How does a Tesla Heat Pump actually work and why does it matter? From first principles!

it's summertime in the northern hemisphere in fact it's very very hot in the state of georgia right now so of course when i drive my tesla around it's doing a whole lot of work to air condition the car and make the interior of the cabin cool enough that we can be in it without suffering too much but in conversation with tesla owners and people who just have air conditioning etc i realize that there's a big misunderstanding about what an air conditioner is what a heat pump is and why it's important that tesla has heat pumps in its cars now rather than air conditioners let's take a look and find out [Music] hey y'all it's doctor know it all so i want to actually back up a little bit today and i want to talk about kind of working from first principles what air conditioning is how it actually operates tesla's heating and cooling system is actually rather complicated and i'll touch on it to some extent but basically it's not just trying to deal with thermal management of the cabin which is of course us and our comfort but it's also trying to deal with thermal management for the batteries which is really critical because of course as batteries are used and as they charge up they both of those times they produce a lot of heat in that process and so a lot of thermal management has to happen with that and so i'm sure a lot of tesla owners i'm sure most of you have probably heard of the opto valve etc it has a big function in terms of how teslas actually operate efficiently but today i really want to focus more on kind of the primary principles of how a heat pump operates and this actually holds true for your house as well if you have a heat pump or even if you just have an air conditioner it works like that in cooling mode so i think this is actually going to be useful for people but if you're really interested in how the octo valve works and how the heat pump specifically in a tesla works i can do another episode on that but this one's going to be you know enough information just contained in this one particular area so we're going to go kind of from first principles up and we're going to talk about how a heat pump actually operates and then of course why it's so important that tesla now has heat pumps rather than air conditioning and heating units in its cars all right so let's start with what heat actually is there are three types of heat transfer one is radiative and that is something you're probably familiar with just in the sense if you go outside and you look up at the sun and primarily what you're getting the heat from the sun is radiative in other words what it is is electromagnetic waves that go you know 140 that million kilometers or 93 million miles approximately and they go from the sun and they hit the earth and so that's radiation it's direct electromagnetic radiation that hits you same basic thing as you know x-rays or microwaves etc etc so that's all just radiative stuff it's just different frequencies of the electromagnetic spectrum it's what we call infrared is what we feel as heat and of course light is what we see as light but that's radiative heat transfer right there and it's rather inefficient as it turns out and this is actually something that matters a lot in space because in space to get rid of heat from you know if you're on the international space station or something like that to get rid of heat out of the iss there's no good way to do it because radiative heating and cooling is actually very very inefficient but anyway that's the first kind that's from the sun the second is conductive heat transfer and this is something of course if you've ever burned your hand on like a cast iron skillet on the stove you'll understand conductive heating that's basically if you have a material like iron or metal or something like that and you heat part of it it conducts that heat to another portion of that same object right so in other words you're only heating the body of the skillet but the handle will also get hot unless you have something on top of it to keep it from doing that and you're stupid enough to put your hand on it and then you're like oh i burned my hand right so that is conductive heating then the third type of heat is convective heat and that's what we actually deal with most of the time convective heat is air transfer so you've got molecules of air all around you right now and those molecules move at different velocities right so some of them are moving fairly slowly and some of them are moving super super fast but most of them are kind of in the middle and what they do is one that moves like too fast it'll bump into another air molecule that's moving slower you know statistically on average inside of a room and it will transfer some of its high velocity energy into the slower moving particle that thing will speed up the other one of course will slow down somewhat and so therefore the air molecules will actually come into balance so that they're all within a relatively narrow range of velocities and of course anyone that's moving too slow will eventually get hit by something with higher energy which will raise its energy so eventually the air molecules in the room will all move you know like in a bell curve so most of them are in a relative range of velocity and what we feel as heat is simply those air