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Chest Freezers; What they tell us about designing for X

Jun 07, 2021
This is a video about how we design things. It's a video about priorities and how we sacrifice things like energy efficiency for the sake of convenience and vice versa, and why we need to meaningfully consider those sacrifices we make and the priorities

they

enable. As I'm sure you've deduced from the title, we're talking about

freezers

. Well, actually, refrigeration in a broader sense. But to make it clear

what

I would like with this video, we will talk about one of these little beauties. This is a perfectly normal

chest

freezer. It is a box with a lid that keeps things very cold.
chest freezers what they tell us about designing for x
Now, at first glance this is nothing extraordinary. But, if you know anything about

chest

freezers

, you know that

they

use an almost comically small amount of energy to do their thing. And the reason this is possible is because of its efficiency-first design. To start, let's consider

what

refrigerators and freezers do. Its most basic task is to transfer thermal energy from its interior to the outside world. They are in a constant battle with environmental energy. If you want there to be a space that is colder than its surroundings, you will discover pretty quickly that all the energy around that space would really like to spread out and will eventually find its way into your cold box.
chest freezers what they tell us about designing for x

More Interesting Facts About,

chest freezers what they tell us about designing for x...

Entropy is a pernicious little monster. The miracle of refrigeration has allowed us to fight against this impulse of nature. Using nothing more than a compressor, a couple of heat exchangers, a metering device, and specific chemicals, we can say "Fuck you, entropy!" and reverse the natural order of things. As? Well, we don't need to go into details here and I know I've shown a video on refrigeration... several times, and, uh, I'm doing it... once again. I... I really just want to find or create a better demo for you all, so I'm sorry. Suffice it to say that we take a chemical substance and use the properties of latent heat to move energy at our command.
chest freezers what they tell us about designing for x
By manipulating the pressure at which the chemical is, we can change its boiling point, and by controlling where and when it boils and recondenses, we can exploit the latent heat of vaporization. The miracle of refrigeration is that the energy we put into the system by mechanically compressing the refrigerant is only a fraction of the energy the refrigerant is capable of moving. In other words, let's say you spend 100 watts of electrical energy on a compressor in a refrigeration system. That system is now capable of moving the equivalent of 400 watts of thermal energy, or possibly even more. It's really cool, and using reverse cooling to concentrate thermal energy instead of dispersing it (we usually call this device a heat pump) will likely be critical in our fight against climate change.
chest freezers what they tell us about designing for x
All we need are refrigerants with a small global warming potential, which fortunately are starting to be implemented commercially, such as R-1234yf. Anyway, leaving aside the mechanical parts that make the heat go out, what every piece of refrigeration equipment in this world wants to do is create a thermal barrier between its interior and the outside world. Because no matter how miraculously efficient your heat pump design may be, unless you can slow the spread of energy from a high concentration to a low concentration, the cooling device will need to run a lot and will therefore consume a lot. energy.
I'm sure you've used one of these before. It's a cooler! The walls of the refrigerator are well insulated, which slows the progress of thermal energy trying to enter. And that allows you to keep the things inside colder for longer. Look, what you need to keep in mind is that things that are cold actually lack energy. Whe... I'm going to leave this. When you feel a cold can of your favorite drink from the refrigerator, the reason it seems cold to you is because it is absorbing the thermal energy from your hand, and our body interprets that sudden loss of energy as a cold sensation.
Seriously, your hand is warming the can. The can steals the energy that is in your hand, simply because the energy wants to spread and equalize. Aluminum is a good conductor of heat, which makes it look especially cold. If you simply take a bunch of cold cans and put them in a grocery bag, the thermal energy from the room (or the environment in general) will reach the cans relatively unhindered. Air is not very good at heat transfer, but it will happen. However, if you take these cans and put them in a cooler and close the lid, now the cooler has become a barrier.
The thermal energy around the refrigerator has a difficult time passing through its insulated walls. This way, the cans stay colder for longer. Fill it with ice and you now have a higher thermal mass, meaning the effect of thermal energy entering the cooler causes a smaller temperature rise since there is more mass to heat. The result is that things stay colder for longer. And now a curious fact. A refrigerator or freezer is nothing more than a fancy refrigerator with a small heat pump. Marginal note; Here in the US we use the term heat pump to generally refer to a reversible air conditioning system, which is how I used it before when I talked about how they would be critical in our fight against climate change.
