1 00:00:00,160 --> 00:00:02,010 Well, I’m pumped. 2 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 3 00:00:06,089 --> 00:00:06,885 winter day 4 00:00:06,885 --> 00:00:09,407 could be found… outside? 5 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, 6 00:00:14,066 --> 00:00:18,585 you could make yourself comfortable using a fraction of the energy of other methods? 7 00:00:18,585 --> 00:00:20,449 Sounds impossible at first, doesn’t it? 8 00:00:20,449 --> 00:00:22,734 If it’s colder outside than in, 9 00:00:22,734 --> 00:00:24,768 what heat is there to take? 10 00:00:24,768 --> 00:00:27,782 But it’s very possible, and thanks to heat pumps 11 00:00:27,782 --> 00:00:29,920 we can do it right now. 12 00:00:29,920 --> 00:00:31,907 And that’s what this video is all about. 13 00:00:31,907 --> 00:00:34,699 Heat pumps are simultaneously a very old 14 00:00:34,699 --> 00:00:37,802 yet also emerging home heating technology. 15 00:00:37,802 --> 00:00:40,348 Using a heat pump under ideal conditions 16 00:00:40,348 --> 00:00:45,225 requires as little as one fifth the energy of ordinary electric heat. 17 00:00:45,225 --> 00:00:48,136 With a coefficient of performance of 2.5 or greater, 18 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 19 00:00:53,093 --> 00:00:57,144 than you could get by burning that fuel onsite in your home. 20 00:00:57,144 --> 00:01:01,013 This tremendous efficiency all but guarantees that the heat pump 21 00:01:01,013 --> 00:01:03,526 is the heating technology of the future. 22 00:01:03,526 --> 00:01:05,750 But what is a heat pump? 23 00:01:05,750 --> 00:01:09,340 Ah, well here’s where we need to talk about some terminology 24 00:01:09,340 --> 00:01:12,920 and also who the primary audience of this video is. 25 00:01:12,920 --> 00:01:16,198 I’m making this video mostly for an American audience 26 00:01:16,198 --> 00:01:19,090 because we’ve gone about this in a weird order. 27 00:01:19,090 --> 00:01:23,066 We’ve had air conditioning in a lot of homes (and cars, for that matter) 28 00:01:23,066 --> 00:01:25,500 for a very long time now. 29 00:01:25,500 --> 00:01:28,845 Air conditioning has been more or less standard equipment in American homes 30 00:01:28,845 --> 00:01:30,327 for more than 50 years, 31 00:01:30,327 --> 00:01:34,160 even in a climate like mine where winters can be brutally cold. 32 00:01:34,160 --> 00:01:36,301 And in places like the Southern US, 33 00:01:36,301 --> 00:01:40,161 air conditioning is practically a requirement for basic survival. 34 00:01:40,161 --> 00:01:44,262 And the thing is, air conditioners ARE heat pumps. 35 00:01:44,262 --> 00:01:46,954 Yet heat pumps, especially in regions like mine, 36 00:01:46,954 --> 00:01:49,286 are a rather new thing. 37 00:01:49,286 --> 00:01:50,859 Confused yet? 38 00:01:50,859 --> 00:01:54,025 Well, in some other parts of the world what we call a heat pump 39 00:01:54,025 --> 00:01:56,714 is referred to as a reverse cycle air conditioner, 40 00:01:56,714 --> 00:01:59,951 and that should give you a pretty solid idea of what’s going on. 41 00:01:59,951 --> 00:02:04,599 But, because this wouldn’t be Technology Connections without an explanation of the refrigeration cycle, 42 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. 43 00:02:09,905 --> 00:02:12,314 If you’d like to skip this part, skip to 44 00:02:12,314 --> 00:02:14,258 [a computer voice reads 7:38] 45 00:02:14,258 --> 00:02:16,051 Let’s start with a refrigerator - 46 00:02:16,051 --> 00:02:18,009 nearly everyone has one of those. 47 00:02:18,009 --> 00:02:22,109 What does your refrigerator or freezer do exactly? 48 00:02:22,109 --> 00:02:26,235 Well, it needs to make its insides colder than its outsides. 49 00:02:26,235 --> 00:02:29,280 That’s trickier to accomplish than it seems at first glance. 50 00:02:29,280 --> 00:02:32,822 It has to get heat energy out of itself. 51 00:02:32,822 --> 00:02:35,011 See, that’s the thing about temperature. 52 00:02:35,011 --> 00:02:40,061 What we call temperature is really the concentration of heat energy in a given space. 53 00:02:40,100 --> 00:02:43,360 If there’s a lot of energy crammed in a space, it’s hot. 54 00:02:43,360 --> 00:02:46,413 If the energy is really spread out, it’s cold. 55 00:02:46,413 --> 00:02:49,778 And thanks to entropy, energy always wants to spread out, 56 00:02:49,778 --> 00:02:54,230 or move from areas of high concentration to low concentration. 57 00:02:54,230 --> 00:02:58,370 This freezer’s insides are at about 5 degrees below zero. 58 00:02:58,370 --> 00:03:02,796 But the room it’s sitting in is much warmer than that, about 65 degrees. 59 00:03:02,796 --> 00:03:06,190 Because the energy around the freezer is more concentrated, 60 00:03:06,190 --> 00:03:09,569 ambient energy wants to spill into it. 61 00:03:09,569 --> 00:03:11,579 Wherever there’s a temperature gradient, 62 00:03:11,579 --> 00:03:16,178 nature is hot and bothered, frankly, and would very much like it to achieve equilibrium. 63 00:03:16,178 --> 00:03:20,090 So eventually the insides of the freezer will warm up. 64 00:03:20,090 --> 00:03:23,181 We can slow that down by adding a whole bunch of insulation 65 00:03:23,181 --> 00:03:24,925 or tweaking its design 66 00:03:24,925 --> 00:03:29,821 (in fact, this freezer and this footage was featured in a video discussing that very topic) 67 00:03:29,821 --> 00:03:33,265 but eventually we need to work to reverse this process 68 00:03:33,265 --> 00:03:37,080 and keep its insides cold relative to its outsides. 69 00:03:37,080 --> 00:03:39,714 And to do that, we use a heat pump. 70 00:03:39,714 --> 00:03:43,490 A refrigeration system collects heat energy in one place 71 00:03:43,490 --> 00:03:45,284 and disperses it in another. 72 00:03:45,284 --> 00:03:47,030 It pumps heat. 73 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 74 00:03:51,815 --> 00:03:55,437 is that even though the inside is very cold, 75 00:03:55,437 --> 00:03:57,827 there is heat energy in there. 76 00:03:57,827 --> 00:04:01,509 The freezer’s heat pump is collecting it from a very cold place, 77 00:04:01,509 --> 00:04:04,510 yet in doing so it creates warmth. 