Dear Colleagues,

In the original ‘hydrogen economy’ concept created by John Bockris in the 1970s, hydrogen was produced via water electrolysis and transported through pipelines to factories, homes, and fuelling stations, where it would be converted back to electricity in on-site fuel cells. Since then, discrete efforts have been progressing to put forth plans for a ‘hydrogen society’. However, in recent years the hydrogen economy has changed from being a distant concept to become imperative. Decarbonising the global economy is a priority to limit the harmful effects of the huge amounts of greenhouse gas emissions to the atmosphere. In order to enable a 100% renewable energy society, the hydrogen economy is the keystone for green energy storage. Hydrogen and electricity will work in tandem to service all energy-related sectors.

In the coming years, green hydrogen will be progressively integrated into industry, transportation, buildings, heating, and power sectors. In this scenario, water electrolysis technologies are attracting a great deal of attention and gathering numerous efforts to quickly improve their readiness level. This Special Issue is devoted to analysing the current state-of-the-art intending to provide a general overview of relevant factors for its implementation in a mid-term hydrogen economy. Studies providing a fundamental reference for experts to complete their assessments on available technological options, their progress and integration with renewable energy sources; providing models for the scalability of plants, as well as distribution and optimal localization; as well as techno-economic analyses and the most probable scenarios in the near future are expected to be essential tools for actors involved in project planning, implementation, decision making and monitoring.

Although this Special Issue is open to all contributions related to hydrogen production by water electrolysis, the main potential focus areas are summarized as follows:

• Comparative evaluation of different types of technologies: alkaline water electrolysis (AWE), anion exchange membrane water electrolysis (AEMWE), proton exchange membrane water electrolysis (PEMWE);
• Electrolysis materials, components and systems;
• Technical and operational challenges;
• Integration with renewable energy sources: models and configurations;
• Balance of plant engineering;
• Modelling and simulation;
• Economic factors: cost optimization;
• Environmental impacts/benefits;
• Water resources: seawater vs. freshwater; water recycling for hydrogen production;
• Recycling processes and sustainability;
• Life-cycle and risk assessments.

Dr. Paloma Ferreira-Aparicio
Dr. Araceli Fuerte
Dr. Concepción Caravaca Moreno
Dr. Alba Fernández-Sotillo
Guest Editors

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• green hydrogen
• water electrolysis technology
• renewable energy integration
• socio-economic and lifecycle assessments
• balance of plant engineering