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Heat Pumps: the Future of Home Heating

Apr 12, 2024
Well, I'm excited. What if I told you that all the energy you need to

heat

your

home

on a cold winter day can be found... outside? And if you could capture

heat

energy from outside and move it inside your

home

, you could feel comfortable using a fraction of the energy of other methods? It sounds impossible at first, right? If it is colder outside than inside, how hot can you stand? But it is very possible and thanks to heat

pumps

we can do it right now. And that's what this video is about. Heat

pumps

are a very old but also emerging home

heating

technology.
heat pumps the future of home heating
Using a heat pump under ideal conditions requires only one-fifth of the energy required by ordinary electric

heating

. With a coefficient of performance of 2.5 or greater, a heat pump will produce more heat per unit of fuel burned in a power plant than you could get by burning that fuel in your home. This tremendous efficiency virtually guarantees that the heat pump will be the heating technology of the

future

. But what is a heat pump? Oh well, this is where we need to talk about some terminology and also who the primary audience is for this video. I'm making this video primarily for an American audience because we've made it in a strange order.
heat pumps the future of home heating

More Interesting Facts About,

heat pumps the future of home heating...

We've had air conditioning in many homes (and cars, for that matter) for a long time. Air conditioning has been more or less standard equipment in American homes for more than 50 years, even in a climate like mine where winters can be brutally cold. And in places like the American South, air conditioning is practically a requirement for basic survival. And air conditioners ARE heat pumps. However, heat pumps, especially in regions like mine, are a fairly new thing. Confused yet? Well, in some other parts of the world what we call a heat pump is known as reverse cycle air conditioning, and that should give you a pretty solid idea of ​​what's going on.
heat pumps the future of home heating
But, since this wouldn't be Technology Connections without an explanation of the refrigeration cycle, let's get into the nitty-gritty of latent heat and the magic of refrigerants. If you want to skip this part, go to Let's start with a refrigerator - almost everyone has one of those. What exactly does your refrigerator or freezer do? Well, it needs its inside to be colder than its outside. This is more complicated to achieve than it seems at first glance. It has to extract thermal energy from itself. See, that's what happens with temperature. What we call temperature is actually the concentration of thermal energy in a given space.
heat pumps the future of home heating
If there is a lot of energy accumulated in a space, it is hot. If the energy is really dispersed, it is cold. And thanks to entropy, energy always wants to spread or move from areas of high concentration to areas of low concentration. The inside of this freezer is about 5 degrees below zero. But the room it's in is much warmer than that, around 65 degrees. Because the energy around the freezer is more concentrated, ambient energy wants to spill into it. Wherever there is a temperature gradient, nature is hot and bothered, frankly, and would very much like to achieve equilibrium.
Thus, over time, the inside of the freezer will warm up. We can slow it down by adding a lot of insulation or modifying its design (in fact, this freezer and this footage were featured in a video discussing that very topic), but eventually we must work to reverse this process and keep its interior cold. in relation to its exteriors. And for this we use a heat pump. A cooling system collects thermal energy in one location and disperses it to another. Pumps heat. We'll see how it does this shortly, but the key thing I want you to recognize here is that even though it's very cold inside, there is thermal energy there.
The freezer's heat pump collects it from a very cold place, but in doing so it generates heat. The sides of the freezer get hot when it's running, and that's the heat it draws from the inside and exhausts into the surrounding air. What makes this possible is a coolant. Refrigerants are gaseous chemical compounds with a particularly useful property: boiling points are easy to manipulate. For example, R-134a boils at 15 degrees below zero, or -26 degrees Celsius. That's pretty cold. But here's a can. It's a liquid here. How can it be? Well, like any chemical substance, its boiling point is affected by ambient pressure.
Do you know how the boiling point of water at sea level is defined? This is because in higher areas of the atmosphere, where there is less atmospheric pressure, it is easier for water to boil. A rather crude way of thinking about it is that being under pressure squeezes all the molecules together and that force provides an additional barrier to the phase change from liquid to gas. When there is less pressure, it can change phases a little more easily, which reduces the amount of heat energy it needs to start boiling and therefore its boiling point. When there is more pressure, everything stays together and the opposite happens; its boiling point increases.