78 00:04:04,510 --> 00:04:07,334 The sides of the freezer get warm when it’s running, 79 00:04:07,334 --> 00:04:12,930 and that’s the heat it pulled from inside itself being rejected into the surrounding air. 80 00:04:12,930 --> 00:04:16,055 What makes this possible is a refrigerant. 81 00:04:16,055 --> 00:04:20,637 Refrigerants are gaseous chemical compounds with a particularly useful property: 82 00:04:20,637 --> 00:04:23,074 easy to manipulate boiling points. 83 00:04:23,074 --> 00:04:26,995 For example, R-134a boils at 15 below zero, 84 00:04:26,995 --> 00:04:29,503 or -26 Celsius. 85 00:04:29,503 --> 00:04:31,381 That’s quite cold. 86 00:04:31,381 --> 00:04:33,512 But here’s a can of it. 87 00:04:33,512 --> 00:04:35,747 It’s a liquid in here. 88 00:04:35,747 --> 00:04:37,510 How can that be? 89 00:04:37,510 --> 00:04:42,112 Well, like any chemical, its boiling point is affected by ambient pressure. 90 00:04:42,112 --> 00:04:45,388 You know how the boiling point of water is defined at sea level? 91 00:04:45,388 --> 00:04:49,142 That’s because higher up in the atmosphere where there’s less atmospheric pressure, 92 00:04:49,142 --> 00:04:51,466 it’s easier for water to boil. 93 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, 94 00:04:57,044 --> 00:05:02,112 and that force provides an additional barrier to changing phases from liquid to gas. 95 00:05:02,112 --> 00:05:05,868 When there’s less pressure, it can change phases a bit more easily 96 00:05:05,868 --> 00:05:09,137 which lowers the amount of heat energy it needs to start boiling 97 00:05:09,137 --> 00:05:11,432 and thus its boiling point. 98 00:05:11,432 --> 00:05:16,223 When there’s more pressure, everything is held tightly together and the opposite occurs; 99 00:05:16,223 --> 00:05:18,452 its boiling point goes up. 100 00:05:18,452 --> 00:05:20,929 Because this is trapped in this can, 101 00:05:20,929 --> 00:05:24,025 it's under higher pressure and can remain a liquid. 102 00:05:24,025 --> 00:05:29,296 But when anything changes phases, it needs to absorb or release heat as it does so. 103 00:05:29,296 --> 00:05:33,194 This latent heat isn’t something we can feel directly, 104 00:05:33,194 --> 00:05:35,658 but it is a tremendous amount of energy. 105 00:05:35,658 --> 00:05:39,377 For example, getting a given quantity of water to vaporize 106 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. 107 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, 108 00:05:51,471 --> 00:05:56,115 it will take 70 minutes on top of that for it to all boil away. 109 00:05:56,115 --> 00:05:59,211 That extra energy is being used to free the molecules 110 00:05:59,211 --> 00:06:01,500 from their liquid phase into the vapor phase, 111 00:06:01,500 --> 00:06:04,256 but it doesn’t make the water any hotter. 112 00:06:04,256 --> 00:06:08,400 This is, incidentally, the principle on which automatic rice cookers work. 113 00:06:08,400 --> 00:06:09,407 Another plug? 114 00:06:09,407 --> 00:06:11,129 Why yes! 115 00:06:11,129 --> 00:06:12,441 How ‘bout a third one? 116 00:06:12,441 --> 00:06:15,263 We just saw what the release of latent heat is like 117 00:06:15,263 --> 00:06:17,441 in the reusable hand warmer video. 118 00:06:17,441 --> 00:06:20,275 Simply by falling from the liquid phase into the solid, 119 00:06:20,275 --> 00:06:23,164 the sodium acetate gets hot. 120 00:06:23,164 --> 00:06:26,528 Its latent heat of fusion is being released as it crystalizes, 121 00:06:26,528 --> 00:06:30,417 which means it gets warm - about as warm as its melting point. 122 00:06:30,417 --> 00:06:34,236 To reset it, you put a solid hand warmer in boiling water where, 123 00:06:34,236 --> 00:06:36,525 now that it’s colder than its surroundings, 124 00:06:36,525 --> 00:06:39,373 heat will spill into it, causing it to melt. 125 00:06:39,373 --> 00:06:42,702 As it does so, it re-absorbs its latent heat of fusion, 126 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. 127 00:06:47,949 --> 00:06:51,077 Refrigerants, just like water and sodium acetate, 128 00:06:51,077 --> 00:06:55,001 have to absorb and release latent heat to change phases. 129 00:06:55,001 --> 00:06:59,226 What makes them useful is that thanks to their flexible boiling points, 130 00:06:59,226 --> 00:07:02,813 we can force this to happen and use it to our advantage. 131 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. 132 00:07:09,799 --> 00:07:15,147 Refrigeration systems are nothing more than a closed loop of piping filled with a refrigerant 133 00:07:15,147 --> 00:07:19,291 that exploits its latent heat of vaporization to move energy. 134 00:07:19,291 --> 00:07:22,392 Using a compressor to create a pressure gradient 135 00:07:22,392 --> 00:07:28,183 allows us to force the refrigerant to condense thus releasing its latent heat of vaporization. 136 00:07:28,183 --> 00:07:32,405 We can then force it to evaporate and reabsorb its latent heat. 137 00:07:32,405 --> 00:07:38,831 Do this in two different locations and you pump heat across a thermal barrier. 138 00:07:38,889 --> 00:07:41,230 Now I’d like to show you what this looks like. 139 00:07:41,230 --> 00:07:43,810 Those of you that skipped to here, welcome back! 140 00:07:43,810 --> 00:07:48,039 We’re still talking about how refrigeration works but I wanted you back for this. 141 00:07:48,039 --> 00:07:52,289 Thanks to a student at Front Range Community College's Center for Integrated Manufacturing 142 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. 143 00:07:58,940 --> 00:08:02,072 This is used to demonstrate all sorts of refrigeration technologies 144 00:08:02,072 --> 00:08:04,091 and learn how to troubleshoot them, 145 00:08:04,091 --> 00:08:06,768 but for now I just want to highlight the basics. 146 00:08:06,768 --> 00:08:09,245 Inside these pipes is a refrigerant. 147 00:08:09,245 --> 00:08:12,045 If you follow them, you’ll see that they form a circuit. 