molecules bouncing off of our skin or to be more precise the water molecules so air contains water molecules in it and those water molecules are particularly good at transferring heat they have a high heat capacity so a lot of what we feel so if you go to the desert and they always go it's a desert heat it's a dry heat when they're talking about that they really are actually meaning that there are fewer water molecules in the atmosphere in the air that's around you and because there are fewer water molecules there's less convective heat transfer to your body so it actually does feel cooler in the desert even if it's you know 40 degrees centigrade or something like that if it's 40 degrees centigrade in phoenix arizona versus 40 degrees centigrade in atlanta georgia and atlanta georgia has a much much higher relative humidity than does phoenix arizona normally it's going to feel cooler in phoenix arizona because there are fewer water molecules so anyway water molecules in particular have a big effect on how we feel heat and so relative humidities that go up will cause it to feel hotter because there's more convective heating going on with our skin but basically it's just molecules of air molecules of water etcetera that are floating around impacting our skin that makes us feel hot or cold or something it's the velocity of those things so if they're moving slower than the molecules remember we've got molecules of skin in our skin right and molecules of blood etc if those are generally moving faster than the air molecules around them when you hit it's going to transfer energy away from your skin into those air molecules and so it's going to make you feel cold because you're going to be losing energy to the environment whereas on the other hand in the summertime like it is in the northern hemisphere the air molecules will tend to be hotter than your skin in other words they're going to have a higher velocity and they're going to hit your skin and they're going to transfer energy to your skin and your blood vessels etc and they will make you feel hot and then you will sweat to try to evaporatively cool yourself all right so that's convective heat and that's what really matters convective heat is what we're dealing with with an air conditioner or a heat pump or pretty much any heating unit that you're used to so the goal with convective cooling is to pass warmer air over cold something these happen to be coils and i'm sure you've all seen those little coils with the fins etc in a car in your house or whatever you pass the air over those those fins over those coils and you transfer some of the energy out of the cool liquid or whatever is inside of those coils to the air so so the actual liquid inside of these coils heats up the air cools down and then you blow that out with a fan and of course you blow it into your room or into your car or whatever and that area gets cooler and then of course the opposite happens with heating with heating you take something warmer than the ambient air so you blow cooler air which has lower velocities remember you have a warmer liquid you blow it over those coils again there's an energy transfer from this warmer liquid to the cooler air which is going to increase the velocity of those air molecules you then blow that into the cabin of your car or your house and it feels warmer and interestingly enough this actually tails into a 19th century physicist maxwell who thought of maxwell's demon as a little entity demon not as in like an evil demon even though that's the picture i could find but anyway so he's like a little creature that sits there and he looks around in a room right so imagine you've got a room that's divided in half and it's got equal amounts of like you know some high velocity air molecules some low velocity air molecules and what it does is it has a little gate and it opens and closes that gate whenever it sees like a low velocity air molecule in the room this side my right hand room it'll allow it through when it gets by there and when it sees a high velocity one in my left hand room it allows that through but it blocks it off when other ones are going and what's going to happen over time is that the two rooms will go out of equilibrium right so they started off at the same temperature which is the same velocity generalized velocity of the particles but by separating out these particles you eventually get a bunch of slower moving ones or cooler air in the my left hand room and you get faster moving particles of air or higher temperature in the right hand one and that is a really fascinating thing you can disequilibrium this without any work so this actually created a bit of a conundrum in the 19th century about entropy because the second law of thermal dynamics which is that entropy always has to increase was confused by this whole thing right he was saying basically no work would happen yeah i know it has to open and close a gate but whatever so assuming that there's no actual work going on what is happening well it turns out in the world of physics that information is entropy and that is a very very important aspect of physics and we're not going to get into that today because it's way too far afield but i'd be happy to do an episode on that as well it's a fascinating thing but anyway the idea here is you know to do maxwell's demon is to separate out the cold air from the hot air