Design of Storage Systems Using Multiple Storage Technologies in Renewable Systems

Energy systems that rely on intermittent renewable sources typically use storage devices to improve their reliability. Large scale systems can be expected to cycle the storage capacity on cycles ranging from a day to a year. It can be cost effective to use several storage technologies as a system. A very efficient technology can be used for the smaller daily cycles even if it has a high capital cost. Conversely, a technology having a low efficiency but a low capital cost can be used for the larger longer period cycles. This paper presents a method for determining the optimal capacities for a set of storage technologies. It is analogous to techniques used in electric generation capacity planning that use a load duration curve along with the capital and operating costs of various generations technologies. Here we derive a function that describes throughput as a function of capacity and use it along with the capital and operating costs (including efficiencies) of the storage technologies to derive the optimal capacities