Solar subsystems for short-term power outages

[scott c.]

Hello,

I would like to get the group's input on a solar installation. I am completely new to solar. My goal is not to save money, or get entirely off of the grid just yet.

I simply want to be able to limp along during potential long-term power outages. Speaking of long, this is a long post. But I wanted to give everyone as much background as possible. Thanks for bearing with me.

I am of limited funds. So I am putting together small subsystems based on priority, adding them as money allows.

I plan to select components for each system from the same vendor for interchangeability. Solar is plentiful, limited only by crappy Ohio weather. I have diversified my emergency preparations and I can go without power if absolutely necessary. So I don't need to oversize it just yet. That comes later.

I can set up each system with a very short run. I plan to put them in secure housings attached to the outside of my home, one on the north, one on the south, and one on my garage.

I have two sources of heat. I have plenty of food, but I will need to keep it cold and prepare meals. But I will ask that question in another post as it is priority #2.

First, I want to take care of water and sanitation. I'm on bored well and septic so I am in good shape there. My well pump is ideally placed for solar. It sits on the north side of our house and gets plentiful sun. I want to put together a system that is capable of powering the pump, take short showers (cold water is a heck of a motivator), and an occasional use of the washing machine on its lowest setting (also without hot water).

I need 35 amp hours to keep water flowing, based on the pump specs and the cycle time. I have a 10 gallon bladder that I can pressure bleed to flush toilets overnight. This is a guesstimate as I have not measured the actual load, nor my wife's flush frequency.

I need approximately 35 amp hours to run the washing machine on a short duty cycle. Again, this is based on specifications and cycle times. But if you think my calculations are way off, please let me know.

I want to size a system that will always keep my water running. I've bailed buckets from my pond to flush the toilets. That was no fun. The pump requires 750 watts with a 2000 watt surge.

And I would rather not have to use a washboard to do laundry in my pond. My washing machine requires 1100 watts with a 2200 watt surge. Mine is a 2 person household and I will likely buy a smaller washing machine in the near future.

I will ask about a second system for food storage and preparation in another post.

Thanks in advance for your help!


Scott

 

[Rednecktek]

Lot of project here so just a few thoughts to get you started:

Convert everything into watt hours, it makes the math much easier down the line.

Start keeping a rough log of well, fridge, washer, etc usage so you can figure out watt hours needed for your loads.

Once you have usage numbers, do a power audit. That's important! There's a form in the Resources section that helps the math on that.

Unless you've got an infinite budget don't worry about keeping to a single brand name. Victron or Renogy are about the only brands that I can think of that carry all the parts sans panels.

Figure out where you're gonna stick the parts. A dozen rackmount batteries sounds great until you're sleeping in the kitchen because there's no space anywhere else.

 

[Mattb4]

Since you are just getting started I would suggest looking at utilizing an off grid All In One (AIO). There are several available in the cost range of ~$400 and up that can handle a fair amount of loads. One thing you did not mention is if you need split phase 240vAC for your well pump. This will impact what you select for PV equipment.

Why the AIO? Because it allows you to use your grid as a backup to the solar. AIO's consist of a SCC (solar charge controller), ATS (Automatic transfer switch- think UPS functionality), AC battery charging, and inverter (DC to AC), programmable settings in one box.

Personally I am doing fine with a dual 3KW - 120vAC AIO setup and 2400w PV. My present battery storage is 24vDC -320ah. It means I am mostly off grid for my house loads. The only things I can not power are my electric clothes dryer (30a -240vAC) and my 240vAC electric Range. My water pump is a 1/2hp -120vAc surface jet pump feeding a 30gal. equivalent bladder tank (30-50psi) and it runs just fine on the AIO output.

My setup is not all from the same vendor. I buy where I get the best deal.

 

[Delmar]

To run washing machines and pumps on solar you will need lots of panels, inverter, and batteries. Since you are only planning for short-term power outages, and "of limited funds" I would instead recommend a hybrid system with a generator for the big loads and inverter for the small loads.

You can forgo the huge panel bank and instead invest in batteries that can be easily charged from the generator. Adding small amounts of panels will extend the runtime between generator recharges. You will have nice quiet power for long periods (especially while sleeping) then run the generator for laundry and pressurizing the water tank. Look for a good AIO inverter that has a generator start function.

