Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 13-07-2011, 15:43   #16
Registered User

Join Date: Dec 2010
Posts: 262
Images: 1
Re: Electric Propulsion

Why not use Li batteries ? And would it make sense to combine house and propulsion batteries ?
__________________

__________________
Zonker is offline   Reply With Quote
Old 14-07-2011, 23:15   #17
Registered User

Join Date: May 2011
Location: Philippines
Boat: custom 42' catamaran
Posts: 262
Re: Electric Propulsion

I have a catamaran just built here in the Philippines. I only have a single 22 hp Volvo Penta marine diesel in the port hull because I didn't want the heat, noise, and smell in the starboard hull where the owner's berth is located. Other more experienced sailors (everyone) suggested that I might need two engines. I mentioned this to the designer/builder and while he doesn't think that I need another engine, he suggested that it might be possible to cannibalize an electric scooter for its motor and electronics and fit it into the starboard hull. Since there are few marinas here, I am not sure that I need the extra weight for the better maneuverability - still, it is an interesting concept. Does this idea seem workable to the more knowledgeable here?

Another thought - if one has a propeller attached to a shaft to propel the boat, when one is sailing is it likely that the motion will spin the propeller and charge the batteries - and possibly the house batteries?
__________________

__________________
Bruce626 is offline   Reply With Quote
Old 15-07-2011, 02:54   #18
Senior Cruiser

Cruisers Forum Supporter

Join Date: Aug 2009
Location: between the devil and the deep blue sea
Boat: a sailing boat
Posts: 9,987
Re: Electric Propulsion

I think for a boat based at a marina the electric option is right now pretty cool - I could easily motor out and in on one charge. The issue is that once I get the engine and some quality batteries, the total weight and price is way above an inboard diesel. Way above, but not prohibitively so.

For an offshore job the boat will need a reliable genset too - so it is no longer electric but rather a diesel-electric thing.

b.
__________________
barnakiel is offline   Reply With Quote
Old 15-07-2011, 04:05   #19
Registered User
 
fastcat435's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: Amstelveen Netherlands
Boat: FastCat 445 Green Motion
Posts: 1,649
Images: 10
Send a message via Skype™ to fastcat435
Re: Electric Propulsion

So far the Green Motion Catamaran has covered more than 12000 NM with out any problems, we have made some changes to the setup after the trip from Durban to Amsterdam , these changes have improved efficiency ( different props and a changed solar charging setup.) the second Green Motion equipped cat was launched and handed over to the owners and they are happy with the results. I expect the owner to do a write up on the system and how life is on a all electric boat ( no liquid gas electric cooking )
__________________
fastcat435 is offline   Reply With Quote
Old 15-07-2011, 04:28   #20
Registered User
 
fastcat435's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: Amstelveen Netherlands
Boat: FastCat 445 Green Motion
Posts: 1,649
Images: 10
Send a message via Skype™ to fastcat435
Re: Electric Propulsion

Quote:
Originally Posted by barnakiel View Post
I think for a boat based at a marina the electric option is right now pretty cool - I could easily motor out and in on one charge. The issue is that once I get the engine and some quality batteries, the total weight and price is way above an inboard diesel. Way above, but not prohibitively so.

For an offshore job the boat will need a reliable genset too - so it is no longer electric but rather a diesel-electric thing.

b.
You are right off course , we have a back up gen set on board with the Green Motion system, however having used less than 300 liters of diesel in 9000 NM compares well with the same length trip in 2004/2005 with a diesel powered FastCat 435 where we used in excess of 2000 liters.
Using diesel or not has everything to do with being a a hurry or not.
The crew was asked to use all systems including the generator during the trip to see if all worked well and if any improvement could be made to the complete system.
In mean while we have made trips that lasted between 3 days and a week with out ever having to start the generator, it takes some planning but once used to the idea of not using the generator it is easy to live with out it.
__________________
fastcat435 is offline   Reply With Quote
Old 15-07-2011, 04:37   #21
Senior Cruiser
 
skipmac's Avatar

Cruisers Forum Supporter

Join Date: Oct 2007
Location: 29° 49.16’ N 82° 25.82’ W
Boat: Pearson 422
Posts: 7,209
Electric Propulsion for a larger boat

Have been researching electric propulsion but have yet to find a viable commercially available system for a larger boat.

