WEBVTT Kind: captions Language: en 00:00:00.240 --> 00:00:01.791 This is a Peltier element. 00:00:02.291 --> 00:00:05.427 It may look like a rather unassuming hunk of material, 00:00:05.427 --> 00:00:13.310 but sandwiched between these two plates are a whole bunch of semiconductor junctions that have been carefully arranged to do something remarkable: 00:00:13.310 --> 00:00:19.401 when I apply a DC voltage across these two wires, the plate becomes cold. 00:00:19.401 --> 00:00:24.342 This is called thermoelectric cooling, and it’s happening thanks to the Peltier effect. 00:00:24.342 --> 00:00:30.194 With advances in manufacturing, we are now able to produce these devices quickly and cheaply. 00:00:30.194 --> 00:00:33.317 These ones here cost less than $3 each. 00:00:33.317 --> 00:00:37.956 There’s just one little issue with this technology: 00:00:37.956 --> 00:00:40.090 it’s not very good. 00:00:40.090 --> 00:00:42.129 Like, at all. 00:00:42.129 --> 00:00:44.248 OK, we’re gonna need some context. 00:00:44.248 --> 00:00:46.611 I’m making this video for a couple of reasons: 00:00:46.611 --> 00:00:51.143 First, you may know about my one true love, the refrigeration cycle. 00:00:51.143 --> 00:00:56.339 I adore a good heat pump and could talk your ear off about them for hours on end, 00:00:56.339 --> 00:01:01.775 but vapor-compression based refrigeration systems are bulky and mechanically complex affairs. 00:01:01.775 --> 00:01:06.137 They also have some environmental issues stemming from the refrigerants they use. 00:01:06.137 --> 00:01:10.697 Because of those downsides, with a regularity you could practically set a watch to 00:01:10.697 --> 00:01:16.423 well-meaning people discover Peltier elements and question why we don’t use these instead. 00:01:16.423 --> 00:01:23.231 A device with no moving parts and which makes cooling happen simply by putting voltage across it does feel like the future! 00:01:23.231 --> 00:01:27.125 That’s gotta be better than all the faff  we go through to build a fridge, right? 00:01:27.125 --> 00:01:29.991 Well, “better” is a slippery word. 00:01:29.991 --> 00:01:41.774 For one thing, the Peltier these are named for is Jean Charles Athanase Peltier, and he discovered this phenomenon back in 1834. 00:01:41.774 --> 00:01:47.492 We’ve been taking cracks at this for a long time, yet it still hasn’t changed the world. 00:01:47.492 --> 00:01:52.041 It is true that this form of cooling offers some unique advantages 00:01:52.041 --> 00:02:00.221 and in very specific applications with equally specific design constraints, using a Peltier element can make some sense. 00:02:00.221 --> 00:02:07.140 However, the situations in which these are truly appropriate to use are very, very rare. 00:02:07.140 --> 00:02:14.327 You will absolutely understand why that is by the end, but for now (and this leads into the second reason I’m making this video) 00:02:14.327 --> 00:02:19.093 you should know that the majority of products on sale  today which use these things 00:02:19.093 --> 00:02:25.434 are being made purely to capitalize on the fact that we just  can’t stop ourselves from buying cheap crap. 00:02:25.434 --> 00:02:30.256 Speaking of cheap crap, you’ve probably seen these little personal refrigerators before. 00:02:30.256 --> 00:02:35.946 The idea is you can keep a few cans of your favorite  beverage cool on your desk! 00:02:35.946 --> 00:02:38.760 You’ll be the talk of the office, for sure! 00:02:38.760 --> 00:02:44.393 All of these things use Peltier elements to cool their insides for a very simple reason: 00:02:44.393 --> 00:02:45.566 cost. 00:02:45.566 --> 00:02:49.462 These have to be cheap enough for people to pick them up impulsively. 00:02:49.462 --> 00:02:53.296 And they are - this was priced just over $30. 00:02:53.296 --> 00:03:01.243 You can’t build a proper fridge that cheaply, but you can build a little plastic box with a cheap power supply and $2 Peltier module in it. 00:03:01.243 --> 00:03:03.339 And people will buy it. 00:03:03.339 --> 00:03:05.786 Look, I’m a people, and I bought it! 00:03:05.786 --> 00:03:07.604 But is it any good? 00:03:07.604 --> 00:03:08.963 Spoiler alert: 00:03:08.963 --> 00:03:10.279 No! 00:03:10.279 --> 00:03:12.973 Let’s turn it on and put it through its paces! 00:03:12.973 --> 00:03:16.575 It has a power switch helpfully labeled “Off” and “Cold.” 00:03:16.575 --> 00:03:18.756 That's a sign of quality, that is. 00:03:18.756 --> 00:03:20.235 Here goes nothing! 00:03:20.235 --> 00:03:23.934 [a fan spins up] Ooh, it’s even got an interior light! How thoughtful. 00:03:23.934 --> 00:03:28.521 But, uh, that’s a lot of noise for something with no moving parts. 00:03:28.521 --> 00:03:30.407 What gives? 00:03:30.407 --> 00:03:38.484 Well, the Peltier element itself doesn’t have any moving parts but when I showed you it in the beginning, I only showed one side of it. 00:03:38.484 --> 00:03:46.355 That side was getting cold, yes, and in this... alleged fridge the cold side of the element is bonded to the rear wall 00:03:46.355 --> 00:03:49.776 which we can see getting cold in the thermal camera. 00:03:49.776 --> 00:03:57.542 But as the peltier element generates cooling on the one side, the other side of the element gets hot. 00:03:57.542 --> 00:03:59.582 Very hot. 00:03:59.582 --> 00:04:01.954 Problematically hot. 00:04:01.954 --> 00:04:04.992 Why? Well, two reasons. 