Hybrid Power for Your Next Boat, Part II
This MTU powered superyacht can employ its electric power system to accelerate top speed when desired, as well as to ease the yacht silently into a harbor at idle speed.
It’s likely that yachts of the future will be powered depending on their mission or most likely use, with those designed for coastal cruising and harbor-hopping all-electric, since they can recharge nightly, while those aimed at longer ranges will be powered by combination systems of internal combustion and electric.
Improvements in batteries and in electric motors is likely to swing the balance in favor of all electric boats in the future, but at present, hybrid systems seem to offer the best solution for eco-friendly boating in a changing world. Here’s a look at some that may work for your next boat—or replace your existing power system.
Twin Disc parallel hybrid marine propulsion systems can use both the electric motor and the combustion engine, simultaneously or separately, for propulsion. Both the combustion engine and the electric motor are directly connected–via a gear with a PTI(Power Take In) for an electric motor–to the drive shaft for the propeller. This gear allows power transfer between two sources.
The electric motor, the combustion engine, or both in parallel, can power the propeller. During normal operation, the parallel hybrid marine propulsion system will typically run on both the electric motor and the combustion engine throughout the driving cycle. The combustion engine can be used when it is most efficient to do so. Electric propulsion contributes to reduced fuel consumption and less emissions as well as acting as a backup for the ICE.
E-Motion Systems, in business since 2015,now offers both parallel and serial hybrid designs. The serial systems are engineered for displacement and semi-displacement yachts where the emphasis is on relaxed cruising rather than speed, while the parallel systems are preferred where planning performance is important to the owner.
E-motion also provides a sport fishing package with extra-large battery pack, allowing extended trolling at 5 knots up to 5 hours. The system uses a separate generator for rapid charging of the battery banks, which allows extended cruising on electric power. The system greatly reduces hours on the main engines, which results in reduced fuel costs and extended time between rebuilds. The isolated generator also produces less noise and vibration than operating the main engines, a plus when only low speeds are needed.
The system also includes high-output generators that can fully recharge the battery banks in 30 to 40 minutes to handle the hotel load for up to 24 hours. Over 1200rpm, the electric system automatically switches back to e-motor mode to boost the diesels, reducing fuel use and extending range. E-Motion says that in some applications the system can cut the diesel hours per year by 90 percent.
Greenline Hybrid yacht line—largest hybrid boat company in actual production--is currently available in eight different models including the sleek NEO sports boat, the family cabin cruising 33, 39 and 40, and the 45 Fly, 48 Fly, 48 Coupe and the 65 OC. The Slovenian-based company can lay claim to kick-starting the current trend for electric boats, launching the first affordable diesel electric hybrid boat in 2008.The Greenline 40 hybrid model is fitted with twin 220hp Volvo D3 diesel engines boosting the speed to 22 knots but still allowing electric-only cruising at 5 knots for up to 20nm.
The semi-custom Hardy Hybrid 42 has a single 440hp Yanmar diesel shaft-drive engine for powering across open water at speeds of up to 16 knots, but once in the harbor or perhaps easing along the canals of Europe it can switch to electric power, using its 20kW motor to slip silently along at 5-6 knots for up to two hours on battery power alone. Once this is depleted a small generator kicks in to keep the motor spinning while recharging the batteries.
MAN hybrid diesel-electric power systems are available in V6, V8 and V12 systems for yachts. The company points out that as long-time builder of quality diesel power, they are in an ideal position to provide the best hybrid systems and offer dependable world-wide installation and service. The systems include high-capacity batteries with shore-power, gen-set or main engine charging capabilities. Twin-engine installations also offer cross-over mode, with one engine providing propulsion, the other providing house power via the battery banks. The systems also have a boost mode which increases available power about 20 % over the straight diesel power for maximum speed.
MTU offers hybrid diesel-electric packages custom fitted to a variety of recreational yacht-class boats. The setups are typical for parallel hybrid systems, with the large e-motors also functioning as alternators to rapidly charge battery banks during diesel-powered operation and also separate diesel generators for charging while at anchor.
The company offers “entry level” eco-setups with small electric motors, small battery pack and small generators, through a mid-level solution and also a high-end “Sport ”package for maximum electric power. The electric motors in the sport package can also assist the diesels for maximum power and speed when desired.
OXE Marine lays claim to the first diesel-electric outboard motor. The company has been building diesel outboards since 2008, but now offers a 300-hp turbo-charged diesel in concert with an axial flux electric motor that produces the equivalent of 150 hp, according to the company. The electric motor is located under the cowling, connected to the drive-belt for seamless operation.
Not only does this enhance performance, but it also allows the motor to serve as an alternator, providing the ability to charge the batteries while running in diesel mode. For added power, both electric and diesel power can be combined to produce a max of 450 horsepower. The diesel can also run on bio-diesel, making the unit particularly eco-friendly. Production models are not yet available but the company is running tests in concert with Nimbus Marine this spring on various models.
Sunreef Yachts is building semi-custom catamaran designs to 100 feet, available with either full electric or hybrid power. Most of these Polish-built yachts have massive solar panel charging and some also add sails or wind-powered generators to the power-delivery systems. The interiors are fully customizable. The Sunreef 45 Ultima-Eco is a hybrid design that delivers high-speed performance when needed, but that can also operate for extended distances on e-power alone. The company reportedly has 10 orders on the books.
Volvo-Penta hybrid diesel-electric systems are still in the testing stages, but the company has been working with several IPS-drive units that likely will see production as the market develops. Reportedly they are testing dual systems in a 50’ aluminum fast cruiser. On this setup, at least, while in hybrid mode the system itself will select whether to use the electric motor, the diesel engine or both depending on factors such as speed and battery state. In power mode both the diesel engine and electric motor will run concurrently to boost acceleration and speed.