But more correctly, any cooling system is essentially a heat pump. The function of a heat pump is to concentrate and relocate thermal energy using a refrigerant. Whether we use it to heat or cool a space is entirely up to us. Anyway, the walls of the refrigerator are insulated just like the refrigerator itself, and its job is to prevent thermal energy from the room it is in from entering and heating the food. Now, it can't keep heat out forever, it can only slow down the rate of heat transfer, so we need a heat pump to run periodically to be able to force it out.
That is the job of the compressor. Well, technically the compressor is just one part of the heat pump, but it is part of the pump. When you hear someone talk about a refrigerator compressor, this is the component that makes the hum and causes it to cool. The compressor compresses the gaseous refrigerant, forcing it into a high-pressure confined heat exchanger known as a condenser, where it can release its excess heat and condense into a liquid as it does so, all so that after passing through a device dispenser, the Now the liquid refrigerant can enter the refrigerated space, where it will evaporate thanks to the relief of this new low-pressure heat exchanger called an evaporator, which in doing so removes the heat from the interior of the space and cools it, but I said No.
I would focus too much on the mechanics and here I go talking about it again, so let's move on. One thing I would like to highlight here is that unless you load it with a ton of hot food, the only thing your refrigerator will have to deal with is the power of the room it is in. Once the temperature arrives, it is a relative constant. Many people will suggest that you avoid an empty refrigerator because more thermal mass inside will cause it to run less frequently. This is only true. The amount of energy that enters does not change with the amount of food inside.
Which means it doesn't affect how much it needs to run. What really changes is how quickly the energy coming in from outside will cause the inside temperature to rise. Without much thermal mass, the same energy input causes a faster temperature increase. Therefore, the compressor may need to run more frequently. But! That also means it won't need to run as long to get back up to temperature. Again, less thermal mass means that the same change in energy causes a larger (or faster) change in temperature. What you really avoid with a fuller refrigerator is short cycling, where the compressor comes on more frequently in shorter bursts, which could theoretically reduce the life of your refrigerator and slightly affect its energy efficiency.
But it's probably not as important as you think. So, if we want to increase the energy efficiency of a refrigerator, we have exactly two possible courses of action. We can design a more efficient heat pump. Or we can minimize ambient heat intrusion through better insulation design and application. And here is an important fact; There are not many advantages that we can find in the heat pump part. However, anyway. We've gotten pretty good at this whole refrigeration thing. Even though we have discovered that the coolants we used to use are not great for many reasons, thank you, Thomas Midgely Jr.! - we have adapted to new chemicals and we really have that part quite mastered.
But there is a lot we can do with the design part. And now we return to the humble chest freezer. These simple white basement boxes of turkey and popsicles from last year's grandma are truly extraordinary. Because? Due to its crazy energy efficiency. This is as close as you can get to a literal heat pump refrigerator. Because that is precisely what they are. It is a box. With cap. With thick insulated walls. And a small heat pump works to periodically move heat from inside the box to the outside, keeping its temperature below zero and regulated with the help of a thermostat.
Now, if you go to buy a chest freezer online and look at its energy consumption, you'll soon discover that... well, that's almost negligible! And well, compared to many things in your house, you would be right! I hooked this little chest freezer up to a Kill-a-watt to check it out for myself and...well, I was surprised at how efficient it is. When in operation, it only consumes about 100 watts of power. And over a three-day period, it consumed only 600 watt hours per day. Taking into account average electricity prices in the United States, this means that the operating cost of this freezer is just over $2 per month.
That's nothing! I mean, seriously, if you put just one frozen pizza in this freezer, that pizza would cost more than an entire month's electricity supply to preserve. You could put hundreds of dollars worth of food in here and keep it for a few cents a day. Its absolutely thrifty power consumption means you could easily power it with the output of a single commercial solar panel. A 250-watt panel that receives an average of just three hours of sun per day would do the trick just fine, assuming there's some storage involved, of course. And this particular freezer isn't even that efficient!
All things considered, it's actually pretty lousy. Considering that this model with almost double its capacity uses virtually an identical amount of energy, this is actually starting to seem a bit bad. But I mean it's still only two dollars! That is amazing! So what makes this so efficient? Well, a couple of things. First, this is a manual defrost freezer, meaning it will build up frost over time and will need periodic downtime to melt it. But that doesn't need to happen as often because of the second fact that makes it so efficient. Its door is at the top.
