Renewable Energy at Sea: Harnessing Wave Energy

Generating Renewable Energy from Ocean Waves

Wave power refers to the energy of ocean surface waves and the capture of that energy to do useful work – including electricity generation, desalination, and the pumping of water (into reservoirs). Wave power is a form of renewable energy. Though often co-mingled, wave power is distinct from the diurnal flux of tidal power and the steady gyre of ocean currents. Wave power generation is not a widely employed technology, and no commercial wave farm has yet been established (although development for the first commercial wind farm in the Orkneys are well under way).

Below you will find a selection of technologies used to convert wave energy into electricity.

Pelamis Wave Energy Converter: The Pelamis is a semi-submerged, articulated structure composed of cylindrical sections linked by hinged joints. The wave-induced motion of these joints is resisted by hydraulic rams, which pump high-pressure oil through hydraulic motors via smoothing accumulators. The hydraulic motors drive electrical generators to produce electricity. Power from all the joints is fed down a single umbilical cable to a junction on the sea bed. Several devices can be connected together and linked to shore through a single seabed cable.

Finavera’s AquabuOY: The AquaBuOY is a floating buoy structure that converts the kinetic energy of the vertical motion of oncoming waves into clean electricity. It utilizes a cylindrical buoy as the displacer and the reactor is a large water mass enclosed by a long vertical tube underneath the buoy.

Aegir Dynamo: The Aegir Dynamo functions in a unique fashion by generating electrical current from the motion of the prime mover in one phase via a direct mechanical conversion and the use of a bespoke buoyancy vessel.

Wave Dragon: Wave Dragon is a floating, slack-moored energy converter of the overtopping type that can be deployed in a single unit or in arrays of Wave Dragon units in groups resulting in a power plant with a capacity comparable to traditional fossil based power plants.

OWC Pico Power Plant: Wave enters in the “hydro-pneumatic chamber” (resembling a cave with entry below the waterline). Up-and down- movement of water column inside chamber makes air flow to and from the atmosphere, driving an air turbine. The turbine is symmetric and is driven indifferently in which direction the air flows.

AWS Wave Energy Converter: The AWS (Archimedes Wave Swing) wave energy converter is a cylinder shaped buoy, moored to the seabed. Passing waves move an air-filled upper casing against a lower fixed cylinder, with up and down movement converted into electricity.
As a wave crest approaches, the water pressure on the top of the cylinder increases and the upper part or ‘floater’ compresses the gas within the cylinder to balance the pressures. The reverse happens as the wave trough passes and the cylinder expands. The relative movement between the floater and the lower part or silo is converted to electricity by means of a hydraulic system and motor-generator set.

OpenHydro: The company’s vision is to deploy farms of open-centre tidal turbines under the world’s oceans – silently and invisibly generating electricity at no cost to the environment. OpenHydro’s technology enables the ocean’s immense energy to be harnessed for the benefit of all. The Open-Centre Turbine, with just one moving part and no seals, is a self-contained rotor with a solid state permanent magnet generator encapsulated within the outer rim, minimising maintenance requirements.

SPERBOY: Developed and patented by Embley Energy, is a floating wave energy converter based on the ‘oscillating water column’ principle. Air displaced by the oscillating water column is passed through turbine-generators. Designed to be deployed in large arrays 8 to 12 miles off shore SPERBOYTM provides large-scale energy generation at a competitive cost.