Browsing by Subject "Electricity"

Now showing 1 - 6 of 6

Open Access
A dynamic multi-level iterative algorithm for clearing European electricity day-ahead markets: an application to the Turkish market
(Taylor and Francis Ltd., 2023-05-12) Büke, B.; Sayın, M.; Tanrısever, Fehmi
Designing and clearing day-ahead electricity market auctions have recently received significant attention from academia and practice alike. Given the size and the complexity of day-ahead market auctions, clearing them within the time limits imposed by the market is a major practical concern. In this paper, we model all the practical details of the Turkish day-ahead electricity market and provide a new multi-level iterative heuristic to clear the market. We compare our results with a commercial solver using data provided by Energy Exchange Istanbul. Our heuristic achieves an average optimality gap less than 0.09%, with an average solution time of just 14 s; whereas the commercial solver takes, on average, 18 min (and in some cases up to three hours) to find the optimal solution. We also demonstrate that using our heuristic solution to warm-start the commercial solver further reduces the solution time by 25%, on average. Overall, our heuristic proves to be very efficient in clearing the Turkish day-ahead market. We also test the performance of our algorithm as the problem size grows.
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Cumhuriyet'in ilk termik santrali: ÇATES
(Bilkent University, 2020) Bulat, Doğa; Yılmazer, Emine İpek; Aydemir, Fehmican; Mandaf, Ilgın Tutku; Oburaş, Yağmur
1948 yılında Zonguldak ilinin Çatalağzı beldesinde kurulan Çatalağzı Termik Santrali A ünitesi (ÇATES A) döneminin en büyük sanayi yatırımlarından biri olmasını yanı sıra Türkiye'nin elektrik üretimi için attığı ilk adım olmuştur. Kırk üç sene boyunca Anadolu'yu aydınlatan ÇATES A, ekonomik ömrünü 1991 yılında tamamlamıştır. Ardından, aynı yıl devreye alınan ÇATES B elektrik üretimine başlamıştır. Değişen ekonomik ve sosyal koşullar sebebiyle 2014 yılında özelleştirilen ÇATES B, son zamanlarda elektrik üretimine olan katkısından çok bulunduğu çevreye ve çevre halkı üzerine olan etkileriyle gündeme gelmektedir. Bacalarında filtre bulunmadığı gerekçesi ile mühürlenen santral 2020 yılının Ocak ayından itibaren çalışmamaktadır.
Open Access
Experimental verification of metamaterial loaded small patch antennas
(Emerald Group Publishing Limited, 2013) Alici, K. B.; Caliskan, M. D.; Özbay, Ekmel; Bilotti, F.; Toscano, A.; Vegni, L.
Purpose - Metamaterial unit cells composed of deep subwavelength resonators brought up new aspects to the antenna miniaturization problem. The paper experimentally demonstrates a metamaterial-inspired miniaturization method for circular patch antennas. In the proposed layouts, the space between the patch and the ground plane is filled with a proper metamaterial composed of either multiple split-ring or spiral resonators (SRs). The authors have manufactured two different patch antennas, achieving an electrical size of ?/3.69 and ?/8.26, respectively. The paper aims to discuss these issues. Design/methodology/ approach - The operation of such a radiative component has been predicted by using a simple theoretical formulation based on the cavity model. The experimental characterization of the antenna has been performed by using a HP8510C vector network analyzer, standard horn antennas, automated rotary stages, coaxial cables with 50 O characteristic impedance and absorbers. Before the characterization measurements we performed a full two-port calibration. Findings - Electrically small circular patch antennas loaded with single layer metamaterials experimentally demonstrated to acceptable figures of merit for applications. The proposed miniaturization technique is potentially promising for antenna applications and the results presented in the paper constitute a relevant proof for the usefulness of the metamaterial concepts in antenna miniaturization problems. Originality/value - Rigorous experimental characterization of several meta material loaded antennas and proof of principle results were provided. Copyright © 2013 Emerald Group Publishing Limited. All rights reserved.
