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As part of the ReDAPT, a project commissioned and co-funded by the ETI (Energy Technologies Institute), the first standard for certification of horizontal axis tidal turbine (HATT) has been commissioned to DNV GL in order to accelerate the development of the tidal technology and its commercialization. Although the development of the standard is limited to one turbine concept and unlike the wind turbines, the possible variations of configurations and the limited track record of the technology provided great challenges to define requirements and parameters to be considered in all aspects of the turbine. A risk based approach has been used on the different HATT configurations, addressing all the systems, subsystems and main components. The process, as described in the DNV OSS-312 – Certification of Tidal and Wave Energy Converters, addressing technology assessment and FMEA leading to a certification plan and definition of standards from Oil & Gas / Wind to be applied, was implemented in a level of detail sufficient to define the failure modes and associated risks that were the basis for definition of design, construction, commissioning and in-service life requirements. The work on failure modes and risks as well as data and definitions necessary for an effective risk based process were carried out with the support and assistance of ALSTOM during the ReDAPT project and the experience accumulated by DNV GL in the verification / certification projects carried out so far. Although every standard has a risk based background (even if based on field experience for many years), this standard has a direct connection between the identified risks and requirements. As the risks can vary for a specific configuration of HATT, technology matures and data is harnessed with the passing of the time, the approach used will allow for a faster and consistent adaptation of the standard now and in the future. This paper, describes the process in detail, presents the structure used for the risk assessment process, its conclusions and highlights the connection between the findings and the content of the standard.

This paper presents the design and implementation of a wave excitation force estimator based on the cubature Kalman filter (CKF) for a CETO 6, a submersed wave energy converter controlled using three power take-off systems attached to the tether lines. Wave excitation force estimation is required by many advanced wav energy converter (WEC) control approaches. However, contrary to the single degree-of-freedom (1-DoF) case, the literature on the design of wave estimators is quite scarce for devices with multiple degrees-of-freedom. The advantages of CKF wave estimator described in the paper are its performance and ease of tuning when working with a high-order system, as it is the case for the 6-DoF linear model used for the design. Preliminary results for all the 6 directions are presented in nominal conditions and also in mismatch conditions, where the estimator is applied to a full nonlinear model of the system, under the action of long-crested and short-crested waves.