Case study: Microgrid at Princeton University

Case study: Microgrid at Princeton University

The most advanced microgrids use multiple fuel sources, multiple power-generating assets, energy storage, CHP production, and modern digital controls. They operate with an awareness of the real-time commodity costs of fuel and electricity.

An example is the microgrid at Princeton University. Recognized among the best-in-class microgrids, Princetons gas-fueled CHP plant produced the heating, cooling, and electricity for the campus during Hurricane Sandy, keeping the university up and running when much of the state was dark.

While the initial motivation to build a cogeneration plant was to reduce lifecycle costs, the school also benefits from a much lower carbon footprint and the higher reliability associated with behind-the-meter CHP. Princetons critical research projects and computing services, for example, were able to continue uninterrupted by the storm.

Princetons microgrid normally operates synchronized (connected) with the local utility. This benefits both the university and other local ratepayers. When the price of utility power is lower than Princetons cost to generate, the microgrid draws from the utility grid. However, when Princeton's microgrid can produce power less expensively than the utility, it will run to meet as much of the electricity needs of the university as possible. When Princetons microgrid can generate more than the university needs, and when the price of power on the utility grid is high, Princeton exports some power to earn revenues while lowering the net price of power for all other grid participants.

Since the creation of new ancillary services markets, Princeton is able to use its existing cogeneration assets to produce new revenue streams by selling voltage and frequency-adjustment services back to the larger power grid. This is less costly for the utility than building up its own power grid infrastructure and increasing generation at its plant. It is implemented in a way that does not reduce Princetons reliability.

Basic requirements for microgrid reliability include:

  •     One or more generators behind an electric meter that can meet the needs of at least the most critical loads
  •     The ability to run isochronous; i.e., to control voltage, frequency, and power output without the main power grid
  •     The ability to black start at least one generator, i.e., start the generator when no utility power is available
  •     The ability to shed less critical loads to reduce demand during island-mode operation.

Source: Consulting-Specifying engineer

SMART GRID Bulletin March 2017

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