Battery shed needed in Minnesota

[Nod51]

I am in the early planning stages of planning a 19kW solar (roughly 115m^2 area) with 20-60kWh LiFePO4 UL rated batteries (likely rack mount). I tend to go from "it will work with duct tape" to "over engineered with titanum screws" quickly so asking for some feedback.

* Minnesota St. Paul area
* I want the battery because frequent power outages/surges and maybe get some RoI by switching to time of day billing
* During June and July I have used ~40kWh a day average (according to my bill).
* I have -22F mini splits and backup restive heaters but don't have any usage data for that yet, I expect it to be more than summer. (100% electric)
* Was hoping I could get 40kWh+ in winter, though doing some research at 4m^2 per kWh that is closer to 28kWh, so batteries for cheap(er) grid electricity.
* Xcel Energy (not sure it matters but thought I would mention it)

I started by asking the housing inspector and the first concern that came up was where to put batteries and fire saftey. I have an unfinished utility room with a water heater, washer, and drier.
* Initnally I was just going to finish what I could with Firecode X sheetrock then a fire would need to go ~10ft before it got to the other side of the room with exposed stuff that I can't easily finish (water/drain pipes going everywhere).
* Next I thought I could make a few 5'x3' closets lined with Firecode X sheetrock and put on metal doors. I would need ventilation into the house as there would be a lot of heat buildup I would like to use anyhow.

Then I found the Minnesota fire code things got more difficult over 20kWh because if I am reading it right I need fire suppression system and exterior veltlation for anything betwen 20kWh and 600kWh. There seems to be hydrogen/gas concern for lithum batteries which I thought was a weird concern for normal operation. Meanwhile I have 150kWh+ of NCA batteries sitting in my garage but I digress....

* So then I thought at that point it may not be much more money to build a 8x10 shed, 6in or 8in wood walls (I think metal would be overkill), Firecode X sheetrock, insulated, no windows, mini split, metal self closing door, 5ft+ from the house (I believe the fire code), cement slab, metal roof, and run 2x 3/0 AWG Aliminum circuits (200A) about ~50ft from my main panel (so basically all house grid goes through this shed). I will then put the MID, inverters, batteries, and such in this shed and some way to byapss it all if a MID fails. Some side positives is it moves the inverter noise out and I don't lose any starge space in the house. If I go with EG4 (TBD) I would also need to run the solar DC down my roof and to the shed so that could be 100ft from the furthurest panel too (though at 400V+ 100ft may not be a big deal vs 240V).

so... did I go too far or not far enough? I am planning to consult the fire marshal and would like to get my options/questions in order before making an appointment. After I figure out the details where it will go work with Xcel Energy and open the proper permits to do the work (whatever we come up with).

NOTE: I haven't got brand/model details down, this is just a general saftely question for any lithium battery based system. I would like whole house backup which is why I am leaning toward a MID and 10kW - 48kW worth of battery power generation.

 

[Brucey]

* Was hoping I could get 40kWh+ in winter, though doing some research at 4m^2 per kWh that is closer to 28kWh, so batteries for cheap(er) grid electricity.
* Xcel Energy (not sure it matters but thought I would mention it)

Problem is maybe you get an overcast system for 2 weeks. Pvwatts is good on average but you won't see those types of days without downloading the hourly numbers.

 

[Zwy]

You are 2.5 hours directly north of me, I'm an hour south of Rochester. I have 74 Kwh of batteries in the house system and if we cut usage to a minimum(around 8 Kwh per day), we can get by for 6 days of no sun. Our normal usage is in line with yours but late December/January we do have to run the propane furnace and I might turn off the heat pump water heater and run off the propane water heater. The biggest problem is mid winter if we get those overcast conditions for 3 weeks in the winter.

With 19Kw of panels, you should have enough generation provided any snow does not remain on the panels for more than a few hours. I tilt to 65° off vertical in winter and snow is not a problem for me. Roof top and fixed mount arrays around here might be covered with snow for 2 weeks during the below 0°F weather which I'm quite certain you are aware of. It many times takes a thaw to get the frozen ice/snow off the panels.

The battery shed will need to be heated and if using electricity it will also play into your daily Kwh load. Double the size of your bank now as it will be easier to install now instead of later. Plus plan for more expansion.

Are you in the cities or in the country? HOA?

If in the country, I strongly suggest a ground mount and preferably tilting. I did a video on tilting panels in winter, watch this part of the video.

You could use an insulated reefer box which helps for construction, you can always dress the outside up. Also, you could install some of the array on top of the reefer, preferably tilting.

You are more than welcome to make the drive down here and look at my system if you desire. DM me if desired. I don't have to play by any rules here as county is not zoned and systems are off grid.

If you have to play by rules with inspections, start with grid tie. Later, add batteries with a hybrid inverter AC coupled to your grid tie array.

 

[Nod51]

You are 2.5 hours directly north of me, I'm an hour south of Rochester. I have 74 Kwh of batteries in the house system and if we cut usage to a minimum(around 8 Kwh per day), we can get by for 6 days of no sun. Our normal usage is in line with yours but late December/January we do have to run the propane furnace and I might turn off the heat pump water heater and run off the propane water heater. The biggest problem is mid winter if we get those overcast conditions for 3 weeks in the winter.

With 19Kw of panels, you should have enough generation provided any snow does not remain on the panels for more than a few hours. I tilt to 65° off vertical in winter and snow is not a problem for me. Roof top and fixed mount arrays around here might be covered with snow for 2 weeks during the below 0°F weather which I'm quite certain you are aware of. It many times takes a thaw to get the frozen ice/snow off the panels.

