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Old 29-08-2017, 06:18   #31
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Re: How feasible is 100% renewable electric cruising right now?

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Originally Posted by ranger42c View Post
Given our propulsion system, I'm really always an outsider to conversations like this...

But FWIW, that seems like an OK use case assuming one is willing to work the boat that way. I understand Columbus and Magellan and so forth sailed similarly in open waters, i.e., depending on wind alone.

But... even if that's the paradigm a user adopts... a situation that would seem to be critical is about any need for motoring in heavy weather, if necessary to maintain steerage, power nav equipment, whatever. The calculation of how long batteries might last relative to how long dangerous weather might last... seems to me like a big deal.

And of course, budget. Cost of a boatload of LFP batteries and related systems versus cost of a new (or maybe a rebuild) diesel? (I don't have a clue what that specific comparison would be like for OP's boat/engine, but doing that analysis may be useful if not already done...)

-Chris
The electric power question comes up every couple of months or so and the answer hasn't changed nor do I expect it to for the foreseeable future.

Final answer, unless you add a large diesel generator and a large battery bank, electric power is only suitable for very short range, typically leaving and returning to the dock or anchorage. Of course once you add the large generator and battery bank electric becomes much more expensive than just putting in a new engine.

There have been several advocates who said they could build an electric powered boat with long cruising range without running on a generator, refuting all the advise and data from the forum that shows otherwise. So far not a single one of these has ever come back to the forum with a finished project to say I told you so.
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Old 29-08-2017, 06:28   #32
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Re: How feasible is 100% renewable electric cruising right now?

... The size of the battery will be (a single cell is: 560×130×356 mm)

1.2m x 1.04m x 35.6cm - a pretty small footage of 4ft x 3ft x 1ft.



and here another one: https://cleantechnica.com/2017/04/24...ewable-energy/



http://www.guinnessworldrecords.com/...r-powered-boat

http://newatlas.com/turanor-planetso...es-trip/22421/
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Old 29-08-2017, 06:46   #33
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Re: How feasible is 100% renewable electric cruising right now?

On the last boat show in La Grande Motte I saw this one:

https://www.designboom.com/technolog...ht-01-16-2016/

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Old 29-08-2017, 08:50   #34
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Re: How feasible is 100% renewable electric cruising right now?

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On the last boat show in La Grande Motte I saw this one:



https://www.designboom.com/technolog...ht-01-16-2016/





Stunning vessel !
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Old 29-08-2017, 09:07   #35
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Re: How feasible is 100% renewable electric cruising right now?

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I've been very impressed with how much juice I can get from the sun to run all sorts of things on my boat without ever plugging in or running the motor - my wife's 2000 watt 110v hair dryer being the thing I'm probably most proud of.

I have a Pearson 424 (22,000lb disp). Some folks in my owner's group are re-powering with Electric Yacht's Quiet Torque 20 motor with supposedly great results. I'm not sure if they're doing hybrid (diesel generator) or all electric. There will probably come a day where I too will have to replace my good old W58 motor. Our boat lives on a mooring, and when we cruise we either anchor or pick up a mooring - so we never plug in.

If I remove the motor and diesel tank, I now have a massive empty engine bay - roughly 5'x4'x4' and the space where an 80 gal diesel tank was (about 5'x4'x3') behind that. The electric yacht QT 20 will supposedly fit where my old V-drive was under the cabin sole. So, I have a ton of space for batteries. I imagine weight would likely be my limiting factor for batteries, not space.

For experiment's sake, let's say on average I have to motor my boat for 2 hours every day at 6 knots with the Electric Yacht QT 20. Let's also say I'm in a sunny, windy place at low latitude - say Curacao.

Assuming these things, how much solar, hydro-generator, and wind charging wattage do I need to be a completely "off the grid" yacht?
a 42' boat at 6kt for 2 hours calls for a really big battery bank. You can roughly figure it this way. 1HP = approx 746w. Let's say you require 10HP to achieve that speed. So you estimate that you need 8kw for 2 hours, or 16kw/hrs Let's say you elect to use a 48v bank, or the prefab system calls for a 48v bank. If a different voltage, just do the math. Anyway, so you need 333ah of usable storage. For flooded lead acid batteries, you should not routinely discharge to below 50% SOC, so to get 333ah of USABLE storage you need 666ah rated capacity. Except that does not allow for high discharge rate Peukert Effect allowance. So you will need about 1000ah of storage at 48v. This would recommend single cell Rolls Surette 1000ah batteries, 24 of them. One likely candidate would be the S-1400EX. Weight wet is 127.5lb and remember, you need 24 of these. 17"H 13-3/8"L 7-1/8"W. Yes, you can reduce the weight by going with a slightly smaller bank of LiFeP04s since they can be discharged more deeply, but higher tech batteries come with their own set of problems in this type of application. Explore that idea, sure, but don't fall in love with it.