148 00:08:12,045 --> 00:08:14,890 The compressor is the heart of any refrigeration system 149 00:08:14,890 --> 00:08:16,759 (it does pump, after all) 150 00:08:16,759 --> 00:08:18,153 and it’s right here. 151 00:08:18,153 --> 00:08:20,709 Hermetic refers to the fact that the black canister 152 00:08:20,709 --> 00:08:24,980 hermetically seals an envelope for the mechanical compressor and its motor to sit inside 153 00:08:24,980 --> 00:08:27,283 without letting the refrigerant escape. 154 00:08:27,283 --> 00:08:30,238 On the left and right are two heat exchangers. 155 00:08:30,238 --> 00:08:32,831 These are the evaporator and the condenser. 156 00:08:32,831 --> 00:08:36,349 They are also the condenser and the evaporator. 157 00:08:36,349 --> 00:08:38,054 See, they’re labeled both. 158 00:08:38,054 --> 00:08:39,580 Because they are. 159 00:08:39,580 --> 00:08:41,967 This rig’s operation is reversible, 160 00:08:41,967 --> 00:08:46,921 meaning whether the heat exchanger is an evaporator or a condenser is arbitrary. 161 00:08:46,921 --> 00:08:49,198 We’ll see how that works in practice shortly 162 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. 163 00:08:54,181 --> 00:08:58,774 Many refrigeration systems will have a sight glass like this which is useful for diagnostics, 164 00:08:58,774 --> 00:09:01,820 but glass piping? That’s a rarity. 165 00:09:01,820 --> 00:09:07,356 The refrigerant is only able to liquify because the pressure in this pipe is fairly high. 166 00:09:07,356 --> 00:09:10,085 It first entered the compressor as a low pressure gas, 167 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. 168 00:09:16,190 --> 00:09:19,325 The act of compression also made it quite hot. 169 00:09:19,325 --> 00:09:22,562 The job of the condenser is to cool it back down, 170 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. 171 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. 172 00:09:34,529 --> 00:09:37,739 At this pressure, if the refrigerant were R134a, 173 00:09:37,739 --> 00:09:41,736 its boiling point would be raised to about 130°F, 174 00:09:41,736 --> 00:09:44,718 much higher than the ambient air temperature. 175 00:09:44,718 --> 00:09:47,788 After exiting the compressor it’s hotter than even that, 176 00:09:47,788 --> 00:09:51,312 but airflow through the heat exchanger helps cool it down. 177 00:09:51,312 --> 00:09:54,889 Once the refrigerant has cooled to its artificially raised boiling point, 178 00:09:54,889 --> 00:09:56,769 it will start to condense. 179 00:09:56,769 --> 00:10:00,534 And as it does that, it releases its latent heat of vaporization. 180 00:10:00,534 --> 00:10:03,969 Now even more energy is being released from the refrigerant, 181 00:10:03,969 --> 00:10:08,487 and it will stay near its boiling point until the gas has condensed into a liquid. 182 00:10:08,487 --> 00:10:12,786 The upshot is that the condenser gets very hot. 183 00:10:12,786 --> 00:10:15,452 But where did that heat energy come from? 184 00:10:15,452 --> 00:10:19,038 Well, some of it came from the act of compression itself; 185 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, 186 00:10:24,179 --> 00:10:28,665 but most of it came from the refrigerant itself mere moments ago. 187 00:10:28,665 --> 00:10:31,089 See, after it’s all a liquid 188 00:10:31,089 --> 00:10:35,612 it gets held back by some sort of metering device at the end of the condenser. 189 00:10:35,612 --> 00:10:38,147 There are various types of metering device out there, 190 00:10:38,147 --> 00:10:40,616 the simplest of which is a capillary tube, 191 00:10:40,616 --> 00:10:43,890 and their job is to create a restriction in the refrigerant flow 192 00:10:43,890 --> 00:10:48,550 and thus maintain the pressure gradient we rely on to make this all work. 193 00:10:48,550 --> 00:10:51,524 Once the liquid refrigerant makes it through the metering device, 194 00:10:51,524 --> 00:10:55,777 it finds itself in another heat exchanger, just like the condenser. 195 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. 196 00:11:01,564 --> 00:11:06,227 What exactly the pressure is will depend on the refrigerants used and also conditions, 197 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. 198 00:11:12,585 --> 00:11:15,799 For sake of explanation we’ll assume it’s zero degrees. 199 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. 200 00:11:21,953 --> 00:11:25,364 And now that its boiling point is below ambient temperature, 201 00:11:25,364 --> 00:11:29,662 it will spontaneously start boiling and get very cold. 202 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. 203 00:11:36,887 --> 00:11:40,429 From there, it will pull energy from ambient air. 204 00:11:40,429 --> 00:11:42,896 See, now that it’s colder than ambient air, 205 00:11:42,896 --> 00:11:46,402 energy from the air will flow into the refrigerant. 206 00:11:46,402 --> 00:11:49,176 Remember, energy always wants to spread out, 207 00:11:49,176 --> 00:11:53,771 and now there’s a place that’s colder than its surrounding for that to happen. 208 00:11:53,771 --> 00:11:58,795 Thus the refrigerant is absorbing the energy from its surroundings as it boils. 209 00:11:58,795 --> 00:12:03,551 This heat exchanger is called the evaporator because that’s what the refrigerant does. 210 00:12:03,551 --> 00:12:05,170 It evaporates here, 211 00:12:05,170 --> 00:12:07,335 and condenses over there. 212 00:12:07,335 --> 00:12:11,104 So, finally, here’s where we get into how we make this work for us 213 00:12:11,104 --> 00:12:13,339 and why heat pumps are so cool. 214 00:12:13,339 --> 00:12:14,591 I mean hot. 215 00:12:14,591 --> 00:12:15,496 Hotly cool, 216 00:12:15,496 --> 00:12:16,898 or cooly hot. 217 00:12:16,898 --> 00:12:21,890 And why many American audiences may find this whole idea a little perplexing. 218 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. 219 00:12:26,889 --> 00:12:30,396 We have refrigerators which make their insides colder. 220 00:12:30,396 --> 00:12:33,769 And we have air conditioners which make our living spaces colder. 221 00:12:33,769 --> 00:12:35,967 Refrigeration is for cold! 222 00:12:35,967 --> 00:12:37,628 See, here’s an air conditioner. 223 00:12:37,628 --> 00:12:39,028 This is the condenser, 224 00:12:39,028 --> 00:12:40,376 that’s the evaporator. 