Multi-objective performance optimization of irreversible molten carbonate fuel cell-Stirling heat engine-reverse osmosis...Published: 12 November 2018 by Wiley in Energy Science & Engineering
This paper aims to investigate a hybrid cycle consisting of a molten carbonate fuel cell (FC) and a Stirling engine which, by connecting to a seawater reverse osmosis desalination unit, provides fresh water. First, a parametric evaluation is performed to study the effect of some key parameters, including the current density and the working temperature of the FC and the thermal conductance between the working substance and the heat reservoirs in the Stirling engine, on the objective functions. The objective functions include the energy efficiency, the exergy destruction rate density, the fresh water production rate, and the ecological function density. After investigating each double combination of these objective functions, two scenarios are defined in quest to concurrently optimize three functions together. The first scenario aims to optimize the energy efficiency, the exergy destruction rate density, and the fresh water production rate; and the second scenario attempts to optimize the energy efficiency, the fresh water production rate, and the ecological function density. A multi‐objective evolutionary algorithm joined with the nondominated sorting genetic algorithm (NSGA‐II) approach is employed to obtain Pareto fronts in each case scenario. In order to ascertain final solutions between Pareto fronts, three fast and robust decision‐making methods are employed including TOPSIS, LINMAP, and Fuzzy. Finally, a sensitivity analysis is conducted to critically analyze the performance of the system.
Numerical simulation of solar-driven Kalina cycle performance for centralized residential buildings in IranPublished: 08 July 2016 by Informa UK Limited in Intelligent Buildings International
The building sector is responsible for most of the worldwide electrical energy consumption, having surpassed both the industry and transportation sectors. In this article, a detailed thermodynamic model was proposed for a solar-driven Kalina cycle with an auxiliary superheater to meet the electrical demands of high-rise buildings in Iran’s climatic condition. A combination of correlations characterizing the Gibbs free energy of an ammonia–water mixture was utilized to describe the behaviour of the working fluid. Then an energy analysis of the cycle was studied to solve the system state points as well as the system performance. So its maximum monthly power generation is estimated. A long-term balance is considered between the electricity production and consumption for residential sectors based on the available 10-year recent data for 113 suitable sites. The energy consumption of residential buildings in each province is averaged to calculate the energy consumption of a typical building in that province. Then, the results were shown in terms of solar electrical coverage for each site. The Kalina solar system was able to cover the annual electricity demand of a residential building of at least 20.34% for Hormozgan and at most 164.36% for Isfahan.
Simulation and multi-objective optimization of a combined heat and power (CHP) system integrated with low-energy buildin...Published: 01 March 2016 by Elsevier BV in Journal of Building Engineering
Highlights•Proposed a methodology for design of MGT-based CHP systems to be used by decision makers.•A computer simulation for the performance of the building integrated CHP system.•A Pareto multiobjective genetic optimization approach for system performance.•Offered suggestions to reduce the overall system irreversibilities.•Optimum levels for thermoenviroeconomic objective and exergetic efficiency. AbstractOne of the novel applications of gas turbine technology is the integration of combined heat and power (CHP) system with micro-gas turbine which is spreading widely in the field of distributed generation and low-energy buildings. It has a promising great potential to meet the electrical and heating demands of residential buildings. In this study, a MATLAB code was developed to simulate and optimize the thermoeconomic performance of a gas turbine based CHP cycle. Three design parameters of this cycle considered in this research are compressor pressure ratio, turbine inlet temperature, and air mass flow rate. Firstly, two objective functions including exergetic efficiency and net power output were chosen to achieve their maximum level. Variation of exergy destruction rate and exergetic efficiency with three turbine inlet temperatures (1000, 1100, and 1200 K) and three air mass flow rates (0.25, 0.3, and 0.35 kg/s) were also studied for each component. Exergetic efficiency increased relatively to maximum 3% within this temperature limit. Based on the exergetic analysis, suggestions were given for reducing the overall irreversibility of the thermodynamic cycle. To have a good insight into this study, a sensitivity analysis for important parameters was also carried out. Finally, based on the exergy analysis and utilization of economic and environmental functions, a multi-objective approach was taken to optimize the system performance. Graphical abstract
While solar energy can be utilized for passive space heating, efficient passive space cooling is achievable through lower temperature ambient thermal sources. In this study, a model was proposed for the combined solar heating and radiative cooling and a MATLAB code is developed to simulate combined space heating and cooling of a small building in Louisville, Kentucky. The combined system consists of the glazing/transparent insulation subsystem and the thermal storage subsystem. The space is passively heated and cooled by means of natural convection from the surfaces of the storage subsystem where the storage tank is heated by solar radiation and cooled by night sky radiation as a low temperature thermal source. The model for this system consists of several transient energy balance equations based on the lumped capacitance approach and it has been implemented utilizing MATLAB. Using the aforementioned system and the auxiliary heating/cooling units, the room temperature can be kept within the prescribed comfort range. The simulation is carried out to find the monthly and annual solar fraction, required heating demand, auxiliary heating demand as well as the unwanted heat gain during heating months. Also, the radiative cooling fraction, required cooling demand and auxiliary cooling demand during cooling months are obtained. The optimum value for transparent layer absorptivity was found to avoid unwanted heat gain. Parametric sensitivity was evaluated for material and design features related to the combined system. Simulation results for temperature profiles of the room and storage tank are also illustrated.
Thermo-ecological analysis and optimization performance of an irreversible three-heat-source absorption heat pumpPublished: 01 January 2015 by Elsevier BV in Energy Conversion and Management
In a Stirling cycle a huge amount of energy is wasted due to the losses. This wasted energy may be utilized as a heat source for the boiler of an organic Rankine cycle. Combination of these two cycles leads to an increased cycle efficiency compared to a single Stirling cycle and the analysis and optimization of the integrated system is carried out. Optimization is performed using the genetic algorithm and considering three decision variables: the temperature of the cold tank of the Stirling cycle, the pressure ratio and the temperature of the ORC condenser. In the optimization, the efficiency is considered as the objective function and the highest value is achieved by adjusting the decision variables. Using this method, the efficiency of the overall combined cycle was improved in which the highest efficiency was obtained to be 41.5%.
Renewable energy systems have much lower environmental impact than conventional energy technologies. Tidal energy is one of the most important forms of renewables which carry the electricity production capacity within its height differences and current flow. In this paper, a time-dependent mathematical model for green energy generation from a single-pool tidal system is developed. Using current model with available tidal data, the extracted energy from this system can be calculated. Model results have shown that such system has the capacity of producing 40.6 Megawatts electricity from tidal energy for a specific area.