WEBVTT Kind: captions Language: en 00:00:00.160 --> 00:00:02.010 Well, I’m pumped. 00:00:02.010 --> 00:00:06.089 What if I were to tell you that all of the energy you need to heat your home on a cold 00:00:06.089 --> 00:00:06.885 winter day 00:00:06.885 --> 00:00:09.407 could be found… outside? 00:00:09.407 --> 00:00:14.066 And that if you could capture the heat energy out there and move it inside your home, 00:00:14.066 --> 00:00:18.585 you could make yourself comfortable using a fraction of the energy of other methods? 00:00:18.585 --> 00:00:20.449 Sounds impossible at first, doesn’t it? 00:00:20.449 --> 00:00:22.734 If it’s colder outside than in, 00:00:22.734 --> 00:00:24.768 what heat is there to take? 00:00:24.768 --> 00:00:27.782 But it’s very possible, and thanks to heat pumps 00:00:27.782 --> 00:00:29.920 we can do it right now. 00:00:29.920 --> 00:00:31.907 And that’s what this video is all about. 00:00:31.907 --> 00:00:34.699 Heat pumps are simultaneously a very old 00:00:34.699 --> 00:00:37.802 yet also emerging home heating technology. 00:00:37.802 --> 00:00:40.348 Using a heat pump under ideal conditions 00:00:40.348 --> 00:00:45.225 requires as little as one fifth the energy of ordinary electric heat. 00:00:45.225 --> 00:00:48.136 With a coefficient of performance of 2.5 or greater, 00:00:48.136 --> 00:00:53.093 a heat pump will produce more heat for you per unit of fuel burned in a power plant 00:00:53.093 --> 00:00:57.144 than you could get by burning that fuel onsite in your home. 00:00:57.144 --> 00:01:01.013 This tremendous efficiency all but guarantees that the heat pump 00:01:01.013 --> 00:01:03.526 is the heating technology of the future. 00:01:03.526 --> 00:01:05.750 But what is a heat pump? 00:01:05.750 --> 00:01:09.340 Ah, well here’s where we need to talk about some terminology 00:01:09.340 --> 00:01:12.920 and also who the primary audience of this video is. 00:01:12.920 --> 00:01:16.198 I’m making this video mostly for an American audience 00:01:16.198 --> 00:01:19.090 because we’ve gone about this in a weird order. 00:01:19.090 --> 00:01:23.066 We’ve had air conditioning in a lot of homes (and cars, for that matter) 00:01:23.066 --> 00:01:25.500 for a very long time now. 00:01:25.500 --> 00:01:28.845 Air conditioning has been more or less standard equipment in American homes 00:01:28.845 --> 00:01:30.327 for more than 50 years, 00:01:30.327 --> 00:01:34.160 even in a climate like mine where winters can be brutally cold. 00:01:34.160 --> 00:01:36.301 And in places like the Southern US, 00:01:36.301 --> 00:01:40.161 air conditioning is practically a requirement for basic survival. 00:01:40.161 --> 00:01:44.262 And the thing is, air conditioners ARE heat pumps. 00:01:44.262 --> 00:01:46.954 Yet heat pumps, especially in regions like mine, 00:01:46.954 --> 00:01:49.286 are a rather new thing. 00:01:49.286 --> 00:01:50.859 Confused yet? 00:01:50.859 --> 00:01:54.025 Well, in some other parts of the world what we call a heat pump 00:01:54.025 --> 00:01:56.714 is referred to as a reverse cycle air conditioner, 00:01:56.714 --> 00:01:59.951 and that should give you a pretty solid idea of what’s going on. 00:01:59.951 --> 00:02:04.599 But, because this wouldn’t be Technology Connections without an explanation of the refrigeration cycle, 00:02:04.599 --> 00:02:09.905 let’s get down and dirty in the nitty gritty of latent heat and the magic of refrigerants. 00:02:09.905 --> 00:02:12.314 If you’d like to skip this part, skip to 00:02:12.314 --> 00:02:14.258 [a computer voice reads 7:38] 00:02:14.258 --> 00:02:16.051 Let’s start with a refrigerator - 00:02:16.051 --> 00:02:18.009 nearly everyone has one of those. 00:02:18.009 --> 00:02:22.109 What does your refrigerator or freezer do exactly? 00:02:22.109 --> 00:02:26.235 Well, it needs to make its insides colder than its outsides. 00:02:26.235 --> 00:02:29.280 That’s trickier to accomplish than it seems at first glance. 00:02:29.280 --> 00:02:32.822 It has to get heat energy out of itself. 00:02:32.822 --> 00:02:35.011 See, that’s the thing about temperature. 00:02:35.011 --> 00:02:40.061 What we call temperature is really the concentration of heat energy in a given space. 00:02:40.100 --> 00:02:43.360 If there’s a lot of energy crammed in a space, it’s hot. 00:02:43.360 --> 00:02:46.413 If the energy is really spread out, it’s cold. 00:02:46.413 --> 00:02:49.778 And thanks to entropy, energy always wants to spread out, 00:02:49.778 --> 00:02:54.230 or move from areas of high concentration to low concentration. 00:02:54.230 --> 00:02:58.370 This freezer’s insides are at about 5 degrees below zero. 00:02:58.370 --> 00:03:02.796 But the room it’s sitting in is much warmer than that, about 65 degrees. 00:03:02.796 --> 00:03:06.190 Because the energy around the freezer is more concentrated, 00:03:06.190 --> 00:03:09.569 ambient energy wants to spill into it. 00:03:09.569 --> 00:03:11.579 Wherever there’s a temperature gradient, 00:03:11.579 --> 00:03:16.178 nature is hot and bothered, frankly, and would very much like it to achieve equilibrium. 00:03:16.178 --> 00:03:20.090 So eventually the insides of the freezer will warm up. 00:03:20.090 --> 00:03:23.181 We can slow that down by adding a whole bunch of insulation 00:03:23.181 --> 00:03:24.925 or tweaking its design 00:03:24.925 --> 00:03:29.821 (in fact, this freezer and this footage was featured in a video discussing that very topic) 00:03:29.821 --> 00:03:33.265 but eventually we need to work to reverse this process 00:03:33.265 --> 00:03:37.080 and keep its insides cold relative to its outsides. 00:03:37.080 --> 00:03:39.714 And to do that, we use a heat pump. 00:03:39.714 --> 00:03:43.490 A refrigeration system collects heat energy in one place 00:03:43.490 --> 00:03:45.284 and disperses it in another. 00:03:45.284 --> 00:03:47.030 It pumps heat. 00:03:47.030 --> 00:03:51.815 We’ll get into how it does that shortly but the key thing I want you to recognize here 00:03:51.815 --> 00:03:55.437 is that even though the inside is very cold, 00:03:55.437 --> 00:03:57.827 there is heat energy in there. 00:03:57.827 --> 00:04:01.509 The freezer’s heat pump is collecting it from a very cold place, 00:04:01.509 --> 00:04:04.510 yet in doing so it creates warmth. 