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Abstract In the subway system, passenger crowding in peak hours is likely to cause train delays that easily propagate to following trains, resulting in a lower efficiency of the system. Consequently, this paper focuses on determining a robust timetable for the trains on the one hand, i.e., finding a better timetable to avoid delay propagation as much as possible in case of a crowded subway system. On the other hand, this paper considers the energy efficiency, i.e., reducing the total energy consumption during operations by selecting appropriate speed profiles and maximizing the utilization of regenerative braking energy. A related mathematical optimization model is formulated with the objective of maximizing the robustness and minimizing the total energy consumption. In order to solve this model, an efficient algorithm, i.e., simulation-based variable neighborhood search algorithm, is presented to obtain a good timetable in reasonable amount of time. Finally, experiments are implemented to show the performance of the proposed algorithm.

Abstract The analysis was completed on the main production factors which determine energy characteristics of an electrically-driven hydraulic roller-bit drilling rig during drilling operations under the condition of the Far North deposit. In addition, the correlation ratio between the parameters and electric energy consumption was analyzed for the DM-H drilling rig. The equations expressing the relation of the drilling rig load to the drilling speed have been identified. In order to improve the quality of rock crushing, we have modified the method of determining the properties and condition of the rock mass in order to correct the connection layout of the blasting circuit, the activation system, the change in the type of an explosive agent, as well as the composition and weight of the blasthole charge. The proposed approach allows reducing the cost of drilling and blasting operations by 6 % through the improvement in the accuracy of the designed physical and mechanical properties in terms of both the stratum depth and the strike of the mining block.

Research on wind power capacity credit at the operational level plays an important role in power system dispatching. With the popularity of energy storage devices, it is increasingly necessary to study the impact of energy storage devices on wind power operational capacity credit. The definition of wind power operational capacity credit is given. The available capacity model of different generators and the charging and discharging model of the energy storage are established. Based on the above model, the evaluation method of wind power operation credible capacity considering energy storage devices is proposed. The influence of energy storage on the wind power operation credible capacity is obtained by case study, which is of great help for the power system dispatching operation and wind power accommodation.

The rapid development of metro transit systems brings very significant energy consumption, and the high service frequency of metro trains increases the peak power requirement, which affects the operation of systems. Train scheduling optimization is an effective method to reduce energy consumption and substation peak power by adjusting timetable parameters. This paper proposes a train timetable optimization model to coordinate the operation of trains. The overlap time between accelerating and braking phases is maximized to improve the utilization of regenerative braking energy (RBE). Meanwhile, the overlap time between accelerating phases is minimized to reduce the substation peak power. In addition, the timetable optimization model is rebuilt into a mixed integer linear programming model by introducing logical and auxiliary variables, which can be solved by related solvers effectively. Case studies based on one of Guangzhou Metro Lines indicate that, for all-day operation, the utilization of RBE would likely be improved on the order of 23%, the substation energy consumption would likely be reduced on the order of 14%, and the duration of substation peak power would likely be reduced on the order of 66%.

AbstractRecent crises - both economic and geopolitical - and the rise of new competitors in the form of low-cost carriers and Middle East carriers have put a heavy strain on the profitability of traditional legacy airlines worldwide. Many airlines are struggling to survive and are looking for ways to cut their operational costs.Continuously increasing fuel prices further contribute to the financial difficulties, and although airlines (and aircraft manufacturers alike) have put a significant effort on reducing the operational fuel consumption, fuel still accounts for approximately 35% of airlines’ operating expenses. Therefore many airlines seek new ways to further reduce the operational costs through improved fuel efficiency.One of the less self-evident methods to potentially significantly reduce the total operational fuel consumption is the introduction of intermediate refueling stops. Previous studies have already shown that operating existing aircraft on a long-haul flight with one or two intermediate stops can lead to potential fuel savings varying from 5% to 25% by reducing the additional fuel burn on long-haul flights referred to as transport loss. On the other hand, the concept of intermediate stop operations will also affect the operational costs through higher landing fees, an increased required maintenance effort, a longer total flight time and different crew costs. As previous studies have not addressed the additional costs or benefits of intermediate stop operations, this study aims to identify the total potential of the concept.For this purpose, a software tool was developed to analyze individual long-haul origin-destination pairs to identify the optimal operation: either direct or including an intermediate stop. Within the tool crew cost, maintenance cost and local fuel prices are determined for simulated flights according to typical operating procedures. A Dijkstra's algorithm then selects the most suitable and cost-efficient airport from a large database if an intermediate stop proves a viable option for the city-pair.A number of case studies has shown that although in all cases intermediate stops proved beneficial to reduce the total fuel burn, reducing the total operating cost depended highly on city-pair specific conditions, mainly the local fuel prices, changed crew-composition and wind direction. Still, the case studies do indicate that the concept of intermediate stop operations may offer significant cost reductions for many typical long-haul flights across the world, and could prove a viable concept to gain a competitive advantage for specific airlines and routes.

