Solomon Technologies - "Electric Wheel" electric motor propulsion systems

Help David - I'm HUNG UP on batteries and weight! <smile>

It sounds to me as if the more batteries you add, the less your depth of discharge (all else equal). So things become a trade-off between the additional energy needed (and space) to carry `round the extra weight, vs. the replacement cost of the batteries, which'll shrink as you can get more cycles between replacement because of the smaller DoD?

Thank you for your post

Lock

 

Batteries

It is only a nit, but Solomon uses either AGM31 in their single system, which are group 31 batteries that are 105 AH and 69 lbs and $150 each or AGM4D in their twin systems which are 4D batteries that are 210 AH, 135 lbs and $240 each. So if you use the AGM31 you would save $300 and if you use the AGM4D you save $480.

The AGM31 figure to $1.42/AH and the AGM4D are $1.14/AH, so if you need a lot of amp hours you are better off with the AGM4D. OTOH getting 135 lb versus 69 lb batteries into the boat is physically more challenging.

Using 120 volts instead of 144 volts will reduce power by 5/6, so you will have 5 HP instead on 6 HP or 8.33 instead of 10. This means that your ferry will go proportionally slower for a given efficiency. In reality you will design the most efficient hull form you can and then select the power level that provides the speed you desire.

Your calculations are essentially correct, if speed/power is held constant, then fewer batteries will mean deeper depth of discharge which equates to shorter battery life and higher operating cost. If you design the system so that your daily DoD is 40% and the ferry operates 365.24 days per year, then you will replace the batteries about every 4 years. Likewise at 50% DoD you will replace batteries every 2.7 years and at 60% DoD you will replace batteries every 2.3 years.

Once you figure out your daily power requirements, then you can play with the battery options and optimize your life cycle cost. For example lets just say you determine your daily power requirement are 100 amp hours at 144 volts. To do this with one set of AGM31 batteries would require a 100/105 = 95% DoD. At this DoD you would get about 365.24 cycles and you would replace your batteries once per year $150 X 12 = $1,800/yr = $ 4.92/day. Is you use 12 AGM4D batteries the DoD = 100/210 = 47.6% so you get about 1,000 cycles or 2.73 years cost is $210 X 12 = $2,520 every 2.73 years or $923/yr = $2.53/day. If you use 24 AGM31 batteries DoD is 100/(2*105) = 47.6%. Cost will be 2 X 150 X 12 = $3,600 and cost per day is $3.60.

Another factor to keep in mind is we commonly treat battery capacity as though it is constant, but the definition of end of life is when the fully charged capacity is less than 80% of the new battery fully charged capacity. So the AGM31 batteries will actually have 84 AH capacity at their end of life and the AGM4D will have 168 AH capacity. As you can see, when you start approaching the end of battery life the DoD actually increases because capacity is decreasing, which causes a shortening of the battery life.

Cheers;
Mike Schooley

 

Solomon Technologies Electric Wheel

Gentlemen...First...our motors are designed to be capable of 4KW (6HP) at 120VDC....that means you can actually get more power out of them at 144VDC (but we limit the control so you can't...sorry!...they last longer). Depth of discharge is really independent of voltage...but for one principle...in watts ...voltage and current are inversly proportional...and...the true measure of how much depth of discharge you can get on a battery without doing damage to it is current....lower current and you can discharge them lower. To blanket applications with generalized statements doesn't work with lead acid accept when you talk current. Batteries do not like high current draws....that's why we went to a higher voltage. 4KW...at 24VDC=166amps(bad do not discharge more that 40-50%).....at 120vdc=33amps(much better and you can take them down to 60%)....at 144vdc=27amps (even better still and we have taken them to 80% without any damage). It' all in the current...actually we recomend to our users that they only do this in emergency and when they do reduce the throtle control to 2KW(or about 13.5 amps) so damage is prevented. More volts actually yields larger depth of dischare because of reduced amperage to produce the same power.
Also....we are not trying to send every one out there with just batteries! 3/4 of the boats we have done todate are diesel electric hybrids...think about this.....a 4KW diesel generator weighs in at about 200 lbs. with fuel (or 3 group 31 batteries). This means you could go with less amp hours for normal operation but still have the ability to have unlimited motoring if necessary. The key is NORMAL, or cycle of use, or mission profile, or standard operational scinario. The size of the generator(or shore charging capability) and batteries are both on a sliding scale. You must first figure out what your cycle of use is. Also, there is no where in anything I have read or experienced that indicates if you use 30% of the batteries power that it comprises a whole cycle. We have AGM that have been routinely charge and discharged to 40% hundreds of times with no degradation in performance at all.
This is not how FF motors work and there is more to think about.....BUT....you can taylor a diesel electric hybrid/electric system to your specific needs and minimize energy usage or increase energy usage with more power and ammenities. I personally chose more power....Yes I have a 28 ft. sailboat with TV/VCR, Microwave, electric stove, refrigerator, stereo and electric back masager......for me more power.