225 00:12:40,376 --> 00:12:42,036 The evaporator goes inside. 226 00:12:42,036 --> 00:12:44,002 Condenser goes outside 227 00:12:44,002 --> 00:12:46,063 (unless of course you have a portable air conditioner). 228 00:12:46,063 --> 00:12:49,676 But, but but the job of the air conditioner is to take heat out. 229 00:12:49,676 --> 00:12:50,333 Duh. 230 00:12:50,741 --> 00:12:52,348 Here’s a central air conditioner. 231 00:12:52,348 --> 00:12:54,042 This is the condensing unit. 232 00:12:54,042 --> 00:12:56,407 It has the compressor and the condenser. 233 00:12:56,407 --> 00:12:59,840 Heat comes out of here, and that’s - that's just the way it is. 234 00:12:59,840 --> 00:13:02,888 The evaporator sits above my furnace and makes the air colder 235 00:13:02,888 --> 00:13:05,759 and seven months out of the year, uh, sits pretty. 236 00:13:05,759 --> 00:13:07,425 Here’s a mini-split air conditioner. 237 00:13:07,425 --> 00:13:08,877 This is the condensing unit, 238 00:13:08,877 --> 00:13:12,805 and inside is a self-contained evaporator and blower. 239 00:13:12,805 --> 00:13:16,145 Ah but this is also the evaporating unit, 240 00:13:16,145 --> 00:13:20,150 and inside is a self-contained condenser and blower! 241 00:13:20,150 --> 00:13:24,676 This is reversible, and so is also a heat pump. 242 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, 243 00:13:30,547 --> 00:13:35,765 but mechanically they're something like 95% identical. 244 00:13:35,765 --> 00:13:38,841 There are some technological improvements in the mini-split 245 00:13:38,841 --> 00:13:43,670 like a variable-speed compressor and more intelligent controls which help it gain efficiency, 246 00:13:43,670 --> 00:13:48,286 but fundamentally the heat pump is no different from the air conditioner. 247 00:13:48,286 --> 00:13:52,753 It’s a compressor, a metering device, a refrigerant lineset, two heat exchangers, 248 00:13:52,753 --> 00:13:56,584 and a fan of some sort to force air through each heat one. 249 00:13:56,584 --> 00:14:00,907 The main difference is that the central system uses the furnace as its indoor blower motor, 250 00:14:00,907 --> 00:14:04,703 and the mini-split has one of its own in the wall-mounted unit. 251 00:14:04,749 --> 00:14:07,659 But the minisplit has one additional component 252 00:14:07,659 --> 00:14:13,449 that changes it from a cooling-only device to efficient year-round climate control. 253 00:14:13,449 --> 00:14:15,589 Let’s start with a closer look at it. 254 00:14:15,589 --> 00:14:21,740 This is a 1.5 ton unit, or 18,000 BTU or about 5250 watts. 255 00:14:21,740 --> 00:14:24,885 The outside unit contains most of its guts and unfortunately 256 00:14:24,885 --> 00:14:27,000 is not very easy to take apart. 257 00:14:27,000 --> 00:14:31,858 That’s not that important, though, as we can see the heat exchanger and refrigerant hoses. 258 00:14:31,858 --> 00:14:32,858 They’re here. 259 00:14:32,858 --> 00:14:33,909 And here. 260 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. 261 00:14:40,429 --> 00:14:42,812 The inside unit is practically the same thing 262 00:14:42,812 --> 00:14:47,009 but it doesn’t have the compressor and the fan’s a linear blower type thing. 263 00:14:47,009 --> 00:14:50,699 Lift this up and there’s the other heat exchanger, plain as day. 264 00:14:50,699 --> 00:14:56,269 The fan forces air through it and exhausts through this swinging vent guide thingy. 265 00:14:56,269 --> 00:15:00,248 The metering device also lives here, I believe it’s a simple capillary tube - 266 00:15:00,248 --> 00:15:02,670 uh, please correct me if I’m wrong. 267 00:15:02,670 --> 00:15:05,406 In any case, it lives at the end of the liquid line, 268 00:15:05,406 --> 00:15:06,985 that’s the smaller of the two, 269 00:15:06,985 --> 00:15:12,321 and is the very last thing the refrigerant goes through before it enters this heat exchanger. 270 00:15:13,200 --> 00:15:14,428 Sometimes. 271 00:15:14,679 --> 00:15:17,417 Let’s get out the thermal camera and observe this thing. 272 00:15:17,417 --> 00:15:22,784 Note that the displayed temperature is likely inaccurate due to different emissivities of materials, 273 00:15:22,784 --> 00:15:24,956 but it’s the visuals that are more important anyway. 274 00:15:24,956 --> 00:15:28,034 When it’s not running, there is no pressure gradient 275 00:15:28,034 --> 00:15:31,761 and the refrigerant pressures in both heat exchangers are roughly equal. 276 00:15:31,761 --> 00:15:36,596 In cooling mode, the compressor works to pull gas out of this heat exchanger 277 00:15:36,596 --> 00:15:38,837 and lower the pressure inside of it. 278 00:15:38,837 --> 00:15:41,125 This lowers the boiling point of the refrigerant, 279 00:15:41,125 --> 00:15:44,956 and any liquid refrigerant remaining in the heat exchanger boils away. 280 00:15:44,956 --> 00:15:47,770 This causes the heat exchanger to get very cold - 281 00:15:47,770 --> 00:15:53,026 in this mode, it’s the evaporator and the refrigerant absorbs latent heat to boil. 282 00:15:53,026 --> 00:15:57,830 It has become a thermal sink and energy in the room is naturally moving into it, 283 00:15:57,830 --> 00:16:00,122 sped up with the help of the fan. 284 00:16:00,122 --> 00:16:02,834 That ultimately makes the air colder. 285 00:16:02,834 --> 00:16:05,861 Meanwhile the outside unit is getting warm. 286 00:16:05,861 --> 00:16:11,096 The compressor is forcing the gas it just pulled out of the evaporator into the condenser. 287 00:16:11,096 --> 00:16:14,563 Under this higher pressure, its boiling shoots up - 288 00:16:14,563 --> 00:16:20,489 way above the ambient temperature out here, so the refrigerant will condense inside the pipes. 289 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 290 00:16:27,334 --> 00:16:30,907 is now being expelled out here as it recondenses. 291 00:16:30,907 --> 00:16:34,890 That heat energy was pumped from inside to outside, 292 00:16:34,890 --> 00:16:37,656 and that’s what air conditioners do. 293 00:16:37,656 --> 00:16:39,367 But here’s where things get interesting. 294 00:16:39,367 --> 00:16:41,328 Let’s ask a simple question. 