Power that comes from capturing and converting the energy available in the
motion of ocean waves. There are several methods of getting energy from
waves, but one of the most effective works like a swimming pool wave machine
in reverse. At a swimming pool, air is blown in and out of a chamber beside
the pool, which makes the water outside bob up and down, causing waves.
At a wave power station, the waves arriving cause the water in the chamber
to rise and fall, which means that air is forced in and out of the hole
in the top of the chamber. A turbine
placed in this hole is will turned by the air rushing in and out, and, by
connecting it to a generator, can be
used to produce electricity.
Energy derived from waves is renewable and clean. However, it is variable
and needs a suitable site, where waves are consistently strong. A wave power
facility must also be resilient enough to withstand rough weather.
Some wave power schemes
Limpet (Land Installed Marine Powered Energy Transformer) is a shoreline
energy converter sited on the island of Islay, off Scotland's west coast.
The current Limpet device, called Limpet 500, was installed in 2000 and
produces power for the UK national grid. It uses the principle of an oscillating
water column described above, and has been optimized for annual average
wave intensities of between 15 and 25 kW/m. The water column feeds a pair
of counter-rotating turbines, each of which drives a 250kW generator, giving
a nameplate rating of 500kW. The company behind Limpet, Wavegen, is developing
the technology used in Limpet to build a series of commercial power generators.
| Limpet wave power generator
| Pelamis wave power generator
Another Scottish company, Ocean Power Delivery, is developing a method of
offshore wave energy collection that uses a floating tube called the Pelamis.
This long, hinged tube (about the size of 5 railway carriages) bobs up and
down in the waves. As the hinges bend they pump hydraulic fluid which drives
generators. The Pelamis has an output similar to a modern wind turbine.
Based in part on text developed by Andy Darvill,
Broadoak Community School, UK