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GHG emissions and energy performance of wind power

LCA of two existing onshore wind power farms and six offshore wind power conceptual designs

This study has been carried out as a part of the Energy Trading and Environment 2020 project, funded by 
the Norwegian Research Council and the partner consortium. The aim of the study was to present LCA 
GHG emissions and energy performance of two Norwegian onshore wind farms and six different offshore 
conceptual designs. 
The LCA GHG emissions from the onshore wind power farms Kjøllefjord and Fjeldskår are 11.0 and 15.1 
g CO2-equivalents/kWh, respectively. The turbine components (nacelle, rotor and tower) are the main 
GHG emissions contributors representing about 80% and 72% of the total GHG emissions from Kjøllefjord 
and Fjeldskår wind farms, respectively. As these turbine components mainly consist of steel, this steel 
production activity is the main contributor to the overall GHG emissions. 
The Energy Payback Ratio (EPR) is 21 and 14 for Kjøllefjord and Fjeldskår wind farms, respectively. 
Thus, for every unit invested energy the respective payback energy is 21 and 14. The respective Energy 
Payback Time (EPT) indicators are 0.9 and 1.4 years for Kjøllefjord and Fjeldskår wind farms. 
The investigated offshore conceptual designs all result in higher LCA GHG emissions and lower energy 
performance compared with the results from the onshore wind farms. The GHG emissions vary between 
18.0 and 31.4 g CO2-equivalents/kWh, a difference representing 77% increase compared to the lowest 
GHG emissions. The foundation/platform materials contribute the most to the overall GHG emissions, 
varying from 35% to 63% of the total GHG emissions. The variations between the concepts are placed in 
this category, since the tower and RNA are identical. Thus, one major conclusion from this study is that 
specific platform/foundation steel masses are important for the overall GHG emissions relating to offshore 
wind power. The second largest contribution to GHG emissions comes from the installation and 
decommissioning activities. 
The investigated concepts achieve EPR and EPT values between 7.5 and 13 and 1.5 and 2.7 years, 
respectively. The Umaine Semi-S and Spar concepts result in the worst energy performance, while the 
MIT TLP and OC4 Jacket give the best performance, which is in line with the GHG emissions result. This 
would be expected since the use of conventional energy within an analysed system generally represents 
the main contributor to GHG emissions from the same system. 
It is significant for the further development of offshore wind turbines that there is an increased 
understanding of the parameters and activities which have the greatest impact on the overall GHG 
emissions and energy performance of wind power. This may be affected both by the various different 
platform concepts and by varying locations and weather conditions. Some platform concepts, for example, 
can handle larger turbines without increasing the platform sizes, while others have to be scaled up. In 
addition, some concepts may be more suitable for rough weather conditions than others. Further studies 
should focus on how such variations impact the resulting GHG emissions and energy performance. 
Lastly, it should be emphasised that GHG emissions and energy performance represent only two 
environmental indicators. With regard to decision making and guiding policy, several other environmental 
indicators need to be taken into consideration. These include land use, visual aspects, biodiversity and 
noise. This is particularly relevant when comparing onshore and offshore turbines. 
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