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Ventilated Auto Seats Can Improve Fuel Economy By Reducing A/C Load
3 March 2006
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| This is not an election map. It depicts the annual consumption of vehicle fuel for cooling and dehumidification by state. Source: NREL |
Ventilated automotive seats not only can improve passenger comfort but also a vehicle’s fuel economy by reducing the power need for air conditioning, according to a study done by the US Department of Energy’s National Renewable Energy Laboratory (NREL).
Ventilated seats increase the comfort of drivers and passengers locally (near the body), reducing the need to cool the entire cabin.
NREL’s Vehicle Ancillary Loads Reduction (VALR) team has been working with industry to try to reduce fuel consumption from air conditioning in cars and trucks.
An NREL study showed that the United States uses 7 billion gallons (26.4 billion liters) of fuel per year for light-duty vehicle air conditioning, equivalent to 5.5% of the total national light-duty vehicle fuel use and 9.5% of the imported crude oil. The fuel use percentages are based on a total annual light-duty vehicle fuel use of 125.9 billion gal (477 billion liters) and imported oil of 73 billion gallons (276 billion liters).
If all passenger vehicles had ventilated seats, we estimate that there could be a 7.5 percent reduction in national air-conditioning fuel use. That translates to a savings of 522 million gallons of fuel a year.
—John Rugh, VALR project leader
W.E.T. Automotive Systems Ltd. provided NREL with ComfortCools seats for testing. Each seat contains two fans that pull air from the seat surface and out from underneath the seat. General Motors currently offers this ventilated seat as an option for the Cadillac STS.
Using its suite of thermal comfort tools and subjective test data, NREL measured improvement in human thermal sensation for the ventilated seats and the potential for a 7% reduction in air-conditioning compressor power.
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| ADAM sweats it out. |
NREL developed its thermal comfort tools to help the automotive industry design smaller and more efficient climate-control systems in vehicles. The tools consist of a one-of-a-kind thermal comfort manikin called ADAM (ADvanced Automotive Manikin) along with a physiological model and psychological model.
ADAM is a human body-shaped surface sensor that measures heat loss at 120 independently controlled zones. As the manikin “sweats” and “shivers,” corresponding data goes into a computer model that simulates human thermoregulatory responses. Another computer model predicts human thermal comfort.
Linked together, these tools assess comfort in a transient, nonhomogeneous environment, unlike other commonly used models based on steady-state, uniform environmental data.
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March 3, 2006 in Fuel Efficiency, Vehicle Systems | Permalink | Comments (17) | TrackBack (1)
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Comments
When I was growing up back in the 60s and 70s a low tech version of this was commonly used in the summer. You could buy cheap seat cooling cushions that went in the seat and kept your butt and back away from the seat itself. The cushions were made of an open mesh screen material to let air flow freely between you and the seat. In those days car air conditioning was an expensive luxury and these seat cushions did a good job of keeping you cooler when you drove (of course with the windows down!).
Posted by: Hal | Mar 3, 2006 8:41:01 AM
Am I reading that right? Are they claiming that 5.5% of the fuel we put into light duty cars goes to air conditioning? Because if they are I think they need to put down the crack pipe. I think it might be that in the summer, but over a year?
JRod.
Posted by: JRod. | Mar 3, 2006 8:56:22 AM
No, it's about 0.4% (552 million out of 137 billion).
Posted by: Engineer-Poet | Mar 3, 2006 9:35:13 AM
As an aside, my Prius and I have gotten 50 mpg for hours on end, with the air conditioning running ("low" or next up) at 70 mph, through 105F heat ... and been totally comfortable.
This site says that is not supposed to be possible:
http://www.hybridcars.com/air-conditioning-effects.html
I suspect there is better savings to electrically driven air conditioning than is commonly accepted.
... but sure, ventilated seats are fine too.
Posted by: odograph | Mar 3, 2006 10:10:19 AM
"No, it's about 0.4% (552 million out of 137 billion)."
The 552 million gallons is the amount of fuel ventilated seats would save. The total amount of fuel they estimate is used for light-duty vehicle air conditioning is 7 billion gallons. 552/7000 = .079, or basically the reduction they claimed would be achieved (7.5%).
I can't vouch for the accuracy of either estimate, but that's their claims and numbers, if you reread the text.
Posted by: Joseph Willemssen | Mar 3, 2006 10:34:41 AM
5.5% does sound high. However, how many times do you see people sitting in a parking lot, running the engine just to keep the A/C going?
Posted by: An Engineer | Mar 3, 2006 2:05:08 PM
I would support a law banning black leather interiors.
Posted by: Robert Schwartz | Mar 3, 2006 3:00:15 PM
I did a per capita look at Florida and the amount came to 47.11 gal/yr for air conditioning. That's less than a gal/wk per capita. There are certainly less expensive ways to save a gal/wk such as making fewer trips with only one person in the car.
Posted by: tom deplume | Mar 4, 2006 8:58:09 AM
Sure, but do that on top of having more efficient vehicles and you get even more savings.
