PV Module efficiency analysis and optimization


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PV Module efficiency analysis and optimization

  1. 1. PV Module efficiency analysis andoptimization Ingrid Haedrich1, Harry Wirth1, Michael Storz2, Gerhard Klingebiel2 1 Fraunhofer Institute for Solar Energy Systems ISE, 2 Schmid Technology Systems How to rate Solar Energy Efficiency to maximize returns? Webinar, 18th September 2012 www.ise.fraunhofer.de© Fraunhofer ISE
  2. 2. Outline Fraunhofer ISE Introduction Determination of series resistance Analysis of optical properties Modeling of module power Sensitivity analysis Conclusions Module Technology Center, interior view© Fraunhofer ISE
  3. 3. Photovoltaic Modules, Systems and ReliabilityFields of activity Module technology Durability analysis and Quality Assurance environmental Modules and Power . simulation Plants. Interconnection  Reliability Testing  Yield certificates technology  Material analysis  Power plant inspec- Module efficiency tion and testing  Testlab PV Modules and new concepts  Monitoring Module Technology  CalLab PV Modules Center (MTC)© Fraunhofer ISE
  4. 4. Photovoltaic Modules, Systems and ReliabilityObjectives Efficiency and electric yield improvement Enabling of advanced cell technologies Material cost reduction Production yield improvement Estimated cost structure for poly-Si PV module Module technology responsible for: 35-40% of product cost, 15% of product efficiency, 95% of prod. reliability© Fraunhofer ISE
  5. 5. Work areas and topics product development process development material proving PC backsheet paste/adhesive vac. carrier vac. carrier flip 4 PC backsheet cells encapsulant (2) encapsulant (1)front glass 1 2 3 5 One-Layup process for back-contact module production© Fraunhofer ISE
  6. 6. Work areas and topics Interconnection processes  qualification of new cell metallization  lead free/flux free soldering  Al contacting Cell interconnector design  back contact technology Bi-metal effect, unilateral soldered, 160 µm  stress reduction cell  electrical/optical efficiency Module efficiency  optical, electrical improvements  inactive area reduction© Fraunhofer ISE
  7. 7. Introduction cell to module losses efficiency losses from solar cell to complete module: typ. 10-15 percent especially for high efficiency cells it is important to understand how to keep the efficiency inside a moduleapproach establish procedure for predicting module efficiency from material and geometry data investigate effects on efficiency change for specific module built-up analyse sensitivity of module power with respect to material and design improvements© Fraunhofer ISE
  8. 8. IntroductionBasic effects:1. electrical losses generated by string formation and cables2. optical losses and gains generated by the various interactions between cell, encapsulant, glass and backsheet3. module format including inactive areas© Fraunhofer ISE
  9. 9. Introduction module Optical gains and electrical format losses losses© Fraunhofer ISE
  10. 10. Series resistance losses Ploss ,mod = Ploss ,base + Ploss ,emitter + Ploss ,gap + Ploss ,sc + Ploss ,cable© Fraunhofer ISE
  11. 11. Series resistance losses Ploss ,mod = Ploss ,base + Ploss ,emitter + Ploss ,gap + Ploss ,sc + Ploss ,cable© Fraunhofer ISE
  12. 12. Series resistance losses Ploss ,mod = Ploss ,base + Ploss ,emitter + Ploss ,gap + Ploss ,sc + Ploss ,cable© Fraunhofer ISE
  13. 13. Series resistance losses Ploss ,mod = Ploss ,base + Ploss ,emitter + Ploss ,gap + Ploss ,sc + Ploss ,cable© Fraunhofer ISE
  14. 14. Series resistance losses Ploss ,mod = Ploss ,base + Ploss ,emitter + Ploss ,gap + Ploss ,sc + Ploss ,cable© Fraunhofer ISE
  15. 15. Series resistance lossesPloss ,mod = Ploss ,base + Ploss ,emitter + Ploss ,gap + Ploss ,sc + Ploss ,cable 2 l Ploss ,base = I BB ⋅ ⋅ Rb ,eff 3IBB current per busbarl length of the cellRb,eff effective resistivity (ribbon, metallization) Assumption: continuous soldering joint over cell length© Fraunhofer ISE
