Techno-environmental assessment and machine learning-based optimization of a novel dual-source multi-generation energy system

The utilization of high-temperature hybrid energy systems has a vital and promising role in reducing environmental pollutants and coping with climate change. So, in the present research, a dual-source multigeneration energy system composed of a gas turbine, a supercritical carbon dioxide recompression Brayton cycle, an organic Rankine cycle, an absorption refrigeration system, and a reverse osmosis desalination unit is designed and analyzed from thermodynamic, environmental and economic perspectives. The system supplies power with a stable load to follow the changes in the demand side which is important for off-grid distributed energy systems. The dual-source operation of the system makes it possible to generate sustainable electricity leading to less utilization of fossil fuels in the gas turbine subsystem and reduction in environmental pollution, and furthermore, malfunctioning of a subsystem will not lead to the failure of the entire plant. Three multi-objective optimizations with different objective functions are accomplished using artificial neural network from data learning and genetic and Greywolf algorithms to obtain the best-operating conditions. Under the base conditions, for the total input energy of 699 MW to the entire system, the energy and exergy efficiencies, the unit exergy cost of products, the carbon dioxide emission index, and the payback period, respectively, were found to be 45%, 54%, 15.3 $/GJ, 112.2 kg/MWh, and 7.2 years. The net output power of the proposed system was calculated as 288.2 MW. A sensitivity analysis revealed that with a change in the pressure ratio of the supercritical carbon dioxide cycle, the net generated power and overall efficiency take maximum values of 293.9 MW while the unit exergy cost of products and carbon dioxide emission index take minimum values of 15.3$/GJ and 110.1 kg/MWh, respectively. Furthermore, increasing the pressure ratio of the gas turbine leads to maximum values of 45 and 54% in overall energy and exergy efficiencies, respectively

Thermodynamics modelling and optimisation of a biogas fueled decentralised poly-generation system using machine learning techniques

In the forthcoming era of smart energy systems, decentralised solutions are gaining increasing prominence due to their superior adaptability for interconnecting sectors, reduced inefficiencies, and environmentally friendly operation. This study introduces a new medium-scale biogas-based power plant that utilises a gas turbine to meet the energy needs of a specific locality, encompassing electricity, heating, cooling, and water supply, all whilst considering the system's environmental impact. To optimise the plant's performance, three different multi-objective optimisation scenarios employing machine learning methodologies and Greywolf algorithms with distinct objective functions are analysed. Under the base conditions, the proposed plant showcases impressive capabilities, delivering 1372 kW of electricity, 246.2 kW of heating, 293.3 kW of cooling, and 4.1 kg/s of distilled water. It operates with first and second law thermodynamics efficiencies of 72.3% and 41.4%, respectively, while maintaining a CO2 emission index of 0.778 kgCO2/kWh. Furthermore, the net present value and investment return period for the investment are estimated to be approximately 4.4 million USD and 4 years, respectively. Through optimisation (scenario 1) that prioritises maximising efficiency while minimising product costs and environmental impact, the following parameters are achieved: an exergy efficiency of 42.7%, a cost of products at 28.8 $/GJ, and a reduced CO2 emission index of 0.762 kgCO2/kWh. The results reveal that the proposed system not only excels in efficiency but also proves to be economically viable and environmentally beneficial

Techno-environmental assessment and machine learning-based optimization of a novel dual-source multi-generation energy system

Publisher Copyright: © 2023 The Institution of Chemical EngineersThe utilization of high-temperature hybrid energy systems has a vital and promising role in reducing environmental pollutants and coping with climate change. So, in the present research, a dual-source multigeneration energy system composed of a gas turbine, a supercritical carbon dioxide recompression Brayton cycle, an organic Rankine cycle, an absorption refrigeration system, and a reverse osmosis desalination unit is designed and analyzed from thermodynamic, environmental and economic perspectives. The system supplies power with a stable load to follow the changes in the demand side which is important for off-grid distributed energy systems. The dual-source operation of the system makes it possible to generate sustainable electricity leading to less utilization of fossil fuels in the gas turbine subsystem and reduction in environmental pollution, and furthermore, malfunctioning of a subsystem will not lead to the failure of the entire plant. Three multi-objective optimizations with different objective functions are accomplished using artificial neural network from data learning and genetic and Greywolf algorithms to obtain the best-operating conditions. Under the base conditions, for the total input energy of 699 MW to the entire system, the energy and exergy efficiencies, the unit exergy cost of products, the carbon dioxide emission index, and the payback period, respectively, were found to be 45 %, 54 %, 15.3 $/GJ, 112.2 kg/MWh, and 7.2 years. The net output power of the proposed system was calculated as 288.2 MW. A sensitivity analysis revealed that with a change in the pressure ratio of the supercritical carbon dioxide cycle, the net generated power and overall efficiency take maximum values of 293.9 MW while the unit exergy cost of products and carbon dioxide emission index take minimum values of 15.3$/GJ and 110.1 kg/MWh, respectively. Furthermore, increasing the pressure ratio of the gas turbine leads to maximum values of 45 % and 54 % in overall energy and exergy efficiencies, respectively.Peer reviewe

