Performance Analysis of a Wind Turbine Based on a Solar Nozzle

A modified method has been proposed for conversion of wind energy into mechanical energy accelerates because of the narrowing constriction. Heat energy acquired from the wall is converted into the kinetic energy of flow. Critical dimensions are calculated for the convergent nozzle that made of glass. This study focuses up on the benefits of using solar nozzle on the wind energy. The study is an attempt to raise the local wind velocity (1 m.sec -1 ) to a high velocity that gives good energy allowed the wind plant to generate power, other words in order to increase the efficiency of the plant. From the results, it is observed that the velocity of wind increases by the increment of heat gain and decrement of the area. The exit velocity value in the case of heat added is reached to (19 m.sec -1 ), while in the case International Journal of Environment & Water ISSN 2052-3408 _____________________________________________________________________________ Vol 2, Issue 3, 2013 29 Page of no heat transferred is about (18 m.sec -1 ). Calculation indicates that maximum heat gained could give (2.5 KW) output power. Nomenclature A Area (m) Cp Specific heat capacity, for air (1005 J.kg .K) d Diameter of the nozzle (m) h Heat transfer coefficient (W.m. K) I Incident radiation (W.m) K Thermal conductivity (W.m.K) m Mass flow rate (kg.sec) Pr Prandtl No., for air (0.7) q Heat added (J.kg) R Gas constant, for air (287.1 J.kg.K) V Velocity (m.sec) θ Incidence angle μ Dynamic viscosity (kg.m.sec) ρ Density (kg.m) CFD Computational fluid dynamics Introduction The improvement of any power plant needs to know what the components that depending on it. In the case of wind plant, it is necessary to know the behavior of the wind. There are several factors affect on the wind state such as velocity, temperature and flow direction. Power of the wind can be extracted by allowing it to blow past moving wings that exert torque or rotor. The wind profiles show that the wind energy conversion device with a certain amount of confidence to extrapolate better wind speed taken at a height more than (10 m) [1]. Solar power is the technology of obtaining usable energy from sun light. The advantages of used renewable energies (solar and wind) are; no pollution, no fuel needed and low costs [2]. It is clear that the using of solar energy at latitudes with higher levels of radiation will improve the performance of wind system and make it possible to cover loads with smaller and less expensive systems. Attempts to parameterize the solar radiation received at the ground are made for the global radiation (direct plus scattered, and for tilted planes also radiation reflected onto the surface), rather than separately for normal incidence and scattered radiation [3]. Padki and Sherif [4] suggested a small model solar chimney of radically different geometry. In this case the chimney is conical with the turbine placed at the narrowing of the cone. The paper is mainly theoretical but they argue that there is no upper bound on the efficiency. The efficiency is rise up to 20% by the heat gained. Unfortunately the practical results reported are much less impressive. An international study of power system impacts of wind power [5] has been formed in 2006 under the IEA implementing agreement on wind energy; the task would analyze case studies from different power systems. The results are not easy to compare, for example the incremental regulation due to wind was found to be 36 MW in a location in USA while in another International Journal of Environment & Water ISSN 2052-3408 _____________________________________________________________________________ Vol 2, Issue 3, 2013 29 Page location in Netherlands it is about 6000 MW. Williams [6] propose theoretically a prototype convergent nozzle made of glass and arranged vertically. A solar absorber abundantly perforated and several layers thick or of metallic honeycomb structure is arranged in the lower levels but above the base of the nozzle. The convergent solar nozzle has base diameter of (10 m), throat diameter of (1 m), and height of (10 m). Calculation indicated that the maximum output power in the summer of UK is about (59 KW) and the temperature difference through the nozzle is (1.2 o C). Sakonidou ,et al. [7] determine the tilt that maximizes natural air flow inside a solar chimney. The model starts by calculating the solar irradiation components absorbed by the solar chimney. The calculations have been obtained by a simulation program solves the relevant conservation of mass, momentum and energy equations (CFD) for solar chimney using finite difference methods. The model predicts the temperature and velocity of the air inside the chimney as well as the temperatures of the glazing and the black painted absorber. The experimental chimney duct has the shape of a narrow parallelepiped with dimensions: 1 m height, 0.74 m width and 0.11 m gap. Black painted aluminum sheet is used for the construction of walls of the chimney. The walls have absorptance of (0.95). Comparisons of the experimental model predictions with CFD calculations delineate that there is a good agreement between them at different tilt positions. The objective of the present study is introducing an analysis and procedure of using solar nozzle. The solution was merging between analytical of wind energy and solar energy to increase the wind energy to a rate allowed the wind plant to generate power, also in order to increase the efficiency of the plant by using a convergent nozzle arranged horizontally and exposed to solar radiation. A wind turbine placed in the throat of the nozzle converts flow kinetic energy into electricity, (figure 1). Figure (1) Supposed Wind Plant Method and Materials The fact that the amount of solar radiation received at a given location at the Earth surface varies with time due the Earth’s rotation (Diurnal Cycle) and also depending on the latitude [3]. The average rate of the solar radiation incidence on a horizontal plate in Iraq (Baghdad) for July is about (450 W/m 2 ) [1]. SSuppose that the nozzle is solar collector, so the iinput radiation power (qR) is [8]:   N R I q (1) Nozzle q Wind Air Turbine q International Journal of Environment & Water ISSN 2052-3408 _____________________________________________________________________________ Vol 2, Issue 3, 2013 29 Page   Cos I I S N (2)        Sin Sin Cos Cos Cos


