Electric Climate Control

[IamIan]

This kind of thing has come up from time to time in various other threads...

The idea is to use a electrically driven climate control, so the engine does not see the load and thus has an easier time cruising on the highway and is more likely to go into Auto Stop Idle.

My first effort was a 150 to 200 watt 12V heater for the car that plugged into the 12V Accessory outlet... while this had some benefits... I could get hot air in the cabin faster in the winter since I didn't have to wait for the ICE to warm up... and If stopped for a while I could keep the cabin warm without turning the engine back on... ultimately it had many disadvantages.

My thoughts are leaning toward a second generation version... I see a few different ways I am liking so far to go and was wondering what others thoughts about each method or other methods and about the concept as a whole?

Option#1
Add some type of thermal storage device and a heat exchanger holds colder mass in hot weather and hotter mass in colder weather... The thermal storage should be some type of well insulated thermos ... the thermal storage could be removable if small enough... which would allow it to be filled with the thermal mass desired in the house before a trip...

Option#2
Thermal Electric Semi-Conductor Devices... Attached to a heat exchanger... they create a temperature difference between the two sides of the device when a current is supplied... up to the thermal watt limits of the particular device... The nice thing is that which side is the hot side and which side is the cold side is just a matter of DC polarity which can be switched making it a heater or a cooler... either way the undesired temperature side Hot or Cold can be put / pumped out of the car maybe via the rear vent.

Option#3
A combination of options #1 & #2.

Option #4
You tell me what would be a better way to do this and why?

[Roger Crier]

Would it not be easier to find and fit an electric motor capable of driving the existing aircon pump using the power/ signal provided to the redundant electric ac clutch to trigger a relay that then supplies power to the motor. If you then keep the heating system as it is, you have removed the biggest cause of power consumption and have a near standard system. Having said that, all the power comes from the fuel in the end, but you will have made the fuel consumption due to aircon use invisable.

Rog

[james]

"My first effort was a 150 to 200 watt 12V heater for the car that plugged into the 12V Accessory outlet... while this had some benefits..."

BAD idea! Remember that the normal heat is just waste from the cooling system - if it doesn't go in the cabin, then it goes to the radiator - while the electric heater uses electricity generated by running the engine.

Electric A/C might not be a bad idea, though.

[IamIan]

I am in the process of moving, but after that is done.. I hope to finish my PHEV Battery project...

Once the Secondary / booster battery is ready additional Electric power does not have to necessarily come from Gasoline anymore.... and even if it does, it can come from surplus energy such as during regen braking and such.

Using a electric motor to drive the AC compressor is a 4th option... but fitting and attaching it I thought would be difficult... that would also still have the reduced auto stopping from climate control usage...

I agree using the 12V electric heater has many limitations / down sides... but it helps prevent the running of the car to warm it up on bitter cold days... and it reduces the amount of time it takes to defrost windshield and to warm up the HV IMA battery... also on a bitter cold day when stopped the 12V heater could keep running... the stock climate control system gives out on heating the cabin pretty quickly once the ICE stops.

[japanev1]

The Prius has fully electric climate control... It runs off the traction battery when the ICE is off, but boy does it suck down the battery! If you are sitting at a stop light on a hot day with the A/C on, the traction battery would go from full to half in just a few minutes and the ICE would kick on after about a minute to stop the battery from being depleted too fast. I read that during the mkII Prius development they completely redesigned the climate control system and it was twice as efficient as a standard car's system and fully electric. I bet it would be hard to set up the Insight to run the A/C off the traction battery as it wasn't designed for the high current loads. I just use A/C ECON with fan speed manually set to the lowest setting which allows cool air to be brought in on a hot day with the ICE in AUTO-STOP...

[IamIan]

just casually discovered an additional problem ... the Insight's AC compressor according to the service manual ( 2-13 )... is a Sanden Scroll that pumps out up to 12,700 BTU per Hour of cooling... In addition to the drive system load it also pulls up to 300Watts of electrical power.

