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...)
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...)
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!
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.
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!
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5 Comments
gtoal 11 years ago
gtoal 11 years ago
schou 11 years ago
gtoal 11 years ago
G
MacOSJoey 11 years ago
Good instructable and good luck in the green tech contest!