1. 1 Solar Photovoltaic Technologies, Applications and Why Solar Now ? David Pham

2. 2 Photovoltaic Solar System categoriesPhotovoltaic Solar System categories Residential < 15kW Commercial > 15kW Some commercial projects require ARRA Government > 15kW meets ARRA American Recovery & Reinvestment Act (ARRA) Proudly made in the USA Utility > 1MW Some projects require ARRA 3. 3 Grid Tied PV System Outline Facing South @ 30 degree Tilt in Central Texas 4. 4 Yearly Sum of Global Irradiance Solar Irradiance : Total amount of solar radiation per unit area Germany USA From 2004 to 2010: ~60% of all solar modules made world wide were consumed by Germany. Less than 1% were consumed by the USA. Germany has nearly half the world's installed solar cell capacity, thanks to a generous national policy feed in tariff program. 5. 5 Photovoltaic (PV) Solar Energy statistics, factsPhotovoltaic (PV) Solar Energy statistics, facts 6. 6 Photovoltaic (PV) Solar Energy statistics, factsPhotovoltaic (PV) Solar Energy statistics, facts The Earth receives more energy from the sun in an hour than is used in the entire world in one year. It would take only around 0.3 per cent of the world's land area to supply all of our electricity needs via solar power. According to the United Nations 170,000 square kilometers of forest is destroyed each year. If we constructed solar farms at the same rate, we would be finished in 3 years. Wind is a form of solar power, created by the uneven heating of the Earth's surface. 92 Square Miles of Solar Photovoltaic (PV) could power the entire USA. ~ Size of DFW 385 sqm. The first solar cell was constructed by Charles Fritts in the 1880s - it had a conversion efficiency of just 1%. In 2014 a C-Si solar cell made by SunPower (USA company 2007) has 25% efficiency. Theoretical maximum efficiency for a C-Si solar cell is 29%. Weight for weight, advanced silicon based solar cells generate the same amount of electricity over their lifetime as nuclear fuel rods, without the hazardous waste. All the components in a solar panel can be recycled, whereas nuclear waste remains a threat for thousands of years. Manufacturing solar cells produces 90% less pollutants than conventional fossil fuel technologies. The solar industry creates 200 to 400 jobs in research, development, manufacturing and installation for every 10 megawatts of solar power generated annually. 7. 7 GO SOLARGO SOLAR Tom Brady and Gisele Bundchens Residence Solar System 8. 8 w/o Solar System electric bill- residential Year $ Rate Increase 7% per year Today $250/month @ $0.13 per kWh 9. 9 Utility Companies INCREASING Rate From Austin Energy 10. 10 Utility Companies Decreasing CO2 Emission From Austin Energy 11. 11 Lights-On 2007 12. 12 Lights-On ~2030 13. 13 Utility Companies Promoting Renewable Energy SOLAR From Austin Energy 14. 14 Solar System Adds A Premium To a Homes Resale Value The exact numbers vary from property to property and installation to installation, but recent research shows an average increase in resale value being $5,911 for each 1 kilowatt (kW) of solar installed. (costofsolar.com) March 2014 15. 15 How Tough are Solar Modules Study: Jet Propulsion Laboratories (JPL) Pasadena, California * Hail Impact with a 1 in ice ball traveling at a terminal velocity of 52 mph * All Solar Modules have a 25 years Warranty At 25 years the Solar Modules still have an output > 80% of original specification 16. 16 Investment Comparison Risks and Returns 17. 17 How to read your electric bill ? In Nov-Dec = 850 kWh Cost per month from 850 kWh + fees = $110.90 Cost per kWh = $110.90 / 850 kWh = 0.13 $/ kWh Do this for every month and take the average kWh, cost and $/kWh 18. 18 Calculate How Much Solar Do I Need ? Ave. kWh use/month (from your 12 months electric bills) a) 2,500 kWh x 1000 = AC Watts/month = a x 1000 b) 2,500,000 AC Watts used per day = b/30.5 (days in a month) c) 81,967 AC Watts used per day/Sun Hours per day (TX = 5.4) = c / 5.4 d) 15,179 DC Watts needed per hour per day = d x 1.29 e) 19,581 Solar array to ZERO electric bill in DC Watts f) 19,581 Solar Array in KiloWatts, or kW DC = f / 1000 g) 19.581 Solar Array in KiloWatts DC = kW DC (round up) h) 20.00 We want to 50% the cost = 20 kW DC x .05 = 10 kW DC 19. 19 How much money can I save from my Solar System ? http://pvwatts.nrel.gov/ 20. 20 How much money do I have to spend ? Avg./month ~$250 Increasing Every Year NO Solar Lender (Bank, Family,etc..) Avg./month ~$125 Increasing Every Year YES Solar X Solar Saving ~4-6 years ROI $ Solar Loan Solar Cost Utility rebate, Fed. Tax rebate, Deprec., State Tax Incentives $$$$$ Solar Out of Pocket 21. 21 Why Solar Now ? Incentive Programs for Distributed PV Solar System Soon to be phased-out Local Utility Value of Solar Energy Feed in Tariff (FIT) (Local Utility) Local Utility Rebate Residential (Local Utility) Performance Base Incentive for Commercial (Local Utility) 30% Federal Tax Rebate (USA) Ending 2016 5 year depreciation Federal Tax Savings (USA) Commercial projects Texas Franchise Tax (corporate tax) savings (Texas) Commercial projects Facing South @ 30 degree tilt angleFacing South @ 30 degree tilt angle All Local Utility Rebates can be phased out at any time by the Utility Companies. 22. 22 Return on Investment (ROI) and Rate of Return (ROR) Example 70kW DC ROI ROR Rebate & Incentives Commercial Solar System Please consult your CPA or qualified tax consultant for more details. 23. 23 Return on Investment (ROI) and Rate of Return (ROR) Example 10kW DC ROI ROR Rebate & Incentives Residential Solar System Please consult your CPA or qualified tax consultant for more details. 24. 