Oscillating water column

Using the pressurised air from above an oscillating water column.

LIMPET: Land Installed Marine Powered Energy Transformer

In 1998 Queen's University Belfast in partnership with Wavegen Ireland Ltd., Charles Brand Ltd, Kirk McClure Morton and I.S.T. Portugal were commissioned to construct and test a 500kW shoreline wave power plant.  The plant has been operating remotely since 2000 and is supplying energy to the electrical grid in the United Kingdom. The successful unattended operation of the plant since commissioning has demonstrated the potential of shoreline wave energy for contributing towards national energy supplies.

The device comprises three water columns contained within concrete tubes each measuring internally 6m by 6m and inclined at 400 to the horizontal giving a total water surface area of 169m2. The upper part of the tubes are inter-connected and power conversion is via a single turbine generator unit connected to the central column. The water columns with an external width of 21m are located 17m inland from the natural shoreline in a man-made recess with a water depth of 6m at mean water level. The sides of the recess are virtually parallel and vertical.

The power take off system comprises a single 2.6m diameter counter-rotating Wells turbine in which each plane of blades is directly mounted on the shaft of a modified wound rotor induction generator rated at 250kW, giving an installed capacity of 500kW.

The output from the generators is rectified and inverted prior to the grid connection and this enables variable speed operation with the range of 700 and 1500 r.p.m. The operational characteristic of the plant is software driven and can be altered. Noise produced by the airflow past the turbine rotors is attenuated in an acoustic chamber prior to discharge to the atmosphere. The turbine generator module also comprises a butterfly and a vane valve between the rotors and the plenum chamber.

From Voith Hydro Wavegen: Wave Power Stations:

Installed on breakwaters, they not only generate power, but reduce the energy hitting the breakwater.

 

There is an installation at Pico in the Azores Website

Isle of Islay off the west coast of Scotland

 

 

 

Oceanlinx

The structure pictured foundered as it was being towed into position. The company is now in receivership.

Oscillating water column generators can be installed offshore. They can sit on the ocean floor or float in deeper water.

 

 

At Port MacDonnell the Ocean lynx project is exposed to waves driven by the roaring 40s.

Oceanlynx  use the air compressed above an oscillating water column to drive a turbine. the blades automatically reverse as the air is drawn back in again.

GreenWAVE is made of simple flat packed prefabricated reinforced concrete. It sits under its own weight on the seafloor without the need for seabed preparation, in approximately 10-15m of water.

Each greenWAVE device is initially sealed, resulting in a buoyant structure. It is floated to its deployment site, where the buoyant seal is removed and the device is lowered to its final resting position. 

 In a very good climate, a single greenWAVE device would be rated at 1MW or more. 

It can also be incorporated into a sea wall or breakwater structure.

airWAVE - Bidirectional Reaction Turbine

Most turbines are designed to function with a constant flow in a single direction. Our patented airWAVE turbine can continue to generate electricity regardless of a change of direction under varying flow conditions.

The blueWAVE structure comprises a cluster of floating OWCs joined by a space-frame. It is an anchored floating steel device, located in approximately 40-80m of water.

Ocean Energy - OE Buoy

The OE buoy from Cork Ireland works on the same principle. Not sure who has which patents.

Play video                  Ocean Energy website

The mighty whale​

The mighty whale is a floating version looking like a whale. Here is is pictured actingas a power generating breakwater.  Source

 

"SPERBOYTM, developed and patented by Embley Energy, is a floating wave energy converter based on the 'oscillating water column' principle.  Air displaced by the oscillating water column is passed through turbine-generators."  Website

Wells turbine

To use air coming from both directions, a turbine blade could change direction with each gust. But this requires moving parts, and moving parts eventuall  The Wells turbine has only one moving part, the rotor.

The blades are aerofoil shape at right angles to the flow. When the air hits it pushes it forwards.  The same happens if the wind comes from the other side. 

What it loses in efficiency, it gains in reliability.