Developing countries scramble to contain and mitigate the spread of coronavirus disease 2019 (COVID-19), and world leaders demand equitable distribution of vaccines to trigger economic recovery. Although numerous stra...
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Developing countries scramble to contain and mitigate the spread of coronavirus disease 2019 (COVID-19), and world leaders demand equitable distribution of vaccines to trigger economic recovery. Although numerous strategies, including education, quarantine, and immunization, have been used to control COVID-19, the best method to curb this disease is vaccination. Due to the high demand for COVID 19 vaccine, developing countries must carefully identify and prioritize vulnerable populations and rationalize the vaccine allocation process. This study presents a mixed-integer linear programming model for equitable COVID-19 vaccine distribution in developing countries. Vaccines are grouped into cold, very cold, and ultra-cold categories where specific refrigeration is required for their storage and distribution. The possibility of storage for future periods, facing a shortage, budgetary considerations, manufacturer selection, order allocation, time-dependent capacities, and grouping of the heterogeneous population are among the practical assumptions in the proposed approach. Real-world data is used to demonstrate the efficiency and effectiveness of the mathematical programming approach proposed in this study.
The growth of the global economy is accompanied by significant energy consumption, and greenhouse gas emissions create various problems such as global warming and environmental degradation. To protect the environment,...
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The growth of the global economy is accompanied by significant energy consumption, and greenhouse gas emissions create various problems such as global warming and environmental degradation. To protect the environment, governments are seeking to reduce carbon emissions. Production systems that operate solely based on economic factors in the workshop only consider problems such as production speed, cost, and processing time. Two aspects can be effective in saving energy and reducing emissions at the production planning level: using routing to find the shortest path for collecting workpieces to the workshop, and turning off machines with long idle times and restarting them at the appropriate time. If the workshop production problem is combined with vehicle routing, a new problem arises. According to the research conducted so far, an integrated mathematical model for production routing has not been designed in a situation where the routing is before the production workshop. In this research, this bi-objective model is introduced, and it is solved using the augmented epsilon-constraint (AEC) method. The proposed mixed-integer linear programming model of this research includes three dimensions: environmental, social (customer satisfaction), and economic simultaneously. Given the high complexity of the mathematical model, MATLAB software and MOPSO and NSGA-II algorithms were used to solve it at higher dimensions. Seven evaluation criteria were used to compare the two proposed algorithms, and the results show that the MOPSO algorithm performs better. The findings suggest that minimizing pollution may involve sacrificing on-time delivery to customers. Consequently, decision-makers must carefully weigh the trade-off between reducing environmental impact and maintaining satisfactory delivery performance, ultimately deciding on an acceptable pollution level.
Efficient operation of the gas field supply chain is an important guarantee for oil and gas energy security, and it needs to dynamically adapt to upstream and market fluctuations. This paper proposes an innovative des...
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Efficient operation of the gas field supply chain is an important guarantee for oil and gas energy security, and it needs to dynamically adapt to upstream and market fluctuations. This paper proposes an innovative design and operation optimization mixedinteger nonlinearprogramming (MILP) method for distributed supply chain based on skid equipment. Unlike the traditional methods, the proposed MILP method can simultaneously obtain upstream production planning, midstream modular equipment and processing capacity allocation, and downstream transportation allocation schemes for various natural gas products such as liquefied natural gas (LNG), compressed natural gas (CNG) and pipeline natural gas (PNG) of each time periods by making the maximum net present value (NPV) of the full development cycle as the target. In order to prove the superiority and usability of the proposed method, four operation scheduling modes are compared through two comprehensive case analysis. Additionally, the effects of gas well productivity, market demand and product price are investigated through sensitivity analysis. The results show that comparing with the traditional method, the proposed method can effectively improve the loading rate of the processing equipment, increase the overall revenue of gas field development, integrate the operation in the upstream, midstream and downstream of the supply chain, dynamically adapt to the gas production and marketing fluctuations. This study provides a creative way to obtain better profit, reduce energy utilization and promote cleaner production for sustainable supplies management in gas industry.
