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- Category: Articles
What Stock Prices and Wind Loads Have in Common
Extreme loads that occur only once or a few times in the life of a wind turbine play an important role in the design process. The time series of loads typically look like a mixture of oscillations and random fluctuations, the latter caused by the turbulent wind. From the fluctuating time series we need to be able to determine reliable loads equipped with probabilistic properties like ‘exceeded on average once within 50 years’. For a long time the methods used to determine ultimate loads for wind turbines have been relatively simplistic. However, nowadays, because of increasing turbine size and value, more sophisticated methods are recommended. In this article we give an introduction to extreme value theory that provides the tools to determine ultimate loads and also introduce our computer program GumbelWind as a tool for the practical application of the theory.
By M. Hänler and U. Ritschel, Windrad Engineering GmbH, Germany
- Category: Articles
Identifying Promising Areas for Wind Farm Installation and Energy Prediction
This article describes the development of a computational tool designed to help the electric power utilities in the planning and operation of a system that integrates wind energy into the electric grid.- Category: Articles
Imagine a kite that looks like an aircraft and can be flown like one. An efficient, reliable and stable design. Such a kite is a portable pulling force in the air. With this force it is possible to do all kinds of exciting things such as pull ships and generate energy. At the Delft University of Technology, Faculty of Aerospace Engineering, kites are maturing from ‘toys’ to a serious force to be reckoned with.By Jeroen Breukels, PhD student, and Prof. Dr Wubbo J. Ockels, Chair ASSET, TU-Delft, The Netherlands
- Category: Articles
For many years most modern large wind turbines were erected in areas like Denmark and northern Germany, where earthquakes are rare and normally weak. However, more recently wind farms have been developed in Asia, Africa and southern Europe, where strong earthquakes are much more likely to occur. As a consequence, the question arises as to how wind turbines perform in an earthquake of a given magnitude, and especially to what extent the stability of the overall structure and integrity of the machinery are guaranteed. This article describes how building codes for seismic loading of structures are used for site approvals for wind farms and shows results for the simulated dynamical behaviour of a wind turbine in an earthquake. The simulation has been carried out with the new simulation code SiWEC, which is also introduced in this article.
By M. Hänler, U. Ritschel and I. Warnke, Windrad Engineering GmbH, Germany
- Category: Articles
With increasing turbine size, dynamic loading of the tower increases. With dampers, these loads can be reduced. The mass of conventional pendulum dampers is approximately 4% of the total turbine. The Tuned Liquid Column Damper (TLCD) provides a new solution that enables significant tower mass reduction, using only 2% of the effective mass. The tuning possibility facilitates on-site optimisation of damping characteristics. The TLCD enables reduction of the ‘cost of energy’ for both new and existing turbines.
By Arnold Wilmink and Ferdy Hengeveld, Mecal, The Netherlands
- Category: Articles
Over the past decade, land-based wind turbines have grown considerably. This up-scaling has caused problems by subjecting gearboxes and drive trains to heavy loads and stresses. In order to reduce loads and increase turbine lifespan, Clipper Windpower of Carpinteria, California, USA, has developed the 2.5MW Liberty wind turbine.- Category: Articles
Wind energy is environmentally friendly, yet it is not without competition. Preferences can quickly change to other sources of energy if wind turbines turn out to be too expensive or technically insecure. Despite the competitive struggle the wind energy business has with other sources of energy, there is also competition among the turbine manufacturers. The last few years have provided a little time to relax from the disaster of gear damage that shook almost the entire business. Mostly it was constantly hard applied fail-safe brakes that caused the damage to stall regulated machines. Fortunately, things have changed, but there are emerging Asian countries where manufacturers should learn from mistakes and experience in Europe so that they do not repeat the mistakes.By Andreas Gerken, Svendborg Brakes, Germany
