Bare Bones refrigeration in a grid down world

Discussion in 'Off Grid Living' started by TnAndy, Feb 23, 2012.

  1. TnAndy

    TnAndy Senior Member Founding Member

    OK....the world has ended as far as reliable grid power is's either intermittent for a few hours/day like many parts of the world, or it's now unaffordable, or it's just plain gone due to an EMP or CME event.

    You've decided that the real value of electric power is just a small amount consistently reliable refrigeration because the iceman doesn't deliver ice anymore, and because while propane/kero fridges are fine, you still need a supply of fuel, and maybe a few electric lights for use to see what goes bump in the night would be a handy thing too.

    So, HOW to design a small solar power system that gives you BASIC refrigeration and a few lights ? You know....the things that really made the 20th century a whole lot better than those previous centuries.....

    Here's my suggestion:

    First, abandon the idea of a freezer, if you want "bare bones"....and we're basically talking money here.....a consideration in most folks minds.

    You could upsize what I'm gonna lay out if you want to spend the money, but start with the premise that a freezer is simply too expensive, energy wise, and really, ask yourself....if the world gets to the point this level of equipment would suggest, are you REALLY gonna find Ben and Jerrys or TV dinners to stick IN the freezer ?

    OK....on to basic refrigeration.

    First off, plan on moving that current late 20th century/early 21st century model fridge outside, take the shelves out, flip it on it's back, fill it with dirt and start a worm composting ranch in it. Your garden will thank you.

    The energy efficiency of the best on on the market still sucks if you have to produce the energy. The best one out there ( and odds are, you don't own one ) is still about 1 kw/hr per day.....I have a new GE model that uses 550kw/hrs per year, or about 1.5kw/hrs/day, and it is a HECK of an improvement over the previous 95 Whirlpool that used 3/day......and still to much power use for "bare bones".....something to keep milk, butter and last night's road kill safe to eat for a couple days.

    For bare bones, you want to get in the Watt/hr range....not KILOWATT/hr range.

    Here's how you do it:

    Get a fairly new 7-9 cubic foot chest that you can use for your home now, using grid power, and use as a freezer. Buy a late model, energy star rated one.

    Then buy an external thermostat like this:


    They are 60-70 bucks from, or, you might find them a little cheaper shopping around, but that's the one you need.

    The thermostat plugs into a 120v source ( described in "how to build" below ), then the freezer plugs into the double plug, which is controlled by the external thermostat. You put the bulb part inside the freezer to sense temperature, and set the dial to what you wan the freezer to go to, and STOP running when that temp is hit. This simply over rides the thermostat control that comes with the freezer, shutting off the electric power when the selected temp is reached.

    For refrigeration, you want something in the mid to upper 30's on the dial. Say 38

    Now you have a freezer converted to a refrigerator that will only use in the 150 to 200 watt/hr/day range....5 to 7 times better than the very best UPright conventional fridge out there.....meaning you can get by with 5-7 LESS times the power to run it.

    DON'T roll the thing back in the house...keep it in a garage, or carport, or basement, or someplace cooler than the 70 degree kitchen IF you have such a place ( though don't set it out in REALLY freezing cold weather either....refrigeration compressors can lock up in REALLY cold temps )....try to pick a place that is as cool as possible to begin with so the unit isn't having to fight ambient temps....every watt counts here.
  2. TnAndy

    TnAndy Senior Member Founding Member

    How to build a system for the above.

    Assuming you got your bare bones fridge set up as above, you now have a power requirement of, say 250w/hrs/day ( allowing a little extra in case you live in a warm climate)

    Let's also say you want another 250w/hrs/day to run some electric lighting, or maybe do a few other small things, like radio com, or you can't seem to break yourself of the habit of looking in the fridge with the door opened for 10 minutes trying to decide between a glass of milk or a glass of cold water.

    So we'll design a 500w/hr/day system....that's 1/2kw/hr/day. Look at your most recent electric bill....if you're like the average US household, it was 900kw/hrs for a month.....30 per day....and we're now talking 1/2 of 1kw/hr per day. Big difference.

    Don't start thinking microwave, coffee pot, dryer, AC, all that kinda crap....we're talking BARE BONES here. You're gonna have to figure out how to make coffee (you have coffee ? )on a campfire or a propane campstove, or whatever.....and hang the clothes you washed in a washtub on a clothes line or some bushes to dry....and forget a whole lot of other 20th century electrical goodies UNLESS you want to spend a whole lot more on your system than BARE BONES.

