Improving the Performance of a Small-Scale Wind Turbine System

Saiful Huda

, Prastyono Eko Pambudi

and Sudarsono

Department of Mechanical Engineering, Institut Sains & Teknologi AKPRIND Yogyakarta, Indonesia

Department of Electrical Engineering, Institut Sains & Teknologi AKPRIND Yogyakarta, Indonesia

Keywords: Improving Performance, Blades, Hubs, A Small-Scale Turbine System

Abstract: This research aims to improve the performance of a small-scale wind turbine system. It is done by varying the

inertia energy through designing different wights of hubs and blades. One is heavy blades with light hub and

the other is a light blade with the heavy hub. The assumption is that the starting point of the blade to run will

be at the lower wind speed due to the smaller torsion moment. However, when the blades have run, the turbine

gets the power from the centrifugal post stored in the hub. The research result shows that both sets of blades

and hubs produce relatively the same power, that is 12 watts. The difference is on the speed of the wind to run

the turbine. The one with the lighter blade and heavier hub start running at 3 m/s and the other is that of 4m/s.

The conclusion is that the use of the lighter blade and heavier hub is effective to improve the performance of

a small-scale turbine system.

1 INTRODUCTION

Indonesia is an archipelago country with 2/3 of its

territory is the ocean and has the longest coastline in

the world (± 81,000 km), located on the equator line,

and has more than 17,000 islands. Under these

circumstances, wind energy is a potential that must be

developed and utilized. Based on LAPAN data

(Daryanto, et al., 2005), wind in Indonesia has

varying speeds but generally is categorized as low-

speed winds.

The utilization of wind energy sources as a power

plant is one of the efforts to meet the needs of electric

energy, which is increasing in the number of needs

for households, industries, and commercials. Wind

power generation can be developed as alternative

energy, which is renewable and environmentally

friendly. To develop this potential, we need a tool to

convert the kinetic energy of the wind into electrical

energy in the form of a windmill that works to rotate

an electric generator. This research study the

performance test of windmill propeller with blade

material from wood composite with flax fiber

reinforcement. The windmill model used in this study

is a propeller type windmill with a comparison of the

number of blade 5 which is made of wood as core

material (a type of balsa wood) with hemp fiber and

the polymer matrix. Data retrieval on the windmill is

done in two ways, first from the generator, and the

second is mechanical power by measuring the torque

and speed of the spinning shaft rotation (rpm)

Wind speeds in Indonesia are not as big as in

countries like the Netherlands that have used

windmill energy. The wind speed around the southern

coast of Yogyakarta ranges from 3-5 meters per

second. So it needs to be combined with low-speed

generators and solar thermal energy. Alternative

energy is acknowledged to be still difficult to replace

conventional energy, but at least renewable energy

can be a supporting energy, especially for areas that

have not been electrified.

Research by Wakui, et al. (2002) compared three

types of windmills, namely Savonius-Darius, Darius,

and horizontal shaft two winder types of propellers.

The results showed that the combination of Savonius

Darius had the advantage of being able to start

independently compared to Darius even though there

was a decrease in the quantity of output power. The

propeller horizontal windmills have a large power

output, with a note they must have a good Yaw

mechanism to respond to wind direction

Research to determine the speeds characteristic

range of the wind machines and to make easy the

choice of the suitable wind turbine for a given site, in

order to maximize the delivered energy for a given

amount of available wind energy has done by

Bencherif et. al (2014).

Huda, S., Pambudi, P. and Sudarsono, .

Improving the Performance of a Small-Scale Wind Turbine System.

DOI: 10.5220/0009006900930098

In Proceedings of the 7th Engineering International Conference on Education, Concept and Application on Green Technology (EIC 2018), pages 93-98

ISBN: 978-989-758-411-4

The results of Setiawan's research (2016) show

that the change in pitch angle of the two H-type

Darrieus wind turbine blades affects the power

produced by wind turbines in real wind conditions.

The greater the pitch angle, the lower the power

produced. Changes in pitch angle also affect the

efficiency of wind turbines in real wind conditions.

The more pitch angle increases the greater the

efficiency. Purwono's research (2016) states that

there is a significant difference in the average power

produced by NACA 3412 Vertical Axis Windmill

(KASV) at 5% real level and there is a tendency that

the increased wind speed and number of blades used

will increase the power produced by KASV.