00:04:04.510 --> 00:04:07.334 The sides of the freezer get warm when it’s running, 00:04:07.334 --> 00:04:12.930 and that’s the heat it pulled from inside itself being rejected into the surrounding air. 00:04:12.930 --> 00:04:16.055 What makes this possible is a refrigerant. 00:04:16.055 --> 00:04:20.637 Refrigerants are gaseous chemical compounds with a particularly useful property: 00:04:20.637 --> 00:04:23.074 easy to manipulate boiling points. 00:04:23.074 --> 00:04:26.995 For example, R-134a boils at 15 below zero, 00:04:26.995 --> 00:04:29.503 or -26 Celsius. 00:04:29.503 --> 00:04:31.381 That’s quite cold. 00:04:31.381 --> 00:04:33.512 But here’s a can of it. 00:04:33.512 --> 00:04:35.747 It’s a liquid in here. 00:04:35.747 --> 00:04:37.510 How can that be? 00:04:37.510 --> 00:04:42.112 Well, like any chemical, its boiling point is affected by ambient pressure. 00:04:42.112 --> 00:04:45.388 You know how the boiling point of water is defined at sea level? 00:04:45.388 --> 00:04:49.142 That’s because higher up in the atmosphere where there’s less atmospheric pressure, 00:04:49.142 --> 00:04:51.466 it’s easier for water to boil. 00:04:51.466 --> 00:04:57.044 A rather crude way to think about it is that being under pressure squeezes all the molecules together, 00:04:57.044 --> 00:05:02.112 and that force provides an additional barrier to changing phases from liquid to gas. 00:05:02.112 --> 00:05:05.868 When there’s less pressure, it can change phases a bit more easily 00:05:05.868 --> 00:05:09.137 which lowers the amount of heat energy it needs to start boiling 00:05:09.137 --> 00:05:11.432 and thus its boiling point. 00:05:11.432 --> 00:05:16.223 When there’s more pressure, everything is held tightly together and the opposite occurs; 00:05:16.223 --> 00:05:18.452 its boiling point goes up. 00:05:18.452 --> 00:05:20.929 Because this is trapped in this can, 00:05:20.929 --> 00:05:24.025 it's under higher pressure and can remain a liquid. 00:05:24.025 --> 00:05:29.296 But when anything changes phases, it needs to absorb or release heat as it does so. 00:05:29.296 --> 00:05:33.194 This latent heat isn’t something we can feel directly, 00:05:33.194 --> 00:05:35.658 but it is a tremendous amount of energy. 00:05:35.658 --> 00:05:39.377 For example, getting a given quantity of water to vaporize 00:05:39.377 --> 00:05:46.393 takes about seven times as much energy as it does to bring it from room temperature to its boiling point. 00:05:46.393 --> 00:05:51.471 In other words, if it took 10 minutes to bring a pot of water to boil on high heat, 00:05:51.471 --> 00:05:56.115 it will take 70 minutes on top of that for it to all boil away. 00:05:56.115 --> 00:05:59.211 That extra energy is being used to free the molecules 00:05:59.211 --> 00:06:01.500 from their liquid phase into the vapor phase, 00:06:01.500 --> 00:06:04.256 but it doesn’t make the water any hotter. 00:06:04.256 --> 00:06:08.400 This is, incidentally, the principle on which automatic rice cookers work. 00:06:08.400 --> 00:06:09.407 Another plug? 00:06:09.407 --> 00:06:11.129 Why yes! 00:06:11.129 --> 00:06:12.441 How ‘bout a third one? 00:06:12.441 --> 00:06:15.263 We just saw what the release of latent heat is like 00:06:15.263 --> 00:06:17.441 in the reusable hand warmer video. 00:06:17.441 --> 00:06:20.275 Simply by falling from the liquid phase into the solid, 00:06:20.275 --> 00:06:23.164 the sodium acetate gets hot. 00:06:23.164 --> 00:06:26.528 Its latent heat of fusion is being released as it crystalizes, 00:06:26.528 --> 00:06:30.417 which means it gets warm - about as warm as its melting point. 00:06:30.417 --> 00:06:34.236 To reset it, you put a solid hand warmer in boiling water where, 00:06:34.236 --> 00:06:36.525 now that it’s colder than its surroundings, 00:06:36.525 --> 00:06:39.373 heat will spill into it, causing it to melt. 00:06:39.373 --> 00:06:42.702 As it does so, it re-absorbs its latent heat of fusion, 00:06:42.702 --> 00:06:47.949 and thanks to the fact that it can be supercooled without freezing it can store it for later use. 00:06:47.949 --> 00:06:51.077 Refrigerants, just like water and sodium acetate, 00:06:51.077 --> 00:06:55.001 have to absorb and release latent heat to change phases. 00:06:55.001 --> 00:06:59.226 What makes them useful is that thanks to their flexible boiling points, 00:06:59.226 --> 00:07:02.813 we can force this to happen and use it to our advantage. 00:07:02.813 --> 00:07:09.799 All we need to do is create a machine which allows us to manipulate the ambient pressure the refrigerant experiences. 00:07:09.799 --> 00:07:15.147 Refrigeration systems are nothing more than a closed loop of piping filled with a refrigerant 00:07:15.147 --> 00:07:19.291 that exploits its latent heat of vaporization to move energy. 00:07:19.291 --> 00:07:22.392 Using a compressor to create a pressure gradient 00:07:22.392 --> 00:07:28.183 allows us to force the refrigerant to condense thus releasing its latent heat of vaporization. 00:07:28.183 --> 00:07:32.405 We can then force it to evaporate and reabsorb its latent heat. 00:07:32.405 --> 00:07:38.831 Do this in two different locations and you pump heat across a thermal barrier. 00:07:38.889 --> 00:07:41.230 Now I’d like to show you what this looks like. 00:07:41.230 --> 00:07:43.810 Those of you that skipped to here, welcome back! 00:07:43.810 --> 00:07:48.039 We’re still talking about how refrigeration works but I wanted you back for this. 00:07:48.039 --> 00:07:52.289 Thanks to a student at Front Range Community College's Center for Integrated Manufacturing 00:07:52.289 --> 00:07:58.940 who had hands-on learning with these I have some great footage to share of a refrigeration demo rig. 00:07:58.940 --> 00:08:02.072 This is used to demonstrate all sorts of refrigeration technologies 00:08:02.072 --> 00:08:04.091 and learn how to troubleshoot them, 00:08:04.091 --> 00:08:06.768 but for now I just want to highlight the basics. 00:08:06.768 --> 00:08:09.245 Inside these pipes is a refrigerant. 00:08:09.245 --> 00:08:12.045 If you follow them, you’ll see that they form a circuit. 00:08:12.045 --> 00:08:14.890 The compressor is the heart of any refrigeration system 00:08:14.890 --> 00:08:16.759 (it does pump, after all) 00:08:16.759 --> 00:08:18.153 and it’s right here. 00:08:18.153 --> 00:08:20.709 Hermetic refers to the fact that the black canister 00:08:20.709 --> 00:08:24.980 hermetically seals an envelope for the mechanical compressor and its motor to sit inside 00:08:24.980 --> 00:08:27.283 without letting the refrigerant escape. 