30th Street Station Smokestack

I have often wondered about the enormous smokestack just northwest of 30th Street Station? Why was it built, when was it built, what purpose did it serve, why is it still standing, can it be torn down, is it still being used, etc?

Given the fact that it's clearly in the middle of an ex-PRR yard, I assumed it belonged to the Pennsy, so forgive me if I posted this question in the wrong forum.

I've been able to find out that it's the Pennsylvania Railroad's Steam Plant. However, I have not been successful in determining what it was for -- was it used to generate electricity for the PRR's electric operations? Was it kept burning so that it would be easy to get steam locomotives started?

I believe the steam plant was used primarily to heat 30th Street Station and the adjoining Post Office. Surplus steam was also sold to surrounding properties such as the University of Pennsylvania and the old Conrail HQ building at 32nd and Arch. Electric power for the NEC was and still is generated at the PECO plant in Bridesburg alongside the Betsy Ross Bridge.