Wave Power

2006.05.07

Discussion

Wave power is a renewable form of electricity derived from energy in ocean waves.

Wave power, generated by a number of facilities located along suitable sections of the Australian coastline, could partly substitute for greenhouse intensive electricity from coal fired stations.

One drawback is visual - unsightly industrial, steel and concrete infrastructure cluttering up otherwise pristine coastal settings.

Readings

Wave Power

Earthbeat, 26 January 2002

Wave power is a renewable energy technology that makes sense in a country like Australia, with its enormous coastline.

Energetech Australia is building a prototype electricity generator based on wave power on the breakwater at Port Kembla in New South Wales.

A submerged chamber is open below the water level. When the waves rise up around the chamber, the water inside the chamber rises and falls with the waves. This compresses and decompresses air above the water in the chamber, creating airflow which drives a turbine. The turbines work with the air flowing in both directions. The blades change angle, depending on the speed and direction of the airflow.

An ocean wall in the shape of a parabola concentrates the wave energy onto a central point where the power station is located.

The opening of the parabolic bay is 40 metres wide; the chamber, about 10 x 10; the turbine 1.4 metres in diameter - a small turbine. For larger plants, in parts of the world where the waves are on average much bigger, we still don’t envisage having a turbine any more than 2 metres in diameter. The high tech part is the turbine. It can be manufactured locally in Australia and shipped throughout the world.

This first plant at Port Kembla is going to be half a Megawatt.

Probably at Port Kembla a single device long-term is not going to be cost-competitive with coal-fired power. But placing a number of them along a breakwater significantly reduces the per kilowatt hour cost of the electricity .

Wave Power - energy from the wind on the sea

Andy Darvill's Science Site

Ocean waves are caused by the wind as it blows across the sea. Waves are a powerful source of energy. At a wave power station, the waves arriving cause the water in the chamber to rise and fall, which means that air is forced in and out of the hole in the top of the chamber. We place a turbine in this hole, which is turned by the air rushing in and out. The turbine turns a generator. The rushing air can be very noisy, unless a silencer is fitted to the turbine. But the waves make quite a bit of noise themselves.

Ocean Wave Energy

PESWiki

Wind is caused by differences in temperature due to the solar heating of the earth's atmosphere. When this wind skims over the sea, energy is exchanged between the wind and the sea surface. At first, little ripples arise on the surface. Then, the wind that skims along these ripples causes higher air pressure at the front of the wave than at the back. As a result the ripples change into small waves. The waves become higher and the distance between the tops (wave length) becomes longer. Wave energy, then, can be seen as a concentrated form of solar energy. During this process of conversion, the energy is concentrated more and more, [sometimes] up to a power level of over 100 kW per meter of wave front. The amount of converted energy depends on the wind speed, the time the wind blows over the waves, and the distance it covers. During a wave's voyage, it shapes into a more regular wave, commonly referred to as a swell. At ocean shores, swells are very regular and discernable, even when the sea is calm.

Ocean Energy

California Energy Commission

Generating technologies for deriving electrical power from the ocean include tidal power, wave power, ocean thermal energy conversion, ocean currents, ocean winds and salinity gradients. Of these, the three most well-developed technologies are tidal power, wave power and ocean thermal energy conversion. Tidal power requires large tidal differences which, in the U.S., occur only in Maine and Alaska. Ocean thermal energy conversion is limited to tropical regions, such as Hawaii, and to a portion of the Atlantic coast. Wave energy has a more general application, with potential along the California coast.

Some systems extract energy from surface waves. Others extract energy from pressure fluctuations below the water surface or from the full wave. Some systems are fixed in position and let waves pass by them, while others follow the waves and move with them. Some systems concentrate and focus waves, which increases their height and their potential for conversion to electrical energy.

A floating buoy system or an offshore platform placed many kilometers from land is not likely to have much visual impact (nor will a submerged system). Onshore facilities and offshore platforms in shallow water could, however, change the visual landscape from one of natural scenery to industrial.

The incidence of wave power at deep ocean sites is three to eight times the wave power at adjacent coastal sites. The cost, however, of electricity transmission from deep ocean sites is prohibitively high.

Wave power densities in California's coastal waters are sufficient to produce between seven and 17 megawatts (MW) per mile of coastline.

A breakwater to harness wave energy

The Asian approach to connect coastal protection with energy production

Dr.-Ing. Kai-Uwe Graw

Since India has a lot of potential for new fishing harbours in the near future, the development of new cost effective breakwater systems is useful. A wave energy breakwater becomes profitable because the costs are being shared between the breakwater wall and the power plant. An energy absorbing breakwater is also a better engineering design as compared to a rubble wall breakwater which takes all the beating from the waves.

Links

Energetech Australia

Centre for Energy and Greenhouse Technologies