24 Economic Impact of Renewable Energies in the USA Study Finds U.S. Solar Jobs Grew Nearly 20% In 2013, solar employers are optimistic about 2014, expecting to add another 22,000 jobs over the coming year. by Solar International Staff on Monday 27 January 2014 25. 25 Carbon Dioxide (CO2) Concentration vs. Temperature Change Concentrations of atmospheric greenhouse gases (mostly CO2) and their radiative forcing have continued to increase as a result of human activities. - Third Assessment Report of the IPCC, 2001 26. 26 Environmental Benefits of a 71kW PV System in Houston, TX 27. 27 Why Solar Energy and Wind Power? Reverse CO2 pollution Future for your family Energy Independence Displaces natural Gas Reduce import of foreign Oil Endless supply of SUN ENERGY Electricity Prices/Save/Earn money Increase property Value Energy Security Stabilizes grid by reducing peak power demand $$$$ save 28. 28 Win Win - Win Win USA Stimulate the Economy, Oil dependence, etc.. Win Earth A step in helping to reduce CO2 pollution Win You & Family Save Money, Increase Property Value, etc 29. 29 Gift Solar Energy and Energy Efficiency Audit: Usually, the Solar Energy and Energy Efficiency Audit of a Commercial building costs $250, and costs $150 for a residential. With this voucher you have a chance to receive this service for FREE with NO OBLIGATION. As part of the Solar Energy and Energy Efficiency Audit, our professional team of auditors will: 1) Give the property a review, looking for drafts, leaks, and other things that could lead to increased energy usage. 2) Review your electricity payment monthly for a proposal to zero-out or decrease this payment using latest technology solar photovoltaic system and energy efficiency package. We will help you to maximize your property energy efficiency with an energy efficiency package including solar photovoltaic energy system thus lower or zero-out the monthly electrical bill. There are solar renewable energy rebates from the Federal Government and the energy companies that will soon be phased-out. We will help you to take advantage of these rebates and have the government and the energy company to pay for more than 50% of the cost for the property to be energy independent. Gift for your Interest in Solar RE 30. 30 Photovoltaic Solar Cell TechnologiesPhotovoltaic Solar Cell TechnologiesSourceECN,Petten.nl 31. 31 Thin Film PV Commercially C-Si & Thin Film Photovoltaic Technology Type Appearance Cell Efficiency Module Efficiency Amorphous Silicon Thin Film Flexible / Rigid 7% - 10% 7% - 10% CdTe Thin Film (Cadmium Telluride) Flexible / Rigid 9% - 11% 9% - 11% CIGS Thin Film (Copper Indium Gallium Selenide) Flexible / Rigid 10% - 12% 10% - 12% Multi-Crystalline Silicon Cell Conventional & Selective Emitter 14% - 17% 12% - 15% Mono-Crystalline Silicon Cell Conventional & Selective Emitter 15% - 19% 13% - 17% Metal Wrap Through C-Si MWT 16% - 20% 14% - 18% Emitter Wrap Through C-Si EWT 17% - 22% 15% - 20% Inter-Digitated Back Contact C-Si IBC 22% - 24% ~+20% C-Si PV High EfficiencyHigh Efficiency C-Si PVC-Si PV 32. 32 PV C-Si & Thin Film Chain of Production to Installation Crystalline Silicon Chain of Production to Installation (Residential / Commercial / Utility (IBC)) Wafer production (Silicon to Wafer) Factory 1 Cell Manufacturing (Wafer to Cell) Factory 2 Module Manufacturing (Cell to Module) Factory 3 Cell-Module Manufacturing (Materials to Module) Factory 1 Thin Film Chain of Production to Installation - (Commercial/Utility) 33. 33 Commercially C-Si vs. Thin Film Photovoltaic C-Si Solar Thin Film Solar High power to area ratio (smaller array for same output) Lower output to area ratio (larger array for same output) Higher cost of technology Lower cost of technology Lower cost of installation Higher cost of installation (larger array therefore more labor and materials required for the installation) Requires installation in areas not subject to shading Able to operate in greater light range and with partial shading of the array More suitable to temperate climates Ability to perform well in extreme heat Green = pros black = cons >95% Residential 34. 34 C-Si (Crystalline Silicon) Solar Cell Processing Ag/Al sreen-printed Crystalline Silicon (C-Si) Photovoltaic (PV) solar cells Electrons (-) charge Holes Holes (+) charge _ + DC Theoretical limiting Max-efficiency of C-Si Solar cell = 29% N- type = doped Silicon with Phosphorus PH3 (phosphine gas) = rich in electrons (-) P- type = doped Silicon with Boron B2H6 (diborane gas) = rich in holes (+) 35. 35 C-Si Multi (Poly) Solar Cells (Ag FS, Ag BS Tabbing, Al BSF) Front Back Cell Thickness = 120 um lower grade silicon with more impurity 36. 36 Mono-Crystalline Solar Cell (Ag FS, Ag BS Tabbing, Al BSF) Front Back Cell Thickness = 120 um higher grade silicon with less impurity 37. 37 Al ink forms full covered back electrode and provides passivation. Ag(Al) tabbing ink provide the soldering for module assembly C-Si Solar Cell Contact Formation and Metallization Process Step 1. Contact Formation Solar Wafer PH3 doped + SiN APCVD Front grid print and dry Rear Ag/Al and Al print and dry Flip 80o C/sec 600o C800o C 80o C/sec 800o C600o C Drying Firing Cross section P-Type Silicon PH3 doped N-Type Emitter Ag (frits) Ag/Al Al Al(BSF) Co-fire Step 2. Rapid Thermal Process (RTP) SiN AntiReflective layer Heat ~800 C 38. 38 C-Si PV SE X-Section: C-Si Selective Emitter (SE) (part 1) conventional Ag FS, Ag BS Tabbing, Al BSF Cross Section P-Type Silicon N-Type Emitter N ++ SE 39. 39 Selective Emitter (SE) Process Selective Emitter Process - Why SE is being used? 0 20 40 60 80 100 300 500 700 900 1100 Wavelength (nm) IQE(%) Spire : 60 Ohm/sq Spire : 80 Ohm/sq Increased energy from blue (UV) light 40. 