy production supplied by a solar power plant, in particular a plant equipped with panels fitted with photovoltaic modules. More specifically, estimation device 1 is designed to estimate the impact of soiling on the power plant's energy production. Device 1 is further adapted to estimate the soiling rate of the power plant's panels intended for energy production. These panels intended for energy production are referred to as production photovoltaic panels.

[0033] Generally, the device 1 comprises first and second units 2, 3. Each unit 2, 3 comprises at least two zones ZI to Z8 for receiving solar radiation. Each zone ZI to Z8 comprises at least one photovoltaic module 4 to 11. Preferably, each zone ZI to Z8 comprises a single module 4 to 11, and thus each module 4 to 11 characterizes a specific zone of the unit 2, 3.

[0034] Figure 1 shows an embodiment of the first and second units 2, 3. The first unit 2 comprises a first receiving zone Z1 located in the upper part of the first unit 2 and a second receiving zone Z2 located in the lower part of the first unit 2. The second unit 3 comprises a first receiving zone Z5 located in the upper part of the second unit 3 and a second receiving zone Z6 located in the lower part of the second unit 3. Preferably, the first unit 2 comprises four zones ZI to Z4. A first zone ZI located in the upper third of the first unit 2, a second zone Z2 located between the lower and upper thirds of the first unit 2, a third zone Z3 located in the left half of the lower third of the first unit 2, and a fourth zone Z4 located in the right half of the lower third of the first unit 2. Preferably, the second unit 3 comprises the same configuration as the first unit 2. In other words, the second unit 2 comprises four zones Z5 to Z8.A first zone Z5 located in the upper third of the second unit 3, a second zone Z6 located between the lower third and the upper third of the second unit 3, a third zone Z7 located in the left half of the lower third of the second unit 3, and a fourth zone Z8 located in the right half of the lower third of the second unit 3.

[0035] A photovoltaic module 4 to 11 comprises one or more photovoltaic cells for converting a portion of solar radiation 14, 15 into electrical energy. The photovoltaic cells of the same module may be electrically connected in parallel, but preferably they are electrically connected in series. In particular, when the cells are connected in series, the weakest cell limits the module's current.

[0036] Modules 4 to 11 can each include several so-called safety diodes, for example, three diodes per module, so as to form a string of photovoltaic cells coupled to a safety diode. Furthermore, when a cell is affected by soiling, the current supplied by the module, also called the short-circuit current, will decrease proportionally to the decrease in photon transmission. However, beyond a certain threshold that depends on the characteristics of the safety diodes (generally 40% of the surface area of ​​a completely shaded cell), the current will bypass the string containing the affected cell by passing through the safety diode. Consequently, the module's short-circuit current will return to its original level, while energy production will be significantly impacted by the voltage drop (33% when a module includes three safety diodes).Thus, by using first and second units 2, 3 each having at least two modules 4 to 11, when a module is affected by soiling, the drop in current of the module does not affect the current supplied by the other modules.

[0037] Furthermore, the device 1 includes a protection system 20, in particular against soiling. The protection system 20 is configured to protect the second unit 3 against soiling. Conversely, the first unit 2 lacks a protection system 20. In other words, the first unit 2 is placed in environmental conditions similar to those of the photovoltaic panels of The power plant's output is to be estimated. Generally, the protection system 20 is movable between a protected position, in which it is configured to shield areas Z5 to Z8 of the second unit 3, and a measured position, in which areas Z5 to Z8 of the second unit 3 are exposed to solar radiation. Thus, the protection system 20 maintains the second unit 3 in a clean state, meaning a state free from any dirt that might be present on the photovoltaic modules 8 to 11 of the second unit 3. The protection system 20 can be a screen, in particular a movable screen that can be deployed and retracted between the measured and protected positions. The screen can be partially or fully opaque, transparent, or translucent to solar radiation.Alternatively, the protection system 20 can be a drawer configured to house the second unit 3 and mounted movably in translation at the rear of a protective frame, between the protection position where the drawer is placed behind the protective frame and the protective frame masks the second unit 3, and the measurement position where the drawer is placed next to the protective frame and the second unit 3 is exposed to solar radiation.

