Wave power
What is wave power?
Waves are a free, endless source of energy, created by winds blowing across the surface of the ocean. Wave energy technology harnesses this energy to produce electricity either on the shoreline, where the waves break, or in deeper water offshore.
Wave power is largely untapped and is the most concentrated form of renewable energy. The total wave resource around the UK is equivalent to 2-3 times our current electricity demand.
How does the technology work?
The are several types of technology for generating electricity from waves.
Oscillating water column
Oscillating water columns are partially submerged shoreline devices for capturing the energy from breaking waves.
Below the water line there is an opening to the sea, enclosing a column of water in a chamber. When the water rises, it compresses air inside the chamber and when it falls the air expands. The compression and decompression causes air to flow through a turbine, which can turn in the same direction regardless of the way the air is flowing. This generates electricity.
Oscillating water column technology is in use in the Isle of Islay, Scotland, where a system called LIMPET has been installed since 2000. This system has a maximum output of 500 kW.
It is ideal for locations where there is strong wave energy, such as breakwaters, coastal defences, land reclamation schemes and harbour walls, and is suitable for producing power for the national grid.
In Islay, the electricity generated is being used to power an electric bus, the first bus in the world to use wave power as its fuel.
Buoyant moored device
A buoyant moored device floats on or just below the surface and is moored to the sea floor. The device resists the motion of the wave to generate power when part of the machine moves while another remains still.
The Salter's Edinburgh duck works by rotating around a long linkage spanned across wave crests. It generates electricity by bobbing up and down with the waves
Hinged contour device
A hinged contour device works with the motion of the waves, creating power from the motion of the joints. The structure is semi submerged and loosely moored to the seabed to hold it in place.
The Pelamis system uses cylindrical sections linked by hinged joints. The motion at the joints produced by the wave is resisted by hydraulic rams, which pumps high-pressure oil through hydraulic motors. The motors drive generators to produce electricity.
Overtopping device
An overtopping device uses the same principles as traditional hydropower plants in an offshore platform. The waves are channelled by reflectors, overtop the ramp and fill a reservoir situated at a higher level than the surrounding sea. This acts as the 'head' for power production through turbines.
Wave reflectors concentrate the wave energy and water overtopping the ramp. Wave Dragon have a test site for this technology.
Suitable for the UK?
The UK has a large potential to develop wave power. Large waves are created by the prevailing winds blowing across the Atlantic, making the west coast of Europe ideal for this kind of technology.
Detailed regional studies have suggested that wave energy in the UK could produce as much as 700TWh per year. Estimates of the amount of wave power that can be utilisted vary, but the overall consensus is that wave energy has massive potential for the UK.
The benefits
There are many benefits and few potential problems with wave energy technologies.
The devices could attract and promote a biodiverse marine environment, as offshore wind turbines have been shown to do.
Any noise from wave power would be mostly associated with the turbine used in shoreline oscillating water columns and offshore applications are virtually silent in operation.
By incorporating radar and visual warning devices into the technology the risks to shipping are minimal. One of the main issues would be transmitting the electricity generated offshore to the grid.
The market for wave power technology is estimated to be worth £500 billion. The UK can lead Europe and world in wave power if we give appropriate support to the industry.
Other green energy sources
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Wavegen LIMPET wave power on the Isle of Islay
Islay's 'Wave Bus' - picture from Greenpeace
How Islay wave power station works. Picture from BBC
Wave power potential in the UK is enormous
European Wave Resource Chart: The chart shows annual average wave power in kilowatts per metre of crest width for various European sites. Source: Ocean Power Delivery Ltd
Artists impression of a Pelamis hinged contour device wave farm Source: Ocean Power Delivery Ltd
A Pelamis device.
Salter's Edinburgh Duck. Source: Fujita Research
Wave Dragon overtopping device. Source: Wave Dragon
Wave Dragon prototype in use
