Four options for electric drive propulsion sailboat

Installing electric drive propulsion

Currently electric drive propulsion is a hot topic for both cars and boats because electric drive propulsion is a clean and sustainable solution for the future.  For BarcelonaSail the conversion to electric drive propulsion presents particularly challenging questions, such as, maintenance, costs, drag, autonomy and additional holes in boat hull.

Electric Drive Options

Below we summarize the four options to convert an inboard diesel engine with an electric drive propulsion system:

1. Shaft-drive:

   Install an electric motor in the location of the diesel engine, shaft-drive solution. This is a complex installation and requires a specialist. Using the existing shaft and propeller is a problem for BarcelonaSail. The shaft is often the root cause of multiple problems, most import water entering near the stuffing box, and vibration as a result of shaft alignment issues.

   • Water can enter the motor cabin and causing the electrical motor to operate in a moist environment affecting its lifetime.
   • Vibration causes damage to electric motors in several ways. First, it can accelerate bearing failure by causing indentations on the bearing raceways at the ball or roller spacings. Secondly, it can loosen windings and cause mechanical damage to the insulation by fracturing, flaking or eroding of the material. Third, the excessive movement it causes can result in lead wires becoming brittle. Fourth, it can cause brush sparking at commutators or current collector rings.

2. Sail-drive:

   Install a sail-drive system at the current propeller location. This option is often not possible because the space is simple not available. An electrical sail-drive system has an 80cm to 100 cm height. Secondly a sail-drive requires an opening in the hull of 30cm x 15cm. Obviously, a work that can only be done by specialists.  This option was indeed not possible for BarcelonaSail.

   

3. Pod-drive:

   A Pod-drive is an alternative to the sail-drive system. The electrical motor system is completely built under water. The entire system needs to be bolted onto the hull in a waterproof manner. There is no access to the engine from the inside the boat, rendering maintenance impossible without the expense of taking the boat completely out of the water.

4. Electric outboard:

   Install an electric outboard motor. This can be done by the owner without hiring a specialist and maintenance can be done with ease. The big drawback of outboard motors is that they do not work well at sea in rough conditions, this is a safety concern, and the outboard motor doesn’t appeal to boat owners having an “invisible” inboard engine.

Conclusion by BarcelonaSail

In conclusion we didn’t really like any of the four options presented to us. First of all is the fact that all inboard solutions cause more drag, because for regeneration requires a larger propeller. Minimizing the drag to the current situation is one of the criteria, see our earlier blog. Furthermore the installation is all inboard solutions is complex and requires making additional holes in the hull.

The Pod drive is BarcelonaSail’s favorite solution, no shaft, no vibration, no noise and a very small thru-hull. The disadvantage is that the whole unit (electrical motor included) is under the boat. In case something doesn’t work the boat needs to go out of the water.

The electric outboard is practical and easy in maintenance but not ideal at rough seas and not appealing.

As a result BarcelonaSail started to work on our own new electrical BLDC engine drive design. We expect it to be better and more affordable than the mentioned solutions in this blog.