electric or multifuel engines?

Hi Longliner,

I think your concerns about fuel are very valid. The "peak oil" thing isn't just something to scare the rubes, it is very real. And just like with "global warming" governments are trying to suppress info about it so their buddies can just keep on looting as long as possible. We, of course, ultimately get screwed, and that seems to be the Bush plan in a nutshell.

Getting back to your question, One horsepower is equivalent to 745.7 watts. So, if your generator produces 5 KW, and you go to an electric drive you will have 5,000/745.7 or 6.7 horsepower, less about 15% for conversion losses, so lets call it 5.7 horsepower delivered to the prop. This does not give the whole picture though. From my reading I understand that because electric motors can deliver full torque at zero RPM, the equivalent performance horsepower is really about three times the rated horsepower when comparing to an internal combustion engine drive system. So, with your 5 KW generator and some electronics and electric motor drive, you should get the performance of roughly a 17 horsepower diesel engine from your 5 KW generator. I tend to give the three to one claim credance having used an electric trolling motor before. Those things can really pull!

But you can exploit such a system in a couple of other interesting ways.

Brushless DC motors are constructed with a bunch of permanent magnets in the rotor (the part that turns) and the windings to react with this field are usually mounted in a stationary part (the stator). Any time you are sailing and there is plenty of wind to drive the boat to hull speed, any excess energy your sails collect is simply wasted because of the hull speed limit. If your prop is in the water (I plan on making mine retractable and rotatable) the water passing by will spin the prop (it becomes a turbine), which means that those magnets are moving relative to the stationary coil of wire. This is exactly how a generator works. So, with a little of Walrus's electro-trickery you can collect the energy that would otherwise be wasted and charge some batteries.

If you have some battery capacity this can be used to power the motor when needed, and to supplement the generator when more power is needed than the generator can provide. This means that instead of powering the boat with a 6 horsepower motor as above, you might want to put in a 12 horsepower one and couple it to the batteries AND the generator when you really need some temporary power to get off a lee shore or whatever. This is basically what the hybrid cars like a Prius do.

Personally, I think that for most ordinary sailing you will end up keeping your batteries well charged by using your brushless DC motor for a generator when out in the wind, and you will discharge these batteries a small amount when getting into or out of a slip. Otherwise you will use the power for your lights, microwave, entertainment system, refrigeration and whatever else you want to use it for. If you want to take a run up the intracostal waterway and chug along all day, then you would run the diesel generator just like you would be running any other motor, except you will be more efficient.

As for costs, I really can't comment because I haven't looked into it. A brushless DC motor will be a bit pricy compared to an equivalent induction motor because the magnets (rare earth) are expensive. The engineering of the electronics will be a factor also, but doesn't sound at all difficult to me. And besides, once done, its done. There are the usual details, of course. The motors need to be cooled, as do the electronics, for example. I'm planing a metal hull, so I will incorporate a heat exchanger in the keel. There are lots of details, but nothing I see that can't be dealt with. And you could end up with a boat that, under normal circumstances, uses no fuel at all, ever.

Bill

 

Schock's Harbor 20 uses a swing-up electric outboard to get in and out of the slip, to make it to the starting line after work, and home when the wind dies. It's charged at the dock.

Duffy's top of the line model has an auxiliary generator.

This is not too different from what Solomon has been doing with their hybrid powertrains. Solomon has built a small trimaran and a couple of charter cats with just electric power, and regen under sail. There's probably a trickle charge from a solar panel too. If you can rely on wind for the regen, there's no reason it shouldn't work.

The only problem is the cost -- this is a lot of expensive gear and custom work to put into a boat. If you can do the design and installation yourself, you may be able to put together a similar system for a lot less.

 

Matt,

The costs will certainly mount up. Diesel motor/generators are reasonable because of the volume they are made in, and batteries are certainly available as well. That leaves the actual drive motors and the circuitry to tie it all together, possibly including some solar panels for a trickle charge, at least.

