Harnessing wave power to achieve the most from our natural resources

Wave energy presents the world's most abundant source of renewable energy. The trick is capturing the relentless motion of the tides and waves, and converting this into a non-polluting, continuous source of electricity.

The University of Limerick has an active research group studying how wave motion could be harnessed to produce power. Its Wave Energy Research Team (WERT), headed by Dr Ajit Thakker, is involved in a number of international collaborations, and is designing and building turbine components that will be used on the first EU-funded wave power-generating pilot plant, which is under construction in the Azores.

Dr Thakker initiated the university's involvement in wave energy 12 years ago, when it was still the National Institute for Higher Education. "It started from my own personal interest in harnessing energy from a renewable resource."

WERT involves 14 research engineers and academics, and attracts research funding from home and abroad on the basis of its expertise in wave energy turbine technology.

Dr Thakker has set ambitious goals for WERT, including making it the leading turbine research centre in Europe and using this to attract £250,000 (€317,660) a year in research funding. Its role would be to design, test and manufacture bespoke turbine systems for world markets, and to export expertise to create spin-off industries.

"We want to train graduates and engineers for this market," Dr Thakker said.

Many wave energy designs have come and gone. Early versions involved using the water to drive turbines that, in turn, were used to spin a generator and so produce electricity. A much more promising approach - and the one being applied in the Azores - uses wave power to produce a moving column of air to drive the turbine.

It involves building a permanent "plenum chamber", like an inverted glass with its open end dipped into the sea. It is a rigid structure that would be built right into the water's margin, with a small opening at the top where a self-rectifying air turbine could be mounted. The rise and fall of the waves creates an "oscillating water column" inside the chamber that pushes air out as it rises and sucks it back in as the column falls.

This pneumatic power is converted to mechanical energy via the turbine, which spins in only one direction regardless of the direction the air flows. The mechanical energy is used to power an electricity generator that can feed power into the national grid.

Dr Thakker's team is involved in the second element of this, designing a turbine that makes the most efficient use of the air to produce mechanical energy. The key is the shape and size of the turbine blades, and this varies from site to site depending on the characteristics of the plenum chamber, he said.

Turbine blades will vary on the basis of two main factors, the pressure of the air moving in the chamber and the volume flow rate entering the turbine, he explained. WERT is the turbine technology "task leader" for the Azores project, he said, in collaboration with Queen's University Belfast and the Institute Superior Technico, Portugal.

The work is exceptionally interdisciplinary. WERT is based in the university's department of mechanical and aeronautical engineering but its activities also employ engineering expertise from the department of manufacturing and operations engineering. Areas of investigation include computational fluid dynamics, computer-aided engineering, design, experimental analysis, mechanical design and manufacture, concurrent engineering, and stress analysis.

WERT has designed and built a 0.6 metre experimental Wells Turbine rig and analysing its performance on the basis of various blade designs. WERT has developed modelling techniques that allow it to define blade shapes and then measure their efficiency.

Other international partners in the overall project include University College Cork, Saga University in Japan, the Republic's Marine Institute, the University of Reading, the Pacific Society, Japan, and companies such as ESB International; EFACEC Sistemas de Electronics SA and Electricidade dos Acores SA, both in Portugal; and TurboTech Precision Engineering (Pvt) Ltd, India.

Wave energy still has a way to go before it is proven a viable proposition that can deliver commercial electricity. The Azores project and another under way in Scotland will go a long way towards demonstrating commercial potential. "The success of the power plant will be defined by the success of the technology," Dr Thakker said.

Even moderate success would have huge financial potential given the abundance of the resource, which effectively is delivered to us free. In the meantime, Dr Thakker is training graduates and engineers, and is also making Government departments aware of the value of "green energy".

[SBX] Dr Thakker can be contacted by e-mail at: ajit.thakker@ul.ie and the WERT Web address is: www.ul.ie/wert