Because it is trapped in this can, it is under higher pressure and can remain liquid. But when something changes phase, it needs to absorb or release heat as it does so. This latent heat is not something we can directly feel, but it is an enormous amount of energy. For example, getting a given amount of water to vaporize requires approximately seven times more energy than bringing it from room temperature to its boiling point. In other words, if it took 10 minutes to boil a pot of water over high heat, it will take 70 more minutes for it to completely evaporate.
That extra energy is used to release the molecules from their liquid phase to the vapor phase, but it does not heat the water further. This is, by the way, the principle according to which automatic rice cookers work. Another plug? Just because! How about a third? We just saw what the release of latent heat looks like in the reusable hand warmer video. Simply by falling from the liquid phase to the solid, sodium acetate heats up. Its latent heat of fusion is released as it crystallizes, meaning it gets hotter, almost as hot as its melting point. To reset it, a solid hand warmer is placed in boiling water where, now that it is colder than the surroundings, the heat will spill over and cause it to melt.
In doing so, it reabsorbs its latent heat of fusion and, because it can be supercooled without freezing, can store it for later use. Refrigerants, like water and sodium acetate, have to absorb and release latent heat to change phase. What makes them useful is that thanks to their flexible boiling points, we can force this to happen and use it to our advantage. All we need to do is create a machine that allows us to manipulate the ambient pressure that the refrigerant experiences. Refrigeration systems are nothing more than a closed circuit of pipes filled with a refrigerant that uses its latent heat of vaporization to move energy.
Using a compressor to create a pressure gradient allows us to force the refrigerant to condensate, thus releasing its latent heat of vaporization. We can then force it to evaporate and reabsorb its latent heat. Do this in two different places and you will pump heat through a thermal barrier. Now I would like to show you what this looks like. Those of you who stopped by, welcome back! We're still talking about how refrigeration works, but I wanted you to come back for this. Thanks to a student at Front Range Community College's Integrated Manufacturing Center who had hands-on learning with these, I have some great images to share of a refrigeration demonstration rig.
This is used to demonstrate all kinds of cooling technologies and learn how to fix them, but for now I just want to highlight the basics. Inside these pipes is a refrigerant. If you follow them you will see that they form a circuit. The compressor is the heart of any refrigeration system (it pumps, after all) and it's right here. Airtight refers to the fact that the black container hermetically seals an envelope so that the mechanical compressor and its motor sit inside without letting the refrigerant escape. On the left and right there are two heat exchangers. These are the evaporator and the condenser.
So are the condenser and evaporator. See, they're labeled as both. Because they are. The operation of this platform is reversible, meaning that whether the heat exchanger is an evaporator or a condenser is arbitrary. We'll see how this works in practice shortly, but what's really interesting about this platform is that we can see the liquid refrigerant traveling through it. Many cooling systems will have a sight glass like this, which is useful for diagnosis, but glass pipes? That's a rarity. The refrigerant can only liquefy because the pressure in this pipe is quite high. It first entered the compressor as a low-pressure gas, but when compressed on the high-pressure side it raised its boiling point well above ambient temperature.
The act of squeezing also made him quite hot. The condenser's job is to cool it down again, and it does this by forcing air through metal fins densely bonded to copper pipes. This forms a heat exchanger with a large surface area to help transfer heat from the refrigerant to the air. At this pressure, if the refrigerant were R134a, its boiling point would rise to approximately 130°F, much higher than ambient air temperature. After it leaves the compressor, it is hotter than that, but the air flow through the heat exchanger helps cool it. Once the refrigerant has been cooled to its artificially elevated boiling point, it will begin to condense.
And in doing so, it releases its latent heat of vaporization. Now the refrigerant releases even more energy and will remain near its boiling point until the gas has condensed into a liquid. The result is that the condenser becomes very hot. But where did that thermal energy come from? Well, part of it came from the act of compression itself; Simply compressing a gas heats it because you have compressed its thermal energy into a smaller space, but most of it came from the refrigerant just moments ago. You see, after everything is liquid, some type of metering device retains it at the end of the condenser.
There are several types of metering devices, the simplest of which is a capillary tube, and its job is to create a restriction on the flow of coolant and thus maintain the pressure gradient that we rely on to make all of this work. Once the liquid refrigerant passes through the metering device, it is in another heat exchanger, just like the condenser. But here the pressure is very low thanks to the suction on the inlet side of the compressor. The exact pressure will depend on the refrigerants used and also the conditions, but the pressure is low enough that the boiling point of the refrigerant plummets below ambient temperature.
