smkettner wrote:If it was hot out there is no need to circulate the motor coolent through the cabin.
When it is cold out there is no need to warm the motor.
Agreed. A 3-way valve and injection loop prevent both of these scenarios from occurring.
smkettner wrote:There is not a circumstance to share the heat.
Disagree. After ~10 minutes of steady driving I'd wager the motor and inverter have generated enough heat to be worthwhile. Similar to an ICE, but an EV would probably have significantly less thermal mass. Add to this the speculation that heat is generated during the charging process - which would mean there is less warming up to do.
smkettner wrote:I speculate the engine coolent may not get more than 20 degrees over ambient.
Maybe not with a radiator, but even if that is the case (and I speculate otherwise) heating water that is already +20 above ambient is better than heating water that is at or close to ambient.
The viability really depends on how much waste heat the motor/inverter generates, and the max temp the components are allowed to reach. Heat would vary considerably with speed, but if we assume 90% efficiency that's still several kW on average. Max temp is likely up around 200F so that's plenty hot. Throw in supplemental resistance heat and call it good I say.