The goal of this book is to introduce energy conversion phenomena and materials at multiple levels. With limiting amount of fossil fuels and increasing demand of energy, we are facing the grand challenge of energy sustainability. Energy saving strategies may help to extend the usage of hydrocarbon fossil fuel, but can not solve the problem completely. Renewable energy seems to be the only solution. All the renewable energy sources, solar energy, wind energy, biomass rely on effective energy conversion materials and systems to benefit human beings. Various energy conversion materials and systems including photovoltaic (PV) solar cells and wind turbines have been developed for generating electricity from renewable energy sources such as sunlight and wind. High energy conversion efficiencies are critical for large scale applications of these systems. To understand the fundamentals of energy conversion mechanisms is the very first step. Materials have taken indispensable roles in energy conversions. Therefore, it is necessary to introduce the latest research progress on energy conversion materials to readers at various levels. The content of the book deals with various materials and processing techniques for energy conversions. A comprehensive state-of-the-art review on nanomaterials, related processing technologies and applications will be provided. Considerable effort has been made to elaborate the technological aspect of energy conversion materials, processing and manufacturing these materials.