    I'll start with the batteries.

    You'll need something that will supply 500w/hrs at 120v.....we're gonna invert the power from 12v batteries in this small system (to keep it simple) to 120v.

    500w/hrs divided by 12v is 40.16amp/hrs.

    But you loose some for inverter loss, and other system losses, so I'm going to round up to 50amp/hrs per day.

    Batteries shouldn't be discharged more than 50% of their rated amount, or the number of times you can do that REALLY goes down. Ideally, 20-30% will give you far better life, but let's go with 50.

    That means you need a 100amp/hr battery (basically....I won't get into discharge rates and all to keep this simple) FOR ONE DAY, assuming you're not putting anything back in the battery.

    So, let's assume 4 days you don't put anything back in the battery ( ain't seen 4 days of crappy weather where you live ? Good for you)....that means you need to buy 400/amp hours worth of battery. There are a WHOLE lot of batteries out there, but let's say I wander down to the local Deka, or Interstate battery dealer, and ask for that. They have some L16's there for $300 each. Since they are 6v, I need two of them to make a 12v set up. $600. Add another 50 for cables between them and to the inverter later. $650.

    Now for some solar panels to fill up what we're taking out of the batteries.

    We need to shoot for that 500w/hrs a day, PLUS enough to fill the batteries if we just went thru several crappy solar days (clouds, rain, fog, snow ), so let's see:

    Figure 4 hours of GOOD sun to be safe....if you get more, great, if you get less, add more to this...but I'll use 4 hours as a safe average.

    500/4hrs = 125w of panels, not allowing for any system loss, which there will be, and not allowing for the fact that panels REALLY don't put out what the STC rating I'd up that by 50% that right off. Say 200w of panels. Now that only keeps up with ONE day of use, remember, so if we want to "refill" the batteries from 4 days of crappy weather ( and God forbid it should go longer ), we need 800w of panels.

    A quick check over on CHEAPEST PANEL PRICES shows panels can be bought in the $1.25/w range....say $1.50 time you pay shipping on a small order, so you can expect to pay something like $1200 for the panels to your door.

    Charge Controller:

    You have to have a charge controller for a couple reasons.....mainly to keep from overcharging your batteries. But the new generation of CC's, called MPPT (MaxPowerPointTracking) also have the ability to use about ANY panel, meaning you aren't limited to just "12v" panels..which only go to about 130w in size. Many of the newer panels run on up in the mid 200 range, and operate on voltages in the 30v range.

    So, lets pick an MPPT charge controller that lets us use 800, but is still "somewhat" affordable. I like Outback products, personally, and the FM60 is rated for 800w of panels on 12v output....exactly what we need.

    $525 bucks.

    Now, we need an inverter.

    You can buy little "truck stop" inverters....they are modified sine wave, and may well play hello with your freezer motor, as well as being only 60-80% efficient in converting DC to AC, as well as having a fairly short life in general, or you can go ahead and bite the bullet and get a decent Outback inverter ( again, I like Outback, because they flat build good stuff)....the FX2012T 2000 Watts, 12 VDC Inverter/Charger...runs 1700bucks....ouch....but it will last many many years, and perform like a champ.

    SO, what have we got in this BB system so far ?

    Inverter 1700
    Charge Controller 525
    Panels 1200
    Batteries 650

    Add another 400 for various other pieces

    and a Bare Bones system to provide reliable refrigeration and a few lights/etc will run:

  3. Nadja

    Nadja RIP 3-11-2013 Forum Leader

    Andy, very nice post. Now, this would be a bare bones "solar generator" for real. The only problem is, that just to get a "bare bones" system" you would not find it real portable at all. This is why I tend to Jump on people for wasting their money on the advertised portable units. We both know they are not going to put out squat. I just hate to seep people get conned out of their money just because a few people jump on the band wagon to get rich quick.
    rsbhunter likes this.
  4. TXKajun

    TXKajun Monkey+++

    Thank you for this post! It explained solar set-up in a way even I could understand.

    Great job.

    Cephus, TheEconomist and Alpha Dog like this.
  5. Alpha Dog

    Alpha Dog survival of the breed

    Enjoyed the read I was also able to understand thanks great post.
    steeled, Cephus and TheEconomist like this.
  6. hank2222

    hank2222 Monkey+++

    Andy you break this down so much better than i could said to someone the other day and i going to print this out for someone i know let them see for themselfs about what i have been talking to them about basic solar power for place .