00:08:27.283 --> 00:08:30.238 On the left and right are two heat exchangers. 00:08:30.238 --> 00:08:32.831 These are the evaporator and the condenser. 00:08:32.831 --> 00:08:36.349 They are also the condenser and the evaporator. 00:08:36.349 --> 00:08:38.054 See, they’re labeled both. 00:08:38.054 --> 00:08:39.580 Because they are. 00:08:39.580 --> 00:08:41.967 This rig’s operation is reversible, 00:08:41.967 --> 00:08:46.921 meaning whether the heat exchanger is an evaporator or a condenser is arbitrary. 00:08:46.921 --> 00:08:49.198 We’ll see how that works in practice shortly 00:08:49.198 --> 00:08:54.181 but what’s really neat about this rig is that we can see liquid refrigerant traveling through it. 00:08:54.181 --> 00:08:58.774 Many refrigeration systems will have a sight glass like this which is useful for diagnostics, 00:08:58.774 --> 00:09:01.820 but glass piping? That’s a rarity. 00:09:01.820 --> 00:09:07.356 The refrigerant is only able to liquify because the pressure in this pipe is fairly high. 00:09:07.356 --> 00:09:10.085 It first entered the compressor as a low pressure gas, 00:09:10.085 --> 00:09:16.190 but being squeezed into the high pressure side raised its boiling point well above the ambient temperature. 00:09:16.190 --> 00:09:19.325 The act of compression also made it quite hot. 00:09:19.325 --> 00:09:22.562 The job of the condenser is to cool it back down, 00:09:22.562 --> 00:09:28.010 and it does this by forcing air through densely packed metal fins attached to the copper piping. 00:09:28.010 --> 00:09:34.529 This forms a heat exchanger with a large surface area to help transfer heat in the refrigerant to the air. 00:09:34.529 --> 00:09:37.739 At this pressure, if the refrigerant were R134a, 00:09:37.739 --> 00:09:41.736 its boiling point would be raised to about 130°F, 00:09:41.736 --> 00:09:44.718 much higher than the ambient air temperature. 00:09:44.718 --> 00:09:47.788 After exiting the compressor it’s hotter than even that, 00:09:47.788 --> 00:09:51.312 but airflow through the heat exchanger helps cool it down. 00:09:51.312 --> 00:09:54.889 Once the refrigerant has cooled to its artificially raised boiling point, 00:09:54.889 --> 00:09:56.769 it will start to condense. 00:09:56.769 --> 00:10:00.534 And as it does that, it releases its latent heat of vaporization. 00:10:00.534 --> 00:10:03.969 Now even more energy is being released from the refrigerant, 00:10:03.969 --> 00:10:08.487 and it will stay near its boiling point until the gas has condensed into a liquid. 00:10:08.487 --> 00:10:12.786 The upshot is that the condenser gets very hot. 00:10:12.786 --> 00:10:15.452 But where did that heat energy come from? 00:10:15.452 --> 00:10:19.038 Well, some of it came from the act of compression itself; 00:10:19.038 --> 00:10:24.179 simply compressing a gas makes it hot because you’ve squeezed its thermal energy into a smaller space, 00:10:24.179 --> 00:10:28.665 but most of it came from the refrigerant itself mere moments ago. 00:10:28.665 --> 00:10:31.089 See, after it’s all a liquid 00:10:31.089 --> 00:10:35.612 it gets held back by some sort of metering device at the end of the condenser. 00:10:35.612 --> 00:10:38.147 There are various types of metering device out there, 00:10:38.147 --> 00:10:40.616 the simplest of which is a capillary tube, 00:10:40.616 --> 00:10:43.890 and their job is to create a restriction in the refrigerant flow 00:10:43.890 --> 00:10:48.550 and thus maintain the pressure gradient we rely on to make this all work. 00:10:48.550 --> 00:10:51.524 Once the liquid refrigerant makes it through the metering device, 00:10:51.524 --> 00:10:55.777 it finds itself in another heat exchanger, just like the condenser. 00:10:55.777 --> 00:11:01.564 But here, the pressure is very low thanks to the suction on the input side of the compressor. 00:11:01.564 --> 00:11:06.227 What exactly the pressure is will depend on the refrigerants used and also conditions, 00:11:06.227 --> 00:11:12.585 but the pressure is low enough that the boiling point of the refrigerant will plummet to below ambient temperature. 00:11:12.585 --> 00:11:15.799 For sake of explanation we’ll assume it’s zero degrees. 00:11:15.799 --> 00:11:21.953 And here’s the key: to boil, the refrigerant has to absorb its latent heat of vaporization. 00:11:21.953 --> 00:11:25.364 And now that its boiling point is below ambient temperature, 00:11:25.364 --> 00:11:29.662 it will spontaneously start boiling and get very cold. 00:11:29.662 --> 00:11:36.887 To boil, it initially gets the latent heat it needs from itself which brings the remaining liquid down to the new boiling point. 00:11:36.887 --> 00:11:40.429 From there, it will pull energy from ambient air. 00:11:40.429 --> 00:11:42.896 See, now that it’s colder than ambient air, 00:11:42.896 --> 00:11:46.402 energy from the air will flow into the refrigerant. 00:11:46.402 --> 00:11:49.176 Remember, energy always wants to spread out, 00:11:49.176 --> 00:11:53.771 and now there’s a place that’s colder than its surrounding for that to happen. 00:11:53.771 --> 00:11:58.795 Thus the refrigerant is absorbing the energy from its surroundings as it boils. 00:11:58.795 --> 00:12:03.551 This heat exchanger is called the evaporator because that’s what the refrigerant does. 00:12:03.551 --> 00:12:05.170 It evaporates here, 00:12:05.170 --> 00:12:07.335 and condenses over there. 00:12:07.335 --> 00:12:11.104 So, finally, here’s where we get into how we make this work for us 00:12:11.104 --> 00:12:13.339 and why heat pumps are so cool. 00:12:13.339 --> 00:12:14.591 I mean hot. 00:12:14.591 --> 00:12:15.496 Hotly cool, 00:12:15.496 --> 00:12:16.898 or cooly hot. 00:12:16.898 --> 00:12:21.890 And why many American audiences may find this whole idea a little perplexing. 00:12:21.890 --> 00:12:26.889 See, a lot of us are used to energy flow in a refrigeration system going one way. 00:12:26.889 --> 00:12:30.396 We have refrigerators which make their insides colder. 00:12:30.396 --> 00:12:33.769 And we have air conditioners which make our living spaces colder. 00:12:33.769 --> 00:12:35.967 Refrigeration is for cold! 00:12:35.967 --> 00:12:37.628 See, here’s an air conditioner. 