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Solor fridge..

With a freezer, vertical doors lose cold air, but the bad thing is they GAIN water filled moist air that condenses and forms thick frost. A fridge doesn’t. It has a warm (compared to a freezer) coil that can collect the moisture, and drain it out of the box. It is true the air in a full fridge is inconsequential to the temp of the products inside, but it DOES require electricity to remove the heat gained by it, and opening the door several times a day requires several times more electricity.
ever notice you can buy large and small upright refrigerators, but you cannot buy large and small upright freezers...
at a certain point, upright freezers take up too much space with evaporator shelving to handle the heat gain from opening the door, so chest freezers just function better...
 
Electric Night said:
If you have ever opened an upright freezer door with bare feet you will feel the "cold" escaping this "colder air is replace by warmer air entering, which then needs to be re-cooled. this doesn't happen with a chest freezer.
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This is what I initially thought too (and the principle is correct). What you are not accounting for is that water and dense solids (i.e. the stuff you put in the fridge/freezer) have massively more thermal mass (ability to hold heat/cold) than the air. So with a full fridge it doesn't matter whether the air 'spills out' or not, it could spill out dozens of times in a day and still not effect the temperature of the contents by a meaningful amount. Or at least that's how it was explained to me, and the physics makes sense at least on a conceptual level.

All other things being equal a chest style fridge/freezer would be more efficient, but I now believe that the difference is not nearly as important as I was once thought.

As for retail stores, there is a pretty big variety of upright and chest style units, the grocery store nearest me only has upright units, as does the nearest drug store, but most convenience stores have chest style freezers and lots of grocery stores have both chest and upright units.

Here is a good thread on the topic (and many other topics related to fridge efficiency, its a good read if you are interested in the subject). I believe the relevant debate about top loading fridges and the effect of the air not leaking out begins on page 3 or 4.
 
Dzl said:
This is what I initially thought too (and the principle is correct). What you are not accounting for is that water and dense solids (i.e. the stuff you put in the fridge/freezer) have massively more thermal mass (ability to hold heat/cold) than the air. So with a full fridge it doesn't matter whether the air 'spills out' or not, it could spill out dozens of times in a day and still not effect the temperature of the contents by a meaningful amount. Or at least that's how it was explained to me, and the physics makes sense at least on a conceptual level.

All other things being equal a chest style fridge/freezer would be more efficient, but I now believe that the difference is not nearly as important as I was once thought.

As for retail stores, there is a pretty big variety of upright and chest style units, the grocery store nearest me only has upright units, as does the nearest drug store, but most convenience stores have chest style freezers and lots of grocery stores have both chest and upright units.

Here is a good thread on the topic (and many other topics related to fridge efficiency, its a good read if you are interested in the subject). I believe the relevant debate about top loading fridges and the effect of the air not leaking out begins on page 3 or 4.
Click to expand...
Keep this in mind when considering efficiencies...

in a grocery store, cooler/freezers lost energy out of the box, helps keep the store cooled, lowering the massive AC bill the store has with all the heat people give off...

In a home, the lost cool air from the freezer, actually causes the house to be warmer... because the cooler’s condenser and compressor are inside the space.
 
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Supervstech said:
It is true the air in a full fridge is inconsequential to the temp of the products inside, but it DOES require electricity to remove the heat gained by it, and opening the door several times a day requires several times more electricity.
Click to expand...

This is a good point, and expanding on that, if the thermostat is quick to adjust to short term fluctuations in air temperature this could lead to a longer duty cycle and more energy consumed, but if the thermostat has a short delay opening the door may not effect things much at all (as the contents of the fridge/freezer will also be working to cool the air down).

For me upright is the best option regardless of how much more efficient it is, so its not a consideration I worry too much about, but it would be interesting to know exactly what sort of difference we are talking about 1%, 5%, 10%.

According to what I have heard, the math points to the difference being very small to negligible in theory, but in practice there are a lot of factors to consider and so many variables that I'm not convinced the math accurately accounts for.
 
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Here is a relevant excerpt from the other thread I linked to:

LuthJ from expeditionportal.com said:
The actual energy content of the air in a fridge is tiny. Even if you swapped the air in the fridge out 30-50 times a day, its still less energy than it takes to cool down a bottle of water.

The specific heat of air is about 0.718kJ/kg C while water is 4.18kJ/kg C. A bottle of water is about 1kg, so 4kJ. With a 20C difference between room temp and fridge temp, a bottle of room temp water will need 80kj of energy removed to bring down to fridge temp. 80kJ=22 watt-hours.

To equal that amount of energy, you would need to cycle 5kg of air through the fridge. 5kg of air is about 4.5 cubic meters of air. For a 60 liter fridge that is completely empty, that would require replacing the air in the fridge 75 times.

Insulation is much more important than door type. High efficiency home units will have 4-6" of insulation, while many mobile units will only have 2-3"

If you wanted to offset the energy lost from air leaving the fridge, you could just put your condiment bottles away immediately after use. Or avoid putting warmed food directly into the fridge after eating.
Click to expand...
...
LuthJ from expeditionportal.com said:
The fridge has a temperature sensor. It takes several minutes for it to adjust to changes in the fridges internal temp. If you open the door the air temp in the fridge will change for a minute or so, but the contents of the fridge will bring the temp back down quickly. This is generally not enough to cause an immediate cycle. The energy you just gained (cold air lost) will be removed from the fridge at the next cycle.