40 C-Si Multi-crystalline Solar Module 156mm156mm 72(612pcs) Multi-Crystalline cells in a module Module Multi-Crystalline Module Encapsulation Glass/EVA/Cells/EVA/TPT Size and Number of cells 156mm156mm 72 (612pcs) Maximum power Wp 230Wp Maximum power voltage(Vmp)V 35.28V Maximum power current(Imp)A 6.52A Open circuit voltage(Voc) V 43.92V Short circuit current(Isc) A 7.26A Model size(mm) mm 195699250 Weight Kg 23.0Kg Operating Temperature C -40C to+85C Warranty 25 years SunTechs 230 Wp Multi-C Module (made in China) 41. 41 C-Si Mono-crystalline Solar Module 125mm125mm 72 (612pcs) Mono- Crystalline cells in a module Module Mono-Crystalline Module Encapsulation Glass/EVA/Cells/EVA/TPT Size and Number of cells 125mm125mm 72 (612pcs) Maximum power Wp 180Wp Maximum power voltage(Vmp)V 35.65V Maximum power current(Imp)A 5.05A Open circuit voltage(Voc) V 44.28V Short circuit current(Isc) A 5.60A Model size(mm) mm 158080845 Weight Kg 15.5Kg Operating Temperature C -40C to+85C Warranty 25 years Advanced Solar Photronics (all American made) 180 Wp Mono-C Module 42. 42 Traditional C-Si Module Manufacturing Process LABOR INTENSIVE In actual use, cells are connected in series, to accumulate sufficient voltage from the 0.6V that a standard cell delivers to deliver usable voltage levels. Industrial grade solar modules are built from individual cells, interconnected with wiring and sandwiched between glass plates and polymer films for protection. Cells Encapsulation of a cell string into a module. From top to bottom: tempered glass sheet, EVA encapsulant, solar cells, EVA encapsulant and tedlar back-sheet foil. EVA EVA (EthyleneVinylAcetate) GLASS TEDLAR Dupont Module Efficiency < 18% High Failure Rate Requires Visual Inspection 65% of module mfg cost 43. 43 Traditional C-Si Module Manufacturing Process LABOR INTENSIVE 44. 44 C-Si Module and operation a. Solar Cell b. In a module, cells are usually connected in series P type silicon Al(BSF) Ag front conductor Neg. charge Ag back Conductor Pos. Charge Tabbing-String interconnected Tin (Sn) coated Copper (Cu) Wire Solar Radiation shadow N type emitter Al reflector SiN (silicon nitride) anti-reflective coating (ARC) Decrease performance of the solar modules 45. 45 IBC Inter-Digitated Back Contact C-Si Solar Cell Advanced Solar Cell Inter-Digitated Back Contact (IBC) SunPower (Cypress Semiconductor) USA company Headquarter San Jose, California Manufacturing plants in 2 Taiwan, 2 Malaysia, 3 Philippines Original application for CPV 46. 46 Inter-Digitated Back Contact (IBC) C-Si PV: Inter-Digitated Back Contact (IBC) C-Si Solar Cell Cu USA Patent Back Contact Solar Cell and Method of Manufacture William P. Mulligan, Michael J. Cudzinovic SunPower Corporation Pub No: US 7,339,110 B1 Date: March 4, 2008 Cu electroplate + Al/TiW/Cu barrier metal semiconductor processes 47. 47 Back Contact C-Si Solar Cells Metal Wrap-Through (MWT) Contact diameter ~ 1 mm 48. 48 EWT Back Contact C-Si PV cell: Back Contact C-Si Solar Cells Emitter Wrap-Through (EWT) USA Patent Contact Fabrication of Emitter Wrap-Through Back Contact Silicon Solar Cell Peter Hacke & James M. Gee Applied Materials Inc Pub No: US 2011/0086466 A1 Date: April 14, 2011 SEM images 49. 49 C-Si Processing Back Contact Solar Cell (SunPower, AMAT) Mono-Crystalline IBC Back Contact cell SunPower Corporation Multi-Crystalline EWT Back Contact cell Applied Materials/Advent Solar 50. 50 IBC, MWT, EWT C-Si PV Pick & Place automated BC Module process: EWT, MWT, I BC Back Contact C-Si PV Module BackSheet Circuit Board by Applied Materials MWT module Efficiency > 18% EWT module Efficiency > 19% IBC module Efficiency > +21% 51. 51 Back Contact C-Si Solar Metal Wrap-Through (MWT) PV module Images from Solland Solar Pick and place back contact module No front string ribbon wires Low failure rate 52. 52 Photovoltaic Thin Film Solar Cell TechnologiesPhotovoltaic Thin Film Solar Cell Technologies 53. 53 Thin Film PV Technologies (Amorphous Si, CIS/CIGS, CdTe, Organic) 54. 54 Amorphous Silicon Thin Film Solar Module Cross Section ~10% Efficiency 55. 55 CdTe Thin Film Module Cross Section Tin Oxide Trans. conductive Oxide Soda lime Glass Substrate Glass Substrate ZnTe Mo CdTe CdS ZnO TCO Glass Front Transparent Front Contact 200 nm Metallic Back Contact 200 nm P-doped (absorber) 4-10 um N-doped (window layer) 100 nm Cadmium Telluride (CdTe) Thin Film Solar Phoenix, AZ ~12% Efficiency 56. 56 CIGS Thin Film Module Cross Section P-Type N-Type Austin, TX Copper Indium Gallium Selenide (CIGS) Thin Film Solar ~14% Efficiency 57. 57 Basic Photovoltaic System (Cell to Module) Solar Cell: The basic photovoltaic device that is the building block for PV modules. Connect Cells To Make Modules. One silicon solar cell produces ~ 0.5 volt. 36 cells connected together have enough voltage to charge 12 volt batteries and run pumps and motors. 72-cell modules are the new standard for grid- connected systems having a nominal voltage of 24-Volts and operating at about 30 Volts. Modules listed to UL1703/UL1730 At 25 years manufacture warranty on solar modules. 58. 58 Basic Photovoltaic System (Module in Series, String in Parallel ) Modules in Series Voltage (V) = Increases Current (I) = same - + - + - + - - -+ + + + - 24VDCnominal 4.4Amps 24VDCnominal 4.4Amps 24VDCnominal 4.4Amps 24VDCnominal 4.4Amps 24VDCnominal 4.4Amps 24VDCnominal 4.4Amps 24VDCnominal 4.4Amps 24VDCnominal 4.4Amps 1 2 3 2 Modules in Series in String 1, 2, and 3 Voltage (V) = 24 VDC x 2 = 48 VDC Current (I) = 4.4 Amps 3 Strings in a Parallel PV Array Voltage (V) = 48 VDC Current (I) = 4.4 Amps x 3 = 13.2 Amps Modules in Parallel Voltage (V) = same Current (I) = increases 48 VDC @ 13.2 Amps 59. 59 Residential use Single-phase (3kW - 10kW) DC/AC mounted inverter Direct Current (DC) to Alternating Current (AC) Inverters DC to AC Power conversion 3-phase (50kW 500kW) DC/AC central inverter 3-phase (3kW -30kW) DC/AC inverter Commercial/Utility use 60. 