Demystifying Rooftop Solar

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Douglas Powell
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1 Demystifying Rooftop Solar Week 2 OLLI at Illinois Study Group Fall :30 pm Tuesdays Blue Room

2 Demystifying Rooftop Solar Study Group From Today s MidWestEnergy.com news 11/14/2017 Rooftop Solar 2 (Illinois Commerce Commission)

3 Proposed Session Outline 1. Overview of solar power in general. How PV works with demos. Types of solar electric residential systems and their general characteristics. How they are rated and specified. 2. Details of rooftop solar systems, including panels, roof mounting, inverter types, grid tie, structural issues, tracking, etc. 3. Planning and installation: Site issues, shading, climate, sizing and capacity, esthetics, regulations, roof mounting systems. Satellite photo surveys. 4. Economics. Cost and cost trends, incentives, projecting energy savings, payback modeling and scenarios, internal rate of return, effects on real estate values, financing alternatives. 5. Performance monitoring and results, environmental impacts (positive and negative), maintenance issues. Lessons learned. Combinations with EV autos or Geothermal Heating/Cooling. 11/14/2017 Rooftop Solar 3

4 11/14/2017 Rooftop Solar 4

5 Czochralski Major Silicon Solar Cell Types Poly-Crystalline Cast Ingots Single Crystal Boule Mono-C % Si + Dopant Poly-C or Multi-C Saw off wafers Saw off square slices 11/14/2017 Rooftop Solar 5

flexible plastic Must be well protected from moisture Shorter life than Silicon

6 Thin Film Solar Modules Very thin (~ 1 m) deposited semiconductor films CdTe (Cadmium Telluride) CIGS (Copper Indium Gallium Selenide) Substrates: glass or flexible plastic Must be well protected from moisture Shorter life than Silicon Lower efficiency but improving Glass CdTe Panels Flexible CIGS Panel 11/14/2017 Rooftop Solar 6

7 Historical Improvement of Laboratory Solar Cell Efficiencies Poly-Si Mono-Si (Cu In Ga Se) Fraunhofer Photovoltaics Report 12 July /14/2017 Rooftop Solar 7

8 Current (Amps) Varying the Load on a Solar Cell - + V Power Curve Maximum Power Point MPP I Amps Power Formula: Power(watts) = Amps x Volts P = I V 11/14/2017 Rooftop Solar 8

9 MMP Varies with Solar Intensity and Module Temperature [60 cell module] Full Sunlight 60% Sunlight I-V Curves vs Temperature -10 C 50 C 20% Sunlight 11/14/2017 Rooftop Solar 9

10 Direct Types of Solar PV Systems Example: Attic Fan Standalone Off-Grid Yard Light Grid-Tied Utility Interactive -$ Battery Bi-Modal -$ $ Battery Battery $ Drivers: Cheaper Li Ion Batteries Unfriendly Utilities 11/14/2017 Rooftop Solar 10

11 DC AC No Battery: The Grid is the Storage When Grid fails, Solar shuts down for safety. 11/14/2017 Rooftop Solar 11

12 String Inverter System Two Different Inverter Approaches DC ~ 300 Volts ~ 10 Amps Inverter Micro-Inverter System DC AC 240 V AC Key Inverter Functions: Run Solar Panels at MPP* Convert resulting DC to AC Report Status via Internet * MPP = Maximum Power Point AC 240 V 11/14/2017 Rooftop Solar 12

13 Optimizer Inverter System Yet Another Inverter Approach: Optimizers DC 350 Volts ~ 10 Amps (varies) Special Inverter Optimizer Unit Behind Each Panel Functions: Operates each panel at own MPP* Adjusts Output Voltage Reports status to main Inverter AC 240 V Special Inverter Functions: Coordinate Optimizers Convert DC to AC Report Status to Cloud Individually for each panel * MPP = Maximum Power Point 11/14/2017 Rooftop Solar 13

14 These are collectively called Module Level Power Electronics (MLPE) Systems Micro-Inverter System Optimizer Inverter System DC AC DC ~ 300 Volts ~ 10 Amps Special Inverter AC 240 V AC 240 V 11/14/2017 Rooftop Solar 14