I survive just fine with my FLA golf cart batteries, 400W of solar and 2500W of inverter. My subdivision supplies the pressurized water. And I can run my furnace blower, like it never gets cold in south Texas. My moms house with 14KW Generac is nearby for a recharge (but have never needed to do yet).

An electric golf cart makes a handy self-propelled power station and wheelbarrow if you have acreage that requires maintenance. Buy the cart, get the batteries for free.

 

[scott c.]

Thanks for the advice. There is a lot of good information here. I should have mentioned that I am converting my well pump to 110v. I’ll look into the AIO option. I will also look at a hybrid generator.

I will be back with more questions soon. Thanks again!

And my wife definitely wouldn’t like batteries in the bedroom. ?. I guess the man cave has to go. It is going to get crowded in there when my wife puts me in the doghouse!

 

[HarryN]

I grew up in OH. It is worth looking at batteries that can be mounted and used outdoors such as AGMs vs taking up valuable indoor space.

Also the sun angle is very low in the winter, so the panel mount angle for winter will be much lower than is typical, of course it depends on where you are in OH. Mounting them in a way that avoids snow accumulation can be a big deal.

It is also worth considering wind as an alternative.

 

[Johno1066]

Shucks Scott c, when you mentioned long power cuts, I thought another poor South African! However I am doing all you would want with 2 3000 watt inverter chargers fom EG4, I could get away with using just one but I would then have to manage loads as all things could not run at the same time. I have 6 EG4 48 volt batteries which is where the greatest cost lies but feel I could have managed with half of them. Use propane and wood for heat and have a propane range. I have about 6 kwatts of 2nd hand panels from Santan Solar cheap and effective, but maybe I am lucky.

 

[Delmar]

I should have mentioned that I am converting my well pump to 110v.

Changing the pump from 220V to 110V will double the amps, and increase the required wire size. As before I recommend powering from the generator. Spend the savings on the AIO inverter.

 

[Johno1066]

The EG4 300 inverter handles a 3/4 HP well pump without any problems whatsoever, it also runs a Maytag washer. the washer pulses some as if the motor runs fwd then backwards continuously so there will be a flicker in the LED lights but as we do the laundry during the day it is not a problem. I also have a 1.5 kwatt water heater, so that is the reason I have two inverters although if I manage the loads I could get away with just the one.

 

[chrisski]

I am of limited funds. So I am putting together small subsystems based on priority, adding them as money allows.

I stopped reading here. Limited funds and battery backup do not go hand in hand.

I would expect the real cost of the system to include tooling up to be at least $3k, but more towards $10k. There are a bunch of hidden costs like wires, wire strippers, crimpers, etc.

 

[Johno1066]

The cost of starting would depend on many things, first your location, are you bound by regulations or property that has not got a good south facing direction. No sun , no good. If you can find good used solar panels you can set up a 5 panel array for about $300 which will include the cost of the panels. The EG4 3000 watt inverter was under $700, however a battery storage system is the highest expence. I considered starting with lead acid batteries but would require at least 4 -12 volt batteries which would end up being half the cost of a lifepo4 rackmount 48 volt battery which would give me a greater lifespan and useable capacity. Although I have the crimpers for small and large cables I have only used the small crimper for #10 and #12 conductors as the inverter came with cables with lugs attached. By mounting the inverters on a south facing wall in my laundry getting the conduit from the arrays into the laundry was quite simple and as the batteries were also in the laundry all the wiring was much the same. Most of what can be easily done depends on the persons skillsets, so if you are of sound mind and are handy with your hands all is possible with a little planning.

 

[Vigilant24]

Scott,
My situation is a lot like yours. I'm in Ohio, I'm on a bored well, I want a minimalist backup solar system for essential loads, I want to be able to power them for weeks/months, my budget is limited. Some details here in a thread a I started about a year ago:
https://diysolarforum.com/threads/d...sential-home-electric-loads.45793/post-579840https://diysolarforum.com/threads/d...sential-home-electric-loads.45793/post-579840
Some thoughts (lengthy post ):
- Your first post doesn't match the title of the thread. Are you interested in backup power for a long-term outage (weeks/months) or a short term outage (a day or two)? If it is for less than a week or so, then a regular gasoline generator is going to be much less expensive and provide more reliable capacity than you can get with solar for the same money. Even with solar, you may want a small efficient generator so you don't have to immensely oversize your battery bank to cover a long cloudy period.

