Browsing by Author "Peker, Meltem"

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Open Access
A robust Logistics-Electric framework for optimal power management of electrified ports under uncertain vessel arrival time
(Elsevier Ltd, 2024-01-18) Sarantakos, I.; Nikkhah, S.; Peker, Meltem; Bowkett, A.; Sayfutdinov, T.; Alahyari, A.; Patsios, C.; Mangan, J.; Allahham, A.; Bougioukou, E.; Murphy, A.; Pazouki, K.
Maritime transport is responsible for producing a considerable amount of environmental pollution due to the reliance of ports and ships on the carbon-based energy sources. With the increasing trend towards port electrification to reduce carbon emissions, the operation of ports will be increasingly relying on the electricity network. This interconnection creates multiple challenges due to the complexity of power flow in the port network, uncertainty of vessel arrival time and fluctuation of power generation of renewable energy sources. These uncertainties can lead to an overload in electricity networks and delays in cargo-handling activities, resulting in increased vessel handling times and environmental emissions. This paper presents a joint logistics-electric framework for optimal operation and power management of electrified ports, considering multiple uncertainties in the arrival time of vessels, network demand, and renewable power generation. An optimal power flow method is developed for a real-life port, with consideration for multiple port logistic assets such as cargo handling equipment, reefers, and renewable energy sources. The proposed model ensures feasible port operation for all uncertainty realisations defined by robust optimisation, while minimising operational costs. Simulation results demonstrate that the probability of a network constraint violation can be as high as 70% for an electrified major UK port if the uncertainty in the port operation is neglected, presenting an unacceptable risk of disruption to port activities. Furthermore, such uncertainty can cause 150% increase in emissions if the ships use their auxiliary engine instead of using shore power. The numerical study shows that such challenges can be handled by a 0.3% increase in the robustness in face of uncertainty, while the cost increase in the worst case does not exceed 4.7%. This shows the effectiveness of the proposed method enhancing robustness against uncertainty at the minimum cost.
Open Access
Benefits of transmission switching and energy storage in power systems with high renewable energy penetration
(Elsevier, 2018) Peker, Meltem; Kocaman, Ayşe Selin; Kara, Bahar Y.
Increasing the share of renewable energy sources in electricity generation helps address concerns about carbon emissions, global warming and energy security (i.e. dependence on fossil fuels). However, integrating intermittent and variable energy sources into the grid imposes new challenges for power system reliability and stability. To use these clean sources in electricity generation without endangering power systems, utilities can implement various control mechanisms, such as energy storage systems, demand side management, renewable energy curtailment and transmission switching. This paper introduces a two-stage stochastic programming model that co-optimizes transmission switching operations, and transmission and storage investments subject to limitations on load shedding and curtailment amounts. We discuss the effect of transmission switching on the total investment and operational costs, siting and sizing decisions of energy storage systems, and load shedding and renewable energy curtailment in a power system with high renewable penetration. An extensive computational study on the IEEE 24-bus power system with wind and solar as available renewable sources demonstrates that the total cost and total capacity of energy storage systems can be decreased up to 17% and 50%, respectively, when transmission switching is incorporated into the power system.
Open Access
Covering vehicle routing problem: application for mobile child friendly spaces for refugees
(Springer, 2021-02) Buluc, Elfe; Peker, Meltem; Kara, Bahar Y.; Dora, M.
The world is facing a large-scale refugee crisis because of the ongoing war in Syria, and it is important to improve refugees’ life conditions from a humanitarian point of view. In order to analyse the living conditions of refugees, we conduct fieldwork in a district in Ankara, Turkey, and interview refugees, the local population and humanitarian practitioners from several organizations. Among the many challenges refugees face, we observe that addressing the problems of refugee children is critical. Thus, in this study, we focus on increasing the efficiency of the education services provided to refugee children. We investigate a service provided via mobile trucks that supply informal education and psychological support to children. By analysing the operational dynamics of these trucks, we introduce two problems to the logistics literature, which we refer to as the covering vehicle routing problem and the covering vehicle routing problem with integrated tours. In the first problem, we either visit or cover all nodes, such that every node not in one of the tours is within a predetermined distance of any visited node. In the second problem, we generate smaller tours for covered (or unvisited) nodes originated at the visited ones. We first propose mathematical models for the problems and then introduce heuristic methods to overcome the computational challenge of the second problem. In the computational study, we compare the optimal solutions obtained using the models with a solution of real-life application. We then test the models and heuristics on medium and large real data sets gathered from Turkey and conduct sensitivity analysis on the model parameters.
Open Access
Green hub location problem
(Elsevier, 2019) Dükkancı, Okan; Peker, Meltem; Kara, Bahar Y.
