With the onset of winter it crossed my mind that a heat exchanger fitted in the air intake to the cabin fed by coolant from the inverter transmission circuit before the coolant rad would serve three useful functions, 1 increase cabin heat, 2 improve mpg (less heat required from ICE), 3 allow complete blocking of grills. The heat loss from this coolant rad appears to be in the region of 2kwh depending on driving conditions. Can any one see why this cannot be reasonably done, I know this would probably make bleeding the air out of the system even more difficult but not impossible.
Sounds possible and even beneficial, but the problem is the return coolant from the ICE side will be much hotter (unless the engine is cold), so it could work backwards, sinking engine heat into the inverter loop!
FYI: I'm having a similar problem as I'm running a PHEV in EV mode and never starting the engine. Since I don't have really cold winters here in the San Francisco area, I might do something easy, but the heat exchanger sounds difficult. A block heater is probably the easiest for me. I wish Toyota would have added a simple reversing valve to the A/C system, then it could heat as well as cool!
Having recently acquired a Toyotomi Room Air Conditioner that does just that, also operates as a heat pump, I've wondered the same thing... at least down to a couple of degrees celsius below zero... the AC could be reversed to operate as a heat pump.
The ice loop would remain as it is, just the trans/ivert coolant would run through the added heat exchanger positioned where the external air enters the cabin below the windscreen.
Sorry, In my haste I somehow read that you were going to fit a liquid-to-liquid heat exchanger in the system. If you preheat the air coming into the plenum, I don't see any problem with that, though like you mentioned, it might be harder to effectively bleed the system. (vacuum bleeding should still work ok.) If you add a 3-port 12v solenoid valve to the system, you can hook it up in parallel with the stock valve, and then when you don't need heat, it will bypass the new heater core and you'll have cool air.
Peef, you are now thinking exactly along the same lines as my self, this heat source could also be fed to a heat pump to increase output.
If you are running in permanent EV mode the heat output from the inverter and motor/gens will be even greater and the extra cooling for the inverter can only be of benefit.
