Life cycle greenhouse gas emission from wind farms in reference to turbine sizes and capacity factors

This study analyzes the global warming potential (GWP) of wind power plants within an LCA framework. Therefore, secondary data from studies on wind turbines, which were published in the past 20 years were assessed. The data was categorized into three configurations, i.e. onshore single turbines, onshore wind farms and offshore wind farms. Within a multivariate analysis, featuring a linear regression model approach, the datasets retrieved from the literature were evaluated. The effect variable was the specific GWP, normalized to the function unit gCO2-equ/kWh electricity. Cause variables were (i) the capacity factor, (ii) the rated power and (iii) the annual energy yield (AEY), (iv) the hub height and (v) the rotor diameter. In a secondary part this study showed the quantity of uncertainty, which is present in LCA studies on wind turbines by evaluating generic wind turbine configurations, which were present in the ecoinvent database. Conclusively, a sensitivity analysis on the influence of the capacity factor on the GWP was conducted. For onshore single turbines and wind farms a negative correlation was observed between the turbine size and the GWP. A highly significant negative correlation was found between the AEY and the GWP. However, the AEY needed to be log-transformed first. Other cause variables were either collinear to the AEY or showed a weak correlation. For offshore wind turbines similar results could not be presented and none of the cause variable could explain the effect variable. The sample size was however low, as only few studies were conducted for offshore plants. The uncertainty analysis showed that generally low uncertainties are present during the modelling phase of the LCA of wind turbines, which suggests that the processes are well understood and documented. The sensitivity analysis on the capacity factor resulted in a non-linear, hyperbolic progression with respect to the GWP.