I have a 42' fairly heavy cruiser. Current diesel is 58 HP (+/- 45 KW) and I feel is slightly on the small size for the boat. Even allowing for the improved efficiency of electric power to the prop due to reduction of the parasitic loads you have on a diesel I think I would still want at least 35-40 KW. Green Motion's website shows the largest system as 25 KW.

Have not seen a price for the Green Motion system but after adding a diesel generator to power the electric on long cruises the cost for other systems I've looked at were about double the cost of straight diesel.
__________________
The water is always bluer on the other side of the ocean.
skipmac is online now   Reply With Quote
Old 15-07-2011, 05:16   #22
Registered User
 
fastcat435's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: Amstelveen Netherlands
Boat: FastCat 445 Green Motion
Posts: 1,649
Images: 10
Send a message via Skype™ to fastcat435
Re: Electric Propulsion for a larger boat

Quote:
Originally Posted by skipmac View Post
Have been researching electric propulsion but have yet to find a viable commercially available system for a larger boat.

I have a 42' fairly heavy cruiser. Current diesel is 58 HP (+/- 45 KW) and I feel is slightly on the small size for the boat. Even allowing for the improved efficiency of electric power to the prop due to reduction of the parasitic loads you have on a diesel I think I would still want at least 35-40 KW. Green Motion's website shows the largest system as 25 KW.

Have not seen a price for the Green Motion system but after adding a diesel generator to power the electric on long cruises the cost for other systems I've looked at were about double the cost of straight diesel.
Hallo Skipmac

Electric propulsion is much more expensive than a straight diesel propulsion, there are however other advantages like no noise, smoke, sooth, diesel consumption, vibration, autonomy and a cleaner earth.

In order to replace your present engine you would need a 18/ 20 Kw electric propulsion system and this will get you about the same speed.
__________________
fastcat435 is offline   Reply With Quote
Old 15-07-2011, 05:59   #23
Senior Cruiser
 
skipmac's Avatar

Cruisers Forum Supporter

Join Date: Oct 2007
Location: 29° 49.16’ N 82° 25.82’ W
Boat: Pearson 422
Posts: 7,209
Re: Electric Propulsion for a larger boat

Quote:
Originally Posted by fastcat435 View Post
Hallo Skipmac

Electric propulsion is much more expensive than a straight diesel propulsion, there are however other advantages like no noise, smoke, sooth, diesel consumption, vibration, autonomy and a cleaner earth.

In order to replace your present engine you would need a 18/ 20 Kw electric propulsion system and this will get you about the same speed.
Hello FastCat

You don't have to sell me on the advantages of electric. Very aware and that's why I am so interested in the concept. However for my boating I would not realize some of the advantages you mention. More often than I like I end up motoring for hours or days which will require running a diesel genset so will still have some noise, smoke and vibration. Since a diesel/electric system allows you to decouple the diesel engine from the drive and boat I would expect a large reduction in the noise and vibration compared to a traditional direct drive diesel.

Also, for long range motoring would expect similar or even lower mileage from a diesel/electric compared to a traditional diesel.

Regarding the power, I have to say I am skeptical that an 18-20 KW (24-27 HP) electric would give me the same performance as a 58 HP diesel. Maybe have a similar cruising speed in calm conditions but do not think I would be able to realize the same speed motoring against a strong headwind and seas. My other concern is the power available when docking and motoring in tight spots where wind, current or other conditions occasionally require a short burst of max power to maneuver.