Two-Objective Optimization of a Cogeneration System Based on a Gas Turbine Integrated with Solar-Assisted Rankine and Absorption Refrigeration Cycles

The current study investigates a cogeneration system based on a gas turbine, integrated with a Rankine cycle and an absorption refrigeration cycle, considering energy and exergy perspectives. The fuel used in the gas turbine’s combustion chamber is obtained through biomass gasification, specifically using wood as the biomass fuel. To enhance the system’s performance, solar energy is utilized to preheat the working fluid in the Rankine cycle, reducing the energy required in the heat recovery steam generator. Additionally, an absorption refrigeration cycle is incorporated to recover waste heat from exhaust gases and improve the plant’s exergy efficiency. A two-objective optimization is conducted to determine the optimal operating conditions of the proposed system, considering exergy efficiency and carbon dioxide emission index as criteria. The case study reveals that the gasifier and combustion chamber contribute the most to system irreversibility, accounting for 46.7% and 22.9% of the total exergy destruction rate, respectively. A parametric study is performed to assess the impact of compression ratio, turbine bleed steam pressure, gas turbine inlet temperature, and solar share (the ratio of energy received by solar collectors to biomass fuel input energy) on system performance. The findings demonstrate that maximum energy and exergy efficiencies of the power generation system are achieved at a pressure ratio of 10. Furthermore, a 1% reduction in the gas turbine’s compression pressure ratio can be compensated by a 9.3% increase in the solar share within the steam Rankine cycle

Coupling a Gas Turbine Bottoming Cycle Using CO₂ as the Working Fluid with a Gas Cycle: Exergy Analysis Considering Combustion Chamber Steam Injection

Gas turbine power plants have important roles in the global power generation market. This paper, for the first time, thermodynamically examines the impact of steam injection for a combined cycle, including a gas turbine cycle with a two-stage turbine and carbon dioxide recompression. The combined cycle is compared with the simple case without steam injection. Steam injection’s impact was observed on important parameters such as energy efficiency, exergy efficiency, and output power. It is revealed that the steam injection reduced exergy destruction in components compared to the simple case. The efficiencies for both cases were obtained. The energy and exergy efficiencies, respectively, were found to be 30.4% and 29.4% for the simple case, and 35.3% and 34.1% for the case with steam injection. Also, incorporating steam injection reduced the emissions of carbon dioxide

Proposal and Comprehensive Analysis of a Novel Combined Plant with Gas Turbine and Organic Flash Cycles: An Application of Multi-Objective Optimization

Environmental, exergo-economic, and thermodynamic viewpoints are thoroughly investigated for a state-of-the-art hybrid gas turbine system and organic flash cycle. For the proposed system, the organic flash cycle utilizes the waste thermal energy of the gases exiting the gas turbine sub-system to generate additional electrical power. Six distinct working fluids are considered for the organic flash cycle: R245fa, n-nonane, n-octane, n-heptane, n-hexane, and n-pentane. A parametric investigation is applied on the proposed combined system to evaluate the impacts of seven decision parameters on the following key operational variables: levelized total emission, total cost rate, and exergy efficiency. Also, a multi-objective optimization is performed on the proposed system, taking into account the mentioned three performance parameters to determine optimum operational conditions. The results of the multi-objective optimization of the system indicate that the levelized total emission, total cost rate, and exergy efficiency are 74,569 kg/kW, 6873 $/h, and 55%, respectively. These results also indicate the improvements of 16.45%, 6.59%, and 3% from the environmental, economic, and exergy viewpoints, respectively. The findings reveal that utilizing n-nonane as the working fluid in the organic flash cycle can yield the lowest levelized total emission, the lowest total cost rate, and the highest exergy efficiency

