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Old 30-06-2020, 10:16   #196
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Re: Replace Diesel with electric engine

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Originally Posted by moseriw View Post
joelhemington just check for yourself! for say 50 KWh you need how much m² of Panels if your 1 m² Panel gives you 130 Watts PEAK? This is 60 Watts real for say 8 hrs a day.

60 W / 48 V = 1,25 Ampere OK skip it let us stay on Watts 60 W x 8 hrs = 480W /Day
48.000W / 480W = 100 m² of solar panels to go for one hour.

OK sayin this is only a 16% panel (We are on 24% Now)
No matter - double it up to 32% makes 50 m² of panels IF you got enough sunlight at all
Your explanation makes perfect sense but I was referring to using 425 watt panels - who the hell buys a 60 watt solar panel? Yes, I know that solar panels rarely put out their maximum capacity, certainly not 12 hours a day, and it does rain in Panama but with a 2400 watt capacity and regen, I figure you could make the Panama crossing at 5 knots. After that it's just a matter of setting the hook or maneuvering into a Marina.
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Old 30-06-2020, 10:51   #197
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Re: Replace Diesel with electric engine

Going thru the canal on solar and batteries alone probably isn’t possible except for a few specific boats that are very light, have very big LiFePo battery banks for their size and can track the sun at less at somewhat.

The 5kt requirement is just too high with the distance involved.
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Old 30-06-2020, 10:51   #198
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Re: Replace Diesel with electric engine

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Your explanation makes perfect sense but I was referring to using 425 watt panels - who the hell buys a 60 watt solar panel? Yes, I know that solar panels rarely put out their maximum capacity, certainly not 12 hours a day, and it does rain in Panama but with a 2400 watt capacity and regen, I figure you could make the Panama crossing at 5 knots. After that it's just a matter of setting the hook or maneuvering into a Marina.
2400w of panels will generate their rated wattage times about 4 in WH...so let's be generous and say 10,000wh or 10KWH.

Let's assume your system is 100% efficient at storing and retrieving power (it's not).

If you need 5KW to maintain 5kts, you have 2hr of motoring time or about 10 miles...did the Panama Canal get shorter?
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Old 30-06-2020, 11:06   #199
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Re: Replace Diesel with electric engine

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2400w of panels will generate their rated wattage times about 4 in WH...so let's be generous and say 10,000wh or 10KWH.

Let's assume your system is 100% efficient at storing and retrieving power (it's not).

If you need 5KW to maintain 5kts, you have 2hr of motoring time or about 10 miles...did the Panama Canal get shorter?
If you have a 2.4kW array and need 5kW to maintain 5kts speed, then you only need 2.6kW from the battery bank.
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Old 30-06-2020, 11:32   #200
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Re: Replace Diesel with electric engine

Until the technology improves or more proven it's a gamble to go too far with auxiliary electric.
A well maintained diesel is so dependable. Why make your life probably miserable?
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Old 30-06-2020, 11:43   #201
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Re: Replace Diesel with electric engine

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If you have a 2.4kW array and need 5kW to maintain 5kts speed, then you only need 2.6kW from the battery bank.
Sort of...the multiplier assumes the full days output. You won't get 4 hours where it's pumping out a steady 2.4kw. You might get an hour or two at the peak output but then lower output for the shoulder hours and very little in morning and late afternoon, so total output results in about 4hr at the rated output.

A large battery bank with a few days hanging out at anchor to charge up could mitigate to a degree.

For the Panama Canal, it's a little over 50 miles but call it 60 miles as they aren't going to let you tie up at the locks and you may have to motor in circles staging to get in.

At 5kt, that's looking like 12hr. So if you can generate enough solar to provide 2hr over the course of the day, you need battery sufficient for the remaining 10hr. Assuming 5kw output to maintain 5kt and you maintain a 20% margin in case something goes wrong, you need about 60kwh of battery (yes, I'm mixing miles and nautical miles but close enough for estimation).

Of course, if you hit a strong headwind crossing the lake, that all goes out the window and you will run out of power. To fill 60kwh with the solar will take 6 days...they aren't going to be happy about you sitting half way thru for 6 days waiting to get charged up.
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Old 30-06-2020, 11:53   #202
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Re: Replace Diesel with electric engine

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Until the technology improves or more proven it's a gamble to go too far with auxiliary electric.

