diy solar

diy solar

Off Grid Solar System, opinions and advice welcomed

PV panels are cheap ($0.025/kWh amortized over 10 years).
Batteries are expensive ($0.50/kWh by end of cycle life, for AGM or top-name lithium; FLA $0.25/kWh, recycled or DIY can reach $0.05/kWh)

Therefore, I favor over-paneling, and limiting charge current to what is health for battery. Cheaper to throw away unused power.
 
I'll try and provide a bit more infomation on what we are wanting and expecting out of our solar set up.

By going off grid and building a homestead we are wanting to get closer to the land to live a more simplistic and independent lifestyle closer to nature. We will be working with the flow of seasons. Waking up and going to sleep with the sun. Our aim is to reduce our energy consumpion to a minimum. Obviously we are not going Amish and want some of our modern comforts, especialy with a young son.
We want to be conscious about our energy consumption. Instead of having the mentality of being able to do whatever, whenever we want with our electricity we would like to work within our means.

Most of our time will be spent outside. Our main electrical consumption will be from fridges and chest freezers and this will be reduced by the construction of root cellars and keeping blocks of ice in our freezers.

Our habitations will be constructed with insulation from the heat and cold in mind. As our property is flat and fully forrested the trees we cut down to clear a couple of acres to build on will be used in the construction of these structures. Roundwood timber framing with earthen roofs is what we are going for. very strong and great insulation. especially with 2' thick straw bale walls.

Our property is in South Eastern Oklahoma. Oklahoma has a sun index of 0.98 and is ranked 6th best state for solar potential. Winters are dry and sunny. the rain happens mostly in the spring and a bit in the fall.

Our property has full southen exposure and the panels can be located with no obstruction from sunset to sunrise, even in the winter.

The system we are setting up is by no means the end goal. We want to start with a decent foundation that we can build on over time. It would be nice to have more solar panels and battery capacity but with all of the money outgoing on the purchase of the land, buying a trailer to live in during construction and development of the land this is all we can afford right now. By the end of the year we will be able to upgrade our system so this really is quite temporery.

The transformer is sold as part of a kit with the growatt inverter/charge controller from signature solar based in texas. It is so we can run a single phase 120v system.

We dont ever see ourselves needing more than a 10kw system. As and when money comes in we will invest in more batterys and panels.


This is my very basic Power audit: Please don't laugh

10cu.ft. Fridge/freezer 810wh
Hood vent 90wh
4xfans 720wh
laptop 500wh
cell phones 50wh
lights 180wh
water pumps 120wh
outdoor lights 80wh
power tool charging 800wh
Window AC 2200wh
small chest freezer 1500wh
Washing machine 500wh
propane dryer 500wh

8050wh

This is a power audit for all of our electrical need (maybe a few small things missed). We will not need to run all these appliances every day.

For example: the fans and Ac unit will only be required for a couple of months out of the year and this will be during optimal solar conditions.
The propane dryer will only be needed during the winter when AC and fans, etc wont be needed.

The only big draw essential items on this list are the Fridge freeze and chest freezer and lights. These use 2310wh per day.

All the lights, extractor fans and pumps on the 5th wheel are on a 12v system. energy efficient led bulbs are used. The only AC appliance in the 5th wheel is the 10cu.ft. fridge freezer. and the wall outlets.
The water heater is propane, we have a wood burning stove installed for heat

We aren't opposed to running the generator for an hour or two a day to suppliment the solar system. If there are days of bad solar we can charge the batterys with the generator. We would take advantage and while the generator is running charge our power tools, do laundry etc.

I cant emphasize enough that this is a stepping stone system that is intended to be built upon.

It is clear that the battery capacity is our biggest weakness. Followed by the solar array.

What do people think our next step should be? Cough up $1500 and double our battery capacity or spend $500 on panels and double our array.
What added costs are there in a 8S2P array? do i need a combiner box?
would splitting the panels half facing SE half SW compensate for our battery capacity?

Thanks for all of the input, I appreciate the time people have spent in helping us out.
 
Links to solar components:

5000W LVM- ES Off-Grid 240V Growatt Inverter with Solar Charge Controller + Growatt Split Phase Transformer for true 120V/240V Split Phase Electricity!

48V 100AH LiFePower4 Battery by EG4​


8 x SanTan Solar T Series 250W​

Specifications:

  • Rated Power: 250W
  • Open circuit voltage (VOC): 37.6 V
  • Max power voltage (VMP): 30.3 V
  • Short circuit current (ISC): 8.85 A
  • Max power current: 8.27 A
 
This is my very basic Power audit: Please don't laugh

10cu.ft. Fridge/freezer 810wh

Sounds reasonable.

