That depends on a lot of things, especially the motor that the fan is driving. There is a correlation between RPM and energy used / produced however the amount will be dependent on the system involved.

I assume you are wanting to turn the fan externally to use the motor as a generator.

EDIT: Thanks for the additional info. That's not going to work. The AC fan motor won't work as a generator. Even if it did, it wouldn't produce enough electricity to run the pump.

Those are good answers. Typically fans use a motor that won't run as a generator. A 40 watt fan will produce up to 30 watts if it has the right motor and you have a strong enough wind to turn the fan it's design speed which might be 1400 RPM. Neil

RPM alone can not produce power.The power produced will be less than the power consumed by the fan motor.You may couple a small generator that rated at 1400RPM to fan and get some power but it will be less than the power consumed by the fan.

RPM is to be kept constant.

Energy can not be created only we can covert from one form to another.

ZERO , BECAUSE IT WAS AN AC MOTOR.





READ MORE BOOK ABOUT BASIC GENERATOR BEFORE MAKING SUCH SAME MISTAKE HAS BEEN ASKED BY MANY STUDENTS OVER HERE.

I wanna make a project about generation of electricity by Rpm .. We all know that average rpm of a cooler fan is 1400 rpm .. I wanna know how much electricity will produced by this rpm ?