Techno-economic analysis and resilience enhancement of a hospital microgrid under grid outage scenarios

Hospitals are critical infrastructures where power continuity is paramount. This study presents a techno-economic and resilience analysis of a grid-connected hybrid microgrid for a medium-sized hospital, comprising solar photovoltaics (PV), a battery energy storage system (BESS), and a diesel generator. Using a mixed-integer linear programming (MILP) model via NREL's REopt^® platform, we optimized the system design to minimize the Net Present Cost (NPC) while ensuring an uninterrupted power supply to critical loads during grid outages. The analysis evaluated a wide range of outage scenarios, varying in duration (7-24 h), timing, season, and critical load level (50-100%). This study shows that a design of a microgrid for enhanced resilience is both technically and economically beneficial. The microgrid design with optimization achieves a net present cost savings of 14% for the financial optimization scenario and 9% to 14.2% for all the resilience-constrained scenarios compared to the business-as-usual case of 100% grid dependence. Most importantly, compared to the financial optimum rather than the business-as-usual case, the cost of including resilience constraints is a mere 0.4% to 2.4% of net present cost, showing that increased energy resilience can be delivered at a minimal cost. A key finding is that systems designed for summer outages yield higher savings due to greater solar availability, and a strategic deep-discharge protocol for the battery during emergencies is crucial for cost-effectiveness. This work provides an actionable framework for hospital administrators to enhance energy resilience without incurring a financial penalty, and in many cases, while realizing significant long-term cost savings.