Wind Turbine Installation for High Elevations

The strong drive to exploit wind energy has recently led to new types of location for wind turbine installations being considered, including mountain regions and, to be more specific, areas at elevations coming between 800 and 2,500 m asl. Authoritative sources, such as the European Wind Energy Association (EWEA), have estimated that 20–25% of the approximately 60,000 MW expected to be installed in Europe between now and 2010 will be situated in cold-climate areas, and a part of them will be on hills and mountains. The installation of wind farms in the mountains consequently demands an in-depth analysis, in the design of such plant, into both the methods for assessing the resource and the more or less direct transfer of procedures and technologies developed for conventional sites. For the time being, the IEC standards (originally developed to provide a reference picture relating to conventional sites) fail to provide recommendations on this type of site, where the structure of the flow field is substantially more complex in terms of its effect on the stresses involved. The present work outlines the main features of mountain wind farm sites and discusses the effects of some of said features on the structural assessment of the turbines destined for such installations in the light of the IEC standard requirements. The work illustrate that the installation of wind turbines in mountain sites must consider different site-related features from those used to develop the requirements of the IEC standards. The examples given here indicate that, based on the standards, these features influence both energy generation and the turbine’s working life. Only an adequate understanding of these features can lead to a cost-effective sizing of the turbines. This type of approach can lead to a site-specific design concept, and only certain components are structurally adequate for the stress characteristics of a given site. These procedures will then have to be transferred to the standards, overcoming the conflict between the minimum standard requirements specifying the fundamental elements to consider in the project and the set of parameters describing the external conditions that demand a turbine of equivalent sturdiness in comparable applications.