SAN-EI AM Solar Standards 2025 — Edition B
Prepared by
SAN-EI ELECTRIC Co., Ltd.
Author: Hiromitsu Nagatsuka
Osaka, Japan
Classification: International Submission Draft
1. Abstract
This technical document presents the unified SAN-EI AM Solar Standards 2025, a framework defining both the AM0 (1 SUN = 1348 W/m²) irradiance constant and the Class A++ Spectral Match Standard for solar simulators.
It aims to harmonize terrestrial (AM1.5G) and extraterrestrial (AM0) calibration methodologies, ensuring optical consistency for photovoltaic and aerospace research.
The standard introduces ±7.5 % tolerance (measured ±5 %) across 300–2200 nm, verified using SAN-EI’s Dual Air Mass Solar Simulator.
All developments comply with Japan’s Foreign Exchange and Foreign Trade Act (FEFTA) and uphold the principle of Technology for Peaceful Use
2. Background and Objectives
Solar simulator standards such as IEC 60904-9 and ASTM G173 define spectral and irradiance requirements primarily for AM1.5G conditions.
However, no equivalent specification exists for AM0, despite its increasing relevance in space and high-altitude photovoltaic applications.
To address this gap, SAN-EI ELECTRIC CO., LTD. established the SAN-EI AM Solar Standards 2025, integrating:
- A precise physical definition of AM0 irradiance (1348 W/m², 280–4000 nm)
- An enhanced spectral match classification (Class A++) extending to 2200 nm
- Experimental validation with Dual Air Mass (AM1.5G / AM0) measurements.
This framework provides a transparent, reproducible, and internationally consistent reference for research institutions and standardization bodies.
3. Definition of AM0 (1 SUN = 1348 W/m²)
The AM0 (1 SUN) irradiance is defined as the total spectral power integrated over 280–4000 nm, yielding 1348W/m², derived from ASTM E490 extraterrestrial reference data.
For consistency, the integration range mirrors that of the AM1.5G standard (IEC 60904-3 / ASTM G173), ensuring comparability of measurement methodology.
“The same spectral integration range (280–4000 nm) was adopted for consistency with AM1.5G reference methodology, ensuring direct comparability in measurement principles.”
4. Measurement Principles and Methodology
AM1.5G irradiance (1000 W/m²) is measured using reference cells or pyranometers calibrated to Si detectors with a 400–1100 nm response.
Although this sensitivity does not cover the full 280–4000 nm band, correction factors allow its use as a standardized reference.
No dedicated AM0 radiometer currently exists.
Based on ASTM reference data, the integrated irradiance was calculated as follows:
At 280–4000 nm, AM1.5G = 1000.37 W/m² and AM0 = 1347.93 W/m².
At 400–1100 nm, AM1.5G = 759.01 W/m² and AM0 = 908.13 W/m², giving an AM0/AM1.5G ratio of 1.20.
Accordingly, when using an AM1.5G-calibrated detector, a signal output 1.2× higher represents 1 SUN under AM0 (1348 W/m²).
5. Class A++ Spectral Match Standard (300–2200 nm)
The current IEC 60904-9:2020 defines Class A+ spectral match within ±12.5 % over 300–1200 nm.
| IEC 60904-9:2020 | Wavelength range to be evaluated | ||
|---|---|---|---|
| 400–1000nm | 300–1200nm | ||
| Divisions | quantity | 6 | 6 |
| percent | 12.5 – 19.9% | 16.7% | |
| Spectral Match | |||
| Accuracy | Class | ||
| ≤ ±12.5% | 87.5 – 112.5% | —– | A+ |
| ≤ ±25% | 75 – 125% | A | —– |
| ≤ ±40% | 60 – 140% | B | —– |
| ≤ ±60% | 40 – 200% | C | —– |
SAN-EI introduces a refined and extended classification as shown below.
| SAN-EI AM Solar Standards 2025 | Wavelength range to be evaluated | |||
|---|---|---|---|---|
| 300–1200nm | 300–1800nm | 300–2200nm | ||
| Divisions | quantity | 6 | 8 | 10 |
| percent | 16.7% | 12.5% | 10% | |
| Spectral Match | ||||
| Accuracy | Class | |||
| ≤ ±7.5% | 92.5 – 107.5% | A++ | S++ | — |
| ≤ ±12.5% | 87.5 – 112.5% | A+ | S+ | SS+ |
| ≤ ±25% | 75 – 125% | A | S | SS |
| ≤ ±40% | 60 – 140% | B | — | — |
| ≤ ±60% | 40 – 200% | C | — | — |
6. Air Mass Filter Development and Spectral Match Improvement
To achieve higher spectral conformity beyond 1100 nm, SAN-EI has developed new Air Mass Filters extending measurement control from 300 to 1800 nm (8 bands) and 300 to 2200 nm (10 bands).