So any type of alternative would have to put out around ~12,000 BTU in order just to equal the OEM system.

of course generally it is more efficient to drive a compressor directly... to use electrical power you add in additional losses... there are a few benefits... one is that it would work while in Auto-Stop.. so the engine wouldn't need to idle to keep cool... one is that it would allow you to do a load balancing system for the cooling needs over a larger period instead of having the AC pull the power from your drive system at inconvenient times... another is that the electric powered Air conditioners are more driven to be efficient , thus it might be possible to trade the less efficient electrical usage for a more efficient system, the combination might balance out.

the Insight AC system seems to add ~31 Pounds to the vehicle which is very light... probably a primary concern.
The Saden Scroll power graphs look like the power consumed is ~6 kW ( ~7HP ) for those 12,700 BTU... or about 2 BTU per W... which is not so good... this seems ~ about right... I would have guessed closer to ~5 HP of loss but... maybe Honda has a more efficient model than the normal Saden Scrolls.... maybe as much as double at most ~4 BTU per W... which would still be ~3kW or ~4 HP.

If you are willing to drop to ~1/2 the cooling capacity down to ~5,000 BTU per Hour...
dcbreeze
Runs on 12VDC or 24VDC and uses ~580W which is better than the standard Saden Scroll at ~8.6 BTU per W
Now in addition to the 1/2 cooling power, you also gain the ~50 Pounds of this unit... so it weighs ~18 pounds more than the Honda OEM system.

The most efficient electric AC unit I know of is
SolCool
Unfortunately this model is built for stationary use and is far too big and heavy for vehicle use...
But it does dish out ~15,700 BTU and only consumes ~1,000 Watts to do it.
This gives 15.7 BTU per W of energy...
So while no one seems to make one for vehicle applications ... this level would at least be technically possible.

Unfortunately you can't directly compare the Watts ... because the Watts of the Insight compressor come directly from the ICE... where will you get the electrical watts from... if you say the ICE via alternator function... ~10% loss ICE to Electrical High Voltage ~10% loss High Voltage to Low Voltage DC-DC... means you loose an additional ~80%... if you use the batteries to store extra energy .. which seems like a given... you can knock that down again by ~80%... so you end up with about ~65% maybe ~70% of the energy you take from the ICE combing back to the electric AC unit... this means it has to do at least ~35% better just to break even.

Thankfully the DCBreeze looks like it is more than ~35% better ... but you take a 18 pound hit... you have to find some place to put the thing... it won't use the stock Climate control system.... and a fully charged OEM battery Insight will only power the thing during Auto-Stop for ~45 Minutes at most.

Now once you start pulling that much power you will pretty much force the IMA into forced charging... which takes away the power you saved .... unless you have some other larger source of electrical power not related to the ICE...

But would this be a good use of electrical power?? ... I have my doubts... After all if you have the electrical power to run this thing ... then you might just be further ahead to use that electrical power to drive the IMA system to move the car.

but there you go.

[Hybrid-Battery-Repair]

Originally Posted by IamIan

This kind of thing has come up from time to time in various other threads...

The idea is to use a electrically driven climate control, so the engine does not see the load and thus has an easier time cruising on the highway and is more likely to go into Auto Stop Idle.

My first effort was a 150 to 200 watt 12V heater for the car that plugged into the 12V Accessory outlet... while this had some benefits... I could get hot air in the cabin faster in the winter since I didn't have to wait for the ICE to warm up... and If stopped for a while I could keep the cabin warm without turning the engine back on... ultimately it had many disadvantages.

My thoughts are leaning toward a second generation version... I see a few different ways I am liking so far to go and was wondering what others thoughts about each method or other methods and about the concept as a whole?

You tell me what would be a better way to do this and why?

Okay, how about this? Your major problems are:

1. The car won't autostop if it's below 40 degrees
2. The car won't autostop until the cabin reaches the temperature you specified
3. After stopping, it cools off fast.