Hood vent 90wh
4xfans 720wh

While fans are very beneficial in a residence allowing one to run A/C less in off-grid, they are pretty brutal. These are about 15% of your total battery capacity.

laptop 500wh

Seems high unless you're running 10hr/day.

cell phones 50wh
lights 180wh
water pumps 120wh
outdoor lights 80wh
power tool charging 800wh
Window AC 2200wh
small chest freezer 1500wh
Washing machine 500wh
propane dryer 500wh


Well, you just covered it with your 8 panels. Better in summer. Worse in winter.

This is a power audit for all of our electrical need (maybe a few small things missed). We will not need to run all these appliances every day.

For example: the fans and Ac unit will only be required for a couple of months out of the year and this will be during optimal solar conditions.
The propane dryer will only be needed during the winter when AC and fans, etc wont be needed.

Diminished loads in winter.

The only big draw essential items on this list are the Fridge freeze and chest freezer and lights. These use 2310wh per day.

Yep.

All the lights, extractor fans and pumps on the 5th wheel are on a 12v system. energy efficient led bulbs are used. The only AC appliance in the 5th wheel is the 10cu.ft. fridge freezer. and the wall outlets.

12V achieved via 48V to AC to 12VDC will be about 70% efficient.

The water heater is propane, we have a wood burning stove installed for heat

Nice! Was wondering about heat.

We aren't opposed to running the generator for an hour or two a day to suppliment the solar system. If there are days of bad solar we can charge the batterys with the generator. We would take advantage and while the generator is running charge our power tools, do laundry etc.

You really want the generator to be the outlier, i.e., when weather is just trash OR if you really have high demand items it doesn't make sense to power via solar. My friend used to have to run his generator every time he wanted to pump out of his 700' well - a couple hours a few days a week.

Given the cost of panels, another $400 to double the size of your array is hands down the best bang for the buck.

I cant emphasize enough that this is a stepping stone system that is intended to be built upon.

"Building upon" needs to consider the end goal. Unfortunately, without that level of planning, you may find that this is system #1 and will be replaced with system #2. It's probably not in your case, given the scalability of the unit.

It is clear that the battery capacity is our biggest weakness. Followed by the solar array.

What do people think our next step should be? Cough up $1500 and double our battery capacity or spend $500 on panels and double our array.

This by an order of magnitude. More battery doesn't help you when you're consuming more than you can replenish. The battery just limits you on power expended between charging. You already have the generator to make up for that. I see it this way:

$1500 for 5kWh of capacity
$500 for 8kWh of solar

What added costs are there in a 8S2P array? do i need a combiner box?

That's generally how it's done, but with only 2P, you don't NEED one. You technically don't even need fuses/breakers on 2P - only 3P and more.

Your ground mount will be double, but DIY can be pretty cheap.

would splitting the panels half facing SE half SW compensate for our battery capacity?

Not so much compensating for it, but it helps. It makes power use more flexible in that it would widen the hours in which you will be producing elevated power at the expense of peak power at noon. It would look like this:

1641935232260.png

Red horizontal line is max array. Blue/red bell curve is a south facing array (jagged stuff is clouds). Red lumps are SE + SW arrays.
 
Sounds reasonable.



While fans are very beneficial in a residence allowing one to run A/C less in off-grid, they are pretty brutal. These are about 15% of your total battery capacity.



Seems high unless you're running 10hr/day.





Well, you just covered it with your 8 panels. Better in summer. Worse in winter.



Diminished loads in winter.



Yep.



12V achieved via 48V to AC to 12VDC will be about 70% efficient.



Nice! Was wondering about heat.



You really want the generator to be the outlier, i.e., when weather is just trash OR if you really have high demand items it doesn't make sense to power via solar. My friend used to have to run his generator every time he wanted to pump out of his 700' well - a couple hours a few days a week.

Given the cost of panels, another $400 to double the size of your array is hands down the best bang for the buck.



"Building upon" needs to consider the end goal. Unfortunately, without that level of planning, you may find that this is system #1 and will be replaced with system #2. It's probably not in your case, given the scalability of the unit.



This by an order of magnitude. More battery doesn't help you when you're consuming more than you can replenish. The battery just limits you on power expended between charging. You already have the generator to make up for that. I see it this way:

$1500 for 5kWh of capacity
$500 for 8kWh of solar



That's generally how it's done, but with only 2P, you don't NEED one. You technically don't even need fuses/breakers on 2P - only 3P and more.

Your ground mount will be double, but DIY can be pretty cheap.



