IJE TRANSACTIONS A: Basics Vol. 30, No. 10, (October 2017) 1555-1564 Please cite this article as: A. Kumar, A. Biswas, Techno-economic Optimization of a Stand-alone Photovoltaic-battery Renewable Energy System for Low Load Factor Situation- a Comparison between Optimization Algorithms, International Journal of Engineering (IJE), TRANSACTIONS A: Basics Vol. 30, No. 10, (October 2017) 1555-1564 International Journal of Engineering Journal Homepage: www.ije.ir Techno-economic Optimization of a Stand-alone Photovoltaic-battery Renewable Energy System for Low Load Factor Situation- a Comparison between Optimization Algorithms A. Kumar, A. Biswas* Department of Mechanical Engineering, National Institute of Technology Silchar, Silchar, India PAPER INFO Paper history: Received 12 September 2016 Received in revised form 22 May 2017 Accepted 07 July 2017 Keywords: Photovoltaic Renewable Energy System Levelized Cost of Energy Reliability Meta-heuristic Algorithms Cost Optimization Load Factor Autonomy Days ABSTRACT For remote places having less-strong wind, single resources based renewable energy system (RES) with battery storage can sustainably and economically generate electrical energy. There is hardly any literature on optimal sizing of such RES for very low load demand situation. The objective of this study is to techno-economically optimize the system design of a Photovoltaic (PV)-battery storage RES for an institutional academic block in Silchar, India having maximum demand less than only 30 kW. The sizing process of various subsystems of the RES is first discussed. Then the RES is techno- economically optimized under 100% reliability to power supply condition, i.e. 0% unmeet energy (UE) and least excess energy. In this, performances of three different optimization algorithms- genetic algorithm (GA) and two meta-heuristics, namely Firefly Algorithm (FA) and Grey Wolf Optimizer (GWO) algorithms are investigated and compared. The optimal configuration under least levelized cost of energy (COE) is further examined. Results demonstrate that GWO is the best optimization tool for optimizing the cost of energy (COE) in comparison with the other optimization algorithms. It has been shown that a single optimization method might not always guarantee that the objective function has converged successfully in fulfilling all the requirements of least excess energy, autonomy days, and least COE. The present research provides a useful reference for the design optimization of single resource based RES for low load demand situation. doi: 10.5829/ije.2017.30.10a.17 1. INTRODUCTION 1 In most of the remote villages and islands around the world, the access to electricity is still a distant dream, which creates a huge barrier in the development of these regions. Hence, a stand-alone renewable power system is considered to be a feasible solution for providing electricity in the absence of utility grid. The system sizing and optimization of hybrid solar-wind systems for stand-alone power generation have been studied substantially over last few decades [1-11]. Borowy and Salameh [1] did work on the optimal sizing of photovoltaic array in hybrid mode with wind generator system and obtained promising performance of such hybrid system for standalone application. Bagul et al. [2] performed sizing of a stand-alone hybrid wind *Corresponding Author’s Email: agnibis@yahoo.co.in (A. Biswas) photovoltaic system using a three-event probability density approximation and such approximation successfully simulated the performance of the hybrid system. Diaf et al. [3] developed a methodology for optimal sizing of autonomous hybrid PV/wind system. Bernal-Agustin and Dufo-Lopez [4] simulation and optimized the performance of a stand-alone hybrid renewable energy system using solar-wind and storage system. Zhou et al. [5] did an extensive review on the current status of research on optimum sizing of stand- alone hybrid solar-wind power generation systems as of 2010 for guiding researchers towards further researches in this area. Dali et al. [6] did an experimental investigation on the control and energy management for grid connected and standalone hybrid solar–wind system with battery storage and compared their performances. Ren and Li [7] simulation and optimized the performance of a hybrid wind-solar-pumped storage