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Old 28-03-2021, 13:35   #1
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Solar panel and AC advice

Greetings,
Planning to buy my first sailboat this Winter and need to rig it for living in the Florida summer heat.
Any advice on outfitting and cost for a 35' sailboat would be very helpful.
I guess the main question is how many solar panels will I need and how many batteries will I need to pump my cabin with AC for at least 8 hours?

Thank you
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Old 28-03-2021, 13:44   #2
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Re: Solar panel and AC advice

More than you could fit!
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Old 28-03-2021, 14:09   #3
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Re: Solar panel and AC advice

6kw generator.
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Old 28-03-2021, 14:15   #4
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Re: Solar panel and AC advice

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Overkill, just a Honda EU2200
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Old 28-03-2021, 17:05   #5
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Re: Solar panel and AC advice

What do you mean more than I could fit? I see Sailboats same size running clothes washers, charging stations and a tons more.
I think so far Ive seen disinformation.

Thanks I'll do my own research from here
Obviously you have not been to South Florida. You cannot run generators at night when surrounded by million dollar mansions.
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Old 28-03-2021, 17:16   #6
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Re: Solar panel and AC advice

Quote:
Originally Posted by Projectfreedom View Post
Greetings,Planning to buy my first sailboat this Winter and need to rig it for living in the Florida summer heat.
Any advice on outfitting and cost for a 35' sailboat would be very helpful.
I guess the main question is how many solar panels will I need and how many batteries will I need to pump my cabin with AC for at least 8 hours?
Thank you
Find an AC Unit that will cool the interior cubic feet of your boat, probably one recommended for one room in a house. Deep Cycle Marine Batteries will list the storage capacity. As you probably know, there is a difference between RV Deep Cycle Batteries and Marine Deep Cycle Batteries. Find the batteries you will need to produce the needed power for the AC. Double that. Find out the charging rate for those batteries.
Read the power consumption of that AC Unit. Any solar panel manufacturer will list the output of their solar panels, and the final KW after conversion to 115VAC. Buy solar panels that will supply the current needed to charge the batteries you selected.
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Old 28-03-2021, 17:24   #7
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Re: Solar panel and AC advice

Ok, Ill bite.

Using our 5kbtu unit for the example.
Operating voltage 120vac.
Current consumption while cooling including water pump. 7.8 amps

Typical duty cycle overnight after cabin is cooled typical august water temperatures. 70% (best guess). After roughly 2 hours full time running to cool down. Blower runs continuously (1 amp out of the 7.8).

Now Im going to generalize here.

7.8 amps 120vac using an inverter pulls 80 ish amps @12vdc.

So we run 160 amp-hours out of the batteries in the first 2 hours. Every hour after that were around 65 amp-hours. So weve burnt through 550 ish amp hours in our 8 hour period.

Solar to reliably replenish 550 amp-hours in a 6 hour reliable daylight period (sun angle on panels, shading,etc) turns out to be around a 1200 watt solar array.

A single 400 watt panel is roughly 40x 80....so figure out where to put 3 of those on a 35 boat and 700 ah of lithium batteries and youre golden.
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Old 28-03-2021, 17:30   #8
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Re: Solar panel and AC advice

[QUOTE=Projectfreedom;3375587]What do you mean more than I could fit? I see Sailboats same size running clothes washers, charging stations and a tons more.
I think so far Ive seen disinformation.

Thanks I'll do my own research from here
Obviously you have not been to South Florida. You cannot run generators at night when surrounded by million dollar mansions.[/QUOTE

Didnt want the answer I guess, just some fantasy
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Old 28-03-2021, 17:32   #9
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Re: Solar panel and AC advice

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[

Didnt want the answer I guess, just some fantasy

Im waiting for a response to my dose of reality post.
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Old 28-03-2021, 18:08   #10
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Re: Solar panel and AC advice

Ok so. Your options are a regular AC air conditioner powered by a generator. Or.... We have been experimenting with DC air conditioners my knowledge is based on the 12 volt unit made in China. There are two options a 12000 BTU unit that draws around 40 amps DC. My friend with 2000 watts of solar could not support that full-time in the daytime. Second option is the 12 volt 7000 BTU air conditioning good for most sleeping quarters. That draws around 20 amps DC. And it's a portable with the big battery bank and around 1500 watts of solar. I think for you the AC air conditioner and the Honda portable generator would be best. I've been living aboard full-time since 2010. I am not in the marina but anchored out. I find there's only a few nights in the summer that I really suffer. I have a bunch of DC fans and find those to be mostly okay. Your comfort level will vary
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Old 28-03-2021, 18:57   #11
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Re: Solar panel and AC advice

I want to see all these 35' sailboats with clothes washers, run on solar panels, which would suggest that they also have a water maker...
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Old 28-03-2021, 19:34   #12
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Re: Solar panel and AC advice

Quote:
Originally Posted by Projectfreedom View Post
What do you mean more than I could fit? I see Sailboats same size running clothes washers, charging stations and a tons more.
I think so far Ive seen disinformation.

