Introducing the Solmetric PV Analyzer and the New Features of v2.0 PVA Software

Transcription

1 Introducing the Solmetric PV Analyzer and the New Features of v2.0 PVA Software Next PVA Webinar November 29, 10am PST webinar.html Paul Hernday Senior Applications Engineer cell November 8, 2012

2 Upcoming Webinars Tools for Solar Site Assessment and Design November 20, am PST Introducing the Solmetric PV Analyzer and the New Features of Version 2.0 PVA Software November 29, am PST To register:

3 Topics Brief introduction to I-V curves and the PV Analyzer Introducing free Version 2.0 PVA Software Upgrade Commissioning PV arrays Troubleshooting PV arrays Meg testing with the Megger MIT430

4 I-V and P-V* Curves Expect this general shape for healthy cells, modules, strings, or arrays Isc Imp I-V curve Pmax Current P-V curve Power Voltage Vmp Voc *P-V curve is calculated from the measured I-V curve

5 I-V Curve Abnormalities Isc Current (A) Reduced current Normal I-V curve Increased slope Mismatch losses (incl. shading) Any reduction of the knee of the curve means reduced output power. Reduced slope Max power point Voltage (V) Reduced voltage Voc Conventional Isc and Voc measurements do not reveal many of these effects

6 Solmetric PV Analyzer Users EPC organizations System Integrators Electrical contractors Module Manufacturers Consulting Engineers Inverter Manufacturers O&M Companies Technical colleges Training Organizations IBEW Training Centers

7 How it works Wireless Measurement Network Irradiance sensor Module backside temperature sensor Module, tilt, orientation Built-in Analysis Irradiance & temperature Built-in PV models Wireless WUSB1 WUSB2 Your PC 5 dots predict the shape of the curve I-V Measurement Unit Array Screen shot Data analysis and reporting are automated

8 Expected I-V Curve Shape determined by the advanced PV models The five dots indicate the expected curve shape The dots appear whenever an advanced performance model (Sandia or 5- Parameter) is selected Dot 1 (Isc, 0) Dot 2 (I, Voc/2) Dot 3 (Imp, Vmp) Dot 4 (I, [Vmp + Voc]/2) Dot 5 (0, Voc) 5 The middle red dot is the predicted max power point The yellow dot on the P-V curve marks the peak of that curve, and is not a prediction of the PV model.

9 I-V Measurement Setup Example: Measuring strings at a combiner box Attach the thermocouple well away from module edges, using polyimide (Kapton) tape for best mechanical properties at high temperatures.

10 Example Measurement Setup Courtesy of: Integrated Energy Systems Pittsburg Unified School District Sage Renewables Stellar Energy Solutions

11 Example Measurement Setup Courtesy of Chevron Energy Solutions 2011

12 Wireless Sensor Kit Irradiance & temperature sensors Irradiance transmitter. K-type thermocouple Omega Part # 5SRTC-GG-K Receiver (USB) Temperature transmitter

13 Deploying irradiance & temperature sensors Guarantee that the irradiance sensor is in the plane of the array by placing it on a module (that s not in the string you are measuring) or mounting it to a corner of a module. ** MOCAP MCD-PE 1.75 poly dot ~$80/roll of 1000 dots customerservice@mocap.com Mount the thermocouple 2/3 of the way between the corner and center of a module. Use high-temperature tape (eg 1-3/4 inch Kapton dots**). Press TC into contact with backside.

14 Topics Brief introduction to I-V curves and the PV Analyzer Introducing free Version 2.0 PVA Software Upgrade Commissioning PV arrays Troubleshooting PV arrays Meg testing with the Megger MIT430

15 Features of v2 PVA PC software Faster setup -Project Wizard -Web tool for azimuth, latitude, longitude Large displays of Irradiance & temperature on every measurement screen Array Navigator for touch-based data save and recall Translates I-V curves to STC 5000 more module models, and automatic update of equipment databases History tab shows tabular values for the last 20 measurements Archiving of Meg Test data -Saves manually entered meg test data to the new database (Solmetric now offers the Megger MIT-430 Insulation Tester) Report generation capability via the updated I-V Data Analysis Tool (optional accessory for analyzing large quantities of test data)

