How do hybrid vehicles produce heat for the cabin?
A google search for various models and “heater core” revealed enough hits to convince me that most produce heat much like a normal vehicle, by circulating engine coolant through a small radiator inline with the ventilation system. There might be some models that use electrical resistance heating, or a combination of the two, but I did not turn up anything in my brief search that led me that way.
Bear in mind that a hybrid vehicle gets the energy for any longish trip by burning fuel in a heat engine, the waste heat of which is an excellent source for cabin heat.
Cabin heat for a 100% electric vehicle is a much bigger problem; basically, it must come from diverting stored energy that otherwise would be useful for propulsion.
Agreed. Hybrids still have a good old internal combustion engine that is liquid cooled.
AFAIK, there is no pure electric car for sale by a major manufacturer. The method of heating such a car however would likely be a small electric water heater with a water to air heating core like a traditional vehicle.
Still, what if you want heat, and the hybrid is in battery mode? Does it start the engine just so you’ll have a heat source? Or do you not get heat until whenever the engine kicks in?
Why the water?
Water can be heated much hotter than the desired air temperature, and a tank can store the heat for quite a while. That’s probably a lot more efficient than exposing an electric heat element to the air directly.
Yeah, but any kind of electric heat is going to severly crimp the mileage of a single charge of the batteries.
It seems to me that a simple heat element would be efficient, lightweight, compact and relatively inexpensive. How would a heated-water system gain efficiency?
Yes, the engine kicks in for passenger comfort, just like air conditioning in a hot environment.
People misunderstand hybrids. They are not econoboxes that are trying to squeeze the last possible mpg out of the gas tank. They are cars that are designed to perform as good as, or better, than what the buying public expects while delivering better gas milage and lower emmissions.
The engineering behind the hybrids is not to force buyers to suffer and make sacrifices. It’s to move the auto technology ahead. If that means keeping the passenger cabin at a comfortable temperature then the car is designed to do that. Of course, all cars are computer controlled these days. If the engineers want to program the car for nothing other than gas milage than they could adjust the software and make the passengers dress accordingly.
You can store heat in the tank when you’re driving down-hill (generating electricity) and release it later when the cabin gets cold. With an exposed heating element, you have to draw power immediately when you need heat, regardless of how much you’re already drawing from the electrical system.
Our Escape hybrid gives you the choice: if you want heat (or A/C) when the gasoline engine’s not running, you can turn the climate control to the appropriate setting and it’ll kick the engine on. Then you have the choice of watching your little gas mileage graph get all depressing or of toughing it out until your engine comes on for power. If you set it for defrost (windshield or rear window), the gas engine will stay on.
The car stays in gasoline mode until the engine is warmed up. At that point, even if it drops into electric and stays there, I still get a decent amount of warmth from the heater for between five and ten minutes, depending on how cold it is. And I’m very rarely able to keep the car on solely electric for much longer than that anyway.
Right, but you could also store the energy in the battery and release it later.
True. OTOH, when you start the vehicle you have to draw off a bunch of energy to heat the water, a charge of heat that is ultimately going to be wasted (when the vehicle shuts down).
:smack:
How severely? I’m guessing that even a slow electric vehicle is going to have at least a 20kW engine (<30bhp), and probably wouldn’t need more than 0.5kW for electric heating. That’s a 2.5% hit for the heating.
For the record, 30 horsepower in a compact car is enough to push you along at a good 55-65 MPH.
If you’re tooling around in town at 30-40 MPH at a steady speed, you may be operating on more like 10-15 HP.
People don’t realize the power reserves modern vehicles have. You can run a car the size of a Ford Taurus at Interstate Superhighway speeds on a 70 HP engine all day long as long as you’re not trying to climb the Appalachian mountains with it.
Everybody here seems to be assuming that you can’t just use the waste heat from the engine in an electric car, just like you would in a car with an IC engine. Why not? Are electric motors really so efficient that they don’t produce enough waste heat to warm the cabin?
The 200$+ Prius airc conditioner compresser runs off an electric motor, and so the gas engine doesn’t need to start to run the compressor. (earlier models the compressor did run off the gas engine).
Of course, eventually the gas engine will need to run to renew the battery.
For heating, it is a convential system, thogh I have read there is also an electric heater that helps out. Toyota Prius/FAQ - Wikibooks, open books for an open world
The gas engine will run for a while in the cold, this isn’t so much for passenger comfort, but to get the catalytic converter hot for emission reduction.
Hot coolant (oxymoron alert) is stored in a thermos to help speed up warming.
Brian
Well, yeah. Waste is why they’re so efficient. If you removed the waste heat and exhaust from a gasoline engine, then they’d be equally efficient.
I realize that they’re more efficient, but are they so much more efficient that there’s not enough waste heat to heat the cabin?
Just going by the numbers mentioned in this thread, 500 W needed for heat and a 20 kW electric motor (mentioned as being near the lower limit of what you’d find in a production car), that’s 97.5% efficiency. The reasonable assumption of a more powerful engine makes the ratio even higher. I find it hard to believe that electric cars are much more efficient than that. Even if the engine is, the battery’s got to get pretty warm while it’s discharging.
The Tesla roadster has a water cooling system for the battery, so clearly there’s some serious heat being produced there. Assuming that the radiator is in the front of the car, that heat is already close to the front of the cab.