These filters improve accuracy particularly in the near-infrared region, reducing cumulative deviation to within ±10 % (Class S++/ Class SS+) while maintaining stable optical throughput.
The filter optimization also allows single-lamp operation (Xe-only) without additional halogen light sources, improving cost efficiency and long-term stability.
| Product | Light Source Type | Wavelength | Spectral Match | Reference |
|---|---|---|---|---|
| XES-70S1 | Xenon Lamp | 300 – 1800nm | 95 – 105% | ≤ ±5% Next part Chart 01 |
| 300 – 2200nm | 91 – 109% | ≤ ±9% Next part Chart 02 | ||
| XHS-500S1 | Xenon Lamp + Halogen Lamp | 300 – 1800nm | 87 – 119% | ≤ ±19% Next part Chart 03 |
Each row shows the spectral conformity range measured under different Air Mass Filter configurations, corresponding to the specific wavelength control ranges of each filter type.
Charts 01 and 02 illustrate the transition from 8-band to 10-band Air Mass Filters (300‒1800 nm → 300‒2200 nm), while Chart 03 provides a reference comparison using the previous Xenon + Halogen configuration.
7. Experimental Verification and Results
All measurements were performed on SAN-EI’s latest generation solar simulators equipped with precision air mass filters for both AM1.5G and AM0 conditions.
Measurement Setup:
- Dual array detectors (Si + InGaAs) calibrated with traceability to NMIJ standards
- Ambient temperature 25 ± 1 °C
- Spectral range 300–2200 nm
- Stability and repeatability within ±2 % between systems
Summary of Results:
- Spectral match error ≤ ±5 % for both AM1.5G and AM0
- Uniform irradiance distribution across field (within 2%) (Measured uniformity ≤ ±2 % across 400 mm × 400 mm irradiation field, evaluated by IEC 60904-9 multi-point method.)
- Reproducibility confirmed through cross-device tests (n = 4)
Figure 1. Spectral Comparison between Measured Output and ASTM References (placeholder)
Figure 2. Band Deviation Map, 300–2200 nm (placeholder)
8. Technical Significance and Standardization Perspective
The SAN-EI AM Solar Standards 2025 represent a unified framework for terrestrial and space PV evaluation.
Major advantages include:
- Precision Improvement: ±5 % actual spectral match, surpassing IEC Class A+.
- Wavelength Extension: Up to 2200 nm, enabling evaluation of next-generation multi-junction cells.
- Dual Air Mass Capability: Single system for AM1.5G and AM0 testing.
- Standardization Potential: Provides technical foundation for future IEC Annex proposal.
“This dual-air-mass capability bridges terrestrial and space photovoltaic evaluation under a unified calibration scheme.”
SAN-EI intends to collaborate with NREL, JRC, ESA, and other institutions to validate and harmonize measurement protocols globally
9. Statement on Peaceful Use and Compliance
This technology has been developed under the philosophy of “Technology for Peaceful Use.”
All design, manufacturing, and export activities comply fully with the Foreign Exchange and Foreign Trade Act (FEFTA) of Japan.
SAN-EI ELECTRIC CO., LTD. does not support or authorize any military or offensive applications of its products.
“SAN-EI ELECTRIC is committed to advancing solar simulation technologies solely for peaceful and sustainable scientific progress.”
10. References
[1] ASTM E490-00a(2014), “Standard Solar Constant and Zero Air Mass Solar Spectral Irradiance Tables,” ASTM International, West Conshohocken, PA, USA.
[2] ASTM G173-03(2020), “Standard Tables for Reference Solar Spectral Irradiances: Direct Normal and Hemispherical on 37° Tilted Surface,” ASTM International.
[3] IEC 60904-9:2020, “Photovoltaic Devices – Part 9: Solar Simulator Performance Requirements,” International Electrotechnical Commission.
[4] JIS C 8904-9:2021, 「太陽電池―第 9 部：ソーラシミュレータの性能要求事項」, 日本産業規格.
[5] NREL Reference AM0 Spectrum, National Renewable Energy Laboratory (NREL), Golden, CO, USA.
Confirmed and issued by:
SAN-EI ELECTRIC CO., LTD.
Hiromitsu Nagatsuka, President
Osaka, Japan
April 2025
Ethical and Legal Compliance Statement
All SAN-EI solar simulator systems are developed and provided exclusively for peaceful and scientific purposes.
Their design, manufacturing, and export fully comply with Japan’s Foreign Exchange and Foreign Trade Act (FEFTA) and related international regulations.
Unauthorized military or weapon-related applications are strictly prohibited.