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Old 05-24-2018, 06:40 PM   #1
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Constructive Solar AC ideas

With all of the opinions surrounding solar ac, lets try to have some constructive conversation here. If you donít think itís possible, no worries, just move on to the next thread.

If youíd like to have a discussion about designing a solar system around being able to boondock with ac with minimal generator use or want to theorycraft on ideas surrounding massive solar arrays and massive battery banks, letís go ahead and talk it out.

With that being said, the good news is, even if no-one else is able to or wants to actually try building a system like this right now, Iím pretty much up for the challenge by default. Iím beginning a build on a 40íer right now and have a very high solar power budget to meet some requirements for my families lifestyle. So as the build and thread progresses I would be able to design our actual power system and document the components and processes to help further the topic.

Letís talk. What kind of system would you design?
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Old 05-24-2018, 06:51 PM   #2
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Seems you've given this much thought so why not just go ahead and lay out your proposal and lets see where that goes. Jack
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Old 05-24-2018, 06:51 PM   #3
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Every discussion around power installations starts with an Energy Audit.

You need to know two things:

1. How much power will my appliances consume in a 24-hour period?

2. How many days do I want to be off-grid.

#1 is a bit flexible as you could run more economically if you needed to ... so maybe two power schemes. One for "sod it let's just run everything" and another for"how frugal can we be if we have to".

Once you have the hard numbers you can start to think about where the power will come from.

Be realistic about the amount of amp-hours your batteries will actually receive from a solar installation, and balance the need to help the panels out with a generator at times of either peak demand or lower sunshine.

Throwing AC into the mix is possible, but be aware that it is an enormous demand that would mean designing just for that as everything else would be relatively small in comparison ... and that is why most people don't do it unless they expect to be hooked to shore-power or run a genny. It's not that it isn't possible, it's that it is very expensive and needs a great deal of roof real-estate to even fit the panels.

The technical side of the installation is a completely separate conversation, and some of the decisions you make will affect the efficiency of the system and its cost.

Things like tiltable or fixed panels, MPPT charge controller(s) or not. Parallel or series wiring, Mono or polycrystalline. Well you get the drift.

Just my 2c ... it's worth what you paid for it
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Old 05-24-2018, 07:21 PM   #4
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Originally Posted by Twigg View Post
Every discussion around power installations starts with an Energy Audit.

You need to know two things:

1. How much power will my appliances consume in a 24-hour period?

2. How many days do I want to be off-grid.

#1 is a bit flexible as you could run more economically if you needed to ... so maybe two power schemes. One for "sod it let's just run everything" and another for"how frugal can we be if we have to".

Once you have the hard numbers you can start to think about where the power will come from.

Be realistic about the amount of amp-hours your batteries will actually receive from a solar installation, and balance the need to help the panels out with a generator at times of either peak demand or lower sunshine.

Throwing AC into the mix is possible, but be aware that it is an enormous demand that would mean designing just for that as everything else would be relatively small in comparison ... and that is why most people don't do it unless they expect to be hooked to shore-power or run a genny. It's not that it isn't possible, it's that it is very expensive and needs a great deal of roof real-estate to even fit the panels.

The technical side of the installation is a completely separate conversation, and some of the decisions you make will affect the efficiency of the system and its cost.

Things like tiltable or fixed panels, MPPT charge controller(s) or not. Parallel or series wiring, Mono or polycrystalline. Well you get the drift.

Just my 2c ... it's worth what you paid for it
Thank you for this copy and paste but this is intended to be more of an open discussion than what every other solar ac thread inevitably turns into.

If youíd like to discuss actual technical points of a system that could handle various amounts and types of ac units, and for various amounts of time, letís do that. Or any other relevant topic to large solar systems, letís discuss that.

