Solar-Powered Desktop Fans

Summer is almost here (in Canada) and it is the perfect time to harness the power of the SUN!

Cooling homes in the summer has quite an affect on energy loads and demands, so why not decrease your impact with solar powered fans!

Actually, this can be used for anything that runs on 12 V DC . If you by a 12 V to 110 V inverter you can plug in pretty much anything that isn't too power-demanding. This would depend on the size of your storage battery though.

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Step 1: Parts

You will need:

- 1 or more solar panel(s) that can output about 12 V
- rechargeable battery (I used an emergency car booster pack. These are good because they have 12 volt cigarette lighter plugs which are ideal for a computer fan.)
- cigarette lighter outlet adapter
- adapter plug that fits into the input of your battery (I was able to scavenge through some old adapters. The input is there for a 110V adapter that can be used to charge the battery using a regular wall outlet. Not very GREEN charging it that way though!! )
- breadboard (not very necessary, but makes things a lot more customizable)
- 1 or more 12 V computer fans
- shrink tube or electrical tape
- soldering iron (optional)

gtoal says: May 26, 2012. 12:52 PM

Try this: get a Peltier unit (extracted from any old dead cooler - it's seldom the Peltier that fails) and have one fan blow the cold air towards you and the other fan blow the hot air away from you. This won't cool the room but it should cool your forehead. (I've been thinking about incorporating this and the solar panel into the canopy of our outdoor garden swing chair...)

gtoal in reply to gtoalMay 26, 2012. 12:57 PM

PS for outdoor use you simply plug the 12V computer fan directly in to the solar panel outputs. It blows when it shines which is when you need it. No battery required. I've also driven the Peltier directly from a panel and used it to cool my drinks when enjoying the sun in our back yard. (Of course South Texas sun is a bit hotter than Canadian sun so gives more power, but then you need more cooling so it all balances out...)

schou (author) in reply to gtoalMay 26, 2012. 2:51 PM

Good ideas. I have checked the voltage coming from each solar panel and even at moderate sun intensity they put out about 20 volts each. I'm not sure if the fans can handle that much voltage. Will definitely try something with a Peltier though!

gtoal in reply to schouMay 26, 2012. 6:16 PM

Only one way to find out :-) But I suspect that 20V will be OK - it was for mine. Or... you can use a voltage limiter chip - 12 cents from your local Radio Shack and trivially easy to use. One pin is ground, one is the input from the panel, and the third is the regulated 12V out. (or less, it steps down but not up - you need a Joule Thief circuit for that...). The heatsink does get very hot though. Maybe screw it down to the cooling fins of the Peltier and use some thermal paste. It'll loose a little efficiency but may save you from a nasty burn. On the other hand the hot side of the Peltier is probably nearly as hot as the voltage regulator so you're going to have to be careful anyway.

G

MacOSJoey in reply to gtoalJul 3, 2012. 5:01 AM

Even though the panel puts out 20 volts, that's NO LOAD voltage. Notice how the voltage instantly drops when connected to a load (the battery?) If the fans use a little less than the panel puts out, it will reduce the voltage. BECAUSE these run on DC, they really don't care what voltage comes in. It will just control the speed. By the looks of it you're using 1 - 2 watts of solar panels, so either way the voltage may be high but the current is so low nothing crazy will happen. I would not go for a limiter chip because of the wasted heat energy. It's just not worth it.

Good instructable and good luck in the green tech contest!