How To Cool Down Your Car Without A/C

so, you're changing the air from outside to inside? cool!

 

Excellent example of how to refresh the ambiance of your car after dining at Taco Bell.

 

While this may work well for exchanging interior air with exterior air, and it will reduce the air temperature, it will not get most of the heat out of the car. Air holds very little heat per degree of temperature. Most of the heat in the car will be in materials. In the video, they drop the air temp by 10°C, that amounts to maybe 100 BTU (0.03 kWh). The rest of the car is still hot, it has about 5000 BTU of heat at that higher temperature, and will rapidly heat that air back up,

 

Just get the Solar Roof if heat is that much of a problem where you live and park.

 

still, when you get in a hot car that has been in the sun for awhile, i would think it would help the a/c work a little more efficiently.

 

I would say you're absolutely correct. But I think the perceived benefit of this exercise or any "Hot Day" pre-entery exercise isn't to affectively cool down interior materials that may of heated up...so much as it is to reduce the immediate air tempature.

Concievably once you are in the vehicle and moving, your options for decreasing the air tempature and increasing the air circulation greatly increase. Even if this means reaching for the button marked AC.

I try to use a sunshade..and crack windows to avoid the heat build up to start with...

Curiosity will probably have me try this...but I don't know if I wouldn't rather simply sweat for 10 seconds longer as opposed to repeatedly swinging my door open and shut...

A hot day, is a hot day outside...regardless of what you are driving.

Unless you have the solar roof package...I'd think the best recomendation is use of a sunshade, cracked windows, and/or window tinting. My unscientific purely "butt in the car" observation is when I employ these measures...the tempature in my car doesn't feel much greater or greater than the surrounding outside air..

 

Let's consider a sunshade, estimating at 1 meter^2 of glass, 1kW of sunshine per m^2, maybe 50% transmittance = 0.5 kWh after sitting in the sun for an hour. Or taken another way, a sunshade reduces the heat by more than the above pumping technique every 4 minutes.

 

Do I understand that the heat is not pushed out by closing the door, but sucked out by opening the door?

 

Rowing like a galley slave in 90-100 degree heat for 4 or 5 minutes isn't my cup of tea. For those of us with a Prius just try opening the rear hatch and let convection take place. Yeah, I wish we all lived near an ocean... well on second thought.

 

I think both must occur, although the heat generated by repeatedly pushing and pulling the door, while standing in the sun, may create the greatest discomfort. Wouldn't you move more outside air into the car and inside air out in the first 20 feet of driving, with windows down?

 

Several previous cars I've driven had auto-open windows & sunroof (press & hold open button on remote and they all open). On really hot days I would open all as I was approaching the car, and when I drove off whatever hot air was still in the car would be flushed out.

Going through what's shown in the vid seems like more effort than it's worth.

 

I saw this, and I was thinking about posting it here. The Japanese huh?

 

I have that in the Lexus and it works really well, especially if it's done from a distance when approaching the car. People who normally park outside in the sun can just get the SR option in the Prius to avoid that hassle.

 

The operation shown won't cool down the car, as titled, though it will replace the hotter air inside with relatively cooler air from outside. I don't like the idea of opening and closing the door repeatedly for several reasons, not the least of which is what the kids are doing in the parking lot while I'm fanning the car.

Thermal mass is still the issue, as it is with a home, a building, or the road surface. Cooling down the thermal mass (seats, dash, panels, etc.) cools down the car.

When the sun is beaming down, I toss one end of a towel over the steering wheel. This keeps the steering wheel (thermal mass) from becoming too hot to the touch.

What would really help is an infrared reflective (IR) membrane or fabric that we could use to cover the whole car when parked. I want one that pops up like some window shades. Preferably with cool Japanese art on it.

Buildings with an IR membrane roof or IR-coated metal roofing stay remarkably cooler in the sun due to never heating up the thermal mass. Maybe someday we'll have dark-colored IR paint and plastic for vehicles!

 

Open and close the hatch instead of the door. This way, you'll finish it in 5 strokes instead of 10.

 

CAn I do this while the car is in motion? Running the AC really lowers my MPGs and it's all about the MPGs

 

Umm, 'Dark' means absorbing light, and converting it into heat. Infrared is a small portion of all sunlight. So get a light colored car (and cover the windows with something light colored as well) and you are most of the way there.