Observations from structural testing of fullscale tidal turbine blades

In recent years, tidal energy has emerged as a potential key player in future energy security, as it provides a reliable, predictable and dependable source of renewable energy, where, in 2022, the cumulative installed capacity of tidal stream energy in Europe, since 2010, reached 30.2 MW. As tidal energy strives towards commercial viability, optimisation of structural components, along with their derisking through structural testing, has become more prevalent. Full-scale structural testing of tidal turbine blades provides a mechanism to ensure the blades can withstand the high operational loads when deployed, in a controlled laboratory environment. In recent years, this type of testing has been used to de-risk prototype blades in advance of operational trials. However, a limited number of these tests have been performed globally. Therefore, in this paper, observations during the structural (static, dynamic and fatigue) testing of 5 full-scale tidal turbine blades are presented and discussed. The length of these blades range from 2-8 metres, for devices of 70kW to 2MW. A case study of a large blade from a 2MW floating tidal turbine has been used to illustrate some of the results obtained from the structural testing. The experience gained from these structural testing programmes highlighted a number of best practices that could be introduced to the next revision of both the IEC 62600-3:2020 test specification and the DNVST- 0164 standard.