IEC 60904-4:2019

Overview

IEC 60904-4:2019 - "Photovoltaic devices - Part 4: Photovoltaic reference devices - Procedures for establishing calibration traceability" specifies requirements for calibration procedures that establish the traceability of photovoltaic (PV) reference devices to SI units. The standard applies to PV reference solar devices used to measure irradiance from natural or simulated sunlight for quantifying PV device performance. Written with single‑junction technologies in mind (particularly crystalline silicon), the second edition (2019) updates the traceability chain by including a working reference, aligns WRR traceability to the SI, revises calibration methods and uncertainties, and harmonizes symbols and formulae with related IEC standards.

Key Topics and Requirements

• Calibration traceability to SI units: Procedures required to link PV reference devices through validated transfer instruments and methods back to SI.
• Scope of reference devices: Focus on single‑junction PV reference devices (e.g., crystalline silicon) but generally applicable to other single‑junction technologies.
• Inclusion of a working reference: The traceability chain now formally includes a working reference (WRR) and updates for its relation to SI.
• Annex A - Validated methods: Practical, validated calibration methods are described, including:
  • Global Sunlight Method (GSM)
  • Differential Spectral Responsivity calibration (DSR)
  • Solar Simulator Method (SSM)
  • Direct Sunlight Method (DSM)
• Uncertainty analysis: Requirements for documenting measurement uncertainties and typical uncertainty components for each method are provided.
• Calibration reporting and marking: Required contents of calibration reports and marking of reference devices to ensure traceability and transparency.
• Harmonization and normative references: Aligns with IEC 60904-1/-2/-3, ISO/IEC 17025, and the GUM for uncertainty expression.

Applications and Who Uses It

IEC 60904-4:2019 is intended for:

• Calibration laboratories and national metrology institutes establishing SI traceability for PV reference devices.
• PV test labs and certification bodies that require calibrated irradiance references for accurate IV testing and performance claims.
• Manufacturers of PV reference cells and solar simulators implementing validated calibration procedures and uncertainty budgets.
• Research institutions and field measurement teams performing irradiance measurements under natural or simulated sunlight.

Practical benefits include consistent irradiance measurement across labs, improved comparability of PV performance data, and robust uncertainty statements supporting conformity to PV measurement standards.

Related Standards

• IEC 60904-1: Measurement of PV current‑voltage characteristics
• IEC 60904-2: Requirements for reference solar PV reference devices (traceability requirement)
• IEC 60904-3: Measurement principles with reference spectral irradiance data
• ISO/IEC 17025: Competence of testing and calibration laboratories
• ISO/IEC Guide 98-3 (GUM): Uncertainty of measurement

Keywords: IEC 60904-4:2019, photovoltaic reference devices, calibration traceability, SI units, PV reference solar devices, crystalline silicon, working reference, uncertainty analysis, solar simulator, differential spectral responsivity.