Conventional tidal devices resemble wind turbines in being moored to the seabed, incurring enormous deployment and engineering costs. In contrast CoRMat  is a small, free-floating capsule, tethered to a surface float, which uses a novel, contra-rotating rotor system to effectively harness tidal energy.

It can be used in water depths of up to 500m and, because its closely spaced rotors move in opposite directions, it remains steady in the face of strong tidal flows, avoiding catastrophic stresses experienced by single rotor devices.

Nautricity is one of several companies that has been selected by the Crown Estate to bid for the first round of licenses to generate wave and tidal energy in the Pentland Firth. A proof of concept version of CoRMaT has already successfully generated electricity. Later this year, a pre-commercialisation device will undergo further rigorous testing at the European Marine Energy Centre (EMEC) in Orkney.

Greater reliability, efficiency, ease of maintenance and environmental impact than conventional subsea rotors, means developers are confident it can be the first device on the market to effectively deliver "commercially competitive" electricity to the national grid.

First generation tidal energy devices are short of producing affordable power, according to Nautricity. While natural gas, one of the most efficient energy sources, produces 1MW/hour of electricity for around £48.90, according to latest estimates, the cost of offshore wind generation is around £57.80 per MW/h. There is no evidence that any tidal device so far has been capable of generating electricity for less than several hundred pounds per MW/h.

Several devices have failed within days of being seabed deployment  because rotors could not withhold the imposed stresses and strains. In many cases, it can takes engineers months to replace damaged or dislocated blades, adding significantly to costs.

“We anticipate that within the next year we will be capable of producing electricity that is competitive with offshore wind generation,” says David Pratt, Nautricity co-founder.

“First generation tidal devices are nothing more than wind turbines in the sea. They require very heavy foundations and engineering to take place on the seabed which means they have a very high fixed cost.

“Our device is small, easier to handle and engineer and significantly simpler to deploy. We have lots of small units in the water compared with a few very big units.”

Nautricity launched in 2009 and has so far invested more than £2m in CoRMaT with support from private equity investors. It plans to begin rigorous testing in the autumn, but could switch testing to Canada, the Mediterranean or Asia, depending on level of support received from government and private sources.

“Several factors will determine where we test,” said oil and gas industry veteran Pratt. “It will ultimately come down to the kind of support and encouragement we get in any given site.

“If we are getting grant support from overseas companies there is usually some sort of string attached such as the requirement to site manufacturing or operations in that country. We just have to look at these things on a case by case basis.

“We very much think of this as a global industry and market. We hope to capture a significant share of the world’s tidal generation market. In addition to some world class tidal resources off the Scottish Coast, we have looked at sites in Canada, The United States, Chile, India, Korea and China.

“While Scotland was quick to realising the value of its tidal resources, other countries are catching up. Ideally, we’d like stockholdings in schemes in several countries within five years.

“To put it all in context, once this is a fully commercial proposition, what we will be doing is building big power stations. These are enormous capital projects which require us to raise tens of millions of pounds.”

Nautricity is co-owned by David Pratt 52 and Cameron Johnstone, 44, (right) formerly a senior lecturer and researcher in the Engineering Faculty at Strathclyde University.


It has several technology partners, including the Energy Systems Research Unit (ESRU), based at Strathclyde University; Mooring Systems Limited, the patent holder for the TCMS mooring and loading system; and SmartMotor, which has developed innovative and breakthrough technologies for making highly efficient customized generator assemblies.

Advisers, spread around Scotland, include Ernst & Young, Inverness, the Bank of Scotland, Aberdeen and MacRoberts Solicitors, Glasgow.

UK’s tidal energy resource has been estimated as being sufficient to generate 94 TW/hrs/pa of electricity or a quarter of the country’s current annual electricity consumption.