Authors have tried to strike a balance between a short book chapter and a very detailed book for subject experts. There were three prime reasons behind doing so: first, the field is quite interdisciplinary and requires simplified presentation for a person from non-parent discipline. Second reason for this short-version of a full book is that both the authors have seen students and technically oriented people, searching for this type of book on wind energy. Third reason and motivation was considering engineers who are starting their career in wind industry. This book is targeted to present a good starting background to such professionals.