A possible way to keep your fridge cold in long term blackouts.

[Alti]

I can tell you that mass market products (like fridges) are optimized to the very last cent and keeping all parameters constant - it is unlikely you can improve anything here and extending robustness against blackouts without serious investment.

If you have some money - get a small gasoline generator.
I doubt you can reliably power fridge from PV because blackout can happen during lousy weather. So most likely a serious battery bank is a must here anyway.
If you have some space - you could use a chest freezer and convert it into a fridge (replace temp control). Chest freezers are much better insulated than freezers and do not flush cold air when opened. Not a very practical fridge but a cheap off-the-shelf solution.
The advice of keeping fridge full is also a possibility but this decreases useful internal volume and might not be very comfortable. So you need to buy a fridge that is bigger than your actual needs, which affects running cost. How much are you willing to spend for this comfort?
Then, external insulation. Well I do not know how much heat/cold is escaping through side walls and you won't be able to insulate back of it because there sits the condenser. Also, flushed cold air won't be saved, no matter how thick this wall insulation is.

Interesting problem with a lot of potential solutions but without precise definition of OP's goals (in terms of devoted time, money, space, etc) it is hard to point into the right direction.

[SeanB]

Extra insulation is hard, because most units these days use the steel case as condenser, with steel coils glued to the steel sheet, held down with tape, before the insulation is foamed in place. Thus no coil on the back, and the interior coils are the same, placed on the plastic case to cool that way. no way to insulate, though the first run of the hot gas out of the compressor does run around the door frame, so that the seals do not freeze onto the metal. Best is to not open during power failures, and for longer use a chest freezer is good, and many also have enough control range to act as a fridge as well. Yes the fill with ice works, a lot of energy stored in that phase change.. BVut for longer than 8 hours you probably want a generator, or inverter and battery, charged from some source, solar, generator or even that pedal bike, just needs to have enough energy put in to run the compressor for an hour a day.

Tip for the freezer is to take a small plastic bottle, fill with water half way, and freeze. Then remove, open, and place a coin on top of the ice, close, and place back inside. That will tell you that, since you last looked at it, that there was a power failure long enough for the ice to melt, as the coin will be in the ice, and not on top.

[tooki]

The advice of keeping fridge full is also a possibility but this decreases useful internal volume and might not be very comfortable. So you need to buy a fridge that is bigger than your actual needs, which affects running cost. How much are you willing to spend for this comfort?

No, the idea is to keep full any empty space in your fridge, not to get a bigger fridge! The point is to not have extra air. If it’s full of actual food and drinks, that’s fine. You only add extra bottles if your fridge has unused space. If you need the space, take them out.

[antenna]

Tip for the freezer is to take a small plastic bottle, fill with water half way, and freeze. Then remove, open, and place a coin on top of the ice, close, and place back inside. That will tell you that, since you last looked at it, that there was a power failure long enough for the ice to melt, as the coin will be in the ice, and not on top.

You can save that coin for laundry and just put an ice cube on the rack or in a bag.  If it is a frozen puddle on the bottom of the freezer or otherwise no longer shaped like a cube, there you go...  This is one of those simple problems people always over-engineer a solution for...

[Siwastaja]

* Keep the fridge full
* Add extra insulation around the walls and the door.
   * Be careful not to insulate the condenser coils
   * Condensation of water can occur. The outer envelope of the newly added insulation should optimally be vapor tight.
* Avoid opening the fridge as much as you can during the emergency. Do bookkeeping so you know what you have without looking. Plan ahead and get everything out at once once or twice a day.

Maybe doing all that you could reduce the consumption by 30-40% It won't still be practical to be human-powered, but at least a smaller battery pack or PV panel will do.

But all hope is not lost: during coldest and darkest wintertime, you won't get much PV, but you could store foods outside.

During hot seasons, you definitely have enough sunlight to easily power the fridge, even during cloudy days.

So PV + battery + inverter, it is.

[SiliconWizard]

Many people do not realize that their average amount of power consumption is easily an order of magnitude more than what they could generate themselves with their body (and with great effort) - and depending on your activities and lifestyle, that could be more like 2 orders of magnitude.

[antenna]

Just call it a small fridge and assume 1kwh per day energy consumption.  1kwh = 860421 calories.  Get eating!  Wait... the fridge is now empty, you ate it all on day 1.  Congratulations, you no longer need a refrigerator!!!  Problem solved!!!!!

[Cerebus]

I think people are underestimating the power output quite ordinary people are capable of. Here's a chart of the brake power I could output a while back. Note my age on the chart, this isn't a fit young athlete but a very average healthy man in late middle age - no superman me, that's for sure. It's an interval session, so there are high peak power outputs, but the ~100W baseline is cruising speed, a warm up before, and gentle relaxation between the intervals. I could keep up that ~100W pace for several hours - I've certainly done it for at least 4 hours in a day. I'll emphasise that this is measured brake power, i.e. physical power available to drive a generator or machinery with the cycle inefficiencies already accounted for. Mean brake power across the whole session is 114W.

