Abstract
Senate Bill 100 of California passed in 2018 establishes the requirement that 100% of the state’s retail electricity be generated from eligible carbon-free resources by 2045. Given the high land prices and limited onshore wind resources in California, floating offshore wind represents a new carbon-free energy resource that can help California meet the Senate Bill 100 target. In order to facilitate the development of floating offshore wind projects in federal waters off the coast of California, the Bureau of Ocean Energy Management (BOEM) Pacific Region has tasked the Bren School with characterizing and assessing the greenhouse gas (GHG) emissions associated with the integration of offshore wind energy into California electricity markets. By performing a life cycle assessment (LCA) for a representative floating offshore wind project, this report presents the first analysis of the life cycle GHG emissions of any offshore wind project in California. Our results show that supplying 1 MWh of electricity through floating offshore wind power generates ~15kg CO2-equivalent GHG emissions over its life cycle, which is comparable with the literature for conceptual floating offshore wind turbine models. Monte Carlo simulation establishes a 90% confidence interval range of emissions from 11.60 to 25.04kg CO2-equivalent. Our results are within the combined range of both onshore and offshore wind projects at a utility scale. Compared with other energy sources, life cycle GHG emissions from floating offshore wind in California are similar to those from hydro and nuclear. These results indicate that floating offshore wind in California produces at least 92% less GHG emissions per MWh supplied to the grid compared to natural gas. In-depth analysis of our results indicates that the turbine manufacturing stage is responsible for the majority of the life cycle GHG emissions, that recycling rates for materials have strong implications for reducing life cycle GHG emissions, and that the life cycle GHG emissions are most heavily influenced by capacity factor of the turbines and the operational lifetime of the windfarm. These results imply that, first, offshore wind has the potential to provide low-carbon electricity in California, and, second, mitigation efforts should prioritize the manufacturing and recycling phases, and the factors influencing capacity factor (i.e. site selection and generation capacity) and operational lifetime of the windfarm (i.e., maintenance schedule and mechanical durability). Our study demonstrates the potential for floating offshore wind projects to curb GHG emissions and to meet the Senate Bill 100 target.