Persona: Montes Pita, María José
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Montes Pita
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Publicación Optimization of a New Design of Molten Salt-to-CO2 Heat Exchanger using Exergy Destruction Minimization(MDPI, 2020-08-08) Linares Hurtado, José Ignacio; Moratilla, Beatriz Yolanda; Montes Pita, María José::virtual::3127::600; Barbero Fresno, Rubén::virtual::3128::600; Montes Pita, María José; Barbero Fresno, Rubén; Montes Pita, María José; Barbero Fresno, Rubén; Montes Pita, María José; Barbero Fresno, RubénOne of the ways to make cost-competitive electricity, from concentrated solar thermal energy, is increasing the thermoelectric conversion efficiency. To achieve this objective, the most promising scheme is a molten salt central receiver, coupled to a supercritical carbon dioxide cycle. A key element to be developed in this scheme is the molten salt-to-CO2 heat exchanger. This paper presents a heat exchanger design that avoids the molten salt plugging and the mechanical stress due to the high pressure of the CO2, while improving the heat transfer of the supercritical phase, due to its compactness with a high heat transfer area. This design is based on a honeycomb-like configuration, in which a thermal unit consists of a circular channel for the molten salt surrounded by six smaller trapezoidal ducts for the CO2. Further, an optimization based on the exergy destruction minimization has been accomplished, obtained the best working conditions of this heat exchanger: a temperature approach of 50 °C between both streams and a CO2 pressure drop of 2.7 bar.Publicación Thermodynamic Cycles for Solar Thermal Power Plants: A Review(WIREs (Wiley Interdisciplinary Reviews), 2021-10-17) Muñoz Domínguez, Marta; Rovira de Antonio, Antonio José; Montes Pita, María JoséSolar thermal power plants for electricity production include, at least, two main systems: the solar field and the power block. Regarding this last one, the particular thermodynamic cycle layout and the working fluid employed, have a decisive influence in the plant performance. In turn, this selection depends on the solar technology employed. Currently, the steam Rankine cycle is the most widespread and commercially available power block option, usually coupled to a parabolic trough solar field. However, other configurations have been implemented in solar thermal plants worldwide. Most of them are based on other solar technologies coupled to a steam Rankine cycle, although integrated solar Combined cycles have a significant level of implementation. In the first place, power block configurations based on conventional thermodynamic cycles -Rankine, Brayton and combined Brayton-Rankine- are described. The achievements and challenges of each proposal are highlighted, for example, the benefits involved in hybrid solar source/fossil fuel plants. In the second place, proposals of advanced power block configuration are analyzed, standing out: supercritical CO2 Brayton cycles, advanced organic cycles and innovative integrated solar combined cycles. Each of these proposals show some advantages compared to the conventional layouts in certain power or source temperature ranges and hence they could be considered attractive options in the medium term. At last, a brief review of proposals of solar thermal integration with other renewable heat sources is also included.Publicación Proposal of a new design of central solar receiver for pressurised gases and supercritical fluids(Elsevier, 2023-07-10) Guedez Mata, Rafael; Linares Hurtado, José Ignacio; González Aguilar, José; Romero, Manuel; Montes Pita, María José; D Souza, David JonathanThis work presents a novel design of microchannel central receiver for pressurised gases and supercritical fluids in solar tower plants. It consists of a radial arrangement of vertical absorber panels that converge on the central axis of the tower. The absorber panels comprise compact structures, whose compactness is increased in one flow pass compared to the previous one, as the fluid is heated. This concept reduces radiation heat losses due to its light-trapping geometry and increases heat transfer to the thermal fluid without over penalising its pressure drop. For the receiver assessment, it has been developed a thermal resistance model characterising the fluid heating along the panel height and the temperature gradient between parallel channel rows of the compact structure across the panel thickness. Once the thermal and optical boundary conditions are defined, an optimisation analysis of the main geometrical parameters of the receiver has been accomplished. The receiver performance is evaluated by means of a global exergy efficiency referred to the solar subsystem, which computes the receiver heat losses, the fluid pressure drop and the optical efficiency of the heliostat field in which the receiver is integrated. For each parametric optimisation, the configuration that maximises this efficiency