Offgrid living

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Everything off grid; power, water, self-sufficiency; whether you're doing it or aspiring.

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CadeJohnson

perestroika

DIY Solar Power (self.offgrid)

submitted 1 year ago by CadeJohnson to c/offgrid

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I was looking back at reddit posts (while deleting them), and I realized I'd written a book worth of stuff about this topic. I would write it all again, if it is helpful. But for a brief synopsis of "how it works", here is what one does:

Assess power needs - look at your living standard and catalog all the devices you power, and estimate the time they operate - power is measured in watts, and time in hours. Multiply to get watt-hours; then divide by 1000 to get kilowatt hours. Compare with your utility bill.

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[–] poVoq 3 points 1 year ago* (last edited 1 year ago) (6 children)

I think in DIY solar PV it is very useful to think about not trying to connect your entire 240V AC house network like most commercial turn-key solutions do.

Sometimes the better place is to look for options to directly utilize the 12/24V power or use smaller inverters at specific places, like directly connecting a heat-pump that's near the battery pack anyway or something like that.

Of course this assumes that you are not entirely off-grid. Although then it is worth considering to have the main house network use 12/24V DC similar to a caravan or a boat.

[–] CadeJohnson 2 points 1 year ago (5 children)

When we built an off-grid house, I considered building in 12V circuitry throughout, but decided against it. There were two reasons: 1) providing a significant system of 12V circuitry required a bit investment in wire - at 12V, the amperage for delivering significant power is relatively high and power dissipates in wire proportional to the square of the amperage. You have to provide big wires compared to the size of AC circuits (10X more voltage means 10X less current). and 2) the market for 120VAC devices is huge compared to that for 12V devices. This means there is a lot of efficiency of production and distribution. A 12V refrigerator is a specialty item and few are made or kept in inventory - if they are, it is for a luxury market and prices tend to be inflated. But people are replacing 120V refrigerators every day so an appliance store can stock them. Repairmen are familiar with them. There are a lot of choices of models.

[–] perestroika 2 points 1 year ago* (last edited 1 year ago)

I went for a compromise: my house is equipped with 24 V DC cabling (PC PSU sockets as wall sockets) and likewise has a 240 V inverter.

Small stuff that is always on (router, alarm system) connects to the DC lines with DC/DC converters. Also: circulation pump, LED lights, 3D printer, small battery chargers - these use DC.

Most rooms have fairly limited wiring, so a huge amount of copper wasn't spent... except in the direction of the water tank. In that direction, wires are massive because my opportunistic heat storage system (when the season is cold and excess solar energy becomes available) also uses DC.

Big stuff (charging the car, pumping heat or irrigation water, drilling, welding, cutting) uses AC.

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