Off grid barn - need only lighting solution

[CharlieInSoCal]

I think this is the correct place to post ...

We are putting in a barn that if I brought grid power to it I'm looking at about 450 ft away from the closest sub panel in the garage. To run a single 15 amp circuit calls for 3 AWG wire to keep voltage to below recommended 3%, and this is about $2300 in THHN/THWN wire alone. Add in conduit, trenching, and other costs, not happening.

So, looking at solar just for lighting, and use a 4000 watt generator I already own for any non lighting needs.

I already have solar for my house (3000 excess kWh last year, will go to zero or near zero with out addition of PHEV vehicles), so I've got real world monthly numbers of solar generation at my specific location.

I'm planning to use twelve (12) four foot LED tube fixtures that are 24 watts each and produce 3100 lumens at 6500K. I will use six fixtures in the center aisle and three fixtures on each side of the barn (one fixture in the center of each stall). We would use the lighting maybe an two hours max per day in winter, half of that spring/fall, and likely very little summer. As to summer, depending on how temps play out, we may have some ceiling fans for air movement -- though we have excellent prevailing winds from the cooler coastal air (we are 12 miles as the crow flies to the Pacific), and the barn is a raised center aisle with one foot of open space top of barn wall to roof eave overhang along the entire length of both sides, and the same one foot gap along the sides of the raised center aisle roof -- i.e. should get good ventilation.

So, with maybe two hours max use per day use of 300 watts (rounded up), this should be roughly 25 to 50 amp hours max, and typically much less as the lights will be on three separate switches (center and each of the two sides of the barn) and my wife says she would probably most of the time use just the center aisle switches.

PVwatts and real history say the planned single 72 cell 370 watt panel will give me 30 kWh in the worst month and about 58 kWh in the best months (about 535 kWh for the year), I'm leaning to a single 12 volt battery with 100 AH to 150 AH (can always add another battery if needed).

I like the All in Ones (such as MPP Solar LV1212) but it looks like I can't set up the inverter to be switched on/off via an external switch. So, maybe separate charge controller (40 amp MPPT) and 1000 watt pure sign wave inverter with remote on/off (equipment is likely going to be away from the entry light switches (I'll rewire remote on/off to a light paddle switch), and then the appropriate fuses.

Permit application submitted this week. Permit process could be months (sad), then grading. Barn will be installed in two days (pre engineered barn). Then sprinkler system installed and final inspection. All solar (or electric if I did run power) after barn is signed off and approved.

So, questions are:

- Any feedback on approach?
- All in One or separate charge controller and inverter?
- Best battery technology with least fire risk (AGM, LifePO4, or Bolt Ultra Silicate-Salt)? FYI, building codes require barn to have fire sprinkler system.

Thanks in advance for comments and feedback.

 

[RStone13]

FYI I have a Mpp Solar and just learned that it charges the battery from PV even if unit is turned off.

 

[CharlieInSoCal]

FYI I have a Mpp Solar and just learned that it charges the battery from PV even if unit is turned off.

Interesting. I called Ian at the Utah MPP Solar USA site and asked about a remote kit for the inverter portion. He said I just had to rewire to on/off switch to something remote but I thought he was thinking I wanted to turn the whole unit on or off and not just the inverter.

So, what you are saying is you turn off the switch, and the display is off and supposedly the "unit" is off, but the battery is charging. Maybe that does make sense because the MPPT would be powered by the battery. I'll have to cogitate that, but if true, it certainly puts the PIP-1012LV-MS as the probably should by unit if I go All In One.

 

[RStone13]

Interesting. I called Ian at the Utah MPP Solar USA site and asked about a remote kit for the inverter portion. He said I just had to rewire to on/off switch to something remote but I thought he was thinking I wanted to turn the whole unit on or off and not just the inverter.

So, what you are saying is you turn off the switch, and the display is off and supposedly the "unit" is off, but the battery is charging. Maybe that does make sense because the MPPT would be powered by the battery. I'll have to cogitate that, but if true, it certainly puts the PIP-1012LV-MS as the probably should by unit if I go All In One.

Yes, turn the switch to off. Display still works but shows only panels & battery.(weather full or charging). Then if you turn it on it also shows load info. (power out)

 

[iamrich]

So, what you are saying is you turn off the switch, and the display is off and supposedly the "unit" is off, but the battery is charging. Maybe that does make sense because the MPPT would be powered by the battery. I'll have to cogitate that, but if true, it certainly puts the PIP-1012LV-MS as the probably should by unit if I go All In One.

