The Different Forms of Ocean Energy

Excluding

offshore

Term used to designate offshore exploration or exploitation areas and operations (e.g. wind f...

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wind energy

Energy derived from the wind. Wind power involves converting the kinetic energy of moving air...

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, ocean energies are categorized as:

• Tidal energy: Like conventional hydroelectric dams, tidal

  power

  In physics, power is the amount of energy supplied by a system per unit time. In simpler term...

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  plants, built on river estuaries, hold back huge amounts of water twice a day, which generates power when released (See Close-Up: "Tidal Energy").
• Wave energy: The force of waves can drive mechanical systems to generate power. Originally located just off the coastline, increasingly large experimental plants are now moving to the open sea (See Close-Up: "Wave Energy: Harnessing the Constant Motion of Waves").
• Ocean current energy: The energy of ocean currents under the surface is comparable to the wind above it. Underwater turbines — large propellers tethered to the seabed — are used to derive power from this source.
• Ocean thermal energy: Oceans a huge

  heat

  In the field of statistical thermodynamics today, heat refers to the transfer of the thermal ...

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  reservoirs. The temperature differential between warm surface waters and cold deeper layers in intertropical regions can be used to generate steam and then power (See Close-Up: "The Ocean, an Underused Heat Reservoir").
• Osmotic energy: This technique — the most surprising — produces energy from the movement of water across a membrane between a saltwater reservoir and freshwater reservoir.

These forms of energy have undeniable advantages. They are abundant, constant and predictable and can be harnessed in many different regions around the world. Some countries have started experimenting and some facilities are already generating power on a commercial scale¹.

Research Avenues for Ocean Energy Sources

The sheer scale of the oceans means that potential production could in theory reach 100,000 to 150,000 TWh a year. In comparison, the world's current power generation capacity stands at 22,000 TWh².

However, this calculation is purely theoretical as the investments required — which are still very significant — and the uncertainty of the marine environment must be taken into consideration. Commercial-scale installations come with several risks:

corrosion

The gradual degradation of a material by a physical or physicochemical reaction with its envi...

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of materials due to the salinity of seawater and microorganisms, offshore maintenance difficulties, the

environmental impact

Any change to the environment, whether adverse or beneficial, wholly or partially resulting f...

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on landscapes, the marine environment, and competition in these areas from other marine activities such as fishing.

A drop in production costs is also a prerequisite for the growth of ocean energies, even though turbines and wave energy converters are already being developed at lower costs than those seen in early days of wind energy.

Sources:

1. French Ministry of Sustainable Development  (French only)
2. Inter-Mines (French only)