Courtesy Volvo Penta
Krossholmen, Sweden, June 5, 2023
Electric marine propulsion is not the future of recreational boating.
However, electrification aboard boats can provide a more sustainable boating experience, and also a boating experience that’s different, and enhanced, in a couple of ways, compared to the current status quo of combustion-only power. I saw proof of this while running a Beneteau NC 37 powered by Volvo Penta’s diesel hybrid electric system last week.
There’s little downside to combining the best aspects of electric motors and combustion engines, though cost is probably one factor. We’ll leave that aside for the moment, since I could not pry a dollar amount from either Volvo nor Beneteau. Both promised pricing soon.
It’s also relevant to state that neither Groupe Beneteau–the world’s largest boatbuilder, by the way-or Volvo Penta, maintains that electric or hybrid propulsion will suit every, “use case,“ which is corporate-speak for individual boaters. The basic mission is to create easier, more intuitive, more pleasant and accessible boat operation and ownership while simultaneously taking environmental and sustainability wins where feasible.
Finally, this system is not just about drives, and batteries and motors and engines and their physical installation aboard a boat. The ways in which the system integrates with a variety of control, navigation and monitoring technologies is also important (Perhaps even more important). As are several implications that can change some of the ways some of us go boating. The whole is larger than the sum of its parts.
How do I know all this?
For one thing, I was at boot Dusseldorf in January of this year, when this partnership was announced publicly.
Then, last week I joined a handful of marine journalists from around the world at the Volvo Penta Test Center, located in Krossholmen, Sweden (Itself part of the Gothenburg Archipelago—a bucket list boating destination). The invitation came from both Volvo Penta and Groupe Beneteau in order to see, run and experience a new diesel-electric hybrid propulsion system aboard a Beneteau NC 37. I spent hours at the helm, inspected the physical installation, and all the while had the engineering and tech staffs at my side, not to mention Volvo Penta President, Johan Inden, and Groupe Beneteau’s Design Vice-President of Power and Motoryacht Development, Erik Stromberg.
Plug-in Parallel Hybrid Diesel-Electric
The system installed in the NC 37 is a plug-in parallel hybrid system. There is a 60kW electric motor installed on each engine’s output shaft, between engine and drive. This adds nine-or 10-inches in length, compared to a standard sterndrive installation. The motor couples to the shaft on demand, hydraulically, and rotates, providing propulsion.
This motor runs off of—and can charge—a 67kW Li-On NMC battery bank that was divided into two places aboard the NC 37: beneath a hatch in the salon sole and, belowdecks, behind some furniture. Bright, orange-sheathed cabling houses the high voltage conductors. There is a separate 24-volt conventional battery bank for engine starting and marine electronics.
With the system as installed, the 15,000 lb. NC 37, can make 10 knots at WOT on electric (not for long, though) and offers three hours of running at 5 knots. The monitoring software displays easy to read data for things like battery state of charge-and the all-important range-on the Volvo Penta Glass Helm MFD. This is live data, so the captain knows at a glance how much time and distance she can run on electric.
The boat is quieter when running on electric. With the diesels, at 5 knots, I recorded 82 decibels (db-A). On electric, at 5 knots, I recorded 72 db-A.
Since sound levels are logarithmic, a 10-db-A difference is effectively a doubling of the perceived sound.
In practical terms, it’s much easier to carry on quiet conversation and just plain more pleasant to be in a quieter environment. This might payoff for boaters who regularly transit no-wake zones, who troll for fish or who simply enjoy slow cruising of an evening with family or friends.
Another positive about running on electric for slow speeds is that there is no fume smell. Anyone who has idled their boat knows that, more often than not, going slow means bringing aboard smelly, and possibly harmful, engine exhaust fumes. (See our article about the Station Wagon Effect). Going slow with electric, you experience no fumes to make your crew seasick. And, no risk of CO poisoning.
NC 37 Hybrid Driveline Data
|Top Speed||35 knots|
|Top Speed Electrical||10 knots|
|Electrical Range at 5 knots||3 hours (15 NM)|
|Number of Electrical Machines||2|
|Total Continuous Power||2 x 60 kW|
|Batteries and Charging|
|Number of Battery Modules||8|
|Total Energy Storage Capacity||67 kWh|
|Charging Capacity from Land Grid||Up to 20 kW using AC|
|Charging Capacity via Combustion Engines||Up to 60 kW|
|Combustion Engine Configuration||2 x D4-320|
|Total Combustion Engine Power||2 x235 kW (2 x 320 hp)|
|Combustion Engine Fuel||HVO or Diesel|
|Drive Configuration||2 x DPI Aquamatic Sterndrive|
The, “electric boost,” mode Volvo Penta engineered into this system wowed me.
When activated, the electric motors turn while the diesels are operating. This gets the boat on plane demonstrably faster than without the electric boost. Our independently-captured numbers showed that the NC 37 reached 30-mph in 17.8 seconds with electric boost compared to 26.7 seconds without it.
Putting the stopwatch aside, I could really feel the difference, not just as a function of time, but as a matter of responsiveness. Achieving plane quicker is a great thing. But, commanding acceleration proves helpful transiting an inlet, running in following seas and other scenarios. Plus, it’s fun!
A thought-provoking implication of electric boost was put forth by Volvo Penta’s Inden.
“With such great acceleration, and given the fact that many boaters hardly ever run at wide-open throttle, might some boaters choose lower-powered combustion engines for their hybrid system after they experience electric boost?“
Doing so, would, of course, lower the carbon footprint further, because smaller engines burn less fuel. Note that Inden stated this as a possibility only; a what-if scenario.
