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The aim of this paper is to determine the main costs and the feasibility of repowering wind farms. For this purpose, two study methods, which depend on legal and wind turbines issues, have been considered. They will provide nine alternatives, whose study will be developed. The methodology has been applied to the particular case of Galicia (North-West of Spain), where there is a good onshore wind resource. Calculations indicate the costs, the Net Present Value (NPV), the Internal Rate of Return (IRR), and the Pay-Back Period of these alternatives. In addition, a sensitivity study has analyzed the main variables of dependence in repowering wind farms. Results show that repowering can be a new alternative for onshore wind farms in areas where old wind turbines are currently installed. [ABSTRACT FROM AUTHOR]

Despite the fact that offshore wind energy will tend towards the floating technologies their economic impact has not been practically evaluated yet. In this context, the aim of this article is to characterize the possible economic alternatives which can be considered in the life-cycle of floating offshore wind farms based on their life-cycle costs. Several groups of variables have been considered for determining these alternatives: wind turbines, floating platforms, mooring system, anchoring process, kind of seabed, electric system, installation, shipyard and maintenance. The method proposed has been applied to the case of the North-West coast of Spain (Galicia region). For this case test three different platforms have been analyzed: Tensioned Leg, Spar and Semisubmersible platforms. Results, which are presented by using maps of the area, conclude that offshore substation, string electric configuration and “tree fall” decommissioning method are the best options for minimizing the costs. In addition, the installation method will be conditioned by the type of floating platform and mooring material, whereas the disposition and anchor decisions are dependent on the geographic location. Results show how the methodology proposed is useful to characterize economically the life-cycle of a floating offshore wind farm. [ABSTRACT FROM AUTHOR]

Castro-Santos, L. and Diaz-Casas, V. 2015. Cost comparison of three floating offshore wind platforms. This paper proposes a method to calculate the total cost of a floating offshore wind farm. The method is based on the phases of the life cycle of such a farm. Each phase is defined by a cost, the value of which is either a constant or a variable parameter depending on the characteristics of a particular region. The tool so developed results in a georeferenced map of the total cost implied in the development of a floating offshore wind farm. Additionally, this method is applied to a floating offshore wind farm located in Galicia (in northwest Spain), as well as the three most important types of floating platforms: semisubmersible, tensioned leg, and spar. This paper is novel in that it helps to estimate the economics of floating offshore wind farms. In this sense, this study is one of the first of its kind to calculate the various costs associated with these types of wind farms. [ABSTRACT FROM AUTHOR]