Direct-drive wind turbines offer the potential for high efficiency and reliability but they require large and heavy electrical generators. Large electrical machines require significant structural material to maintain the small airgap clearance between rotor and stator. This structural mass can be modelled, and optimised by either choosing lightweight materials or by adding to the airgap stiffness or using air-cored topologies. A new topology (the ‘E-generator') combines the structural and active material in a ‘C' core module, which can be supported lightly for high torque machines.

One of the issues to be solved to make upscaling of wind turbines a reality is the design of improved structural components. Since finite element computations are already in widespread use in the industry, the aim is now to find new simulation tools and improved failure criteria which could be used to design lighter but stiffer and stronger components. The application of fracture mechanics in the analysis of composite materials is a relatively new trend, which provides solutions for the former objectives. The aerospace industry has already proposed new criteria that try to improve the accuracy offered by the usual failure criteria by using fracture mechanics to analyse local phenomena such as fibre kinking and in situ effects. Other fracture mechanics related techniques offer the possibility to consider mechanical degradation caused by delamination and loss of adhesion. This article describes these new criteria and techniques. These are ready to use and will be employed regularly in the wind energy industry in the upcoming years.

For many years the Dutch style of Horizontal Axis Wind Turbine (HAWT) has dominated the market, but now, for a number of reasons, developers and investors alike are taking another look at what Vertical Axis Wind Turbines (VAWT) can offer. This article takes a brief look at the technical reasons why this type of machine deserves closer scrutiny in the form of smaller machines for the built environment, or larger machines for wind farms and offshore applications. It tries to explain the commercial reasons why many people are now starting to recognise the benefits of VAWT machines and why this type of machine could be the next growth area within the industry.

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.