Persona: Ibarra Mollá, Mercedes
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Publicación Evaluación tecno-económica de sistemas basados en ciclos Rankine orgánicos de pequeña potencia para su integración en sistemas termosolares(Universidad Nacional de Educación a Distancia (España). Escuela Técnica Superior de Ingenieros Industriales. Departamento de Ingeniería Energética, 2016-06-22) Ibarra Mollá, Mercedes; Rovira de Antonio, Antonio José; Alarcón-Padilla, Diego-CésarEl objetivo de este trabajo era el estudio tecnoeconómico de una planta de ciclo Rankine orgánico (CRO) de baja potencia (<10 kWe) que funcionara con energía solar de media temperatura (100-250ºC). Uno de los primeros objetivos era desarrollar una metodología de diseño del sistema, tanto del sistema solar como del sistema CRO. Para ello se ha presentado, un modelo para la simulación anual de un campo solar y la experimentación realizada con el captador NEPSolar Polytrough 1200, que permitió obtener Ja curva de rendimiento de dicho captador. Por otro lado, en esta tesis se ha desarrollado el modelo de simulación de CRO, que permite el análisis de varios diseños, fluidos (SES36 y R245fa) y condiciones de trabajo. Una instalación experimental permitió la validación del modelo, corroborando su capacidad de previsión de cálculo de la potencia producida. Este modelo de simulación de CRO ha permitido analizar detalladamente el comportamiento de los CRO a cargas parciales, tanto con un expansor, como con dos expansores, en ros que se estudió el comportamiento de los ciclos a diferentes condiciones de trabajo. Los resultados de este análisis han permitido proponer una metodología para seleccionar el punto de operación de los ciclos más adecuado para cada potencia demandada. En el diseño del sistema, el primer problema a resolver en ros CRO con dos expansores en serie ha sido la selección de los parámetros de diseño que optimizara el comportamiento del ciclo a cargas parciales. En particular, la elección de la presión intermedia entre expansores adecuada era fundamental para el buen funcionamiento del ciclo posterior. Para ello se analizaron diferentes metodologías, siendo la que tenía mejores resultados la estrategia de elegir el conjunto de valores que hace que los rendimientos de los expansores sean similares. Los modelos CRO desarrollados en esta tesis han permitido la generación de los mapas de operación, que a su vez han permitido determinar la operación del sistema a cargas parciales con menores tiempos de computación. Utilizando estos mapas se ha realizado la simulación anual del comportamiento de un sistema CRO acoplado un campo solar. Se han analizado cuatro sistemas, combinando CRO de uno y dos expansores y captadores cilindroparabólicos de pequeña apertura y captadores planos de ultra-vacío. Por último, se ha realizado un análisis económico, en el que se incluye un cálculo determinístico del LCOE, la optimización del par múltiplo solar-almacenamiento térmico (minimizando el coste nivelado de la energía), un análisis de sensibilidad de los costes y un análisis estadístico de los resultados. Por tanto, el trabajo desarrollado en la tesis ha permitido identificar una ventana de diseño en cuanto a posibles captadores solares, fluidos de CRO, condiciones de trabajo y máquinas de expansión, considerando siempre la operación real y el comportamiento real de ras máquinas y equipos involucrados, tanto del ciclo Rankine orgánico como del sistema solar y pudiendo determinar las ventajas y desventajas de cada diseño.Publicación Proposal of a microchannel receiver for Fresnel technology to supply solar heat for industrial processes(Elsevier, 2023-09-30) Stojceska, V.; Reay, David A.; Montes Pita, María José; Ibarra Mollá, MercedesThis work is focused on the linear Fresnel technology to supply solar heat for industrial processes, proposing a new microchannel receiver design for pressurised gases. This design consists of two absorber panels converging at the focal line of the Fresnel system; each of these panels consists of a compact core fin structure attached to both front and back plates. The fluid flows through the receiver along its length in several passes, so that the compactness is constant and greater than in the previous pass. This arrangement improves heat transfer and, therefore, the cooling of the more thermally stressed areas of the panel, without over penalising the pressure drop. A thermal resistance model has been formulated to quantify the fluid heating along the panel