Center High School

Energy Efficiency Upgrade:

Center School District in Kansas City partnered with Navitas for energy conservation projects. PM Contracting and Trane Technologies installed an innovative ice storage system at Center High School, replacing a 350-ton chiller with a 230-ton chiller that freezes ice overnight for cooling during peak hours. This system is expected to save the school around $50,000 annually and can benefit other large buildings seeking energy and cost savings through thermal ice storage technology.

Prior to the completion of the project, the heart of Center High School’s cooling system was a large 350-ton air cooled chiller. In conjunction with old, inefficient hot water boilers, the building used a 4-pipe hot water/ chilled water distribution system. Due to chiller and boiler over sizing and inefficient control strategies, a significant amount of energy was being wasted. 

Evergy (KCPL) provides substantial energy rebates based on electrical demand reduction. PM Contracting, Inc. was tasked to design a new system that could deliver the same cooling capability yet utilize less electricity during the high demand times of 9 am to 9 pm.  How could we reduce power to a 350-ton machine that draws 400 kw of electricity during peak hours?

The answer was to make ice. 

How does ice reduce electrical consumption during peak usage?

Our state-of-the-art thermal ice storage system makes ice overnight during off peak hours (lower demand charges) and the ice melts during the day to cool the high school. 


A 350-ton (400 kw) chiller worked hard during the entire peak time to cool the high school. The chiller turned on and off during the day to deliver 44-degree water. 


A 230-ton (250 kw) chiller works hard at night (off peak) to freeze six (6) large tanks with ice. At 9 am in the morning when Evergy switches their demand charges, the chiller switches off and circulating pumps flow the warm water from the school across the ice, transferring the heat from the school to the ice bank. The cold water from the heat transfer across the ice coils supplies 44-degree chilled water to the school. The chiller only operates during the day if the ice is depleted, but at a much lower electrical cost.


A more efficient control strategy (when to use the chiller verses the ice storage tanks) and a reduced rate from Evergy will result in energy savings for the building. The new system is projected to save Center High School approximately $50,000 per year. This equates to approximately $150 per ton in savings.

Thermal ice storage can be used for any large building that currently uses an air or water-cooled chiller for cooling. Water cooled systems can be switched to air cooled systems and save on water and electrical usage. Large air-cooled chillers can be downsized which yields lower demand and electrical costs to operate the chiller. Integration of this system through the building’s automation system provides constant monitoring of the system with real time usage and electrical savings.  

Thermal Ice Storage for cooling buildings is just one of the new technologies that PM Contracting, Inc. is experienced in designing and installing. 

Please contact PM Contracting, Inc. for more information on how you can save energy.