<Admin Edit: Post moved into the main thread>

 

Gentlemen...sorry the other post for answers to the 120/144 quandry was poseted in the wrong place...I somehow pushed the wrong buttons....now...some questions:
1. What is the typical efficiency of a Generator making 85% of the KW it was designed to make?
2. What is the typical efficiency of a fossil fuel motor through it's normal cycles of use(No...not motoring for two weeks to cross the Atlantic....normal cycle of use...idling at warm up...around dock...in weather...etc.)?
3. What was the typical HP of a steam engine and what size prop did it push?
4. How does that differ from todays Gas motor? Todays Diesel motor? Why are diesels thought of as "more powerful"
5. How important is torque to overall system efficiency and propeller size/efficiency?
Hope this helps.

 

`s OK David. Wasn't hard to spot. Thought this particularly interesting:

Hehe... HELPS??? Just makes my head spin David.

My quandary (?) with electric gets back to a wide range of load and wind/water conditions. Our "sheltered waters" can kick up 3ft.waves and 60kts of wind some days. Very rare, but needs to be considered. Plus the boat (40-people ferryboat) I'm interested in can be running from 1 person to 40 persons plus gear.

I'm leaning toward something like a Bobkat 1050 with seats removed (39-passenger + driver limit) to make more cargo room:

http://www.boatloft.co.za/fe10.htm

Or something like the Aquabus C60:

http://www.mwline.ch/references.htm

These are both catamarans...

I'm also interested in what Water Taxi, Inc. and Canal Boats are launching for Fort Lauderdale (interesting, they went monohull):

http://www.watertaxi.com/WaterTaxiHome/WTHome.Asp

My very uneducated thought on the range of power requirements (from light ship, flat water & dead air to 40 persons, gear, 60kts wind and 3 foot waves with chop), would be twin motors/props at the light end of conditions, and a THIRD (electric) outboard in the middle of the transom, which could be lifted entirely out of the water when not in use, but pressed into service if/as needed. Something like James M. Graham's Reservoir Runner.

http://www.qis.net/~jmgraham/resrun.htm

Question is, could twin ewheels handle things if/as things get hot and heavy? I don't think the battery bank would be much of a concern (all else equal), as I believe the heavier conditions would mean a deeper DoD in the short-term. (We have more light air days on Lake Ontario in the summer - when the boat runs for longer hours - and windier days spring and fall, when the boat operates for fewer hours daily.) This just seems to me to be perfectly complementary, electric propulsion-wise!

BTW, I don't see the waves as much of a hinderance for a slippery hull(s) - more the winds and fully loaded craft. I'd be looking at a pretty slippery superstructure as well, to minimize windage.

Lock

 

Loch.... Sorry for the questions but I am hoping that some of the respondents will soon realize what we are talking about here and I won't have to spend to much time arguing with folks that don't get the point. The questions....here are the answers:
Torque is all important to pushing props...our motors are somewhere between a steam engine and a diesel...diesels develop more torque than gas engines and our motors develop more torque than diesels...this means you can have a bigger, more agressive prop....that means you will have more ballard pull/push which will give you better ability to punch through waves. Case in point: We did a Cheribini 44 that had a 50HP perkins and a 17"14pitch three blade....in heavy weather and waves it lost speed from 7 knots down to 4 1/2 knots. It now has a Solomon 74 and a 20"16pitch 3 blade and does the same 7 knots but in heavy weather only looses 1 knot down to 6. (This Cheribini left England in January gales and came accross the Atlantic to Tortolla....I think the English channel is probably as rough in January as your gonna see....)
Not to worry...Solomon does not do Fast at this point...we do slow and powerful(Fast will come later).

 

David - please take it (the heated stuff) just as discourse. Reason will prevail, and if not, just tack around <smile>

Gotcha. You should let me scratch my head a bit more though, first ...

Punch through waves? Hmmmm... I'm actually more concerned about punching through WEEDS. Seriously, our lagoon has mats of broken weeds on the surface, and growing from 4-6 feet down.