You can go higher voltage, but that won't really do much for reducing the weight and size of the bank. The only thing you could do to make it cheaper would be to go with a voltage high enough to get the same amount of energy from a series of golf cart batteries, but that would be about 145V and you would need a high voltage controller and motor for this. Also with that many connections, you will be continually busy just checking your intra bank connections.

So, you probably would want to re examine your power requirement and therefore your target speed. If you were okay with half that speed, you would probably cut your power needs to 1/3 of the above case, maybe less. You can still engineer the system to give you a reasonable top speed. One nice thing about electric is there is very little energy penalty for having a high power motor if you don't use it at high power. A big diesel at idle still sucks more fuel than a tiny diesel at idle. What I a saying is you could easily go with a 10kw or12kw motor and controller, but when you are running it at 1kw or less you get about the same performance as a 5kw motor running at 1kw. So, go with a big motor, but only use the power when you need it, not just when you are in a hurry or bored with going 2 or 3 knots.

If you can get your batteries down to lets say L-16 size, it would be a lot easier to place them not to mention buy them. I will let you find the specs and do the math on that one. Remember that 48v is sort of the sweet spot voltage for budget systems because of the large amount of equipment available such as chargers, inverters, controllers, DC/DC converters for your 12v loads, etc, and also wiring standards are different above 50v since it is considered the lethal voltage. (don't get carried away thinking about that... 48v CAN kill you, and 96v CAN be survivable, depending on a lot of factors.) Higher voltages mean higher reduction ratio, too. If you are going over 48v then you may as well go 96v or 120v or whatever, because 72v is already over the 50v threshhold. There is little to recommend a 60v or 72v system.

Electric propulsion is an idea that is easy to fall in love with. By that, I mean become so enamored with the concept that you pay little heed to reason, logic, or empirical data. Sort of like falling in love with the prom queen who later turns out to be the wife from hell, even though your friends all told you she was poison in a skirt before you married her. Don't dream too much into the idea. It can be VERY practical and economical, depending on your use. For a day sailer or weekender that has access to shore power charging and only needs power for docking, electric is wonderful, and is totally superior to infernal combustion propulsion in every way. For others, it is marginally better, or inferior. For some others it is totally impractical. At your performance specifications, it isn't very practical. Loosen up on the speed and it might be worth considering.

I love my electric boat. I have about a quart of diesel onboard, and that is just for cooking. I never visit the fuel dock, never spill fuel, never smell fuel. Shore power charging is waaaaaay cheaper than liquid fuel. Pennies to putter around all day. Very quiet, especially at low power settings and with the hatch closed. Sometimes I can't even hear my motor. Instant power. No warmup. No maybe maybe when I hit a start button. Crazy maneuverability due to not having a minimum idle speed. For a sailboat, especially one that is hard to tack, a twist of the knob and suddenly you are hove to if you kept the jib aback, or on the other tack if you shifted to the new jib sheet. The instant burst of speed can be very handy if you find yourself being blown down on a bridge abuttment or something like that. I installed my drive system for about 1/4 of what a new diesel would have cost, and that includes my batteries. But I had to come to terms with the limitations imposed by having only 220ah at 48v, and being unable to afford bigger batts than that.

You should probably check with your owner's group and see if anyone else has electrified the same boat, what their performance data looks like, and the specs for the system. Start with some actual empirical data as you decide whether or not to go electric.

Hybrid can work, yeah, but if you can't charge from shore power and can't mount a minimum of 600w of solar where the sails won't shade the panels, you would be better off with just the diesel. Shore power is nearly free energy. Solar too, except of course for the considerable cost of panels and controllers. Hybrid is inherently inefficient energy wise, but free energy can make up the difference. Of course there are other reasons to consider hybrid, but make sure that they are really important to you.

