With more than 1,900 guest rooms and 220,000 sq ft of meeting and exhibit space, Coronado Springs Resort at Walt Disney World in Orlando, Fla., is among the premier single-level hotel convention facilities on the East Coast. The newest addition to the resort is 101,000-sq-ft Veracruz Exhibit Hall, completed in June 2005.
The hall's mechanical-system design included a new chiller and boiler plant, 13 air-handling units (AHUs), and 17 variable-air-volume (VAV) boxes. The chiller plant employs a variable-flow primary system with variable-speed-drive chillers. HVAC operation is controlled with an EMS designed using Disney's EMS-design, procurement, and operation process.
Submetering of chiller-plant operation was part of the original EMS design. Each chiller came with an on-board electric meter, as well as chilled-water supply- and return-temperature sensors. A chilled-water flow meter was added to each chiller to allow chilled-water tons to be calculated. Additional electric submeters for measuring condenser and chilled-water-pump motors and cooling-tower fans were included. The EMS was designed to collect energy data, chiller operational parameters, and space-temperature and relative-humidity values.
As with most projects, there was a period of test and adjustment as the mechanical system progressed from drawing board to operation. In collaboration with the chiller manufacturer and design engineer, Disney's energy-management team made the following changes to the original sequence of operation:
The chiller leaving-water-temperature set point was raised from 40°F to 44°F.
Minimum chilled-water flow through each chiller was lowered from 600 gpm to 400 gpm, which increased the differential temperature at each chiller.
The AHUs were set up as single-zone VAV systems. The discharge-air temperature was fixed, with variable-speed drives on each unit modulating fan speed to maintain the space-temperature set point.
The minimum speed of each AHU variable-speed drive was lowered from 75 percent to 20 percent.
Carbon-dioxide (CO2) sensors were employed to measure occupancy. As long as CO2 levels stay below set point, outside-air dampers remain minimally open. As CO2 levels increase, outside-air dampers modulate open.
During unoccupied periods (11 p.m. to 6 a.m.), the entire chiller plant is shut down, as are all AHUs and exhaust fans. Temperature and humidity are monitored and quickly recovered in the morning, before any convention activity occurs.
During winter, when outside air is cool and dry, the chiller plant is shut down, and outside-air dampers are modulated to cool the exhibit hall using outside air.
These changes resulted in a 30-percent reduction in chiller-plant energy use (and, in part, earned co-author Christopher D. Sandberg a Networked Controls Leadership Award from HPAC Engineering1).
Best practices in BAS/controls. (2007, May). HPAC Engineering, pp. 40-44, 46, 47.