Naviwatt, specialist in electric propulsion for more than 10 years

Designing an electrically propelled boat requires a global approach, Naviwatt shares his experience with us. From the conception to the realization, including the hull design.

Naviwatt, the French specialist in electric propulsion boats was present at the Düsseldorf Boat Show 2020. BoatIndusty takes advantage of this event to take stock of the development of this propulsion mode and its applications.

Naviwatt, 12 years of experience

From design to construction of electric boats, Naviwatt offers a range of semi-rigid, monohulls and catamarans mainly for professional use.

Created in 2008 and based in Arzon in the Gulf of Morbihan (56), the team of 8 people, including 3 naval architect engineers, works on all aspects of electric propulsion. In its 12 years of existence Naviwatt has produced about 40 electrically propelled boats.

Naviwatt Laurent Bérenger

Adapt the boat to electric propulsion.

Laurent Bérenger, in charge of Naviwatt's business development, gets to the heart of the matter: "We quickly realised that fitting an existing hull with electric propulsion was not the right approach. An electric propulsion system should not be installed in a boat that is not intended for electric propulsion. All experiments, especially on semi-rigids, have resulted in poor performance. »

Naviwatt Laurent Bérenger

For Laurent Bérenger, electric propulsion can be broken down into 2 main subjects:

  • The design of the electric propulsion integrating motors, batteries, chargers and all the related environment
  • The navigation program that will determine the boat design.

Thus for each project, the team of naval architect engineers develops a concept in all-electric propulsion specifically for each use. For 12 years Naviwatt has made this a speciality.

At the very beginning of the shipyard's activity, Naviwatt manufactured small pleasure boats for rental propelled by a 4 kW engine, i.e. less than 6 hp, then passenger transport boats of 15 m in size propelled by 2 engines of 20 kW (less than 30 hp) each, for a speed of 12 to 15 km/h (8 knots), a power low enough to offer an autonomy of one day of operation.

Naviwatt Laurent Bérenger

For some applications, electric propulsion is the right choice: " The electric drive is suitable for predictive use with a constant daily consumption without being high ", says Laurent Bérenger.

« Depending on the use, it is possible to consume a lot of fuel (petrol or diesel) during the year, even if daily consumption remains low. In this case, electric propulsion becomes financially attractive and many professionals have converted to electric propulsion, especially in passenger transport in "closed areas" such as ports. For example, electrically powered passenger shuttles work very well. Daily use generates low energy consumption which, when reduced to the year, is significant. In the long run, financial savings are made e," insists Laurent Bérenger.

« The main advantages of electric propulsion are ease of use, low maintenance and manoeuvrability thanks to its wide range of use compared to an internal combustion engine. An electric motor can operate at very low speed with a high torque available immediately ", Laurent Bérenger bids

Unfortunately, for a typical intensive maritime use, of the yachting type, i.e. intensive, over a short period of time - i.e. consuming a lot during one day and little over the year - electric propulsion is not necessarily suitable.

Define the need before designing

Naviwatt Laurent Bérenger

So for each boat project, Naviwatt starts by defining a need and then draws up a specification that will define the storage and then the propulsive power and then the boat is developed to be as light and efficient as possible in terms of the hull for its precise use. For example, for a RIB that is likely to go to open sea, a fairly pronounced V-shaped hull will be preferred, whereas for a boat that stays in flat, calm waters this is not necessary.

Improvements needed

Naviwatt Laurent Bérenger

Naviwatt assumes that power generation remains onshore, even though some vessels are almost autonomous (but this is a small minority). Charging time and storage of electricity remain the necessary points of improvement for the development of electric propulsion.

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