With annual electricity costs approaching the $5-million mark, Monte Carlo management began looking at ways to reduce costs while still maintaining a comfortable environment for guests.
The resort’s engineering department tracked facility temperature using its building-automation system and employee measurements to locate areas where adjustments could be made. They then added variable orifices to five chillers to save energy by allowing the tower water entering the chillers to run as low as 55 degrees F. The project team installed medium-voltage variable-speed drives (VSDs) on chillers, and they also installed a central-plant energy-management system (EMS) to properly sequence the chillers.
Special Design Feature
The new VSDs and the EMS will reduce electricity usage by as much as 1.5 million kWh, or $150,000 per year based on a cost of 10 cents per kWh, a savings of about $3 million over the remaining 20-year life of the chillers. The resort anticipates energy rebates of about $100,000 from the local utility for energy-saving projects.
Since the chiller operates at off-peak conditions 99 percent of the time, the lower operating speed provides a significant reduction in audible noise. A 24-pulse converter design with isolation transformer provides a sinusoidal input current load to the power grid, which exceeds the IEEE 519-1992 standard for harmonic control. This standard feature eliminates any concern over harmonic-voltage distortion proliferation on the building’s power grid that is associated with drive installation.
Design/Construction Challenge
Because the retrofit was performed during the winter, the need for cooling was less. Two chillers provided the cooling that was required for guests while the retrofit was performed, unnoticed, on the three other chillers.