00:04:04.992 --> 00:04:13.139 Peltier modules produce cooling by absorbing heat on the cold side and moving it through the element to the hot side. 00:04:13.139 --> 00:04:19.691 That’s how all cooling works - energy doesn’t just disappear, so to lower the amount of heat energy in one location, 00:04:19.691 --> 00:04:23.957 you have to absorb it from that location and move it somewhere else. 00:04:23.957 --> 00:04:26.050 Which is exactly what these do. 00:04:26.050 --> 00:04:32.700 They absorb heat on this side (which to us feels like coldness) and reject it on the hot side. 00:04:32.700 --> 00:04:40.723 But since the heat is only moving across a thin little barrier with very little mass, it builds up really quickly. 00:04:40.800 --> 00:04:42.164 But that’s not all! 00:04:42.164 --> 00:04:45.781 The element itself creates heat as it runs. 00:04:45.781 --> 00:04:55.518 These here are rated 5 amps at 12 volts, so when running at full capacity they’re dissipating 60 watts of heat in a really small space, 00:04:55.518 --> 00:04:59.710 and that’s on top of the heat it’s pulling from the cold side. 00:04:59.710 --> 00:05:06.775 So, to keep it from destroying itself, you need a finned heat sink bonded to the hot side to spread that heat out, 00:05:06.775 --> 00:05:12.721 and you’ll also need a fan to force air across the  heat sink to spread the heat even more quicklier. 00:05:12.721 --> 00:05:20.639 And as we can see here, the itty bitty fridge  has a generously sized heat sink hanging off the back with a fan blowing right at it. 00:05:20.639 --> 00:05:30.080 A fan and heat sink pair isn’t complicated or expensive, but it means this is noisier than you might expect and, ya know, adds a moving part. 00:05:30.080 --> 00:05:33.979 But noise is forgivable, the real question is how well does it work? 00:05:33.979 --> 00:05:37.209 And the answer to that question is: not! 00:05:37.209 --> 00:05:41.420 And by every conceivable metric you can imagine. 00:05:41.420 --> 00:05:45.212 For a start, you may have noticed this has no temperature settings. 00:05:45.212 --> 00:05:47.698 It’s just cold or off. 00:05:47.698 --> 00:05:55.390 That’s because it only promises to lower the internal temperature by up to 30 degrees below ambient temperature. 00:05:55.390 --> 00:05:57.122 That’s it. 00:05:57.122 --> 00:06:03.157 I appreciate its honesty, but if you know anything about food safety, you’re gonna be getting the willies right now. 00:06:03.157 --> 00:06:09.600 Because in an office environment during the summertime where, say, the room temperature might be 75 degrees Fahrenheit, 00:06:09.600 --> 00:06:18.774 this thing will - at best - get the interior down to 45 degrees Fahrenheit which by US standards is not food safe. 00:06:18.774 --> 00:06:20.881 So… strike one. 00:06:20.881 --> 00:06:25.657 But ok, let’s say you just want to cool some  beverages and you don’t care about food. 00:06:25.657 --> 00:06:31.157 Well, to see how well it manages that I loaded it up fully with 6 room temperature beverage cans 00:06:31.157 --> 00:06:35.624 then shoved one of my temperature data loggers in the void space between them. 00:06:35.624 --> 00:06:41.207 After running for two hours, it hadn’t even gotten below 60 degrees inside here. 00:06:41.207 --> 00:06:45.588 After 12 hours it had only managed to drop to 48 degrees Fahrenheit, 00:06:45.588 --> 00:06:51.413 and after 24 hours the temperature had plateaued at about 46 degrees. 00:06:51.413 --> 00:06:53.924 Not very impressive. 00:06:53.924 --> 00:06:57.654 Somehow it got a bit of a second wind right near the 24 hour mark, 00:06:57.654 --> 00:07:01.626 which I believe happened just because the room it  was in had cooled off a little, 00:07:01.626 --> 00:07:04.962 and we ended up bottoming out at 45.5 degrees. 00:07:04.962 --> 00:07:09.492 Which, in fairness, was about 30 degrees below the room temperature. 00:07:09.492 --> 00:07:14.494 So it did what it said it would, but it sure took ages to get there. 00:07:14.494 --> 00:07:22.113 However, I was measuring the air temperature in the center of the fridge and since the cans are all touching the sides, 00:07:22.113 --> 00:07:28.991 I found that the actual temperature of the liquid in those  cans was a slightly warmer 50 degrees. 00:07:28.991 --> 00:07:32.663 Chilled, I suppose, but I wouldn’t want a beer that warm. 00:07:33.000 --> 00:07:35.578 So… strike two. 00:07:35.578 --> 00:07:38.377 But okay, so it’s not technically a refrigerator 00:07:38.377 --> 00:07:39.680 and it takes forever to cool down 00:07:39.680 --> 00:07:41.371 and it doesn’t keep things that cold 00:07:41.371 --> 00:07:43.507 and it’s louder than the box implies 00:07:43.507 --> 00:07:45.927 but that doesn’t mean it’s not useful! 00:07:45.927 --> 00:07:49.758 And to that I’d say, you’re not technically wrong! 00:07:49.758 --> 00:07:56.919 Some people use these things to keep certain cosmetic items in a cool, dry place, and from what I can tell they’re happy to have these! 00:07:56.919 --> 00:08:02.784 And if 50 degrees is cold enough for you, and you’re  diligent about rotating cans in and out, 00:08:02.784 --> 00:08:06.611 you might actually enjoy this as a beverage cooler. 