[0038] Furthermore, the device 1 includes an electronic control unit 21 configured to receive a current supplied by each photovoltaic module 4 to 11. Generally, the electronic control unit 21 is configured to measure the current supplied by each of the modules 4 to 11, and more particularly to measure the currents successively. The device 1 includes a first selection device 70 configured to successively measure the currents supplied by modules 4 to 7 of the first unit 2, and a second selection device 71 configured to successively measure the currents supplied by modules 8 to 11 of the second unit 2. In addition, the selection devices 70 and 71 can be coupled respectively to memories 72 and 73 of the electronic control unit 21 to record the measured currents.Advantageously, the electronic control unit is configured to perform current measurements in less than a millisecond, so the measurements can be considered almost simultaneous. Furthermore, each photovoltaic module 4 to 11 produces an electric current proportional to the solar radiation received. In other words, the current supplied by a 4 to 11 module is proportional to the photons impacting the photovoltaic cells of the 4 to 11 module. More specifically, each 4 to 11 module has a connector 30 to 37 for electrically coupling the 4 to 11 module, via a connection 40 to 47, to the electronic control unit 21. For example, the connectors 30 to 37 can be junction boxes. A 30 to 37 connector supplies the electric current produced by the 4 to 11 module to the unit. electronic control 21.

[0039] Advantageously, the electronic control unit 21 is coupled, via a connection 50, to the protection system 20 so as to control the protection system 20 to switch from the protection position to the measurement position, and vice versa. The electronic control unit 21 may be a printed circuit board comprising electronic components capable of performing logic operations. The electronic control unit 21 may be a computer.

[0040] Furthermore, the electronic control unit 21 is configured to determine at least one parameter relating to the distribution of soiling on the first unit 2. This estimation can be used to estimate the distribution of soiling on the photovoltaic production panels of a photovoltaic power plant, i.e., a photovoltaic power plant. In particular, a photovoltaic power plant comprises a plurality of production panels. Each production panel comprises at least one photovoltaic module, referred to as a production module, intended to produce electricity. The device 1 is configured to determine the soiling state of the first unit 2, in order to estimate the soiling state of the power plant's production panels. The soiling state is understood to be the distribution of soiling.

[0041] Figures 3 to 8 illustrate different types of soiling distribution. In particular, soiling is represented by hatched areas, and the absence of soiling by unhatched areas. In [Fig. 3], the first unit 2 is in a clean state, meaning that the first unit 2 is free of soiling in its reception areas Z1 to Z4. In [Fig. 4], a first configuration is shown in which the distribution is said to be homogeneous, meaning that soiling is present in all reception areas Z1 to Z4 of the first unit 2 and is distributed homogeneously over all areas Z1 to Z4. In this case, the current loss is directly proportional to the optical transmission loss. The optical loss depends primarily on the spectral response of the cell in combination with the spectral filter generated by the soiling.Figures 5 to 7 show a second configuration in which the distribution is described as localized preferential, meaning that soiling is not present on the upper part of the first unit 2. This localized preferential distribution is due to the tilt of the first unit relative to the ground, which promotes the movement of soiling towards the lower part of the first unit 2. Indeed, under the effect of cleaning caused by dew, light rain, etc., the soiling concentrates on the lower part of the module. For a module 4 to 11 where the photovoltaic cells are mounted in landscape orientation, i.e., with three strings placed horizontally one below the other, the current loss can be 33% because soiling on the lower part only affects one of the three strings. the lowest of the three occurrences. Furthermore, if the photovoltaic cells are mounted in portrait orientation, meaning three strings are placed vertically side by side, the current loss can be 100% because dirt on the lower part affects all three strings. Figure 8 shows a third configuration in which the distribution is localized by spot, meaning the dirt corresponds to a spot located on a receiving area, or straddling two adjacent areas, of the first unit. The localized spot distribution will depend on the current drop on the most affected cell. The localized spot distribution will also depend on the fact that if the current drop is too significant, the cell will then experience a reverse voltage, causing the entire string of cells to short-circuit across a safety diode.In the case where modules 4 to 11 are equipped with three safety diodes, the production loss for a severely impacted cell will be around 33%.