00:12:37.628 --> 00:12:39.028 This is the condenser, 00:12:39.028 --> 00:12:40.376 that’s the evaporator. 00:12:40.376 --> 00:12:42.036 The evaporator goes inside. 00:12:42.036 --> 00:12:44.002 Condenser goes outside 00:12:44.002 --> 00:12:46.063 (unless of course you have a portable air conditioner). 00:12:46.063 --> 00:12:49.676 But, but but the job of the air conditioner is to take heat out. 00:12:49.676 --> 00:12:50.333 Duh. 00:12:50.741 --> 00:12:52.348 Here’s a central air conditioner. 00:12:52.348 --> 00:12:54.042 This is the condensing unit. 00:12:54.042 --> 00:12:56.407 It has the compressor and the condenser. 00:12:56.407 --> 00:12:59.840 Heat comes out of here, and that’s - that's just the way it is. 00:12:59.840 --> 00:13:02.888 The evaporator sits above my furnace and makes the air colder 00:13:02.888 --> 00:13:05.759 and seven months out of the year, uh, sits pretty. 00:13:05.759 --> 00:13:07.425 Here’s a mini-split air conditioner. 00:13:07.425 --> 00:13:08.877 This is the condensing unit, 00:13:08.877 --> 00:13:12.805 and inside is a self-contained evaporator and blower. 00:13:12.805 --> 00:13:16.145 Ah but this is also the evaporating unit, 00:13:16.145 --> 00:13:20.150 and inside is a self-contained condenser and blower! 00:13:20.150 --> 00:13:24.676 This is reversible, and so is also a heat pump. 00:13:24.676 --> 00:13:30.547 This mini-split heat pump system has a different form factor from the central air conditioning system next to it, 00:13:30.547 --> 00:13:35.765 but mechanically they're something like 95% identical. 00:13:35.765 --> 00:13:38.841 There are some technological improvements in the mini-split 00:13:38.841 --> 00:13:43.670 like a variable-speed compressor and more intelligent controls which help it gain efficiency, 00:13:43.670 --> 00:13:48.286 but fundamentally the heat pump is no different from the air conditioner. 00:13:48.286 --> 00:13:52.753 It’s a compressor, a metering device, a refrigerant lineset, two heat exchangers, 00:13:52.753 --> 00:13:56.584 and a fan of some sort to force air through each heat one. 00:13:56.584 --> 00:14:00.907 The main difference is that the central system uses the furnace as its indoor blower motor, 00:14:00.907 --> 00:14:04.703 and the mini-split has one of its own in the wall-mounted unit. 00:14:04.749 --> 00:14:07.659 But the minisplit has one additional component 00:14:07.659 --> 00:14:13.449 that changes it from a cooling-only device to efficient year-round climate control. 00:14:13.449 --> 00:14:15.589 Let’s start with a closer look at it. 00:14:15.589 --> 00:14:21.740 This is a 1.5 ton unit, or 18,000 BTU or about 5250 watts. 00:14:21.740 --> 00:14:24.885 The outside unit contains most of its guts and unfortunately 00:14:24.885 --> 00:14:27.000 is not very easy to take apart. 00:14:27.000 --> 00:14:31.858 That’s not that important, though, as we can see the heat exchanger and refrigerant hoses. 00:14:31.858 --> 00:14:32.858 They’re here. 00:14:32.858 --> 00:14:33.909 And here. 00:14:34.160 --> 00:14:40.429 The fan forces air through the heat exchanger which wraps around the side so we can see its piping and fins. 00:14:40.429 --> 00:14:42.812 The inside unit is practically the same thing 00:14:42.812 --> 00:14:47.009 but it doesn’t have the compressor and the fan’s a linear blower type thing. 00:14:47.009 --> 00:14:50.699 Lift this up and there’s the other heat exchanger, plain as day. 00:14:50.699 --> 00:14:56.269 The fan forces air through it and exhausts through this swinging vent guide thingy. 00:14:56.269 --> 00:15:00.248 The metering device also lives here, I believe it’s a simple capillary tube - 00:15:00.248 --> 00:15:02.670 uh, please correct me if I’m wrong. 00:15:02.670 --> 00:15:05.406 In any case, it lives at the end of the liquid line, 00:15:05.406 --> 00:15:06.985 that’s the smaller of the two, 00:15:06.985 --> 00:15:12.321 and is the very last thing the refrigerant goes through before it enters this heat exchanger. 00:15:13.200 --> 00:15:14.428 Sometimes. 00:15:14.679 --> 00:15:17.417 Let’s get out the thermal camera and observe this thing. 00:15:17.417 --> 00:15:22.784 Note that the displayed temperature is likely inaccurate due to different emissivities of materials, 00:15:22.784 --> 00:15:24.956 but it’s the visuals that are more important anyway. 00:15:24.956 --> 00:15:28.034 When it’s not running, there is no pressure gradient 00:15:28.034 --> 00:15:31.761 and the refrigerant pressures in both heat exchangers are roughly equal. 00:15:31.761 --> 00:15:36.596 In cooling mode, the compressor works to pull gas out of this heat exchanger 00:15:36.596 --> 00:15:38.837 and lower the pressure inside of it. 00:15:38.837 --> 00:15:41.125 This lowers the boiling point of the refrigerant, 00:15:41.125 --> 00:15:44.956 and any liquid refrigerant remaining in the heat exchanger boils away. 00:15:44.956 --> 00:15:47.770 This causes the heat exchanger to get very cold - 00:15:47.770 --> 00:15:53.026 in this mode, it’s the evaporator and the refrigerant absorbs latent heat to boil. 00:15:53.026 --> 00:15:57.830 It has become a thermal sink and energy in the room is naturally moving into it, 00:15:57.830 --> 00:16:00.122 sped up with the help of the fan. 00:16:00.122 --> 00:16:02.834 That ultimately makes the air colder. 00:16:02.834 --> 00:16:05.861 Meanwhile the outside unit is getting warm. 00:16:05.861 --> 00:16:11.096 The compressor is forcing the gas it just pulled out of the evaporator into the condenser. 00:16:11.096 --> 00:16:14.563 Under this higher pressure, its boiling shoots up - 00:16:14.563 --> 00:16:20.489 way above the ambient temperature out here, so the refrigerant will condense inside the pipes. 00:16:20.489 --> 00:16:27.334 That makes this the condenser, and the very energy that just got absorbed inside as the refrigerant boiled 00:16:27.334 --> 00:16:30.907 is now being expelled out here as it recondenses. 00:16:30.907 --> 00:16:34.890 That heat energy was pumped from inside to outside, 00:16:34.890 --> 00:16:37.656 and that’s what air conditioners do. 00:16:37.656 --> 00:16:39.367 But here’s where things get interesting. 00:16:39.367 --> 00:16:41.328 Let’s ask a simple question. 00:16:41.328 --> 00:16:43.697 What if the roles could be reversed? 00:16:43.697 --> 00:16:49.772 Is it possible to collect heat energy in the outside unit and expel it from the inside unit? 00:16:49.772 --> 00:16:53.316 That would be pumping heat but in the other direction. 