Hybrid Home
07:11 Saturday, 22 March 2025
Current Wx: Temp: 46.78°F Pressure: 1021hPa Humidity: 63% Wind: 5.75mph
Words: 641
I've been thinking about how we could go about improving our home energy resilience in Winterfell. Much of the grid infrastructure is above ground, vulnerable to tree damage from either high winds or heavy snowfall.
Generators are one solution, but I was wondering if there might not be a somewhat more efficient solution involving a battery or batteries and a generator. The current house on the property is a small place, 960 square feet, and I expect that once we get settled in there, its electrical load will be relatively low.
We have radiant heating though, and that's a huge power demand when it's on. So you'd have to size a generator large enough to meet that power demand, or go without heat for a while. I'll need to get more data, but just judging from the data I have from my home weather station, which has two interior temperature sensors, the system came on twice a day to maintain 58°F in temperatures down in the 20s.
The implication seems to be that it's not like a heat pump or other forced-air type heating, where it comes on and goes off several times a day. It comes on and warms up the thermal mass of the slab, which then radiates heat into the house for some number of hours before it comes on again.
When the heating system isn't on, the high loads would be things like the hot water heater, clothes dryer, or the oven, and I'll probably get a hybrid hot water heater.
So, perhaps something like a one kilowatt generator could run basic lighting and IT loads, but its main purpose would be to recharge the battery. In the event of an outage, we switch to battery power. When the battery is depleted to 80%, perhaps, the generator comes on, picks up the light loads and any excess power is sent to the battery for charging.
It'd be like the house here when the sun is shining. If we're making more power than the house is using, we're getting all our power from the array and the excess is going to recharge the battery. If a load comes on that exceeds what the array is delivering, the battery discharges to make up the difference. When that load goes off, it goes back to charging. Likewise with a smaller generator. I don't need a generator sized to run all the household loads, I just need it big enough to keep the battery charged up. The only difference is that we'd never have "excess" power feeding back into the grid, like we do here when the batteries are at 100% and we're making more power than the house is using.
I'm not an expert, but I believe all ICE generators are most efficient when running at full load. So a generator sized to meet the highest demand in the house is going to spend most of its run time well below full load, where it's less efficient.
The idea for the small house isn't to be "off grid," or carbon-neutral. We'll try for that with the larger home we hope to build on the property. The idea is that the battery is for whole-home backup in the event of an outage, to meet high power demand services. The generator is intended to keep the battery charged enough to meet the high power loads. Small generator, running fully loaded, meeting "normal" household loads and recharging the battery. Battery discharging to meet high demand loads.
This is probably going to require some math, sizing the battery and the generator. Batteries are expensive. Generators are expensive. Fuel is expensive. There must be a way to "triangulate" an optimum configuration that uses the least amount of resources to meet the need.
Somebody has probably already figured this out for me.
✍️ Reply by emailThis Morning's Moon 3-22-25
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The beat goes on...
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