Experimental Study Influence of High Fin on Naca Airfoil 0018 On Performance Of H-Type Darrieus Wind Turbine

Energy is something that is needed in life, as technology develops the need for energy is increasing as well, while the role of New Energy Darrieus wind turbine is one of the solutions for renewable energy because it utilizes energy from wind and is converted into electrical energy, but this turbine has a low starting torque. In this study, the performance of the Darrieus wind turbine was improved by adding a fin to each blade with variations in height (0 cm, 1,5 cm, 2,5 cm, and 3,5 cm). In addition, testing was also carried out with variations in fluid flow speeds (3 m / s; 5 m / s; and 7 m / s). The subjects used in this study were H-type Darrieus wind turbines with a diameter of 40 cm and a height of 50 cm. Experiments were carried out to find out how the effect of fin addition with variations in height on the coefficient of power (Cp) and coefficient of torque (Ct) of the darrieus wind turbine. The final results showed the best performance improvement of the savonius wind turbine occurred at a variation in the fin height of 2.5 cm at a wind speed of 5 m/s. The coefficient of torque (Ct) increased by 7.64% and the coefficient of power (Cp) by 48.38% against conventional H-type darrieus wind turbines. This is because the addition of an effective fin is to reduce the tip of the vortex at the end of each blade so that the flow of fluid that flows becomes more regular and maximum.


Introduction
The Electrical energy is crucial for human life, as a source of light, energy sources, heat generators, and others.The need for electricity is increasing parallel with the development of technology energized by electricity.Other side, the availability of non-renewable electrical energy decrease.The potential of Renewable Energy as a solution of increased energy demands as well as environmentally friendly, by using wind turbines to utilize wind energy(BPPT 2021).
Wind turbine is an equipment to convert kinetic energy of the wind into electrical energy or mechanical energy of the turbine shaft and converted again by a generator into electrical energy.There are two types of wind turbines based on the position of shaft, Horizontal Axis Wind Turbine (HAWT) and Vertical Axis Wind Turbine (VAWT) (Qistiyan, 2021).VAWT are known by several names and forms, as Darrieus Turbine and Savonius Turbine [1].Darrieus Wind Turbine work at low fluid flow velocities and high torque, but has low Cp value as weakness.Darrius turbine efficiency is affected by the number of blades.Research shows variations in the number of blades 2, 3 and 4, so the number of blades is 2 which produces the highest power.(Fachrudin, 2018).In other types of vertical turbines, the efficiency of the turbine is affected by the number of fins in the turbine.Variations in the addition of 4 fins accelerate the ability to cut in speed at a speed of 1.8 m/s.(Pamungkas et al., 2017) In this study, researchers compared several models and types of H-type Darrieus wind turbines to determine which type of turbine has the best efficiency.The results of this study show that the H-type Darrieus wind turbine gives the best results.The Darrieus turbine has a low rotor torque but has a higher rotation than the Savonius wind turbine, so it is preferred to generate electrical energy.But this turbine requires initial energy to start rotating.Darrieus wind turbine rotors generally have angle variations, namely two or three angles.The modification of the Darrieus wind turbine rotor is called the H wind turbine(Nur Fridayana et al., 2018).In this study the type of foil used was NACA 0018 which means that the foil profile is symmetrical.NACA 0018 has a good ratio of lift and drag forces.Comparison of the NACA 0018 foil profile with other types can be seen in Figure 1 (Sentosa, 2017).

Experimental Methods
The Several steps are needed for research, as follows In this study, starting with identification of problem by literature studies and field studies, data collection, Darrieus Wind Turbine manufacture, equipment settings, testing and data collection, continued with analysis and discussion, conclusions and suggestion.To start this research, several steps are needed, as follows.

Experiment Flow Chart
Turbine Manufacture

Turbine Manufacture
Manufacture of conventional H-type Darrieus wind turbine adapted to existing variations and specifications using NACA Airfoil 0018 with 40 cm diameter and 50 cm height.