60 AC Solar Panel with DC-AC Micro-Inverter build-in Panel level DC to AC power conversion. Maximum Panels Per Branch Circuit is 17 panels Benefits: Simplifies system design, with panel level DC to AC power conversion Improves your energy harvest, with power optimization at the panel level Enables detailed energy monitoring of each individual panel Headquarter in Austin, TX 61. 61 Grid Tied PV System Outline Facing South @ 30 degree Tilt in Central Texas 62. 62 Grid Tied PV System Outline Facing South @ ~ 30 degree Tilt in Central Texas 63. 63 Basic Grid Tied PV System w/o Battery Backup Most Popular configuration Residential & Commercial 64. 64 Grid Tied PV System with Battery backup A charge controller, sometimes referred to as a photovoltaic controller or battery charger, is only necessary in systems with battery back-up Charge controllers are selected based on: PV array voltage The controllers DC voltage input must match the nominal voltage of the solar array. PV array current The controller must be sized to handle the maximum current produced by the PV array. 65. 65 Off Grid PV System with Battery Bank Weak point 66. 66 Basic Photovoltaic System (Module to System) PV Module is the basic building block of systems. Can connect modules together to get any power configuration. Listed to UL 1703/1730. PV Array is a number of modules connected in series strings connected in parallel. PV System includes PV modules, Inverters, (perhaps batteries) and all associated installation & Control components On-grid system Grid-tied Grid-connected Utility-interactive Grid-interactive Interactive-system Off-grid Stand -alone 67. 67 Balance of Systems (BOS) BOS listed to UL1741 DC Solar Disconnect DC to AC Solar Inverter Solar Meter AC Solar Disconnect Internet Service Box from 3rd party AC House Mains Panel Usage Meter 68. 68 Why Solar Now ? Incentive Programs for Distributed PV Solar System Soon to be phased-out Local Utility Value of Solar Energy Feed in Tariff (FIT) (Local Utility) Local Utility Rebate Residential (Local Utility) Performance Base Incentive for Commercial (Local Utility) 30% Federal Tax Rebate (USA) Ending 2016 5 year depreciation Federal Tax Savings (USA) Commercial projects Ending 2016 Texas Franchise Tax (corporate tax) savings (Texas) Commercial projects Facing South @ 30 degree tilt angle 69. 69 Investment Comparison Risks and Returns 70. 70 Return on Investment (ROI) and Rate of Return (ROR) Example 70kW DC ROI ROR 71. 71 Win Win - Win Win You & Family Save Money, Increase Property Value, etc Win USA Stimulate the Economy, Oil dependence, etc.. Win Earth A step in helping to reduce CO2 pollution 72. 72 Environmental Benefits of a 10kW PV System in Austin, TX 73. 73 GO SOLARGO SOLAR Tom Brady and Gisele Bundchens Residence Solar System 74. 74 Gift Solar Energy and Energy Efficiency Audit: Usually, the Solar Energy and Energy Efficiency Audit of a Commercial building costs $250, and costs $150 for a residential. With this voucher you have a chance to receive this service for FREE with NO OBLIGATION. As part of the Solar Energy and Energy Efficiency Audit, our professional team of auditors will: 1) Give the property a review, looking for drafts, leaks, and other things that could lead to increased energy usage. 2) Review your electricity payment monthly for a proposal to zero-out or decrease this payment using latest technology solar photovoltaic system and energy efficiency package. We will help you to maximize your property energy efficiency with an energy efficiency package including solar photovoltaic energy system thus lower or zero-out the monthly electrical bill. There are solar renewable energy rebates from the Federal Government and the energy companies that will soon be phased-out. We will help you to take advantage of these rebates and have the government and the energy company to pay for more than 50% of the cost for the property to be energy independent. Gift for your Interest in Solar RE 75. 75 Photovoltaic C-Si Solar Cells ManufacturingPhotovoltaic C-Si Solar Cells Manufacturing SourceECN,Petten.nl 76. 76 Environmental Benefits of a 10kW PV System in Austin, TX 77. 77 C-Si, TF cells and modules Conventional C-Si PV Mono - Multi Conventional C-Si PV Selective-Emitter Back Contact C-Si PV EWT, MWT, IBC TF CdTe PV Flex TF CdTe PV Rigid Back Contact C-Si PV IBC Module TF CIGS PV Flex TF CIGS PV Rigid TF A-Si PV Flex TF A-Si PV Rigid Organic TF PV Module Residential Commercial / Utility Residential 15 kW Largest in US 2014 utility 400 MW CPS energy San Antonio, TX As of April 2013, the largest individual photovoltaic (PV) utility power plants in the world is Agua Caliente Solar Project, (Arizona, over 251 MW, 397 MW DC when completed) 78. 78 Photovoltaic Power Equations for C-Si Solar Cells Metal Interconnect Current Flow Solar Active Area Emitter Diffusion Finger Metal + - + - + - + - + - Current Flow Flow Through MetalPower = I2 R = I2 * (Re + Rc + Rf + Rbb) Re= emitter resistance = Sheet Resistance * L/W Rc = contact resistance = Contact R * area metal Rf = metal resistance finger = sheet resistance * (metal length/metal width) Rbb = bus bar resistance = sheet resistance* (metal length/metal width) W L Schematic symbol of solar cell 79. 79 Selective Emitter (SE) C-Si PV process: C-Si Selective Emitter (SE) (part 2) Selective Emitter is to increase cell efficiencies for both mono- and multi crystalline cells by up to as much as 1 percent in absolute terms Key to performance is reducing losses (Rs & Rsh) 80. 