Combined Power System Research Articles

RETRACTED: Life cycle analysis of biowaste-to- biogas/biomethane processes: Cost and environmental assessment of four different biowaste scenarios organic fraction of municipal solid waste and secondary sewage sludge

Biowaste-to-biogas processes have been introduced to design a valuable and green renewable plant to achieve a sustainable society and environment. The biomethane production process through biogas upgrading instead of designing a combined heat and power (CHP) system can be more attractive. This study presents a life cycle analysis (LCA) from both cost and environmental standpoints for four biowaste-to-biogas/biomethane process scenarios. Biogas production is achieved through anaerobic co-digestion of the organic fraction of municipal solid waste (OF-MSW) and secondary sewage sludge (S-SS), incorporating a pre-treatment process based on the dark co-fermentation process (DCFP). Each scenario offers distinct methods for utilizing the hydrogen-rich gas and biogas, with varying degrees of energy recovery and efficiency. Two sensitivity studies were conducted under various utilizations of the recovered biomethane and the anticipated electricity mix. Scenario SC-1 (CHP-from-biogas) was found to be the most co-friendly favorable in eight out of eleven impact categories (under the CML/IA technique). Further, biogas upgrading-integrated options exhibited lower impacts. Replacing biomethane instead of petrol in scenarios with upgraded biogas was identified as the most effective approach against climate change. Financial analysis indicated that all layouts are economically viable, each demonstrating a positive NPV over a 20-year period (up to $11.57 million).

Thermo-economic optimization on a combined heat and power system with supercritical Rankine cycle for power-to-heat batteries

The global energy structure is transforming to low-carbon, and it is urgent to construct a sustainable energy system mainly based on renewables. The power-to-heat batteries (P2HBs) show great potential for large-scale energy storage by converting low-cost renewable power to heat. This paper aims to study the thermodynamic and economic advantages of the P2HB integrated with a supercritical steam Rankine cycle (RC) to achieve combined heat and power (CHP) generation. Firstly, a system model of P2HB-CHP consuming grid valley power is developed. The system includes three sub-systems: P2HB, steam generator, and CHP. Thermodynamic and economic analysis models are developed, and the average exergy efficiency (ηav) and net present value (NPV) are formulated as performance evaluation targets, respectively. The genetic algorithm is used to perform multi-parameter optimization of the system. The thermodynamic optimization results show that the maximum ηav of supercritical P2HB-CHP is 0.47 %, 1.16 %, and 1.44 % higher than that of subcritical P2HB-CHP when the high working temperature of the molten salt reaches 505 °C, 570 °C, and 640 °C, respectively. The largest proportion of anergy is generated by electric heaters, over 72 %. The next largest proportion is heat exchangers, which is related to the heat transfer temperature differences. The results of the economic analysis show that the maximum NPV of supercritical P2HB-CHP is lower by 158 M$, lower by 74 M$, and higher by 55 M$ than that of subcritical P2HB-CHP when the high working temperature of the molten salt is reached 505 °C, 570 °C, and 640 °C, respectively. The high efficiency of supercritical RC reduces the costs of electric heaters and molten salts, but sets high demands on the heat exchangers. Although high-temperature molten salt results in high energy efficiency, the increased cost of molten salt reduces the profitability of the system.

Performance analysis and optimization of multi-energy complementary combined heat and power system considering the influence of time-of-use price

Abstract The multi-energy complementary system can meet the increasingly abundant and diversified energy consumption needs of users and, at the same time, help to improve energy utilization efficiency, reduce environmental pollution, and optimize the balance of energy supply and demand. In this paper, a multi-energy complementary cogeneration system with a gas turbine distributed photovoltaic, gas boiler, and heat storage tank is proposed, and the operation scheduling optimization model of the system is constructed. Aiming to minimize the comprehensive cost of economy and carbon emission, the model adopts a linear programming method to optimize the operation scheduling of multi-energy complementary systems. Taking a multi-energy complementary cogeneration system as an example, the key equipment of the system is optimized under three different scenarios with different time-of-use prices, and the influence of time division of time-of-use electricity price on the comprehensive cost of the system is analyzed. The results show that the time division method, which is more in line with the system net load curve, can effectively reduce the comprehensive cost of the complementary system and increase the consumption space of new energy.

