Advanced structural testing and modelling of a novel full-scale helical shape tidal turbine foil

Abstract

The utilisation of tidal energy holds significant promise for sustainable power generation, particularly in regions with tidal resources. In this context, tidal energy sector is targeting to develop innovative tidal energy systems for tidal potential sites and rivers to enhance the green power generation and achieve United Nation’s sustainable development goals. However, ensuring the structural integrity of tidal turbine components, particularly the blades, is key for their effective operation, as blades play a pivotal role in determining the system's performance, lifetime, reliability, and efficiency. Therefore, the research aims to assess the structural integrity of a 5 m long crossflow helical tidal turbine foil, featuring a 1.8 m rotor and three foils designed to generate 40 kW, through structural testing and numerical modelling. The testing procedures adhere to DNVGL-ST-0164 and IEC DTS 62600–3:2020 standards, encompassing dynamic, static, fatigue, and residual strength assessments. A unique testing set up and testing protocol were followed to undertake the structural testing program for this innovative tidal foil compared to the commonly used horizontal axis tidal turbine blades. During the testing programme, the foil underwent 1,300,000 fatigue cycles, which is the highest number of fatigue cycles recorded on a tidal turbine blade in dry laboratory conditions, and, in the final static testing stage, the foil sustained damage at 110 % of the idealised full loading condition. A numerical model, based on the finite element method, of the foil has been initially developed using material properties from test coupons and datasheets. This model was then improved by using the mechanical properties obtained from coupons extracted from the foil after testing, however only a slight difference in the two models was observed. A comprehensive assessment of all the test results and selected numerical studies validated the novel design of the tidal foil, while developing a knowledge base to accelerate the structural testing programs of tidal turbine blades, has been presented. This paper also highlights the utilisation of modern tools and adaptations in testing methodologies to accommodate diverse design variations, thus mitigating industry risks for potential low tide and river deployments in the future.