Development of Diffused Solar Radiation Maps using GIS Software for Malaysia

Transcription

1 evelopment of iffused Solar Radiation Maps using GIS Software for Malaysia A.W. AZHARI 1,, M.A. ALGHOUL 1, S.H. ZAII 1, A.H. IBRAHIM, J.M. ABULAF, A. ZAHARIM 1 & K. SOPIAN 1 1 Solar nergy Research Institute Universiti Kebangsaan Malaysia UKM Bangi, Selangor School of nvironmental ngineering Universiti Malaysia Perlis Kangar, Perlis Malaysia -mail: ayuwazira@yahoo.com, dr.alghoul@gmail.com, ksopian@eng.ukm.my Abstract:- he maps for diffuse solar radiation will be very helpful in designing of solar energy system as well as interior illumination of a building. If the presentation of diffuse solar radiation is in maps form, it will facilitate engineers and architect purposes and applications. In this study, measured and estimated global solar radiation at different locations over Malaysia was used. he estimation of diffuse radiation from global radiation data can give results at acceptable accuracy and low cost to establish solar mapping of monthly and yearly average diffuse radiation using GIS software. On average, Malaysia receives from.65 kwh/m to.977kwh/m of diffuse solar radiation in a year. he highest diffuse solar radiation is estimated at 3.10kWh/m in September while the lowest is 858 kwh/m in ecember. Keywords:- solar, measured and estimated global radiation, diffuse radiation, GIS software, radiation map Nomenclature δ angle of declination B direct solar radiation diffused solar radiation extra extraterrestrial solar irradiation R reflected solar radiation global solar irradiation I o solar constant, kw/m K L n clearness index latitude number of the day 1 Introduction In assessing the performance of systems utilizing solar energy, an important input parameter is the diffuse solar irradiation component at the location of interest. iffuse irradiation also has an application in illumination inside buildings [1]. In Malaysia, global solar radiation data have been recorded at many meteorological stations, but the corresponding diffuse radiation records are scarce. hus, the diffuse radiation must be estimated through models and correlations. Since data for global solar irradiations are widely available, most of the models developed relate diffuse solar irradiation to global solar irradiations [, 3]. Many researchers have studied the correlations with data from various regions. Some researchers have found that the regression parameters in correlations determined by linear regressions using the daily global and diffuse solar radiation at different sites often show remarkable similarity [4]. However, when the monthly average daily global and diffuse radiation is used to form the regression correlations, the regression parameters have been ISBN:

2 found to vary substantially between sites and the accuracy of the correlation reduced [5]. In recent years, various methods have been used in estimates of diffuse solar radiation for different locations [6-10]. However, very little work has been done for Malaysia and most of it was on the prediction of global solar radiation only [11-15]. In this study, diffuse solar radiation maps was constructed by using Geographical Information System (GIS) software where the data used was based on global solar radiation data from Azhari et.al [13] and the recommended equation model developed by Khatib et. al. [15]. Method and Material he maps for diffuse solar radiation will be very helpful in designing of solar energy system as well as interior illumination of a building. If the presentation of diffuse solar radiation is in maps form, it will be facilitate engineers and architect purposes and applications. Geographical Information System (GIS) is a convenient model to be used in modeling and mapping of geographical entities. GIS software was used to map diffuse solar radiation based on monthly and yearly average for the year of Solar Radiation ata ata used in this study consist of global solar radiation data. he measured diffuse solar radiation in Malaysia is not available for all weather stations. he use of global solar radiation data seems to be the best available method to model and construct the diffuse solar radiation maps. In estimating and constructing the diffuse solar radiation maps, the global solar radiation data has to be available. he methods for estimation of global solar radiation are discussed elsewhere in Azhari el. al. [13].. etermination of iffuse Solar Radiation In formulating the model, the extraterrestrial solar irradiation ( extra ) and the global solar irradiation ( ) have to be calculated. extra is the total solar energy above the atmosphere while is the total solar energy under the atmosphere. xtra can be calculated by using these equations: πn xtra = I cos aylength 365 (1) aylength = 15 cos 1 ( tan Ltanδ) ( 84 n) () δ= 3. 45sin (3) 365 where I o is the solar constant, 1.367kW/m, n is the number of the day, L is the latitude, andδ is the declination angle. Where else, the global solar irradiation ( ) consists of three parts, which are direct solar radiation ( B ), diffused solar radiation ( ) and reflected solar radiation ( R ). Since on horizontal surface the reflected solar radiation ( R ) is equal to zero, on a horizontal surface is given as below: + + = 0 (4) = B R R = + (5) B he clearness index (K ) can also be calculated by using the below equation: K = (6) xtra After finding the clearness index, can be calculated by using this equation. ( K) * = f (7) Muneer [16] has recommended an equation that is appropriate for most locations worldwide based on different function from different individual international sites. he recommended equation is as below: K K K = (8) However, Khatib [15] has developed a new and more accurate equation for Malaysia based on derived data collected from different stations in Malaysia K K K = (9) Measurement of global solar radiation has been obtained from meteorological department of Malaysia for the year 006. In these available data there are still some daily or monthly missing ISBN:

