‘Flexible Tripile’ Developed for Japanese Offshore Wind Sites

Japanese energy company J-Power and the University of Tokyo have jointly developed and patented a new foundation for fixed-bottom offshore wind turbines specifically designed for Japan’s topography, dubbed “flexible tripile”.

J-Power says the design provides seismic isolation from the ground, improving constructability in areas with shallow bedrock and reducing vibrations caused by earthquakes.

The foundation consists of three piles and a main steel pipe that connects to the wind turbine tower. The connection between the piles and the main pipe uses newly developed square steel pipes and plates, and wire ropes.

The square steel pipes and plates in the foundation’s base plate create a flexible structure that can deform relatively easily, and the long, integrated main steel pipe section allows the entire wind turbine to sway slowly. This reduces the risk of tower oscillations being amplified due to resonance with seismic motion, J-Power said in a press release from 15 October.

The company and the University of Tokyo have analysed the foundation’s effectiveness and conducted model experiments. According to J-Power, the model tests demonstrated that the “flexible tripile” reduces earthquake-induced vibrations more effectively than conventional designs.

The components making up the “flexible tripile” are also said to allow for lower construction costs than conventional technologies and the new foundation design is anticipated to be easily adaptable to larger wind turbines in the future.

J-Power is also involved in developing new floating wind technology as part of two consortia. Last year, J-Power, TEPCO, Chubu Electric Power, “K” Line, and Albatross entered into a joint research agreement for a next-generation floating axis wind demonstration project offshore Japan.

This September, a consortium comprising J-Power, Albatross, TEPCO, “K” Line, and Sumitomo Heavy Industries Marine & Engineering was selected to conduct a feasibility study on large-scale floating vertical axis wind turbines.