Thanks I'll do my own research from here
Obviously you have not been to South Florida. You cannot run generators at night when surrounded by million dollar mansions.
Didn't like the answers, huh?
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Old 28-03-2021, 20:13   #13
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Re: Solar panel and AC advice

Quote:
Originally Posted by Sailmonkey View Post
Ok, Ill bite.

Using our 5kbtu unit for the example.
Operating voltage 120vac.
Current consumption while cooling including water pump. 7.8 amps

Typical duty cycle overnight after cabin is cooled typical august water temperatures. 70% (best guess). After roughly 2 hours full time running to cool down. Blower runs continuously (1 amp out of the 7.8).

Now Im going to generalize here.

7.8 amps 120vac using an inverter pulls 80 ish amps @12vdc.

So we run 160 amp-hours out of the batteries in the first 2 hours. Every hour after that were around 65 amp-hours. So weve burnt through 550 ish amp hours in our 8 hour period.

Solar to reliably replenish 550 amp-hours in a 6 hour reliable daylight period (sun angle on panels, shading,etc) turns out to be around a 1200 watt solar array.

A single 400 watt panel is roughly 40x 80....so figure out where to put 3 of those on a 35 boat and 700 ah of lithium batteries and youre golden.

In my experience with 1200ah and 2100w of solar and a ~10A/120vAC HVAC, you need more than me for it to be reliable day after day. Probably 1800ah and 3000w. The water and air are very hot so the aircon has to work harder, and boats just leak heat - they're generally not well thermally insulated. You don't get maximum Sun for 6 hours on the best day possible. That only lasts for an hour tops and outside of that it falls off kind of quickly. And even in south Florida there are clouds

We would run the aircon for a couple hours to knock down the heat and humidity for bed time and then switch it off.

Also, you're not considering running everything else on the boat, like a fridge. If you're airconning the boat I bet you've got a lot of other stuff too.

I've attached my solar output chart from December 25, 2019 through February 16, 2020, for our time between south Miami and Key West. You can see how much variation there is. Certainly Summer is going to make more power, but I doubt it'll be any more reliable with the weather that sweeps through.

Incidentally our biggest solar production day was June 28, 2019. We were northbound from St Augustine to Hilton Head with our solar panels getting full Sun exposure and produced 12,990 Wh through 570 minutes of BULK, 87 minutes of ABSORB, and FLOAT for 166 minutes - so I could have easily cracked 13,000 - possibly even 15,000. But we obviously weren't running any aircon underway
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Old 28-03-2021, 21:37   #14
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Re: Solar panel and AC advice

Quote:
Originally Posted by Projectfreedom View Post
What do you mean more than I could fit? I see Sailboats same size running clothes washers, charging stations and a tons more.
I think so far Ive seen disinformation.

Thanks I'll do my own research from here
Obviously you have not been to South Florida. You cannot run generators at night when surrounded by million dollar mansions.
Do let us know how many panels after you have done your own research as I would be interested to know the number. While I already know it will be more than you can fit, I would like to know the actual number.
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Old 29-03-2021, 01:38   #15
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Re: Solar panel and AC advice

Projectfreedoms post leaves more questions than he asks. His past posts show he is a newbie to sailboats, and we all know running an AC wont be the least of his problems if he buys an old boat.
I suggest he parks it in a marina, at least for the first year of experience, where the learning curve will be vertical. He says hes a chef, so working in or near a marina should be possible, and shore power leads will solve his AC problems, until he decides how to run it, (and all the other electrical equipment), on the hook.
Im in Cape Canaveral and know full well how intolerable it can be without AC, but toleration levels vary, especially with age. All our electrical consumption problems are satisfied with a 6.5Kw inboard generator, including a washer/dryer. The noise is undetectable 20 feet from the boat, and with well-insulated floorboards the sound level inside is acceptable. Of course, how you fit one of these in a 36-footer is another question, which leads to a question, which leads to
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