Solar powered AC air conditioning, a bummer or a challenge?

[K7ABE]

Geez. I feel like I'm repeating things so I'll repeat my goals expectations from the beginning and I'll even give $ figures this time.

Budget
Inexpensive but capable solar array <$1000
Inexpensive but capable inverter and charge controller<$300
Inexpensive battery bank <$1000 (I can bend more on this for the right thing)
660 watt 120VAC air conditioner

My expectations to prove this model sustainable:
-This system would work just the air conditioner in a well-insulated 25x11' off-grid home addition.
(The 12v electrical outlets and lights would all be working off a separate, smaller, 12volt system.)
-The air conditioner should run estimated 5-7 hours per day for 150-200 days a year.
-The larger array and battery bank will not be in use the other 6 months of the year.
-Batteries should last for at least a couple years.


I have constantly been told by naysayers in my city and state and people who've expressed no interest in investigating the matter that it's pointless and can't be done without an extreme startup cost and pricey components.

My ONLY goal is to prove first that off-grid Air conditioning is sustainable in the Deep South with only inexpensive components, DIY knowledge, good insulation, and conscientiousness. If it can be done, I can change the thinking around here one person at a time, and perhaps apply the principles into a future home later in life.

If it can't be done, then I can probably still build the home addition with more conventional methods.
I don't have anything against the power company. I am aware the cost of power will be higher than a regular home addition with the new electrical added. I have no interest at this time for grid-tie or conventional methods. I would gladly investigate them only if I admitted defeat first.

I believe this can be done. But I'm not certain. This is the only reason I've joined the forum.

This sounds very doable to me if you are frugal where you shop, The room is well insulated and on the north side of the building with double or triple pane glass in vinyl frames. The main problem I see would be the same with the refrigerator door if there are frequent trips to the bathroom , the kitchen, and kids fanning the door, this probably won't work. But for a retreat to take a nap out of the heat it sounds like an excellent idea.

I hit garage sales during the winter in Oregon and buy AC units for $10 to $30 each. then take three to five of them each time I go to Texas to use in the rentals. Two of them in the last few trips have been 5500 BTU Using only 480 watt. They do not drain the water it stores in a pan and the fan picks it up and throws it into the condenser to cool it. I only bring this up to point out if you are not getting over 10 BTU's per watt it may be more cost effective to use a more efficient AC.
Abe

[K7ABE]

I am going to stick my neck out with an educated guess or bet. I bet those installations are at altitude?

My used 35A AGMs, a set of 10, lasted about 4 years with quite a bit of abuse and intermittent use. They were on the same copper bus bars made from 7/8 inch flattened tubing.
Abe

[PhillyTitan]

This sounds very doable to me if you are frugal where you shop, The room is well insulated and on the north side of the building with double or triple pane glass in vinyl frames. The main problem I see would be the same with the refrigerator door if there are frequent trips to the bathroom , the kitchen, and kids fanning the door, this probably won't work. But for a retreat to take a nap out of the heat it sounds like an excellent idea.

I hit garage sales during the winter in Oregon and buy AC units for $10 to $30 each. then take three to five of them each time I go to Texas to use in the rentals. Two of them in the last few trips have been 5500 BTU Using only 480 watt. They do not drain the water it stores in a pan and the fan picks it up and throws it into the condenser to cool it. I only bring this up to point out if you are not getting over 10 BTU's per watt it may be more cost effective to use a more efficient AC.
Abe

Dude I swear I can hear you mumble every time I read one of your non-sensical rants.
You're getting better but I need some Good stuff to get on your wavelength.

[K7ABE]

Not in your wildest dream Raymond. All the mentioned battery manufacture cycle life chart follow the same cycle life curve. There is a direct relationship between DOD and cycle life. The real answer is the battery warranty. Trojan RE line is 24/60 exact same as Rolls 4000 Series. That means a 5 year battery period. Abuse them by more than 20% in hot conditions you will get much less.

Trojan Cycle Life Chart

Many of us look at the manufacturer information with a grain of salt. Then we try to find people actually using the products to see what is happening in the real world.
Abe (several generations of Raymond's so most of us go by our middle names, mine is Abraham)

[Sunking]

(several generations of Raymond's so most of us go by our middle names, mine is Abraham)

OK Raymond A Mitchel of Lebanon Oregon.

[Sunking]

Many of us look at the manufacturer information with a grain of salt.

I agree and every battery chart is make believe born in a test lab. Warranty is where the truth lies.

[PhillyTitan]

OK Raymond A Mitchel of Lebanon Oregon.

Aka Rain Man

[K7ABE]

Aka Rain Man

Mild autism has helped me pay attention to detail. It shows in my carvings.

[PhillyTitan]

Mild autism has helped me pay attention to detail. It shows in my carvings.

HA! I knew I had you pegged. Every time I read your posts I hear Rain Man's voice.

[billvon]

My ONLY goal is to prove first that off-grid Air conditioning is sustainable in the Deep South with only inexpensive components, DIY knowledge, good insulation, and conscientiousness. If it can be done, I can change the thinking around here one person at a time, and perhaps apply the principles into a future home later in life.

You can hit all those goals except "inexpensive." Again, going to a very efficient A/C (a mini-split) will be the best first step in getting close to your goal.

The "DIY knowledge" is troubling, though. You can certainly DIY. But if you are worried about installing a mini-split - which after all comes with detailed instructions, mounting templates, on line support etc - then building the kind of solar system you describe is going to be ten times harder. There won't be any instructions or manuals or videos showing you exactly what to do, and you'll still have to do all the drilling, venting, pulling wire etc that either project entails.

