Analysis of spatial fixed PV arrays configurations to maximize energy harvesting in BIPV applications

This paper presents a new approach for efficient utilization of building integrated photovoltaic (BIPV) systems under partial shading conditions in urban areas. The aim of this study is to find out the best electrical configuration by analyzing annual energy generation of the same BIPV system, in terms of nominal power, without changing physical locations of the PV modules in the PV arrays. For this purpose, the spatial structure of the PV system including the PV modules and the surrounding obstacles is taken into account on the basis of virtual reality environment. In this study, chimneys which are located on the residential roof-top area are considered to create the effect of shading over the PV array. The locations of PV modules are kept stationary, which is the main point of this paper, while comparing the performances of the configurations with the same surrounding obstacles that causes partial shading conditions. The same spatial structure with twelve distinct PV array configurations is considered. The same settling conditions on the roof-top area allow fair comparisons between PV array configurations. The payback time analysis is also performed with considering local and global maximum power points (MPPs) of PV arrays by comparing the annual energy yield of the different configurationsPeer ReviewedPostprint (author’s final draft

DETERMINATION OF OPTIMUM PENETRATION LEVEL IN THE DISTRIBUTED GENERATION INTEGRATED POWER SYSTEMS

Bu çalışmada, dağıtılmış enerji üretim tesisleri (DEÜ) entegre edilmiş elektrik şebekelerinin daha güvenilir çalıştırılabilmesine ve yönetilebilmesine yardımcı olması noktasında bazı kurallar geliştirilebilmesi amacıyla üç farklı şebeke üzerinde farklı sayıdaki DEÜ tesislerinin optimum katılım oranlarının (KO) ve bağlanma noktalarının belirlenmesine yönelik analizler yapılmıştır. DEÜ entegre edilmiş şebekelerin detaylı bir analizi yapılmaksızın şebekeye rastgele dahil edilmesi şebekenin güvenilirliğinin ve veriminin azalmasına neden olabilmektedir. DEÜ konsepti her ne kadar şebeke kayıplarında azalma ve gerilim profillerinde iyileştirmeye yardımcı olsa da, mevcut iletim hatlarının kapasiteleri bazı KO seviyelerinde yetersiz kalabilmektedir. Bu nedenle, bu çalışmada şebeke kayıpları ve gerilimlerin yanı sıra mevcut hat kapasiteleri de analizlerde dikkate alınmıştır. Bu bağlamda, tek ve birden fazla DEÜ bağlantılarında bir eşik KO değerinin olup olmadığı araştırılmıştır. Optimizasyon sonuçları neticesinde, şebeke planlaması açısından bazı temel kuralların elde edilmesi amacıyla şebeke kayıpları minimize edilirken gerilim profili ve hat akışları IEEE test şebekeleri üzerinde gözlemlenmiştir. In this study, the optimization of the penetration level and allocation of distributed generation (DG) in single- and multiple- DG concepts are investigated on three typical test networks in order to obtain more reliable DG-integrated power system and develop some rules to be used at network management centers. An improper integration of DG units, without detailed analysis, decreases the reliability and efficiency of power networks. Although DGs can decrease power loss and improve voltage profile, they can cause the congestion on transmission lines at some penetration levels. For this reason, line flows are also considered besides power loss and voltage profile in this paper. In this manner, a threshold penetration level is investigated by considering both single- and multiple- DG concepts. According to the results of optimization, voltage profiles and line flows are observed on the IEEE test networks while minimizing power loss in order to reveal some rules in terms of power system plannin

Performance enhancement of photovoltaic array through string and central based MPPT system under non-uniform irradiance conditions

Energy Conversion and Management, Vol. 62, No. 10, pp. 131???140, 2012Mismatching losses reduction of photovoltaic (PV) array has been intensively discussed through the increasing penetration of residential and commercial PV systems. Many causes of mismatching losses have been identified and plenty of proposed methods to solve this problem have been recently proposed. This paper deals with reducing method of mismatching losses due to the non-uniform irradiance conditions. It is well-known that a certain number of multiple peaks occur on the power???voltage curve as the number of PV modules in one-string increases under non-uniform operating conditions. Since the conventional control method only drives the operating points of PV system to the local maxima close to open circuit voltage, only small portion of power can be extracted from the PV system. In this study, a radial basis function neural network (RBF-ANN) based intelligent control method is utilized to map the global operating voltage and non-irradiance operating condition in string and central based MPPT systems. The proposed method has been tested on 10 x 3 (2.2 kW), 15 x 3 (2.5 kW) and 20 x 3 (3.3 kW) of series???parallel PV array configuration under random-shaded and continuous-shaded patterns. The proposed method is compared with the ideal case and conventional method through a simple power-voltage curve of PV arrays. The simulation results show that there are significant increases of about 30-60% of the extracted power in one operating condition when the proposed method is able to shift the operating voltage of modules to their optimum voltages