For the sake of explanation, we will assume that it is zero degrees. And here's the key: to boil, the refrigerant has to absorb its latent heat of vaporization. And now that its boiling point is below room temperature, it will spontaneously start to boil and become very cold. To boil, it initially obtains the latent heat it needs from itself, which brings the remaining liquid to the new boiling point. From there, it will extract energy from the ambient air. See, now that it's colder than the ambient air, the energy from the air will flow into the refrigerant. Remember, energy always wants to spread and now there is a place that is colder than its surroundings for that to happen.
Therefore, the refrigerant absorbs energy from its surroundings as it boils. This heat exchanger is called an evaporator because that is what the refrigerant does. It evaporates here and condenses there. Finally, this is where we look at how we make this work for us and why heat pumps are so great. I mean hot. Very cold or very hot. And why many American audiences may find this whole idea a little baffling. You see, many of us are used to energy flowing in a cooling system in one direction. We have refrigerators that cool the interior. And we have air conditioners that cool our living spaces.
Refrigeration is for the cold! Look, here you have an air conditioner. This is the condenser, that is the evaporator. The evaporator goes inwards. The condenser comes out (unless of course you have a portable air conditioner). But, but the function of air conditioning is to remove heat. Duh. There is a central air conditioning here. This is the condensing unit. It has the compressor and the condenser. The heat comes out of here, and that's how it is... that's how it is. The evaporator sits on top of my boiler and makes the air colder and seven months out of the year, it's nice.
Here you have a mini-split air conditioner. This is the condensing unit and inside there is a self-contained evaporator and fan. Oh,but this is also the evaporation unit and inside there is a self-contained condenser and fan! This is reversible, just like a heat pump. This mini-split heat pump system has a different form factor than the central air conditioning system next door, but mechanically they are about 95% identical. There are some technological improvements to the mini split such as a variable speed compressor and smarter controls that help it gain efficiency, but fundamentally the heat pump is no different from an air conditioner.
It is a compressor, a metering device, a set of refrigerant pipes, two heat exchangers, and some type of fan to force air through each of them. The main difference is that the central system uses the boiler as the indoor blower motor and the mini-split has its own in the wall-mounted unit. But the mini-split has an additional component that turns it from a cooling-only device to efficient year-round climate control. Let's start by taking a closer look. This is a 1.5 ton unit, or 18,000 BTU or approximately 5250 watts. The outdoor unit contains most of its innards and is unfortunately not very easy to disassemble.
However, that's not so important since we can see the heat exchanger and coolant hoses. They are here. And here. The fan forces air through the heat exchanger which wraps around the side so we can see its trim and fins. The indoor unit is practically the same but it does not have a compressor and the fan is a linear blower type. Lift this up and there's the other heat exchanger, plain as day. The fan forces air through it and exhausts it through this oscillating vent guide. The measuring device also lives here, I think it's a simple capillary tube.
Correct me if I'm wrong. In either case, it lives at the end of the liquid line, which is the smaller of the two, and is the last thing the refrigerant passes through before entering this heat exchanger. Sometimes. Let's get out the thermal camera and look at this thing. Please note that the temperature shown is probably inaccurate due to the different emissivities of the materials, but it is the images that are most important anyway. When not running, there is no pressure gradient and the refrigerant pressures in both heat exchangers are approximately equal. In cooling mode, the compressor works to remove gas from this heat exchanger and reduce the pressure inside it.
This lowers the boiling point of the refrigerant and any liquid refrigerant remaining in the heat exchanger evaporates. This causes the heat exchanger to become very cold; In this mode, it is the evaporator and the refrigerant absorbs the latent heat to boil. It has become a heatsink and the energy in the room naturally moves towards it, accelerated with the help of the fan. Ultimately, that makes the air colder. Meanwhile, the outdoor unit is heating up. The compressor is forcing the gas it just removed from the evaporator into the condenser. Under this higher pressure, your boiling goes through the roof, well above the ambient temperature out here, so the refrigerant will condense inside the pipes.
That makes it the condenser, and the same energy that was just absorbed inside when the refrigerant boils is now expelled here as it recondenses. That thermal energy was pumped from the inside to the outside, and that is what air conditioners do. But this is where things get interesting. Let's ask a simple question. What if the roles could be reversed? Is it possible to collect thermal energy in the outdoor unit and expel it from the indoor unit? That would be pumping heat but in the other direction. Well, of course, it's absolutely possible and frankly stupidly easy to achieve.
