Page 217 - Materials Chemistry, Second Edition

Life-Cycle Assessment of Wind Energy 205

foundations, 95 % of that of the tower, 85 % of that of the nacelle, and 85 % of
that of the rotor.
• All data on the emissions from and characteristics of the energy used in the
manufacturing processes are taken from the Ecoinvent database and refer to
Spain, because that is where the turbine manufacturer’s plants are located.
• Modern, multimegawatt wind turbines are assumed to have a useful lifetime of
20 years.
• The estimates made in regard to the decommissioning of the turbine at the end
of its useful lifetime and the subsequent processing of waste products are based
on decommissioning projects prepared by the company that holds the operating
rights to the turbine. Basically, it is considered that 90–95 % of the metal (iron,
steel, and copper) is recycled, PVC plastics, fiberglass and concrete are land-
filled, and oils and other types of plastic are incinerated.
• The annual output from the wind turbine is worked out on the basis of an appropriate
figure in equivalent hours of production to ensure the economic viability of a wind
farm, i.e., 2,000 equivalent hours of production per year. For a turbine with a rated
power of 2 MW, this is equivalent to an annual output of 4 GWh.
• In the context of corrective maintenance work on the turbine, in the course of its
useful lifetime, it is estimated that one replacement generator will need to be
installed due to malfunction (the complete new generator is considered,
including manufacturing and assembly).

Finally, allocation as per the recommendations of standard ISO 14044 (which
sets out the characteristics to be met by life-cycle analyses) is not used (Guinée
et al. 2001; ISO ISO 2006a, b). The only function considered in the system
analyzed and in all its components is that of generating electricity, so all the
environmental impacts associated with the system are allocated to electricity
generation. It is considered that the material recycled at the end of the useful life
replaces virgin material used in the manufacturing stage of the turbine.

3.2.5 Methodology and Impact Categories Analyzed
When conducting an LCA, an environmental impact assessment method must be
selected, and it must be decided which impact categories are to be analyzed. In this
case, the assessment method chosen is CML Leiden 2000 (Guinée et al. 2001), and
the categories are the following:
• Abiotic depletion: this category is linked to the extraction of minerals and fossil
fuels associated with the inputs of the system under analysis and their effects on
human health and the ecosystem.
• Acidification: this category is linked to the effect of various acidifying sub-
stances on the soil, groundwater, surface water, organisms, ecosystems, etc.
• Eutrophication: this category is linked to excess micronutrients in the envi-
ronment as a result of emissions of nutrients into the air, soil, and water.