Life cycle assessment of a floating offshore wind farm in Italy

Mitigation of climate change requires consistent actions toward the reduction of emissions from the energy sector: in the last years, renewable energy technologies, such as wind power, have become a cost-effective option to pursue the transition to low emission systems for power generation. Offshore wind energy can provide access to additional wind resources, also overcoming some issues related to onshore wind deployments such as land-use competition and social acceptability. The Life Cycle Assessment (LCA) methodology can be used to gain insight into the environmental performances of different technologies, e.g. renewable energy generation technologies, along the lifecycle stages and across a number of impact categories. This paper reports the cradle-to-grave LCA of a floating offshore wind farm, consisting of 190 wind turbines with 14.7 MW rated power, intended to be deployed in the Mediterranean Sea. The employed technology is represented by the IEA 15 MW reference wind turbine supported by the reference semi-submersible platform. The selected functional unit is the delivery of 1 GWh of electricity to the onshore grid and the impact assessment method is the EPD (version 2018), which is usually used for the creation of Environmental Product Declarations (EPDs) and considers 8 impact categories. The results of the analysis show that the supply of raw materials, especially steel, for aerogenerators and floaters is the most significant contributor to the overall potential impacts in all the impact categories, except for abiotic depletion of elements, where power cables are the hotspot. In the perspective of decarbonisation, the estimated carbon intensity is 31 g CO2eq/kWh and so it results competitive with other low emissions electricity generation technologies. To compare the estimated global warming impacts to other studies, some harmonisations efforts on capacity factor and lifetime of turbines are made. Moreover, the wind farm performance has been evaluated in terms of carbon and energy payback time, estimated in 2 and 3 years respectively, showing a substantial benefit when compared to the expected 30-year lifetime. As a conclusion, despite the number of approximations and conservative assumptions, floating offshore wind power, represented by the modelled case study, can be considered a promising technology and has been found to be already competitive with other renewable electricity generation technologies. Future research should address the uncertainty rooted to the data: repeating the analysis relying on the executive project, and therefore on a more detailed modelling, would help to get more accurate results.