length and the thermal gradient along the panel thickness. This model has been used to perform a thermo-exergy optimisation based on several characteristic parameters: the aperture half-angle of the cavity shaped by the two converging panels; and the channels dimensions in each pass of the panel. For each of these parameters, a maximum exergy efficiency has been obtained accounting for the receiver heat losses, the fluid pressure drop and the optical performance of the primary mirror field.Publicación Advances in aerosol optical depth evaluation from broadband direct normal irradiance measurements(Elsevier, 2021-06) Salmon, Aloïs; Quiñones, Gonzalo; Soto, Gonzalo; Polo, Jesús; Gueymard, Christian; Ibarra Mollá, Mercedes; Escobar, Rodrigo; Marzo, AitorAerosols are part of the attenuation processes that impact solar radiation within the atmosphere. They influence the availability and spectrum of the solar resource for each location at the earth’s surface. The present study presents advances in the development of a methodology intended to estimate the aerosol optical depth (AOD) at a given location from broadband direct normal irradiance (DNI) measurements and an appropriate radiative transfer model (RTM) operated backwards. For this purpose, databases provided by AERONET and BSRN at 16 stations throughout the world are jointly employed as inputs to the proposed methodology. The validation of two RTMs (SMARTS and SOLIS) is first undertaken to estimate DNI under clear-sky conditions at each station, assuming both AOD and additional atmospheric inputs are known from sunphotometric measurements. Results indicate that both models achieve good performance, characterized by a relative rRMSE of 3.2% for SMARTS and 3.8% for SOLIS. In the second, and most important stage, the AOD at 550 nm (AOD550) is derived using these models again, but in an iterative mode, now using the 1-minute DNI measurements as inputs. Periods of clear line of sight to the sun first need to be selected from the irradiance measurement record. This, along with other difficulties, make this operation prone to errors when only DNI measurements are available. In spite of this, the results show that AOD can be estimated with a 16-site average mean bias error of only between −0.024 and 0.015 AOD unit and an absolute RMSE between 0.025 and 0.050 AOD unit (compared to the AERONET ground truth), depending on model. Notable improvements are obtained if secondary atmospheric variables are extracted from the MERRA-2 reanalysis and are included as inputs for local computations. The present results suggest that the method is able to compare favorably with AOD estimates from MERRA-2 predictions or MODIS observations, for instance.Publicación Theoretical technical–economic comparison of hybrid energy for gas and solar concentration plants in the Region of Antofagasta Chile(Elsevier, 2023-02) Hernández Moris, Catalina; Felbol, Carlos; Cerda, Maria Teresa; Ibarra Mollá, MercedesElectricity demand from mining industry in Chile will increase up to 34 % in the next 10 years. The Antofagasta region has several mining operations and gas pipelines, in addition to being an area with very high solar resource availability. This study focuses on reviewing hybridization alternatives for combined cycle plants with concentrating solar generation technologies. In this work a techno-economic analysis of two alternative small scale hybridized solar-combined cycle technologies is developed, a solarized combined cycle with STP and a solarized combined cycle with PTC. To perform the solar concentration systems simulations, TRNSYS software was used for PTC, and Solstice software for STP system, while the thermodynamic simulation for the combined cycle system was developed using EES software. The LCOE was calculated for all plants considering a fuel cost of 66 USD/MWh. LCOE obtained for combined cycle is 202 USD/MWh, while LCOE for combined cycle with STP integration is 149 USD/MWh, and LCOE for combined cycle with PTC integration is 197 USD/MWh. The lowest LCOE is achieved with the STP integration, since part of the fuel that feeds the combined cycle is replaced by solar energy, avoiding the emission of 16,603 tons of CO2.Publicación Integration enhancements of a solar parabolic trough system in a Chilean juice industry: Methodology and case study(Elsevier, 2021-08) Crespo, Alicia; Muñoz, Iván; Platzer, Werner; Ibarra Mollá, MercedesA Chilean company dedicated to grape juice production used a 696 m2 parabolic trough collector