TEST The whole truth about electric propulsion in boats

There is a lot of talk about it today, but few have actually tried a full-electric propulsion boat. The opportunity presented itself to me at the Cannes Boat Show, where I had the opportunity to sail on a Lucia 40 sailing catamaran by Fountaine Pajot (11.73×6.63 m) equipped with a saildrive electric motor system developed by Volvo Penta. “For now it’s a prototype,” the Swedish giant’s engineers tell me, “and some details still need to be optimized”: such as the ability to take advantage of the propeller’s movement to recharge the batteries while sailing, which is missing here but will be a key point in future installations.

HOW THE SYSTEM WORKS
Let’s start by understanding what the system consists of. The technology behind the electric Saildrive is based on Volvo Group’s proven automotive designs-and many components are shared. The starboard and port aft lockers house the two 15 kW motors with saildrive and their respective 20 kW lithium battery pack (charging time, 3 hours) attached. Since this is a prototype, we were not provided with data on the total weight of the installation. Two 5-kW chargers and as many 7.2-kW gensets complete the system (the genset, i.e., a diesel generator that recharges the batteries, is essential if you want to do a lot of motor boating, this is unavoidable for now): when the battery level is low, full discharge is prevented by the automatic genset ignition.

It is possible, I am told, to have larger battery packs as needed (but beware, more batteries also means more weight and more power consumption). The batteries also power on-board services, and many conveniences such as air conditioning-they tell me on board-can stay on for up to 12 hours without the use of the generator, ensuring total silence.

EVERYTHING UNDER CONTROL
Next to the helmsman’s station, all the data needed to keep an eye on the engines and battery status are clearly shown on a display: this is thanks toVolvo Penta’s Electronic Vessel Control System declined on electric propulsion. The energy output of batteries in kW and percentage of charge, their durability in terms of time and miles, boat speed, and “throttle” control. Also displayed at the bottom is the energy provided by other “green” sources such as solar panels (0.4 kW in the photo), possible wind generators, and hydro generators.

IN NAVIGATION.
We leave Port Pierre Canto in Cannes by taking advantage of electric propulsion. The catamaran responds very well to the controls, acceleration is good, and the buoyancy generated is also superior, in my opinion, to that of a diesel engine. You are not sailing in total silence, let’s be clear: but the difference is stark when compared to the noise of a traditional inboard, it’s a humming noise that goes along with the lapping of the wake water (and then, since this is a prototype assembled in relative haste pre-saloon, the peaks are not soundproofed as they are in classic engine compartments).

In the open sea, I have the opportunity to test speed and consumption. With the batteries 90% charged, at about 4 knots of speed you can sail 29 miles, with a range of about 6 hours. Increasing the speed to 5 knots the range drops to about 14 miles (about 3-4 hours of sailing), at 6 knots we are at 11 miles (1.9 hours), at 7 knots 7.5 miles (1.1 hours). At 8 knots the range is, according to the display, 5.3 miles and 0.7 hours. This is data to be taken with a grain of salt because there was a fixed parameter (AC, alternating current, set at 1.8 A as can be seen on the display screen) that, according to the technicians, adversely affected the duration shown. Under optimal conditions, they say, the engine can propel the boat 27 miles at 5 knots and 17 miles at 6 knots. Anyway, the behavior of the engine is easy to understand: efficient at low speeds-certainly more so than a diesel, less efficient if you “push on the throttle.”

CONCLUSIONS
For those who make daily use of the boat and sail a lot, or for those who take cruises stopping every night in port, full-electric propulsion is already the best solution. Less noise and access to marine protected areas are two important advantages. Unlike the automotive world, where charging spaces are rare, in boating it is easier because all ports are already equipped with charging stations. Certainly, by adding a state-of-the-art variable-rpm genset-and thus taking advantage of a diesel-electric system-the range is greatly increased, and the solution is also palatable to those who sail longer and roadstead often. The cost of the system? “To be determined,” yet to be determined, each installation is its own. It may not be low, but on larger boats it will certainly have less impact on the final cost of the boat.

Eugene Ruocco