Multi-objective optimization of the hydrogen fuel production of a solar-based cobalt-chlorine (Co–Cl) thermochemical cycle with grey relational analysis

Abstract

In this paper, multi-objective optimization of the hydrogen production (m˙H2) of a solar-based cobalt-chlorine (Co–Cl) thermochemical cycle with grey relational analysis (GRA) has been performed. Monthly total irradiance averages (A), wind velocity (B), receiver height (C), receiver radius (D) and number of heliostats (E) are considered to achieve the highest the useful energy absorbed by the solar receiver (Q˙abs), efficiency of the receiver (ηrec), the overall efficiency of the system (ηoverall) and hydrogen production (m˙H2). Orthogonal experimental design is planned according to L18 orthogonal array created by Taguchi method. The percent contribution rates (PCR) on the Q˙abs, ηrec, ηoverall and m˙H2 are determined with the help of ANOVA analysis. The optimal parameters are identified as monthly total irradiance average of 143.8 kW h (A3), wind velocity of 5 m/s (B2), receiver height of 8 m (C1), receiver radius of 3 m (D1) and number of heliostats of 850 (E3), respectively. The highest Q˙abs, ηrec, ηoverall and m˙H2 values corresponding to A3B2C1D1E3 are obtained as 50.2 GW; 64.1%; 22.2% and 122.59 (tons/month), respectively. The PCR of the A, B, C, D and E parameters influencing the f-factor are determined to be 12.6 %, 1.92 %, 0.48 %, 15.03 %, and 53.20 %, respectively. Also, empirical equations are developed with regression analysis (RA) to estimate the Q˙abs, ηrec, ηoverall, m˙H2 values. The statistical coefficients (R2-value) for training and testing data's are determined in the range of 0.771167–0.99608 for Q˙abs, ηrec, ηoverall and m˙H2, respectively.