The Princeton Energy Plant is a district energy facility that provides electricity, steam, and chilled water to power, heat, and cool the buildings on the Princeton University campus. It is listed here in "Energy and Environmental Projects" because it is in a constant state of process improvement and mechanical upgrades happen quite often. The creation of the plant and the continuous refinement of its operation have had a very positive impact on Princeton's carbon footprint. Princeton's carbon emissions reduction goal, as stated in the Sustainability Plan, is to reduce emissions to 1990 levels by 2020.
The plant has four main components: steam boilers, water chillers, an electric generator, and a large thermal energy storage system. (The TES is essentially a 2.6 million gallon tank of chilled water.) The plant boilers and water chillers have capacities of 300,000 pounds of steam per hour and 20,000 tons of cooling capacity, and 40,000 ton-hours of storage capacity, respectively. The electric generator, powered by a General Electric LM-1600 gas turbine that burns natural gas or diesel fuel, is a cogeneration facility; that is, (what is normally) wasted exhaust heat from the turbine is recovered to heat water and make steam. The typical efficiency for a utility energy plant is 25 – 45%. Through cogeneration and other waste heat recovery, the efficiency of Princeton’s plant rises to the range of 80%. The cogeneration plant can generate 15 megawatts of electricity (about equal to Princeton’s average electricity needs on a given day). The Princeton turbine was the first of its kind in the world to earn certification to operate on bio-diesel fuel.
Princeton imports energy in the form of electricity, natural gas, diesel and bio-diesel fuel. In 2001, Princeton developed an economic dispatch model of the plant with an outside consultant. This system was designed to provide "expert guidance" for the plant operators. The prices of imported electricity, natural gas, and diesel fuel are monitored in real time, as are the campus demands for electricity, steam, and chilled water. Operators make decisions on how much electricity to generate on campus and how much to import from the regional power grid based on that model. The generating plant also has the ability to switch from natural gas to bio-diesel as price or supply dictates. (On extremely cold days when natural gas is in high demand, the gas provider can ask that the plant operators to switch to diesel operation. This allows Princeton to pay lower prices for natural gas.) Electricity, imported or generated on campus, can be readily converted to chilled water and stored in the TES when it is cost effective to do so. To support our research needs, Even on the coldest or hottest days there is a continuous need for both chilled water and steam on the Princeton Campus.
It is important to note that while some plant operations could be automated, the most important decisions are made by trained, licensed human operators. Those decisions are made with regards to the following criteria: safety, legal/regulatory, reliability, environmental impact, and life cycle cost. The professional operators of the plant are absolutely essential to getting the greatest value from the facility. Safety, reliability, efficiency, and flexibility are the goals of the operation.
It is this efficiency and flexibility that make this plant a key part of Princeton’s sustainability strategy and much more than a simple “back-up” generator. The award-winning facility’s emissions are rigorously monitored by its experienced staff (and state and federal authorities) to ensure the very highest standard of environmental compliance.
Current Campus Energy Production and Use
Our plant operators have access to real-time energy usage and production on campus. The campus solar collector project has become operational and some of its energy production data can be seen at the SunPower website dedicated to our system.
NEW September, 2016: View campus energy data, including our power plant and grid power, on our new and improved Princeton live energy dashboard, TigerEnergy.