energies Review A Review on Failure Modes of Wind Turbine Components Abdul Ghani Olabi 1,2, * , Tabbi Wilberforce 2 , Khaled Elsaid 3, * , Enas Taha Sayed 4,5 , Tareq Salameh 1 , Mohammad Ali Abdelkareem 1,4,5, * and Ahmad Baroutaji 6   Citation: Olabi, A.G.; Wilberforce, T.; Elsaid, K.; Sayed, E.T.; Salameh, T.; Abdelkareem, M.A.; Baroutaji, A. A Review on Failure Modes of Wind Turbine Components. Energies 2021, 14, 5241. https://doi.org/10.3390/ en14175241 Academic Editor: Francesco Castellani Received: 26 May 2021 Accepted: 5 August 2021 Published: 24 August 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Department of Sustainable and Renewable Energy Engineering, University of Sharjah, Sharjah P.O. Box 27272, United Arab Emirates; tsalameh@sharjah.ac.ae 2 Mechanical Engineering and Design, School of Engineering and Applied Science, Aston University, Aston Triangle, Birmingham B4 7ET, UK; awotwet@aston.ac.uk 3 Chemical Engineering Program, Texas A&M University at Qatar, Doha 23874, Qatar 4 Centre for Advanced Materials Research, University of Sharjah, Sharjah P.O. Box 27272, United Arab Emirates; e.kasem@mu.edu.eg 5 Chemical Engineering Department, Faculty of Engineering, Minia University, Minya 61519, Egypt 6 Department of Mechanical Engineering, University of Wolverhampton, Wulfruna St, Wolverhampton WV1 1LY, UK; a.baroutaji@wlv.ac.uk * Correspondence: aolabi@sharjah.ac.ae (A.G.O.); khaled.elsaid@qatar.tamu.edu (K.E.); mabdulkareem@sharjah.ac.ae (M.A.A.) Abstract: To meet the increasing energy demand, renewable energy is considered the best option. Its patronage is being encouraged by both the research and industrial community. The main driving force for most renewable systems is solar energy. It is abundant and pollutant free compared to fossil products. Wind energy is also considered an abundant medium of energy generation and often goes hand in hand with solar energy. The last few decades have seen a sudden surge in wind energy compared to solar energy due to most wind energy systems being cost effective compared to solar energy. Wind turbines are often categorised as large or small depending on their application and energy generation output. Sustainable materials for construction of different parts of wind turbines are being encouraged to lower the cost of the system. The turbine blades and generators perform crucial roles in the overall operation of the turbines; hence, their material composition is very critical. Today, most turbine blades are made up of natural fiber-reinforced polymer (NFRP) as well as glass fiber-reinforced polymer (GFRP). Others are also made from wood and some metallic materials. Each of the materials introduced has specific characteristics that affect the system’s efficiency. This investigation explores the influence of these materials on turbine efficiency. Observations have shown that composites reinforced with nanomaterials have excellent mechanical characteristics. Carbon nanotubes have unique characteristics that may make them valuable in wind turbine blades in the future. It is possible to strengthen carbon nanotubes with various kinds of resins to get a variety of different characteristics. Similarly, the end-of-life treatment methods for composite materials is also presented. Keywords: composite material; turbine blade; failure mode; cost analysis 1. Introduction Climate change continues to remain a major issue for both research and industrial communities [1,2]. As the yearly energy demand of the world increases, carbon dioxide emissions increase, as well. This is because fossil products continue to be the main driving force for the energy industry to date [3,4]. The instability of prices for fossil products, coupled with their reserves depleting at a faster pace, has necessitated the urgent need for an alternative form of energy generation [5,6]. Most countries have supported this clarion call by actively formulating policies that seek to expand the renewable energy sources [7,8]. Obviously, the signing of the Kyoto agreement and the Paris agreement by 192 and 197 countries around the world, respectively, is an indication of the massive support Energies 2021, 14, 5241. https://doi.org/10.3390/en14175241 https://www.mdpi.com/journal/energies