[0042] In order to determine at least one parameter relating to the distribution of soiling on the first unit 2, the electronic control unit 21 is configured to calculate, for each zone Z1 to Z4 of the first unit 2, a parameter relating to a current transmission loss rate. For example, the parameter relating to the soiling distribution could be the soiling distribution as defined above, i.e., a homogeneous, localized preferential, or localized spot distribution. Furthermore, the parameter relating to the current transmission loss rate could be, for example, the current transmission loss rate TL(Z1). The rate TL(Z1) corresponds to the transmission loss of a receiving zone Zi of the first unit due to the presence of soiling on that zone Zi.The reference Zi corresponds to one of the receiving zones ZI to Z4 of the first unit 2, where i is an integer representing the number of a receiving zone ZI to Z4 of the first unit 2. For example, when the first unit 2 comprises four zones ZI to Z4, i is between 1 and 4. The TL(Zi) rate is therefore associated with a receiving zone ZI to Z4 of the first unit 2. In particular, the TL(Zi) rate is calculated from a ratio between the current supplied by the photovoltaic module(s) of the zone ZI to Z4 of the first unit 2 and the current supplied by the photovoltaic module(s) of a zone Z5 to Z8 of the second unit 3.

[0043] For example, TL(Zi) is calculated from the following equation (1):

[0044] TL(Zi) = 1- (I(Zi) / I(Zj)) (equation 1)

[0045] where:

[0046] TL(Zi) is the current transmission loss rate of a zone Zi of the first unit 2 (unitless);

[0047] I(Zi) is the current (in Amperes) supplied by the module(s) of the Zi zone of the first unit 2;

[0048] I(Zj) is the current (in Amperes) supplied by the module(s) of a zone Z5 to Z8 of the second unit 3. The reference Zj corresponds to one of the receiving zones Z5 to Z8 of the second unit 3, where j is an integer representing the number of a receiving zone Z5 to Z8 of the second unit 3. For example, when the second unit 3 comprises four zones Z5 to Z8, j is between 5 and 8. Preferably, the first and second units 2, 3 have the same number of receiving zones. In [Fig. 1], an embodiment is shown in which units 2, 3 comprise two zones Z1, Z2; Z5, Z6 respectively. In Figures 2 to 8, another embodiment is shown in which the units comprise four zones Z1 to Z4; Z5 to Z8 respectively.

[0049] In addition, the electronic control unit 21 is configured to compare two current transmission loss rates TL(Zi).

[0050] In particular, the electronic control unit 21 determines a soiling distribution based on at least one comparison between two calculated TL(Zi) rates.

[0051] For example, the electronic control unit 21 calculates a unitless average TLm of the current transmission loss rates TL(Zi). When the first unit 2 has four distinct zones Z1 to Z4, the average TLm can be calculated according to the following equation (2):

[0052] TLm = ( TL(Z1) + TL(Z2) + TL(Z3) + TL(Z4) ) / 4 (equation 2).

[0053] In addition, the electronic control unit 21 determines a homogeneous distribution soiling occurs when the mean TLm is strictly greater than a principal threshold Al, called the principal soiling threshold, and an eigenstate of the first unit 2 occurs when the mean TLm is less than or equal to the principal soiling threshold AL. For example, the principal soiling threshold Al can be chosen close to zero, for example the principal threshold Al is equal to 0.1. In this case, the comparison between the mean TLm and the principal soiling threshold Al corresponds to a comparison between two TL(Zi) rates.

[0054] Advantageously, the electronic control unit 21 is configured to calculate at least one rate deviation DTL(Zi,Zm). A rate deviation DTL(Zi,Zm) corresponds to the difference between two current transmission loss rates of two zones Z1 to Z4 of the first unit (2). In other words, a rate deviation DTL(Zi,Zm) can be calculated according to the following equation (3):

[0055] DTL(Zi,Zm) = TL(Zi) - TL(Zm) (equation 3)

[0056] where:

[0057] TL(Zi) is the current transmission loss rate of a zone Zi of the first unit 2 (unitless), and

[0058] TL(Zm) is the current transmission loss rate of another zone Zm of the first unit 2 (unitless). In particular, zone Zm is distinct from zone Zi. Furthermore, m is an integer representing the number of a receiving zone Z1 to Z4 from the first unit 2.

