this post was submitted on 28 Nov 2024
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What kind of heating element did you use for the water? What type of control system to send power to it?
I'm using 220V/6kW heating element. When used with 60VDC directly from the panels, it's about 0,45kW. No need for control system, since that is too weak to bring the water to boil. It's function is just to decrease the consumption of heating oil. Oil burner is set to start at eavening just before enyone needs hot water and panel output goes down. Oil burner heats the water in the tank to 80ΒΊC. It's about 40-60ΒΊC next morning when the sun rises, depending on the consumption.
Did you manually switch it on once your battery storage was full?
At first yes, and I was planning to put raspberry + HAL-sensor + relay to handle the switch when average current to the batteries lowered, but to my surprise batteries charged enough with both connected. Battery charge controller is right next to the panels and there is some distance to the heating element. It appears that the MPPT battery charge controller so much lower resistance path that the current favors it.
My test setup only has 300Ah of battery, capacity at 12V, so it's charged quite quickly. Battery power only runs living room devices 50" TV, monitor, laptop, steamdeck, cable modem that are used about 4-6h a day and rarely on at the same time.
If it's a hot summers day, I might manually direct all to AC
... or if there's some catastrophic blackout during winter I can connect batteries to a radiator water circulation pump and heat the home by burning wood. This is very improbable, but at least there's something.
That sounds awesome. There seems to be a bit of a gulf in investment between getting a few panels to charge a backup battery or run some devices while camping, and actually doing a proper home integration. I'm in the midst of that gulf where I can generate more than I can easily store and use later, so I'd like to find some worthwhile uses for direct use of solar energy.
Don't know if you've seen it before, but here's an interesting article about direct solar.
https://solar.lowtechmagazine.com/2023/08/direct-solar-power-off-grid-without-batteries/