The airfoil used for the turbine blade base profile

is the airfoil through which low-velocity winds

(maximum 10 m/s) flow, so the lift ratio parameter to

the maximum drag force becomes the focus of

developing airfoil characteristics for wind turbines

with a wind speed range of 0-10 m / s (Timmer and

Rooij, 2003). Timmer and Rooij (2003) also stated

that in the early 1980s to 1990, profiles that were

widely used as the basic form of wind turbine blades

were airfoils developed by NASA which were given

4-digit NACA codes (NACA 44xx series) and 5-digit

NACA (NACA 63xxx series ). Parezanovic, et. al

(2005) state that the most important aspect of wind

turbines is their aerodynamic effectiveness, the base

of which is the design of the airfoils forming the

blades. It is possible to predict airfoil performance by

using commercial CFD programs, and furthermore, to

design new airfoils with better performance, based on

those predictions.

At present, windmill propellers, which were

previously made from metal materials, have begun to

be made from GFRP (glass fiber reinforced plastic)

skin composite materials. From previous studies, it is

known that the Sengon Laut Wood (Albizia falcata)

has a high tensile stress and buckling stress.

Meanwhile, hemp has a high tensile stress and impact

strength as well. The sandwich composite structure

has the ability to withstand a greater load than that of

the lamina composite (Sudarsono, 2013). The

description above shows that the windmill propeller

engineering from the GFRP skin composite needs to

be developed into a composite structure in order to be

able to withstand external loads (collisions) and have

a lightweight to easily rotate when blown in the wind.

In this study, a composite sandwich with balsa wood

and hemp fiber will be developed as a reinforcement

for propeller-making raw materials. Testing will also

be done to determine the effect of the position

/location of the center of gravity (C.G) of blade and

hub on the performance of the windmill. The variable

of the center of gravity of the windmill is obtained by

making the windmill hub and blade different in

weights. The first hub was made of Aluminum

material whereas the second one used AISI 1030 steel

material. While the windmill blade was made from

composite using glass fiber while the other was made

from composite using balsa wood core and hemp

natural fiber, this way the different weight of the hub

and blade were obtained.

2 METHOD

This research was conducted to determine the

effect of the position/location of the center of gravity

/ C.G blade and hub on the performance of the

windmill. This was done by observing the power

generated by the windmill and the wind speed needed

for the initial round of the windmill. The variable

location of the center of the windmill is obtained by

making the windmill hub and blade have different

weights. The first hub was made of Aluminum, while

the second used AISI 1030 steel material. The first

windmill blade was made from composite using glass

fiber and the second was made from composite using

balsa wood core and hemp natural fiber, this way the

different weight of the hub and blade were obtained.

Forces that work on C.G. windmill blades due to

wind flow theoretically consist of tangential force t,

axial force a and centrifugal force S. The different

position of C.G. will result in the different T torque

produced by the windmill. This is because the

distance of the tangential force t to the axle weight

point is different so that a different P Power is

produced assuming the windmill shaft rotation is the

same. A different T torque will also affect the initial

rotation of the windmill in which theoretically for the

same wind speeds the torque of C.G. which is farther

from the center of the shaft axis will be bigger so that

at the farther the CG, the windmill will rotate at a

lower wind speed.

The kinetic energy of K rotation is a function of

the mass of a rotating object and angular velocity, by

making a mass variable from the hub and blade, the

rotational kinetic energy produced by the windmill

also changes. In this research, a hub made of steel

with a weight of 550 g and aluminum with a weight

of 320 g was made. The windmill blade is made of

fiberglass composite which has a weight of 300 gr and

a composite with balsa wood core and hemp fiber that

weighs 280 gr. Both are made according to the NACA

4415 standard. The distance between the C.G. and the

center of the axis for the blade made of fiberglass is

EIC 2018 - The 7th Engineering International Conference (EIC), Engineering International Conference on Education, Concept and

Application on Green Technology

150 mm while the blade made of natural fiber with a

balsa wood core is 209 mm.

(a)

(b)

Figure 1: (a) Forces that work on C.G. and (b)

location of C.G on a windmill blade.

Figure 2: Measurement of electrical power and

mechanical power.

In order to find out the power generated by the

windmill, electrical power is tested by using an AC

generator and mechanical power testing using torque

meters. While wind energy is obtained from a simple

wind tunnel that is specifically designed (figure 2).

3 RESULTS AND DISCUSSION

The data to determine the performance of the

windmill in this research were obtained using two

different methods, first, by finding the relationship

between wind speed and electrical power produced

by windmill generators, while the second is finding

the relationship between wind speed and mechanical

power produced by the windmill using a torque tester.

This is done to determine the possibility of a

generator performance that is not optimum. The test

results are presented in the following discussion.

