I bought one of the first-generation versions of these around 10 years ago. It was annoying to install, and you can't really leave it installed while driving (I believe I read somewhere that this was fixed). Also, it needed a lot of sunlight to get it going. Still, it did work, and it was an improvement over leaving windows partially open, especially in areas where rain is unpredictable.

I agree with DavidE's observations, but they also make your vehicle more susceptible to breakins as they are easily broken which then leaves a nice gap for a coathanger to flip up the inside door handle.

David, why could you not leave it on while driving?

My family first bought one of these 16 years ago while living in Florida, they've been around for a while. It fit snuggle in the widow, no gaps, and worked great. Before using it we would could not even get in the car during a bright hot sunny day, the car was too hot and everything was burning to touch. After starting to use one of these the car, while still hot, was now possible to enter and touch everything in the car.

If you want to cool down your car's interior before driving it, just open the doors and wait a few minutes. When you start driving, leave the windows down instead of cranking the AC.

There is no technological breakthrough needed to reduce AC usage in cars (or homes for that matter). The change has to come from the user, not the machine.

When you drive, the air rushing by causes the fan to turn and it makes a lot of noise.

My parents had a Mazda from the late 80s/early 90s that came with a factory installed version. There were photovoltaic cells in the sunroof that would power a fan somewhere in the ventilation system to do this exact thing. It worked really well, but I haven't seen anything like it since.

Leaving a car window open in an urban area is not a good idea. You risk theives, vandalls and vagrants. I want to try one of these gadgets. But I am a sucker for anything solar!

A feature I like on my Accord is I can use the key fob to lower the windows remotely. That lets me open them a bit from my office and when I get down stairs I can fully open them before I reach the car.

Like Randy said, Mazda had solar-powered vents as optional equipment on their 929 model in the early 1990s.

Like Randy said, Mazda had solar-powered vents as optional equipment on their 929 model in the early 1990s.

While this won't keep hot leather seats from burning your bum, driving the first few minutes with the windows down will cool your car a lot faster than using A/C. By displacing the hot air in the car with the less hot air outside, your A/C has much less work to do. I doubt this saves any energy, however it does cool your car off faster.

I got one of these window vents as a gift. Pros: it's well designed, easy to use, fun science project, and blows some* hot air out of the car. Cons: *Doesn't blow very much hot air...If you come back and open your car doors all the way for about 15 seconds, it will cool the car more than this gadget does. Get a good reflective sun shade instead. And if you really want cool, make a window shade for your side windows too (scissors and suction cups).

While trying to conserve the energy used by AC is a noble goal, overall AC in a car does not use a significant amount of fuel.

I believe it's somewhere around 35mph where keeping the windows down actually makes your vehicle consume more gas than simply running the AC due to aerodynamics.

I live in Southern california, and I use the AC all the time. I do 3 things to conserve gas, and they have been significant improvements (way more than not using AC).

1.) I got a car with a more fuel efficient engine (downgraded from a 6 cylinder jeep to a 4 cylinder chevy S10)
2.) I use the cruise control as much as possible, as often as possible (HUGE gas saver)
3.) I have lowered my overall driving speeds, always keep my engine under 3000rpm, and pacified my driving style.

These are the real energy savers. And just recently I started carpooling with a co-worker. I practically only ever drive my own vehicle now on the weekends.

Devices like this are awesome, and they do work. But in reality, they are comfort-savers, not energy-savers.

Interesting idea, why can't it be adapted to home use as well ?

Audi has (as an option available on the A8L, too bad it's not available on other models as well) a sunroof equipped with solar panels that is used to power fans while the engine is off and cool the interior of the car.
See http://www.audi.co.uk/audi/uk/en2/tools/glossary/operation_comfort/solar_sunroof.html
Also, ventilated seats help reduce the need for AC as well. See
http://www.greencarcongress.com/2006/03/ventilated_auto.html for more details.

