This book explores the four forms of solar energy: photovoltaic, thermal, thermodynamic and passive solar energy, a solution not to be overlooked! It presents the basic principles, how they work, their applications, and their potential for integration in various environments. Through case studies, this book guides the reader through the challenges of optimizing the capture and use of solar energy. It also emphasizes the importance of energy efficiency, sustainability and innovation in the development of solar systems, in order to contribute to a cleaner, more responsible energy future. And at the end of the manuscript, there are ten exercises with solutions.