diy solar

diy solar

(New to Solar) I'm trying to run a small 5000 btu air condition in my shed on solar, Can someone tell me what I need/dont need?

T

TxCoolGuy94

New Member
Joined
Oct 18, 2022
Messages
14
I'm in Texas trying to get a small ac running on my shed (trying to keep it at 75 even on a hot summer to preserve electronics). So I'm assuming that means I need a 5000 btu unit (I have a 100 sq ft shed). Also insulation, r-35 (possibly 38), sealing up the cracks, and a dehumidifier I think would help with the heat?
My question is, I've been on a scavenger hunt collecting things for this build as I find them cheap, and I'm wondering what exactly I need, and is there anything below I can keep, or should I sell? I did not intentionally grab these items, I just found them from different places.
 
Yes on insulating.
No on off-brand electronics. You surely don't need an 80A SCC when your 80W panel will put out about 4A.

You'll want a heat-pump or scroll compressor type AC unit or you're likely to get in-rush current that will over draw such a small system. The smallest units pull about 400W or 4A running, or about 40A from 12V with an inverter. So conceivably if you have enough solar input you could keep a small battery going enough to power an inverter to supply the AC unit. Figure you'll need closer to 600W of panels to do this, and even then I'm not sure it would always keep up. My pair of 215W panels are flat-mounted and I generally see about 300W max, or about 22A to 12V. If you can point directly at the sun, then figure about 80% efficiency out of your panels. It takes a LOT of 12V power to make 120VAC - about ten times.

And it doesn't make sense to me to run a 40A charger off 120VAC to power a 20A battery to run a 40A draw from a 120VAC air unit. Just run the AC direct off grid power. Perhaps some kind of switching to connect it to your solar power when available.

You're on the right track, but going to need to tweak your output estimates. Perhaps one of the old pros here will chime in with some actual recommendations of components to meet a projected daily draw.

And what about cloudy days, or early/late? It's a lot of expense when you could just plug a $200 AC unit into a wall outlet and be done with it. Air conditioning and heating are the highest draw appliances we generally run into for solar. Larger systems will generally run a 48V system on the solar side. It makes converting to 120V output a lot easier.
 
Is running power from the main house not an option?

Even a small ac still uses a significant amount of power, if we assume 500w power consumption even running 10hrs a day that's 5kwh.

To get 5kwh of usable storage would require more than 4 100ah lithium batteries, or eight 100ah lead acid batteries. The battery you linked is only 20ah, so you'd need 20 of them.

For panels, I wouldn't bother with the 80w you already have. Do you have space for a ground mount array? It's unlikely you can fit enough panels on the roof of a small shed to power the ac for any length of time, a 1000w array is around the size you would need.
 
Charleswgibbs said:
Is running power from the main house not an option?

Even a small ac still uses a significant amount of power, if we assume 500w power consumption even running 10hrs a day that's 5kwh.

To get 5kwh of usable storage would require more than 4 100ah lithium batteries, or eight 100ah lead acid batteries. The battery you linked is only 20ah, so you'd need 20 of them.

For panels, I wouldn't bother with the 80w you already have. Do you have space for a ground mount array? It's unlikely you can fit enough panels on the roof of a small shed to power the ac for any length of time, a 1000w array is around the size you would need.
Click to expand...
Its an option, I'm just worried how much it would impact my light bill? Also would I have to get a mini split then? Is there anything on my list I should ditch besides the panels?
 
Browneye said:
Yes on insulating.
No on off-brand electronics. You surely don't need an 80A SCC when your 80W panel will put out about 4A.

You'll want a heat-pump or scroll compressor type AC unit or you're likely to get in-rush current that will over draw such a small system. The smallest units pull about 400W or 4A running, or about 40A from 12V with an inverter. So conceivably if you have enough solar input you could keep a small battery going enough to power an inverter to supply the AC unit. Figure you'll need closer to 600W of panels to do this, and even then I'm not sure it would always keep up. My pair of 215W panels are flat-mounted and I generally see about 300W max, or about 22A to 12V. If you can point directly at the sun, then figure about 80% efficiency out of your panels. It takes a LOT of 12V power to make 120VAC - about ten times.