15 Acronyms & Units PV PhotoVoltaic CSP Concentrated Solar Power kw kilowatt (1000 watts) -- measure of Power kwe kilowatt electric kwh Kilowatt-hours (measure of Energy) MPP Maximum Power Point MPPT Max Power Point Tracking MLPE Module Level Power Electronics 11/14/2017 Rooftop Solar 15

16 System Components 1. Solar PV Modules 2. Roof Mounting Systems 3. Inverters 4. Wiring & Meters 5. Internet Communications Balance of System BOS 11/14/2017 Rooftop Solar 16

17 System Components 1. Solar PV Modules Overview Solar Shingles Regular Modules 2. Roof Mounting Systems 3. Inverters 4. Wiring & Meters 5. Internet Communications Balance of System BOS 11/14/2017 Rooftop Solar 17

18 Key Ratings for a Solar Panel (Module) Width Typical Values 39 (1.00m) 65 (1.64m) 300 watts 14-22% %/Year Width Length Nominal DC Power ( Nameplate Power ) DC Output at MPP with 1000 Watts/m 2 Sunlight Pointed directly at sun T = 25 C Lab Measurement Efficiency (%) Fraction of sunlight converted to DC power Number of Cells Degradation Rate Down 12% in year 25 11/14/2017 Rooftop Solar 18

19 Rating a Solar Array Width 28 Typical Values 39 (1.00m) 65 (1.64m) 300 watts 16-21% %/Year 1 Module Width Length Nominal DC Power ( Nameplate Power ) DC Output at MPP with 1000 Watts/m 2 Sunlight Pointed directly at sun T = 25 C Lab Measurement Efficiency (%) Fraction of sunlight converted to DC power Number of Cells Degradation Rate Example Values W 8.4 kw (DC) Number of Modules N Module Power Rating P DC Nominal DC System Power ( Nameplate System Power ) DC Output at MPP with 1000 Watts/m 2 Sunlight Pointed directly at sun T = 25 C Simply N P DC 11/14/2017 Rooftop Solar 19

20 Module Construction 11/14/2017 Rooftop Solar 20

21 Shingle Style Modules A type of Building Integrated PV device BIPV Others: Semitransparent Window PV devices Wall PV coverings 11/14/2017 Rooftop Solar 21

22 BIPV: Building Integrated PV Shingle Style Modules 1 Certainteed Apollo II Mono-Crystalline Silicon 63 watts 14 cells 47 inches 11/14/2017 Rooftop Solar 22

Powerhouse 3 Poly-Crystalline Silicon (probably) Coming Mid 2018 Sold only through RGS

23 BIPV: 2a Shingle Style Modules Dow Chemical Powerhouse I, II CIGS Thin Film -- low efficiency About 1000 installations from 2011 Discontinued ~2016 2b Dow Chemical Powerhouse 3 Poly-Crystalline Silicon (probably) Coming Mid 2018 Sold only through RGS Solar Installation Co. Note: Picture is probably an earlier CIGS version 11/14/2017 Rooftop Solar 23

BIPV: Shingle Style Modules 3 Tesla Solar Roof Tiles

Tempered Glass Cells Underneath Cell Type: Secret

Active Tiles and Dummy Tiles, which look identical.

24 BIPV: Shingle Style Modules 3 Tesla Solar Roof Tiles (Elon Musk) Just introduced, may be available 2018 Tempered Glass Cells Underneath Cell Type: Secret (Probably mono- Crystalline Silicon) Unique idea: Active Tiles and Dummy Tiles, which look identical. Most of roof would be glass Dummy Tiles. 11/14/2017 Rooftop Solar 24

25 BIPV: Solar Shingle Issues Pricey Improved esthetics Wiring and maintainability concerns Many more electrical connections, inaccessible Require exact replacement tiles No air circulation: Run hot? Probably Series String Inverters only Module Level Power Electronics (MLPE) not easily incorporated 11/14/2017 Rooftop Solar 25

26 Illinois Law 765 ILCS 165/ Homeowners Energy Policy Statement Act (2011) Homeowners Associations, etc., may not prevent rooftop Solar Energy Installations, including both thermal and PV. They may impose architectural standards which do not impede the function However, Wind Energy collection could be prohibited. 11/14/2017 Rooftop Solar 26

