Book excerpt: This book discusses renewable energy systems and applications, and demonstrates how an accelerated transition to 100% renewable energy can be achieved. It examines the systems from a thermodynamic perspective, focusing on the irreversible aspects of the current energy system and highlighting the solutions developed to date. Presenting global research and developments, this book is intended for those working within the field of renewable energy research and policy who are interested in learning how they can contribute to the transition from fossil fuels to renewable resources.