And it doesn't make sense to me to run a 40A charger off 120VAC to power a 20A battery to run a 40A draw from a 120VAC air unit. Just run the AC direct off grid power. Perhaps some kind of switching to connect it to your solar power when available.

You're on the right track, but going to need to tweak your output estimates. Perhaps one of the old pros here will chime in with some actual recommendations of components to meet a projected daily draw.

And what about cloudy days, or early/late? It's a lot of expense when you could just plug a $200 AC unit into a wall outlet and be done with it. Air conditioning and heating are the highest draw appliances we generally run into for solar. Larger systems will generally run a 48V system on the solar side. It makes converting to 120V output a lot easier.
Click to expand...
So ditch the mppt controller and panel? I'm just trying to get an idea of what I should sell/keep, and try to get? Thanks for the help!
 
A split system is another option, but they're about five times the price. I know, I installed two of them in my house when the central air system went out. They're definitely awesome, but I have more than a couple of grand in them.

For a solar controller, mppt yes, but size it to suit your power generation needs - or array size. Since it seems you're only using a battery as a buffer between the panels and your inverter, and assuming you need 40A @ 12 volts, you'll need a solar array that will output 40 amps. That's a pretty good size array. In making calculations with panels, assume about 80% efficiency based on their spec.

Some solar controllers have a good display on their own, and some have an app that goes with them for monitoring. Popular brands are Victron, Epever, and some offerings from Rich Solar potentially. Some of those off-brand electronics from amazon are just not reliable. I cannot speak to the one you linked to.

For me, I would have enough battery capacity to run the system for at least a couple of hours. So assuming you're going to pull 40 amps running, I would want at least a 100 to 200 amp hours of battery capacity.

You're looking at some substantial cost for components to power a very inexpensive AC unit. At some point you have to decide if it's worth it - do some cost calc/analysis to determine payback time from just using grid power. A 4A AC unit running 10 hours a day is 40 amps, times 30 days, is 144kWh. If your power is $.30/kwh that's $43.20. You can do the same calc with your actual cost for electricity. Based on a system that costs $2000, that would take about four years to pay back, verses just using grid power. If you run it longer per day, or your power costs more, then payback or ROI might be a bit less. You have to also assume you won't move, or that you would take your stuff with you.
 
Browneye said:
A split system is another option, but they're about five times the price. I know, I installed two of them in my house when the central air system went out. They're definitely awesome, but I have more than a couple of grand in them.

For a solar controller, mppt yes, but size it to suit your power generation needs - or array size. Since it seems you're only using a battery as a buffer between the panels and your inverter, and assuming you need 40A @ 12 volts, you'll need a solar array that will output 40 amps. That's a pretty good size array. In making calculations with panels, assume about 80% efficiency based on their spec.

Some solar controllers have a good display on their own, and some have an app that goes with them for monitoring. Popular brands are Victron, Epever, and some offerings from Rich Solar potentially. Some of those off-brand electronics from amazon are just not reliable. I cannot speak to the one you linked to.

For me, I would have enough battery capacity to run the system for at least a couple of hours. So assuming you're going to pull 40 amps running, I would want at least a 100 to 200 amp hours of battery capacity.

You're looking at some substantial cost for components to power a very inexpensive AC unit. At some point you have to decide if it's worth it - do some cost calc/analysis to determine payback time from just using grid power. A 4A AC unit running 10 hours a day is 40 amps, times 30 days, is 144kWh. If your power is $.30/kwh that's $43.20. You can do the same calc with your actual cost for electricity. Based on a system that costs $2000, that would take about four years to pay back, verses just using grid power. If you run it longer per day, or your power costs more, then payback or ROI might be a bit less. You have to also assume you won't move, or that you would take your stuff with you.
Click to expand...
What about this unit:

Blueridge BM09Y18 9,000 BTU (.75 Ton) 18 SEER - S2 SERIES - 208/230V Single Zone Ductless Mini-Split Heat Pump System - WiFi Capable

www.alpinehomeair.com www.alpinehomeair.com
 
I'm sure they're fine. Mr. Cool is another DIY-friendly option/brand.

