The applications of mild forms of energy have shown significant activity since the early 1980s. However, only in the last ten years have they made substantial progress, in a desperate effort by modern humanity to meet its increasing energy needs with respect for the environment, while simultaneously pursuing the energy sustainability of the planetary ecosystem.

The implementation of this effort requires a systematic examination of the technological, economic, and environmental parameters involved in the respective energy applications, with the aim of a quantitative and not just qualitative assessment of potential energy options.

For this purpose, the authors have gathered in this book their long-term experience from dealing with practical applications as well as their relevant experience from teaching energy-related courses, particularly those concerning the utilization of wind energy and hydropower.

The result of this arduous effort is the collection and processing of approximately one hundred (100) computational applications in the field of harnessing wind and hydropower. These applications are solved in a model way, presenting on the one hand the required reasoning for solving each problem, and on the other hand, a detailed account of the numerical results of the necessary calculations.

Emphasis is placed on the organized use of tables that contain the numerical calculations, as well as on the graphical representation of the main results. The aim of the authors' effort is to contribute to the understanding and solving of the problems accompanying the utilization of wind and hydropower, through the application of fundamental laws of physics and the organized development of a comprehensive methodology for addressing such applications.