Marine HybridsCome of Age

A handful of well-financed efforts bring together boatbuilders,battery companies, marine electronics developers and suppliers,and engine and generator manufacturers to deliver increasingly

advanced hybrid propulsion systems.

by Nigel Calder As a Professional BoatBuilder con-tributing editor. I've written about

the early development of marinehybrid power options i.n these pages.For in-depth explanations of earlymarine hybrid systems, see PBB Nos.107 and 108. NOw, I'm also techni-cal director of t11C European HybridMarine (HyMar) project, one of theefforts mentioned in this article.

1 believe we'll look back on 2010as the year marine hybrid propuJ-aion systems began to move from

the edge of the marketplace into themainstream. The move is being pro-pelled by the entry of some heavyhitters; the collaboration betweenZF and Beneteau=-two companieswith billion-dollar balance sheets; thecooperation between Volkswagen andthe Slovenian Seaway group--one ofthe larger recreational marine designgroups in the world; and the acqui-sition of hybrid-developer Bellmanby Dutch marine electrical companyMastervolr, Increasingly sophisticated

Above-Zogo, a 29' (8.8m) launch builtby French & Webb of Belfast, Maine,was designed by Stephens, Waring &White Yacht Design in Brooklin, Maine,around a Steyr parallel diesel/electrichybrid power plant, which includesa 110-hp (82-kW) marine diesel and a7-kW electric motor.

30 PROFESSIONAL BOATBUILDER

systems are also coming from smallerplayers, and the European Union-funded HyMar project. Human andfinancial resources are pouring intothe sector at an unprecedented rate.

Before exploring those changes,well review some hybrid basics.

All marine hybrid systems can bebroadly divided into two categories:serial and parallel.

In a serial system, the engine drivesa generator, which provides powerto charge batteries, run an electric-propulsion motor, feed an inverterfor the house AC loads, ere The onlyconnection between the engine andthe propeller shaft is electrical.

In a parallel system, the engine isconnected to the propeller shaft justas in a conventional installation, withthe addition of an "electric machine"between the engine and the propeller,functioning as an electric motor and agenerator, depending on whether it isdriving or being driven. It is a parallelsystem because, from a diagrammaticperspective, there are parallel propul-sion systems operating on the samepropeller shaft. The parallel systemhas an engine clutch between theengine and the electric machine, anda shaft dutch between the electricmachine and the propeller, allowingfor three principal operating modes:

• With both clutches dosed, theengine drives the propeller in con-ventional fashion with the electricmachine either providing boost pro-pulsion, or functioning as a generator.

• With the engine dutch open andthe shaft clutch closed, the electricmachine drives the propeller. (Onsailboats under sail, a freewheelingpropeller can be used to drive theelectric machine as a generator in thismode.)

• With the shaft clutch open andthe engine clutch closed, the enginedrives the electric machine as a stand-alone generator.

A majority of players in the marinehybrid game rely on permanent magnet

ZF/Beneteau's parallel hybrid systemoffers 35-kW electric propulsion drawnfrom a 500V lithium-Iron-phosphatebattery pack. A sophisticated Boschengine controller shifts seamless/y amongelectric propUlsion, diesel propUlsion,and electric power generation,

DC (PMDC) motors and generators.Most are brushless, but a few havebrushes. All motors include a motorcontroller, which accepts a DC inputand chops it up to create a pulsewidth modulated (PWM) multiphase(generally, three-phase) AC output.The output is fed to windings to createthe pulsating magnetic fields neces-sary for the motor to function. Thecontrollers operate like a DC-to-ACinverter, and in fact are often calledinverters rather than motor control-lers. For OUr purposes it's important toknow that it takes sophisticated engi-neering, and a considerable amountof software, to create an efficientmotor controller. The better ones nowboast efficiencies as high as 98%;.

Spin a PiVIDCmotor with an engineor freewheeling propeller; and itbecomes a generator producing multi-phase AC, with voltage and frequencyvarying with speed. Rectify the out-put, and you get back to DC power.

The generator in a serial system istypically run within a narrow speedrange determined by the DC systemvoltage. Relatively simple rectifica-tion electronics and software provide:suitable DC output for propulsion;storage in a battery pack; stepping upand down via DC-to-DC convertersfor house DC systems; or conversionto house AC power with a conven-tional DC-to-AC inverter.

In a parallel system, the generatorruns over a much broader and con-stantly changing speed range, yieldingoutputs that vary widely in voltageand frequency. The same electronic

device that acts as a motor controller alsoworks as a rectifier to return to DCpower. A parallel system typicallyrequires more sophisticated engineer-ing and electronics than does theserial generator, and more complexsoftware, to efficiently produce therequired DC and AC outputs.

To limit cable sizes and optimizeefficiency, all marine hybrid sys-tems operare at higher voltages thanconventional marine DC systems.Voltages vary between systems-from a low of 48V to as high as 650V.Commonly there is a battery bankwith enough cells in series to achievethe system's correct voltage, and abattery charger to output the samevoltage.

In a sophisticated system, the vari-ous electronic components are linkedto a communications bus, and someform of central system controller; thegreater the degree of intercommuni-cation, the 1110re complex the controlfunctions and software.

