To mitigate utility disruptions — while cutting both energy costs and carbon emissions — the hospital engaged Unison Energy to construct, own, and operate a 1.2 MW CHP system consisting of one 1,200 kW engine that functions as a microgrid with island mode capabilities. A new Hering heat recovery steam generator now converts exhaust heat into steam, which enables more efficient space heating, while engine jacket heat is recovered to supplement the hospital’s domestic hot water supply. Unison provided the upfront capital, with no third-party financing required, to design and build a system that offsets 87% of the site’s annual electricity consumption and insulates it from harmful utility outages.
For Union Hospital, it was also a top priority that its air conditioning would be able to run during an island mode event. This presented a challenge for Unison’s engineers because chillers have a high inrush current during startup, and without precautionary measures this load could cause the CHP engines to trip offline. To ensure the microgrid would support the chillers during island mode, Unison Energy took the extra step of financing and installing new variable frequency drives (VFDs) from Trane on three of the existing five chillers. Unison temporarily took out multiple doorways and made wooden mockups of the equipment to ensure the large VFDs would fit in the limited space.