I got a couple of these. Not bad, pretty well constructed, but doesn't move a huge amount of air. Really just a loud whisper worth. There is a provision for putting a couple in parallel, which is why I have several, but haven't done it yet. There is a plastic filler piece that goes in the window gap where the fan isn't, or the two fans, and once you've cut it to fit your window you can't move it to a different window without attaching a filler that fits that window; which means that you need to park with the same side of the car facing the sun all the time. They do tell you not to drive with it in the window, but I've tried and there doesn't seem to be a big problem; but I don't see why you would do it, because it moves less air than it would just with the window open a crack though. Maybe in a traffic jam, but then you could just use the vehicle ventilation fan. Anyway, bottom line, it'll take the edge off high temps but not keep the car really cool; I thought it was an OK enough item for one that I decided to invest in a second in the belief that that would be worth it.

PS I saw an ad in a catalog recently that claimed "new improved model". My "buy price" for them is $19.95, BTW; they usually list for more, so when I see them at that price, that's a decent discount.

Re: "overall AC in a car does not use a significant amount of fuel."

You may wish to read:
http://www.nrel.gov/docs/fy00osti/28960.pdf

The more 'efficient' your car is the higher percentage burden AC will have on fuel consumption (so I guess it just depends on your definition of 'a significant amount'). This report claims:

"Current air-conditioning systems can reduce the fuel economy of high fuel-economy vehicles by about 50% and reduce the fuel economy of today’s mid-sized vehicles by more than 20% while increasing NOx by nearly 80% and CO by 70%."

When I lived in Arizona, when entering my car one particularly hot day I noticed that a soda can that had left inside the car had exploded, covering the entire inside of the leather interior with carmelized sugar. Also, a couple of CDs that were resting on the dash had melted...

I couldn't remove either and had to junk the car: goodbye a nice $9,000 vehicle!

Glad I live in the NW now, don't have to worry about that. Oh, and most of the cars in Arizona have 1-inch thick felt pads installed over all the plastic components, such as the dash (mine didn't).

RPM says:
"Current air-conditioning systems can reduce the fuel economy of high fuel-economy vehicles by about 50% and reduce the fuel economy of today’s mid-sized vehicles by more than 20% while increasing NOx by nearly 80% and CO by 70%."

I drive a Prius, 1l:22,5km. With or without AC.
What mathers for the fuel-economy is wind, temperature and rain.
The AC is electrical and specialy made to preserve energy.

if the window ones don't work very well - how about designing one that has a more powerful fan, and using a larger higher powered solar pannel that say sits on the parcel shelf? - it could be used to ventilate the car AND recharge the battery (if it was big enough) - say 1w??

My friends I have 3 different solar powered fan models, all of them you must put in your window but the problem is the devices do not fix very well in the window so is a litle bit open in the sides.
also the electrical windows in the cars is so strong that crash the device.
it must be constructed more strong, I do not care the price because I live in a place very hot.
please if you know a device very well constructed please let me know and I will buy it.
thank you very much
raul

It is stupid to think that because a car window is down a 1/4 inch that it will be more prone to break-ins. If you have something a thief wants he/she will break the window and just take it! To break a window is about 1 sec to pick a lock with a coat hanger minutes.

I have a 96 Toy previa. They have side panel windows that pop and lock open perhaps an inch which exposes a vertical slot over a foot long. Leaving one of these open goes a long way in keeping my vehicle at normal outdoor temperatuires.

Also keeping a sunroof open an inch releases the hotest air, but keep the sunblocking panel in place. If i forget to ensure it is nearly closed, a closed sunroof with no sun protection can turn your vehicle into a solar oven in which you can cook.

Does anyone know who manufactures these solar window fan units? i have friends that like them at low cost.

I have a 96 Toy previa. They have side panel windows that pop and lock open perhaps an inch which exposes a vertical slot over a foot long. Leaving one of these open goes a long way in keeping my vehicle at normal outdoor temperatuires.

Also keeping a sunroof open an inch releases the hotest air, but keep the sunblocking panel in place. If i forget to ensure it is nearly closed, a closed sunroof with no sun protection can turn your vehicle into a solar oven in which you can cook.

Does anyone know who manufactures these solar window fan units? i have friends that like them at low cost.