The last decade has seen a remarkable growth in the rated power of wind turbines throughout the world, particularly in Europe, with a 170m diameter 10MW turbine thought technically feasible by 2015. It has been an increasing challenge for the wind turbine industry to meet these technical requirements and in doing so the industry has employed a large amount of innovation in the detailed use of materials, design, analysis and testing. In this article, the authors propose a new damage tolerance methodology for the design and testing of wind turbine blades. This has the potential to radically reduce the test programme requirements for large wind turbine blades.

By Josef Kryger Tadich and Jakob Wedel-Heinen, DNV Wind Energy, Denmark

A summary is given of some of the developments that have taken place over the last 10 years in the field of wind farm software. The visualisation side of the development process has advanced the most and now sees the introduction of 3D landscape tools.

By Alan Harris, ReSoft Ltd, UK

The Concept of the PrimAero Wind Sensor

Have you ever seen standard meteorological wind measurement devices like wind vanes or anemometers on aeroplanes? Certainly not. The most important reason is that the measurement bases would be wrong. When you compare measurement devices, the most obvious differences are the measurement principles they are based on (i.e. the use of laser, sound waves or other techniques to detect a signal and the physics behind this). But this is only one aspect. Even more interesting than 'how' a device works is 'what' it measures. Clarity about the measurement target is the most important factor to consider for any measurement device. From this point of view, the PrimAero wind sensor is unique for wind measurement on wind turbines because it not only measures the wind speed but also the wind pressure as a whole.

By Klaus Ritzinger, Head of Research & Development, IXIST Messtechnik, Germany

Based on the lightning leader model of Cooray et al., the electric field distribution on a wind turbine induced by the leader has been simulated using the Finite Element Method (FEM). Because of its dimensions and complexity, the wind turbine has been simplified to its lightning protection system and by simulating only one blade. The derived electric field distribution has then been used as input for a detailed blade-tip model. The detailed model can be used to analyse the influence of the down-conductor shape on the electric breakdown emergence.

The wind turbine sector is growing quickly. The number and capacity of wind turbines has grown substantially in the last few years, and there is the prospect of greatly increased capacity as newly developed turbines are installed. This article will discuss the current requirements for the monitoring and inspection of wind turbines and explain the importance of regular inspections, carried out by accredited experts. There will be a discussion of the current position, based on the experience gained during the more than 2,000 wind turbine inspections carried out by GL Wind Energy.

By Torsten Muuss, Germanischer Lloyd Industrial Services, Germany

Accurate assessment of the resource at potential wind-energy sites is becoming more critical. The 60m met towers most commonly used for site assessment are decreasingly effective as turbines grow taller. Sodar devices, which measure wind speed and direction at any height up to about 200m, are a potential solution. Although manned sodar products are now common for short-term profiling, they have many shortcomings for long-term assessment. In this article, the author describes the innovations of Second Wind's Triton sonic wind profiler, which was designed to replace met masts for many assessment applications.

By Walter Sass, CEO and Chief Engineer at Second Wind, USA