00:08:06.611 --> 00:08:09.835 But here comes strike three, and it’s a doozy 00:08:09.835 --> 00:08:13.649 (and also why Peltier devices are generally terrible). 00:08:13.649 --> 00:08:20.000 If you’re at all concerned with how much energy this thing will use to do its job not very well, 00:08:20.000 --> 00:08:26.941 you should know that this thing consumes about 55 watts of power all the time. 00:08:26.941 --> 00:08:32.978 That’s not a ton of power, no, but guess what uses less power than that? 00:08:32.978 --> 00:08:36.598 Well, lots of things but most relevant to this discussion - 00:08:36.598 --> 00:08:39.433 an actual refrigerator. 00:08:39.433 --> 00:08:45.391 This here is what I call the standard cube fridge, the most basic mini-fridge you can buy. 00:08:45.391 --> 00:08:52.751 They’re generally around $100 and while they are incredibly basic they are also actual refrigerators. 00:08:52.751 --> 00:08:59.283 We have a lil’ baby compressor back here pumping refrigerant through an honest-to-goodness refrigeration circuit. 00:08:59.283 --> 00:09:04.970 Now, it did cost significantly more money to purchase than the blue... thing, 00:09:04.970 --> 00:09:08.044 but it can also hold a lot more stuff. 00:09:08.044 --> 00:09:10.700 Including the blue fridge. 00:09:10.700 --> 00:09:16.224 By the internationally recognized metric of “how many cans of La Croix can you shove in there per dollar” 00:09:16.224 --> 00:09:18.800 the real fridge wins by a lot. 00:09:18.800 --> 00:09:27.283 It’ll hold 33 cans easily, and 36 if you’re a little bit creative,  which works out to $2.77 per can. 00:09:27.283 --> 00:09:35.080 And the blue fridge, despite only costing $30,  only holds six cans so that’s $5 per can. 00:09:35.080 --> 00:09:36.727 But that’s not the real issue. 00:09:36.727 --> 00:09:41.735 Remember, the blue fridge uses 55 watts all the time. 00:09:41.735 --> 00:09:44.031 Guess how much power this thing uses? 00:09:44.031 --> 00:09:50.295 Once the refrigeration circuit has stabilized, it pulls between 45 and 50 watts from the wall. 00:09:50.295 --> 00:09:58.618 I’ve consulted with some math scholars who have confirmed for me that that figure is less than the 55 watts the stupid blue fridge pulls. 00:09:58.618 --> 00:10:00.192 But that’s not all! 00:10:00.192 --> 00:10:07.549 This, because it’s an actual refrigerator, has a thermostat to maintain food safe temperatures inside! 00:10:07.549 --> 00:10:10.791 And that means it doesn’t run all the time. 00:10:10.791 --> 00:10:17.831 I monitored its energy use when loaded up with 15 already-chilled beverage cans, and to keep them cool over three hours, 00:10:17.831 --> 00:10:24.706 it consumed just 65 watt-hours representing an average draw of 21.7 watts. 00:10:24.706 --> 00:10:30.000 And, by the way, the room it was in during that test was a pretty warm 78 degrees. 00:10:30.000 --> 00:10:32.267 Now, electricity isn’t free. 00:10:32.267 --> 00:10:35.075 So let’s do a little cost comparison. 00:10:35.075 --> 00:10:43.007 The blue fridge, with its constant 55 watt draw, will consume 39.6 kilowatt-hours per month. 00:10:43.007 --> 00:10:52.228 Going by the average cost of electricity in the US of $0.14 per kilowatt-hour, it will cost about $5.50 per month to use continuously. 00:10:52.228 --> 00:10:55.611 So about $66 a year. 00:10:55.611 --> 00:11:04.561 The much larger mini fridge, on the other hand, drawing 22 watts continuously will consume 15.8 kilowatt-hours in a month, 00:11:04.561 --> 00:11:10.176 which costs $2.21 per month, or $27 bucks a year. 00:11:10.176 --> 00:11:13.589 That’s $39 less than the blue fridge per year, 00:11:13.589 --> 00:11:20.805 so it doesn’t even take two years of operation for the extra $70 you spend on the real fridge to pay for itself. 00:11:21.423 --> 00:11:24.488 Seems like this blue fridge might be kind of bad! 00:11:24.488 --> 00:11:31.501 Now I could stop here, but I’m not gonna because this thing's awful efficiency just gets funnier the more context you have. 00:11:31.501 --> 00:11:33.488 You remember this goofy thing. 00:11:33.488 --> 00:11:39.307 It’s moved into my office and has an actual temperature controller now which fixes its major flaw. 00:11:39.307 --> 00:11:48.590 It’s still by no means a good refrigerator - stick a twelve pack of room temperature cans in there and it runs nonstop for almost four hours. 00:11:48.590 --> 00:11:51.559 It’s really not built for making warm things cold. 00:11:51.559 --> 00:11:57.258 But as far as its ability to maintain food safe temperatures, it does the job just fine. 00:11:57.258 --> 00:11:59.708 And how much energy does it use? 00:11:59.708 --> 00:12:08.789 Well, after adding 6 room temperature beverage cans, I measured its energy use over 24 hours and it needed only 970 watt-hours, 00:12:08.789 --> 00:12:12.557 meaning on average it only pulled 40.4 watts. 00:12:12.557 --> 00:12:16.778 Which, believe it or not, is less than 55. 00:12:16.778 --> 00:12:21.997 And that’s despite the rather pronounced size difference between these two machines. 