All you need to do with a basic system like this is move the coolant to the rear. That's all. Now, you can't just run the compressor backwards. Refrigerant can only pass through it in one direction. But with just a little extra tubing and a special valve, you can change the direction it flows through the rest of the system. About the only difference between this mini-split unit and the central air conditioner next to it (aside from the variable speed compressor and a few other details) is that the mini-split has a reversible valve and its associated plumbing. This allows the coolant to flow in the opposite direction, and that turns the system around.
Remember in cooling mode the restriction was just before the evaporator? High-pressure liquid refrigerant accumulated just before entering this space in the capillary tube. It would then evaporate in this coil once it passed because the pressure here was quite low. But, if the refrigerant is going the other way, now the restriction is at the end of this coil! The high pressure liquid refrigerant will accumulate inside here, making it the condenser where the refrigerant will reject the latent heat. Once it does, it's back outside in a low-pressure environment where it will boil and absorb latent heat from the air.
That makes the outdoor unit the evaporator. Have a look. Here, the mini-split is operating in cooling mode. The indoor unit is the evaporator, which absorbs heat, and the outdoor unit is the condenser, which rejects it. This is how we expect air conditioning to work. But switch it to heating mode and after a few minutes of inactivity to allow the pressures to equalize, the reversing valve changes the direction of coolant flow and the roles are reversed. When the compressor starts again, the outdoor unit becomes the evaporator, absorbing heat into the refrigerant, and the indoor unit becomes the condenser, rejecting that heat and heating the space.
In a sense, it is about conditioning the outside air and using the heat collected in that process to heat the space. Here's why this is so important. The real work done here is compressing a gas. Yes, the fans use some power, but almost all of the electrical power this unit consumes goes to the electric motor that drives the compressor. The refrigerant changes phase in a natural and spontaneous process. We simply create the right conditions for that to happen. Thanks to this, this heat pump is capable of moving up to five and a half times more thermal energy than it actually consumes in electricity.
That's downright amazing. It's like running five heaters for the cost of one. And why does it work even when it's cold outside? Well, remember that thermal energy always wants to spread. And also remember that the boiling point of refrigerants is very, very cold at low pressures. As long as you can cool the evaporator more than the air around it, you can capture heat energy as the refrigerant boils. The ambient temperature here was about 40 degrees, but the evaporator coil is much colder than that, so it becomes a place where ambient energy wants to go. Once the refrigerant is compressed and brought to the indoor unit, it will condense and release the acquired energy that heats the space.
It doesn't matter that the outside air has less energy than the inside. All we do when we heat or cool a room is affect the concentration of energy in that room. The outside air may have a lower energy concentration, but the energy concentration of the refrigerant may be even lower than that. That's all it takes: make one region colder than another and thermal energy will always flow to the colder one. Since the refrigerant will hold that energy and release it when it condenses, simply compress it to raise its boiling point, move it in, and boom! Heat from the cold.
But it's not all sunshine and rainbows. The most complicated thing about these types of heat pumps (they are known as air heat pumps) is that as it gets colder outside, their effectiveness is reduced. The coefficient of performance, or COP, describes how much thermal energy the heat pump moves compared to how much it consumes. A COP of 1 is… bad. That's just a one to one ratio, the same as resistive heating. But a COP of 4 is easily achievable in decent conditions. That happens pretty much any time the temperature is a few degrees above freezing. However, once you're about to freeze, a complication arises.
You probably know that an air conditioner removes humidity from inside your home. This happens because the cold surface of the evaporator causes water in the air to condense on it. Well, if the evaporator is outside... then it will probably accumulate some moisture. He does it. Now, that actually helps with heating, since water releases latent heat when it condenses, but if it's near or below freezing outside... well, the water turns to ice once the pump heat has consumed its thermal energy. Over time, heat pumps like this build up a layer of frost on the outdoor unit. How quickly this happens depends largely on environmental conditions: if it's a dry day, it will happen slowly.
But if there is humidity, it happens pretty quickly. And this reduces its effectiveness. Ice on the coils not only provides a layer of insulation that slows down the process of removing heat from the air, but eventually the ice completely prevents air flow through the coil by filling the spaces between the fins. How do we deal with this? Well, it's actually quite easy. You can defrost the coil by simply briefly reversing the refrigerant flow. That will melt the frost that has built up at the expense of getting some energy outside. Since this unit has no other means of defrosting, it has to be done quite cleverly.
