This 800-page premier book on energy focuses on energy sources, utilizations, legislations and sustainability as it relates to a state, a province, or a country, or a community within a state. This book presents various kinds of energy sources, ways to convert energy for end use, better use of energy towards conservation and energy- and environmental-sustainability. As a very proper model-state the authors chose the State of Illinois which has the largest overall fossil energy reserves, including the largest strippable bituminous coal reserves; the largest user of nuclear energy in USA and has also been investing in all kinds of renewable energies including wind energy, solar energy, biofuels, geothermal energy, and various energy storage options. In the authors' opinion, State of Illinois is a pioneer in legislations for proper development and use of all kinds of energy. Their motivation to do this project was to educate the public (including students, energy engineers and planers, as well as state- and country-wide policy makers) about all aspects of energy.In this book, the authors present various energy sources, conversions technologies, and conservation possibilities. In every case, the authors have presented various options available for a country, for a state, or for a community to achieve its goal of energy sufficiency, clean environment and as a result, sustainability. Variety of schemes related to each energy source and its related conversion technologies are presented and sustainability of renewable energy sources is discussed. All the possible energy sources including coal, natural gas, petroleum, nuclear, solar, wind, biofuels and geothermal energy are presented in this book, as well as energy storage options. The authors have also presented various ways of dealing with carbon dioxide, which is produced from fossil fuels combustion, including its collection, transportation, storage and sequestration. The energy storage systems presented in this book will facilitate reliable and full integration of renewable power to the grid.