  16. 16. Series resistance lossesResistivity of emitter and base busbarTLM measurement results for a commercial mc cell 2 mOhm/cm effective for base busbar (including aluminium screen print) 11 mOhm/cm for emitter busbar© Fraunhofer ISE
  17. 17. Series resistance losses polycrystalline full square 6” cell STC power from cell flasher: 4,54 W short circuit current: 8,35 A total power loss due to stringing electrical resistivity: 0,156 W/cell power loss 60-cell module with 3 mm cell distance: 9,9 W© Fraunhofer ISE
  18. 18. Analysis of optical properties Effective reflection and absorption losses of glass and encapsulation material Direct coupling gain due to encapsulation air EVA Optical gains due to an increasing cell space© Fraunhofer ISE
  19. 19. Analysis of optical propertiesEffective transmission-, reflection and absorption coefficientFrom sheet to material properties R01 = R10 = R12 = ( n1 − 1) 2 τ measured sheet transmissivity (1 + n1 ) 2 ρ measured sheet reflectivity Txy transmissivity from T01 2 ⋅ R12 ⋅ t 2 ρ = R01 + 2 2 medium x (air) to medium y 1 − R01 ⋅ t Rxy reflectivity at the surface T01 2 ⋅ t from medium x (air) to medium y τ= 2 1 − R01 ⋅ t 2 t bulk transmissivity nx refractive index of medium x© Fraunhofer ISE
  20. 20. Analysis of optical propertiesEffective transmission-, reflection and absorption coefficient Relative spectral response / AM 1.5 0,20 1,0 Absorption / Reflection 0,8 0,15 0,6 0,10 0,4 0,05 0,2 0,00 0,0 400 600 800 1000 1200 Wavelength air glass reflectivity relative spectral response bulk absorptivity glass AM 1.5 spectrum standardized bulk absorptivity EVA© Fraunhofer ISE
  21. 21. Analysis of optical propertiesEffective transmission-, reflection and absorption coefficient Determined optical properties for glass and encapsulation bulk reflectivity bulk absorptivity transmission air/medium glass 99,2% 4,1% 0,3% encapsulant 97,9% 3,2% 2,1%© Fraunhofer ISE
  22. 22. Analysis of optical propertiesCoupling effects due to encapsulation Change of Iscaircell Isc,air air encapsulant Isc,EVA cell© Fraunhofer ISE
  23. 23. Analysis of optical propertiesCoupling effects due to encapsulationThe measured change of Isc results from several optical effects: reflection at air/EVA surface effective bulk absorption of EVA material direct coupling gain, due to increased refraction index at cell interface coupling effects indirect coupling gain, due to multiple reflection between cell surface and encapsulant/air interface© Fraunhofer ISE
  24. 24. Analysis of optical properties Coupling effects due to encapsulation coupling gain(Isc,encapsulated-Isc,air)/Isc,air [% ] 10% 8% measured total current gains/losses 6% 4% 2% 0% -2% -4% -6% Poly (Typ A) Mono (Typ B) Mono (Typ C) Mono (Typ D) © Fraunhofer ISE
  25. 25. Analysis of optical propertiesOptical gains due to cell spacing with white backsheet 2,0% Isc change (Isc,enc-Isc,air)/Isc,air [%] 1,0% Linear (Isc change) y = 0,0046x - 0,0174 0,0% -1,0% -2,0% -3,0% 0 1 2 3 4 5 6 cell distance [mm] Measurement on 8 samples with increasing cell distances average Isc gain: 0.5 %/mm spacing© Fraunhofer ISE
  26. 26. Modeling of module power The predicted module power was found to be within the range of module flasher measurement uncertainty = +/- 3%© Fraunhofer ISE
  27. 27. Sensitivity analysis 3,0% cross section area cell connector ribbon reduction width module border 2,5% reduction width cell distance∆ module efficiency reduction resistivity emitter busbar 2,0% 1,5% 1,0% 0,5% 0,0% 0% 10% 20% 30% parameter increase [% ] Sensitivity of module efficiency of four different parameters © Fraunhofer ISE
  28. 28. Conclusion Major effects and sensitivities have been shown Efficiency analysis tool has been set up Module efficiency depends strongly on cell/module interaction New cell technologies will require adapted module materials Outlook: additional evaluation of electric yieldthis work has been performed in cooperation with:Schmid Technology Systems© Fraunhofer ISE
  29. 29. Thank You Very Much for Your Attention!Fraunhofer Institute for Solar Energy Systems ISEIngrid Haedrichwww.ise.fraunhofer.deIngrid.haedrich@ise.fraunhofer.de© Fraunhofer ISE