MAN Engines: How to deliver an effective hybrid system

MAN Engines has introduced a new hybrid system for its marine diesel engines from 388 to 1972 hp (290 to 1471 kW).

The MAN Smart Hybrid Experience is composed of a diesel engine, clutch and electric motor/generator. The permanent magnet, synchronous motor/generator is available in two sizes with nominal power of 247 and 494 hp (184 and 368 kW) and operating efficiencies up to 96%, the company said.

The MAN Smart Hybrid Experience is available for all MAN marine diesel engines from 388 to 1972 hp. Shown here with a six-cylinder inline diesel, the hybrid system includes a clutch and an electric motor/generator unit positioned ahead of the marine gearbox.

The motor/generator is 6.3 in. long and 22 in. in diameter (160 x 560 mm) or 12.6 in. x 22 in. (320 x 560 mm) in diameter, depending on the output, and is mounted on the engine ahead of the marine gearbox. It can be decoupled from the diesel engine by the electromagnetic clutch, which allows propulsion mode to be changed without interruptions to propulsion power.

The MAN Smart Hybrid Experience
The MAN Smart Hybrid Experience is available for all MAN D2862 series (12-cylinder vee configuration), D2868 series (eight-cylinder vee configuration) and D2676 series (inline six-cylinder) marine diesel engines. The installation of the hybrid system allows to reach a hybridization degree of up to 56% of the diesel power output, the company said.

“For example,” Reiner Roessner, MAN Engines’ head of Sales, explained, “a six-cylinder inline diesel with 290 kW power output (388 hp) can be combined with the 184 kW (247 hp) electric motor/generator unit to reach a combined output of 474 kW (635 hp).

“On the other hand, a 12-cylinder unit with 1471 kW power output (1972 hp) can be combined with the bigger electric motor/generator unit to reach a total output of 1839 kW (2466 hp). That is a hybridization degree of about 25%.”

With the MAN Smart Hybrid Experience the company said it can supply a complete hybrid system from a single source, insuring the best combination of complex components such as electric motors, batteries, power electronics, and voltage management for single marine application. MAN said its bench testing, along with comprehensive field tests, have been a key step in the development of the system and ensure that the company maintains its quality standards even with completely new products.

How do the batteries work?
The hybrid system incorporated three power sources – the diesel engine, the onboard gen-sets and high-voltage batteries. The batteries can be recharged as a Plug-in-Hybrid through an integrated land connection to shore power when docked, or during boat operation through the diesel engines or onboard gen-sets. Even solar cells can be an option to be integrated in the power management system, MAN said.

One of the six operational modes available, Boost mode allows the diesel engines and electric motor/generator to work together to reach higher power output.

For the high-voltage batteries, MAN has chosen components from different manufacturers that operate at voltages over 600 V, which means the batteries can be flexibly operated at voltages between 500 and 750 V. “Sourcing for batteries from external suppliers is a first step for us,” said Roessner. “In the future, plans are to produce our own batteries, profiting of the experience within the MAN Group on batteries for commercial vehicles. Our plant in Nurnberg, Germany, has already been partially transformed to host battery production for on-highway vehicles and features also a new, dedicated test area.”

MAN Engines parent, the MAN Truck & Bus group, already has an electric bus on the field (with a 650 kWh battery pack for the 59 ft. vehicle), along with a van with 36 kWh battery. Truck applications are to follow, specifically an electric truck that is expected to come into production in 2024 that utilizes a 223 kWh battery and 250 kW (335 hp) electric motor that delivers an operating range of 112 miles (180 km).

Roessner added that it has always been MAN’s aim to develop standard drivelines with its diesel engines and the same is true for hybrid drivelines. Thus while the MAN hybrid solution is flexible, scalable and can deliver the degree of hybridization suited to the specific customer, the system utilizes standard series-production components and is available for any marine gearbox configuration, including V-drive, IV-drive, parallel gearboxes, and Down Angle.

The MAN Smart Hybrid Experience can be operated in different modes.

Zero-Emissions mode: The vessel uses power from the batteries for propulsion and all auxiliary functions, providing – as the name indicates – zero exhaust emissions and super-quiet operation.

Diesel-Electric mode: Propulsion and onboard electrical service are delivered by the gen-sets with the support of the batteries upon demand.

Cross-Over mode: When the boat has a twin-engine propulsion arrangement, the cross-over option allows to operate each propulsion train in a different mode. When one propulsion train is operating in diesel mode, the electric motor acts as a generator, taking energy from the first diesel engine and producing the electricity for use onboard. The diesel engine is operated at higher load with a better fuel efficiency, MAN said. In the second propulsion train, the diesel engine is decoupled and power for propulsion is supplied by the electric machine.

When the Cross-Over mode engaged, the system selects which diesel engine is operated depending on which unit has clocked fewer operating hours.

Hotel mode: In this mode, all power is derived from the batteries and MAN said the technology used in the MAN Smart Hybrid Experience allows for an extended use of the batteries with no need to start the engines. Independently from the power production, the batteries can be recharged in parallel via the land connection, the company said.

The additional components for the MAN Smart Hybrid system add 6.3 in. to 12.6 in., depending on the output of the motor/generator selected.

Boost mode: In this mode the diesel engines and the electric motor act together and complement each other. When power is needed, the electric motor output is added to engine output to reach higher power levels. For example, using the Boost mode, a 12-cylinder engine operating with the electric motor can achieve a power output comparable to a 16-cylinder engine, the company said.

Diesel mode: The classic diesel operation that can provide power for propulsion without the electric motor/generator producing energy. Additionally, diesel operation can provide the electricity needed to recharge the batteries without using the onboard gen-sets, thus sparing operation hours and reducing wear.

The MAN Smart Hybrid Experience became available to the global market in mid-September, when the first commercial installation was released. Classification with the major marine societies in is progress, MAN said.

While we wait to see a vessel actually equipped with the MAN Smart Hybrid Experience, Roessner gave an example of how a typical configuration will work: “In an 80- to 100-ton yacht with twin diesel engines, a 250 kW battery will cover 12 hours of electricity supply in Hotel mode or two hours pure electric cruising at a speed of 7 knots,” he said. “On such a vessel, the hybrid solution will add about 3.0 tons more weight and need a bit over 3 m3 (104.9 cu. ft.) of additional installation space – approximately 1.3 m3 (45.9 cu. ft.) for the battery pack and about 2 m3 (70 cu.ft.) for the power management system.”

MAN expects various marine segments to be interested in its Smart Hybrid system. “Applications such as yachts will look for hybrid solutions mainly for the comfort aspect, while super-fast boats will be attracted by the performance,” said Roessner. “Passenger transport boats will also be interested, looking mostly at the environmental aspect and the capability of entering ports and environmental-sensitive areas in full-electric mode.”