Overview
EN ISO 24078:2025 (ISO 24078:2025) - Hydrogen in energy systems - Vocabulary - is a harmonized European/International vocabulary standard prepared by ISO/TC 197 in collaboration with CEN-CENELEC JTC 6. It establishes the terms, definitions, symbols and abbreviations used across hydrogen-related energy systems. The standard provides high-level, standardized language to improve clarity and interoperability among standards, regulators and industry stakeholders.
Key points:
- Purpose: standardize terminology for hydrogen in energy systems (gaseous and liquid hydrogen, hydrogen-based fuels, infrastructure, safety, metrology, etc.).
- Not applicable to: biological methanation; reactors for hydrogen production from other sources; road, maritime and aviation transport; aeronautics and space (these are planned for future editions).
- Excludes carbon capture, storage and utilisation, and services.
- Adopted as EN ISO 24078:2025 and expected to be implemented by CEN members as national standards (implementation deadline: January 2026).
Key topics
EN ISO 24078:2025 organizes vocabulary into clear technical categories, including:
- Energy and energy carriers (e.g., hydrogen, hydrogen-based fuel, liquid hydrogen)
- Energy systems and markets (integration, smart grid interactions)
- Electric power networks and electrical energy storage
- Hydrogen production systems and equipment (electrolysis, production-related terms)
- Hydrogen infrastructure (components, stations, transmission, distribution)
- Hydrogen storage (types and storage-related vocabulary)
- Hydrogen-fuelled heat and power generation devices (fuel cells, turbines)
- Hydrogen-to-X pathways and gas mixtures
- Safety, risk reduction and hydrogen detection
- Metrology, quality of energy carriers, testing, certification and materials compatibility
The document is primarily a terminology resource - it defines and standardizes language rather than prescribing engineering requirements or test methods. It also references related standards where more technical specifications are available (for example, ISO 14687:2019 for hydrogen fuel quality and ISO/IEC terminology resources).
Applications and users
Who benefits:
- Standards writers and technical committees aligning cross‑disciplinary documents
- Engineers and system integrators designing hydrogen systems and infrastructure
- Regulators and policymakers drafting legislation and permitting frameworks
- Certification bodies, metrology labs and testing organizations
- Manufacturers, suppliers and project developers ensuring consistent definitions in procurement and contracts
- Researchers and educators seeking standardized terminology for publications and training
Practical uses:
- Ensuring consistent definitions in technical specifications, safety plans and contracts
- Clarifying interfaces between electrical systems, hydrogen production (power‑to‑hydrogen) and storage
- Improving interoperability across national and international hydrogen projects
Related standards and resources
- ISO 14687:2019 (hydrogen fuel quality) - cited within the vocabulary
- ISO/IEC terminology resources: ISO Online Browsing Platform and IEC Electropedia
- Prepared by ISO TC 197 and CEN‑CENELEC JTC 6 (Hydrogen in energy systems)
Keywords: Hydrogen in energy systems, EN ISO 24078:2025, hydrogen vocabulary, hydrogen terminology, hydrogen standards, hydrogen infrastructure, hydrogen safety.
