The penetration of renewable energy has been increasing rapidly through out the world. But its generation is intermittent unlike conventional sources. Energy storages provide an environmentally sustainable mechanism to reduce its variability. And given the geographically distributed nature of renewable energy sources, using a network of energy storages instead of using centralized ones can be helpful in avoiding congestion in transmission networks. In this paper we study a power system with such a network of storages. We provide a stochastic formulation to obtain the optimal scheduling policy for it. We show that the problem of calculating that policy is not convex in general and we find sufficient conditions for convexity. We also propose and numerically evaluate a heuristic algorithm which provides sub-optimal policies when the problem is non-convex.