Comparison of solar radiation models and their validation under Algerian climate – The case of direct irradiance Omar Behar a,⇑ , Abdallah Khellaf b , Kamal Mohammedi a a L.E.M.I Laboratory, University of M’Hammed Bougara, UMBB, Boumerdes, Algeria b Centre de Développement des Energies Renouvelables, CDER, Bouzareah, Algeria article info Article history: Received 4 November 2014 Accepted 19 March 2015 Available online 11 April 2015 Keywords: Clear-sky models DNI prediction Solar irradiance Broadband models Validation abstract The accurate prediction of direct solar irradiance is essential in many solar energy applications, particu- larly those relying on concentrating solar technologies. The present paper is aimed at a detailed assess- ment of a large range of clear-sky solar radiation models under Algerian climate to select the more accurate one for estimating the performance of solar power projects where meteorological and radiomet- ric measurement stations are not available. To this end, seventeen models have been reviewed and their performance compared to measured irradiance of Ghardaia (Southern Algeria). The validation methodol- ogy presented herein is very helpful for ranking the models. A new statistical accuracy indicator has been originally introduced to find out the most accurate ones. A thorough analysis of selected models has shown that the more complex models, that seem at first sight more sophisticated, are not necessary the most accurate; while simpler models depending on a lim- ited number of parameters are more suitable. In other words, the suitability and accuracy of a model do not necessarily improve with an increase in the number of its parameters. This important finding is in good agreement with the previous published studies. This fact is important to take into account, in the case where measured data are not available, for the selection of the most suitable locations for the instal- lation of the future concentrating solar power plants in Algeria or even in other countries. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction As a result of continuous increase in energy demand, the actual energy sources, that comprise mainly fossil fuels, are under stress. Moreover, it has been reported that the remaining recoverable hydrocarbons will not be enough to meet the world energy needs by 2050 [2]. There is then high risk of shortage and eventually to depletion [1,2]. This fact has led more and more countries to be more in favor of a strategy focused on the development and the expansion of the renewable resources use. To this end, Algeria has initiated a very ambitious program to develop its huge renewable energy potential [3,4]. It is hoped that, through this program, renewable energy resources will eventually replace hydrocarbons; moving from a fossil fuels era to a clean and sustainable energy era. In this program, renewable energy-based power plants totalling about 22 GW of power are expected to be installed in the period extending from 2011 to 2030. Due to its huge potential, solar energy is the major focus of the Algerian renewable energy program and it is intended to provide about 37% of the national electricity demand by 2030. On other words, solar energy will produce about 92.5% of clean electricity since renewables will share around 40% of the total power for domestic consumption. Around sixty power generation units, including solar photovoltaic fields, wind farms as well as solar thermal and hybrid power plants, are actually in the development and/or in the planning stage but should be in operation by 2020 [4]. These power generation units require huge investments. With such important investments, accurate radiation data are necessary. These data are crucial in the design, sizing, equipments selection and performance prediction of these power generation units. Recent studies have indicated that small uncertainty in the quantitative evaluation of solar resources can jeopardize the eco- nomic viability of large scale solar-based projects [5,6]. This is due to the error cancelations through various design-engineering phases which result in higher uncertainty in the estimation of Levelized Electricity Cost [5,6]. In this context and in order to reduce the financial risks, high quality solar radiation data are required for the development and deployment of the Algerian renewable energy program. Up to now, the most accurate data are obtained from a combination of ground solar measurement stations data and satellite image http://dx.doi.org/10.1016/j.enconman.2015.03.067 0196-8904/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +213 555 82 71 29. E-mail address: beharomar@yahoo.fr (O. Behar). Energy Conversion and Management 98 (2015) 236–251 Contents lists available at ScienceDirect Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman