An Exergy Analysis of Recompression Supercritical CO2 Cycles with and without Reheating

Abstract

Concentrated Solar Power using supercritical CO 2 (S-CO 2 ) recompression Brayton cycles offer advantages of similar and even higher overall thermal efficiencies compared to power cycles using superheated or supercritical steam. The high efficiency and compactness of S-CO 2 , as compared with steam Rankine cycle at the same high temperature, make this cycle attractive for central receiver applications, since both attributes lead to decrease in levelized cost of energy and therefore make this technology economically feasible. The current research in S-CO 2 is focused on thermodynamic analysis and system components. In this paper energy and exergy analyses of a supercritical CO 2 Recompression Brayton cycle are presented. Energy, exergy and mass balance are carried out for each component and first law and exergy efficiencies are calculated with and without reheat scenarios. Optimization is then carried out by using Sequential Least SQuares Programming (SLSQP) and optimum operating conditions based on maximum first law efficiency are determined. The results showed that the exergy efficiency reaches a maximum value at 600 °C while the first law efficiency increases monotonically with highest temperature of the cycle.

Modelado termodinámico de una planta solar térmica hibrida de ciclo Brayton en Colombia

“…2. En el software se realiza este procesamiento, con las temperaturas estimadas en el análisis energético y la relación de presiones, tomando como referencia la temperatura de entrada el compresor de 115000 Pascales; teniendo en cuenta que los procesos de transferencia de calor son isobáricos, adicionalmente en el caso de la destrucción de exergía del concentrador solar se utilizan los parámetros de la Tabla 5, tomados de [16], [22], [23] En la Fig. 9 se muestra la destrucción de exergía en los componentes en los que varía el intercambio de energía a lo largo del día y por lo tanto la destrucción Respecto a la eficiencia global del ciclo, en la Fig.…”

“…Desde el punto de vista de análisis de exergía, se han desarrollado trabajos en plantas de ciclos con aporte solar por torre y Heliostatos para estimar su eficiencia [19], junto a ciclos combinados o inferiores [20] y otros enfocados en ciclo Brayton, específicamente con aire y dióxido de carbono en condiciones supercríticas como fluidos de trabajo con recalentamiento [21], o con doble compresión [22], incluyendo ciclos inferiores supercríticos y transcríticos para evaluar su operación y la capacidad de generación [23].…”

Thermodynamic, Exergy and Environmental Impact Assessment of S-CO2 Brayton Cycle Coupled with ORC as Bottoming Cycle

“…Vasquez Padilla et al [7] conducted a detailed energy and exergy analysis of four Brayton S-CO 2 cycle configurations (single Brayton cycle, recompression Brayton cycle, partial cooling recompression, and main compression with intercooling) with and without reheating to investigate the effect of replacing the reheater and heater by a solar receiver. In the same year, Ricardo Vásquez et al [8] also performed the energy and exergy analysis of a supercritical Brayton cycle with recompression CO 2, but a bottoming cycle was not proposed.…”

Investigating the effect of dry cooling system design on the performance of supercritical CO2 cycle in concentrated solar power application

“…Padilla et al [171] also considered dry cooler as the heat rejection component and investigated the cycle irreversibility and efficiency performance by the influence of pressure drop in the heat exchanger and solar receiver. The influence of reheating on the cycle efficiency and exergetic performance was performed where the dry cooler and central receiver contributed the majority of the total exergy losses [172]. The RBC, RC, PC, and MC cycles were considered to compare the thermal performance with respect to cycle highest temperature ranging from 500 0 C to 850 0 C [173].…”

“…At higher ambient temperatures, increasing the compressor inlet pressure helped to maintain the design-point thermal efficiency. Padilla et al [172,173] performed the detailed irreversibility analysis of four different sCO2 power cycles with dry cooling.…”