Evaluating power and environmental performance in mobile microgrid generator systems

Abstract

Mobile microgrid generator systems can provide power to electrical loads during grid outages and for off-grid applications. These systems are often configured using conventional generator sets, but can also be used with parallel energy storage. The addition of energy storage may provide advantages in terms of power quality and emissions. This paper introduces a procedure to experimentally assess mobile microgrid generator systems operating on natural gas (NG) fuel in conventional and energy storage coupled types, for several power and environmental emissions metrics: thermal efficiency, voltage and frequency stability, harmonic distortion, and air pollution from total hydrocarbons (THC), carbon monoxide (CO), nitrogen oxides (NOx), and carbon dioxide (CO2). The analysis of thermal efficiency and detailed gas composition and engine emissions analyses are described. Also included is a method of synthesizing realistic load profiles for laboratory testing, based on statistical sampling of metered load data. Implementation of the proposed test procedure is experimentally demonstrated on two types of mobile microgrid generator systems of differing engine sizes: a conventional 22 L NG generator set and a hybrid system consisting of an 11 L NG generator set, in parallel with battery energy storage. Significant differences in power quality, fuel usage and emissions metrics were observed between the two systems using the procedure. Measurements using the procedure are also used as inputs to an example economic and environmental cost analysis for a remote microgrid design. These findings suggest the potential usefulness of the procedure for evaluation of competing generator sizes and configurations, which can also provide input to mobile microgrid designs.