Looking at the Technologies being Developed to Extract Energy from the Oceans

Renewable energy is often dominated in the discussions by solar, wind and biomass. While they already have a wide fan base, yet another promising emerging technology is marine power.

Marine power is a renewable source classified as "third-generation," or those that need further research and development efforts in order for them to make large contributions to the global energy mix.

According to analyst Global Information, Inc., the global marine energy sector's installed capacity in 2009 was 270 megawatts. This figure is expected to balloon to over 46,000 MW by 2020.

There are five technologies being developed which aim to extract energy from the oceans. These are tidal and wave power, and marine current, temperature gradient and salinity gradient technologies. Tidal power and wave power are the most active, having the greater extent of developments.

Tidal power is the potential energy associated with tides that can be harnessed by building a barrage or other forms of construction across an estuary or bay. The first tidal barrage power plant to be built is located in La Rance, Bitanny, France. It has been operating since 1966, producing 240 MW of power.

The Sihwa Lake Tidal Power Station in South Korea is the world's largest tidal power installation, with a capacity of 254 MW. It was opened in 2011.

Wave power refers to technology that takes advantage of the ocean waves caused primarily by the interaction of winds with the ocean surface. A number of technologies have been developed to harness the potential of this energy. The most prominent among them are the Pelamis, the PowerBuoy, the Aqua Buoy, the Wave Dragon and the Oyster. All of them are designed to convert splashing waves into energy.

Other technologies

Other marine power innovations that can be used for maximizing energy from the oceans - when given more attention - are ocean thermal energy conversion (temperature gradient technology), osmotic power (salinity gradient technology) and marine currents.

Ocean thermal energy conversion uses the temperature difference between the cooler deep and warmer shallow surfaces of ocean waters to run a heat engine and produce electricity. However, the temperature differential is small. This affects the economic feasibility of ocean thermal energy conversion for electricity generation. This is the main challenge that has to be overcome to optimize this technology.

Osmotic power is the energy that comes from the difference in the salt concentration between seawater and river water, and this could be captured through osmosis. This technology remains young, with the first osmotic power plant in the world in Norway only capable of producing an output of 4 kilowatts.

Marine current is potential energy associated with tidal currents and can be harnessed with the use of modular systems. This is still untapped as broad developments are needed to gauge this technology.

Generally, none of these technologies are widely deployed so far, but significant potential exists, according to the International Energy Agency. Significantly, these technologies could start to play a sizable role in the electricity mix by around 2030, the same agency predicts.

Countries take on marine power

Sitting on areas ideal for ocean power harvesting, Britain and Australia, among others, are well-positioned to take advantage of these water power technologies.

Britain has released a study that trains the spotlight on marine power's potential significant contribution to the state's energy mix. Its marine energy report under the Technology Innovation Needs Assessments suggests that the country has a large natural resource for marine power, particularly from waves and tidal streams.

Effectively exploiting marine energy could make Britain the undisputed global market leader, delivering more than 75 terawatts per year - a capacity that is over 10 percent of the state's projected electricity needs by 2050. Significantly, this could also help the state achieve its emissions reduction and renewable energy deployment targets.

Britain's recent step toward boosting this budding technology is the opening of two marine energy parks this year. The first was in the South West last January and the other was just this end of July in Pentland Firth and Orkney Waters. They will also serve as a technology hub for tidal and wave prototypes of developers from across the world.

Unlike Britain, which has already done a number of activities on marine technology, Australia has just begun.

Ocean energy from waves, currents and tides offer as much as 10 percent of Australia's energy mix by 2050, a report from the Commonwealth Scientific and Industrial Research Organization found. This amount of energy is enough to power a city as big as Melbourne.

Areas in the southern shore have the greatest wave reserves in the country brought by strong southern ocean winds that consistently generate large waves, driving northwards to Australia's southern coastline.

Meanwhile, tidal power could be used to provide energy for niche areas like northeast Tasmania and the Kimberley region in west Australia. While Australia sees promise from ocean wave power, further studies and innovations have to be done to optimize this resource for it to play a big part in the country's energy future.

As its first move to explore marine technologies options, the Australian government has been encouraging research and development, which in turn would be the basis for scaling up the country's marine energy sector.

By. Catherine Dominguez