The chiller plant will cool over two million square feet of space

Cooling millions of square feet of retail, transit, and museum space requires an enormous engineering feat. At the World Trade Center (WTC), it means building a central chiller plant that spans two stories, totaling about 80,000 square feet -- much larger than a football field.
 
The WTC chiller plant’s scope comes with many impressive figures. For instance, a total of 13,500 tons of cooling capacity will provide air conditioning for well over two million square feet, including the WTC Transportation Hub, National 9/11 Memorial & Museum, Vehicular Security Center, Performing Arts Center, and new retail areas that alone will occupy a half-million square feet and seven stories.

This central chiller plant is brand new, replacing the two original plants that once cooled the base buildings of the original WTC complex. But the new central plant still operates similarly to its predecessors and even uses the same Battery Park City river-water pump station to circulate up to 30,000 gallons of water per minute from the Hudson River through the plant. The pump station is now being upgraded to adhere to the current environmental regulations and site-wide energy codes.

Located beside the Memorial’s underground spaces, the plant is now in its final stages of completion. On a recent tour, Port Authority Senior Program Manager Ranjit Sahni pointed out pipes with diameters as large as 42 inches and as small as 3/4-inch traversing the space, all ready to serve as conduits for either water or power.  The heart of the plant consists of the gargantuan chillers which generate chilled water for cooling each weighing in around 125,000 pounds apiece.
 
Sahni explained that the chiller units draw in river water that has been thrice filtered, which is used to generate chilled water -- around 42 degrees -- that is distributed to the various air-handling units across the site to cool spaces with the help of coils and fans. During summer, Hudson River water temperatures average around 78 degrees; in the winter, around 55 degrees -- but by the time it leaves the chiller plant and goes back to the Hudson river, its average temperature is raised by 10 degrees.
 
Energy efficiency and water conservation have influenced the design of the new chiller plant, says Sahni. Just 25 percent of the total river water that the original system pumped from the Hudson will be used in the new system. Additionally, using river water through an underground system avoids water loss through evaporation. Noise and hot discharge air also are minimized, compared with a conventional cooling tower–type system, and therefore helps maintain the serenity of the soon-to-be-complete Memorial fountains and plaza.
 
Once the river water has circulated through the plant, it flows back through the same 60- and 66-inch diameter pipes used by the original WTC, under the West Side Highway, and returns to the Hudson, says Sahni.
 
The central chiller plant is now about 65 percent complete. The Port Authority expects it to be in the testing phase in early 2011, on schedule for operation in time to serve the Memorial by the 10th anniversary of 9/11.

The central chiller plant is now about 65 percent complete, says Port Authority Senior Resident Engineer Trevor Wright, who works with contractor KSW/Five Star Electric. The team expects the initial portion of the plant to be in the testing phase in early 2011, on schedule for it to serve the Memorial by the 10th anniversary of 9/11 -- and in time for the other WTC facilities as those are completed.
 
Meanwhile, construction across the other areas of the WTC continues, including construction of the four new office towers, which will each be using their own cooling systems.

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