Transcript marine electric propulsion

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 Through
the 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 Do
GRAB 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 Properties
To Push More Water
•
•
•
•
More Blades
Larger Diameter
More Blade Angle (Pitch)
Spin Faster
Props Don’t
Care What
(or who)
Is Turning Them
To Push Less Water
• Fewer Blades
• Smaller Diameter
• Less Pitch
• Spin Slower
Boat Properties I
Less 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 II
More 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
Consider a Displacement Hull Vessel With a
Maximum Operating Speed of 6 Knots Under Power
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
What A Prop Really Wants
Consider a Displacement Hull Vessel With a
Maximum Operating Speed of 6 Knots Under Power
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
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?”
…Your diesel engine keeps asking itself
• 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!
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
Electric Propulsion Solves All Of
These Problems….
…While Introducing No New Ones,
Right?
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 enginetransmission 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; lowload operation nearly eliminated
– With DC-DC converter, one generator charges
both propulsion batteries & house batteries
– Quiet (when gen’s off), precise control, etc.
RECAP
Thanks 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
[email protected]
David M. DiQuinzio PE
443 924 4484
THIS PRESENTATION CAN BE VIEWED AT
www.annapolishybridmarine.com/
marine-electric-propulsion-presentation.php