Project Profile: Princeton Healthcare System Builds in Cost-Effective Energy Reliability

Oct. 5, 2015
Because of stringent patient-care needs, hospitals traditionally insist on two energy sources: their local utility and their emergency generators. Princeton Healthcare System took it a step further with a highly advanced and efficient on-site system.

The Opportunity

When the Princeton Healthcare System first envisioned building a new 630,000-square-foot acute-care hospital with 237 single-patient rooms in Plainsboro, New Jersey, plans called for a conventional HVAC system to address the facility’s requirements. Because of stringent patient-care needs, hospitals traditionally insist on two energy sources: their local utility, which acts as the primary power source; and their emergency generators, which can deliver a limited power supply in the event of an unexpected grid failure. Visionary leadership prompted an exploration of non-traditional energy-efficiency solutions, to determine if there was an opportunity to capitalize on more significant cost savings.

The Challenge

The institution’s decision makers altered their plans and opted to build in absolute energy reliability for their new hospital – choosing a sophisticated energy-efficiency solution that, in the words of Princeton HealthCare System President and CEO, Barry Rabner, “…will fully meet our hospital’s energy needs while reducing our operating costs and protecting the environment.”

NRG Energy recommended the installation of a highly cost-efficient combined heat and power (CHP) plant that would produce enough electricity onsite to power the entire facility, without having to draw from the local grid. This state-of-the- art CHP plant would also generate sufficient amounts of steam for heating and chilled water for air conditioning the hospital year-round.

The Solution

Under a multiyear contract, NRG will provide the facility with electricity from a 4.6-MW gas turbine-powered CHP, plus a cogeneration plant that will serve as the hospital’s primary energy resource, meeting 100 percent of its heating, cooling and sterilization needs. This plant is backed up by 6-MW diesel-fired generators in an N+1 scheme that can be supplemented by an interconnection to the local utility’s power grid, if the need arises.

NRG’s energy-efficiency solution also uses electricity from a one million-gallon chilled water thermal-energy storage tank—literally a thermal “battery” that can be charged during off-peak hours and discharged during peak-demand periods—plus a 200-kW solar array with panels distributed over the parking lot.

The integrated nature of this solution enhances the hospital’s energy reliability at an overall cost that is significantly less than the costs needed to provide and implement these energy sources individually. It dramatically reduces the facility’s monthly electric bills and harmful emissions. And it provides the institution with the flexibility to export power to the local grid when rates are high or quickly draw power from the grid when rates are low (or if additional energy is needed).

This solution establishes Princeton HealthCare System’s energy independence while also enhancing its ability to generate a welcome revenue stream that can fund critical services.


  • OUTAGE PROOF: This integrated solution can operate continuously, even in the event of a total local grid outage.
  • “BLACK START”: Even after the local grid goes black, backup generators can start up this system’s gas turbines.
  • ADVANCED CONTROL: Each component is managed by a programmable logic controller to optimize plant performance
  • “WIRE-TO-WATER”: Drives system efficiency by using a control algorithm that finds the most efficient speed to run cooling water and chilled water pump motor.

For a free PDF of this microgrid case study, visit NRG. To see other Microgrid Knowledge microgrid case studies, visit the case studies channel.

About the Author

Cara Goman

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