Like a cooler! Consider what happens when you open the lid. The air inside the freezer is very, very cold. Which means it's very dense. You've no doubt heard before that hot air rises and cold air falls. Well, if this is full of cold air and there are walls on all four sides that keep everything in, opening the lid doesn't help... almost nothing. There is a strong temperature gradient maintained just by the boundary between the warm air in the room and the cold, dense air found in the freezer. If the door is on the front, like on an upright freezer or any refrigerator, every time you open it, the cold air inside comes out.
You've probably seen this happen on a humid day when you open the freezer: the clouds of steam you see falling are the result of the cold air in the freezer mixing with the warm air in the room, drawing water vapor out of the freezer. air and making it visible as it falls to the ground. It is literally a cloud in your kitchen. And of course, if all that cold air has fallen, it must have been replaced by the warmer, less dense air in the room. You've probably noticed before that when you close your freezer door, the door seems to be sucked in after you close it, making it difficult to open again immediately.
This happens because the hot air that came in while you were browsing Food Netflix is ​​now sealed in the freezer, so it cools down quickly thanks to all the cold material inside and actually shrinks. This creates a dramatic pressure imbalance between the inside and outside, making it difficult to open the door again until the pressure equalizes. And of course the freezer will eventually have towork to remove the additional thermal energy introduced by this hot air. This hardly happens with a chest freezer. There is some suction force when you close the lid, but it is very weak and very brief.
Faint. This is because there is almost no new air coming in thanks to the literal tub filled with cold, dense air. It can't just spill out. Do you want proof? If you get a leaf blower and push a lot of air out of the room with the force of a hurricane, now when you close the lid there is noticeable suction. And it lasts quite a while. There you have it, proof that freezer walls keep cold air in place. Seriously, if you have a chest freezer and a leaf blower, try this at home! It's fun! And getting back to the defrosting part, the fact that the cold, dense air stays inside helps minimize the need to defrost it.
In this freezer and many similar ones, the evaporator (which is the part that cools) is built into the walls of the freezer. This means that the walls become very cold and moisture in the air condenses on them and subsequently freezes. Over time, this causes ice to build up. But, since the amount of ambient air entering the cooled space with each opening is quite small, that buildup is relatively slow. However, here's the thing. Chest freezers, no matter how clean, are not the easiest things to handle. While they've surely been endorsed by the Royal Society for Putting Things on Top of Other Things, the fact of the matter is that filling them with food means burying some of the other foods in the food.
If accessibility is at all important to you, this design frankly sucks. I'm very happy to have a chest freezer full of food right now, but getting to the food at the bottom involves a little digging. And of course, that means digging into frozen food. You may want to consider investing in a warm pair of gloves if you decide to purchase a chest freezer. And of course, if you want a freezer with more capacity to hold food, well, in the land of chest freezers, that means you need more space. You can't just make the chest deeper... well, okay, you could, but... good luck with that, so it needs to be wider.
If, on the other hand, you have a vertical freezer, you can make it higher, which will give you more interior volume with the same space. And so, we return to the introduction. Chest freezers are undoubtedly the best design if your main goal is energy efficiency. But, to achieve that goal, you have to make sacrifices in terms of convenience. And I think it's okay to not be willing to make those sacrifices. But that doesn't mean we shouldn't think about them. I would say that, as with most things in life, there is a sweet spot to find. That may be different from person to person, but I think it's too easy to get carried away with what's trendy and popular without thinking about whether that really suits your needs.
And refrigerators in general are just one of many places where we see this in action. Let's go buy a refrigerator, okay? We'll take a look at several models and compare how much power they use. You will soon discover that the design of the refrigerator has a significant impact on its energy consumption. And let's start with a strangely contradictory fact; Freezers tend to consume less energy than a refrigerator of the same size. Let's take a look at this large 15 cubic foot chest freezer. This huge freezer still manages to consume less than a kilowatt hour a day. And it's a freezer.
It has to be kept inside near zero degrees Fahrenheit, or minus 17 degrees Celsius. Everything inside. So your entire interior space may be fighting a 60 or 70 degree temperature difference. Probably more. Now let's look at a basic kitchen refrigerator. This is about the same size as our chest freezer, just a little smaller. Your intuition might