3.1 Electrical Power Testing

Figure 3 (a) shows that blades made of natural

fibers with lighter weight at 3 m / s wind speed can

produce a voltage of 22 V. While heavier blades are

only able to produce a voltage of 7 V even though the

wind power produced is equal. This is consistent with

the following [Yeni Yusuf Tonglolangi, 2014]:

W =





ρ A V

watt ……………………..(1)

Where : W = Wind Energy watt , ρ = Air density

(kg / m

), A = Wind catching area (m

) and V = Wind

Speed (m / s).

This shows that the lighter blade has a better

initial rotation because of the tangential force

generated by the wind at the beginning of the rotation

of the windmill against the smaller blade weight with

smaller kinetic energy. This is in accordance with the

following equation.







I 



 ……………………………..(2)







m 







……………………...(3)

Where V is the wind speed m / s, while m is the period

of rotating objects in kg. At larger wind speeds with

the same air density will produce greater power as the

following wind power equation:   0.5



watt ……………………...(4)

Where P is wind power (watts), ρ is wind density

(Kg / m

), A is the section of the wind channel (m

)

and V is the wind speed (m / s). With wind density in

Yogyakarta [Kifli, 2016] of 1.17 kg / m

, wind power

of W is 157.5 watt, so the power produced as in

Figure 3 (c) has very low efficiency, both for the

blade made of glass fiber and natural fiber both have

Improving the Performance of a Small-Scale Wind Turbine System

(a)

(b)

(c)

(d)

Figure 3: The results of the windmill electrical power

test versus (a) Voltage (b) Electric Current (c) Power

output (d) Energy.

almost the same performance. The total efficiency of

a wind turbine can be calculated using the equation: γ

= P / W x 100%; so that for wind speeds of 7 m / s

turbine efficiency γ is 8%.

3.2 Mechanical Power

Mechanization factors. In order to know the parts that

cause the low efficiency of wind turbines, whether

turbine generators or mechanical factors of

windmills, mechanical efficiency is calculated by

comparing the wind power and the shaft mechanical

power produced by the windmill. The mechanical

power of the Pm shaft is calculated based on the

equation:







watt

……………………...(5)

where :

T = Torque N-m

n = Shaft Rotate rpm

Mechanical power on the shaft generated by

windmills with blades made of glass fiber and that of

made of natural fibers is relatively the same. At a

wind speed of 6 m / s glass fiber blade has a power

(P) of 40 watt, while the blade of natural fiber has a

power of 52 watt. While at wind speeds of 7 m / s

fiberglass fiber blades produce 80 watts of power, and

natural fiber blades produce 65 watt of power. Wind

power at wind speeds of 6 m / s and 7 m / s are 85

watt and 157 watt respectively, so the average

mechanical efficiency of windmills is 50.1%, much

higher than the efficiency of wind turbines using

electric generator windmill. Figure 4 shows the

results of mechanical tests of power and wind speed

relations.

Figure 4: Results of mechanical tests of power and

wind speed relations.

34567

Voltage (V)

WindSpeed(m/s)

FiberglassBlade

NaturalFibreBlade

0.5

34567

ElectricCurrent

(Ampere)

WindSpeed(m/s)

FiberglassBlade

NaturalFibreBlade

34567

Power (watt)

WindSpeed (m/s)

FibreglassBlade

NaturalFibreBlade

34567

Energy(Watt/jam)

WindSpeed(m/s)

FibreglassBlade

NaturalFibre…

100

200

34567

Power(watt)

WindSpeed(m/s)

WindSpeedvsPowerOutput

WindPower

PowerofFiberglassBlade

PowerofNaturalFibre

Blade

EIC 2018 - The 7th Engineering International Conference (EIC), Engineering International Conference on Education, Concept and

Application on Green Technology

3.3 Torque and Windmill Rotation

The rotational kinetic energy of an object that rotates

depends on the angular velocity ω radians / second

and the magnitude of the moment of inertia I Kg. m

of the object. Rotational kinetic energy can be

calculated using the equation:







I 



……………………………(6)

(a)

(b)

Figure 5: Results of mechanical tests of rotational

speed, torque, and wind speed relations.

Figure 5 (a) and (b) shows that the rotational speed of

the glass fiber blade can achieve greater rotation at

the same wind speed when compared to blade from

natural fiber, this occurs because the blade of glass

fiber has a higher weight so that the rotational kinetic

energy is greater and more stable at higher speed and

wind speed. On the other hand, the torque produced

is higher in the blade with natural fiber than the blade

using glass fiber.