and what you do is when you're cooling something you want to separate the cold air for the interior of your car's cabin or the interior of your house or something like that and you move the hot air to the outside world to the rest of the universe and you exhaust it right so that's what you're doing and then obviously the opposite happens when you're heating you're moving the warmer high velocity air molecules into the cabin of your car or into the interior of your house and you're exhausting the cold into the universe outside so anyway that's the setup so how does a heat pump actually work well carrier happens to have a really good picture of this which is quite simple and explanatory so i'm going to put that up and talk our way through it and of course i'll put a link to their article in the description so you can look at it if you're interested so let's start on the left hand side of this image so if you look at that indoor coil right before that is a little green arrow that's pointing to the left so what we've got is we've got the flow of fluid in this case it's freon or something along those lines and the reason why we use freon in such a case is because freon just happens to have good properties it happens to boil at around room temperature or 20 degrees centigrade and it happens to recondense there so it's actually a pretty good fluid for that and it also has a high thermal capacity etc you could do the exact same thing with water boiling into steam but the temperature of your house would have to be above 100 degrees centigrade so you know that would be a bit of a problem you would have to live in a place that was hotter than boiling water in order for this to work but it would work with water too so if it's easier for you to imagine this you can imagine this with water but freon just happens to be the same thing as water but it boils around room temperature so it's much better for us humans and also it doesn't really interact with the pipes and things like that so it doesn't corrode the pipes it's in and everything now it does happen to be a terrible greenhouse gas and that was something that we all discovered in the 1970s and 80s so oopsie so you know they're still looking for other compounds that can actually do as well as freon but it turns out freon is really really good at doing this job so the basic deal is to keep these systems as closed as possible and not release freon into the atmosphere as much as possible but that's why we use freon just because it happens to have really good heating and cooling properties right around the temperatures that we are comfortable with so anyway back to this image the indoor coil right so that's the thing that has all the little fins on it that i'm sure you've seen if you've looked at any air conditioner system or anything like that and by the way the heat pump in the cooling mode is exactly like an air conditioner so this actually will tell you how an air conditioner works there's a reversal process that happens for the heating mode and we'll get to that in a minute but in the air conditioning mode it operates like an air conditioner so it's relatively easy to transfer these from one to the other all right so anyway we have a cool liquid that passes through these grid fins which have a lot of contact with the air and remember air molecules are moving around they're bouncing around and they're transferring energy back and forth to this coil so what we're going to do is with that indoor fan we're going to blow warm air over this coil and as we blow this warm air so let's say that you know you're trying to cool your the temperature of your house to like 22 degrees centigrade or something like 74 degrees fahrenheit so what happens is the temperature of that liquid inside the coil is lower than 22 degrees centigrade and so you've got higher let's say it's 25 degrees centigrade inside the house you blow 25 degree centigrade air over this coil energy is transferred to the liquid inside the coil and it's removed from the atmosphere from the air molecules and so that effectively cools the air molecules down and just remember again that what i mean by cooling it down is you're lowering the overall velocity of the air molecules in the room right so they're moving around like this and by passing them over and passing energy into this coil they're now moving around like this so they're slower right a huge exaggeration but that's kind of what happens here so again the way that i'm feeling temperature is just little molecules of air and water bouncing off of my skin so we're just reducing the velocity of those air molecules that's all we're doing here and we're putting that energy we're transferring it right because the energy is conserved we're transferring that energy into this liquid and what's going to happen is as we transfer that energy into the liquid the liquid will evaporate and turn into gas so if we look at the top left of the image here we can see that we've got an evaporation cycle so essentially the liquid that we had at the beginning of the coil turns into gas by the end of the coil it's it's absorbed a whole bunch of energy so again you can imagine something like like water right you're boiling it it takes energy to boil that water so we're boiling that water but we're boiling freon which just so happens to boil around 20 degrees centigrade and we're doing that and