Abstract
A modified method has been proposed for conversion of wind energy into mechanical energy accelerates because of the narrowing constriction.Heat energy acquired from the wall is converted into the kinetic energy of flow.Critical dimensions are calculated for the convergent nozzle that made of glass.This study focuses up on the benefits of using solar nozzle on the wind energy.The study is an attempt to raise the local wind velocity (1 m.sec -1 ) to a high velocity that gives good energy allowed the wind plant to generate power, other words in order to increase the efficiency of the plant.From the results, it is observed that the velocity of wind increases by the increment of heat gain and decrement of the area.The exit velocity value in the case of heat added is reached to (19 m.sec -1 ), while in the case

Introduction
The improvement of any power plant needs to know what the components that depending on it.In the case of wind plant, it is necessary to know the behavior of the wind.There are several factors affect on the wind state such as velocity, temperature and flow direction.Power of the wind can be extracted by allowing it to blow past moving wings that exert torque or rotor.The wind profiles show that the wind energy conversion device with a certain amount of confidence to extrapolate better wind speed taken at a height more than (10 m) [1].
Solar power is the technology of obtaining usable energy from sun light.The advantages of used renewable energies (solar and wind) are; no pollution, no fuel needed and low costs [2].It is clear that the using of solar energy at latitudes with higher levels of radiation will improve the performance of wind system and make it possible to cover loads with smaller and less expensive systems.Attempts to parameterize the solar radiation received at the ground are made for the global radiation (direct plus scattered, and for tilted planes also radiation reflected onto the surface), rather than separately for normal incidence and scattered radiation [3].
Padki and Sherif [4] suggested a small model solar chimney of radically different geometry.In this case the chimney is conical with the turbine placed at the narrowing of the cone.The paper is mainly theoretical but they argue that there is no upper bound on the efficiency.The efficiency is rise up to 20% by the heat gained.Unfortunately the practical results reported are much less impressive.
An international study of power system impacts of wind power [5] has been formed in 2006 under the IEA implementing agreement on wind energy; the task would analyze case studies from different power systems.The results are not easy to compare, for example the incremental regulation due to wind was found to be 36 MW in a location in USA while in another Page location in Netherlands it is about 6000 MW.
Williams [6] propose theoretically a prototype convergent nozzle made of glass and arranged vertically.A solar absorber abundantly perforated and several layers thick or of metallic honeycomb structure is arranged in the lower levels but above the base of the nozzle.The convergent solar nozzle has base diameter of (10 m), throat diameter of (1 m), and height of (10 m).Calculation indicated that the maximum output power in the summer of UK is about (59 KW) and the temperature difference through the nozzle is (1.2 o C).
Sakonidou ,et al. [7] determine the tilt that maximizes natural air flow inside a solar chimney.The model starts by calculating the solar irradiation components absorbed by the solar chimney.The calculations have been obtained by a simulation program solves the relevant conservation of mass, momentum and energy equations (CFD) for solar chimney using finite difference methods.The model predicts the temperature and velocity of the air inside the chimney as well as the temperatures of the glazing and the black painted absorber.The experimental chimney duct has the shape of a narrow parallelepiped with dimensions: 1 m height, 0.74 m width and 0.11 m gap.Black painted aluminum sheet is used for the construction of walls of the chimney.The walls have absorptance of (0.95).Comparisons of the experimental model predictions with CFD calculations delineate that there is a good agreement between them at different tilt positions.
The objective of the present study is introducing an analysis and procedure of using solar nozzle.The solution was merging between analytical of wind energy and solar energy to increase the wind energy to a rate allowed the wind plant to generate power, also in order to increase the efficiency of the plant by using a convergent nozzle arranged horizontally and exposed to solar radiation.A wind turbine placed in the throat of the nozzle converts flow kinetic energy into electricity, (figure 1).