00:16:53.316 --> 00:16:59.181 Well, of course, it is absolutely possible and frankly stupidly easy to accomplish. 00:16:59.181 --> 00:17:02.133 All you need to do with a basic system like this 00:17:02.133 --> 00:17:05.390 is move the refrigerant through it backwards. 00:17:05.390 --> 00:17:06.842 That’s it. 00:17:06.842 --> 00:17:09.566 Now, you can’t just run the compressor backwards. 00:17:09.566 --> 00:17:12.265 Refrigerant can only go through it in one direction. 00:17:12.265 --> 00:17:15.642 But with just a little bit of extra piping and a special valve, 00:17:15.642 --> 00:17:19.247 you can change the direction it flows through the rest of the system. 00:17:19.247 --> 00:17:24.416 Virtually the only difference between this mini-split unit and the central air conditioner next to it 00:17:24.416 --> 00:17:27.965 (aside from the variable speed compressor and a few other particulars) 00:17:27.965 --> 00:17:32.579 is that the mini-split has a reversing valve and its associated piping. 00:17:32.579 --> 00:17:36.128 This allows refrigerant to flow in the opposite direction, 00:17:36.128 --> 00:17:39.359 and that flips the system on its head. 00:17:39.359 --> 00:17:43.882 Remember how in cooling mode the restriction was just before the evaporator? 00:17:43.882 --> 00:17:49.331 High-pressure liquid refrigerant built up right before it entered this space at the capillary tube. 00:17:49.331 --> 00:17:52.729 It would then evaporate in this coil once it made it through 00:17:52.729 --> 00:17:55.270 because the pressure in here was quite low. 00:17:55.270 --> 00:17:58.508 But, if refrigerant is going the other way, 00:17:58.508 --> 00:18:02.536 well now the restriction is at the end of this coil! 00:18:02.536 --> 00:18:06.406 High-pressure liquid refrigerant will build up inside of here, 00:18:06.406 --> 00:18:11.063 turning this into the condenser where the refrigerant will reject latent heat. 00:18:11.063 --> 00:18:16.225 Once it makes it through, it finds itself on its way back outside in a low-pressure environment 00:18:16.225 --> 00:18:19.707 where it will boil and absorb latent heat from the air. 00:18:19.707 --> 00:18:23.165 That makes the outside unit the evaporator. 00:18:23.165 --> 00:18:23.972 Take a look. 00:18:23.972 --> 00:18:26.803 Here, the mini-split is operating in cooling mode. 00:18:26.803 --> 00:18:29.886 The inside unit is the evaporator, absorbing heat, 00:18:29.886 --> 00:18:33.040 and the outside unit is the condenser, rejecting it. 00:18:33.040 --> 00:18:36.340 This is how we expect air conditioning to work. 00:18:36.340 --> 00:18:41.803 But switch it into heating mode and after a few minutes of idle time to allow the pressures to equalize, 00:18:41.803 --> 00:18:44.867 the reversing valve switches the direction of the refrigerant flow 00:18:44.867 --> 00:18:46.988 and the roles become reversed. 00:18:46.988 --> 00:18:48.811 When the compressor starts up again, 00:18:48.811 --> 00:18:53.529 the outside unit becomes the evaporator, absorbing heat in the refrigerant, 00:18:53.529 --> 00:18:59.015 and the inside unit becomes the condenser, rejecting that heat and warming the space. 00:18:59.015 --> 00:19:02.314 In a sense, it’s air conditioning the outside air 00:19:02.314 --> 00:19:06.876 and using the heat collected from that process to warm the space. 00:19:06.876 --> 00:19:08.764 Here’s why this is a big deal. 00:19:08.764 --> 00:19:13.051 The actual work being done here is compressing a gas. 00:19:13.051 --> 00:19:19.104 Yeah a little energy is being used by the fans but nearly all the electrical energy this unit consumes 00:19:19.104 --> 00:19:22.679 goes into the electric motor which drives the compressor. 00:19:22.679 --> 00:19:27.340 The refrigerant changes phases in a natural, spontaneous process. 00:19:27.340 --> 00:19:30.631 We just create the right conditions for that to occur. 00:19:30.631 --> 00:19:36.619 Because of this, this heat pump is able to move up to five and a half times as much heat energy 00:19:36.619 --> 00:19:39.647 as it actually consumes in electricity. 00:19:39.647 --> 00:19:41.754 That’s frankly amazing. 00:19:41.754 --> 00:19:46.224 It’s like running five space heaters for the cost of one. 00:19:46.224 --> 00:19:48.847 And why does it work even when it’s cold outside? 00:19:48.847 --> 00:19:52.731 Well, remember that heat energy always wants to spread out. 00:19:52.731 --> 00:19:58.737 And also remember that the boiling point of refrigerants is very, very cold at low pressures. 00:19:58.737 --> 00:20:02.944 So long as you can get the evaporator colder than the air around it, 00:20:02.944 --> 00:20:06.908 it will be able to capture heat energy as the refrigerant boils. 00:20:06.908 --> 00:20:09.557 Here the ambient temperature was about 40 degrees, 00:20:09.557 --> 00:20:16.329 but the evaporator coil is much colder than that so it becomes a place ambient energy wants to go. 00:20:16.329 --> 00:20:19.799 Once the refrigerant is compressed and brought to the inside unit, 00:20:19.799 --> 00:20:24.689 it will condense and release that acquired energy which warms the space. 00:20:24.689 --> 00:20:28.224 It doesn’t matter that the outside air has less energy in it than inside. 00:20:28.224 --> 00:20:33.197 All we’re doing when we heat or cool a room is affect energy concentration in that room. 00:20:33.197 --> 00:20:36.229 The outside air may have a lower energy concentration, 00:20:36.229 --> 00:20:40.871 but the refrigerant’s energy concentration can be made even lower than that. 00:20:40.871 --> 00:20:47.834 That’s all it takes - make a region colder than another and heat energy will always flow into the colder one. 00:20:47.834 --> 00:20:52.325 Since the refrigerant will hold onto that energy and release it when it condenses, 00:20:52.325 --> 00:20:57.159 just compress it to raise its boiling point, move it inside and boom! 00:20:57.159 --> 00:20:59.313 Heat from the cold. 00:20:59.313 --> 00:21:01.501 But it's not all sunshine and rainbows. 00:21:01.501 --> 00:21:06.224 The trickiest thing about heat pumps like this (this is known as an air-source heat pump) 00:21:06.224 --> 00:21:10.781 is that as it gets colder outside, their effectiveness is reduced. 00:21:10.781 --> 00:21:16.603 The Coefficient of Performance, or COP, describes how much heat energy the heat pump moves 00:21:16.603 --> 00:21:18.850 compared to how much it consumes. 