we're absorbing energy and it's being transferred to turning this thing into gas and that's how this all works it's a simple energy transfer that's going on thus far we really haven't had to do much work right we have a fan that's blowing and we have to circulate the freon through the system but really there's not a lot of work that's going on the next step is where all of the work and why your air conditioning units at your house burn so much energy during the summer and that is the compressor cycle so what happens in the compressor cycle which is the middle top of the image we've got a relatively low pressure gas coming in from the left which is the blue it compresses it in other words it squeezes that and it turns it into a very high pressure gas and as you might or might not know compressing gas causes it to heat up it's the opposite thing i don't know if you've ever used like a spray paint can or something like that but you know you shake it up and you spray it and it'll start to feel really cold on your hand because what happens is just because the faster moving molecules are going to get out of the can faster you're effectively cooling the can down the velocity of the molecules inside decreases opposite thing happens when you squish air and you you compress that air you're doing work on that air and you're increasing the velocity of that air so the temperature goes up so it becomes a very very hot gas so now we've gone through the compressor stage which takes a huge amount of work right so a lot of electricity and then we have a very very hot gas and now what we're going to do is basically the exact opposite we're going to pass that really hot gas so again let's say the outside temperature is like 30 degrees centigrade but this hot gas inside of this freon pipe is like 40 degrees centigrade so the outside air even though it feels warm to us is going to be very very cool compared to that freon so as we blow air over that hot gas it's going to condense down into a cooler liquid we will of course transfer a great deal of heat energy to the outside atmosphere and that's of course why if you stand next to the outside part of a heat pump or the outside part of an air conditioner and you put your hand up it's blowing out really really hot air it's because it's that energy transfer from the hot gas the hot freon it's cooling that freon down into a cooler liquid it's still a little bit warm but it's fairly cool now but it's transferring all of that heat energy again the velocity of the air molecules into the atmosphere and exhausting it into the universe outside so anyway now we've gotten down to the bottom right of this image which is the condensation part of that image so as it goes through those little fins it condenses out and becomes a liquid again and then finally we get to what's called the expansion valve and the expansion valve is just a way of releasing pressure so this is the same thing as opening up like a soda can so basically you've got this liquid that's still under some pressure but what you're going to do is release that pressure you're expanding it back out again and that expansion causes it to cool down very very rapidly so now we go from a warm liquid right it's condensed but it's still pretty warm but by expanding it out it cools down so it's the opposite of the compressor cycle right but this doesn't take any real work you just open up a valve basically and it expands out and it gets cooler and now it's cool and it's ready to go back and start the whole cycle again right it's ready to receive energy from the atmosphere as you blow warmer air over it inside the house and then it spins around and it goes back through the compressor and it goes back through the evaporative part on the outside and it goes back through the expansion cycle etc etc so that's how a heat pump works in air conditioning mode the cool part about a heat pump is it's completely reversible so what you can do is basically just switch the flow around and so you change the condensation part to the outside so now your outside atmosphere maybe is like five degrees centigrade or like 40 degrees fahrenheit and you're inside you're trying to keep it like 20 degrees centigrade or like 68 70 degrees fahrenheit or something right but what you can do is you can steal some of the fast-moving particles of the outside air to cause the freon liquid to evaporate outside it evaporates and therefore it builds up a whole bunch of heat and then you pass that heat into the inside where it condenses and it transfers the heat as it's condensing it's losing energy it's condensing back into a liquid again it transfers the energy into the interior of your house or into the interior cabin of your car or something right so now you've got a symmetrical system that goes back and forth now the problem with all of this comes about when you get too big of a temperature differential between the inside and the outside usually this happens in cold weather so basically a heat pump stops being very effective around zero degrees centigrade or around freezing or 32 degrees fahrenheit below that it gets less and less efficient because it's trying to pump energy across too high of a gradient so in georgia where i live where the temperatures don't get below freezing often you know they do at night a little bit etc but it's not that big of a deal so a heat pump is a really