9K btu is even more draw, and that one is 230V. Which is even more complicated to convert to solar.
Some of the smaller capacity split units run fine on 120VAC - I have a 12K btu one in one end of the house - it's ice cold.

Mini-splits are nice, and they are heat-pump type scroll compressor units, so they ramp up and down as needed - no in-rush current for a big compressor motor. And they're super quiet. And they heat as well.

Without guessing how elaborate your 'shed' is, it's hard to make a recommendation.

Frankly, I couldn't advise how to convert solar energy into two-phase 220V power. You now need an HVAC professional, and an electrician. :)
 
Browneye said:
I'm sure they're fine. Mr. Cool is another DIY-friendly option/brand.

9K btu is even more draw, and that one is 230V. Which is even more complicated to convert to solar.
Some of the smaller capacity split units run fine on 120VAC - I have a 12K btu one in one end of the house - it's ice cold.

Mini-splits are nice, and they are heat-pump type scroll compressor units, so they ramp up and down as needed - no in-rush current for a big compressor motor. And they're super quiet. And they heat as well.

Without guessing how elaborate your 'shed' is, it's hard to make a recommendation.

Frankly, I couldn't advise how to convert solar energy into two-phase 220V power. You now need an HVAC professional, and an electrician. :)
Click to expand...
Well to be honest we are talking about a pretty small shed (under 100 sqft, and when you count insulation, even smaller), so almost any ac that that can do about 64sqft would do. I'm kind of looking at the cheapest way to keep it climate controlled for electronics.
 
get a kill-o-watt meter, set the unit up in your house. let it run for 24-48 hours straight. then look at the kw used and the amp draw. this will help you size the system you need to run it on solar. ( the amp draw is very little and so is the kw)
 
Well thats what I'm trying to figure out before I purchase it. I saw this video here with the same unit. Not sure if this would help figure out that:

 
TxCoolGuy94 said:
I'm kind of looking at the cheapest way to keep it climate controlled for electronics.
Click to expand...
Then just use the grid power to run AC. Solar isn't going to be cheaper, unless you plan for the long haul. Say 10 years to recoup your investment and start turning a profit. Assuming your equipment doesn't fail in that time. And you must size it appropriately, so you don't under or over size it and come out with the best bang for your buck. Very easy to over or undersize the system.

When the electric company's equipment fails, they don't send you a bill to replace/repair it. Some of their equipment to run your local grid costs tens of thousands of dollars, some it hundreds of thousands.

Now you could run a basic fan(s) with an 80W panel, plus controller and battery (12V, skip the inverter), but it's just going to cool a little bit, not really enough for electronics.

Another idea is to run the AC unit at a higher temp, say 80F or even 82F. Not sure how expensive your electronic equipment is or how mission-critical it is, but I would think that 80F isn't all that warm for electronics to operate at and would be significantly less energy to cool than 75F. I'm pulling numbers out of a hat here, but let's say that to cool at 75F with outdoor temp of 95F, you'd need a $3500 system, but at 82F, you'd only need a $1800 system. No ideas if those numbers reflect reality at all, but my guess is they'd give you a sort of an idea as to how quickly cost is going to go up for a solar system for every degree cooler you want it to be.
 
Tomthumb62 said:
Then just use the grid power to run AC. Solar isn't going to be cheaper, unless you plan for the long haul. Say 10 years to recoup your investment and start turning a profit. Assuming your equipment doesn't fail in that time. And you must size it appropriately, so you don't under or over size it and come out with the best bang for your buck. Very easy to over or undersize the system.

When the electric company's equipment fails, they don't send you a bill to replace/repair it. Some of their equipment to run your local grid costs tens of thousands of dollars, some it hundreds of thousands.

