Extracts from NATTA's journal
Renew, issue 145Sept-Oct 2003

2.Tidal turbines proliferate

The summer has seen tidal turbine systems being tested around the UK. First in the water, in June, was Marine Current Turbines who successfully installed their 300kW sea bed mounted Seaflow turbine 3km off the N. Devon coast near Lynmouth. We’ll be reporting on progress in Renew 146: but meanwhile see: http://www.marineturbines.com.

Then sea trials started off the coast of Orkney on a new development- the Sea Snail, developed by Professor Ian Bryden of Aberdeen’s Robert Gordon University (RGU). A 30-tonne half sized prototype of the Snail, nicknamed Brian, which is capable of generating 150 kilowatts, has been built at the Stonehaven-based subsea specialists Ross Deeptech Initiatives. A 15 metres high frame supports a system of hydrofoils which use the down-thrust from tidal currents to hold the structure firmly on the seabed. The concept avoids the need for expensive gravity or anchoring systems on the ocean floor. Prof Bryden told the Scotsman: ‘At present, the potential to use tidal energy is limited by installation methods for turbines, which require firm attachment to the seabed. This is very expensive and requires turbines to be placed in depths greater than 25 metres and less than 50 metres. The full-size snail is a prefabricated tidal device that can be cheaply installed in shallow and deep water. This will significantly increase the number of suitable sites for turbines and reduce installation costs.’

Alan Owen, of RGU’s Faculty of Design and Technology who helped to develop the device, added. ‘Uniquely, the Sea Snail can take a turbine down to any depth on the sea floor and back on command. This ease of installation and maintenance offers interesting potential for smaller, single-turbine sites.’

The device was developed with the aid of a research grant of £158,000 from Scottish Enterprise’s proof of concept fund. Should the field trials in the Eynhallow Sound in Orkney go according to plan, RGU plans to pursue funding to build a £400,000 full-sized prototype, capable of generating 750 kilowatts. The Sea Snail is the first initiative to be developed since the establishment of the Aberdeen Renewable Energy Group (AREG).

In parallel, EB’s Stingray tidal device is moving ahead:

Stingray gets £2.1m more

One of Brian Wilsons last acts as Energy Minister, was to confirm that the DTI will provide a further grant of £2.1m for the continued development of the Stingray hydroplane tidal current device. During a visit to the Engineering Business (EB), its developer, he commented "Generating energy through tidal stream technology is an important part of the future picture that will help us reduce Carbon Dioxide emissions and produce a clean, renewable source of electricity".

The new funding has allowed for futher development work and more tests at sea. Dr Tony Trapp, EB Managing Director said ‘This is tremendous news- the data gathered last summer has further strengthened our case that the Stingray technology can be economically and technically viable. With ongoing support from the DTI, EB can continue its test programme offshore in 2003 with the aim of developing a commercial Stingray system in the shortest possible time frame.’

EB upgraded the 180 tonne Stingray demonstrator and reinstalled it in Yell Sound off the Shetlands in July. Additional instrumentation and a more flexible control system have been fitted to allow the performance of the generator to be accurately controlled and recorded over an extended period.

EB’s Engineering Director, Mike Watchorn, said they were "looking forward to returning to Shetland where we have enjoyed great support from the local council, local businesses and residents. The test programme will be used to optimise the design of Stingray, to undertake durability testing and to verify energy capture. We then plan to use the results of the test programme to successfully engineer a 5MW Stingray power station."

At the same time EB has continued to develop its system for the rapid and safe installation of offshore wind turbines. Now christened ‘Merlin’, it can be mobilised on a simple flat bottom barge and uses an A-frame based handling system to install fully assembled turbines in a single lift.

See: www.engb.com