ideal solution here if you live in the arctic circle you know in like norway or something where it's consistently below freezing for a large chunk of the year you're going to want something like a gas furnace or coal or oil or something like that it's much more efficient in those cases but for us in these more moderate climates heat pumps are actually really really useful and as it turns out the heat pump of course for the tesla is super super useful too because teslas don't have internal combustion right a traditional ice car or internal combustion engine car what it does is if it's winter time and you want to heat your car up and you know it takes forever to heat your car up in the winter because what has to happen is the engine has to turn over and it has to generate a bunch of heat and then you pass air you exchange heat from the engine itself over something right a heat exchanger and then you pump that into the cabin so eventually the cabin will become warm well an electric car has to use resistive heating if it doesn't have a heat pump and resistive heating is just exactly what you imagine it's just a very big resistor so it's like one of those little things that glows red right and you pass air over that and it gets warm inside but that is incredibly energy inefficient it sucks a huge amount of battery power down that's not what you want to do whereas a heat pump can be i think up to five times more efficient in terms of heating than a resistive heater so in air conditioning mode a heat pump doesn't really save all that much it's you know it's basically the same thing as an air conditioner but what you get is you get that reverse cycle where you're able to take heat out of the atmosphere and pump it into the interior of the cabin rather than having to use a resistive heater and of course as an added bonus tesla batteries produce a lot of heat as they're being utilized right so as you're driving it they're generating heat so you can pull that there's a liquid cooling system in the battery compartment you can pull that heat and using the octo valve in a very clever way you can actually heat exchange some of the heat off the batteries and help to heat the interior of your car's cabin as well so you can use the heat pump in combination with a heat exchanger which causes all of this to work even more efficiently so it's really amazing the technology behind how all this works and especially in a tesla is just amazing and if you look at how small the tesla heat pump is compared to ice cars just their air conditioning units it's remarkable how compressed they've got all of this stuff it's really just amazing so anyway there's a huge amount of engineering that goes into this but this episode was mostly just to talk about in principle how all of this works and i hope this has helped to explain you know even if it just helps to explain how your air conditioner or your heat pump in your house works hopefully that's useful but it's also really amazing to see how tesla has miniaturized everything right if you look at your house's heat pump those outside units are just these huge things and then you have an inside blower unit so you've got the two symmetrical things but you've got these two massive units in your house and tesla squished that all down to you know the size of like a can or something it's maybe like two two liter cans worth of volume or something so it's really amazing anyway it's so cool how tesla's done all this stuff all right i hope you enjoyed this episode and found it fun and informative if you did definitely like the video so other people can find it and of course consider subscribing for more of this as always a huge shout out to my patrons on patreon you all are wonderful i really really appreciate your help and your support thank you so much and for those of you interested in investing check out weibull an amazing platform for buying and selling stocks and now cryptocurrencies like bitcoin dogecoin and others open an account and get a free stock valued at up to two hundred dollars and fund your account and get another free stock valued at up to sixteen hundred dollars check out the link in the description and help the channel at the same time thank you and don't forget about our merch store which now has physics as the law everything else is a recommendation which is a quote by elon musk as well as other t-shirts mugs tumblers etc etc check it out in the description and finally don't forget we are both tesla and amazon affiliates if you look in the description you can see how clicking on a link and going shopping helps out the channel and as always feel free to ask me questions in the comments or at my email address which is drno at all knows gmail.com until next time bye [Music] you

Channel: Dr. Know-it-all Knows it all

Views: 80,754

Keywords: dr know it all, dr know-it-all, deep neural networks, Artificial intelligence, self driving, tesla, elon musk, ai, tesla news, tsla, tesla stock, elon, tweet, elon tweet, cybertruck, model 3, model y, Tesla ai, Tesla vision, twitter, vision only, full self driving, fsd, heat pump, Tesla heat pump, how does a heat pump work, Maxwell's demon, entropy, model y heat pump, how does air conditioning work, ac, heat, heat pump vs ac, why is a heat pump better, what is heat, physics, cool

Id: ANSVelhx7ec

Length: 22min 28sec (1348 seconds)

Published: Thu Aug 12 2021