Not so much compensating for it, but it helps. It makes power use more flexible in that it would widen the hours in which you will be producing elevated power at the expense of peak power at noon. It would look like this:

View attachment 79256

Red horizontal line is max array. Blue/red bell curve is a south facing array (jagged stuff is clouds). Red lumps are SE + SW arrays.
Thank you so much for your responses. You are making things clearer for me.
It sounds like the first thing we should do is get more panels, put them in 2p and face them SE and SW. This kind of makes up for our low battery capacity and high draw inverter. (widens the hours of producing power therefore less time of just draw from the inverter)
 
Just over paneling all facing south (if your charge controller allows it) makes a huge difference. We went from about 6-8kWh in winter production to an average of 14.2kWh in Jan production so far by simply doubling our array size from 2565w to 5130w on a single midnite solar classic 150.
 
I just found this fourm so am going to be doing some digging around before I ask any more questions.

I've already ordered all the components mentioned above so am commited now.

I've got to wait until beginning March for the battery so i've got time to do more research.

I'm based in California at the moment, will be driving down to Oklahoma at the end of this month via Phoenix to pick up a pallet of solar panels (25) from santan solar. I promissed my neighbor who sold us the land I would bring him back some panels. I've just got to tell him now that we want half of them.
12 panels should be 2400w based on 80% efficiency.
 
Just over paneling all facing south (if your charge controller allows it) makes a huge difference. We went from about 6-8kWh in winter production to an average of 14.2kWh in Jan production so far by simply doubling our array size from 2565w to 5130w on a single midnite solar classic 150.
Where abouts are you based? Do you know what your average kwh production was on your 2565w array during good solar conditions?

thanks
 
Where abouts are you based? Do you know what your average kwh production was on your 2565w array during good solar conditions?

thanks
North Central FL

I've been at this for over 4 years now. 4000w Schneider Conext SW4024 and Midnite Solar Classic 150 System has worked flawlessly. (build is in my signature).

Before the array up grade the largest production I ever saw was a rare 12kWh ever once in a while in late spring or early fall on a perfect day. I used to keep a spread sheet of daily production for about 2 years. Averaged probably 9.5 per day in a year. Biggest daily max at any given moment I would see would be 2200 ish watts then it'd settle back down Around 2000-2100 on a great day

Since upgrading the array, now my average in Jan as of today is 13.8 (down a little Bc of 2 crap days). But I routinely seen the system clipping at 2480 ish from 11am to 3pm. And if I turn off the old or new array (each 3s3p), each array is producing a max of about 1900w at solar noon on a cloudless day in Jan.

The Midnite Solar class maxes out right at 2600w input total at 94 amps and 27.9 vdc charging volts, but I set it to limit out put to 88 amps because of heat. At 88 amps the FETs are at 72°c, at 94 amps the FETs are at 88°c +. Midnite solar says 72c is perfect.

Here is Dec before and after. New array went online Dec 18. The next 4 days were crap. Then we settled in a more typical weather pattern.

Capture+_2022-01-11-18-52-35~2.png
 
Long story short
-PV is cheap, at least cheaper than batteries
-some (not all) SCCs (solar charge controllers) and all in one's allow for over paneling . There is a resource down load here of which do and don't allow over paneling
-sadly, as best we can tell here from research and antidote evidence, the Growatts with transformers like the 12kw do not allow for over paneling

I am about to install a fully off grid 12kw Growatt inverter at my daughter's farm. No power there . Poco wanted $35k+ to bring lines out a 1/4 mile for the privilege of being charged monthly for power. We are building the system for just over $15k. Sig Solar told us we could install 11.8kw of array split into the 2 PV inputs. Then another member here smoked there scc over paneled and it appeared u can only do 7kw arrays split into 3500w + 3500w input into the Growatts.

Since Sig Solar had already sold us the 11.8kw of panels, so we decided to get a second scc and use the full array no clipping.
 
I just found this fourm so am going to be doing some digging around before I ask any more questions.

I've already ordered all the components mentioned above so am commited now.

I've got to wait until beginning March for the battery so i've got time to do more research.

I'm based in California at the moment, will be driving down to Oklahoma at the end of this month via Phoenix to pick up a pallet of solar panels (25) from santan solar. I promissed my neighbor who sold us the land I would bring him back some panels. I've just got to tell him now that we want half of them.
12 panels should be 2400w based on 80% efficiency.

You can simulate your array performance based on location and weather here:


Here's a run for Altus, OK, 2400W, 30° tilt, south facing:


1641946267150.png


Divide the AC Energy number by the # of days in the month, and that's your daily kWh harvest., so Jan, 295/31 = 9.5kWh.

It does factor in average weather over the last 30 years for each day.

If you're feeling brave, you can download hourly data, which gives you an idea of how many consecutive days you might get poor charging.