295 00:16:41,328 --> 00:16:43,697 What if the roles could be reversed? 296 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? 297 00:16:49,772 --> 00:16:53,316 That would be pumping heat but in the other direction. 298 00:16:53,316 --> 00:16:59,181 Well, of course, it is absolutely possible and frankly stupidly easy to accomplish. 299 00:16:59,181 --> 00:17:02,133 All you need to do with a basic system like this 300 00:17:02,133 --> 00:17:05,390 is move the refrigerant through it backwards. 301 00:17:05,390 --> 00:17:06,842 That’s it. 302 00:17:06,842 --> 00:17:09,566 Now, you can’t just run the compressor backwards. 303 00:17:09,566 --> 00:17:12,265 Refrigerant can only go through it in one direction. 304 00:17:12,265 --> 00:17:15,642 But with just a little bit of extra piping and a special valve, 305 00:17:15,642 --> 00:17:19,247 you can change the direction it flows through the rest of the system. 306 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 307 00:17:24,416 --> 00:17:27,965 (aside from the variable speed compressor and a few other particulars) 308 00:17:27,965 --> 00:17:32,579 is that the mini-split has a reversing valve and its associated piping. 309 00:17:32,579 --> 00:17:36,128 This allows refrigerant to flow in the opposite direction, 310 00:17:36,128 --> 00:17:39,359 and that flips the system on its head. 311 00:17:39,359 --> 00:17:43,882 Remember how in cooling mode the restriction was just before the evaporator? 312 00:17:43,882 --> 00:17:49,331 High-pressure liquid refrigerant built up right before it entered this space at the capillary tube. 313 00:17:49,331 --> 00:17:52,729 It would then evaporate in this coil once it made it through 314 00:17:52,729 --> 00:17:55,270 because the pressure in here was quite low. 315 00:17:55,270 --> 00:17:58,508 But, if refrigerant is going the other way, 316 00:17:58,508 --> 00:18:02,536 well now the restriction is at the end of this coil! 317 00:18:02,536 --> 00:18:06,406 High-pressure liquid refrigerant will build up inside of here, 318 00:18:06,406 --> 00:18:11,063 turning this into the condenser where the refrigerant will reject latent heat. 319 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 320 00:18:16,225 --> 00:18:19,707 where it will boil and absorb latent heat from the air. 321 00:18:19,707 --> 00:18:23,165 That makes the outside unit the evaporator. 322 00:18:23,165 --> 00:18:23,972 Take a look. 323 00:18:23,972 --> 00:18:26,803 Here, the mini-split is operating in cooling mode. 324 00:18:26,803 --> 00:18:29,886 The inside unit is the evaporator, absorbing heat, 325 00:18:29,886 --> 00:18:33,040 and the outside unit is the condenser, rejecting it. 326 00:18:33,040 --> 00:18:36,340 This is how we expect air conditioning to work. 327 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, 328 00:18:41,803 --> 00:18:44,867 the reversing valve switches the direction of the refrigerant flow 329 00:18:44,867 --> 00:18:46,988 and the roles become reversed. 330 00:18:46,988 --> 00:18:48,811 When the compressor starts up again, 331 00:18:48,811 --> 00:18:53,529 the outside unit becomes the evaporator, absorbing heat in the refrigerant, 332 00:18:53,529 --> 00:18:59,015 and the inside unit becomes the condenser, rejecting that heat and warming the space. 333 00:18:59,015 --> 00:19:02,314 In a sense, it’s air conditioning the outside air 334 00:19:02,314 --> 00:19:06,876 and using the heat collected from that process to warm the space. 335 00:19:06,876 --> 00:19:08,764 Here’s why this is a big deal. 336 00:19:08,764 --> 00:19:13,051 The actual work being done here is compressing a gas. 337 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 338 00:19:19,104 --> 00:19:22,679 goes into the electric motor which drives the compressor. 339 00:19:22,679 --> 00:19:27,340 The refrigerant changes phases in a natural, spontaneous process. 340 00:19:27,340 --> 00:19:30,631 We just create the right conditions for that to occur. 341 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 342 00:19:36,619 --> 00:19:39,647 as it actually consumes in electricity. 343 00:19:39,647 --> 00:19:41,754 That’s frankly amazing. 344 00:19:41,754 --> 00:19:46,224 It’s like running five space heaters for the cost of one. 345 00:19:46,224 --> 00:19:48,847 And why does it work even when it’s cold outside? 346 00:19:48,847 --> 00:19:52,731 Well, remember that heat energy always wants to spread out. 347 00:19:52,731 --> 00:19:58,737 And also remember that the boiling point of refrigerants is very, very cold at low pressures. 348 00:19:58,737 --> 00:20:02,944 So long as you can get the evaporator colder than the air around it, 349 00:20:02,944 --> 00:20:06,908 it will be able to capture heat energy as the refrigerant boils. 350 00:20:06,908 --> 00:20:09,557 Here the ambient temperature was about 40 degrees, 351 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. 352 00:20:16,329 --> 00:20:19,799 Once the refrigerant is compressed and brought to the inside unit, 353 00:20:19,799 --> 00:20:24,689 it will condense and release that acquired energy which warms the space. 354 00:20:24,689 --> 00:20:28,224 It doesn’t matter that the outside air has less energy in it than inside. 355 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. 356 00:20:33,197 --> 00:20:36,229 The outside air may have a lower energy concentration, 357 00:20:36,229 --> 00:20:40,871 but the refrigerant’s energy concentration can be made even lower than that. 358 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. 359 00:20:47,834 --> 00:20:52,325 Since the refrigerant will hold onto that energy and release it when it condenses, 360 00:20:52,325 --> 00:20:57,159 just compress it to raise its boiling point, move it inside and boom! 361 00:20:57,159 --> 00:20:59,313 Heat from the cold. 362 00:20:59,313 --> 00:21:01,501 But it's not all sunshine and rainbows. 363 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) 364 00:21:06,224 --> 00:21:10,781 is that as it gets colder outside, their effectiveness is reduced. 