Energy

The Wave Dragon sets sail

Along with bracing winds, marine currents and strong tides, the sea offers another source of energy, as researchers experiment with different ways of generating electricity from the rise and fall of the waves. We take a closer look at Wave Dragon, a device which produces electricity from the swell.

Similar to a  “floating atoll”, Wave Dragon stores  up water in a central, slightly raised tank, thanks to its two long  arms. The water then activates turbines as the tank is emptied. ©Earth-vision.biz Similar to a “floating atoll”, Wave Dragon stores up water in a central, slightly raised tank, thanks to its two long arms. The water then activates turbines as the tank is emptied. ©Earth-vision.biz

In 1986 Danish engineer Erik Friis-Madsen watched the waves breaking onto the beaches of a South Pacific atoll. The strongest waves cross the strips of beach and accumulate in the lagoon at the centre of the atoll. Once the lagoon is over-full, the waters sluice back out into the sea through passages in the atoll. Madsen was convinced that it was possible to reproduce this natural phenomenon to generate energy. He started making his first sketches of what, a decade later, was to become the Wave Dragon: a circular structure similar to a “floating atoll” with a turbine in the centre through which the excess water can run off.

From dream to prototype

But it was only in 1997 that the project really got off the ground. Erik Friis-Madsen put together a team to work on this invention, whilst Hans-Christian Sorensen took over the management of the company Wave Dragon (DK), which he is still coordinating today. With scientific and logistic support from business and universities, the two founding fathers perfected their knowledge of hydraulics and electricity. Several models were laboratory tested. “The basic idea,” Erik Friis-Madsen explains, “is to use the well-known principles of traditional hydroelectric installations, but in an offshore version. It’s really quite simple. The Wave Dragon consists of two long arms which concentrate the waves at the centre of the installation, floating slightly above sea level. The water builds up in a large tank, and then runs off via the centre, activating a series of electricity-generating turbines.”

In 2002 the European Union joined in the project, providing € 1.5 million for producing and installing a 1:4.5 scale model. Weighing 237 tonnes, it was launched into the sea in June 2003 off the Danish coast. For Hans- Christian Sorensen, “this was probably the most important movement in Wave Dragon’s development: when we began regularly supplying electricity to the Danish grid.” But this reduced-scale prototype generates no more than a modest 20kW.

A real off-shore generator

“But we now have better,” Mr Sorensen continues. “A further contribution from the European Union (€2.4 million) enabled us to conclude an agreement with the Welsh government to install a full-size production unit (7 MW) off the Welsh coast. We are hoping that this will be operational by August 2008. In the three years after that we could create another ten additional units, giving a total production of 77 MW.”  

Wave Dragon is obviously unable to compete with a traditional nuclear power station generating between 500 and 2000MW of electricity. Even so, the system offers several far from negligible advantages. First, it is possible to modulate the size of the production units – for example by building a ‘station’ of ten or twenty individual ‘dragons’ – and the number of turbines in each (up to 24). Second, Wave Dragon requires only minimal, low-cost maintenance. Its visual and environmental impact is also modest, which should endear it to investors, politicians and public opinion. All of these are good reasons to be optimistic about its viability.

Matthieu Lethé


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