Investigating Energy Efficiency Of Photovoltaic Panels Mounted On Exterior Walls

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2015Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2015Enerji, teknolojik gelişmeler ile birlikte insanoğlunun yaşamını sürdürmesi için en temel ihtiyaçlardan biri haline gelmiştir. Hızla büyüyen toplumların enerji ihtiyaçlarını genellikle fosil yakıtlardan karşılaması; dünyamızı kirletmekte, hava kalitesini bozmakta, canlılara zarar vermekte ve küresel ısınmaya sebep olmaktadır. Bu çevresel etkilerden dolayı, fosil yakıtlara güçlü bir alternatif oluşturan yenilenebilir enerji kaynaklarına yönelmek kaçınılmaz hale gelmiştir. Bu kaynaklardan biri olan güneş enerjisi, binalarda pasif ve aktif olarak iki şekilde kullanılabilmektedir. Aktif sistemlerden biri olan fotovoltaik (FV) sistemler, güneş enerjisini direkt olarak elektrik enerjisine çevirebildiği için, dünyada hızla yaygınlaşmaktadır. Tezin amacı, FV sistemlerin mevcut binaların dış duvarlarında kullanımı halinde göstereceği etkinliğin, farklı tespit şekillerine ve yerleştirileceği yöne göre incelenmesidir. Bu doğrultuda, çalışmada kaynak taraması ve deney yöntemlerinden yararlanılmıştır. Çalışma altı bölümden oluşmaktadır. İlk bölümde; çalışmanın amaç, kapsam ve yöntemine dair bilgilerin verildiği giriş kısmı yer almaktadır. İkinci bölümde; güneş enerjisi sistem çeşitleri anlatılmış, Türkiye’nin güneş enerjisi potansiyeli açıklanarak bölgelere göre dağılımı verilmiştir. Aktif sistem çeşitlerinden biri olan FV sistemlerin Türkiye’de kullanımına değinilerek, bu konudaki kısıtlamalar ve teşvikler açıklanmıştır. Üçüncü bölümde, FV kullanımının tarihsel gelişimi, hücre yapısı ve çeşitleri, sistem çeşitleri, performansını etkileyen etmenler ele alınarak panel performansının araştırıldığı bazı deneysel çalışmalardan örnekler verilmiştir. Dördüncü bölümde, FV panellerin binalarda kullanım biçimleri açıklanmış ve dış duvara tespit edilen ya da bütünleşik olarak uygulanan sistemler irdelenmiştir. Beşinci bölümde ise, deneysel yöntem ile yapılan çalışma açıklanmıştır. Bu kapsamda; öncelikle iklimsel veriler, ölçüm periyotları ve değerlendirilecek günler belirlenmiş, deney düzeneğini oluşturan bileşenler ve düzeneğinin kurulumu anlatılmıştır. Sonrasında tez amacı doğrultusunda seçeneklerin nasıl geliştirildiği açıklanmış, seçeneklere ilişkin ölçüm sonuçlarının analizi yapılmış ve elde edilen sonuçlar değerlendirilmiştir. Sonuç olarak; mevcut bir bina dış duvarının farklı yönlerine tespit edilmiş FV panellerin her yönde belirli miktarda elektrik ürettiği ve bu değerlerin birbirine çok yakın olduğu, üretim miktarının güneşlenme süresine ve yüzeye dik olarak gelen güneş ışınımı miktarına göre değiştiği, elektrik üretiminin yazın daha erken başladığı ve daha geç sonlandığı, güneş ışınımının yoğun olduğu yönlerde duvara arkasında boşluk bırakılarak yerleştirilen panellerin arkalarındaki havalandırma sayesinde daha iyi performans gösterdikleri görülmüştür. Sonuç bölümünde ise, çalışmadan elde edilen sonuçlar özetlenmiş, Dünya ülkeleri arasında güneş enerjisi potansiyeli açısından şanslı olan ülkemizde, bu potansiyeli değerlendirmede bina cephelerinden de yararlanılması gerekliliği vurgulanmış ve panel performansının arttırılmasına yönelik önerilerde bulunulmuştur.In the world, in Turkey as well, need for electricity energy is increasing rapidly depending on the increasing population and technology development. The usage and development of renewable energy is flourishing because of shortages in fossil energy resources and impacts on environment and energy. Of all renewable energy resources, solar energy is the most productive one in Turkey. It is very important to evaluate solar energy in Turkey, because this country lies in a sunny belt between 36oN and 42oN latitudes. In the country which has five kinds of climatic zones, for instance, South East Anatolia Region with hot-dry climate has almost 1800 kWh/m2 solar radiation per year while Black Sea Region with temperate-humid climate has approximately 1500 kWh/m2 solar radiation per year. Solar energy can be used as active and passive systems in buildings. Solar thermal systems are the widely used active systems in Turkey. Solar thermal systems are especially used in Turkey’s Mediterranean region, which is efficient due to the weather conditions. Solar electricity is generated by using PV technology which is the direct generation of electricity from sunlight. These systems, however, are rarely used in Turkey. PV modules convert 10–15% of the solar energy into electricity, therefore the vast majority of the incident energy is converted into heat. The efficiency of the panel decreases as panel temperature increases. Its modules work silently with no moving parts, minimal maintenance and no pollutant emissions. They are clean, safe and efficient devices that have been considered as a logical material for use in buildings. Unfortunately, PV systems are not commonly used in Turkey although this country has the aforementioned high solar energy potential because of legal constraints, unconsciousness and high prices. PV systems differ from each other according to the application systems in two ways. A PV system can be firstly planned at the beginning of architectural design. In this case, in addition to energy