System Levelized Cost of Energy Analysis for Floating Offshore Vertical-Axis Wind Turbines

Abstract

The levelized cost of energy for an offshore wind plant consisting of floating vertical-axis wind turbines is studied in this report. A 5 MW Darrieus vertical-axis wind turbine rotor is used as the study turbine as this architecture was determined to have the greatest ability to reduce the system cost. The rotor structural design was used with blade manufacturing cost model studies to estimate its cost. A two-bladed, carbon fiber rotor was selected in this analysis since the lower topside mass resulted in a reduction of the platform costs which exceeded the increased rotor cost. A directdrive, medium efficiency drivetrain was designed which represents 25% of the costs and 45% of the mass of the combined rotor/drivetrain system. A direct-drive, permanent magnet generator drivetrain was selected due to the improved reliability of this type of system, while the cost was not significantly higher than for geared drivetrains. A platform was designed by first identifying the optimal architecture for the vertical-axis wind turbine at a water depth of 150 m. A survey was performed of floating platform types, and six characteristic designs were analyzed which span the range of stability mechanisms available to floating systems. A multi-cellular tension-leg platform was identified as the lowest cost platform which additionally provided some interesting performance benefits. The small motions of the tension-leg platform benefit the system energy capture while limiting inertial loads placed on the rotor's tower and blades. A final design was produced for the multi-cellular tension-leg platform considering operational fatigue, storm wind and wave conditions, and tow-out design cases. The driving design load was stability during tow-out while

Experimental study of the wake interaction between two vertical axis wind turbines

“…38,39 Therefore, inspecting the momentum and turbulence distribution under the wake interaction has been of increasing interest for HAWTs (e.g., previous studies 37,40,41 ), and it would be of similar interest for that of VAWTs, as the wind energy industry is seeing a potential boost of offshore VAWT farms due to their advantages in floating environments. 42,43 Hence, experimental investigation on the wake interaction of VAWTs located upwind and downwind is desirable. This work investigates the wake interactions of VAWTs placed inline and with offset employing stereo-PIV, focusing on whether the wake deflection of VAWT gives more energy to an array configuration.…”

“…Nevertheless, these models are subject either to oversimplified governing equations such as linear superposition or to the ill‐defined superposition of turbulence fields 38,39 . Therefore, inspecting the momentum and turbulence distribution under the wake interaction has been of increasing interest for HAWTs (e.g., previous studies 37,40,41 ), and it would be of similar interest for that of VAWTs, as the wind energy industry is seeing a potential boost of offshore VAWT farms due to their advantages in floating environments 42,43 …”

Open-Loop Control Co-Design of Floating Offshore Wind Turbines Using Linear Parameter-Varying Models

“…The maintenance costs and the total lifetime energy output are dependent on how the system operates and, consequently, depend on the environment and how it is controlled [21,22]. Recent studies have shown that advanced control strategies for offshore wind applications can increase the power extracted from the turbine and minimize the levelized cost [23,24]. Most conventional LCOE estimates have not incorporated detailed dynamic assessments nor the impact of novel control strategies.…”

Parked and Operating Loads Analysis in the Aerodynamic Design of Multi-megawatt-scale Floating Vertical Axis Wind Turbines

“…the meantime HAWT research gained momentum and it became the industry standard for multi-megawatt scale wind energy conversion systems. Despite these issues, interest in VAWTs have resurfaced especially in offshore deep-water conditions and it has been discovered VAWTs might challenge HAWTs in terms of efficiency and cost-effectiveness (Simão Ferreira (2009); Griffith et al (2018); Ennis and Griffith (2018)).…”