• Energy Research

Modern societies need energy to satisfy needs such as protection, security, and housing. Fossil fuels are used to meet this energy demand created by a soaring population. But as we all know, fossil fuels are limited and will be extinct in the near future. Also, using fossil fuels causes emission of greenhouse gases such as carbon dioxide, sulfur dioxide, and nitrous oxide. The rapid increase of fossil fuel consumption creates dust and soot which in turn cause environmental pollution that results in deaths; and emission of carbon dioxide and greenhouse gases ruin the ecosystem, causing climate changes that are threatening life itself on the entire planet. Therefore, heading towards alternative energy sources is almost obligatory. Our country has fossil fuel resources like hard coal, lignite, asphaltite, crude oil, natural gas, uranium, and thorium; and potential renewable sources like hydraulic energy, geothermal energy, solar energy, sea wave energy, and biomass energy. The sun is an endless, eco-friendly renewable energy source, and when it comes to solar energy, Turkey is one of the luckiest countries in the world. One of the technologies for benefiting from solar energy is a photovoltaic system, and it's becoming widespread day by day. The purpose of this study is to create a guide for both consumers and designers, referring to the usage of photovoltaic systems as shading components on buildings. For preparation of this study, literature review and computer simulation methods are used accordingly. This study consists of five sections. First section contains the introduction part, where the purpose, extent and the method of the study are presented. In the second section, the importance of the sun as a renewable energy source, solar energy potential in Turkey and in the world, and the systems being used for realizing this potential are explained; and as one of these systems, amount of usage of photovoltaic systems in our country and other countries are mentioned. In the third section, history, structure and working, components, production methods and types of photovoltaic systems were examined, and by emphasizing how these systems were used on buildings, the parameters affecting the system performance were discussed. Fourth section contains the application study by simulation method. Steps of this study are as follows:  Fixed and variable data are determined for the building model to be used in the simulation. - Fixed data: The modeled building is assumed to be used as an open office. It's square shaped with the dimensions of 24x24 meters, and consists of 10 floors. Each floor has a height of three meters. Total construction area is 5.760 square meters. A total of 290 people work in the building and working hours are between 08.00 and 17.00 on weekdays. An air conditioning system is used for heating and cooling the building, and the air is ventilated naturally. Heating system is activated if indoor temperature drops below 220, and cooling system is activated if indoor temperature rises above 260. The photovoltaic panels are made of polycrystalline silicon cells and 130 panels with 260Wp power are used. The installed power of the system is 33,8kWp. - Variable data: Five provinces are selected for the building location. These provinces are İzmir, İstanbul, Ankara, Van, and Erzurum. For the facade, directions of north, south, east and west are examined. Preferred inclination angles of photovoltaic panel are 00 and 300.  45 different alternatives are created using variable data.  Computer programs are selected to be used in the simulation. - Climate data of the provinces are gathered by Meteonorm; energy loads needed for the alternatives are calculated by Ecotect; and energy levels obtained by the photovoltaic panels are measured by Pvsol.  Simulation results for the created alternative are evaluated. - Evaluation of the results are explained by charts and comparisons under three major topics: necessary heating and cooling loads, PV system performance, and determining the benefit ratio of the PV system to the heating and cooling loads. After these evaluations, it can be argued that the location variable for the highest ratio is İzmir, the direction variable is south, and the inclination angle is 300. The fifth and the final section argues that based on the simulation and the results of the simulation, photovoltaic systems can be an important solution for meeting the energy demand by using solar energy, one of the renewable energy sources. Although photovoltaic systems have lots of applications in the world, they failed to gain enough popularity in our country, and considering their benefits of fulfilling the energy demands their use should be more encouraged. Toplumlar yaşamlarını sürdürebilmek için enerjiye ihtiyaç duymaktadır. Hızla artan nüfustan doğan enerji ihtiyacını karşılayabilmek için büyük ölçüde fosil yakıtlar kullanılmaktadır. Fosil yakıtların neden olduğu hava kirliliği, küresel ısınma, canlı türlerinin zarar görmesi gibi çevresel etkiler, günümüzde alternatif enerji kaynaklarına yönelmeyi zorunlu hale getirmiştir. Güneş tükenmeyen, çevre dostu yenilenebilir enerji kaynaklarından birisidir ve Türkiye güneş potansiyeli açısından dünyadaki en şanslı ülkelerden birisidir. Güneş enerjisinden faydalanmakta kullanılan teknolojilerden birisi olan fotovoltaik sistemler ise dünyada günden güne yaygınlaşmaktadır. Bu çalışmanın amacı, fotovoltaik sistemlerin binalarda gölgeleme bileşeni olarak kullanımına yönelik kullanıcı ve tasarımcılara yol gösterebilecek bir rehber oluşturmaktır. Bu doğrultuda çalışmanın hazırlanmasında kaynak taraması ve bilgisayar ile benzetim yöntemleri birlikte kullanılmıştır. Çalışma beş bölümden oluşmaktadır. İlk bölümde; çalışmanın amaç, kapsam ve yöntemine dair bilgilerin verildiği giriş kısmı yer almaktadır. İkinci bölümde; güneşin yenilenebilir enerji kaynakları içindeki önemi, Türkiye ve dünyadaki güneş enerjisi potansiyeli ve bu potansiyeli değerlendirebilmek amacıyla kullanılan sistemler anlatılmış, bunlardan birisi olan fotovoltaik sistemlerin ülkemizde ve diğer ülkelerde kullanım miktarlarına değinilmiştir. Üçüncü bölümde; fotovoltaik sistemlerin tarihçesi, yapısı ve çalışması, bileşenleri, üretim yöntemleri ve sistem türleri incelenmiş, binalarda kullanım şekilleri üzerinde durularak, sistem performansına etki eden parametreler ele alınmıştır. Dördüncü bölümde; benzetim yolu ile yapılan uygulama çalışması yer almaktadır. Öncelikle benzetimde kullanılacak bina modeli tasarlanarak bu model için sabit ve değişken veriler belirlenmiştir. Daha sonra değişken veriler doğrultusunda seçenekler oluşturulmuştur. Seçenekler için benzetim yoluyla elde edilen sonuçlar değerlendirilerek grafikler yardımıyla sonuçlar arasında karşılaştırmalar yapılmıştır. Beşinci ve son bölümde ise; uygulama bölümünde elde edilen sonuçlar doğrultusunda, fotovoltaik sistemlerin yenilenebilir enerji kaynaklarından güneş enerjisini kullanarak enerji ihtiyacını karşılamada önemli çözümler sağlayabileceği ortaya koyulmuştur. Dünyada birçok örneğine rastlanmasına rağmen ülkemizde henüz yeterince yaygınlaşmamış olan fotovoltaik sistemlerin enerji ihtiyacına sağladığı faydalar göz önünde bulundurularak kullanımının yaygınlaşması doğrultusunda teşvik edilmelidir. Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2015 Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2015 Yüksek Lisans M.Sc.

