I-V curve measurement

^{Created by M.L., OST, on 19.03.2025}

• Description: Measurement of the variation of current and voltage from the open-circuit to short-circuit condition by applying a variable load [1].
• Equipment: Dedicated hardware (IV-curve tracer) with sensors for onsite measurement (like pyranometer or sunlight irradiance sensor and thermometer). Some inverters can do this remotely.
• Requirements: Stable sunny conditions.
• Gained insights: Evaluation of power generation performance and detection of fault conditions, device degradation or ageing effects (PID, failed bypass diode, shunt resistance, series resistance, mismatches and local shading, soiling)[2,3].
• Recommended frequency: Once a year. Allows for performance check and monitoring of ageing.
• Advantages: The I-V curve shape provides detailed information on PV generator performance and fault detection.
• Disadvantages: Uncertainties from translation from measured conditions to STC.
• Effort:
  • Global: medium
  • Costs: medium, if permanent remote measurement implemented; low if sporadic on-site measurements.
  • Time: low, if remote measurements implemented; medium, if sporadic on-site measurements.
• Providers (non-exhaustive list):
  • IV-curve tracers: HT instruments, Benning, Fluke.
  • Remote IV-curve tracers: Gantner Instruments [4,5], Entec Solar, Keithley.
  • Inverters with IV-measurement implemented: Huawei Smart PVMS, SMA Solar Technology AG, Danfoss Solar, Schneider Electric [6].
• Links:
  • Brief explanation of I-V measurements technique: https://www.pveducation.org/pvcdrom/solar-cell-operation/iv-curve
  • Overview of I-V measurement technique: See pages 33 ff of [2].
• Additional notes: Due to higher irradiance and colder temperatures in the alpine regions compared to the lowlands, the measurement conditions might actually be closer to STC, presenting for once an advantage. The irradiation might even be higher, reaching values up to above 1600 W/m² [7,8].

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References

1. Augusto A, Killam A, Bowden SG, Wilterdink H. Measuring outdoor I–V characteristics of PV modules and systems. Prog Energy 2022;4:042006. https://doi.org/10.1088/2516-1083/ac851c.
2. Hermann W, Eder G, Farnung B, Friesen G, Köntges M, Kubicek B, et al. Qualification of  Photovoltaic (PV)  Power Plants using  Mobile Test Equipment. International Energy Agency (IEA); 2021.
3. Sarikh S, Raoufi M, Bennouna A, Benlarabi A, Ikken B. Fault diagnosis in a photovoltaic system through I-V characteristics analysis. 2018 9th Int. Renew. Energy Congr. IREC, 2018, p. 1–6. https://doi.org/10.1109/IREC.2018.8362572.
4. Sutterlüti J. Interview about alpine PV: Gantner Instruments 2025.
5. Cavalli J. Innovation in alpiner Photovoltaik: Wie die Schweiz ihr Winterstromlücke meistern will. Gantner Instrum 2023. https://www.gantner-instruments.com/de/blog/innovation-in-alpine-solar-winterliche-energieherausforderungen-meistern/ (accessed November 21, 2024).
6. Spataru S, Sera D, Kerekes T, Teodorescu R. Monitoring and Fault Detection in Photovoltaic Systems Based On Inverter Measured String I-V Curves, Hamburg: 2015. https://doi.org/10.4229/EUPVSEC20152015-5BO.12.2.
7. Hügli A. Alpine untility scale PV: Challenges of Constructability and Operations 2025.
8. Heierli C. Interview about alpine PV: AXPO, Alpin Solar (Muttsee-Staumauer) 2025.