Sustainable energy conversion and management processes increasingly require an integrated approach, especially in the context of addressing the climate crisis. This editorial puts forth related research frontiers based on 28 research articles of the special issue that is dedicated to the 13th Conference on Sustainable Development of Energy, Water and Environment Systems and regional series based on the 1st Latin American and 3rd South East European Conferences. Seven research frontiers are reviewed, the first three of which are (i) sustainable technologies for local energy systems, (ii) energy storage and advances in flexibility and (iii) solar energy penetration across multiple sectors. These research frontiers contain contributions based on renewable energy for wastewater treatment in islands, energy savings across urban built infrastructure, advanced district heating and cooling networks, power-to-gas and hydrogen production technologies, demand response in industrial systems, hybrid thermal energy storage, hybrid solar energy power plants, novel photovoltaic thermal technologies, and improved solar energy dispatchability. The research frontiers continue with (iv) wind, water based energy and the energy-water nexus, (v) effective valorization and upgrading of resources, (vi) combustion processes and better utilization of heat and (vii) carbon capture, storage and utilization. Significant contributions include innovative wind and hydrokinetic turbines, osmotic power technologies, synergetic solutions for water desalination, efficient catalytic pyrolysis, upgrading to reduce particle pollution, co-processing for alternative fuels, combustion characterization, electricity generation from waste heat sources, advances in heat exchangers and heat transfer, oxy-fuel combustion, post-combustion capture, and fly ash recycling for energy storage material. The research frontiers in this editorial provide ample opportunities to support societal transformations in the next decades to sustain planetary life-support systems.