is identified.Publicación A new design of multi-tube receiver for Fresnel technology to increase the thermal performance(Elsevier, 2022-03-05) Abbas, Rubén; Montes Pita, María José; Barbero Fresno, Rubén; Rovira de Antonio, Antonio JoséSolar heat for industrial processes is a promising way to meet the high thermal demand required by the industry, while this application becomes an important niche market for solar technology. In this research line, it is proposed a novelty concept based on a rotary Fresnel solar collector to supply heat above 150 °C. This work is focused on the multi-tube receiver for this Fresnel collector, proposing a thermal design based on three criteria that can be generalized for any multi-tube receiver: the fluid flow layout is arranged to meet the symmetry of the solar flux map; the fluid circulates from the lower to the higher flux density zone; and the fluid velocity is modified by modifying the tube diameter, to optimize the heat transfer. Following these criteria, the final configuration of the receiver is chosen based on an exergy optimization, in which both heat loss and pressure drop must be quantified. It has been also accomplished a generalization of the optimization methodology for Fresnel collectors providing heat at different temperatures, showing that, in these cases, the configuration that maximizes the exergy efficiency does not correspond to the one with the highest energy efficiency. This thermal design method can be applied to multi-tube receivers working at higher temperatures in longer Fresnel loops, in which case the optimization will result in more marked differences between the optimal values and the standard ones.Publicación Energy and exergy analysis of microchannel central solar receivers for pressurised fluids(Elsevier, 2023-01-25) Romero, Manuel; González Aguilar, José; Montes Pita, María José; D Souza, David JonathanWithin the new generation of advanced central solar receivers, microchannel pressurised gas receivers are emerging as reliable and efficient alternatives to operate at high temperatures and pressures. This paper presents an optimisation and comparative analysis of different compact plate-fin type structures, constituting the receiver’s absorber panels, classified according to the type of fin arrangement inside: plain rectangular, plain triangular, wavy, offset strip, perforated, and louvred fin. A versatile thermo-fluid receiver model is implemented, allowing simple variation of characteristic geometric parameters of each structure. Exergy efficiency is chosen as the optimisation function, as it considers both heat and pressure losses. The framework of the analysis is set by the receiver’s boundary conditions, operating at the design point conditions of a solar thermal power plant. For each compact structure, the optimal configuration is determined, providing interesting findings that have not been reported in the state-of-the-art to date. Although all geometries show good thermal performance, the perforated and plain rectangular configurations demonstrate the best exergy efficiencies of 59.21% and 58.80%, respectively, favouring taller and narrower channels. This analysis methodology could be seamlessly extrapolated to other gases and working conditions, owing to the thermo-fluid model’s versatility, to reveal the optimal configuration for each case.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 Bibliometric Analysis on Supercritical CO2 Power Cycles for Concentrating Solar Power Applications(MDPI, 2021-09-27) Reyes Belmonte, Miguel Ángel; Guedez Mata, Rafael; Montes Pita, María JoséIn recent years, supercritical CO2 power cycles have received a large amount of interest due to their exceptional theoretical conversion efficiency above 50%, which is leading a revolution in power cycle research. Furthermore; this high efficiency can be achieved at a moderate temperature level; thus suiting concentrating solar power (CSP) applications, which are seen as a core business within supercritical technologies. In this context, numerous studies have been published, creating the need for a thorough analysis to identify research areas of interest and the main researchers in the field. In this work, a bibliometric analysis of supercritical CO2 for CSP applications was undertaken considering all indexed publications within theWeb of Science between 1990 and 2020. The main researchers and areas of interest were identified through network mapping and text mining techniques, thus providing the reader with an unbiased overview of sCO2 research activities. The results of the review were compared with the most recent research projects and programs on sCO2 for CSP applications. It was found that popular research areas in this topic are related to optimization and thermodynamics analysis, which reflects the significance of power cycle configuration and working conditions. Growing interest in medium temperature applications and the design of sCO2 heat exchangers was also