Optimizing Fuel Efficiency on Isolated Microgrid with Energy Storage System under Varying Loads

By ENS Joo W. Lee, USN

A major drawback of generating power in an isolated environment is the ability to withstand time-varying loads. The time-varying demand characteristics introduce difficulty in successfully satisfying the power demands due to generator ramping limits. To help analyze the impact of time-varying loads on optimal generator operation and fuel consumption, we formulate a mixed-integer optimization model to plan generator and energy storage system (ESS) operation to satisfy known time-varying demands using minimal fuel. In the optimization model, we introduce an additive penalty to the existing generator fuel consumption calculation to reduce rapid power fluctuation. Our results show that the change in fuel efficiency between scenarios with the integration of ESS is minimal regardless of the imposed penalty placed on the generator. However, without the assistance of the ESS, the fuel consumption increases dramatically as the penalty imposed on the generator becomes greater. The integration of ESS shows a drastic improvement in fuel consumption, where the ESS allows the generator to minimize power output fluctuation to maximize fuel efficiency. The insignificance of penalty type and weight imposed on the generator provides potentially useful insight for future studies in developing a real-time controller.  The exploration of a microgrid controller to save fuel consumption will contribute to minimizing the Department of Defense's operational costs in the future.