00:21:18.850 --> 00:21:22.676 A COP of 1 is… bad. 00:21:22.676 --> 00:21:26.104 That’s just a one to one ratio, the same as resistive heating. 00:21:26.104 --> 00:21:30.209 But a COP of 4 is easily attainable under decent conditions. 00:21:30.209 --> 00:21:33.489 That’s pretty much any time it’s a few degrees above freezing. 00:21:33.489 --> 00:21:38.113 Once you’re close to freezing, though, well there’s a complication. 00:21:38.113 --> 00:21:42.630 You probably know that an air conditioner removes moisture from inside your home. 00:21:42.630 --> 00:21:48.554 This happens because the evaporator’s cold surface causes water in the air to condense on it. 00:21:48.554 --> 00:21:52.359 Well, if the evaporator is outside... 00:21:52.359 --> 00:21:55.208 then it’s probably gonna collect some moisture. 00:21:56.308 --> 00:21:57.561 It does. 00:21:57.561 --> 00:22:02.912 Now, that actually helps with heating since water releases latent heat when it condenses, 00:22:02.912 --> 00:22:06.776 but if it’s close to or below freezing outside… 00:22:06.776 --> 00:22:12.484 well that water turns to ice once the heat pump has gobbled up its heat energy. 00:22:12.484 --> 00:22:17.593 Over time, heat pumps like this build up a coating of frost on the outside unit. 00:22:17.650 --> 00:22:21.168 How quickly this happens depends a lot on environmental conditions - 00:22:21.168 --> 00:22:23.530 if it’s a dry day, it’ll happen slowly. 00:22:23.530 --> 00:22:26.650 But if it’s humid, it happens pretty fast. 00:22:26.650 --> 00:22:28.970 And this reduces its effectiveness. 00:22:28.970 --> 00:22:33.937 Not only does ice on the coils provide a layer of insulation which slows the process 00:22:33.937 --> 00:22:35.903 of scavenging heat from the air, 00:22:35.903 --> 00:22:43.030 but eventually the ice impedes the airflow through the coil entirely by filling the gaps between the fins. 00:22:43.030 --> 00:22:44.250 How do we deal with this? 00:22:44.250 --> 00:22:46.490 Well, it’s actually pretty easy. 00:22:46.490 --> 00:22:50.910 You can defrost the coil simply by briefly reversing the refrigerant flow. 00:22:50.910 --> 00:22:52.899 That will melt the frost that’s built up 00:22:52.899 --> 00:22:56.440 at the expense of pulling a little energy back outside. 00:22:56.440 --> 00:23:01.710 Since this unit has no other means of defrosting, it has to do it fairly cleverly. 00:23:01.710 --> 00:23:04.419 Sensors help it determine when it needs to defrost - 00:23:04.419 --> 00:23:07.993 a huge benefit of the unit being self contained like this 00:23:07.993 --> 00:23:11.266 is that it knows both the inside and outside temperature, 00:23:11.266 --> 00:23:15.606 and by monitoring refrigerant pressure it can determine how well it’s working. 00:23:15.606 --> 00:23:20.210 Observe here that prior to defrosting, it kept increasing the speed of the compressor 00:23:20.210 --> 00:23:22.869 to counteract the slowing effects of the ice. 00:23:24.430 --> 00:23:32.117 [a mechanical buzzing which successively increases in pitch and intensity] 00:23:43.770 --> 00:23:47.173 Eventually, though, it decides to defrost. 00:23:47.833 --> 00:23:49.401 [buzzing stops] 00:23:49.401 --> 00:23:54.920 When it defrosts, it first stops the compressor and then stops both fans. 00:23:54.920 --> 00:23:57.326 That makes sure it doesn’t blow cold air inside 00:23:57.326 --> 00:24:00.560 and allows the outside coil to get hotter. 00:24:00.560 --> 00:24:03.347 It then restarts the compressor in cooling mode, 00:24:03.347 --> 00:24:06.940 once again turning the outside coil into the condenser. 00:24:06.940 --> 00:24:10.978 The heat it’s pulling from inside quickly melts the ice. 00:24:11.826 --> 00:24:14.326 [compressor buzzing again] 00:24:16.839 --> 00:24:18.963 Once it’s concluded that it’s done, 00:24:18.963 --> 00:24:21.925 it stops, reverses the refrigerant flow again 00:24:21.925 --> 00:24:26.687 and starts the outdoor fan and compressor to begin collecting heat once more. 00:24:26.687 --> 00:24:32.440 But it waits to turn the indoor blower back on until the inside coil has warmed up a bit. 00:24:32.440 --> 00:24:36.763 To the user, a defrost simply seems like a pause in heating, 00:24:36.763 --> 00:24:40.556 but as you’ve seen it’s actually much more complicated than that. 00:24:40.556 --> 00:24:44.880 However, this reduces its efficiency and ultimately its effectiveness. 00:24:44.880 --> 00:24:51.926 On cold, humid days it has to defrost rather frequently, limiting its output, and reducing efficiency. 00:24:51.926 --> 00:24:54.196 How do we measure efficiency? 00:24:54.196 --> 00:25:00.397 Well, because this is the US, we use weird units like SEER and HSPF. 00:25:00.397 --> 00:25:04.766 This unit has a SEER of 19, which is pretty great actually! 00:25:04.766 --> 00:25:07.950 That’s equivalent to a COP of 5.5. 00:25:07.950 --> 00:25:12.009 But the seasonal energy efficiency ratio describes cooling. 00:25:12.009 --> 00:25:16.009 Its HSPF, heating seasonal performance factor, 00:25:16.009 --> 00:25:17.624 is 10. 00:25:17.624 --> 00:25:23.829 Luckily we can convert that to the COP, and that means this thing’s average coefficient of performance for heating is, 00:25:23.829 --> 00:25:27.312 at least according to how it’s tested, 2.9. 00:25:27.312 --> 00:25:29.791 So over a typical heating season, 00:25:29.791 --> 00:25:35.920 you can expect this to deliver almost 3 times as much heat energy as it cost to run. 00:25:35.920 --> 00:25:38.713 Some days it’ll be better, others worse. 00:25:38.713 --> 00:25:44.275 Over time, though, it would need roughly a third the electricity of a plain resistive heater 00:25:44.275 --> 00:25:46.433 to produce the same amount of heat. 00:25:46.433 --> 00:25:47.965 But there’s a catch. 00:25:47.965 --> 00:25:51.817 This thing is only rated to work down to 5 degrees. 00:25:51.817 --> 00:25:54.498 Now, it will work below that temperature! 00:25:54.498 --> 00:25:58.075 In fact, here’s some footage I made when it was ten below zero. 00:25:58.986 --> 00:26:01.303 [camera audio] Oh my goodness it's cold out here. 00:26:01.303 --> 00:26:04.990 Like it's, it's dangerously cold out here especially to be standing in front of it 00:26:04.990 --> 00:26:09.642 blowing colder than ambient air at me! 00:26:09.642 --> 00:26:11.739 Yeah, so I'm gonna go inside. 