Why and How of Testing Solar PV Emona Instruments Mustafa Keskin Overview • Why Test Solar PV • How to Test Solar PV •  Basic tests required for Solar PV- Seaward PV150  IV testing  Visual Inspections on Solar PV  Thermal Imaging on Solar PV  Performance Verification- Array DC Output  Performance Verification -Inverter Efficiency  Performance Verification- AC output Conclusion Basic Tests Required for Solar PV AS/NZS 5033 specifies tests to verify safety and correct system operation. Basics Tests Required for Solar PV Effect of Temperature and Irradiance Effect of Temperature on Voltage Output Effect of Irradiance on Current Output Manufacturer specification for voltage and current are at Standard Test Conditions (STC) – 25 deg C and 1000 W/m2 Basics Tests- Seaward PV-150 Video I-V Test Basics I-V Curve is the voltage current characteristic based on a variable loads Parameters listed on the data sheet of a module, Isc,Voc,Pmax,Vmp,Imp,FF IV Curve model applies to cell, module, whole array IV Curve Impairments 1. Series losses: (loss of slope) :Increased Series resistance • Breaks, Connection faults • Corrosion • in-correct dimensioning 2. Shunt Losses: (downward tilt near Isc) • Imperfection in cell material. • Cracked or damaged cells. 3. Mismatch Losses: (notches or steps) Source: SolarPro Aug 2011 • Shading, Uneven soiling • Cracked cells, • Faulty bypass diode • Mismatch module 4. Reduced current: (height of curve) • Uniform soiling • low irradiance. 5. Reduced Voltage: (width of curve) affected by module temp Equivalent circuit model for Solar Cell • Poor air circulation • shorted bypass diodes • other system problems Reasons for Decreased Output and Yield for Solar Generators No power generated Check metering Turn switch to on position Visual Inspections on PV Modules IV tests on 250 modules to measure degradation Discoloration Delamination:back blistering Browning around junction box Delamination: front Arc Fault Electrochemical Delamination or Corrosion Burnt housing and 3 broken substrings and 4 broken bypass diodes Ref:University of Arizona: IV Analysis of PV modules deployed Tucson 2012 Emily Kopp Infrared Imaging- Solar PV Ref :SolarPro Magazine Patchwork Pattern-defective bypass diode Red spots-faulty connections Source:: ZAE Bayern e.V,”Quality Testing in Photovoltaics modules using infrared imaging” 2007 Infrared Imaging- 20 year old Solar PV installation-Patras Greece Ref: Kaplani-International Journal of Photoenergy Mortar (induced shading) Siemens M55 Modules Severe browning causing blisters on back Corrosion of busbars and contacts Back Back Front Front Back Back Back Hotspots around junction box front and back Severe browning causing hotspots front and back Hotspot more than 170 deg. Infrared Imaging- Installation Faulty Connector Can test all parts of the installation : Inverters, Fuses, Cables, Connectors Performance Verification -Array DC Output 23 Modules (235Watt) in Series Pstc Watts A V V INSTALTEST PV REPORTS Performance Verification -Array DC Output 23 Modules (235Watt) in Series INSTALTEST PV REPORTS Performance Verification -Array DC Output IV Characteristic and Power Graph- 235 Watt Module-1 Cell Shaded STC INSTALTEST PV REPORTS Performance Verification -Inverter Efficiency Inverter Conversion Efficiency= Pac/Pdc Inverter Efficiency Curve - SMA Sunny Boy 2500 INSTALTEST PV Inverter efficiency affected by temperature should be mounted in shade. Performance Verification-Inverter Maximum Power Point Tracking Efficiency Power Curve Module with Shaded Cell P INSTALTEST PV REPORTS INSTALTEST INSTALTEST PV Verifying AC Output for PV Systems INTERACTIVE PV SYSTEM PERFORMANCE WORKSHEET PV Array DC Power Rating at STC - 1000 W/m2, 25 °C (kW) .. ...................................................................................... 10 kW Derating Factors Nameplate Ratings ..........................................0.95 Inverter & transformer.....................................0.95 Module Mismatch.............................................0.98 DC Wiring .........................................................0.98 AC Wiring .........................................................0.99 Soiling Age (dusty area's 20% or more) ...................1.00 0.5 to 1 % per year...................................1.00 Combined Derating Factor ................................................................................................... 0.86 Estimated System AC Power Output at STC - 1000 W/m2, 25 °C ................................. ………………………… 8.6 kW Temperature Adjustments Array Power-Temperature Coefficient (%/°C) . ................................................................ ...-0.5 Measured Array Operating Temperature (°C) . ..(60-25)X0.5=17.5%....................................................60 Estimated System AC Power Output at 1000 W/m2 and Operating Temperature ..............................................7.1 kW Solar Radiation Adjustments Measured Solar Irradiance in Plane of Array (W/m2) ...................................................... 850 Estimated System AC Power Output at Operating Temperature and Solar Irradiance …………………..................... 6.0 kW Conclusion Seaward PV150 -Quickly verify correct system operation. Multifunction Tester: IV Testing Benefits: • True array Pmppt • Degradation rates over time (voltage/power) • Changes in Rs/Rshunt • Identify wiring problems , module or bypass diode failures. • Analyze effects of shading. • Losses due to module mismatch and array wiring methods. • Establish array ratings for performance guarantees. Thermal Imaging - See much more than the eye. Emona Instruments: Seaward,Metrel,PVE,Trotec, Amatrol Solar Trainers (IV testers,Cameras $2k) New Installations: Last 4 years more than 1 million Solar PV installations have come online.