Numerical and Mechanical Modeling of Reciprocating Type of Wind Harvester for Rural and Remote Areas to Generate Electrical Power

Now day’s energy is the fourth basic needs for human beings after food, cloth and shelter. On the other hand energy has also its own  draw back to our living environment especially if we are using   fossil fuels as source of energy .Wind energy  is among the recently flourishing technologies and get more acceptance from time to time to meet the energy demand of the societies and to reduce the environmental crises happen  due to fossil fuels. Thus, Small wind turbines are the best options to provide power for those which have limited power access and areas far from the central grid. Areas which have a lot wild diversity especially birds reciprocating type of small wind turbines are good alternative to save the life of the birds. Designing a reciprocation type wind power harvester which is able to produce electricity with low cost, designing analysis, manufacturing and maintenance was the main objectives of the work. The overall procedure for completing the project starts by collecting relevant data for the design up to finalizing the project as a methodology. The Core parties were designed and suitable material by considering different criteria were selected for individual components. The design made ware safe and turbine is economically feasible and environmentally friendly. Finally, this technical document concluded that the capacity of the Reciprocating Type Wind Power Harvester produces the ideal output power of 10.125kw at the tower high of 20m above the ground with cut in speed of 3m/s wind speed Keywords: Energy, Wind energy, reciprocating type, small wind turbine DOI: 10.7176/JETP/10-3-01 Publication date: July 31 st 2020


INTRODUCTION
The benefit of energy is clear for everyone no matter its profession he or she is. We use energy to cook and baking our daily food, to entertain(to listing music to watch tv etc. ) ,to transport from place to place(using cars, motor cycles , airplane etc.),to run our industries, to keep our personal comfort using (ventilators, heaters and different air conditioning systems),to communicate with peoples ,to iron our clothes etc. So, no one can argue us we can say that energy the fourth basic needs for human beings' after food, cloth and shelter.
In our country Ethiopia Hydro power sources will remain the most important electrical energy sources for the country, however this source of power is just limited ln urban and semi urban areas only. However, about 85% of the total population of the country are living in rural areas. From this huge number only few of the rural population have access to the electricity from grid. This is because of scattered way of settlement; difficult geographical landscape and low population density of the communities providing grid electricity for the rural population of Ethiopia require huge budgets for its implementation. So, to overcome such problems small scale wind turbines are the best alternatives to expand electricity to society. However, the current turbines which are available in the market are very expensive to buy ,expensive to build, difficult access to repair, difficult for ecosystem, they are so noisy etc. such type of draw backs can be avoided by using the new concept design which is called reciprocating type of wind turbine is introducing here.

Data Collection
The relevant information about wind speed and wind variations depend on the altitude of wind vane are collected.
Thus, relevant data were taken from South Nations Nationalities and Regional of peoples of Ethiopia (SNNPR) Metrological agency which is located in Hawassa. The data that we take from Metrological Station at Hawassa for the successive four years of (2017-2018) about wind speed and wind variations are the basic of this project to start the design analysis.

Material selection
The factors which should were considered while we select the material for the machine component are availability, low cost, mechanical properties, ease of handling, ease of use, environment friendly, portability, low noise, ease of maintainable etc.

3.RESULT, DISCUSSION AND CONCEPT DEVELOPMENT OF THE PROJECT
Here under this title the core parts of the harvester were designed and different materials and numerical were taken from standard. The average wind speed of the site for the year 2017 and 2018 of the selected site varies between 3.5m/s and 6.5m/s. So, in this project for simplicity we have took average wind speed as 5 m/s.

Design of main parts of Reciprocating Type Wind Power Harvester
There are different kind forces which can be considered in the design of wind turbine blade. The most commons are Stochastic loads, Cyclic loads, Steady (Static and rotating), resonance-induced loads [1-10]

Design of Rectangular Plate (Blade)
The plate is a place in which the wind strikes and the power of wind is absorbed. The plate is not fixed or rigid instead as we see from the figure3 below it has three modules which is connected to the frame by freely pin connection. This rectangular blade has reciprocating motion i.e. forward and backward motion. In the forward direction the modules are closed so the wind power absorbed and stored on the flywheel. Due to the power stored on the flywheel the rectangular blade returns to original position and in this backward direction the modules are opened so the wind by pass the module. The opening and closing of modules are controlled by cylindrical cam mechanism. This cam mechanism helps to rotates only the central module therefore we use rod which helps to turn the sides module because the rod connects the modules include the central one. N.B all the design formulas which are used were taken from reference [2 and 3].

