Utility grid power outages in the U.S. are increasing in frequency and duration and can have serious human as well as economic consequences. Long-term events pose a particular concern for Department of Defense (DoD) facilities due to potential national security implications. Conventional building technologies tethered to the alternating current (AC) utility grid cannot function during power outages and quickly render the building uninhabitable, resulting in a loss of the services associated with the facility. The objective of this project is to demonstrate a low-cost solution deployable during standard building equipment upgrade cycles which dramatically improves the resiliency of ordinary facilities to sustained power outages.
This project demonstrates a unique commercial building power distribution system that uses rooftop solar energy and other localized energy sources in an innovative, economical way which is more energy efficient and provides lifetime cost savings while also enabling backup power to the critical building systems in case of a power outage. The system employs a direct current (DC) connection between the solar photovoltaic array and other DC sources and high efficiency air conditioning, lighting, and IT/communications systems, eliminating multiple energy-draining conversions to and from AC and allowing key building systems to seamlessly continue operation during emergency outage situations. The energy and economic benefits of this “DC microgrid” will be measured and compared to conventional AC approaches to quantify the savings. In addition, the conditions for occupancy will be evaluated and confirmed under various power outage scenarios. The selected demonstration site is located at the Fort Bragg Army Base in North Carolina.
The demonstrated DC microgrid system is applicable to retrofit commercial buildings as well as new construction, and can be installed in phases to correspond with the needed replacement of old equipment such as lighting and air conditioning. Higher energy efficiency, lower maintenance, and less upfront investment all contribute to significant lifetime cost savings for the DC system as compared to convention AC approaches to building resiliency. The system is scalable in size and has options for varying levels of resiliency, allowing application to a wide variety of DoD building types and usage profiles.