ARCHITECTURE AND TECHNOLOGY-PHOTOVOLTAIC APPLICATIONS IN BUILDINGS

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1 Trakia Journal of ciences, Vol. 7, uppl. 2, pp , 2009 Copyright 2009 Trakia University Available online at: IN (print) IN (online) Original Contribution ARCITECTURE AND TECNOLOGY-POTOVOLTAIC APPLICATION IN BUILDING Türkan Göksal Özbalta 1, emiha Kartal 2, Necdet Özbalta 3 1* Ege University Engineering Faculty Civil Engineering Department, Turkey 2 Trakya University Faculty of Engineering and Architecture, Edirne, Turkey 3 Ege University Engineering Faculty Mechanical Engineering Department ABTRACT Buildings have notable functions in the global energy balance. Increasing energy consumption initially requires renovations in heating insulation in buildings. In that sense, getting benefit from solar energy for heating in buildings is inevitable. Therefore, solar energy conversion systems are important building energy strategies to produce clean energy and save the building electricity expenditures. In architecture, one of the sustainable technologies is the use of photovoltaic (PV). PV, converting solar energy into electric energy with no moving parts, is clean, safe and efficient devices in buildings. PV can be mounted on special support structures or even be made an integral part of the building envelope. Recent technological advances have made PV suitable for direct integration into building construction. In this study, the amount of energy produced by PV systems in a school building under İzmir climate conditions was investigated. Besides, the decrease in CO 2 emissions, which cause the global warming, was discussed. Key Words: solar energy conversion systems, CO 2 emissions INTRODUCTION Photovoltaic systems are important in energy technology for many reasons. As a solar energy technology, they have numerous environmental benefits and contribute to the nations energy security as a domestic source of electricity. 1 As they cost increasingly less to produce and use, they become more affordable and available. PV produces no air pollution or hazardous waste. It doesnt require liquid or gaseous fuels to be transported or combusted. The most significant benefit is that since their energy source - sunlight - is free and abundant, PV systems can guarantee access to electric power. Photovoltaic modules have been used in different ways on exterior walls and/or roof covers. They are efficient means of energy *Correspondence to: Türkan Göksal Özbalta, Ege University, Engineering Faculty, Civil Engineering Department; tel: 0 (232) /5185; turkan.ozbalta@ege.edu.tr production by reducing energy consumption of buildings. Besides, they have gradually gained importance because they create sustainable and healthy environments by using solar energy among the renewable energy sources. POTOVOLTAIC YTEM Photovoltaic systems (PVs) produce electricity directly from solar radiation [1]. The raw material of the cells within these systems is silicon which makes the systems semi conductive. The cells have two poles with positive and negative loads. When solar radiation is reflected on the surface, electric current occurs on the joint point of those two poles. The more powerful the solar radiation is, the denser the electric current is. In addition to the direct radiation, diffused radiation is also efficient on electric production (Fig. 1). PV modules are classified in various types such as aluminium framed, unframed,

2 metal plated, and double glazed [1]. on roof OZBALTA T. et al. on balcony parapets on roof Figure 1. The different forms of photovoltaic The efficiency of the modules increases in parallel to technological developments and the increase varies between 5-25% [2]. On the other hand, efficiency changes depending on the inclination angels of the plates. The photovoltaic plates on the buildings need to be designed and oriented in accordance with the direction of the sun for gaining productivity. Photovoltaic modules contribute to energy gain on the buildings by their application on the inclined and slope surfaces (roof, walls) and other building components (parapet, balustrade, entrance eaves, sun breakers, etc). Moreover, the modules produced in different colours and forms contribute to creating various facade designs (Fig.2). The factors such as geographical position, topography, climate, average solar radiation, temperature, rainfall, humidity, dust, wind, and seismic events need to be taken into account during PV module applications on buildings [3]. Figure2. PV applications on different building elements ome sample applications of PV modules are displayed below: olar ouse Diyarbakır/Turkey olar-fabric building, Freiburg/D 258 Trakia Journal of ciences, Vol. 7, uppl. 2, 2009

3 OZBALTA T. et al. A Cafe in Muğla University/Turkey Figure 4. The entrance facade Climatic figures ample Model of the tudy PV tower The sample building of the study is the Civil Engineering Building in Ege University Campus which was oriented in the east-west direction (Fig.3,4). The shape of the fourstoried building with its offices and classrooms is rectangle. Due to its shape, the offices and classrooms are situated in the north and south faces. The building is m 2, and its volume is m 3. In this study, PV panels are assumed to be attached to the south brick wall of the building. Total panel area is square meter. The slope of the PV panel is 36 o. According to EIE (the administration of electric issues in Turkey) statistics, the total solar radiation values of İzmir vary between kwh/m 2 year (Fig.5). Moreover, in a study carried out by EIE, the annual energy gain rates through different PV applications under İzmir climatic conditions were also found out and displayed in Figure 6. Figure 5. Total solar radiation values Figure 3. The plan of the sample building Figure 6. PV type-area-energy gain (KWh-year) Trakia Journal of ciences, Vol. 7, uppl. 2,