3 measurements. hese missed data has been estimated by [13]. For the purpose of this study, the new equation derived from Khatib [15] along with the measured and estimated global solar radiation will be used to estimate and map the diffuse solar radiation for Malaysia by using GIS software. 3 Results and iscussion Maps of diffuse solar radiation are very useful especially in design of solar energy system as well as interior illumination of a building. Figure 3.1 shows the yearly average daily diffuse solar radiation map of Malaysia. he map shows that, Malaysia receives about.885 kwh/m /year of yearly diffuse solar radiation compared to 4.96 kwh/m /year for global solar radiation. he maximum yearly average daily diffuse solar radiations received is.977 kwh/m /day mostly in Northern region of Peninsular Malaysia and Southern region of ast Malaysia. he Southern and Northeast region of Peninsular Malaysia as well as most parts in Sabah receives the lowest diffuse solar radiation. he trend is almost the same between global and diffuse solar radiation for most parts in Malaysia. Figure 3. (a-l) show the monthly average daily diffuse solar radiation of Malaysia for the month of January until ecember. In general, the constructions of monthly average daily diffuse solar radiation maps provide a clearer picture of the changes in diffuse solar radiation throughout the year. he value for monthly average daily diffuse solar radiation varies from.1 kwh/m up to 3.3 kwh/m for most months except for ecember where the value ranges varies from 8 kwh/m up to 3.1 kwh/m. (a) (b) (c) Fig. 3. (a-c) Monthly average daily diffuse solar radiations of Malaysia for January March. (d) Fig. 3.1Yearly average daily diffuse solar radiations for Malaysia. (e) ISBN:

4 (f) (k) Fig. 3. (d-f) Monthly average daily diffuse solar radiations of Malaysia for April - June (l) (g) (h) (i) Fig. 3. (g-i) Monthly average daily diffuse solar radiations of Malaysia for July September (j) Fig. 3. (j-l) Monthly average daily diffuse solar radiations of Malaysia for October November. 4 Conclusion In general, the estimation of diffuse solar radiation from global solar radiation data can give results at acceptable accuracy and lower cost. his method is applicable especially for developed and under developed countries in manipulating diffuse solar radiation data for various purposes. On average, Malaysia receives from.65 kwh/m to.977kwh/m of diffuse solar radiation in a year. he highest diffuse solar radiation is estimated at 3.10kWh/m in September while the lowest is 858 kwh/m in ecember. References: [1] K. K. Gopinathan,.Solar sky radiation estimation techniques, Solar nergy, 49(1), 199, [] S. Janjai, P. Praditwong and C. Moonin.A new model for computing monthly average daily diffuse radiation for Bangkok. WRC 1996, [3] K. K. Gopinathan and A. Soler, iffuse radiation models and monthly average, daily, diffuse data for awide latitude range, nergy, 0(7), 1995, [4] Surapong Chirarattananon, Pipat Chaiwiwatworakul, Singthong Pattanasethanon. aylight availability and models for global and diffuse horizontal illuminance and irradiance for Bangkok. Renewable nergy 6 (00) ISBN:

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