Persona: Ibarra Mollá, Mercedes
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Ibarra Mollá
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Publicación Experimental analysis of an air gap membrane distillation solar desalination pilot system(Elsevier, 2011-09) Guillén-Burrieza, Elena; Blanco Galvez, Julian; Zaragoza, Guillermo; Alarcón-Padilla, Diego-César; Palenzuela, Patricia; Ibarra Mollá, Mercedes; Gernjak, Wolfgang; https://orcid.org/0000-0003-4145-9224; https://orcid.org/0000-0001-7329-380X; https://orcid.org/0000-0002-4452-9980; https://orcid.org/0000-0002-8843-8511; https://orcid.org/0000-0001-8044-969X; https://orcid.org/0000-0001-9859-2435; https://orcid.org/0000-0003-3317-7710Freshwater shortage difficulties make it necessary to find new sources of supply. Nowadays desalination is the solution adopted in many countries to solve this problem. All around the planet, regions with lack of freshwater match up with those with large amounts of available solar radiation. Therefore, solar desalination can be a suitable and sustainable option to tackle the water scarcity problems in those particular areas, especially in the coastal ones where the majority of human population lives. Membrane distillation (MD) is a thermal membrane technology developed since late 60´s which uses low exergy heat to drive a separation process in aqueous solutions. One of its applications is desalination where thanks to its separation principle, very high distillate quality can be obtained. Amongst its advantages, its low operating temperatures, ranging between 60-90º C [Lawson and Lloyd, 1997] make possible the use of low-grade heat, the kind of energy easily delivered by static solar collectors, as the only thermal supply. This, jointly with its low operational pressure and small footprint, make MD coupled with solar energy (Solar Membrane Distillation) in principle, a promising technology. Under the framework of a European project (MEDESOL Project) funded by the European commission, an innovative desalination system based on solar air gap membrane distillation has been investigated. The system is intended to be technically simple to operate, robust and able to cover water demands of small settlements. The experimental set-up was built at Plataforma Solar de Almería facilities (leading partner) and tested during 4 months. The desalination system consists of a three MD desalination modules system supplied with the thermal energy of a static collector’s solar field. Desalination and solar circuits are connected through a plate heat exchanger especially coated to withstand hot seawater operational conditions. The system was run during solar hours (as the layout doesn’t contemplate heat storage) and the experiments were designed to characterize the system. The overall performance of the system was evaluated with both tap water and a 35 g L-1 NaCl aqueous solution. The distillate production and quality were evaluated as a function of the operational parameters, as well as the thermal consumption and specific desalination parameters such as performance ratio (PR). The system can work at temperatures up to 95ºC on the hot feed side and up to 60 ºC on the refrigeration side. This paper will show the experimental results as well as the operational experiences of the system.Publicación Performance of a 5kWe Organic Rankine Cycle at part-load operation(Elsevier, 2014-05) Ibarra Mollá, Mercedes; Rovira de Antonio, Antonio José; Alarcón-Padilla, Diego-César; Blanco Galvez, Julian; https://orcid.org/0000-0002-8843-8511; https://orcid.org/0000-0001-7329-380XThis paper analyzes the performance of an Organic Rankine Cycle (ORC) system at part load operation. The objective is to understand its behavior from a thermodynamic perspective, identifying which elements are the most critical and which are the best operating points for each level of demanded power. This paper also compares two working fluids: R245fa and Solkatherm ES36 (SES36) for the same cycle specifications. The results have shown that the scroll isentropic efficiency has a great influence on the cycle performance and its thermal efficiency and that SES36 arises as a potential better fluid than R245fa. At the given maximum and minimum temperatures, the best operation point was determined. This allows reaching a maximum efficiency for each demanded level of power; depending on the required amount of power, the expander speed and the working pressure are adjusted.Publicación Comparative evaluation of two membrane distillation modules(Elsevier, 2011-07) Guillén-Burrieza, Elena; Blanco Galvez, Julian; Alarcón-Padilla, Diego-César; Zaragoza, Guillermo; Palenzuela, Patricia; Ibarra Mollá, Mercedes; https://orcid.org/0000-0003-4145-9224; https://orcid.org/0000-0001-7329-380X; https://orcid.org/0000-0002-8843-8511; https://orcid.org/0000-0002-4452-9980; https://orcid.org/0000-0001-8044-969XFreshwater shortage difficulties make it necessary to find new sources of supply. Nowadays desalination is the solution adopted in many