Just guessing without giving it too much thought, I would think that two 10 HP brushless DC motors should do the job for yachts up to 45' or so. Does anyone know what these would cost? Or, is this amount of power way off? I'm suggesting two motors because it would be handy to have them port and starboard to enhance maneuvering control. The motors could be mounted vertically in the engine compartment, with the shafts running through the hull to right-angle gearboxes and props. Then some linkage could be incorporated to enable rotating each vertical shaft/gearbox independently. This would give the driver an enormous control advantage. Each motor could be easily reversed as well.

A bank of 10 twelve-volt batteries makes some good ballast! Expensive ballast, but very useful.

Now about that circuitry. I'm going to get a little technical here, so if Electro-trickery isn't your thing you might want to skip this part!

Brushless DC motors are available that have three-phase stator windings and Hall-effect sensors looking at shaft position. Hall-effect sensors basically have a voltage output that is a function of magnetic intensity, so if three sensors are mounted with 120 degree spacing around the stator such that they see the magnetic field of the rotor (or a separate magnet), then the output of these sensors will be an exact analog of the currents that must be applied to the three stator windings to drive the motor, except that they will not be phase-shifted. (That is, if they aren't mounted with an intentional phase shift.) To actually make the motor turn, however, these signals must be phase-shifted a few degrees in the direction you want the motor to turn.

The signal from each Hall sensor can be digitized with an A/D converter. (Zilog makes lovely little microprocessors that can easily do the A/D conversion and subsequent logic. These sell for something like $2 each.)

The current from the batteries and the motor/generator (rectified, obviously) needs only a switching transistor on each stator winding that can handle the amperage. So, with a 10 HP motor we are talking about an IGBT (a type of switching transistor) that must handle the current associated with 7,457 watts at 120 volts . . . and using Ohm's law this works out to a little over 62 amps. We will actually be using three of them for this one motor, so we have a 3 to one safety factor there. I just skipped over to Digikey.com and did a quick look: a IRG4PSC71UD-ND sells for $21, can dissipate 350 watts of heat, can take a pulse current of 200 amps, a continuous current of 85 amps, and is rated at 600 volts. The collector-emitter voltage drop is 2 volts. We would be using a heat exchanger with most of an ocean to put heat into and cool this critter, so that 2 volt voltage drop at 62 amps (and this is assuming continuous current, not pulsed) works out to 124 watts of heat, no problem. Three of them, then, for $21 each, $63.

A little programming on that Zilog microprocessor, and we can go forward or in reverse and can adjust our speed from nothing to full out simply by phase shifting the control signals to those three transistors and adjusting the width of the pulses driving them.

Now assume you get lucky and catch a good breeze. The same equipment you have in the water to get out of the harbor will be free-wheeling in the current (if you leave it there) turning that big magnet adjacent to those three stator windings. I would need to work this out in a little more detail, but all the circuitry is already there to charge those batteries: your microprocessor knows what the phase of this output is because of the Hall sensors, and (a switch is probably needed here to get the polarity right) can pulse width modulate the output of the motor to the input of the battery . . . thus charging it. Battery charging is a tricky business to do right, but we have a microprocessor to handle that and monitor battery condition, etc. Charging with a series of pulses is well known to break up sulfides in the battery as well. It's very good for them.

So, after rattling on way too much already, I would guess that the electronics to tie this system together might run as little as a few hundred dollars. There is a large investment in engineering, of course, but you do that just once.

Perhaps we should start a sort of “open source” design effort. Any takers?

Bill

 

billy dock keep rattaling .I undersand most of it .as for voltage drop If I use heavier copper wire ,should fix that, now if I can use a small onan generator with dc and ac currant and a good electric drive unit Ill probably go that way.I feel really fortunate to be in this day and age were we can gather info from around the world at the speed of light, Im really thinking this will work for me (dc and ac for electronics)maybe 2 systems on board. Now wieght will be a factor.

 

Longliner and BillyDoc,

The reason I posted the links is to encourage you to look under the hood of some proven designs, particularly Duffy, who build electric boats by the thousands. I'm sure there are a bunch of Duffies in Florida. Dunno about Ohio. Go rent one.

Besides the electronic controls and charging system, you have to make sure your motor(s) are good quality and well-marinized. Otherwise they'll corrode in a jiffy. Duffy has solved these problems for themselves, which they can afford to do because they build so many boats. I don't know if you can buy a Duffy motor and controller separately though, or if the Duffy motor is a good choice for regen. ???

