Elektrokromik Kaplamalı Camın Farklı İklim Bölgelerine Göre Enerji Performansı Değerlendirilmesi

Abstract

Enerji verimliliği iklim değişikliği ile mücadele ve enerji güvenliğini geliştirmek için en etkili yoldur. Bina sektörü enerji verimliliğini artırmak ve birincil enerji tüketimini azaltmak için önemli bir yer tutar. Genellikle binalarda ısıl kayıpları sebebiyle, enerji verimliliği düşük kabul edilen cam yüzeyler, yeni gelişmelerle birlikte binalarda farklı kullanım alanları da bulabilmektedir. Estetik kaygılardan ve iyileştirilmekte olan yalıtım özellikleri sebebiyle camın mimari yapılarda kullanımı önemli ölçüde artmıştır. Bina cephesindeki cam yüzeyleri seçilirken camın hem ısıtma hem de soğutma yüklerine olan etkileri dikkate alınmalıdır. Bu durum değişken iklim şartlarına göre cam yüzeylerin farklı özellik gösterebilme ihtiyacını doğurmuştur. Örneğin soğuk iklim bölgelerinde güneş ışınlarının daha fazla geçirimini sağlayan yüksek solar faktörlü ürünler tercih edilirken, sıcak iklim bölgelerinde güneş ışınlarını engelleyen düşük solar faktörlü ürünler tercih edilir. Bina cephesi ve çerçevesinde uygulanabilecek gölgeleme ekipmanları veya farklı mimari çözümlerle de amaca ulaşılabilir. Bu anlamda gelişmekte olan bir teknoloji olan elektrokromik dinamik cam kaplama sistemleri enerji verimliliği açısından önemli potansiyel sahiptir. Elektrokromik cam sistemleri kullanıcı ihtiyaçları doğrultusunda ısı ve ışık geçirgenliğini değiştirebilmektedir. Elektrokromik camlar varlık sensörü, günışığı sensörü vs. gibi ekipmanlarla farklı kontrol sistemleri ve senaryolara göre yönetilebilmektedir. Bu çalışmada Türkiye'nin iklim bölgelerine göre elektrokromik tipinde dinamik cam kaplamalı pencere ile standart düz camlı ve yüksek performanslı statik camlı pencerelerin enerji performans özelliklerine göre karşılaştırması yapılmıştır. Farklı ticari cam sistemlerinin bina enerji simülasyonu, DOE-2.2 tabanlı E-Quest 3.65 yazılımı kullanılarak gerçekleştirilmiştir. Çalışma için sekiz katlı bir ofis binası seçilmiş, ASHRAE 90.1-2007 standardı baz alınarak modelleme yapılmıştır. Bu analiz TS825 standardında tanımlanan 5 farklı iklim şartı için yapılmıştır. Oluşturulan bina enerji modellemesinde çalışmasında 500 lüks aydınlanma şiddetine göre hesaplama yapılmıştır. Bu çalışmada günışığı kontrolü, ayarlanabilir aydınlatma ekipmanlarının veya pencerelerden gelen doğal aydınlatmanın düzenlenmesine dayanmaktadır. Hava şartlarına (bulutlu, açık vs.), güneşin pozisyonu veya kullanılan cama göre uygulanacak günışığı sensörü iç ortamda istenen optimum aydınlanma seviyesini ayarlamaktadır. Kapalı havalarda elektrokromik cam ortamda istenen aydınlatma seviyesine ulaşılana kadar saydamlaşmakta, açık havalarda kararak ışık ve ısı geçirgenliğini istenen seviyede tutmaktadır. Aynı zamanda zaman çizelgesine göre de kontrol edilmektedir. Yapılan çalışma sonucunda farklı iklim bölgeleri için sonuçların benzer çıktığı görülmüştür. Eski binalarda yaygın olarak bulunmakta olan tek camlı pencere sistemlerine göre elektrokromik olanların yaklaşık %40'lar mertebesinde tasarruf sağladığı sonucuna varılmıştır. Elektrokromik cam yıllık tüketimin yanı sıra belirli dönemlerde gerçekleşen azami yüklerin azaltılması gibi önemli faydalar sağlayabilmektedir. Bu sayede ofis binasında kullanılabilecek mekanik ekipmanlar daha düşük kapasiteli tercih edilebileceği görülmüştür.

