Full Off Grid Solar - Design Help Needed

iamrich

Solar Addict
Joined
Dec 17, 2020
Messages
767
Location
Elgin, Texas
It is a solar tracker based on data from some database. So the panels move with the sun's angle and such to get maximum solar.
I would just buy more panels. Don't know what that rig costs for each panel, but I am betting more than $50 each (which is the cost of another panel). If you have 16 acres, panel the crap out of it :D

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iamrich

Solar Addict
Joined
Dec 17, 2020
Messages
767
Location
Elgin, Texas
For batteries, you could go with something like this (if they are ever in stock again)


Two would probably get you through 24 hours, three no issues. And you can add from there as needed if you end up on the generator more than you like, and they are rack mountable so you can make the pretty.
 

boondox

Chief Engineer, RedNeckTech Industries
Joined
Mar 1, 2020
Messages
657
I agree that more panels is the way to go vs a tracker. I have helped build two trackers, back when solar cost a lot more than it does now. Luckily I got to spend other people's money . In the end the owners agreed that a fixed array would have been better. One is still working and the other died less than 5 years after being built.

As to the Magnum inverters, that is what I run. I have some nits to pick but overall I am happy with them. They have run 24/7 for years. They are true split phase. They stack and Magnum makes nice mounts and boxes for them. I like having two, they load share and charge together seamlessly and if one craps out (knocks on wood) I still have 4.4kW worth of inverter to get by on until I can get a replacement shipped to me.
 

blaise

New Member
Joined
Apr 21, 2021
Messages
10
I agree that more panels is the way to go vs a tracker. I have helped build two trackers, back when solar cost a lot more than it does now. Luckily I got to spend other people's money . In the end the owners agreed that a fixed array would have been better. One is still working and the other died less than 5 years after being built.

As to the Magnum inverters, that is what I run. I have some nits to pick but overall I am happy with them. They have run 24/7 for years. They are true split phase. They stack and Magnum makes nice mounts and boxes for them. I like having two, they load share and charge together seamlessly and if one craps out (knocks on wood) I still have 4.4kW worth of inverter to get by on until I can get a replacement shipped to me.
It looks like the better/later model is the MS4448PAE so I'll go with that. I guess it stacks better or something.

I told my wife about what I'm learning here and the idea that we should run more things while the sun is out and batteries are charged to use the extra power we have. She said "sun's out, guns out!".
 

Wellbuilt

Solar Addict
Joined
Sep 14, 2020
Messages
664
Hi all new guy here ,
11000 kw is a lot of power .
The more battery you have the more solar panels you need , the larger the system .
My cabin is 2800 plus sq feet
I have a 430 AH battery 16 6 volt golf cart battery’s @89 $ each 48 volt out back system .
I use 15% of my battery in 22hrs with 2hours worth of charging .
This time of year I use less then 10% of my battery over night .
I run a freezer frig radio tv cell booster water pump phone I pad chargers lights lights .
I dont use more then 2/300 watts day and night .
If you had 3 times your needed battery capacity on day 3 you would be sulfating your battery’s .
2x battery capacity is better .
So look at a outback flex power one unit , its a 36/48 inverter charger fm80 charge controler
It has a mate program computer and a hub to Connect every thing and battery monitor .
It has all the fuses and disconnects built in and it’s a very small package.
You just hook up your solar and battery’s and you are done .
I have my fm80 over paneled a little 4500 watts .
Last winter was cold and snowy my panels where covered for 10 weeks .
I have a second fm80 and 15 more panels to ground mount .
 

