If the A/C was electric, the system controller could turn it 'on' as needed, and factor in other variables too, like critical need (cabin is 10 degrees hotter than temp setting), power available (down-hill regeneration is occurring), power stored (batteries fully charged), etc.

The A/C could, then, run with the ICE or without ICE. I mean, nothing says it has to run without the ICE running, it is just an available option.

Currently, the A/C can only run with the ICE. It is that designed-in limitation, and its lack of flexibility, that I question.

Come to think of it, where does the heat come from, in the winter, when the ICE isn't running?

 

Theoretically, its more efficient to pull it off the engine. The battery energy used by the electric airconditioning system on the other vehicle gets it energy from the ICE at some point. Converting to charge in a battery and back is pretty efficient, but not as efficient as running it off the engine itself. In the end... that electric system may SEEM better, but as far as the car getting better mileage because of it, you'd be wrong.

 

The big "problem" would still be when you are in EV mode. An extended EV period with the a/c on would drain the battery more quickly resulting in the need to run the ICEto recharge. I've gotten used to it the way it is and still believe it is the most efficient way of doing it. But then, I live in New England where a/c is only "needed" for maybe 2 months a year.

As for the heat, I think it works the same way as a regular car heating system except I believe there is an electric water pump. I have shut off the engine in mine, turned the key back to the run position without starting and get good heat for much longer than a regular car.

 

What I'm trying to say is... the A/C will consume the same energy either way. So if its pulling it from the battery then its draining charge placed there by the ICE. The losses in the mechancial to electrical to mechanical might be fairly small but they aren't insignificant. So.... running your A/C on and ELECTRIC system all the time will be a bigger MPG hit then running the system directly off the ICE in the red setting.

You don't gain free energy.... Its coming from the ICE one way or the other.

 

Answer for heat is the same as the A/C. From the ICE. The difference is that the ICE has alot more thermal mass than the A/C coils and doens't cool off very fast.

An electric A/C will allow you to cycle on and off (you can do that to the ICE too). But everyone is saying you only get about 30 sec of cool air so its going to be on almost constantly. Maybe the real best option is to provide a system with some more thermal mass to it so that once the coil gets cool... it stays that way longer. Problem is it would also take longer to cool in the first place.

 

Hi All

http://web.mit.edu/newsoffice/2006/tpv.html

This is a link to an MIT study which in part, is funded by Toyota.

It is a sort of solar energy that can eliminate the need for the battery or ICE running the A/C compressor and many other electrical auto systems. The write-up says the system would be for hybrid vehicle that the ICE shuts off and trucker's who must sleep in the cabs, and run the diesel for A/C use.

A system like this would be perfect For FE!

GaryG

 

Maybe it is I see it this way...

The best of a Hybrid is in stop and go traffic, where you are spending a considerable amount of time just sitting there going no where fast.

Now, as the title of this thread states, put that stop and go traffic into a Very Hot Area. Say, its 100 deg in the shade, 120 deg on the blacktop roadway, and the sun is baking down on you. That is what I consider to be a very hot area.

Normally, the ICE would be 'off', saving gas. With A/C running only on the ICE, my Hybrid will be failing me when I need it the most; no A/C!


The only other thing to do, is to switch to Max A/C, and now the ICE would be 'on', using gas, just to run the much needed A/C. If the ICE needs to run constantly, I might as well have bought a non-Hybrid.

That's why I thought that having an A/C which runs off the electric, instead of the ICE, would be nicer.

 

Hi Walt

Here is what I do in the heat with my FEH.

In temps above 85F, the compressor will run to cool the battery while the ICE is running, so I run the cabin recir A/C. This keeps the battery functioning much better for EV anyway. If I start getting hot, you can bet the battery is getting hot, and that causes a lost in FE.

After running some tests, I found I can push the FEH in the 60mpg range with the cabin recir A/C running. It gets pretty warm in EV, but that is pushing things to the max. Now, I control EV and the ICE to meet the demand of my cooling needs. Some days, depending on the heat, I still can push 50mpg and stay cool. On real hot days, I run less EV and > than 50% battery SOC and still stay above 40mpg. Mainly just take the FEH to 43mph and go EV at 40mph so the ICE is off till I coast to 30-35mph, then restart and pulse back to 43mph and repeat. Now, sometimes I must do high speed pulse and glides (50mph down to 40mph or even higher) with the ICE ON to get the cabin nice and cool and fully charge the battery. With a fully charged battery, you can look at my Steady State test and see you still can get great FE. My next test will be with the A/C on to compare.

There are so many choices I have to drive and stay cool now. Wish I had this info last summer!

GaryG

 

You're not wrong necessarily.... but the equation might not lean as far to the electric A/C as you think....MOST of the time the A/C is running with the engine on... its only stopped at lights sometimes. So the losses from the mechanical-electrical-mechanical conversion are constant... even when going down the road compared to the losses of the engine idling at an intersection to keep the A/C on when only the days its hotter than all get out. Its hard to say... It certainly SEEMS like the idling might be the most wasteful--but you'd be suprised how often such assumptions are wrong.

Also... hybrids aren't efficient JUST because they shut off the engine at intersections. They also have more efficient smaller engines because of the electric low end torque of the electric motor AND there is the regenerative breaking. The 6-cylinder 4WD gets something like 19MPG on the freeway. I do 28-29 EASY in my 4WD hybrid and the engine is running all the time.

So... its not like you are giving up EVERYTHING hybrid if you turn that A/C to max

 

WOW.... Interesting comments!

I'm going to have to think about our family needs a bit before I make a commitment to the FEH. I really need a small SUV to haul our family "stuff" from time to time. However, most of my travel is commuting 15 miles each way.

For those of you who haven't tried the TCH, I've got to say that the A/C will get you so cold that you are looking for a sweater, even in those 100 degree days. The sytem does run on the electric side of the house. As it relates to A/C, the ICE only comes on when the battery need charging.

Thanks!