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Ocean Power: Harnessing the Ocean's Untapped Energy Source
The ocean contains vast amounts of energy in the form of waves, tides, ocean currents, salinity gradients, and temperature differences. Capturing and converting this renewable ocean energy into usable electricity can play an important role in the global energy mix. Ocean power technologies are still under development but show significant potential to provide clean, renewable energy on both small and large scales.
Wave Energy Conversion
One of the most promising sources for harvesting ocean power is wave energy. Waves are formed by wind blowing over the surface of the ocean. Areas with highly energetic ocean swell or coastal regions exposed to strong winds create optimum conditions for extracting energy from waves. Several technologies have been devised to convert the energy in ocean surface waves into electricity.
The most developed wave energy conversion devices include oscillating water columns, attenuators, overtopping devices, and point absorbers. Ocean Power column works like a reverse turbine, with incoming waves pushing air through a turbine that drives an electrical generator. Attenuators resemble a series of floating buoys connected by hinged joints that undergo relative motion from passing waves. This motion drives hydraulic pumps or linear generators. Overtopping devices are partially submerged structures that allow waves to enter an elevated reservoir, from which water then falls to drive a low-head turbine. Point absorbers are small, floating devices that capture wave power directly from the passing wave front.
Wave energy has the potential to provide a significant portion of worldwide electricity demand. However, the intermittent and unpredictable nature of wave resources remains a challenge. Overall costs also need to come down before wave power can compete in large-scale energy markets without subsidies. Progress is being made through continued testing and optimization of device designs.
Tidal Energy Conversion
Another renewable ocean energy resource is tidal power, which exploits the rise and fall of ocean tides. Tidal ranges or differentials of over 6 meters are generally considered minimums for economically viable tidal power projects. Top tidal sites are found around Canada, Europe, Russia, China, and Korea. Tidal power technologies take two main forms - tidal barrages and tidal stream generators.
Tidal barrages or dams are barrier constructions built across tidal estuaries, rivers, or inlets. As tides ebb and flow, water is trapped or released through turbines to generate power. While tidal barrages can provide reliable, predictable power outputs on a large scale, they significantly alter coastal ecosystems and marine habitats. The most well-known tidal barrage scheme is at La Rance in Brittany, France, which has been in operation since 1966.
Tidal stream generators operate like reverse wind turbines, capturing the kinetic energy of moving water currents. They are typically free-floating or bottom-mounted structures with horizontal or vertical axis rotors. Tidal stream turbines offer an alternative to barrages by leaving coastal environments relatively unchanged. However, deployment and maintenance pose engineering challenges due to harsh ocean conditions. Like wave energy devices, tidal generators also suffer from intermittency as tides shift on a daily and monthly cycle.
Overall, tidal power has potential for much greater development, but technology and infrastructure costs must be reduced before widespread commercialization can occur. Successful trials are helping to drive down costs and validate performance. As with wave technologies, tidal power deployment will likely increase over coming decades as part of coastal and ocean renewable energy portfolios.
Ocean Thermal Energy Conversion
The temperature differences between surface and deep ocean waters can be harnessed through a process called ocean thermal energy conversion (OTEC). Warm tropical surface waters (25-28°C) are used to vaporize a working fluid like ammonia or propane. The low-density vapor then spins a turbine, after which it condenses using the cold water (4-10°C) from depths below 1,000 meters.
Closed-cycle OTEC systems avoid evaporating sea water directly and can operate continuously at tropical and subtropical coastal sites. They also produce potable water as a byproduct in a process analogous to conventional distillation desalination. OTEC has potential for carbon-free baseload power and integrated seawater air conditioning or industrial applications using waste heat.
However, capital costs for OTEC plants are still very high—estimated at over $2000/kW installed. Significant engineering and component cost reductions would be needed before OTEC is commercially viable on utility scales. But government and company R&D efforts continue, including pilot plant deployments, to demonstrate technical feasibility and drive down expenses over the long-term. Remote island microgrids may offer early niche opportunities for OTEC to play a role in energy mixes.
Saline Gradient Power
Another category of ocean power technology takes advantage of differences in salt concentration between fresh river water and seawater. This process is known as blue energy or salinity gradient power. It involves usingReverse Osmosis membrane technology to separate fresh and salt water streams, with the higher salt water concentration exerting osmotic pressure.
This pressure difference is then used to drive hydro-turbines or piston pumps connected to electrical generators. Prototype devices have achieved power densities of 8-10 W/m2 membrane area. While salinity gradient power has the benefit of being highly predictable, current systems are not economically viable owing to high capital costs and modest power outputs from early prototypes.
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About Author:
Alice Mutum is a seasoned senior content editor at Coherent Market Insights, leveraging extensive expertise gained from her previous role as a content writer. With seven years in content development, Alice masterfully employs SEO best practices and cutting-edge digital marketing strategies to craft high-ranking, impactful content. As an editor, she meticulously ensures flawless grammar and punctuation, precise data accuracy, and perfect alignment with audience needs in every research report. Alice's dedication to excellence and her strategic approach to content make her an invaluable asset in the world of market insights.
(LinkedIn: www.linkedin.com/in/alice-mutum-3b247b137 )