.2 Design of Module on Rectangular Blade
There are three identical modules on the rectangular blade with the same material, the same dimension and they have same pressure distribution. So, we can consider the single plate for design iiste.org ISSN 2224-3232 (Paper) ISSN 2225-0573 (Online) Vol. 10, No.3, 2020 Now let us take, the dimension of the module (sheet metal) Height(H) = 2.5m, Width(w) = 0.67m The cross section of link is 20mm*20mm and it is hollow square with thickness of 1.5.

3.1.2.1The Stress Analysis on The Module
As we see from figure 4 above the thin sheet metal welded on the link (instead of use think sheet metal) which experience bending stress due to wind power. And this structure helps to reduce the weight of rectangular blade and cost. Find stress on link means find stress on module this stress is bending stress. The design or selection of material is based on central link (i.e. the inclined one) because there is high binding stress induce on it. The length of inclined link is L = √2.5 + 0.67 = 2.59m , w×b = 20mm×20mm and hollow square, t = 1.5mm The area of the link which is perpendicular to the wind force in mm is A = L × W = 2590mm × 20 mm = 51,800 The force exerted by wind on the link at center is  The material that can withstand this stress with low cost is aluminum

Design of Frame
The frame helps to carry modules and the module attached to the frame by freely movable pin. The force and stress analysis on frame are the same as the link (where the sheet metal welded) but here welding strength also considered. The frame made from four link or plate welded at the corner and the cross-section is hollow square with dimension of 40mm × 40mm. The frame is rectangular with the longest link length is 2.5m and the smallest one is 2m with the thickness of 2mm so the design is based on the longest link. Based on the cost, availability and its ability to withstand the above stress cast iron is selected for our design purpose.

Design of Follower and Cam
A cam is a rotating machine element which gives reciprocating or oscillating motion to another element known as follower. The cam and the follower have a line contact and constitute a higher pair. The cams are usually rotated at uniform speed by a shaft, but the follower motion is predetermined and will be according to the shape of the cam. In this design the cam has reciprocating motion and the follower follow the profile. The cam and follower are one of the simplest as well as one of the most important mechanisms found in modern machinery today. The main purpose of the cam in this design is to control the opening and closing of the module which is found on the rectangular frame where the winds strike.

Design of Cylindrical Cam
 The cam is hollow shaped and has roller in the interior part which travel through the profile on the follower.  It has hole for rope to tight and connect with the base of reciprocating plate therefore the motion of plate directly transferred to up-down movement of cylindrical cam Figure 5: cylindrical cam drawn on Solid work Outer diameter (Do) =96mm Inner diameter (Di) = 92mm Steel 40C8 is selected due to its good wearing resistance property which has the maximum allowable shear stress of F 144561.47 = <G?/H1

Stress Analysis on cylindrical cam
The cylindrical cam has reciprocating motion due to the pulling rope and pushing spring. In this motion maximum stress induced in the roller (which is attached to the cylinder internally) because when it moves downward by pulling the rope through the profile it compresses the spring or resist the spring force. If the roller is unable to resist the stress, it is sheared off. The resistance offered by a roller to be sheared off is known as shearing resistance or shearing strength or shearing value of the roller. We know that shearing area or the area of the roller to be sheared off can be; Where d = diameter of roller inside the hole of the cam profile=15mm There fore I J = 176.700 ? The shearing force that is exerted on the roller in cylindrical cam is equal to the maximum force exerted on rectangular plate by the wind.

=675N
Thus, the shearing force (Fs) or the maximum force required to shear of the pulling cam is equal to the maximum force exerted on the rectangular plate by the wind.
28Mpa Therefore, since the shear stress induced in the roller by the effect of wind is smaller than the maximum allowable shear stress of the material of the roller then we say that our design is safe ( F < F 144561.47 ⟹ <G?/H1 > =. ?C/H1) thus, the design is safe 3.

Design of Cylindrical Follower
 This follower has profile to follow the predetermined motion and it has circular motion but it does not complete one revolution the maximum turning angle is 90. where T = The torque on rope r = distance from center of rotation Deflection of spring or the distance it compresses from its free length is e= ?C@00

Stress Analysis on Spring
The stress induced on spring due to the axial force exerted by the rope are torsional shear stress direct shear stress, stress due to curvature of wire etc.

