ISO 20256:2026

Overview

ISO 20256:2026 is an international standard developed by the International Organization for Standardization (ISO) that specifies the requirements and procedures for the calibration of primary and secondary reference solar cells under the air mass zero (AM0) spectrum. This document is essential for the calibration of solar cells used in space systems and is applicable to both single-junction and multi-junction photovoltaic devices. The procedures outlined in this standard ensure traceability to SI units, supporting precise and reliable solar cell calibration for space applications.

Key Topics

• AM0 Spectrum Calibration: Describes procedures for calibrating reference solar cells under the air mass zero (AM0) spectrum, simulating extraterrestrial solar irradiance conditions relevant for space environments.
• Types of Reference Solar Cells:
  • Single-junction solar cells: Calibration methods and considerations, including mitigation of photon recycling effects and linearity requirements.
  • Multi-junction solar cells: Dedicated methods for reference devices with multiple active junctions, primarily relying on high-altitude calibration procedures.
• Primary and Secondary Reference Devices: Differentiates between primary reference solar cells (used to calibrate secondary references) and secondary reference solar cells (used for routine measurements and as working standards).
• Calibration Methods:
  • High-altitude procedures: Perform calibration under quasi-extraterrestrial conditions, typically using balloon or aircraft platforms to replicate the AM0 spectrum above the Earth’s atmosphere.
  • Synthetic calibration procedures: Utilize ground-based equipment with traceability to SI units for single-junction devices.
• Measurement Requirements: Guidelines for temperature measurement, electrical connections, and data recording to ensure accuracy and repeatability.
• Traceability and Stability: Emphasis on establishing a clear, documented calibration chain to SI units and ensuring the long-term stability of reference solar cells.

Applications

ISO 20256:2026 provides standardized procedures crucial for:

• Space Systems: Calibration of solar panel reference cells for satellites, space probes, and other aerospace applications, ensuring accurate power generation assessments.
• Solar Cell Manufacturers: Supporting the accurate characterization and quality control of photovoltaic devices intended for operation under AM0 conditions.
• Calibration Laboratories: Enabling laboratories to perform traceable calibrations of reference solar cells, supporting the global harmonization of space photovoltaics measurements.
• Research and Development: Facilitating scientific studies and technological advancements in high-performance solar cells, particularly when benchmarking new devices against recognized standards.
• Testing under Simulated Conditions: Ensuring the accuracy of AM0 sun simulators by providing calibration procedures aligned with real extraterrestrial solar conditions.

Related Standards

ISO 20256:2026 aligns closely with several key international standards in the field of photovoltaic measurement and calibration, including:

• IEC 60891: Procedures for temperature and irradiance corrections to measured current-voltage (I-V) characteristics.
• IEC 60904 Series:
  • Part 1: Measurement of photovoltaic current-voltage characteristics.
  • Part 2: Requirements for photovoltaic reference devices.
  • Part 4: Procedures for establishing calibration traceability.
  • Part 7: Computation of the spectral mismatch correction for photovoltaic measurements.
  • Part 8 & 8-1: Measurement of spectral responsivity of photovoltaic devices, including multi-junction cells.
  • Part 9: Solar simulator performance requirements.
  • Part 10: Methods of linearity measurement.
• ISO 16378:2022: Vocabulary for space systems - Solar cell and array terms.
• Standards from ISO/TC 20 (Aircraft and space vehicles) and related photovoltaic standards from IEC/TC 82.

By adhering to ISO 20256:2026, organizations and laboratories ensure that their solar cell calibration practices for space applications are scientifically rigorous, globally recognized, and traceable to international units, enabling reliable power supply and accurate performance evaluation for space missions. This standard is essential for advancing the accuracy and reliability of space solar power systems.