The produced voltage readings and the respective turbine rotations are recorded. The ambient pressure and temperature are recorded using the manometer and thermometer for the evaluation of air density in the Laboratory environment of Universiti Industri Selangor.

The power produced by the wind speed is also calculated which is shown in the specimen calculation section. The main test is performed at open hall in the Thermal Laboratory of Faculty of Engineering, UNISEL, where wind speeds are measured between 4 and 6 m/s, with gusts up to 7 m/s.

During the test, the turbine has been run based on the design, then the blades are opened and the wind has been propelled, and finally it has been checked about sufficient production of lift when the blades are closed. It has been seemed as though the turbine would slow down too much in the regions where lift is not produced thus the blades are kept opening up just to allow rotation. Next the blades have been opened to check the maximum attainable rotational speed in the drag position. In this position it is observed that there is plenty of windswept area to rotate the turbine. Specimen calculation Absolute pressure p = 1.01×105N/m2 and temperature, T = 38.5oC=311.5K.Using equations of state for perfect gas the air density,ρ∞ is 1.13 kg/m 3 and is defined as (Bertin, 2002):

P???(8)

RTwhere, pressure p is 1.01 × 10 5 N/m2,temperature T is 311.5 K, and gas constant of air R is 287.05 Nm/kg K.The air viscosity,μ∞is determined using the Sutherland’s equation (Bertin, 2002) described belowwhere μ∞ is the dynamic viscosity.

T1.5???1.458*10T?110.4(9)

?6At T of 311.5 K, Eq.(9) gives value of μ∞ of 1.90×10-5kg/m s.Reynolds number based on the chord length is defined as (Anderson, 1996).

R??????c (10) ??Using air densityρ∞of 1.13 kg/m3,free stream velocity ν∞ of 5.89 m/s; dynamic viscosity μ∞of 1.90×10-5kg/m s and chord length c of 0.1397 m in Eq.(10),Reynolds number is obtained as Re = 0.4×105

For the remaining velocities ，the corresponding Reynolds numbers are given in Table 1.

Table 1.Free stream velocity and Reynolds number Serial Number Free streamvelocity(m/s) Reynolds number

1 5.89 0.49 × 105 2 6.08 0.51 × 105 3 7.02 0.58 × 105

For a rectangular blade, frontal surface area for a single surface is defined as (Bertin, 2002):

S = bc (11)

For a wind turbine, total frontal surface area ST is 1.145 m2and is defined as (Bertin, 2002):

ST = (S1)T + (S2)T(12)

where, the total frontal area for blade (S1)T is 0.4482 m2 and the total frontal area for drag surface (S2)T is 0.6968m2.

Wind power of the turbine is defined as (Bench &Cloud, 2004)

13Pwind???STv?(13)

2where, the density of airρ∞ is 1.130kg/m3 , the total frontal area ST is 1.145m2 , and wind velocity ν∞ is 5.89m/s.Putting the values into Eq.(13), we have:

Pwind3??1kgm??32?*1.130*1.145*5.89?3*m*???2?s????m?

Pwind?132.19WFor the remaining velocities corresponding wind power are given in Table 2.

RESULTS AND DISCUSSIONS

Experiments have been carried out at open hall UNISEL at the three different velocities of 5.89 m/s, 6.08m/s and 7.02 m/s. Based on the measurement of velocity the wind power for this prototype is calculated at the previous section and is given in Table 2. The calculated values for the Reynolds number in Table 1 have been presented in the previous section.

The further understanding of the relationship between the variables measured as velocity as well as calculated wind power and Reynolds number from the test conducted has been discussed in term of graphs. Table 2. Velocities and Corresponding wind power Serial No. Velocities (m/s) Wind power (W) 1 5.89 132.19 2 6.08 145.40 3 7.02 223.80

Reynolds number

The higher values in Reynolds number indicate the wind turbine has ability to produce more power due to increase in value of the wind velocity and this value is calculated and recorded in tests conducted at the wind velocity of 7.02 m/s.

