We have been in a fossil fuel era and ended up with such a desperate picture! The key question here is: how to cure this problem? The common consensus to tackle this problem is that we need sustainable energy solutions which cover the following six key pillars, namely, (1) better efficiency, (2) better cost-effectiveness, (3) better resources use, (4) better design and analysis, (5) better energy security, and (6) better environment. These are essentially the main pillars and what makes this book really unique as "sustainable energy systems and applications."This book is research oriented, and therefore includes extensive practical features not found in solely academic textbooks. This book is essentially intended for use by senior undergraduate and graduate students in various disciplines ranging from mechanical to chemical engineering, and as a basic sustainable energy source on, even a handbook, for practicing energy engineers. Analyses of sustainable energy systems and their applications are undertaken throughout this comprehensive book, providing new understandings, methodologies, models, and applications, along with several illustrative examples and case studies. The coverage is extensive, and the amount of information and data presented is quite sufficient for several energyrelated courses, if studied in detail. We strongly believe that this book will be of great interest to researchers, scientists, students, engineers, and energy experts, and that it provides a valuable and readable reference text for those who wish to learn more about sustainable energy systems and applications.Chapter 1 addresses general aspects of thermodynamics to furnish the readers with background information on thermodynamic aspects, covering essentially two main laws (first and second law of thermodynamics) through energy and exergy analyses and efficiency assessment, along with some examples related to the analyses of sustainable energy systems and their applications. Chapter 2 discusses energy and environmental issues and energy sources and options and their impact of environment. Chapter 3 is a continuation of Chapter 2 by focusing primarily on global warming and climate change issues and their consequences. Chapter 4 focuses on energy conservation with some specifics on issues, measures, policies, strategies, and their assessments, and offers some illustrative examples. Chapter 5 vii viii Preface