In the next few years, there are plans to connect a variety of ambitious offshore wind projects to the European grids. In addition to new grid connection lines and grid reinforcement measures it is expected that additional measures for overall system operation will be required because of the intermittent nature of wind generation. In the short term, on timescales from less than a second to several hours, a variety of balancing services are necessary in order to maintain stable system operation. In the long term, wind generation can provide only limited contributions to guaranteed system capacities (e.g. in the event of peak demand). In this article, these aspects are addressed comprehensively when analysing the economics of large-scale intermittent wind generation. An approach is presented to estimate the additional system-related cost elements for different wind penetrations in a system.

By Hans Auer, Vienna University of Technology, Austria

A critical property of an offshore wind turbine is its reliability. The concept presented here aims to improve turbine reliability via the use of a permanent magnet induction machine. This allows the gearbox and converter to be abandoned, thereby reducing the total number of parts. To adapt the rotation speed to the wind speed, a new control concept with just one central converter is used to control the frequency of the park grid. At partial load a maximum power point control is applied to find the optimal frequency. Active stall and pitch control have been investigated at rated load.

By Eckehard Tröster, Technische Universität Darmstadt, Germany

The grid integration of wind energy is an important issue in Japan. Offshore wind development is likely to play an important role in overcoming the limitations of the grid integration of wind energy. This article describes the results from a joint research project by Tokyo Electric Power Company (TEPCO) and the University of Tokyo, including wind resource assessment using a mesoscale meteorological model and a geographical information system (GIS).
           
By Takeshi Ishihara and Atsushi Yamaguchi, University of Tokyo, Japan

The very large growth of wind turbines during the last 20 years has led to a significant increase in some component prices. The need to meet the strong pressures to deliver electricity from wind as cheaply as possible has resulted in a very close cooperation between turbine and blade developers. The generic blades of the past have almost totally disappeared. This article describes some of the resulting effects in terms of more efficient material use and the design criteria at the interface between blade and turbine design (which cannot be optimised from just one side). This design integration is essential for smaller or start-up turbine manufacturers in order to enable them to survive in a market that is more and more dominated by ‘all-in-one-house’ global players.

By Roland Stoer, EUROS Entwicklungsgesellschaft für Windkraftanlagen mbH, Germany