[0059] The electronic control unit 21 is further configured to determine a localized distribution of soiling when at least one rate deviation DTL(Zi,Zm) is strictly greater than a second threshold A2, referred to as the second soiling threshold. For example, the second soiling threshold A2 can be chosen close to zero, for example, the second soiling threshold A2 is equal to 0.1. In this case, the comparison between the rate deviations DTL(Zi,Zm) and the second soiling threshold A2 corresponds to a comparison between two TL(Zi) rates.

[0060] In order to determine a preferred localized distribution of soiling on the first unit 2, each unit 2, 3 comprises a first zone Z1, Z5, referred to as the upper zone, and second and third zones Z3, Z4 and Z7, Z8, referred to as the lower zones. The electronic control unit 21 is further configured to determine a preferred localized distribution on the lower zones Z3, Z4 of the first unit 2 when the difference in the DTL(Z1,Zm) rate between the two lower zones Z3, Z4 is less than or equal to a third threshold, referred to as the third soiling threshold.

[0061] In other words, the electronic control unit 21 calculates the rate deviation DTL(Z3,Z4), according to the equation DTL(Z3,Z4) = TL(Z3) - TL(Z4), and compares the calculated rate deviation DTL(Z3,Z4) with the third threshold.

[0062] For example, the third soiling threshold can be chosen close to zero, for example the third soiling threshold is equal to 0.1. In this case, the comparison between the difference in rates DTL(Z3,Z4) and the third soiling threshold corresponds to a comparison between two rates TL(Zi).

[0063] In the case where at least one rate difference DTL(Zi,Zm) is strictly greater than the second threshold A2, and the rate difference DTL(Z3,Z4) between the two lower zones Z3, Z4 is strictly greater than the third threshold, then a localized distribution by spot is determined. In particular, for each zone Z1 to Z4 of the first unit 2 for which the electronic control unit 21a calculated a current transmission loss rate TL(Zi) strictly greater than the main threshold A1, the transmission loss is considered to be the direct consequence of a spot on the zone Z1.

[0064] In order to estimate the position and number of tasks present in a zone Z1 to Z4 of the first unit 2, the electronic control unit 21 is configured to perform the following steps. Generally, a task is considered to have a circular shape having a diameter

[0065] [Math.l]

[0066] with

[0067] $: the diameter of a spot (in centimeters);

[0068] TL(Zi): the current transmission loss rate of the area Zi where the spot is located;

[0069] Sz: the surface area of ​​the zone Zi where the spot is located (in square centimeters).

[0070] Furthermore, given that the size of units 2, 3 is different from that of the panels of production of the power plant, a scaling factor Fs = Sr / Sc is used, where Sr corresponds to the area of ​​a module of a power plant production panel (in square centimeters) and Sc corresponds to the area of ​​a reception zone Zi of the first unit 2.

[0071] Generally, the number of spots Np in the production panel module is estimated based on the presence of a spot in at least one area Zi of the first unit 2 and the scaling factor Fs. For example, the number of spots Np in the production panel module is determined by the equation: Np = Fs x nzi, where nzi = 0 in the absence of a spot and nzi = 1 when a spot is present in area Zi. In other words, nzi is considered to be 0 when the current transmission loss rate TL(Zi) of area Zi is less than or equal to the second threshold A2; and nzi is considered to be 1 when the current transmission loss rate TL(Zi) of area Zi is strictly greater than the second threshold A2.Thus, it is estimated that when a localized distribution per spot is determined and when Fs = 1, the module of the production panel has one spot; when Fs = 2, the module of the production panel has two spots; and when Fs = 3, the module of the production panel has three spots.

