This textbook provides a strong foundation in the basic thermodynamics needed to analyze real-world engineering applications of thermodynamics in the field of energy systems. Written in a format readable to students new to the subject, this book will also help entrepreneurs venturing into the world of energy and power without a background in mechanical engineering.This book presents the basic theories of thermodynamics by focusing on the application of the subject matter to the most common applications of thermodynamics. It takes real-world problems from the author's over 40 years of experience as a practical, professional engineer and provides in-depth solutions to each problem using concepts the student has learned from earlier chapters. The case studies provide both examples of how thermodynamics is used in state-of-the-art tools to solve the case studies' problems, as well as ideas for future energy-efficient systems.