4 OZBALTA T. et al. Calculation Method The monthly average daily total radiation on horizontal surface ( ) includes three terms: the beam, the diffuse and the groundreflected terms: = b + d + g The monthly average daily extraterrestrial radiation on a horizontal plane as 0 is given G = C 360 n πω cosϕ cosδ sin ω + sin ϕ sin δ where G C is the π solar constant (1367 W/m 2 ), n is the average day of the year, φ is the latitude of the location, δ is the declination and w s is the sunset hour angle. The sunset hour angle is found from the equation ω = arccos( tanϕ tanδ ) the declination is given as δ = sin 360 n The monthly average daily total radiation on horizontal surface is related to the monthly average daily extraterrestrial radiation. This relation is named the clearness index and is given by K T = / 0 By using the value of the monthly average clearness index, the diffuse component of monthly radiation can be calculated. Equations for these calculations are as follows: For ω o s and 0,3 K T 0, d / = 1,391 3,560 K T + 4,189 K T 2,137 K T For ω 81, 4 and 0,3 K T 0, d / = 1,311 3,022 K T + 3,427 K T 1,821K T The beam component of monthly radiation is found by the following equation: b d = The monthly mean solar radiation on the tilted surface is given by T = b R b + d d [( 1 + cos β )/ 2] + ρ b + [( 1 cos β )/ 2] where ρ is ground reflectance, β is the slope R of PV panel, b is the ratio of beam radiation on the tilted surface to that on a horizontal surface at any time, and for the northern hemisphere is given by Rb cos( ϕ β ) cosδ sinω + = cosϕ cosδ sinω + ( π /180) ω sin( ϕ β ) ( π /180) ω sinφ sinδ sinδ ω where is the sunset hour angle for the tilted surface for the mean day of the months [4]. Thin film silicon, in particular, both in the amorphous and microcrystalline form, constitutes at present one of the most promising material options for low cost-large are applications of photovoltaics. Thin film silicon technology is an industrially nature in the range 6-8 % with a declared durability of 20 years [5]. 260 Trakia Journal of ciences, Vol. 7, uppl. 2, 2009

5 Findings In this study, the efficiency of the PV panels square meters- which are assumed to be attached to the south wall of the sample building is investigated under the climatic conditions of İzmir. It was found that the monthly average daily incident solar radiation on the horizontal surface varied between kwh/m2 day and daily average ambient changed between C (Fig. 7). Figure7. Variations of climatic data in İzmir The monthly average daily incident solar radiation on the PV panel varied between kwh/m2 day and electrical output varied kwh/day (Fig. 8). With this PV system, kwh per year of electricity per m 2 could be generated under İzmir climatic conditions. OZBALTA T. et al. DICUION AND CONCLUION Depending on the overall findings of the study, it can be concluded that PV brings many benefits to buildings. PV is a renewable energy source that can provide clean, green electricity direct to where it is needed. PV also produces no harmful carbon emissions and is virtual maintenance free. Further, it is an exceptional system which produces electricity from solar radiation, proven to be renewable energy source. It is available now and is not hampered by planning restrictions. Additionally, due to high demand, its cost gets decreased. REFERENCE 1. ullmann,., Photovoltaik in Gebauden, andbuch für Architekten und Ingenieure, Fraunhofer IRB Verlag, tuttgart Oktik, Ş., Güneş-Elektrik Dönüşümleri, Fotovolatik Güneş Gözeleri ve Güç istemleri, TEMEV, Ankara Thomas, R., Fordham, M, Photovoltaics and Architecture, pon Press, Duffie, J., A. and Beckman, W., A., olar Engineering of Thermal Proceses, Wiley, J and ons, Inc., NewYork, L.V. Mercaldo, M.L. Addonizio, M.D. Noce, P.D. Veneri, A. cognamiglio, C.Privato, Thin film silicon photovoltaics: Archiectural perspectives and technological issues, Applied Energy V 86, ( ), Figure 8. Variations of incident solar radiation on PV panel and electrical output Trakia Journal of ciences, Vol. 7, uppl. 2,