Bioprocess Design and Technoeconomic Analysis of 2,3-Butanediol Production in Wood-Based Biorefineries

2,3-Butanediol (BDO) is a crucial precursor in various industries, traditionally derived from fossil resources, raising environmental concerns. This study evaluates the techno-economic feasibility of producing BDO from wood residues, a sustainable resource abundantly available in Nordic countries. By modeling a biorefinery plant with a daily capacity of 100 metric tons of wood chips, three scenarios (Sc.) were explored: Sc. 1, where BDO is the sole product; Sc. 2, where BDO is produced alongside methane and biofertilizer; and Sc. 3, which incorporates a combined heat and power system using biogas from the waste stream. The analysis emphasizes the minimum selling price (MSP) of BDO, revealing it to be lowest in Sc. 1 at USD2.97/kg, compared to USD3.20/kg and USD3.48/kg for Sc. 2 and Sc. 3, respectively. Notably, sensitivity analysis highlighted the impact of processing capacity on economic performance, suggesting a potential for higher scalability and profitability in Sc. 2. This study contributes novel insights into the role of processing capacity and fermentation yield in optimizing BDO production, providing a valuable framework for technology developers aiming to establish wood-based biorefineries. These findings not only enhance understanding of economic thresholds but also underscore the importance of resource efficiency and strategic planning in bio-based production setups.Graphical abstract

Heat pumps to upgrade existing CHP-DHN systems towards new generation thermal networks

District heating networks with combined heat and power systems and renewable energies are one of the most promising solutions for efficient and sustainable energy supply. In many cases, however, especially for district heating networks prior to the 4th generation, significant renovations are required to meet decarbonization targets. In this paper a study is proposed to evaluate the integration of high temperature heat pumps in an existing combined heat and power - district heating plant to reduce fossil fuel consumption and increase the exploitation of renewable energy sources. The plant is currently operating in central Italy and connects more than 1250 users. The identified solution implies lowering the district heating networks operating temperature and supplying power peaks with a high temperature heat pump acting as a booster. Results showed significant improvements in system performance especially in the winter months, due to the greater impact of lowering the temperature level of the district heating network during these months. Overall, the updated scenario allows the overall demand and ground heat losses to be reduced annually by 5.3 % and 13.5 % respectively. This reduces natural gas consumption by 13.3 % and avoids the emission of about 836 tCO2. The analysis provides guidelines for the upgrade of 3rd generation district heating network that can be useful for planning improvements towards newest generation thermal networks.

Elephant Grass (Pennisetum purpureum): A Bioenergy Resource Overview

Elephant grass (EG), or Pennisetum purpureum, is gaining attention as a robust renewable biomass source for energy production amidst growing global energy demands and the push for alternatives to fossil fuels. This review paper explores the status of EG as a sustainable bioenergy resource, integrating various studies to present a comprehensive analysis of its potential in renewable energy markets. Methods employed include assessing the efficiency and yield of biomass conversion methods such as pretreatment for bioethanol production, biomethane yields, direct combustion, and pyrolysis. The analysis also encompasses a technoeconomic evaluation of the economic viability and scalability of using EG for energy production, along with an examination of its environmental impacts, focusing on its water and carbon footprint. Results demonstrate that EG has considerable potential for sustainable energy practices due to its high biomass production and ecological benefits such as carbon sequestration. Despite challenges in cost competitiveness with traditional energy sources, specific applications like small-scale combined heat and power (CHP) systems and charcoal production show economic promise. Conclusively, EG presents a viable option for biomass energy, potentially playing a pivotal role in the biomass sector as the energy landscape shifts towards more sustainable solutions; although, technological and economic barriers need further addressing.

Energy management strategy for accurate thermal scheduling of the combined hydrogen, heating, and power system based on PV power supply

To solve the negative impact of renewable energy volatility on the power system, a combined hydrogen, heating and power system integrating alkaline water electrolysis, metal hydride hydrogen storage, and proton exchange membrane fuel cells (PEMFCs) is proposed. However, water electrolysis, hydrogen adsorption and PEMFC all generate heat, and how to use this heat is the key to improving the system efficiency. Therefore, four energy scheduling schemes are proposed in this study, aiming at making full use of waste heat to improve its energy utilization efficiency. The results show that the system heat is almost entirely utilized under the proposed four strategies. Meanwhile, the peak-valley strategy is more suitable for on-grid operation, and heat priority, peak clipping and load reduction strategy are more suitable for off-grid operation. Under the heat priority strategy, residual electricity and heat are the lowest. Under the peak clipping strategy, the current density of the PEMFC fluctuates the least and is maintained at 0.59 A cm−2 during the heat-led period. Under the load reduction strategy, during the heat-led period (5:00 p.m. ∼ 6:00 a.m.), the system electric power is lower than the power load for the shortest time, accounting for 23.93% of this operating duration.

