“…To obtain the solution of the CHPED problem is challenging due to the interdependence of heat and power generation of the CHP unit, and it requires highly efficient algorithms to obtain the optimal solution. The metaheuristic algorithms such as gravitational search algorithm in [34], grey wolf optimization in [35], improved genetic algorithm (GA) in [36], [37], modified PSO in [38], Cuckoo optimization in [39], [40], civilized swarm optimization in [41], exchange market algorithm in [42], the differential algorithm in [43], bee colony optimization in [44], [45], artificial immune system algorithm in [46], oppositional teaching learning based optimization in [47], the harmony search algorithm in [48], [49] and its variants in [50], the squirrel search algorithm in [51], group search optimization in [52] and other methods such as Lagrangian relaxation in [53], benders decomposition approach in [54] are used in literature to obtain the optimal solution of the CHPED problem. The hybrid methods that have been successfully employed to solve the CHPED problem are the hybrid bat and ABC algorithm in [55], hybrid harmony search and PSO algorithm in [56], hybrid harmony search algorithm and Nelder-Mead numerical method in [57].…”