Open Access
Futures hedging in electricity retailing
(Springer, 2022-09) Tanrısever, Fehmi; Büke, B.; Jongen, G.
This paper is concerned with the risk management practices of an electricity retailer motivated by the Dutch electricity market. We examine the effectiveness of the existing base- and peak-load futures contracts as a risk management tool for the electricity retailers. We analytically characterize the retailer’s optimal hedging policy as a function of the serial correlation of the prices and the demand profiles of its customers. We find that the retailer typically over-hedges in the futures market, and the over-hedging amount increases when both base- and peak-load contracts are used. Our findings indicate that although the existing contracts in the futures market are quite efficient to replicate the exposure from profiled customers, when industrial consumers and renewable generation are included to the retailer’s portfolio, the effectiveness of such contracts decreases substantially. In our motivating example, hedging the risk of the profiled customers with base-load contracts, the firm may reduce the variance of its cash flows by 85.9%. In addition to the base-load contracts, including peak-load contracts into the hedging portfolio of the retailer increases the efficiency of hedging to 89.3%. However, when we consider the aggregate portfolio of the retailer including profiled customers, industrial consumers and renewable contracts, the efficiency of hedging through the existing futures contracts goes down as low as 32.8% during certain periods. © 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
Open Access
Molecular entrapment of volatile organic compounds (VOCs) by electrospun cyclodextrin nanofibers
(Elsevier, 2016-02) Celebioglu A.; Sen, H. S.; Durgun, Engin; Uyar, Tamer
In this paper, we reported the molecular entrapment performance of hydroxypropyl-beta-cyclodextrin (HPβCD) and hydroxypropyl-gamma-cyclodextrin (HPγCD) electrospun nanofibers (NF) for two common volatile organic compounds (VOCs); aniline and benzene. The encapsulation efficiency of CD samples were investigated depending on the various factors such as; CD form (NF and powder), electrospinning solvent (DMF and water), CD (HPβCD and HPγCD) and VOCs (aniline and benzene) types. BET analysis indicated that, electrospun CD NF have higher surface area compared to their powder form. In addition DMA measurement provided information about the mechanical properties of CD NF. The encapsulation capability of CD NF and CD powder was investigated by 1H-NMR and HPLC techniques. The observed results suggested that, CD NF can entrap higher amount of VOCs from surroundings compared to their powder forms. Besides, molecular entrapment efficiency of CD NF also depends on CD, solvent and VOCs types. The inclusion complexation between CD and VOCs was determined by using TGA technique, from the higher decomposition temperature of VOCs. Finally, our results were fortified by the modeling studies which indicated the complexation efficiency variations between CD and VOC types. Here, the inclusion complexation ability of CD molecules was combined with very high surface area and versatile features of CD NF. So these findings revealed that, electrospun CD NF can serve as useful filtering material for air filtration purposes due to their molecular entrapment capability of VOCs.
Open Access
Resonant and coherent transport through Aharonov-Bohm interferometers with coupled quantum dots
(The American Physical Society, 2005) Moldoveanu, V.; Ţolea, M.; Aldea, A.; Tanatar, Bilal
A detailed description of the tunneling processes within Aharonov-Bohm (AB) rings containing two-dimensional quantum dots is presented. We show that the electronic propagation through the interferometer is controlled by the spectral properties of the embedded dots and by their coupling with the ring. The transmittance of the interferometer is computed by the Landauer-Büttiker formula. Numerical results are presented for an AB interferometer containing two coupled dots. The charging diagrams for a double-dot interferometer and the Aharonov-Bohm oscillations are obtained, in agreement with the recent experimental results of Holleitner et al. [Phys. Rev. Lett. 87, 256802 (2001)] We identify conditions in which the system shows Fano line shapes. The direction of the asymetric tail depends on the capacitive coupling and on the magnetic field. We discuss our results in connection with the experiments of Kobayashi et al. [Phys. Rev. Lett. 88, 256806 (2002)] in the case of a single dot. ©2005 The American Physical Society.