00:12:21.997 --> 00:12:23.928 I mean… just look at them! 00:12:23.928 --> 00:12:33.017 It’s frankly ridiculous that such a tiny little “fridge” is using more energy than the comparatively gigantic one next to it. 00:12:33.017 --> 00:12:36.492 In an earlier 24 hour test when the weather was a little cooler, 00:12:36.492 --> 00:12:47.673 the red fridge consumed just 890 watt-hours in 24 hours while the stupid little blue one needed 1,290 watt hours over the same period. 00:12:47.673 --> 00:12:53.218 Because it’s always pulling 55 watts whenever it’s switched on. 00:12:53.218 --> 00:12:59.481 That’s 45% more energy spent only kind of cooling six cans. 00:12:59.481 --> 00:13:02.335 And ya know how many cans this sucker will hold? 00:13:02.335 --> 00:13:10.532 If you fill the crisper drawer, all the door shelves, and double stack on the top shelf, it’ll hold 135 cans. 00:13:10.532 --> 00:13:19.816 It’ll take it forever to make them all cold but once they get there the fridge will use roughly the same 900 watt-hours per day keeping them all ice cold. 00:13:19.816 --> 00:13:23.547 Are you starting to understand why I keep calling this stupid junk? 00:13:23.547 --> 00:13:28.690 And let’s not forget the red fridge has a freezer compartment for ice cream and pizza and stuff! 00:13:28.690 --> 00:13:36.748 Now, as I’ve covered before, mini-fridges are actually some of the least energy-efficient refrigerators out there thanks to their minimal insulation. 00:13:37.572 --> 00:13:43.253 And by the way, I need to clear something up for the  Europeans who keep badgering me about this: 00:13:43.320 --> 00:13:46.467 I never said the red fridge was a mini-fridge! 00:13:46.467 --> 00:13:53.435 A bunch of you heard me say that somewhere but I would never consider a fridge which goes up to my chest to be a mini-fridge. 00:13:53.435 --> 00:13:59.542 I called it little, and I called it a bit on the small side but I also said, and I quote, 00:13:59.542 --> 00:14:06.095 “it’s much bigger than a typical mini-fridge and served me well as a decently competent refrigerator.” 00:14:06.095 --> 00:14:13.680 At the very end of that video I did lump it into the category  of mini-fridges because of its thin walls,   00:14:13.680 --> 00:14:17.811 but that’s as close as I ever got to calling it a mini-fridge. 00:14:17.811 --> 00:14:22.151 Methinks your confirmation bias kicked in a little early and a little strong. 00:14:22.151 --> 00:14:25.085 Maybe those 230 volts are gettin’ to your head. 00:14:25.085 --> 00:14:28.100 But speaking of Americans and their giant American fridges, 00:14:28.100 --> 00:14:31.896 [banjo music starts] at home I’ve got a GIANT AMERICAN FRIDGE! 00:14:31.896 --> 00:14:36.686 [said in a thick Southern accent] My 360 pound behemoth (that’s 163 kilograms for you commies) 00:14:36.686 --> 00:14:39.942 features automatic defrost for maintenance-free operation, 00:14:39.942 --> 00:14:45.798 is plumbed to a water line for its built-in ice maker because we want ice in our drinks, goshdarnit, 00:14:45.798 --> 00:14:53.813 and it has 16.35 All-American Cubic Feet of Fridge Capacity and a 5.59 cubic foot freezer compartment. 00:14:53.813 --> 00:14:59.604 That’s 461 liters in the fridge and 158 litres in the freezer. 00:14:59.604 --> 00:15:03.376 And guess which of those two fridges uses more energy? 00:15:03.376 --> 00:15:05.795 THIS STUPID THING! 00:15:05.795 --> 00:15:12.468 Yes, according to government testing (I didn’t do my own, sorry about that) my bottom-freezer, French door fridge 00:15:12.468 --> 00:15:15.405 (which are two dings against its energy efficiency), 00:15:15.405 --> 00:15:21.589 despite being able to hold over 50 times as  much stuff before we even count the frozen food, 00:15:21.589 --> 00:15:30.115 and which features heated defrost uses slightly  less energy over a year than it takes to run this toy. 00:15:30.115 --> 00:15:39.643 It needs 1,270 watt-hours per day to attain actual refrigeration compared to the 1,290 this stupid thing used 00:15:39.643 --> 00:15:43.743 to keep six cans of la croix only kind of chilled. 00:15:43.743 --> 00:15:48.302 I ask again, are you starting to understand why I think these things are stupid junk? 00:15:48.302 --> 00:15:53.236 Side note, I used the Canadian energy stats because as I found out the last go-round, 00:15:53.236 --> 00:15:58.920 the American EnergyGuide label is very very  pessimistic thanks to the way the tests are run. 00:15:59.680 --> 00:16:04.320 It includes a lot more food browsing  in hot weather than I think is typical,   00:16:04.320 --> 00:16:10.846 and the energy guide label for the red fridge was  about 20% higher than my own stress testing. 00:16:10.846 --> 00:16:15.643 But even if we go with the 633 kWh annual figure, 00:16:15.643 --> 00:16:24.948 then my actual fridge uses only 35 percent more energy for approximately 7,000 percent more refrigerated space 00:16:24.948 --> 00:16:27.313 with a freezer on top of that. 00:16:27.313 --> 00:16:29.518 Or, below it, actually. 00:16:29.518 --> 00:16:36.785 So, why is this blue lump of sadness so much less efficient than any of the refrigerators we’ve discussed? 00:16:36.785 --> 00:16:39.609 Because all the rest have… 00:16:39.609 --> 00:16:41.985 heat pumps! 00:16:41.985 --> 00:16:48.181 Now, very out of character for me,  I’m going to keep my explanation of the refrigeration cycle pretty brief. 00:16:48.181 --> 00:16:49.130 Kind of brief. 