SCOTTISH renewables specialist AWS Ocean Energy has sold a 40% stake in the company to Alstom, one of Europe's largest engineering groups.

The move is part of a plan to expand operations and accelerate the development of its revolutionary floating doughnut wave-power machine.

No value was put on the deal, which was announced by First Minister Alex Salmond at an event at Edinburgh Castle last night, but it is understood to be worth multi-millions.

However, Simon Grey, AWS’s chief executive, told the Herald that the deal was structured through both the issuing of new shares and sale of some of the minority stakeholdings.

He declined to name the minority investors, but said: “Some of them have exited with cash in their hands, which is probably a first in the UK wave power sector.”

According to documents obtained by The Herald from Companies House, AWS’s shareholders include the Shell Technology Ventures Fund, Credit Suisse Client Nominees, Tersus Energy, and Isleburn. The latter, which operates out of the yard at Nigg, at the mouth of the Cromarty Firth, is involved in the fabrication of AWS’s wave machine. Mr Grey is also a shareholder, as is the Scottish Co-investment fund.

Asked if he had sold his stakeholding as part of the deal, Mr Grey said: “It was one of the stipulations that I didn’t exit the company. You’ve heard the term golden handcuffs.”

As part of the expansion, the pioneering Inverness-based marine power company will also increase its workforce from 14 to 30 to fast-track the development of its doughnut-shaped AWS-III offshore wave energy generator.

Although Paris-based Alstom has previously provided turbines for ScottishPower’s Whitelee and Clachan Flats wind farms, last night’s deal marks the French engineering giant’s first-ever investment in wave energy.

A small-scale prototype of the wave-power device was trialled last year in Loch Ness and, in the wake of the multi-million pound Alstom investment, the next phase will be to deploy and test a full-size, single-cell device.

Following that, the company aims to launch the prototype of the 60 metre-diameter floating ring with 12 wave-cell-absorbers, capable of generating 2.5 megawatts of power – very large by wave-power standards.

The deployment of the first, fully functional AWS-III is scheduled for 2014 and is expected to be located in the coastal waters off Orkney.

Ultimately, the company intends to launch its first array of four devices in Scottish coastal waters in 2016.

The AWS-III floats on the surface of the ocean, where the rising and falling motion of the waves forces air forward and backwards through a number of turbines installed inside the device, which then produce electricity.

Mr Grey added: “Alstom’s investment is a significant boost for AWS and Scotland’s wave energy sector as a whole.

“The company is already number one in hydro power. Now it wants to be number one in wave power, and they have chosen our technology to get there.

“Alstom’s decision to invest in our company, as well as the support of the Scottish Government, are endorsements of what we have achieved so far, and a major source of motivation to accelerate the commercial development of our technology.”

To date, the company and its research and development work have been financed by a combination of private and public sector investment, and government grants.

In 2010 it secured a £2 million investment from Scottish Enterprise’s Scottish Co-investment Fund and the Shell Technology Ventures Fund, and it received £1.4 million of funding support through the Scottish Government’s Waters programme.

It also received a £350,000 grant last year from the UK Government sponsored Technology Strategy Board.