Wave Energy in the North Sea


Innovation

The Slow Mill Effect

An open flow of water, be it a current or wave, will choose the path of lowest resistance. This makes it hard to move along in the same direction as the flow and extract a good deal of energy out of it. The Slow Mill has a unique system of blades that changes the direction of flow temporarily to optimise the angle of attack, enabling more energy to be extracted from the current. As shown in the lab tests at TUD, high resistance to open flow and high effficiency can be observed in the models. "The Slow Mill Effect" is deffined as; enhancing energy transfer from an open flow to a barrier that moves in the same direction by temporarily deflecting the flow to create an optimum angle of attack. 


Hyper Resonance

The Slow Mill "sees" a wave and moves toward it in order to capture the full movement. Then it goes up, following the wave path, moves along the wave direction and comes down when the wave passes. The model is tuned to make the same motion as the wave but move a bit slower and take the inside bend, aiming to maintain a minimum phase gap to provide an optimum energy extraction situation. We call this "hyper resonance", deffined as; the smallest possible phase gap between a wave and a floating object extracting energy from it. 

"The effect of the wave period on the Slow Mill at regular and irregular waves is small"