00:16:49.130 --> 00:16:49.880 Brief-ish. 00:16:49.880 --> 00:16:52.650 But here’s why it’s such a big deal: 00:16:52.650 --> 00:16:58.878 a vapor-compression heat pump like the one we  find in even this very cheap and basic mini-fridge 00:16:58.878 --> 00:17:05.202 can move more heat energy out of the fridge's interior than it takes to run the heat pump. 00:17:05.202 --> 00:17:10.757 That may sound impossible, but the compressor is the only thing in here doing any work, 00:17:10.757 --> 00:17:18.672 and all it’s doing is using an electric motor to  spin some pumpy parts inside this enclosure which pressurizes a gas. 00:17:18.672 --> 00:17:22.395 In the case of this fridge,  that’s literally the only thing it’s doing. 00:17:22.395 --> 00:17:28.765 All the rest of its parts are just pipes and tubes  which are exposed to the air inside and out. 00:17:28.920 --> 00:17:31.744 The gas it’s compressing is called a refrigerant. 00:17:31.744 --> 00:17:36.089 Refrigerants are a category of gasses that we’ve discovered (or sometimes engineered) 00:17:36.089 --> 00:17:41.153 that have really useful relationships between their pressure and their boiling point. 00:17:41.153 --> 00:17:47.263 This fridge, like most on the market today, uses isobutane which at atmospheric pressure is a gas. 00:17:47.263 --> 00:17:56.284 But if you pressurize isobutane to about 80 PSI, its boiling point shoots up to 110 degrees Fahrenheit. 00:17:56.284 --> 00:17:58.840 That’s much hotter than typical room temperatures, 00:17:59.360 --> 00:18:05.120 so if you feed that high pressure gas through  some tubes that are exposed to ambient air,   00:18:05.120 --> 00:18:12.794 the air will cool it down to the point that it can’t be a gas anymore and it will spontaneously condense into a liquid. 00:18:12.794 --> 00:18:21.420 That condensing action releases a ton of heat energy because of a thing called the latent heat of vaporization which to save time I am not getting into right now, 00:18:21.420 --> 00:18:25.389 but you can see this heat being released in the thermal camera. 00:18:25.389 --> 00:18:31.465 You can even make out the tubes the refrigerant is traveling through just below the surface of the fridge’s outer skin. 00:18:31.465 --> 00:18:37.560 Thanks to the pumping action of the compressor,  the refrigerant is actively pushed through those tubes. 00:18:37.560 --> 00:18:43.485 At the entrance it’s purely hot gas (and it’s hot because the compressor just compressed it), 00:18:43.485 --> 00:18:48.869 but as it makes its way through it sheds heat energy and begins to liquify. 00:18:48.869 --> 00:18:54.629 By the time it makes it to the end of the tube, a slug of liquid refrigerant will have bunched up. 00:18:54.629 --> 00:19:00.676 Then, that liquid refrigerant gets sent through a restriction  which limits the volume of fluid flow. 00:19:00.676 --> 00:19:07.806 Because of the restriction and the pumping action of the  compressor, a pressure imbalance is maintained on either side. 00:19:07.806 --> 00:19:14.658 And once the liquid makes it through it finds itself inside the evaporator where the pressure is very low, 00:19:14.658 --> 00:19:22.126 in fact so low that the boiling point of isobutane plummets to something like -20 degrees Fahrenheit. 00:19:22.126 --> 00:19:29.510 Even the air inside a freezer is warmer than that, which means there’s energy available to boil the refrigerant. 00:19:29.510 --> 00:19:35.709 That causes it to absorb latent heat energy which means it gets very, very cold. 00:19:35.709 --> 00:19:44.480 Once the refrigerant has completely boiled away and becomes a gas once more, it finds itself back at the compressor and the whole thing starts over again. 00:19:44.480 --> 00:19:47.390 The gas it’s compressing is called a refrigerant. 00:19:47.390 --> 00:19:52.311 Refrigerants are a category of gasses that we’ve discovered (or sometimes engineered) that — 00:19:52.311 --> 00:19:53.784 okay that’s enough of that. 00:19:53.784 --> 00:20:01.360 Key to understanding this process is that the refrigerant, through boiling away, absorbs a lot of heat energy. 00:20:01.360 --> 00:20:04.528 That heat energy is then stored in the refrigerant. 00:20:04.528 --> 00:20:12.064 But, when we compress it and it condenses back into a liquid, it releases the energy it had just absorbed. 00:20:12.064 --> 00:20:18.885 Since we’re in control of where that happens, we can move heat energy from one place to another. 00:20:18.885 --> 00:20:24.090 In the case of a fridge, we’re pumping the heat out of the fridge’s interior which cools it down 00:20:24.090 --> 00:20:27.189 and then releasing that heat to the outside air. 00:20:27.189 --> 00:20:33.685 And the only thing we’re doing to make that happen is compress a gas and pushing it through some pipes. 00:20:33.685 --> 00:20:37.679 The refrigerant does the heat transfer stuff all on its own. 00:20:37.679 --> 00:20:45.087 That is how a vapor-compression heat pump is able to move  more energy than the machine itself consumes. 00:20:45.087 --> 00:20:52.174 The heat moving capacity compared to its power draw is a metric known as the coefficient of performance. 00:20:52.174 --> 00:20:55.827 Now, not many people calculate the COP of a fridge, 00:20:55.827 --> 00:21:04.106 but if I assume it has a COP of 3 then we get a threefold increase in cooling power compared to input power. 