Torsional Shear Stress
The force tends to rotate the wire due to the twisting moment set up in the wire. Thus, torsional shear stress is induced in the wire.

Buckling Of Compression Springs
It has been found experimentally that when the free length of the spring (LF) is more than four times the mean or pitch diameter (D), then the spring behaves like a column and may fail by buckling at a comparatively low load.
Free length > 4 ×D = 4 ×92 = 368mm Thus, ⇒ 450mm > 368mm It orders to avoid the buckling of spring; it is either mounted on a central rod or located on a tube. In this design the spring is located in the cylindrical cam so the buckling problem cannot be created.

=0.866t
Since for buckling of the link in the vertical plane, the ends are considered as hinged, therefore equivalent length of the link (L) =2.294m and Rankin constant a= < D>@@ According to Rankin's formula, buckling load (Wcr) from sub title 3.1.8.1 =258/2 solving for t=√<?G=11.35mm So the width will be, b=3t=3×11. -.™wš›) =15.34MPa which is less than 320Mpa and thus the design is safe.

Design of Flywheel 3.1.9.1 Force Analysis of Flywheel
A flywheel used in machines serves as a reservoir which stores energy during the period when the supply of energy is more than the requirement and releases it during the period when the requirement of energy is more than supply. A little consideration will show that when the flywheel absorbs energy, its speed increases and when it releases, the speed decreases. Hence in this design the flywheel does not maintain a constant speed, it simply returns the plate to its original position or to create backward motion. Being the wind strikes the plate then the plate moves in the direction of wind i.e. it create forward motion and some of energy of wind stored in the flywheel which is used to return the plate i.e. it creates backward motion.

Stresses in A Flywheel Rim
A flywheel, as shown in Figure 10 consists of a rim at which the major portion of the mass or weight of flywheel is concentrated, a boss or hub for fixing the flywheel on to the shaft and a number of arms for supporting the rim on the hub. So, stresses such as tensile stress due to centrifugal force, tensile bending stress caused by the restraint of the arms, and shrinkage stresses due to unequal rate of cooling of casting are induced in the rim of a flywheel. These stresses may be very high but there is no easy method of determining. This stress is taken care of by a factor of safety. 3.1.9.2.1 Tensile stress due to the centrifugal force: The tensile stress in the rim due to the centrifugal force, assuming that the rim is unstrained by the arms, is determined in a similar way as a thin cylinder subjected to internal pressure. Let b = Width of rim, t = Thickness of rim, A=cross-sectional area of rim, D=mean diameter of fly wheel, R=mean radius of flywheel, ρ = density of flywheel, ω = anguler velocity of flywheel, V=linear velocity of flywheel and ' • = ÁÂÃÄÅAEÂ ÇÈ ℎÇÇÊ ÄÁÂÈÄÄ Due to the centrifugal force acting on the rim, the arms will be subjected to direct tensile stress whose magnitude is same as discussed in the previous article. Therefore, Tensile stress in the arms, y ÎÏ = = ; × y Î = = ; ×103,746.5 N/w ? =77,809.9 N/w ?

Bending stress due to the torque transmitted
Due to the torque transmitted from the rim to the shaft or from the shaft to the rim, the arms will be subjected to bending, because they are required to carry the full torque load. In order to find out the maximum bending moment on the arms, it may be assumed as a cantilever beam fixed at the hub and carrying a concentrated load at the free end of the rim as shown in Let T = Maximum torque transmitted by the shaft = Mean radius of the rim r = Radius of the hub, n= Number of arms, and Z = Section modulus for the cross-section of arms The cross-section of the arms is usually elliptical with major axis as twice the minor axis, as shown in Fig and it is designed for the maximum bending stress. @.@>×š < = = 5.93Mpa For š < = C@ww ,assuming,z < = @. >š < the dimensions of the arms may be obtained from eq (1) and eq (2) and bending stress of material is 5Mpa.Therefore,z < = ;@ ww 3.

