Various techniques for harnessing the energy of oceans and offshore wind have been the subject of many studies and experiments around the world. But the ocean environment isn’t very friendly.
Ocean Power Potential
Everyone knows what the powerIn physics, power is the amount of energy supplied by a system per unit time. In simpler terms, power can be viewed as energy output... of a wave, the pull of a current or a strong sea wind feels like. If you think about these forces and the sheer size of the ocean – 70% of the Earth’s surface, nearly 1.5 billion cubic kilometers of water – it’s easy to imagine the amount of potential energyEnergy contained in an object or physical system that has the potential to be converted into kinetic energy... locked within these naturally occurring phenomena.
According to experts, oceans could technically produce 150,000 terawatt-hours (TWh)1 of energy per year, which is well above current global electricityForm of energy resulting from the movement of charged particles (electrons) through a conductor...
output of around 23,000 TWh. In theory, ocean energy could meet 650% of current electricity demand.
Obstacles to Overcome
These calculations are highly theoretical. At present, ocean energy accounts for barely 0.3% of global electricity generation.
To turn theory into practice – which isn’t entirely impossible – it would be necessary to:
- Install a large number of imposing, complex ocean/shore equipment requiring significant investment and energy.
- Maintain and care for the equipment amid harsh ocean conditions (seawater and microorganisms cause rapid corrosionThe gradual degradation of a material by a physical or physicochemical reaction... , known as biofouling).
- Minimize the installations’ environmental impactAny change to the environment, whether adverse or beneficial, wholly or partially resulting from human activity... on landscapes and marine biodiversityRefers to the natural diversity of living organisms. It can be measured through the study of species, genes and ecosystems. .
- Share the sea space with other marine activities, especially fishing.
The Rise of Offshore Wind
OffshoreRefers to sea-based oil exploration and production operations, as in "offshore license" or "offshore drilling". wind, which accounts for most of ocean energy’s 0.3% contribution to power generation, captures the energy of wind, rather than that of the sea. Since 2015, there has been a surge in offshore wind development.
Although 0.3% may seem small, this percentage could increase 15-fold by 2040, according to International Energy Agency (IEA)An independent, intergovernmental organization founded within the framework of the OECD...
experts2. The advantage of offshore wind is that it is deployed in large areas – usually more than 10 kilometers from the coast – and uses turbines that are significantly taller and more powerful than their onshoreRefers to land-based oil exploration and production operations, as in "onshore seismic data acquisition" or "onshore drilling".
counterparts. In 2020, the world’s largest turbine had a 222-meter rotor diameter and a capacity of 15 megawatts, compared to an average of 2 megawatts for an onshore turbine.
Other Ocean Energies
- Tidal energy: Tidal barrages built on estuaries hold back huge amounts of water twice a day. When released, the water generates power. Only a few barrage stations exist in the world. They require major infrastructure and have a big environmental footprint.
(See Close-Up: Tidal Energy).
- Ocean current energy: Ocean current energy can be harvested using tidal turbines, or large propellers that are usually moored to the seabed. While the number of projects is growing, production remains low.
(See Close-Up: Ocean Current Energy).
- Wave energy: Using pistons, the force of waves can drive mechanical systems to generate power. Projects are still in the experimental stage.
(See Close-Up: Wave Energy: Harnessing the Motion of Waves).
- Ocean thermal energy: The sea is a vast reservoir of heat. The temperature difference between surface water and deep water is leveraged to heatIn the field of statistical thermodynamics today, heat refers to the transfer of the thermal agitation of the particles making up matter...
a fluid and produce electricity. The technology is still in the experimental stage.
(See Close-Up: The Ocean, an Underused Heat Reservoir).
- Osmotic energy: This technique – the most surprising – produces energy from the movement of water through a membrane between a saltwater reservoir and freshwater reservoir. A large-scale project is operating in Norway.
(See Close-Up: Salt Water, Driving Osmotic Energy).
What About Biomass?
Of the hundreds of thousands of microalgae species found in nature, around 300 have been identified as having the ability to produce large quantities of oil. Currently, however, the production of algal biofuelA fuel produced from plant or animal matter. There are currently two types of biofuel...
and biomethane is still at the research and development stage.
(See the Close-Up for more details: Microalgae Biomass Conversion).
Ocean energy shouldn’t be confused with hydroelectric energy, which uses flowing water in mountain lakes and large rivers to produce power. Hydropower has been around since ancient times (in the form of water mills) and is today by far the leading renewable energyEnergy sources that are naturally replenished so quickly that they can be considered inexhaustible on a human time scale...
source for generating electricity.
(See the Close-Up for more details: Hydropower, the Leading Renewable Energy).
1 Tera denotes multiplication by one trillion. Kilo means one thousand, mega one million, giga one billion and tera one trillion (one thousand billion).
2 See the IEA report