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Ocean Energy

Learn what ocean energy is, how it’s used today, and what opportunities it offers for the future.

What is ocean energy?

Ocean energy describes the process by which the ocean’s movement, or its physical and chemical state, is transformed into thermal or mechanical energy. This type of energy is kinetic (like wind): it utilizes the natural ebb and flow of waves, currents, and tides as well as temperature differences in the water to produce electricity. People first began harvesting energy from the ocean over 1,000 years ago, when it was used to operate grain mills.

The moon and sun’s gravitational pull on the Earth plus the Earth’s rotation is what creates tides in the ocean.

How does ocean energy work?

The world’s ocean energy resources can be harnessed using a variety of technologies—many of which rely on underwater turbines or paddles to power generators that produce electricity. The size, scale, and design of the device depend on the type of energy it seeks to harness, the amount of power required, and other factors. We’ve outlined the most prevalent types of ocean energy technologies for you below.

Wave energy

Wave energy converters use surface waves to generate power. One example of this type of technology is a device that generates power by using wave motion as a piston to drive air in and out of a chamber—the moving air drives a turbine. A simpler example is a buoy that harnesses energy from the vertical rise and fall of ocean waves or their side-to-side movements.

Tidal energy

A tidal stream generator uses the horizontal movement of tidal currents to generate power, usually via underwater turbines. Currents spin the turbine’s propellers (like the wind does for a wind turbine), which then powers a generator.

Ocean thermal energy

Ocean thermal energy is generated by transforming the temperature difference between the ocean’s surface water and deeper water into energy. Ocean thermal energy conversion (OTEC) plants may be land-based, floating, or grazing.

What is the state of ocean energy today?

Tidal stream and wave energy technologies are picking up speed and progressing around the world. Ocean energy is currently being used to produce electricity that powers homes, buildings, and entire cities. A total capacity of 12.91 megawatts (MW) of tidal stream and wave energy is now operational (i.e. 2.31 MW wave and 10.6 MW tidal). Electricity generation from marine technologies increased an estimated 400 GWh (+33%) from 2019 to 2020, which is significantly above the levels of the previous three years, mainly owing to capacity additions of ~200 MW from Denmark.

A significant number of devices for both technologies are being scaled up quickly, and units of 1 MW and higher are being successfully deployed. Tidal stream energy is more advanced and closer to reaching commercialization, with several tidal arrays in the pipeline, than wave energy. Wave energy is also advancing quickly but is less mature compared to the other technologies, as it largely remains in the prototype and demonstration phase.

In the longer run, more capacity additions are expected. As of 2020, wave and tidal stream projects with combined capacities of 2.83 GW are in the pipeline. The International Renewable Energy Agency (IRENA) estimates that around 10 GW could be commercially deployed by 2030.

Spotlight

The world’s first commercial-scale tidal power station was installed in 2007 in Northern Ireland at Strangford Lough. The turbines are located in a narrow strait between the Strangford Lough inlet and the Irish Sea. There, the tide moves at a speed of 13 feet per second across the strait, which is capable of generating 1.2MW of electricity. In 2012, the Strangford Lough tidal power station reached a milestone: it had produced a total of 5GWh power since its inception (enough energy to power 1,500 households!).

What is the future of ocean energy?

In the Net Zero by 2050 report commissioned by the IEA, ocean power generation grows an average of 33% between 2020 and 2030, which corresponds to ~1 GW of average annual capacity additions. However, in much of the world, ocean energy is still in its nascent stages, requiring further research and development plus policy support to enable the cost reductions necessary for larger commercial plants.

Advanced marine projects of 10 kW to 1 MW for power generation have been deployed in the United Kingdom, Canada, Australia, China, and, recently, Denmark, however, these demonstration and small commercial projects remain expensive because the economies of scale necessary for significant cost reductions have not yet been realized.

Industry leaders predict that ocean energy will likely first be used to provide power for island and coastal communities as well as offshore activities, which should help advance the technologies and make ocean energy cost-competitive in additional markets.

What are the advantages and challenges of ocean energy?

Ocean energy is a clean energy source, providing an economically sound, greener alternative to fossil fuel burning. However, as with any energy source, there are advantages and challenges to its use. We’ve rounded up some of the pros and cons for you below:

Advantages

Clean, renewable energy

Ocean energy provides heating and electricity without the use of fossil fuels. What’s more, supply issues are not a concern, as there will always be waves crashing against the coasts, which are often highly populated with people needing electricity. The IEA estimates that global ocean energy production could reduce emissions from fossil fuel-driven electricity generation by an estimated 500 million tons by 2050, helping to mitigate the effects of climate change.

Predictable and stable

Ocean energy is more predictable compared to other renewable energy sources and provides constant electrical generation. When combined with other intermittent renewable energy sources, like solar or wind, ocean energy technologies could offer support and stability to electrical grids.

Offshore power

Ocean energy could provide local and reliable power to offshore industries, systems, and activities, like farming, navigation, and deployed ocean sensors that most commonly rely on batteries.

Support for coastal and rural island communities

Ocean energy helps reduce the country’s dependence on foreign energy sources and could help meet the water and energy needs of rural coastal and island communities by providing locally sourced power.

Disadvantages

High costs

Ocean energy technologies require hefty initial investments to get up and running. Additionally, further operation and maintenance costs are not easily predictable, as harsh ocean environments or storms can damage equipment. Many supply chains are also underdeveloped, which presents additional infrastructure challenges and costs.

Location-specific

Only power plants and towns near the ocean will be able to benefit from ocean energy— landlocked nations and cities will need to establish alternative forms of power generation.

Environmental damages

The installation of ocean energy technologies disturbs the seafloor, changes the habitat of marine life, and creates noise that disrupts the sea life around them. Additionally, collision with underwater turbines often results in death for local marine life. Research is needed to assess the long-term effects of ocean energy technology on the environment.