365 00:21:10,781 --> 00:21:16,603 The Coefficient of Performance, or COP, describes how much heat energy the heat pump moves 366 00:21:16,603 --> 00:21:18,850 compared to how much it consumes. 367 00:21:18,850 --> 00:21:22,676 A COP of 1 is… bad. 368 00:21:22,676 --> 00:21:26,104 That’s just a one to one ratio, the same as resistive heating. 369 00:21:26,104 --> 00:21:30,209 But a COP of 4 is easily attainable under decent conditions. 370 00:21:30,209 --> 00:21:33,489 That’s pretty much any time it’s a few degrees above freezing. 371 00:21:33,489 --> 00:21:38,113 Once you’re close to freezing, though, well there’s a complication. 372 00:21:38,113 --> 00:21:42,630 You probably know that an air conditioner removes moisture from inside your home. 373 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. 374 00:21:48,554 --> 00:21:52,359 Well, if the evaporator is outside... 375 00:21:52,359 --> 00:21:55,208 then it’s probably gonna collect some moisture. 376 00:21:56,308 --> 00:21:57,561 It does. 377 00:21:57,561 --> 00:22:02,912 Now, that actually helps with heating since water releases latent heat when it condenses, 378 00:22:02,912 --> 00:22:06,776 but if it’s close to or below freezing outside… 379 00:22:06,776 --> 00:22:12,484 well that water turns to ice once the heat pump has gobbled up its heat energy. 380 00:22:12,484 --> 00:22:17,593 Over time, heat pumps like this build up a coating of frost on the outside unit. 381 00:22:17,650 --> 00:22:21,168 How quickly this happens depends a lot on environmental conditions - 382 00:22:21,168 --> 00:22:23,530 if it’s a dry day, it’ll happen slowly. 383 00:22:23,530 --> 00:22:26,650 But if it’s humid, it happens pretty fast. 384 00:22:26,650 --> 00:22:28,970 And this reduces its effectiveness. 385 00:22:28,970 --> 00:22:33,937 Not only does ice on the coils provide a layer of insulation which slows the process 386 00:22:33,937 --> 00:22:35,903 of scavenging heat from the air, 387 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. 388 00:22:43,030 --> 00:22:44,250 How do we deal with this? 389 00:22:44,250 --> 00:22:46,490 Well, it’s actually pretty easy. 390 00:22:46,490 --> 00:22:50,910 You can defrost the coil simply by briefly reversing the refrigerant flow. 391 00:22:50,910 --> 00:22:52,899 That will melt the frost that’s built up 392 00:22:52,899 --> 00:22:56,440 at the expense of pulling a little energy back outside. 393 00:22:56,440 --> 00:23:01,710 Since this unit has no other means of defrosting, it has to do it fairly cleverly. 394 00:23:01,710 --> 00:23:04,419 Sensors help it determine when it needs to defrost - 395 00:23:04,419 --> 00:23:07,993 a huge benefit of the unit being self contained like this 396 00:23:07,993 --> 00:23:11,266 is that it knows both the inside and outside temperature, 397 00:23:11,266 --> 00:23:15,606 and by monitoring refrigerant pressure it can determine how well it’s working. 398 00:23:15,606 --> 00:23:20,210 Observe here that prior to defrosting, it kept increasing the speed of the compressor 399 00:23:20,210 --> 00:23:22,869 to counteract the slowing effects of the ice. 400 00:23:24,430 --> 00:23:32,117 [a mechanical buzzing which successively increases in pitch and intensity] 401 00:23:43,770 --> 00:23:47,173 Eventually, though, it decides to defrost. 402 00:23:47,833 --> 00:23:49,401 [buzzing stops] 403 00:23:49,401 --> 00:23:54,920 When it defrosts, it first stops the compressor and then stops both fans. 404 00:23:54,920 --> 00:23:57,326 That makes sure it doesn’t blow cold air inside 405 00:23:57,326 --> 00:24:00,560 and allows the outside coil to get hotter. 406 00:24:00,560 --> 00:24:03,347 It then restarts the compressor in cooling mode, 407 00:24:03,347 --> 00:24:06,940 once again turning the outside coil into the condenser. 408 00:24:06,940 --> 00:24:10,978 The heat it’s pulling from inside quickly melts the ice. 409 00:24:11,826 --> 00:24:14,326 [compressor buzzing again] 410 00:24:16,839 --> 00:24:18,963 Once it’s concluded that it’s done, 411 00:24:18,963 --> 00:24:21,925 it stops, reverses the refrigerant flow again 412 00:24:21,925 --> 00:24:26,687 and starts the outdoor fan and compressor to begin collecting heat once more. 413 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. 414 00:24:32,440 --> 00:24:36,763 To the user, a defrost simply seems like a pause in heating, 415 00:24:36,763 --> 00:24:40,556 but as you’ve seen it’s actually much more complicated than that. 416 00:24:40,556 --> 00:24:44,880 However, this reduces its efficiency and ultimately its effectiveness. 417 00:24:44,880 --> 00:24:51,926 On cold, humid days it has to defrost rather frequently, limiting its output, and reducing efficiency. 418 00:24:51,926 --> 00:24:54,196 How do we measure efficiency? 419 00:24:54,196 --> 00:25:00,397 Well, because this is the US, we use weird units like SEER and HSPF. 420 00:25:00,397 --> 00:25:04,766 This unit has a SEER of 19, which is pretty great actually! 421 00:25:04,766 --> 00:25:07,950 That’s equivalent to a COP of 5.5. 422 00:25:07,950 --> 00:25:12,009 But the seasonal energy efficiency ratio describes cooling. 423 00:25:12,009 --> 00:25:16,009 Its HSPF, heating seasonal performance factor, 424 00:25:16,009 --> 00:25:17,624 is 10. 425 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, 426 00:25:23,829 --> 00:25:27,312 at least according to how it’s tested, 2.9. 427 00:25:27,312 --> 00:25:29,791 So over a typical heating season, 428 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. 429 00:25:35,920 --> 00:25:38,713 Some days it’ll be better, others worse. 430 00:25:38,713 --> 00:25:44,275 Over time, though, it would need roughly a third the electricity of a plain resistive heater 431 00:25:44,275 --> 00:25:46,433 to produce the same amount of heat. 432 00:25:46,433 --> 00:25:47,965 But there’s a catch. 433 00:25:47,965 --> 00:25:51,817 This thing is only rated to work down to 5 degrees. 434 00:25:51,817 --> 00:25:54,498 Now, it will work below that temperature! 