I like what the good folks at Asmo Marine are saying.

http://www.karvi.com/technology/tech-speednozzle.htm

I'd like to see twin steerable korts/speednozzles at the end of the rudder shafts, replacing rudders. Could you characterize an electric setup like this, with the korts, as "QuisineArt" for weeds?
Also wondering how much weeds can degrade prop efficiencies, if the props are fouled, even a bit.

hehe... cool.. Thanks David

Lock

 

Lock...I have heard about Court Nozzles...and the Lifeboats we are doing with Alexander Ryan have them. They will only help prop efficiency and like everything that pushes water, blade surface area and slow turning speeds are the key to optimization. To answer your question about degradation in prop performance based on weeds....I don't really know other than we can probably assume that it will take more weeds to foul a larger prop than a smaller one....as far as the nozzles...they can only help prop efficiency.

 

Sorry.....that is Kort nozzle....and spelling used to be my strong suit. So I guess none of the experts decided to answer the questions about prop size.....well here ya go.
Steam launches had props in the order of 26"-40" because the engines were not more that 200-300 RPM's. The resultant efficiencies were incredible...some times transferring 85% of the power to the water in movement. Typical prop efficiencies today are 40-50%loss for gasoline and 35-45% for diesel engines. Brushless DC Electric motors do not have a torque curve like these motors...they have a torque plateau...or constant torque, it is the same at 1 RPM as 1000 RPM's. These motors can push very large diameter props with ease because they do not have to build velocity to build torque....the same motor can push a 16", 17", or even a 20" prop. Taking advantage of this phenomenon allows the boater gain what would have been losses on other systems...amazingly these gains are as much as 30% of the power being expended. When you think of it in Horse Power....if you had a 50HP diesel and lost 40% to the prop you would be loosing 20 HP. This also means that if you could decrease prop loses to only 20% you could push the same boat to the same speed with a 30HP motor. The key to boating efficiency is props...the bigger and slower the better.
Now add to this a substantial reduction in complexity...what number of parts is a diesel engine and it's transmission comprised of?......oh....about 1,500. How many of those parts can cause a hard failure and complete loss of propulsion?....oh...about 1,000. How many moving parts does a Brushless DC motor have?....1 (ONE, UNO, UN). How is Mean Time Between Failure (MTBF) calculated ?.....simply put.....Number of Parts X Possible Failure Modes...The higher the number of parts the lower the mean time between failure. This is why the US Navy's top analyst's at Office of Naval Research are hell bent to have Electric Ships...Better MTBF...less tools...easier to understand...easier to replace...better prop efficiency....
Oh...did I mention that Solomon motors have a design life of 250,000 hours......compare that to your diesel....planned obsolence...what....we don't play that!!

 

I Beg to Differ

In Dave Gerr's propeller handbook the graph on page 80 shows that the maximum propeller efficiency of 79% is achieved for Bp values (N*Pd^2/Va^2.5) between 4 and 5 and delta of 80 to 90 where N = propeller speed in RPM, Pd = power at propeller in HP, Va = Vs*(1-Wf) where Vs = vessel speed in knots and Wf = wake factor and delta = N * Dp / Va where Dp is the propeller diameter. For displacement vessels Wf is a function of the hull block coefficient and is provided in a graph on page 68. The lowest Wf value of 0.64 occurs for a block coefficient of 0.8. Using N=200 rpm, Pd = 6 HP, Bp reaches 5 at a speed of 17+ knots and 4 at 19 knots. Solving for the propeller diameter that provides a delta of 90 at 17 knots yields a required propeller diameter of 2.75 feet or 33 inches. If you increase power then the value of Bp goes up and the speed where a 79% efficiency can be achieved increases. Decreasing power to 1 HP returns a Bp is 5 at 14 knots. I think that reaching a propeller efficiency of 79% is very difficult and exceeding 79% is impossible.

It is true that electric motors have a flat torque curve and gas and diesel engines tend to develop their maximum torque and power at higher speed than high efficiency propellers operate. That is why most gas and diesel engines have transmissions. It is also true that an engine needs to supply adequate power and torque to meet the propeller demand. This is the reason that diesels can out perform gas engines. Most gas engines do not meet the torque demand curve so they are torque limited.

For boats that operate at less that 35 knots you always use the largest propeller that the boat can accommodate with sufficient clearance to achieve the maximum efficiency. Many times the propeller diameter is limited by the maximum draft requirement. For a given propeller diameter (limited by clearance and draft) and assuming a properly sized transmission the propeller efficiency for the electric motor and diesel engine should be the same. Typical propeller efficiency for displacement craft is 55% but with good design 60% to 65% is achievable. The diesel drive will have a 2% to 3% power loss in the transmission.

