Thinking about how well a refrigerator could run on solar power alone, without a storage battery.
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@MLE_online I'm pretty sure a chest freezer could do it unmodified.
@attoparsec Yea, but what would I do with stuff I didn't want frozen?
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@HowardGees My parents had an icebox for the trailer, and it kept things cold for a very long time with just one block of ice in it
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Thinking about how well a refrigerator could run on solar power alone, without a storage battery. If some fridge and freezer space were sacrificed in exchange for thermal mass (jugs of water), how well would it keep things cold from dusk to dawn while it's unpowered? Pretty well, I bet, if you didn't open the door much.
@MLE_online This is similar to the methodology of keeping cryogenic gases. The mass matters a lot.
My mum used to fill gallon milk bottles with water and freeze them and store in the fridge during the frequent power outages. Worked very well. Even when the power was out for more than a day.
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@attoparsec Yea, but what would I do with stuff I didn't want frozen?
@MLE_online Chest fridge -- maximal frustration in the search for thermal efficiency!
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@MLE_online This is similar to the methodology of keeping cryogenic gases. The mass matters a lot.
My mum used to fill gallon milk bottles with water and freeze them and store in the fridge during the frequent power outages. Worked very well. Even when the power was out for more than a day.
@MLE_online And if you happen to have a fridge that is actually a dewar, it is really great.
No one makes any dewars suitable for home freezer/fridge use, though.
Vacuum-insulated freezers. This may be an overlooked opportunity.
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Thinking about how well a refrigerator could run on solar power alone, without a storage battery. If some fridge and freezer space were sacrificed in exchange for thermal mass (jugs of water), how well would it keep things cold from dusk to dawn while it's unpowered? Pretty well, I bet, if you didn't open the door much.
I’ll bet if we separated the hot parts from the cold, we’d get there.
Also: what if we just cooled a storage tank at night? With propylene glycol could we get a decent -10F? Or run a water to Freon condenser and reradiate that heat with a thermosiphon?
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Thinking about how well a refrigerator could run on solar power alone, without a storage battery. If some fridge and freezer space were sacrificed in exchange for thermal mass (jugs of water), how well would it keep things cold from dusk to dawn while it's unpowered? Pretty well, I bet, if you didn't open the door much.
@MLE_online I've been trying to get my act together and assemble such a thing for a while now
Ice/Water phase change heat of fusion energy is so big, it feels certain it could work just fine for a chest style <5C fridge that doesn't spill all its cold air out when opened
I bet that if you depressed the heat sink freezing point enough with an antifreeze or salt or something (enough, but not so much that it does not solidify since "melting" gives the constant cold) it could work as a freezer too
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I’ll bet if we separated the hot parts from the cold, we’d get there.
Also: what if we just cooled a storage tank at night? With propylene glycol could we get a decent -10F? Or run a water to Freon condenser and reradiate that heat with a thermosiphon?
@BenHM3 that glycol thing would probably work well, but would be a lot less practical than just having a fridge. Who has space for a glycol storage tank in their kitchen?
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Thinking about how well a refrigerator could run on solar power alone, without a storage battery. If some fridge and freezer space were sacrificed in exchange for thermal mass (jugs of water), how well would it keep things cold from dusk to dawn while it's unpowered? Pretty well, I bet, if you didn't open the door much.
@MLE_online I've read that people who live off grid sometimes get chest freezers and replace the thermostat with a fridge thermostat, because the horizontal door is so much more efficient - no vertical door that dumps all the cold air out the bottom when it's opened.
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@MLE_online I've been trying to get my act together and assemble such a thing for a while now
Ice/Water phase change heat of fusion energy is so big, it feels certain it could work just fine for a chest style <5C fridge that doesn't spill all its cold air out when opened
I bet that if you depressed the heat sink freezing point enough with an antifreeze or salt or something (enough, but not so much that it does not solidify since "melting" gives the constant cold) it could work as a freezer too
@MLE_online my thought for a design was to set it up as a stratified cold bucket with an insulated floor between the merely refrigerator upper layer and the actually frozen lower layer which is in contact with the heat sink that gets cooled during sunlit periods. Basically I was going to trial and error various thicknesses of insulation or possibly like a layer of plastic fluid filled icecube sheets over the frozen part, below a refrigerated part, in a chest freezer that cools from the bottom up
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Thinking about how well a refrigerator could run on solar power alone, without a storage battery. If some fridge and freezer space were sacrificed in exchange for thermal mass (jugs of water), how well would it keep things cold from dusk to dawn while it's unpowered? Pretty well, I bet, if you didn't open the door much.
