Life cycle assessment of floating offshore wind farms: An evaluation of operation and maintenance

One of the key objectives for renewable energy technologies is to reduce the environmental impact of energy generation. Floating offshore wind technologies have been developed in recent years to exploit the wind energy resource available at deep waters where bottom-fixed technologies are not economical. However, few studies exist that analyse the environmental impact of such technologies. Particularly, offshore activities such as those required for Operation and Maintenance (O&M) are not represented in detail in previous studies. The present study addresses these gaps by performing a Life Cycle Assessment using an advanced O&M model to quantify the environmental impact of a floating offshore wind farm. Different O&M philosophies – assuming towing to shore for major operations vs. performing all operations on site – and their impact are evaluated and discussed for two case studies inspired by real pilot park deployments. The results show mean Global Warming Potential (GWP) values between 25.6 and 45.2 gCO2 eq/kWh depending on the assumed O&M strategy and vessels, with the contribution of the O&M phase to GWP ranging from 21 to 49%, and of O&M vessels from 6 to 40%. Assuming O&M strategies to be the same for fixed and floating offshore wind could result in a 20.4% underestimate of GWP, whereas the vessel choice resulted in up to 34.8% difference in the estimated GWP. An environmental impact perspective provides key insights on the choice of different designs, operation strategies and asset management, and thus should be used in the decision-making process.