Is 3 Volts enough to power a cpu fan

3v will run many fans, albeit at a slower speed. Some fans need more voltage to start, so there is no specific answer. The fan will often have a voltage range listed on the label. Chances are it's a 12v fan, and if it will run on 3v, will not provide much cooling. A Guy

JBmorris said:

So 3 volts could possibly 50%/50% turn the fan but at slower speed?

Possibly but it's highly unlike you will find a fan that can start at 3v. 5-7v is usually about the lowest starting voltage you will find and that will be only in the highest quality fans. And, as A Guy said, it won't move very much air. You may need to use a DC to DC inverter to power a 12v fan but that would at least quadruple your 3v current draw.

I did a quickie search for 3v fans and didn't find much of anything. This outfit sells 3.3v fans, which may work for you, but I don't know how reliable or safe the company is (my guess is not very).

I'd say 99% no. Many fans need more then 5v just to "kick" it into motion. At 3 volts you might get 100-200rpm and that wouldn't move any air. Anything running at 3v would probably be some tiny little fan. A CPU fan from 20 30 years ago won't work. A Guy

What exactly are you trying to build?

Air conditioner or ventilation fan? There is no way in this universe you will ever power an refrigeration type air conditioner with only 3-6v or even 12v and you aren't going to move enough air to ventilate a room using computer fans. You will need a really large, not to mention really expensive, PV array just to power a fan powerful enough to ventilate a room.