Optimal Component Sizing and Forward-looking Dispatch of an Electrical Microgrid for Energy Storage Planning

Optimal design of an electrical microgrid and sizing of its components seeks to balance capital investment with expected operational cost while meeting performance requirements. Calculating operational cost requires scheduling each microgrid component over some time period (dispatching) for each design evaluated. Heuristic or rule-based dispatch strategies typically consider only single time instances and are computationally efficient but do not include scheduling energy storage for future time periods. In this paper, we propose to optimize microgrid designs using forward-looking optimal dispatch for future energy storage planning. We present a case study of an ‘islanded’ military base microgrid with renewable and non-renewable electricity generation, battery storage, and plug-in vehicles with electrical export power capability. The optimal design and forward-looking dispatch strategy are compared to results obtained using the publicly available rulebased dispatch strategy in HOMER Energy software. Results show that the forward-looking strategy uses storage batteries to plan for future energy shortfalls rather than simply as a buffer for variable renewable energy supply, resulting in a 7.8% reduction in predicted fuel use. For the given cost assumptions, sensitivity analysis of the optimal design with respect to fuel price shows that investment in renewable energy technology is justified at prices greater than $5 per gallon ($1.32/liter) with an attendant reduction in fuel use of 3–30%.