Design of Shaft and Hub of Flywheel
The diameter of shaft for flywheel is obtained from Maximum shear stress theory or Guest's theory. It is used for ductile materials such as mild steel. We know that the maximum torque transmitted by shaft is Ñ wš› = <<<Btw = 1,116,000Nmm The binding moment on cantilever shaft at the end due to the mass of flywheel is Ó wš› = Õ × u = =@@t × =@@ww= 90,000Nmm The equivalent twisting moment, Ñ Ö = ƒÑ wš› ? + Ó wš› ? = √<<<B@@@ ? + G@@@@ ? Te = 1,119,623.1Nmm Take material of carbon steel of grade 40C and its allowable shear stress (×) is 192Mpa The equivalent twisting moment (Te) can also given by Ñ There is also a plate attached to the bottom of the vertical one which carries pulley, gear and generator. Therefore, it has to be strong and design at high factor of safety.

Stress Analysis for The Tower
There are two common type of stress induce in the tower the first one is bending stress and the other one is compressive stress. As explained above the tower has two components vertical and horizontal rod. The horizontal rod experience bending stress but the vertical rod experience both bending and compressive stress. Thus, stress induces due to the wind force and the mass of each component flywheel, blade, generator and etc. The design is based on the maximum stress induce in the component.

Stress in The Vertical Component of Tower
Compressive stress is the stress induces in the vertical component of the tower due to the mass it carries and the cross section of the tower is circular but it is hollow. We select a material of 40c8 steel for the tower that has the ultimate tensile or compressive strength of 560-670Mpa the material (i.e. ' àá• =560Mpa).The total load applied to the tower can be the sum of mass of pulley, connecting rod fly wheel, generator and mass of plate which is equals to 200 Kg Thus, F = m*g = 10*200=2000N Take factor of safety (fs) = 3 and Therefore, the force(F) will be 6000N The cross section of the tower is circular hollow with 50mm outer diameter and 2mm thickness. The total stress induced in the tower is, ' í = ' ž + ' ! = 15åaeç + 15åaeç = 30åaeç Thus, since the total stress induced in the tower is less than the ultimate strength of the material the design is safe.

Working Principle of the Wind Harvester (turbine)
When the vertically lifting rectangular plate opposing the direction of wind then the wind exerts some amount of force and push the plate forward to some distance. This rectangular plate is the combination of three small rectangular plates (modules). these plates move forward together and they never allow the wind pass b/n them until the cam mechanism start to separate them. When the rectangular plate reaches at required position then the cam starts to operate. three plates separate each other and the wind pass b/n them. So, the rectangular plates return back to its original position by the energy stored in the flywheel. The closing and separating condition of the rectangular plates (Modules) are controlled by the cam mechanism. always on the return condition modules are moving backward separately to decrease the force exerted on the surface of plates by allowing the wind pass b/n Journal of Energy Technologies and Policy www.iiste.org ISSN 2224-3232 (Paper) ISSN 2225-0573 (Online) Vol. 10, No.3, 2020 13 them by turning the open surface to 90 degrees from its original position. Then this gained wind power transfer into the flywheel and converting the reciprocating motion into rotational motion by four bar linkage mechanism depends on grashofs principle. After converting the reciprocating motion into rotational motion, the rotating crank angular speed is multiplied by gear reduction mechanism i.e. pulley belt and spur gear with pinion gear. Then after getting the required rpm the appropriate electric generator will be select and electric power will produce. 66,010 In this cost estimation there are some components which quantity is not specified or described above and there may be additional components that are required to accomplish our design project like Cam and follower, key, pin, bolt and others.so by considering all those components we would design our project with total initial investment cost of which does not exceed 150,000 Ethiopian Birr or $5357.14

CONCLUSSION
Wind energy has been a reasonably successful renewable energy technology developed and widely distributed in the world. it also reduces the green house emission, reduce the demand of wood and charcoal for cooking therefore it helps us to preserve forested areas indirectly when all the cooking methods replaced by electricity power.so this project will play a vital role for increasing the supply of electric power in developing countries like Ethiopia due to its low manufacturing and maintenance cost. The capacity of this reciprocating type wind power harvest is depending on the wind speed and area of the rectangular plate so in this design at a given area of rectangular plate in a. specified altitude it produces the ideal output power of 10.125kw, So this output power will used for many minimum power consuming purposes like television, cooking foods, light etc. We can also increase the capacity of this machine by increasing the area of the plate and height of the wind harvester.
The output power of 10125 watt produced by the maximum wind speed can operate 56.25 lamps per day for