Her er noget om det.
http://www.hybridcars.com/...abin-heating-system/
Is there any waste heat floating around in a BEV that could be used for cabin heating?
Yes there is. It is waste heat from the electronics and from the traction motor.
Tesla has a patent on just such a system. The schematic from the patent describing the system is shown below.
Tesla patent shows waste heat from the drive motor and electronics being used to heat the cabin.
A simplified version is shown below.
Simplified version of patent schematic.
The patent shows four separate cooling loops. The top cooling loop is
a glycol loop that cools the drive motor and electronics. In hot
weather this loop just rejects heat to ambient from a radiator in the
front of the car.
The cooling loop right below the electronics cooling loop is the
cabin heating and cooling loop. This glycol loop can cool the car via
the refrigerant loop (shown below the cabin loop) or in heating mode the
cabin cooling loop uses a resistive element for heating.
The ingenious part is that the motor/electronics loop can communicate
with the cabin heating loop via some flow control valves. With the two
loops connected, waste heat from the motor and electronics can be used
to heat the cabin with the resistive heating element used as a second
source of heat. Scavenging the waste heat lowers the load on the battery
and increases range.
A simplified version of the Tesla patent in “waste heat cabin heating mode” is presented in the figure below.
Simplified schematic showing cabin heating using waste heat from the drive motor and electronics.
Could this patent be what is used in the production Tesla Model S?
We don’t have positive information from Tesla itself, however based
the following write up in the Tesla Motor Club it appears that this
patent probably is used in the production Model S.
Insert blockquote:
The Model S cabin heater has two (hidden) modes. If the
drive train is cold, all heat comes via resistive heaters, which can
draw up to about 6 kW. That’s a lot of power.
As you drive the car, the drive train will naturally heat up. Once
that happens, Model S uses the drive train coolant to help heat the
cabin. Essentially it takes waste heat from the motor and inverter and
uses that to heat the cabin. This makes a huge difference to the power
consumption – a fully warmed-up car will only need 1-2 kW to keep the
cabin warm even in extreme cold conditions. In comparison, the original
Tesla Roadster needs 4 kW to keep its tiny cabin not-terribly-warm using
only resistive heaters. This is a big advantage of Model S engineering
that Tesla never talks about!”
The upshot here is that cabin heater power consumption gets better quite dramatically after you’ve been driving for a while.
No Heat Pump?
Let’s look at a simplified sketch of the Refrigerant loop in the Tesla patent.
Simplified schematic of the Tesla patent Refrigerant cooling loop shows no heating mode.
There are no reversing valves shown in the Tesla patent. Also there are to expansion bypass valves shown in the patent.
Therefore, there is no heating mode in the Refrigerant loop.
That’s the patent but does the Model S incorporate a heat pump in production?
Again we have no direct information from Tesla but all indications
from Google search suggest that there are no reversing valves and
therefore no heating mode for the refrigeration system in the model S.
