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March 14, 2012
Dear Sustainability Watch Reader,  

I am pleased to provide you with your weekly Sustainability Watch newsletter. This week's topic is "Marine Energy."

Marine power has been slow to catch on as a major energy source, despite its staggering potential: it is estimated that 0.1% of the energy in ocean waves alone could be capable of supplying the entire world's energy requirements five times over. The United Kingdom is positioned to change that, however, by solidifying its status as the world leader in the development of wave and tidal energy technologies.

 

The UK already hosts seven of the eight full-scale prototype devices installed worldwide, in addition to several small-scale projects. Scotland in particular (the "Saudi Arabia of marine power") comprises one-tenth of Europe's wave power, and new wave and tidal energy projects have recently been approved for the Pentland Firth, the Orkney Islands, and the Sound of Island. Scotland has more than 11 gigawatts of offshore wind, wave, and tidal energy products planned for completion by 2020. 

 

In late 2011, however, the British government withdrew its support for a 10-mile-long tidal barrage across the Severn Estuary - what would have been the biggest construction project in the world and by far the largest renewable energy project in history. A February 2012 report by the British Energy and Climate Change Committee is now warning the British government that an overly cautious development strategy could cost the UK its lead in this fast-growing industry.

full report 2Executive Summary

   

The ocean is an enormous source of energy: It is estimated that 0.1% of the energy in ocean waves could supply the entire world's energy requirements five times over. A number of technologies aimed at harnessing this potential are in different stages of investigation and development: tidal energy, wave energy, tidal or marine currents, temperature gradient, and salinity gradient. To date, wave and tidal energy are the most advanced types of ocean energy systems under development; more than 300 wave and tidal systems have been proposed, and more than 25 countries are participating in the process. 

 

Wave energy is the most significant of the marine energy resources, as it extracts energy from surface wave movements. There are three main types of technology designs for wave energy: buoyancy devices, subsurface wave devices, and shoreline or seabed mounted wave devices. Research shows that wave energy may be a viable renewable energy source for coastlines in Australia, the United States, the United Kingdom, the Pacific Islands, Japan, China, Western Europe, South America, and Africa. Wave resources are strongest, however, around the Pacific Rim and Western coasts.

 

Wave power is distinct from tidal power, which uses the currents created by the rising and falling tides. Currently, most tidal energy is harnessed using a  barrage: a dam composed of sluices and turbines stretched across a channel or estuary. This technology has already been proven to be productive, and it uses technology similar to a hydroelectric dam. In 2011, the Sihwa Lake Tidal Power Station in South Korea was completed, surpassing France's La Rance station as the largest barrage tidal power installation in the world.

 

Conversion of tidal energy into electricity can be compared to the technology used in hydroelectric power plants. Tidal power can also be captured use tidal stream or ocean current systems, which operate much like underwater wind turbines. There are three main types: tidal turbines, tidal fences, and tidal lagoons. The world's largest tidal power array began construction in 2008 in Brittany, France, and is scheduled to be completed in 2012. The Roosevelt Island Tidal Energy project, which was approved a commercial license in January 2012, aims to be the world's first grid-connected kinetic hydropower system. While tidal technologies are only feasible in areas where the strength of tidal currents is sufficient to run turbines, they are gaining attention due to lower costs and less environmental degradation.

 

Research into ocean thermal energy (OTEC) and salinity gradient energy is still in mostly experimental and/or preliminary stages, however. With OTEC, the difference of temperature between cold, deep seawaters and warm, shallow waters creates a thermodynamic cycle, which can be used for producing electricity. In the case of salinity gradients, the difference in salinity between seawater and fresh water creates a pressure difference which can be exploited to extract energy.

 

Marine energy stations may be more politically palatable than wind energy devices for several reasons. Marine energy technologies are usually invisible from shore, and there is more open space available in the ocean than on land. However, electricity from wave and tidal generators is costly, and significant obstacles remain in terms of funding and financing, government will, and utility support. WaveGen sells electricity to Pacific Island nations for 40 to 50 cents per kilowatt hour (kWh). In contrast, in the continental United States the per kWh cost of electricity averages around 7 to 8 cents, and can reach 20 cents in some regions.

 

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Emily C. Ryan
Managing Editor, Evidence Based Content
Business Development
EBSCO Publishing
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