Thank you for the obligatory warning post though. I am not at all trying to sound condisending, just hoping to better define the scope of the thread.
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Old 05-24-2018, 07:24 PM   #5
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Seems you've given this much thought so why not just go ahead and lay out your proposal and lets see where that goes. Jack
My thought was actually not to open with my proposed plans as the thread would then steer in the direction of my build right off the bat. I was hoping to have a more unbiased untainted discussion about systems (and people’s thoughts on components) that can handle that load.
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Old 05-24-2018, 07:30 PM   #6
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I'm 100% with Twigg. Figure out how much power you need, We can't guess that for you. There is a level of power generation and storage where solar can do the job, no question about that. Your requirements will dictate your needs. Just don't say this is for a short bus.
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Old 05-24-2018, 07:34 PM   #7
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I’m not asking for help building MY build. I’m asking for the forum community to have a constructive thread based around solar AC. So far, it’s off to a rocky start, though.
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Old 05-24-2018, 07:43 PM   #8
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Someone did mention the small efficient dc units from a Prius, idk the btu on them or if they are anymore efficient than a good minisplit but it seems workable for a well insulated bedroom
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Old 05-24-2018, 07:45 PM   #9
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Maybe I'm missing something, but it seems like it should be fairly easy to figure out?

  • How much energy does an AC system require?
  • How much battery storage is required to power the AC system?
  • How much solar energy do you need to recharge the batteries that power the AC system?
Once you have those numbers, the only real variable is the temperature.


So then, you size the AC system based on your room size and size the solar & battery bank accordingly.

Then again, I could very well be missing something due to faulty logic.
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Old 05-24-2018, 07:50 PM   #10
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Iím not asking for help building MY build. Iím asking for the forum community to have a constructive thread based around solar AC. So far, itís off to a rocky start, though.
"Rocky start..." funny. #foolserrand

I plan to run a mini split off mine. 2600W on the roof, 18.4kWh of lithium, and a Magnum Energy 4000W inverter.
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Old 05-24-2018, 07:51 PM   #11
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Thank you for this copy and paste
Copy and paste?

From where?

The irony of your response to an early reply, and your stated aim to have an open discussion almost beggars belief.
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Old 05-24-2018, 08:00 PM   #12
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Having a build plan to share is often a good starting though, just saying.

I am experimenting with solar to see what it will really do. Have my fridge running on shore power right now through a kill a watt meter, have checked amp draw on all the lights, and fans. Water pump is not in yet so no load testing on that yet, although could test my current campers water pump. So I am starting to get real good numbers for useage.

Big thing I see is shade.... this is more of a problem then I thought it would be. Right now the bus is in almost total shade most of the day. I am getting 1/5th power output from the panels, and not going over 13.4 volts. So it seems that I could put enough panels on the roof for my basic needs even at 1/5th output, however it seems then I would never get a full charge on the batteries.

Anyone have any ideas? ok yes I know they are "solar" panels and lots of sun is good for them. However....

I will have to say that in normal use they will be in mostly full sun, but was hoping to keep the fridge going all the time when it is here at home. Maybe shore power is the better option for that. Being this is a solar discussion....

My charge controller is not an MPPT. would that boost voltage for chargeing? so I would get a proper charge?

In real world experiance are some panels more tolerant of lower light levels?

In that vein my cheapy horrible freight 45 watt ( about 10 years old)panels put out .44 amps when part shaded. The same as my 100 watt Renogy panel. Both using a 30amp Renogy charge controller. By the way two seperate systems set up for testing. The Renogy panel is a mono crystaline, no idea what the horrible freight ones are. They are three 15 watt panels wired in parallel, versus a single 100 watt panel.
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Old 05-24-2018, 08:00 PM   #13
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If I were designing system to run AC from solar, I would copy ComfortEagle's plan very closely with maybe a few numbers adjusted but that's the right ballpark... And I'd still pack a generator.
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Old 05-24-2018, 08:26 PM   #14
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If I were designing system to run AC from solar, I would copy ComfortEagle's plan very closely with maybe a few numbers adjusted but that's the right ballpark... And I'd still pack a generator.
If only I had that budget....
That set up is awesome

I will for sure have some form of ac probably a mini split, and as much panel and old school lead acid as the budget allows. Also planning to pipe a largish propane tank to hot water, cooking stove and generator
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Old 05-24-2018, 08:29 PM   #15
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I'm doing it a different way. Best part is they came with the bus.IMG_20180523_180709_366.jpeg
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Old 05-24-2018, 09:27 PM   #16
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Oh I’ll have to go dig through ComfortEagles build and take a peak!

