This book covers all major areas where optimization techniques have been applied to reduce uncertainty or improve results in renewable energy systems (RES). It begins with an introduction to optimization, then covers a wide range of applications in both large and small scale operations, including optimum operation of electric power systems with large penetration of RES, power forecasting, transmission system planning, and DG sizing and siting for distribution and end-user premises. The book is an excellent choice for energy engineers, researchers, system operators, system regulators, and graduate students.