Enabling city-scale multi-energy optimal dispatch with energy hubs

This paper further extends the class of energy hubs that can be modeled with a concise system description and in a computationally efficient optimization framework to permit rapid analysis of multi-energy systems. The new hub models are then embedded in the multi-energy system analysis tool Hubert and solves the multi-period optimal dispatch (MPOD) problem for a broad class of energy hub systems. Specifically, this paper presents recent improvements developed for Hubert, including the use of piece-wise linear modeling to capture nonlinear converter efficiencies, limits on hub component outputs to reflect physical limits of converters, and hub emission limits. These developments enable appropriate modeling of multi-energy micro-grids and cities and are illustrated with a multi-energy model of The University of Vermont's campus under different capital planning scenarios and modeling assumptions. Interestingly, the shortcomings of using a traditional constant-efficiency hub converter model are illustrated with an energy storage sizing application for multi-energy systems. It is shown that the traditional hub models can significantly undersize energy storage as compared to the more accurate piece-wise linear energy hub formulation.