[0072] In order to deduce the impact of the spot on the power output of the power plant's generating panels, and therefore on the energy produced, it is assumed that the spot can be positioned randomly within the Zi zone. The positioning of one or more spots on the generating panel is also random. Based on the diameter of the spot <e>Having previously calculated, a task with the calculated diameter is virtually positioned. <e>at different locations on the production panel module. A Monte Carlo algorithmic method is applied, taking into account all possible positioning scenarios to obtain the most probable minimum, maximum, and average values ​​for energy loss. The Monte Carlo algorithmic method is a classic method, well-known to those skilled in the art, for calculating an approximate numerical value using random processes, i.e., probabilistic techniques. More specifically, it is assumed that if two photovoltaic cells are part of the same string, they both generate the same current. Similarly, the position of the load on a single cell has no significant influence. It is therefore sufficient to consider three scenarios: the load is entirely on one cell, the load overlaps two cells, or the load overlaps four cells. cells. Thus, a possible task distribution on a module of a production panel can be determined as follows. The diameters are calculated <e>of each spot present in a zone Zi, that is, zone Zi of the first unit 2 for which the TL(Zi) current transmission loss rate of zone Zi is strictly greater than the second threshold A2. Then, the number of spots Np of the production panel module is calculated from the equation Np = Fs x nzi. For each zone Zi, a spot with the previously calculated diameter is created and positioned at different locations on 1, 2, or 4 cells of the production panel module, and the currents supplied by the production panel module are measured for each spot position. Then, the measured currents are compared with the previously calculated TL(Zi) current transmission loss rate of zone Zi to estimate the most probable spot position, that is, the position of a spot supplying a current closest to the TL(Zi) current transmission loss rate.

[0073] In order to improve the accuracy of determining the distribution of soiling on the first unit 2, the photovoltaic modules 4 to 7 of the first unit 2 have identical characteristics, in particular in terms of size and number of photovoltaic cells, to those of the photovoltaic modules 8 to 11 of the second unit 3.

[0074] Such an energy production estimation device 1 may include units 2, 3 having a different size than the photovoltaic production panels of the power plant. Advantageously, the photovoltaic modules 4 to 11 of units 2, 3 have sizes smaller than or equal to those of the photovoltaic production modules of the power plant. In particular, using units 2, 3 that are smaller than the production panels facilitates the manufacturing and transport of units 2, 3.

[0075] Figure 9 shows the main steps of a method for estimating photovoltaic energy production. The method can be implemented by the device 1 as defined above. The method includes an initial step in which the protection system 20 is placed in the measurement position, and a step of measuring the currents supplied by each photovoltaic module 4 to 11 of the first and second units 2, 3. Then, the method includes a calculation step SI, for each zone Z1 to Z4 of the first unit 2, of a parameter relating to a current transmission loss rate TL(Zi) from a ratio between the current I(Zi) supplied by the photovoltaic module(s) 4 to 7 of zone Zi of the first unit 2 and the current I(Zj) supplied by the photovoltaic module(s) 8 to 11 of a zone Zj of the second unit 3.More specifically, the current transmission loss rates TL(Zi) are calculated when the protection system 20 is placed in the measurement position. The method includes a step S2 for determining at least one parameter related to . a distribution of soiling on the first unit 2 from a comparison between two current transmission loss rates TL(Zi).

[0076] When units 2, 3 respectively comprise four receiving zones ZI to Z8, the calculation step SI may include the following calculations:

[0077] TL(Z1) = 1- (I(Z1) / I(Z5);

[0078] TL(Z2) = 1- (I(Z2) / I(Z6);

[0079] TL(Z3) = 1- (I(Z3) / I(Z7);

[0080] TL(Z4) = 1- (I(Z4) / I(Z8).

[0081] The calculation step SI may further include a calculation of an average TLm of the current transmission loss rates, for example according to equation 2 cited above.

[0082] The determination step S2 may include an identification of a homogeneous distribution of soiling S21 when the mean TLm is strictly greater than the main soiling threshold Al, and of a clean state S22 of the first unit 2 when the mean TLm is less than or equal to the main soiling threshold AL. In other words, the determination step S2 includes a comparison S4 of the mean TLm with the main soiling threshold Al to identify a distribution of soiling.

[0083] The calculation step SI may also include a calculation of at least one rate deviation DTL(Zi,Zm), each rate deviation DTL(Zi,Zm) corresponding to a difference between two current transmission loss rates TL(Zi) of two zones ZI to Z4 of the first unit 2.

