E. Hau - Wind Turbines

Foreword to the Third English Edition

This revised and greatly enlarged third edition is an attempt at keeping abreast of developments in wind energy technology and especially of the meteoric expansion in wind energy utilisation for generating power. Since the first edition appeared in 1988, the book has kept pace with this development with five editions in German and now three editions in the English language.

In 1988, the idea of utilizing the energy of the wind for generating electricity was still the dream of s few enthusiasts and was not taken very seriously by the established electricity industry. Today, generating power from wind energy has gained its rightful place in the electricity supply spectrum. In almost all the countries, more and more wind turbines are being used to supplement conventional power stations and their number is increasing throughout the world. The rate of increase being counted in double figures. In some countries, notably in Germany, the utilisation of wind energy has already become an indispensable part of the effort of switching power generation increasingly to renewable energies and bringing the age of atomic energy to an end.

However, it is not only ecological concerns – and in many cases also apprehensions about the hazards of atomic energy – which provide the driving force for current development and future hopes. By now, the profitability achieved by generating electricity from wind energy is also playing an increasing role. In a fair comparison – that is to say a comparison of the costs of generating electricity from power stations newly to be built with the costs of generating electricity from wind energy, the latter are found to be scarcely higher and, in the long term and under favourable conditions, even prove to be the cheaper alternative. The large producers of electricity are increasingly aware of this fact and, after initially hesitating for a long time, are now also investing in wind energy. The visible result of this assessment is the construction of large offshore wind farms.

The enormous expansion of wind energy utilisation would not have been possible without an improved technology of the wind turbines. Even though the basic concept of the wind turbines used commercially has remained unchanged for several decades, significant advances have been achieved in their detailed development and contribute decisively to improved efficiency, increased reliability and more advantageous production costs. Examples of this are the evolved aerodynamics of the rotors or the development of gearless designs with electrical generators driven directly by the rotor, or control technology with ever-increasing intelligence which, coupled with modern frequency inverters, improves the quality of the electricity delivered and reduces the system loading. The increasing size of the turbines also requires novel technical solutions, for example for assembling turbines having a rotor diameter of more than 150 meters and towers of corresponding height. The development of offshore technology has only just begun. In the coming years, large offshore wind farms will be erected which will require new designs and considerable investments for the transmission and distribution of power on land to consumers located far in the interior. The present third edition also attempts to analyse the current state of the art in these areas and to clarify it by quoting examples.

These general remarks about the present state of wind energy utilisation apart, I will refrain from commenting further on the self-evident importance of wind energy for the global energy crisis and for the environmental crisis. However, I do feel that some helpful hints on what this book is about will not be misplaced.

The title wind turbines refers to industrially developed and manufactured machines for generating electrical power. Those looking for a do-it- yourself manual for putting together a windwheel, as interesting a hobby as this may be, will, therefore, be disappointed. Instead, this book is intended to give a general overview of modern wind turbine technology and to provide a means of orientation in the associated technical and economical fields and its contents and form of representation are structured with this objective in mind.