00:21:04.106 --> 00:21:13.857 In other words, the 45 watts of power this fridge pulls from the wall when it’s running generates 135 watts of cooling power in the evaporator. 00:21:13.857 --> 00:21:17.979 That is why we bother with a compressor and all this piping and junk, 00:21:17.979 --> 00:21:20.942 it’s just really, really efficient. 00:21:20.942 --> 00:21:25.784 And that’s also why heat pumps for heating our homes are becoming such a big deal: 00:21:25.784 --> 00:21:31.243 just as there’s heat to be pulled out of a freezer, there’s heat to be grabbed from the air outside. 00:21:31.243 --> 00:21:40.134 And so long as the COP of an operating heat pump is over 1, we're getting some free heat compared to running an electric heating element. 00:21:40.134 --> 00:21:42.609 But anyway, this video isn't about that. 00:21:42.609 --> 00:21:48.984 Peltier elements, because they move heat from one side to the other, are technically heat pumps. 00:21:48.984 --> 00:21:52.532 And that means we can measure their coefficient of performance. 00:21:52.532 --> 00:22:01.883 But that’s tricky to do because unlike a vapor-compression heat pump, their efficiency will vary wildly depending on the temperature difference it’s fighting 00:22:01.883 --> 00:22:05.198 as well as how much current you’re shoving through it. 00:22:05.198 --> 00:22:07.754 Remember, this is really thin. 00:22:07.754 --> 00:22:13.227 And the materials used to construct this conduct heat even when it’s not running at all, 00:22:13.227 --> 00:22:17.016 so the higher the temperature difference between the hot and cold sides, 00:22:17.016 --> 00:22:23.428 the more heat energy leaks through the element itself and the less efficient it becomes. 00:22:23.428 --> 00:22:25.439 And the effect there is dramatic. 00:22:25.439 --> 00:22:33.743 On top of that, the more current you try to push through this, the more heat it generates inside itself which also makes things worse. 00:22:33.743 --> 00:22:41.956 In theory, if everything is perfect and you can run these at very low current, you can get a COP between 1 and 2. 00:22:41.956 --> 00:22:50.964 But that will hardly generate any cooling at all, so in practice, the COP of a device using a Peltier element for cooling 00:22:50.964 --> 00:22:54.384 is somewhere between zero and very bad. 00:22:54.384 --> 00:23:01.326 And that’s why this stupid little blue fridge is using so much more energy than this actual fridge. 00:23:01.326 --> 00:23:02.813 Or that actual fridge. 00:23:03.078 --> 00:23:05.259 Or THAT actual fridge. 00:23:05.259 --> 00:23:08.686 Now, in fairness, there is more going on here. 00:23:08.686 --> 00:23:14.435 Its reliance on the Peltier effect is of course the major factor in this fridge’s terrible efficiency, 00:23:14.435 --> 00:23:17.295 but it’s also got a lot to do with its design. 00:23:17.295 --> 00:23:25.486 Any actual fridge is subject to regulations  which mean it has to have enough insulation in its walls to pass performance tests. 00:23:25.486 --> 00:23:32.299 The blue toy is a toy, and honestly I could barely even detect any insulation at all! 00:23:32.299 --> 00:23:34.586 The walls all feel hollow. 00:23:34.586 --> 00:23:42.013 So I drilled some exploratory holes and determined that it does have what appears to be Styrofoam in the side walls 00:23:42.013 --> 00:23:44.920 but the door is in fact hollow. 00:23:44.920 --> 00:23:46.438 That’s great. 00:23:46.438 --> 00:23:55.120 If this had more insulation it could probably get its insides cooler using less energy, but it would then also need some sort of temperature control. 00:23:55.120 --> 00:24:00.134 I think it’s actually relying on heat intrusion  through the door to keep things from freezing. 00:24:00.134 --> 00:24:02.970 But any time you’re using a Peltier element, 00:24:02.970 --> 00:24:11.763 even the best designs with lots of thermal insulation are going to run into the fundamental problem of a terrible coefficient of performance. 00:24:11.763 --> 00:24:19.143 These are just not very good at what they’re supposed to do and will always lose a fight with a grown-up heat pump. 00:24:19.143 --> 00:24:24.134 And, not for nothing, while people fixate on the harm refrigerants cause 00:24:24.134 --> 00:24:30.167 (because they have been truly awful to the environment and many in use today still are in one way or another) 00:24:30.167 --> 00:24:33.752 isobutane is not really a problem at all. 00:24:33.752 --> 00:24:39.147 It’s flammable which presents some practical challenges, especially when the systems require service, 00:24:39.147 --> 00:24:45.660 but it has a global warming potential of only 3.3 and its other environmental effects are negligible. 00:24:45.660 --> 00:24:48.111 Plus, there’s hardly any of it in a fridge. 00:24:48.111 --> 00:24:52.514 Even my big one at home has a refrigerant charge of just 55 grams. 00:24:52.514 --> 00:24:58.354 So when it comes to domestic refrigerators, you honestly don’t need to be worried about that anymore. 00:24:58.440 --> 00:25:06.235 You may remember, though, that I did say Peltier elements have some very specific advantages in very specific applications. 00:25:06.235 --> 00:25:12.195 I’ve already covered the main one - if you need some cooling as cheaply as possible, they are an option. 