Abstract: A method and system are provided. The method includes co-optimizing a placement, a sizing, and an operation schedule of at least one energy storage system in an energy distribution system. The energy distribution system further has at least one renewable energy resource and at least one distributed energy resource. The co-optimizing step includes generating a placement-sizing-scheduling co-optimization model of the at least one energy storage system by integrating therein a distribution optimal power flow optimization model of the energy distribution system and components thereof. The distribution optimal power flow optimization model integrates therein at least an energy storage system model, a renewable energy resource model, and a distributed energy resource model.