In the fall of 2023, Millig was selected through a competitive selection process as the partner for Washington State University to develop and design a number of upgrades across their campus, including the redesign and replacement of a chilled water plant.

The plant was located in the basement of the Smith Center for Undergraduate Education (SCUE) and consisted of a 400 ton water-cooled chiller. This chiller served the building as well as supplying chilled water to the campus chilled water loop. The chiller had recently failed and was in need of replacement. Additionally, the University was interested in increasing the size of the replacement chiller, if possible, to provide additional CHW capacity to the campus.

Through a rigorous analysis process, Millig generated detailed models of the performance of several manufacturer’s specific chiller models and also different sized units to see how they would operate in the SCUE building.

Physical space limitations in the SCUE Basement restricted chiller size, and existing equipment was insufficient for larger chillers. However, a full electrical analysis confirmed capacity for expansion, and the owner had a suitable larger cooling tower available.

To optimize the system, Millig built a detailed model of the SCUE chiller plant and campus chilled water system using 8,760-hour operational data. This analysis revealed the campus lacked a high-efficiency base load chiller for cold weather operation. Existing chillers operated at 0.751 kW/ton in winter, highlighting the potential for significant improvement with a more efficient option.

By evaluating various design and control schemes within the model, Millig identified optimal parameters for energy efficiency. The team determined that implementing variable speed primary water flow, a 12 degF cooling tower approach temperature, and a 1.8 gallons per minute per ton condenser water flow would significantly reduce energy consumption. These changes resulted in a projected 30% reduction in annual plant energy use.