SYSTEM AND METHOD FOR CLEANING COVER GLASSES OF PHOTOVOLTAIC MODULES

Abstract

In a system for cleaning cover glasses (1) of photovoltaic modules (2, 2a) with an autonomous cleaning device (6, 6.1, 6.2, 6.3), a comparison device (3) and an inspection module (4) are to be provided in addition to the autonomous cleaning device (6, 6.1, 6.2, 6.3), the autonomous cleaning device (6, 6.1, 6.2, 6.3) a megasonic transducer (17, 67), and the autonomous cleaning device (6, 6.1, 6.2, 6.3) and the inspection module (4) being transportable to the photovoltaic modules (2, 2a).

Claims

1. System for cleaning cover glasses (1) of photovoltaic modules (2, 2a) with an autonomous cleaning device (6, 6.1, 6.2, 6.3) comprising a megasonic transducer (17, 67), a comparison device (3) comparing the efficiency of a photovoltaic module field with the efficiency of a clean reference photovoltaic cell (48) and an inspection module (4) to map the photovoltaic module field and the photovoltaic modules (2, 2a), providing reference points for the collection and return points for the autonomous cleaning device (6, 6.1, 6.2, 6.3), wherein a flow of process fluid through an acoustically activated gap (44) between the cover glass (1) of the photovoltaic module (2, 2a) and an active surface (45) of the megasonic transducer (17, 67) is provided for the particles/impurities to be transported away from the cover glass (1) of the photovoltaic module (2, 2a) and the autonomous cleaning device (6, 6.1, 6.2, 6.3) and the inspection module (4) being separately transportable to the photovoltaic modules (2, 2a) by means of a drone (5).

2. System according to claim 1, wherein the drone (5) can transport the inspection module (4) or the autonomous cleaning device (6, 6.1, 6.2, 6.3) from a base (7) to the photovoltaic module (2) or from the photovoltaic module (2) and a further photovoltaic module (2a) and back to the base (7).

3. System according to claim 1, wherein the autonomous cleaning device (6, 6.1, 6.2) comprises an exchangeable battery (37) and an exchangeable liquid container (20).

4. System according to claim 1, wherein the autonomous cleaning device (6.3) comprises one exchangeable POD (54, 55) with a container (57) for liquid and/or a compartment (58) for a storage battery.

5. System according to claim 3, wherein the drone (5) supplies the autonomous cleaning device (6, 6.1, 6.2), a further exchangeable battery and/or a further exchangeable liquid container and the exchangeable battery (37) and/or the exchangeable liquid container (20) can be delivered or collected by means of the drone (5).

6. System according to claim 4, wherein the drone (5) supplies the autonomous cleaning device (6.3), a further exchangeable POD and/or a further exchangeable container for liquid and/or a compartment for a storage battery and/or the exchangeable POD (54, 55) with the container (57) for liquid and/or a compartment (58) for a storage battery can be delivered or collected by means of the drone (5).

7. System according to claim 1, wherein information from the drone (5), the autonomous cleaning device (6, 6.1, 6.2, 6.3), the base (7), the inspection module (4) and the comparison device (3) can be collected and evaluated in a computer.

8. System according to claim 1, wherein the autonomous cleaning device (6, 6.1, 6.2, 6.3) comprises the following: an RF (Radio Frequency) generator module (11), a megasonic transducer and process liquid distributor module (16), a process liquid supply module (19), a motion and positioning module (24) and a control communication module (29).

9. System according to claim 1, wherein the drone (5) detects and transmits by means of a process parameter position and location of the photovoltaic modules (2, 2a) respective to the inspection module (4).

10. System according to claim 1, wherein one of the comparison devices (3) is arranged under identical process parameters as the photovoltaic modules (2, 2a), the comparison device (3) detecting and transmitting information about contamination of the photovoltaic modules (2, 2a) and their cover glasses (1) under the respective conditions of the process parameters.

11. System according to claim 10, wherein a reference photovoltaic cell (48) with a cover (49) is provided, a reference state of a photovoltaic module being readable from the reference photovoltaic cell (48).

