On the project scheduling problem under stored resource constraints

For the resource constrained project scheduling problem (RCPSP) we introduce a notion of stored resources. Like it is for renewable resources, a predetermined number of units of a stored resource is available for every unit period of the planning horizon. But if some quantity of the resource is not utilized in period t, it can be utilized in any subsequent period t´>t. We prove that for the RCPSP which contains only stored resources, the optimal solution can be found in polynomial time under arbitrary resource requirements, resource availabilities, and job deadlines.