Would be interested in any test results or data you have showing relative performance in a broad range of conditions with electric vs diesel in a monohull. Plus very interested in the cost of a system. PM with details if you like.
__________________
The water is always bluer on the other side of the ocean.
skipmac is online now   Reply With Quote
Old 15-07-2011, 06:15   #24
Registered User
 
fastcat435's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: Amstelveen Netherlands
Boat: FastCat 445 Green Motion
Posts: 1,649
Images: 10
Send a message via Skype™ to fastcat435
Re: Electric Propulsion for a larger boat

Hallo Skipmac I forgot to mention a few other advantages, we have the system build in to a Catamaran that standard is equipped with 2 x 30 HP diesel sail drives, in case of electric propulsion we use 2 x 10 Kw electric Motogens ( motors/generators)
Top speed with the 2 x 30 hp diesels 8 knots
top speed with the 2 x 10 Kw motogens 8.2 knots

Yes you are right , your fuel consumption is lower with the diesel electric setup and while sailing you can regenerate so you can actually fill your ( electric ) tank
If we are in a hurry under power the single 22 KW generator is started ( it has a Volvo d 40 diesel inside ) and at a speed of 6 knots the generator cycles on and off while powering the motors and charging the batteries , once these batteries are at 90 % the gen set switches off again.
Our maximum speed under power with the genset running is 7.5 knots with out discharging the batteries. With this speed the fuel consumption is 4.5 liters per hour , this is 40 % less than what we would use in the diesel powered version at the same speed .

The torque on the electric motors is much better than the mentioned diesels, max torque at 0 RPM is fantastic, docking and motoring cannot get any better i believe.
I am not allowed to post costs of the system but if you send me a mail I can forward you details
Attached Files
File Type: pdf grafiek speed versus amps consumed.pdf (132.0 KB, 91 views)
__________________
fastcat435 is offline   Reply With Quote
Old 20-07-2011, 09:04   #25
Commercial Member
 
SReuther's Avatar

Join Date: Nov 2010
Location: Annapolis, MD
Boat: Moody376 37'10"
Posts: 3
Re: Electric Propulsion

Hello Skipmac,

Fastcat is right about the torque! An electric propulsion motor has instant torque, so at low speeds you have the same torque as at high speeds. As for your concern about bursts of speed, the electric propulsion system will handle bursts of speed very well in order to get you out of the way of danger quickly. Coupled with the right diameter prop with a good pitch, an electric motor can move even a heavy boat quite easily. Because of the torque at the prop shaft you actually don't need as many kW as you may believe. There are companies that have systems which will be large enough for your boat, and when used in conjunction with a good genset, you have a wonderful, more energy efficient, and greener solution to cruising. Check out ASMO Marine. They currently have systems up to 12kW in DC and will be introducing larger AC systems this fall at the boat shows in the US.

SR
__________________
SReuther is offline   Reply With Quote
Old 20-07-2011, 09:50   #26
Registered User

Join Date: Dec 2009
Location: Puerto Galera, Philippine Islands
Boat: Santa Cruz 50
Posts: 2,962
Images: 4
Re: Electric Propulsion for a larger boat

Quote:
Originally Posted by fastcat435 View Post
...The torque on the electric motors is much better than the mentioned diesels, max torque at 0 RPM is fantastic
Torque never moved a boat. Power, horsepower, moves the boat. You do know that your huge torque at zero RPM is zero horsepower, right? A long range cruiser who thinks she can replace her 58hp diesel with a 24hp electric motor is going to be seriously disappointed when some real power is needed.

