| Summary: | This study focused on investigating the bottoming power cycles operating with CO<sub>2</sub>-based binary mixture, taking into account exergetic, economic and exergo-environmental impact indices. The main intent is to assess the benefits of employing a CO<sub>2</sub>-based mixture working fluid in closed Brayton bottoming power cycles in comparison with pure CO<sub>2</sub> working fluid. Firstly, selection criteria for the choice of suitable additive compound for CO<sub>2</sub>-based binary mixture is delineated and the composition of the binary mixture is decided based on required cycle minimum temperature. The decided CO<sub>2</sub>-C<sub>7</sub>H<sub>8</sub> binary mixture with a 0.9 mole fraction of CO<sub>2</sub> is analyzed in two cycle configurations: Simple regenerative cycle (SRC) and Partial heating cycle (PHC). Comparative analysis among two configurations with selected working fluid are carried out. Thermodynamic analyses at varying cycle pressure ratio shows that cycle with CO<sub>2</sub>-C<sub>7</sub>H<sub>8</sub> mixture shows maximum power output and exergy efficiency at rather higher cycle pressure ratio compared to pure CO<sub>2</sub> power cycles. PHC with CO<sub>2</sub>-C<sub>7</sub>H<sub>8</sub> mixture shows 28.68% increment in exergy efficiency with the levelized cost of electricity (LCOE) 21.62% higher than pure CO<sub>2</sub> PHC. Whereas, SRC with CO<sub>2</sub>-C<sub>7</sub>H<sub>8</sub> mixture shows 25.17% increment in exergy efficiency with LCOE 57.14% higher than pure CO<sub>2</sub> SRC. Besides showing lower economic value, cycles with a CO<sub>2</sub>-C<sub>7</sub>H<sub>8</sub> mixture saves larger CO<sub>2</sub> emissions and also shows greater exergo-environmental impact improvement and plant sustainability index.
|
|---|
