Abstract:
A method for automatically cleaning a solar panel, includes: obtaining an environmental intensity of sunlight in the outside environment with an environmental light sensor; obtaining a transmitted intensity of incident sunlight throughout the protection panel with a transmission light sensor; deriving a detection difference value between the environmental intensity and the transmitted intensity; comparing the detection difference value with a predetermined value. Wherein if the detection difference value is larger than the predetermined value, the solar panel will be cleaned; if the detection difference value is smaller than the predetermined value, the solar panel will not be cleaned; the driving device sends execution signals to a perfusion device and a driving device so as to the driving device drives a cleaning device to clean the solar panel when the solar panel needs to be cleaned.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a divisional application of a commonly-assigned application entitled “AUTOMATIC CLEANING SYSTEM FOR SOLAR PANELS AND METHOD”, filed on Dec. 12, 2008 with application Ser. No. 12/333,624. The disclosure of the above-identified application is incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The disclosure relates to cleaning systems and, particularly, to a cleaning system and method for automatically cleaning solar panels. 
         [0004]    2. Description of Related Art 
         [0005]    Nowadays, with the resources on the earth being depleted day by day, the cost of investment for energy increases significantly. Solar energy has drawn attention from the energy industry as an alternative source of energy, and found widespread applications in a variety of fields. 
         [0006]    Solar cells convert photons from solar radiation into electrical energy through semiconductor equipment using solar cells (please refer to “Grown Junction GaAs Solar Cell” by C. C. Shen and G. L. Pearson, Volume 64, Issue 3, Proceedings of the IEEE, pages 384-385, March 1976.) The phototransducing process produces electron-hole pairs when the radiated photons reach a solar panel, combining the photons with atoms and valence electrons in the semiconductor material. Because of the electron-hole pairs, photovoltaic electromotive forces are formed close to the P-N junction, providing electrical power when P section and the N section in the semiconductor material are wired. Connecting the semiconductor materials parallel or in series provides a solar panel that outputs constant voltage and current. 
         [0007]    To maximize reception of solar energy, the solar panel is normally in an elevated position and angled. This, combined with exposure to the elements, creates a need for frequent cleaning, especially since even a thin coating of dust or dirt can seriously affect the efficiency of photovoltaic energy production. Cleaning the solar panel is accordingly difficult. Existing cleaning devices for solar panels normally utilize mechanical structure, but still require manual operation. As well, such systems cannot detect contaminant on the surface of the solar panel in a timely manner, nor can they remove the dirt automatically. The cleaning device or system can thus significantly affect performance of the solar panel. 
       SUMMARY 
       [0008]    The disclosure provides a method for automatically cleaning a solar panel. The method comprises: obtaining an environmental intensity of sunlight in the outside environment with an environmental light sensor; obtaining a transmitted intensity of incident sunlight throughout the protection panel with a transmission light sensor; deriving a detection difference value between the environmental intensity and the transmitted intensity; comparing the detection difference value with a predetermined value. Wherein if the detection difference value is larger than the predetermined value, the solar panel will be cleaned; if the detection difference value is smaller than the predetermined value, the solar panel will not be cleaned; the driving device sends execution signals to a perfusion device and a driving device so as to the driving device drives a cleaning device to clean the solar panel when the solar panel needs to be cleaned. 
     
    
     
       BRIEF DESCRIPTION FOR THE DRAWINGS 
         [0009]      FIG. 1  is a schematic view for a first embodiment of an automatic cleaning system for solar panels. 
           [0010]      FIG. 2  is a cross-section view taken along the line A-A in  FIG. 1 . 
           [0011]      FIG. 3  shows a second embodiment of an automatic cleaning system for solar panels. 
           [0012]      FIG. 4  is a flowchart of a first embodiment of an automatic cleaning method for solar panels. 
           [0013]      FIG. 5  is a schematic view of a third embodiment of an automatic cleaning system for solar panels. 
           [0014]      FIG. 6  is a flowchart of a second embodiment of an automatic cleaning method for solar panels. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]      FIGS. 1 and 2  show an automatic cleaning system  1  for solar panels, which comprises a solar panel  14 , a detection device  6 , a perfusion device  8 , a driving device  10 , and a cleaning device  12 . 
         [0016]    The solar panel  14  comprises a transparent protection panel  16  and a plurality of solar cells  17  covered thereunder. The detection device  6  detects dirt on the protection panel  16  and instructs the perfusion device  8  and the driving device  10  clean the solar panel  14  based on the detection result. The cleaning device  12  is driven by the driving device  10  to clean the solar panel. 
