ABSTRACT

In the study of semi-submersible Floating Offshore Wind Turbine (FOWT) platforms, a special parameter is the pitch response. Then, with the aim of improving cost-efficiency, a size reduction can be consider. However, the platform cost and size cannot be reduced without consideration of appropriate reduction of the pitch response. Therefore, passive motion reduction surfaces arises as an alternative. A conventional heave plate is designed to reduce the heave platform response, but effects on pitch are also perceived. However, these disks are non-optimal for rotational motion. Then, a novel study of angled disks as a passive rotational motion reduction strategy is conducted. The study was achieved by using two different numerical approaches, potential flow and computational fluid dynamic Reynolds-averaged Navier–Stokes equations.

INTRODUCTION

The excessive emission of greenhouse gases has generated an accelerated climate change. To mitigate our impact in the global ecosystem, long term strategies about decarbonizing our energy system must be undertaken. Therefore, renewable energy sources are a key strategy to reduce our carbon emissions.

It has been proved that onshore wind energy has a great potential to be part of the renewable energy portfolio, being reliable and competitive. However, this technology can create visual and noise impact and deployment locations are limited. Therefore, the industry has been moving to offshore locations, that can also benefit from greater and less variable wind resources. The offshore wind technology can be categorised as bottom fixed and floating devices. The first, being the most developed at pre-sent, but limited to water depths of less than 50 metres. Furthermore, as our energy demand and the necessity of decarbonisation increase, deeper water sites can offer more space and resources for wind energy, whereas bottom-fixed structures are not cost-efficient in water depth greater than 50 metres (James & Costa Ros, 2015).

On the other hand, to ensure good stability, survivability and performance, floating foundations are much larger and more expensive than bottom fixed ones. The Floating Offshore Wind Turbines (FOWT) technology is currently in an early stage, with some testing and demonstration projects underway, with farm projects being planned.

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