Dear Colleagues,

Currently, the global economy is being confronted with issues related to the exploitation of fossil fuels and to the rising demand for energy. On one side of the issue are increased atmospheric pollution, the widely discussed effects of carbon dioxide emissions, etc. The other consequence is the inevitable depletion of fossil resources.

Therefore, the search for new energy resources and the development of corresponding technologies is urgently needed. Therefore, a broad range of research on alternative resources, including those that are renewable and those that appear to be inexhaustible, is required (e.g., solar energy, wind energy, hydro energy, biomass energy, geothermal energy).

The energetic efficiency of processes occurring in the harvesting and exploitation of energy derived from both fossil and alternative resources is an important factor. It can be expressed as a ratio of the energy delivered by the converting system to the total energy fluxes required to ensure the system's operation. The search for conversion routes that consume a negligible portion of the delivered energy is possibly the greatest challenge for technological development.

The present Special Issue is devoted to themes that reveal the state-of-the-art in the knowledge and technological development of any area linked to alternative energy sources and green hydrogen production. Papers on both new and existing topics are encouraged for submission. New developments in areas such as photovoltaics; solar thermal energy; wind, hydro, geothermal, and biomass energy; hybrid energy systems; hydrogen energy; green hydrogen generation; and hydrogen as a fuel are very much appreciated. Additional themes will be explored. Original studies as well as reviews discussing the mentioned topics and their links to economic or environmental challenges are also of interest.

I also would like to emphasise that the reputable scientific publication of Sustainability has an open access policy, making it widely available.

Dr. Qusay Hassan
Dr. Itimad D.J. Azzawi
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sustainability is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

• energy harvesting
• renewable energy
• solar energy
• wind energy
• hydro energy
• tidal energy
• geothermal energy
• hydrogen energy
• green hydrogen
• hydrogen production, storage, and utilization