This tool also has a simulator that can estimate how many days per year your battery will be tapped:

 
North Central FL

I've been at this for over 4 years now. 4000w Schneider Conext SW4024 and Midnite Solar Classic 150 System has worked flawlessly. (build is in my signature).

Before the array up grade the largest production I ever saw was a rare 12kWh ever once in a while in late spring or early fall on a perfect day. I used to keep a spread sheet of daily production for about 2 years. Averaged probably 9.5 per day in a year. Biggest daily max at any given moment I would see would be 2200 ish watts then it'd settle back down Around 2000-2100 on a great day

Since upgrading the array, now my average in Jan as of today is 13.8 (down a little Bc of 2 crap days). But I routinely seen the system clipping at 2480 ish from 11am to 3pm. And if I turn off the old or new array (each 3s3p), each array is producing a max of about 1900w at solar noon on a cloudless day in Jan.

The Midnite Solar class maxes out right at 2600w input total at 94 amps and 27.9 vdc charging volts, but I set it to limit out put to 88 amps because of heat. At 88 amps the FETs are at 72°c, at 94 amps the FETs are at 88°c +. Midnite solar says 72c is perfect.

Here is Dec before and after. New array went online Dec 18. The next 4 days were crap. Then we settled in a more typical weather pattern.

View attachment 79277
Nice, Thanks for the infomation.
My array will be a similar size to your original one so its nice to see your figures
 
You can simulate your array performance based on location and weather here:


Here's a run for Altus, OK, 2400W, 30° tilt, south facing:


View attachment 79283


Divide the AC Energy number by the # of days in the month, and that's your daily kWh harvest., so Jan, 295/31 = 9.5kWh.

It does factor in average weather over the last 30 years for each day.

If you're feeling brave, you can download hourly data, which gives you an idea of how many consecutive days you might get poor charging.

This tool also has a simulator that can estimate how many days per year your battery will be tapped:


Nice, thank you.

so 3890/365 =10.65kwh per day on average

That seems good for our energy consumption needs.

If we were to do a 6s2p array. half facing SE half SW do you have any advice on how far off south we should have the panels facing? like SE and SW or SSE and SSW?
 
Link the inverter? All I can find is a link to the transformer.

But I would think your biggest issue to watch will b VOC, operating input volts at a specific system voltage, and not exceeding array input. At least not much. Different orientations will mitigate it some, and allow a little more over paneling
 
Can the SCC do 6s?I was only going to run our growatt 12kw 250voc on 4s or 192voc operating. 5s was getting me too close
 
James,
I would encourage you to not think too small. After all, solar is "free" after the first $25,000 LOL

I have spent right at 20k, but I have a beast of an 18 kw inverter that can handle 3X the rated surge current.
So I'm running a 2.5 ton central ac heat pump, water heater, freezer, fridge and large air compressor.

It may take you some time to build your system large enough, but why not ?
A freakin' cheap car costs more than my system. I say go big !
 
Link the inverter? All I can find is a link to the transformer.

But I would think your biggest issue to watch will b VOC, operating input volts at a specific system voltage, and not exceeding array input. At least not much. Different orientations will mitigate it some, and allow a little more over paneling
Link to inverter/SCC

 
Link the inverter? All I can find is a link to the transformer.

But I would think your biggest issue to watch will b VOC, operating input volts at a specific system voltage, and not exceeding array input. At least not much. Different orientations will mitigate it some, and allow a little more over panel

450VOC
 
Can the SCC do 6s?I was only going to run our growatt 12kw 250voc on 4s or 192voc operating. 5s was getting me too close
as I understand it 6s of my panels at 37.6 V per panel is 225.6VOC
The charge controller is rated at 450VOC max so well under
 
James,
I would encourage you to not think too small. After all, solar is "free" after the first $25,000 LOL

I have spent right at 20k, but I have a beast of an 18 kw inverter that can handle 3X the rated surge current.
So I'm running a 2.5 ton central ac heat pump, water heater, freezer, fridge and large air compressor.

It may take you some time to build your system large enough, but why not ?
A freakin' cheap car costs more than my system. I say go big !
Go big or go home! hahaha

This is just the start for our system. We'll probably spend around $4000 on this begining stage.

Once the initial development stage of our homestead is complete and I can dedicate some time to making money and not spending it we will upgrade. I see us spending $15,000 total and we should be good.

I'm doing the whole build myself so got my hands full. Going down end of Jan to start clearing. my neigbours got a bobcat so clearing 2 acres and building roads first. Then throwing up a couple of temporery structures and getting our water sorted.

getting all the solar components begining of March so will be a big relief from living off a generator for a couple of months
 
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