Battery energy management strategies are difficult. Ideally one needs to know what the car will be asked to do in the near future, but of course that's impossible... with one exception: at initial startup the engine (almost?) always runs for a minute or so to bring itself and the catalytic converter up to operating temperature. This is the least efficient and dirtiest operating phase, so perhaps the best use of a fully-charged greater-capacity traction battery is to electrically pre-heat the engine and converter, and so reduce or eliminate that initial engine run.
Preheating would mean some planning ahead, in which case there would be time for a hypothetical rapid-rise engine-block heater to do the same thing more efficiently. The extra efficiency to come from not having wasted energy in the conversion/charging/discharging/conversion steps involved in sending the energy through the traction battery system. Conventional block heaters, which don't assume you know when you want to use the car, probably are more wasteful, spending power making it warmer than need be early in the night. So I'm speculating on a much higher rate heater which can be started by a careful owner or a timer just before need. Does anyone make such a product? Does anyone make a converter pre-heater? I'm not speaking against the idea that preheating could improve operation, just wishing not to use the traction battery energy for the task.
It takes a LOT of energy to heat the cat. I don't think it's a very practical idea. The engine actually doesn't run to heat itself up, at least Pearl doesn't. Once the cat is hot the ICE shuts off. Coolant temp can be 30C at this time. That isn't warm. Now if you have the heater on the ICE will run to try to get the cabin warm. This IS a waste of energy, as the ICE will not get warm enough to run the fan to heat the cabin, or at least Pearl operates this way during "real" winter. I leave the A/C Auto off until I am moving (and the ICE is running because I'm moving). I would say a plug-in Prius would be most efficiently used by running on electric from the beginning (using the EV switch, which I presume the plug-in Prius will have), so you will create "head room" for regeneration. But perhaps they have it leaving enough for that anyway. We shall see.
No, I'm thinking, the driver unplugs the car, gets in and pushes ON (not "hmm, I'm going to use the car in a half-hour, I better go warm it up"). In this case the car has already been told what's expected via the ON button; there's nothing for the car to predict, and the only decisions the car has to make are whether the engine and converter are already warm enough, and whether there's enough energy in the battery. But heating the engine and converter does require a lot of energy, and it would be hard to arrange heaters on the order of 100 kW, so this is probably not practical.
Actually, on further thought, it's not the actual -amount- of energy required that makes it impractical first, it's the temperature the electric heater would have to get to. Resistive heaters that reach that temperature wouldn't last very long. I suppose you -could- design an arc based heater that would work, but it would be expensive as it would need a high tech electronic control plus filtering so it wouldn't damage the rest of the electronics in the car! Then there -IS- the amount of energy to deal with.
I think that electric resistive heaters can last quite some time. It is more an issue, that electricity converted into heat would decrease autonomy of electric powered car significantly. Especially during freezing winter days. Internal combustion engine is a heat engine and is basically quite efficient at providing heat. It is basically inefficient way of propulsion mainly due to its enormous heat losses, which come handy during winter times. During very cold winters you would spend around 3 kW of electric energy on heating alone. So this needs to be in equation. In any case I think that fully electric cars have a future, including having fully electric heating. Using a heat pump and not just resistive heaters would improve energy efficiency in that area.
heat pumps don,t work below a certain temperature threshold (around minus 10-15 deg C). One solution for winter heating would be a combustion heater for the coolant, such as the Espar or Webasto Blue Heat. It uses much less fuel than idling the ICE, and emissions are very low due to a slower, more complete combustion.
We want ZEV. I think that combination of heat pump and electric heater would be best. Heat pump would increase autonomy, when it is not so cold. Electric heater would kick in when temperatures are so low, that heat pump can not keep up and in the beginning just to speed up warm up period.
Something that would work great in hot states; use that added energy to run the A/C. When its the summer, and I get in my car, I generally leave the A/C on for five minutes or so to let the cabin cool down. After that five minutes the battery generally depletes. Then I have the ICE come on, have crappy acceleration and not-ideal fuel economy. If the Prius could have an alarm function whereby, if you know you are going out to your car every weekday morning at 7:30, it could maybe turn on at 7:00 using just electricity from the socket and cool down the cabin. That would work out cheaper for me as my electricity cost is bargained into the rent; I can use as little or as much as I want and it costs not a dime extra. It would also be much more comfortable if I could do that.
There is speculation that the hinted solar roof on the top end prius will be sued for exactly this sort of thing. It won't make enough power to make too much difference in PHEV range, but it could be used to keep the cabin at a reasonable temperature while parked. In turn, that would greatly improve mileage during what would usually be your "cool down" period. Might help negate the AC load effect on mileage while driving around too. I generally skeptical of solar on PHEVs/BEVs, but this idea makes a lot of sense to me. The sunnier it is, the more AC you need, and the more power the solar produces. There's a certain elegance to that. Rob
It might be popular. I think the "guilt-free comfort" aspect might be attractive. Running the A/C while parked would make initial driving much more comfortable in a sunny town for everyone, and even subsequent driving more comfortable for the folks who avoid A/C to improve economy. Of course the hardest core economizers might insist on using solar cell power solely to charge the traction battery until it is topped up. But Toyota might legitimately nix that for increased battery wear and thus reduced lifetime reasons. I doubt it will actually pay for itself on a strict analysis. Solar cells are still so expensive a way to produce power that they need an application with very high in-service rate, plus something that inhibits supply from more conventional sources to make them prove in. Car roofs are probably not the highest and best use for solar cell capacity. But as they get cheaper this use sounds nice, and even at the start it make better sense than the various conversions that stuff lots of extra batteries in.