435 00:25:54,498 --> 00:25:58,075 In fact, here’s some footage I made when it was ten below zero. 436 00:25:58,986 --> 00:26:01,303 [camera audio] Oh my goodness it's cold out here. 437 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 438 00:26:04,990 --> 00:26:09,642 blowing colder than ambient air at me! 439 00:26:09,642 --> 00:26:11,739 Yeah, so I'm gonna go inside. 440 00:26:11,739 --> 00:26:16,258 I know this is a terrible tool for this job but it’s what I had. 441 00:26:16,258 --> 00:26:21,766 It was still running and producing some heat, but to be fair it was pretty tepid. 442 00:26:21,766 --> 00:26:23,649 It was also running its guts out 443 00:26:23,649 --> 00:26:28,456 so its coefficient of performance in this scenario may have been just 1, 444 00:26:28,456 --> 00:26:30,777 or maybe slightly better. 445 00:26:30,777 --> 00:26:34,858 This particular heat pump just isn’t equipped to handle weather this cold. 446 00:26:34,858 --> 00:26:37,203 Which, to be clear, is fine for me. 447 00:26:37,203 --> 00:26:40,704 This thing is in my garage and the heating is mostly a bonus. 448 00:26:40,704 --> 00:26:45,639 I installed it mainly to remove moisture because summers here are stupid humid. 449 00:26:46,161 --> 00:26:49,960 Seriously, I left the leather seats from my family’s old minivan’s in here 450 00:26:49,960 --> 00:26:55,820 my first summer and by the fall they were completely covered in mold. 451 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 452 00:27:01,161 --> 00:27:04,270 air conditioning was practically a must. 453 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. 454 00:27:09,140 --> 00:27:13,320 When it’s above freezing, the air this thing blows is proper hot! 455 00:27:13,320 --> 00:27:15,770 Like, it genuinely surprised me. 456 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. 457 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. 458 00:27:28,870 --> 00:27:31,895 And even when it’s colder and not that efficient, 459 00:27:31,895 --> 00:27:35,576 it has a freeze protection mode that keeps the temperature at 45 degrees, 460 00:27:35,576 --> 00:27:39,348 which is enough to melt the snow off my car after a drive and, well, 461 00:27:39,348 --> 00:27:42,525 that is a very nice luxury, I'll tell ya that. 462 00:27:42,525 --> 00:27:44,649 I usually leave it in that mode. 463 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. 464 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. 465 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. 466 00:28:00,797 --> 00:28:04,059 But it could also be natural gas or another fuel. 467 00:28:04,059 --> 00:28:08,480 In whole-home systems with heat pumps, the backup heat is often called emergency heat 468 00:28:08,480 --> 00:28:14,210 or auxiliary heat, and many thermostats are designed to control these systems as one. 469 00:28:14,210 --> 00:28:19,681 But, even in my climate, on many days a heat pump would be all I need. 470 00:28:19,681 --> 00:28:24,084 In fact, that’s the case for the vast majority of the winter. 471 00:28:24,084 --> 00:28:28,500 It’s not actually all that often that it dips below 5 degrees here. 472 00:28:28,500 --> 00:28:32,920 And still, some heat pumps like this are rated down to 20 below zero! 473 00:28:32,920 --> 00:28:36,540 It’s extremely rare for it to get colder than that here. 474 00:28:36,540 --> 00:28:40,920 Heat pumps can be made to work in colder temperatures through different refrigerants, altered designs, 475 00:28:40,920 --> 00:28:44,961 or through electric defrost coils where the outside unit has dedicated heaters 476 00:28:44,961 --> 00:28:48,685 to allow it to defrost while still operating in heating mode. 477 00:28:48,685 --> 00:28:50,930 But let’s set aside those potential fixes. 478 00:28:50,930 --> 00:28:54,315 Here’s a question I’ve been asking a lot lately: 479 00:28:54,315 --> 00:28:57,543 Why isn’t this thing also a heat pump? 480 00:28:57,543 --> 00:29:00,087 This HVAC system isn’t even two years old 481 00:29:00,087 --> 00:29:03,789 but no one even bothered giving me the option for a heat pump. 482 00:29:03,789 --> 00:29:08,435 Yes, it’s cold enough where I live that a gas-fired furnace is the norm, 483 00:29:08,435 --> 00:29:13,453 but I’ve got 95% of a reversible heat pump sitting right here! 484 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, 485 00:29:20,066 --> 00:29:24,116 but on mild days - so the ones a heat pump would be best at - 486 00:29:24,116 --> 00:29:26,359 that’s more than I need anyway. 487 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. 488 00:29:33,431 --> 00:29:36,685 30,000 BTU continuously would have covered that, 489 00:29:36,685 --> 00:29:40,190 but yes I know that output wouldn’t have been possible at that ambient temp. 490 00:29:40,190 --> 00:29:42,000 I'm just spitballin’ here. 491 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. 492 00:29:46,390 --> 00:29:48,905 In fact, a patron of the channel has one and 493 00:29:48,905 --> 00:29:51,650 they’re actually a little farther North than I am! 494 00:29:51,650 --> 00:29:56,259 This outdoor unit is practically the exact same thing as the condensing unit 495 00:29:56,259 --> 00:30:01,970 for my A/C system, save for the reversing valve and a more complicated compressor setup. 496 00:30:01,970 --> 00:30:07,470 It functions exactly as the mini-split does, doing the same periodic reversing to defrost. 497 00:30:07,470 --> 00:30:11,500 I mean, there’s snow on the ground yet it’s still working! 498 00:30:11,500 --> 00:30:16,891 Since this is almost the exact same machine as mine, it annoys me endlessly 499 00:30:16,891 --> 00:30:21,190 that reversibility isn’t just standard at this point. 500 00:30:21,190 --> 00:30:25,268 In fact, in the South reversible heat pumps in this form factor are pretty common, 501 00:30:25,268 --> 00:30:27,052 and have been for years. 502 00:30:27,052 --> 00:30:30,343 Since heating demand is usually mild if any in the South, 503 00:30:30,343 --> 00:30:33,510 relatively few folks have natural gas for heating. 504 00:30:33,510 --> 00:30:35,910 When you’re all-electric and have air conditioning, 505 00:30:35,910 --> 00:30:39,720 you might as well have a heat pump to save money on heating costs. 