Page 356 - Sustainable On-Site CHP Systems Design, Construction, and Operations

Princeton University District Ener gy System 329

Service Availability and Reliability

Electric Service Availability and Reliability to Campus Was 100 Percent
over a 1 Year Period
Princeton has installed two independent power feeds from the local utility to each of
the two major substations serving the north and south halves of the campus. Although
the utility had a 101-minute service interruption to the south substation, the gas turbine
automatically picked up the campus load—so there was no customer impact.
Steam service reliability to campus was 99.9 percent as indicated by steam header pres-
sure above 100 psig. There were no unplanned interruptions of more than 3 hours.
Steam service availability was 99.7 percent.

Energy Production Efficiency
12
In fiscal 2007, Princeton Energy Plant purchased 1.497 × 10 Btu of natural gas and
diesel fuel and delivered to the campus: 27,944,000 ton-h of cooling, 584,121,000 lb of
steam, and 35,412,000 kWh of electricity, representing a net thermal efficiency of over
73 percent. When the 87,360,000 kWh of purchased power are included, total energy
delivery efficiency rises to 77.8 percent! This translates into important energy and envi-
ronmental savings. But equipment dispatch is based primarily on minimizing the cost
of energy delivered to the campus, not strictly on maximizing thermal efficiency.
Princeton selects all equipment for high efficiency if it is expected to run with high
capacity factors during peak cost hours. The university specifies premium efficiency
motors and typically uses variable-frequency drives on pumps and fans with variable
loads above 5 hp. Chillers CH-1 and CH-2 (described earlier) are typically base loaded
during peak hours. These are both highly efficient machines. The cogeneration system
regularly operates with measured efficiencies above 80 percent.

Environmental Benefits, Compliance, and Sustainability
Through the use of combined heat and power, Princeton Energy Plant avoided nearly
12,000 metric tons of carbon dioxide production this past year compared to equivalent
energy delivery from the local electric utility and heating boilers.
The plant is designed and operated to meet all emissions requirements and includes:
turbine water injection for NO control, a carbon monoxide catalyst, low-NO burners,
x x
and flue gas recirculation in the auxiliary boilers. The primary fuel is natural gas with
ultralow sulfur diesel as a backup fuel. Continuous emissions monitors measure CO,
O , and NO and document compliance with emissions regulations.
2 x
Princeton has shown leadership in developing one of the most aggressive sustain-
ability plans of all colleges and universities. By year 2020, Princeton has committed to
reduce all CO emissions to year 1990 levels—by making changes on campus as shown
2
in Fig. 19-3—and without purchasing “offsets.” The plan includes greenhouse gas
reduction, resource conservation, primary research, education, and civic engagement.
The central energy plant and district energy systems will be key to the success of this
major campus initiative.