Fossil fuel-fired power plants are still the principal power producers in most power systems. Retrofitting these pollutant generators with carbon capture and storage (CCS) technology can be a key solution to decarboni...
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Fossil fuel-fired power plants are still the principal power producers in most power systems. Retrofitting these pollutant generators with carbon capture and storage (CCS) technology can be a key solution to decarbonisation, especially for power systems with low expansion potential for renewable and hydroelectric energy resources. This study presents a coordinated generation and transmission expansion planning (G&TEP) and CCS expansion planning model for carbon emission constrained power systems. The proposed model determines the optimal order and time of retrofitting carbon emitter generators with CCS technology coordinated with the G&TEP. The limits on renewable resources capacity expansion potential and the yearly emission reduction targets are considered. Additionally, the proposed model allows for determining the incentives that are to be offered by the central planning authority to the pollutant generators to incentivise their participation in emission reduction through CCS retrofitting. The problem is formulated as a mixed-integer linear programming model and is decomposed into a master and three subproblems to tackle the large-scale nature of the developed optimisation problem. Numerical results demonstrate that a coordinated G&TEP and CCS expansion planning is a least-cost planning solution for emission constrained power systems with low expansion capacity potential for renewable and hydroelectric resources.
With the rising energy prices and increasing environmental awareness, the energy efficiency of metro transit system has attracted much attention in recent years. This study proposes a two-step optimisation method to o...
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With the rising energy prices and increasing environmental awareness, the energy efficiency of metro transit system has attracted much attention in recent years. This study proposes a two-step optimisation method to optimise speed profile and timetable, aiming to reduce the operational energy consumption of metro transit system. First, a coasting point searching algorithm is designed to reduce tractive energy consumption by optimising speed profile and running time distribution scheme. Then, a mixed-integer linear programming model is constructed to maximise the overlap time between the accelerating and braking phases by optimising headway and dwell time, in order to improve the utilisation of regenerative braking energy (RBE). Furthermore, numerical simulations are presented based on the data from a Guangzhou Metro Line. The results show that the tractive energy consumption can be reduced by 8.46% and the utilisation of RBE can be improved by 11.6%.
This study proposes an operation task-aware energy management strategy for ship power systems that consist of main engines, diesel-electric engines, and energy storage systems. The proposed strategy aims to meet the f...
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This study proposes an operation task-aware energy management strategy for ship power systems that consist of main engines, diesel-electric engines, and energy storage systems. The proposed strategy aims to meet the fuel consumption and task-dependent objectives of the vessel by optimally dispatching the generation and storage units. Firstly, rule-based decisions are made based on the operational task requirements and specifications by the classification societies. Then, in the optimisation stage, these decision variables are used as inputs to formulate and update the operational constraints and the objectives of the optimisation. The optimisation problem is formulated as a mixed-integer linear programming model, and with the help of rule-based decision variables, the problem can be efficiently solved by the exhaustive search algorithm. Four case studies with different operation task sequences and ship topologies are performed to demonstrate the effectiveness of the dispatching scheme. Furthermore, the results indicate the simplicity and practicality for the actual implementation, as well as flexibility and applicability of the proposed optimal energy dispatch for different types of vessels.
Wind power application in producing electrical energy is an integral part of the increased eco-friendly generation. Accordingly, wind power producers may have a dominant position in some electricity markets. This stud...
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Wind power application in producing electrical energy is an integral part of the increased eco-friendly generation. Accordingly, wind power producers may have a dominant position in some electricity markets. This study mainly concerns a strategic wind power investor who owns a number of units and seeks to optimise its expansion plans on sizes and sites of new generation capacities in a horizon year. Here, the investor is a price-maker in both day-ahead (DA) and intraday (ID) markets, while acts as a deviator in the balancing market. A stochastic bi-level model is proposed wherein the upper-level, the investor maximises the expected profit. Both DA and ID market clearings are considered in the lower-level (LL). The model is formulated as a mathematical program with equilibrium constraints (MPEC) by replacing the LL problem with its Karush-Kuhn-Tucker (KKT) conditions. The MPEC model is then converted to a mixed-integer linear programming model. A three-bus illustrative example and IEEE 24-bus reliability test system are used to demonstrate the effectiveness of the proposed model. The results confirm that the presence of the ID market in the investment model has increased the expected profits of the investor and also increases invested wind capacity.