00:25:12.195 --> 00:25:18.157 You just have to be aware of how energy-intensive they are and decide whether that trade-off is worth it. 00:25:18.157 --> 00:25:20.558 And sometimes it might be! 00:25:20.558 --> 00:25:28.181 If, for example, you’re only using something occasionally, the poor efficiency of these things might not matter that much. 00:25:28.181 --> 00:25:32.361 One example would be a portable cooler you can bring with you in the car. 00:25:32.361 --> 00:25:38.885 If it’s only ever going to be used on occasional car rides, and it’s got the energy source of a car to supply it, 00:25:38.885 --> 00:25:41.696 its energy efficiency isn’t that critical. 00:25:41.696 --> 00:25:46.058 And portability is another area where Peltier elements can shine. 00:25:46.058 --> 00:25:51.854 The elements themselves weigh almost nothing, and even finished products are quite light. 00:25:51.854 --> 00:25:57.850 This little thing doesn’t even weigh 4 pounds (it’s 1.68 kilograms to be precise in metric fashion). 00:25:57.850 --> 00:26:03.069 Meanwhile the mini-fridge, despite having the most adorable little compressor I’ve ever seen, 00:26:03.069 --> 00:26:07.505 weighs a much heftier 33 pounds (15 kilograms). 00:26:07.505 --> 00:26:14.668 In fairness the bulk of its weight isn’t from the refrigeration circuit, just the metal parts that make up its body and frame and the door, 00:26:14.668 --> 00:26:17.099 but it’s still a pretty huge difference. 00:26:17.099 --> 00:26:22.411 And when it comes to portability,  vapor-compression based systems have an Achille's heel: 00:26:22.411 --> 00:26:25.229 they are orientation-sensitive. 00:26:25.229 --> 00:26:32.929 The compressor that’s inside this little black ball is made of metal parts which rub against each other and thus need lubrication, 00:26:33.000 --> 00:26:40.124 and to provide that lubrication (and also cooling for the windings of the electric motor) the system has oil in it. 00:26:40.124 --> 00:26:47.208 The compressor housing forms an oil sump, and we rely on gravity to keep that oil pooled in the bottom of the sump 00:26:47.208 --> 00:26:51.497 so that the compressor has the lubrication and cooling that it requires. 00:26:51.497 --> 00:27:00.911 And Earth’s gravity, famously, only ever pulls things towards the center of the Earth, so you have to have this upright for it to work without destroying itself. 00:27:01.382 --> 00:27:09.286 And, if you move anything with a refrigeration compressor in it and you aren’t 100% sure it stayed upright as you moved it, 00:27:09.286 --> 00:27:18.171 you need to let these sit upright for at least a few hours before you switch them on so any oil that might have gone somewhere it shouldn’t can drain back to the sump 00:27:18.171 --> 00:27:23.397 (many manufacturers will tell you to wait a full 24 hours before switching them on after they've been moved). 00:27:24.040 --> 00:27:29.064 Peltier elements, because they don't have any mechanical parts, don’t care about that! 00:27:29.064 --> 00:27:31.655 You can operate this fridge however you like, 00:27:31.655 --> 00:27:34.910 though of course you need to make sure the cooling vents aren’t blocked, 00:27:34.910 --> 00:27:37.477 and you'll never have to wait to switch it on after you move it. 00:27:37.477 --> 00:27:38.785 It’s always ready. 00:27:38.785 --> 00:27:43.150 And Peltier elements also have one last trick up their sleeves: 00:27:43.150 --> 00:27:47.939 when you reverse the polarity, they move heat in the opposite direction! 00:27:47.939 --> 00:27:52.762 That means you can offer a device which both heats and cools quite trivially. 00:27:52.762 --> 00:27:58.502 In fact, heated and cooled cupholders in cars is one application for this in real life. 00:27:58.668 --> 00:28:03.177 You can bond a Peltier element to a thermally conductive  ring surrounding a cup holder 00:28:03.177 --> 00:28:06.439 (and use some sort of heat spreader for the other side of the element) 00:28:06.439 --> 00:28:11.856 and you can keep hot drinks hot or cold drinks cold just by flipping a switch. 00:28:11.856 --> 00:28:15.832 But, in all honesty, that’s mostly a gimmick. 00:28:15.832 --> 00:28:21.405 I saw it at the auto show when I was maybe 12  and it hasn’t taken the world by storm yet. 00:28:21.405 --> 00:28:23.337 But back to the present. 00:28:23.337 --> 00:28:30.471 When the design requirements of very cheap to build, easily portable, and only occasional use all collide, 00:28:30.471 --> 00:28:34.731 using Peltier elements for cooling makes some sense. 00:28:34.731 --> 00:28:44.177 But if this is going into something that’s going to be in anything close to continuous use and energy efficiency matters either for cost or scarcity reasons, 00:28:44.177 --> 00:28:46.792 it just doesn’t make any sense at all. 00:28:46.792 --> 00:28:52.424 There is in fact a very good reason refrigeration  is still happening the way it always has. 00:28:52.424 --> 00:28:57.174 And if you’re looking at a product like this and thinking that might be useful, 00:28:57.174 --> 00:29:03.696 I would highly suggest you think long and hard about whether one of these cube fridges might fit your needs. 