Estimating Electric Consumption

Discussion in 'Electric Propulsion' started by Jedidiah, Mar 18, 2018.

  1. Rumars
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    Rumars Senior Member

    The problem is the EP 100 only makes 42.5kW continuous. Peak power that can be sustained for 1 or 5 minutes is irrelevant. And for the price they want you can get a lot better. Just take a look at what evwest sells you for that kind of money. And truth be told I doubt if you open the Elco package you will find something to justify the price.
     
  2. Jedidiah
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    Jedidiah Junior Member

    How much power do you think it takes to puckle along at a who-cares-when-we-get-there pace on sheltered inland & coastal waterways? If you'll recall, in my first mention of ELCO I said clearly that I have issues with them & am still looking - primarily for a more favorable power density, but I'm not going to fault them as a company.

    You're basing your opinion of ELCO, of course, on vast personal experience with ELCO hardware, right? Obviously, you've had that disappointing unboxing experience yourself.

    I have seen their hardware, & it's anything but shoddy. It's very conservatively designed, perhaps too conservatively designed for my own purpose, but it's extraordinarily well built & it should be utterly bullet-proof. It's the caliber of hardware that gets passed on to grandkids.

    It was ELCO that showed up at the Chicago World's Fair in 1893 with 55 electric launches that stole the show. They went on to build who knows how many electric boats & had a significant involvement with early submarine development. Additionally, they built around 3,000 internal combustion yachts, all highly regarded, & 1,500 or more military craft, 400 of which were PT boats. Finally, they were one of the 4 companies that consolidated to form what we now know as General Dynamics.

    Having no interest in building plastic tubs for the masses, they got out of the private marine market for many years, but now they're back with electric propulsion units that are designed to replace internal combustion in a wide variety of boats, including the heavier cruisers that they built themselves back in the day.

    Tell you what - I'll take care of building the boat, & then I'll go enjoy it with absolutely NO concern for having spent the money that was saved & invested over 40 yrs time for precisely that purpose. You can stay here & argue with people for no particular purpose.
     
  3. gonzo
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    gonzo Senior Member

    That kind of attitude is uncalled for. If you enter your project in a public forum, people will have different opinions than yours. That difference of opinion is not a license to insult other posters.
     
  4. Jedidiah
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    Jedidiah Junior Member

    Gonzo, I agree completely. If you'll read through the thread you'll find the nonsense that I lost patience with.
     
  5. gonzo
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    gonzo Senior Member

    There are some basic wrong assumptions you are making. For example, the the efficiency rating of an internal combustion engine is compared to a 100% efficient electric motor. Even when you buy electric power from a company, there are significant losses in the production and transmission of the electricity. Also, you are comparing engines of different power ratings. If you want to only go at 10 knots, then a much smaller internal combustion engine would be appropriate, and that is what should be used in the comparison to electric. Further, batteries discharge even when not being used. Gasoline or diesel, if stabilized, last for many years without losing energy content. Further, your efficiency rating of a diesel, even old ones, if artificially low to prove your point. Mechanically injected diesels are about 40% efficient; twice what you claim.
     
  6. Jedidiah
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    Jedidiah Junior Member

    FINALLY somebody calls me on the 20%. I was looking to qualify comments with that, & wOw did that ever work. I think you're bang-on for newer, state of the art engines but the thermal efficiency of antiques like those 6-71s is closer to 30-33%. My old Cummins buddies are tight-lipped about hard data & they for sure don't like talking about electric vehicles, but I'll ask them the same question I asked here & see what they have to say.

    IIRC, Cummins publishes brake specific fuel consumptions for their own engines, & they've been testing the products of every diesel manufacturer in the world for at least 80 of their nearly 100 yrs in business. I haven't looked at Cummins numbers because Cummins engines don't appear in the elderly ladies that interest me, but they do have decades of test data. My own most difficult barrier to the archive might be the guys that don't like it when I take their poker money.

    I'm not a cheetos-chomping basement dweller looking to prove a point. As very clearly stated, I'm looking for a quick & reasonably valid assessment of any given hull. Liquid fuel consumption should be all it takes to ballpark electric consumption if all other factors remain equal, & just say'n, grid transmission losses have squat to do with that. If you'll look again you'll see NO suggestion of 100% electrical efficiency in my original or any other post. The relevant & real electrical efficiencies to consider will occur within the hull, just as the liquid fuel efficiencies do.

    ... & THAT's the topic. If anybody wants a potential gold mine of a forum to function, yeah - a little decorum might be in order. The topic isn't what anybody thinks of a business they don't know anything about, or what anybody should do with their own money, or BS arguments against what specifically has NOT been said, or even whether or not a contemplated project is practical unless THAT's the topic stated.

    Of course it's not practical, it's development - of an electric-can-replace-ICE paradigm if nothing else - & development never is practical in the short term. Financial feasibility comes on the other side of the adoption curve along with more common usage & attendant economies of scale. To make that happen with electric vehicles, those who truly believe that we no longer need to burn stuff for power need to make it happen - & then take everybody they know out for a boat ride.

    Right?

    I'll talk about the engineering all day & night, & do it with high hopes of LEARNING something from people who know what they're talking about, but I have zero time for flaming, off-topic forum squabbles.

    Life's too short, it just is.
     
  7. Joakim
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    Joakim Senior Member

    Calculating a few points from this, the efficiency seems to be over 35%. Only at very low power (around 100 hp) the efficiency drops below 35% and even to 30%. But why would one install a 485 hp engine, if only 100 hp is typically used?
     