12. System according to claim 10, wherein the cover (49) is detachably connected to the comparison device (3).

13. Method for cleaning a cover glass (1) of a photovoltaic module (2, 2a) by means of an autonomous cleaning device (6, 6.1, 6.2, 6.3) comprising the following steps: an inspection module (4) detects and transmits the position and location of the photovoltaic modules (2, 2a); a comparison device (3) detects and transmits information about contamination of the photovoltaic modules (2, 2a) and their cover glasses (1); if a predetermined degree of contamination of the cover glasses (1) of the photovoltaic modules (2, 2a) is reached, a cleaning sequence is initiated, a first autonomous cleaning device (6.1, 6.3) is transported to a first cover glass (1) of a first photovoltaic module (2); the first autonomous cleaning device (6.1, 6.3) cleans the first cover glass (1) of the first photovoltaic module (2); wherein a megasonic transducer (17, 67) is positioned relative to a first cover glass (1) of a first photovoltaic module (2), a gap (44) having a predetermined width (b) is formed between the cover glass (1) of the photovoltaic module (2) and an active surface (45) of the megasonic transducer (17, 67), the gap (44) is at least partially filled with a process fluid, megasonic oscillations are transmitted by the megasonic transducer (17, 67) into the process fluid in the gap (44) and to at least part of the cover glass (1) of the photovoltaic module (2), cavitation bubbles are generated in a region of a surface (47) of the cover glass (1) of the photovoltaic module (2), wherein upon collapse of the cavitation bubbles local shock waves are emitted to dislodge the particles/impurities adhering to the surface (47) of the cover glass (1), by the flow of the process fluid through the gap (44), the particles/impurities are transported away from the surface (47) of the cover glass (1) of the photovoltaic module (2) the first autonomous cleaning device (6.1, 6.3) is transported to a further cover glass of a further photovoltaic module (2) or to a base (7); repeating steps 4 to 6 with the same or further autonomous cleaning devices (6, 6.1, 6.2, 6.3) until all cover glasses (1) of all photovoltaic modules (2, 2a) are cleaned.

14. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0085] Further advantages, features and details of the invention result from the following description of preferred execution examples as well as from the drawings; these show in:

[0086] FIG. 1 shows a schematic view of components of an invention system for the inspection and cleaning of cover glass of photovoltaic modules;

[0087] FIG. 2 a schematic view of a base for use in the system shown in FIG. 1;

[0088] FIGS. 3a-3i a flow chart from the inspection of cover glasses of photovoltaic modules to the cleaning of cover glasses of photovoltaic modules; and

[0089] FIG. 4 shows a plan view of an autonomous cleaning device for use in the system shown in FIG. 1;

[0090] FIG. 5 shows a perspective view of the autonomous cleaning device in FIG. 4;

[0091] FIG. 6 shows another perspective view of the autonomous cleaning device in FIG. 4 with an extracted resonator bar;

[0092] FIG. 7 shows another perspective view of the autonomous cleaning device in FIG. 4;

[0093] FIG. 8 a schematic view of a megasonic transducer for use in the autonomous cleaning device shown in FIG. 4 and in the system shown in FIG. 1;

[0094] FIG. 9 shows a functional block diagram, in particular of the components of the autonomous cleaning device;

[0095] FIG. 10 shows the autonomous cleaning device at different angled photovoltaic modules.

DETAILED DESCRIPTION

[0096] FIG. 1 shows a system S for checking and cleaning cover glasses 1 of photovoltaic modules 2, 2a. In addition to the photovoltaic modules 2, 2a to be cleaned, System S comprises a comparison device 3 (Solar Power Comparator=SPC), an inspection module 4 (Airborne Inspection Unit=AIU), a drone 5 (Flight System Platform=FSP), one or more autonomous cleaning device(s)/unit(s) 6 (Autonomous Cleaning Unit=ACU) for cleaning the cover glasses 1 of photovoltaic modules 2, 2a and a base 7 (Flight Operations Center=FOC) shown in FIG. 2.

[0097] The comparison device 3 is arranged in the area of photovoltaic modules 2, 2a and serves to compare the solar field yield of photovoltaic modules 2 with a reference photovoltaic cell 48 preferably arranged in the comparison device 3. The comparison device 3 compares the efficiency of photovoltaic module 2, 2a or field with the efficiency of this reference photovoltaic cell 48 of the same type in the comparison device 3, which is however “clean”. This means that a reference state of a photovoltaic module is read from the reference photovoltaic cell 48, which represents an optimal state (=clean state) of a cover glass 1 of a photovoltaic module 2. The reference photovoltaic cell 48 is arranged under a cover 49, which is detachably connected to the comparison device 3 in an unspecified manner, and can be opened or removed to release the reference photovoltaic cell 48 when the comparison measurement is to be performed.

