I have been thinking a bit about this... Already have stock AC but electric would be nice to give cooling without the engine power loss.... I don't use AC much now but on some of the hot days it is very nice to have.
I have been looking around... and have been having trouble finding out how much BTU the stock AC unit does / can do.... Any Ideas?
Concidering the very small space it has to cool my first thought was 1,000 BTU or less... but then it occured to me that it will have to keep up with a good bit of solar heating and such so it might be more... but I can't imagine much more... If it even needs that much.
Depending on the amount of power / BTU's needed the Electric AC could come off the 12V System or use its own Battery to augment the 12V system... Unless your useing Mike's Boost Battery the power will ultimately still come from the Gas Engine... But if it is Electric Based then we can use the Car's 144V to 12V Charging system to keep a small Eelectric AC unit running as long as the 144V battery has a good charge on it.
I have found a few AC units that might do the job but wanted to check here to see if anyone knows / has any other ideas about the BTU's that would be required???
The Insight is a poorly insulated greenhouse with the heat from an ICE blowing around it. . I suspect that direct mechanical linkage is still the most efficient source of power. Did you try calculating the solar energy falling on the total glass surface as a brain teaser?
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Kip Munro
The laws of physics don't need changing, but rather our attitude and values. 72.8 LMPG
Basicly.... the worst case sinario in the US if you had a clear glass box about the size of the 60 cubic foot Insight interior parked it in direct Summer Sun in the southern US and a dark surface inside the glass box absorbs 100% of the radiant solar energy of the sun that reaches the surface ... I figure the Box will get ~6,800 BTU's of radiant solar energy per hour to the Interior.... which given the aproximate conductivity of glass as the insulating material between the inside of the car and the outside temperature... the inside temperature under those conditions would reach an aproximate max value at about ~1,373 degrees C above Ambiant outside Temperature this is the worst case sinario.... Now the Insight is not a complete glass box and will not absorb 100% of the radiant energy coming in... but 1,000 BTU's inside will reach a temperature diference of over 200 degrees C with Ambiant...
Conclusion.... 1,000 BTU's will not come any where near enough to compete with the sun's radiant heating in the Summer.... and I doubt the air vents & fans will move enough ambiant air to make much difference....
If the Honda Stock AC unit can compete with the 6,800 or so BTU's per hour of radiant solar energy of southern US and still keep the car cooler than the ambiant outside temperatures.... it has to be putting out well over 5,000 BTU's per hour even with the ambiant air flow.... 5,000 BTU's per hour if converted at 100% effeciency would be about 2HP .... I would say the stock system feels like it pulls about 3 or 4HP....
So.... If the Insight is to be converted to an electric AC system that does not rob the car of power... then the best approach might be to use the exsisting honda AC unit but drive the compressor with a electric motor instead of coming off the engine.... but such an Motor would more than likely weigh at least 20 Extra Pounds ... and you would have to power it which would mean at least 2 or 3 kWh of electrical energy storage for every hour of electric AC use....
So The Idea is a bad one..... It would be better to use that 2 or 3 kWh to power a booster battery like Mike is doing and just leave the Stock AC unit where it is.... Operate is Electric Priority mode where the stock 10kW IMA motor is at full power any time the car goes down to 100MPG.
The early Prius I owned had a belt driven A/C compressor. The 2004 Prius and up, the Highlander and Lexus 400h all use electric drive compressors. They are hermatic units driven by 3 phase A/C power from a small secondary inverter. On the Prius and Highlander, you can stop the vehicle and still have A/C without the engine running. I am sure that the losses in the electric drive A/C are lower then the belt drive system. The Toyota systems (including my Rav4 EV) all use variable speed to use a minimum amount of power to achieve the required cooling. The electric A/C draws 2 amps (or less) from the Rav4's 288 volt battery and has a marginal effect on vehicle range. The S10e's that I own also use a 3 phase A/C compressor, but with a couple of speed ranges, not fully variable. One of these compressors on an Insight with a small dedicated inverter would really help the vehicle in areas where a lot of A/C is required. One of my least favorite things about the Insight is the mileage hit when using the A/C and the constant fiddling with the throttle when the compressor starts and stops. I would think Honda would be using something like this on the Accord or Civic---I don't know about these vehicles, or what kind of compressor they have, but if they did, the voltage the vehicle runs on is close enough to the Insight that parts might be usable. BTW on the Kurbwatt---just slide open the doors for A/C!
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2006 Insight #459
2002 Rav4 EV
1998 Chevrolet S10e
1997 Chevrolet S10e
1983 Grumman "Kurbwatt"
The Accord Hybrid and 06 Civic Hybrid has what Honda calls a "dual scroll" compressor. It runs off the engine belt drive when the engine is on and switches over to the electric when the engine is off. The compressor basically has a small electric motor in the back end of the compressor which scrolls another piston in the compressor. If you have the air set to full bore it will keep the engine running to provide maximum cooling, but once the car has cooled down sufficiently and your just maintaining cab temp the electric portion of the compressor gets used a good bit. It works very well, there is also an electric coolant pump for heat in the winter.
This setup deffinitely is much more efficient than belt only driven compressor. With the Civic I can still get 45mpg fairly easily with the AC running whereas with the Insight mpg would drop as low as 55mpg, and I've been using more air in the Civic than I did with the Insight. An interesting note too is that the Civic won't shut the engine off until the cab has cooled down sufficiently if the ambient temperatures are about 100 degrees or higher.
