NRG’s Harrisburg energy center (now owned by Clearway Energy Group) generates electricity for sale to a grid, and generates and distributes steam for space heating, domestic water heating, humidification, and industrial processes. In 2015, when one of the center’s two 200-foot-tall stacks was beginning to deteriorate and needed to be repaired or reduced in height, Barr was asked to conduct air dispersion modeling to demonstrate that even with a reduced stack height, the facility would remain in compliance with national ambient-air-quality standards (NAAQS).
To analyze the new operating scenario, Barr needed to set up the dispersion model to reflect not only emissions from the center’s four boilers and two internal-combustion engines, but also the site’s location in an urban area with several nearby buildings, other sources of air emissions, and a heavily trafficked elevated highway.
Our modeling results allowed for a 20-foot reduction in the stack height. During deconstruction, NRG determined that an additional 7 feet of stack needed to be removed due to deterioration. Barr provided supplemental modeling to show that despite the further reduction in stack height, the facility’s emissions would still meet the NAAQS permit limits.