Now that the solar plant is completely up and running, I’m having an unexpected problem. I’m generating too much electricity. Let me explain.
We run from batteries overnight. Right now, we use up about 30% of our battery capacity before morning. By around 7:30 am, the panels are generating more power than we’re using even though it’s December and the weather has been partly overcast (though generally nicer than I expect it will be as the winter wears on). Generally by noon, on a reasonably sunny day, the batteries are approaching a full charge.
As the batteries approach full charge, the rate at which they can charge slows. Often, the solar panels are capable of producing more power than the batteries can absorb. If the demands of the house and the capability of the batteries combined are less that what the panels can put out, then we’re wasting capacity. Having lived with energy scarcity my whole life, that seems wrong.
The first step is to start charging the car. That can almost always absorb most of the excess the panels can produce, although my current charging setup is limited to 8KW while the panels can peak at a bit over 10KW. More troublesome is that, eventually, the car batteries will be as full as I can reasonably get them. It’s not good for them to charge above about 80%. Since replacements are in the $30,000 range I tend to want to treat them gently. (The house batteries are lithium-iron-phosphate, and can be safely charged to 100%.)
HA has asked if we should buy more batteries, but I really don’t think so. We’ll know more after we’ve had a long stretch of overcast and rainy weather, but it appears as though our panel capacity is enough to keep us in light. More batteries would take longer to fill up, but fill up they would and I’d be back in the same situation.
As we get the house wiring replaced, we’ll be bring the laundry equipment online and water heaters and maybe occasionally space heaters and ceiling fans to help with the milde and moldew abatement. Those things might keep us from reaching energy excess quite as quickly, but I still think (hope!) that our generating capacity exceeds our needs.
I suppose the only real answer is to learn to be comfortable with excess capacity.
—2p