to pre-heat the feed water of a liquefied petroleum gas boiler in a temperature range of 20–90 °C. During 2017 the solar field generated 241 MWhth of heat, a low value for a concentration collector of such dimensions located in a place with high irradiation. This study presents a methodology to identify enhanced scenarios of solar heat integration into a grape juice industry and among them select the best scenario from an energetic perspective. This methodology started with data gathering of the thermal processes of the industry and the solar field (monitoring campaign and logbook of the industry) to generate the annual thermal demand. In a second step, the maximum theoretical generation potential of the solar field (1,107 MWhth) was obtained with simulations in TRNSYS 18. Then, a Pinch Analysis to the process streams was performed to confirm that a higher solar heat integration potential (520 MWhth) existed. The next step consisted of identifying different scenarios to increase the solar heat integration and analyzing them with simulations in TRNSYS 18 to identify the best-case scenario. The main increase on the solar fraction was achieved for the scenario when the collector working temperature was increased up to 140 °C and when heat was integrated at process level. Furthermore, it was concluded that one of the reasons for low solar fraction was the low thermal demand during months with high solar irradiation.Publicación Potential map for the installation of concentrated solar power towers in Chile(MDPI, 2020-04-28) Hernández, Catalina; Barraza, Rodrigo; Saez, Alejandro; Ibarra Mollá, Mercedes; Estay, DaniloThis study aims to build a potential map for the installation of a central receiver concentrated solar power plant in Chile under the terms of the average net present cost of electricity generation during its lifetime. This is also called the levelized cost of electricity, which is a function of electricity production, capital costs, operational costs and financial parameters. The electricity production, capital and operational costs were defined as a function of the location through the Chilean territory. Solar resources and atmospheric conditions for each site were determined. A 130 MWe concentrated solar power plant was modeled to estimate annual electricity production for each site. The capital and operational costs were identified as a function of location. The electricity supplied by the power plant was tested, quantifying the potential of the solar resources, as well as technical and economic variables. The results reveal areas with great potential for the development of large-scale central receiver concentrated solar power plants, therefore accomplishing a low levelized cost of energy. The best zone is located among the Arica and Parinacota region and the northern part of the Coquimbo region, which shows an average cost of 89 USD/MWh, with a minimum of 76 USD/MWh near Copiapó.Publicación Solar extinction map in Chile for applications in solar power tower plants, comparison with other places from sunbelt and impact on LCOE(Elsevier, 2021-06) Marzo, Aitor; Salmon, Aloïs; Polo, Jesús; Ballestrín, Jesús; Soto, Gonzalo; Quiñones, Gonzalo; Alonso Montesinos, Joaquín; Carra, Elena; Ibarra Mollá, Mercedes; Cardemil-Iglesias, José Miguel; Fuentealba, Edward; Escobar, RodrigoDirect normal solar irradiation is a crucial parameter for site selection and design of solar power tower plants. It also has a high impact on economic studies, such as the levelized cost of electricity (LCOE). However, direct solar irradiation can be partially extinguished in its path between heliostats and receivers. Therefore, considering only direct normal solar irradiation in the solar resource assessment for tower plant projects is insufficient and leads to errors. This paper presents an improved methodology to estimate the extinction of radiation in the first 150 m of the lower atmosphere, where solar power tower plants are located. This work also shows the first atmospheric extinction maps, which in this case are elaborated for Chilean territory, and the intercomparison of extinction values with other places of interest in the sunbelt. Chile stands out for having the lowest annual atmospheric extinction values, below 4% for 1 km of slant range, while elsewhere annual losses can reach up to 17%. These values limit the amount of local useful solar resource available directly impacting on the LCOE values calculated for solar tower power plants. A new equation for the