Tidal Energy Ltd Tests DeltaStream Device in Welsh Waters, UK

Welsh marine energy company Tidal Energy Ltd is preparing to deploy a prototype of its DeltaStream device in the Ramsey Sound off St Davids Head, southwest Wales.

Tidal Energy, which is controlled by principal shareholder Eco2, a company committed to financing and developing renewable energy projects throughout the UK and Europe, plans to test the tidal device with a view to installing a commercial array by 2017.

The DeltaStream device, which sits on the seabed under its own gravity, comprises three independent 400kW turbines mounted on a triangular frame. The device is primarily designed to be located on the seabed, but could also be installed in suitable rivers and estuaries. For the first deployment later this year, one 400kW turbine will be installed, in order to minimise project risk, with a view to scaling up to the full scale device later in 2014, or 2015.

“The Ramsey Sound project is an opportunity for prototype development,” explains Tidal Energy managing director Martin Murphy. “We have secured operating consent from the regulators (the Department of Energy & Climate Change and the Welsh government) to install our prototype on the seabed and we have a seven year lease from The Crown Estate.

“Looking forward, we have also secured an agreement for lease on another site about two miles north for the installation of a 10MW commercial demonstration array,” he continues. “In parallel with the Ramsey Sound prototype project we have started development work for our array.”

When the DeltaStream device goes into the water later this year it will be the first at-sea test of the device. “We have done a huge amount of computational analysis of the design and used tank test facilities to prove the concept as far as we can,” adds Murphy.

The thinking behind the DeltaStream concept is to keep the technology involved as straightforward as feasible. “Since the marine tidal stream environment is very harsh we have tried to keep the engineering systems that will go on the seabed as simple and as robust as possible,” explains Murphy. “We have adopted equipment that already exists in such an environment and have also taken the perspective that what we want to put on the seabed is something that is easily installed (with no drilling or piling) and is easily removed.”

Nevertheless, a great deal of clever engineering has gone into the device’s design. Martin Murphy continues: “What we want from a turbine is rotational energy, but there is also an element of axial thrust that is trying to push it along the seabed and that is undesirable in terms of the stability of the device. We have a turbine design, for which we have been granted a patent, that enables us to limit axial thrust whilst at the same time getting really meaningful levels of power out of the turbine.”

The company has looked carefully at the question of installation and favours using its own modified barge rather than chartering a heavy-lift vessel as the former option, according to Murphy, will be much less costly and will allow Tidal Energy to carry out installation as and when it is required.

The upcoming prototype trial is to involve close analysis of the maintainability of the underwater components of the device. “Our original maintenance plan for DeltaStream was to recover the whole device to the surface to carry out maintenance,” says Murphy. “However, we are investigating the practicalities of removing one turbine at a time as we see that as a more cost-effective solution to long-term O&M.

“The next three to five years are absolutely pivotal for the marine industry to demonstrate that it has got commercial-scale prospects,” adds Murphy. When prototype testing is completed, Tidal Energy plans to install a 10MW array off St Davids Head – this would use nine DeltaStream devices at its current power rating, although it is possible that the drivetrain will be scaled up so that there will be fewer devices in the array.

“It is good news for the industry that the likes of Siemens, Alstom, Andritz and other OEMs have chosen to invest in the tidal stream space,” concludes Murphy. “The fact that they bring their balance sheet, their gravitas, and strength in engineering resource means that this industry is going to work. These major players are coming in because they see there is real potential here.”

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Press Release, March 28, 2013