ABSTRACT

Wind resource assessment is essential for the development of offshore wind energy. In this study, we propose a design of tension-leg platform (TLP) based met mast for wind measurements. To evaluate the design, a time-domain numerical model is developed for the dynamic analysis of the TLP under wave, wind, current or earthquake excitations. Based on this model, the performance of the TLP under extremely harsh environmental conditions is numerically examined. The results show that (1) the developed numerical model is capable of predicting TLP motion responses and tendon tensions under various environmental conditions; (2) the performance of the present TLP design is satisfactory in the considered extreme sea state and seismic situation.

INTRODUCTION

Nowadays, offshore wind energy is a fast-growing industry due to increasing investments. This directly leads to a growing demand for wind resource assessment tools. In conventional wind measurement methods, measuring devices are usually placed on fixed towers. However, this manner is generally not economical as the measurement location gradually moves to deep water with a depth of over 30 or 50 meters. Hence, new measurement approaches have been proposed, for example, installing a floating Lidar (light detection and ranging) system on a buoy (Gottschall et al., 2017). Recently, FloatMast® proposed a floating met mast design based on a TLP (Foussekis and Mouzakis, 2021). Compared with the conventional buoys, the advantages of TLP in wind measurement are mainly three-fold: (1) its vertical and rotational motions are small, and horizontal motions are generally in low frequency, which has a limited influence on wind measurement accuracy; (2) TLP is able to support a met mast and other equipment, for instance, current anemometer; (3) the required seabed footprint of TLP is relatively smaller compared with traditional catenary mooring lines, and hence TLP may have minimal impact on fishery industry. Additionally, it is worth pointing out that TLP-based floating met mast systems are usually redeployable in various locations.

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