Applications Engineering

High Performance Chiller Plant

As energy engineers, we have been continually looking for opportunities to reduce chiller plant energy usage through the use of high efficiency water cooled chillers, “pony” chillers, variable frequency drives, premium efficient motors, low approach/high efficiency cooling towers, sophisticated control strategies, etc... 

In most cases energy professionals focus on increasing the efficiency of individual components and optimizing the plant based on outdoor wet bulb temperatures, condenser water temperatures, and chilled water and differential pressure reset strategies. In almost all cases building operators try to minimize the amount of online equipment and stage chillers based on their ability to maintain chilled water set point (or when they hit 95% FLA). After analyzing over 300 central plants we have found that current strategies for energy efficiency and sustainability are just not cutting it. Commissioning and retro-commissioning have offered short term solutions to the many issues these systems face.
Measuring HVAC Performance
Figure 1 showcases the average annual efficiency of the chiller plant (wire-to-water efficiency). Exceptions to this rule are air-cooled chiller plants and water cooled plants less than 300-tons. For smaller water cooled plants add a factor of 0.1 kW/ton to this chart. For air-cooled systems add a factor of 0.35 kW/ton to the values shown on this chart.