[0084] When units 2, 3 respectively comprise four receiving zones ZI to Z8, the calculation step SI may include the following calculations:

[0085] DTL(Z1,Z2) = TL(Z1) - TL(Z2);

[0086] DTL(Z1,Z3) = TL(Z1) - TL(Z3);

[0087] DTL(Z2,Z3) = TL(Z2) - TL(Z3);

[0088] DTL(Z3,Z4) = TL(Z3) - TL(Z4).

[0089] Alternatively, other additional rate differences can be calculated according to the following equations:

[0090] DTL(Z1 ;Zbas) = ​​TL(Z1) - (TL(Z3) + TL(Z4)) / 2, where Zbas corresponds to the bottom zones of the first unit 2; and

[0091] DTL(Z2;Zbas) = ​​TL(Z2) - (TL(Z3) + TL(Z4)) / 2.

[0092] When calculating the rate differences DTL(Zi,Zm) and the additional rate differences DTL(Z1;Zbas) and DTL(Z2;Zbas), the differences can be calculated in absolute value, so as to obtain rate differences with a positive value. The positive value of the rate differences allows for a single comparison with the second soiling threshold A2.

[0093] The determination step S2 includes the identification of a localized distribution S23 soiling occurs when at least one rate deviation DTL(Zi,Zm), or at least one additional rate deviation DTL(Z1;Zbas) and DTL(Z2;Zbas), is strictly greater than the second soiling threshold A2. In other words, the determination step S2 includes a comparison S3 of the rate deviations DTL(Zi,Zm), DTL(Z1;Zbas), and DTL(Z2;Zbas) with the second soiling threshold A2 to identify a soiling distribution. Furthermore, when at least one rate deviation DTL(Zi,Zm) is less than or equal to the second soiling threshold A2, a comparison S4 is performed of the mean TLm with the primary soiling threshold A1 to identify a clean state or a homogeneous soiling distribution.

[0094] Furthermore, based on the previous results, the energy impact of soiling on the photovoltaic power plant's production panels can be estimated. The photovoltaic energy production estimation process comprises the steps as defined below.

[0095] For example, a current loss Dip (in amperes) of the first unit 2 is calculated based on the soiling distribution estimated above. The current loss of the production panels, and more specifically the energy production loss of the production panels, can then be estimated from the calculated current loss Dip. Generally, the current loss Dip (in amperes) of the first unit 2 is calculated based on the type of soiling distribution determined previously.

[0096] In the case where an eigenstate of the first unit 2 is determined, it is assumed that there is no current loss. In other words, the current loss Dip is zero, that is, Dip (eigenstate) = 0 A. Thus, the power plant's energy production is not affected.

[0097] In the case where a homogeneous distribution of soiling is determined, the current loss Dip is considered to be homogeneous across all photovoltaic cells of the production panels and proportional to the average TLm of the current transmission loss rates. Thus, the (homogeneous) current loss Dip can be calculated according to the following equation:

[0098] Dip (homogeneous) = Im x (1 - TLm),

[0099] where Im (in amperes) corresponds to the average of the currents I(Zj) supplied by the module(s) of zones Z5 to Z8 of the second unit 3. In other words, Im = (I(Z1) + I(Z2) + I(Z3) + I(Z4)) / 4.

[0100] In the case where a preferred localized soiling distribution is determined, the Dip (preferred) current loss is estimated to be proportional to an average TLms (unitless) of the current transmission loss rates of the soiled areas of the first unit 2.

[0101] An area of ​​the first unit 2 is determined to be dirty when the rate difference The DTL(Zi,Zm) of the zone is strictly greater than the second threshold A2. Conversely, a zone of the first unit 2 is determined to be clean when the rate difference DTL(Zi,Zm) of the zone is less than or equal to the second threshold A2.

[0102] Thus, the (privileged) Dip current loss can be calculated according to the following equation:

[0103] Dip (preferred) = Ims x (1 - TLms),

[0104] where Ims (in amperes) corresponds to the average of the currents I(Zj) supplied by the module(s) of the zones of the second unit 3 corresponding to the zones of the first unit 2 which have been determined to be dirty.