16 Array Navigator Array Navigator Represents the PV system architecture Created by the Project Wizard Touch a string location to save or recall data Also contains information needed by the PV model (eg wire gauge and lengths) Currently limited to sequential labeling schemes (numbers or letters)

17 The Project File Version 1.X Software Version 2.X Software (legacy) Project file (legacy) Contains array details, performance model, and measurement data Easy to share between offices Foundation for future advanced analysis and reporting capabilities

18 Saving a measurement result with V1.2.csv Windows file save interface

19 Saving a measurement result with V2.0

20 Additions to the Module Database v v param: 4,991 8,722 Sandia: Simple: 0 11,454 Unique modules: 11,821 Roughly 2,178 module models exist with only the simple model (11,454-8, ).

21 Live Software Demo Demo uses saved data Screens are also captured on the following slides

22 Traces tab

23 Project Wizard, Step 1 Notes & Info

24 Project Wizard, Step 2 Performance Model

25 Project Wizard, Step 3 Site Info

26 Roof Measurement Tool

27 Project Wizard, Step 4 Array Navigator Autofill icon

28 Autofill Tool

29 System Tree

30 Saving a test result

31 Traces screen

32 Environmental Inputs controls

33 Table screen

34 Verify screen

35 History screen

36 Meg Test tab

37 Topics Brief introduction to I-V curves and the PV Analyzer Introducing free Version 2.0 PVA Software Upgrade Commissioning PV arrays Troubleshooting PV arrays Meg testing with the Megger MIT430

38 Recommended environmental conditions for performance testing with any type of instrument Clear sky For high irradiance and normal curve shape For stable irradiance and more meaningful statistics 4 hour window centered on solar noon* For representative irradiance, spectral and reflective effects Low wind For stable temperature and more meaningful statistics In practice, it is sometimes necessary to measure under less than optimum conditions. *Solar Noon Calculator:

39 Why do we want stable conditions? Meaningful comparison of measured and modeled performance requires knowledge of the irradiance and temperature at the time of the performance measurement Under changing conditions, any time delay between the performance and irradiance/temperature measurements translates into irradiance/temperature measurement errors The greater the time delay & change of conditions, the greater the error. (The Wireless Sensor Kit keeps this delay minimal). The performance models translate these errors into apparent string-to-string variations in Isc, Pmax, Performance Factor, etc. Translating data to STC suffers from the same type of error. Accuracy & precision cannot be regained by translation (to STC or other conditions) This limitation applies to all forms of performance measurement, not just curve tracing

40 Unstable sky conditions

41 Example Measurement Setup

42 I-V Measurement Setup Example: Measuring strings at a combiner box Attach the thermocouple well away from module edges, using polyimide (Kapton) tape for best mechanical properties at high temperatures.

43 Measurement Process 860kW 7-inverter system 1. Open the DC disconnect for the sub-array you want to test. Courtesy of Portland Habilitation Center and Dynalectric Oregon

44 Measurement Process 2. Locate the combiner box Courtesy of Portland Habilitation Center and Dynalectric Oregon

45 Measurement Process 3. Lift all of the fuses Courtesy of Portland Habilitation Center and Dynalectric Oregon

46 Measurement Process 4. Clip the PV Analyzer to the buss bars 5. Push down one fuse at a time, take the I-V trace, view and save results. Takes ~ seconds per string. Courtesy of Portland Habilitation Center and Dynalectric Oregon

47 Displays Generated by the I-V Data Analysis Tool* Current (Amps) Voltage (Volts) Frequency *Optional accessory $ Pmax (Watts)

48 Histograms A histogram worksheet is created for each performance parameter, revealing patterns in the data Each histogram represents the frequency of different values of a measured parameter, across a group of string measurements In this example, the spread of Pmax values (upper graph) is largely explained by variation of irradiance (lower graph)