- Yes, working in watt hours makes everything much easier.

- Main components of my system will be/are: four 100W solar panels, a 3000 W high frequency 12V inverter, two 110AH 12V flooded lead acid batteries (so, usable storage capacity of about 1300 watt hours, if the batteries are discharged down to 50%), an inexpensive MPPT solar controller. It looks like everything will cost about $1200 including cables, fuses, etc. This is minimalist: Recharge power tools, recharge flashlights, run a CPAP machine, provide pressurized water of about 50 gallons per day, run a load or two in the washing machine when it is sunny, no air conditioning in the house ("sorry, honey, but we have fans"), maybe run the furnace blower if we have available natural gas and cold weather, etc.

- I'd recommend you give strong consideration to using flooded lead acid batteries. I bought 12v "deep cycle" marine batteries made by Exide, I purchased two at Rural King for less than $200 total. Each one is 110 AH, so if I discharge them down to 50%, I'll have 1320 WH of capacity. That works out to 6.6 watt hours per dollar of initial expenditure (typical lithium batteries today: about 3 watt hours per dollar). These are NOT high-quality industrial true deep cycle batteries that would be appropriate for daily cycling. I expect to need to replace/add to my pack after about 5 years as the batteries age out. But they are rugged, inexpensive, readily available, and in a pinch I can charge them with my car's alternator, use one to start a small car, etc. In a tough spot ("we need power and I'm willing to sacrifice future battery cycles to get it now") I can decide to discharge them further and get some more juice. So, they provide a lot of flexibility. There's no circuitry in them (BMS) that can fail and leave my system dead. For thse reasons, for this particular application I think flooded lead acid batteries are more suitable than LiFePo4. I'd go with a lithium chemistry battery (and pay 2+ times the price per watt hour) if I were planning to use this system daily and cycle the batteries a lot, but I'm not.

- Similarly, I went with a 12V system because it provides a lot of flexibility. I can take my 12V inverter to my neighbor's house and provide him/us some 120VAC electrical power using his running car, etc. 12V water pumps, fans, small inverters, etc, are easy to find and inexpensive. If one of my 12V batteries shorts out/leaks, etc, I can still operate the inverter with the other battery if the inverter is built for 12V. For short cable runs, the difference in cable costs weren't significant to me and 24V or 48V wasn't worth the loss of flexibility in my intended application. Again, I'd choose differently if this was a daily-use off grid system.

- Water: As you identified, this is a biggie. My well pump is a conventional 1/2 HP 120VAC 2 wire system. The running load is about 900 watts, the startup load is a LOT more than that (LRA of 50 amps by the nameplate, so a very brief load of 6000 watts can be expected). This is definitely the biggest surge load I've got. I bought a 3000W high frequency (i.e. cheap Chinese) inverter with a listed surge capacity of 6000W, but I very much doubt it will do the job (I haven't tried it yet). Honestly, water is so important that I wouldn't be entirely comfortable depending on this minimalist solar electrical system, running at the very edge of its capability, to provide it (short term or especially long term). Too many single-points of failure (especially the inverter, but also the pump, etc). What I'd >ideally< like is an inexpensive, low-capacity (1 GPM is fine) 12V well pump that is thin enough to snake down into my 5" well bore alongside my "regular" well pipe and wiring. I'd like to put it about 70' below grade (about 30' below the static water level) and have it provide pressurized water to my existing tank. That way I wouldn't need to first pull out my existing pump/piping/wires, etc to go into backup mode. There are some pumps that can do this (made for water sampling) but they have an anticipated service life of a few hundred hours and they cost about several hundred dollars. If your budget allows, a nice Grundfoss permanent magnet motor pump is one you could replace your existing pump with, it has a much lower startup load than most conventional pumps (so, you could get by with a smaller inverter or generator) and is well made, but they are not inexpensive.
If my present inverter and batteries can't run my present well pump, then my plan will be:
1) Use a DIY PVC hand pump to lift water out of my well and into a barrel. This pump and downpipe (1 1/2" PVC) can be placed inside my well without removing my existing pump and piping/electrical wires, which is a major advantage. It is also low cost, should also be very reliable, and fixable if it breaks. Its not especially convenient, but pumping 50 gallons or so shouldn't take more than about 20-30 minutes. Hey, good exercise and what else will I have to occupy my time? :}
or:
2) Pull the well pump and water line/electrical wires (ugh). Drop a 12VDC pump down the well and run it directly from my batteries/panels in the daytime. Chinese-made pumps are about $150. I don't know how reliable they'd prove to be, and when they break I'd by out of business and very sad.
or:
3) Pull the well pump and use a well bucket. 100% reliable. Very low cost (4' long 4" dia PVC "bucket", 100' of cord, pulley, some 2x4s for a tripod). Inconvenient, but it's gonna work.
Once the water is out of the ground and in a barrel, it's easy to use a 12V RV style pump to move water into the regular pressure tank and keep the house taps supplied with water, have hot water if natural gas is still available, run it through filters, etc for drinking.