80 Photovoltaic Power Equations (all solar cells) Efficiency , Eta - A solar cell's energy conversion efficiency is the percentage of power converted (from absorbed light to electrical energy) and collected, when a solar cell is connected to an electrical circuit. This term is calculated using the ratio of the maximum power point, PM, divided by the input light irradiance (E, in W/m2) under standard test conditions (STC) and the surface area of the solar cell (AC in m2).(Higher is betterHigher is better) Fill factor (FF) - Another defining term in the overall behavior of a solar cell is the fill factor (FF). This is the ratio of the maximum power point divided by the open circuit voltage (Voc) and the short circuit current (Isc). The fill factor is directly affected by the values of the cells series and shunt resistance. Increasing the shunt resistance (Rsh) and decreasing the series resistance (Rs) will lead to higher fill factor, thus resulting in greater efficiency, and pushing the cells output power closer towards its theoretical maximum. (Higher is better)Higher is better) JSC = Short Circuit current density PM = Peak Power Pmax VOC = Voltage Open Circuit ISC = Current Short Circuit RS = Resistance Series I = Output current (amperes) IL = Photo-generated current (amperes) ID = Diode current (amperes) ISH = Shunt current (amperes) RSH = Shunt resistance I = IL ID ISH 81. 81 Photovoltaic Electrical Properties Rs = Rbulk Si + Remitter + Rcontact + Rgrid line + Rbus bar Key to performance is reducing losses (Rs & Rsh) 82. 82 IBC C-Si PV processes: Inter-Digitated Back-Contact (IBC) Metallization formation Silicon Substrate Aluminum (Al) Layer Titanium-tungsten (TiW) Layer Copper (Cu) Seed Layer Copper Layer Copper Layer Copper LayerCopper Layer Tin (Sn) Layer Tin (Sn) LayerTin (Sn) Layer Tin (Sn) Layer PR N-TypeSilicon Substrate Silicon dioxide (SiO2) Silicon dioxide (SiO2) Silicon dioxide (SiO2) Silicon dioxide (SiO2) Aluminum (Al) Layer Titanium-tungsten (TiW) Layer Copper (Cu) Seed Layer Copper Layer Copper Layer Copper LayerCopper Layer Tin (Sn) Layer Tin (Sn) LayerTin (Sn) Layer Tin (Sn) Layer PR PR Sputter, or Plating of Barrier/Seed Layers Al/TiW/Cu Electrolytic Plating Layer Semiconductor Copper Electroplating Process N+ = Phosphorus PH3 (phosphine gas) = rich in electrons (-) P+ = Boron B2H6 (diborane gas) = rich in holes (+) 83. 83 Photovoltaic Power Equations (all solar cells) Efficiency , Eta - A solar cell's energy conversion efficiency is the percentage of power converted (from absorbed light to electrical energy) and collected, when a solar cell is connected to an electrical circuit. This term is calculated using the ratio of the maximum power point, PM, divided by the input light irradiance (E, in W/m2) under standard test conditions (STC) and the surface area of the solar cell (AC in m2).(Higher is betterHigher is better) Fill factor (FF) - Another defining term in the overall behavior of a solar cell is the fill factor (FF). This is the ratio of the maximum power point divided by the open circuit voltage (Voc) and the short circuit current (Isc). The fill factor is directly affected by the values of the cells series and shunt resistance. Increasing the shunt resistance (Rsh) and decreasing the series resistance (Rs) will lead to higher fill factor, thus resulting in greater efficiency, and pushing the cells output power closer towards its theoretical maximum. (Higher is better)Higher is better) JSC = Short Circuit current density PM = Peak Power Pmax VOC = Voltage Open Circuit ISC = Current Short Circuit RS = Resistance Series I = Output current (amperes) IL = Photo-generated current (amperes) ID = Diode current (amperes) ISH = Shunt current (amperes) RSH = Shunt resistance I = IL ID ISH 84. 84 How the manufacturing process affects the parameters 1. Saw damage removal (wet etch) 2. Texturization (wet etch) 3. Anti-reflective coating (ARC) (sputtering) 4. Emitter formation (thermal diffusion) 5. Edge isolation (laser etch) 6. Back surface formation (screen printing) 7. Front contact formation (screen printing) 8. Contact firing (furnace) Voc Isc Fill Factor Metallization Focus on step 6, 7, 8 Edge Isolation can also be done after step 8 85. 85 Solar Cell parameters (Voc, Isc, FF, Efficiency, Rs, Rsh) Voc (Higher is best) Open Circuit Voltage : determined by purity of the cell, surface passivation (SiNx passivation and Al-BSF passivation) Isc (Higher is best) Short Circuit Current : determined by purity of the cell, amount of sunlight in, conversion efficiency of the cell (fewer recombination of electrons is best) FF (Higher is best) - Fill Factor: Determined by shunt resistance Rsh (Higher is best) and series resistance Rs (Lower is best). Efficiency (Higher is best) : Determined by Voc, Isc and FF Crystalline silicon devices are now approaching the theoretical limiting efficiency of 29%. 86. 86 How to look at the data Comparing data: FF, Voc, Isc, Efficiency, Rsh: Higher is better Rs, Rc: Lower is better Voc: Al-BSF material and processing Isc, FF: Ag FS and processing FF affected by Rs and Rsh Efficiency affected by Voc, Isc and FF 87. 87 Factors for Voc Impurities in the solar cell are on the surface and inside the wafer Surface passivation is the process by which impurities on the surface are reduced so charge lives longer Saw damage and texturing create such impurities. Passivated by SiN coating (front) and Al-BSF paste (back) 88. 88 Rshunt (Rsh) Shunt Resistance (Rsh): A low-resistance connection between two points in an electric circuit that forms an alternative path for a portion of the current. High Rsh is best. Low shunt resistance causes power losses in solar cells by providing an alternate current path for the light-generated current. Such a diversion reduces the amount of current flowing through the solar cell junction and reduces the voltage from the solar cell. Shunts can be created during processing by residues of the emitter at the cell edge, by material induced, and by scratches. Shunts can also occur below grid lines due to the metallization. Shunts due to the metallization - Front metallization shunts become difficult to avoid when low contact resistance (Rc) values need to be achieved. Shunts due to scratches - handling issue Material induced shunts - material contamination induced during crystal growth Edge shunts - poor edge isolation 89. 