Hello all.

Here is the personnal project I have. My goal is to power a 12v fan (look like a computer fan) by 18v solar cells. If I plug the fan directly in the solar pannel, it works fine in high sun (the fan turn really fast), and of course, if there is not enough sun, the fan stop.

I was wondering if I can make the fan run more reliable : do not send too much current or voltage (to not damage the fan), and enable the fan to start in lower sun condition (and eventually make it start-and-stop in a few second if there is not enought light).

My main constraint is that I do not want to use a battery (I do not have enough space and I must keep the weight as low as possible).

I was thinking of using a "Zener solar engine" circuit (the one on solarbotics.net website), with a 12V Zener, but I have no idea of the NPN/PNP transistor I have to use. Can I use a 2N3055 for that ?

Are you aware of a better circuit to power a Fan with a Solar Panel which can make the fan run "safe" (keep V beetween 7v and 12v) ? Also, It would be great if in low light condition, the fan run slowly or by short pulse.

Here are the characteristics of the elements I have :
- Fan : Sunon ME80251V1 (12V, current 145mA/Max 167mA , 1.7W / Max 2W , Operating voltage : 4.5V to 18V)
- Solar module : Phaesun Sun Plus 10 (12V, Max Power 10W, Volt at max pow Vmp 17V, current at max pow Imp 0.59A, Short circuit current Isc 0.66A
- I also have a bunch of component (2N3055, LM7812, resitors, capacitors...)

Ps : sorry for my bad english.

 

Hello,

If you do not want to have some form of energy storage then you would have to have an over specified solar panel so that you would cut back a lot when there is full sun but no cut back when there is little sun. The fan would run longer that way. You'd loose a lot of the available energy over the course of a whole day though that way.
So if you need say 100ma normally then try a panel that can put out 1000ma for a simple example, but regulate the output. Obviously this will require a bigger more expensive solar panel.

 

Thank you for your reply. I can accept some form of energy storage with a capacitor. It is not as effecitient as a rechargeable battery, but it can store a little storage (for a few second maybe).

 

Thank you for your reply. I can accept some form of energy storage with a capacitor. It is not as effecitient as a rechargeable battery, but it can store a little storage (for a few second maybe).

Why would you choose a capacitor over a battery? A battery is more effective by cost and volume. The only other practical solution is the larger panel as mentioned, with a shunt regulator that dumps the excess power when appropriate.

 

Because with a battery/, I also need to have a charge regulator. And 12V battery are a bit too heavy and take too much space for me. The whole circuit (excluding the fan and the panel) need to be fitted in a box like a cigarette pack.
But thanks for your advice, I will try a shunt regulator circuit.

No other suggested design ?

 

How about 2 x 9V Nicad rechargeables in series? I doubt you'd need a charge controller and they'd easily fit that size.

You're basically asking us how to store electrical energy but rejecting batteries. Yes, capacitors can be used but they're seriously deficient compared to batteries and I doubt a capacitor circuit would be worth the bother except for one aspect - giving a boost when starting the fan in low light where the fan might run once it's started but doesn't have enough current to get started.