4 CONCLUSIONS

The test results show that at a wind speed of 3 m / s

the blade made of natural fiber produces a voltage of

22 V while the blade of glass fiber produces a voltage

of 7 V. This indicates that the lighter blade has a

better initial rotation, due to the tangential force the

wind was generated at the beginning of the rotation of

windmills against the smaller blade weight with less

kinetic energy.

The speed of the glass fiber blade can achieve greater

rotation at the same wind speed when compared to the

blade of natural fiber, at the same wind speed of 7 m

/ s, RPM of the fiberglass blade is 3.600 rpm. While

natural fiber blade is 2.500 rpm. This happens

because the blade of glass fiber is heavier so that the

rotational kinetic energy is larger and more stable at

higher speeds and wind speeds. On the other hand, the

torque produced is higher in the blade with natural

fiber than that of the blade using glass fiber. From the

results of the analysis, a conclusion can be drawn that

the blades made of natural fiber have a better

performance than the blades made of glass fiber.

ACKNOWLEDGMENTS

Our thanks go to the Directorate General of Higher

Education, Ministry of Research Technology and

Higher Education, which has funded research

activities in accordance with the Letter Agreement

Research Assignment Number: 02/SPP/LPPM/

PL/II/2018, through Applied Product Research

Competitive Grant funds.

REFERENCES

Bencherif, M., Brahmi, B.N.,Chikhaoui, 2014. A. Optimal

selection of Wind Turbine Generators, International

Journal of Computer Applications, 92, 1-10.

0.5

1.5

2.5

34567

Torque(N.m)

WindSpeed(m/s)

TorquevsWindSpeed

PowerofFiberglassBlade

PowerofNaturalFibreBlade

500

1000

1500

2000

2500

3000

3500

4000

34567

RotationalSpeed(rpm)

WindSpeed(m/s)

RotationalSpeedvsWindSpeed

PowerofFiberglassBlade

PowerofNaturalFibreBlade

Improving the Performance of a Small-Scale Wind Turbine System

Daryanto, Y., F. A. Yohannes, F. Hasim, 2005. Potensi,

Peluang dan Tantangan Energi Angin di Indonesia,,

BPPT Tangerang.

Kifli, M.D., 2016. Analisa Pengaruh Massa Jenis Udara

Terhadap Pengujian Labu Ukur, Thesis, Universitas

Gadjah Mada.

Ostowari C. and Naik D., 1985. Post-Stall Wind Tunnel

Data for NACA 44XX Series Airfoil Sections, U.S.

Department of Energy.

Parezanovic, V., Rasuo B., Adzic, M., 2005. Design of

Airfoils for Wind Turbine Blades, University of

Belgrade, Belgrade, Serbia, pp. 192-200.

Purwono, B.S.A, Masroni, Muqit, A.,2017. Strategi

Pemanfaatan Kincir Angin Sumbu Vertikal Type

NACA 3412, Prosiding Seminar Nasional Teknik

Mesin Politeknik Negeri Jakarta, pp. 533-541

Ria, M., 2018.https://www.matadunia.id/ 2016/01/sumber-

daya-energi-angin.html, (accessed on 25 July 2018)

Rooij, R.V & Timmer, N., 2004. Design of Airfoils for Wind

Turbine Blades, Delft University of Technology, The

Netherlands.

Setiawan, I.B., 2016, Pengaruh Perubahan Sudut Pitch Pada

Blade Terhadap Kinerja Turbin Angin Darrieus Tipe-H

Dua Tingkat Dengan Pengarah Angin Pada Kondisi

Angin Real, Jurnal Teknik Mesin, 04, 267-273.

Sudarsono, 2013. “Optimasi Rancangan Kincir Angin

Modifikasi Standar NACA 4415 Menggunakan Serat

Rami dengan Core Kayu Sengon Laut Yang Tahan

Terhadap Iklim Pesisir Pantai Pandansimo”, Disertasi,

Universitas Diponegoro,.

Wakui, T., & Hashizume, T., 2001. “Optimal Operating

Method of the Wind Turbine-Generator Systems

Matching the Wind Condition and Wind Turbine Type”,

Waseda University. Japan.

Wakui, T., Tanzawa, Yoshiaki & Hashizume, Takumi &

Outa, Eisuke & Usui, Akira, 2000. Optimum Method

of Operating the Wind Turbine-Generator Systems

Matching the Wind Condition and Wind Turbine

Type. Proceedings of the World Renewable Energy

Congress-VI. 4. 2348-2351.

EIC 2018 - The 7th Engineering International Conference (EIC), Engineering International Conference on Education, Concept and

Application on Green Technology