Obviously, considering the weight, your old fuel tank location is not necessarily the best place for your batteries. Typically you want them near the keel area, and mine are right where the companionway steps used to be. It was tempting to put them where the old fuel tank was, but nah. I didn't want all that weight so far aft. I can probably add a second bank up forward and not put her too far out of trim. Figure out the weight of batteries and battery trays and hold downs and cable and stuff, then have an equal weight of people move around foreward and aft while you look at the trim. It could change the way your boat handles under sail. Down by the head and she will probably have a tedency to round up. Down by the stern and she will want to fall off. Sure, you can compensate with sail adjustment, but that is not always a perfect fix if it changes your slot enough to degrade performance. If you are talking 600lbs of batteries, no big deal unless they are waaaaay aft or forward. 1800lb of batteries is a whole nother critter.
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Old 29-08-2017, 09:25   #36
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Re: How feasible is 100% renewable electric cruising right now?

I'm pretty sure large ships use direct drive diesel engines. Trains are diesel/electric because of the high torque from O rpm of an electric motor needed to get all that weight moving from a dead stop. Ships don't need torque from low rpm as slippage on the props doesn't negates the need for low rpm torque. FWIW, large ships can't slow their engines enough to meet low speed requirements in ports. They typically have a tug astern powering in the opposite direction of the ship to slow them down to meet slow speed limits.

If you are going nowhere electric power makes sense. A boat that needs 50 hp to power into wind and waves will still need that hp whether it's electric or diesel. If you run a 50hp electric motor flat out your run time will be measured in minutes because of the huge drain on the batteries at full power. You will need a huge generator to power the electric motor in such conditions, not a 2,000 watt Honda. At a lesser hp output the electric motor will eat less electrons but your powering time will still only be a few hours. To get a decent range with solar panels will require covering most of the boat with them and that would be a catamaran deck area. Even then you'd be SOL once the sun went down and may mean powering for part of one day and waiting for the batteries to charge back up the next before powering again on the 3rd day, repeat till you get where you're going.

To give you an example of the real world. On a recent voyage from SF Bay to Oceanside, CA. had rigging issues and had to power for 10 hours to get to the closest port to effect repairs. Once the low passed, had to power for 72 hours straight as there was no wind to get to my destination. On another trip got stuck in the doldrums that required powering for more than 24 hours into large long period seas. In the first instance, if I didn't have the diesel would have been stuck at sea with 50k winds from the passage of a low. In the second instance, might still be stuck in the miserable conditions of the doldrums. On a solo sail to Hawaii had the self steering breakdown because of a lost nut. Had to turn around and power back to Sausalito for 36 hours. That day and a half could have been a month or more IF relying on solar to charge the batteries as there was a constant heavy overcast offshore that lasted for weeks. Okay, get a generator you say. Why have a diesel on board if you aren't going to use it to directly power the boat. I sympathize with the noiseless, smokeless powering of electricity, hate to have to turn on the engine, but sometimes you just can't get around it. Going electric so you have to run a diesel to get anywhere just doesn't make sense.

Until batteries that will allow long time powering bouts become available AND affordable, diesel auxiliary is the only propulsion system that makes sense for a cruiser.
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Old 29-08-2017, 09:33   #37
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Re: How feasible is 100% renewable electric cruising right now?

There are large hybrid car / truck ferries between Germany and Sweden running half way on batteries having large diesel generators on board to recharge.

So diesel-electric propulsion is already there in the commercial world in every day use.

The cat up there is really neat, you can close the lid of the flybridge deck by push-button in bad weather and steer from inside the salon. And you got a more aerodynamic shape while going windward. really nice and spacious, but $$$.



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Old 29-08-2017, 09:37   #38
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Re: How feasible is 100% renewable electric cruising right now?

Oh and as for wind, forget it. A wind gen is okay for keeping a small 12v bank topped up, but they are all too small for charging a big propulsion bank. Check with your battery manufacturer for proper charge current, multiply that by the voltage to get charge watts. Add a percentage for converting to 48v. That is how much sustained output you need from the wind generator at normally encountered wind speeds. I was considering building a wind charger from a homebrew alternator or a 5kw BLDC motor, but someone smarter than me took the time to sit me down and show on paper that to get 1kw output reliably I would need a rotor with a swept area diameter of about 10 feet. And gadgets usually work better on paper than in real life. Most ready made wind generators are from about 75w to 300w rated. I will eventually go solar, but I will have a hard canopy over the entire boat and no mast, and between 1800w and 2000w of solar panels. Basically all I can mount over the entire boat. Maybe more hanging aft over the pushpit rail. You can't do that so well with mast, sails, and rigging in the way. For most sailing boats, about 600w is pretty much all you can crowd on and not have shading problems, and even that can be difficult.

