Overview
ISO 22975-3:2014 - "Solar energy - Collector components and materials - Part 3: Absorber surface durability" specifies procedures to assess the long‑term behaviour and service life of selective solar absorbers used in vented flat‑plate solar collectors (typical solar domestic hot water systems and combisystems). The standard addresses durability by measuring changes in the absorber’s optical performance - solar absorptance and thermal emittance - and prescribing accelerated qualification tests that simulate high temperature, condensation and humid polluted atmospheres.
Key topics and technical requirements
- Performance criterion (PC): Durability is assessed by a combined performance function based on changes in solar absorptance (Δα) and thermal emittance (Δε). The document explains how to calculate PC (the standard uses a weighting for thermal emittance; e.g., PC formulations such as PC = −Δα − 0.5·Δε are discussed) and how to interpret failure times against a design service life.
- Sample preparation and characterization: Test specimens must be sampled and conditioned as specified; initial characterization requires low scatter (standard deviation < 0.01 for solar absorptance and < 0.04 for thermal emittance).
- Adhesion requirement for coatings: For coated absorber surfaces, adhesion testing (ISO 4624 pull‑off) is required; the standard sets a minimum adhesion threshold (> 0.15 MPa) for qualification.
- Three independent test blocks:
- Thermal stability / high‑temperature exposure (Clause 6)
- Resistance to condensed water / constant condensation (Clause 7)
- Corrosion resistance in high humidity air containing sulfur dioxide (Clause 8)
- Measurement methods and annexes: Normative annexes cover procedures for measuring solar absorption and thermal emittance, temperature/failure time criteria, temperature/condensation schedules, and suggested test apparatus designs.
Practical applications and users
ISO 22975-3:2014 is intended for:
- Manufacturer R&D - validating new selective absorber coatings and materials.
- Test laboratories - performing standardized qualification and acceptance testing.
- Product certification bodies and specifiers - setting procurement requirements and comparing absorber durability claims.
- Design engineers and system integrators - estimating design service life of collectors and selecting absorber materials for domestic hot water and combisystems.
Use cases include product development, lifetime prediction, quality control, and supplier qualification.
Related standards
- Normative references: ISO 4624, ISO 8407, ISO 9050, ISO 10062 (cited for test methods and corrosion procedures).
- Other parts in the ISO 22975 series under development cover evacuated tubes (Part 1) and heat‑pipes (Part 2).
Keywords: ISO 22975-3:2014, absorber surface durability, selective solar absorbers, solar absorptance, thermal emittance, durability testing, condensation resistance, high humidity sulfur dioxide, vented flat plate solar collectors.
Open preview (PDF)Solar energy — Collector components and materials — Part 3: Absorber surface durability