         [0017]    The detection device  6  comprises an environmental light sensor  62  external to the protection panel  16 , a received light sensor  64  provided under the protection panel  16 , and a comparison and analysis module  66 . The environmental light sensor  62  directly detects intensity of sunlight incident thereon. The received light sensor  64  detects the intensity of sunlight passed through the protection panel  16 . 
         [0018]    The comparison and analysis module  66  compares intensity detected by the environmental light sensor  62  with that detected by the received light sensor  64 , and determines if the solar cell panel  14  needs to be cleansed. Accumulated dirt and dust on the solar panel will reduce the amount of sunlight passed through the protection panel  16 . A difference value Y2 between the sunlight intensity detected by the environmental light sensor  62  and the intensity detected by the transmitted light sensor can be derived. The comparison and analysis module predetermines a standard intensity difference value Y1based on an ideal condition of the protection panel  16 . If the detected intensity difference value Y2 is less than or equals the standard intensity difference value Y1, the protection panel  16  satisfies the predetermined clean standard and does not need to be cleaned. If the detected intensity difference value Y2 exceeds the standard intensity difference value Y1, the protection panel  16  cannot satisfy the predetermined standard, and the comparison and analysis module issues an execution signal to the perfusion device  8  and the driving device  10 . 
         [0019]    The perfusion device  8  is an auxiliary cleaning device provided on the top of the solar panel  14 , which comprises a conduit  82  comprising an outlet tank  84 . After receiving the execution signal from the detection device  6 , the perfusion device  8  sprays water and cleaning agent to clean the protection panel  16 . 
         [0020]    The driving device  10  comprises a slide slot  102  provided on both sides of the solar panel  14 , a pulley  104  sliding in the slide slot  102 , a driving motor  106  moving the pulley  104 , and a pair of commutation sensors  108  provided on the motor  106 . 
         [0021]    Each of the slide slot  102  comprises a pair of slides  1021  connected to the solar panel  14 , a sidewall  1022  extending upward along the outer edge of slides  1021 , and a baffle  1023  provided on the top of the sidewall  1022  which extends toward the center of the solar panel  14 . The slides  1021  are wider than the pulley  104  so as to limit the range of motion thereof. The sidewall  1022  prevents the pulley  104  from diverging outward. The baffle  1023  separates the pulley  104  and the driving motor  106  connected to the pulley  104  to prevent dust and dirt entering the slides  1021 . The commutation sensor  108 , provided on the inner side of the baffle  1023  toward the slides  1021  and on the motor  106 , comprises a primary commutation sensor  108   b  and two secondary commutation sensors  108   a.  The primary commutation sensor  108   b  is provided close to one side of driving motor  106  which is opposite to the baffle  1023 , and the secondary commutation sensors  108   a  are provided on inner sides of the baffle  1023  which correspond to the primary commutation sensor  108   b.  When the driving motor  106  moves the cleaning device  12  to the two ends of the solar panel  14 , the secondary commutation sensor  108   a  is opposite to the primary commutation sensor  108   b,  and the driving motor  106  obtains a commutation signal to change the moving direction of the cleaning device  12 , so that the cleaning device  12  move to the other end of the solar panel  14 . 
         [0022]    The cleaning device  12  comprises a holding part  122  connected to the driving device  10  and a washer  124  provided on the holding part  122 . The holding part  122  is provided between the pulleys  104 , and is moved by the rotation of the pulleys  104 . The washer  124  comprises a rolling brush  1242  with a rolling axle  1241 , and the rolling axle  1241  is driven by a motor (not shown) provided within the holding part  122 . 
         [0023]      FIG. 3  shows a second embodiment of an automatic cleaning system for solar panels including an automatic cleaning device  24 , differing from the previous embodiment only in that a washer  242  of cleaning device  24  is not rotatable, and a number of flexible members  243  provided within a holding part  241  impels the washer  242  to contact the solar panel to be cleaned. 
         [0024]      FIG. 4  is a flowchart of a first embodiment of an automatic cleaning method for solar panels, comprising step S 801 , providing an automatic cleaning system  1  for solar panels, and step S 802 , wherein the environmental light sensor  62  obtains an intensity of direct sunlight and transmission light sensor  64  obtains an intensity of sunlight passed through the protection panel  16  of the solar panel  14 . In step S 803 , it is determined whether the protection panel  16  is to be cleaned, wherein the comparison and analysis module  66  of the detection device  6  obtains an acquired difference value Y2 between the environmental sunlight intensity and the transmitted sunlight intensity, compares the difference Y2 with a predetermined standard difference value Y1, and if the acquired difference Y2 exceeds the standard difference Y1, indicating that dirt and dust on the protection panel  16  exceed a predetermined tolerance, the detection device  6  issues an execution signal to the perfusion device  8  and the driving device  10  to clean the solar panel  14 . If the acquired difference value Y2 is less than the standard difference value Y1, indicating that the protection panel  16  does not exceed the tolerance, step S 802  is repeated. 
