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Saturday, September 27, 2014

solar fridge


SOLAR FRIDGE

There was just a most excellent article on converting your chest freezer to a refrigerator:


Now, this is nothing new.  If I’m not mistaken Rawles covered this years ago when an Oz dweller came up with the idea ( I might be fuzzy on the details- please refrain from rude comments ).  But that was one of those home hacked systems in its infancy.  The above article points you to a simple plug in $50 part that does all the conversion for you- it’s plug and play!  That’s what is new and exciting.  I don’t necessarily advocate such a system, as it is a luxury rather than a necessity.  I still think you are much better off with an actual ice box.  I’ll compare the two systems, but the main thing to keep in mind is that if you are trying to get the wife to move out to the boonies this might very well be one of those necessities you must splurge on.  Kind of like spending a grand on a factory built composting system instead of the $4 bucket one.  If you have some spare lumber and a window, composting toilets are one bucket and one black plastic lined hole away.  But the “ick” factory must be considered.  If you have to spend a little more to get the missus out to the country, it still saves you big bucks in the end.

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Okay, bare minimum for the electric fridge is going to be $600.  This is usually cheaper than a propane fridge, not counting in fuel.  But say you got the propane unit for free.  In two years you’ve spent $720 in propane fuel, at current $3 a gallon cost.  Solar compares very favorably.  A new freezer is give or take-it’s been a few years since I’ve priced them-$150 ( no sense in going cheap and getting a used one, not since you’ll be spending so much on the rest of the system ).  A 250 watt mono solar panel is $350.  I’d prefer a lot more watts to make sure the power drain on the battery is never serious, but you can futz by on this.  $50 for the conversion unit and $50 in tax or another battery or whatever.  Now, compare that $600 to an ice chest.  The freezer, not needing to be functional-you are using it for an insulated box- is best used.  Free to $20 for a scraped unit.  A new dorm size fridge is $80 ( you need the compressor and parts from the back, not the box ).  $20 for the book “Sunshine To Dollars” for the instructions.  A 50 watt panel is $130 ( you are making ice at about 90 watts, which takes about two hours on a hot day ).  $230 total, close to one third the cost ( you will need salt in this process, but I count it as a negligible cost ).  Also, beware.  Neither system is long term post-apocalypse ready.  This is for off grid modern living.  The batteries needed are your weak link.

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15 comments:

  1. why don't you lend me the book for a few days?
    I'll save $ 20.oo

    El cheapO.

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    1. I'll need your AR for collateral. I don't like them, but you do so I know I'll get my book back.

      Delete
  2. I built a two 55 gallon drum and a piece of 2 inch pipe septic system for a friend who couldn't afford a "real septic"! They used it for two years before they upgraded. How the hell are you Jim?

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    1. Doing better than most days. Thanks for asking.

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  3. Appropriate skepticism. Batteries are the weak link in solar-powered electrical refrigerators. 120v ac systems can add losses and complexity of inverters. Even so, refrigerated food will extend your life like good water and sewage systems did. Hot water for washing is worth the effort of civilization.

    If you have the scratch, there is a Danfoss compressor that will start and run without a battery (with enough panels and steady sun, natch'). For overnight cold carryover, cold plates or lots of insulation and empty space packed with 1/2 gallon bottles of water. Next-generation insulation (aerogels) are very good, if you have money and are willing to spend it on bleeding-edge sailboat tech.

    I have a Norcold DE-4-cubic foot 12-24vdc/120vac model with a rocker pump that uses 45W/hr peak and about 450W/hr per day (measured) during hot summer in the sun. Insulation is wimpy compared to Sunfrost, but it was $100 used (~$1250 new in 2003) and I can move it by myself. The freezer is not nearly as cold as the ammonia freezer in the trailer (+20, not +2 F) so chocolate ice cream is soft but drinks do get ice cubes. Better performance might be cheaply had by installing on North side of house and adding block foam where it won't bother air flow over coils.

    4 cubic feet holds 12 half gallons of milk on the main rack (3 deep, 4 wide) and 5" high under that for eggs (2-cartons high) and condiments, with 2 ice cube trays and a pint of Ben & Jerry's in the "freezer". Planning is important for shopping and leftovers, even for just 2 peeps.

    Off-grid power is pv + Kubota EL300 (300cc horizontal single Diesel- 3hp) 100A DC 24v charger that runs on a pint an hour OR grid/conventional genset/500W sine inverter. The pv is really just a trickle charge system ("316W rated" in panels) to save fuel and engine run time. What's great is that it all fits inside a vintage (repaired exterior screams "poverty DIY") Apache Mesa pop-top trailer (gutted) to tow behind car or rv. No obvious tech or wealth showing when panels are stowed.

