Consolidated Utility Base Energy (CUBE) Performance Test Report

This report provides performance test results for a PV-Battery-Diesel hybrid power system developed by the National Renewable Energy Laboratory (NREL) for the U.S. Army Rapid Equipping Force (REF) and the Expeditionary Energy and Sustainment Systems (E2S2) to provide power to Forward Operating Bases (FOBs). The cornerstone of the hybrid power system is the Consolidated Utility Base Energy (CUBE) system. The CUBE provides the power conversion, distribution, and protection necessary to integrate the various power sources and was built from the ground up to provide a flexible platform which can be modified to meet specific FOB needs. The CUBE was tested to demonstrate fuel savings as well as power quality relative to a baseline diesel generator only system. The fuel savings were verified by performing two 24-hour tests, one test with the complete CUBE system operating with two 30-kW diesel generators, 21.2 kW of PV, and a 30 kW / 40 kWh lithium-ion battery and one test with the two diesel generators only. The tests were performed using a measured 24-hour FOB load profile and a measured 24-hour solar profile. Over the 24-hour period, the CUBE system was able to achieve a 31% reduction in fuel use and a 42% reduction in overall diesel run-time relative to the diesel only case. These benefits were achieved with a total battery throughput of less than 1.4% of the total load energy, with only one additional generator start, and while maintaining power quality comparable with that provided by the diesel generators alone. Additional tests were performed to demonstrate CUBE power quality during load steps, mode transitions, and a black start. Results demonstrated ability of the CUBE to provide comparable load step response as a diesel generator, to maintain high power quality during transitions from diesel generator as grid-forming unit to CUBE as grid-forming unit and vice versa, and to provide high power quality during a black start onto a load.