    Now i went to a super small 2.2.cuft sized rv fridge for the place because of wanting to have a little bigger unit than a normal sized unit in the place to keep my drinks and few other things cold intill i need them
    larryinalabama and TheEconomist like this.
  7. rsbhunter

    rsbhunter Monkey+


    Thank you for showing the freezer conversion into a frige...i had read about it. but didn't know if the people "in the know"(yourself, BTPost and Nadja, and others) endorsed the idea....i think it would be great as you layed it out...not to be used as an everyday thing while we have grid power..but in the event.....What are your thoughts of having two freezers, one reg, one set up this way, if your system is large enough to handle it? Thanks again, to you and Nadja for all the excellent , thought provoking subjects...rsbhunter
    steeled likes this.
  8. TnAndy

    TnAndy Senior Member Founding Member

    I have a couple of the external thermostats I referenced above, and have several weeks of test data with a 9cuft freezer, and using a Kil-a-Watt meter, so yes, it works, and I know how much power it takes.

    As to having a another freezer AS a freezer, or anything else, that would be up to you. I intend to have one, but I've expanded my system to the point it now produces 450-500kw/hrs/month.....I can afford a freezer.

    But that was not the intent of this thread....the intent was to show what a BareBones system for some refrigeration, and a few lights would involve.
  9. rsbhunter

    rsbhunter Monkey+

    bare bones

    And that you did, but what % of the people are going to be able to do with just bare bones....BUT, it does show what kind of $$$ outlay it will take if you want to have a back up system...rsbhunter
  10. ColtCarbine

    ColtCarbine Monkey+++ Founding Member

    I guess there is more than one way to look at it. For myself it would be a step towards going solar and with the ability to upgrade the system as money allows. Not everybody has the financial capability to start out with a whole solar home. It also helps me realize what I can actually run with it, puts things into a realistic perspective.

    For myself, if the grid went down I would not need much electricity. There are a lot of electrical things that people could do without if they had to. Would it be nice to have more capacity, sure but it is better than a poke in the eye.

    Single largest energy consumption item is heat, so having a alternate source of heat would be needed. If you have a wood stove, there is your heat source, cook stove and way to heat water with one item, thus eliminating three high power consumption items.

    If nothing else it might help others here realize what they might actually be able to live without but have a few conveniences, if the light go out.

    Andy thank you for taking the time to post this, it is very much appreciated.
    larryinalabama and TnAndy like this.
  11. TnAndy

    TnAndy Senior Member Founding Member

    I agree....the most important things to take care of FIRST in the area of energy are the ability to cook, then heat, then heat water, probably in that order.

    IF you live in a area with trees, and that means most of us, then wood is the obvious and traditional source of fuel, and should be the primary focus of efforts. Electric power is nice, but should be way down the list of priorities, IMHO.

    I have a wood cookstove set up in our auxiliary kitchen, which would make for nice summer cooking, not heating the main house, but if I could have worked one into the main kitchen, I'd have one there too, or as the primary if I only had a choice of one location.


    Right now, we use propane for a cook top in the main kitchen, with electric wall oven. I store two extra 500gal tanks of propane, ( we also use with the water heater), and without re-supply, we could go several years. We use about 350-400gal/yr in those two areas (plus have the grill on the deck plumbed into the gas line ).

    For water heating, as I said above, we use propane, but most likely I'd switch to wood water heating IF it looked like the ability to get propane delivery stopped.

    I ran up on a stainless steel water heater tank several years had a coil up inside that the exhaust gas from using propane/natural gas was routed to heat the water. Took it to a machine shop, had them cut the bottom off the tank ( it was the top), invert it back up in the new "bottom", take out the coil, AND run me a 5" stainless pipe "flue" up thru the center of the tank. Then had them pressure test it to 150psi. My welding skills simply aren't up to that, so I had them do it.

    The resulting tank is this:


    Tank already had couple 3/4" female thread ports, and there is one 4" port near the bottom on the side not showing that is a cleanout if needed.....REALLY nice tank.

    My plan is to build a wood fire box out of 1/4" sheet steel, probably not even bother with a door, and install the tank in my basement where I have a wood stove now, connect to that flue, and plumb into the house lines. Then, when we need hot water, build a fire in the fire box, let it rip, and heat the tank of water....then use it.