production, it is a part of building envelope and serves to provide thermal and acoustic insulation, solar control, and to protect building from weather conditions. This type of systems are called Building Integrated Photovoltaic (BIPV) systems, and some of the versions are shading systems, rainscreen systems, stick system curtain walls, unitized curtain walls and double skin façades. Recent technological advances have made PV systems suitable for directly integration into building construction. PV module size, cost, appearance and reliability have advanced to the point where they can function within the architectural parameters of conventional building materials. A building essentially provides an area and a structural support for a PV module. Second application type is mounted systems. Less energy production is provided with PV panels which are mounted on building envelope, compared to integrated systems. However, mounted systems have the advantage of making PV systems available for old or historical buildings. In this case, the subject of how to generate maximum energy from the panels mounted on façade is significant. Designers should know how to increase panel efficiency depending on air temperature, its installation type and position on exterior wall. The purpose of the thesis is to analyse the efficiency of PV systems mounted on exterior walls of existing buildings according to different fixing types and orientations. Literature research and experimental study is used accordingly for this research. This study consists of six sections. First section contains the introduction part, where the purpose, extent and the method of the study were presented. In the second section, solar energy systems and solar energy potential in Turkey according to the regions were first mentioned. The usage of PV systems in our country, and limitations and motivations from the government about solar energy in Turkey were then explained. In the third section, history, structure and working, components and types of photovoltaic systems were examined, and the parameters affecting the system efficiency were discussed. Some experimental studies related to efficiency of PV system were briefly given. In the fourth section, using types of these systems in buildings were explained, and the systems which are mounted on building exterior wall or integrated with it were examined. Less energy production is provided with PV panels which are mounted on building exterior wall, compared to integrated systems. However, mounted systems have the advantage of making PV systems available for old or historical buildings. In this case, the subject of how to generate maximum energy from the panels mounted on the wall is significant. Fifth section explains the application study made by experimental method. Weather conditions, measurement periods, experimental set up and its assemblies were first explained. After the alternatives were generated in relation to the aim of the thesis. Finally the results were analysed and assessed. In the assessments, the amount of generated energy was discussed depending on whether or not there is a cavity between the wall and panel and the orientation of the PV panels. In the experiment, six panels with monocrystalline cell were used to evaluate the efficiencies of PV panels at different orientations. The study aiming to investigate the efficiency of PV system mounted on the exterior wall has been performed at Energy Institute of Istanbul Technical University (ITU) which was located in the Ayazaga Campus of ITU. An empty area faced to weather conditions, which was built as a lift shaft of the building, was selected for the measurements. The measurements were performed for the coldest and warmest days in February, March, June and July. In conclusion, the energy production of the panels mounted on the exterior walls of a building at different orientations were measured in approximate values. In addition, the amount of the energy produced by PV panel was affected by installation type of the panel and its orientation and solar radiation amount. In the panels mounted with a cavity on the wall, the cavity between the wall and the panel caused to reduce the temperature at the back of panel when solar radiation amount is high which results in increasing panel efficiency. Thus, in the orientation where solar radiation is dense, south wall in winter and west wall in summer, the panels with cavity had higher performance because of the ventilation occurring at the back of the panels. The other result is that the generated energy in summer is more than in winter. In the result section, the results obtained from the study were summarized and the necessity of PV system usage on exterior walls of existing buildings was emphasized for our country, which is one of the luckiest countries in the world in terms of solar energy potential. The aim of this study is to analyse the PV panel’s efficiency which mounted on different façades with different installation types. This study obtained low amount of energy becaouse of using small scaled PV panels. If bigger PV panels were used, the results could be more prominent. In the further studies, panel efficiency depending on panel temperature can be investigated besides the aforementioned issues.Yüksek LisansM.Sc