Jones-Lang-LaSalle is a global investment real estate manager, which has supervised the mall property since 1988. The mall is an 800,000-sq-ft retail facility not far from the Kennedy Space Center. It is located in a growing commercial and residential area, and is a primary route between Orlando and Cocoa Beach/Cape Canaveral. Because of its centrality, it receives extensive traffic from both residents and area visitors. The mall is owned by John Hancock Life Insurance and was originally completed in 1969, with a major expansion in 1988.
Most of the space in the mall is single-story, though parts of two department stores have two stories. The mall has been continually updated, and few shoppers would guess it is over 30 years old. Neither would shoppers guess that the considerable electric requirement of the mall is generated on-site.
A cogeneration concept was woven into the design from the beginning. The plan was to increase the efficiency of the facility by using the heat recovered from the water-cooled natural gas electric generators to supply absorption cooling equipment. The plan also called for electric centrifugal chillers as a backup for the absorption chillers.
According to the property managers, the concept of on-site electric generation with heat recovery for absorption cooling has been periodically reviewed. The property managers say it continues to be seen as the best system for this property. With additions and upgrades, the electric generation plant today consists of seven Waukesha diesel units with a total capacity of 5.8 MW. The engines operate at 1,200 rpm and can meet the full electrical requirement of the mall, with at least one engine always in reserve.
The combined electric generation and chiller plant is located within the mall building itself. The normal fuel for the engines is natural gas purchased under contract from City Gas Corp. of Florida, a division of the NUI Corp. Because of the need for uninterrupted electric service, the mall also maintains a three-day backup supply of propane gas.
The engines receive a complete overhaul each 40,000 operating hours, which, in this application, works out at about seven to eight years. At the time of the engine overhauls, the units are commonly upgraded with the most recent improvements for heat recovery and capacity enhancement.
The hot water from the engine plant goes to two Trane absorption chillers. These consist of a 550-ton Trane Model ABSC single-stage absorption unit installed in 1986 and a Trane Horizon®, Model ABSD single-stage absorption unit, installed in 2000. These are the primary chillers for the mall and at least one unit is in use year-round.
The units receive water from the engines at approximately 245?F (118?C), using it to generate chilled water at about 42?F (7?C). The cooling tower design calls for condenser water going to the tower from the chillers at 102?F (39?C) and returning at 85?F (29?C).
Four Marley cooling towers, located on the roof of the structure, serve the four chillers. The towers, rated at 700 tons each, are on a common loop. Makeup water for the cooling towers is of generally good quality and is supplied by the city of Cocoa’s system. A local firm provides routine makeup water treatment services.
According to chief engineer, Warren Meissner, the base-loaded absorption chillers require relatively little maintenance. "Generally we inspect and clean the condenser tubes annually. Other than that, there have been very few outages for the absorbers. And for much of the year, they run around the clock."
The combined control room for the electric generation facility and the chiller plant is staffed around the clock, seven days a week. The operators are instructed to ensure that the hot water flowing to the absorbers remains within the required range and that the cooling towers are performing as needed. "We have operators on duty because of the electrical plant," said
Meissner, "so they operate the chiller plant too. Otherwise we could have designed the chiller plant controls for unattended operation."
Two 100-hp chilled water pumps distribute the chilled water from the plant. The water is pumped to air handlers throughout the mall that discharge conditioned air through ductwork. Because of its Florida location, the facility requires chilled water year-round. This long operating season
contributes to the overall energy efficiency of the cogeneration application.
Publication date: 11/26/2001