[0098] The comparison device 3 is arranged under identical process parameters as the photovoltaic modules 2, 2a, whereby the comparison device 3 collects and supplies information on contamination of the photovoltaic modules 2, 2a and their cover glasses 1 under the respective conditions of the process parameters.

[0099] The inspection module 4 is used for “mapping”, i.e. the mapping of the individual photovoltaic modules 2, 2a or the arrangement of the entire photovoltaic modules. It provides information on where exactly the photovoltaic modules 2, 2a are arranged.

[0100] The drone 5 performs inspection and imaging flights with the inspection module 4. The drone 5 also serves to transport the autonomous cleaning device 6 to the photovoltaic modules 2, 2a and back to the base 7 after a cleaning sequence has been completed.

[0101] The autonomous cleaning device 6 is used to clean the cover glasses 1 of the photovoltaic modules 2, 2a. For this purpose, the autonomous cleaning device 6 has the following elements shown in FIG. 9: [0102] an RF generator module (RFM) 11 with an MPU control module 12, circuits and sensors 13, an impedance matching network 14 and an RF generator 15, [0103] a megasonic transducer and process fluid manifold module (TMM) 16 with a megasonic transducer 17 and a liquid distributor 18, [0104] a process fluid supply module (PFM) 19 with a process fluid reservoir 20 and a control mechanism 21, sensors 22 and pumps/valves 23, [0105] a motion and positioning module (MPM) 24 as a base carrier unit for operative modules such as motors and actuators, sensors, module frame lock and interlock 25, XYZ motion devices 26 and column control and sensors 27. Further, the motion and positioning module 24 comprises an overhead coupling device (OCD) 28 preferably integrated in the upper part of the frame. The OCD 28 may be replaced by capture funnel features as described in correspondence to the detailed description of the autonomous cleaning device 6.3 further below. I.e., there are multiple coupling points for the drone 5 to the autonomous cleaning device and the drone 5 to PODs (see below) and not jus one single point. [0106] a control communications module (CCM) 29 comprising a main MPU 30, associated input/output circuits and main memory elements 32, main fixed value memory elements 34 and bidirectional data communication functions 36 together with power source 37 in the form of preferably replaceable batteries and a backup power source 38. In addition to the main MPU 30, a second redundant MPU 31 with reserve RAM 33 and ROM 35 can be provided.

[0107] The basis 7 initiates flight operation of the drone 5 and deployment of the drone 5 with payload through the inspection module 4. Furthermore, it serves to store and provide the autonomous cleaning devices 6, the drone 5 and the inspection module 4 in idle mode. For this purpose, the base 7 preferably has a kind of hangar 8 in which the autonomous cleaning devices 6, the drone 5 and the inspection module 4 can be stored in idle mode. Furthermore, the base 7 has a landing platform 9 on which the autonomous cleaning devices 6 and the inspection module 4 can be provided when they are needed to be simply picked up by the drone 5.

[0108] The flow chart from the inspection of cover glasses 1 of photovoltaic modules 2, 2a by the comparison device 3 to the cleaning of cover glasses 1 of photovoltaic modules 2, 2a by autonomous cleaning devices 6 is shown schematically in FIGS. 3a to 3i.

[0109] According to FIG. 3a, an initial state of system S for checking and cleaning cover glasses 1 of photovoltaic modules 2, 2a is shown. As mentioned above, the comparison device 3 is located near the photovoltaic modules 2, 2a to determine the degree of contamination of the cover glasses 1. For this purpose, the comparison device 3 compares at regular intervals a solar field yield of the photovoltaic modules 2, 2a with a solar yield of its reference photovoltaic cell 48. For this purpose, the cover 49 is temporarily removed and an efficiency of the conversion of the radiation energy of sunlight into usable electricity in the “clean” reference photovoltaic cell can be compared with the efficiency of the conversion of the radiation energy of sunlight into usable electricity in the photovoltaic module 2, 2a. If a predetermined degree of pollution of the photovoltaic module 2, 2a is reached, a cleaning sequence is initiated.

[0110] In base 7 the autonomous cleaning devices 6, the drone 5 and the inspection module 4 are in idle mode as long as no mapping of all photovoltaic modules and/or a cleaning sequence has been triggered by the comparison device 3.

