Sunday, November 20, 2:30 PM. Brewer.

It’s Sunday and we’re resting as usual. Garrett is doing better and better. He’s sitting up and moving around more. Still a lot of pain but less than before. Thanksgiving is coming up this week. We have a lot to be thankful for.

I’ve been thinking about our electrical needs for the solar setup.

The farm generally uses 5 or 6 kW. When everything’s going full bore it’s closer to 12 kW. Our generator gives 24 kW, which is plenty. But I’m assuming the generator is running on borrowed time: the propane will go bad or run out, or generators in general will become impossible to maintain. Let’s say we want a solar, wind, and battery system that can provide our full 12 kW. What would it take to do that?

The first question is how long we need the batteries to run without being recharged. If we have a really dark, still spell in the middle of winter, how long is it liable to last?

I can only guess. It could be cloudy for weeks at a time, but I can’t believe we go without either sunlight or wind for more than three or four days running. Let’s see what it would take to run on batteries for four days. If that turns out to be not enough storage, we can always expand the system.

In the homesteading magazines I’m seeing 18.5 kWh battery systems. If we cut our usage in half when we’re on battery, we’d still drain that out in three hours. That’s not nearly long enough.

There are only two ways to do better than that: connect more batteries or use less power.

Let’s plan for more batteries. If we’re draining 6 kW per hour for four days, that’s 96 hours, about 600 kWh. To deliver that we’d need 32 batteries chained together. These are big, 300 pound batteries. I’d have to build some kind of building where I could put them. No. I don’t think we can have 32 batteries. Not yet.

Okay, that tells me one of my contraints, then. I can’t see fitting more than a dozen batteries in the garage. Twelve batteries at 18.5 kWh each would give us 222 kWh of storage, enough for a day and a half of running the house pretty much like we normally do. That’s assuming absolutely nothing coming from the solar panels or windmills. We could run off the batteries for four or five days by cutting back our usage, just the fridge and water pump and a few lights. Since winter is the main problem for solar and we don’t need the air conditioning then, running lean wouldn’t be so much of a hardship.

I’m feeling pretty good about this. I asked Trevor to check my calculations and he says they are a-okay.

Now I need to find twelve of those batteries. Maybe there’s a dealer or warehouse somewhere around here.