Posted by: Schwa | Mar 4, 2006 11:19:33 PM
Installing ventilation ducts in seat is possible but quite tricky because you need to adjust their position as well.
I reckon you could achieve similar benefits be gently sucking hot air out of the passenger compartment (through the roof or toward the rear) as well as blowing fresh air in. This would be especially helpful in the first few minutes of driving after the vehicle has been parked in the sun for a while. In that situation, the rate of cooling is more important than the absolute temperature. High temperatures near the driver's head cause heat stress, impacting not only comfort but also reaction times and hence, traffic safety.
Of course, you should also reduce the heat entering the car in the first place, e.g. with a big piece of cardboard you place on the inside of the windscreen while it is parked, using natural shade or covered parking where available etc.
Longer-term, it may become technically and economically feasible to jettison the traditional system based on a mechanical compressor and R134a refrigerant (better than the now-banned R12 but still a potent greenhouse gas; vehicle a/c will lose up to 8% of refrigerant volume per year through pores in hoses etc., even if you don't use it).
Instead, you would use an ammonia-based absorption chiller powered by the engine coolant. Here's a link to a related academic research project:
http://www.itt.uni-stuttgart.de/~schaal/index.en.html
This might yield fuel savings of up to 0.6l/100km (a/c at full blast during summer). Moreover, you can make do with a smaller engine and gain 5-8kW of power for acceleration.
Posted by: Rafael Seidl | Mar 5, 2006 12:49:59 AM
I think increasing air flow from the seat is is an excellent approach.
The old woven wire cushion did increase comfort in the summer. Some were tough on the butt too. But that depends on design.
I don't see how AC loses 8% of refrigerant per year. My 16 year old Honda has never had a recharge.
Mazda had a feature on the Millenia to exhaust hot air from the passenger compartment even when the car was parked and unused. Most people open the sunroof or windows a little during a flaming startup.
One thing I have noticed is that the air (AC off) from the vent system comes out hotter than the outside air. I think it is being compressed too much because the ducts are small to save space and weight. If the vent system really worked maybe people wouldn't flip the AC on when it is 80 degrees outside.
Posted by: K | Mar 5, 2006 6:00:46 PM
Air flow from the seat? Sounds good, and i guess this will boost up a total comfort for the passengers ride. Quiet sensible for summer driving, this will give a lot of fun so heat won't bother me when i drive. Toyota News
Posted by: Mark Clarkson | Mar 6, 2006 5:39:51 PM
I find this wierd. I am familiar with the Ford and GM Australian family cars (4 litre v6 usually and rear drive). On both, if you use the fan to ventilate the cars, hot air comes out the vent even with the heater off.
Its mostly very warm here but a well ventilated car should usually be tolerable. At speed though, open windows are not viable. Even if the air volume were sufficient from the fan (which it isnt), it is heated.
Not only does poor design (lack of isolation or insulation of ventilator tubes etc) result i n compulsory use of air con, but the aircon has to first wastefully negate the extra heat in the airflow before it has any cooling effect.
A rule of thumb I have heard is aircon adds 10% to fuel use so it isnt a trifling waste.
This flaw isnt rocket science. Its hard to believe the flaw hasnt been discovered and fixed in previous models. My guess is it has and then promptly forgotten or overridden by the stylist of a subsequent model.
Posted by: peter connell | Mar 9, 2006 6:34:14 PM
Manikin?? eets bad eenuf dat i see "BOKAY" dees played at lokal flawer shaps but at GREENCARCONGRESS??!
With spell check and the Internet, there is NO excuse for spelling errors unless of course, civilization just wants to spell everything phonetically while driving fuel efficient vehicles.
Posted by: Dexter Tan | Mar 12, 2006 10:38:00 AM
Actually, "manikin" is in Webster's dictionary, as, of course, is mannequin.
Posted by: Mike | Mar 12, 2006 11:36:00 AM
In 1968, when a CUSO Volunteer in Kenya, I bought an 8-year old, tired, Land Rover. Since I had been a pit crew for a racing driver, I knew a thing or two about vehicles and kept this car running well for the next 16 years.
Some parts of Kenya are uncompromisingly hot, yet this vehicle was never as cruelly hot as a modern car on a summer day. It had three design features which helped a lot: (1) an air vent below the windshield which blasted you with outside air at any speed above 10kmph, (2) a double skinned roof (called the "tropical roof") which allowed ram air to flow between the two skins, and (3) near vertical windows all round.
I bought a further (local) device which ensured my comfort - a beaded seat cushion/back. This simply lay over the stock plastic seat cover, allowing your back and bum to keep cool/dry. These deteriorated and usually had to be replaced once a year.
I eventually drove this vehicle across Africa to Gibraltar, and on to England. In the Sahara (unfortunately I got there in June), the temperature was hot enough to fry eggs (slowly) on the bodywork. Still, my girlfriend (now wife), the Landy, and I survived, not that uncomfortably . . .
Posted by: Peter Bursztyn | Mar 20, 2006 8:40:06 AM
Looks like I should order two custom Herman Miller Aeron Chairs for my car.
Posted by: Josh Shirley | Mar 20, 2006 5:37:13 PM
