Theoretically, you will not see most of the differences in advance until you start using it. The movement of the boat is just the "surface of the iceberg", in fact the changes are deeper. I will write in this article about the differences in as much detail as possible.
The first thing a person thinks about when he hears "electric motor on a sailboat" is that the boat on it can only leave the pier and go back. This statement was true before the advent of lithium batteries. Now it’s quite realistic to install a sufficient capacity of batteries that are lightweight, comparable to the weight of a diesel engine. At the current level of development of lithium batteries, at the same weight as a diesel with a full tank of fuel, it is possible to install comparable electric motors with a power reserve of up to 100-120 km per charge with economical running. This is already more than just going in and out. However, even lithium does not provide such autonomy as an ICE running on fossil fuels, so my boat has a generator for long-distance trips.
A logical question: what is the benefits of use electric motor with a battery and generator compared to classic diesel propulsion? Here is the fun part.
Most boats rarely travel constantly long distances under the engine. More precisely, it’s quite rare. My practice has shown that a generator is not required at all while the boat does weekend trips. This means that you almost never listen to the noise of the internal combustion engine and do not waste fuel.
The batteries can be charged from a variety of sources: a wind generator, solar panels, energy regeneration during sailing, an outlet on the pier. In long passages - also an internal combustion engine generator.
Some people wrote to me so that I get used to hear the constant noise of the generator in the passages. In fact, it turned out differently: for each hour of operation of the generator I get energy for 4 hours of economical run under the electric motor. Therefore, the generator does not work constantly, but periodically, in my two distant passages first and two - the generator worked on average 2 hours a day.
Why is that? Why is it necessary to run diesel engine constantly during the boat run, but when the hybrid boat is running, the generator only work from time to time?
The fact is that the ICE generator is installed more powerful than the required power on the electric motor for economical running and there is also a capacious lithium battery onboard. These two factors make the hybrid attractive compared to a diesel boat.
And now it’s completely unobvious what comes to mind when there is already a hybrid engine. The voltage of the running battery is greater than 12V or 24V. Usually this is 36V or 48V - this allows you to install a cheaper DC generator than alternating current generators paired with a 220V charger. In addition, a DC generator without a separate charger is much simpler in design and has fewer electronic components, which produce a increased reliability and maintainability. A higher voltage reduces the heating of the wires, as current is lower at the same power - do not require excessively thick wires from the generator to the battery.
I must say a few words about maneuverability of a boat with an electric motor. The engine turns on instantly, does not require heating, switching reverse - also instantly. This is convenient when you need to quickly respond to an unexpected situation (tore off the anchor, avoid a collision with a late-sighted vessel, etc.). There is no concept of "minimum speed". For the exact mooring of the vessel it is very convenient when you can choose the speed smoothly from 1 RPM to full speed.
A large energy bank onboard allows you to do many things silently for which a diesel boat must have a main engine worked:
- Work with steering wheels and windlass in silence, do not waste time on the factory and warming the main engine.
- Use of 110V/220V devices in the cabin without the operation of the main engine, via the inverter. Microwaves, washing machines, quiet night electric heating, electric kettles, etc.
- The presence of a variety of sources of battery charge allows you not to save on household appliances.
For example, a situation from real life: we stay the night on a boat on a pier in the fall and here the 220V shore supply disappears and harbor master say that it will be fixed only tomorrow. It was cold - air temperature 5 degrees. A diesel boat would have to run the engine burning fuel and listening to the noise. I spent only 4 kWh of battery power to maintain a cabin temperature of 20 degrees for 10 hours at night. And in the morning, when shore power was restored, I charged back these 4 kWh for free from the outlet. If shore supply had not been repaired, I would have charge these power from the generator in two hours. At least the ICE noise would not have to be heard at night (to generate 4 kWh of energy, my generator requires 2 liters of gasoline).
For boats that make continuous long travels under the engine, diesel is still a good option, because it is simpler. In this case, it makes sense to sacrifice comfort provided by hybrid engine to more reliable at long distances diesel.
The fuel consumption on the generator of a hybrid boat will be comparable to the consumption of diesel fuel on diesel in case you need to go fast for a long time. On an economical move, the hybrid is more efficient because part of the energy can be achieved, for example, from solar panels. I conducted an experiment in August - the boat was running at 200 watts at a speed of 3 km/h - the same amount of energy I was getting at that moment from a solar panel with a rated power of 250 watts. If you add power at engine, the energy will be taken from the battery, but less by the amount of energy generated from the solar panel. At full speed, energy production from the solar panel is comparetely low.
The economical speed of the diesel boat is in the range 40% - 60% of the maximum speed. If the speed increases above 60% or decreases below 40%, the speed decreases (fuel use increases by 1 hour of operation). The economical course of the electric boat starts at 10% of max RPM and the efficiency gradually decreases with increasing speed. So the electric motor teaches not to rush)
The cost of an electric motor with a lithium battery is comparable to the cost of a diesel engine, which makes it possible to use this system on boats today. More on this will be later.