Awhile back I saw a really simple system with no controller per se, just a switch between 12V and 24V. The example boat was in the 30' range. This could work well for a sailboat, because all you need is a low power setting for maneuvering, and a high power setting for cruise. Many people just goose their boat in and out of gear while maneuvering in tight quarters anyway. This system could be built with with dead standard 12V and 24V marine parts. A genset could be added if desired.

 

mattoole thanks I will look into them .they have an up and running product .may be advantagous to me .I was wondering if anyone is online with what I want ,,,,,thanks again to all of you . buy the way Duffy makes a great downeaster

 

You never heard?

C'mon you guys - you never heard of Global Warming????

Longliner - maybe you need to talk to these guys!

http://www.tilleyfoundation.com/

On a dark night you could snatch the electrickery motor outta their cessna!

Cheers!

 

just my luck . the site is under construction...........do electric motors put off a lot of heat?I mean compard to diesle?

 

Heat is just another form of energy Longliner

yes - if a electric engine is putting off a lot of heat - then it ISN'T using the energy supplied to it efficiently and is instead "wasteing" all that potential energy that COULD be transposed into momentum for the vessel, as wasted energy in the form of heat!.

Notice just about all electrickery stuff today needs "heat sinks or fans" to get air to cool it?

Thats becasue electrickery isn't well enough understood - to be used efficiently...so much is lost becasue we DON'T understand it fully - we are well on the way but not 100%

I post stuff from last century or this, on Mass and Time (which are BOTH just different forms of energy!) and unless people can buy it at home depot and take it home and plug it in they say pooh pooh....

MEGS for example, Motionelss Electromagnetic Generators....free energy from the vacuum of space.. I post links to websites where all the details are, but still we have the knockers!

We are at "end of days" for oil or "peak oil".....and still people refuse to believe...

Einstein was considered the greatest scientist to have lived - for giving us
E = MC^2
(which lead to the nuclear bomb)

Bearden gave us
E = Delta TC^2

Which led to MEGS (and other tactical battlefield electromagnetic weapons)

I gave us

M=Delta T

You know what?

No one understands...

E = MC^2 gave us:-

Nuclear energy - made America a superpower, won WW2 with Nuclear bombs on Nagasaki & Hiroshima..

The US fleet have been sailing the worlds oceans (on top and underneath) now for 40 years on nuclear power!. (Energy in Mass)

You know what?

Time is just another form of energy like Mass is.

You know what else?

Theres as much energy within Time as their is within Mass.

(Thats what my theorem proves!)

You wanna know how MUCH energy is within the time domain?

9 x 10^16 JOULES per second (or thereabouts!)..

You know how much that is?

Bout the same energy as is in a molecule of enriched plutonium in a nuclear bomb!

Ask yourself this ONE crucial question.

Would the world be ruled by a nuclear superpower USA IF another nation grasped the import of M = Delta T BEFORE the USA, and weaponised it or ran it's INDUSTRY on that free energy?

How will the USA remain the worlds superpower (and get out of annihilating the whole gaddam world over the last few drops of oil soaked into those arab sands)...if they AAREN'T savvy enough to realise when they have the next great ages advance at their doorstep NOW?.

Has anyone from the USA military machine contacted me?

Nope!



And you guys are the most advanced nation on earth?

I dunno - but color me dumb - you really have to wonder some times.

Cheers!

 

Don't say much for the rest then does it?

 

damn; troutys got me so shook up Im just gonna get 2 long sticks and just pole my way in and out.,,,,,just kidding!IM really looking at electric power, maybe tilly has something. I would prefer a up and running unit........as far as being the most advanced nation, everyone has thier day in the sun ,,egypt rome exctra,,,exctra ... and they all crumble from whitin. ya never know when a good ocean going boat will come in handy. thanks everyone ,,,longliner

 

electric, heat, future, if getting desperate, just want to remind water cooled electric motors

 

That's right Yipster, and water cooled electronics too!

Not desperate at all.

Yet.

But then, it's early in the morning, there's still time.

Bill