[0105] For example, in the case illustrated in [Fig. 6], the first zone Z1 of the first unit is clean, and the other zones Z2, Z3, and Z4 of the first unit 2 are dirty. Thus, the zones of the second unit 3 corresponding to the dirty zones of the first unit 2 are zones Z6, Z7, and Z8. In this case, we calculate

[0106] Ims = (I(Z6)+I(Z7)+I(Z8)) / 3; And

[0107] TLms = (TL(Z2) + TL(Z3) + TL(Z4)) / 3; And

[0108] Dip (preferred) = [ (I(Z6)+I(Z7)+I(Z8)) / 3 ] x [1 - (TL(Z2) + TL(Z3) + TL(Z4)) / 3].

[0109] The calculations of the current loss Dip, in particular the calculations of current losses according to the different cases of soiling, Dip (clean); Dip (homogeneous); Dip (privileged), can be carried out by the electronic control unit 21 from the parameters relating to the current transmission loss rate previously calculated and from the type of soiling distribution previously determined.

[0110] The electronic control unit 21 may include a computer program comprising instructions for controlling the protection system 20. The computer program further includes instructions which, when executed by the electronic control unit 21, enable the electronic control unit 21 to perform the steps of the process for estimating the soiling of the photovoltaic panels as defined above. In addition, the electronic control unit 21 may perform the steps of the process for estimating photovoltaic energy production as defined above. The electronic control unit 21 includes a processor or a microprocessor for executing the program instructions.

[0111] Thus, by determining the soiling distribution pattern, the impact of soiling on the photovoltaic energy production of a power plant can be estimated. Advantageously, the impact of soiling can be estimated over a long production period, for example, a quarter or a year, in order to make appropriate choices for cleaning the production panels and estimate the energy production gain. For example, the frequency and type of cleaning can be adjusted. The architecture and type of panels can also be adapted. Production is optimized for energy output based on the environment. For example, a horizontal or vertical cell configuration can be chosen to suit the environment. The size of the panels and the number of cells per panel can also be adjusted.< / e> < / e> < / e>

Claims

Demands

1. A photovoltaic panel soiling estimation device, comprising first and second units (2, 3), each unit (2, 3) comprising at least two zones (ZI to Z8) for receiving solar radiation, each zone (ZI to Z8) comprising at least one photovoltaic module (4 to 11), the device comprising a protection system (20) movable between a protection position in which the protection system (20) is configured to mask said at least two zones (Z5 to Z8) of the second unit (3) and a measurement position in which said at least two zones (Z5 to Z8) of the second unit (3) are exposed to solar radiation, and an electronic control unit (21) configured to receive a current supplied by each photovoltaic module (4 to 11), characterized in that the units (2, 3) have the same number of receiving zones (ZI to Z8),The photovoltaic modules (4 to 7) of the first unit (2) have identical characteristics, particularly in terms of size and number of photovoltaic cells, to those of the photovoltaic modules (8 to 11) of the second unit (3), the electronic control unit (21) is configured to calculate, for each zone (ZI to Z4) of the first unit (2), a parameter relating to a current transmission loss rate from a ratio between the current supplied by said at least one photovoltaic module (4 to 7) of the zone (ZI to Z4) of the first unit (2) and the current supplied by said at least one photovoltaic module (8 to 11) of a zone (Z5 to Z8) of the second unit (3), and in that the electronic control unit (21) is configured to determine at least one parameter relating to a soiling distribution on the first unit (2) from at least one comparison between two current transmission loss rates.

2. Device according to claim 1, wherein the electronic control unit (21) is further configured to calculate an average of the current transmission loss rates, and to determine a homogeneous distribution of soiling when the average is strictly greater than a principal threshold, called the principal soiling threshold, and a clean state of the first unit (2), free of soiling, when the average is less than or equal to the principal soiling threshold.