With the inverter off, the unit still draws power from the battery(ies), but much less. I am using the hybrid LV2424, but I have a big enough battery pack that I just leave the inverter on. Another option might be to have a small 24vdc LED light for the interior hooked directly to the battery on a switch right at the door that gives you enough light to get to the inverter to turn it on and power up the main lighting.

 

[RStone13]

W

With the inverter off, the unit still draws power from the battery(ies), but much less. I am using the hybrid LV2424, but I have a big enough battery pack that I just leave the inverter on. Another option might be to have a small 24vdc LED light for the interior hooked directly to the battery on a switch right at the door that gives you enough light to get to the inverter to turn it on and power up the main lighting.

With unit off it will charge battery and only draw power for display screen & fans if controller gets too warm. After sun goes down display shuts off and power consumption is about 1 watt. In morning when sun comes up it will wake up and charge battery again. There will be no out put power unless you turn unit back on. So basically the switch only turns inverter on & off.

 

[iamrich]

My fans stay on all the time (Hybrid LV2424), and they use more than 1 watt, but regardless it's not much. I have a ~6kw battery pack with no draw and a 2.25kw array, so there is not much danger of running out of power

 

[RStone13]

My fans stay on all the time (Hybrid LV2424), and they use more than 1 watt, but regardless it's not much. I have a ~6kw battery pack with no draw and a 2.25kw array, so there is not much danger of running out of power

I could be wrong, but the way I understand it. In morning charge cycle starts in bulk (funs will run). When it reaches bulk setting goes into absorb mode for 2 hrs (fans still run). After the 2 hrs goes into float mode and my fans turn off. They (fans)will auto back on if either inverter or controller get too warm. FYI My unit in on with no load pulls 15w x 24hr= 360w

 

[CharlieInSoCal]

With unit off it will charge battery and only draw power for display screen & fans if controller gets too warm. After sun goes down display shuts off and power consumption is about 1 watt. In morning when sun comes up it will wake up and charge battery again. There will be no out put power unless you turn unit back on. So basically the switch only turns inverter on & off.

That sounds good. If I go with 100 AH battery, then I'm going to be wanting to conserve those 360w for 24 hours of leaving on. If I go 150 AH or 200 AH battery, I'll probably just leave it on full time. When I looked at solar data for the 14 months in the house, I couldn't find any 3 day period in the winter where I wasn't producing over 1 kWh per 315 watt panel. With my planned use of a 370 watt panel, I'm not worried about being able to keep a battery charged, especially a winter day with sun is going to be 1 kWh per day, not to mention if there was an issue with not enough solar, just run the 4000 watt generator I already own that will be kept at the barn.

 

[GXMnow]

Have you thought about 12 volt DC lighting? Just a charge controller, the battery and switches. Have a 12 volt inverter for running the ceiling fans and/or power tools when you need it.

 

[CharlieInSoCal]

I would consider 12 volt DC fixtures, but I don't think I can get the lumens I want at anywhere close to the price of the four foot LED fixtures (24 watts each, 3100 lumens each).

I've ordered these fixtures https://www.amazon.com/gp/product/B08RXTWBBD/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1 to check out in my garage at night. Twelve fixtures for $89.99 (with the $10 off discount) are tough to beat. I will have cee purlins centered over the stall and two cee purlins at 4' and 12' in the 16' wide aisle that I will either mount the included clips to the purlin or more likely zip tie to the bottom of the purlin.

 

[GXMnow]

So you need 16 x 24 = 384 watts to run all the lights at once. I would go with at least a 1,000 watt inverter so you can also run a power tool or the fans etc. You will lose a bit of power in the conversion, but it should not be a problem. Using 50% of a 12 volt 100 AH battery would give you a useable 500 watt hours at night. That is not even 90 minutes with all the lights on. You can run an LFP battery lower, say 80% with some safety margin, that will get you just past 2 hours. I think you are going to want more like 200 AH to be safe once you add the fans. One solar panel may keep up with just the lights, but they are a fairly cheap part of this project, so while you are up there, just put up 2. The MPPT will work better with a bit more voltage as well. Maybe use 2 cheap 300 watt 60 cell panels in series instead of the single 72 cell. SanTanSolar has 250 watt panels for just $50. Two of those and a 40 amp MPPT would work great.

500 watts x 5 sun hours = 2.5 kwh on a good day. That is just under 200 amp hours into a 12 volt system. Peak charge current could hit 42 amps or so, but you can probably get by on a 40 amp charge controller as long as it can handle 600 watts of input power. Maximum voltage from the solar panels should not exceed 80 volts, so most controllers will take that.