Most chillers (AC systems, fridges etc) have a coefficient of performance between 2-4. That means that for every watt hour of electrical energy they consume, they remove 2-4 watt hours of power from the fridge (as heat). So that bottle of water which needs 22 watt hours of cooling will need 5.5-11 watt hours of electricity to recover. That is about 0.5-0.8AH at 12V.
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...
LuthJ from expeditionportal.com said:
If the fridge is stabilized (steady state) adding a bottle of water etc will increase the cooling load by the amount I calculated. Obviously you have the existing cooling load + 22 watt-hours. This energy usage (about 8 watt hours of electricity) will be spread out over an hour or two. It is a specific and easily calculated value. I work with this type of stuff for a living, this is an engineers bread and butter really.

The whole purpose of this exercise in physics is to describe/define the size of various factors on a fridges cooling load. As described above air loss is a minor impact on cooling load for fridges that are not opened and closed constantly.

A fridge is system, in physics energy in minus stored energy must equal energy out.
Click to expand...
 
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Dzl said:
This is a good point, and expanding on that, if the thermostat is sensitive to short term fluctuations in air temperature this could lead to a longer duty cycle and more energy consumed, or if it wasn't it may not effect things much at all (as the contents of the fridge/freezer will also be working to cool the air down).

For me upright is the best option regardless of how much more efficient it is, so its not a consideration I worry too much about, but it would be interesting to know exactly what sort of difference we are talking about 1%, 5%, 10%.

According to what I have heard, the math points to the difference being very small to negligible in theory, but in practice there are a lot of factors to consider and so many variables that I'm not convinced the math accurately accounts for.
Click to expand...
It also depends on usage of the freezer.
If the food is mostly in the freezer for long term storage, and rapid freezing of large loads from like a fresh load of meat from a butcher, where rapid freezing is most important... upright is a clear winner. If upright is used and food is daily placed in and out, there will be a LOT of frost needing a monthly defrosting...

A chest freezer can be repeatedly opened with little frost buildup.
Upright is also more convenient for a more varied mix of contents.

bottom line is... with solar, and squeezing every watt to its best use... chest freezers converted to a refrigerator set of temps is quite efficient.
 
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of course the freezers have more insulation because they are often designed to keep things <0F and the "refrigeration system" is designed to remove more heat that most "refrigerators"
 
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that is why most upright freezer use drawers, so the loss is minimal when you open the door.
Most women do not like the chest type because you have to dig inside to get the stuff at the bottom and very often
things are stuck together with ice, so it could be a painful task to retrieve something.
chest type is great if you are hunter/farmer and need to freeze big piece of meat.
 
So yesterday after reading this I walked out my front door and my neighbor across the street had a small chest freezer for sale. I bought it for 50 bucks and will do some tests with power draw and report back. I will look for a similarly sized refrigerator maybe and compare.
 
I chose to use an external thermostat just in case I wanted to use the chest freezer as a freezer. Just remove the inline thermostat. However, in researching these, I found replacement internal thermostats, one-for-one exact replacements that regulated to fridge temps. 10 minute, low cost conversion.

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best fridge set up ?

Hi Iam uk based Solar novice i have a XLWB 2013 Transit running 4 x 100w renogy mono going to renogy DC 2 DC / MPPT combined with 1x 200AH lucas AGM battery adding another in the near future. In my van I Would like as big a fridge as i can get but a 12v 3 way fridge is expensive £600 for a...
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Disaster relief solar for Abaco in the Bahamas. Hurricane Dorian.

In my mind... Can't say I haven't been thinking the same thing. It's one thing to salvage parts, put together a working couple of systems, but the reality is that these systems need to be pretty bullet proof, ruggedized, simple for anyone to use. No way a team of tech geeks is going down just...
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Dzl said:
Lots of youtube videos about it, doesn't look that difficult. I haven't seen any realistic consumption figures, I would be very curious to know how much electricity they consume vs a traditional fridge of similar size and vs a 12v fridge of similar size.

The video I watched claimed "100 watts per day," which probably means 100 watt-hours per day (which would be borderline impossible) or maybe means 100 watts draw when running (which is much more feasible but doesn't help us understand the overall consumption as we have no idea what the duty cycle is).

Does anyone have any ballpark figures on consumption?
Click to expand...
I bought a 3.5 CF chest freezer and did the coarse thermostat adjustment described in this thread. Got the temperature up to a max of 34 deg. The unit is operating off of a 1200W inverter in a non-insulated, off-grid cabin where inside temps range from 70 to 100+ in the summer months. When running, the draw indicated by the inverter LED readout is 100W, consistent with the freezer specs that indicate a 1A normal draw with a 4A startup surge. I leave only the freezer running when I'm not there. My Victron controller data indicates daily consumption of 500-600 watts per day.

Just as a side note, this was not my first choice for refrigeration. The DC powered units I wanted were not available. The pro to this setup is cost, $150. The con is inverter fan noise. Will stick with it over the upcoming fall/winter to see how it operates under milder temps. If the inverter fan issue persists, I'll be looking for a DC unit again.
 
That video was about 300WH a day and to takeoff for sunny day people was that 100W panel would run it. Fine if you just want to cool drinks and nothing to spoil. I have a lot of solar panels 2KW and just a single battery that is only used for surge current. That sounds like a lot of panels, but all of them are under trees and extensively shaded. I can still run my fridge in the pouring rain for days.
 
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