[0111] The explanations on the reference numbers for FIG. 3a also apply to FIGS. 3b to 3ij. This applies in particular if the same features have the same reference numbers. Therefore, a repetition of all features described in FIG. 3a is omitted.

[0112] First of all, the location and locations of all photovoltaic modules must be mapped. The inspection module 4 is placed in landing platform 9 of base 7 and can be taken there by means of the drone 5 (see FIG. 3b). The drone 5 then flies with the inspection module 4 over all photovoltaic modules to precisely map their position and location (see FIG. 3c). The data is returned to the base 7 for analysis and programming of the cleaning sequence with one or more autonomous cleaning devices 6.

[0113] At regular intervals, a comparison measurement is carried out by the comparison device 3. If a predetermined degree of contamination of the cover glasses 1 of the photovoltaic modules 2, 2a is reached and a cleaning sequence is initiated, the base 7 initiates a flight operation of the drone 5 and an operation of the drone 5 with the autonomous cleaning devices 6.

[0114] According to FIG. 3d, the autonomous cleaning devices 6 are now provided in landing platform 9 of base 7. At the same time the drone 5 has finished its inspection and imaging flights and the drone 5 flies with the inspection module 4 back to base 7 and delivers the inspection module 4 again to landing platform 9 (see FIG. 3e) where it is stored. The drone 5 then picks up the first autonomous cleaning device 6.1 (see FIG. 3e) to fly it to a first position on the photovoltaic modules 2 (see FIG. 3f).

[0115] The drone 5 then returns to base 7 to pick up another autonomous cleaning device 6.2 (see FIG. 3g) and fly it to another position on photovoltaic modules 2a (see FIG. 3h). Only two autonomous cleaning devices 6.1 and 6.2 are shown. Of course, system S can also include a single autonomous cleaning device 6 or more than two autonomous cleaning devices 6.

[0116] The steps of FIGS. 3d to 3i are carried out until all cover glasses 1 of all photovoltaic modules 2 are cleaned. Once the autonomous cleaning device 6 has finished its work and does not need to be flown to another photovoltaic module 2, it can be flown back from drone 5 to landing platform 9 or base 7, where it is stored, until another cleaning sequence is initiated.

[0117] The drone 5 then returns to base 7 (see FIG. 3i) to recharge and wait for another sequence. If in the meantime the energy source in the form of batteries 37 and/or liquid container 20 of one of the autonomous cleaning devices 6 has been emptied, the drone will return to the corresponding autonomous cleaning device 6 with a replaceable battery and/or liquid container, the battery 37 and/or liquid container 20 will be replaced and the drone 5 will fly back to the base with the empty battery 37 and/or liquid container 20.

[0118] FIG. 9 includes, in addition to the features mentioned above, the indication of data transfer along arrows 39, the flow of process fluid along arrow 40 and the flow of RF energy along arrow 41. The functional block diagram further shows a feeder 42 and a coupling 43 through which the autonomous cleaning device 6 can be coupled to the feeder 42. The feeder 42 can comprise a manual handling or an extended end effector (robot arm) or also an unmanned aircraft (Unmanned Arial Vehicle=UAV), via which the autonomous cleaning device 6 can be placed on a frame of the photovoltaic module 2 and also removed from there, even if the drone 5 is preferably used for this purpose in the present design example.

[0119] Referring to FIG. 8, the function of the inventive method and the device can be explained as follows:

[0120] The method of the present invention introduces a new and unique, non-contact, damage-free physical force process for the in-situ cleaning of cover glasses 1 of photovoltaic modules 2.

[0121] If a contamination of the cover glasses 1 of the photovoltaic modules 2, 2a was detected by the comparison device 3, a cleaning sequence is initiated. This means that the drone 5 picks up the first autonomous cleaning device 6.1 to fly it to a first position on the photovoltaic modules 2. The drone 5 then returns to the base to pick up the second autonomous cleaning device 6.2 if necessary and fly it to a second position on the photovoltaic modules 2a. If further cleaning devices are present, the process is repeated until all autonomous cleaning devices are distributed on the cover glasses 1 of the photovoltaic modules 2 and 2a.

[0122] Once the autonomous cleaning devices 6.1 and 6.2 have arrived at the photovoltaic modules 2, 2a, they are positioned on the respective cover glass 1 of the photovoltaic module 2, 2a, preferably only with contact to a metal frame of the photovoltaic module 2, 2a. In the following, the method is described only for one autonomous cleaning device 6.1. However, the method is identical for all existing autonomous cleaning devices.

