Browsing by Author "Battisti, F. G."

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    Dynamic modeling and control of a solar-powered Brayton cycle using supercritical CO2 and optimization of its thermal energy storage
    (2023) Delsoto, G. S.; Battisti, F. G.; da Silva, A. K.
    Recompression Brayton cycles using supercritical CO2 as the working fluid appear as a prominent alternative for thermo-solar power applications. Also, solar energy's natural variability and intermittence make it difficult for solar plants to operate consistently and predictably. Thus, two of the most explored mitigating alternatives are thermal energy storage and auxiliary heating systems. Hence, this paper used actual meteorological data and transient numerical simulations to investigate the power output dynamics of a 10 MW plant. The modeling of an active control system of the working fluid mass inventory allowed the plant to operate in a stable manner while accounting for the significant variations in the fluid's thermophysical properties. Also, the study investigated the effect of the sizes of the thermal energy storage system and solar collectors field on the dynamics of the system. Finally, statistical analyses with actual meteorological data from Florianopolis/Brazil for nine days between 2017 and 2018 supported determining the optimal thermal energy storage system size. Hence, depending on the daily conditions, the results showed the operating settings that minimize the use of auxiliary heating with reductions of fuel consumption larger than 10%.
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    Modelling the temperature distribution in a horizontal packed-bed thermal energy storage system with copper slag as filler material
    (2025) Calderón Vásquez, Ignacio Andrés; Wolde Ponce Ian; Segovia Araya, Valentina Constanza; Battisti, F. G.; Cardemil Iglesias, José Miguel; Escobar Moragas, Rodrigo Alfonso
    Air-solid packed-bed thermal energy storage (PBTES) systems are potential candidates to reduce implementation costs for renewable energy applications. However, heat transfer modelling requires high computational resources, which makes these models unsuitable for control and management in integrated systems. This work presents a fit parameter estimation model to predict the temperature distribution on an operational PBTES system. Through the non-linear least squares method, we use experimental data to calibrate an analytical solution for the heat exchange within an air-solid porous medium. This model presented a normalised root mean squared error of 4% to predict the temperature and the state of charge (SOC). Using mean values from the mass flow rate time series, the model allows estimating the SOC with a deviation of 0.5% from the one calculated from experimental data, and predicted that approximately 60% of the discharged energy was recovered from the storage tank walls, despite not explicitly modelling them. The proposed model avoids solving differential equations by directly computing the analytical solution, making it computationally efficient. Its accuracy and simplicity make it a strong candidate for integration into control and energy management systems for PBTES technologies.
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    On the analytical solution of the one-dimensional convection-conduction equation for packed-bed thermal energy storage systems
    (2024) Calderon-Vasquez, Ignacio; Battisti, F. G.; Rosales-Vera, Marco; Cardemil, Jose M.; Escobar, Rodrigo
    Temperature distribution modeling within packed-bed thermal energy storage (PBTES) systems is crucial to simulate its integration into heat sources and perform techno-economic analyses to assess the actual benefits associated with its use. This article proposes a one-dimensional convection-conduction equation to model a fluid-solid system by assuming volume-averaged properties for the energy balance and determines the analytic solution through Integral Transforms. The present study analyzes the applicability of this analytic solution considering different operational conditions of PBTES systems. The article revealed that the P & eacute;clet number (Pe) and the fluid-to-solid capacity ratio (kappa) must be limited to obtain stable solutions, while the dimensionless time tau cannot be arbitrary despite computing an analytic solution. A sensitivity study of the solution for parameter a=kappa Pe/2 defined the minimum dimensionless time required for the solution to be stable. This stability was assessed with existing experimental setups, indicating the solution's feasibility for air-solid PBTES systems.