Bob,

In response to your "For a hybrid, this would be very much the wrong way to go" statement, how do you feel about the fact that your electric a/c uses an enormous amount of electrical energy causing a more frequent ice startup to charge the pack, or at least leaving less electrical energy to move the vehicle?
In the design where the ice runs to cool the vehicle, while the ice is running it not only turns the compressor, but is filling up the battery pack at the same time.

So if we set the climate control at 72 and the ice a/c stops running at a stop, there is no extra energy used. (albeit the air does not stay as cool for the 2-3 minutes you are stopped).

If we come to a stop in the electric a/c vehicle, we are burning up electrical energy while stopped to run the a/c. At some point this energy must be replaced and unless we re-adjust the temp, or turn the a/c off we are using energy every time we stop. In the ice-a/c when we stop we are not and we have that option without making a temperature adjustment. We just leave the temp at 72 and as soon as we get going the system goes right back to work cooling for us.

If we go back to the ice run a/c and the driver puts it on MAX/no econ then yes the ice stays running for the 2-3 minutes while stopped, but this is plenty of time to charge the pack right up while it is running, allowing for more electrical assit.

I am not sure which way is more beneficial, I think they both have good points to them.

I just get a kick out of the "know all" statements made in closed mind thinking. This is the second one I have read today and they really show how arrogant some are regarding technology OTHER than what is in the veicle that the POSTING PERSON owns.


food for thought.
08FEH

 

Funny you should post this. Last week, I did a quick test after driving into work, the car was fully warmed up:

ORDINARY IDLE
3,500 MG1 rpm (calculate ICE rpm)
2.04 g/s air flow

MAX AC IDLE
3,500 MG1 rpm (calculate ICE rpm)
2.46 g/s air flow

The compressor load added .42 grams/sec or nearly a 20% increase in idle fuel burn. In the case of ICE driven compressors, you don't get just a 20% increase but have to run the ICE to get any AC, 5 times the additional AC load. In contrast, the electrically driven compressors can average their load into the more efficient, higher power ICE operation. Idle and low power ICE operation is pretty inefficient.

What we need are a set of test runs to measure the impact. An excellent example is:

https://www.greenhybrid.com/discuss/...70&postcount=1

Bob Wilson

Bob Wilson

 

I am not sure I completely understand your post, but you may be onto something.
After sitting at a stop with your A/C on though, when your ice does start (and it will), does it consume more fuel to not only continue to run your compressor but to also recharge the pack with the electricity you burned up while running your compressor off the battery?

08FEH

 

My 2003 Prius, an NHW11 model, still uses the engine to run the compressor. So what I did was measure the change in intake air flow at idle of having the AC on or off. The 'delta' is the additional load of the compressor and adds an additional load, a 20% fuel burn.

Our Prius engines are somewhat inefficient at low power settings. So we get less energy per unit of fuel burned. The additional fuel burn load of the AC is not enough to put my engine in a fuel efficient areas. That is why the electric compressor is such a brilliant solution.

The electric compressor draws upon the battery when the car is stopped so the engine doesn't have to run at fuel-wasting, idle. But when the car pulls out, the higher level of engine power needed to accelerate can easily handle recharging the battery for the past AC compressor energy.

It might take a cup of gasoline to run the AC compressor directly from the engine. But to run the same compressor using the battery method reduces that to a half-cup for the same amount of cooling.

Does that help?

Bob Wilson

 

It does, as long as your cup/half cup was an example and not reality. I am not sure it is that drastic. I also wonder if there is as much additional load on a larger displacement engine, but then of course the larger displacement also uses more fuel. I would have to hook up a scan guage and watch the iac counts also with the a/c on and off.
i wonder what the true fuel consumption difference would actually be between the two systems, taking all information into account (displacement, battery capacity, charging loads etc).
After conversing about it, I understand what you are saying, but I still am not so sure that and ice run a/s is "definately not the way to go". This is not because I own an ice-a/c system, but more based on the efficiency of the FEH as a whole for an suv.


08FEH