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The National Renewable Energy Centre of Spain, CENER, and the Technology & Innovation area of ACS Cobra, as a result of their long term expertise in the CSP field, have developed a high-quality and high level of detail optical and thermal simulation software for the accurate evaluation of Molten Salts Solar Towers. The main purpose of this software is to make a step forward in the state-of-the-art of the Solar Towers simulation programs. Generally, these programs deal with the most critical systems of such plants, i.e. the solar field and the receiver, on an independent basis. Therefore, these programs typically neglect relevant aspects in the operation of the plant as heliostat aiming strategies, solar flux shapes onto the receiver, material physical and operational limitations, transient processes as preheating and secure cloud passing operating modes, and more. The modelling approach implemented in the developed program consists on effectively coupling detailed optical simulations of the heliostat field with also detailed and full-transient thermal simulations of the molten salts tube-based external receiver. The optical model is based on an accurate Monte Carlo ray-tracing method which solves the complete solar field by simulating each of the heliostats at once according to their specific layout in the field. In the thermal side, the tube-based cylindrical external receiver of a Molten Salts Solar Tower is modelled assuming one representative tube per panel, and implementing the specific connection layout of the panels as well as the internal receiver pipes. Each tube is longitudinally discretized and the transient energy and mass balances in the temperature dependent molten salts and steel tube models are solved. For this, a one dimensional radial heat transfer model based is used. The thermal model is completed with a detailed control and operation strategy module, able to represent the appropriate operation of the plant. An integration framework has been developed, helping ACS Cobra to adequately handle the optical and thermal coupled simulations. According to current results it can be concluded that the developed model has resulted in a powerful tool to improve the design and operation of future ACS Cobra's Molten Salts Solar Towers, since historical data based on its projects have been used for validation of the final tool. [ABSTRACT FROM AUTHOR]

Renewable energy generation, led by solar photovoltaics and wind energy, has increased significantly, reaching economic competitiveness against conventional power plants. However, both renewable technologies are nondispatchable, which requires, until now, flexible but polluting power plants to ensure security of supply and guarantee grid stability. To address these flexibility needs while increasing renewable energy (RE) penetration in a grid-friendly manner, GRIDSOL project [1] presents a new concept: "Smart Renewable Hub". A Smart Renewable Hub (SRH) is a flexible hybrid power plant that combines a core of synchronous and nonsynchronous generators like Concentrated Solar Power (CSP), Solar Photovoltaics (PV), Wind, and Biomass; along with Battery Energy Storage System (BESS), Thermal Energy Storage (TES), and a fossil- or bio-fueled turbine with a Heat Recovery System (HYSOL). Thus, the configuration of a Smart Renewable Hub can adopt different shapes depending on the suitability of each technology for each location. In this context, this study presents the evaluation of electricity market rules and mechanisms for integrating GRIDSOL's initial case (CSP + TES + PV + BESS + HYSOL) in Continental Europe and in an European Island. Every solution considers market and grid requirements, providing ancillary services and relieving pressure on the Electricity System Operator. [ABSTRACT FROM AUTHOR]