Small Office Off Grid Solar

[Matthew Robinson]

Hello, Thanks for your time and Help.

We are moving our small office to an old barn, we cannot get grid power to it. There will be one to three employees working on computers only during the daytime, (typ. 9am to 5pm.) The office will be almost completely powered off at night, although we will still probably power a small 1/2 size refrigerator and router at night. We are planning on supplementing with a generator. During the summer running an air conditioner only during the day.(Small AC system like a window unit.) (Spray Foam insulated and using propane for heat.) We are near Atlanta, Ga (Mableton)

I have made a spread sheet and calculated approx. 4 kilowatt hours per day at the High end. Not using the Air conditioning.

We are having a hard time talking with solar companies. Most do not want to offer off-grid, and if they do. they do not understand our usage. (Very Little Power consumption at night.) I have worked with both AC and DC wiring my whole life. But I must say having never worked with solar I am finding the learning curve extremely confusing. i know we will need an inverter, (AGM) battery bank, charger.

I would really appreciate some basic help and/or ideas. Specific inverters and equipment ideas sizing would be great. Thank you for your time and help again!

[Mike90250]

What's your humidity like, do you need air conditioning for humidity control or thermal control ? Carefully research how much AC you need to have comfortable conditions inside, it's critical to get it right because your electricity is expensive. Your functional solar hours are 9:30am - 2:30pm roughly, when the sun is low, your panels won't produce much,

What about the office coffee pot ? 8-9am is not good solar hours for a large load.

An energy star full size fridge uses less power than a conventional dorm fridge (built as cheap and thin as possible)

[bcroe]

Your solar companies want to install a very quick, cheap, simple, cannot fail net metering
system. The off grid system you want is an order of magnitude more difficult/expensive.

The idea of running a business on 4KWH a day is totally unrealistic, any chance you mean
4000 KWH? My suggestion is find a way to get line power out there, which will be far better
than the next alternative, a generator possibly running off a 1000 gallon tank of propane.
An adequate solar system would require massive batteries and still need the generator.

What Mike said about the fridge applies to AC as well, small window units are terrible.
There are some efficient AC units that can be partially or fully solar powered (line backup),
they will work at least when you need them the most. good luck, Bruce Roe

[PNW_Steve]

Another thought on the air conditioner: Have you considered mini-splits?

They are much more efficient than window units and don't have the high current startup like a window unit.

I have seen folks run a 12,000 BTU mini split on a Honda 2000 generator.

[Matthew Robinson]

We live in Georgia and they don't even offer net metering. We can't get a power pole with just the barn, without construction plans and a building permit, it's not available. We do have a power line running from the house who subdivided his property and sold us the lot, and we will put a meter on that line and pay him for the power we use. Maybe we will run the Air conditioning off of this power.

I don't think I am too far off on my energy calculations. 50% of the time I am there by myself. Just one desktop computer running, a few lights, 2 printers in standby mode, and a Wifi router. At the most there is 3 desktops running, same two printers, router and a few more LED lights.

I am thinking about a system like this. https://www.wholesalesolar.com/18914...stem#downloads

I was already going to get this charge controller and prob. the inverter. https://www.wholesalesolar.com/29401...rge-controller https://www.wholesalesolar.com/29400...a-12v-inverter

[Matthew Robinson]

PNW Steve, I was just looking at the mini splits. We are building the barn out right now and we can do about anything we want. We don't have an unlimited budget, but my boss has deep enough pockets. We have 6+ acres... We are doing a composting toilet. We get water from the neighbor.

20k solar quotes and 12k in batteries seem overkill when literally nobody will be there at night. Everything but the router and small fridge will be shut off.

[SunEagle]

PNW Steve, I was just looking at the mini splits. We are building the barn out right now and we can do about anything we want. We don't have an unlimited budget, but my boss has deep enough pockets. We have 6+ acres... We are doing a composting toilet. We get water from the neighbor.

20k solar quotes and 12k in batteries seem overkill when literally nobody will be there at night. Everything but the router and small fridge will be shut off.

Unless you plan on not working during the daytime even if there is major cloud cover you still have to figure a battery bank without any help from solar panels.

To safely get 4kWh a day from the batteries you will need a system that is rated at least 16kWh. That would require a 48V 340Ah battery bank a 40 amp MPPT CC and about 1700 watts of panels.

[NorthRick]

The idea of running a business on 4KWH a day is totally unrealistic, any chance you mean
4000 KWH?

4,000 KWh a day isn't right either for 3 people working on computers. 4KWH over an 8hr day would be 500 watts continuous. Probably too low but it wouldn't be 500,000 watts either.

[SunEagle]

4,000 KWh a day isn't right either for 3 people working on computers. 4KWH over an 8hr day would be 500 watts continuous. Probably too low but it wouldn't be 500,000 watts either.

I use about 60kWh daily but I have AC and a number of electrical items such as a stove, coffee maker, 3 TV's, a couple of large refrigerators, fans, etc. So it is possible that a small office with minimal hardware could use only 4kWh during an 8 hour period. Unfortunately it costs about $1500 for each kWh a solar battery system can generate a day.

[J.P.M.]

I use about 60kWh daily but I have AC and a number of electrical items such as a stove, coffee maker, 3 TV's, a couple of large refrigerators, fans, etc. So it is possible that a small office with minimal hardware could use only 4kWh during an 8 hour period. Unfortunately it costs about $1500 for each kWh a solar battery system can generate a day.

FWIW, I use ~ 20 kWh/24 hrs. and ~ 8-10 kWh/24 hrs. when SWMBO is away. I'd guess 500 W/hr. might be a possible load for an office w/ few/no vampire loads, lots of information and attention to detail with respect to energy use,habits, knowledge of what office appliances use, and very tight load management, but I'd bet off grid will be a lot more expensive and more maint. than the OP may think.

[Mike90250]

Here's a chart with my household basic daily usage, and a day with running the water pump for 3 hours

Will your business be able to rely on your neighbors good will to sell you power and water for the business ? What happens when that parcel changes hands?


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