The Tesla Model Y that you will not find in the other Tesla's and this is a heat pump so the challenges with heating the cabin of an electric vehicle and many electric vehicles use resistive heaters for their cabins which are basically a hundred percent efficient so how could there be a better solution than something that's nearly a hundred percent efficient and first off a big the different components involved with the Tesla Model Y heat pump and if you'd like to see a more detailed breakdown of the Tesla Model Y I will include
better understand the problem with electric heating first let's talk about combustion vehicles which happen to be extremely inefficient however this inefficiency turns out to be an advantage in terms of heating the cabin so if you look at an engine a combustion engine well there are coolant jackets around those piston cylinders and these coolant jackets take the heat from those piston cylinders and they circulate it throughout the engine
they circulate it either to the front of the car where you have a radiator and you can reject that heat to the atmosphere or you can send it to a heater core in your cabin and put that heat from the engine and stick it inside your cabin so if you look at the efficiency of a combustion engine if you take the total amount of energy that you have in that fuel about a third of it is wasted as heat in the coolant about a third of it is wasted as heat out the exhaust you just send that energy out in a way and about a third of that energy is then useful to do create mechanical power and do useful work
so from that basically this the coolant wasted heat and this exhaust wasted heat is just completely wasted there's no real use for it however in the case of heating the comment let's say it's cold outside well suddenly there is a use for that wasted heat and so from the coolant you're able to take a portion of that heat and simply stick it inside the cabin and because it was not going to be used otherwise this means it doesn't actually reduce your vehicle's range so if it's cold outside you're not going to lose efficiency because you're simply taking heat from the Accor so how does this differ with electric cars well electric cars often use PTC or resistive heaters and so they are getting the energy to heat that cabin from the battery so the battery is going to send a current through a resistive element that resistive element heats up you blow air across that and then you heat your cabin so you're directly pulling energy from your battery and sticking it inside the cabin
now the way that we measure how efficient these are how effective they are is the coefficient of performance so the coefficient of performance is equal to the heat supplied that's going into your cabin divided by the work required the energy that's coming from your battery and so for these resistive heaters that tends to be about a hundred percent efficiency there so of the heat supplied of the amount of energy that you stick in to that cabin to turn into heat it all turns into heat wonderful the challenge however obviously as you can note is that that heat is coming from the energy from the battery so that means you're actually reducing your range by using this battery to heat the cabin that's why you know in electric cars they'll say use your seat heaters use the steering wheel heater because heating the entire cabin takes a lot more energy than just heating up a seat or maybe a steering wheel so it does actually affect your range the advantage of using these resistive heaters is that it's instant the second you get in the car you turn on the heat
you're already getting hot air that's a beautiful thing no electric cars still have radiators so why don't we use those radiators that wasted heat that it's obviously being rejected from the motors and controllers and battery why aren't we using that heat to heat the cabin well you can but there are a few challenges associated with it so those three challenges are first of all electric cars are significantly more efficient which means there's just less heat overall that you're going to reject now because they're so much more efficient that means it's going to take a lot more time to heat up that coolant so that means if you're gonna wait for the coolant to be hot so that you can be warm in the cabin it's gonna take forever to do so you have to wait with combustion vehicles but because combustion vehicles are so inefficient it doesn't take that long to get some heat out of it
finally electric carsten have lower peak temperatures with their coolant electronics are more sensitive to temperature than combustion engines and so the coolant temperature is often kept lower meaning your differential in temperature between your coolant and your cabin will be smaller so it's not going to be as effective at heating your cabin versus using that really hot coolant that engines make
so what does the Tesla Model Y do well the Tesla model is a heat pump and heat pumps are nothing new they've been around for quite some time and in fact Nissan claims they were actually the first to use one in a production vehicle in a mass-produce vehicle Nissan had the first in the Nissan Leaf but it is certainly a more efficient way of putting heat within the cabin of an electric vehicle so how does it work so here we have a diagram of a simplified heat pump
essentially it operates just like an air conditioning system however the order of operations is reversed and so we have our four components are four main components here in actuality it will be a bit more complicated than what we have on the whiteboard but as a basic overview you have a compressor a condenser and expansion valve and an evaporator
so you're taking that compressor and you're compressing a gas refrigerant so you have a refrigerant circulating throughout this cycle here and it's entering the compressor at a low pressure in a low temperature as a gas you then compress that refrigerant and now is at a high pressure and a high temperature and it is still I guess it then goes into the cabin of your vehicle and it enters the condenser so the condenser starts to cool down this very high pressure very high temperature gas and so it changes from a gas into a liquid as it's passing through and you're blowing air across this condenser into the cabin in order to heat the cabin so you're taking heat out of this condenser and putting it into the cabin so you now have still a very high pressure high temperature liquid that is leaving this condenser not too much heat overall compared to how hot this is was actually extracted from