Equipment Settings
Equipment settings are carried out for experimental tests as predetermined criteria.Equipment is laid out according to a planned scheme.

Calculation, Analysis and Discussion
Data analysis from testing will be carried out at this stage.Calculation and analysis results based on data taken from testing tool.Next, comparison results of variation experiment are carried out to get the most significant modification improvements.Coefficient of Power is a calculation that determines the amount of wind turbine performance.The Coefficient of Power itself is influenced by 2 main factors, namely the mechanical power of the turbine due to the wind and the kinetic power of the wind itself.The value of the Coefficient of Power is directly proportional to the performance of the wind turbine (PHILIP J. PRITCHARD, 2011).

Conclusion and Suggestion
After testing and data analysis, the researchers find out which variations experienced an increase or decrease in performance on the H type Darrieus turbine.

Analysis Effect of Additional Fin with Variations of Fin Height on H-Type Darrieus Wind Turbine
Additional fin on each blade with variations in fin height affects the performance of Darrieus wind turbine.This analysis is used to determine the effect of variations additional height of fin in 1.5; 2.5; and 3.5 cm to Darrieus wind turbine RPM with fin variations.Based on two graphs above, it shown an increase in turbine performance with additional fins with variations height 1.5; 2.5; and 3.5 cm.When position fin height is 3.5 cm, turbine performance decreases due to secondary flow arising from an imbalance between pressure and centrifugal force on outer wall channel.Secondary flow creates turbulence even in laminar flow.
In fin height 1.5 cm, turbine performance has increased compared to conventional wind turbines.It proved that additional fin height is effective.Due to additional fin height, it reduces the tip vortex that arises in each blade so fluid flows more regular and effective.
In variation fin height 2.5 cm, produces the highest performance due to wind flow passes through each blade evenly distributed.Due to additional fin height, it effectively reduces the drag force generated on leading edge, then the difference in lift force increases, so increases performance and tip vortex that arises on each blade reduced and fluid flows more regular and effective.
The longer height of additional fin increase weight of each blade and cause a new secondary flow.As a result, the power produced also decreases and causes coefficient of power value to decrease along with additional fin height used.

Conclusions
Based on results of simulation and analysis, conclusions as follows: 1.Effect of additional fins with variation height on fluid flow velocities 5 m/s; 6 m/s and 7 m/s increase the coefficient of torque (Ct).Result of increasing coefficient of torque (Ct) shown as graph in Figure 9 Tip Speed Ratio (TSR) to Coefficient of Torque (Ct) is a linear graph.The percentage increase in coefficient of torque (Ct) shown in Graph 2 Value of increase in coefficient of torque (Ct) for variations of fin height in 1.5 cm; 2.5 cm; and 3.5 cm. 2. Effect of additional fins with variation height on fluid flow velocities 5 m/s; 6 m/s and 7 m/s increase the coefficient of power (Cp).Result of increasing coefficient of power (Cp) shown as graph in Figure 8, coefficient of power (Cp) to Tip Speed Ratio (TSR) is a parabolic graph.The percentage increase in coefficient of power (Cp) shown in Graph 3 Value of increase in coefficient of power (Cp) for variations of fin height in 1.5 cm; 2.5 cm; and 3.5 cm. 3. Best performance of H-Type Darrieus wind turbine with additional fins height 2.5 cm on fluid flow velocity 5 m/s has coefficient of power value of 0.638, Tip Speed Ratio (TSR) value of 0.696 with higher turbine performance by 48.379% from conventional H-type Darrieus wind turbine.
.The Research conducted by Siddiqui & Alam, 2018 in their journal entitled A Review Study: Distinct Recent Advancements In H-Type Darrieus Wind Turbine To Improve Aerodynamic Performance.

Figure 11 .
Figure 11.RPM Graph -Variation of Fin Height on Fluid Flow Velocity