2. Materials and methods
To develop a wind power system for the rear side of ventilation fans, this study took the following four steps: step 1 – analyze airflow at the rear side of the ventilation fan, step 2 – design wind turbine blades based on the characteristics of the airflow at the rear side of the ventilation fan, step 3 – evaluate the efficiency of the wind turbine and the generator through lab experiments, and step 4 – install the wind power system, including a power-converting system, on an actual broiler house to evaluate the system.
The first step was conducted by Hong et al. (2012a), and it is briefly cited in the results and discussion. In this study, the researcher undertook the blade design, wind power system installation, and the evaluation of the system, which are the most important elements of wind power design.
2.1. Physical descriptions of the blade design
2.1.1. A Brief Description of blade element momentum method
Blade element momentum (BEM) method combines momentum theory and blade element theory (Griffiths, 1977, Burton et al., 2001 and Lanzafame and Messina, 2009). It is the most widely used classical theory, both to interpret the dynamics of rotor blades and to design a blade section. Momentum theory describes the relationship between the power upon rotors and the fluid velocity generated by the power. Using momentum theory, one can estimate rotor efficiency. However, momentum theory does not stipulate how to design rotor blades. Blade element theory divides the blades into several elements and calculates the power that affects each blade element in terms of fluid velocity. The power upon the blade element relies on the lift force (FL), drag force (FD), fluid velocity (Vr) and direction (α). These relationships are described in Fig. 1.