Field investigation into mooring Load Reduction Device performance in hurricane conditions at an offshore test site

Floating Offshore Wind (FOW) is the next frontier in clean and renewable wind energy exploitation of particular significance to the European economy. To keep the FOW competitive against other resources, the Levelised Cost of Energy (LCoE) should keep up with projections in the next decade for the commercial floating wind farms to be economically viable. One of the contributors to LCoE is the cost of the mooring system for the Floating Offshore Wind Turbine (FOWT). This paper presents a field investigation of a quarter scale Mechanical Compliance Device (MCD) added to an inline heavy chain mooring attached to a test platform. The MCD (i.e. Dublin Offshore’s Load Reduction Device aka LRD) is aimed at peak load mitigation in the mooring line of an FOWT, while allowing for geometric compliance during operational conditions. This field campaign happened in Q4 2020 at Smart Bay Test Site (SBTS), Ireland. The test platform survived Hurricane Epsilon and Storm Aiden during the test period. The tests validated the Load Extension Curve of the selected MCD, demonstrating its effectiveness in mitigating peak loads. These tests along with prior scaled tank testing show that the LRD is a prime candidate for reducing the demand for a high Minimum Breaking Load for the mooring line. This leads to substantial reduction in the line specification, thus, keeping capital as well as operating costs down. Moreover, the construction of LRD is simple, robust and comprised of easy to source materials.