3. Device according to claim 2, wherein the electronic control unit (21) is configured to calculate at least one rate deviation, each rate deviation corresponding to a difference between two current transmission loss rates of said at least two zones (ZI to Z4) of the first unit (2), the electronic control unit (21) being further configured to determine a localized distribution of soiling when at least one rate deviation is strictly greater than a second threshold, called the second soiling threshold.

4. Device according to claim 3, wherein each unit (2, 3) comprises a first zone (Z1, Z5) referred to as upper and second and third zones (Z3, Z4 and Z7, Z8) referred to as lower, the electronic control unit (21) is further configured to determine a preferred localized distribution on the lower zones (Z3, Z4) of the first unit (2) when the rate difference between the two lower zones (Z3, Z4) is less than or equal to a third threshold, referred to as the third soiling threshold.

5. Device according to claim 4, wherein each unit (2, 3) comprises a fourth zone (Z2, Z6), referred to as intermediate, located between the first zone (Z1, Z5) and the second and third zones (Z3, Z4 and Z7, Z8).

6. Photovoltaic energy production estimation system, comprising a photovoltaic panel soiling estimation device according to any one of claims 1 to 5, wherein the electronic control unit (21) of the estimation device is configured to calculate a current loss (Dip) of the first unit (2) from said at least one parameter relating to a soiling distribution on the first unit (2).

7. Photovoltaic power plant comprising a plurality of production panels, each production panel comprising at least one photovoltaic module, referred to as a production module, intended to produce electricity, the photovoltaic power plant comprising at least one estimation device according to any one of claims 1 to 5.

8. Power plant according to claim 7, wherein the photovoltaic modules (4 to 11) of the units (2, 3) of the estimating device have sizes less than or equal to those of the power plant's production photovoltaic modules.

9. A method for estimating the soiling of photovoltaic panels using an estimation device according to any one of claims 1 to 5, characterized in that it comprises an initial step in which the protection system (20) is in the measurement position, a step of measurement of the currents supplied by each photovoltaic module (4 to 11) of the first and second units (2, 3), a calculation step, for each zone (ZI to Z4) of the first unit (2), of a parameter relating to a current transmission loss rate from a ratio between the current supplied by said at least one photovoltaic module (4 to 7) of the zone (ZI to Z4) of the first unit (2) and the current supplied by said at least one photovoltaic module (8 to 11) of a zone (Z5 to Z8) of the second unit (3), and a step of determining at least one parameter relating to a distribution of soiling on the first unit (2) from at least one comparison between two current transmission loss rates.

10. A method according to claim 9, wherein the calculation step includes calculating an average of the current transmission loss rates, and the determination step includes identifying a homogeneous distribution of soiling when the average is strictly greater than a principal threshold, called the principal soiling threshold, and a clean state of the first unit (2), free of soiling, when the average is less than or equal to the principal soiling threshold.

11. A method according to claim 10, wherein the calculation step includes a calculation of at least one rate deviation, each rate deviation corresponding to a difference between two current transmission loss rates of said at least two zones (Z1 to Z4) of the first unit (2), and the determination step includes an identification of a localized distribution of soiling when at least one rate deviation is strictly greater than a second threshold, referred to as the second soiling threshold.

12. A method according to claim 11, wherein each unit (2, 3) of the estimation device comprises a first zone (Z1, Z5) called upper and second and third zones (Z3, Z4 and Z7, Z8) called lower, and the determination step comprises an identification of a preferred localized distribution on the lower zones (Z3, Z4) of the first unit (2) when the rate difference between the two lower zones (Z3, Z4) is less than or equal to a third threshold, called the third soiling threshold.

13. A method for estimating photovoltaic energy production, comprising an estimation of the soiling of photovoltaic panels according to any one of claims 9 to 12, and a calculation of a current loss (Dip) of the first unit (2) from said at least one parameter relating to a distribution of dirt on the first unit (2).

14. Product computer program comprising instructions which, when executed by an electronic control unit (21), enable the electronic control unit (21) to perform the steps of the method for estimating the soiling of photovoltaic panels according to any one of claims 9 to 12.

15. Product computer program according to claim 14, comprising instructions which, when executed by the electronic control unit (21), enable the electronic control unit (21) to perform the steps of the photovoltaic energy production estimation process according to claim 13.

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