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Rondal’s Hydro Generators enables regenerative sailing for all large sailing yachts, independent from the propulsion system. These systems are designed for efficiency, to minimize drag while maximize electrical output. With the Rondal Hydro Generator system, the diesel generators can be turned off, while the sailing speed is sustained, to enjoy the experience of sustainable sailing under sail.
REGENERATIVE
SAILING
Regenerative sailing has been feasible for several hybrid and diesel-electric superyachts that use the propulsion propeller for both propulsion and regeneration. Rondal has developed the Hydro Generator series to provide a standalone solution for refits that do not have such a dual-purpose propeller. The Hydro Generator is an electric pod with a specially designed fixed-pitch propeller. Rondal developed the Hydro Generator in collaboration with Norwegian pod specialist SeaDrive and the research institute MARIN. The propeller was designed using optimization software, and the Hydro Generator was validated in the MARIN towing tanks.
Since the efficiency of the dedicated regeneration system is much higher compared to dual-purpose systems, it offers a simpler solution without requiring modifications to the propulsion system. The Hydro Generator features a fixed-pitch propeller with a low-drag ‘freewheeling’ mode when not in use. For a typical yacht, the additional drag from a Hydro Generator in freewheeling mode is not noticeable.
THREE
HYDRO GENERATORS
The Hydro Generator family has three variants: the Hydro Generator 5000, the Hydro Generator 9000 and the Hydro Generator 15000.
Hydro generator 5000
The Hydro Generator 5000 is designed for sailing yachts between 16 and 30 meters in length, with sailing speeds ranging from 6 to 13,5 knots. The propeller is optimized for maximum output at low speeds (6 to 8 knots), while freewheeling drag is kept to a minimum.
Hydro generator 9000
The Hydro Generator 9000 is designed for sailing yachts between 20 and 50 meters in length, operating at typical sailing speeds of 9 to 18 knots. The e-motor is engineered with a compact diameter to reduce drag, while the propeller is optimized for performance at 11 to 13 knots, achieving an 72% efficiency.Hydro Generator 15000
The Hydro Generator 15000 is designed for sailing superyachts over 40 meters in length, with cruising speeds under sail between 12 and 18 knots. The propeller achieves high efficiency across a broad speed range and shares the same standardized shaft and bracket system as the other models in the Hydro Generator family. DESIGNED
FOR EFFICIENCY
Operational data from yachts that are using regeneration shows that the feature is used the most when the drag is low. Therefore, the Rondal Hydrogenerator is designed for the highest efficiency. This includes the use of the right e-motor and gearbox, but the highest gain is made with the propeller design at MARIN. The dedicated propeller design by MARIN has led to an unparalleled efficiency of 0.73 to 0.76 (depending on the model). The regeneration efficiency is depending on the propeller power, the speed and the drag of the total unit.
LOW DRAG DURING REGENERATION
The data models of MARIN are validated by measurements in one of the towing tanks of MARIN. These measurements showed that the propeller performed according to the calculations. The tank tests even showed a lower drag than calculated.
LOW DRAG DURING FREEWHEELING
When not in use, the propeller is freewheeling to reduce the drag. Since there is no propulsion requirement, the shape and pitch of the propeller is very different compared to a normal propeller. This leads to a much lower drag during freewheeling and therefore it is not necessary to create additional complexity by folding of feathering the propeller. The freewheeling drag at 10 knots is between 0.22 and 0.25 kN, for which the speed loss is not noticeable on a typical yacht.
