In the recent years, considering aridity problem of the country and high potential of desalinating the seawater in the southern and northern coasts, focusing on the poly-generation cycles of power and distillate with the lowest possible cost and emission of the pollutants has been increased. In this research, the study of the trigeneration system of power, heat and desal water located in the Qeshm island has been conducted. The potentials of the existing unit have been evaluated and the different scenarios have been proposed to improve the performance of the system. Setting the inlet air cooling system up to the gas cycle is one of the schemes proposed to diminish the undesirable effects of the ambient conditions. Also integrating the existing MED desalination unit with RO system and using solar thermal collector field in order to improve the performance of the system and to propose the optimal scheme for the operating unit has been investigated. The conventional and the advanced exergy, exergoeconomic and exergo-environmental analyzes based on life cycle assessment have been used to evaluate the existing and the proposed systems. The multi objective optimization process has been performed to maximize the exergetic efficiency and to minimize the cost and environmental impact of the product of the system. Considering the complexity of the problem, using the genetic programming to generate the objective functions has been conducted. In order to apply the optimization process on the existing and the proposed system, multi objective genetic algorithm (MOGA) and multi objective water cycle algorithm (MOWCA) have been used. Multi objective water cycle algorithm has been performed for the first time at the energy problems in this research. The results shows that using the inlet air cooling system has decreased the fuel consumption, total costs and environmental impacts of the system by 1019 tons/year, 914 k$/year and 197 kpts/year, respectively. Also integrating the existing unit with the solar thermal collector field to achieve an increase of 4.77% in efficiency of the system has been investigated. Five different types of STC at two configurations have been evaluated and the thermodynamic, economic and environmental optimal solution has led to calculate 9081 m(2) area of required collectors. Using RO desalination unit in the downstream of MED has prevented the energy leakage and increased the distillate production rate by 255.12 tons/h. The optimization processes using two methods shows the capability of the MOWCA and lead to an increase of 12.66% in exergetic efficiency and decreased the total cost and environmental impact rate of the system by 47.4$/h and 49.2 pts/h, respectively. (C) 2020 Elsevier Ltd. All rights reserved.