Modeling and thermodynamic optimization of distributed combined heat and power system based on biomass chemical looping hydrogen generation process

Distributed biomass combined heat and power (CHP) system is becoming an important way to use local biomass for ensuring regional energy supply and reducing CO2 emissions. In this work, a high-efficient CHP system based on a new separated-type biomass gasification process is proposed. The gasification system includes a chemical looping hydrogen generation (CLHG) process combined and a tar catalytic steam reforming (TCSR) unit, in which the general CLHG process includes a fuel reactor (FR), a steam reactor (SR) and an air oxidation reactor (AR), but in this study, the AR is removed and instead, the FR is decoupled into two reaction stages, namely, pyrolysis and gasification. In addition, the biomass pyrolysis-gasification-hydrogen generation (BPGH) combined cycle system is established by using oxygen carrier to couple pyrolysis, gasification and hydrogen generation stages. The TCSR process is used to convert volatiles generated by pyrolysis into syngas. To maximize thermodynamic efficiency of the system, the influences of temperature for the catalytic steam reforming (TCSR) and the ratio of steam to carbon (S/C) on the overall energy and exergy efficiency are mainly studied. The results show that the overall energy and exergy efficiencies reach the highest values of 75.93% (LHV) and 32.61%, respectively, when TSCR=800 °C and S/C = 3 while the net power generation energy and exergy efficiencies are 27.43% (LHV) and 27.54%, respectively.

Efficient and sustainable power propulsion for all-electric ships: An integrated methanol-fueled SOFC-sCO2 system

To address marine pollution caused by fuel usage and reduce carbon emissions in ships, the development of alternative fuel electric propulsion ship power systems presents a promising solution. In this study, an integrated Methanol-fueled SOFC-sCO2 combined power system is proposed for all-electric ships. The system efficiently utilizes waste heat from SOFCs by integrating it into a partial heating sCO2 power cycle to generate additional power. Through the utilization of a thermodynamic model, parametric sensitivity analysis and multi-objective optimization are conducted to maximize the system's energy efficiency while reducing investment and maintenance costs. Comprehensive energy, exergy, and economic analyses are performed on the optimized system. The achieved energy efficiency and exergy efficiency are 66.10 % and 57.74 % respectively, with an investment and maintenance cost of 16.96 $/h and a payback period of 2.2 years. When applied to container ships and compared with other ship power systems, the proposed system demonstrates the highest energy efficiency, delivering an impressive output power of 65,092 kW. The energy efficiency design index (EEDI) of the system is moderate, reaching 5.94. Despite the relatively high fuel cost, the proposed system offers a simpler design compared to existing SOFC-sCO2 systems and is only slightly more complex than integrated systems like SOFC-GT.

Techno-economic and performance assessment of a hybrid fuel cell-based combined heat and power system for dairy industry

Techno-economic and performance assessment of a hybrid fuel cell-based combined heat and power system for dairy industry

Advancements and Challenges in Integrating Renewable Energy Sources Into Distribution Grid Systems: A Comprehensive Review

Abstract The issues in integrating renewable energy sources (RES) into distribution grid structures are thoroughly examined in this research. It highlights how important this integration is to updating the energy system and attaining environmental goals. The study explores the specific problems confronted by means of on-grid power structures, along with overall performance metrics and compatibility issues. Additionally, it presents a thorough assessment of the attributes of various RES hybrid systems, together with technology from the fields of solar, wind, batteries, and biomass. To be able to spotlight the significance of innovative solutions inside the dispersed technology environment, the integration of RES with combined heat and power system structures is investigated. This study addresses the numerous problems with RES integration into the grid to better comprehend their intricacies. The viability of RES integration is supported by real-world case studies that provide operational examples of dispersed generation systems. The study concludes by discussing the technical, financial, and grid-related problems associated with distributed generating systems' limits and highlighting the contribution of cutting-edge technology and artificial intelligence to their removal. In conclusion, the report highlights the development toward smarter grids and improved distributed generating capacities as the essential component of a robust and sustainable energy future.

