.

News – What`s happening in energy research

read short description
subscribe News

In the Tidal Power project, Schottel Hydro is developing a tidal power plant. The image shows the Triton platform.
© Schottel Hydro
Tidal power plant
29.07.2015

Platform in the operating mode (above) and maintenance mode (below): To enable maintenance work to be carried out on the platform, the water-filled hulls are emptied and the platform floats upwards. This enables the turbines to be serviced on the water surface.
© Schottel Hydro

The computer render shows Schottel’s instream turbine
© Schottel Hydro

Energy thanks to lunar power

Researchers are developing a new approach for generating energy from tidal currents. Here they are combining a semi-submerged platform with several small-sized instream turbines. This means that the tidal power plant requires less maintenance than is usually required. However, in order to achieve the highest possible energy yields it requires strong water currents. Canada’s Bay of Fundy has an exceptionally high tidal range exceeding 15 metres. This is where it is planned to build the hydropower plant so that it can provide the first electricity in 2017.

Tidal power plants utilise the tidal range of the world's oceans. Tides depend on the position of the moon and the sun from the earth. Unlike wind, wave and solar energy, this means that the tidal range is predictable. Tidal power plants therefore generate reliable and predictable electricity from renewable energy. Estuaries and certain bays provide ideal locations for tidal power plants. However, flow rates of more than 5 metres per second occur very rarely worldwide.
Most of the previously used technical concepts for harnessing tidal energy are based on free-flow axial turbines that produce approximately one megawatt of power. These systems are firmly anchored to the seabed using a support structure. This entails very high installation and maintenance costs.

Schottel Hydro has achieved a more economical version with a semi-submerged platform support system in combination with a new turbine concept. The scientists want to implement a tidal power plant in Canada’s Bay of Fundy in Nova Scotia, which is renowned for its high tidal range. Here there are particularly high tides exceeding more than 15 metres. Compared with previous systems, the platform system has significantly reduced the operation, installation and maintenance costs. In addition, far lower investment costs are also incurred. The demonstration plant, with 40 instream turbines from Schottel Hydro is set to produce 2.5 megawatts from 2017 onwards. “From 2016, 16 turbines will already be generating 1.1 megawatts of electricity and feeding it into the North American grid. That will be enough to supply around 1,700 three-person households with electricity for a year,” explains Dr Ralf Starzmann, head of the Tidal Power project at Schottel Hydro. He adds: “The remaining turbines will be installed a few months later to enable the plant to generate 2.5 megawatts.”

Simple turbine structure

The Schottel instream turbine (pictured below left) has a simple structure: The standard drive train is equipped with a two-stage planetary gear and asynchronous generator that is cooled by the water flowing around. During the design process, the researchers focussed on developing a turbine that is as lightweight and robust as possible. Other manufacturers rely on hydrokinetic turbines weighing between 130 and 200 tonnes. This new turbine weighs just one tonne.
The number of turbines can be adjusted in accordance with the energy requirements: 20 turbines produce approximately one megawatt of rated power. “The economic viability very much depends on the interrelation between the turbine size, number of turbines, anchoring and platform system,” summarises the project leader. Each turbine also has its own connection to the power grid and ensures the operation of the plant.

Supporting platform anchored to the seabed

The turbines are fixed to the semi-submerged platform called Triton. The platform is secured to the seabed using gravity foundations, drilled pile foundations or other foundation solutions. By means of a universal joint, the platform is automatically oriented towards the water flow. Two hulls enable the plant to float and also act as the supporting structure for a variable number of cross-members on which the turbines are mounted. Maintenance-friendly platform: The hulls break through the water surface and can be accessed at any time for servicing the electrical and control systems. Emptying or filling the ballast tanks in the lower part of the hulls enables the platform to change between its operating and maintenance positions.

(ad)

notepad

BINE subscription

Subscribe to newsletter

Addresses

Turbine system and the conceptual design of the support and fixing structure
SCHOTTEL HYDRO GmbH

Optimisation of the blades for tidal current turbines
Universität Siegen, NT

Hydrodynamic study of the platform
HSVA GmbH

Laboratory-scale modelling of the turbine grid
Schiffbau-Versuchsanstalt Potsdam GmbH

Development of the operational and control functions
Fraunhofer IEE