Optimum use of wave energy using oscillating water column system

Mar 29, 2011

Engineers Modesto Amundarain and Mikel Alberdi have presented the first two PhD theses at the University of the Basque Country (UPV/EHU, Spain) on the use of oscillating water column (OWC) converters for extracting renewable energy from waves. According to these two engineers, the technology of the plant, currently being built in the coastal town of Mutriku in the Basque province of Gipuzkoa, is the most suitable for taking advantage of energy from the waves along the Basque coast.

Both research theses present proposals for enhancing the operation of this kind of plant. Mr Amundarain's thesis (Control of wave-driven turbo-generators) puts forward a number of strategies for resolving the problems of control of these installations. Mr Alberdi focused on solving the power problems arising with generators of this nature (and entitled, Design and development of power plant control strategies for converting from the sea and for power sags in the ). The results of this research have been published by the Department of Systems Engineering and Automation at the UPV/EHU, where Mr Amundarain and Mr Alberdi work, in the IEEE Transactions on Industrial Electronics journal.

The OWC system

In OWC technology, it is not the waves that move the turbines directly, but a mass of compressed air that is pushed by these waves. It involves a structure usually located in a breakwater, the upper part of which houses an air chamber (thus the compressed mass of air) and its lower part is being submerged under the water. In this way, the turbine takes advantage of the movement caused by waves, both when they come in and when they go out, and the doubly-fed generator (both by its rotor or mobile part and by the stator or fixed part) to which it is coupled feeds energy to the grid.

One of the principal problems described by the two researchers is the loss behaviour of the turbine. The turbine used in these installations is the Wells type and, given its characteristics, on a particularly strong wave hitting it, the turbine can become stuck or rotate much more slowly than normal. It is thus necessary to adapt the speed of the turbine. The research also aimed to identify the maximum power obtainable or to fix a reference power, also related to the control of the turbine.

In the quest for more efficient solutions, Mr Amundarain and Mr Alberdi emulated a whole plant using a computer (including the Wells turbine, which they had to build from scratch, not having any model) and validated their trials experimentally. They managed to establish that the most effective measure was controlling the velocity of the turbine through the doubly-fed generator to which it is coupled. The same generator makes the turbine rotate at the optimum speed to give the maximum power, adapting itself depending on the pressure caused by the waves at each moment. They also combined this measure with the control of the air flow, based on a valve usually found in the reception chamber of these OWC systems, and involving controlling their level of opening according to the air flow.

Losses of grid voltage

These two measures are valid in helping to solve another problem tackled by these two researchers, largely dealt with in Mr Alberdi's thesis: the power sags in the grid which cause imbalances when operational. Mr Alberdi coordinated a series of strategies amongst which are those mentioned above. The researcher also proposes the control of active power (the part that is in fact consumed) and reactive power (not consumed) fed into the grid in a decoupled manner. Also, in order to control electricity generation, whatever the state of the sea, the researcher proposed monitoring the continuity of supply during a power sag and making use of a system of generation of references.

Explore further: Lifting the brakes on fuel efficiency

Provided by Elhuyar Fundazioa

2.6 /5 (5 votes)
add to favorites email to friend print save as pdf

Related Stories

Higher energy yield with torque vectoring gears

Feb 23, 2011

Wind turbines have a problem: Depending on the wind's force, the rotational speed of the turbine and thus of the generator changes. However, alternating current must be fed into the grid with precisely 50 (or 60) hertz. Typically ...

Enhancing the efficiency of wind turbines

Nov 22, 2010

A milestone in the history of renewable energy occurred in the year 2008 when more new wind-turbine power generation capacity was added in the U.S. than new coal-fired power generation. The costs of producing power with wind ...

Vertiwind: Floating wind turbine project launched

Feb 07, 2011

(PhysOrg.com) -- Technip, a French-based oil and gas engineering company, and Nenuphar, a wind-power startup, announced that they will soon launch Vertiwind, a newly designed wind turbine.

Tilting at wind farms

Jan 07, 2009

A way to make wind power smoother and more efficient that exploits the inertia of a wind turbine rotor could help solve the problem of wind speed variation, according to research published in the International Journal of ...

Recommended for you

Lifting the brakes on fuel efficiency

Apr 18, 2014

The work of a research leader at Michigan Technological University is attracting attention from Michigan's Governor as well as automotive companies around the world. Xiaodi "Scott" Huang of Michigan Tech's ...

Large streams of data warn cars, banks and oil drillers

Apr 16, 2014

Better warning systems that alert motorists to a collision, make banks aware of the risk of losses on bad customers, and tell oil companies about potential problems with new drilling. This is the aim of AMIDST, the EU project ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Mar 29, 2011
Why not put a one-way valve between two air chambers and use the pumping action of the water to drive air into this volume, which would result in steadying the output and allowing the turbine to work constantly without stops.

You can make it double action if you build two chambers, one always under positive pressure and another always under negative pressure, and the turbine lets air flow between them. The water simply draws air out of the negative chamber on the downstroke, and pushes it into the positive chamber on the upstroke.
not rated yet Mar 29, 2011
@Eikka Essentially you plan on utilizing an annular flow inline jet induction pump ^_^, smart move especially if you wish to boil things like helium from renewable sources.

More news stories

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Airbnb rental site raises $450 mn

Online lodging listings website Airbnb inked a $450 million funding deal with investors led by TPG, a source close to the matter said Friday.

Health care site flagged in Heartbleed review

People with accounts on the enrollment website for President Barack Obama's signature health care law are being told to change their passwords following an administration-wide review of the government's vulnerability to the ...

A homemade solar lamp for developing countries

(Phys.org) —The solar lamp developed by the start-up LEDsafari is a more effective, safer, and less expensive form of illumination than the traditional oil lamp currently used by more than one billion people ...

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...