Energy efficiency is the most effective way to fight climate change and improve energy security. Because of the vast potential of energy efficiency for future energy savings, goverments implement mandatory policies that include codes and standards. The building sector plays an important role in increasing energy efficiency and reducing primary energy consumption. Generally beacause of high thermal losses, glass surfaces in buildings considered low energy-efficient but with new developments it does find different usage areas. Even though the main function of windows is to provide daylight and visual contact with the external environment, due to aesthetic concerns and improved insulation properties, their use in architectural structures has increased significantly. When selecting the glass surface, the effects on both heating and cooling loads must be considered. Thus necessity of using different glass surfaces which offer different optical properties according to the change in climatic conditions occur. For example in cold climates to provide more transparency high solar factor products are preferred while in warm climates to prevent radiation low preferred. A proper choice of windows can reduce both heating and cooling loads of buildings. This can also be achieved with applying shading equipment or different architectural solutions to facade and framework. In this sense, developing electrochromic dynamic glass coating systems have significant potential for energy efficiency. Electrochromic glass systems can change the heat and light transmittance according to user needs. Electrochromic glazing can be managed by equipments like occupancy sensor, daylight sensor etc. with different control systems and scenarios. Different studies have shown that the use of electrochromic windows could lower the energy consumption of buildings. The energy efficiency of electrochromic windows is still under research worldwide. Intelligent (dynamic) glass systems can be classified as passive and active controlled. Passive controlled dynamic glass systems do not require an electrical stimulus. These systems react independently from user by a natural stimulus such as light or heat. Active dynamic glass systems can be controlled either directly or through automated building management systems. Active dynamic glass systems can adjust the penetrating visible and infra-red light intensity according to many different parameters, such as indoor and outdoor conditions or user demands. In this way, heating, cooling and lighting systems can achieve significant gains in energy consumption. Dynamic glass systems became a considerabe option for both newly built buildings and restoration projects to change the energy and light transmission values according to exterior conditions or user requests. The best example for this is transparent chromic materials that can provide selective and dynamic control of thermal energy and instant solar radiation. Despite the availability of high-efficiency products in terms of thermal insulation properties, static glass systems considered insufficient in terms of instantaneous solar radiation control, energy efficiency and comfort. In general, it is preferable to eliminate these deficiencies by using dynamic shading systems. Despite their widespread use because that dynamic shading systems installation and maintenance is costly, not suitable for renovation projects and vision restrains have led to the use of next-generation products. In the market there are active dynamic glass systems integrated with systems such as photovoltaic to provide electrical self-sufficiency, using diffrerent technologies which can be controlled with smart phones and can be operated remotely. Most common examples are electrochromic (EC), suspended particulate (SPD) and liquid crystal (LC / PDLC) glass systems. These technologies may be preferred for different applications or needs (privacy, switching speed, solar heat gain reduction) due to their different operating characteristics, costs and performance. Another advantage of active dynamical systems over passive systems is that all glass units in the building envelope can function independent of each other. Increased use of smart glasses in other areas of the automotive, aerospace and transportation sectors is another indication of increased demand. In this study energy performance characteristic comparison was made between the electrochromic type dynamic glass, standard single pane glazed and high performance static glass windows installed in an office building at diffrerent climatic regions of Turkey. Building energy simulations of different commercial glass systems were performed using DOE-2.2 based E-Quest 3.65 software. An eight-storey office building was selected for the study, based on the ASHRAE 90.1-2007 standard. This analysis was carried out for the 5 different climatic conditions defined as TS825 standard. This standard aims to define the standard calculation methods and values to be used in the calculation of the energy consumption of the buildings in Turkey to save energy and to calculate the net heating energy requirement. According to the determined modeling conditions, energy analysis was performed for each city at different regions in TS825. The effects on the energy performance of the entire building of glass for 11 different scenarios and 5 different glass types were examined. While all opaque surfaces of the building are determined according to the values in TS825, the glasses used are based on the properties of the selected glasses. Glass in use is selected as single glass, double glass, triple glass. Analyzes were made on the glass properties specified in the ASHRAE standard and the results were evaluated by making a comparison between the selected alternatives. ASHRAE 90.1-2007 code performance targets for both SHGC and U value impact of glass to buildings. By using the architectural, mechanical and electrical projects of an existing office building, a hypothetical office model was created. In the generated model, calculations was made according to 500 lux illumination intensity. In this study, daylight control has been achieved with adjustment of natural illumination from windows or dimmable lighting equipment. Depending on weather conditions (cloudy, clear, etc.), the sun's position or the glass type used, daylight sensor adjusts the desired optimum illumination level in the interior environment. In cloudy weather, the electrochromic glass become transparent until the desired illumination level is reached and become tinted in clear weather to keep the light and heat transmittance at desired level. Also a time schedule is considered for the control scenario. Similar results has been achieved for different climate regions. Electrochromic windows save %40 compare to single pane windows which are common in old buildings. In addition to the reduction of energy in annual consumption of electrochromic glass, it can also provide significant benefits such as reducing the peak loads that occur during certain periods. By this way mechanical equipments which can be used in the office can be chosen with lower capacity.