that high-pressure high-temperature liquid then goes to an expansion valve and that expansion valve basically controls the rate at which you allow the liquid to enter an so you're slowing down the rate at which this liquid is entering here and so that's dropping its temperature and dropping its pressure dramatically so it's still a liquid but you've reduced its pressure and temperature and then it moves through an evaporator and so now the outside air is blowing across this evaporator and it's heating it up so it's heating up that liquid and then the liquid is boiling absorbing a bunch of energy and changing into a gas so then you have a gas that is entering that compressor that's at a very low temperature and a very low pressure and you compress it and the cycle repeats itself so you're compressing that energy and you're taking energy from outside the vehicle compressing it down sticking it in a condenser and then extracting that heat extracting that energy and putting it inside of the cabin and this gives you a coefficient of performance of about three to four so remember before we're looking at the amount of work required versus the heat supplied we're getting a coefficient of about three to four verses with the resistive heater we're looking at a coefficient of performance of just one so how in the world can something be three or four hundred percent efficient well it's not really really what's happening is it's just doing something different so it's taking energy from outside and it's sticking it inside your car so if you look at the cycle and what's happening there's two places where energy is coming in and there's one place where energy is going out so you're bringing in energy and that evaporator in this stage right here you're bringing in energy from outside yes
the outside air is cold but your evaporator is even colder because of that refrigerant passing through it and so because it's colder than the outside air you're actually heating up that evaporator heating up that liquid that refrigerant passing through it so you're adding energy in from outside even though it's cold outside then you add more additional energy in from the battery which runs the compressor and then combining that energy you dump it all in the cabin and then the cycle repeats itself so the important thing is that you can pull in a lot of energy from outside even though it's cold outside there's still plenty of energy out there that you're basically compressing down and then sticking inside of your versus the resistive heater you're just taking energy from inside your battery and moving it to the inside of the car so it's just going from your battery into your car rather than from outside into your car so that's why this looks like it's operating at a higher efficiency it's because it's taking energy that already exists and just changing where it's located sticking it inside of the car so as an example of what this coefficient of performance means let's say in order to heat your cabin you need three kilowatt hours total of energy to bring that to a nice toasty temperature well using a resistive heater because it has a coefficient of performance of one it's going to take three kilowatt hours from your battery to do that using a heat pump you're only going to need one kilowatt hour from the battery because of that coefficient of performance being 3.0 now unfortunately the conversation often ends there and there's a major point left out so don't just simply go off thinking okay well heat pumps are three to four times better than using resistive heaters the end when in reality the colder it is outside the less effective your heat pump is and now you're thinking wait a minute if it's colder outside that's when I want to be using a heat pump and that's absolutely right so eventually remember we're taking energy from outside so the colder it is outside the smaller our temperature differential between outside and our evaporator and thus the less energy we can pull in from outside so eventually there will come a temperature at which your evaporator and outside are the same temperature you're no longer pulling in any energy and as a result of that in your coefficient of performance all of your energy going in goes to turning into heat and so you have a coefficient of performance of one again instead of three to four so it's some cold temperature that starts to level off and the advantage of it starts to go away now it's massively helpful in most driving conditions most of us don't live in Antarctica I know those of you that do are going to be sure to let everyone know in the comments that it's minus four you see where you live every day and that sounds cold that sounds very cold so it's unfortunate heat pumps won't be as effective for you than a lot of the folks out there that live you know freezing temperatures not a problem it's still going to be useful I I don't have an number I read through a good number of studies and I couldn't find an exact number but trusty ol Wikipedia was saying that your coefficient of performance will get to about 1.0 by the time you're at about minus 20 C or zero degrees Fahrenheit in real-world conditions and part of it too is the evaporator obviously it gets very cold and so you can have frost start to form on it and so as you build up ice and frost on that evaporator it's not going to be as effective at transferring ambient temperatures to the refrigerant circulating within it so still all of it is very cool and is a massive improvement as far as real-world efficiency is concerned driving in cold temperatures for electric vehicles which is going on this Tesla Model Y very neat system quite clever packaging again if you're interested in seeing
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