89 Rseries, Rcontact and Isc - Front grid tradeoffs Emitter Base resistance (Re) Lateral Emitter resistance (RL) Gridline/Emitter contact resistance (RC) Gridline resistance (RG) RSeries = RG + RC + RL + RE Need to maximize Fill Factor (FF) by reducing RG, RC from gridline (RL, Re determined by wafer) Contact resistance (Rc) > 50% of resistance in best cells, largest impact on overall resistance. Contact resistance is highly specific to firing conditions Need to maximize Isc by reducing lines and linewidth 90. 90 Key questions we need to know from customers What is your Voc/Isc/Efficiency/FF baseline in production? (What are future targets?) What is your emitter sheet resistance? What line width (Critical Dimension CD), aspect ratio are you targeting? We have shown that efficiency can be increased with Al-BSF in a DoE to optimize process conditions in our presentation, can we start with an Al-BSF evaluation with your company? Our backside Ag Tabbing paste is formulated to perform best with our Al-BSF, can we send a sample of our Ag Tabbing with the Al-BSF With these 5 questions to the customers we can have high chance of succeed in an evaluation. Front side Ag Back side Al-BSF and Ag Tabbing 91. 91 Lets analyze the Evergreen Solar DoE data together Split Al Dry Firing N Eff Voc Isc FF Rs Rsh RBB RDD 5 Toyo 200/220 875/865 495 15.12% 0.6031 3.945 76.70 0.0068 208 0.039 0.0091 1 Dongjin-1 200/220 875/865 508 15.20% 0.6057 3.953 76.61 0.0068 129 0.034 0.0135 3 2 Sun-3 200/220 875/865 497 15.14% 0.6051 3.928 76.88 0.0062 163 0.034 0.0102 3 2 Sun-4 200/220 890/880 506 15.14% 0.6053 3.926 76.88 0.0063 166 0.033 0.0101 7 5 Sun-5 200/220 905/895 512 14.96% 0.6049 3.914 76.22 0.0076 161 0.033 0.0107 4 3 Sun-6 160/180 875/865 512 15.13% 0.6053 3.924 76.87 0.0061 176 0.034 0.0102 2 1 Sun-7 160/180 475/525/625/650/855/865 513 15.15% 0.6049 3.925 76.99 0.0060 157 0.033 0.0104 6 4 Sun-8 160/180 475/525/625/650/870/880 505 15.11% 0.6052 3.914 76.94 0.0062 157 0.033 0.0104 5 Dongjin-2 180/200 475/525/625/650/870/880 470 15.12% 0.6051 3.940 76.51 0.0069 97 0.032 0.0142 ComparingDongjin-1andSun-7:Efficiencydeltais.05%ismainlyduetobothlowerVocandIsc.HoweverVocdeltaisonly.8mVor.0008VsoefficiencyismainlyaffectedbyIscwith Sun-7islowerthanDongjin-1.Withthisdataweareverycompetitiveasaleadfreetoaleadedmaterial.Thisbecomeaprice,logistic,supportplayandfocusonleadedmaterialhas largerCostofOwnershipduetowastedisposalofpasteandprocess 92. 92 Good Installation Practices Wire Management 93. 93 Good Installation Practices Support Structure and Attachment 94. 94 Good Installation Practices Nice Work 95. 95 Good Installation Practices Nice Work 96. 96 Good Installation Practices Nice Work 97. 97 Balance of PV Systems (BOS) Inverter (On-Grid, Grid-Tied) Inverters take care of four basic tasks of power conditioning: Invertersarethebrainsandthepointofconnectiontotheloads ConvertingtheDCpowercomingfromthePVmodulesorbatterybanktoACpower EnsuringthatthefrequencyoftheACcyclesis60cyclespersecond Reducingvoltagefluctuations EnsuringthattheshapeoftheACwaveisappropriatefortheapplication,i.e.apuresinewavefor grid-connectedsystems(VaryinqualitySquareWave,Mod-SquareWave,SineWave) Criteria for Selecting a Grid-Connected Inverter The following factors should be considered for a grid-connected inverter: AUL1741listingoftheinverterforuseinagrid-interactiveapplication ThevoltageoftheincomingDCcurrentfromthesolararrayorbatterybank. TheDCpowerwindowofthePVarray.MaximumDCinputcurrentasregulatedbytheinverter Characteristicsindicatingthequalityoftheinverter,suchashighefficiencyandgoodfrequencyand voltageregulation Additionalinverterfeaturessuchasmeters,indicatorlights,andintegralsafetydisconnects Manufacturerwarranty,whichistypically10years(forrebateatleast10years) MaximumPowerPointTracking(MPPT)capability,whichmaximizespoweroutput Maximumcontinuousoutputpowerat40degreeC MaxACOutputCurrent-Maximumrateofelectricityflow,inamperes,thattheinvertercanexport 98. 98 Balance of PV Systems (BOS) Inverter (On-Grid, Grid-Tied) Waveform Types Alternatingcurrent(AC)signalsaredescribedintermsoftheirwaveform SquareWave:Onlyappropriateforsmallresistiveheatingloads,somesmallappliances& incandescentlight ModifiedSquareWaveorQuasi-SineWaveorModifiedSineWave:Appropriateforwiderangeof loadsincludingmotors,lights,andstandardelectronicequipment SineWave:Bestforsensitiveelectronicdevicesastheyprovidethehighestqualitywaveform AC Waveforms 99. 99 Balance of PV Systems (BOS) Inverter (On-Grid, Grid-Tied) Key Specifications for Grid-Tied Inverter: WaveformType PeakEfficiency VoltageInput OperatingRange MPPTRange Maximum MinimumtoTurn-on CurrentInput OperatingRange Maximum OutputVoltage120/240VACandOutputFrequency50Hz/60Hz OutputContinousPower-ACTotalConnectedWatts SurgeCapacity 100. 100 Balance of PV Systems (BOS) Inverter (On-Grid, Grid-Tied) Maximum Power Point Tracking: Voltage Range Definition:Thevoltagewindowwithinwhichaninvertercanmaximizearrayoutputpowerbyfinding thekneeofthearraysI-Vcurve Keepthemaximumpowerpoint(MPP)ofanarraywithintheinvertersMPPTwindowthrougha widevarietyofoperatingconditions AmbienttemperaturehasthemostdirectcorrelationtoPVoutputvoltage.Calculatethe expectedoperatingvoltageattheaveragehightemperatureforthesite TheexpectedarrayMPPvoltageneedstobecomfortablywithintheinvertersMPPTrange Anadditionalvoltagecushionfortheeffectsofmodulepowertolerance,degradationandhigh temperatureconditions Maximum Input Current Definition:ThemaximumDCinputcurrentasregulatedbytheinverter DesignersshouldusearrayshortcircuitcurrentforallNECcalculationsontheDCsideofthe system,notthemaximuminverterinputcurrent Oneplacethatdesignerswillusethemaximuminverterinputcurrentisforvoltagedrop calculations 101. 