Register to reply

Power output of a simple generator

by treplag
Tags: generator, output, power, simple
Share this thread:
Jan9-13, 09:58 PM
P: 6
How do I convert the RPMs of a simple turbine (e. g. a windmill) into the power it generates? Let's say that I want to know if a single windmill of a certain size can power a refrigerator. Assume that I already know how long the blades have to be to produce the RPMs, and I know the energy requirements of the refrigerator. I am only looking for a basic equation of RPMs to power (watts or joules). Thank you.
Phys.Org News Partner Engineering news on
Greater safety and security at Europe's train stations
Fingerprints for freight items
On the way to a safe and secure smart home
Jan10-13, 01:30 AM
I_am_learning's Avatar
P: 669
I don't know the answer, but I at least know that its not that simple.
RPM alone don't tell the full story. You could get a small baby-toy scale turbine to rotate at the same RPM as a big power turbine.
What you can get is - for a given wind speed, and for a given turbine type of certain size you can find out the mechanical power output. The mechanical to electrical conversion is often >90% efficient.
The theoretical limit to the maximum power that can be harnessed is given by
Power_max = 0.5 x Swept Area x Air Density x Win_Velocity^3
But to get anywhere near the maximum power you need to have a state-of-the art turbine design.
Jan10-13, 01:54 AM
P: 6
Hi, I_am_learning - Thanks for your input. I was afraid it might not be as simple as I had hoped. Apparently I will have to keep digging.

Jan10-13, 05:26 AM
P: 22,303
Power output of a simple generator

Power is rpm times torque divided by 5252 (English units).
Jan10-13, 09:32 AM
P: 6
Thanks, Russ!
jim hardy
Jan10-13, 12:55 PM
Sci Advisor
PF Gold
jim hardy's Avatar
P: 3,686
Quote Quote by russ_watters View Post
Power is rpm times torque divided by 5252 (English units).
Thanks Russ !

i've been looking for an easy to remember number for that conversion, and 5252 is it .
52 twice makes me think of Tex Ritter's "Deck of Cards"

So at 5252 RPM torque and horsepower have the same number. That's right in operating band of small outboard motors i tinker with.

old jim

Register to reply

Related Discussions
DC motor and AC generator's output Classical Physics 1
Calculating the Power Output of an AC Generator. Classical Physics 7
Generator Output Question Mechanical Engineering 11
Generator Shaft Power (Input) to Generator Out Mechanical Engineering 1
Generator's output Electrical Engineering 5