Wondering how a wave energy converter turns moving water into power? It is a machine that captures wave motion and converts it to electricity, and EMEC groups the designs into eight main types, from floating attenuators to air-driven columns.
This guide is part of our wider coverage of ocean renewable energy, where waves sit alongside other marine sources.
| Item | Value |
|---|---|
| Main wave energy converter types identified by EMEC | 8 types |
| Theoretical global wave energy potential | 29,500 TWh per year |
| Latitude band where most wave energy is found | 30° to 60° |
| Water depth of those deep-water locations | More than 40 meters |
| Wave energy patents registered by 1980 | More than 1,000 patents |
| Year of the first known wave energy patent | 1799 |
These figures come from EMEC’s wave devices page and a February 2024 review of floating oscillating water column converters. Figures can change, so check the sources before you rely on them.
How does a wave energy converter work?
A wave energy converter, or WEC, is a machine that captures the motion of ocean waves and converts it into electricity. EMEC, the European Marine Energy Centre, says WECs have been developed to extract energy from the shoreline out to the deeper waters offshore. It describes waves as having the potential to be a completely sustainable source of energy (EMEC).
Every design faces the same task. Waves move water up, down and sideways, and the machine needs a power take-off, the system that turns that motion into something a generator can use. The designs differ mostly in what moves and in how the power take-off works.
The resource is large on paper. A February 2024 review cites a theoretical potential of 29,500 TWh per year, found mainly between 30° and 60° latitude and in deep water locations of more than 40 meters. Theoretical potential is not what can be built and delivered, so read it as the size of the resource rather than a forecast.
The eight main types of wave energy converter
EMEC has identified eight main types of WEC and adds an “other” group for designs that do not fit. The descriptions below follow EMEC’s wave devices page in plain terms.
- Attenuator: a floating device that operates parallel to the wave direction and effectively rides the waves, capturing energy from the relative motion of its arms as the wave passes.
- Point absorber: a floating structure that absorbs energy from all directions through its movements at or near the surface, converting the motion of its buoyant top relative to its base into electrical power.
- Oscillating wave surge converter: a device that extracts energy from wave surges and the movement of water particles within them, using an arm that oscillates like a pendulum on a pivoted joint.
- Oscillating water column: a partially submerged, hollow structure open to the sea below the water line. Waves make the water column rise and fall, which compresses and decompresses the air above it and drives a turbine.
- Overtopping or terminator device: a device that captures water as waves break into a storage reservoir, then returns it to the sea through a conventional low-head turbine.
- Submerged pressure differential: a device typically located near shore and attached to the seabed, where the rising and falling sea level above it creates a pressure differential that pumps fluid through a system to generate electricity.
- Bulge wave: a water-filled rubber tube moored to the seabed and heading into the waves. A passing wave creates a bulge that grows as it travels along the tube and drives a standard low-head turbine at the bow.
- Rotating mass: a device whose heaving and swaying motion drives either an eccentric weight or a gyroscope, attached to an electric generator inside the device.
The other group covers designs with a unique and very different approach, or ones whose characteristics could not be determined. EMEC gives the Wave Rotor, a turbine turned directly by the waves, as an example, and notes that flexible structures that change shape or volume have been suggested as part of the power take-off (EMEC).
How the wave energy converter types differ in practice
Where the machine sits
The first split is location. Some designs float on the surface, others are tied to the seabed, and others are hollow structures or reservoirs that the waves flow into.
- Floating on the surface: attenuators and point absorbers.
- Attached or moored to the seabed: submerged pressure differential devices and bulge wave tubes.
- Partly submerged structures and reservoirs: oscillating water columns and overtopping devices.
- Pivoting arms: oscillating wave surge converters.
- Internal moving mass: rotating mass devices.
Location also hints at where a device is meant to work. Submerged pressure differential devices are typically located near shore, while EMEC says WECs as a whole have been developed for waters from the shoreline out to the deeper waters offshore.
How the power is made
The power take-off is where the designs diverge most. EMEC notes that even for a single type, the point absorber, the take-off may take a number of forms depending on the configuration of displacers and reactors.
- Air through a turbine: oscillating water columns, whose turbine usually can rotate regardless of the direction of the airflow.
- Water through a low-head turbine: overtopping and bulge wave devices.
- Pumped fluid: submerged pressure differential devices.
- Generator inside the hull: rotating mass devices.
This variety is why comparing designs by name alone can mislead. A more useful question is what moves, and what that movement drives.
Why has no single wave design won?
Wind power settled on a familiar turbine shape, but wave power has not. A February 2024 review says wave energy technologies have not seen a convergence towards one type of design, as has happened in other renewable technologies such as wind energy.
The patent record shows how crowded the field is. The same review says the first known patent to extract energy from ocean waves dates to 1799, and it cites more than 1,000 patents registered by 1980, with the number increasing remarkably since then (review).
Progress is uneven. The review says considerable progress has been made globally over the last 30 years, with some technologies at or near commercialization while others require further R&D.
What makes oscillating water columns stand out?
The review describes oscillating water column converters as among the first energy converters to be developed and deployed into the sea. It credits their relative simplicity of operation and relatively small number of moving parts (review).
The structure is hollow and open to the sea below the water line, so the moving working fluid is the trapped air. That air flows to and from the atmosphere through a turbine, and EMEC says that turbine usually can rotate regardless of the direction of the airflow (EMEC).
Research on floating versions focuses on the converter’s geometry and type and on its mooring system design, aiming to amplify the absorbed wave power. The review frames the wider design challenge as ensuring structural integrity over a life cycle in harsh environments while staying financially competitive (review).
Comparing designs and where to read next
When you read about any new device, a short checklist keeps the claims in context.
- Where does it sit: floating, attached to the seabed, or in a hollow structure?
- What moves: an arm, a buoy, a column of water, a tube or an internal mass?
- What is the power take-off: a turbine, a pumped fluid or a generator?
- How will it survive harsh seas while staying financially competitive?
If you want to compare wave machines with tide-driven ones, the guide to tidal stream vs tidal barrage covers that split. If you are weighing how marine power might serve other needs, the piece on renewable energy for desalination is a natural next step.
Frequently asked questions
What is a wave energy converter?
Show answer
A wave energy converter is a machine that captures energy from ocean waves and converts it into electricity. EMEC calls these machines WECs and says they have been developed for waters from the shoreline out to the deeper waters offshore.
How many types of wave energy converter are there?
Show answer
EMEC identifies eight main types, plus an “other” group for unusual designs, according to its wave devices page. They are attenuators, point absorbers, oscillating wave surge converters, oscillating water columns, overtopping devices, submerged pressure differential devices, bulge wave devices and rotating mass devices.
Which wave energy converter types sit on the seabed?
Show answer
Submerged pressure differential devices are typically located near shore and attached to the seabed, and a bulge wave tube is moored to the seabed. Floating types such as attenuators and point absorbers sit at or near the surface instead.
Is there one best wave energy converter design?
Show answer
No single design has emerged. A February 2024 review says wave energy technologies have not converged on one type of design, unlike wind energy, and it notes that some technologies are at or near commercialization while others need more research.
