Papers by Andrés Sebastián Herrera
Innovative thermal storage strategies for Fresnel-based concentrating solar plants with East-West orientation
Applied Energy, 2018
Concentrated solar power plants using molten salts as heat transfer and storage fluid have emerge... more Concentrated solar power plants using molten salts as heat transfer and storage fluid have emerged as the preferred commercial solution for solar thermal electricity in central receiver technology. Despite their ability to store large amounts of thermal energy and efficient receiver designs, further efficiency improvements are constrained by tight temperature restrictions when using molten salts (290 C e565 C). In this work, a novel heat transfer fluid based on a dense particle suspension (DPS) is used due to its excellent thermophysical properties that extend the operating temperature of solar receiver and allow its coupling with higher-efficiency power cycles. In this paper, the design of a DPS solar receiver working at 650 C has been optimized for two commercial sizes (50 MW th and 290 MW th) coupled to an optimized subcritical Rankine cycle. The results showed that a five-extraction reheated Rankine cycle operating at 610 C and 180 bar maximizes power plant efficiency when coupled with a DPS central receiver, giving 41% power block efficiency and 23% sun-to-electricity efficiency. For optimization purposes at design point conditions, in-house code programmed into MATLAB platform was used while TRNSYS software was employed for annual plant performance analysis.
Performance comparison of different thermodynamic cycles for an innovative central receiver solar power plant
The potential of using different thermodynamic cycles coupled to a solar tower central receiver t... more The potential of using different thermodynamic cycles coupled to a solar tower central receiver that uses a novel heat transfer fluid is analyzed. The new fluid, named as DPS, is a dense suspension of solid particles aerated through a tubular receiver used to convert concentrated solar energy into thermal power. This novel fluid allows reaching high temperatures at the solar receiver what opens a wide range of possibilities for power cycle selection. This work has been focused into the assessment of power plant performance using conventional, but optimized cycles but also novel thermodynamic concepts. Cases studied are ranging from subcritical steam Rankine cycle; open regenerative Brayton air configurations at medium and high temperature; combined cycle; closed regenerative Brayton helium scheme and closed recompression supercritical carbon dioxide Brayton cycle. Power cycle diagrams and working conditions for design point are compared amongst the studied cases for a common reference thermal power of 57 MWth reaching the central cavity receiver. It has been found that Brayton air cycle working at high temperature or using supercritical carbon dioxide are the most promising solutions in terms of efficiency conversion for the power block of future generation by means of concentrated solar power plants.
Optimization of a recompression supercritical carbon dioxide cycle for an innovative central receiver solar power plant
Peculiar thermodynamic properties of carbon dioxide (CO 2) when it is held at or above its critic... more Peculiar thermodynamic properties of carbon dioxide (CO 2) when it is held at or above its critical condition (stated as supercritical CO 2 or sCO 2) have attracted the attention of many researchers. Its excellent thermophysical properties at medium-to-moderate temperature range have made it to be considered as the alternative working fluid for next power plant generation. Among those applications, future nuclear reactors, solar concentrated thermal energy or waste energy recovery have been shown as the most promising ones. In this paper, a recompression sCO 2 cycle for a solar central particles receiver application has been optimized, observing net cycle efficiency close to 50%. However, small changes on cycle parameters such as working temperatures, recuperators efficiencies or mass flow distribution between low and high temperature recuperators were found to drastically modify system overall efficiency. In order to mitigate these uncertainties, an optimization analysis based on recuperators effectiveness definition was performed observing that cycle efficiency could lie among 40%e50% for medium-to-moderate temperature range of the studied application (630 Ce680 C). Due to the lack of maturity of current sCO 2 technologies and no power production scale demonstrators, cycle boundary conditions based on the solar application and a detailed literature review were chosen.
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Papers by Andrés Sebastián Herrera