Buoys ride North Sea’s waves to generate power


Flemish and international engineers are turning Ostend’s coastline into a testing ground for the next generation of renewable energy technologies

Rule the waves

It’s not always windy enough at the North Sea for the existing offshore wind turbines to provide a constant supply of energy. One solution would be to tap into the energy of the water, instead of the air.

According to its proponents, wave energy is a more reliable and stable source of power for the North Sea’s ubiquitous wind parks. Wave energy is also known as blue energy because the electricity is generated from the rivers and oceans.

The idea is simple: a buoy – or another floating object – is in constant motion, pushed up by the waves and pulled down by gravity. A cable connecting the buoy to an alternator converts the mechanical energy into electricity.

Over the past couple of years, engineers from both the private sector and academia have been working on prototypes of wave-to-energy convertors. Among the first was the energy buoy Wave Pioneer, developed by the FlanSea consortium, which unites Ghent University and five Flemish companies, including the dredging outfit Deme.

The first Wave Pioneer was tested in the harbour of Ostend four years ago to see how the technology fares in seawater. It didn’t do so well, prompting FlanSea engineers to begin works on another prototype.

Testing the waters

In the meantime, the Ostend company Laminaria has busied itself working on a similar technology. It is based on the principle that the buoy and the wave convertor should automatically detect the most efficient horizontal waves, because these carry the highest amount of energy.

In recent years, the company has conducted several prototype tests in the waters near Ostend, but, like FlanSea, it has struggled to overcome the same challenge – salty water would eventually damage the convertors.

A potential solution is to separate the buoy from the power generator. Jan Peckolt, a German engineer and former Olympic sailor, created a new type of convertor called Nemos Hydro that does just that.  Philippe De Backer, secretary of state for North Sea matters, recently announced that the prototype will be installed in Ostend later this year.

Our coastline is an ideal testing ground for this kind of energy production

- Philippe De Backer

The Nemos Hydro consists of a floating structure that’s anchored to the sea floor with three cables. Another cable connects the float to the top of a mast above the surface, where the alternator is located.

“This way we can protect the electrical components from the seawater,” explains Peckolt. The end goal is to connect the floats to existing wind turbines, so that no new structures have to be build.

According to Peckolt, “the generated power can flow through the same cables as the wind power”. A full-scale float can generate one megawatt of electricity. With several, adds Peckolt, you could generate as much power as a small conventional power plant.

“The advantage is that the sea has a much higher energy density in the waves than in the air,” he says Peckolt. “The energy from waves also correlates perfectly with wind energy, as waves always come a bit later than the wind, and continue coming even when the wind has died down.”

The Nemos Hydro is only a prototype, but it will be the first large-scale project to generate electricity from waves. “The waves in our part of the North Sea are of course smaller than the ones found in the oceans,” says De Backer. “But they also last longer, making our coastline an ideal testing ground for this kind of energy production.”

The secretary has also announced the development of a new marine spatial plan, which focuses on efficient use of space in the North Sea. Blue energy, including wave and tidal energy, is at its core.