Tidal Energy from Deep and Slow-Moving Waters
Schottel Hydro will deliver a customized turbine solution for Deep Green, an underwater kite construction from the Swedish company Minesto, in 2016. The turbine complements the first full-scale Deep Green device. The underwater power plant will be deployed in 2017 at the Holyhead Deep site off the coast of Anglesey, Wales. During the coming three years, nineteen more devices will follow and eventually form an array with an overall capacity of 10 MW.
Deep Green is the first device that allows the harvesting of tidal energy in slower waters, which have been thought unproductive so far, with low current velocity of two metres per second and in great depth of 60 to 120 metres. Deep Green resembles an underwater kite and consists of a wing and a turbine. The kite has a wingspan of 12 metres and is attached by a tether to the seabed. It moves along a pre-programmed 8-shaped trajectory and thus increases the water current velocity around the kite by its own speedy movements. The attached turbine therefore works with an up to ten times higher current velocity than originally available. The obtained energy is transferred onshore via a cable connection on the seabed.
For Minesto, Schottel Hydro develops a new turbine variant that will optimally fit the requirements of Deep Green. The lightweight nacelle power-take-off system includes turbine, drive train, power electrics and auxiliary devices. All components will be tailor-made to fit the electric system of the kite. The drive train concept is based upon the proven concept of the Schottel Instream Turbine (SIT) with its inline arrangement of open rotor, rotor shaft including sealing and bearing, planetary gearbox and generator. In contrast to this readily available device with rotor diameters between 3 and 5 metres, the Deep Green turbine will be significantly smaller and operate at higher speeds. In addition to the turbine engineering and manufacturing, Schottel Hydro will also carry out a full-load test series on a specially built test stand prior to installing the turbine in Q3 2016.
The first commercial project with Deep Green will start with the deployment of the first full-scale device in Holyhead Deep 2017. Holyhead Deep provides low-flow tidal velocities at a depth of 80 to 100 metres. Twenty devices with a capacity of 500 kW each will be installed in an array until 2019 and reach an overall capacity of 10 MW, enough energy to power 8,000 homes.