Still, proposing the sale of smaller, less powerful engines is not what I typically expect from a top marine engine executive.
Charging the 67-kW battery bank is handled several ways. There is a 20kW charger built-in and that boat owners will plug into when shore power is available. The connection will be a standard automotive EV connector. Adaptors that make these work with shore power cables can be readily purchased.
The Li-On battery bank can also be charged underway. The electric motors become alternators when charge mode is engaged. With this charging method, the batteries can be taken to 80-percent state of charge (SOC).
An interesting feature is the ability to charge while at anchor. In this mode, the engines rev to 1,500 rpm, turning the electric motors as chargers, and delivering 60kW in about an hour! That’s fast!
The battery bank can be taken to 100 SOC using this method. This capability provides self-sufficient confidence to the captain. Of course, you will have to be considerate of those sharing your anchorage before running your engines at 1,500 for an hour. And, the risk of CO poisoning would exist during the process—though diesel engines are much safer than gasoline engines in this regard. Still, take the same precautions you would were a genset in use.
Learn More: Carbon Monoxide Fact Sheet Fatal Fumes
Speaking of generators, the battery pack for a hybrid system such as the one being described here, can replace a generator for some boater’s usage. Doing so means no noise for your crew to endure and no noise to bother neighbor boaters. Also, boats without generators present less of a CO poisoning risk. If the battery pack is charged from shore power, there will be reduced pollution in the aquatic environment.
To find out if the battery pack will substitute for a genset for your use, you need to do two things: estimate the amp-hours ( Ah) required to use the appliances you’d run during a typical overnight or weekend.
Second, convert the kilowatt-hours (kWh) of the battery pack to Ah. To do so, first divide the kWh by volts. Then, multiply by 1000. Doing so for a 120-volt system, and using the 67kW battery bank aboard the NC 37 hybrid demo boat as an example, gives us 550 Ah. Let’s make 80-percent of that available, so we don’t draw the battery down completely and we have 445 Ah available.
Typical Appliances and the Amps Required to Run Them for One Hour on 120V AC
|8000 btu Air-Conditioner||7.0 amps|
|20w LED Light ( 5 @.10 a each)||.5 amps|
|32-inch TV||3.0 amps|
|15-amp Battery Charger* (*Running 12-volt appliances, like pumps and electronics)||15.0 amps|
|Total:||32 amps per hour|
This means the Volvo Penta battery pack as installed in aboard the hybrid electric Beneteau NC 37 would allow running the suite of equipment listed for 13 hours. On the one hand, losses due to resistance, comprressor surge startups, and other realities will reduce that running time to some extent. On the other hand, it’s not likely that we’d need to run all those appliances constantly. Either way, a quiet, exhaust-free overnight or weekend can be experienced.
The hybrid electric system integrates with DPS—Volvo Penta Dynamic Positioning System. DPS uses GPS and joystick maneuverability to provide the ability to keep the boat in one place at the touch of a button. This is usefuf while waiting on a drawbridge or lock, while queued up at the fuel dock and even in some fishing applications. Engage DPS and the drives turn independently, while the engines shift and accelerate independently, and the boat stays more or less in place using GPS to fix the location. It’s a station-keeping system and it works just fine.
But, I discovered that I prefer using DPS on electric rather than combustion. For one thing, the instant torque provided by electric motors means the system responds even quicker than it does with a combustion engine input. The boat seemed to stay in a tighter position and with the system making fewer corrections.
Secondly, DPS on electric it is much quieter than with combustion input. This is great for crew aboard the boat, but the benefit extends beyond that. Coming into, or leaving, a marina or anchorage late at night or early in the morning can be done with less chance of disturbing fellow boaters. While visiting pristine areas, quieter maneuvering is less likely to disturb wildlife or marine life and helps preserve the tranquility.
The Future of Boating
It’s admirable that companies such as Groupe Beneteau and Volvo Penta have taken a forward-looking approach to product development. With respect to the environment, Groupe Beneteau’s Erik Stromberg, noted his company’s commitment to sustainability, stating: ”It’s not just something we have to do. We want to do it.”
Stromberg cited Groupe Beneteau’s use of bio-sourced resin and recyclable materials in boatbuilding, a recycling plant in France to deal with boats at end-of-life, and seeking new propulsion solutions, like the Volvo Penta hybrid electric system, as all part of that commitment to, “expand accessibility through the creation of solutions in harmony with nature.”
Volvo Penta’s Johan Inden also spoke passionately with regard to accessibility and sustainability. His stated company’s commitment to lessen the impact on the environment while providing increased accessibility to boating and more convenient boating. (Volvo Penta uses the term, ”Easy Boating.”). He noted Volvo Penta’s extensive testing of this hybrid system in the extreme-yet sensitive- environment at Svalbard, at the Arctic Circle. He detailed all that has been required to bring this to the recreational boat buyer.
Notably, Volvo Penta just released a new version of its IPS propulsion system that comes standard with two engines per drive. While suited for large yachts, Volvo Penta iw laying the ground work for more universally useful drive systems capable of operating off of multiple inputs. He cited petroleum, electric and hydrogen as just some possible examples. That capability allows the boat owner/ operator to select the input that best suits a given situation.
And to expand upon the concept of accessibility, it means to make boating more available to more people. Quiet, joystick-operated marine propulsion, with touchscreen monitoring and integrated turning, trimming, course- , speed-, and position-keeping, all gives new boaters a leg up on the learning curve to operating a boat. For those of us with “old school” experience, these systems provide a layer of redundancy and increased convenience.
Hit a boat show, or make an appointment with either Beneteau or Volvo Penta, to see this hybrid electric system for yourself.