Bossrox

Solar tinkerer
Joined
May 21, 2021
Messages
140
Location
Columbia, SC
Batteries wired in series doesn't raise the a/hrs but it does doubles the watt hours. The web has a handy a/hr to kw converter. but if you're daily kw usage is 11kw, you need to determine how much of that is your overnite use & size your batt bank accordingly plus factor in days of low solar. At your best senerio it's best to have 75% more a/hrs in batts than you expected draw if using lead-acid, 10-15% more for lithium. I don't like drawing more than 25% off my bank. But when you factor in dim solar days you need way more batt power & For ideal conditions I would plan your bank at the very least like this. Say your overnite draw is 500 a/hrs. Then the minimum, you'll need 2000 a/hrs if your using lead acid & about 700 a/hrs if it's lithium. But then take into account you'll have some days of total overcast & depending on your solar panel capacity you might be making enough to cover your daytime usage but won't have anything to charge the batts. Unless you have piles of $$$ to throw at batts, most systems won't go a full day on batteries.
 

wkyongae

New Member
Joined
May 30, 2021
Messages
22
First post here. Sorry for not being a contributor before asking for help. If there is an Amazon referral link for this forum or a donation page, I'll be more than happy to give back.

I'm designing/building my primary residence in E. Washington state. 16ac of very secluded land. No power available anywhere. I have some background back in the day as a 2 year residential journeyman electrician but that was 20+yrs ago and my math is bad. ;)

I've done quite a bit of reading but want any advice from the vets if I'm on the right/wrong track.

Here is where we are:
1. We have done our power audit and we are a solid 8500/11,000(w/loss) daily watts on the worst day (Mini split, laundry, vacuuming). This includes everything except my shop which will have its own system but not for 12-18 months after the house is finished.
2. Just my wife and I and our 2 dogs. No kids and probably not many visitors.
3. Budget build. Every for the house build is cash unfortunately and will have to make every dollar go as far as we can.
4. House is 1 bedroom/1 bath total of 1232sq. Won't have a garage.
5. Well pump power has been figured out and is on its own system.
6. According to all the maps and charts I feel good about the number of 4hrs of sun light a day.
7. Solar panels will be free of any obstacles and on rotating platforms ran by an Arduino board to get the maximum sun.
8. I have decided on a 24v system.
9. Will have a dual fuel generator for those cloudy times and as a backup.
10. This will be 99% DIY. The extra 1% will be the help and advice everyone gives me!

Here are a couple questions I have.

If I'm at 11kw daily at 24v then I need 460ah of battery. Is this correct? (Wh)/(V) =(Ah)

Then I have to double that so I don't discharge more than 50%? So does that means I want 940ah of batteries?

And then I want 3 days of total battery capacity so I want 2820ah of batteries?

I've decided on 12v 100ah (C20) batteries. This is all I can afford unfortunately and I have 4 of these in our Sprinter van so I'm familiar with them. So does this mean I need 29 batteries? Wait, I'm 24v so now I need 58 batteries because I have to double my voltage but it doesn't double my amp hours. Is this all correct so far before I go any further?
Hi, my wife and I live in the Davenport, Wa. area for almost a year now completely off grid. We have a separate well system as well. Our main power comes from 6 - 310watt panels, 24 volt system with a 2kw generator. Bought from Altestore it's called the tiny house base kit 3. 8 - 6 volt Trojan fla batteries. Personally, could use more batteries and more panels but not in the budget. We also are in the process of building our place. What we power during the day, refrigerator, freezers, barn lights, washing machine, sump pump, vacuum cleaner. Granted all this is not on at once, but alot is. Nothing at night unless we want to run the generator. I on drain my batteries 20 to 30 percent, longer life, so less replacement cost.
 