27 Regular Modules Width Typical Values 39 (1.00m) 65 (1.64m) watts 15-22% %/Year yrs 0.5% Width Length Nominal DC Power ( Nameplate Power ) Efficiency (%) Number of Cells Degradation Rate Warranties Workmanship Degradation (25 yr) 11/14/2017 Rooftop Solar 27

28 Module Efficiencies by Manufacturer <15% > 21% ET Solar Grape Solar Heliene LG Mission Panasonic Solaria EnergySage.com SunPower 11/14/2017 Rooftop Solar 30

29 Solar Panel Brand Power Poly/ Price per Country of Eff. % Watts Mono Watt Manufacture Vendor Yingli YLM M 17.00% $0.55 Beyond Oil Solar Q CELLS Q.PLUS BFR-G P 16.50% $0.57 The Solar BiZ Talesun Energy TP672P/ P - $0.58 The Solar BiZ Upsolar UPM255P 255 P 15.70% $0.59 ECO Distributing REC Solar TwinPeak 280TP2 280 P 16.80% $0.60 Beyond Oil Solar Canadian Solar CS6K-280M 280 M 17.40% $0.60 Beyond Oil Solar Hanwha Q Cells BFR-G % $0.62 ECO Distributing Thaisun TSG72-300P 300 P 15.46% $0.64 ECO Distributing Csun Solar CSUN P 305 P 16.26% $0.65 The Solar BiZ REC TwinPeak 280TP 280 P - $0.68 Beyond Oil Solar Canadian Solar CS6X-320P 320 P 15.90% $0.68 ECO Distributing SolarWorld SW 285 ALL BLACK 285 M 17.00% $0.68 The Solar BiZ Canadian Solar CS6X-305P 305 P 15.90% $0.73 ECO Distributing Astronergy CHSM6612P P 15.80% $0.77 Wholesale Solar EcoSolargy 240 P 14.00% $0.87 SolarPanelsOnline Suniva OPT M 16.73% $0.87 The Solar BiZ Suniva OPT Mono 275 M 16.60% $0.88 Beyond Oil Solar Conergy 240 P 14.40% $0.96 SolarPanelsOnline Suniva OPT M 17.18% $0.96 Wholesale Solar Conergy 250 P 15.20% $0.98 SolarPanelsOnline Canadian Solar CS6X-280P 280 P 14.59% $1.00 SolarPanelsOnline Canadian Solar CS6P-245M 245 P 15.23% $1.02 SolarPanelsOnline SolarWorld SW295 Plus Silver Mono 295 M 17.59% $1.02 Wholesale Solar 11/14/2017 Suniva OPT Rooftop 285 Solar M 17.34% $1.05 Wholesale Solar 31 Sample of Low end Solar Panel Offerings [sorted by retail price] Note: All US made panels use imported cells. ecobusinesslinks.com/surveys/ free-solar-panel-price-survey/

30 Examples of Solar Modules Plain Aluminum Frames Bypass Diodes Black Anodized Aluminum Frames MLPE ( Inverter or Optimizer) 72 Cell 60 Cell 60 Cell (Front) (Back) (Front) (Back) 11/14/2017 Rooftop Solar 32

72 Cell 60 Cell Examples of Solar Modules Plain Aluminum Frames Bypass Diodes

As a byproduct, the Bypass Diodes also permit current from other parts of the

31 72 Cell 60 Cell Examples of Solar Modules Plain Aluminum Frames Bypass Diodes across each group of 20 or so cells prevent destructive reverse voltages on cells which are heavily shadowed. This prevents module damage and possibly fires. As a byproduct, the Bypass Diodes also permit current from other parts of the module which are not shadowed to continue to flow, bypassing the darkened cell(s). They also allow other modules in the string to operate, albeit with some loss of power. (Front) (Back) Bypass Diodes Black Anodized Aluminum Frames 60 Cell (Front) MLPE ( Inverter or Optimizer) (Back) 11/14/2017 Rooftop Solar 33

32 Hundreds of Bulbs in Series Effect of Shade/Blockage Hundreds of Cells in Series Full Illumination: all cells contributing equal current. + _ 11/14/2017 Rooftop Solar 34

33 Hundreds of Bulbs in Series Effect of Shade/Blockage Hundreds of Cells in Series One or more cells in darkness cuts current in whole array. It also causes a hot spot at the shaded cell. Deep Shade + _ 11/14/2017 Rooftop Solar 35

