Wind Energy Conversion System for Electrical Power Generation in

Izelu Christopher

Wind Energy Conversion System for Electrical Power Generation in

Abstract

As one of the fifth major urban cities in Nigeria, high demand for electricity in Port Harcourt, Rivers State, Nigeria is evident, and hence, requires high installed capacity for steady conventional energy source. At present this is hardly met, coupled with its attendant risk of undesirable emissions and other identified disadvantages. This paper considers that the conventional energy source may be supported or entirely replaced by the alternative or renewable sources to meet demands for electricity as well as minimize risks of undesirable emissions including other limitations of the conventional sources. It therefore presents a study of wind energy conversion system to be installed along the Choba banks of the New Calabar River. The system should be capable of serving electricity need of the University of Port Harcourt and the University of Port Harcourt Teaching Hospital all in Port Harcourt. The study is focused on the horizontal axis wind farm turbine rotor aerodynamic performance analysis, using the blade element momentum theory, and economic evaluation of the wind energy conversion system. It showed that, to meet with the total power requirement of 21 [MW] in the University and its Teaching Hospital for a projected period of 20 years, rotor blades of each of the wind farm turbines, which are optimally designed for capacity of 1.5 [MW], wind velocity of 17.5 [m/s], and for airfoil shape of NACA 2412, are desired. The power and torque of the designed turbines, using these blades and having positive non linear relationship with wind velocity, were achieved. Besides, an economic study of the system revealed savings in costs of N8, 633,032,101.98 in comparison with the existing diesel plant.

Figures (16)

Figure 1: Components of a Wind Energy Conversion system (Source: A barzadeh et al [7]) high efficiency and low blade fatigue. Most HAWT have two or three blades, which may be oriented upwind or downwind of the tower [28]. They may also be actively or passively yawed to face the rotor in the wind direction. The actively yawed wind turbines use wind direction sensor and yaw motor to position the rotor. They are usually very large Figure 2: Alternative Configurations of WECS (Source 3ureau of Energy Efficiency, India) Wind energy conversion technology is not entirely new, however more efforts are required from, and has been exerted by, numerous researchers to further its development and applications. Some of the major developments are discussed in the works of Johnson [3] and Munteanu et al [4 on wind energy conversion systems; Stiebler [5] and Abarzadeh et al [6] on wind energy conversion systems for electric power generation; Ragheb and Ragheb [7] on wind turbine theory based on the Betz aerodynamic actuator disc concept; Ingram [8, 9], Cowgill et al [10], Schubel and Crossley [11], Tenguria et al [12], Shateri [13], Rathore and Ahmed [14], Leisshman [15], Bak et al [16], Zhang [17] and Claessens [18] on vertical and horizontal axis wind turbine blade design, analysis and performance evaluation based on the blade element momentum theory; Ahlstrom [19] on wind turbine dynamics; Martens and Albers [20], Khemiri et a 21] and Belfedhal et al [22] on wind energy conversion systems drives, generators and controls; and Website [23], Jacob et al [24] and Moran [25] on wind turbine blade airfoils. These works are quite relevant in the present study to aid understanding, and subsequently, to establish criteria to aid understanding, and subsequently, to establish criteria A wind energy conversion system (WECS), also known as wind turbine (WT), performs the function of wind energy capture or extraction, and its subsequent direct conversion into mechanical energy achieved through its capacity to cause rotational motion of the turbine rotor. The mechanical energy may be used either for electric power generation, or for numerous other purposes. The various components of WECS designed for power generation are schematically depicted in Fig 1 [7]. As shown in Fig 2 [27], its main alternative configurations, based on the rotor design and its shaft orientation, are the vertical-axis wind turbine (VAWT) and horizontal-axis wind turbine (HAWT).

The initial guesses for iterative solution of the above system of equations are obtained from the following equations.

for a finite number ( N ) of blade elements to determine the optimal blade design. These equations are given as follows:

The turbine blade surface profile coordinates are defined by the standard NACA 4-digit series formulae. Moran [25] gives one of such formulae for symmetrical NACA 4-digit series airfoils as, Note that, in this equation, * [m] is the position on the

Figure 3: Surface Profile for Un-twisted 0th NACA - 412 Blade Element (S/N =0) The swept diameter of the designed rotor is 40.1931 [ m] which results in a reduction of about 20 [m] when compared with a wind turbine of the same capacity available in market which has a swept diameter of 60.25 [m] [27] .T the his results in large savings in material cost for both the blades and the tower, since the larger the blade size the larger tower. The minimum geographical area required when the the market turbine is used is 2851.044 X 920 [m2] when compared with that required when the designed turbine used, which is only 1265.392 X 920 [m2]. It is seen that is the land area required has been reduced by 1585.652 X 920 [m2].

Figure 5: Surface Profile for Un-twisted 10th NACA- 2412 Blade Element (S/N =10) Figure 4: Surface Profile for Twisted 0th NACA -2412 Blade Element (S/N = 0)