    Wouldn't be "on demand" hot'd have to think ahead an hour or so about a shower, or washing clothes, etc, BUT it would be hot water....which would sure beat NO hot water !

    Space heating ? Wood stoves, of course. The wood cook stove can double as space heating depending on where you install one...or a plain jane wood stove can double as a cooking surface.....all kinds of ways and options to burn wood.

    Of course, if you plan to burn wood, you better plan to CUT wood also.

    Couple chainsaws, plenty of spare chains, bars, sprockets, plug or two, 2 cycle oil mix, bar oil, and a 55gal drum of non-ethanol gasoline with PRI-G in it will keep you in firewood for a LONG dadgum time before you have to break out the crosscut saw and axes.


    And it doesn't hurt to have a small tractor with the ability to skid out wood for firewood, construction lumber and so on, as well as general duty farm work....


    So, electric, IMHO, is way, way, way down the list of crap one ought to be spending their bucks on....cause there are a whole lot of OTHER things that take more priority. Electric power is simply a luxury to be enjoyed after that other stuff is covered....not the absolute NECESSITY we assume it to be in our modern society.

    But,hey....WTF do I know....ahahahahaaaa
    steeled, rsbhunter, hank2222 and 2 others like this.
  12. TnAndy

    TnAndy Senior Member Founding Member

    Hank.....put a Kil-a-Watt meter on that mini fridge, and then don't be surprised to find out if it uses MORE than doing the doing a 7-9cuft freezer-to-fridge conversion....MOST of those little "dorm room" fridge suck the power like you wouldn't believe.....they are made with the bare minimum of insulation, and such.

    An RV one may be made better, but don't always assume smaller means less power consumption.
    hank2222 likes this.
  13. rsbhunter

    rsbhunter Monkey+

    supplies ready

    Thank you TNAndy for the info on what will be needed and nice to have in the case of a grid down, etc. situation...I honestly think that as humans, we like to believe that even in the event of a catastrophic event, OUR lives won't be uprooted, or hardly even different! As Americans , we have had every convience since we can remember, and i don't think "most" people can picture not sitting in the living room every night with the 60" jumbotron and 4 100 watt lights burning, and a thermastat set at 78 degrees....Not that life has to be driven by all the "what ifs"..but now and then, look around and imagine only having what you would HAVE to have, to protect you and yours, as well as have the day to day items that would allow you to endure a long term situation....rsbhunter
  14. Nadja

    Nadja RIP 3-11-2013 Forum Leader

    I think a better way to look at it, would be to act like the grid went down today, and then see where your lacking. Keep in mind that if the grid were to crash totally, food, transportation and communications would be gone. Now where are you going to be ? Me, I think I will go to Andy's house ! LOL
    steeled and rsbhunter like this.
  15. TnAndy

    TnAndy Senior Member Founding Member ain't the only one with that idea, which is why there is a plan for that too......
  16. Cephus

    Cephus Monkey+++ Founding Member

    Another reason not to talk to much to natives !!! ;)[stirpot][respect]
  17. hank2222

    hank2222 Monkey+++

    I have a small Rv/Sailboat style 12.volt powered unit that is more of design to keep things cold like drinks or other items after they are opened .The small unit is a basic after the fact item i did put into the unit for keeping with the some of the basic comfort level i would like to have after the socalled Shtf type living
  18. irayone

    irayone Monkey+

    Stop and look at all the sailboat set ups. The ENGLE portable freezer / reffer uses 2.5 AMH Hr. cost aprox 1,500.oo. On my boat i have one 100watt solar pannel, controler and two AGM 56 AMp Hr batteries. I have enough power to make ice, DVD, the reffer and all the lights I need. I never seem to run out of power.
  19. BTPost

    BTPost Stumpy Old Fart,Deadman Walking, Snow Monkey Moderator

    irayone, does you sailboat have an HF SSB Radio? if not you should invest. that way you can have Worldwide Comms, for SHTF Preparation..... .... YMMV...
  20. irayone

    irayone Monkey+

    BTPOST.....YES I am working on my Ham LC. now....It's only a coastal craft. I wish It was a blue water. The most important thing on the boat is the Kayden 35 salt water desalinator. Everyone should have one that lives by the beach. Produces 1500 gal on one filter. at 1 gal per hr.
    BTPost likes this.
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