The new central cooling station for the Honolulu Seawater Air Conditioning (HSWAC) System is designed to provide up to 25,000 tons of cooling for the downtown Honolulu district utilizing deep ocean sea water as the primary source of cooling. The central cooling station will consist of a single story concrete reinforced building with an underground pump vault. The cooling station will house the primary seawater pumps, heat exchangers, distribution chilled water pumps, supplemental chillers and ancillary pumps, electrical substation and switchgear, emergency generators, and all other supporting systems to provide chilled water to the downtown Honolulu district. The building will also be designed to support a 6 level parking structure that will be built over the cooling station under a future phase of the redevelopment of the parcel.
Cold 45 degree F seawater will be drawn from a deep seawater intake located approximately 4 miles off-shore.
The pipeline will terminate in an underground vault located in the basement of the new cooling station. The seawater will be drawn from the intake by three large seawater pump, of which one will be redundant, located in the vault and will be pumped through plate heat exchangers and returned to the ocean via a discharge.
The chilled water that is indirectly cooled by the cold seawater via the plate heat exchangers will be cooled down to a temperature of approximately 46 degrees F. In order to maintain proper cooling and dehumidification for the buildings that will be connected to the chilled water distribution system, supplemental centrifugal chillers will cool the chilled water down to 43.5 degrees F. The 43.5 degree chilled water generated at the central cooling station will be circulated via a closed loop chilled water distribution system to the various buildings that will be connected in the downtown service area.
Each building will be provided with a service connection where secondary building pumps will be used to circulate the chilled water from the loop to the air handling units that cool the building. The heat that is extracted from each building will warm the water in the chilled water return pipe to approximately 54 degrees F. This warmer return chilled water will be returned to the central station plant and re-cooled using the cold seawater heat exchangers and supplemental chillers before being re-circulated back through the district cooling system chilled water supply pipes.
The central cooling station is currently being designed with InSynergy Engineering, Inc. as the prime consultant responsible for the overall coordination of the design. We are also responsible for the detailed MEP/FP design for the central station building, including the central seawater/chilled water cooling system, coordination for exterior electrical utilities for power, telephone, and data, interior power, lighting, and telecom data distribution, and building plumbing, ventilation, air conditioning, fire sprinkler protection, and fire alarm system.
Our scope of work also included evaluating alternatives and design schemes for the central station plant. We also evaluated various options for the layout, operating parameters, and process flow diagram for the chiller plant which will be designed to provide a maximum of approximately 30% of the total system cooling load that will be between 20,000 to 25,000 tons.