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please critique my solar ideas

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Other than heating my house and hot water with a wood fired water stove, I'm currently very conventional in my electricity use, but I'm curious about solar and wondering what my options are for using some solar without disconnecting from the grid. 

My main motivations would be (1) to have at least some power in the event of a power outage, (2) to defray some of the cost of the system by reducing my regular power usage, and (3) to get some experience with solar in case I decide to build a fully off-grid house in the future. 

The things that would be nicest to be able to keep going in the event of a power outage would be (1) two to three large chest freezers, (2) the well, enough to water a couple cows, some other animals, and for some limited household use, (3) a computer, and in the winter months (4) a small pump that circulates water from our outdoor wood fired water stove to the house and the fan in our blower unit to get the heat into the house.  I have less convenient back-ups for water and heat, and I can make do without a computer, but the freezers are the most critical thing if the power goes out long enough for them to start to thaw.

Since I don't so much need power at night, I'm wondering what a bare minimum of batteries would be just to make a system work.  I'm thinking if I can get my freezers really cold during the day, they could make it through the night without running.  And I can get by very well without water at night.

Any thoughts or recommendations (including books or other ways of learning more)?  Should I be thinking about DC systems at all?


For what you describe, a grid-tied system using batteries for storage and and inverter tied into your domestic power service would be best. It just needs to be sized based on your requirements. You may benefit from new freezers. Probably best to consult with someone who with expertise in those systems. 

Instead of a grid-tied system I could run certain loads off solar + a very limited battery bank and use the grid for a back-up battery charger, right?  Would that possibly make more sense?

I think a decent generator will do you better for now.  It will not go unused if you end up building off grid.

What you are envisioning is called a hybrid system. So basically a grid tied solar, with standalone battery backup in case of mains failure. 

With a system like that you normally have full mains power available, but may need to limit off-grid draw depending on the size of the inverter and battery pack. The inverter size determines how much stuff you can run, while the battery size limits how long you can power it for. 

Working out how much power you need is the interesting part. You probably want a watt-meter to connect to the various things and work out their peak power, and average daily power use. Things like water pumps and freezers are simple enough to work out the power draw when they are operating, but they are intermittent. Do they run 5% of the time or 50%?. Once you know your peak draw, and your daily watt / hours you can start sizing the system. 

A quite small inverter could keep 3 freezers cold and a water tank topped up if you ran each for 6 hours a day? It just means you don't have "regular" unlimited mains power where you can turn on everything and not worry if it's peaking at 10kW.  

And a standby generator isn't a silly idea no matter what other system you go with. Just it only solves issue one. It won't reduce your power bill, and you won't learn anything about solar power. 


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