Limitation of CO2 emission is one of the main goals and regulations introduced by the international institutions’ rules. In the case of ships using oil-related and gas fuels this problem is dealt with by the International Maritime Organization (IMO) introducing the methodology of Energy Efficiency Operational Indicator (EEOI) determining for ships being under exploitation. The methodology allows for determining EEOI for seven types of ships, for which the value of this index depends on the amount of transported cargo or number of passengers, type of and amount of fuel used, as well as distance travelled by the ship. Such a methodology cannot be used for the specialized ships, whose exploitation tasks are different to the ships of the trade fleet that transport the cargo or the passengers. The methodology allows for determining EEOI for seven types of ships and it does not include specialized ships. The article presents a new methodology of determining EEOI for specialized ships that takes the characteristics of their exploitation into consideration. The way of its use has been presented taking into account the results of exploitation studies carried out on the chosen research and training ship. Obtained results and their analysis allowed for energy efficiency assessment of research and training ships depending on exploitation tasks, voyage time, type of fuel used, distance travelled and ship’s speed. EEOI index value determines energy efficiency of the vessel power system that is directly connected to the amount of the liquid or gas fuel used and the amount of emitted CO2. The aim should be to minimalize the value of EEOI index through planning of the exploitation tasks realization order and adjusting the speed of the ship as well as realization time of particular exploitation tasks, in the case of specialized ships. The analysis results can also be used when managing energy efficiency of these types of ships.

Fuel efficiency is vital for commercial airlines as fuel is one of the most costly items for airline operations. This study aims to compare fuel efficiencies of selected airlines around the globe and to build a benchmark of fuel efficiency that can be referred to by airlines. By using data on fuel consumption and traffic output collected from various sources including airline annual reports, environmental reports and sustainability reports, this study calculated fuel efficiencies measured by liters of fuel consumed per revenue tonne kilometer (RTK) for the selected airlines in the calendar year 2011 or financial year 2010–2011. Airlines were also compared and ranked by their respective fuel efficiencies. It was found that, depending on whether the passenger equivalent freight mass (PEFM) was 91 kg or 160 kg, the average fuel efficiency of the airlines studied is 0.4 L/RTK or 0.278 L/RTK, respectively. Variances in fuel efficiency among airlines from different regions and airlines of different business models were also found by this study.

Abstract In the daily operation of metro systems, the train scheduling problem aims to find a set of space-time paths for multiple trains that determine their departure and arrival times at metro stations, while train operations are in charge of selecting the best operational speed to satisfy the punctuality and operation costs. Different from the most existing researches that treat these two problems separately, this paper proposes an integrated approach for the train scheduling problem on a bi-direction urban metro line in order to minimize the operational costs (i.e., energy consumption) and passenger waiting time. More specifically, we simultaneously consider (1) the train operational velocity choices that correspond to the energy consumption of trains on each travelling arc, and (2) the dynamic passenger demands at each station for the calculation of total passenger waiting time in the planning horizon. By employing a space-time network representation in the formulations, this complex train scheduling and control problem with dynamic passenger demands is rigorously formulated into two optimization models with linear forms. The first model is an integer programming model that jointly minimizes train traction energy consumption and passenger waiting time. The second model, which is formulated as a mixed-integer programming model, further considers the utilization of regenerative braking energy on the basis of the first model. Due to the computational complexity of these two models, especially for large-scale real-world instances, we develop a Lagrangian relaxation (LR)-based heuristic algorithm that decomposes the primal problem into two sets of subproblems and thus enables to find a good solution in short computational time. Finally, two sets of numerical experiments, involving a relatively small-scale case and a real-world instance based on the operation data of Beijing metro are implemented to verify the effectiveness of the proposed approaches.