Sure, the 400Wh/day I could generate isn't enough power to run a typical domestic fridge but it shows that we're a lot closer than some people posit. If this old git can manage it then pretty much anyone who's not in poor health can.


Created on an instrumented cycle ergometer.

[Cerebus]

Just call it a small fridge and assume 1kwh per day energy consumption.  1kwh = 860421 calories.  Get eating!  Wait... the fridge is now empty, you ate it all on day 1.  Congratulations, you no longer need a refrigerator!!!  Problem solved!!!!!

Yeah, but the 'calories' used for food are actually kilocalories, so that 860421 calories is a 860 kcal meal - there's 770 kcals in a Big Mac and fries.

I'm cheating a little here, people are around 20% efficient. So that's about 4300 kcals, just under eight Big Macs (no fries). A 70 kg adult male would need another 1700 kcals/day just to support their basal metabolic rate.

[Zero999]

Just call it a small fridge and assume 1kwh per day energy consumption.  1kwh = 860421 calories.  Get eating!  Wait... the fridge is now empty, you ate it all on day 1.  Congratulations, you no longer need a refrigerator!!!  Problem solved!!!!!

Yeah, but the 'calories' used for food are actually kilocalories, so that 860421 calories is a 860 kcal meal - there's 770 kcals in a Big Mac and fries.

I'm cheating a little here, people are around 20% efficient. So that's about 4300 kcals, just under eight Big Macs (no fries). A 70 kg adult male would need another 1700 kcals/day just to support their basal metabolic rate.

The energy requirements for very active men i.e. on an polar expedition is around 6000 kcal/day.

No doubt it's possible to human power a refrigerator. If the control system is redesigned and the compressor is put on a variable speed drive, I'd imagine the efficiency would be higher, not lower. It's obviously impractical though. To avoid malnutrition and dehydration you'd need to eat a lot of food an drink more, so it would make more sense to just have more tins and dry food, which doesn't require refrigeration.

[Seekonk]

I read a lot of posts about how people prepare for the grid going down. I live 5 months of the year at my summer home in the northeast and my grid is always down, there is no electric. It is actually surprisingly cheap to live quite well off solar if you have engineering experience.  I have two water heaters, one just for the laundry, washing machine, dishwasher, fridge, pump and everything runs on a micro from PV. All loads are prioritized. Even a couple things that keep me alive at night. And all that runs on a car battery which has to have a near full charge as evening rolls around. The fridge only runs when the sun shines and if the charge drops 5% it will shut off.  The battery is just there for starting and I store all the "cold" I can till it gets down to 35F. I take up dead space with liquids. I don't have spoiled food and amazingly reliable thru rain and clouds. It is a dirt cheap system if you have programming skills. And why spend money on a system that will be used only once in a while. The battery can be from your extra car, boat, or garden tractor. Those solar $500 worth of panels can be heating water when there is no emergency. The payoff is just as good as a heat pump water heater.

[BrianHG]

Just a power output example....
If only the sprinter could maintain that wattage for 12 minutes...

[Someone]

Just a power output example....
If only the sprinter could maintain that wattage for 12 minutes...

Which is the point I brought up that everyone seems to be trying to work around. Human power output vs duration is well known, the whole "I did XXX for YY minutes/seconds, and am sure I could do that all day long" is just wrong. The human body is layers and layers of squishy dynamic systems, unique to each person, each having their own endurance limitations. Your legs feel ok? no use when your brain is starved for energy.

[james_s]

My refrigerator consumes about 130W steady state once the compressor has been going for a bit and things are settled in after starting at about 75W. The duty cycle is pretty close to 50% so let's say the average continuous power is about 65W. From my own experience, I can generate around 100W on a stationary bicycle but only when I'm peddling flat out and I can only sustain that for maybe 20 seconds. Someone who is more physically fit than me could probably sustain 65W continuously for a few hours but it's going to require several people working in shifts to keep the fridge cold. Seems like a small gasoline, propane, natural gas or diesel generator is a lot more practical. A modest solar installation could also work well here, maybe 300-400W of panels and several deep cycle batteries.

[Zero999]

My refrigerator consumes about 130W steady state once the compressor has been going for a bit and things are settled in after starting at about 75W. The duty cycle is pretty close to 50% so let's say the average continuous power is about 65W.

How hot is your kitchen? That sounds like a very high duty cycle. It sounds like the gas is running out. My fridge probably has a duty cycle of under 10%, but I haven't measured it.

[james_s]

My refrigerator consumes about 130W steady state once the compressor has been going for a bit and things are settled in after starting at about 75W. The duty cycle is pretty close to 50% so let's say the average continuous power is about 65W.

How hot is your kitchen? That sounds like a very high duty cycle. It sounds like the gas is running out. My fridge probably has a duty cycle of under 10%, but I haven't measured it.