         [0025]    In Step S 804 , the driving device  10  drives cleaning device  12  to clean the protection panel  16 . The perfusion device  8  sprays cleaning water, cleaning agent, or other medium onto the solar panel  14 . 
         [0026]      FIG. 5  shows a third embodiment of an automatic cleaning system for solar panels, differing from the previous embodiment only in the further incorporation of a time controller  4 . 
         [0027]    The time controller  4  is electrically connected to the detection device  6 , the perfusion device  8  and the driving device  10  through a cable  18 , and sets time values for execution of the detection device  6  and/or the perfusion device  8  and the driving device  10 . 
         [0028]    The time controller  4  comprises a clock signal generator  42 , a time setting module  44 , and a cache register  46 . The clock signal generator  42  is a crystal oscillation circuit providing precise time pulses for the system. 
         [0029]    The time setting module  44  integrates the working time of all devices of the system. An initial time is set for the system according to the local time, and regular detection time point TC, cleaning time point TW, and cleaning duration TL for each cleaning time are set. The time setting module  44  receives time pulses frequently from the clock generator  42 , and provides an execution signal to the detection device  6  when a pulse representing a detection time point TC is received, and the protection panel  16  is checked accordingly. After receiving a pulse representing the cleaning time point TW, the time setting module  44  issues an execution signal to the driving device  10  and the perfusion device  8  to clean the protection panel  16 . 
         [0030]    When the driving device  10  and the perfusion device  8  begin to clean the panel, a timer signal is sent to the time setting module  44 , which in turn begins timing the cleaning After the predetermined cleaning duration TL passes, the time setting module  44  issues a stop signal to the driving device  10  and the perfusion device  8  to stop the cleaning. 
         [0031]    The cache register  46  stores and caches the information set by the time setting module  44 . 
         [0032]      FIG. 6  is a flowchart of a second embodiment of an automatic cleaning method for solar panels, comprising step S 901 , providing an automatic cleaning system  2  for a solar panel, and step S 902 , wherein an initial time is set for the time controller  4  according to the local time, and a regular detection time point TC, a cleaning time point TW and a cleaning duration TL are further set for each cleaning. In step S 903 , clock signals are received through the time controller  4  comprising a clock generator  42  generating regular clock signals to a time setting module  44 . In step S 904 , the time setting module  44  determines whether the current time conforms to the regular detection time point TC or the cleaning time point TW, and if the current time conforms to the regular detection time point TC, the time setting module  44  issues an execution signal to the detection device  6 , and if the current time conforms to the cleaning time point TW, the time setting module  44  issues an execution signal to the driving device  10  and the perfusion device  8 . In step S 905 , the detection device  6 , comprising an environmental light sensor  62 , a transmission light sensor  64 , and a comparison and analysis module  66  checks the solar panel  14 , implementing the environmental light sensor  62  and the received light sensor  64 . In step S 906  the comparison and analysis module  66  in the detection device  6  obtains an intensity difference Y2 by comparing the intensity value detected by the environmental light sensor  62  with the intensity value detected by the transmission light sensor  64 , and compares the intensity difference Y2 with a predetermined standard intensity value Y1. If the acquired difference Y2 exceeds the standard difference Y1, indicating that dirt and dust on the protection panel  16  exceed a predetermined tolerance, the detection device  6  issues an execution signal to the perfusion device  8  and the driving device  10  to clean the solar panel  14 . If the acquired difference Y2 is less than the standard difference Y1, indicating that the protection panel  16  does not exceed the tolerance, step S 902  is repeated. In step S 907 , after receiving the execution signal from the time setting module  44  or the detection device  6 ; the perfusion device  8  sprays cleaning water, cleaning agent or other medium onto the solar panel  14  to co-operate with the cleaning device  12  to do cleaning The driving device  10  and the perfusion device  8  send a timer signal to the time setting module  44 , and the time setting module  44  issues a stop signal to the driving device  10  and the perfusion device  8  after a predetermined cleaning duration TL passes. 
         [0033]    The disclosed automatic cleaning system and method for solar panels provides prompt detection and effective cleaning for solar panels, and avoid dangerous and inconvenient practices. 
         [0034]    The foregoing description of the exemplary embodiments of the disclosure has been presented only for the purposes of illustration and description, and is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to explain the principles of the disclosure and their practical application so as to enable others skilled in the art to utilize the disclosure and various embodiments and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which this disclosure pertains without departing from its spirit and scope. Accordingly, the scope of this disclosure is defined by the appended claims rather than the foregoing description and the exemplary embodiments described therein.