34 Hundreds of Bulbs in Series Effect of Shade/Blockage Hundreds of Cells in Series Deep Shade + _ 11/14/2017 Rooftop Solar 36

35 Hundreds of Bulbs in Series Effect of Shade/Blockage Hundreds of Cells in Series With only moderate shade on a few cells, Bypass Diodes may not cut in. Moderate Shade + _ 11/14/2017 Rooftop Solar 37

36 MLPE vs String Inverter With Chimney 11/14/2017 Rooftop Solar 38

37 System Components 1. Solar PV Modules 2. Roof Mounting Systems 3. Inverters 4. Wiring & Meters 5. Internet Communications Balance of System BOS 11/14/2017 Rooftop Solar 39

_ AC Guts of SunnyBoy 3000 Inverter 120 peaks/sec Energy is stored between output peaks on

38 0 Power Voltage 0 Example: Automobile Inverter Inverters 12 VDC -> 115 VAC + DC Series String Inverters are the most unreliable components in typical Grid-Tied Solar PV systems. _ AC Guts of SunnyBoy 3000 Inverter 120 peaks/sec Energy is stored between output peaks on the blue capacitors They take a beating They eventually die Time 11/14/2017 Rooftop Solar 40

39 String Inverter System Two Different Inverter Approaches DC ~ 300 Volts ~ 10 Amps Inverter Micro-Inverter System DC AC 240 V AC Inverter Functions: Run Solar Panels at MPP Convert resulting DC to AC 60 Hz Synchronized to Grid Report Status to Cloud via Internet AC 240 V 11/14/2017 Rooftop Solar 41

40 Safety Cutoff Bidirectional Meter String Inverters String Inverter Internet 3 12 kw Various models 11/14/2017 Rooftop Solar 42

41 Inverter is a Misnomer DC from Series String Array Safety Shutdown Darkness Grid Failure Other faults Data Logging and Communication WiFi Internet Data MPPT (Max Power Point Tracking) DC/DC Converter DC/AC Inverter DC (variable Voltage) DC (fixed Voltage, e.g. 350V) AC (240V 60 Hz) What s inside a String Inverter box? Option: Backup AC Power when Grid is Down 11/14/2017 Rooftop Solar 43

42 Many Inverters Can Handle Several Strings! DC from Series String Array Safety Shutdown Darkness Grid Failure Other faults Data Logging and Communication WiFi Internet MPPT (Max Power Point Tracking) DC/DC Converter DC/AC Inverter DC (variable Voltage) DC (fixed Voltage, e.g. 350V) Inverter with Dual String Capability Data AC (240V 60 Hz) West Facing Array South Facing Array 11/14/2017 Rooftop Solar 44

Micro-Inverters Have All the Same Functions DC DC from from

Failure Other faults Data Logging and Communication WiFi

43 Micro-Inverters Have All the Same Functions DC DC from from Series One String Module Array Safety Shutdown Darkness Grid Failure Other faults Data Logging and Communication WiFi Internet MPPT (Max Power Point Tracking) DC/DC Converter DC/AC Inverter DC (variable Voltage) DC (fixed Voltage, e.g. 350V) watts Data AC (240V 60 Hz) 11/14/2017 Rooftop Solar 45

44 MLPE: MicroInverters make every Solar Module Independent Micro-Inverter System Reduced Power from this Module only Advantages: DC AC Shading localized Failure localized Detailed Reporting Very easy to add Modules Mix brands AC 240 V 11/14/2017 Rooftop Solar 46

45 Optimizer Inverter System Yet Another Inverter Approach: Optimizers DC 350 Volts, e.g. ~ 10 Amps (varies) Special Inverter AC 240 V MLPE Optimizer Unit Behind Each Panel Functions: Operate each panel at own MPP* Convert power to a consensus current determined by Inverter DC-DC converter Voltages coordinated to add up to 350V! Report status to main Inverter Shut down panel if necessary Inverter Functions: Coordinate Optimizers! Convert 350 V DC to AC 60 Hz, Synchronized to Grid Report Status to Cloud via Internet Individually for each panel 11/14/2017 Rooftop Solar * MPP = Maximum Power Point 47

46 System Components 1. Solar PV Modules 2. Roof Mounting Systems 3. Inverters 4. Wiring & Meters 5. Internet Communications Balance of System BOS 11/14/2017 Rooftop Solar 48

47 Solar Modules Need to Be Supported Flat Roof Gravity Ballast Ground Mount 11/14/2017 Rooftop Solar 49

near eaves & corners Roof Integrity: Leak Proofing Who is responsible?

