Persona: Montes Pita, María José
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mjmontes@ind.uned.es
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0000-0002-2020-8242
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Montes Pita
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María José
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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 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; 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 Towards a general design framework for external tubular solar receivers using pressurised gaseous or supercritical fluids(Elsevier, 2025-12-05) Montes Pita, María José; Linares Hurtado, José Ignacio; Kwan, Pok-Wang; Ireland, Peter; Guedez Mata, Rafael; Comunidad de Madrid (CAM)This work presents a comprehensive analysis of the thermo-fluid parameters governing the design of external tubular solar receivers operating with pressurised gaseous and supercritical fluids. Contrary to the state of the art regarding the use of these fluids in central receivers, this study identifies an optimum threshold operating pressure of 40–50 bar, corresponding to energy efficiencies of approximately 82 %. Beyond this range, efficiency gains become marginal and do not offset the higher investment cost of a high-pressure installation. Although the thermal performance of solar receivers is generally influenced by both pressure loss and total heat loss, the analysis shows that pressure loss has only a limited impact on external tubular receivers, whereas heat losses are the dominant factor. These losses primarily depend on the receiver's cooling effectiveness and external surface area. Cooling effectiveness improves with a higher overall heat transfer coefficient and a lower mean operating temperature. The primary parameters that reduce the external surface area are higher fluid pressure, a greater temperature rise between the receiver inlet and outlet and a larger tube diameter, provided that the maximum temperature remains below the material's allowable limit. This study also demonstrates that the total annualised cost of these pressurised receivers mainly depends on the investment cost, which is proportional to receiver dimensions. Consequently, all parameters that reduce the external surface area also reduce cost. Finally, different working fluids were compared. Among them, CO2 provides superior thermal performance and lower cost, primarily due to its high density at intermediate pressures, which decreases both pumping power requirements and receiver surface area.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 Comparison of Different Technologies for Integrated Solar Combined Cycles: Analysis of Concentrating Technology and Solar Integration(MDPI, 2018-04-25) Sánchez, Consuelo; Abbas, Rubén; Muñoz Antón, Javier; Ortega, Guillermo; Rovira de Antonio, Antonio José; Valdés Fernández, Manuel Tomás; Barbero Fresno, Rubén; Montes Pita, María José; Muñoz Domínguez, Marta; Varela Díez, FernandoThis paper compares the annual performance of Integrated Solar Combined Cycles (ISCCs) using different solar concentration technologies: parabolic trough collectors (PTC), linear Fresnel reflectors (LFR) and central tower receiver (CT). Each solar technology (i.e. PTC, LFR and CT) is proposed to integrate solar energy into the combined cycle in two different ways. The first one is based on the use of solar energy to evaporate water of the steam cycle by means of direct steam generation (DSG), increasing the steam production of the high pressure level of the steam generator. The other one is based on the use of solar energy to preheat the pressurized air at the exit of the gas turbine compressor before it is introduced in the combustion chamber, reducing the fuel consumption. Results show that ISCC with DSG increases the yearly production while solar air heating reduces it due to the incremental pressure drop. However, air heating allows significantly higher solar-to-electricity efficiencies and lower heat rates. Regarding the solar technologies, PTC provides the best thermal results.Publicación A novel energy conversion system based on supercritical CO2 recompression Brayton power cycle for power tower concentrating solar plants(Elsevier, 2020-02-09) Linares Hurtado, José Ignacio; Cantizano, Alexis; Sánchez, Consuelo; Montes Pita, María JoséPower tower concentrating solar plants with thermal energy storage will play a key role in the transition to a low carbon scenario, thanks to be a dispatchable renewable energy system. The ternary MgCl2/KCl/NaCl salt appears as one of the most promising due to its lower melting point, higher heat capacity, lower cost and stability up to 800 °C. A cavity-type receiver has been selected because minimizes radiation heat loss at high working temperatures, compared to an external-type receiver, since all commercial selective coatings degrade in air. Supercritical Brayton power cycle is chosen for the power block because it can surpass 50% efficiency, even when working in dry cooling conditions, and printed circuit heat exchangers are usually recommended due to its ability to support the high pressures. However, plugging/clogging issues arise in their small channels when using molten salts. This paper proposes a novel supercritical CO2 Bayton power cycle whose heat power is supplied through the low pressure side (over 85 bar) allowing the use of shell and tube heat exchangers, achieving a higher compactness and a lower investment. Thus, different options based on the recompression layout with intercooling and reheating have been investigated in both dry and wet cooling scenarios. Reheating is recommended for wet cooling, reaching 54.6% efficiency and an investment of 8662 $/kWe; intercooling with reheating is the best option for dry cooling, reaching 52.6% efficiency and an investment of 8742 $/kWe.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.