Bossrox

Solar tinkerer
Joined
May 21, 2021
Messages
140
Location
Columbia, SC

Heya blaise, I don't know how summer weather is up there in Wash but here in SC 11kw a day would just run my fridge, freezer, lights & electronics. Just those running averages 500 watts an hour. I live in a mini house & have a shed, both have window A/C's, 1 is 15,000 the other is 10,000 btu. I can get by in the spring & fall with 11kw but once the A/C's get going I'm in the 30kw range so I'm skeptical that will get it for you but anyways, I'm running a 24v system too but about to go to 48v & I can just about make all I need with 36 300 watt panels & 1300 a/hrs in batteries which carries me over for the night @ a 35% draw for summer & about 20% for spring & fall but that would be 2600 a/hrs @ 12v, but I have an average of double the sun hours you have.​

You might want to look over at the battery & bulbs store if you have 1 around your area for their duracell 4d batteries. Their about $200 apiece & 190 a/hrs, I have 20 but I got them used so their capacity isn't like new. That will cut your battery count in half with less wiring, you gotta figure that expense, wire is pricey. Look on craiglist for used panels, you should be able to find 300+ watt panels for about $100 apiece & there's places on the net that sells palates about the same price or less minus the shipping.​

With only a 4hr average of sun, you'll need at least 48 300+ watt panels. That's overkill when the suns out but when there's dim sun, that amount of panels will still kick out some decent power​

Your ? about a/hr's when stringing batts in series is, no matter how many you put in series, the a/hrs remains the same as just a single batt but the kw hours multiples by the # in series.​

I would assume in your state you likely don't need to run an A/C much at night in the summer & here mine runs minimally at night & my nightly average power use is about 35% of my batt bank capacity. If you want 3 days of battery power, I'd say you'd need about 5-6000 a/hrs @24v to keep your draw below 50% & that's not an ideal goal. You'll get years more lifespan limiting it to 65-70%.​

I'd highly suggest you invest in a trimetric battery monitor to keep accurate tabs on your batts state. With that much invested in your system, guessing could be costly. Most other monitors are rough gauges & not trustworthy. I got a youtube channel of my goings on down here, you might could pick up some useful info from there @ Link Best of luck to ya!​

 

Bri from IA

New Member
Joined
Nov 27, 2020
Messages
16
Units are everything. Blaise, when you mention "11kw a day" I pretty sure that means 11kWH per day.

If you had 11kW in panels, and the sun shined on them for one hour, that would get you 11kWH. If there were 5.5kW in panels, at 2 hours, you'd end up with the same 11kWH. With the predicted 4 hours of sun, that's a minimum of 2.75kW (2,750 watts) of panels. (Had a mental math error, hence the edit.)

But the 4 hours per day according to the charts is a seasonal average. You'll need to be prepared to deal with a an extended period of overcast clouds. We just emerged from 2 weeks of that in Iowa. What I've experienced with my off-grid system is anywhere between 5-25% panel output on a cloudy day, really varaiable on how dense the clouds are. Bigger battery and/or generator with fuel storage is the way to go. Its probably impractical to size your solar array using 10% output rating, super overkill for sunny days, but one way to avoid a generator.

I'd agree with everyone else that more panels is the way to go. For my system, the panels were about 1/4 of the overall system cost. Ground racking, inverter/charge controler and batteries were the other major cost areas.
 

Bossrox

Solar tinkerer
Joined
May 21, 2021
Messages
140
Location
Columbia, SC

Heya blaise, I don't know how summer weather is up there in Wash but here in SC 11kw a day would just run my fridge, freezer, lights & electronics. Just those running averages 500 watts an hour. I live in a mini house & have a shed, both have window A/C's, 1 is 15,000 the other is 10,000 btu. I can get by in the spring & fall with 11kw but once the A/C's get going I'm in the 30kw range so I'm skeptical that will get it for you but anyways, I'm running a 24v system too but about to go to 48v & I can just about make all I need with 36 300 watt panels & 1300 a/hrs in batteries which carries me over for the night @ a 35% draw for summer & about 20% for spring & fall but that would be 2600 a/hrs @ 12v, but I have an average of double the sun hours you have.​

You might want to look over at the battery & bulbs store if you have 1 around your area for their duracell 4d batteries. Their about $200 apiece & 190 a/hrs, I have 20 but I got them used so their capacity isn't like new. That will cut your battery count in half with less wiring, you gotta figure that expense, wire is pricey. Look on craiglist for used panels, you should be able to find 300+ watt panels for about $100 apiece & there's places on the net that sells palates about the same price or less minus the shipping.​

