Because car batteries need to be able to start a cold engine while they themselves are cold, during the summertime car batteries have enormous reserve capacity beyond what's actually needed. It would be useful to have an option to run the car's fan intermittently while the car was parked to keep the interior temperature at least somewhat reasonable; it should not be hard to design the device so that if the car was parked for too long it would shut off rather than draining the battery below the point that it could start the car.-- supercat, Dec 13 2000 Mini air-conditioner http://www.outdoor-...air_conditioner.htmHow about modifying one of these to fit in the window? Wonder how long would it take to drain that enormous reserve capacity? [lbjay, Dec 13 2000, last modified Oct 04 2004] (??) Solar Powered Car Fan http://www.sun-matecanada.on.ca/247.htmBaked. Solar panel means it doesn't even draw down the battery... [rmutt, Dec 13 2000, last modified Oct 04 2004] (??) This is it http://www.neptune-singapore.com/I think this product is exactly what you are describing. [monkeynotes, Oct 04 2004] Solar-powered fans that attach to the inside of a closed window are already available, but I don't think this is quite what you had in mind, since there is no active cooling mechanism. It just stirs the already warm air.-- centauri, Dec 13 2000 The interior fan on a car circulates air between the outside of the car and the inside. In the summertime, it's common for the interior of a car that's left in the sun to get to 140 degrees or hotter; circulating in outside door wouldn't get the car very cool if the outside air was 100 degrees, but it could still keep the temperature close to 120 degrees.-- supercat, Dec 14 2000 The available solar-powered ventillators DO move air in/out of the car. They're clamped in the side window for that reason. Their size makes me doubt that they can move enough air to make much difference but I've never tried one.-- rdmiller3, May 23 2001 Have a liquid nitrogen tank in the boot and circulate the stuff through pipes under the floor...-- RobertKidney, Jun 25 2001 I remember a car that had this feature. They had a TV commercial in the US (maybe 8 years ago?) which mentioned the automatic fan. I guess it never caught on, or I dreamed up the idea 8 years ago.
If I didn't imagine this, I'm reminded of four-wheel steering. What ever happened to that good idea??-- randydarden, Jun 26 2001 There would have to be some sort of kill switch, else a lot of mechanics would lose fingers/arms/pirate hooks.-- AfroAssault, Sep 20 2001 The Mazda 929 had a fan built in to keep it cool when parked. The solar panel seemed to be embedded in the moon roof. Pretty slick.
The idea is to keep a car from having to have a big AC. I heard somewhere that car AC's could be a lot smaller if they didn't have to cool a hot car interior as rapidly as the marketers say customers want. So- in order to get a baking parked car cooled fast, you need a big AC. Big AC means worse gas mileage. It doesn't take a big AC to keep a car cool. So enter the solar powered vent. Keeps the car cooler --> smaller AC needed --> better gas mileage. But the 929? 18 mpg!-- pine5, Jul 14 2002 A fairly tried-and-tested way of cooling houses in hot climates is to build a very tall chimney. Air is drawn up through the chimney (by wind passing across the top of the chimney) and this creates a draft of air coming into the house at ground level. Ideally, the air which is drawn into the house is pre-cooled by the vegetation surrounding the house. So, what is needed are:1. Huge Telescopic Chimneys for Cars2. Car Window Boxes-- hippo, Jul 14 2002 Hippo, if I could croissant your anno, I would.-- salachair, Jul 15 2002 I had a little side window mounted solar-powered fan. I didn't think it really made a whole lot of difference but on the otherhand, I don't know if I can actually differentiate between 120 and 140 degrees. Both are PDH (Pretty Darn Hot).-- bravesirrobin, Jul 16 2002 It would depend on the climate, but the solar gain of the average car is scary. Check out the US Department of Transportation website for exact figures - they have doen some interesting research. I don't think a small solar powered fan will do a great deal to help. Of you could keep the main ventilation system running, that would do something, but the current drain is substantial (many amps) and would soon flatten the battery. You'd need an awful lot of photovoltaics to provide that sort of power.
I would say that a large silvered mylar parasol sunshield that tracked with the sun's position would be a better idea. I haven't checked that for being baked, by the way. It would need to auto retract in the event of strong wind to protect itself from damage.-- 8th of 7, Jul 16 2002 But [8th of 7], if everyone had small highly-reflective Zeppelins tethered to their cars when parked, it then wouldn't matter about wind or the angle of the sun - if you were parked in the middle of a big parking lot, you'd be in shade.-- hippo, Jul 16 2002 don't RV's have little air thing on the top of them, why not use one of those and turn it on by remote before you leave by the time you get to your car, WALLLAA-- Half-Life, Sep 03 2002 Cars today have "flow-through" ventilation, in which fresh outside air is pulled into the car from the vents in the cowl in front of the windshield. Use solar cells to power the heater/AC fan to circulate air while the car is parked- cheap installation, uses mostly existing car systems and components.
Part of the downside is that the fan gets a lot more wear and dies a lot sooner. Replacing heater/AC fans is expensive and very not fun.
I've thought about powering the AC unit with a separate engine, like a leaf-blower or lawn mower engine, not for parking in a mall parking lot, but for sitting in traffic with the main engine running on a hot day.
When I drove a big truck a few years ago, I pulled "reefer" trailers that had a diesel-powered refrigerator unit. A 50 gallon tank of fuel ran the reefer for 3 or 4 days continually, keeping a constant inside temp of -15 F. A similarly efficient unit for passenger vehicles could possibly maintain a temp of 70-75 F for probably less than a quart or a liter of fuel a day. (might be a good exercise, calculating how much fuel is consumed hourly by existing car AC units, maybe it's published somewhere.)-- whlanteigne, Jul 20 2003 The toy solar powered car fan I own (that clamps on the top of a cracked window) barely worked. It dropped the interior temps about 2 degrees f 88 vs 90 on similar days.
It also lets the rain in.-- popbottle, May 03 2013 Why not use it to your advantage? Black car with black interior, with a small roof vent, and closable vents at the bottom of the doors, you should be able to dry jerky while you are at work for the day.-- not_morrison_rm, May 03 2013 This idea was made for me. I love summertime parked cars.-- MaxwellBuchanan, May 03 2013 If you arrive at your all-day parking spot early in the day, while the spot is still cool from overnight darkness, and your car keeps that parking spot shaded all day, the ground surface will probably remain pretty cool.
Create a flat box that pulls the cool air from near the ground under the car, and blows it into the car through a flexible duct. Leave windows down a bit for hot air to get away. Put up reflective window shades to keep out as much heat as possible. All passive, and will make a major difference.-- lurch, May 03 2013 One I toyed with in Thailand was a roof rack with lots of cheap cotton sheets and small pump and a water tank.
Cotton sheets cover the bodywork, water is dripped onto it by the pump and evaporative cooling etc.
Problem was, I was too mean to buy a car to test it on.-- not_morrison_rm, May 04 2013 The new Prius has solar panels on the roof which run the car's fans while it is parked. I trust it works better than the window hook fan.-- DIYMatt, May 05 2013 random, halfbakery