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How does wave energy work?

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Quick answer

Wave energy devices turn the motion of ocean waves into electricity. Some trap air in a chamber so rising and falling water pushes it through a turbine; others are floating buoys or hinged rafts whose movement drives pumps or generators. A seabed cable then brings the power ashore. Most designs are still at trial stage.

Wave energy converters capture the up-and-down and back-and-forth motion of ocean waves and turn it into electricity using air turbines, hydraulic systems or direct-drive generators. The waves themselves carry energy that wind has transferred to the sea surface over long distances.

Step by step

  1. Wind blowing across the ocean surface transfers energy to the water and builds waves.
  2. Waves reach a converter such as a buoy, hinged float or shoreline air chamber.
  3. The wave motion lifts, tilts or flexes part of the device, or forces trapped air through a turbine.
  4. That movement drives a hydraulic motor, air turbine or linear generator that produces electricity.
  5. Power electronics steady the fluctuating output, and a cable carries it to the shore grid.

Key things to understand

  1. Wind blowing over open water transfers energy to the surface, building waves that can travel thousands of kilometres with little loss.
  2. An oscillating water column traps air in a chamber above the sea, and rising waves push that air through a turbine.
  3. Point absorbers are floating buoys whose bobbing motion drives a hydraulic pump or linear generator anchored below.
  4. Attenuators are long hinged floats lying along the wave direction, and the flexing joints pump fluid through hydraulic motors.
  5. Power electronics smooth the irregular output, and a subsea cable carries the electricity to shore.

Labelled diagram

  1. Incoming wave

    Wind-driven waves reach the open mouth of a partly submerged concrete chamber.

  2. Air chamber

    Water rises inside and compresses the trapped air above its surface.

  3. Wells turbine

    Air rushing out and back in spins the turbine the same way.

  4. Generator

    The spinning turbine shaft drives a generator that sends power ashore.

How an oscillating water column captures wave energy

Real-world examples

  • An oscillating water column built at Vizhinjam in Kerala by IIT Madras was one of India's first wave power plants.
  • The Mutriku breakwater in northern Spain houses a row of air chambers with turbines that feed the local grid.
  • The LIMPET plant on Scotland's Isle of Islay ran a shoreline oscillating water column from 2000.
  • Snake-like Pelamis attenuators were tested off Portugal and Orkney, flexing at hinged joints to pump hydraulic fluid.

Common mistake

✗ Myth: Water in a wave travels across the ocean, so wave power is just harnessing moving water.

✓ Fact: Water in a wave mostly moves in small circles and stays roughly in place; it is the energy that travels. Wave devices capture that passing energy by responding to the up-and-down and orbital motion.

People also ask

How do wave energy converters work?
They respond to the rising, falling and rocking motion of waves. Buoys move up and down against an anchored base, hinged floats bend at their joints, and shoreline chambers use rising water to push air through a turbine. Each motion drives a generator, pump or turbine that produces electricity sent ashore by cable.
What are the disadvantages of wave energy?
Wave devices must withstand storms, saltwater corrosion and constant motion, which makes them expensive to build and maintain. Output varies with weather, and good sites are often far from where power is needed. Few designs have operated commercially for long, so costs remain higher than wind or solar.
Is wave energy renewable?
Yes. Waves are created by wind, and wind is driven by the Sun heating the Earth unevenly, so the supply is continually replenished. Wave energy produces no fuel emissions while operating, though building and installing the equipment does involve materials and energy use.
Where is wave energy strongest?
Wave energy is strongest on coasts facing long stretches of open ocean in the mid to high latitudes, where steady westerly winds build large swells. Western Scotland, Ireland, Portugal, southern Australia and the Pacific coast of the Americas are well-known examples.
Why is wave power still rare?
Devices must survive violent storms, corrosion and constant motion for years while still capturing energy from small everyday waves. Designing machines that do both cheaply has proved difficult, so most projects have remained pilots or small demonstrators.
What is a Wells turbine?
A Wells turbine has symmetrical blades that spin in the same direction whichever way air flows through it. This suits oscillating water columns, where air is pushed out as waves rise and sucked back in as they fall.
How is wave power different from tidal power?
Wave power uses surface waves raised by wind, so it depends on weather and storms far out at sea. Tidal power uses the twice-daily rise and fall of the sea caused by the Moon's gravity, which is far more predictable.

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