Persona: Ibarra Mollá, Mercedes
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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 Latent thermal energy storage for solar process heat applications at medium-high temperatures – A review(Elsevier, 2019-11) Crespo, Alicia; Barreneche, Camila; Ibarra Mollá, Mercedes; Platzer, Werner; https://orcid.org/0000-0003-4616-0221; https://orcid.org/0000-0003-3636-3180Solar thermal energy has the potential to cover the heat demands of industrial processes. However, there may be a time mismatch between energy supplied by the solar field and the process demand. In this case, a thermal energy storage (TES) allows the use of heat at hours without solar irradiation available. Thermal energy storage (TES) for solar hot water or heating systems using low temperatures have been optimized since many decades and are in a mature stage. Developments at high temperatures (above 200 °C) for CSP applications have also been deeply studied. However, until this present paper, limited attention has been paid to TES for solar thermal industrial applications at medium-high temperatures (120 - 400°C), where there is a potentially huge demand. When discussing TES several aspects have to be discussed: the energy demand that TES is going to be designed to supply, the material where the energy will be stored and the performance of the TES system which includes not only the material but also tanks, piping and connections. In this review, food, brewery and chemical industries were identified as the industries with higher potential in which TES and solar energy could be integrated. Heat integration methodologies have been reviewed to optimize the use of the solar energy by the industrial processes. Regarding the material, latent heat storage or phase change materials (PCM) were selected because they are a very promising type of storage to be integrated in thermal industrial processes, although the state of the art of latent heat thermal storage (LHTES) systems is still far from broad commercialization. Until now, no reviews of latent heat storage for industrial applications at medium-high temperatures (120 - 400 °C) have been published. Therefore, literature related to PCM and LHS systems using PCM materials to be used in industrial thermal processes is here reviewed in order to have a general overview of the available technologies for their integration together with solar thermal energy in industrial processes at both experimental and numerical level. More than 100 potential PCMs for heat storage applications in the range of temperatures 120 - 400 °C have been found. Inorganic eutectic compositions are the group with more potentially available PCM for these applications, with values of heat of fusion between 74 and 535 kJ/kg. Finally, the works related to the performance of the system from the experimental and modelling point of view were presented. The review of experimental TES systems which include PCM in the studied range of temperatures 120 - 400 °C showed that most of the experimental set-ups were developed for direct steam generation for CSP applications. Regarding numerical modelling, the type of configuration more simulated is the shell and tube configuration.Publicación Performance of an Organic Rankine Cycle with two expanders at off-design operation(Elsevier, 2019-02-19) Ibarra Mollá, Mercedes; Rovira de Antonio, Antonio José; Alarcón-Padilla, Diego-CésarThe objective of this work was to simulate the behavior of an Organic Rankine Cycle (ORC) system with two expanders in series at off-design working conditions. The influence of both the intermediate pressure and the volumetric expansion ratio of the expanders on the off-design performance of the ORC was studied and the irreversibilities of the components were analyzed. The performance of the ORC with two expanders for two different designs was also discussed. The thermal efficiency reached using two expanders was higher than the obtained using only one. However, this increase conveyed an increase in the complexity of the design and control of the expanders. As an additional conclusion, it was found that the influence of the intermediate pressure is higher than that of the volume expansion ratio of each expander. The irreversibility of the first expander was mainly due to leaks. However, the performance of the second expander was particularly affected by the difference between the discharged pressure and the condensation pressure. The off-design analysis allowed the definition of a methodology to achieve the desired power with the maximum thermal efficiency, and the identification of the best actuation for the part load operation.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 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 Modeling of the heat transfer of a solar multi-effect distillation plant at the Plataforma Solar de Almería(Elsevier, 2011-07) Palenzuela, Patricia; Alarcón-Padilla, Diego-César; Blanco Galvez, Julian; Guillén, Elena; Ibarra Mollá, Mercedes; Zaragoza, Guillermo; https://orcid.org/0000-0001-8044-969X; https://orcid.org/0000-0002-8843-8511; https://orcid.org/0000-0001-7329-380X; https://orcid.org/0000-0003-4145-9224; https://orcid.org/0000-0002-4452-9980Potable water supply by desalination systems has a significant role in today’s developing world. Multi-effect distillation (MED) is a progressing, low cost and easy operating system to produce drinking and pure water for both social and industrial applications. It is very important to understand in detail the process elements in order to determine the effects of the important design and operating variables on the parameters controlling the performance of the plant. A model is developed for the MED 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. The model has been developed dividing the MED plant into four blocks: the heater (consisting of the first effect), the evaporators (consisting of effects 2 to N), the pre-heaters (for effects 1 to N – 1) and the condenser (after effect N). To solve the model, a parameterization of the overall heat transfer coefficient of the four blocks has been carried out with experimental data for a wide range of operation, based on correlations found by other authors for similar plants. The adjustments were good for all the components with the exception of the condenser, which seems to behave differently than in other cases reported in the literature.Publicación Comparative evaluation of two membrane distillation modules(Elsevier, 2011-07) Guillen 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 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, 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.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 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.