Innovation
The Blades
Power Take Off
The Wake
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 optimize 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 efficiency can be observed in the models. The prototype will be made from fiberglass composites that have no corrosion nor fatigue and thus a long lifetime without much maintenance. It's also light weight so that the machine is sensitive to moderate forces as well.
After a work stroke the unit has to return to its starting position for the next work stroke. Usually this cost a lot of energy, making a normal buoy with the same (small) counter weight rather inefficient. But the blades of the Slow Mill, designed to be driven back by the returning wave, restore the unit to its starting position, greatly enhancing efficiency. Wave energy is unevenly distributed with high peaks and large gaps, thus the Slow Mill is equipped with unique energy storage features to provide high quality predictable power on demand. Main cost drivers of energy storage like location, cooling, electric systems, connections and maintenance are already budgeted for wave energy, making storage extremely economical.
Further development resulted in hyper resonance whereby the Slow Mill follows the orbital path of the wave at a more or less constant fraction of its phase, increasing efficiency by more than 50%. Little energy is left in its wake, even when a 1:5 scale model as shown is put in actual waves. This would be a perfect place to have other activities like a wind farm, anchorage, fishing, dredging, aqua farming, etc. Most floating WECs don't dampen waves significantly or stop doing so when they get bigger but the Slow Mill still takes about one third of the energy out of the larger North Sea waves. If a consecutive line of Slow Mills protects a wind farm, freak waves that hammer the monopoles of wind turbines could be mitigated by damping their component parts.