Endurance
There are advantages and disadvantages in having electric propulsion. The range is the factor that concerned me the most, however after my sea trials I was positively surprised to see the amount of power I required to drive the boat.
The electric motor uses around ⅓ of the energy used by the diesel engine to do the same work. Volvo Penta use diesel energy density of 11,36 kWh per litre as their benchmark, other sources specifies between 9,96-10,7 kWh per litre.At cruise of 5,3 kts fuel consumption would average 1,1 litre/hr. Power consumption of between 2,6-3,6 kWh on the electric motor gave the same speed. The graph data on this page is derived from my sea trials.
The limited range on our current battery technology is perhaps not so much a concern as an inconvenience. I enjoy the sailing experience and have always minimised the motoring. I motor when need be but try to sail in and out of the harbour if weather and traffic allows in a safe manner and when dropping and weighing anchor. It's not only fun but an excellent set of skills to have should whatever motor you have break down.
Getting more power
Installing a 260 Watt solar panel eliminated having to run the diesel engine purely as a generator for charging the batteries. I always consider this practice very wasteful.
Solar panels are truly great investments I can highly recommend as it is relatively cheap and perhaps the most reliable equipment out there.
Wind generator requires more maintenance as they are more complex, but can balance the power production on cloudy days.
The last few years I've had to sail 45 NM to get the boat hauled out for the season. Normally I could do this in a straight run with the diesel. On the batteries I normally did it on two charges but due to the 2,5-3 kts speed I used for endurance and facing a near gale this last autumn I had to add an extra charge break. I do however have a petrol generator for backup should I need extra power. I plan a long sail back through the Kiel Canal in the near future where they prohibit wind driven propulsion. more...