506 00:30:39,720 --> 00:30:43,006 And since all it really takes is a reversing valve and a few other particulars 507 00:30:43,006 --> 00:30:46,779 to make that happen, I see it as a no-brainer. 508 00:30:46,779 --> 00:30:48,779 Well, usually. 509 00:30:48,779 --> 00:30:52,917 When a large, disruptive weather event takes hold that causes an entire region 510 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, 511 00:30:57,991 --> 00:31:01,760 that can put an untenable strain on the electric grid. 512 00:31:01,760 --> 00:31:06,860 When this video was published, Texas had just gone through one of these extreme events. 513 00:31:06,860 --> 00:31:10,956 Heat pumps certainly were not the cause of the grid failures, to be clear, 514 00:31:10,956 --> 00:31:14,218 as a lot of issues occurred on the generation side of things 515 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. 516 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. 517 00:31:25,179 --> 00:31:29,120 But so far, we’ve just been talking about air source heat pumps. 518 00:31:29,120 --> 00:31:34,210 These are definitely the most common because, well, they’re easy and simple to make. 519 00:31:34,210 --> 00:31:37,700 But there are other sources of heat to be tapped into. 520 00:31:37,700 --> 00:31:41,259 And heat pump technology is finding itself in more and more places 521 00:31:41,259 --> 00:31:45,290 as we discover the benefits of moving heat rather than creating it. 522 00:31:45,290 --> 00:31:48,424 In part 2, we’ll look at some of these solutions 523 00:31:48,424 --> 00:31:51,552 and discuss where heat pumps have to go from here. 524 00:31:51,552 --> 00:31:55,802 We’ll also look at some cost/benefit comparisons both from a financial perspective 525 00:31:55,802 --> 00:31:58,450 and from a climate change perspective. 526 00:31:58,450 --> 00:32:02,521 And that’s a key reason heat pumps will undoubtedly see more widespread use 527 00:32:02,521 --> 00:32:03,840 as time goes on. 528 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 529 00:32:09,762 --> 00:32:13,050 than you would burning natural gas onsite. 530 00:32:13,050 --> 00:32:14,336 Let me explain that. 531 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 532 00:32:19,588 --> 00:32:22,290 according to the Energy Information Administration. 533 00:32:22,290 --> 00:32:26,042 Now, if you run electric resistive heat from this source of energy, 534 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. 535 00:32:32,480 --> 00:32:36,624 Not bad, but you can also burn natural gas in an onsite furnace 536 00:32:36,624 --> 00:32:39,960 and get more than 90% of the energy out of it. 537 00:32:39,960 --> 00:32:44,815 It’s for that reason that areas like mine tend to have natural gas infrastructure 538 00:32:44,815 --> 00:32:47,150 capable of delivering it directly to homes. 539 00:32:47,150 --> 00:32:50,990 Historically it’s been cheaper, easier, and more efficient. 540 00:32:50,990 --> 00:32:54,630 But, when a heat pump is running at a COP of 2.5, 541 00:32:54,630 --> 00:32:58,967 sure you’re still only getting 40% of the energy from the natural gas, 542 00:32:58,967 --> 00:33:03,148 but with it you’re moving 2.5 times that amount. 543 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. 544 00:33:08,977 --> 00:33:11,309 And you can even get more than that! 545 00:33:11,309 --> 00:33:15,941 A heat pump is frankly the most effective way to turn electricity into heat, 546 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 547 00:33:21,333 --> 00:33:23,580 and can help lower emissions. 548 00:33:23,580 --> 00:33:28,559 And they also make renewable energy sources much more feasible in cold climates. 549 00:33:28,559 --> 00:33:33,640 While you certainly can use the output from wind or solar to heat your home resistively, 550 00:33:33,640 --> 00:33:37,429 that takes a lot of output and makes storage hard to manage. 551 00:33:37,429 --> 00:33:42,120 If everyone had very efficient heat pumps, that energy demand could be cut into a quarter 552 00:33:42,120 --> 00:33:44,120 or perhaps a little less. 553 00:33:44,120 --> 00:33:47,292 And while heat pumps like this struggle in cold weather, 554 00:33:47,292 --> 00:33:48,815 there is an alternative. 555 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 556 00:33:55,435 --> 00:33:58,479 with heat pumps even in cold climates. 557 00:33:58,479 --> 00:34:01,527 And we’ll talk about those, some other novel uses for heat pumps, 558 00:34:01,527 --> 00:34:06,283 as well as the need for more climate-friendly refrigerants in the next video. 559 00:34:06,283 --> 00:34:08,607 For now, stay warm! 560 00:34:09,455 --> 00:34:12,146 ♫ coefficient of smooth jazz ♫ 561 00:34:13,277 --> 00:34:17,723 and that, if you could capture the heat energy out of... 562 00:34:18,634 --> 00:34:19,674 [goofy noise] 563 00:34:19,674 --> 00:34:22,570 well we're gonna restart this line because. Oh cripe. 564 00:34:23,732 --> 00:34:25,349 Eurggh! 565 00:34:25,349 --> 00:34:28,802 Just my terrible teleprompter causing me problems again. 566 00:34:28,802 --> 00:34:31,053 And the thing is, air condish... 567 00:34:31,053 --> 00:34:32,398 and the..pff 568 00:34:32,398 --> 00:34:33,324 heh. 569 00:34:33,324 --> 00:34:33,943 Ehehhe. 570 00:34:33,988 --> 00:34:38,444 ...allows us to manipulate the ambient pressure the refrigerants experience. 571 00:34:38,444 --> 00:34:40,227 The S is on the wrong word. 572 00:34:40,227 --> 00:34:42,446 That line needs an on-the-fly re-write! 573 00:34:42,446 --> 00:34:43,802 Those are always great. 574 00:34:44,651 --> 00:34:48,320 ...boiling point shoots way up. Wayyu... 575 00:34:48,320 --> 00:34:50,705 the, there are words missing! 576 00:34:50,705 --> 00:34:54,905 This is, incidentally, the principle on which automatic rice cookers work. 577 00:34:54,905 --> 00:34:56,629 Another plug? 578 00:34:56,629 --> 00:34:58,862 Dammit! 579 00:35:01,563 --> 00:35:05,708 I hope you're pumped for part 2. 580 00:35:05,708 --> 00:35:08,151 I know I am. 581 00:35:08,151 --> 00:35:10,823 Gonna talk about them coolant pipes. 582 00:35:10,823 --> 00:35:12,777 Digging wells. 583 00:35:12,777 --> 00:35:13,489 All that.