00:26:11.739 --> 00:26:16.258 I know this is a terrible tool for this job but it’s what I had. 00:26:16.258 --> 00:26:21.766 It was still running and producing some heat, but to be fair it was pretty tepid. 00:26:21.766 --> 00:26:23.649 It was also running its guts out 00:26:23.649 --> 00:26:28.456 so its coefficient of performance in this scenario may have been just 1, 00:26:28.456 --> 00:26:30.777 or maybe slightly better. 00:26:30.777 --> 00:26:34.858 This particular heat pump just isn’t equipped to handle weather this cold. 00:26:34.858 --> 00:26:37.203 Which, to be clear, is fine for me. 00:26:37.203 --> 00:26:40.704 This thing is in my garage and the heating is mostly a bonus. 00:26:40.704 --> 00:26:45.639 I installed it mainly to remove moisture because summers here are stupid humid. 00:26:46.161 --> 00:26:49.960 Seriously, I left the leather seats from my family’s old minivan’s in here 00:26:49.960 --> 00:26:55.820 my first summer and by the fall they were completely covered in mold. 00:26:55.820 --> 00:27:01.161 Some other stuff got damaged, too, so if I wanted to keep anything in here of value 00:27:01.161 --> 00:27:04.270 air conditioning was practically a must. 00:27:04.270 --> 00:27:09.140 But it certainly is handy on milder winter days to be able to use this as a workspace. 00:27:09.140 --> 00:27:13.320 When it’s above freezing, the air this thing blows is proper hot! 00:27:13.320 --> 00:27:15.770 Like, it genuinely surprised me. 00:27:16.304 --> 00:27:22.611 In retrospect it shouldn’t have, 18,000 BTU is more than three US-spec space heaters. 00:27:22.611 --> 00:27:28.870 But knowing that the heat it produces is coming from outside makes that feel almost like magic. 00:27:28.870 --> 00:27:31.895 And even when it’s colder and not that efficient, 00:27:31.895 --> 00:27:35.576 it has a freeze protection mode that keeps the temperature at 45 degrees, 00:27:35.576 --> 00:27:39.348 which is enough to melt the snow off my car after a drive and, well, 00:27:39.348 --> 00:27:42.525 that is a very nice luxury, I'll tell ya that. 00:27:42.525 --> 00:27:44.649 I usually leave it in that mode. 00:27:44.649 --> 00:27:50.817 However, it’s true that on its own this could not reliably provide me with sufficient heat throughout the winter. 00:27:50.817 --> 00:27:54.966 I would need a backup source of heat when conditions weren’t ideal for a heat pump. 00:27:54.966 --> 00:28:00.797 That’s often electric resistive heating which will always work but needs a ton of energy to do so. 00:28:00.797 --> 00:28:04.059 But it could also be natural gas or another fuel. 00:28:04.059 --> 00:28:08.480 In whole-home systems with heat pumps, the backup heat is often called emergency heat 00:28:08.480 --> 00:28:14.210 or auxiliary heat, and many thermostats are designed to control these systems as one. 00:28:14.210 --> 00:28:19.681 But, even in my climate, on many days a heat pump would be all I need. 00:28:19.681 --> 00:28:24.084 In fact, that’s the case for the vast majority of the winter. 00:28:24.084 --> 00:28:28.500 It’s not actually all that often that it dips below 5 degrees here. 00:28:28.500 --> 00:28:32.920 And still, some heat pumps like this are rated down to 20 below zero! 00:28:32.920 --> 00:28:36.540 It’s extremely rare for it to get colder than that here. 00:28:36.540 --> 00:28:40.920 Heat pumps can be made to work in colder temperatures through different refrigerants, altered designs, 00:28:40.920 --> 00:28:44.961 or through electric defrost coils where the outside unit has dedicated heaters 00:28:44.961 --> 00:28:48.685 to allow it to defrost while still operating in heating mode. 00:28:48.685 --> 00:28:50.930 But let’s set aside those potential fixes. 00:28:50.930 --> 00:28:54.315 Here’s a question I’ve been asking a lot lately: 00:28:54.315 --> 00:28:57.543 Why isn’t this thing also a heat pump? 00:28:57.543 --> 00:29:00.087 This HVAC system isn’t even two years old 00:29:00.087 --> 00:29:03.789 but no one even bothered giving me the option for a heat pump. 00:29:03.789 --> 00:29:08.435 Yes, it’s cold enough where I live that a gas-fired furnace is the norm, 00:29:08.435 --> 00:29:13.453 but I’ve got 95% of a reversible heat pump sitting right here! 00:29:13.453 --> 00:29:20.066 This 2.5 ton air conditioner may only be able to put out half of what my furnace can with its fire tubes, 00:29:20.066 --> 00:29:24.116 but on mild days - so the ones a heat pump would be best at - 00:29:24.116 --> 00:29:26.359 that’s more than I need anyway. 00:29:26.359 --> 00:29:33.431 Heck, even when it was -10 outside, my 70,000 BTU furnace only ran for about 10 hours a day. 00:29:33.431 --> 00:29:36.685 30,000 BTU continuously would have covered that, 00:29:36.685 --> 00:29:40.190 but yes I know that output wouldn’t have been possible at that ambient temp. 00:29:40.190 --> 00:29:42.000 I'm just spitballin’ here. 00:29:42.000 --> 00:29:46.390 And it’s not like heat pumps systems are unheard of in my neck of the woods. 00:29:46.390 --> 00:29:48.905 In fact, a patron of the channel has one and 00:29:48.905 --> 00:29:51.650 they’re actually a little farther North than I am! 00:29:51.650 --> 00:29:56.259 This outdoor unit is practically the exact same thing as the condensing unit 00:29:56.259 --> 00:30:01.970 for my A/C system, save for the reversing valve and a more complicated compressor setup. 00:30:01.970 --> 00:30:07.470 It functions exactly as the mini-split does, doing the same periodic reversing to defrost. 00:30:07.470 --> 00:30:11.500 I mean, there’s snow on the ground yet it’s still working! 00:30:11.500 --> 00:30:16.891 Since this is almost the exact same machine as mine, it annoys me endlessly 00:30:16.891 --> 00:30:21.190 that reversibility isn’t just standard at this point. 00:30:21.190 --> 00:30:25.268 In fact, in the South reversible heat pumps in this form factor are pretty common, 00:30:25.268 --> 00:30:27.052 and have been for years. 00:30:27.052 --> 00:30:30.343 Since heating demand is usually mild if any in the South, 00:30:30.343 --> 00:30:33.510 relatively few folks have natural gas for heating. 00:30:33.510 --> 00:30:35.910 When you’re all-electric and have air conditioning, 00:30:35.910 --> 00:30:39.720 you might as well have a heat pump to save money on heating costs. 