By Jeanne Erdmann
From Portugal to Scotland to the United Kingdom to the United States, countries all over the world are using the pull of the tides and the rhythm of the waves to generate power. In fact, marine energy technology has shown so much recent growth that the IEC is enlisting energy experts worldwide to begin developing standards for wave and tidal energy systems. The IEC’s new Technical Committee, 114, Marine Energy – Wave and Tidal Energy Converters, will facilitate efforts by the International Energy Agency to develop best practices for marine energy. Standards will also help integrate wave and tidal energy converters into the International marketplace, especially as more and more governments mandate efforts for sustainable energy.
Sustainable energy source
World energy demand shows no signs of slowing. Humans now use huge amounts of energy every year. Developing economies continue to grow and thus require more energy. Meeting these energy demands by burning fossil fuels already accounts for most of the human-generated carbon dioxide in Earth’s atmosphere and the worst damage from greenhouse gases. Although clean, renewable energy sources, such as ocean energy technology, won’t clear carbon already in the atmosphere, technology of this sort is more environmentally friendly.
The need for sustainable energy has spurred recent growth in wave and tidal energy systems, explains Ken Street, Business Manager of offshore energy systems for Converteam Group SAS, a company headquartered in France. Converteam supplies electrical system solutions for wave and tidal generation devices of all types. Harnessing the forces of nature for energy is nothing new; windmills have been around for a long time. Using the predictability of waves and tides helps turn those forces into energy grid requirements. “First, wind alone cannot satisfy the targets set by international governments, and second, wind, because of its fickle nature, cannot be allowed to become more than 10 - 15% of the grids' supply. Waves are much more predictable than wind, they are more constant compared to wind. Tidal power is obviously even more predictable than wave and will provide a sizable contribution of the power generated by the sea but wave will dominate - there is just so much more of it,” comments Street.
Oh, buoy. Power!
In general, wave systems have many different devices with different shapes. The movement of the waves causes a design in the device to drive an electrical generator, which then transmits power to shore via a cable. Device designs fall into several categories, explains Street:
The amount of ocean real estate taken up by wave devices relates to the amount of power needed. “Like any fuel source, such as coal or oil, which have a certain energy value, waves are no different. So to capture a meaningful amount of power you need to absorb that from an area of sea,” explains Street. Waves have a certain kW/metre, explains Street. For California’s north coast that power translates to 30 - 40kW/m. To extract say 500kW, you need a device around 40m in diameter. The area taken up by the device is also a factor of its anchoring system. How different designs are moored determines how much space they need. Also, spacing needs to account for boat access and to avoid creating an energy shadow for the device behind the craft.
“Yes wave devices are large - they need to be,” comments Street. Although wave power, compared with a fossil fuel, provides low levels of energy, this energy is “free”, self-sustaining and comes in unlimited quantities.
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