ZF/Beneteau HybridFrom a technical perspective, the most

interesting new entry into the marinemarketplace is the parallel hybrid fromZF/Beneteau. The complete systemwas unveiled at the Paris boat showin December 2009. Key in its devel-opment has been ZF, best knownin the marine world for its transmis-sions. The company is also a giantautomotive conglomerate with wide-ranging expertise, and has drawnfrom automotive advances to developits sophisticated hybrid package,

OCTOBER/NOVEMBER 2010 31

Other partners include: VolkswagenMarine, for the diesel engine; ValenceTechnologies, for the lithium-iron-phosphate battery pack; and Frenchboat manufacturer Beneteau.

At the core of the ZF system is "-powerful electric machine builtinside an enlarged flywheel housing.The machine can be used as an elec-tric motor, with a peak power of 35k\v, and also as a generator, with acomputer-controlled output of 10 kW.It's a considerably more powerfulvariant of the flywheel machine pio-neered by Steyr Motors of Austria andfeatured in PBB No. 122. Mounted ontop of the electric machine's housingis a box containing: the motor con-troller to drive the electric motor;electronics to manage the output fromthe generator; a battery charger forwhen the boat is plugged into shorepower; a lO-kw DC-to-AC inverter tosupply power to the boat's AC cir-cuits; and DC-to-DC converters tostep down the hybrid system's highvoltage for the boat's 12V and 24Vsystems. That's a mind-boggling arrayof powerful electronics integrated intoan amazingly small package.

The system operates at a nomi-nal 500V and is connected to a SOOVlithium-iron-phosphate battery packthat Valence produces exclusively forBeneteau. The pack comes completewith its own battery-managementsystem. The lithium-iron-phosphatechemistry is the safest available lithium-ion option. Other chemistries carrya greater risk of catching fire, andonce they start to burn it's difficultto extinguish the flame.

Because the Zli/Beneteau system'shigh-voltage electronics are inside thebox atop the flywheel housing, the only500V connections emerging are thepositive and negative leads to the bat-tery pack Also, for the battery chargerthere is: shore power going in;220V!50Hz power coming out tosupply house AC loads: and 12V and24V to supply the boat's conventionalDC systems. All connections are madethrough two waterproof plugs thatcannot be mixed up. The engineeringis superb.

The system has a sophisticated con-troller, or vessel management unit,based on a standard Bosch enginecontroller from the automotive world,Just as in a hybrid car, it's designedto move seamlessly among electricpropulsion (35 kW), diesel propulsion(75 hp!55 kW), and power genera-tion (10 k\\1) by opening and closingthe necessary clutches, starting andstopping the engine, and switchingthe electric machine from propulsionto generation, with no need for userintervention. Boatbuilders can controlthe extent to which those processesare automated by adjusting the soft-ware to meet the boat's needs,

The user display shows the batterypack's state of charge and allows theoperator to select operating modes:diesel, electric, ere. If necessary, theboat operator can run the electricmotor at up to the full 35 kW for 30scconds=-S knots in the Beneteau testboat. Electric propulsion is commonlyrestricted to relatively low speeds-5 knots in the test boat-s-above whichthe diesel engine takes over. This

minimizes the load on the bat-tery pack and optimizes rangeunder electric power. Oncethe diesel kicks in, the electricmachine shifts to generatormode to recharge the batteriesand power the boat's housesystems.

In a departure even fromother hybrid systems, there is

32 PROFESSIONAL BOATBUILDER

The high-voltage electronicsof ZF/Beneteau's system areinside a box atop the flywheelhousing, All external connectionsare made through waterproofplugs designed so thatthey cannot be mistakenlyswitched and connected tothe wrong circuits,

no reverse gear. Reverse propulsionis achieved by running the electricmotor in reverse-meaning, the boaris totally reliant on the electric systemand batteries for reverse, Also, thepropeller is mounted on a modifiedsail-drive leg that can be rotated 180°.The forward-facing position enablesthe water flow to open the foldingpropeller for regeneration on sailboatswhen under sail. \vhen regenerationis not wanted, the propeller is rotatedaft, where it automatically folds tominimize drag.

The system relies on a bucket-load of sophisticated hardware andsoftware to operate successfully. Ithas taken the automotive industry adecade to develop such refined sys-tems. With some of that automotiveinnovation in its back pocket, in justtwo years ZF/BcnCteau has builtworking prototypes currently installedin two test boats. And, ZF is offeringthe flywheel and electronics packageas a module to be added to a rangeof engines and transmissions.

ZF/Beneteau touts efficiency thatreduces fuel consumption up to 50%in a sailboat, but has not releaseddata to back up the claim. (It's clearthe benefits claimed depend on fullyexploiting the regeneration capabilityunder sail.)

Beneteau's persistence as a part-ner is particularly noteworthy. Fora decade the company has investedin hybrids, beginning with a half-dozen catamarans employing serialsystems from Dave Tether (PBB No.109) and Solomon Technologies.The goal was a cost-effective modelwith broad market potential, suchas the Lagoon 420 Beneteau devel-oped in conjunction with the Frenchcompany Leroy-Somer. That model'was a disappointment. Undaunted,Beneteau redoubled its efforts, againwith Tether (who had left SolomonTechnologies and created ElectricMarine Propulsion) and concurrentlywith Volkswagen and ZF. The com-pany has invested heavily to achievethe latest parallel hybrid, No otherboatbuilder in the world has demon-strated that level of commitment tomarine hybrid development

The Zf'/Beneteau system will be ondisplay once again at the Paris BoatShow in December, this time installedin the first of a new generation ofEuropean canal boats-c-designedby J&J Design (see next page) and