[PhillyTitan]

You can hit all those goals except "inexpensive." Again, going to a very efficient A/C (a mini-split) will be the best first step in getting close to your goal.

The "DIY knowledge" is troubling, though. You can certainly DIY. But if you are worried about installing a mini-split - which after all comes with detailed instructions, mounting templates, on line support etc - then building the kind of solar system you describe is going to be ten times harder. There won't be any instructions or manuals or videos showing you exactly what to do, and you'll still have to do all the drilling, venting, pulling wire etc that either project entails.

Not worried about installing a mini-split. It wouldn't be easy but I have seen how to vids on YouTube and the difficulty is not that high.
It's really kind of like this: First and foremost I don't want to install one because success of this experiment is contingent on low-priced components. Second, Wall construction to a home addition is not permenent, and if I find that I don't like the configuration or if I don't want to have to deal with solar panels anymore and decide to tie it all in to the grid electricity, or the city discovers that I have changed this once carport-converted storage room into a heated and cooled space without permits, then I can easily change it to make code.
With a permenent mini split system installed working exclusively on the solar system,,,well that is an extra layer of garbage I'd have to deal with when I do change it. A 600watt window unit is easily changed into a mini split later, but getting a mini split now leaves me with fewer options later, more headache later, higher start up cost, and thus a failed experiment.

By the way, you're like the third guy to praise the mini split. Unless I'm wrong, and I often am, I was under the impression that whole house mini split saves a bunch of energy compared to a ducted system, but it's not like it's over 50% better...right? Good but not great isn't enough to spend the extra $ on the components when I'm purposefully attempting to keep them low.

[PhillyTitan]

And did I forget to mention that a mini split isn't attractive in your room?
They stand out like sore thumbs in a room that is less than 11' wide. More so than window and through the wall units anyway.. The cool and new technology factor will wear off very quickly after looking at a bulky wall component for a few weeks.

[russ]

And did I forget to mention that a mini split isn't attractive in your room?
They stand out like sore thumbs in a room that is less than 11' wide. More so than window and through the wall units anyway.. The cool and new technology factor will wear off very quickly after looking at a bulky wall component for a few weeks.

Look at the various models available - some are quite OK. Your analysis is 100% off.

[K7ABE]

Hey Sunking, I really mean types of batteries not brands. I really have no knowledge at all about the subject, only that AGM is supposedly very good and low on maintenance.




Abe I've said this before, but I don't mind saying one more time. It's the individual components that I'd like to keep down in cost. For instance, a 24VDC 12,000 BTU air conditioner would be at least $1700.00 (<-- the only one I found with a price tag on it). Or a solar array professionally installed for $10k. A few batteries for a couple hundred each is not an extreme cost. The first question on this thread was is it viable to have a sustainable working system that won't break the bank when one of the individual components fail.

The weakest link I saw in your model was the inverter. Eliminate the charge controller the inverter and the batteries and put that money into an AC that would work directly off of the solar panels. There is at least one refrigerator company on the market that does not need an inverter a charge controller or batteries. it is designed to work during the day time directly from the solar panel and you are advise not to use a refrigerator in the evening or at night. It was four or five years ago when I priced that compressor at $1250. I did not check on the duty cycle to see if it would work for an air conditioner, I was investigating refrigeration.
Abe

[billvon]

It's really kind of like this: First and foremost I don't want to install one because success of this experiment is contingent on low-priced components. Second, Wall construction to a home addition is not permenent, and if I find that I don't like the configuration or if I don't want to have to deal with solar panels anymore and decide to tie it all in to the grid electricity, or the city discovers that I have changed this once carport-converted storage room into a heated and cooled space without permits, then I can easily change it to make code.
With a permenent mini split system installed working exclusively on the solar system,,,well that is an extra layer of garbage I'd have to deal with when I do change it. A 600watt window unit is easily changed into a mini split later, but getting a mini split now leaves me with fewer options later, more headache later, higher start up cost, and thus a failed experiment.

Going with an inefficient window unit now will probably also result in a failed experiment one of two ways:
1) A cheap inverter + battery bank will have trouble starting the A/C, and won't last long, leading to expensive and frequent battery and A/C replacements
2) A good inverter + battery bank + solar panel capable of starting and running the less efficient unit will be quite expensive - likely more than the mini-split

By the way, you're like the third guy to praise the mini split. Unless I'm wrong, and I often am, I was under the impression that whole house mini split saves a bunch of energy compared to a ducted system, but it's not like it's over 50% better...right? Good but not great isn't enough to spend the extra $ on the components when I'm purposefully attempting to keep them low.

For solar, a good inverter driven mini split can be over 50% better. Lower starting surge means your inverter can be smaller (and hence more efficient overall.) Lower power requirements means cheaper battery bank and solar array.

And did I forget to mention that a mini split isn't attractive in your room? They stand out like sore thumbs in a room that is less than 11' wide. More so than window and through the wall units anyway.. The cool and new technology factor will wear off very quickly after looking at a bulky wall component for a few weeks.

Well, I guess you can choose a bulky sore thumb high up on a wall or a bulky sore thumb blocking a window. You'll pay a lot more for the bulky sore thumb blocking your window in the long run.

Of course you can do whatever you want. But in your first post it sounded like you were looking for advice on "a low cost solution (low cost build and maintenance) for a completely off-grid addition that I'm planning for my house." You're free to ignore the advice and proceed with what you want to do, we're just pointing out that there are better ways to do what you want to do that will increase your odds of (at least partial) success.