I’m currently looking at running a 48v system with approx 400ah lithium at that voltage. Minus my 10’ roof deck I have enough room to put 3650 watts of solar on the roof.

I’ll have a 12k mini split at the front and rear of the bus, and also a Honda eu7000 underneath for when needed in a pinch.

The system isn’t completely designed yet, but we are getting there slowly but surely.
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Old 05-24-2018, 10:29 PM   #17
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I'm doing it a different way. Best part is they came with the bus.Attachment 22500
Those the stock jobs? Aren't they massive for an insulated living space? what are you using to power the compressor? I'm totally not being negative I'm genuinely curious. Looking for solutions myself
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Old 05-24-2018, 11:00 PM   #18
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Originally Posted by Flowstatebus View Post
Oh Iíll have to go dig through ComfortEagles build and take a peak!

Iím currently looking at running a 48v system with approx 400ah lithium at that voltage. Minus my 10í roof deck I have enough room to put 3650 watts of solar on the roof.

Iíll have a 12k mini split at the front and rear of the bus, and also a Honda eu7000 underneath for when needed in a pinch.

The system isnít completely designed yet, but we are getting there slowly but surely.
You were asked to show us all how your insight led you to accuse me of copying and pasting.

You made the accusation, I'm still waiting for the answer.

ps ... as you laid waste to your own "let's all be nice" thread, I feel zero remorse about asking you to explain why a perfectly reasonable and on-topic post should have been treated so disparagingly.
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Old 05-25-2018, 07:26 AM   #19
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I'm not exactly sure what ideas you are looking for. At the present time, it is very doable given enough real estate for panels, budget, and realistic expectations. The last two are subjective and, it seems to me, this is where the typical disagreements start. One person has an X thousand dollar budget which seems crazy to the fellow with an X hundred dollar budget. On the expectations side, it seems that some basic understanding of solar and electrical power is necessary. Occasionally someone asks about cooling their 40' coach in the Houston summer using their 100 watt panel and single 12V battery. I generally steer away from those threads.

The following thread has at least three (from memory) really great posts/installations.
http://www.skoolie.net/forums/f49/so...a-c-22293.html

The following is my opinion (ONLY). I think a system such as this would generally:
  1. Operate at least four hours from battery alone.
  2. Operate from panel array power while the sun is available (meaning, not discharge the battery bank). This means the panel array would be capable of producing (in good sun) at least what the A/C units are consuming.
  3. Utilize lithium batteries. I don't think this is requirement but is my preference. Having used lithium for a year, I am sold on it. Yes, it is spendy but many of the 'issues' with lead-acid simply go away (charge and discharge rates, string length, etc.).
  4. Utilize high voltage residential panels. This is for efficiency, maximize use of roof space, and energy transmission efficiency (cables).
  5. Utilize MPPT technology.
  6. Utilize tiltable panels. As much as I dislike the idea of babysitting panels, this will go a long ways towards maximizing panel production.

Obviously, individual requirements will change the above list. And that list is just my opinion, something to start punching holes in.
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Old 05-25-2018, 08:11 AM   #20
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Those the stock jobs? Aren't they massive for an insulated living space? what are you using to power the compressor? I'm totally not being negative I'm genuinely curious. Looking for solutions myself
Yep this 32 ft bus has dual engine driven AC. My 24 ft short bus has 2 big AC units as well but none of he insulation. After living in it for 18 months you discover which shortcuts you shouldn't have taken, so I'm going all out on it this time.
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