As the core sub-problem of both network reconfiguration and service restoration of the electrical distribution system (EDS), the load pick-up (LPP) problem in EDS searches the optimal configuration of the EDS, aiming ...
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As the core sub-problem of both network reconfiguration and service restoration of the electrical distribution system (EDS), the load pick-up (LPP) problem in EDS searches the optimal configuration of the EDS, aiming to minimise the power loss or provide as much power as possible to load ends. The piecewise linearisation (PWL) approximation method can be used to tackle the network power flow constraints' non-linearity in the LPP problem model, and transform the LPP model into a mixed-integer linear programming model (LPP-MILP model). The errors in the PWL approximation of the network power flow constraints may affect the feasibility of the solving results of the LPP-MILP model. The single method to reduce the PWL approximation errors by increasing the number of discretisations in PWL function is not stable. Moreover, the solution efficiency of the LPP-MILP model is sacrificed severely. In this study, a warm-start PWL approximation-based solution for the LPP problem is proposed. The variable upper bounds in the PWL approximation functions are renewed dynamically in the warm-start solution procedure to reduce the PWL approximation errors with higher computational efficiency. Modified IEEE 33-bus radial distribution test system and a real and large distribution system, 1066-bus system, are used to test and verify the effectiveness and robustness of the proposed methodology.
In this paper, a comparison is made between two bilevel programmingmodels to design time-of-use tariffs in the electricity retail market. The upper-level objective function consists of the maximization of the retaile...
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ISBN:
(数字)9783030436803
ISBN:
(纸本)9783030436797;9783030436803
In this paper, a comparison is made between two bilevel programmingmodels to design time-of-use tariffs in the electricity retail market. The upper-level objective function consists of the maximization of the retailer's profit and the lower-level problem relates to the minimization of the consumer's cost. In the first model, the periods in which prices apply are pre-defined and the aim is to determine the price values. In the second model, which is developed for the first time in this paper, both the periods and prices are decision variables, thus leading to a very large search space for the upper-level problem due to the number of combinations periods-prices. For the model with variable periods, a hybrid approach combining a genetic algorithm for the upper-level search with a mixed-integerlinearprogramming solver to obtain optimal solutions to the lower-level problem is herein developed. Computational results comparing the two models are presented.
This study proposes a novel resilience-directional robust dispatch (RRD) model for an islanded AC/DC hybrid microgrid (HMG). The inherent uncertainties on the source-load power and the occurrence of meteorological dis...
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This study proposes a novel resilience-directional robust dispatch (RRD) model for an islanded AC/DC hybrid microgrid (HMG). The inherent uncertainties on the source-load power and the occurrence of meteorological disasters are considered in this model. When a meteorological disaster strikes, the wind turbine (WT), photovoltaic (PV), and bidirectional converter of the HMG should be offline to ensure the stability of the HMG and the safety of these sensitive units. When affected by such double uncertainties, the output constraints of the WT, PV and load are bilinear but are linearised via big-M approach. The proposed RRD model manifests as a min-max-min tri-layer problem with mixed-integer recourse variables, which is difficult to solve directly. Therefore, a nested column-and-constraint generation algorithm is adopted to convert the tri-layer problem to a two-stage mixed-integerlinearprogramming (MILP) model. The MILP problem is addressed by the commercial solver, thereby obtaining the minimal operating cost and establishing robust scheduling plans with the worst disaster scenario. The effectiveness and rationality of the proposed RRD model and its solution methodology are verified in numerical tests.
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