Plans Announced for a Wave Power Plant in Hawaii

Oceanlinx, an Australian wave energy company, announced plans for a $20 million project to install three floating wave energy converters (WECs), i.e. wave-powered turbine platforms, to supply up to 2.7MW of electricity to the island of Maui, Hawaii. The company has signed a Memorandum of Understanding with Renewable Hawaii, Inc. (RHI), for potential passive investment in a project . RHI is owned by the Hawaiian Electric Company, Inc.

The project could be operational by the end of 2009.

Oceanlinx’s unit combines the established science of the Oscillating Water Column (OWC) with its own patented turbine technology, and has successfully completed a full scale trial at its pilot unit at Port Kembla, Australia.

Each WEC is about 65 by 100 feet and 15-25 feet high and will not likely affect views from land.

An OWC, is a chamber which is open underneath the waterline and allows the water inside the OWC to rise and fall, compressing and displacing the air inside, driving it past a turbine which is housed at the narrowest point in the chamber, located above the waterline.

Since the OWC chamber narrows, the air is accelerated to its highest velocity as it passes the turbine allowing for maximal extraction of the energy. The oscillatory wave motion causes a similar oscillatory airflow through the chamber, and the turbine converts energy on both the up and down stroke.

The unique characteristic of this turbine is its blade pitch control system which enables it to rotate in the same direction irrespective of the direction of the air flow. This turbine, converts the energy in the airflow into mechanical energy which drives an electrical generator. The Oceanlinx turbine uses variable pitch blades which, with the slower rotational speed and higher torque of the turbine, improves efficiency and reliability and reduces the need for maintenance.

The turbine uses a sensor system with a pressure transducer which measures the pressure exerted on the ocean floor by each wave as it approaches the capture chamber, or as it enters the chamber. The transducer sends a voltage signal proportional to the pressure which identifies the height, duration and shape of each wave to a Programmable Logic Controller (PLC) which adjusts various parameters, such as the blade angle and turbine speed, in real time.

An underwater cable will run from the WEC array along the sea-bed to feed a substation on the Maui Electric Company grid.

Oceanlinx claims the advantage of its system are that all the technical equipment operates above the water, thereby improving reliability and providing easy access for maintenance and repair and that it has only one principle moving part, the turbine, which is also located above water. (Isn't the generator a principle moving part?)

Comments

[Sepp Hasslberger]

and that it has only one principle moving part, the turbine, which is also located above water.

... and that it has only one principal moving part, the turbine/generator assembly, which is also located above the water.

[Alex]

At 7 million $ a piece; producing 0.9MW are these contraptions considered cost effective ? Surely the formula should be: cheap=low-tech=durable.

[DavidJ]

That was my instinct when I first came across the design. However they must be doing something right (even if it is just the marketing) as they claim to be involved in a lot of projects.

[doug nicodemus]

i think this is a great idea. i have been waiting for it for a long time. lunar power is the "wave" of the future...sorry join us at www.censys.org

[Fifi]

Variable pitch turbine? With full reversal on up and down stroke. That's a lot of moving parts and, to make things worse, in a high corrosion, saline environment. Sounds pretty awful to me.

It seems to me that they are trying to solve mechanically an issue that would be much easier to solve full solid-state at the alternator level. The recipe would be a very light turbine and alternator rotor for low inertia and an electronically controlled stator exciter and a solid-state converter behind to deal with the alternation in the up-down cycle.

[Terry]

I agree that the constantly changing turbine blade pitch is overly complex. Why not take a lesson from the Iron Age smithy who had a bellows that worked on the up and down stroke. By having a simple flap-valve that would allow air flow out over one turbine and in over another? They could even drive the same alternator with a simple non-corroding drive belt system.

[bigTom]

Hopefully if this tech pans out, the price will come down. Wave power is promising, but tricky. Presumably the air pressure turbine greatly reduces the ability of the salt to get to the moving parts. It is a good that a lot of different wave power concepts are being tested. Most will be found impractical. Hopefully at least one design will be found practical.

Capacity utilization for a good site is going to be much higher than for solar and wind, and the temporal variability is probably decorrelated with wind/solar. So if this stuff can be made to work it would be a good addition to the time variable renewable component.

[Al Fin]

We are in need of a functional "energy island" approach to sea energy. Energy islands take all the low amplitude sea energy sources, combine them with baseload OTEC, and provide reliable power. At least on paper. Most wavepower-only approaches look like hunks of junk.

True, wavepower is promising, but current approaches to wavepower are not even close to what is needed. "If you build it, they [the suckers] will come--and pay." Only not always will they pay.

[Kit P]

There is a huge gap between planing, MOUs, and sustainable electricity production. Hydroelectric, geothermal, and biomass are the only forms of sustainable renewable energy so far. Wind is on the verge if the new machines can stand up top the elements for any reasonable length of time.

Anyone know the salvage value of wave contraptions?

[pbean]

Wave power is still in the early, let-one-hundred-flowers-bloom stage. I'm happy investors are willing to take such risks. Let's hope one or more healthy blossoms are left standing a few years from now.

[Rob]

Flap valves and such have been tried by various groups and found to be generally inferior. Variable pitch blades or a design known as the "Wells Turbine" are the favoured solution right now in terms of optimizing performance.