SIMPLE CALCULATION OF PHOTOVOLTAIC/PV SOLAR ELECTRICITY PRODUCT IN BUILDINGS (Case Study: Jakarta Office Buildings)

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1 SENVAR 5-UNIVERSITI TEKNOLOGI MALAYSIA, SKUDAI, JOHOR BAHRU, MALAYSIA 10 TH 12 TH DECEMBER 2004 SIMPLE CALCULATION OF PHOTOVOLTAIC/PV SOLAR ELECTRICITY PRODUCT IN BUILDINGS (Case Study: Jakarta Office Buildings) Eka Sediadi Architecture Department, Trisakti University Building C, 1 st floor, Campus A Trisakti University Jl. Kiai Tapa no.1 Grogol, Jakarta Barat Tel ext 201, Fax sediadi@indo.net.id Abstract A few months ago the problem of instability electricity supply emerge again in Indonesia especially in some cities in West Sumatra region. The generators could not feed their proper electricity supply because of the dry season and the lack of water supply. In August 14,2003 some USA s big cities like New York, Detroit, Boston, Cleveland and Toronto in Canada suffered from the longest black out in their history of electricity supply. Meanwhile buildings with PV solar electricity support still could do their function uninterrupted. In comparison, the problems of electricity supply and demand in urban/city area are bigger than similar problem in rural area. The constant increase of population and building density are some reasons of the high increase of electricity demand in cities. Sometimes the public service authority cannot fulfil this demand. The black out case in USA and Canada has proven that the use of PV solar electricity in buildings is very useful and safe. It shows also that the integration of the PV technology in buildings is already well known and dependable. It could cut the daily peak electricity demand in big cities and could function as a supporting sub system in the whole electricity supply system in these cities. This paper will discuss the use of PV system in buildings and its electricity product calculation in a very simple way to help architect. It will use some climate data for Jakarta. The calculation will illustrate the mean electricity product for Jakarta in different year seasons and the comparison of using PV electricity in some office buildings. Key words: Building integrated photovoltaic/pv, electricity peak demand, energy calculation, solar global radiation.

2 A. INTRODUCTION One important factor for electricity energy output produced by the PV modules is the sum of the global radiation (= the sum of the direct and indirect solar radiation) (2) received by the PV surfaces in a certain angle and orientation. The yearly solar trajectory in the tropics seen from the earth forms vertical curves. To make it visually clearer, the position of the sun in June and December in Jakarta, Indonesia (6º11 S) and Braunschweig, Germany (52º18 N) at its local solar time is shown in figure (1). The solar trajectory in Jakarta, Indonesia are vertical curves, meanwhile in Braunschweig, Germany they are inclined to the South. The direct solar radiation at local solar time in Jakarta in June (dry season) is 62º from the horizontal surface and coming from the North. In December (rainy season) is 75º from the horizontal surface, coming from to South. In Braunschweig the direct solar radiation in June is 61º and in December is 14º (sommer and winter season) both are coming from the South. Figure 1: The yearly solar movement in Jakarta, Indonesia (6º11 S) and Braunschweig, Germany (52º18 N) at local solar time (3). Based on this climate condition, the PV integration in Jakarta is preferably on the building roofs or as PV roofs. The electricity energy output will be the highest in comparison with the PV façade integration because it has the highest global solar radiation on horizontal surface (see also figure 2). Furthermore base on the observation research of the global solar radiation on vertical surfaces in Jakarta from Soegijanto (4), the highest daily sum in Jakarta is on the west

3 oriented surfaces. Consequently the second possibility for PV integration on vertical surfaces in Jakarta is an integration on the west façade of a building. Figure 2 : Monthly mean of global solar radiation In Jakarta on horizontal and vertical surfaces (4) The basic consideration of PV roof integration is to use the open useless flat roof spaces in the city and cover it with PV modules to form the grid connected PV system. The electricity product can then be used by the building itself or distributed to the local grid. In tropical climate with its high solar radiation, this PV grid connected system could supply additional electricity energy to the city. Also in Jakarta, there are already many modern buildings, which have flat roof surfaces, which could be used as place for PV modules. Two examples of PV roof integration can be seen in figure 3 and figure 4. Figure 3 shows the Roof PV Integration in the building of Thali AG firm in Hitzkirsch in the Switzerland. It is a grid connected system with inverter and started to operate in 1991 with 268 m 2 PV module surface. The PV surface angle is 35º from horizontal and facing South. This giant roof can be clearly seen as PV roof of the building. Figure 4 shows PV modules on the roof of a hotel in California, USA which uses solar electricity for its building. The PV modules are put together on the flat roof of the