For best battery life, bulk phase charging should not be at too low a current. You want a little action in the batteries to desulphate and destratify.

Another important consideration is equalization. An equalizing charge for a 48v bank is about 62 volts. You will want access to mains current for a manual charger. I have never seen a "smart" charger that performs a proper equalization. The reasons are obvious. People get the idea that they don't have to be constantly monitoring batteries during equalization if a "smart" charger is doing it. So rather than be sued on a daily basis, manufacturers don't build true equalizing capability into their chargers. Equalizing a few times a year will greatly increase battery life and performance for flooded lead acid batteries. Your solar charge controller wont do that and honestly you dont want it to do that when you are not there watching it. So you will want at least occasional access to shore power, and a fully manual charger. I just use a big Variac and a rectifier from an old welding machine. I can do them all together or one at a time.
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Old 29-08-2017, 10:11   #39
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Re: How feasible is 100% renewable electric cruising right now?

Unless the electric motor and batteries are produced using renewable energy then the system is not 100% renewable.

I had electric propulsion and was able to achieve good speed and range using only solar panels.

I have since realized I can sail everywhere and propellers are ridiculous.

I use a sculling oar. My sculling oar is 100% renewable. The effort of pushing a shopping cart moves me 1 knot.
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Old 29-08-2017, 10:15   #40
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Re: How feasible is 100% renewable electric cruising right now?

On the issue of electric being 'more powerful' than diesel the way I read it is that the additional low speed torque enables you to swing a larger more efficient propeller. Combustion engines are much less efficient and powerful at lower rev's so it is really a claim thet a smaller electric engine is 'as useful' rather than 'as powerful' but I have no experience to know if the claim is true. Certainly diesel electric has some significant advantages including range so if your batteries are going to be heavier and more expensive it would seam to make sense to fit smaller batteries and a generator (DC if possible).
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Old 29-08-2017, 10:26   #41
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Re: How feasible is 100% renewable electric cruising right now?

Simple math: one one side there is consumption, say 20 kw for 5 hrs is 100 kwh, on the oher side there is production. To harvest 100 kwh (100,000 Wh) on 10 hrs perfect sunshine with all panels perfectly aligned to the sun you would need 10,000 W of PV-Power, this is 100 Panels with each 100 W (no losses assumed). Propulsiontime * Propulsionpower = Loadtime*Loadpower/efficiency.

For my boat and my intended use i answered the question behind this equotation with Propulsiontime : Loadtime like 1:20 plus a 5kw Diesel-genset ;-) 100% Renewable is no option for me, but i hope to reach the 80% on the long run.
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Old 29-08-2017, 10:34   #42
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Re: How feasible is 100% renewable electric cruising right now?

Some people cruise without any engine at all. So 100% renewable cruising is absolutely feasible. It all comes down to how much reduction in power and range you're willing to live with. You don't need all that much if you're ok sailing everywhere, and being willing to wait for wind.

If on the other hand you expect to be able to use mechanical propulsion just like you did when you had diesel power, you'll be disappointed, for the reasons others have explained above.
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Old 29-08-2017, 10:55   #43
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Re: How feasible is 100% renewable electric cruising right now?

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Shore power is nearly free energy.

Umm... well... not so much, actually.

I take your overall point, but...

Our shorepower is individually metered. For others at marinas, it's likely calculated into the cost of the slip. Presumably for those with their own docks, the cost of shorepower might be incorporated into the household usage. And so forth...

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Old 29-08-2017, 11:24   #44
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Re: How feasible is 100% renewable electric cruising right now?

Our boat is much smaller than a 42' Pearson, being a Tartan 27-2, but it is electric, and I love it for what we do with it. The motor comes on for getting down our narrow creek, docking, and sometimes to get us upwind when needed. Our charger puts out about 25 amps, and our cruising speed is around 50 amps@48V. A solar array to cover that is not practical yet for us, so we plug in at the dock. There are many wonderful things on the drawing board, like PV sails and full spectrum panels, mentioned previously. In 5 years it has been very reliable and economical. When we go to a bigger boat someday, we will probably go electric with a diesel generator, and keep solar panels for the house batteries.
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Old 29-08-2017, 11:48   #45
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Re: How feasible is 100% renewable electric cruising right now?

It's a great compromise between engineless sailing and a diesel inboard. Most of the pros and cons of engineless but with ability to navigate in and out of slips and tight anchorages.
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