Big Data Meets Telcos: A Proactive Caching Perspective

Mobile cellular networks are becoming increasingly complex to manage while classical deployment/optimization techniques and current solutions (i.e., cell densification, acquiring more spectrum, etc.) are cost-ineffective and thus seen as stopgaps. This calls for development of novel approaches that leverage recent advances in storage/memory, context-awareness, edge/cloud computing, and falls into framework of big data. However, the big data by itself is yet another complex phenomena to handle and comes with its notorious 4V: velocity, voracity, volume and variety. In this work, we address these issues in optimization of 5G wireless networks via the notion of proactive caching at the base stations. In particular, we investigate the gains of proactive caching in terms of backhaul offloadings and request satisfactions, while tackling the large-amount of available data for content popularity estimation. In order to estimate the content popularity, we first collect users' mobile traffic data from a Turkish telecom operator from several base stations in hours of time interval. Then, an analysis is carried out locally on a big data platform and the gains of proactive caching at the base stations are investigated via numerical simulations. It turns out that several gains are possible depending on the level of available information and storage size. For instance, with 10% of content ratings and 15.4 Gbyte of storage size (87% of total catalog size), proactive caching achieves 100% of request satisfaction and offloads 98% of the backhaul when considering 16 base stations.Comment: 8 pages, 5 figure

Big Data Caching for Networking: Moving from Cloud to Edge

In order to cope with the relentless data tsunami in $5G$ wireless networks, current approaches such as acquiring new spectrum, deploying more base stations (BSs) and increasing nodes in mobile packet core networks are becoming ineffective in terms of scalability, cost and flexibility. In this regard, context-aware $5$G networks with edge/cloud computing and exploitation of \emph{big data} analytics can yield significant gains to mobile operators. In this article, proactive content caching in $5$G wireless networks is investigated in which a big data-enabled architecture is proposed. In this practical architecture, vast amount of data is harnessed for content popularity estimation and strategic contents are cached at the BSs to achieve higher users' satisfaction and backhaul offloading. To validate the proposed solution, we consider a real-world case study where several hours of mobile data traffic is collected from a major telecom operator in Turkey and a big data-enabled analysis is carried out leveraging tools from machine learning. Based on the available information and storage capacity, numerical studies show that several gains are achieved both in terms of users' satisfaction and backhaul offloading. For example, in the case of $16$ BSs with $30\%$ of content ratings and $13$ Gbyte of storage size ($78\%$ of total library size), proactive caching yields $100\%$ of users' satisfaction and offloads $98\%$ of the backhaul.Comment: accepted for publication in IEEE Communications Magazine, Special Issue on Communications, Caching, and Computing for Content-Centric Mobile Network

Fuzzy wavelet network identification of optimum operating point of non-crystalline silicon solar cells

The emerging non-crystalline silicon (c-Si) solar cell technologies are starting to make significant inroads into solar cell markets. Most of the researchers have focused on c-Si solar cell in maximum power points tracking applications of photovoltaic (PV) systems. However, the characteristics of non-c-Si solar cell technologies at maximum power point (MPP) have different trends in current???voltage characteristics. For this reason, determining the optimum operating point is very important for different solar cell technologies to increase the efficiency of PV systems. In this paper, it has been shown that the use of fuzzy system coupled with a discrete wavelet network in Takagi???Sugeno type model structure is capable of identifying the MPP voltage of different non-c-Si solar cells with very high accuracy. The performance of the fuzzy-wavelet network (FWN) method has been compared with other ANN structures, such as radial basis function (RBF), adaptive neuro-fuzzy inference system (ANFIS) and three layered feed-forward neural network (TFFN). The simulation results show that the single FWN architecture has superior approximation accuracy over the other methods and a very good generalization capability for different operating conditions and different technologie

Fiber radyo haberleşme sistemlerinde kılavuz-takipçi yanband enjeksiyon kilitleme tekniği ve erbium katkılı yükselticilerin etkisi