With only a 4hr average of sun, you'll need at least 48 300+ watt panels. That's overkill when the suns out but when there's dim sun, that amount of panels will still kick out some decent power​

Your ? about a/hr's when stringing batts in series is, no matter how many you put in series, the a/hrs remains the same as just a single batt but the kw hours multiples by the # in series.​

I would assume in your state you likely don't need to run an A/C much at night in the summer & here mine runs minimally at night & my nightly average power use is about 35% of my batt bank capacity. If you want 3 days of battery power, I'd say you'd need about 5-6000 a/hrs @24v to keep your draw below 50% & that's not an ideal goal. You'll get years more lifespan limiting it to 65-70%.​

I'd highly suggest you invest in a trimetric battery monitor to keep accurate tabs on your batts state. With that much invested in your system, guessing could be costly. Most other monitors are rough gauges & not trustworthy. I got a youtube channel of my goings on down here, you might could pick up some useful info from there @ Link Best of luck to ya!​

1 other thing, I'd shoot for a 48v system right off the bat & here's why. All charge controllers I'm aware of have limits on the amount of panel power you can feed them. Example: My victron 150/100 max input is 3000 watts of panels @ 24v but @ 48v it doubles. So when you find out you'll need more panels & you will, to make what you need, your 24v inverter will hold you back half the potential you can get from the charger.

My suggestion for a good quality & fairly reasonable cost system would be 2 victron 150 or 250/100's, about $750 apiece if you know where to get them that cheap, a genetry solar 48v 6kw inverter $1000, & since you're off grid, another inverter for a backup, at least 24 duracell 4d's, $200 apiece & that'll cover you for just a day running off batts, at least 36 300+ watt panels $100-125 apiece but 48 would be a better goal for your main equipment costs then you have the structure to mount the panels, a battery cabinet & wiring, easily another couple grand so there's the range you're looking at in costs to get a decent system that'll provide a reliable amount of power..
 

Wibla

Engineer
Joined
Jun 6, 2021
Messages
193
With a flat 11 kWh per day consumption in east Washington, I'd go with 10+kW solar, a 30 kWh battery (48V lifepo4, forget 24V) and make peace with having to run the generator a fair bit during December and January.
 

wkyongae

New Member
Joined
May 30, 2021
Messages
22
Forgot to mention, in eastern Washington there is just a wee bit of wind. Wind gusts can exceed 60 mph. Not stable enough for a wind turbine. And we get alot of mini tornadoes that constantly can move things. I would not want my panels on the roof or on a rotating platform. Just not worth the risk.
 

dustonlarsen

Solar Enthusiast
Joined
Jan 23, 2021
Messages
25
Go 48V. No, you will not need more batteries. 48V means smaller wiring and better equipment options.

Also, you may not need as much power as your audit indicates. For example, you can do laundry during the day. If so then you don't need to factor it into the battery size. I haven't done laundry at night for over 20 years. I do all my high power stuff like welding, laundry etc. during the day. That way your battery only needs to be sized for what you have to have at night.
 

Wellbuilt

Solar Addict
Joined
Sep 14, 2020
Messages
664
^^^^^^
this is what I do.
at dinner time the house is jump we are using power after dinner it quiet time we run 2 TVs some ceiling fans lights and our regular bace load we pump water during the day run the dish washer in the morning do Landry .
you only need battery’s for night time and bad weather but even in bad weather this time of year I get good power .
I don’t need ac at all the place stays 67o ish all summer .
i only get 2.5 hours of sun in December and then it snows every night just enough to cover the solar panels so it takes until 12 to melt off then the sun go’s down 🤬 I make on average 4500 to 5500 watts a day and my battery’s are full at about 3000 +watts so I use 2000 watts during the day
my inverter uses about 1200 just being on
 
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