A well maintained diesel is so dependable. Why make your life probably miserable?


It’s a values choice. For some people the lack of noise and/or not using fossil fuels is worth giving up the convenience of an ICE.

Making the change to electric drive means a few things become very difficult or impossible (Panama Canal) and others become inconvenient but not necessarily impractical if there is no schedule to keep.
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Old 30-06-2020, 12:12   #203
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Re: Replace Diesel with electric engine

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Originally Posted by valhalla360 View Post
Sort of...the multiplier assumes the full days output. You won't get 4 hours where it's pumping out a steady 2.4kw. You might get an hour or two at the peak output but then lower output for the shoulder hours and very little in morning and late afternoon, so total output results in about 4hr at the rated output.

A large battery bank with a few days hanging out at anchor to charge up could mitigate to a degree.

For the Panama Canal, it's a little over 50 miles but call it 60 miles as they aren't going to let you tie up at the locks and you may have to motor in circles staging to get in.

At 5kt, that's looking like 12hr. So if you can generate enough solar to provide 2hr over the course of the day, you need battery sufficient for the remaining 10hr. Assuming 5kw output to maintain 5kt and you maintain a 20% margin in case something goes wrong, you need about 60kwh of battery (yes, I'm mixing miles and nautical miles but close enough for estimation).

Of course, if you hit a strong headwind crossing the lake, that all goes out the window and you will run out of power. To fill 60kwh with the solar will take 6 days...they aren't going to be happy about you sitting half way thru for 6 days waiting to get charged up.
Well no it’s 10 hours, not 12. It may take 12 hours but only 10 at the energy consumption we’re talking about. Drifting a circle in front of a lock means that you are recharging the battery at 2kW or something, not consuming 2.6kW.

Also, a 2.4kW array in Panama will generate considerably more than 2.4kW and for more hours. From my experience in Panama (been there for 11 years!) I would say you get 15kWh of charge from that array in a day. As you need 50kWh, you need to be able to come up with 35kWh from battery banks, generators etc. A Honda will do 25kWh so with just 10kWh batteries one can pull it off.
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Old 30-06-2020, 12:34   #204
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Re: Replace Diesel with electric engine

Quote:
Originally Posted by valhalla360 View Post
Sort of...the multiplier assumes the full days output. You won't get 4 hours where it's pumping out a steady 2.4kw. You might get an hour or two at the peak output but then lower output for the shoulder hours and very little in morning and late afternoon, so total output results in about 4hr at the rated output.



A large battery bank with a few days hanging out at anchor to charge up could mitigate to a degree.



For the Panama Canal, it's a little over 50 miles but call it 60 miles as they aren't going to let you tie up at the locks and you may have to motor in circles staging to get in.



At 5kt, that's looking like 12hr. So if you can generate enough solar to provide 2hr over the course of the day, you need battery sufficient for the remaining 10hr. Assuming 5kw output to maintain 5kt and you maintain a 20% margin in case something goes wrong, you need about 60kwh of battery (yes, I'm mixing miles and nautical miles but close enough for estimation).



Of course, if you hit a strong headwind crossing the lake, that all goes out the window and you will run out of power. To fill 60kwh with the solar will take 6 days...they aren't going to be happy about you sitting half way thru for 6 days waiting to get charged up.


Rule of thumb is 3.5-4.0 times nameplate power in watts is what you can expect to get in W-hr per day using an MPPT controller, 3.0-3.6 using a PWM controller.

If you have a tracking system for the panels production will be higher, perhaps much higher.

My understanding is that a lot of smaller boats anchor overnight halfway thru the canal. That said you’ll get nothing out of the panels thru the night. If you had a small generator that could run all night you’d probably be topped up by morning.

Making it thru the canal is going to depend on:
A. How much power it takes to maintain 5kt.
B. The capacity of your battery bank.
D. How much solar capacity you have.
D. Wind turbine capacity.
E. ICE generator capacity & charger capacity (doesn’t matter how big the generator is if you can’t pack it all into the battery).
F. If you get unlucky about head winds.
G. If you get unlucky about insolation.
H. If you get unlucky and the canal authority requires you to go all the way thru in one day.

