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Frequently Asked Questions

What is ocean energy?

The oceans are the world’s largest untapped source of energy. Ocean energy technologies exploit the power of tides and waves, as well as differences in temperature and salinity, to produce energy.

Tidal stream: The changing tides produce currents that can be harnessed by tidal turbines to generate clean, predictable renewable energy. These devices work in a similar way to a wind turbine, but because water is 800 times denser than air, individual machines and entire projects can be relatively compact whilst producing the same amount of energy.

Tidal range: Tidal range technology uses the same principles as hydropower and requires a dam or barrier to hold back a large body of water. The difference between the tide height on either side of the barrier pushes water through turbines inside the structure, generating energy.

Wave energy: Wave energy converters (WECs) capture the physical movement of swells and waves and transform it into energy – usually electricity. The energy created is proportional to the speed, height and frequency of the wave.

Ocean Thermal Energy Conversion (OTEC)/Sea Water Air Conditioning (SWAC): OTEC exploits the difference between warm surface water and cold deep water to produce energy. Using a temperature difference of at least 20°C produces a steady, on-demand power supply. SWAC plants use similar technology to provide heating and cooling, and can use smaller temperature differences.

Salinity gradient: Today, the most advanced salinity gradient technology is Reverse ElectroDialysis (RED). Using stacks of membranes, energy can be harvested from the difference in the salt concentration between seawater and fresh water.

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What do ocean energy devices look like?

Ocean energy devices are usually installed on or under the water’s surface, so they are practically invisible from the shore.

Tidal stream turbines come in a variety of shapes and sizes, including 2 or 3 blades attached to a rotor (similar to a wind turbine) or subsea ‘kites’. Some devices float, others sit on the seabed or in a seawall.

In wave energy technology, different designs cater for different sites and different wave strengths. Among common concepts are: large buoys that absorb the vertical movement of the waves; flaps anchored close to shore, which are pushed backwards and forward; and hulls that rotate with the movement of the sea.

OTEC/SWAC and salinity gradient plants are typically buildings located on the shore, that house a heat pump system including pipework, membrane, pumps, tanks etc.

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How much electricity does an ocean energy device produce?

Today, the largest tidal turbines stand around 2MW and the most powerful wave energy converters around 1MW. This is comparable to a medium-sized onshore wind turbine. They respectively produce enough electricity to cover the consumption of 1900 and 700 average EU households for a year. OTEC and SWAC plants can reach tens of MW, covering proportionally more households.

Ocean energy devices and farms are generally directly connected to the electricity grid, like any other power plant. Smaller machines can directly power fish farms, offshore sensing stations, desalination plants, oil & gas platforms.

In 2019, the pilot farms installed in the EU produce about 13 GWh/year, enough to power 3500 EU households. By 2050 we estimate that ocean energy could produce about 10% of the EU’s current electricity consumption.

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Why do we need ocean energy if we have wind and solar?

Bloomberg New energy Finance estimates that wind and solar power will be the backbone of a future electricity grid powered by 90% renewables. In such a system, generation will be inherently variable and other renewables will be needed when the wind drops, or the sun doesn’t shine. Ocean energy is a perfect partner to these mature renewables, with each technology bringing its own benefit to the system:

  • All ocean energy technologies can produce at different times from wind and solar, reducing overall variability.
  • The highly predictable nature of tidal energy makes it easier to manage an energy system.
  • Wave energy is a great complement to offshore wind energy, as swells continue to provide power long after the wind has subsided.
  • Ocean thermal energy conversion (OTEC) and salinity gradient technologies can deliver non-stop power and can be ramped up or down according to demand and/or production from other sources.

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How predictable is ocean energy?

Tides, and therefore tidal energy, are generated by the pull of the moon and are fully predictable – even hundreds of years into the future. Even before construction of a project begins, it is possible to predict the volume of water and the level of power the equipment will likely generate. Coupled with a classic lithium battery or alternative storage solutions, this technology can provide electricity 24/7.

Wave conditions can be accurately predicted days in advance, both for localised wind-generated waves’ and for ocean swells that travel for hundreds or thousands of kilometres.

In warm seas areas, OTEC and SWAC can generate energy on demand, at any time.

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Where are ocean energy projects located?

The vast majority of ocean energy development is currently taking place in Europe. Europe has one of the largest ocean energy resource worldwide: 363 TWh/year of tidal and 2628 TWh/year wave energy (theoretical potential). This accounts for 90% of Europe’s current energy demand.1

71 TWh/year of tidal and 325 TWh/year of wave energy can be harvested with the current level of technology development. This represent 11.8% of the European electricity demand2 – more than hydropower produced in Europe in 2018.3

Numerous projects are located along the Atlantic and North Sea coasts of the UK, Ireland, France, Portugal, Spain, Belgium and the Netherlands. A number of wave energy projects are also underway along the Italian and Greek shores, as well as Denmark, Sweden, Finland and Norway.