101 Balance of PV Systems (BOS) Inverter (On-Grid, Grid-Tied) Number of String Inputs Definition:ThetotalpairsofPVpositiveandPVnegativeinputterminalplugsprovidebythe manufacturer ThenumberofinputstringsdeterminesthemaximumnumberofPVsourcecircuitsthatcanbe landedintheinverterwithoutparallelinganystringsexternally Typicalastheinvertercapacityincreases,sodoesthenumberofterminalsprovidedinsidethe inverter.Butitisoftenconvenientandsometimesnecessarytoparallelstringsinthefieldbefore pullingconductorstotheinverter.Fusedcombinerboxesaretypicallyusedforthispurpose. KeepinmindthatPVsystemswithmorethantwoparalleledstringsperinvertermayrequire seriesstringfusing. Number of Independent MPPT Circuits Definition:TotalnumberofindependentMPPtrackinginputcircuitssupportedbyagiveninverters design. MostcurrentlyavailableinvertersofferasingleMPPTcircuitandrequireidenticalstringinput characteristics UnlessaninverterwithmultipleMPPTcircuitsisspecified,arraystringswithdissimilarnumbers ormodelsofPVsordifferentstringorientationsshouldfeedmultipleinverterstomaximize energyharvest 102. 102 Balance of PV Systems (BOS) Inverter (On-Grid, Grid-Tied) CEC Rated Maximum Continuous Output Power Definition:Themaximumcontinuousoutputpowerat40degreeCasreportedontheCECinverter performancetestsummary. Ratedcontinuousoutputpowerisoneoftheinvertercharacteristicspublishedinthetestreports fortheCECandpublishedonmanufacturerscutsheets. Designerswillconsideraninvertersratedoutputpowerwhendeterminingthemaximumorideal arraysizefortheirapplication. Maximum AC Output Current Definition:Themaximumrateofelectricityflow,inamperes,thattheinvertercanexporttotheutility grid. MaximumACOutputCurrentisusedforsizingwiringandtheminimumovercurrentprotection device(OCPD)ratingontheinverteroutput. PerNECArticle690.64(B)PVsystemcurrentsareconsideredcontinuous Fordesignpurposes,thismeansthattheminimumOCPDratingforinverteroutputcircuitsis 125%ofthemaximumoutputcurrent.BesuretoupsizetheACOCPDtoastandardsize breakerforuse,withoutexceedingthemaximumOCPDratingfortheinverter. 103. 103 Balance of PV Systems (BOS) Inverter (On-Grid, Grid-Tied) Total Harmonic Distortion Definition:Thepercentage(%)ofthetotalcurrentinacircuitthatisatfrequencieshigherthanthe fundamentalwaveformfrequency.THDdescribesthepowerqualityenteringtheutilitygridfroman interconnectedinverter. TheIEEEistheentityresponsiblefordefiningthepowerqualitystandardsforgridtiedinverters. Becausegrid-synchronousinvertersmeetorexceedthepowerqualityfortheutilitygrid,system designersrarelyneedtoconsiderTHD.Inrarecases,inverterTHDmaycauseinterferencewith otherloads,suchasinterferencewithapowerlinecommunicationcarriersignalfora sophisticatedlightingcontrolsystem. Peak Efficiency Definition:Themaximumpercentage(%)ofDCinputpowerinvertedtoACoutputpowerasmeasured inbenchtestsandreportedbythemanufacturer Everyinverteristestedatarangeofinputvoltagesandpowerlevels.Theresultsofthesetests areoftensummarizedasasingleefficiencycurvethatispublishedonaninvertercutsheet Peakinverterefficiencydefinesanisolateddatapointonaverydynamicscaleandisprimarilya marketingpointformanufacturerswithminimaldesignimplications. Payattentiontothepowerinputrangewiththehighestoverallefficiencyortothedifferent efficiencycurvesresultingfromdifferentinputvoltages.ThisinformationisincludedintheCEC inverterperformancetestsummaries. 104. 104 Balance of PV Systems (BOS) - Inverter Stand Alone (off-grid) Inverters: VaryinqualitySquareWave,Mod-SquareWave,SineWave MaketheirownACsignaloutputDonotneedtheutility Mustbeconnectedtobatteries Arelessexpensivethanutilityinteractive AUL1741listingoftheinverterforuseinagrid-interactiveapplication ThevoltageoftheincomingDCcurrentfromthesolararrayorbatterybank. TheDCpowerwindowofthePVarray.MaximumDCinputcurrentasregulatedbytheinverter Characteristicsindicatingthequalityoftheinverter,suchashighefficiencyandgoodfrequencyand voltageregulation Additionalinverterfeaturessuchasmeters,indicatorlights,andintegralsafetydisconnects Manufacturerwarranty,whichistypically10years(forrebateatleast10years) MaximumPowerPointTracking(MPPT)capability,whichmaximizespoweroutput Maximumcontinuousoutputpowerat40degreeC MaxACOutputCurrent-Maximumrateofelectricityflow,inamperes,thattheinvertercanexport 105. 105 Photovoltaic Performance Parameters V(voltage) = I(Current) x R(Resistance) = Volts (V symbol) I = V / R = Ohms (Omega symbol) R = V / I = Ampere (A symbol) Power (P) (watt) = I x V Energy (kWh) = P x Time Pmp = Imp x Vmp Standard Test Conditions: (STC): 1000W/m2solarirradiance,25 degreeCPVcell/module temperature,1.5AirMass(solar noon) f =EmpiricalDCtoACfactor=0.77 forGridConnected(GC) f=0.66forOff-Grid/GCw/batteries 106. 106 Current varies with Irradiance SiemensSP75SolarModulePerformanceatDifferentIrradiances Sunlightincrease=Currentincrease 107. 107 Impact of Temperature on a Solar Cell SiemensSP75SolarModulePerformanceatDifferentCellTemperatures DifferentPVmoduletechnologieswillhavedifferenttemperaturecoefficients Asaruleofthumb:-0.5%/degreeC(Temp.Increase=VoltageDecrease) 108. 108 Irradiance and Irradiation Solar Irradiance =Solarpowerperunitarea=W/m2or kW/m2 Solar Irradiation =thetotalirradianceovertime Irradiation=ameasurementofEnergyinsunlight=Watt- hours/m2orkWh/m2 Peak Sun Hours = anequivalent measureoftotalsolarirradiationina daywhereirradiancevariesthroughout theday Reference (Good Book): PhotovoltaicSystems(2nd Edition)byJamesP.Dunlop Maximum Power Point Tracking Currentdecreaseas Irradiancefallsinthe afternoonthuschange MaximumPower 109. 