You could achieve an 8% to 10% improvement i.e. 60% goes to 64.8% to 66% (NOT 68% to 70%). You could also get an 8% to 10% improvement from counter rotating propellers.

You are comparing the MTBF of your motor alone to that of the diesel engine and transmission. While this is acceptable for the electric only boats, most are hybrid diesel electric. For the hybrid system you need to compare the MTBF of the diesel engine, generator and motor to that of the diesel engine and transmission. If the diesel engines are the same, then you are left comparing the generator and motor to the transmission.

Cheers;
Mike Schooley

 

Batterys?

Don't you guys listen at all?

No batterys - hook up them electric wheels to MEGS ...Motionless Electromagnetic Generators...end of problem!
Batterys - sheesh - we've sunk back to that level already?



Go read the patent.

http://www.prahlad.org/pub/bearden/patent_meg.htm

It's inside 12 months availability folks.....no need for batterys - London to New York non stop.

You want "FAST"?

No problem couple a few Megs in series - you got all the fast you can handle!

Imagine this - without the fule bills! :idea:

I dunno guys - talk about leadin a horse to water and not makin it drink!

Look it's too simple....

Albert Einsteins theory of relativity (neva loan munney to relatives ) gave us the nuclear age

E=MC2

This powers Air Craft Carriers, Submarines & whole City's.

Beardens Scalar Potential gives us this, The secret to the energy trapped within the space / time continuum.

E= Delta TC2 where delta T is change in time.

Resolve the two and what do you have?

E=MC2
E=DeltaTC2

Therefore

MC2 = DeltaTC2

Therefore

M=Delta T.

Thats right, Mass = Chage in time, & without "change in time" this pissant electric ferry for Canada could damn well "hover" across the water cos it'd have no mass!

It's sooo simple and you "learned folks keep dismissing it outta hand - I'd a expected better from an electric wheel expert frankly!

C'mon guys - lets get with the program eh?

Cheers!

 

Ahhh....Mike....but the Diesels are not the same....it is the duty cycle of any deployed aparatus that comes into play in the MTBF calculation. The generator has a favorable duty cycle and the inboard diesel does not. The generator is ballanced and blueprinted to make electricity with a ballanced load...it starts...goes to optimum efficiency and stays there. The inboard diesel is often started then just shut off....or idled for long periods...or used to charge batteries at an inefficient RPM...or run too hard because of bad weather and currents. The generator is unaffected by this because the batteries are a buffer allowing it to always be in it's happy little environment making electricity. Check with any boater that has had generators in his boat and you will find that they survived several engines and were easier on oil and filters. We have also found that because they are also used for house power they get used more often which is another bad part of the diesel inboards cycle of use.It doesn't get used enough....the oil drains off of the cylinder walls and pistons...and when it does start it bare metal grinding...that's why Yanmar tells everyone to let the diesel Idle for 15 minutes before use....wait a minute...most folks only use their sailboat motors for 10 minues.

 

Re: Batterys?

`Been trying to read Tom Bearden's paper Trouty. Tough slogging for us little guys, ok?

Hey, I asked you for a prototype to play with... but "inside of twelve months"? I can wait. The designed life of the oil burner I want to replace is 50yrs. BTW, don't sell out to the battery mfgrs., OK?

Lock

ps... if we can chuck the batteries, maybe I can get that bar I want on the boat, with the weight saved... yah!

 

Just a thought on refueling - diesel or gas vs electric...

What are the chances of filling up with dirty diesel or gas that can gum up the works?

and

What are the chances of filling up with "dirty" electricity? With the right charging electronics, I assume this is impossible...

I'd rather have electronics doing the "filtering" rather than have to deal with replacing fuel filters, whatever...

Just 2 cents

Lock

 

Trouty,

A couple of comments on the MEGS delta T thing.

It this technology is a powerful as you say, why mess around with powering boats. It can power the world!!!

We went through a bout with cold fusion a few years ago and that disappeared in a shambles.

Some few years before that we were told that nuclear power would make electrical power too cheap to meter. Say what???

I am not dumb but can not find the reason why MEGS doesn't violate the principle of conservation of energy which has never failed us since we got up on two feet.

As far as I know delta T is part of every source of power that we have ever made use of.

Can you give any references where the principles of MEGS has been explained in layman's terms in the scientific press? I don't mean the uneducated layman but one educated in engineering principles.

You have made some denegrating remarks about the lack of understanding or intelligence by members of this forum. Since some of these people seem pretty smart, maybe the fault lies in the clarity of your claims and explanations.

I am not trying to slam you but do need more information in order to get interested. Where's the beef?