49 Fill Factor Histogram Fill Factor is a very useful diagnostic tool (details in the next slides) Compared with Pmax or Isc, Fill Factor has a weak dependency on irradiance, making it a useful metric even under conditions of rapidly changing irradiance In this example, notice the clean, bell-shape of the fill factor (lower graph), compared with the Pmax distribution (upper graph)

50 Topics Brief introduction to I-V curves and the PV Analyzer Introducing free Version 2.0 PVA Software Upgrade Commissioning PV arrays Troubleshooting PV arrays Meg testing with the Megger MIT430

51 I-V Curve Signatures of PV Problems Isc Current (A) Reduced current Normal I-V curve Shunt losses* Mismatch losses (incl. shading) Any reduction of the knee of the curve means reduced output power. Series losses** Max power point Voltage (V) Reduced voltage Voc Conventional measurements do not reveal many of these effects.

52 Useful diagnostics Fill Factor, Current Ratio, Voltage Ratio Isc Imp Current ratio Imp/Isc Max Power Point Current Voltage ratio Vmp/Voc Voltage Vmp Voc Fill Factor = Imp x Vmp (watts) Isc x Voc (watts) = asi: xsi: GaAs:

53 String of Field-aged, Early TF Modules Degraded fill factor, lower output power Array-as-sensor mode for viewing relative changes in curve shape

54 Troubleshooting example Anomalous slope in string I-V caused by single high-resistance module Current - A String 4B14 String 4B Voltage - V

55 Example of a series resistance failure inside a module J-box Probably failure mode: Heat cycling bond degradation resistive heating

56 Dropped Cell String Shorted bypass diode, or Mismatch causing diode to turn on when current starts flowing

57 I-V Curve of a Partially Shaded String Multiple knees multiple power peaks Peaks evolve as conditions change Inverter tries to find and track the highest peak Isc Power Current Voltage Voc

58 Partially shaded residential array Measure the single string mounted along lower edge of roof

59 I-V Curve of the partially shaded string Single string mounted along lower edge of roof Approximately 40% reduction in string s output power

60 Shading one cell string drops 1/3 of PV module voltage and power Shade 2 cells in the same cell-string Single module with 72 cells and 3 bypass diodes

61 The same amount of shade, oriented differently, drops 2/3 of PV module voltage and power. Shade 2 cells in adjacent cell-strings Single module with 72 cells and 3 bypass diodes

62 Summary of PV Analyzer benefits Testing PV array performance faster and better Single connection at combiner box Single measurement for each string Most complete performance measurement possible Independent Pmax measurement for each string Built-in PV models give instant performance check Don t need to bring inverter online Automated data analysis Teaches us to think like a PV array Next topic: Insulation resistance testing I V

63 Topics Brief introduction to I-V curves and the PV Analyzer Introducing free Version 2.0 PVA Software Upgrade Commissioning PV arrays Troubleshooting PV arrays Meg testing with the Megger MIT430

64 Insulation Resistance Testing of PV Arrays Where are we? 1. The industry is trending toward the best practice of meg testing all systems during commissioning and at maintenance intervals. 2. Meg testing is not yet being done on all commercial systems, and is rarely done on residential systems. 3. Source circuits are often tested in aggregate, with string-level testing if the aggregate resistance is low. 4. Methods for sub-array test are not standardized or widely understood. Best reference is Bill Brooks re-wrenches post. 5. In general, string or sub-array resistance values are compared for consistency rather than held to a specific spec. 6. PV module leakage is usually the dominant effect. 7. Insulation problems will be much more common as PV systems age.

65 Meg Testing at the Subarray Level Preparation: Open the DC Disconnect Lift string fuses Lift negative feeder cable(s) Lift Lift Lift Example assumes a negative-grounded array Combiner box

66 Meg Testing at the String Level Preparation: Open the DC Disconnect Lift string fuses Lift negative source cable Lift Lift Lift Example assumes a negative-grounded array

67 Free I-V Curve Poster

68 SolarPro Magazine, Aug/Sep 2011

69 Introducing the Solmetric PV Analyzer and the New Features of Version 2.0 PVA Software Next PVA Webinar November 29, 10am PST webinar.html Paul Hernday Senior Applications Engineer cell November 8, 2012