Some boats will have enough reserve capacity to make it thru despite a windy cloudy day and some won’t. Doing the math is fairly straightforward to figure out if you need to beef up part of your system or if you need to make different plans.
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Old 30-06-2020, 14:27   #205
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Re: Replace Diesel with electric engine

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Making the change to electric drive means a few things become very difficult or impossible
Well, that's my point. Why even deal with possible "very difficult" or "impossible" when you can enjoy the other aspects?
The trade off for less noise is inconsequential. You are going to sit at anchor most of the time anyway while cruising.
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Old 30-06-2020, 14:48   #206
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Re: Replace Diesel with electric engine

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Well, that's my point. Why even deal with possible "very difficult" or "impossible" when you can enjoy the other aspects?
The trade off for less noise is inconsequential. You are going to sit at anchor most of the time anyway while cruising.
Yes well as long as power boats are brought into comparisons while others assume sailboats as this is or used to be a sailboat forum, discussion is impossible. For a sailboat it’s just an auxiliary engine and yes something like the Panama canal means you probably need a genset because you’re not allowed to sail... but you could even rent one for a couple of days if you need more capacity than you have.

For a motorboat sure you need a fixed install diesel genset that can power the electric motor up to cruise speed besides a decent battery bank. I would have that for a sailboat as well.
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Old 30-06-2020, 15:06   #207
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Re: Replace Diesel with electric engine

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We looked at Diesel electric drives but want to drive down the need for the genset as we add solar and understand how well the regen works from the engine while sailing. Ideally over time we don't need the genset but having it adds a layer of security.

No genset?


So how do you make it thru Panama Canal?


Do you go via the Magellan?


b.
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Old 30-06-2020, 15:32   #208
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Re: Replace Diesel with electric engine

The math has been covered; having enough power for any arbitrary trip is easy enough to roughly calculate. I think the issue is more the tendency to not design a large enough system on vague hopes that it will be enough. As one who went the undersized route (18hp) for my 23k# full keel 31' boat I can tell you that it was too often just miserable. It was fine for getting out of high pressure areas, in and out of harbors, and other non-challenging situations. But when the wind and waves came up, I was screwed. The speed would drop to under a knot as I threw everything into getting to the destination. Not fun. I now have a 38hp engine. And if it had been an electric drive there are numerous passages, especially in the Med, that couldn't be done in the summer calms or would at least require an extra night under way. And if the generator is large enough to power the motor continuously (and with a sufficiently large enough tankage) then what has been accomplished by all of the extra cost and complexity? Just hook the diesel genset engine to the prop shaft and get rid of the rest...

Shortly after my last Atlantic crossing I talked to 2 other boats that had crossed with electric drives: neither would buy electric again. One of them was a big cat with a huge solar array who had discovered that it wasn't even keeping up with their freezers' needs. The other was a small boat and his small array didn't make much of a dent on requirements - the genset ran whenever he moved the boat.

Clearly electric drive technology is advancing at a good clip. Still, the power needed to push a boat at cruising speed for any distance must come from somewhere and few if any boats can sport a large enough solar array to accomplish that task, especially if it includes nighttime travel. Today the main alternative source is a diesel genset, which doesn't seem to be a great advance over a diesel directly driving a shaft/prop. Perhaps in the future fuel cells and hydrogen or alcohol will provide a suitable alternative. Whatever future innovation may bring, don't scrimp on motor power and range or you will regret it.

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Old 30-06-2020, 15:46   #209
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Re: Replace Diesel with electric engine

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Whatever future innovation may bring, don't scrimp on motor power and range or you will regret it.
Yes. In the future, probably fifty years from now. Not now.
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Old 30-06-2020, 16:36   #210
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Re: Replace Diesel with electric engine

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Well, that's my point. Why even deal with possible "very difficult" or "impossible" when you can enjoy the other aspects?
The trade off for less noise is inconsequential. You are going to sit at anchor most of the time anyway while cruising.
It's a function of the values of the cruiser. You don't value the quieter running, the lack of fuel and lubricant smell nor the freedom from fossil fuels so you aren't willing to make the compromises needed to accept electric drive. That's fine.

Other people's values are different from yours so some are happy to accept those compromises.
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