Solar Powered Ventilation?
 

I have searched the forum for "Solar Powered Ventilation" and found no result. I presume that the device that I am going to describe has not been discussed in depth.
I have come across a flier which mentioned a device that looks like a ventilation fan to be clipped onto the window. It is powered by the sun and is to be attached onto the top of the car's closed window like a rider (but please read on) whilst the car is parked under the sun. The fan is supposed to keep the car ventilated and thus relatively cool. In theory this should reduce the workload of the AC when the car is driven again after parking and hence help save fuel. It costs $10 Canadian when on sale a few days ago. It is now sold for its regular price of $20.
I have to park under the sun very often and am tempted to give that thing a try because I think it may pay for itself by saving fuel. Just don't know if other members have any experience with this kind of devices. Apart from whether it is effective, my concern is whether the device, which I think will necessarily cause the window to leave a narrow opening whilst it is clipped there, will significantly compromise the car's overall security (from theft).
Can such a device be considered a true fuel saving device and should I buy it or dismiss it? Any comments welcome, please!

I've never tried one myself, but a few people said they didn't work well in a roof mounted solar ventilator thread I started a while ago.

I bought one. It was absolutely worthless. It didn't deliver on its promises. The car was hot, and the cheesy plastic stuff didn't fit the window well at all, leaving it just as insecure as if I merely left the window open.

I have one. I bought it at a thrift store for $1. Yes the truck is still hot, but I don't believe its as hot as if it sat with the windows up. One thing I noticed though, the fan doesn't run unless it gets direct sun. If you don't put it on the "sunny" side of the car, it doesn't work at all.

I don't think it was a total waste of money, I think its worth at least the $1 I paid for it.

-Jay

Thank you ladies and gentlemen, including those who will comment after this post! You have once again proved that this is a really helpful and welcoming site:thumbup: .
I dare not put one on the roof. It rains here;):D . If the dollar shops have them, may be I will buy 1/2 dozen for just $6 and put them on all windows to increase the ventilating power, or may be even more so that they leave no opening anywhere on any window:D. But seriously, I appreciate the useful advice:thumbup: . I am not going to touch them @ $20 each.

They make watertight roof mounted solar vents for RVs (and houses), but you have to cut a hole in the roof (hole for RV ones can be smallish, though). I also haven't found one that'd be suitable for a car. Gave up on it so I stopped looking.

Just a question for those who "tried and failed" -

In addition to the window fan, did you also open another window to get air cross-flow? I would imagine the product would be completely useless if you try to exhaust hot air without providing an inlet for cooler air (most likely on the opposite side of the vehicle).

-Bob C.

Cross-ventilation wasn't the issue, I made sure to provide for it; the thing just didn't run well, even in direct sunlight.

Thank you for stopping me
 

I kid you not, I was planning on buying one of those window slit solar fans this month. I have a black car and its Baltimore and it gets hot. If I can I leave the windows and the sun roof cracked a quater inch if Im lucky. If you live on the East Coast, you will get humidity and heat in the 90's and then pause for a hour or two for showers, so you have to keep an eye out for the weather so you dont get your car washed from the inside out.

What I have been looking for is those 2 inch tinted platic forms that stick to your upper window seal of your door, that way you can leave the windows down an inch and get flow through. They also function during those summer rain storms while driving to get the steam out of the car.

The most common brand name is VentVisor, if you're having difficulty searching.

I've actually be working on putting together a heftier version of one of these things. So far I've got 3 of the ~$13 (when on sale) harbor freight 1.5 watt battery maintainer panels and a 3" bilge blower with a motor scavenged from an old inkjet printer installed in it. I couldn't get the blower's original 40 watt motor to even twitch when driving it directly, and it barely spun when using an electronic speed control from an old cordless drill and a fat capacitor. The printer motor has the same size case and shaft as the stock motor but runs nicely with the solar panels in parallel, in spite of being a 24 volt motor.
I haven't gotten to installing it all yet, but I intend to put the panels inside at the top of the rear hatch glass (ideally I would get a bunch more of them and set them up louver-style) and connect the blower output to the existing air exhaust vents in the rear quarters of the car.

I think the custom solution is the way to go. A good ball bearing 12V computer fan can provide a fair amount of airflow without drawing allot of current.

I just crack the windows an inch. If thieves want in, they'll get in regardless, so don't worry about that. The only thing that I worry about is dust buildup inside.

Adding to Snax's coment...

How about working the A/C system backwards while on Vent from outside (as opposed to ReCirc). I don't mean using the A/Cs fan but maybe shutting off all to the vents but the top and adding a decent fan attached to the appropriate amount of solar panels which will be layed out on the dash?
The fan will need to be powerful enough to push air back out via the a/c ductwork.

It really isn't necessary to provision for the outflow of air in many (most?) vehicles, as there is already an outflow vent present - usually hidden and exhausting through the bodywork. Even lacking that, most cars are far from sealed. With a recirculating AC, the outflow vent still exhausts some air, so it's really more matter of getting the fresh air in. Just don't try to move air the other direction without other accomodation, as the outflow vent often contains a one-way baffle.

I have one of those fans but this one plugs into the cig lighter, so it will run continuosly despite clouds, etc, STILL -- it doesn't do much.

You don't have shade to park under, so why not make your own shade? Clip one of those aluminum sun shades under the wipers and leave the windows cracked an inch or so.

I was thinking that a powered solar ventilator hooked to the battery might makes sense provided you had a low power shutoff. I guess you could still have solar panels to top off the battery as well.

A similar tactic would be to use a small dedicated deep-cycle lead acid, or maybe a NiMH battery pack. Hard wire the pack to a charger/controller circuit of some sort so it charges up when the engine is running and discharges through the blower(s) when parked. That way you don't have to worry about having enough power left to start the engine... The blower(s) can run the dedicated battery flat and not touch the car's main battery. Where would solar panels fit into such a setup? I guess they could be set up to charge the battery/drive the blower(s) at all times, but they wouldn't really be necessary for operation.

A temp switch would be pretty useful as well, I would think.

Yeah, that occurred to me as well. The CRX is a rolling greenhouse... Even more so with a japanese market glass roof (not that I have one). One of the reasons I've resisted installing window tint is that solar heating occurs in the winter too. A 130?F interior sucks in the summer, but stepping out of the 20?F wind into a nice room-temperature interior is worth it in my book. Venting the interior during the winter would kill that heating effect.
A simple interior temp switch set at around 80?F would probably do the job, though a seasonal toggle switch could handle it too. Have it switch off the blowers and use the solar power to charge the two batteries.

I'm wondering about the possibility of a solar driven chimney type affair... a large flat one that sits over the windshield and covers the vents, black! Leave the vents open and the rear windows cracked, parked facing the sun, and theoretically, your black solar collector/chimney should start to convect and draw air up from the vents....

Enwisage this, as Mr Chekov might say...

Get one of those cheapy pressed/rolled steel curtain rails, the ones shaped like |________| that are expand to fit... stick either big magnets or suckers on the ends, so it can attach to your car at the top of the windshield (On the outside!) Then get a black shower curtain or something similar, that bunches up tight along the rail, put magnets in the side to hold on the A pillars, and magnets in the bottom to pull it over top of the vents... depending on angle and rake of your windshield you might need another in the middle... Can probably hack it up for $5

Could even epoxy the fittings for the curtain rod to the A pillars, they're fairly low profile... and if you want to get fancy velcro the sides instead of magnets... Might need more bend in the rod if you've got a curvy screen.... Inside the car you might wanna put up a normal sunshield to help keep out long wave IR from it that would warm the car up more.

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