The battery shed will need to be heated and if using electricity it will also play into your daily Kwh load. Double the size of your bank now as it will be easier to install now instead of later. Plus plan for more expansion.

Are you in the cities or in the country? HOA?

If in the country, I strongly suggest a ground mount and preferably tilting. I did a video on tilting panels in winter, watch this part of the video.

You could use an insulated reefer box which helps for construction, you can always dress the outside up. Also, you could install some of the array on top of the reefer, preferably tilting.

You are more than welcome to make the drive down here and look at my system if you desire. DM me if desired. I don't have to play by any rules here as county is not zoned and systems are off grid.

If you have to play by rules with inspections, start with grid tie. Later, add batteries with a hybrid inverter AC coupled to your grid tie array.

Thank you for the detailed reply. I plan to stay connected to the grid but hopefully minimize my dependency on it. I hear the power outage is worse in the summer which is all I have experienced.

I am close enough to St Paul that I can put it as my city and still get packages. I don't have HoA, ew of the houses around me have solar, but the city doesn't allow ground mount anyhow, something about property value, idk. Only place I could put ground mount is in my front yard anyhow, bark yard is surrounded by trees. I am basically limited to the area of my south facing roof and I figure I might as well fill it up as much as I can (at this point it seems solar panels are not the most expensive part).

> The battery shed will need to be heated and if using electricity it will also play into your daily Kwh load. Double the size of your bank now as it will be easier to install now instead of later. Plus plan for more expansion.

Good point for sure. I was hoping 8in walls with insulation and no windows would make heating/cooling minimal but definitely not 0kWh. Also why I wanted to put the setup in the house since it is already air conditioned.
I was hoping with rack batteries adding more would be easy later but fair point multi day overcast + power outage would be really bad. Maybe should plan for 40kWh initially and see what a winter is like then do an upgrade.
If it was just getting stuff to fit I would do this in the house with just sheetrock and insulation (for sound dreading).

I haven't watched the whole video you posted so apologies if this was answered:
With your quantity of batteries did you need to prepare a special place and do any fire prevention measures before the system was approved? If you are off grid and far enough in the country I assume you wouldn't need to worry about those except for maybe insurance?

 

[Zwy]

I'm 60 miles from nowhere in Chickasaw County, IA. 60 from Rochester, 60 from Waterloo but only 50 from Mason City. Electrical inspector lives about 6 miles away, drives by often but has no jurisdiction over an off grid system not exporting to grid. He was here back when the pole was rewired and new meter installed 15 years ago, I never wasted my time with them since. By state law, they can only come on the property if you file for a permit. Alliant Energy has nothing to do with anything after the meter.

I have yet to have anything burn down so I guess I can say insurance has paid out on every claim thus far.

Seriously, they would have to prove it wasn't wired to code to deny coverage. Many farm buildings in the area are fire hazards with older wiring and yet they cover them.

My system in my house is in my basement

You could go underground, drain it well with a footing drain on the inside to a sump pit. Add in a mini split for humidity and temp control. Wouldn't take much with the ground temp year round. I cut the floor in my basement 12" from the wall on the inside, jack hammered that out and dug 18" deep with 4" tile and washed rock to fill it in, then cemented it back over. Tile runs in a sump pump. I have my heat pump water heater down there and that keeps it cool in summer with no humidity. If I was forced to have my battery bank/inverters outside, I'd opt for underground with spray foamed walls- climate control would be easier here in the frozen tundra in winter. You only need to keep the battery bank above 32°F for charging purposes and actually could just add heating pads under the batteries. The heat from the ground should come up thru the floor and keep it warm enough.

If your roof pitch is steep, you might be OK. A ranch with a 4/12 pitch and you will be raking snow off. If so, you might be better off with grid tie first and run off the stored Kwh bank with the utility for those lean PV periods. Then add in batteries later for power backup.

 

[Nod51]

wow that setup looks sweet, hope I can make mine look even close to that. Part of me hopes with a shed I can drop the UL requirement and make a DIY battery like you did but being in the city and grid tied I don't think I am going to get away with it.

> You could go underground, drain it well with a footing drain on the inside to a sump pit.

I considered that but where I used to live didn't normally have basements so I have no experience, but hey I can look into it and learn another thing. My house doesn't have a full basement, ~40in deep and neighbor said there is a high water table, but I can ask around if I can go deeper. My main worry is drainage or sump pump failure, thought maybe I can double up. I think even if I match the house depth it will help and also hide the shed a bit.

> I have my heat pump water heater down there and that keeps it cool in summer with no humidity.

My water heater is in bad shape and rather old. I am considering replacing it with a heat pump version but was going to leave it in the house. Since heating is more a concern than cooling I was just thinking of getting another resistive water heater with a relay timer for when power is cheap or sun is shining (past house my family used ~5kWh of water heater a day, I expect about the same). If I have a mini split in this future shed maybe I can move my water heater to it some day, would be nice to free up some more space in the house. If I read the fire code requirements though I can't put anything else in the shed, it would have to be dedicated, something I need to confirm.

> If your roof pitch is steep, you might be OK. A ranch with a 4/12 pitch and you will be raking snow off.

Yeah it isn't a steep roof, defiantly will get snow buildup. I am planning to be grid tied no matter what but hoping I can at least have enough batteries to buy the "cheap" grid electricity at the low rates when I need to and sell at the high rates when I over produce.

If I lived in the country I would probably go with my plan A, fire rated sheetrock what is easy enough to do then just mount them on the wall, use like 25"x50" worth of space in a corner. Put 2 or 3 fire extinguishers rated for the chemical fire outside and call it good. Sounds like you think a shed is still something worth looking into given the code requirements though.

thanks again for the feedback.