In the second year of the DEEP-Gen IV 1MW turbine operation the deployments were of longer periods than in the first year and this allowed not only the collection of detailed turbine performance data but also the collection of a large amount of data on the environment and the interaction of the turbine with the environment.
Several power curves were created for the turbine following the new IEC 62600-200 standard methodology (2). This measured power curve correlated well with the predictions derived using the DNV GL tool Tidal Bladed. The real life turbine performance and load measurements were used to validate the DNVGL Tidal Bladed (3): this validation now means that the industry has a tool with which to assess and predict the loads and performance of turbines deployed in a given set of site conditions.
The second year of operation presented additional opportunities to learn lessons about the design, maintenance and operation of a commercial scale tidal turbine. A detailed turbine inspection activity was carried out at the end of the ReDAPT programme of testing to maximise the return on experience and key lessons are presented.
A discussion is presented of how the performance of the DEEP-Gen IV turbine accords with the current industry view of the Levelised Cost of Electricity (LCOE) (as represented in the ETI/UKERC roadmap) and then what key challenges in achieving the ETI targets going forward need to be addressed.
An assessment of the power quality performance (voltage flicker, power factor and harmonics) is presented along with a summary of supply interruptions at the Eday substation. This assessment confirms that the DEEP-Gen IV turbine complies with grid regulations and provides control of power factor.
Information has been gathered on the performance of materials and coatings in terms of biofouling and corrosion. The instrumentation fitted to the turbine allowed an assessment of marine life interaction through strain gauge monitoring; this concluded that there were no unwanted interactions and began to show how marine mammals generally avoided the device. Acoustic surveys were carried out to determine the noise footprint of the turbine and this data has been submitted to Marine Scotland for review.
Throughout the course of this project a significant number of lessons have been learned in a variety of areas associated with testing a tidal turbine at a remote site within a complex multi-partner R&D programme. Lessons are presented in the areas of programme management, marine operations, maintenance activities, testing activities, daily operations and the EHS management.