Screw-like tidal wave converter works as promised, says study

The validation was conducted with data from a quarter-sized rig installed in the UK.

Ameya Paleja

Spiralis says its energy converter is inspired by seashells but built to be resilient and durable.

Spiralis

A screw-like tidal energy converter design built by UK-based Spiralis Energy is now a step closer to real-world deployment after computational fluid dynamics (CFD) analysis for a test rig delivered results within a deviation of 1.5 percent. UK-based marine technology consultancy Cape Horn Engineering conducted the validation analysis.

With an increased demand for renewable energy, a wave of technological innovations has been in the tidal energy space. Available round the clock and with predictable intensity, tidal waves can deliver a continuous and reliable supply of electrical energy.

Interesting Engineering has covered multiple designs of tidal wave energy converters, but the screw-like design stands out by a mile. What makes it even more interesting is that it is made using plastic waste instead of mining more elements from the Earth.

Spiralis teamed up with Cape Horn Engineering over a year ago to better understand its technology and future capabilities.

Spiralis has installed a test rig at Poole Harbour in the UK. The screw-shaped energy converter is nearly 20 feet (six meters) long, a quarter of the size of the energy converter Spiralis plans to deploy in the future.

Using computational fluid dynamics, Cape Horn Engineering predicted a peak power production of 2.59 kilowatts (kW). Real-world measurements from the rig showed a peak power production of 2.50 kW at 21 rotations per minute (RPM). Considering rig friction, the two data points are within a 1.5 percent deviation, demonstrating high accuracy.

“With this validation step completed we can have even more confidence in our prediction that the full-size unit will break the 250 kW threshold,” said Rodrigo Azcueta, Managing Director at Cape Horn Engineering.

Spiralis will now move to the next phase of its testing, which will involve a full-scale tidal energy converter. The converter is 52 feet long (16 m) and has a diameter of 16 feet (five meters).

As Interesting Engineering previously reported, Spiralis plans to install two such converters in the English Channel to test performance in the colder winter months. However, Cape Horn Engineering’s CFD analysis will help the company identify structural loads and optimize the shape of the converter to deliver maximum performance.

Spiralis has ambitious aims to supply 11 percent of the UK’s annual energy demand with electricity sourced from the sea. “The UK has the best tidal knowledge in the world,” said Guy Levene, CEO of Spiralis Energy. “Our technology can deliver a renewable energy source that doesn’t harm sea life and sits within the circular economy framework.”

The screw-shaped converter needs to be submerged in the water, but electricity generation occurs above the water in drier conditions. The screw design is 3D printed but entirely modular. So, even if a part of the converter gets damaged, it can printed and fixed using facilities at the nearest location instead of relying on the company to supply spares.

A new wave of clean energy infrastructure is surely on its way.

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Ameya Paleja Ameya is a science writer based in Hyderabad, India. A Molecular Biologist at heart, he traded the micropipette to write about science during the pandemic and does not want to go back. He likes to write about genetics, microbes, technology, and public policy.

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