Abstract
Seaflow has been a project to develop and test a commercially-sized marine current turbine. The turbine was installed in the summer of 2003 off Foreland Point, near Lynmouth on the North Devon coast of England. The objectives of the project were to test the feasibility of constructing and operating such a machine, to ascertain whether the performance would be as predicted, and to evaluate the likely longer-term economics of using such tidal turbines to generate electricity.
The Seaflow turbine is a 300kW, horizontal-axis machine that resembles a 2-bladed wind turbine, but with the rotor underwater. The turbine is mounted on a steel pile fixed into a socket in the seabed, and the powertrain ñ the rotor, gearbox and generator - can be slid up and down the pile and out of the water for servicing.
The project was coordinated by the renewable energy consultancy, IT Power. The other partners were: Seacore, a marine construction company; Marine Current Turbines Ltd, a company set up by the partners to carry forward the development of the technology; Bendalls Engineering, a large engineering fabricator; and Corus, the steel manufacturer.
A parallel project funded by the European Commission also had IT Power as the coordinator and Seacore as a partner, but included as partners ISET, a research organisation attached to Kassel University, and Jahnel-Kesterman, a specialist gearbox manufacturer. The first stage of the project was to identify a site for the turbine and obtain all the necessary permissions to install it, part of which involved conducting an Environmental Impact Assessment into the turbines effects on marine life and processes, the landscape, and other sea users. The consortium then developed the machine from concept to detailed designs, manufactured or purchased the components, and assembled and tested the prototype.
The installation was carried out by a jack-up barge that could stand on legs on the seabed, providing a stable platform for drilling and assembly. No diver operations were required. Testing has confirmed the design philosophy, and the turbine has performed as predicted. At the end 2004 the turbine had been operated on 68 separate days, recording 80 hours of operation. The turbine has served as a testbed, being operated for numerous short runs to test the principles of generation or to develop components. Continuous operation for more extended periods has been limited, as the reliability of the various systems has been developed.
Though the project officially ended in 2004, the turbine has not been decommissioned. Over two years after the installation, the machine is still working, and an extended test programme continues with DTI support. New techniques have been developed to install the turbine in a deep, high current area, and much has been learnt about working in such an environment. The project has increased understanding of the nature of tidal flows, and the behaviour of a rotor in tidal currents.
Seaflow lays the foundations for the development of a new industry, exploiting what is a sizeable renewable energy resource. The partners plan to follow Seaflow with further, larger machines, and to move to commercial farms thereafter.