The power-voltage characteristic of photovoltaic (PV) arrays operating under partial-shading conditions exhibits multiple local maximum power points (MPPs). In this paper, a new method to track the global MPP is presented, which is based on controlling a dc/dc converter connected at the PV array output, such that it behaves as a constant input-power load. The proposed method has the advantage that it can be applied in either stand-alone or grid-connected PV systems comprising PV arrays with unknown electrical characteristics and does not require knowledge about the PV modules configuration within the PV array. The experimental results verify that the proposed global MPP method guarantees convergence to the global MPP under any partial-shading conditions. Compared with past-proposed methods, the global MPP tracking process is accomplished after far fewer PV array power perturbation steps.

Summarization: A methodology is proposed for the effective integration of photovoltaic (PV) devices into the electric utility distribution network operations. The dispersed PV generator is viewed as an active device used to improve system stability by appropriately modulating the power conditioning unit's output power. Disturbances on the utility system can be damped out by injecting this power into the grid in such a way so that the net effect is a cancellation of undesirable oscillations. The approach is implemented by monitoring the oscillating power and generating control signals which shape accordingly the interface unit's output power. Successful implementation of the scheme relies heavily on the speed and flexibility with which the electronic inverter moves power from the primary source/storage facility to the utility lines. Simulation studies, using the proposed control approach, indicate that application of these policies may result in reduced load following requirements for conventional power generating units, increase the value and acceptability of new energy technologies, and improve power quality and stability of the interconnected system. Παρουσιάστηκε στο: Energy Conversion, IEEE Transactions on Δημοσίευση σε επιστημονικό περιοδικό

The advancement in material science has enabled enormous develop-ments of photovoltaic technologies. From an architectural integration viewpoint, the mechanical flexibility of the photovoltaic products represents another key consider-ation, rather than cost and energy conversion efficiency only. This chapter presents descriptions of flexible substrates and thin-film photovoltaic, deepening the two key choices for the flexible photovoltaic in buildings, the thin film, as well as the organic one. This chapter includes the investigation of the main flexible substrate materials for PVs as well as the flexible PV module products. Considering the two important requirements for building applications, the higher transparencies upon visible lights, as well as the multiple color choices, the corresponding potentials and limits are highlighted. Additionally, the state of the art over the manufacturing and market of flexible photovoltaic are introduced. And a frame has been defined regarding the environmental impact assessment of organic photovoltaic technologies and flexible skins.

