Contenu connexe

anti reflective coatings on the solar photo voltaic panel's

  2. In typical installations, approximately 4% of incoming light is reflected off the face of the PV module and is lost.
  4. coating What is antireflective coating ? Antireflective or anti-reflection (AR) coating is a type of optical coating applied to the surface of lenses and other optical devices to reduce reflection.This improves the efficiency of the system since less light is lost. Antireflection is achieved by destructive interference between incident rays. coating
  5. For destructive interference Δ = (2m+1) λ/2 2nd = (2m+1) λ/2 => d = λ/4nc = λ’/4 m=0,1,2,3…………………….. d = minimum required thickness of coating λ’ = wavelength in coating medium ’
  6. About 4% of the light hitting the glass of a solar modules is reflected and thus lost for electricity production. Reflections can be reduced and thus light transmission can be increased by using antireflective (AR) coatings. The higher electricity output results in a reduction of the cost per panel. ‘Traditional’ AR coatings are either expensive or have to compromise on the balance optical vs mechanical properties. Why use anti-reflective coatings on solar cover glass?
  7. binder Glass substrate “Traditional” AR coating Solid silica particles Glass substrate Coating layer (100-150 nm) Modern Coat™ AR coating
  8. Electro deposition Chemical coating Conversion coating Vapour deposition Chemical vapour deposition Physical vapour deposition Spraying Back Formation of antireflection coating Plasma enhance chemical vapour deposition
  9. Spraying process
  10. CHEMICAL COATINGS Advantages  Low temperature treatment  More corrosion resistant than electrodeposited chromium  Can coat complex shapes uniformly  Hard particles can be incorporated to increase hardness .  Can coat most metals and some insulators Disadvantages  More expensive than electroplated chromium  Heat treatment is needed to develop optimum properties
  11. CONVERSION COATINGS  Thin compound layers can be produced by reacting a metal surface with an acidic solution. e.g. Thin (10mm) coatings of metal phosphates are formed on steel substrates exposed to phosphoric acid. These provide low friction surfaces. Advantages  Cheap and simple to perform  Low temperature treatment Disadvantages  Restricted range of materials can be treated  Thin treated layer  Poor treatment durability  Difficult to control treatment quality on heterogeneous materials.
  12. PHYSICAL VAPOUR DEPOSITION  A variety of vacuum deposition  Purely physical process , no chemical reaction involved.  Process involved three steps: • Evaporation • Transportation • Deposition  multiple coating layers possible  MgF2 coating on glass
  13.  Almost any type of inorganic material can be used as well as some kinds of organic materials.  The process is more environmentally friendly than processes such CVD. Advantages of PVD Disadvantages  High capital cost  Equipment size large because vacuum required  Processes requiring large amounts of heat require appropriate cooling systems  The rate of coating deposition is usually quite slow
  14. CHEMICAL VAPOUR DEPOSITION  Gaseous compounds react to form a dense layer on a heated substrate. The most widely deposited wear-resistant coatings are TiC, TiN, chromium carbide and alumina. Deposition temperatures are generally in the range 800-1000C which restricts the range of materials which can be coated and can lead to component distortion. Thicknesses are limited to about 10mm due to the thermal expansion mismatch stresses which develop on cooling which also restrict the coating of sharp edged components.
  15.  Layer deposition involves chemical reactions  Large density films  Good stoichiometry & uniformity over large surface area.  SiO2 SiN, SiON, SiOC , and TiO2 with proper thickness are the common AR material deposited chemically.  Required high temp to produce high quality material and for many application the substrate cannot tolerate being heated so not useful in that case . LIMITITATION :
  16. Advantages  High coating hardness  Good adhesion (if the coating is not too thick)  Good throwing power (i.e. uniformity of coating) Disadvantages  High temperature process (distortion)  Sharp edge coating is difficult (thermal expansion mismatch stresses)  Limited range of materials can be coated  Environmental concerns about process gases
  17.  Combined process of both CVD and PVD  a process used to deposit thin films from a gas state (vapour) to a solid state on a substrate.  Chemical reactions are involved in the process, which occur after creation of a plasma of the reacting gases  The plasma is generally created by RF (AC) frequency or DC discharge between two electrodes, the space between which is filled with the reacting gases.  Processing plasmas are typically operated at higher pressures PLASMA ENHANCED CHEMICAL VAPOUR DEPOSITION
  18. of a few millitorr to a few torr , although arc discharges and inductive plasmas can be ignited at atmospheric pressure
  19.  Plasma enhanced CVD is most useful because it can deposit layers on fragile substrates that cannot withstand the high temperatures of other CVD methods  Plasma enhanced CVD systems allow for greater control of the film composition, density, and film stress.  Higher deposition rate at low temperature relatively  Plasma can cause damage to the substrate surface when either secondary electrons collide with the wafer surface or the energy of the ion bombard- ment becomes too high.  High cost. Advantages of PECVD Disadvantages
  20. How much reflection while using AR coating ? Can be reduced up to ~ 0.2%
  21. APPLICATION OF ANTIREFLECTION COATING  Anti-reflection coated optical windows  Reflex free sight glasses  Laser scanner windows  Contrast enhancement  Anti glare coated instrument windows  Sensor technology  Low reflection camera windows  Holography components  Antireflection coated glass for displays  In microelectronic photolithography to reduce image (substrate) distortions . solar cell with SiO coating Glass with MgF2 coating
  22. TESTING OF ARC SURFACE SAND BLAST TESTING Figure 2: Surface defects post sand blasting test, showing scratches on ARC glass and chipping of the uncoated glass
  24. Figure 1: Temporary staining due to plant residue observed during field exposure of ARC glass modules in heavy pollen areas in California.
  25.   tml  http://hyperphysics.phy-  http://www.rp-  tcom  reflection-coatings  pv_contacts_coatings.html Reference links :