Bu tezin, veri tabanı üzerinden yayınlanma izni bulunmamaktadır. Yayınlanma izni olmayan tezlerin basılı kopyalarına Üniversite kütüphaneniz aracılığıyla (TÜBESS üzerinden) erişebilirsiniz.In this thesis, millimeter wave signals generation and modulation by using master-slave enjection locking technique has been studied. The wireless communications based on fiber-radio technologies are expected to find an increasing role in telecommunication networks over the next decade. Radio over fiber systems utilise optical fibre transmission to deliver radio signals directly to free space radiation. Deployment of this systems are dependent on the development of efficient and straightforward, optical generation, modulation and transmission of millimeter wave signals. Direct modulating of slave laser in a master/sieve optical sideband injection locking mm-wave generation scheme is investigated experimentally and therotically. It is shown that this modulation produces predominantly phase modulation on the 60GHz subcarrier for controlled levels of inj'ection and modulation powers, thereby providing a simple method for information transmission. The EDFA gain-tilt effect in the amplification of mm-wave modulated signals have been investigated experimentally. It is found that the EDFA gain-tilt is negligible over the operating wavelength range and has no effect on the information signals carried on the mm-wave subcarrier.as it could not be detected within the sensitivity. Keywords: Fiber optic,milimeter wave generation, modulation, EDFA.V ÖZET FİBER-RADYO HEBERLEŞME SİSTEMLERİNDE KILAVUZ - TAKİPÇİ YANBAND ENJEKSİYON KİLİTLEME TEKNİĞİ VE ERBİUM KATKILI YÜKSELTİCİLERİN ETKİSİ KARATEPE, Engin Yüksek Lisans Tezi, Elektrik-Elektronik Mühendisliği Bölümü Tez Yöneticisi: Yrd. Doç. Dr. Gökalp KAHRAMAN Şubat, 2000, 63 sayfa Bu tez çalışmasında optik metodlarla milimetredalga sinyali elde etme motodlarından kılavuz/takipçi yanband enjeksiyon kilitleme tekniği incelenmiştir. Fiber-radyo haberleşme sistemleri üzerine kurulu kablosuz haberleşme sistemleri önümüzdeki yüzyılda çok büyük bir rol üstlenecektir. Fiber radyo sistemlerinde iletilmek istenen sinyaller fiber kablolar üzerinden istenen anten ünitelerine iletilirler. Bu sistemlerin gelişimi milimetre dalga sinyallerinin optik üretiminine, modülasyonuna ve iletilme tekniklerinin geliştirilmesine bağlıdır. Kılavuz-takipçî yanband enjekîyon kilitleme tekniğinde takipçi lazer doğrudan modüle edildiğinde elde edilen sinyal üzerinde teorik ve deneysel çalışmalar yapılmıştır. Elde edilen sonuçlar 60GHz mm-dalga sinyali üzerindeki modülasyon tipinin, modülasyon ve takipçi lazere enjekte edilen güçlere bağımlı olduğu ve yüksek güçlerde faz modülasyon elde edilebildiğini göstermiştir. Yapılan deneyler sonucu EDFA kazanç eğiminden kaynaklanabilecek gürültünün çalışılan dalgaboyu aralığında ihmal edilebilir olduğu anlaşılmıştır

Fotovoltaik jeneratörlerin kısmi gölgelenme ve uyumsuzluk koşullarında bulanık mantık kontrolör ile maksimum güç noktası kontrolü ve farklı sistem konfigürasyonlarının karşılaştırılması

Bu tez çalışmasının ilk aşamasında farklı sıcaklık ve ışınım koşulları için güneş pili tek diyot eşdeğer devre parametrelerinin değişimi incelenmiş ve yapay sinir ağları tabanlı yeni bir model geliştirilmiştir. Tezin ikinci aşamasında, geliştirilen güneş pili modeli kullanılarak, seriparalel, tam-çapraz, ve köprü bağlantı konfigürasyonlarında fotovoltaik (PV) örgülerin kısmi gölgelenme ve elektriksel uyumsuzluk koşullarına verdiği cevap, sistem verimi ve maksimum güç noktası takibi geriliminin değişim aralığı açısından ayrıntılı olarak analiz edilmiştir ve birbirleriyle karşılaştırılmıştır. Tezin üçüncü aşamasında, kısmi gölgelenmeden dolayı oluşan güç kayıplarını azaltmak için yeni bir kontrol sistemi önerilmiştir. PV örgüdeki her bir kola, giriş gücünü PV örgünün çıkışından alan bir DC/DC dönüştürücü bağlanarak oluşturulan bu sistem, belirli bir seviyede gölgelenmiş modülleri devre dışı bırakarak, PV sistemi yerel maksimum güç noktalarına takılmadan çalıştırabilmektedir. DC/DC dönüştürücünün kontrolünde bulanık mantık kullanılmıştır