Materials and Technologies for Energy Efficiency is a compilation of research papers whose main aim is to provide an opportunity to gather knowledge about the latest developments and advances in materials and processes involving energy. This volume consists of a series of works which were presented at The Energy & Materials Research Conference (EMR2015), held in Madrid, Spain in February 2015. This compilation of more than 50 papers has been written by researchers from all over the world. Papers focus on topics including biomass and biofuels; solar energy; fuel cells; energy storage, etc. The book is recommended for researchers from a broad range of academic disciplines related to energy and materials. We hope that this set of papers would be useful to stimulate further discussion on energy and materials research.