MARINE ELECTRIC PROPULSION

Rethinking Energy, Motion, Space, & Time On Your Boat

Perfect Propulsion System• Manufacturer

would pay you • Infinite speed• No pollution; it

removes pollutants wherever it goes

• Cures athlete’s foot, ED & psoriasis

• End wars, turns debts into surpluses

Sorry, Can’t Do… But Can We Improve Boat Propulsion With 21st Century Tech? YES!

Back to Basics: Getting A Boat Moving

Push Throughthe Water… Displacement

Skim On Top… Planing

Today’s Focus: Displacement

Planing Hulls? Some Other Time.

WHAT WE NEED – A JET OF WATER MOVING AFT

Another Way…Jet Engines!!

Seriously…What Propellers DoGRAB THE WATER, PUSH IT AFT

How Propellers Do It?FEED THEM TORQUE

Isn’t This Presentation About Electric Propulsion?

WHERE ARE THE AMPS & VOLTS?

Not Yet…Soon

Prop PropertiesTo Push More Water• More Blades• Larger Diameter• More Blade Angle (Pitch)• Spin Faster

To Push Less Water• Fewer Blades• Smaller Diameter• Less Pitch• Spin Slower

Props Don’t Care What (or who)Is Turning Them

Boat Properties ILess Power to push• Longer waterline

length• Less weight• Less beam• Fin keel• Less Speed

Boats Don’t Care What Is Turning Their Props

Boat Properties IIMore Power to push• Shorter waterline

length• More weight• More beam• Full Keel• More Speed

Boats Don’t Care Who Is Turning Their Props

What You Use To Turn The Prop Shaft Is Secondary;

Your Boat’s Design, Weight & Speed Drive The “Power Equation”

Even If You Have These Guys…

What A Prop Really Wants

From 0 to 1 knot• Prop has to overcome

inertia of still water• Must establish

moving jet, but it need not be fast

• Needs lots of torque to do it

• RPM change is small

Consider a Displacement Hull Vessel With a Maximum Operating Speed of 6 Knots Under Power

What A Prop Really Wants

From 5 to 6 knots• Inertia is not an

issue; water jet is already moving

• Prop must accelerate the moving water jet

• Torque increment is small

• RPM change is huge

Consider a Displacement Hull Vessel With a Maximum Operating Speed of 6 Knots Under Power

Props Want High Torque @ Low RPM, High Speed @ High RPM…

…Which Is What Electric Provides

Now Consider A Diesel Engine• Low Torque @ Low RPM• Torque Catches Up @ High RPM• Must be OVERSIZED to address mismatch• This is why so little happens in the first

third of your throttle’s arc of travel

Knock-On Effects Of Oversized Diesel Engines In Sailboats

• When diesels perform best:– At full design temperature, which

means…– At or near full throttle most of the time

• On sailboats, they run intermittently at various throttle settings– “Wet Stacking”– Incomplete fuel combustion– More maintenance, shorter life

• Not easy to “fine tune” prop thrust

Deeply Conflicted Diesels

• Propulsion is not the diesel’s only job

• It also has to spin its alternator for battery charging

• Easy in the old days…not much power needed

• Today…different story

“What Is My Purpose In Life?”

• Propulsion or Power Generation?• Do you run your diesel in neutral to

charge your batteries?• Let’s use a 27 hp diesel as an

example…it’s equivalent to about 20 kW (before losses)

• You upgraded to a 200 amp alternator

• Call it 14 volts – that’s 2.8 kW max• Diesel is grossly under-loaded!

…Your diesel engine keeps asking itself

Recap – Diesel Issues on Sailboats• Mismatch in torque curve → oversized diesels• Mismatch in usage for long, trouble-free life– Diesel likes to run hot most of the time– Sailboat needs intermittent use, often at low load

• Conflict: Diesel is asked to push the boat and make electricity too – totally different uses

…While Introducing No New Ones, Right?

Electric Propulsion Solves All Of These Problems….

We Wish. Electric DOES Offer: • A streamlined way to organize energy

generation, storage and use• A highly modular approach – easy to mix and

match components at various price and performance levels

• A set of trade-offs that make it right for some and not for others

With Electric, Propulsion Is Just Another Load

Energy Sources• Dockside Power• On-Board

generator• Solar Panels• Wind generators• Fuel Cells• Regeneration

under sail

Energy Storage• Lead-Acid

Batteries– Golf Cart– AGM’s– Thin Plate Pure

Lead AGM

• Lithium Ion– LiFePo4– LiMn

• NiFe

Energy Users (Loads)• Propulsion

Motor• Fridge• Air Conditioning• Windlass• Nav & Comm

Instruments• Lights & Fans• Pumps• TV, PC, Tablets

…So Treat It Like Any Other Load

• How much power does it need?• For how long?• Always at max power when it’s on?

Probably not, most of the time• Add its load to all the others• Compare with energy storage capacity• Factor in contributions from sources• Size the storage and the sources such

that the storage always has a reserve

…Just Like They Do In:• Cruise & Navy Ships• Subs• Diesel Locomotives

In fact, small craft, with their diesel engine-transmission drives, are the outliers

Wait A Minute…• Some of the sources are AC, others DC• Some of the loads are AC, others DC• Now add electric propulsion…• it’s 48 Volts DC, 72, 96 or more• Can’t mix and match, Right?

Actually…• AC to DC: rectification• DC to AC: inversion• DC voltage to a different voltage: conversion• All of these are easier, better, cheaper today:– Many manufacturers and products to choose from– Off-the-shelf, proven technology, mass-produced

components, reliable, efficient, affordable

So…• You can focus on:– Energy coming in– Energy stored– Energy going out

• Let geeks like me worry about:– AC-DC & DC-AC

transformations– DC-DC voltage matching– Controls– Monitoring & Display

The Result• Daysailers (no generator): – Go out any time; no winterizing in cold regions– No outboard or diesel engine maintenance– Quiet, precise control, easier handling

• Cruisers (with generator)– Much more effective use of diesel engine; low-

load operation nearly eliminated– With DC-DC converter, one generator charges both

propulsion batteries & house batteries – Quiet (when gen’s off), precise control, etc.

RECAPThanks to recent technology advances,

small craft can feasibly be powered electrically, like large vessels and

locomotives, with lots of benefits and some drawbacks. For many boats and

owners, the case for electric is compelling.

FOR MORE INFO

www.annapolishybridmarine.com

ddiquinzio@annapolishybridmarine.com

David M. DiQuinzio PE443 924 4484

THIS PRESENTATION CAN BE VIEWED ATwww.annapolishybridmarine.com/

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