During recent years renewables have been acquiring gradually a significant importance in the world market (especially in the Spanish energetic market) and in society; this fact makes clear the need to increase and improve knowledge of these power sources. Starting from the results of a Life Cycle Assessment (LCA) of a multi-megawatt wind turbine, this work is aimed to assess the relevance of different choices that have been made during its development. Looking always to cover the largest possible spectrum of options, four scenarios have been analysed, focused on four main phases of lifecycle: maintenance, manufacturing, dismantling, and recycling. These scenarios facilitate to assess the degree of uncertainty of the developed LCA due to choices made, excluding from the assessment the uncertainty due to the inaccuracy and the simplification of the environmental models used or spatial and temporal variability in different parameters. The work has been developed at all times using the of Eco-indicator99 LCA method.
Life Cycle Assessment (LCA) methodology [1] and [2] is useful for analysing the environmental impact occasioned by any type of product or process [3], [4], [5], [6] and [7]. However, the results obtained with LCA present some uncertainties that have to be considered and assessed in an appropriate way. In general, these LCA uncertainties can be classified into, at least, five types: parameter uncertainty [8] and [9], model uncertainty [10] and [11], spatial variability [12] and [13], temporal variability [14], [15] and [16], and life cycle scenario uncertainty [17], [18] and [19].
LCA methodology has been frequently used to study the environmental impact occasioned by different renewable energy technologies [20], [21], [22], [23] and [24]. The LCA of a multi-megawatt wind turbine [25], [62] and [63] has been taken as a reference to develop this work, which is based on the Eco-indicator99 LCA method.
Moreover, studies of sensitivity analysis of LCA have been widely used in different areas, from the field of renewable energy [23] to the industrial field [26] and [27], including many different sectors such as residential construction [28], computers [29], and electronic boards [30]. For instance, [23] analyzes the impact of variations in the input material, the type of power considered in the manufacturing process, the transport, and the maintenance phase. In [28], a sensitivity analysis was carried out to find the impact of variations in life spans of the components, the need for extra room in micro-cogeneration plant, the efficiency of the auxiliary burner, and the electrical and overall efficiencies of the solid-oxide fuel cell plant.
Besides its practical application in several case studies, there also exists relevant literature on the development and analysis of the different methodologies used, from the analysis of different alternative scenarios to the statistical analysis of the uncertainty associated with the data used [31], [32], [33] and [34].
One of the purposes of this work is to analyse and assess the relevance of different choices that have been made during the development of the LCA. Four alternative scenarios have been studied. The first one (AS1) represents an increase in maintenance during the lifetime of the wind turbine. The second alternative scenario (AS2) analyses an increase in the needs of material and energy used. The third scenario (AS3) studies a change in the percentage of recycled materials during the disposal and waste treatment of the wind turbine. Finally, the fourth alternative scenario (AS4) analyses a change in the composite waste treatment of the blades at disposal time, from landfill to recycling.
These scenarios can facilitate to assess the degree of uncertainty of the developed LCA due to the choices made. Outside the limits of this work fall the uncertainty due to imprecise knowledge of the different parameters used in the Life Cycle Inventory (LCI), the spatial and temporal variability in different parameters of the LCI, or the uncertainty due to the inaccuracy and the simplification of the environmental models used.
The different uncertainties arising from the options given during the development of the LCA of a wind turbine have been analysed throughout this work, using the Eco-indicator99 LCA method. Four different scenarios within the LCA of a multi-megawatt wind turbine have been analysed. In addition, the impact that these scenarios may present on the final LCA has also been assessed.
From the results can be clearly emphasized the specific case of large corrections in the maintenance phase. Undoubtedly, the choices made at the turbine maintenance stage have an important effect on the results of the LCA. Therefore, it is necessary to analyze and define more precisely the average of major corrections that may experience a model of wind turbine along its 20 years of life.
Another issue that significantly influences the final results of the LCA study of the multi-megawatt wind generator in question is the considerations made about recycling and reuse of components and materials. A clear example is the impact of materials such as the fiberglass of the blades of the wind turbine when they are not recycled but sent directly to landfill.
The variations in the results of the LCA of the multi-megawatt wind turbine, mainly due to the two issues formerly discussed, are between 14% and 20%; important values that suggest the need to dig further into the future trends for the maintenance and recycling of components associated with the wind turbine, from an environmental point of view.
