The waves around our shores carry enough energy to generate 120 Gigawatts of power – way more than the UK’s peak electricity need. Worldwide, waves have sufficient energy to meet mankind’s current global energy needs at least 100 times over.
Tempting as this vast power-reserve is, tapping it - economically and reliably - has proven difficult.
Research into generating power from waves has been ongoing, at various levels, since the 1970’s when the UK, Norway and Japan conducted extensive tests. In retrospect, it seems early plans were too ambitious and the failure of these programmes to deliver economically viable power set the industry back.
As is the case with other renewable energy sources, interest has increased greatly in recent years due to the imperatives of climate change, energy security and soaring costs of traditional, fossil fuels. The challenges facing the industry remain considerable: the marine environment, especially off-shore, is extremely hostile to machinery; the cost of constructing and maintaining equipment is high; and there are still questions about the longevity of generators, prompted by the loss of a number of prototypes to storms over the last twenty years.
However, today’s wave power leaders have learned from previous mistakes and are now focusing on proving the technology with modestly scaled projects (eg: 2MW). Twenty years of UK off-shore oil and gas production has also produced an engineering and infrastructure legacy to draw on.
How Wave Power Works
Although the first wave power patent was filed in Paris in 1799, it remains a comparatively young industry. There is much experimentation and as yet, no consensus on the best way to turn the kinetic energy of waves into electricity.
Four common forms of generator are free-floating buoys, rafts of surface-following floats (or actuators), float-driven pistons and coastal systems where waves are channelled into the machine. These may be located on shore, near shore or off-shore in deep water where waves are strongest and ocean swells regular.
They make electricity in a number of ways: by having the wave push a column of air past a turbine or drive a hydraulic piston, or by moving electrical coils through a magnetic field – a linear generator. The power produced has to be transferred to homes or the grid via cable.
The Archimedes Float Swing, proposed by UK company AWS Ocean Power, provides yet another variation on the theme: with buoys anchored to the ocean floor but the entire structure remains six metres below the sea surface – minimising the risk from storms. A full-scale prototype is due to be tested at the European Marine Energy Centre in Orkney in 2009.