Persona: Montes Pita, María José
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Montes Pita
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Publicación Proposal of a new design of source heat exchanger for the technical feasibility of solar thermal plants coupled to supercritical power cycles(Elsevier, 2020-10-12) Linares Hurtado, José Ignacio; Montes Pita, María José; Barbero Fresno, Rubén; Rovira de Antonio, Antonio JoséSolar thermal power plants coupled to supercritical CO2 cycles seems to be a way to increase the global solar-to-electric efficiency. For that, the concentrating solar technology that is best integrated is the molten salt central receiver with a thermal energy storage associated. This work is focused on one of the main challenges of this scheme: the source heat exchanger transferring the thermal energy from the molten salt in the solar field to the CO2 in the power cycle. A new design, based on the printed circuit heat exchanger technology is proposed, that withstands the pressure difference and avoids the molten salt plugging when circulating through microchannels. The thermo-mechanic model of this heat exchanger is also calculated. This work also addresses a thermo-economic optimization of the printed circuit heat exchanger proposed. For that, it is considered the global performance of the solar thermal plant for three layouts: recompression, intercooling and partial-cooling cycles. This optimization yields to a great reduction in the investment cost of these source heat exchangers, achieving the lowest cost in the partial-cooling configuration, followed by the intercooling and finally, the recompression. This trend is also observed in the global performance of the solar plant, so the partial-cooling layout is the one with the lowest levelized cost of electricity; this value is similar to that of the intercooling layout, and both are well below from the cost in the recompression layout, which results the most expensive configuration.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 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 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.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.