Novel generator design and performance

This document is a deliverable of the FLOATFARM project, founded by the European Union under grant agreement No 101136091. In Work Package 1 (WP1), the FLOATFARM project aims to advance innovative technologies specifically tailored for Floating Offshore Wind Turbines (FOWTs), with the goal of improving overall performance, reducing material usage, and ultimately lowering the Levelized Cost of Energy (LCOE). The developments focus on rotor aerodynamics, drivetrain dynamics, and control systems, with particular attention to the benefits enabled by their coupling. WP1 will explore the potential of low specific power rotors to enhance energy capture in floating conditions. It will also advance a novel, lightweight, gearless generator technology developed by the partner Hagnesia and will explore its potential in new FOWT design, quantifying its potential benefits in terms of load reduction and turbine dynamics. As a matter of fact, in Floating Offshore Wind Turbines (FOWTs), the generator weight is a critical factor. Placed several hundred meters above sea level, this component can induce significant gravitational and inertial loads on the tower and substructure as the floating platform moves and tilts. In particular, this report focuses specifically on the work carried out within Task 1.2 dedicated to the generator. The scope was to demonstrate the possible benefits in terms of FOWT design disclosed by the new generator technology. The analyses were aimed at investigating potential tower redesign strategies able to allow material saving and loads reduction at tower base and in the substructure. First, a methodology for redesigning the tower is presented, which starts from the design proposed for the IEA 15 MW Reference Wind Turbine (RWT), with the IEA-developed generator being replaced by an equivalent design using Hagnesia’s generator. Building on their novel direct drive generator technology, Hagnesia has developed and evaluated different possible design configurations for a drop-in-replacement of the IEA 15 MW RWT. By developing and comparing key design and performance characteristics for different possible design solutions, two generator suggestions are selected to evaluate system level impact through turbine impact studies. Based on these suggested redesigns, an assessment was made of the potential weight and load reduction achievable through this technology. Aero-servo-hydro elastic simulations are conducted to evaluate the impact of this technology on reducing structural loads. For this analysis, the met-ocean conditions derived from a European site in the H2020 project FLOATECH are utilized. The analysis showed that Hagnesia technology can reduce generator mass by over 90% — from 270 t to approximately 20 t — while increasing conversion efficiency by around 1%. This significant reduction in nacelle weight allows for a redesigned tower, cutting its mass by 30% (approximately 400 t). As a result, redesigning just the generator and tower—excluding additional expected savings in the nacelle and platform—can enable total material savings of around 650 t. These savings also include several critical raw materials, such as copper and rare-earth elements.