Slow Mill device braces up for North Sea waves

Dutch wave energy company Slow Mill Sustainable Power has come closer than ever to the first real sea demonstration of its wave energy prototype, which is currently undergoing final assembly before taking on the challenge of producing clean and renewable energy off the shores of the Netherlands.

The device, Slow Mill – 40, will soon be deployed at a project site located four kilometres offshore the island of Texel, one of the Dutch Wadden Islands, as part of the government-backed pilot to test the Slow Mill wave energy technology ahead of full-scale demonstration.

This is the company’s first wave energy device that will be deployed in real sea to produce energy in real time, according to the Slow Mill co-founder Erwin Meijboom, who added that the scaled prototype will only be generating power for validation purposes.

The electricity generated from the device, rated at 40kW, will be fed to an energy storage system located on the company’s vessel – therefore proving one other potential application of this clean energy technology.

The demonstrator device is a heave and surge wave energy converter, scaled at 1:2.5 and designed for the moderate wave climate of the North Sea, is also equipped with many innovative features to economically harness the short and irregular waves.

It consists of a floater with blades variably connected to an anchor on the seabed. Waves push the floater up and the blades away from the anchor. This way, not only the up and down, but also the back and forth movement of the waves is exploited.

Even at scale, the device still stands 14 metres high, with the width of eight metres. It will be attached to the 5-metre-wide concrete anchor that weighs around 50 tons, which already spent more than two years on project location weathering through the robustness tests with flying colours.

The purpose of the upcoming trials is to advance the technology further to the technology readiness level (TRL) 6, meaning the device underwent demonstration and validation in a relevant North Sea environment.

During try-outs, Slow Mill will work to demonstrate the electricity production – showcasing its energy conversion and storage capabilities – while also tackling the harsh sea environment to display its robustness against corrosion, fouling and various wave forces.

The tests will also serve for advancing the installation procedures for the technology, and to assess its potential impact on biodiversity and environment.

The anchor alone has already shown benefits for the biodiversity of the area, according to the research by the Royal Netherlands Institute for Sea Research (NIOZ), which showed a 30-50% increase in biodiversity and 400 times more organisms on hard substrate around the anchor compared to the soft sand sea floor.

“We live in exiting times. As we experience the urgency of the climate crisis almost daily, people at the same time feel the need for clean, reliable energy. We are on the verge of delivering exactly that to the world”, Meijboom said.

This prototype model will not be feeding any electricity to the Dutch power grid during the trials expected to last through the second quarter of 2022.

However, the company’s full-scale device – to be built and installed next year – will feature a subsea cable connecting it to the land to provide power for 100 households on the island of Texel, Meijboom confirmed.