This paper introduces the green hub location problem that finds the best locations for hubs, assignments of demand nodes to these hubs and speed of trucks/flights so as to route the demand between any origin-destination pairs. The aim of the service provider is to minimize the total amount of emissions that depends on vehicle speed and payload while routing the deliveries within a predetermined service time limit. In this study, we first propose a nonlinear model for this problem, which is then reformulated as a second order cone programming formulation. We strengthen the new model by using perspective reformulation approach. An extensive computational study on the CAB and TR datasets demonstrates the benefits of incorporating green transportation service activities to the classic hub location problems. We also provide insights for the carrier companies by analyzing the solutions with different discount factors, service time limits and number of hubs.
Open Access
Optimizing vaccine delivery with drones for hard-to-reach regions
(I E E E Computer Society, 2024-01-06) Campbell, James F.; Kara, Bahar; Li, Haitao; Enayati, Shakiba; Peker, Meltem; Akenroye, Temi
This research optimizes the use of drones, alongside other transport modes, for delivery of routine childhood vaccines subject to cold chain requirements. We focus on the value of drones to improve vaccine deliveries for hard-to-reach regions. This paper first briefly describes optimization of country-level vaccine distribution from national depots to local health zone distributions centers (DCs) using both large and small drones, along with boats, trucks and planes. Then we focus on research on optimizing local vaccine delivery within one health zone, from the DC to remote aid posts, using small drones, along with walking, boats and trucks. Results using data for the island nation of Vanuatu show that drones can be very useful for vaccine delivery to replace current transportation options, and to resupply health workers with fresh vaccines at remote sites to allow more efficient health worker outreach trips. © 2024 IEEE Computer Society. All rights reserved.
Open Access
P-hub maximal covering problem and extensions for gradual decay functions
(2013) Peker, Meltem
Hubs are special facilities that serve as switching, transshipment and sorting nodes in many to many distribution systems. The hub location problem deals with the selection of the locations of hub facilities and finding assignments of demand nodes to hubs simultaneously. The p-hub maximal covering problem, that is one of the variations of the hub location problems, aims to find locations of hubs so as to maximize the covered demand that are within the coverage distance with a predetermined number of hubs. In the literature of hub location, p-hub maximal covering problem is conducted in the framework of only binary coverage; origin-destination pairs are covered if the total path length is less than coverage distance and not covered at all if the path length exceeds the coverage distance. Throughout this thesis, we extend the definition of coverage and introduce “partial coverage” that changes with the distance, to the hub location literature. In this thesis, we study the p-hub maximal covering problem for single and multiple allocations and provide new formulations that are also valid for partial coverage. The problems are proved to be NP-Hard. We even show that assignment problem with a given set of hubs for the single allocation version of the problem is also NP-Hard. Computational results for all the proposed formulations with different data sets are presented and discussed.
Open Access
The shuffled conic power flow equations: an improved angle-inclusive conic model
(Institute of Electrical and Electronics Engineer, 2023-09-25) Zografou-Barredo N. M.; Peker, Meltem; Greenwood, D. M.
This paper presents the Shuffled Conic Power Flow (PF) equations which enable a novel voltage angle substitution within a second-order cone (SOC) PF model. Computational experiments compare the performance of the novel voltage angle substitution against a conventional approximation used to model voltage angles within a state-of-the-art SOC PF model. Solving the PF problem for four radial distribution networks and the optimal power flow (OPF) problem for four demand scenarios in one of these networks, we show the following. First, voltage angles were improved in around 95% of cases when solving the PF problem and around 96% of cases when solving the OPF problem. Second, there is a particular improvement in voltage angles when voltage magnitudes divert from 1 p.u., and when there is demand growth. The results are also compared to benchmark software, Matpower.
Open Access
A two-stage stochastic programming approach for reliability constrained power system expansion planning
(Elsevier, 2018) Peker, Meltem; Kocaman, Ayşe Selin; Kara, Bahar Yetiş
Probabilistic realizations of outages and their effects on the operational costs are highly overlooked aspects in power system expansion planning. Since the effect of randomness in contingencies can be more prominent especially when transmission switching is considered, in this paper we introduce contingency-dependent transmission switching concept to ensure N-1 criterion. To include randomness of outages and the outputs (i.e. flow on the lines/generation amounts) during the outages, we represent each contingency by a single scenario. Status of transmission lines, generation amounts and power flow decisions are defined as recourse actions of our two-stage stochastic model, therefore, expected operational cost during the contingencies are taken into account in a more accurate manner. A solution methodology with a filtering technique is also proposed to overcome the computational burden. The model and the solution methodology are tested on the IEEE Reliability Test System and IEEE 118-bus power system and the results show that the solution method finds the solutions for these power systems in significantly shorter solution times. The solution method is also tested on a new data set for the 380-kV Turkish transmission network. Suggestions for possible extensions of the problem and the modifications of the solution approach to handle these extensions are also discussed.