A possible solution for # 1 is to inject a fake temperature (say 45 degrees) into the temperature sensor at the nose of the car. I don't think the engine uses this temperature for performance tuning, as my sensor was missing and the car ran fine, but would not auto stop.

Solution for #3: The heater core retains quite a bit of heat. If you bypass the climate controls and run the fan on low in auto stop, you should stay warm. Test this by turning off your climate control, enter auto stop and then turn climate control back on (manual fan low). See how long you stay warm.

[IamIan]

Originally Posted by ogregev

1. The car won't autostop if it's below 40 degrees

I've had mine Auto-Stop well bellow freezing exterior temperatures once the engine, passenger space, and battery are warmed up.

Several people have installed methods to help with these things... like radiator blocks... engine insulating blankets ... etc...

Or just use FAS.

Originally Posted by ogregev

2. The car won't autostop until the cabin reaches the temperature you specified

Only while the temperature you specify is being controlled by the dash climate control system.

If you use a separate system you get Auto-Stop as soon as the engine and battery get to temperature.

Or just use FAS.

Originally Posted by ogregev

3. After stopping, it cools off fast.

only true if you use the stock heating system... an alternative / supplemental climate control system like I am theorizing about here, runs as long as you have electrical power to feed it.

The opposite is also true for warming up in the summer... the stock AC system doesn't provide cooling for long in Auto-Stop... and a supplemental system would , for as long as you feed it.

Originally Posted by ogregev

A possible solution for # 1 is to inject a fake temperature (say 45 degrees) into the temperature sensor at the nose of the car. I don't think the engine uses this temperature for performance tuning, as my sensor was missing and the car ran fine, but would not auto stop.

excellent use for FAS until you get the sensor repaired.

Originally Posted by ogregev

Solution for #3: The heater core retains quite a bit of heat. If you bypass the climate controls and run the fan on low in auto stop, you should stay warm. Test this by turning off your climate control, enter auto stop and then turn climate control back on (manual fan low). See how long you stay warm.

I do this all the time in winter months to stay warm.... and I've used the same thing in the summer to stay cool.

But I would like more...because I'm greedy... spoiled ... can't leave well enough alone... like having 20+ projects running at any given time... gluten for punishment... etc... take your pick

[Hybrid-Battery-Repair]

I'm trying to offer you a way to accomplish what you are trying to do without adding a second heating system, just by tricking the existing system into working.

I was restating the problem that you're trying to solve as I see it.

Originally Posted by IamIan

only true if you use the stock heating system... an alternative / supplemental climate control system like I am theorizing about here, runs as long as you have electrical power to feed it.

The opposite is also true for warming up in the summer... the stock AC system doesn't provide cooling for long in Auto-Stop... and a supplemental system would , for as long as you feed it.

No, my point is that there is plenty of heat in the heater core for you to take, but the fans won't run.

As far as AC is concerned, you could do some major surgery and transplant a Prius AC compressor into the system as it is electric powered and could run with the engine off.

Originally Posted by IamIan

excellent use for FAS until you get the sensor repaired.

I repaired the sensor long before I got my FAS. My point was that the sensor does not appear to be used by anything but the climate control, so it should be safe to trick it.

Originally Posted by IamIan

I do this all the time in winter months to stay warm.... and I've used the same thing in the summer to stay cool.

So automate the process and you're done.

[IamIan]

Originally Posted by ogregev

I'm trying to offer you a way to accomplish what you are trying to do without adding a second heating system, just by tricking the existing system into working.

So automate the process and you're done.

I appreciate your input...

I already use the thermal mass in the winter and summer to the point of it not offering any more heat in the winter and cool in the summer... You are 100% correct that those methods do extend the useful range one can get heat or cool from the system... I just want more than just the extension will offer... the extensions are good but just not enough.

As for automating it... already on my list... I am figuring on adding a small 12VDC fan that I can turn on and off ... so the hot or cool air keeps flowing even when the stock climate control system is turned off... I hope to do that when the weather warms up a bit... it is still too cold for me.