Hybrid Microgrid with Energy Storage Recommendation for the Dry Tortugas Garden Key National Park

Report Number



Buildings; Energy Analysis; Photovoltaics


This report provides a summary of energy measurement findings recorded from the generator serving Fort Jefferson, Garden Key, Dry Tortugas. Data analyzed in the report is used to investigate the implementation of a microgrid system with energy storage. The National Park Service (NPS ' Homestead, FL) goal is to deliver electricity during nighttime hours from an energy storage bank for a clean and noiseless environment and save on diesel fuel. Generator power measurements recorded, include the electric demand of the Garden Key-Fort Jefferson compound plus the Motor Vehicle Fort Jefferson (MVFJ) supply boat, as it was electrically connected at the dock. Power measured during the nighttime hours between 10:00 PM and 6:00 AM were examined for two nights (Sept. 9-10 and Sept. 10-11). Power demand for the 8-hour period averaged 46.4 kW with a peak demand of 56.7 kW. Electricity used averaged 372 kilowatt-hours (kWh) based on the two 8-hour nighttime periods. Sizing considerations for energy storage at Garden Key required direct manufacturer inquiry and literature search on various technologies currently available in 2015. Lithium-ion and Valve Regulated Lead Acid (VRLA) batteries are considered since they provide maintenance-free service and represent the highest percentage of energy storage batteries utilized for energy storage in 2014. Recommendations for energy storage are made based on the 372 kilowatt-hours measured during the 8-hour night time period in September, plus a 10% incurred on charging and discharging losses. Additional storage to operate around a 50% depth of discharge (DOD) suggest that a minimum total storage of 500 kilowatt-hours is needed at Garden key. Recommendations to utilize a renewable photovoltaic array are made to relieve the generator charging the energy storage during daytime hours. Finally, codes and safety regulations applicable to energy storage systems are discussed.

Date Published



Buildings - Energy Analysis; Photovoltaics

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