calculation of the LCOE considering atmospheric extinction is proposed in this paper.Publicación Performance of a 5 kWe solar-only organic Rankine unit coupled to a reverse osmosis plant(Elsevier, 2014) Ibarra Mollá, Mercedes; Rovira de Antonio, Antonio José; Alarcón-Padilla, Diego-César; Zaragoza, Guillermo; Blanco Galvez, Julian; https://orcid.org/0000-0002-8843-8511; https://orcid.org/0000-0002-4452-9980; https://orcid.org/0000-0001-7329-380XOrganic Rankine Cycle (ORC) systems are one of the most promising energy conversion technologies available for remote areas and low temperature energy sources. An ORC system works like a conventional Rankine cycle but it uses an organic compound as working fluid, instead of water. A small ORC unit coupled with a solar thermal energy system could be used to convert solar thermal energy into electricity in remote areas, offering an alternative to Photovoltaic (PV) systems to provide the energy required by desalination applications like reverse osmosis (RO). In this work an analysis of the performance of a specific solar desalination ORC system at part load operation is presented, in order to understand its behavior from a thermodynamic perspective and be able to predict the total water production with changing operation conditions. The results showed that water production is around 1.2 m3/h, and it is stable during day and night thanks to the thermal storage and only under bad irradiance circumstances the production would stop.Publicación Parametric equations for the variables of a steady-state model of a multi-effect desalination plant(Taylor and Francis Group, 2012-07-10) Palenzuela, Patricia; Alarcón-Padilla, Diego-César; Zaragoza, Guillermo; Blanco Galvez, Julian; Ibarra Mollá, MercedesIn the present work a steady-state model is developed of an MED plant. Its development and validation have been carried out by experimental data obtained from an MED pilot plant located at the Plataforma Solar de Almería (PSA), in the southeast of Spain. It is a vertical-arrangement forward-feed MED plant with pre-heaters, which uses hot water as the thermal energy source. In order to run the model a series of parametric equations for these variables: the overall heat transfer coefficient for the first effect (Uh), the overall heat transfer coefficient for the pre-heaters (Up(i)), the vapor temperature inside the first effect, (Tv(1)) and the cooling seawater outlet temperature (Tcwout) have been determined. They have been obtained from a three-level factorial experimental design (3k), performing a total of 81 experiments (34). The results obtained showed a good fit to the estimated models for the response variables.Publicación Assessment of different configurations for combined parabolic-trough (PT) solar power and desalination plants in arid regions(Elsevier, 2011-08) Palenzuela, Patricia; Zaragoza, Guillermo; Alarcón-Padilla, Diego-César; Blanco Galvez, Julian; Guillén-Burrieza, Elena; Ibarra Mollá, Mercedes; https://orcid.org/0000-0001-8044-969X; https://orcid.org/0000-0002-8843-8511; https://orcid.org/0000-0002-4452-9980; https://orcid.org/0000-0001-7329-380X; https://orcid.org/0000-0003-4145-9224The combination of desalination technology into concentrating solar power (CSP) plants needs to be considered for the planned installation of CSP plants in arid regions. There are interesting synergies between the two technologies, like the possibility of substituting the condenser of the power cycle for a thermal desalination unit. This paper presents a thermodynamic evaluation of different configurations for coupling parabolic-trough (PT) solar power plants and desalination facilities in a dry location representing the Middle East and North Africa (MENA) region. The integration of a low-temperature multi-effect distillation (LT-MED) plant fed by the steam at the outlet of the turbine replacing the condenser of the power cycle has been simulated and compared with the combination of CSP with a reverse osmosis (RO) plant. Furthermore, an additional novel concept of concentrating solar power and desalination (CSP+D) has been evaluated: a LT-MED powered by the steam obtained from a thermal vapour compressor (TVC) using the exhaust steam of the CSP plant as entrained vapour and steam extracted from the turbine as the motive vapour of the ejector. This new concept (LT-MED-TVC) has been analyzed and compared with the others, evaluating its optimization for the integration into a CSP plant by considering different extractions of the turbine.