tell

you that this should consume less energy. After all, most of its interior is at a warmer temperature than a freezer. It shouldn't be necessary to work so hard. And yet… it actually uses more energy. Not much more. But… even more. What is happening?
Well, there are three basic differences here. The use of a heat pump for two temperature zones. The design and weaknesses of its thermal barriers. And whether or not the device has an automatic defrosting function. Now, spoiler alert, that last bit is less important than I thought it would be. It still matters a little, but let's put it aside for now and start with the first part. The vast majority of residential refrigerators have a single heat pump. In reality, what they are is a small freezer with an additional compartment that pulls out of the freezer a little to get some cold air.
You've no doubt noticed the hum of a fan at some point, and that's what it's for. Or at least, one of them. It is quite possible that there are several fans in the design of your refrigerator. And of course there are exceptions, don't hesitate to comment on them, it increases engagement! This may not seem very important. After all, it's a pretty smart use of resources! Just oversize the heat pump a little for the freezer and use some of your efforts for the refrigerator. But you'd be surprised how much difference it makes where you place the freezer.
I mean, just compare these two refrigerator models. Same overall size. Same manufacturer. And there is no difference in features, other than the fact that the position of the freezer and refrigerator is reversed. The bottom freezer model uses approximately 20% more energy. That's... significant. Now, I've been trying to get a firm answer as to why that is. I heard at some point in the past, and it makes intuitive sense, that because cold air tends to sink as it becomes denser, it takes less additional effort to move the outlet from the freezer to the refrigerator if the freezer is on the back side. superior.
Simply let the denser air fall into the refrigerator compartment. Whereas if the freezer is at the bottom, or even on the side, you need to actively move the air to achieve the same results. And that could require more energy. But I couldn't find a definitive answer whether this is the exact case or not. Regardless of the exact root cause, conventional freezer-top models tend to be the most energy-efficient design. Just take a look at the list of the most efficient refrigerators on the Energy Star website. The vast majority are models with the freezer on top. Exceptions can be found... but not many.
And freezer location is only part of the equation. One of the most surprising things I found was that converting the freezer into a slide-out drawer causes another 17% increase in energy consumption. That's... honestly, very interesting to me. I don't think that makes a big difference, but apparently it does. Uh oh! Confusing variable alert! The bottom drawer model has an ice maker, while the swing door model does not. That will cause an increase in energy consumption while you are making ice, as you need to remove energy from the water that is being introduced. Without knowing the details of how the power guides explain this, it's not necessarily fair to assume that the sliding drawer is what makes it work harder.
So... Well, the details are unclear, but talk about ice! Another important factor in the energy consumption of a refrigerator is whether or not it has an ice dispenser in the door. Because, and here's a fun fact, if you've never noticed this before, that means there's a hole in the door! Yes, sure it probably has a flap or something to seal the hole when it's not vomiting chunks of ice into the glass at a completely unpredictable rate, but a thin plastic flap doesn't make a good thermal barrier. That would be a wonderful place for ambient energy to find its way inside.
Also...how does that even work with a bottom freezer french door refrigerator? Is there... is there... is there like a... like a whole ice machine inside the door? How...well anyway, this is such an important factor in a refrigerator's energy consumption that it is specifically noted in the energy guide whether the particular model has it or not. It is a very important thing. But… on the other hand, is it really? I mean, let's look at the energy guide again. Sure, there is a big change from the low end to the high end. But honestly, even the most energy-efficient refrigerators out there still cost less than $8 a month.
It gets a little worse with the larger models, but if you have an electric water heater, well, compared to that... even the worst refrigerator is a peanut. However. We all have refrigerators. Many of us have more than one. And that means that, while there is little noticeable difference to our individual pocketbooks when it comes to our electricity bills, a hundred million refrigerators using an extra 250 kilowatt-hours per year means we are using another 25 billion (!) of kilowatt-hours. You can make any comparison you want with that figure, but the one I'll make now is that if every American citizen who drives to work drove an electric car, that would be 128,000,000 cars, based on a fairly conservative estimate of 3 miles.
