Dynamic Performance Enhancement of Vertical Wind Turbine Using Composite Blades Reinforced by Zinc-Oxide Nanoparticles. (Dept. M.)

Abstract

needed drinking clean water. As examples, the wind turbines have been used in wind farms to produce cheap electricity [1, 2]. Moreover, the desalination plants near the seas beach can be powered using solar or wind energy [3-5]. Also, a widespread scientific study in this regard was presented by Ramkissoon et al. [6] to assess the renewable energy sources' potential development in operating a water desalination plant in Trinidad. Unfortunately, on the other hand a few communities in some areas around the world, as on a certain island in Greece, are resisting the renewable energy usage in their regions as discussed by Kaldellis [7]. Generally, there are many research work challenges accompanied by the different renewable energy systems which are developed for generating the needed energies [8,9]. Currently, wind energy has attracted several researchers as one of the important domains of renewable resources in addition to its encouraging opportunities for application in several fields. Most of the research work in the renewable energy field is focused on determining the proper approaches for energy generation in a particular scenario [10] or to improve the efficiency of a certain system [11]. Commonly, two types of wind turbines can be used to convert wind energy to power generation. Those two main types are the Horizontal and the Vertical Axis Wind Turbines known as HAWT and VAWT. Intensive studies devoted to compare HAWT and VAWT performance at typical wind speed range are presented in [12-14]. Generally, HAWT is only economically valuable at steady high-speed wind as discussed in [13-16]. Furthermore, VAWT preserves its performance independently of wind direction. Also, VAWT has a simplified construction design and it can efficiently work via simple maintenance in addition to low cost of operation. Therefore, VAWT is appropriate for using it as dispersed units in rural communities. Moreover, new wind turbines' designs for generating cheap electricity, such as the floating offshore wind turbine were presented in [1, 17-18]. Furthermore, offshore VAWT can be used in compressed air energy storage system [19, 20]. The common shape of the VAWT blades that can be effectively employed is the Savonius type blades. Moreover, different Savonius blades' shape optimization of VAWT was presented in [21]. The VAWT performance analyses in addition to the flow field assessment are focused by many researchers [22-24]. Some research works were focused on manufacturing appropriate prototypes, which were experimentally assessed in wind tunnels, to investigate their performance [25-28]. Moreover, widespread studies were concerned with the computational fluid dynamics (CFD) usage [29-31]. These studies were dealing with the wind turbine simulations by focusing on the aerodynamics and air flow. Otherwise, many research works were focused on the use of composites and polymer based materials in VAWT blades. As examples, an intensive study for studying the feasibility of using fiber-reinforced polymer composite in VAWT blades was presented by Zhong-Jia et al. [32]. It was concluded that the light blade weight resulting from the low density of the blades composite structure could significantly enhance the efficiency and the performance of the wind turbine which has composite blades. Furthermore, a concentrated study dealing with Finite Element (FE) analysis of a composite VAWT blade was introduced by Hameed et al. [33] for studying the effect of the centrifugal forces on the deflection of wind turbine's blade. Moreover, Lin et al. [34] presented a structural analysis study considering the ultimate strength analysis of VAWT composite blades to determine the fatigue-critical locations of the turbine's blades. Also, a widespread study dealing with composite blades' fatigue of large Darrieus VAWT was introduced by Kumar et al. [35]. They inferred that most of the turbine failures are related to the blade's fatigue due to constantly aerodynamic force variations on each revolution. The dipping of inorganic nanoparticles (NPs) into epoxy not only improves their mechanical properties, but also enables to overcome their shortcomings from the point of view of some practical usages by enhancing their flame-retardant, thermal stabilization and other properties [36]. Savonius type wind turbines reduced efficiency was considered by many research works. In order to increase the output torque, modified blades and rotor designs were adapted through the optimization of blade profile and using obstacle shielding to eliminate the negative torque of the non-active side. El-Askary et al. [37] studied the performance of a twisted Savonius wind blade rotor with a modified profiles at various overlap ratios and aspect ratios. Whereas Mohamed et al. [38] achieve their objective through optimizing the position of an obstacle that shields the returning blade of a Savonius wind turbine. This optimization process led to a considerable improvement of the power coefficient in the range of 27%. Khader and Nada [39] also used a rotating shield to orient the inlet flow and used crank-crank mechanism to reorient his model blades to improve its performance. The objective of this research work is to improve the dynamic performance of VAWT composite blades' structure by using reinforced blades composite material with Zinc-Oxide (ZnO) Nanoparticles. To evaluate our goal, a VAWT prototype of multistage Savonius composite blades is manufactured to perform necessary vibration and ultrasonic tests and assess the prototype performance. The theoretical and experimental natural frequencies of the prototype are evaluated to ensure that the proposed model is capable of rotating at considerably high speeds without being exposed to resonance problems. On the other hand, the effect of changing the shift-angle between the turbine blades stages (layers) on the prototype efficiency was assessed.