00:29:03.696 --> 00:29:11.748 No, they’re not going to fit on your desk (at least not easily) but they’ll do a lot more for you using a lot less energy. 00:29:11.748 --> 00:29:16.428 And these, too, can be had in all sorts of  goofy colors if you look in the right places. 00:29:16.428 --> 00:29:23.033 That said… I would be remiss if I didn’t mention  the big downside to some of these, including this model: 00:29:23.033 --> 00:29:28.994 ice builds up on the evaporator over time and so this needs occasional defrosting. 00:29:28.994 --> 00:29:34.431 Depending on what you’re using it for that might be very rare but it’s something to keep in mind. 00:29:34.431 --> 00:29:41.699 However, there are also plenty of these out there which have rear-mounted, vertical evaporators and skip the freezer compartment entirely, 00:29:41.699 --> 00:29:44.021 and those don’t need defrosting. 00:29:44.021 --> 00:29:47.944 I would honestly seek one of those out if you’re looking for a mini-fridge like this. 00:29:47.944 --> 00:29:52.602 Honestly the freezer compartment in here is pretty useless and just eats up space. 00:29:52.602 --> 00:29:55.780 The only reason I grabbed this one was because it was on sale at Menards. 00:29:55.780 --> 00:29:59.571 Only $80 and you know I mailed in that 11% rebate! 00:29:59.571 --> 00:30:04.905 And speaking of cheap things from Menards,  I should say this particular model has a few annoyances. 00:30:04.905 --> 00:30:08.984 Its compressor is oddly buzzy, which is disappointing. 00:30:08.984 --> 00:30:15.740 The red fridge is actually quieter than the thermoelectric fridge, but this baby fridge is louder. 00:30:15.740 --> 00:30:20.674 There’s a good chance I just drew the short straw there and most of these have quieter compressors, 00:30:20.674 --> 00:30:24.116 and besides I don’t think it would really be very annoying under a desk. 00:30:24.116 --> 00:30:26.364 But… something to mention. 00:30:26.364 --> 00:30:33.583 What actually worries me about this model is the fact that the thermostat runs very, very short cycles. 00:30:33.583 --> 00:30:39.577 Like, once it’s down to temp it runs for 2 or 3 minutes and then stops for 3 or 4. 00:30:39.577 --> 00:30:43.293 That’s usually not the healthiest thing for a refrigeration compressor. 00:30:43.293 --> 00:30:48.494 But in this case, because of the design here, I actually think that’s on purpose. 00:30:48.494 --> 00:30:54.439 Since the interior is so tiny,  you’re going to end up with stuff right against the evaporator, 00:30:54.439 --> 00:31:00.343 so if it were to run for too long at once  it would likely freeze some stuff on the top shelf. 00:31:00.343 --> 00:31:04.902 But anyway, now we’re just shopping for mini-fridges so I think I should wrap it up. 00:31:04.902 --> 00:31:13.105 The bottom line of this video is that Peltier elements are interesting and cool devices but they're just not good for general purpose cooling. 00:31:13.105 --> 00:31:18.312 And since we’ve adopted isobutane as the standard  refrigerant in domestic refrigerators, 00:31:18.312 --> 00:31:22.808 to be honest you can stop feeling guilty about bringing another fridge into the world. 00:31:22.808 --> 00:31:26.355 I mean, you probably shouldn't buy one unless you actually need it 00:31:26.355 --> 00:31:32.944 (and I’m 50/50 on whether I’m gonna keep this for storing my color film or donate it so someone else can make better use of it). 00:31:32.944 --> 00:31:38.262 But really this is just a cooler which happens to have a little heat pump in it. 00:31:38.262 --> 00:31:41.907 The steel and copper in here is the only special sauce. 00:31:41.907 --> 00:31:44.467 Ooh, I could keep sauce in here! 00:31:45.232 --> 00:31:47.798 ♫ inefficiently smooth jazz ♫ 00:31:49.476 --> 00:31:53.132 It may look like the teleprompter hasn’t started but that’s cuz it hasn’t. 00:31:53.132 --> 00:31:56.740 Which to us feels like coldness, and reject ahh.. 00:31:56.740 --> 00:31:57.240 [clears throat] 00:31:57.240 --> 00:31:58.896 ehbutehbuDEDABAH 00:31:58.896 --> 00:32:02.056 Because all the rest have… 00:32:02.056 --> 00:32:04.061 HEAT PUUUuuUuuUUUumps. 00:32:04.061 --> 00:32:05.436 Woah that was not good. 00:32:05.436 --> 00:32:07.801 Even if we go with the 633 00:32:07.801 --> 00:32:09.616 kilowattanggguhbuhdeblledyaghbleurf 00:32:09.616 --> 00:32:11.578 Even when it's not running at all. 00:32:11.578 --> 00:32:16.021 So the higher temperature difference between the cot and… 00:32:16.021 --> 00:32:16.933 dah. 00:32:16.933 --> 00:32:21.639 ..american energyguide label is very very pessimistic thanks to the way the depart oh… 00:32:21.639 --> 00:32:24.031 debeduh debeduh debbity duh 00:32:24.031 --> 00:32:28.074 It’s flammable which presents some practical challenges especially when 00:32:28.074 --> 00:32:32.373 ssssssssssssssssshhhwhww 00:32:32.373 --> 00:32:33.291 welp. 00:32:34.881 --> 00:32:36.610 So I think we can sum this up pretty well: 00:32:36.610 --> 00:32:38.423 Peltier elements? Not cool. 00:32:38.423 --> 00:32:40.649 Oh except they are... on the one side. 00:32:40.649 --> 00:32:42.632 But not cool as in, like, good. 00:32:42.632 --> 00:32:44.228 Or hip. 00:32:44.228 --> 00:32:47.024 Or rizz. Is that what the kids say now? 00:32:47.024 --> 00:32:49.214 oh no I looked it up and that is NOT RIGHT 00:32:49.214 --> 00:32:52.335 skibidi heat pump