Paulus Hook Towers: State-of-the-Art Electric Chiller
upgrade; Bi-Level lighting
Constructed in 1973, the 23-story, 275,000 square foot Paulus Hook Towers originally included a heating plant comprised of two, #4 oil-fired steam boilers. Steam was converted to heat and domestic hot water through heat exchangers and distributed building-wide. During the summer months, steam was provided to an absorption chiller. Prior to the project, this central plant was operating at only 65-percent seasonal efficiency, and when oil prices rose significantly, it became incredibly costly to run.
Steven Winter Associates, Inc. (SWA) designed a state-of-the-art facility to replace the central plant. Features included a 400-ton water-cooled, oil-free electric chiller with four modulating compressors, four 3-million-BTU gas-fired condensing boilers, and two 2-million-BTU gas-fired domestic hot water heaters. Dual temperature water pumps were installed, which included variable-frequency drives (VFDs) for seasonal modes. Additionally, a new variable speed booster pump system was installed for domestic water.
However, simply installing the best equipment was not enough to achieve optimum energy efficiency; the most important implementation measures were the application of system controls and their associated means of measurement and verification. Our team’s design included algorithmic controls calculated to run an efficiency optimization program that determines the number of boilers and exact firing rate needed to ensure the highest thermal efficiency. For the chiller plant, a similar program stages each of the chiller’s compressors and simultaneously modulate the newly installed VFDs in the two existing cooling towers. These controls can reset the chilled water temperature of the system to match the load conditions of the building.
Additional energy efficient upgrades for the building include bi-level lighting in the stairwells and hallways, sealing and balancing the ventilation system, and low-flow showerheads. Collectively, these measures’ projected annual electricity and fuel savings were 3% and 45%, respectively. These savings resulted in a total projected cost savings of $171,000 annually.