The Lawrenceville School

The Lawrenceville School, a coeducational boarding schoolfor grades 9-12, is considered one of the most prestigiouscollege preparatory schools in the nation. Most of theschool’s 800 students board on the historic campus, locatedin Lawrence Township, New Jersey, just south of Princeton.

In 2001, the school undertook construction of a centralchiller plant to provide district cooling for 18 campus build-ings, including academic, administrative, athletic, support,and dormitory facilities. The buildings, whose combined sizeis approximately 400,000 to 450,000 sq. ft., are connected tothe chiller plant in the Kirby Arts Center by means of under-ground pipes that supply chilled water to each building’s airhandlers.

Hybrid system provides choice for best prices

The centerpiece of this chiller plant is a 350-ton York direct-fired absorption chiller thatoperates on natural gas. The school already had one 300-ton York electric centrifugalchiller. A 150-ton electric centrifugal chiller was also added, creating a 800-ton-capacityhybrid system that gives the school the flexibility it needs to take advantage of optimumutility prices. The school’s peak cooling load is 550 tons.

“In order to be able to control the school’s energy cost in a deregulated electric and gasmarketplace, the best solution is to have choice,” explains Darren Cassel, a principal inThe Stone House Group, which designed the chiller plant. “We currently base load the

Private School’s Hybrid ChillerPlant Provides Flexibility and Cost Savings

350-ton direct-fired natural gasabsorption chiller

Undergroundwater lines serving18 campusbuildings

Lawrenceville, New Jersey

The hybrid chiller plant

provides the lowest

operating and life-cycle

costs, as well as the

greatest flexibility and

redundancy for cooling,

while minimizing

aesthetic and noise

impacts on the campus.

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gas-fired chiller during the day to avoid thehigh on-peak electric rates, and then run theelectric chillers at night when the campuscooling loads are lower and the price of elec-tricity is cheaper.”

Based in Bethlehem, Pennsylvania, The StoneHouse Group provides the school with a vari-ety of operations support services includingenergy management planning and constructionproject management.

Initial annual cost savings were estimated at$180,000, but because of gas and electric pricechanges over the past five years, a new energyanalysis will have to be conducted to deter-mine current savings, according to Cassel.

“Having this energy flexibility will certainlypay off, considering the volatility of today'senergy market,” says Kenneth Kohr, ProductMarketing Engineer with York, A JohnsonControls Company.

School selects York for its good trackrecord

The school selected a York absorption chillerbased on good past experience with the manu-facturer.

“The existing chillers at the school’s centralchiller plant were York chillers, and the servicework in the past had been very good,” saysCassel. “The school competitively bid theproject and York’s price was very competitivewith the other manufacturers.”

The hybrid chiller plant provides the lowestoperating and life-cycle costs, as well as thegreatest flexibility and redundancy for cooling,while minimizing aesthetic and noise impactson the campus, according to Cassel.

As an additional incentive, The LawrencevilleSchool received an energy rebate from theNew Jersey SmartStart Buildings® programthat covered approximately 50% of the capitalcost of the direct-fired absorption chiller. Therebate program is administered by the NewJersey Board of Public Utilities' Office ofClean Energy and is currently delivered in ajoint effort by the New Jersey electric and gasutilities.

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York, A Johnson Controls Company631 South Richland AvenueYork, PA 17403