One of the difficulties in designing tidal turbine blades is the uncertainty concerning real loading conditions. This can result in considerable over-design as it affects the design safety coefficients. In order to gather data, IFREMER and Sabella worked to instrument one of the composite blades of the Sabella D10 tidal turbine with strain gauges during manufacturing.
Two autonomous data loggers were then mounted inside the turbine protection cover and programmed to record strains at different points along the blade throughout immersion (see figure below). Data were recovered when the turbine was removed from the water.
Blade instrumentation
The figure below shows one example of the type of data recovered after a 6 month immersion period.
Variation in strain on the blade
Such data are very valuable and can be used both to help validate the calculations used to dimension the blade and to define future test programmes.