  8. Joakim
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    Joakim Senior Member

    According to this, a lower power 6-71 has at least as good efficiency. It produces 110 hp (80 kW) at 6 gal/h or for twin installation about 2*45 hp = 90 hp (70 kW) at 2*3 gal/h.
     
  9. Jedidiah
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    Jedidiah Junior Member

    I wouldn't & I don't know why anybody would in a displacement hull. The boat I'm looking at has, at most, 440 HP. The broker says 220 per shaft, the owner says 200. I would call that over-powered for no purpose, given that according to Gerr's it only needs 156 hp to achieve a hull speed of 10.6. With this particular boat, 485 hp would be less than 13 knots & a ferocious rate of fuel consumption, so what's the point?

    ... & I'd have to say that putting boat & crew into more trouble than a hull-speed capable boat can get them out of is a seamanship issue.

    The light duty loads, in my case, are related to where I intend to take the boat. Rivers mostly, the ICW, the Erie Canal, the Great Lakes, etc. Setting aside no-wake & manatee zones, no boat of substantial tonnage needs to be bombing along @ 10 or more knots in confined waterways. There are plenty of places like the Great Lakes, Kentucky Lakes & other navigable reservoirs, Chesapeake Bay, Mobile Bay, etc, where opening her up to speed would be fun, but even a river as substantial as the Ohio looks pretty cramped when you come around a bend & meet a towboat that's setting up to swing the turn with a float of 15 or more barges.

    I suspect that a great deal of my mileage will be in the 6 to 9 knot range, & when I am making turns for 10+ it'll be against a current.

    So maybe the owner's 2 mpg claim is valid, & this is the point. If we know what the boat actually burns at any given speed, we know what the hull needs to achieve that speed. In an electric conversion, we then get range by deleting ICE related junk (& otherwise lightening her up as much as possible), then replacing that deleted weight with electric propulsion & the batteries to power it. This is something that I should be able to do on my feet from any dock within range of a cellular data connection.

    The problem is with finding out EXACTLY what a boat burns at a range of speeds. I can get a manufactur's power curves without respect to the hull their engine's in, but what I'm actually looking for is the consumption curve of a given engine in a given hull.

    Example - around a year ago a 46' 1931 Herreshoff Bridgedeck named Ariel II was on the market (@ $750k it might still be). It looked interesting, but the layout was more Day Cruiser or Launch appropriate than liveaboard, 3/4 of a million dollars was a non-starter for me, & the historical significance of the boat says leave her as-is - but there are other similar boats - a few surviving ELCO cruisers, for example. What would be more appropriate than re-powering an old ELCO Flat-top with a modern ELCO driveline, right? Even so I ran the numbers on that Herreshoff as best I could & ended up deciding that even if I could find one like it at a fraction of the asking price, that I just wouldn't be able to pack enough batteries into it or pull enough power off the roof to make it a cramped but practical liveaboard. The difference between 55+' & a lightly built 46' is significant, so, I'm looking at larger boats in usable or at least salvageable condition.

    Wood required - as an aging mold designer there's nothing I hate more than plastic.
     
  10. gonzo
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    gonzo Senior Member

    I think that the flaw in your argument is that there in no consideration for the coal or gas burned to make electricity, or used on the maintenance and repair.
     
  11. BlueBell
    Joined: May 2017
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    BlueBell "Whatever..."

    Jedidiah,

    You high-jack your own thread!
    Most entertaining, thank you.

    The answer you seek is so simply answered, you're going to blush.
    The low power hull is the light-weight, long and skinny one, duh.
    You didn't even need to mention electric!

    There you go, at a glance, dockside, if it's long, narrow and light-weight it's going to be low drag.
    Simple as that.

    But are you going to find one that meets your needs?
    Have you considered building, or having a hull built specific to your needs?

    It's really all about your needs and what you want, need, expect, the thing to do.

    Oh, and of course the other, all important variable,
    Speed, the ultimate power consumer.

    So, lets cut to the chase, what are you really up to?
    That may best be revealed in a new thread, no?

    PS What are ED Meds?
     
  12. Jedidiah
    Joined: Mar 2018
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    Jedidiah Junior Member

    Oh ffs- y'all just grab another bag of Cheetos & dig in. I'm done here.
     
  13. BlueBell
    Joined: May 2017
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    BlueBell "Whatever..."

    Emotional Dysfunction Medication perhaps...

    Geeze J, I was trying to get you back on track, lighten up.

    I like the idea, but wait... what was the question?

    I thought you were approaching retirement, I'd expect a little more maturity, no?
     
  14. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    I think that reality is a bubble buster. However, it is not an excuse to insult the messengers. Physical laws are what they are; whether they suit you or not.
     

  15. gzs
    Joined: May 2018
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    gzs Junior Member

    Jedidiah: I would begin with thinking what the conversion would mean in terms of capcity, weight distribution, center of gravity, buoyancy...

    You've mentioned 1250 kW.. you can try and use 2170 cells, I wouldn't. A 1250 kW system costs a lot of money. The 2170s will overheat, and no matter what kind of battery cooling system you intend to use, a cylindrical cell will never be as good as a pouch cell in terms of life span and cycle nr (see Lithium Ion Polymer Cells - High Energy High Powerã…£Kokam Battery Cells http://kokam.com/cell/) . I would only use pro batteries.. that means 1,5 USD/Wh. 1,875m USD. Add BMS and motors and hull. If the boat is not operated commercially, it's quite an investment for a weekend boat.
     
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