It would be interesting to see which setup is more efficient, Honda vs Toyota. Honestly this was one of the huge selling points on the new Civic for me. It would be awsome on the Insight, but retrofitting something to do this would probably be very difficult. The only electric AC unit I've ever seen was a Saden unit used in the factory Ford Ranger EV, and it needs something like 300 volts to work. I was looking for something to use in my electric Saturn Conversion, but it's looking more and more like I'll be driving the stock compressor with a separate small electric motor, hopefully directly driven and not belt driven.
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Later, Ricky
02 Red Insight - Sold
06 Silver Civic Hybrid
92 Saturn SC2 Electric, Arizona Alt fuel plate "ZEROGAS"
I think what everybody is missing in this discussion so far is the losses of efficiency on the conversion of gas to electricity.
What allows apparently better efficiency of an electric compressor is the ability to level the load. Meaning on acceleration any compressor load is electric, not added to the acceleration fuel directly used. It's a 5-8% MPG city drive cycle gain to simply unload the AC in acceleration. And some of its energy is derived from "free" regenerative forces (braking or downhill).
So a plain electric vs a belt driven one is likely to be less efficient without some additional control logic.
The only electric AC unit I've ever seen was a Saden unit used in the factory Ford Ranger EV, and it needs something like 300 volts to work. I was looking for something to use in my electric Saturn Conversion, but it's looking more and more like I'll be driving the stock compressor with a separate small electric motor, hopefully directly driven and not belt driven.
There are several I found in a short Web search...
These people make some that are very small... different units put out in the 1,000 to 5,000 BTU range .... but seem to run on AC for the AC .... Alternating Current for the Air Conditioning.... So if you dont' already have the right kind of AC from an inverter than that is another expence and source of loss to change it or get it....
.... Now from what I have seen ... If you already have the Belt driven unit like what is already in the insight it will be much cheeper to use a small electric motor to drive the belt for electric AC .... as those above all seem to be in the $2,000+ Range and a small electric motor should eb less than this.
Quote:
Originally Posted by Insightful Trekker
What allows apparently efficiency of an electric compressor is the ability to level the load.better
Agreed.... The usefulness of an electric AC unit would be to have AC at stops when it is very warm without the engine needing to stay on and burn gas.... Most stops are only for a minute or 2 in traffic anyway.... And to prevent the loss of power so you don't have to add more gas going down the road to maintain speed.... As you said the Electric is not free.... and conversion losses will come in ... so I wonder where it breaks even amount of stops when the AC keeps the ICE running compared to the conversion losses..... I was actually thinking it would be nice to add on... as an after the electric booster pack kind of thing... as the Booster back will give extra electrical power without adding a load ever to the engine ...
The Toyota systems (including my Rav4 EV) all use variable speed to use a minimum amount of power to achieve the required cooling. The electric A/C draws 2 amps (or less) from the Rav4's 288 volt battery and has a marginal effect on vehicle range. The S10e's that I own also use a 3 phase A/C compressor, but with a couple of speed ranges, not fully variable.
*whoa*, are you saying that these compressors are variable output? Whooppeeee! when can we get these for household use? I've never seen a window unit with anything other than a "fixed rate" (on/off) compressor, and you have to pay a hefty surcharge to get variable ones in central units.
(There are a _lot_ of reasons to prefer a, say, 5,000 BTU capable air conditioner assembly with the compressor running 90% of the time as opposed to a more typical 10,000 BTU system with teh compressor running two minuteson, one off, on for two, etc.).
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Very satisfied owner of a used 2001 (cvt) Insight,
a retrofitted cruise control,
and now elated to have a wife with a 2003 (cvt).
How about a swamp cooler. They are sometimes used. Much better for the environment too. Basically a 'wind tunnel' ie. long tube with air sucked in from outside, and water misted or dripping inside the tube. The water is cooled by the air significantly, and cool air is produced. They workr great, even in 100+ days. Only downside, you'd need top off the water. I think it could work, or be an adjunct to the a/c unit and it would only take a bit of simple mods to do it.
Swamp coolers won't work in the southest US.
Or anywhere else with high humidity
Plus it's not ging to work in a car because you need a constant source of water :P
As for electric vs belt AC, the electric wuld help for the same reasons that the hybrid system is beneficial... distributed load. It would help further equalize the load being put on the ICE. Plus the whole auto-stop+AC :P
I think Honda's twin scroll in the accord and civic are actual scroll compressors... no pistons. (Which are far more efficient than piston driven compressors)
If you are going to run the A/C, you are better off, energy usage wise, to turn on the air recirculation... the only reason Honda brings in fresh air is to help keep moisture from accumulating in/around the ducting. But this hot outside air drastically increases the load... and therefor the parasitic drain of the A/C. Hotter air increases the suction pressure and head pressure making the compressor have to work harder in order to compress and circulate the refrigerant.
I personally am not worried about the condensation buildup
Most automotive air conditioning systems are horribly designed as far as energy use goes. Most bring in hot outside unless set to "max"... this is one reason that people think turning thier household stat lower makes it cold faster , and is also a great souce of energy waste...
I applaud Honda for at least putting in a thermostat! :P
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Electric Air Conditioning?
. I suspect that direct mechanical linkage is still the most efficient source of power. Did you try calculating the solar energy falling on the total glass surface as a brain teaser?
, and is also a great souce of energy waste... 
