1 Abstract—Most of the photovoltaic (PV) system models in the literature have extra internal parameters that are not provided by the manufacturers, viz., R s , R p , A, I o , I sat . Such parameters are not given in the PV module datasheet and require numerical methods to be found due to the nonlinear nature of the PV output characteristic. This paper presents an improved and comprehensive PV model characterization method relying only on the values provided by the manufacturer. A new improvement and modification to some of the existing models under standard test condition (STC) and under varying environmental conditions are proposed. The paper serves as a complete guide for PV system designers and researchers to predict PV system performance over a wide range of temperatures and solar irradiance. Simulation and experimental results are provided to demonstrate the validity of the proposed simplified modeling approach, with an array design example for a power smart building. Index Terms—Single-diode model, Photovoltaic modeling, Standard Test Condition (STC), maximum power point (MPP). I. INTRODUCTION he modern power system is increasingly taking advantage of renewable energy systems entering the marketplace. Traditional central power stations with their pollution related problems will likely be replaced with cleaner and smaller power plants closer to the loads. The energy generated by the sun is one of the most promising, nonpolluting, free source of energy [1]. Among their benefits, solar systems are easily expanded. Despite their still relatively high cost, PV systems installed worldwide show a nearly exponential increase [2]. PV systems have proven that they can generate power to very small electronic devices up to utility scale PV power plant. A PV cell directly converts sunlight into electricity, and the basic elementary device of PV systems is the PV cell [3]. The basic building block for PV systems is a PV module consisting of a number of pre-wired cells in series [4]. Modules are then connected in series to increase voltage and in parallel to increase current; the product is power. A PV array is formed by series and parallel combinations of modules [5]. The performance of a PV system is normally evaluated under the standard test condition (STC), where an average solar spectrum at AM1.5 is used, the irradiance is A. Alqahtani and Y. Alsmadi are with the Department of Electrical Engineering, The Ohio State University, Columbus, OH 43210 (e-mail: alqahtani.4@osu.edu, alsmadiy@ece.osu.edu). M. Abuhamdeh is with M.C.Dean, Inc., Dulles, VA 20166 (e-mail: abuhamdeh@yahoo.com). normalized to 1000W/m 2 , and the cell temperature is defined as 25 o C [6]. However, under real operating conditions (i.e., varying irradiance as well as significant temperature changes), most commercial modules do not necessarily behave as in the specifications given by the manufacturers [7]. In addition, PV modules perform differently according to the location, time of day, and season of the year. It is therefore essential with the growing demand for PV systems to develop a simplified and comprehensive method to characterize PV systems under all environmental conditions. The paper is organized as follows: section II reviews the modeling practice of PV modules, section III shows the simplified and comprehensive approach presented in this paper with all the required equations to characterize any PV system, and section IV provide results and discussion implementing what is covered in section III. II. PHOTOVOLTAIC SYSTEM MODELING Many PV system models have been developed in the literature for years to describe the behavior of the PV system. The model can be mathematically modeled based on the theoretical equations that describe the functioning of the PV system using the equivalent circuit [8]-[14]. Other models are empirically-based models that acquire their versatility and accuracy from the fact that individual equations used in the model are derived from individual PV system characteristics, such as the one developed at Sandia National Laboratories [15]. Fig.1 (a)-(c) shows the equivalent electrical circuit model to describe the behavior of the PV module. The ideal PV module model in (a) does not include the parasitic resistances that account for the cells power loss. The single-diode model in (b) is the traditional PV model known as the five parameters model. The double-diode model in (c) is reported in [9] and [11]-[12] to have better accuracy because it takes into account some semiconductor physical phenomena; viz., charge diffusion and recombination in the space charge layer. The mathematical equations describing the three cases in Fig.1 are given respectively by: 1 s T D V N AV ph sat I I I I e             (1) A Simplified and Comprehensive Approach to Characterize Photovoltaic System Performance Ayedh H. ALQahtani, Muthanna S. Abuhamdeh, and Yazan M. Alsmadi T 978-1-4673-1835-8/12/$31.00 ©2012 IEEE