Solar Chimney and Power Tower Techniques for Power Production in Nasiriya City

The solar chimney and power tower are two of modern promised energy which can develop by low losses, simplicity and high power. In this paper, the solar chimney and fossil fuel power tower parameters are studied by using theoretical equations in computational fluid dynamics CFD that substituted in some computer programs such as MATLAP and FLUENT codes with additional related expressions. Five different models are used in this paper (Chimney height is: 12, 15, 20, 25, and 35 meter), (Diameter of collector base is: 5, 8, 10, 15, and 20 meter). The effect of inlet collector height, collector absorbability, solar radiation, ambient temperature, solar collector thickness and solar collector tilt angle are studied to find the other parameters and properties such as velocity distribution, power and efficiency of system. The erecting of power turbine is predicted by findings the velocity distribution between the base and chimney assembly. The numerical analysis was presented by using GAMBIT and FLUENT 6.3 to predict that high velocity at the expansion of chimney near the center of base – chimney bond position because of low density of air as a result to solar radiation flux (and burned gases cover collector in case of using the chimney for combustion of gases in oil refineries).. This position is very suitable for promoting and building the power turbine. The maximum power accumulated from these techniques is more than (6.7×10 Watt) where the velocity is (17.5 m/s). The study concluded that it is easy work to erect these chimney and power tower techniques closed to drilling and oil facilities in remote areas. So, all factors were studied to coincide with previous papers in this field.


Introduction
The solar chimney concept was proposed in 1970s by Schlaich and later in1980s studies were carried out witha 50 kW power prototype in Manzanares, Spain. The prototype had about 11000 m 2 collector installed on a horizontal land area, 200 m height and 10 mdiameter chimney, and a 50 kW nominal power turbine [1] .The three important parts of a solar chimney power plant are the collector system, the chimney and the air turbine as shown in Fig. (1). Ambient air enters the collector system from the periphery of the collector and heated mainly by convection along the hot ground. It enters at the bottom of the chimney due to pressure potential generated by the difference of density between the warm air and ambient air.  Schlaich(1995) was credited as being the first to propose solar chimney as a means to harness energy from the sun [2]. Pasumarthi and Sherif (1998) reported that increase of tower height resulted in higher velocity and mass flow rate; and when the insulation was fixed, an increase in the mass flow rate was accompanied by a lower air temperature at the collector  [3] . Chitsomboon (2001) found that efficiency of the plant was invariant with respect to the insulation level and size [4]. Dai et al. (2003)demonstrated that the power output increased nonlinearly with the size of the plant, rapidly when the size was small and at a slower rate when the size was larger [5]. Schlaich et al. (2005) proposed that the overall efficiency was influenced only by the tower height [6]. More recently, Tingzhen et al. (2006) reported that efficiency should also be affected by solar radiation and collector radius [7]. Xu et al. (2011), performed a numerical simulation of a solar chimney with an energy storage layer similar to the Spanish prototype [8] . Patel et al. (2014), introduced theoretical study of the flow characteristics inside the solar chimney power plant by using a computational fluid dynamics (CFD) software (ANSYS-CFX) [9].
The aim of this study is to analyze the power chimney system by using the solar radiation equations applied by MATLAP and FLUENT program codes at Nasiriya city, so, to study the feasibility of turbine situation erection at the canopy -chimney section of the system base and to use this system closed to drilling and oil facilities in remote areas

Theoretical analysis
The convective heat transfer coefficient between the outer collector plate (W/ m 2 .K) and the surrounding (outside air) can be found as [10]: The pressure developed in chimney is calculated from equation [11]: The velocity of air inlet to chimney is calculated by [12] : The mass flow rate of air inlet chimney is calculated from equation [13]: The power output of solar chimney power plant is calculated from equation [ 14]: The efficiency of solar chimney plant is calculated as:

2-Results and Discussion
In this study, five models are used as demonstrated in table (1) below by changing the chimney height with canopy diameter. The choice of these values depend on some practical and theoretical models that used by researchers before. All equations above are programmed by using MATLAP program code.
The paper results include six cases depending on many parameters such as: ambient temperature, total solar radiation, and wind speed, height of collector and transmittance of collector for solar energy.