Scott,
Hannu has presented the information in a very organized manner. His point is spot on. They are: First, it does not take a very large electric to get you to cruising speed with a boat with a long waterline and modest displacement. Second, battery prices are indeed coming down but we see the tilt of Lithium vs AGM about 2 to years away. Third, the auto industry is driving the costs decreased not the marine with the land based solar also helping out. Fourth, for the boat that is going to cruise the lithium is a good decision because of its ability to stay in a state of partial discharge for an extended period of time and its high number of times it is deep discharged. It is less cost effective than lead acid AGMs compared to day sailing and coastal cruising where the boat is mostly charged from convenient docks. Fifth, with a parallel hybrid arrangement recharge is easy with the diesel. Diesel shares extended passage making while electric is always used around the harbor and marina.
Points to consider. We have done a significant number of parallel hybrids. First, you need to have a diesel that is compatible with electric so that it will allow the sharing of the shaft operations and can be programed and engineered to do so. Transmissions issues, free spinning of the shaft when the engine is in neutral, engineering the hybrid to match the prop rotation associated with a larger diesel drive system. The larger the diesel the less likely you will find this compatibility. We find that boats less than 40ft this is a better solution because of this issues and that boats greater than 40ft then serial electric is normally the better solution.
The last point is not about propulsion but about recharging a battery bank with solar. This is the area that is so difficult for a monohull boat. It will take a lot of cells to move off the grid with solar electric only and there is such a little amount of space on the monohull. The monohull trawler does have advantages of solar covers on the canvas shade canopies. This is also addressed by staying in place longer to recharge the batteries. That solar and lithium is the future is not in dispute. The question is when is the future. I hope it is within the next few years. I am more encouraged every day that it is sooner rather than later but is likely about 5 years off. The technology seems to be driven by the larger industries of home and auto but will be there for us. The undisputed fact is that electric is by far more compatible to the sailing boat than diesel as it is clean, quiet, part of the sail plan, regenerative in larger boats, and cost effective.
Mike
Posted by: mike@electricyachtssocal.com
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