Designing a Stand-By System?

[Nanook]

As in an earlier post of mine I am putting together a stand-by, grid outage use system for our house. I will not be looking to draw power from it as long as we have grid supply.

I also have sufficient inverter gas generator power and fuel for about 5 days (fuel gets rotated quarterly for freshness) demand.

The solar storage system will be pressed into action during the evening when I would envision the gen's getting shut down, if there is a mechanical issue with the gen's or when I run out of fuel if the outage goes that long.

I am trying to build some contingent redundancy into the power plan.

On a rotating basis, power needs will address basic needs only - nat gas furnace operation in winter (as long as the pipelines remain pressurized), fridge and deep freeze.

My initial design questions are:

• it seems to be generally "encouraged" via some of the posts I have read and Will's vid's that if you are able, to go with a 24v system for efficiencies/cost. Does that hold for my intended usage? I have a couple of 100ah 12 v's (not series connection recommended by supplier) already on hand from another project that has a lower priority, recreational use.
• if I assume solar power storage will be 400ah (4x100) and a 2000w pure sine inverter, would this be sufficient for my needs? I have not checked the furnace DC blower to calculate actual start-up and running draw nor the two other appliances so I recognize I am not providing enough info for a completely accurate response.
• panels are so "cheap" relative to storage capacity I will probably be willing to add as many panels as necessary (Toronto, Ontario location)

Any input would be appreciated.

Thanks

 

[DThames]

I would agree with 24v. Or maybe 48v. I have 2, 3000watt Growatt that are 24v and if I were starting over I might go 48v. But only 2000w, (if you don't get more power hungry someday) then 24v should be fine. You will need a 24v battery or two 12v that are the same (put in series).

If you have a generator, you can get by with a battery that is smaller than without a generator. 2, 100ah in series for 24v will be 100ah 24v. That would be about as small as you would want to go for a 2000w inverter. You will need to be able to pull about 100amps for peak demand on a 2000w inverter. 2 parallel, 2 series (4x12v batteries) would double your run time at a given watt load.

 

[wattmatters]

Any input would be appreciated.

if I assume solar power storage will be 400ah (4x100) and a 2000w pure sine inverter, would this be sufficient for my needs? I have not checked the furnace DC blower to calculate actual start-up and running draw nor the two other appliances so I recognize I am not providing enough info for a completely accurate response.

It will be prudent to understand not only the operational energy/power demand for your furnace blower and fridge/freezers but also the start up power draw. The initial surge power demand can be many multiples of the ongoing power draw. So while a 2kW inverter might be ample for the ongoing power draw, it may not be able to cope with the start up requirement for your equipment.

Another is accounting for the inevitable scope creep. Once you have power during outages, you'll begin to wish you could just have this, that or the other running as well. Of course you need to draw the line somewhere but having a little overhead in the power/energy budget isn't a bad thing.

 

[Nanook]

Thanks to you both for the suggestions and guidance! Will have to maybe start scoping a larger inverter. Break out the bank for a Victron - haha.

I get the power creep but during normal times over the last 20 years the power rarely goes out for long here from “natural” causes. So that is why I was just covering basics.

But these days are not normal and I think things will be much worse, unfortunately, before they get better. I hope I am proven wrong - Been on the planet for a while and these are definitely disturbing times.

But regardless of current circumstances, having lived through the ice storm in Quebec in ‘98, that taught me to hope for the best but plan for the worse.

 

[FrederikSchack]

If economy isn´t much of an issue and you´re willing to change the batteries once in a while it might be fine, but else I would be concerned about letting the batteries stand and do nothing in a stand-by situation, I think most batteries go bad if not being used for a couple of years.

If you on the other hand buy a hybrid inverter, you could probably get both emergency (off-grid) system and a system that can cut some of your energy bill, while maintaining the batteries healthy.