ISSN 2277-3061 Volume 15 Number 05 INTERNATIONAL JOURNAL OF COMPUTERS & TECHNOLOGY 6724 | Page council for Innovative Research March 2016 www.cirworld.com Mapping Monthly Average Global Solar Radiation over Iraq Using GIS and Heliosat Model Hussain Z. Ali 1 , Ali. M. AL-Salihi 2 , Ahmed. K. AL-Abodee 2 1 Ministry of Sciences and Technology 2 Department of Atmospheric Science, Collage of Science, AL-Mustansiriyah University Abstract The mapping of global solar radiation is important in designing of solar energy system and renewable energy applications, also the global solar radiation estimation and mapping will facilitate engineers and architect purposes and applications. In present paper measured and estimated global solar radiation data was employed. The estimation of global radiation data can give results with acceptable accuracy to establish solar maps of monthly radiation using Geographic Information Systems (GIS) software. Simple Kriging interpolation was used to derive radiation maps over Iraq. Different models were employed, namely Spherical, Circular, and Gaussian. Solar radiation data for the years 1985,1990,1995,2000 and 2005 were used for the production of solar radiation maps over Iraq. On average, Iraq receives (5000) kWh/m 2 of global solar radiation in year 2005. The highest global solar radiation is estimated at 6790kWh/m 2 in September while the lowest is 1660 kWh/m 2 in December. Cross validation was used to find the best model by comparing the error criteria, namely MPE, RMS, MSPE, RMSS, and ASE. It was found the Spherical model gives best results according to the cross validation error criteria. Keywords renewable energy, solar radiation; GIS; Simple kriging; Iraq; Geostatistics. 1. Introduction Energy is one of the most important factors for economic growth and human development. The sustainability of future energy systems is critical for sustainable development. Renewable energy is a key element for any sustainable solution. One of the first steps for the exploitation of any energy source is its estimation and mapping to identify the most suitable areas in terms of energy potential. To understand the current trend of the renewable energy, it is important to analyze the spatial variation of resources and their deployment. Every second, the Sun transforms about 4 million tons of its mass into energy. For the earth, this enormous quantity represents an energy focus of 1.779×10 11 MW that is directly or indirectly used by the biosphere. Studying the solar radiation that reaches the Earth surface is very interesting in ecological and economic terms, since the Sun provides 99.8% of the energy used for all natural processes. In the field of Earth sciences, mapping solar radiation is important for two reasons. Firstly, it is a climatic factor that can be used when modelling and mapping climatic elements such as air temperature, evapotranspiration or snow cover. Secondly, it is a variable that directly influences biological processes such as photoperiods (flowering and growing seasons, etc.) or biochemical reactions [1]. Solar radiation is one of the important fields of scientific research in renewable energy uses. Daily solar radiation reaching earth surface is very important for different applications of solar energy including assessment for heating and electricity generation, solar system design, and agriculture meteorology [2]. Solar radiation measurements in our country are not easily available because of not being able to afford the measuring equipments and techniques involved, in order to overcome this shortage of solar radiation measurements. Many researchers developed models to estimate the values of solar radiation reaching the earth surface by employing different relations such as linear, multi linear, fourth order and polynomial for different location in Iraq and surrounding country [3]. On other hand, researchers of the neighboring countries such as turkey, Syria, Jordan, Saudi Arabia, Iran investigated empirical and statistical models [4]. Heliosat method was developed to generate solar radiation data from Meteosat-8 images. The main procedure of Heliosat is that the solar radiation for an area is statistically calculated using cloud cover and the albedo of the same area. In present paper monthly average of daily solar radiation were employed in order to create solar radiation maps over Iraq using Kriging interpolation technique, estimating variable at an unmeasured location from observed values at nearer locations [5]. 2. Materials and Methods Heliosat method The Heliosat-2 method is described in details by many authors [6]. The summery of Heliosat-2 can be explained by the following steps; recording the ground albedo maps for each month, computing the cloud index, calculating the clear sky index, and finally estimating the daily global solar radiation. The monthly albedo (p t ) maps obtain from the daily albedo values is calculated for each pixel of Meteosat-8 images (pg) the cloud index is standard measure of cloud cover and can be computed as follows:   (, ) (, ) , (1) (, ) (, ) rt t g t t t g p i j p i j n i j p cloud i j p i j           