# Electric Vehicle A/C



## Foxbat (Mar 4, 2021)

It was quite cold this morning as I went for a wander. During my walk, a rather impressive BMW passed. I noticed that it was an electric vehicle and immediately wondered how much of an energy drain heating and air conditioning was on the batteries so I did a little research. 

Whilst heating and air con does indeed reduce the effective range of an EV, there is technology out there that helps minimise this. The heat-pump cabin heater is one such piece of tech. It is a refrigerant circuit that creates heat from the temperature differential between the refrigerant and external temperatures. This energy is then compressed to produce high temperature heat with minimal electrical drain. It can also be used in reverse as an air conditioning unit on hot days.

So, if you’ve ever wondered about it, that’s how. And if you’ve never wondered or simply don’t care then I am obviously far more nerdier than you.



			Heat-Pump Cabin Heater


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## CupofJoe (Mar 4, 2021)

Heat Pumps feel to me like a perpetual energy machine 
I'm sure its a con, but I know it isn't  
I just haven't got my head around the technology.
The Heat Pump is now being pushed as an alterative to gas central heating for the average home. I think McLaren warm and cool the Woking offices using them.


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## Foxbat (Mar 4, 2021)

I’ve come across similar technologies in my working life. The humble thermocouple, for example, works by having two dissimilar metals joined at one end and subjected to heat. This produces an emf (electro-motive force). This tiny voltage is created via the difference between the hot end and cold ends of the circuit. Of course, when measuring, you have to take ambient temperature into account to get a true reading.

I’m sure that Arthur C. Clarke wrote a story based on this idea. I think his thermocouples went deep into the sea to produce the great temperature differential needed to  generate power for consumers.

You can also measure oxygen levels via  the  differential across a zirconium disc.
Just a couple of examples there

Edit: I’ll just add a fascinating fact. Remember when gas boilers had a pilot light? This was used in conjunction with a thermocouple. The heat from the pilot light produced an emf in the thermocouple which was used to tell  a gas valve to hold in a position where it could be brought on stream when required for central heating. If the pilot light ever went out, the thermocouple would no longer generate an emf and the valve would close. It wouldn’t open again until the pilot light was relit. It was, in effect, a safety device.


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## CupofJoe (Mar 4, 2021)

Oh... I know it works. It just that to my untrained eye, it doesn't look like it should... My dad would have understood this in about 10 seconds.
Bring back the Stirling Engine!!!!


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