- Fridge/freezer: We'll probably do without. Reliably keeping a fridge or freezer cold enough for food safety over a long period (which includes periods of cloudy days) drives up the electrical storage requirement (batterie$) and panel capacity (to recharge that big storage capacity in a brief sunny window) a lot. For the short term (a week?) using a gasoline generator would be the way to go. When I think of the type of cooking we'll be doing during a long-term outage, storing cold food isn't super important. One low-cost approach would be using a >good< well insulated cooler (which you might have around anyway) and a portable countertop icemaker (less than $100). They can churn out 25 lbs of ice per 24 hour period, so you could make at least 8 lbs on a sunny day. Melting that ice will provide about 1200 BTU (about 350 w/h) of cooling. On sunny days, storing excess power from your solar panels (after your batteries are full) as ice would let you coast across a few days of clouds. During "regular" times, keep as much water frozen in your freezer as is practical. This reduces your normal electrical use and will let your freezer keep relatively cold for a longer period if the power goes out. If the outage will last longer than a day or so, put the expensive stuff/any "keep cold" medications/etc into that cooler along with the remaining ice jugs. Then fire up the grill to cook everything you can salvage from it before it spoils.

- Washing machine: When it is time to replace yours you may consider getting a Staber washing machine. We love ours, we've had it for about 15 years. It is unique (top-loading, but it's a horizontal axis "tumbling" washer like a "normal" front loader). It is easy on our clothes, cleans them very well using minimal water, sturdy as a tank and easy to fix yourself (normal "wear" parts are easy to get at and replace--I've done it when required). An efficient soft-start motor. Max "surge" draw is 1320 watts (11A at 120VAC), running load of about 720 W (5-6 A at 120VAC), each load requires 15 gallons of water and 110-150 WH of electricity. They've been popular with the off-grid crowd for decades. I expect ours will soldier on for many more years.

- I'm a fan of having spares, and it doesn't need to cost a lot. For example, I have a smaller (800W) pure sine wave inverter that can still cover a lot of requirements if my 3000W inverter dies. 800w is enough to run a CPAP machine, recharge my power tool batteries and flashlights, run fans, etc, etc. Similarly, a cheap PWM solar charge controller isn't as efficient as a more capable MPPT controller, but they work, are simple, and having one as a backup is probably good insurance. Using individual components (batteries, charge controllers, inverters, etc) rather than an "all in one" (AIO) device allows you some flexibility if individual parts crump out.

Good luck!

 

[DIYrich]

What's your budget? How much up front, how much over time. Parallel small inverters, or buy one larger one. Those are the type of tradeoffs, depending upon your budget. Are the federal tax credits a factor?

 

[0truck0]

By "long-term" are you preparing for grid-down possibilities? shft? govt deeds?
Otherwise, I am confused why you need to wash clothes during power outtages. What is the longerst power has been out? A week, two? I would simply buy a few days worth of clothes and wait for power to come back on rather than have batteries enough to run a washing machine.