Organic Rankine Cycle (ORC) power systems are receiving increased recognition for the conversion of thermal energy when the source potential and/or its temperature are comparatively low. Mini-ORC units in the power output range of 350 kWe are actively studied for applications involving heat recovery from automotive engines and the exploitation of solar energy. Efficient expanders are the enabling components of such systems, and all the related developments are at the early research stage. Notably, no experimental gasdynamic data are available in the open literature concerning the fluids and flow conditions of interest for mini-ORC expanders. Therefore, all the performance estimation and the fluid dynamic design methodologies adopted in the field rely on non-validated tools. In order to bridge this gap, a new experimental facility capable of continuous operation is being designed and built at Delft University of Technology, the Netherlands. The Organic Rankine Cycle Hybrid Integrated Device (ORCHID) is a research facility resembling a state-of-Theart high-Temperature ORC system. It is flexible enough to treat different working fluids and operating conditions with the added benefit of two interchangeable Test Sections (TS's). The first TS is a supersonic nozzle with optical access whose purpose is to perform gas dynamic experiments on dense organic flows in order to validate numerical codes. The second TS is a test-bench for mini-ORC expanders of any configuration up to a power output of 100 kWe. This paper presents the preliminary design of the ORCHID setup, discussing how the required operational flexibility was attained. The envisaged experiments of the two TS's are also described.

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Concentrated Solar Power CSP plants are increasingly being considered for construction worldwide, in order to meet the demand for renewable power generation. The most promising technology considered today employs a central receiver, illuminated by a heliostat eld, using molten salts as working uid. A distinctive feature of these plant is the possibility of thermal energy storage, providing 15 or more hours of full power operation without solar irradiation. The state-of-the-art SAM software is often use for sizing the plant and evaluating the return on investment, assuming a straightforward and short-sighted control strategy. In this paper, a model similar to that used by SAM is developed and then used to demonstrate the potential advantages of optimal control, in a context of variable taris with higher prices during peak hours. The modelling and optimization problems are formulated with the high-level Modelica and Optimica languages, which allows to solve the problem with minimal eort. This paper is a rst step to promote the use of optimal control techniques and high-level modelling languages for the correct evaluation of the potential performance of CSP plants with thermal storage during their design phase.@en