A bad question, as it has been doing that literally (rotationally) since before life started. This power is busy generating the magnetosphere. We would not be enjoying our nice oxygen atmosphere and would be as dead as Mars if Earth's rotation wasn't also powering a dynamo.
Earth's rotation is also generating the power that is moving the Moon's orbit slowly away from Earth. There will be no more total solar eclipses in 600 million years because of this.