Solar ventilation broken?

I noticed that too yesterday. In the heat of the burning sun last 2 months, my Prius' solar powered ventilating fan ran non-stop full-blast untill I stopped it by starting the car. Now I think it behaves like that because the lower angled sun is not so powerful as to supply enough energy to support a non-stop fan. The sun may be shining full-blast to our eyes but for the solar panel it may be much too weak.

Another observation of mine is that I had to clean the glass surface of the solar panel quite often or the road-dusts diminishes the efficiency of the solar panel quite a bit.

 

Hmm, may I suggest you clean the glass surface, and if it still not working bring it to the dealer?

One more thing I noticed yesterday. The Prius made a weired "girgling" noice before the ventilating fan started blowing weakly when it decided it had enough solar power. Did you notice that?

 

Both.

Yes, that's how it's suppose to work. I've noticed that it will stay on for longer periods of time when the sun is directly overhead, and hot outside. That is, it's working harder/longer to cool the cabin down. When cooler, or the sun is at an incline, it's more "bursty", and the fan speed is lower.

But the bottom line is - the system maintains the inside temp at, or near the outside temp...the system will do it's thing (whatever that might be), inorder to keep the inside temp close, or at the outside temp. So, if the system only needs short bursts of outside air to bring the inside air to some set point, that's what it will do. There's no reason to have it run unnecessarily, or continually beyond when it reaches the temperature set point. That just reduces lifetime of the fan and other system components. There's simply no need to do that.

I love it.

 

Yeah, I had similar concerns/questions when I first got mine. I heard all kinds of moans and groans...and it seemed to operate sporatically

But in the final analysis, I checked the inside temp (on a hot day) compared to the outside temp, and it was within 1 degree difference.

It does what it says it will do. Enjoy.

 

RIGHT ON with the cleaning of the panel.

 

Yes, for some time after I first bought my 2010 I was concerned that the fan wasn't working the way it was supposed to. The first few times I actually caught it while it was on, it only lasted a few seconds and then shut down. I thought maybe I was just always catching it at the end of a cycle, but then sometimes it would come back on for a few more seconds before shutting down again. But after another few weeks I did start catching it operating for a reasonable period of time.

 

The temperature of the solar panel is a big factor too. If the panels are hot it takes a lot more sun to start or operate the fan. Mine too makes a grumbly noise before starting and cycles when there is not a lot of excess wattage.

 

The outside temp needs to exceed 70 degrees

 

Short answer: My fan does the pulsing (cycling on and off repeatedly) also under some lighting conditions, and not for any good reason. It's quite annoying.

Here's the long answer: I've been closely observing the performance of the solar system in preparation of adding a solar battery charge feature. The Prius has a vent controller, and this controller decides when to start the fan and when to stop it, it also controls the load on the panels most likely by controlling the "requested" fan speed. The fan in this case is not a simple motor that goes faster with more voltage. At about 19 volts the system will start, and it will run to as low as about 11 volts. In an ideal world it would optimize the load to draw as much current as possible without causing the voltage to fall off, and the fan would simply speed up and slow down with passing clouds, which in some cases it does. However what I'm seeing is that under certain lighting condition, the controller increases the load on the panels until the voltage suddenly (not due to passing clouds!) falls below about 11 volts and causes the system to shut down. It then waits about a minute and repeats the whole process, over and over again. I'm not sure what algorithm it uses, but it is clearly a very poor one.

Two key factors are the temperature of the panels, and the amount of light reaching the cells. I'm experiencing the problem currently with direct sun at 4:00 PM in Seattle. (As mentioned the cabin must be over 70 degrees, but this is not what causes the rapid cycling.) I believe there is also a 10-minute pause any time you toggle the ventilation switch on the dash.

While a really neat feature, it's not very well implemented on the back end in my opinion.