2003 Ford Windstar Noise around lower right part of engine

This car has a whirring sound that seems to be coming from the lower right part of the engine compartment. At idle it increasing or decreasing according to engine speed. While driving, the same and at shift points, it does the same. When engine is running, but car is not moving but in gear, no sound. As soon as we drive, the noise is there. When I stop at a stop sign, no noise. It sounds like a gear drive of some sort. The same sound is evident, in park, neutral and in any gear. Not there when in gear and not moving.