48 Pitched Roof Mounts & Racking Module Orientation Structural Considerations Normally Mount to Joists or Trusses Convective Cooling Leave space beneath Wind Loading Lifting Forces, esp. near eaves & corners Roof Integrity: Leak Proofing Who is responsible? Snow Loads Layout: Access pathways Service Firemen Avoiding chimneys and vents Avoiding Shadows Portrait Landscape 11/14/2017 Rooftop Solar 50

49 Pitched Roof Mounts: Rails vs. Direct Mount 11/14/2017 Rooftop Solar 51

50 112 Mounts Installed by Roofer 11/14/2017 Rooftop Solar 52

51 Panels Bolted to Rails Notes: Rails are NOT black anodized To reach Trusses, rails extend beyond panels Large Fireman Access lanes left at eaves and along ridgeline 11/14/2017 Rooftop Solar 53

52 Hiding the Racking Panasonic 325 w panels with special racking system (sold only by Tesla Solar) Zep Racking System Special module frames no rails Hidden, black mounts Edge skirts 11/14/2017 Rooftop Solar 54

53 Snow Guard Prevents Avalanches over Patio or Door 11/14/2017 Rooftop Solar 55

54 System Components 1. Solar PV Modules 2. Roof Mounting Systems 3. Inverters 4. Wiring & Meters 5. Internet Communications Balance of System BOS 11/14/2017 Rooftop Solar 56

55 How to Route DC Cable DC in DC Disconnect 2-way Net Metering AC out 2 Slots for 240v Breaker AC Safety Disconnect 11/14/2017 Rooftop Solar 57

56 Routing the Power Down from the Roof Outside Route Inside Route thru Attic 11/14/2017 Rooftop Solar 58

$1000-$2000 Now approved in parts of Nebraska, Ohio,

57 Clever Way to Bypass Main Breaker Panel Simplified Electrical Connection bypass Main Panel Save up to $1000-$2000 Now approved in parts of Nebraska, Ohio, Vermont, California but yet not here 11/14/2017 Rooftop Solar 59

58 System Components 1. Solar PV Modules 2. Roof Mounting Systems 3. Inverters 4. Wiring & Meters 5. Internet Communications Verify system operation Diagnose Problems Get performance statistics Report Power Generation for SRECs ($$) Balance of System BOS 11/14/2017 Rooftop Solar 60

59 String Inverter Sends Data Inverter Wi-Fi Transmitter Panel Display 11/14/2017 Rooftop Solar 61

60 Typical Web Site Display: Solar Production for a given day 11/14/2017 Rooftop Solar 62

61 A Week of Production 11/14/2017 Rooftop Solar 63

62 A Full Month: September /14/2017 Rooftop Solar 64

63 Web Portal November 8 11/14/2017 Rooftop Solar 65

64 Issues: Web Portal Reporting is Vendor Specific ( Inverter Manufacturer) November 8 How long will they survive? May be free or subscription based Basic Level may be free Premium level data fee based $$ Data is typically delayed (not real time) Approx ½ hour -- varies Download data? Who gets data? You (password protected) Your Installer Inverter Company SREC Administrator ( Carbon Solutions Inc. in Illinois) Others??? Only Solar Production is measured NOT power usage or exports to grid 11/14/2017 Rooftop Solar 66

65 System Components 1. Solar PV Modules 2. Roof Mounting Systems 3. Inverters 4. Wiring & Meters 5. Internet Communications Balance of System BOS 11/14/2017 Rooftop Solar 67

Capture The Power of Photovoltaics. IEEE Power Engineering Society Meeting May 2005

Capture The Power of Photovoltaics IEEE Power Engineering Society Meeting May 2005 Agenda Photovoltaic Basics Applications Economics Grid Interconnection and Net Metering Grid-Tied System Components Net