Case study: K-8 school upgrades power generation

The U.S. Virgin Islands relies almost completely on diesel fuel-powered generators for its energy. Given the islands’ locations in the Caribbean, they are prone to catastrophic weather events including hurricanes. It is common for the electric grid to suffer significant damage following a major hurricane event. Homes and businesses are left repairing the physical damage caused by the hurricanes and dealing with unreliable electric service.

The generating method and maintenance requirements for the grid and service to customers causes the electric rates in the U.S. Virgin Islands to be among the highest in the United States and U.S. territories.

A K-8 school is an existing education center located on the island of St. Croix. The facility is being redesigned starting in 2021 to modernize the education spaces and update the infrastructure. The facility is also being reimagined to have net zero carbon emissions.

The power infrastructure serving the building will be a grid-connected microgrid using photovoltaics and battery storage as the prime movers. A new gymnasium is part of this renovation. The gymnasium is being designed as a Federal Emergency Management Agency P-361 rated structure. One of the requirements to achieve this rating is to provide a minimum of 24 hours of backup electricity.

The battery energy storage system will be designed to allow the FEMA shelter to operate continuously after a significant weather event. A lithium-Ion battery was selected for this system as the storage mechanism due to the availability and relatively low-maintenance compared to other technologies.

The electrical distribution system was designed so the microgrid can disconnect from the grid and provide power to the entire campus for up to two hours using the BESS. The added reliability created by the microgrid allows the school to operate during power outages experienced by the utility grid without impacting the education experience of the students.

The microgrid offers a financial benefit in addition to the impact to the educational environment previously described. The annual cost for electricity, without the microgrid, was calculated to be $482,000. The construction cost of the microgrid was estimated at $3.8 million. Ownership of the microgrid comes with costs for operations and maintenance. The simple payback for the microgrid is estimated at eight years based on the construction costs, electricity costs avoided and O&M costs expected. The implementation of the microgrid proves to have an economic and social benefit to the community.

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