Development of a micro-combined heat and power powered by an opposed-piston engine in building applications

Residential homes and light commercial buildings usually require substantial heat and electricity simultaneously. A combined heat and power system enables more efficient and environmentally friendly energy usage than that achieved when heat and electricity are produced in separate processes. However, due to financial and space constraints, residential and light commercial buildings often limit the use of traditional large-scale industrial equipment. Here we develop a micro–combined heat and power system powered by an opposed-piston engine to simultaneously generate electricity and provide heat to residential homes or light commercial buildings. The developed prototype attains the maximum AC electrical efficiency of 35.2%. The electrical efficiency breaks the typical upper boundary of 30% for micro–combined heat and power systems using small internal combustion engines (i.e., <10 kW). Moreover, the developed prototype enables maximum combined electrical and thermal efficiencies greater than 93%. The prototype is optimally designed for natural gas but can also run renewable biogas and hydrogen, supporting the transition from current conventional fossil fuels to zero carbon emissions in the future. The analysis of the unit’s decarbonization and cost-saving potential indicate that, except for specific locations, the developed prototype might excel in achieving decarbonization and cost savings primarily in US northern and middle climate zones.

Exergo-environmental cost optimization and thermodynamic analysis for a solar-driven combined heating and power system

Reasonable pricing of each product in a combined heating and power system is essential to improve the economic benefits of the system. However, the whole life cycle pollutant emissions cost of the system and energy level in the conventional exergo-economic method are ignored, leading to irrational pricing of each product. Hence, an exergo-environmental cost optimization methodology that considers the whole life cycle pollutant emissions cost and energy level is developed. The compressor discharge pressure of the transcritical carbon dioxide heat pump is employed as the optimization variable to obtain the lowest unit exergo-environmental cost of the system. The unit exergo-environmental cost is converted to the unit energy-environmental cost to determine the price of each product. Optimization results show that the lowest unit exergo-environmental cost of the system is 0.387 $/kWh when the compressor discharge pressure is 10.15 MPa, the unit exergo-environmental costs of the electricity and space heating water are 0.199 $/kWh and 0.989 $/kWh, respectively. The corresponding unit energy-environmental costs of the space heating water and electricity are 0.047 $/kWh and 0.199 $/kWh, respectively. Compared with the conventional exergo-economic method, the unit exergo-environmental costs of the electricity and space heating water are improved by 16.37 % and 11.37 %, respectively, Furthermore, under optimal configuration, the exergy, energy, and solar to electricity efficiencies of the system are 16.28 %, 88.09 %, and 13.79 %, respectively. The above results prove that the developed exergo-environmental cost analysis and optimization methodology can reasonably determine the price of each product of the building energy system.

Comprehensive analysis and optimization for a novel combined heating and power system based on self-condensing transcritical CO2 Rankine cycle driven by geothermal energy from thermodynamic, exergoeconomic and exergoenvironmental aspects

In this paper, a novel combined heating and power (CHP) system is proposed to realize full-scale utilization of geothermal energy and efficient multi-generation, which not only performs preferable overall performance than previous homogeneous system, but also offers an effective energy cascade utilization approach for self-condensing transcritical CO2 (TCO2) Rankine cycle. Based on the established mathematical models, the performance comparison is conducted for proving the superiority of the novel CHP system. Then, an overall performance analysis is implemented to reveal the combined effects for six key parameters on system thermodynamic, exergoeconomic and exergoenvironmental performances. Furthermore, multi-objective optimization considering system overall performance is conducted. The results show that for the novel CHP system, the largest relative improvement rate of system exergy efficiency (ηexg) and declining rate of total unit product exergy cost (cP,total) versus the previous CHP system are 15.03 % and 18.89 %, respectively. The final optimization results of ηexg, cP,total and total unit product exergy environmental impact (bP,total) are determined as 51.10 %, 14.12 $/GJ and 9.00 mPts/GJ, respectively. This paper fulfills an elaborate performance analysis and optimization for the novel CHP system, which fills the research gap of efficient and promising CHP system based on self-condensing TCO2 Rankine cycle.