While project location depends on the available resource, the impact of developing ocean energy can be felt across Europe, with developers and supply chain (e.g. vessel, cable, component companies) present in many countries, including some without an ocean energy resource like Germany and Austria.

The rest of the world is starting to catch up with Europe. Several tidal energy projects are planned in Nova Scotia, Canada, and the US is supporting the development of wave energy, with dedicated test centres in Oregon and Hawaii. A few tidal stream turbines have also recently been designed and tested in China and Japan will be host to a European turbine in 2020.


1 Eurostat, 2018, Electricity and heat statistics

2 Ibid

3 Sandbag, 2018, The European Power Sector in 2018

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Is ocean energy a good fit for islands?

Ocean energy is a set of flexible technologies, which can be developed at larger scales for mainstream ‘utility’ power, as well as at smaller scales for island systems. Islands are a natural fit for these technologies, as they are literally surrounded by the energy source.

Being indigenous and cheaper than diesel, ocean energy enables islands to be self-sufficient and emissions-free in terms of energy generation. The highly predictable nature of ocean energy also makes it significantly easier to manage potentially isolated island electricity grids.

In addition to powering islands, ocean energy projects are usually built at a larger scale, and the power generated is fed into the national electricity grid. The industry estimates that 100GW of wave and tidal energy capacity can be deployed in Europe by 2050, which would meet around 10% of its electricity consumption.

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Does ocean energy have environmental impacts?

Environmental monitoring is essential in the development of new energy technologies and required for each ocean energy project by the EU Directive on Environmental Impact Assessments.

All studies published in the last decade on potential environmental impacts of ocean energy have concluded that the technologies have no significant impact. Nevertheless, the industry continues to monitor potential impacts, especially for sensitive species such as marine mammals. Recent surveys show that:

  • As the blades of tidal turbines turn very slowly – 6 rotations per minute – the risk of collision with fish and marine mammals is low.
  • Installing ocean energy devices doesn’t disturb wildlife, as it does not require pile-driving into the seabed.
  • Noise from operating ocean energy devices is unlikely to affect marine animals as it is far below commonly accepted ship traffic noise.

Ocean energy installations can also have positive impacts on the environment. Beyond the production of decarbonised electricity, tidal and wave device foundations can act as artificial reefs, creating feeding areas for fish and mammals.

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ocean energy scotland - Orkney Vessel Trials Project (Credit Aquatera)

What are the economic benefits of ocean energy?

Ocean energy has numerous benefits beyond electricity production, ranging from local jobs and revitalisation of coastal economies to energy security or reduction in electricity price fluctuations.

The industry estimates that 100GW of wave and tidal energy capacity can be deployed in Europe by 2050, which would meet around 10% of its current electricity consumption. This would create 400,000 jobs. The vast majority of this employment will directly benefit the European economy, be it through local jobs in coastal areas or further afield in the extensive supply chain.

As with wind turbines, ocean energy devices need to be assembled close to where they are installed and are deployed using local infrastructure, crew and vessels. This means a new lease of life for Europe’s coastal communities, strengthening their highly skilled workforce and compatible infrastructure from traditional shipbuilding, fishing and oil & gas industries.

The supply chain is truly European, with components, materials and specialist services coming from countries across the continent, with or without a coastline.

Furthermore, the EU imports over half the energy it consumes, spending between €266 and €400 billion a year on imports of fossil fuels. Not only does Europe’s dependence on expensive, polluting fuel weakens its decarbonisation goals, but also weakens its political influence, as imports often come from autocratic regimes and unstable regions.

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Who is supporting the development of ocean energy?

According to a recent European Commission study, in the EU and between 2007 and 2015, €2.6 billion has been invested in the ocean energy sector, with 75% coming from private corporate investments.

The European Commission has provided substantial support, with more than €200 million allocated through its research funding programmes. Another €1 billion has been spent or earmarked by Member States and regional governments via EU structural funds and local spending programmes. The rest comes from direct private sector investments.

More recently, individual citizens have also contributed to projects through crowdfunding campaigns.

Scaling up the sector depends not only on up-front capital investments, but also on continuing revenue support for projects in the form of long-term electricity purchase agreements with agreed pricing, and guaranteed grid access. This should be a high priority for national governments to drive the development of the industry.

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