A critical issue concerning the gas turbine is that its power decreases considerably with increasing ambient temperature. Recently, it was proposed to maximize the power output of gas turbines in hot seasons through the simultaneous cooling of inlet air and hot parts cooling air, using an absorption chiller. This study serves to expand this concept and applies simultaneous cooling to combined cycle power plants using an H-class engine, the latest gas turbine model. Two methods for coolant pre-cooling were comparatively investigated and the best option was selected. The proposed dual cooling was compared with other conventional cooling schemes and their combinations. These include simple inlet air cooling using a mechanical chiller or an absorption chiller, and the combination of each of these schemes with independent cooling of the coolant by ambient air. The maximum degrees of coolant pre-cooling and inlet air cooling using the largest capacity commercial absorption chiller were predicted to be 45 K and 11 K, respectively, and the power boost of the combined cycle plant was estimated to be 8.2%, which was larger than that obtained with any other scheme. An economic analysis confirmed the feasibility of the dual cooling scheme. (C) 2018 Elsevier Ltd. All rights reserved.