Sustainability enhances human beings' lives, preserves their ecosystem and conserves natural resources. One of the most important steps towards sustainability is the development of renewable energy systems. Hence, different renewable energy technologies have been introduced, developed and applied in recent decades. Among different renewable energy sources, a solar energy source is one of the most attractive options for a variety of purposes, namely power generation, heating, cooling and freshwater production. The necessity of the development and performance improvement of solar energy technologies require deep insight into their working principles, effective factors and potentials of modifications. In this book, solar collectors and systems are the focus, as well as their use in a number of different applications, from power generation to heating, cooling and desalination. Furthermore, some promising approaches for the improvement of these systems and enhancement of their reliability such as the employment of quantum dots materials and storage units are represented and discussed. This book will be useful for the scholars and engineers working on solar systems and their relevant technologies and components.