In June, Professor of Mechanical Engineering Melody Baglione presented a paper she co-authored with several Cooper students at the 2023 American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Annual Conference.  A collaboration with Kevin Dai ME’22, Jonathan Lerner ME’23, Aditi Pattabhiraman ME’23, Oliver Zhang ME’19 MME’21 and John Rundell from Smith Engineering. The paper demonstrates “Validation of Energy Savings from a Condenser Water Supply Temperature Reset Strategy” from applications of this strategy in the New Academic Building.

For additional information on the presentation, please click here.

ABSTRACT
Reduction of energy spending and carbon emissions are important objectives in the design and operation of building systems. This paper hvalidates a condenser water supply temperature (CWST) reset strategy that seeks to improve chiller plant efficiency for an academic building in an urban setting (41 Cooper Square). Models developed based on manufacturer and building management system data input chilled water supply temperature setpoints, wet bulb temperatures, and chiller loads to output optimal CWST setpoints that minimize total plant power consumption. The reset strategy implemented in the building management system generates the optimal CWST setpoint in real-time using a regression curve fit of CWST setpoints generated by the models and real-time wet bulb temperature and chiller load data. An exploratory analysis of data acquired over two years reveals that the model generated setpoints outperform constant operator setpoints in every measured load range (260-400 tons). During summer conditions, the reset strategy generally suggested higher CWST setpoints. This yielded slightly higher power consumption from the chillers, but significant energy savings from cooling towers. Setpoints under operator control were often set lower than outside air wet bulb temperatures causing excessive cooling tower power consumption. In the fall, the reset used a lower CWST, optimizing the chiller power consumption at the cost of slightly higher cooling tower power. Despite the varying weather conditions, the CWST reset strategy consistently resulted in a net reduction of the total chiller plant power and chiller plant kW/ton. Average energy savings tended to increase with higher loads in the summer months and ranged from 17-41 kW depending on the load range. This study further confirms the theoretical models and recommends the consistent use of condenser water reset to combat climate change and meet New York City Local Law 97 energy efficiency and greenhouse gas emissions targets.