Northwest Community Hospital

Arlington Heights, Illinois

Northwest Community Hospital, exterior


GBA performed an investigation of combined heat and power systems, which was supported by local electrical and natural gas utility energy efficiency programs, at the1.4 million-square-foot, 489-bed hospital in northwest suburban Chicago.

Combined Heat and Power Feasibility Study

Northwest Community Hospital commissioned a study of cogeneration feasibility to examine economically sensible options that would generate incentives from the local electrical and natural gas utilities, as well as cost savings. The hospital has a 4.60-MW combined heat and power system that has been operational since 1997. It includes four existing engine generators that are currently used less than 500 hours a year, at a total observed plant efficiency of about 59%.

GBA determined that generating on-site electricity remains a feasible option for NCH, especially if heat recovery systems can be improved. (Currently, the engines have about a 29% efficient electrical conversion rate, with limited summer heat recovery.)

GBA developed several measures for NCH’s consideration, including:

  • Continuing existing operations (annual cost savings $316,800 compared with baseline). This option includes mitigation of 3,300 kW of capacity charges, currently at $8/kW and charged monthly. Mitigation comes from running generators during the five highest coincident peak days.
  • Repairing the fourth engine (Generator 3), allowing capacity charge mitigation at a rate of 4,400 kW. This would boost annual cost savings to $422,400, at a project cost of $205,182 (payback 1.9 years). Annual plant efficiency would remain at 59%.
  • System modifications, including a heat exchanger retrofit; a deaerator tank; modifications that would allow hot water/steam to be recovered and fed to the hospital’s Wellness Center (for showers, sinks, and pool heat); and hot water absorption. These changes would improve annual plant efficiency to 65%, at a project cost of about $2.9 million with an available utility incentive of nearly $752,000. Annual cost savings would be $49,438, with a payback (counting the incentive) of 14.4 years.
  • Full cogen plant replacement at 3,000 kW, improving plant efficiency to 67%, at a project cost of $4.5 million with an available utility incentive of $2.21 million and annual cost savings of $302,086. Payback (counting the incentive) would be 9.1 years.

GBA recommended that NCH proceed with repairs to Generator 3, which offers a rapid payback based on avoided capacity charges, even without the availability of a utility incentive. The hospital may also consider the more intensive, incentive-supported options, especially if the state EPA allows the site to operate at more than 50 tons a year of NOx emissions, or if the site decides to pursue a Clean Air Act Permit Program application with the state.

With the investigation results in hand, NCH can now move forward with a well-reasoned decision about its combined heat and power capabilities in support of its overall goals for sustainability and cost management.

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