[0123] The autonomous cleaning device 6.1 automatically positions its megasonic transducer 17 over the cover glass 1 of the photovoltaic module 2 and regulates the RF power to the megasonic transducer 17, the process fluid flow from the liquid container 20 to the distributor 18 for filling a gap 44 and the scanning direction and speed to ensure a uniform cleaning process over an entire active surface 47 of the photovoltaic module 2.

[0124] The autonomous cleaning device 6.1 contains all the equipment required to support the cleaning process as described above.

[0125] If the autonomous cleaning device 6.1 or the megasonic transducer 17 has been positioned above the cover glass 1 of the photovoltaic module 2, gap 44 with a predetermined width b between the cover glass 1 of the photovoltaic module 2 and an active surface 45 of the megasonic transducer 17 is formed relative to the cover glass 1. The active surface 45 of the megasonic transducer 17 is preferably flat and thus supports the formation of a gap 44 of approximately uniform width b. Gap 44, for example, can have a width of approx. 1 mm. In particular, the active area 45 of the megasonic transducer 17 is a bonded PZT crystal area (Piezo materials based on lead-zirconate-titanate). The megasonic transducer 17 may comprise a piezoelectric crystal arranged to emit megasonic oscillations or megasonic vibrations through the active surface 45 when activated by the application of a high frequency signal. Instead of a piezoelectric crystal, the megasonic transducer 17 can comprise a variety of piezoelectric crystals arranged along the active surface 45.

[0126] The gap 44 is then at least partially filled with a process fluid from the liquid container 20. The process fluid bridges the gap 44 between a surface 46 of the cover glass 1 of the photovoltaic module 2 and the active surface 45 of the megasonic transducer 17 in at least part of the gap 44. The process fluid completely fills the gap 44 between the cover glass 1 of the photovoltaic module 2 and the megasonic transducer 17.

[0127] According to the inventive method, the megasonic transducer 17 is controlled to transfer megasonic oscillations into the process fluid in gap 44 and to at least part of cover glass 1 of photovoltaic module 2. Thus, the process fluid filling the gap 44 is used to transfer the megasonic oscillations or megasonic vibrations emitted by the megasonic transducer 17 to the surface 46 of cover glass 1 of the photovoltaic module 2 when activated.

[0128] By generating megasonic oscillations or megasonic vibrations with a frequency of at least 400 kHz and coupling the megasonic oscillations or megasonic vibrations into the process fluid, a particularly uniform and uniform sound field can be generated. In addition, the megasonic energy can be efficiently transferred to the surface 46 of cover glass 1 of photovoltaic module 2 in this way. It is assumed that, particularly depending on the properties of the fluid, a density of megasonic energy corresponding to about 0.5 w/cm2 of the active area 45 of the megasonic transducer 17 is sufficient to generate cavitation bubbles near the surface 46 of the photovoltaic module cover glass 1, and in that, upon collapse of the cavitation bubbles, local shock waves are emitted which efficiently remove undetected particles and/or impurities adhering to the surface 46 of cover glass 1 of the photovoltaic module 2 without damaging the surface 46 of the cover glass 1. Furthermore, the detached particles are transported away from the surface 46 of cover glass 1 due to cavitation shock waves and the flow of process fluid through gap 44 and the surface 46 of cover glass 1 of photovoltaic module 2 is not impaired or damaged.

[0129] Preferably, the megasonic transducer 17 is held in a substantially horizontal position above the cover glass 1 of the photovoltaic module 2. An active surface 47 of photovoltaic module 2 comprises a surface 46 of cover glass 1 under which photovoltaic collector cells are located. The active area 45 of the megasonic transducer 17, i.e. the area generating megasonic energy, is located in the same environment and overlays the active area 47 of the photovoltaic module 2.

[0130] According to the preferred design of the invention, the megasonic transducer 17 is moved (scanned) linearly in such a way that the width b of the gap 44 is retained. The scanning rate can be constant or non-linear, depending on the specific process requirements. The gap 44 is continuously filled with fresh process fluid from the liquid container 20 during this scanning movement by means of the fluid distributor 18 mounted adjacent and parallel to the megasonic transducer 17. This distributor 18 can be installed in the described megasonic transducer 17 or be part of the megasonic transducer 17 from the beginning.

