|Drawing showing the position of the retractable drive units. Click to enlarge.|
African Cats, the Dutch company that last year introduced a hybrid version of one of its lightweight, 43-foot catamarans (earlier post), is developing a full-electric retractable propulsion and generation system for sailing yachts.
African Cats plans to use a 40 kW lithium-ion battery pack designed to provide continuous operation for 12 hours at a speed of 6 knots without any recharging. The company is looking at using li-ion cells from A123Systems or Nanoexa.
Solar panels (4 x 210 Watt) and a wind generator (300 Watt) provide renewable power generation to recharge the battery. When the yacht is under sail, the electric motors regenerate power for the battery pack as well.
Regeneration starts at 5 knots. At 8 knots, 3 kW per motor is regenerated out of the 10 kW drive unit. African Cats is developing a range of 8 different electric motors from 5 kW up to 50 kW.
The retractable drives reduce resistance while sailing. When extended, the props hang three feet from the hull, and not in the wake of the keel, enabling a better water flow.
African Cats is currently testing the system with 10 years of simulated usage in its salt water testing facility in Durban South Africa. After 3,000 hours of total run time, the company will disassemble the units to check for wear. Concurrently, it is building the first FastCat 435 Green Motion (no hybrid) and at the end of this year will complete two Atlantic crossings for further testing.
The retractable Green Motion drive system will be made both for monohulls and catamarans.