A method of sizing stand‐alone photovoltaic systems regarding the reliability to satisfy the load demand, economy of components, and discharge depth exploited by the batteries is presented in this work. Solar radiation data simulated by an appropriate stochastic time series model, and not actual measurements, are used in the sizing procedure. This offers two distinct advantages: (a) sizing can be performed even for locations where no actual data exist, (b) the influence of the variation of the statistical parameters of solar radiation in sizing can be examined. The method has been applied and tested for several representative locations all over Greece for which monthly daily average values of solar radiation are given by ELOT (Hellenic Organization of Standardization).

In this thesis, we will explore solar energy and its conversion into electrical energy, covering all components of the solar system and their functionalities. The first part of the study examines the role of solar energy for life on Earth. It provides a detailed analysis of how photovoltaic cells convert sunlight into electrical energy, including their development, operating principles, manufacturing, photovoltaic modules, and an extensive overview of system components. We showcase a photovoltaic power plant on buildings 1, 2, and 3, along with its characteristics. U ovom diplomskom radu upoznat ćemo se sunčevom energijom te pretvorbom u električnu energiju obradit ćemo sve komponente solarnog sustava i načine na koji rade. Prvi dio rada istražuje ulogu Sunčeve energije za život na Zemlji. Detaljno se analizira kako fotonaponske ćelije pretvaraju sunčevu svjetlost u električnu energiju, uz prikaz razvoja, principa rada, izrade, fotonaponskih modula te opsežan pregled sustava i njegovih dijelova. Prikazujemo fotonaponsku elektranu na zgradama 1, 2 i 3 te njezine karakteristike.

This study presents the performance behavior of bifacial photovoltaic (PV) modules in comparison to monofacial standard modules. The novelty lies in the fact to investigate the topic of irradiance enhancement. The impact of meteorological parameters on the performance of different bifacial photovoltaic module types of same cell type was determined. A cloud classification with sky imager was performed for clouds that trigger irradiance enhancements and interpretation of the underlying physical mechanisms was done. The main focus of this study was the appearance of irradiance enhancement events, the change of meteorological parameters during enhancement and the impact of these changes on the performance of photovoltaic bifacial module technologies. The analysis of efficiencies as well as yield performance was done in comparison to mono crystalline reference modules for the full year as well as only during irradiance enhancement. The impact of meteorological parameters on the performance of different bifacial photovoltaic module types was determined time resolved during irradiance enhancement as well as for a diurnal cycle in the period 04/2020–06/2021. Irradiance enhancements exceeding 1000 Wm−2 were found to occur only on days with clouds in Vienna (Austria). For 179 irradiance enhancement situations analysed, 81 % of all enhancements happened for cloudiness greater than 0.4 and still 30 % for a cloudiness greater than 0.7, the latter resulting also in single enhancement events greater than 1150 Wm−2. Cloud genera preferentially causing irradiance enhancements were identified as Altocumulus and Cumulus clouds. The mechanism of irradiance enhancement compatible to the position of the sun towards the clouds were in accordance with the cloud types Mie-scattering and edge reflections, respectively, or a mix of both. The overall photovoltaic long term performance results showed that the average weighted absolute efficiencies of the bifacial photovoltaic modules were 2–4 % higher than the ones of monofacial standard reference modules. The performance of the bifacial modules increased consistently between 17–24 % throughout the 15 month period of investigation independent of orientation with a visible seasonal variation, namely 19–28 % in winter, 18–24 % in spring, 16–25 % in summer and 17–27 % in autumn. This repository contains the pre- and post-measurement of the surface albedo (folder: Albedo), the statistical evaluation of the cloudiness index (folder: Cloud evaluation), the cloud pictures during irradiance enhancements exceeding 1015 Wm-2 (folder: Cloud pictures RE_times_1100-1015), the ambient temperature and irradiance (folder: Wheaterstation_files) and the calculated average wavelength of the solar spectrum during measurement (folder: average_wavelength). Also, the folder Biface data contains the meausrement of the module power and energy yield of the test modules.