It seems that the roof works well to power the fans with the noon sun overhead, but afternoon temps peak later in the day. Many people get off of work at around 5 PM and will be walking to the car at around that time. Will the solar roof do much good to cool the interior when the sun is lower in the sky?
I am not sure on your location but living in Dallas, TX. 5 pm is where the hottest temps are recorded for the day, so I can see it making a big difference around here even if the sun is at a lower position than the middle of the day...
I think you missed my point. 5 PM is a very hot time of the day in the summer, but the sun isn't straight overhead at that time. The sun has to be overhead for maximum charging. So, the fans would help at 5 PM IF the fans still work well enough without the sun overhead to provide charging power. Have people seen the solar roof fans cooling ability at the later times of the day?
I've noticed that about 4:30-5:00pm is when the sun is no longer direct enough on the panels. I feel this is likely because the panels need to produce 10V or higher for the system to work. If this could be lowered a bit while still providing *some* ventilation, we'd have a far more effective system. In AZ, it's still quite hot at 5pm and this is when I'd like the system to be most functional.
Hmm, so it would cool the car for going out to lunch at noon, but not for getting into the car for the commute home at the end of the workday.
That's what I've noticed thus far. I'd like to find a way to see what the panel voltage is to see if it's a threshold that could be adjusted in an ECU flash by Toyota or if it's something we'll have to live with. I know I'd love another hour or two even at low speed if it were doable.
I am also in AZ, and I find the technology amazing. The other huge benefit is that you can start your air before you get in the car by pressing the button on the key, it starts blowing cool immediately when you get in if the solar fan has been on. The car is sweet!
And you have to find a parking spot far away from office building ... so much for hauling around those dead weight. I think an aluminum window shield will do just fine.
That's a bummer. The 5pm-6pm window is the vast majority of when I'd really want it to keep the car cool. I'm in no hurry to buy, though, so I'll continue to keep an eye on people's experiences with it-- particularly those of you in Arizona. I suppose you could always park the car on a huge, tilting platform to keep it lined up...
Then you are back to the issue of not being able to open windows to exhaust the hot air before turning on the a/c. Remote a/c won't do much in the time it takes to walk to the car if the interior is full of 140 degree air and outside temp is 95. Remote window control would have been more effective in that situation.
Always try to park facing east so the angle of the solar panel is toward the west and that bloody big windscreen is facing away from the sun. Isn't it great that the Prius has tiny back windows. (Not according to me but other PCers who complain of bad rear vision.) Ceramic or metallic window tint will help too.
Remember that the solar vent is working to counteract solar heating, not high ambient temperature. Low sun means less solar heating, so less need for venting. As for high temperatures in the late afternoon, it's not going to do any good to pull hot air into the car for cooling. The solar vent is just a vent, not a cooling device. It only works when the external temperature is lower than the internal temperature, which is what happens in the sun. Tom
But the external temperature is lower than internal at 5 PM on a car sitting outside all day. When I go to my car at 5 PM, the car interior is hotter than the external temperature. My car has remote control windows and when I stand next to the car and open the windows at 5PM, I can feel a blast of the hotter air escaping from the car. So, if the solar fans were able to work on the Prius at 5 PM, it would help. Since the exhaust fnas cannot work in the later afternoon, remote windows would be the next best thing, but Toyota doesn't offer remote control windows.
Low sun shines straight in vertical window surfaces but (apparently, from initial reports) does not sufficiently illuminate the horizontal solar panel to run the cooling fans. HTMLSpinnr's observation that his fans stop around 5 are particularly interesting to me-- he's in Arizona as well, and 5pm is not a time of day where the sun has stopped making things brutally hot. It is, however, late enough that a horizontal solar panel might not work well enough to drive the fans. That's why solar panels on buildings are angled up and faced toward the south rather than laid flat. There's probably no easy answer for this, either-- it would require a battery for the fans in the evening, more panels on the sides of the car, or a tracking panel.
Just open all the windows when you get into your car to evacuate all the super hot air in the car, I keep them open until the car start moving for a few minutes, the a/c won't be cooling at 100% anyway. Just help the a/c do its job.
Just a correction - solar panels are angled south to maximum production due to the tilt of the Earth's axis. Depending on your latitude, but assuming you're in the USA, somewhere around 20 degrees angled south will maximize yearly production, but if you are trying to maximize production for summer, the angle will be less (sun is closer to directly over head) or maximum production for winter, the angle will be more (sun is closer to the horizon. To maximize production for 5pm summer heat, the panel needs to be tilted towards the sun, which sets in the west. Ideally, the panel would raise when the car is parked and track the sun. Now that'd be a neat trick!
I have an IR thermometer handy now and will take some temp readings to see just what we're dealing with.
