Buoyancy can ballast control for increased power generation of a floating offshore wind turbine with a light-weight semi-submersible platform

As many countries increase their installed offshore wind capacity, floating offshore wind turbines (FOWTs) are critical to gaining access to deep-water resources where fixed-bottom turbines would not be economically feasible to install. The levelized cost of energy (LCOE) of FOWTs must be minimized to ensure competitiveness with traditional power sources. Innovative substructure designs and advanced control methods can help decrease the LCOE of FOWTs by increasing annual energy production (AEP) and the turbine's lifetime. LCOE can also be reduced by minimizing capital expenditures and operation and maintenance costs. The novel SpiderFLOAT substructure described in this paper decreases the LCOE through its light-weight and easy -to-manufacture design while providing unique opportunities for platform actuation. Specifically, this paper details the design and testing of a buoyancy can ballast controller to achieve a desired platform pitch angle for increasing AEP while also reducing tower-base fatigue loads and maintaining safe operation. The proposed buoyancy can ballast control is shown to increase AEP by 1.1%, reduce tower-base bending damage equivalent loads (DELs) by up to nearly 9%, reduce maximum platform pitch angles, and not interfere with the baseline controller. The robustness of the proposed controller is tested for misaligned wind and wave direction cases and similarly yields promising performance in the metrics of interest.