countries to solve this problem. All around the planet, regions with lack of freshwater match up with those with large amounts of available solar radiation. Therefore, solar desalination can be a suitable and sustainable option to tackle the water scarcity problems in those particular areas, especially in the coastal ones. Membrane distillation (MD) is a thermal membrane technology developed since late 60’s which uses low exergy heat to drive a separation process in aqueous solutions. One of its applications is desalination where thanks to its separation principle, very high distillate quality can be obtained. MD is a thermally driven process that differs from other membrane technologies in that its driving force, rather than the total pressure, is the difference in water vapour pressure across the membrane, caused in turn by a temperature difference between the cold and the hot side of it. In comparison with other membrane-based desalination processes like reverse osmosis (RO), MD shows very high rejection rates and much lower operational pressures, also the nature of MD membranes (larger pore sizes than RO) makes them much less sensitive to fouling. Compared to conventional thermal desalination processes like MSF or MED, MD is less demanding regarding vapor space and building material’s quality [1] leading to potential lower construction costs. Amongst its advantages, its low operating temperatures (ranging between 60–90°C [2]) make possible the use of low-grade heat, the kind of energy delivered by static solar collectors, as the only thermal supply. This, jointly with its low operational pressure and small footprint, make solar membrane distillation (SMD) in principle, a promising technology. Despite these advantages, SMD has been developed to a lesser extent, compared with other solar desalination technologies like PV-driven RO or solar stills, and although many encouraging laboratory experiences can be found in literature, large-scaling and module design is still an issue. It is precisely because of this preliminary state MD is in, that very preliminary, low energy efficiency and not commercial available MD prototypes are still found. In MD there is still a trade-off between efficiency (heat consumption) and production (distillate per square meter of membrane), as a result very high specific distillate fluxes can be attained (up to 80 kg h–1 m–2 of membrane [3]) but heat losses (mainly trough the membrane by conduction) are still substantial. Under the framework of an European project (MEDESOL: Seawater Desalination by Innovative Solar Powered Membrane Distillation) which main objective was to develop a stand-alone desalination system based on multi stage MD to supply decentralized rural areas [4], the status and future possibilities of currently developed MD have been evaluated. This paper presents the results obtained from the experiments realized with two different pre-commercial MD modules, coupled to a solar field comprised of static collectors. Both modules were tested in the same facility under the same conditions, in order to make a reliable comparison between them. Data on energy efficiency, production ratios and operational issues will be shown.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 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 Steady-state analysis of an innovative rotatory Fresnel collector integrated into two industrial processes(Elsevier, 2025-04-01) Ibarra Mollá, Mercedes; Barbero Fresno, Rubén; Rovira de Antonio, Antonio José; https://orcid.org/0000-0001-9859-2435; https://orcid.org/0000-0002-6033-1309; https://orcid.org/0000-0002-6810-3757This study compares the performance of two solar thermal systems, MAND and AMTP, designed for industrial process heat using a rotating Fresnel collector (Sundial) and Phase Change Material (PCM) thermal energy storage (TES). The systems differ in their latitude and in their demand profiles: MAND, located at low latitude, has a continuous 24-hour demand, while AMTP, located at high latitude, has a daytime-only demand. Through steady-state simulations, both daily and yearly performance were analyzed to assess the impact of these differences on system behavior. The designed system achieved annual energy outputs of 26,34 MWh and 25,37 MWh for the two case studies, over the prescribed target of 25 MWh and capacity factors of 30,34% and 32,11%. Results demonstrate that TES plays distinct roles in each system, with carryover storage being crucial for MAND and maximizing heat exchanger operation being more important for AMTP. The analysis highlights the importance of tailoring system design and control strategies to specific industrial process requirements and demonstrated the feasibility of integrating the ASTEP system for industrial applications, even with not favorable conditions like high latitude and daytime-only demand.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 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 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.