'Rubber Snake': Electric energy from ocean waves

A device made up of giant rubber tubes may have the decisive significance in making electromagnetic energy from ocean waves.

"Anaconda", invented in England, is a very creative wave concept. Its simple design means low production and maintenance costs, which allows for clean electricity generation at a lower cost than other wave energy converters. So far, cost has always been a major barrier to the deployment of energy conversion equipment.

Anaconda is named after a snake because of its long, small shape, its ends are sealed and the inside contains water. It is designed to be anchored just below the surface of the sea, with one end catching waves.

The wave that hits one end of the device creates pressure that forms the 'bulge wave' inside the tube. When the bulge wave runs through the tube, the waves create it along the outer part of the tube at the same speed, creating more pressure on the tube and making the bulge wave bigger and bigger. The bulge wave then rotates a turbine located at the other end of the device and the energy generated is transferred to the shoreline via cable.

Since it is made of rubber, the Anaconda is much lighter than other wave energy devices (usually made of metal) and does not need hydrodynamic hammers, joints and hinges. This reduces the amount of capital needed, maintenance costs and the possibility of failure. However, the Anaconda is only in its early stages of development. This concept is only proven in the laboratory scale, so the important question about its potential performance still needs answers.

Anaconda devices can be used in groups of 20 or more.(Photo: Council of Technical and Natural Sciences Research)

With funding from the Natural Science and Technology Research Council (EPSRC) engineers at Southampton University collaborate with inventors and developers Anaconda (Checkmate SeaEnergy) to embark on a chapter. Tests on a larger scale with necessary mathematical research. Using tubes with a diameter of 0.25 and 0.5 meters, the experiment will evaluate the operation of Anaconda in regular waves, irregular waves, and intense waves. The parameters are evaluated including internal pressure, changing the shape of the pipe and the forces that the sea cable suffers. This data will be the basis for a mathematical model that accurately calculates the energy that real-sized Anaconda can generate, as well as providing an understanding of the hydrodynamic performance of the device.

When built, each full-size Anaconda device will be 200 meters long and 17 meters in diameter, deployed at a depth of 40 to 100 meters. The initial assessment shows that the Anaconda will have a capacity of 1 MW (equivalent to the amount of electricity used by 2000 households) and may have a production cost of 6 cents per kWh or less. Although this figure is more than double the cost of electricity produced by traditional coal-fired power stations, it is still better than the cost of other leading wave energy ideas.

Professor John Chaplin, who directed the EPSRC's funding project, said: 'Anaconda could be a valuable contribution to environmental protection by encouraging the use of wave energy. Real-sized 1/3 size Anaconda model can be built next year for sea testing. We can witness first-hand the first full-size device deployed on the coast of England in the next 5 years . ' Anaconda was the invention of Francis Farley (experimental physicist) and Rod Rainey (of Atkins petroleum). The fabrication of parts of inelastic tubes can give certain advantages, but this still has to wait for a specific evaluation.

Wave-generated electricity has no carbon, so it is an advantage in the fight against global warming. Along with tidal energy, wave energy can provide about 20% of the UK's current electricity demand.

The two-year project 'Hydrodynamics of Wave Energy Transformation' was funded by the EPSRC over £ 430,000.

* Bulge wave is a pressure wave created when a liquid vibrates up and down in a tube.