Hydrokinetic Turbines ? Introduction // Rotor Hydrokinetic Turbine Design (Fluid?Solid Interaction)

OLLER MARTÍNEZ, SERGIO.; OLLER ARAMAYO, SERGIO A.; MARTÍNEZ, X.

Composite Materials ? Oriented to a River Bed Hydrokinetic Turbine Design

Oxford Elsevier

Año: 2018; p. 236 - 265

According to United Nations, 20% of the global population does not have access to electricity, and a further 14% lack reliableaccess [1]. The use of an axial flow rotor turbine in remote area was claimed to have for pumping irrigation and electrical powergeneration. Hydrokinetic turbines bring newer, greater possibilities and advantages for hydroelectric power generation. There areapplications in water currents of 0.5 m/s or greater [2]. Development of renewal energy production in rivers and channels stillpreserve a very interesting power production potential, being not subjected to the classical hydraulic power exploitation. Thissolution avoids the construction of expensive dams and reduces considerably the environmental impact produced by classicalhydropower generation [3]. Low speed flux and lack of depth are the main obstacles in hydrokinetic operation. For this reason,achieving a very high lift rotor to take the maximum advantage of the kinetic energy of a slow velocity water flow, which belongs toa lowland river type, is a very important topic. The use of a high lift aerodynamic/hydrodynamic profile and composite materialfor the blades serve to accomplish the task.The main purpose of this chapter is to describe a general procedure to achieve a very low inertia rotor minimizing the start-stopeffect for the axial water flow turbine, in which it is important to take the maximum advantage of the kinetic energy. Thecomposite hydrofoil of the turbine rotor can be designed using reinforced laminate composites, to obtain the maximum strengthand lower rotational inertia. The mechanical and geometrical parameters involved in the design of this fiber-reinforced compositematerial are the fiber orientation, number of layers, stacking sequence, and laminate thickness.For this reason, it will be briefly described the features of hydrokinetic turbines (water current turbine (WCT)) for river use,their basic design requirements and the response by using matrix-reinforced composite structures. Design requirements for theseturbines need a numerical process simulation of the fluid-dynamic problem coupled with the behavior of the structure made ofcomposite materials. From the structural viewpoint it is necessary the use of an advanced composite material formulation thatallows an appropriate structural design. For this purpose, a ?mixing theory? [4?16] and/or ?homogenization theory? [16?25] ofsimple substances are used, with a mapping spaces formulation [26] that allow considering the anisotropy of the constituent andcomposite materials in the most general possible way, and a fiber?matrix debonding formulation [5,9,11,14]. Moreover, withinthese general formulations, it is also taken into account the nonlinear mechanical behavior of the component materials (matrixand fiber), which allows to know precisely the limits of participation of each one of them into the composite.The study of composite materials has been one of the major objectives of computational mechanics in the last decade. Thenumerical simulation of orthotropic composite materials has been done by means of the average properties of their constituents,but this approximation, no model has been found able to work beyond the constituents? elastic limit state. Thus, these proceduresare limited to the numerical computation to elastic cases. Different theories have been proposed to solve this problem, taking intoaccount the internal configuration of the composite to predict its behavior. The two most commonly used are herein remarked.