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CaseStudy

Innovation comes in waves

From CAD User Mechanical Magazine Vol 22 No 6 - JUNE/JULY 2009

Green Ocean's electricity generators win Autodesk's Inventor of the Month for April

As George McDonald said when contemplating the majesty of the Oceans, “Will the time ever come ... when man shall be able to store up even this force for his own ends?” There is vast energy lying untapped in the seas, which we are only beginning to draw down in the minutest of quantities, led by farsighted companies like Green Ocean Energy Ltd, an Aberdeen-based renewable energy company actively pursuing what George MacDonald dreamt of 140 years ago.

Green Ocean Energy is dedicated to developing technology to harness energy from the Earth's oceans in a way that is harmonious to the environment and also economically viable - providing a clean and sustainable source of energy. Two different devices have been developed and tank-tested, and are now being built as full size machines for testing at sea. Called Ocean Treader and Wave Treader, they both work on the same principle - but the first is a floating device, whilst Wave Treader will be built on similar, but smaller, pylons to those used in offshore wind farms.

Ocean Treader, therefore, is a floating device designed to be moored 1 - 2

miles offshore in ocean wave systems, and as such will be largely unobtrusive from the shoreline. It comprises a Sponson at the front, a Spar Buoy in the centre and a second Sponson at the aft end. As the wave passes along the device first the forward Sponson lifts and falls, then the Spar Buoy lifts and falls slightly less and finally the aft Sponson lifts and falls.

The relative motion between these three floating bodies is harvested by hydraulic cylinders mounted between the tops of the arms and the Spar Buoy, pressurising hydraulic fluid which, after smoothing by accumulators, spins hydraulic motors and then electric generators. The electricity is exported via a cable piggybacked to the anchor cable.

Ocean Treader is directional and has been proven to passively weather-vane to face the wave train (tested on the Scale model at Strathclyde University), and it also has active onboard adjustment to allow for offset due to the effects of current.

Ocean Treader is built from steel load bearing members with buoyant bodies moulded from GRP (Glass Reinforced Plastic), allowing standard offshore manufacturing techniques to be used.

The machine is also modular which allows for great flexibility in the manufacturing process.

Wave Treader has grown out of the work with Ocean Treader and uses the same Sponsons and Arms but this time they are mounted on the base of a static offshore structure, typically a Wind Turbine or Tidal Turbine. A great example of different technologies sharing high infrastructure costs foundation costs, cabling costs, etc. enhancing the economics of both devices and improving the energy yield for a given sea area. Both devices are also unique in their respective fields, are patent applied for, and are highly cost effective.

DIGITAL PROTOTYPING TESTS "SEAWORTHINESS"

One of the primary challenges Green Ocean faced was building a device that could withstand the rough waters of the North Atlantic, where wave heights range from a relatively small six to 10 feet, to as much as 30 feet during winter storms. Every working part of the Ocean Treader needed to be thoroughly analysed and tested to help make it have the strength to survive in such a powerful and dynamic environment.

"Fortunately, Inventor is more than just design software; it's an analysis tool too," says George Smith, managing director at Green Ocean. "Inventor allows us to validate our designs on the computer before there's any investment made in constructing a physical prototype." The 3D models were developed in collaboration with Autodesk reseller and training partner Imass Design Solutions, allowing Green Ocean to efficiently develop working prototypes of the Ocean Treader and

Wave Treader, which allowed the company to prove its concept through the extensive indoor wave-pool testing. The team is currently raising funds to develop a full-size prototype to start offshore testing in 2011.

"The race is on to find the best way to harness energy from our natural resources, and Inventor is helping Green Ocean innovate its way into a frontrunner position," said Robert "Buzz" Kross, senior vice president, Manufacturing Industry Group at Autodesk.

Because Green Ocean has been involved in the offshore oil and gas industry, it is well aware of the challenges in deploying such machines, and therefore they have been designed from the outset to be efficient, reliable, and able to withstand their harsh environment.

INVENTOR OF THE MONTH

Autodesk's Inventor of the Month programme recognises the most innovative design and engineering advancements made by the extensive community using Autodesk Inventor software - the foundation of the Autodesk solution for Digital Prototyping. Digital Prototyping is all about testing designs in digital format before they are built as prototypes, or put into production.

Green Ocean Energy Ltd (Green Ocean) was chosen from more than 800,000 users of Inventor as the Autodesk Inventor of the Month for April 2009, for the engineering excellence and innovative use of Autodesk Inventor software in the development of the Ocean Treader and Wave Treader. www.imass.co.uk www.greenoceanenergy.com IOM@autodesk.com

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