Sensors help you determine when you need to defrost; A big advantage of the unit being self-contained in this way is that it knows both the inside and outside temperatures and, by monitoring the refrigerant pressure, you can determine how well it is working. Note here that before defrosting, I kept increasing the compressor speed to counteract the slowing effects of the ice. However, he finally decides to thaw out. When defrosting first it stops the compressor and then both fans. This ensures that you don't blow cold air in and allows the outside coil to heat up. It then restarts the compressor in cooling mode, once again converting the outdoor coil into the condenser.
The heat it extracts from the interior quickly melts the ice. Once it is concluded that it is done, it stops, reverses the refrigerant flow again and turns on the outdoor fan and compressor to begin collecting heat once again. But wait to turn the indoor fan back on until the indoor coil has warmed up a bit. To the user, a defrost appears to simply be a pause in heating, but as you have seen, it is actually much more complicated than that. However, this reduces its efficiency and ultimately its effectiveness. On cold and humid days you have to defrost quite frequently, which limits its performance and reduces efficiency.
How do we measure efficiency? Well, since we're in the US, we use weird units like SEER and HSPF. This unit has a SEER of 19, which is pretty good actually! That is equivalent to a COP of 5.5. But the seasonal energy efficiency index describes cooling. Its HSPF, heating seasonal performance factor, is 10. Fortunately, we can convert it to COP, and that means the average heating performance coefficient of this thing is, at least based on how it's tested, 2.9. Therefore, during a typical heating season, it can be expected to generate almost 3 times more thermal energy than it costs to operate. Some days it will be better, others worse.
However, over time, it would take about one-third the electricity of a simple resistive heater to produce the same amount of heat. But there is a problem. This thing is only rated to operate down to 5 degrees. It will now work below that temperature! In fact, here are some images I took when it was ten degrees below zero. Oh my god, it's cold out here. It's dangerously cold in here, especially standing in front of it, blowing colder than the ambient air at me! Yes, then I'll go in. I know this is a terrible tool for this job, but it's what I had.
It was still running and producing some heat, but to be fair, it was pretty warm. It was also running out, so its coefficient of performance in this scenario may have only been 1, or perhaps a little better. This particular heat pump is simply not equipped to handle such cold weather. Which, to be clear, is fine with me. This is in my garage and the heat is mostly a plus. I installed it mainly to remove humidity because the summers here are stupidly humid. Seriously, I left the leather seats from my family's old minivan here during my first summer and by fall they werecompletely covered in mold.
A few other things were also damaged, so if I wanted to preserve anything of value here, air conditioning was practically a must. But it certainly helps on milder winter days to be able to use it as a workspace. When it's above freezing, the air this thing blows is very hot! It really surprised me. In retrospect, it shouldn't have been that way: 18,000 BTUs is more than three US-spec space heaters. But knowing that the heat it produces comes from outside makes it seem almost magical. And even when it's colder and it's not as efficient, it has a freeze protection mode that keeps the temperature at 45 degrees, which is enough to melt the snow off my car after driving and, well, that's a very nice luxury. nice, I think.
I'll tell you that. I usually leave it in that mode. However, it is true that it alone could not provide me with enough heat throughout the winter. You would need a backup heat source when conditions were not ideal for a heat pump. This is usually electrical resistive heating which will always work but requires a large amount of energy to do so. But it could also be natural gas or another fuel. In home systems with heat pumps, backup heat is often called emergency heat or auxiliary heat, and many thermostats are designed to control these systems as one.
But, even in my climate, many days all I need is a heat pump. In fact, that's the case for the vast majority of winter. In reality, it is not so common here for the temperature to drop below 5 degrees. And yet, some heat pumps like this one are rated as low as 20 degrees below zero! It's extremely rare for it to get colder than that here. Heat pumps can be made to operate in colder temperatures using different refrigerants, modified designs, or using electric defrost coils where the outdoor unit has dedicated heaters to allow it to defrost while still operating in heating mode.
But let's leave those possible solutions aside. Here's a question I've been asking myself a lot lately: Why isn't this also a heat pump? This HVAC system isn't even two years old, but no one bothered to give me the option of a heat pump. Yes, it's cold enough where I live that a gas boiler is the norm, but I have 95% of a reversible heat pump right here! This 2.5 ton air conditioner may only be able to put out half of what my boiler can put out with its fire tubes, but on mild days, i.e. when a heat pump would be better, that's more than what I need anyway.
