Hybrid Power for Your Next Boat , Part I

Until a few years ago diesel and gasoline propulsion systems were the norm for all recreational powerboats, inboard, outboard or inboard/outboard—there were no other choice. That’s far from the case now with the push toward eco-conscious or “green” boating, with both hybrid petroleum/electric drive systems and just this year, a geometric jump in all-electric power systems.

We looked at the all-electric systems in a recent two-part BoatTEST article. While this appears to be the wave of the future, the lack of fast-charge facilities at marinas continues to be a dragon the adaption of all-electric boats. There’s a network of fast chargers already in place along the French Riviera, and plans for more in marinas allover Europe and the UK, but adaption in the U.S. so far has been slower.

Here, we’ll consider hybrid systems, combining the best of both worlds, and not hindered by the lack of fast-charging shore power.

In a hybrid system, the internal combustion engines (ICE) burning diesel or gasoline provide extended high-output power for longer crossings or rapid passage between harbors—or for powering electric propulsion systems--while the electric systems provide silent, fume-free displacement power for operation inside harbors and anchorages.

For the next few years, hybrids present a viable solution to more eco-conscious propulsion.

Hybrid Power Classifications: Serial Vs Parallel

Hybrid power can be seen as having two segments borrowed from battery technology, serial and parallel.

Serial systems use an internal combustion engine only for powering a generator/alternator which charges the batteries, and the boat only moves based on this charge fed to electric motors. The ICE engine is not connected to the drive system directly.

It’s possible to remove the internal combustion engines completely in a dedicated serial system, gaining lots of space as well as a large weight reduction, when replacing standard mechanical power with serial hybrid electric power. The power to recharge the large battery banks usually comes from two or more high-output ICE generators, but these are much smaller, lighter and less fuel-hungry than the standard engines.

This solution is primarily suitable for displacement or semi-displacement boats including sailboats or solar-powered boats, where alternative forms of propulsion are available.

Serial system scan also work for e-boats used only for day-boating, returning to the same dock for overnight recharging as needed. Ferries operating within a harbor are also increasingly using this solution, with high-density batteries providing the needed power to run for the limited distances required in this duty.

Parallel system scan feed either internal combustion or electrical power through the boat’s existing drive train to the propellers—this is what most of us would think of simply as “hybrid” power. Parallel hybrid systems don’t disturb the traditional engine, gearbox, propeller shaft and propeller drive train, which all remain intact and fully functional when high ICE propulsion is required.

The diesel engine(s)provides the propulsion power required to achieve the vessels maximum hull speed, while the electric motor/generators designed to match the vessels mid to low propulsion needs allowing the components to be more compact and more cost effective.

It’s currently a popular solution because the ICE can be used for crossings too extended for the battery system, while the silent electric propulsion is preferred inside harbors and in canals, locks and other close environments where noise and fumes are an issue, but range is not. The silent low-speed power and lack of vibration of running on the electric system might also be appealing for overnight operation where owner and guests are relaxing below while a professional captain handles the navigation.

Using a hybrid system lowers the yacht’s fuel usage, reduces emissions, increases efficiency, and allows the yacht to go further for less. It means greener yachting–something that is more important than ever as the world becomes more aware of the impact of fossil fuels and pollution and of individual carbon footprints.

As a general rule of thumb, with a proper charging system running off the main engines, engineers say up to two hours of electric propulsion can be generated for every hour of ICE power.

This can allow shepherding fuel resources when necessary. In these systems, once battery power is depleted and the diesel engine is engaged to propel the vessel, the electric motor/generator system automatically switches to electrical generation mode and recharges the battery bank. The extra load on the diesel engine caused by both propulsion and thee-motor/generator can improve diesel fuel efficiency in some cases.

Once the battery bank is recharged the diesel engine can be stopped and the electricmotorre-engaged to propel the vessel as desired. Using inverter technology, it’s also possible to run air-conditioning and all the electrical domestic appliances you would expect at home and also eliminate the need foragascooktopon board.

There’s no need for a separate generator on parallel hybrid systems, so none of the noise or exhaust fumes commonly associated with this traditional way of running the “hotel” load. (Some systems like e-Motion do include ICE generators, however, for very rapid automatic recharge of the house power without starting the main engines.)

For those wholove trolling for big game fish off shore but hate the frequent blow-back of diesel exhaust in the cockpit, trolling under electric power provides a whole new way to fish. The silent, vibration-free operation is also less likely to spook fish prowlingnearthe surface.

And the ability to quickly change from forward to reverse is a plus for those who chase giant fish like bluefins and blue or black marlin where “backing down” at speed is often part of the battle.

Some high-performance systems are also designed to operate in concert, with the electric power providing a boost to the diesel engines for maximum speed for short periods.

In Part II, we’ll look at some of the companies offering hybrid systems, both as part of a complete yacht package and as an alternative drop-in package for yachts that have been mechanically driven until now