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Does anyone know if the AC compressor is driven by the IC engine or is it driven by an electric motor of the Insight? Theoretically, if it is driven by an electric motor and the IMA battery system is fairly well charged, there should be little effect on MPG. But, I know that my MPG drops when using the AC, so that leads me to believe that the compressor is driven by the IC engine. Any thoughts?
 

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It's driven by the gas engine off the serpintine belt.

Please remember that since the IMA system gets all it's electric power from the motion of the gas engine, ANY drain on the IMA system will always result in gasoline usesage. :)
 
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The 2004 Prius will have an electric AC compressor. Apparently the first of its kind.
 

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It's actually a heat pump in the 04 prius, which is more efficient than a compressor (similar to what you might have on your house). But actually heat pumps in cars are not a completely new thing, just new to gas vehicles. Electric vehicles of the past have used them. EV1, S10 electric, Ford Ranger electric all had electric heat pumps (no other real way to get heat or cold). The cool thing about it was on the GM's that same compressor was responsible for cooling the battery pack so it was pretty beefy, and when you used it to cool the cabin I gotta say I've never felt an air conditioning so strong. I had the pleasure of riding in a production electric S10 and despite a 112 degree Arizona summer day the temp dial was turned 2/3 of the way to the hot setting and the air was icey cold. I was told that it gets too cold if it is set all the way to cold. Yet, it was only pulling about 3 amps off of the battery pack (at ~300 volts). Wishful thinking I guess, but I want one.
 

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A heat pump is not more efficient than a compressor. It is simply an air conditioner than can reverse the flow of the refrigerant so that the hot and cold coils can reverse their functionality. You can use the refrigerant to move heat from the inside to the outside (air conditioning) or you can use it to move heat from outside to inside (heat).

The only brag that heat pumps have in terms of efficiency is that when used to heat a house, they are much more efficient than the resistive technology of a hair dryer, which is basically what all previous forms of electric heat amount to. An electric furnace was basically a huge hair dryer. Electric baseboards use the same hair dryer technology without a fan.

Any direct burning of fuel will always be much more efficient at heating than a heat pump, and air conditioning with a heat pump is EXACTLY as efficient as air conditioning with an air conditioner. Heating in a car is provided from using some of the excess heat from burning gasoline in the engine.

More recently, there has been electronic means of functioning as a heat pump without refrigerant gases or compressors. This was developed by NASA and is extremely efficient in terms of low consumption of electricity, but it also doesn't pack much of a thermal punch. It warms things and cools them. It doesn't heat them or chill them.

Meanwhile, 3 amps at 300 volts is 900 watts. That's not trivial for a battery pack of this capacity. At 144 volts, that's more than 6 amps, and the battery pack is not much over 6 amp hours. You'd go from fully charged to dead batteries in less than an hour.
 

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Will M said:
Meanwhile, 3 amps at 300 volts is 900 watts. That's not trivial for a battery pack of this capacity. At 144 volts, that's more than 6 amps, and the battery pack is not much over 6 amp hours. You'd go from fully charged to dead batteries in less than an hour.
Well bear in mind that the one I described also had the job of cooling 25 (I think) 90AH lead acid batteries, which was very oversized for cabin cooling needs. I'd imagine you could get away with a much smaller unit for a car the size of the Insight. I doubt we'd be looking at powering the unit by itself for any period of time. I'd just like to have auto stop with air for those two minutes I sit there at a light. Plus, if you went with an electric heat pump I'd imagine you'd eliminate some inefficiencies with the belt drive.
 

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"A heat pump is not more efficient than a compressor."

Technically, I suppose, but the benefit of heat pumps for home heating/cooling is that they're pumping out of a source (the ground) that's at a fairly constant temperature which isn't too far off what you want the inside temp to be. In other words, it takes less work to move the heat where you want it to be, than to create it.

Still, I'll think I'll stick with my passisve solar & wood stove :)

I'm surprised no one has developed an AC unit that runs off exhaust heat, using similar principles to the gas refrigeraters that you find in RVs.
 
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