The purpose of this article is to put forward a methodology in order to evaluate the Cost Breakdown Structure (CBS) of a Floating Offshore Wind Farm (FOWF). In this paper CBS is evaluated linked to Life-Cycle Cost System (LCS) and taking into account each of the phases of the FOWF life cycle. In this sense, six phases will be defined: definition, design, manufacturing, installation, exploitation and dismantling. Each and every one of these costs can be subdivided into different sub-costs in order to obtain the key variables that run the life-cycle cost. In addition, three different floating platforms will be considered: semisubmersible, Tensioned Leg Platform (TLP) and spar. Several types of results will be analysed according to each type of floating platform considered: the percentage of the costs, the value of the cost of each phase of the life-cycle and the value of the total cost in each point of the coast. The results obtained allow us to become conscious of what the most important costs are and minimize them, which is one of the most important contributions nowadays. It will be useful to improve the competitiveness of floating wind farms in the future.
The development of new energy sources is necessary to sustain our current lifestyle. This occurs due to the fact that fossil fuels have a limited life span [1]. Hence, the use of renewable energies, the use of which is unlimited, will be of utter importance. Moreover, in 2009 the European Union (EU) has established that 20% of final energy consumption should come from renewable sources in 2020 [2].
In relation to renewable energies, the future will be directed toward its use in the marine environment. In this sense, offshore wind will make a substantial contribution to meeting the EU's energy policy requirements through a sharp increase – in the order of 30–40 times by 2020 and 100 times by 2030 – in installed capacity compared to present day. Otherwise, the distance to the shore and the depth are the main constraints in this technology. Thus, the next step is to develop floating structures, which can operate in deep waters. In this context, two different floating platforms prototypes have already been installed: spar substructure called Hywind in Norway and the WindFloat semisubmersible platform in Portugal [3].
However, one of the most important difficulties in the development of a new technology is the absence of procedures which allow us to evaluate the costs of the floating structures [4]. In this sense, there is an approximation to the cost of a spar system which describes the general costs, but which has not taken into account the relationships between variables [5]. Furthermore, other studies are focused on technical or theoretical aspects [6]. Considering that the availability of knowledge in relation to floating wind farms is scarce, cost experiences of fixed offshore wind energy or onshore wind energy [7] can be used as a starting point, being useful to determine tariffs in the future [8].
Therefore, the main objective of this article is to become aware of what the main costs are involved in a floating offshore wind farm and which are the fundamental variables involved in each phase of their life cycle. In addition, three different floating platforms will be considered: semisubmersible, Tensioned Leg Platform (TLP) and spar. Results allow us to be conscious of what the most important costs are and minimize them in the future improving the competitiveness of floating wind farms.
The present study has formulated the costs involved in a floating offshore wind farm taking into account the six phases of its life-cycle: definition, design, manufacturing, installation, exploitation and dismantling. Furthermore, their main dependences, whose influences will be developed in future studies, have been defined: wave height, speed of the current, wave period, scale parameter, shape parameter, depth, distance to shore, distance from farm to shipyard, distance from farm to port, among others.
Results have been analysed for the specific place of Galicia, which is located in the North-West of Spain, an area where offshore wind resource is high. In this sense, several types of values have been analysed: the percentage of the costs, the value of the cost of each phase of the life-cycle and the value of the total cost on each point of the coast. Furthermore, all of these issues have been considered for each type of floating offshore wind platform: semisubmersible, TLP and spar.
Results allow us to become aware of the most important costs and minimize these costs in the future, improving the competitiveness of floating wind farms. Furthermore, the results of the percentage for a floating offshore wind farm for the CAPEX (Capital Expenditure) costs do not differ substantially from conclusions reached by Bussel, Snyder and Musial for fixed offshore wind farms. They consider that the sum of definition cost, design cost, manufacturing cost, installation cost and dismantling cost represents between 70% [47] and 78% [38][48] of the total costs, values that in the floating offshore devices will be from 69.1% to 75.5%.
On the other hand, if the present prototypes are borne in mind [13], the floating offshore wind farm considered with 21 semisubmersible platforms is cheaper than other with spar or TLP platforms, with an approximate cost of 349 M€. However, the main costs will be related to manufacturing, maintenance and installation, in this order, for all the types of floating platforms.
Future studies will be used to determine, taking into account these costs, some economic indicators, which will help the investor to know the viability of the project.