Energy saving and flexibility analysis of combined heat and power systems integrating heat-power decoupling technologies in renewable energy accommodation

World energy is undergoing a decarbonization transformation with the rapid growth of renewable energy. Combined heat and power, with its abundant stock and efficient characteristics, can support decarbonization. This study focuses on enhancing the energy saving and flexibility of combined heat and power systems decoupled by the vapor compression heat pump and electric boiler. The characteristics of the governing valves and the governing stage are confirmed as key factors influencing energy saving. A general modeling method is proposed to accurately determine the characteristics of the governing valves and the governing stage. The valve-point effect is obtained from the formation mechanism. With a reference case, applying the heat-power decoupling technologies results in a maximum reduction of power load of up to 70 MW, greatly enhancing the operation flexibility. The fuel saving per unit peak shaving ranges from 0.1355 kg·kWh−1 to 0.1382 kg·kWh−1 in the system decoupled by the electric boiler and from 0.2284 kg·kWh−1 to 0.2481 kg·kWh−1 in the system decoupled by the vapor compression heat pump. The maximal variation ranges of fuel saving per unit peak shaving, with and without the valve-point effect, are 0.0197 kg·kWh−1 and 0.0055 kg·kWh−1, respectively. After considering the valve-point effect, the range of fuel saving per unit peak shaving is tripled. Additionally, there are higher energy-saving regions near valve points. It is recommended to operate the decoupling systems under these working conditions, with governing valves opened at an appropriate opening degree. The energy-saving potential of these systems can be further exploited by accommodating the valve-point effect in the integration of renewable energy.

Dynamic numerical modeling and performance optimization of solar and wind assisted combined heat and power system coupled with battery storage and sophisticated control framework

Incorporating distributed renewable energy sources into heating, power, and cooling systems is facilitating the drive toward intelligent building energy solutions. However, the inherent uncertainties associated with controllable renewable resources pose challenges for the thermo-economic scheduling of smart buildings. Nonetheless, the flexibility inherent in smart buildings can be leveraged through various market mechanisms. Hence, this research introduces a sustainable energy-building system driven by an autonomous solar/dish Stirling engine (SDSE) and wind turbine combined with a sophisticated control strategy and battery storage, which is designed to provide heat and power requirements. The proposed control strategy is also devised to optimize energy generation, ensuring prudent conservation and minimal waste, thereby amplifying overall efficiency and financial viability. The meticulous design of the system is accomplished through advanced MATLAB/Simulink® modeling. A thorough technical sensitivity analysis meticulously hones design parameters, revealing optimal operational thresholds. Simulation outcomes unveil a consistent Stirling engine (SE) efficiency, achieving a pinnacle of 35 %, while the SDSE attains over 28 %, respectively. The horizontal axis wind turbine, encompassing 100 kW and 500 kW modules, demonstrates power coefficients spanning from 0.18 to 0.09, with corresponding land area requirements ranging from 4.22 m2 to 21.10 m2, emphasizing the pivotal roles of module power and land area optimization. This paper also casts a spotlight on the environmental repercussions of the system, illustrating its potential to avert up to 30,000 kg of CO2 emissions per kWh/year. Moreover, the levelized cost of electricity ranges from 0.13 to 0.16 $/kWh, accompanied by an hourly cost that fluctuates between 3 $/h and 40 $/h, respectively. Conclusively, the developed modeling can be regarded as a significant stride in the realm of hybrid renewable energy systems, replacing the conventional photovoltaic/wind models with cutting-edge solar/wind configurations managed by a sophisticated control strategy and battery storage system.

Energy, Exergy, Economic, and environmental assessment of a trigeneration system for combined power, cooling, and water desalination system driven by solar energy

Energy efficiency, exergy efficiency & destruction, economic, environmental, and error analysis analyses have been presented for the proposed trigeneration system. The metrics have provided an inclusive understanding of the proposed system's ability to effectively convert energy inputs to useful outputs while minimizing losses and waste. The goal is to optimize the cycle performance and find the most efficient configuration for meeting the Middle East's energy, cooling, and freshwater needs using a sustainable, solar-driven trigeneration system. The study has observed a system's increased energy and exergy efficiencies by 60.34 to 63.27 % and 25.98 to 29.59 % for the direct normal Irradiance (DNI) values varied from 600 W/m2 to 1000 W/m2. The total energy saving accounted by the proposed configuration is 4,453,220 USD/year as compared to the commercial electricity which includes the net energy production, energy saving through ejector and absorption cooling, and cost of water purification (through Reverse Osmosis Plant) in one year. The payback period of the plant mentioned in this is evaluated by 6.66 years. The CO2 mitigation is evaluated by 22,185.24 MT/year and the other pollutants can also be mitigated like SO2 by 40.425 MT/year and NOx by 136.415 MT/year.

