Powering a chest freezer

[EJM]

Hello All,



I am new to the forum and looking for some help. I want to run a 7.2 Cu. Ft. Chest Freezer (250 KWH per year) on solar. It will be at my off grid cabin that is powered by my generator when we are there. We go there once a month and I wanted to keep hotdogs hamburgers etc for the BBQ and not worry about bringing it in a cooler each time we go to the cabin. What would I need to run just the chest freezer nothing else?



Thanks,



EJM

[Mike90250]

You will be building a bare bones, no margin system on the cheap, and will run a real risk of opening a freezer full of green hotdogs and fuzzy buns.

Your system would be summertime only, unless you want to spend LOT$ of money to keep $10 worth of food frozen in winter too.

Your batteries have to be large enough to run the gear for 4 days of cloudy weather (unless you never need to plan for clouds)

PV array has to be large enough to recharge low batteries in 1 day of good weather.

Vandal resistant for when you are absent

Gear suggested
4 golf cart batteries, wired for 24V
1,000w pure sine wave inverter 24v - 120VAC
about 900w of PV panels
30A true MPPT charge controller
Panel mounting gear
electrical boxes, breakers

See my page at
Garden Solar Power Plant
https://www.facebook.com/media/set/?...1&l=2f55e6c7ee
for something in the scale of what you need to run a 7.2 Cu. Ft. Chest Freezer (250 KWH per year)

[EJM]

Thanks Mike... That is a lot more then I was figuring. I did see some DC freezer kits. Maybe that will be a better choice. They must be super efficient

[peakbagger]

Sundanzer sells vaccine refrigerators that are equipped with phase change material ice packs. Effectively replace PITA batteries with far simpler PCM packs.

[organic farmer]

We have four chest freezers at our home. I have them on power strips with timers, so they only get power from 8am to 4pm [generally when our system has surplus power anyway]. If you do not open a chest freezer daily, it should remain cold for multiple days, even without power.

[EJM]

We have four chest freezers at our home. I have them on power strips with timers, so they only get power from 8am to 4pm [generally when our system has surplus power anyway]. If you do not open a chest freezer daily, it should remain cold for multiple days, even without power.

That's a great idea. I wonder if that would bring down the cost of solar setup. It seemed like a lot of money just to run a chest freezer. Hopefully this idea will help.

[BackwoodsEE]

I have my chest freezer connected via a solid-state relay so that it only runs when the sun is shining if the grid is out. It will run all day long to cool the thing down and then stay cold all night long. It's not perfect; when I've tested it during the summer (it's in a garage that stays warm for hours from the day's heat), the temp inside the freezer does get to a bit higher temperature than I'm comfortable with by morning.

I put bottles of a glycerol/water mix in the freezer to act as a phase change material with a freezing point of around 0 degrees F. That worked great at first, and noticeably extended the cool down and warm up time periods. But the glycerol eventually separates from the water (it's denser) and then I get half the bottle's contents freezing and the other half staying liquid, which limits the PCM behavior.

[Sunking]

I put bottles of a glycerol/water mix in the freezer to act as a phase change material with a freezing point of around 0 degrees F. That worked great at first, and noticeably extended the cool down and warm up time periods. But the glycerol eventually separates from the water (it's denser) and then I get half the bottle's contents freezing and the other half staying liquid, which limits the PCM behavior.

Use Vodka.

[littleharbor]

Use Vodka.

Pure genius, I prefer tequila and Fireball myself.

[J.P.M.]

Use Vodka.

I'd use ice. With a specific heat of ~ 0.50 for ice (not to be confused with the specific heat of liquid water @ 1.0), while its heat capacity is less than that of vodka @ ~ 0.65 -0.75 or so (for what's mostly an aqueous ethanol/H2O mixture), and less dense than an ethanol/H2O mixture, it doesn't cost as much and there's less danger if leakage of the ethanol occurs.

[Mike90250]

Salt water, you add just enough salt to keep the freeze/thaw point where you want it
here's the link:
https://commons.wikimedia.org/wiki/F...zing_point.jpg

Saltwater_freezing_points.jpg

[Sunking]

I'd use ice. With a specific heat of ~ 0.50 for ice (not to be confused with the specific heat of liquid water @ 1.0), while its heat capacity is less than that of vodka @ ~ 0.65 -0.75 or so (for what's mostly an aqueous ethanol/H2O mixture), and less dense than an ethanol/H2O mixture, it doesn't cost as much and there's less danger if leakage of the ethanol occurs.

JPM you missed the point this time my friend. Use vodka and no one gives a crap about science. I know for fact, I am am an expert and alchoholic who has not had a drink in almost 30 years. Still looking where I left my bottle of Crown Royal so I can start drinking again and quit thinking.

[J.P.M.]

JPM you missed the point this time my friend. Use vodka and no one gives a crap about science. I know for fact, I am am an expert and alchoholic who has not had a drink in almost 30 years. Still looking where I left my bottle of Crown Royal so I can start drinking again and quit thinking.

I got it. I like Mike's brine suggestion, but there may be some concerns about concentration gradient vs. depth and the consequent changes in freezing temp. with resultant problems when freeze expansion happens.

Your suggestion just seems a terrible waste of good alcohol.

One other thing we share: My last drunk was on Memorial day, 1982 (or maybe it was '83, don't remember, I was drunk that year). Before that, one of my life's goals (along with making sure all the world's women were Gaelic by injection), was to keep all the world's breweries on 3 shifts. That following Tues, the folks at St. James gate in Dublin turned my portrait that was hanging in their lobby to the wall and draped it in purple.

For me, thinking is better than drinking (at least most of the time).

[gbynum]

Salt water, you add just enough salt to keep the freeze/thaw point where you want it

That's what's in the freezer blocks you see in stores. It's the state change that absorbs heat; -10C should be good (14F) so it is solid in your typical 0F home freezer