Typically about 69F, and the fridge has always run about the same since I bought it ~22 years ago. Keep in mind that US refrigerators are considerably larger than those in UK/Europe and technology has also improved in the time since mine was made. It also varies widely depending on the design, mine uses R134a refrigerant, others using different gasses may be optimized for different duty cycles.

[BrianHG]

If the power has gone out an an hour later you begin pedaling, that duty cycle may be broken and you may need to keep the compressor going for 100% of the time for an hour before the 10% duty cycle comes back.

Battery backup + solar + bike for extra supplemental battery charging may be achievable, but you would need to engineer the bike for an optimum pedaling pace, torque and wattage.  Without such research, you would be left with a devastating loss at the bike generator.

I have a 500watt continuous duty 3phase generator for sale.  You can easily run it at 1kw for 30 minutes, then allow a break for cooling.  It was designed for wind generation and has no cogging.  Short the leads on this baby and it will not turn as it is a neodymium super efficient generator.

See attached photos and data sheet.  If anyone wants it, I'll sell privately or put it up on ebay for 700$ us.
(Model number GL-PMG-500A, original shipping freight boxing)
Highly recommend that you can manufacture or machine the shaft to adapt a normal pulley.

[Cerebus]

From my own experience, I can generate around 100W on a stationary bicycle but only when I'm peddling flat out and I can only sustain that for maybe 20 seconds.

Not being funny, but if that's your maximum exercise capacity then, assuming that you don't have serious health problems that you didn't mention, you ought to talk to your doctor. 100W is a fairly normal cycling effort for someone just using a bike to get about for simple transportation. It's the equivalent of the standard 70kg man riding a heavy "sit up and beg" pushbike at 14 mph.

From https://www.okhane.com/calculators/cycling-wattage-calculator/:

[BrianHG]

With the above generator and proper gearing, with 6 Schottky diodes tied to a 24v or 48v LiFePO4 battery pack (one which contains internal balancing and protection), the more you sweat, the more current you will feed into the batteries.

Expect over 90% efficiency with that neodymium generator.

[james_s]

Not being funny, but if that's your maximum exercise capacity then, assuming that you don't have serious health problems that you didn't mention, you ought to talk to your doctor. 100W is a fairly normal cycling effort for someone just using a bike to get about for simple transportation. It's the equivalent of the standard 70kg man riding a heavy "sit up and beg" pushbike at 14 mph.

I was going off of the built in display on a stationary bicycle I used for a while, it's entirely possible that it was grossly inaccurate. I would rate my physical fitness as better than average for an American although I wouldn't go so far as to call myself athletic. At the time I was pretty regularly going on ~22 mile bike rides and now I walk briskly 1-2 miles every evening in my hilly neighborhood. I've hiked up to the ~5300 ft summit of Mt. Pilchuck quite a few times and did not find it particularly difficult.

[Cerebus]

Not being funny, but if that's your maximum exercise capacity then, assuming that you don't have serious health problems that you didn't mention, you ought to talk to your doctor. 100W is a fairly normal cycling effort for someone just using a bike to get about for simple transportation. It's the equivalent of the standard 70kg man riding a heavy "sit up and beg" pushbike at 14 mph.

I was going off of the built in display on a stationary bicycle I used for a while, it's entirely possible that it was grossly inaccurate. I would rate my physical fitness as better than average for an American although I wouldn't go so far as to call myself athletic. At the time I was pretty regularly going on ~22 mile bike rides and now I walk briskly 1-2 miles every evening in my hilly neighborhood. I've hiked up to the ~5300 ft summit of Mt. Pilchuck quite a few times and did not find it particularly difficult.

I think we can safely conclude then that the power display was, as we British engineers call it, "completely buggered".

[BrianHG]

This guy measures his chest freezer at 600 watts per day.
Figure less power per day to run it at refrigerator temperatures.

https://youtu.be/CGAhWgkKlHI?t=507



Seek to 8:30...

2 adults can reasonably pedal that with a good efficient generator wasting 1 hour each per day.
On my existing cheap bike, because of poor efficiency, make that 2 hours each per day, or 1 hour each, but sweating it out.

[jonovid]

to keep the refrigerator you need a lot of deep cycle battery 200AH or more. to feed the inverter & 400w of solar panels on a good day. IMO
better to use an internal combustion gen-set and keep frige door closed between 2hr runs every 6-8hrs.
a mod'ed elliptical trainer as gen-set is only good for 100w IF you can keep it up for more then an hr.  better ways to .
animals have better endurance if you can get your dog or horse on a treadmill. 
   
long term blackouts in a city?  if metropolitan boondocking the zombie apocalypse.

[james_s]

I just use a Honda EU2000i, it runs all day on about a gallon of gasoline and at light load it drops down to a whisper quiet idle. I can power my whole house with it as long as I do a bit of load management and don't try to run two large loads at once.

[NiHaoMike]

How come so far, no mention of a bucket and a bag of salt (for the freezer) if winter storms are the primary concern?