4 hotel. Because of this placement the PV integration in building cannot clearly be seen. Figure 3: PV Roof Integration in Switzerland (3) Figure 4: PV modules on the roof of The West End Hotel in California, USA (1) Some general guidance for PV integration in buildings for getting the most electricity output are (5) : 1. The sum of global solar radiation on the PV surface should be based on the local global radiation measurement. 2. Clean PV module surface. The PV surface should periodically be cleaned; therefore the cleaning of the PV surface should be as easy as possible. 3. Appropriate PV surface angle. 4. Shadow free. 5. PV generator working temperature.

5 The important factors for the simple calculation of the PV electricity product are (6) : 1. The sum of the global solar radiation. 2. The PV surface area. 3. The efficiency of the PV generator. B. CASE STUDIES The integration of the PV Modules in building could be done on the roof or in the façade of a building. For tropical climate the integration on the building roofs will produce more energy than the one on façade because of the high sum of global radiation on horizontal surfaces. The simple calculation of the electricity product will be given here to show theoretically the PV electricity product of such integration in Jakarta and was made based on some building data of two office buildings in Jakarta. It will show also the coverage percentage of the energy product to the whole electricity consumption in each building. Two buildings in Jakarta are chosen as cases for the calculation, they are the Bank Central Asia (BCA) building and the Wisma Nusantara building. According to the global radiation measurement in Jakarta, the horizontal and the west vertical surfaces receive the highest sum of the radiation; therefore the roof and the west facade area of both buildings are measured and used as one important factor in the calculation. Figure 5: The Bank Central Asia (BCA) building (left) and the Wisma Nusantara building (right) (3) The calculation will illustrate the energy product from the use of PV modules on the roof and the west facade of the buildings. It will use the simple calculation formula (6)

6 with assumption that there is no shadow effect on the PV surfaces and the orientation of the vertical surface is to the west. The Formula is (6) : E = Gd. Apv. ŋ Where, E = The PV electricity product in Kwh/d Gd = the sum of the sun global radiation in Kwh/m 2.d on the same angled and oriented surface Apv = the PV surface area ŋ = the efficiency of the PV generator (= , it depends on the type and material of the PV cell. In this calculation = 0.1 (3) ). PV module surface Angle and orientation June (dry season) Global radiation (Kwh/m 2.d) December (rainy season) Global radiation (Kwh/m 2.d) Horizontal Vertical South North East West Table 1: Daily mean global radiation in Jakarta in June (dry season) and December (rainy season) (4) Figure (1): Comparison of the mean global solar radiation on horizontal and vertical surfaces in Jakarta (3).

7 Example 1 : Bank Central Asia (BCA) Building (3). Roof surface area = 1.555,20 m2 West façade surface area = 3.706,56 m2 Daily electricity consumption (3) : Calculation: Horizontal surface area, Apv roo = 1.555,20 m2 Gd June = 3.85 Kwh/m2.d Gd Dec = 3.62 Kwh/m2.d ŋ = 0.1 Monday Friday = ,00 Kwh/d Saturday = ,00 Kwh/d Sunday = 3.881,00 Kwh/d E June = , = 598,75 Kwh E Dec = , = 562,98 Kwh Vertical surface area: Apv façade = 3.706,56 m2 Gd June = 3.04 Kwh/m2.d Gd Dec = 2.77 Kwh/m2.d ŋ = 0.1 E June = , = 1.126,79 Kwh E Dec = , = 1.026,71 Kwh Total mean electricity product in June and December from example 1: June: December: West façade = 1.126,79 Kwh West façade = 1.026,71 Kwh Roof = 598,75 Kwh + Roof = 562,98 Kwh + Total sum = 1.725,54 Kwh = 1.589,69 Kwh The mean sum =1.725,54 Kwh ,69 Kwh = 1.657,62 Kwh/d