Now you could run a basic fan(s) with an 80W panel, plus controller and battery (12V, skip the inverter), but it's just going to cool a little bit, not really enough for electronics.

Another idea is to run the AC unit at a higher temp, say 80F or even 82F. Not sure how expensive your electronic equipment is or how mission-critical it is, but I would think that 80F isn't all that warm for electronics to operate at and would be significantly less energy to cool than 75F. I'm pulling numbers out of a hat here, but let's say that to cool at 75F with outdoor temp of 95F, you'd need a $3500 system, but at 82F, you'd only need a $1800 system. No ideas if those numbers reflect reality at all, but my guess is they'd give you a sort of an idea as to how quickly cost is going to go up for a solar system for every degree cooler you want it to be.
Click to expand...
What kind of fan? I'm thinking of just buying that unit and running a cord from outside to my home, and then have this running for lights and something to power the dehumidifier:

 
TxCoolGuy94 said:
What kind of fan? I'm thinking of just buying that unit and running a cord from outside to my home, and then have this running for lights and something to power the dehumidifier:

Click to expand...
Here's some 12v fans: https://www.amazon.com/s?k=12v+fan&ref=nb_sb_noss_2

As for the power box unit you linked, I wouldn't trust that thing with a 10 foot pole. Gotta be a truly crap piece of junk likely to start fire and 42Wh isn't going to run a single 12v fan for more than about 3 hours. If you want to run lights and a dehumidifer then expect it to run for 20-60 minutes.

What powers your electronic equipment? The grid? Why not just use the grid to power your cooling equipment? You said you want it cheapest, solar ain't going to be it.
 
Tomthumb62 said:
Here's some 12v fans: https://www.amazon.com/s?k=12v+fan&ref=nb_sb_noss_2

As for the power box unit you linked, I wouldn't trust that thing with a 10 foot pole. Gotta be a truly crap piece of junk likely to start fire and 42Wh isn't going to run a single 12v fan for more than about 3 hours. If you want to run lights and a dehumidifer then expect it to run for 20-60 minutes.

What powers your electronic equipment? The grid? Why not just use the grid to power your cooling equipment? You said you want it cheapest, solar ain't going to be it.
Click to expand...
Sorry if I didnt clarify, this will solely be used as a climate controlled storage shed. I will be storing expensive video games, hard drives, laptops, things like that.
 
To get 40 amps per hour, assuming your AC unit uses 4A at 120VAC - you would need 800W of solar panels. So four 200W panels might do it. And that's only during peak solar gain - find the calcs for your locale. Generally solar gain is considered at an average of 5-6 hours per day. A 60A solar controller would charge a 200A lifepo battery. Concievably your battery could continue to power your AC unit for +/- 4 hours after peak solar gain. Likely you wouldn't have enough excess solar gain to recharge the battery as well as power your AC, but you could always charge it off grid power overnight.

Costs would look something like this:
4 200W panels @$220 ea $880
60A capacity inverter/charger AIO $650
200 lifepo4 battery, like a Chins $650
Wiring, fuses, and ancillary bits $150
5000btu AC unit $200

Estimated total $2,530

If it were me I would dig a trench or run an overhead wire from your main house panel to a subpanel in the shed, and install one outlet circuit and one lighting circuit. And buy the air unit, and plug it in. Live happily ever after. Yes, you could do it with an extension cord, but if you have fancy electronics in there you'll likely need a little more power than an extension cord.

Just for giggles...why are you storing electronics in a shed? Why not put them in a spare room in the house?

I wrote this after you posted consumption. Yes, at low speed/draw it might be 250W. I would read the UL label on the unit tag for peak amps running and at start up. Better yet, get one and plug it into a watt meter as suggested, and then you'll know for sure. I would still budget for 4amps at 120VAC, which is 40A at 12VDC.
 
You must log in or register to reply here.

Similar threads

T
Renovating a Shed to be Climate Controlled - Where do I begin and how much will it cost?
Replies
10
Views
2K
Murphyslaww
M
Back
Top