Philadelphia Energy Solutions Chief Executive Officer Philip L. Rinaldi, who oversaw the revival of the former Sunoco refinery in South Philadelphia but whose industrial activism made him a lightning rod for environmentalists, announced Tuesday he plans to retire in March.

Rinaldi, who turns 71 next year, told employees in a memo that he will remain on the PES board until the end of 2017 to assist in a leadership transition. "And I will continue to have a substantial personal investment in PES, a sign of my confidence in the company's future," he said.

His retirement was first reported by Reuters.

Rinaldi has run the privately held company since 2012, when the Carlyle Group and Sunoco formed a joint venture to operate the troubled refinery complex. The new owners revived the business with $700 million in new investments, including a rail-unloading terminal that allowed the facility to tap into a virtual pipeline of low-cost domestic crude oil shipments.

"Phil's remarkable leadership helped save and modernize the company, as well as save and create more than 1,000 jobs," said Carlyle spokesman Christopher Ullman. "We have begun the process of finding a successor who will build on Phil's accomplishments."

But Rinaldi's attempt to take PES public last year sputtered, and the 330,000 barrel-per-day refinery has struggled with the fall in crude oil prices.

Rinaldi has also been active in promoting an "energy hub" in Philadelphia, for which he became a target of climate activists who dubbed him "Fossil Phil," a name he relished.

Rinaldi plans to remain as chair of the Greater Philadelphia Chamber of Commerce's Energy Action Team, which is promoting the construction of a large pipeline to deliver Marcellus Shale natural gas to Philadelphia to fuel new industrial development, said Cherice Corley, the PES spokeswoman.