Overview
ISO 24078:2025 - "Hydrogen in energy systems - Vocabulary" is the first edition (2025) of an international vocabulary standard that establishes terms, definitions, symbols and abbreviations used across hydrogen-related energy systems. Developed by ISO TC 197 in collaboration with CEN/CENELEC JTC 6, the document provides a harmonized, high‑level lexicon to support standardization, regulation, design and deployment of hydrogen technologies.
The standard covers gaseous and liquid hydrogen concepts and related energy carriers, while expressly excluding certain fields for this edition (biological methanation; reactors for hydrogen production from other sources; road, maritime and aviation transport; aeronautics and space; and carbon capture, storage and utilisation, and services), which are foreseen for future updates.
Key topics and technical scope
ISO 24078 is a vocabulary (terminology) standard; it does not prescribe test methods or performance requirements. Key subject areas included are:
- Energy carriers and basic concepts: hydrogen, hydrogen-based fuel, liquid hydrogen, slush hydrogen, natural gas, biomethane, biogas, syngas, synthetic methane, substitute natural gas.
- Energy systems and markets: energy system terminology, smart grid and systems integration language.
- Electric power networks and storage: electrical energy, electric power, and interface terms relevant to hydrogen production from electricity.
- Hydrogen production and equipment: terms describing production systems and production equipment (e.g., electrolysis concepts referenced at a vocabulary level).
- Infrastructure and storage: transmission, distribution, storage, components, stations and plants, and hydrogen admixture into gas networks.
- Hydrogen usage: fuel cells, hydrogen-fuelled heat and power generation devices, and hydrogen‑to‑X concepts.
- Cross-cutting topics: safety, detection, risk reduction measures, metrology, quality of energy carriers, testing, certification and materials compatibility.
The document provides references and points users to more detailed, prescriptive standards for technical requirements.
Practical applications and intended users
ISO 24078 is intended for anyone who needs consistent, authoritative terminology in hydrogen energy systems, including:
- Standards writers and technical committees
- Engineers and system integrators designing hydrogen production, storage and distribution
- Regulators, policymakers and procurement officers drafting specifications or regulations
- Manufacturers, testing and certification bodies
- Research organizations and academic authors
- Safety and risk-assessment professionals
Using ISO 24078 improves clarity in specifications, contracts, regulatory texts, technical reports and interoperability documents.
Related standards and resources
Relevant referenced and complementary documents include:
- ISO 14687 (hydrogen fuel quality vocabulary and specifications)
- EN 16723 / EN ISO 14532 (biogas/biomethane and related gas terminology)
- ISO/IEC Directives and ISO Online Browsing Platform (terminology resources)
- IEC Electropedia (electrotechnical terms)
Keywords: ISO 24078, hydrogen vocabulary, hydrogen in energy systems, hydrogen terminology, hydrogen standards, hydrogen infrastructure, hydrogen safety, hydrogen production, hydrogen storage.
