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ENCIT 2020
18th Brazilian Congress of Thermal Sciences and Engineering
SUPERCRITICAL CARBON DIOXIDE BRAYTON CYCLES ANALYSIS FOR HIGH CONCENTRATION LINEAR FRESNEL COLLECTOR APPLICATIONS
Submission Author:
Ricardo Hofer Begrow , SC
Co-Authors:
Ricardo Hofer Begrow, Júlio Passos
Presenter: Ricardo Hofer Begrow
doi://10.26678/ABCM.ENCIT2020.CIT20-0500
Abstract
The present work aims the analysis of a supercritical carbon dioxide (sCO2) power cycle with heliothermic energy from a linear Fresnel collector (LFC), by the composition and numerical solution of the governing equations. Both technologies are under development and have great potential for increasing efficiency and reducing costs. Recent advances in Fresnel technology have made it possible to reach temperatures above 500 °C, enabling the use of a sCO2-based cycle. The cycle efficiency dependence on various parameters was analyzed, such as the turbine inlet temperature and pressure, the compressor inlet temperature and pressure, the by-pass ratio in the recompressor, as well as the use of recompression, reheat and intercooler. For the regenerators modeling, the minimum pinch method was used to determine the heat exchange. The performance of the cycle was analyzed for turbine inlet pressures from 160 to 340 bar and temperatures from 350 °C to 570 °C. The EBSILON Professional software was used to estimate the heat losses and efficiency of a Fresnel collector The simple cycle showed a performance about 14% lower than the recompression cycle for temperatures above 350 °C, which limits its practical use. The use of reheating in the recompression cycle showed a 5% average efficiency increase, rising the thermal efficiency from 0.42 to 0.44 for a turbine inlet temperature (TIT) of 500 °C and pressure of 200 bar. In addition, with the use of intermediate cooling in the main compressor, a gain of up to 2% can be achieved, resulting in a thermal efficiency of up to 45% in these conditions. There was a linear gain in the power cycle thermal efficiency with the increase in TIT for all cases. However, the collector efficiency declines exponentially with increasing temperature due to heat losses. Thus, the combined peak efficiency of the collector and the power cycle in relation of TIT under the studied conditions occurs at approximately 550 °C for a perpendicular solar incidence of 1000 W/m2
Keywords
Supercritical carbon dioxide power cycle, Brayton Cycle, concentrated solar power, Fresnel
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