Organic Rankine Cycle (ORC) have principally been used in the past couple of decades to recover medium grade heat from sources such as geothermal, biomass and the exhaust of a realm of different industrial processes (waste heat recovery). In the past few years, this power generation technology has also been proposed in concentrating solar thermal power applications, aiming to exploit its features in intermediate temperature systems (low water consumption, water-free operation, scalability). These inherent features are best exploited if coupled with thermal energy storage systems to enable good performance in spite of the intermittent energy supply and also to increase the average load factor. To achieve these objectives though, a proper storage system tailored to the heat profile captured by the solar collector and to the characteristics of the power cycle must be identified. This paper discusses the cited design criteria and presents an analysis aimed at identifying the potential storage solutions to be implemented into a Concentrated Solar Power (CSP) plant for electricity generation operating at temperatures between (170 degrees C) and (300 degrees C). The system so developed will be integrated in the 1 MWe CSP-ORC facility based on Fresnel technology that is currently under construction at Iresen's premises in Benguerir, Morocco. Detailed transient models of performance of two-tank and thermocline storage systems are presented. The annual simulations carried out reveal that thermocline solutions are globally more attractive, since they exhibit similar thermal performance but at a much lower (30% lower) cost. (C) 2016 Elsevier Ltd. All rights reserved.