Energy, exergy, economic and exergoenvironmental analyses of transcritical CO2 cycle powered by single flash geothermal power plant

Abstract The need for energy is increasing worldwide as the population has a continuous trend of increase. The restrictions on energy sources are becoming tougher as the authorities set these developed and developing countries. This leads to looking for other alternative energy sources to replace the conventional energy sources, leading to greenhouse emissions. Environmentally friendly energy sources (renewable energies), for example, geothermal, solar and wind, are viewed as clean and sustainable energy sources. Among these kinds of energy sources, geothermal energy is one of the best options because, like solar and wind energy sources, it does not depend on weather conditions. In this work, a single flash geothermal power plant is used to power a transcritical CO2 power plant is proposed. The energy and exergy analysis of the proposed combined power plant has been performed and the best possible operating mode of the power plant has been discussed. The effects of parameters such as separator pressure, CO2 condenser temperature and CO2 turbine inlet pressure and the pinch point on the energy efficiency, exergy efficiency and output power are determined and discussed. Our results indicate that the highest exergy destruction is in the CO2 vapor generator of 182.4 kW followed by the CO2 turbine of 106 kW, then the CO2 condenser of 82.81 kW and then the CO2 pump 58.76 kW. The lowest exergy destruction rates occur in the single flash geothermal power plant components where the separator has exactly zero exergy destruction rate. The results also show that the combined power plant produces more power and has better efficiencies (first law and second law) than the stand-alone geothermal power plant. Finally, Nelder–Mead simplex method is applied to determine the optimal parameters such as separator pressure, power output and pumps input power and second law efficiency. The results show that the power plant should be operated at a lower pinch temperature to reduce damage to the environment. As the condenser pressure increases, the environmental damage effectiveness coefficient decreases sharply until it reaches the minimum value of 1.2 to 1.7 MPa and then starts to increase. The trend of the impact of sports on environmental improvement is exactly the opposite of the trend of the effectiveness of environmental damage. Therefore, from an environmental point of view, it is recommended to operate the gas turbine at a high inlet pressure.</jats:p

Energy, exergy, economic and exergoenvironmental analyses of transcritical CO2 cycle powered by single flash geothermal power plant

The need for energy is increasing worldwide as the population has a continuous trend of increase. The restrictions on energy sources are becoming tougher as the authorities set these developed and developing countries. This leads to looking for other alternative energy sources to replace the conventional energy sources, leading to greenhouse emissions. Environmentally friendly energy sources (renewable energies), for example, geothermal, solar and wind, are viewed as clean and sustainable energy sources. Among these kinds of energy sources, geothermal energy is one of the best options because, like solar and wind energy sources, it does not depend on weather conditions. In this work, a single flash geothermal power plant is used to power a transcritical CO2 power plant is proposed. The energy and exergy analysis of the proposed combined power plant has been performed and the best possible operating mode of the power plant has been discussed. The effects of parameters such as separator pressure, CO2 condenser temperature and CO2 turbine inlet pressure and the pinch point on the energy efficiency, exergy efficiency and output power are determined and discussed. Our results indicate that the highest exergy destruction is in the CO2 vapor generator of 182.4 kW followed by the CO2 turbine of 106 kW, then the CO2 condenser of 82.81 kW and then the CO2 pump 58.76 kW. The lowest exergy destruction rates occur in the single flash geothermal power plant components where the separator has exactly zero exergy destruction rate. The results also show that the combined power plant produces more power and has better efficiencies (first law and second law) than the stand-alone geothermal power plant. Finally, Nelder-Mead simplex method is applied to determine the optimal parameters such as separator pressure, power output and pumps input power and second law efficiency. The results show that the power plant should be operated at a lower pinch temperature to reduce damage to the environment. As the condenser pressure increases, the environmental damage effectiveness coefficient decreases sharply until it reaches the minimum value of 1.2 to 1.7 MPa and then starts to increase. The trend of the impact of sports on environmental improvement is exactly the opposite of the trend of the effectiveness of environmental damage. Therefore, from an environmental point of view, it is recommended to operate the gas turbine at a high inlet pressure.Peer reviewe