Researchers from The University of Manchester have released a study which aims to shed more light on the degradation procedures associated with tidal turbines in order to inform more accurate cost projections for potential new installations.
Accurate assessment of the fatigue life of tidal stream turbines requires understanding of the unsteady loading of turbine components over a wide range of frequencies.
By understanding the different loading patterns, a more accurate design life can be estimated along with overall performance, according to the University of Manchester.
New research from the University aims to help improve the accuracy of assessments of the installation and maintenance costs for tidal turbines to determine their feasibility.
“Accurate assessment of the fatigue life of tidal stream turbines requires understanding of the unsteady loading of turbine components over a wide range of frequencies. By understanding the different loading patterns, a more accurate design life can be estimated along with overall performance,” according to the University of Manchester.
The aim of this project is to develop a better understanding of the performance degradation through the design life of a tidal turbine by determining the effect of the operating conditions on fluctuating load range and cycles.
The study, titled ‘Operational loads on a tidal turbine due to environmental conditions’ by Hannah Mullings, Timothy Stallard, Grégory S. Payne, has investigated the loading experienced by the blades due to waves and turbulence over a 6-month time period.
The unsteady loading of a rotor and blade is based on experimental data from tests conducted at the IFREMER test facility during 2015, as part of the EPSRC project XMED. The tests were conducted using a 1. 2-meter diameter turbine, approximately 1:15th scale relative to prototype turbines rated at 1MW. The experiments examined the magnitude and frequency range of loading on rotor and blades due to differing levels of onset turbulence and following regular waves.
A Morison formulation for predicting time variation of thrust close to the wave frequency was within 3% for the majority of the tests conducted. Using the prediction of wave loads and the load spectrum generated by the experimental data; a prediction of the load cycles and magnitudes is found, the University of Manchester said.
These inform an assessment of the extent to which predicted Damage Equivalent Loads (DELs) may vary due to the approach taken for modelling wave-induced loads, turbulence-induced loads and turbine operation.
It is hoped that the findings from this research will inform more accurate estimations of turbine duration in a given location and conditions and will thus facilitate more accurate costings for potential new installations.