The new boiler, which was retrofitted to the university’s existing heating duct system, is expected to produce 150,000 pounds of steam per hour, increasing the 67-year-old power plant’s steam output by 30,000 pounds per hour, and use an estimated 100,000 tons of in-state renewable energy sources such as chipped hardwoods and wood waste.Back at MS&T the number for the heat pump came in part from a WTW heat recovery chiller that the campus had installed in October 2007, and which was saving the campus some $1,500 a day by allowing some of the recovered heat to be produced in useful form. When the campus first looked at the potential they were also able to look at the experience of places such as the Richard Stockton College of New Jersey, which installed a system in 1996. Their installation pioneered many of the decisions made in subsequent operations.
The wells are located on a grid and spaced roughly 15 feet apart. Within each four inch borehole, the installers placed two 1.25 inch diameter high density polyethylene pipes with a U-shaped coupling at the bottom. After the pipes were installed, the boreholes were backfilled with clay slurry to seal them and to enhance heat exchange. In total, the loop system includes 64 miles of heat exchange pipe. In addition, 18 observation wells were located in and around the well field for long-term observation of ground water conditions. The individual wells are connected to 20 four inch diameter lateral supply and return pipes. The laterals, in turn, run to a building at the edge of the field where they are combined into 16 inch primary supply and return lines. These lines are connected to the heat pumps which serve Stockton’s buildings. In the heating mode, the loop serves as a heat source and, in the cooling mode, as a heat sink. The heat pumps range in size from 10 to 35 tons. All are equipped for with air economizers. The equipment is controlled by a building management system using 3,500 data points. This allows the College to take advantage of energy saving options such as duty cycling, night setback and time of day scheduling. The building management system also identifies maintenance needs in the system. . . . . . The system immediately demonstrated that it could carry the entire planned heating load. In the first few years of operation, the average temperature of the well field has drifted upward by several degrees. This occurred because the buildings use more air conditioning than heating. . . . . . Because of the constant changes to the system, and other energy conservation steps, it was difficult to verify energy savings exactly. Based on extensive monitoring, the predictions turned out to be quite accurate.