Per kilowatt-hour, each traveler could drive 585 miles on that extra energy, or about 3 entire weeks of travel. Small wins, when applied across the board, add up much faster than you think. Which is why, of course, we have regulations about how much energy appliances can consume and why utility companies offer rebates for purchasing more energy-efficient appliances, but before we get too far down THAT particular stubborn path Let me repeat that I think it's okay to accept some losses in efficiency if it improves our lives. The question we must ask ourselves is how far we are willing to go.
As with almost everything in this world, well, there is a middle ground. You may be wondering why chest refrigerators don't exist. Well, they almost did; Many people who live off the grid will convert chest freezers to chest refrigerators by modifying their thermostats. I mean, if it can cool down to zero degrees, surely it can stop at 35 and become a tremendously efficient refrigerator. And… it can. But the people who make this modification do it because for them energy consumption is the biggest concern. They are willing to make the necessary sacrifices to achieve that end. And more power to them!
But not all of us need to go to that extreme. On the other hand, it is possible to end up at the other extreme. The most popular (and by that I mean most desirable) refrigerator style these days (whatever that means) seems to be the French door and bottom freezer models. And… well, they are the worst design in terms of energy efficiency. At least, as manufacturers build them today. I have no reason to think that its efficiency cannot be improved. Some manufacturers, such as Samsung, use separate evaporators for the freezer and refrigerator, meaning that while there is still a single compressor and condenser, each compartment is cooled separately, which could help reduce energy consumption.
And, in fact, one of these French door bottom freezer models has appeared on the Energy Star list. But what does it mean that the model we all crave is also the most expensive to maintain? I'm not here to judge. No matter how much I would like to. Because I think it's okay that we have different priorities. But I'm here to suggest that we think about them a little more. The main reason we have energy guides is to encourage consumers to make more frugal choices. Both for your pocket and for the environment. If there's one thing I'd suggest we change, it would be to focus on that label a little... cooler.
Thanks for watching! Yes, it's still there! And I hope you learned something interesting from this video and that it makes you think about your personal sacrifices and priorities. Again, I'm not here to judge. I hope you didn't think that was what I wanted to achieve. I really just want to get your mind spinning. It can be easy to go above and beyond our needs every day, and I am guilty of this in many ways! But every once in a while, I think it's worth considering stepping back a bit. Oh, and the defrosting thing! So… this is probably the main reason why conventional refrigerators consume more energy than a freestanding freezer.
Since no one wants to worry about defrosting their refrigerators anymore, we designed them with a means to remove ice on the evaporator. This is usually done by running the fans while not cooling and/or using heating elements to melt the ice. There is no free lunch, so it requires more energy. But… it's not as important as I thought. It turns out that we have a direct comparison betweenan upright freezer without automatic defrosting and one that does. And it's not as dramatic a difference as I thought it would be. In fact, the freezer still consumes less energy than most refrigerators of similar size.
So... that's why I left it here at the end! I would never suggest anyone look for a kitchen refrigerator with manual defrost, if it exists, because I wouldn't wish that burden on anyone. And now, the mistakes! ♫ Creepy Smooth Jazz ♫ I think everyone has a right to know that I was wearing The Simpsons Christmas pajamas during the filming of this video. It's cooler. The wall --- Oversi -- overheats the size pump. I almost said that. I did not do it! But then it got into my brain. And then I couldn't continue. ...inside it falls... that fff, there was a strange noise on the f there!
Yes, that sentence is a… ooo, why did I write it like that? I'll try to rework it as I go, which always happens... Excellent. No. I said “ense” not “enter” and… I have to start again The most desirable thing…. desirable. ahh, I was saying desired and then I read what the actual word was and then I realized "abort!" So was this video great or what? I especially like the part where we talk about freezers. Additionally, no iMacs were damaged during the making of this video.

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