    Big late 1980's RV's (29-33') are so cheap in Portland Metro that I've been pondering getting a 6mpg beast for a one-way trip to the junk land. There's more room in a 33' Itasca than in a 250 square foot rabbit-warren apt in Portland. I could probably get change from selling an FAL. ;-)

    Cheers.

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    1. You could probably get a bolt action commie round AND the trailer for a FAL.

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    2. Long trailers, esp. 5th wheel trailers, 20+ years old are dirt-cheap. Holiday Ramblers were deluxe, often preserved in barns. Craigslist search and $1000 cash-in-hand can get a never-leaked 30' dual-axle with a real title. Something like a fridge, hwh or furnace might not be fully-good, but so what? Trailer-tech is monkey-simple. No title? No dice.

      I own all the parts needed except batteries. Portland is a great place to pick up Y2K surplus from yuppies who have become fat and complacent or want a new $6000 bicycle. No need to own nice deep cycles (ignoring-storing is bad for batteries) until I leave the land of on-grid super-reliable cheap power.

      Battery capacity is important: too small and they discharge too deep too often (dead early, no reserve power), too big and they are heavy/expensive with need for heavy charging. User-owner maintaining a balance among loads-battery-charging is critical to get long-life & good value from the system.

      The question will be to get a pair of 12v or a 4-pack of 6v to build a 24v bank? 65# (2-girl-lift) is heavy enough, regardless of the L16 advantages. Or, will it be a bank of 2 sets of 9 paralleled used/scrounged car start batteries cycling shallow running the 'fridge and LED lights?

      How many acres of seeds do I need to get oil from to make 100 gallons of SVO to run a genset for a year? That depends....

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    3. I just elected to go with minimal electric which pretty much solves more problems.

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  4. Everything comes back to batteries for off grid electrical.
    homestead sized Windmills provide power when wind is blowing, as long as they provide power the parts could be made to repair them- of course should they go down where is the power?
    Photovoltaic panels last decades (or longer!) as long as they aren't broken, but only provide power when the sun is up- and you don't need it for lighting then!
    Hydro is really the only homestead electric source that might last and provide power when it is wanted, but it is so situation specific that you are unlikely to have it.
    Storage-
    Edison Nickel Iron batteries last decades too- with proper maintance some have lasted 60+ years- but only a few specialty shops make them since, well, they cost less per year but lots more up front so there is little continuous demand for them. A great prepper supply that few preppers can afford to buy.

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    1. Edison batt-I could afford one, but will never buy one. Violates the 1 is none rule, and is a luxury I don't need as it will outlive me.

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  5. " I still think you are much better off with an actual ice box. "

    So do I James. I think that the Michael Bunker approach is better in the long run. Years ago, men would head down to the local pond or lake at the height of the winter freeze, and saw large blocks of ice, and then transport them back to the ice house. Here they would sit and last all through the summer months.

    I think that an ice box of the old style, such as the ones sold by Cumberland general store (It's kind of like Lehman's, with all kinds of cool, old time stuff ) would do well in a root cellar, with block ice lasting for several days, if not weeks, or even months? A simple and quick alternative, is to bury an old freezer or refrigerator on the north side of a building, the cover with peat, Styrofoam, or some other kind of well insulated covering; a poor man's root cellar if you will.

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    1. We just ate week old mayo stored in The Pit. Averaging 68-70 right now. Root cellars are the 80/20 rule of fridges.

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  6. It is critical that you take into account the delta T (temperature change) that the unit will be required to labor under. They make outdoor refrigerators and freezers to deal with this. If the grid is down, these units are going to have to deal with some pretty severe heat conditions. So unless your going to AC, or least cool with fans, your home, solar power alone is not the issue.

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    1. Good point. Never would have thought about that. On another note, thanks for reviewing "Famine". Just got done with it and enjoyed it. Keep up the good work.

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    2. You can "deal" with large delta-T, say in a household freezer, by making the inside of the freezer smaller, with insulating foam. In effect, you now have an "oversized" compressor/heat-exchanger by shrinking the capacity of the cold-box. If the insulation is done right, you might get some insulation advantage, as well.

      Look at an off-grid chest freezer and you find minimum 4" insulation on 6 sides. Home Depot barely-energy-star model has 2.5" insulation and huge interior, while no-energy-star Bi-Mart freezer has 2" insulation (and is really light and cheap, made by Chinese slaves).

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