Method and Materials
The fact that the amount of solar radiation received at a given location at the Earth surface varies with time due the Earth's rotation (Diurnal Cycle) and also depending on the latitude [3].The average rate of the solar radiation incidence on a horizontal plate in Iraq (Baghdad) for July is about (450 W/m 2 ) [1].
SSuppose that the nozzle is solar collector, so the iinput radiation power (q R ) is [8]: Where: ατ = Product of absorptive and transitivity (which is 0.95 for the nozzle material [7]) I S = Solar Radiation for Baghdad at a specific conditions (450 W/m 2 ) [1] The solar angles that used in equation ( 3 ), and (cos θ = 0.97).
The heat loss across the wall is denoted as [8]: Where T a = Local air temperature (35 o C average value in Baghdad, July) T b = Average bulk temperature inside the nozzle (suppose as 36 o C) Principally, the overall heat transfer coefficient (U) can be calculated from [9]: Where, i:-refers to the internal part of the nozzle o:-refers to the external part of the nozzle The convection heat transfer coefficient (h) can be determined from [9] (8) Consequently, the useful heat gained to the flow will be: The heat removed factor (F R ) has value of (0.8) [8].A N is the surface area of the nozzle which represents a semi-cone shape so it is calculated from:

Modeling of Nozzle Flow Fields
The analysis considered the effects of both changing flow area and heat exchanged.The effects of wall friction assumed to be negligible.The quasi one-dimensional assumption will be used.Consider the steady flow through the control volume as shown in figure (2).

Figure (2) One-Dimensional Control Volume
Hence the continuity equation gives [10]: While, the conservation of momentum ggives [11]: The second term on the left hand side represents the force due to the pressure on the wall.By neglecting the second order terms gives [10]: Also, the equation of state gives [10]: From equations ( 11) and (13) yields: From equations ( 14) and (15) yields: Substitute equation ( 17) into ( 16) and rearrange, leads to: This equation gives the variation of pressure across the control volume, it mean that: dP P P The velocity value then can be found from the continuity equation, so: The value of heat added that calculated in equation ( 9) is in (Watt) so it must be divide on the mass flow rate ( m  ) to satisfy that used in equation (20) which is in (J/kg).Also the decrement in area (dA) is depending on linear formula.
The output power then can be calculated at the exit of the nozzle by:


(26) For air at operation design, the critical length is calculated to be (8 m); therefore the design length (10 m) is acceptable.

The Mathematical Procedure
In order to calculate the flow properties inside the nozzle, a program of FORTRAN-90 is adopted and explained in flow chart as shown in figure (3).The nozzle is divided into 40 control volumes, the heat gain (dq) is provided in each control volume and the inlet properties are taken as shown in table (1).The nozzle is made from glass, the inlet diameter is (4 m), the exit diameter is (1 m) and its length is (10 m), and locates in horizontal level (7 m) up of the ground.Equations (18 -24) are used to calculate the properties in the exit of the control volume then take the next control volume and repeat this procedure until reaching to the end of nozzle.

Results and Discussion
Analysis of the design conditions and the interference effects of the free stream velocity and the heat load have been done.The flow velocity and temperature are the dominated parameters for comparison at different conditions.
Figure (4) shows the variation of flow velocity along the nozzle, it is observed that the velocity of the air increase by the decrement of the area.The raise in the value of velocity in the case of heat added is more than that of no heat; it is reached to (19 m.sec -1 ), while in the case of no heat it is about (18 m/sec).The output power in the case of heat gained is (2.5 KW), while in the case of no heat it is about (2.4 KW).These results are compared with that denoted by Williams [6] as showed in figure (5); note that the dimensions are identified in this case in order to satisfy the comparison.
From figure (6), it is observed that the temperature of the air increased rapidly in the case of heat added, while it may be less in that of no heat.The temperature difference in this study is about (1 0 C), while Williams [6] determined that it is about (1.2 0 C) for case of vertical nozzle and solar absorber arranged in the base of the nozzle.Figure (7) show another comparison, it is observed that the percentage error of flow temperature between the experimental work of reference [7] and this study is about (-2 %) when (x < 7 m) and about (+4 %) when (x > 7 m).
Although that the heat gained is a small, but it can be increase by advantages of concentrating the solar radiation [2].The concentrating of radiation can be rise the solar power to about (4500 W/m 2 ), that's mean the exit velocity in the design operation conditions reaches to an increment of (20%) than that of no concentrating (450 W/m 2 ).

Conclusions
Generally, there are several results to be noticed from the whole research according to the fluid energy which can be listed below as: 1-It is an open cycle, where the described solar nozzle is 10 m height, 4 m base diameter and 1 m throat diameter.2-The value of velocity in the case of heat added is reached to (19 m.sec -1 ), while in the case of no heat transferred it is about (18 m.sec -1 ).3-Maximum heat gained could give an output power reached to (2.5 KW).
) are variables and depend on the location and time, hence for Baghdad at noon time in July ( Where, L =Nozzle length (m).D i = Inlet diameter (m) Page D o = Exit diameter (m) of state for perfect gas to determination the density value, hence: Demonstrating the critical length of the nozzle need to achieve the conversion of full solar energy absorbed into the kinetic energy of flow at the exit of the nozzle, it means: