[en] This paper presents a collective analysis of the strategic place that hydrogen, as an energy vector, could occupy in a carbon-free energy transition. In 2015, IHEST Institute questioned eleven auditors about the place of hydrogen in the energy transition. The role of the listeners consisted in meeting selected experts allowing to approach the technical questions as well as the plays of actors. Why such controversies around this potential energy vector? Which actors, which interests, which stakes? What advances in R and D? What locks for industrial transfer? What viability of the economic model? Where are the regulations, standards and safety of use? What positions of competition does this energy vector give rise to?

[en] This report describes and discusses the perspectives of evolution and innovation for three great issues related to renewable energies. The first one is waste methanization, and the report addresses the following topics: practice in France, characterization of organic wastes, quick prediction of the potential associated with solid wastes, integration of methanization within an existing sector, local implantation of methanization, towards the methanization of sewage sludges, for a better management of digestates, the issue of renewability of our wastes, the optimization of microbial processes of waste degradation, analysis of methanization life cycle). The second issue is the use of wood as energy source: quantities, cartography of forest biomass by remote sensing, cartography of exploitability in mountain forests, organisation of a wood-energy supply, cartography of clear cuts, impacts of wood crops on insects, producing more wood while better preserving biodiversity, wood-energy governance. Thirdly, the report addresses issues of energy savings and impacts: energy optimization for agricultural machinery, relationship between irrigation and energy saving, energy saving by energy storage, nebulisation applied to refrigeration equipment, high thermal inertia applied to domestic refrigerators, works and downstream migration of eel, dam hydraulic management and fish population dynamics, reduction of environmental print at work