109 Power and Energy Compared Power Energy InstantaneousmeasurementaRATE MeteredoveraperiodoftimeaCOUNT InElectricalterms: Measuredin Watts(W) Kilowatt(kW) InElectricalterms: Measuredin Watt-hours(Wh) Kilowatt-hours(kWh) Calculations: Power=VxI P(watts)=VoltagexCurrent Calculations: Energy=Power(watts)xTime(hours) Energy=PxTime(h) Irradiance: WattsperSquareMeter=W/m2orkW/m2 Irradiation: Watt-hours/m2orkWh/m2 PeakSun: 1000W/m2=PeakSun=1kW/m2 PeakSunHour: 1000watt-hours/m2=1kWh/m2=1PeakSunHour PVSystemEnergyperDayinkWhs=[(WattsDCSTC)x(f)x(SH)=wattsinAC where: STC=PVArrayratinginWattsDCSTC f=de-ratingfactor(DCtoAC)~77% SH=Sun-HoursperdaygiventhePVarraytilt=Watts/m2measurewiththeirradiance meteraimedatthesunwiththesametiltasthearraytilt Multiplyresultbydaysinmonth=~monthlyperformance Multiplyresultby365days=~annualperformance 110. 110 USA Average Daily Solar Radiation Per Month by NREL 111. 111 Sun Path Chart for 30 degree North Austin, TX 112. 112 NREL - PV Watts Calculation data NRELPVWatts:AperformanceCalculatorforGrid-ConnectedPVSystems http://rredc.nrel.gov/solar/calculators/pvwatts/version1/ 113. 113 Required Information for Permit Site Plan Site plan showinglocationofmajorcomponentsontheproperty.Thisdrawingneednotbe exactlytoscale,butitshouldrepresentrelativelocationofcomponentsatsite. 114. 114 Required Information for Permit Electrical Diagram Electrical diagram showingPVarrayconfiguration,wiringsystem,overcurrentprotection, inverter,disconnects,requiredsigns,andacconnectiontobuilding. 115. 115 Required Information for Permit Specifications Sheets, Install Manuals, One-Line Diagram Specification sheets and installation manuals (ifavailable)forallmanufactured componentsincluding,butnotlimitedto,PVmodules,inverter(s),combinerbox,disconnects, andmountingsystem. One-Line Diagram shouldhavesufficientdetailtocallouttheelectricalcomponents,wire types/sizes,numberofconductors,andconduittype/sizewhereneeded. 116. 116 Codes / Standards / Permits / Guidelines ObjectivesoftheGuidelinesaretofacilitatetheinstallationofsafe systemsataminimumofcost.Provideguidanceonwhatinformation shouldbeprovidedforpermitting.Discouragefly-by-nightsfromthe industrybymakingthemdoallthestepsthatagoodinstallerdoes. Raisetheprofessionalismofinstallingcontractors. Originallybasedonthe2002NationalElectricalCode(NEC),Article 690,andvariousguidelinesfromafewjurisdictionsandusinginput fromseveralexperiencedprofessionalsincludinginstallersand inspectorsthroughouttheU.S.Ithassincebeenupdatedin2008for the2005NEC. Approachistoestablishasetofbestpracticesthatwillhelpensure thatthepublicsafetyispreservedwhenaninstallationmeetsthese guidelines. 117. 117 Applicable Codes and Standards for PV Systems National Electrical Codes (NEC) Article690-SolarPhotovoltaicSystems NFPA70 UL Standard: 1703-Flat-platePhotovoltaicModulesandPanels 1741-StandardforInverters,Converters,ControllersandInterconnection SystemEquipmentforUseWithDistributedEnergyResources IEEE 1547 -StandardforInterconnectingDistributedResourcesw/ElectricPower Systems Building Codes ICC, ASCE 7-05 Uniform Solar Energy Code ICC Electrical Equipment Listing Recognizedtestinglaboratoriesinclude: 1. UL 2. ETLSemko(Intertek) 3. CSA 4. TUV 118. 118 National Electrical Code (NEC) Sections Applicable to PV Systems Article110:RequirementsforElectricalInstallations Chapter2:WiringandProtection(MostoftheChapter) Article250:Grounding Chapter3:WiringMethodsandMaterials(MostoftheChapter) Article300:WiringMethods Article310:ConductorsforGeneralWiring Article480:StorageBatteries Article690:SolarPhotovoltaicSystems I.General(definitions,installation) II.CircuitRequirements(sizing,protection) III.DisconnectMeans(switches,breakers) IV.Wiringmethods(connectors) V.Grounding(array,equipment) VI.Markings(ratings,polarity,identification) VII.ConnectiontoOtherSources VIII.Storagebatteries IX.Systemsover600Volts 119. 119 PV Incentive Programs Varies from each local Utility Providers Federal Tax Incentive 30% LocalUtilitySolar Performance-Based Incentive Program (PBI) (usuallylimitedto 200kW AC @ STC, derate factor of 77%) CommercialPVPBIprogramProcedures,QualificationsandGuidelines. LocalUtilityFeed-in-Tariff (FIT)(usually1kW to 20 kW PVsystem)isapolicy mechanismdesignedtoaccelerateinvestmentinrenewableenergytechnologies.It achievesthisbyofferinglong-termcontractstorenewableenergyproducers,typicallybased onthecostofgenerationofeachtechnology.Technologiessuchaswindpower,for instance,areawardedalowerper-kWhprice,whiletechnologiessuchassolarPVandtidal powerareofferedahigherprice,reflectinghighercosts.Inaddition,feed-intariffsoften include"tariffdegression",amechanismaccordingtowhichtheprice(ortariff)ratchets downovertime.FITvariesfromeachUtilityProviders. LocalUtilityRebate(usually1kW to 20 kW PVsystem)=[NumberofPVmodules]x [STCRating/module(Watts)]x[CECratedInverterEfficiency]x[RebateLevel(thisvaries fromeachUtilityProviders)] HomeEnergyEfficiencyRequirements HomeWaterHeatingSystemRequirements ResidentialSolarPVRebateProgramProcedures,QualificationsandGuidelines 120. 120 Wholesales cost of Solar System ResidentialRetailperWattinstalled=$3.15perWatt CommercialRetailperWattinstalled=$2.45perWatt Wholesalecostforasolarsysteminstalled Items CostperWatt DCSolarPanels $0.80 ACSolarPanelsw/Micro-inverter $1.40 DC-ACInverter $0.32 Racking $0.28 BalanceofSystem(BOC) $0.25 Labor(installationcrew) $0.22 ElectricalPanel $1500.00perpiece(onlyifmandatory) MasterElectrician $500.00perjob Permits/Documentation $400.00perjob Rebates/Documentation $0.10 SolarCalculation/Invoicing $0.10 FinancingCost 2-7%ofloanamount(notcashsale) SalesCommission $0.20(insidesalespeople) Mormonssalescommission $0.35(Mormonssales) Net Profit = $ 0.73 / Watt