Dynamic behaviour and performance evaluation of a biomass-fired organic Rankine cycle combined heat and power (ORC-CHP) system under different control strategies

The dynamic behaviour and performance evaluation of a biomass-fired organic Rankine cycle combined heat and power (ORC-CHP) system under two different control strategies are investigated in this study. The dynamic model is established, while the dynamic characteristics of key operating parameters (superheat degree, evaporating pressure and mass flow rate) with the step change of heat source temperature are examined. The effects of controlled superheat degree and controlled expander shaft work on dynamic behaviours of thermodynamic, economic and environmental performance are discussed and compared under different control methods (feedforward active control, PID passive control and combined control). Results indicate that the superheat degree is significantly influenced by the heat source temperature under the without control strategy, with the variation reaching 8.4 K. The combined control method exhibits the best control performance with overshoot and control response times of 1.2 K and 12.3 s, respectively. Compared to without control, the expander shaft work and ORC thermal efficiency of the control strategy of superheat degree increase by 3.2 kW and 0.8 %, while that of the control strategy of expander shaft work increase by 1.0 kW and 0.3 %, respectively. The control strategy of superheat degree presents a significant improvement in the economic and environmental performance of the biomass-fired ORC-CHP system. This study is expected to provide better guidance for the practical operation and control of biomass-fired ORC-CHP systems.

Thermoacoustic micro-CHP system for low-grade thermal energy utilization in residential buildings

Effectively utilizing low-grade thermal energy is a promising approach to mitigating greenhouse gas emissions while reducing the burden on centralized power grids. Current thermoacoustic heat pumps and power generators face challenges such as high onset temperature differentials and low performance. This paper addresses these challenges by introducing a gas-liquid resonator into a thermoacoustic combined heat and power systems to recover low-grade thermal energy in residential buildings. Through Sage modeling and calculations, the internal characteristics of the proposed system and its output performance under different operating conditions are explored. At a heating temperature of 350 °C, the system can generate 6.4 kW of output thermal power, 0.9 kW of electricity, and overall exergy efficiency is 79.3 %. Combining neural network models with case studies conducted in Spain and Finland, the system can annually save 5.6 MWh and 20.7 MWh in fuel energy, reduce emissions of 1374 kg and 5180 kg of carbon dioxide, and save a total cost of €611 and €2324, respectively. Furthermore, comparisons with other emerging micro-CHP systems highlight the efficiency of the proposed system. These results indicate the high potential of thermoacoustic combined heat and power systems in recovering low-grade thermal energy and achieving energy savings and emission reductions.

Multi-criteria optimization of a combined power and freshwater system using modified NSGA-II and AHP-entropy-topsis

This paper proposed an innovative hybrid system to generate electricity and fresh water with higher energy efficiency. A subsystem is employed by integrating DCMD and heat pump to recover waste heat of PEMFC to produce fresh water. The thermodynamic and exergoeconomic models are established to evaluate the system comprehensive performance. Compared with the PEMFC alone, the results demonstrated that the proposed hybrid system achieves a 42.07 % increase in energy efficiency and provides 177.86 kg/h of fresh water. The components with high exergy destruction are PEMFC, Relief value, Inverter, Separator 2 and DCMD with the exergy destruction rate of PEMFC stack accounting for 54.55 %. The parametric analysis results indicate that the variation of the membrane filament number, feed and permeate flow rates all have evident impacts on the thermodynamic and economic performances of the hybrid system. The multi-objective optimization is conducted by adopting NSGA-II and three decision-making methods. The optimal solution obtained by AHP-entropy-TOPSIS approach for the net power out, exergy efficiency, WPC, and total exergy cost rate are 96059W, 0.5293, 0.2995 $/m3, and 14.27 $/h, respectively. In addition, the obtained results shown that the simulation times of NSGA-II are significantly reduced from 89.30 to 11.20 h by introducing BP-ANN to improve the simulation efficiency.