Heck, even when it was -10 outside, my 70,000 BTU furnace only ran for about 10 hours a day. 30,000 BTUs continuously would cover that, but yes, I know production would not be possible at that ambient temperature. I'm just spitting here. And it's not like heat pump systems are unknown in my danger zone. In fact, one channel user has one and he's actually a little further north than me! This outdoor unit is almost exactly the same as the condensing unit in my air conditioning system, except for the reversing valve and a more complicated compressor setup. It works exactly as the minisplit does, making the same periodic investment to defrost.
I mean, there's snow on the ground but it still works! Since this is almost exactly the same machine as mine, it bothers me to no end that reversibility isn't just standard at this point. In fact, in the South reversible heat pumps in this form factor are quite common and have been for years. Since heating demand is typically light, if any, in the South, relatively few people have natural gas for heat. When you go all electric and have air conditioning, you can also have a heat pump to save money on heating costs. And since all that's really needed is a reversing valve and a few other details to make that happen, I see it as a no-brainer.
Well, usually. When a large, disruptive weather event occurs that causes an entire region to suddenly need resistive heat because it's too cold for its heat pumps to operate effectively, that can put unsustainable pressure on the power grid. When this video was posted, Texas had just gone through one of these extreme events. The heat pumps were certainly not the cause of the grid failures, to be clear, as many problems occurred on the generation side and from what I have read, natural gas backup heat is more common than what I thought. But it's good to keep in mind the occasional need for an energy-intensive backup heat source.
But until now, we have only been talking about air source heat pumps. These are definitely the most common because, well, they are easy and simple to make. But there are other sources of heat that we can take advantage of. And heat pump technology is found in more and more places as we discover the benefits of moving heat rather than creating it. In part 2, we'll look at some of these solutions and discuss where heat pumps should go from here. We will also look at some cost/benefit comparisons from both a financial perspective and a climate change perspective.
And that's a key reason why heat pumps will no doubt see more widespread use as time goes on. I said before that with a COP of 2.5 you will get more heating from a heat pump than from burning natural gas on site. Let me explain that to you. In 2019, the average efficiency of a natural gas power plant in the U.S. was 44 percent according to the Energy Information Administration. Now, if you use resistive electric heat from this energy source, after transmission losses you will end up getting about 40% of the energy from natural gas. Not bad, but you can also burn natural gas in a local furnace and get more than 90% of the energy.
It is for that reason that areas like mine tend to have natural gas infrastructure capable of delivering it directly to homes. Historically it has been cheaper, easier and more efficient. But, when a heat pump operates at a COP of 2.5, sure you are still only getting 40% of the energy from natural gas, but with it you are moving 2.5 times that amount. That means that, in the end, you will get the equivalent of 100% of the natural gas. And you can even get more than that! Frankly, a heat pump is the most efficient way to convert electricity into heat, so even on today's fossil-powered electricity grid, it is a smarter use of limited resources and can help reduce emissions.
And they also make renewable energy sources much more viable in cold climates. While it's true that wind or solar energy production can be used to resistively heat your home, that requires a lot of production and makes storage difficult to manage. If everyone had highly efficient heat pumps, that energy demand could be reduced by a quarter or perhaps a little less. And while heat pumps like this struggle in cold climates, there is an alternative. The geothermal or ground source heat pump is a way to achieve near-constant peak efficiency year-round with heat pumps, even in cold climates. And we'll talk about those, some other novel uses of heat pumps, as well as the need for more climate-friendly refrigerants in the next video.
For now, stay warm! ♫ smooth jazz coefficient ♫ and that, if you could capture the thermal energy of... well, let's restart this line because. Oh, fuck. Eurggh! Only my terrible teleprompter is causing me problems again. And the air conditioning... and the...pff heh. Hahaha. ...allows us to manipulate the ambient pressure that refrigerants experience. The S is in the wrong word. That line needs a rewrite on the fly! Those are always great. ...the boiling point rises. Wayyu... el, words missing! This is, by the way, the principle according to which automatic rice cookers work. Another plug? Damn! I hope you're excited about part 2.
I know. I'm going to talk about those coolant pipes. Digging wells. Everything that.

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