I think electric boat technology is waiting for a new way to convert fuel to electricity. For a cruiser the genset is not the answer.
__________________
daddle is offline   Reply With Quote
Old 20-07-2011, 10:00   #27
Registered User
 
fastcat435's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: Amstelveen Netherlands
Boat: FastCat 445 Green Motion
Posts: 1,649
Images: 10
Send a message via Skype™ to fastcat435
Re: Electric Propulsion for a larger boat

You are rigth off course 0 rpm is also 0 torque however from 1 rpm up to the max rpm setting the torque level is almost the same ,
With a sailing vessel we already have the way to convert wind energy in to electric energy and in a very efficient way with out burning fossil fuel or raising Co2 levels
We fill our electric tanks ( batteries ) with wind and solar power .
__________________
fastcat435 is offline   Reply With Quote
Old 20-07-2011, 14:11   #28
Registered User

Join Date: Mar 2010
Location: Florida
Boat: Pearson 323 - Island Breezes
Posts: 178
Re: Electric Propulsion for a larger boat

Quote:
Originally Posted by daddle View Post
A long range cruiser who thinks she can replace her 58hp diesel with a 24hp electric motor is going to be seriously disappointed when some real power is needed.
Apparently ICE and electric motors aren't rated the same. The 58hp diesel engine is rated at its Max (Peak) HP while the 24hp electric is its Max Continuous Power.

An electric can burst past that rating though.
__________________
LauderBoy is offline   Reply With Quote
Old 20-07-2011, 14:51   #29
Nearly an old salt
 
goboatingnow's Avatar

Cruisers Forum Supporter

Join Date: Jun 2009
Posts: 12,433
Images: 3
Quote:
Originally Posted by daddle

Torque never moved a boat. Power, horsepower, moves the boat. You do know that your huge torque at zero RPM is zero horsepower, right? A long range cruiser who thinks she can replace her 58hp diesel with a 24hp electric motor is going to be seriously disappointed when some real power is needed.

I think electric boat technology is waiting for a new way to convert fuel to electricity. For a cruiser the genset is not the answer.
What nonsense. Torque is a measure of angular force. Max torque at zero rpm is not zero HP that's only a function of the internal combustion engine. It's not a function of steam engines, electric motors or draft horses. ( it's known as stall torque and diesels have zero stall torque)

Electric motors generate far more useable power over their speed range. Diesels don't generate anything like the stated HP over the rev range. Hence a lower rated electric motor can generate far better vessel response then a diesel one. This is especially true for during manoeuvring.

Electric motors also accelerate faster and have significantly fewer parasitic loads ( and that's not including mechanical gearbox losses then exist on diesels )

Electric motors are ideal prime movers the problems are with energy storage.

But a efficient genset/ hybrid system is still more efficient and will return better consumption then a straight diesel.

Dave
__________________
“You can’t believe how bleeding scary the sea is! There’s, like, whales and storms and shit! They don’t bloody tell you that!”
― Libba Bray, Beauty Queens
goboatingnow is online now   Reply With Quote
Old 20-07-2011, 14:53   #30
Senior Cruiser
 
44'cruisingcat's Avatar

Cruisers Forum Supporter

Join Date: Sep 2006
Posts: 3,986
Images: 69
Re: Electric Propulsion

The electric torque talk is nonsense - how can you have maximum torque at zero rpm? Or 1 rpm or 5 rpm? You're supposedly applying the MAXIMUM torque the motor is capable of producing to the propellor, yet it's only turning at 0 or 1 or 5 rpm? Nonsense. Either that or it's a very weak motor.

That stuff applies to cars, but not boats.

Fact is a diesel (or petrol) engine can turn the prop when it's idling. Put it in gear, and it doesn't stall.
__________________

__________________
44'cruisingcat is offline   Reply With Quote
Reply

Tags
electric, propulsion

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
400: Lagoon 400 Lucky Larry Lagoon Catamarans 567 08-10-2012 17:14
Hybrid Electric Conversion for a Cat jdisarro Boat Ownership & Making a Living 41 07-07-2011 14:14


Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

RV & Travel Trailer Communities

Our RV & Travel Trailer sites encompasses virtually all types of Recreational Vehicles, from brand-specific to general RV communities.

» More about our RV Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities


Copyright 2002-2012 Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 04:30.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2014, vBulletin Solutions, Inc.

Sailing News Delivered to your Email!

Stay up-to-date with the latest cruising news.

unsusbcribe at anytime with one click

Close [X]


ShowCase vBulletin Plugins by Drive Thru Online, Inc.