A wind turbine is a rotating machine which converts the kinetic energy in wind into mechanical energy. World-wide interest in renewable energy systems such as wind turbines has increased dramatically, due to environmental concerns like climate change and other factors. Wind power is a major source of sustainable energy, and can be harvested using both horizontal and vertical axis wind turbines. This book addresses wind turbines and provides theoretical background and rationale for these developments. The required guidelines to make wind farms environmentally friendly are addressed, as well as the impact that wind turbines may have on benthic biomass and diversity. Ideas about future developments of wind turbines are also reviewed in this book.