Mobile Energy Storage in Power Network: Marginal Value and Optimal Operation

This paper examines the marginal value of mobile energy storage, i.e., energy storage units that can be efficiently relocated to other locations in the power network. In particular, we formulate and analyze the joint problem for operating the power grid and a fleet of mobile storage units. We use two different storage models: rapid storage, which disregards travel time and power constraints, and general storage, which incorporates them. By explicitly connecting the marginal value of mobile storage to locational marginal prices (LMPs), we propose efficient algorithms that only use LMPs and transportation costs to optimize the relocation trajectories of the mobile storage units. Furthermore, we provide examples and conditions under which the marginal value of mobile storage is strictly higher, equal to, or strictly lower than the sum of marginal value of corresponding stationary storage units and wires. We also propose faster algorithms to approximate the optimal operation and relocation for our general mobile storage model, and illustrate our results with simulations of an passenger EV and a heavy-duty electric truck in the PJM territory.