Performance Assessment of a Multi-Rotor Floating Tidal Energy System

Abstract

Performance assessments of full-scale tidal turbines have been carried out for multiple machines deployed globally and reported in literature. The rotor number and diameter of the demonstrated tidal energy converters differs from single rotor devices in the MW class to scalable arrays of comparably small turbines. For multi-rotor systems (MRS), potential interaction, positive or negative, remains a key research question. Previous studies at Sustainable Marine prototype system (PLAT-I 4.63) have implied that variations in the incoming flow field are highly likely to cause deviations in rotor performance.

Sustainable Marine has developed and built the pre-commercial PLAT-I 6.40 platform. PLAT-I 6.40 has been connected to the Canadian grid in May 2022. Between May and end of September 2022 the system has been undergone comprehensive commissioning and performance trials.  PLAT-I 6.40, carries six 4m diameter SCHOTTEL Instream Turbines (SIT), each rated at 70 kW. This work presents the results of full-scale field tests that focussed on the assessment of differences in the performance between the individual turbines during summer 2022.

To evaluate the variances in the flow field across all rotors, a specific test campaign has been conducted, where a flow speed sensor was sequentially positioned upstream of each turbine while a second flow measurement device was stationary as reference. For all test configurations the power curves have been determined following the guidance of the IEC TS 62600-200 based on the flow speeds measured with both devices.

This paper presents the experimentally obtained power curves for each test configuration and compares it against the reference values. The results show that there are steady differences in the flow field resulting in varying power outputs across the different rotors (Figure 1). However, a comparison of the individual rotor power curves with the design predictions shows good agreement.