00:30:39.720 --> 00:30:43.006 And since all it really takes is a reversing valve and a few other particulars 00:30:43.006 --> 00:30:46.779 to make that happen, I see it as a no-brainer. 00:30:46.779 --> 00:30:48.779 Well, usually. 00:30:48.779 --> 00:30:52.917 When a large, disruptive weather event takes hold that causes an entire region 00:30:52.917 --> 00:30:57.991 to suddenly need resistive heat because it’s too cold for their heat pumps to work effectively, 00:30:57.991 --> 00:31:01.760 that can put an untenable strain on the electric grid. 00:31:01.760 --> 00:31:06.860 When this video was published, Texas had just gone through one of these extreme events. 00:31:06.860 --> 00:31:10.956 Heat pumps certainly were not the cause of the grid failures, to be clear, 00:31:10.956 --> 00:31:14.218 as a lot of issues occurred on the generation side of things 00:31:14.218 --> 00:31:19.130 and based on what I’ve read, natural gas backup heat is more common than I thought. 00:31:19.130 --> 00:31:25.179 But the occasional need for an energy-intensive backup heat source is good to keep in mind. 00:31:25.179 --> 00:31:29.120 But so far, we’ve just been talking about air source heat pumps. 00:31:29.120 --> 00:31:34.210 These are definitely the most common because, well, they’re easy and simple to make. 00:31:34.210 --> 00:31:37.700 But there are other sources of heat to be tapped into. 00:31:37.700 --> 00:31:41.259 And heat pump technology is finding itself in more and more places 00:31:41.259 --> 00:31:45.290 as we discover the benefits of moving heat rather than creating it. 00:31:45.290 --> 00:31:48.424 In part 2, we’ll look at some of these solutions 00:31:48.424 --> 00:31:51.552 and discuss where heat pumps have to go from here. 00:31:51.552 --> 00:31:55.802 We’ll also look at some cost/benefit comparisons both from a financial perspective 00:31:55.802 --> 00:31:58.450 and from a climate change perspective. 00:31:58.450 --> 00:32:02.521 And that’s a key reason heat pumps will undoubtedly see more widespread use 00:32:02.521 --> 00:32:03.840 as time goes on. 00:32:03.840 --> 00:32:09.762 I said earlier that with a COP of 2.5 you’ll get more heating out of a heat pump 00:32:09.762 --> 00:32:13.050 than you would burning natural gas onsite. 00:32:13.050 --> 00:32:14.336 Let me explain that. 00:32:14.336 --> 00:32:19.588 In 2019 the average efficiency of a natural gas power plant in the US was 44 percent 00:32:19.588 --> 00:32:22.290 according to the Energy Information Administration. 00:32:22.290 --> 00:32:26.042 Now, if you run electric resistive heat from this source of energy, 00:32:26.042 --> 00:32:32.480 after transmission losses you’ll end up getting about 40% of the energy out of the natural gas. 00:32:32.480 --> 00:32:36.624 Not bad, but you can also burn natural gas in an onsite furnace 00:32:36.624 --> 00:32:39.960 and get more than 90% of the energy out of it. 00:32:39.960 --> 00:32:44.815 It’s for that reason that areas like mine tend to have natural gas infrastructure 00:32:44.815 --> 00:32:47.150 capable of delivering it directly to homes. 00:32:47.150 --> 00:32:50.990 Historically it’s been cheaper, easier, and more efficient. 00:32:50.990 --> 00:32:54.630 But, when a heat pump is running at a COP of 2.5, 00:32:54.630 --> 00:32:58.967 sure you’re still only getting 40% of the energy from the natural gas, 00:32:58.967 --> 00:33:03.148 but with it you’re moving 2.5 times that amount. 00:33:03.148 --> 00:33:08.977 That means that in the end, you’re getting the equivalent of 100% out of the natural gas. 00:33:08.977 --> 00:33:11.309 And you can even get more than that! 00:33:11.309 --> 00:33:15.941 A heat pump is frankly the most effective way to turn electricity into heat, 00:33:15.941 --> 00:33:21.333 so even on today’s fossil-fired power grid, they’re a wiser use of limited resources 00:33:21.333 --> 00:33:23.580 and can help lower emissions. 00:33:23.580 --> 00:33:28.559 And they also make renewable energy sources much more feasible in cold climates. 00:33:28.559 --> 00:33:33.640 While you certainly can use the output from wind or solar to heat your home resistively, 00:33:33.640 --> 00:33:37.429 that takes a lot of output and makes storage hard to manage. 00:33:37.429 --> 00:33:42.120 If everyone had very efficient heat pumps, that energy demand could be cut into a quarter 00:33:42.120 --> 00:33:44.120 or perhaps a little less. 00:33:44.120 --> 00:33:47.292 And while heat pumps like this struggle in cold weather, 00:33:47.292 --> 00:33:48.815 there is an alternative. 00:33:48.815 --> 00:33:55.435 The ground-source or geothermal heat pump is a way to attain year-round, near-constant peak efficiency 00:33:55.435 --> 00:33:58.479 with heat pumps even in cold climates. 00:33:58.479 --> 00:34:01.527 And we’ll talk about those, some other novel uses for heat pumps, 00:34:01.527 --> 00:34:06.283 as well as the need for more climate-friendly refrigerants in the next video. 00:34:06.283 --> 00:34:08.607 For now, stay warm! 00:34:09.455 --> 00:34:12.146 ♫ coefficient of smooth jazz ♫ 00:34:13.277 --> 00:34:17.723 and that, if you could capture the heat energy out of... 00:34:18.634 --> 00:34:19.674 [goofy noise] 00:34:19.674 --> 00:34:22.570 well we're gonna restart this line because. Oh cripe. 00:34:23.732 --> 00:34:25.349 Eurggh! 00:34:25.349 --> 00:34:28.802 Just my terrible teleprompter causing me problems again. 00:34:28.802 --> 00:34:31.053 And the thing is, air condish... 00:34:31.053 --> 00:34:32.398 and the..pff 00:34:32.398 --> 00:34:33.324 heh. 00:34:33.324 --> 00:34:33.943 Ehehhe. 00:34:33.988 --> 00:34:38.444 ...allows us to manipulate the ambient pressure the refrigerants experience. 00:34:38.444 --> 00:34:40.227 The S is on the wrong word. 00:34:40.227 --> 00:34:42.446 That line needs an on-the-fly re-write! 00:34:42.446 --> 00:34:43.802 Those are always great. 00:34:44.651 --> 00:34:48.320 ...boiling point shoots way up. Wayyu... 00:34:48.320 --> 00:34:50.705 the, there are words missing! 00:34:50.705 --> 00:34:54.905 This is, incidentally, the principle on which automatic rice cookers work. 00:34:54.905 --> 00:34:56.629 Another plug? 00:34:56.629 --> 00:34:58.862 Dammit! 00:35:01.563 --> 00:35:05.708 I hope you're pumped for part 2. 00:35:05.708 --> 00:35:08.151 I know I am. 00:35:08.151 --> 00:35:10.823 Gonna talk about them coolant pipes. 00:35:10.823 --> 00:35:12.777 Digging wells. 00:35:12.777 --> 00:35:13.489 All that.