• Energy Research

Abstract 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, exergo-economic 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$/year and 197 kpts/year, respectively. Also integrating the existing unit with the solar thermal collector field to achieve an increase of 4.77% in efficiency of the system has been investigated. Five different types of STC at two configurations have been evaluated and the thermodynamic, economic and environmental optimal solution has led to calculate 9081 m2 area of required collectors. Using RO desalination unit in the downstream of MED has prevented the energy leakage and increased the distillate production rate by 255.12 tons/h. The optimization processes using two methods shows the capability of the MOWCA and lead to an increase of 12.66% in exergetic efficiency and decreased the total cost and environmental impact rate of the system by 47.4$/h and 49.2 pts/h, respectively.

AbstractThe integration of power plants and desalination systems has attracted increasing attention over the past few years as an effective solution to tackle sustainable development and climate change issues. In this light, this paper introduces a novel modelling and optimization approach for a combined-cycle power plant (CCPP) integrated with reverse osmosis (RO) and multi-effect distillation (MED) desalination systems. The integrated CCPP and RO–MED desalination system is thermodynamically modelled utilizing MATLAB and EES software environments, and the results are validated via Thermoflex software simulations. Comprehensive energy, exergic, exergoeconomic, and exergoenvironmental (4E) analyses are performed to assess the performance of the integrated system. Furthermore, a new multi-objective water cycle algorithm (MOWCA) is implemented to optimize the main performance parameters of the integrated system. Finally, a real-world case study is performed based on Iran's Shahid Salimi Neka power plant. The results reveal that the system exergy efficiency is increased from 8.4 to 51.1% through the proposed MOWCA approach, and the energy and freshwater costs are reduced by 8.4% and 29.4%, respectively. The latter results correspond to an environmental impact reduction of 14.2% and 33.5%. Hence, the objective functions are improved from all exergic, exergoeconomic, and exergoenvironmental perspectives, proving the approach to be a valuable tool towards implementing more sustainable combined power plants and desalination systems.

In this study, integration of RO desalination unit with power and water cogeneration plant located in Qeshm Island in Iran has been investigated. The desalination unit exists in this plant is MED-TVC type. In this regard, energy, exergy, exergoeconomic, and exergoenvironmental (4E) analyses have been performed by developing a computer code using Matlab. Validation of thermodynamic data has been performed through comparing the results of modeling by Matlab with the simulation done in Thermoflex software and the real data gathered from the Qeshm cogeneration plant. The results show the acceptable accuracy of thermodynamic modeling. The exergoenvironmental analysis has been conducted based on Life Cycle Assessment (LCA). In this regard, the weight function of TVC is proposed in this paper based on technical data in different nominal sizes in order to estimate the environmental impacts of this component. The cogeneration plant produces 25.7 MW power, consuming 6 kg/s steam can lead to production of 51.7 kg/s desalinated water. The gained output ratio (GOR) is about 8.7 for the MEDTVC unit. The performance ratio (PR) of RO desalination unit which is added to the downstream of MED-TVC has been calculated about 0.5. Integrating RO desalination unit with MED-TVC enhances the production of fresh water by 255.132 ton per hour.Exergetic efficiency, total cost rate of the system and total environmental impact rate of the system has been calculated 46.86 %, 64.01 $/min and 29.49 pts/min, respectively. Since the largest share of exergy destruction rate of the system belongs to the gas cycle and also Qeshm Island has a warm and muggy climate, adding a chiller type air cooling system to inlet of air compressor can decrease the power demand of air compressor and fuel consumption of combustion chamber which makes the system more efficient and reduce the cost and environmental impact rate of the system.

Abstract The use of solar energy to preheat natural gas before a city gate station (CGS) for reducing fuel consumption and environmental emissions is investigated in a real CGS. All analyses are conducted with a 1-h time-step throughout the entire year so that seasonal climate changes are accounted for precisely. A thermodynamic analysis of the hybrid system is performed with TRNSYS and verified with THERMOFLEX so as to ensure reliability. In addition, dynamic exergetic, exergoeconomic, and exergoenvironmental analyses for the proposed system are carried out. A life cycle assessment (LCA) based on Eco-indicator 99 is performed using SIMA PRO to compute the environmental impacts for each component of the system. The exergetic, exergoeconomic, and environmental analyses are performed in Engineering Equation Solver (EES) software. To perform the transient exergetic, exergoeconomic, and environmental analyses, the results of the thermodynamic analysis from TRNSYS are automatically imported into the EES code. The advanced exergetic, exergoeconomic, and exergoenvironmental analyses are performed to better determine components that have high potentials for improving the system; potentials are considered based on the exergy destruction, exergetic cost of destruction, and environmental impacts associated with exergy destruction.