identified through density visualization maps and confirmed by a review of research projects.Publicación Analysis and comparison of Integrated Solar Combined Cycles using parabolic troughs and linear Fresnel reflectors as concentrating systems(Elsevier, 2015-11-12) Abbas, Rubén; Rovira de Antonio, Antonio José; Barbero Fresno, Rubén; Montes Pita, María José; Varela Díez, FernandoThis paper compares the annual performance and economic feasibility of Integrated Solar Combined Cycles (ISCC) using two solar concentration technologies: parabolic trough collectors (PTC) and linear Fresnel reflectors (LFR). Integration of solar energy to the steam turbine of a combined cycle gives some advantages: the first one is the fuel saving due to the solar contribution and, additionally, the second one is that this contribution takes place especially in highly insolated periods with high ambient temperatures, when conventional combined cycles decrease their power rate and work with decreased efficiency. Previous works showed the convenience of ISCC using PTC and direct steam generation in locations with severe climatology. Besides, LFR technology is currently considered as a good option for reducing the cost of concentrating solar power. Thus, in the present work both concentrating technologies are studied and compared. Solar contribution is only used for evaporating water, increasing the production of the high pressure level of the steam generator. Two locations, Almeria and Las Vegas, are selected for the annual analyses. Results show that the proposed evaporative configurations increase the annual performance. Also, the thermal contribution is higher with PTC, but LFR may improve the economic feasibility of the plant.Publicación Maturation of Critical Technologies for the DEMO Balance of Plant Systems(Elsevier, 2022-04-04) Barucca, L.; Hering, B.; Pérez Martin, Sara; Bubelis, E.; Nevo, A. del; Di Prinzio, M.; Caramello, M.; D'Alessandro, A.; Tarallo, A.; Vallone, A.; Moscato, I.; Quartararo, A.; D'amico, S.; Giannetti, F.; Lorusso, P.; Narcisi, V.; Ciurluini, C.; Sánchez, C.; Montes Pita, María JoséThe Pre-Concept Design (PCD) of the Balance of Plant (BoP) systems of the EU-DEMO power plant is described in this paper for both breeding blanket (BB) concepts under assessment, namely the Water Cooled Lithium Lead (WCLL) BB and the Helium Cooled Pebble Bed (HCPB) BB. Moreover, the results of a preliminary evaluation of a number of BoP variants are discussed. This paper outlines the steps of the BoP design development, highlighting the project objectives and the strategy for their achievement under the very challenging requirements which include, among others, the intermittent nature of the DEMO plasma heat source. The main achievements during the PCD Phase will be reported together with the development plan for the Concept Design (CD) Phase to reach a mature (feasible) BoP concept for DEMOPublicación Advances in solar thermal power plants based on pressurised central receivers and supercritical power cycles(Elsevier, 2023-07-28) Guedez Mata, Rafael; Linares Hurtado, José Ignacio; Reyes Belmonte, Miguel Ángel; Montes Pita, María JoséThis work addresses the comparative thermo-economic study of different configurations of solar thermal power plants, based on supercritical power cycles and pressurised central receiver systems. For all the cases examined, two innovations are introduced in the solar subsystem, compared to other similar studies. Firstly, the heat transfer fluid in the receiver is either a pressurised gas or a supercritical fluid. Secondly, the receiver is composed of compact structures performing as absorber panels, arranged in a radial configuration. The investigation considers different supercritical CO2 recompression cycles of 50 MWe, including a novel proposal of a directly coupled cycle with heat input downstream of the turbine. Furthermore, the study evaluates different heat transfer fluids in the receiver, specifically CO2, N2, and He, concluding that the former is preferred due to its better thermal performance. The main results show that an increase in the receiver inlet pressure yields to a reduction in its size, favouring the thermal efficiency but penalising the optical efficiency of the solar field. Therefore, optimal working pressures may exist for each configuration, depending on the operating temperature. When comparing the optimal configurations, it is observed that the plant based on the intercooling cycle demonstrates the highest overall efficiency, reaching 32.05%. At last, an economic analysis is conducted to assess the viability of the identified optimal configurations. In this regard, the plant based on the partial-cooling cycle exhibits the lowest levelised cost of electricity at 0.15 $/kWh. This is primarily due to its lower investment cost. The innovative directly coupled cycle follows closely with a cost of 0.17 $/kWh, driven by its high electricity production resulting from its low self-consumption.