8 Then the comparison between the whole electricity consumption of the Bank Central Asia building and the PV electricity product or the PV electricity coverage is: Monday Friday = ,00 Kwh/d : 1.657,62 Kwh/d. 100% = 5,88 % Saturday = ,00 Kwh/d : 1.657,62 Kwh/d. 100% = 6,76 % Sunday = 3.881,00 Kwh/d : 1.657,62 Kwh/d. 100% = 42,71 % Example 2: Wisma Nusantara Building (3). Roof surface area: Northern part of the roof = 183,60 m2 Southern part of the roof = 183,60 m2 Roof of the 30 th floor (middle part of the building) = 648,00 m2 West façade surface area until 22 nd floor = 2.138,40 m2 West façade surface area from 23 rd fl to 30 th floor = 432,00 m2 Horizontal surface area, Apv roof surface in June (the southern part of the roof is under building shadow) Northern part + middle part of the roof = 183,60 m m2 = 831,60 m2 Apv roof surface in December (the northern part of the roof is under building shadow) Southern part + middle part of the roof = 183,60 m m2 = 831,60 m2 Daily electricity consumption (3) : Monday Friday = ,00 Kwh/d Saturday = ,00 Kwh/d Sunday = 2.635,00 Kwh/d Calculation: Gd June = 3.85 Kwh/m2.d Gd Dec = 3.62 Kwh/m2.d ŋ = 0.1 E June = , = 320,16 Kwh E Dec = , = 301,04 Kwh

9 Vertical surface area (3) : A façade = 2.570,40 m2 Gd June = 3.04 Kwh/m2.d Gd Dec = 2.77 Kwh/m2.d ŋ = 0.1 E June = , = 781,40 Kwh/d E Dec = , = 712,00 Kwh/d Total mean energy product in June and December from example 2: June December West façade = 781,40 Kwh/d West façade = 712,00 Kwh/d Roof = 320,16 Kwh/d + Roof = 301,04 Kwh/d + Total sum = 1.101,56 Kwh/d = 1.013,04 Kwh/d The mean sum =1.101,56 Kwh ,04 Kwh = 1.057,30 Kwh/d. Then the comparison between the whole electricity consumption of the Wisma Nusantara building and the PV electricity product or the PV electricity coverage is: Monday Friday = ,00 Kwh/d : 1.057,30 Kwh/d. 100% = 5,61% Saturday = ,00 Kwh/d : 1.057,30 Kwh/d. 100% = 6,45% Sunday = 2.635,00 Kwh/d : 1.057,30 Kwh/d. 100% = 40,12% C. CONCLUSION The calculations above illustrate a simple way for architects in finding the electricity product of PV modules integration in buildings in Jakarta especially on the building roof or in its west facade. It is also a calculation which emphasis on the product from its technical point of view without discussing much about their aesthetical aspect or the tropical building designs approach. It could be possible if a building has more tropical building designs influence the PV integration in building will play a bigger role in its electricity consumption policy. The PV modules could be considered as multi function building material for the building. It can replace the function of the conventional material and in the same time produces electricity for the building and the city. This can be seen from the PV

10 electricity coverage of both buildings, which range from 5% on working days to 42% on Sundays/holidays. In realizing this PV integration, a close cooperation between architect and some experts in electrical and mechanical engineering is needed. They will work together to find the best integration possibility in both functional and aesthetical aspects. The effort pursuing better building designs has started and continued along with the development of PV technology in the world. D. REFERENCES 1. ISES, July/August "Rooftop Solar Power. The Solar Energy Potential of Commercial Building Rooftops in USA". In refocus. The international renewable energy magazine. P Palz, Wolfgang, 1984; "Atlas ueber die Sonnenstrahlung Europas Band 1 und 2". Koeln: Verlag TUEV Rheinland GmbH. 3. Sediadi,Eka, 1996; "Die aktive Sonnenenergienutzung in Jakarta". Hanover, Universitaet Hannover. 4 Soegijanto, 1989; "Total Solar Insolation-Jakarta". In: Proceedings Seminar Kebijaksanaan Konsevasi Energi pada Bangunan Gedung, Jakarta. 5. Thomas, Randall; Fordham,Max (Editors), 2001; "Photovoltaics and Architecture". London, Spon Press 6. Weik,H;Engelhorn,H;1986 "Waerme und Strom aus Sonnenenergie". Altlussheim: SET GmbH.