[0131] The advantage is that the megasonic transducer 17 and the distributor 18 are moved in such a way that the gap 44 between the active surface 45 of the megasonic transducer 17 and the cover glass 1 of the photovoltaic module 2 remains constantly and continuously filled with liquid, while the entire active surface 47 of the photovoltaic module 2 is processed. The flow of fresh process fluid through the acoustically activated gap provides acoustically induced cavitation and implosion of the cavitation bubbles as well as a positive flow path away from cover glass 1 of photovoltaic module 2.

[0132] If the cover glass 1 of the photovoltaic module 2 has been completely cleaned by the autonomous cleaning device 6.1, the autonomous cleaning device 6.1 can be detached from the frame of the photovoltaic module 2 and transported back to the base 7 by means of the drone 5 and stored and charged in the housing 10 of the base 7 until the next cleaning sequence.

[0133] The comparison device 3 now again takes over the task of monitoring the degree of contamination of the cover glasses 1 of the photovoltaic modules 2, 2a and triggering a new cleaning sequence when a certain degree of contamination is reached.

[0134] FIGS. 4 to 7 show the autonomous cleaning device 6 in more detail. The explanations given for the reference numbers in FIGS. 1 to 3 also apply to FIGS. 4 to 7, especially if the same features have been given the same reference numbers. For this reason, all the characteristics described in FIGS. 1 to 3 are not repeated. Furthermore, it is pointed out that the above description for the handling of the cleaning device 6, 6.1 and 6.2 was of a general nature with regard to the photovoltaic modules 2, 2a and the following description goes into more detail about the handling of the autonomous cleaning device 6.3 with regard to the photovoltaic modules 2, 2a.

[0135] In addition to the features already listed above for cleaning device 6, 6.1 and 6.2, cleaning device 6.3 shown in FIGS. 4 to 7 shall also include the following features.

[0136] The cleaning device 6.3 has a carrier housing 50, on the upper side 51 of which, i.e. the surface of the carrier housing 50 facing away from the photovoltaic module 2, 2a in the position of use, preferably has two sockets 52 and 53 for one POD 54 and 55 respectively. A POD is a casing or housing forming part of a vehicle, as a) a streamlined external housing that encloses engines, machine guns, or fuel or b) a detachable compartment on a spacecraft for carrying personnel or instrumentation. The PODs 54 and 55 respectively have electrical and hydraulic connections to the carrier housing 50 of the autonomous cleaning device 6.3 (not shown).

[0137] Preferably, two PODs are arranged on the carrier housing 50. Of course, it is also possible to provide only one or more than two PODs on the carrier housing 50. In this case, the carrier housing 50 and/or the PODs need to be adjusted accordingly.

[0138] The individual POD 54 or 55 can be held in the socket 52 or 53 via an adapter 56. The POD 54 or 55 includes a container 57 for liquid and/or a compartment 58 for a storage battery. The electricity from the POD battery powers the controllers, the motion and positioning motor, the megasonic transducer/resonator bar positioning drive and the RF generator that makes the radio frequency signal. The POD 53 or 54 or the liquid container 57 and/or the battery are replaceable, even while using the cleaning device 6.3 on the photovoltaic modules 2, 2a.

[0139] I.e., in addition to the autonomous cleaning device 6.3, the drone 5 also transports replacement batteries and/or replacement fluid containers to the autonomous cleaning device 6.3 and collects the empty and replaceable battery previously located in the autonomous cleaning device 6.3 and/or the empty and replaceable fluid container 57 previously located in the autonomous cleaning device 6.3. If the battery and/or liquid container 57 in the autonomous cleaning device 6.3 is emptied during a cleaning sequence, the drone 5 can replace it without having to transport the entire autonomous cleaning device 6.3 to the base 7.

[0140] The individual POD 54 or 55 still has a lid 59, especially in the transport position, which can close the liquid container 57 and is also equipped with capture funnels 60. These capture funnels 60 can engage with corresponding holding elements on the drone 5, which are not shown in detail, in order to ensure that the POD 54 or 55 can be transported and/or replaced by the drone 5.

[0141] At the same time, the carrier housing 50 is also equipped with capture funnels 61, which can also be engaged with the corresponding holding elements of the drone 5 in order to be able to transport and/or exchange the autonomous cleaning device 6.3 by means of the drone 5.