@MLE_online@afront.org I know that back in the 1920's there existed 'fridges' that used the evaporation of water exclusively to cool stuff.
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@MLE_online I've read that people who live off grid sometimes get chest freezers and replace the thermostat with a fridge thermostat, because the horizontal door is so much more efficient - no vertical door that dumps all the cold air out the bottom when it's opened.
@dragonfrog that makes a lot of sense
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@BenHM3 that glycol thing would probably work well, but would be a lot less practical than just having a fridge. Who has space for a glycol storage tank in their kitchen?
True.
But is it less problematic than bottles of frozen water inside?I guess it needs some thinks-thinking on where the cheapest thermal mass would provide the best bang.
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True.
But is it less problematic than bottles of frozen water inside?I guess it needs some thinks-thinking on where the cheapest thermal mass would provide the best bang.
@BenHM3 Yeah, I would say it's much less problematic, lol. Anyone can put jugs of water in a fridge. It doesn't require special know-how. You aren't modifying a refrigeration system. You don't need large amounts of special chemicals.
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@voxdeb @hotarubiko Ice would for sure keep the fridge colder, but having to cycle frozen bottles into the fridge and melted bottles into a freezer to be frozen would be a lot more work than just keeping jugs of cold water in a fridge -- if that was enough to work
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Thinking about how well a refrigerator could run on solar power alone, without a storage battery. If some fridge and freezer space were sacrificed in exchange for thermal mass (jugs of water), how well would it keep things cold from dusk to dawn while it's unpowered? Pretty well, I bet, if you didn't open the door much.
@MLE_online Sounds plausible. My freezer has two extra-large cool packs in the upper part of the door - according to the manual they help keeping the temperature below -18° Celsius for 24h even when the power is off, as long as you don't open the door.
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Thinking about how well a refrigerator could run on solar power alone, without a storage battery. If some fridge and freezer space were sacrificed in exchange for thermal mass (jugs of water), how well would it keep things cold from dusk to dawn while it's unpowered? Pretty well, I bet, if you didn't open the door much.
@MLE_online With enough thermal mass and pulling the fridge temp down to just above freezing it should hold fine. I've gotten thru power outages running a fridge on generator in daytime only before.
The other consideration is the starting current of a typical 120v fridge compressor. An inverter big enough to do it is going to waste a lot of energy and need some amount of battery for the current pulse. The defrost cycle is a consideration as well.
It's probably much more doable starting with a 12v powered RV/Car style fridge, especially now that tiny inverter compressors are a thing.
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Thinking about how well a refrigerator could run on solar power alone, without a storage battery. If some fridge and freezer space were sacrificed in exchange for thermal mass (jugs of water), how well would it keep things cold from dusk to dawn while it's unpowered? Pretty well, I bet, if you didn't open the door much.
It will be fine overnight, assuming your house isn't super hot
The trick is to have no air space inside the fridge. Not just jugs of water, but square jugs stacked on top of each other, no airspace above the shelf contents, etc
I did this with a mini freezer, for van life. When completely full, it will stay frozen for 72 hours, opening once or twice a day, at reasonable outdoor temperatures
When half full it won't stay frozen for even 24 hours
If you're interested in a fridge temperature sensor that links to an app on your phone using wifi, I highly recommend yolink
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@MLE_online With enough thermal mass and pulling the fridge temp down to just above freezing it should hold fine. I've gotten thru power outages running a fridge on generator in daytime only before.
The other consideration is the starting current of a typical 120v fridge compressor. An inverter big enough to do it is going to waste a lot of energy and need some amount of battery for the current pulse. The defrost cycle is a consideration as well.
It's probably much more doable starting with a 12v powered RV/Car style fridge, especially now that tiny inverter compressors are a thing.
@foundthefault I need a fridge with a hand crank like a model T
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@foundthefault I need a fridge with a hand crank like a model T
@foundthefault Someone on bluesky turned me on to this guy who's doing it without battery storage.