The Aerofoil geometry

Selecting appropriate aerofoil to a 3-bladed vertical axis wind turbine is one of the most important design decisions.Different profiles provide various advantages and disadvantages that must be considered. However,the affection of this wind flow due to airfoils or blades is very small and the amount of the force that depends on the blade during the rotation has been ignored. In addition, the blade that has been designed and used in this model is not considered as NACA 0012 or NACA 0015 which are preferable in the low Reynolds number range, but the shapes selected in the current project still responded and acted with a very high durability and efficient functional to the shaft to rotate during the wind flow. The Drag Devices geometry

The drag devices that have been used in current project provide external support to the blade by collecting the maximum amount of wind flow and initializing the rotation of the blade and the shafts. The drag devices are very sensitive to small amounts of the wind flow and it always causes the blades and shaft to rotate even the wind velocity is very small in magnitude at the considered location. During the test conducted on this model the wind has been blocked by one of the open drag, and diverted around the other. This is factorizing the net torque which drives the open drag around the shaft and induces rotation of the turbine, which leads to centrifugal forces. The rotational speed is increased until a critical point at which the turbine is moving fast enough to be driven by the lift forces. The opening/closing of drag mechanism is designed such that the centrifugal forces overcome the inertial forces and direct forces at this critical speed. In particular, the device has a very strong torque characteristic at low tip speed ratio, which means it is a self-starting. However, difficulties with commissioning of the torque measurement and control systems have delayed the acquisition of definite test data to date. Turbine feasibility comparisons

The calculated wind power from the current 1/3 scale wind turbine and the overall comparisons of the existing turbine according to the type of connection used and the estimated costs are shown in Table 3.

The University of Wollongong project has produced the maximum wind power which of 700 W using agearing system and GriffithUniversity has produced electrical power of 550 W using a similar system(Cooper & Kennedy, 2003; Kirke, 2003). The tested prototype in current project has been produced 167 W using the belt and pulley system. According to the evaluation of wind velocities, the current model can exceed the existing models if the wind velocity is increased. The current prototype would be capable to produce 567.33 W when the wind velocity increases to20 m/s and 709.17 W when the wind velocity increases to 25 m/s. This overall comparison presents evidence that the current prototype,which uses the pulley and belt systems, is more feasible than the other models that uses the gearing system in terms of cost and to produce power. Conclusion

The conclusions drawn from this investigation are as follows:

(a) Wind power produced by the prototype increases maximum of 1000 W with

the increase of maximum wind velocity of about 12 m/s.

(b) From the investigation there is evidence that the current prototype is capable to produce 567.33 W when the wind velocity increases to 20 m/s and 709 W when the wind velocity increases to 25 m/s.

Nomenclature

Symbol Meaning Unit

p Absolute pressure (N/m2) T Temperature (K)

R Gas constant (Nm/kg K) ρ∞ Air density (kg/m3) μ∞Air viscosity (kg m/s)

ν∞Free stream velocity (m/s) c Chord length(m)

Re Reynolds number (Dimensionless) B Blade height (m)

S1 Blade frontal surface area (m2) S2 Drag device frontal area (m2) ST Total frontal area (m2) Pwind Wind power (W)

Acknowledgment The authors are grateful for the support provided by financial assistance from the Universiti Industri Selangor, and faculty of Engineering for the overall facilities.

REFERENCES

Anderson, J.D.Jr. (1999) Aircraft Performance and Design. McGraw Hill Companies Inc., U.S.A.

Bench, S.E., Cloud, P.K. (2004) The Measure, Predict and Calculate the Power response of an Operating Wind Turbine. 1 st Ed., London, Jepson Pub, 366 p. Bertin, J. J. (2002) Aerodynamics for the Engineer. New Jersey, Prentice Hall, Inc., U.S.A.

Cooper, P., Kennedy, O. (2003) Development and Analysis of a Novel Vertical Axis Wind Turbine. Bachelor. Thesis, University of Wollongong, NSW 2522, Australia

Fitzwater, L.M., Cornell, C.A., Veers, P.S. (1996) Using Environmental Contours to Predict Extreme Events on Wind Turbines. Wind Energy Symp., AIAA/ASME, 9, 244–258.

Hammons, T.J. (2004) Technology and Status of Developments in Harnessing the World’s Untapped Wind-Power Resources. Electricity Power Components and Systems. No.12, p. 32.