The College of New Jersey

The central utilities plant on the College of New Jersey campus generates electricity and provides heating and cooling to 95% of the campus. Buildings that are not connected to the central plant consist primarily of small facilities that are cheaper to heat and cool individually rather than through the main network. These buildings are heated by individual packaged boilers and powered by geothermal heat pumps or natural gas [62].

Fuel cells at TCNJ
Energy and central utilities plant at TCNJ [33].

History of the Plant

The College of New Jersey is dedicated to being environmentally conscious. In 2000, the Environmental Protection Agency (EPA) gave the college the Energy Star Award for Combined Heat and Power for its cogeneration plant [121]. The college as a whole consumed 41.7 million kWh in 2007. It would have cost 7.8 million dollars to supply the amount of electricity needed for campus without the cogeneration facility. The cogeneration plant produces 90% of the total electrical demand, generates 37 million kWh per year. The plant not only benefits the environment, but also saves the college millions of dollars [120].

Cogeneration Plant

The College of New Jersey operates the cogeneration plant using dual fuel Solar Turbines. Electricity is the largest expense on the college’s utility bill. In 2007, the Combined Heating and Power (CHP) saves the college $3.5 million: $2.5 million is saved by using the components, and the remaining $1.0 million is saved in steam. The college generates 90% of its electric consumption with the remainder being supplied by a local utility company.

Gas Turbine at TCNJ
Gas turbine at TCNJ [132].
The Solar Turbine is a 5.2 MW dual fuel turbine that can run on either natural gas or No. 2 low sulfur oil. The generator is a 6 MW Ideal generator. The turbine converts the chemical energy into mechanical energy. Unlike four stroke engines – which has four separate combustion processes: intake, compression, combustion/expansion, and exhaust – the turbine, operating under the Brayton cycle, is able to complete all four combustion processes simultaneously. Injectors inject fuel into the turbine that is then combusted to high temperatures within the combustion chamber. The hot gas expands and does work on the multi-stage turbine, rotating the shaft. The internal combustion chamber temperatures rise to 1250°F and the shaft rotates at approximately 15,000 rpm. The rotation of the shaft produces energy to drive the turbines multistage compressor, which consumes 70% of the total mechanical energy produced. Only 30% of the mechanical energy is converted to electrical energy. The exhaust gas exits the turbine at 1000°F and is directed to the Heat Recovery Steam Generator (HRSG), where it extracts the thermal energy from the high temperature flue gas for the production of steam.

Central Steam Plant

The Central Steam Plant is equipped with two high-pressure steam water tube boilers with a total capacity of 100 Mlb per hour of steam. The Superior and Cleve Brooks boilers each have dual fuel capability fueled by natural gas and/or No. 2 fuel oil. A third boiler acts as a Heat Recovery System Generator (HRSG), which is part of the cogeneration facility. The total steam plant capacity, including the HRSG, is 140 Mlb per hour. The central steam plant on campus utilizes that latest technology which includes steam economizers that assist the 85% thermal efficient boilers to make steam for heating and power generation. During cold weather days, the steam atomization of oil is used to provide higher combustion efficiencies. The energy management strategy for steam use is to optimize the steam produced in the ERI HRSG unit year round. This is performed in the fall, winter, and spring and accomplished using the steam turbine-driven centrifugal chillers during the summer.

Central Chiller Plant

The central utilities plant uses the steam produced by the boilers to run the chilled water process. The total refrigeration capacity of the chiller plant is 6200 tons.

Centrifugal chiller at TCNJ
Centrifugal chiller at TCNJ [128].
The chiller plant is set up to provide the first 4000 tons of cooling from the HSRG, which provides the most cost-effective steam production in the boiler plant. This production is achieved using two 2000-ton York steam turbine-powered centrifugal chillers. 1200 tons is produced by an electrical centrifugal chiller, and the remaining 1000 tons is produced by a Trane single stage absorption chiller. The chiller plant provides chilled water to the campus buildings through a 20-inch underground supply line that extends to the northwest side of campus. The chilled water recirculation network also includes two Baltimore 2000 ton cooling towers.

Fuel Cells

Fuel cells at TCNJ
Fuel cells at TCNJ [129].
The College of New Jersey also has three grid synchronous UTC PC25C Fuel Cell Power Plants, which are able to supply 200 kW each of electric power and 900,000 Btu/hr of waste heat.

Seasonal Operation

Because the energy needs for the campus change from season to season, the equipment must be suitable for both winter and summer loads. Thus, the boilers and chillers must be designed to handle variable loads. The steam load during the summer months requires 52 Mlb/hr: 40 Mlb/hr is used for the chiller plant and 12 Mlb/hr is used for domestic heating on campus. The first 40 Mlb/hr is supplied by the HRSG and the remaining load is supplied by the boilers. The winter steam peak demand reaches 80 Mlb/hr. The average demand usually is not as high: 60-70 Mlb/hr. In summer, the HRSG provides 40 Mlb/hr, while the remaining steam is produced by the conventional boilers.

Energy Master Plan

In the college energy master plan, the goal is to reduce its energy and fuel consumption and minimize the annual energy expenditures. All energy conservation methods have justified life cycle cost methodologies and analyses that compare the initial cost and future operation expenses. The college is committed to conserving energy usage and is determined to meet or exceed state standards for energy conservation. As of 2011, the college covered 2.7 million square feet with an additional 1.5 million in progress. The additional space will give the college an opportunity to extend and improve its energy conservation projects.

Information current as of:
Click here to see a line drawing of the TCNJ plant.
Want to know more about TCNJ's Energy Star award? More information can be found here.
Want to know more about the Brayton Cycle? Click here.
Want to better understand steam atomization? Read this explantion.
A ton of refrigeration is the amount of thermal energy required to melt a short ton (2,000lb) of ice.