[0142] The capture funnels 60 or 61 are provided with a locking possibility not shown in detail to ensure that after coupling the capture funnels 60 or 61 with the corresponding holding elements of the drone 5, these do not slip out of the capture funnel 60 or 61 and the autonomous cleaning device 6.3 and/or the PODs 54 or 55 are lost or damaged as a result.

[0143] The capture funnels 60 or 61 are preferably arranged in a hinged manner so that they can rotate about an axis, which is not shown closer. This has the advantage that the holding elements of the drone 5 can pick up the autonomous cleaning device 6.3 and/or the PODs 54 or 55 even from a possibly different angle.

[0144] In this case, the lids 59 of the PODs 54 and 55 as well as the carrier housing 50 of the autonomous cleaning device 6.3 each have four capture funnels 60 and 61. Of course, it is possible to provide fewer or more than four capture funnels per lid and/or carrier housing (multipoint coupler assembly).

[0145] Below the carrier housing 50, the autonomous cleaning device 6.3 has a flat stop 62, which, in the position of use, rests against the metal frame of the photovoltaic module 2, 2a when the drone 5 has placed the autonomous cleaning device 6.3 there. Omi-directional rollers 63 are arranged at a distance from an underside 64 of the carrier housing 50. They ensure that the autonomous cleaning device 6.3 rests evenly on the cover glass 1 of the individual photovoltaic module 2, 2a. [0146] On the side of the stop 62 opposite the metal frame of the photovoltaic module 2. 2a in the position of use, there are preferably two rollers 65 for cable arrays 66. A resonator bar/megasonic transducer 67 is held on the cable arrays 66. This is done by means of cable holders 68 on one side 69 of the megasonic transducer/resonator bar 67. The cable arrays 66 comprise the two elements (not shown) required for the megasonic transducer/resonator bar 67 to function. [0147] RF cable: This coaxial cable is used to provide RF (Radio Frequency) energy to the PZT crystals incorporated in the megasonic transducer, causing them to vibrate the resonator and transmit sound into the fluid; [0148] a fluid tube: Connects the fluid from the POD 54 or 55 respectively to a distributor (manifold) (not shown) located above the resonator bar 67. This fluid then fills the gap between the megasonic transducer and the cover glass of the photovoltaic module 2, 2a.

[0149] At each end, the resonator bar 67 is attached to one resonator carriage 70 each to ensure that the resonator bar 67 moves evenly on the cover glass 1 of the photovoltaic module 2, 2a. For this purpose, the two resonator carriages 70 are each equipped with a sliding roller 71.

[0150] The movement of the resonator bar 67 with the aid of the cable arrays 66 is effected by means of a drive 72 for the rollers 65 and further by means of a drive 73, which is responsible for a longitudinal movement of the resonator bar 67 along a longitudinal axis of the photovoltaic modules 2, 2a.

[0151] To prevent the resonator bar 67 from moving in the transport and rest position of the autonomous cleaning device 6.3, transport safety devices 74 for the resonator bar 67 are provided on the underside 64 of the carrier housing 50. Each of the two resonator carriages 70 has one or more detents 75, which engage in the transport safety devices 74 in the transport or rest position. Preferably, two detents 75 on each resonator carriage 70 are arranged offset and the transport safety devices 74 on the underside 64 of the carrier housing 50 are also arranged offset.

[0152] As far as the mode of operation is concerned, it is also referred to the detailed description above. However, it should also be mentioned that, having arrived at the photovoltaic modules 2, 2a, the autonomous cleaning device 6.3 is positioned on the respective cover glass 1 of the photovoltaic module 2, 2a by placing the omni-directional rollers 63 on the cover glass 1 of the photovoltaic module 2, 2a and the stop 62 against the metal frame of the photovoltaic module 2, 2a. The presence of the stop 62 makes it possible to use the autonomous cleaning device 6.3 at different angles of inclination of each photovoltaic module 2, 2a, as shown in FIG. 10.

[0153] The autonomous cleaning device 6.3 is positioned on the cover glass 1 of the photovoltaic module 2, 2a, preferably only with contact to the metal frame of the photovoltaic module 2, 2a. The autonomous cleaning device 6.3 then automatically positions the megasonic transducer 17/resonator bar 67 over the cover glass 1 of the photovoltaic module 2, 2a and controls the RF power (radio frequency power) to the megasonic transducer 17/resonator bar 67, the process fluid flow to the distributor to fill the gap 44, and the scanning direction and speed to ensure a uniform cleaning process across the entire active area 47 of the photovoltaic module 2, 2a.