California State University Long Beach retained P2S to provide commissioning services to review central plant operations. MBCx, which stands for “Monitoring-Based Commissioning” takes a “fresh look” at the operation of the central plant, evaluates what is operating well, what needs to be improved and what should be done in the future. The work is limited to controls and operational changes. Capital improvement is not included.
The primary challenges of the project were performing the work on a continuously operating central plant and watching for all the potential savings and operational opportunities. It also provided an opportunity for the plant operators to gain a better understanding of controls, and boilers and chiller operation.
The commissioning process revealed that the 1000-ton chillers were operating to maintain load on campus for less than 100-ton load, which was not efficient or operationally healthy. So, the operation was changed to allow depletion of the ice tanks on low load days, including when they were being charged. This improved efficiency and reduced wear and tear on the chillers. We recommended a capital improvement to install a 600-ton VFD chiller that would operate on weekends while the TES tank is charging. This further improves efficiency and extends the TES tank during hot weeks in the summer months.
We discovered the boiler system could not modulate per the original setup, and they staged on and off rapidly without any steady state operation. The boiler controls were then corrected and now modulate with the load, rather than stage on and off—starting and stopping the boilers every half hour rather than every 2 minutes per previous operation.
Prior to commissioning, the annual electrical energy consumption of the chiller plant baseline was 6,939,000 kWh. After MBCx and related adjustments, the electrical energy consumption of the chiller plant was 5,682,000 kWh.
After the installation of the 600-Ton VFD chiller, energy consumption of the chiller plant was reduced further to 4,296,700 kWh.
A total electrical energy savings of 2,642,300 kWh was achieved with the MBCx and new chiller installation with a payback of less than 3 years with all the incentives.