the effect of the blade shape and the blade number of vert…

THE EFFECT OF THE BLADE SHAPES AND THE BLADE NUMBER OF VERTICAL WIND TURBINE FOR SMALL ELECTRICAL POWER GENERATION

MirmantoMechanical Engineering Department, Faculty of Engineering, The University of Mataram

Jl. Majapahit no. 62, MataramPhone (0370)636087, (0370)6570632, e-mail: [email protected]

ABSTRAK

NTB mengalami krisis energi listrik dan terdapat beberapa lahan pertanian tadah hujan sehingga perlu dilakukan usaha-usaha pemanfaatan energi alternative salah satunya yaitu energi angin. Artikel ini merupakan hasil penelitian kincir angin poros vertical guna penghasil listrik rumah tangga. Kincir terdiri dari 2, 3 dan 4 jumlah sudu dan bentuk sudunya lingkaran, bujur sangkar, persegi panjang dan elip. Masing-masing luas sudu dibuat sama yaitu 0,25 m2. Panjang lengan kincir 75 cm. Tinggi tower 6 meter di atas air laut. Lokasi penelitian di daerah Sandik kecamatan Batu Layar, Mataram. Hasil penelitian menunjukan bahwa kecepatan angin rata-rata berdasar BMG adalah 3 m/s sedangkan dilapangan kecepatan angin rata-rata 1,2 m/s sampai dengan 1,33 m/s. Putaran kincir rata-rata yang diperoleh pada penelitian ini adalah 15,08 RPM sampai dengan 16,35 RPM. Daya daya angin dan poros maksimum yang diperoleh dari penelitian adalah 22,343 Watt dan 6,7 Watt. Pengaruh dari bentuk dan jumlah sudu tidak siknifikan.

Katakunci : Energi Angin, Kincir Angin, Kecepatan, Putaran dan Daya.

ABSTRACTNTB has an electrical power crisis seriously and there are some rice fields that dependent on

available rain, therefore it is very important to discover some alternative energy such as wind energy.The result of research on vertical axis wind turbine for generating home electricity is explained in this paper deeply. The wind turbine consisted of several blades (two, three and four blades). The blade shapes were as circle, square, rectangular and ellipse. The blades area was 0.25 m2. The length of the wind turbine arm was 0.75 m. The height of the wind turbine tower was 6 m above the sea. The research location was in Sandik, Batulayar, Mataram. The research result shows that according to BMG, the wind velocity is 3 m/s, but in the research location, the wind velocity is varied from 1.2 m/s to 1.33 m/s. The rotation of the wind turbine was varied from 15.08 RPM to 16.35 RPM. The powers of wind and turbine shaft were 22.343 Watt and 6.7 Watt. The influence of blade shape and number ofblades to the wind turbine characteristics are not significant.

Keyword: Wind energy, Wind Turbine, Velocity, Rotation, and Power.

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INTRODUCTION

NTB region now is undergoing on electrical energy crisis. This crisis is indicated by the

activities PLN on shutting off the current distributed regularly. In addition, almost there is no chance

for new house to have a new electrical connection to the PLN. NTB Government has effort seriously to

solve this crisis but no result shows up yet. According to the secretary of BAPPEDA NTB, at that time

was Ir. Nanang Samudra, MSc, that NTB had planed to build a steam turbine plant like Paiton in East

Java. However, he said that no investor was interested to invest his/her fund.

Globally energy, which is available in the form of mineral fuel energy or un-renewable energy,

is depleted. On the other hand, human being should look for other energy (alternative energy). In the

Universe, there are many alternative energy forms. However, because of limitation of human being

capabilities, not all of the alternative energy forms are explored and advantaged optimally and

integrally yet. Several examples of alternative energy that have been advantaged are wind energy,

hydro energy and solar energy. One thing that can be considered in Mataram is wind energy. NTB is

beach region where the wind ongoing blows with enough velocity so that the wind energy is potential

to be utilized.

In Batu Layar district, there are large dry areas that only can be utilized when the rain drops off

so that these areas are only able to produce rice just once a year. According to BPPS 2002 that dry rice

fields in west Lombok reach almost 2149 ha. These are not worthy if no effort are conducted for

utilizing them in order to result crops/harvest. Therefore, using wind energy for pumping is one of

solution for eliminating those disadvantages. Except those dry rice fields, in Batu Layar, there are also

many houses that have no electrical power and water supplied yet. Therefore, the people get clean

water from well and light from traditional lamp only.

Wind potency in NTB, according to BPPT and several researchers, is big enough so that it can

be possibly used for turning the wind turbine. Gintings (1993), a researcher from LAPAN, revealed

that in East Lombok the wind velocity reached up to 5,4 m/s and it could resulted electrical power of

73,21 kWh/m2 . Based on the condition and situation above, it is important to do research of “The

effect of the blade shapes and the blade number of vertical axis wind turbine for electrical power

generation”.


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LITERATURES REVIEW

Insufficient power generator causes electricity crisis in Mataram. So far, the power generation

supplied by the PLTD has been mainly produced using of Diesel Engine. As known, that Diesel

Engine is only able to produce small power except it is a very big one so that the electrical power

generated from electrical generator turned by Diesel Engine is low. Except low power, diesel engine

also needs fuel that nowadays its price launches highly. The cost of operating the diesel engine for

generating the electrical power is considerably high enough.

NTB Government has tried fully to overcome about the electricity problem, but it cannot be

solved yet. Nanang Samudra explained that no investor wanted to plant fund for this case. Therefore,

people have to look for an alternative energy for fulfilling their demands.

Energy

Energy is a capability to do a work. It cannot be destroyed nor created. It only can be changed

from one form to another form. As an example, in combustion process, chemical energy changes to be

heat energy (Tjokrowisastro et al., 1990; Changel, 1994). Sources of energy are mainly classified into

two groups. The first group is un-renewable energy and the second group is renewable energy. Un-

renewable energy such as earth oil, coal, fossil oil etc is now depleted whereas renewable energy such

as hydro energy, waste energy, wind energy, solar energy and so on is able to be recycled or renewed

(Kadarwati, 2001).

Wind

Wind is the moving air. Wind flows from low temperature or high pressure to high temperature

or low pressure. Usually, the region, which has low temperature, has high pressure and vice versa.

Moving air (wind) can be utilized to turn the blade of wind turbine so that wind energy can be changed

to be useful energy. Wind energy is one of energy that can be obtained freely in the universe and it is

available abundantly. Measurement resulted by BMG that was done in period of 1975-1989 shows that

more than 50 locations in Indonesia have wind that flows with velocity of 3 to 5 m/s. Research resulted

by Suryantini (2003) reveals that average daily power of energy in NTB reaches 975.644 watt. Wind

energy in this area has also been utilized for turning 7-wind turbines. Those turbines were as example

projects conducted by LAPAN in the period of 1992-1997 in Selayar, East Lombok. The similar


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projects were also conducted in Irian Jaya. Those turbines used horizontal axis so that they were

constructed by using strong and rigid material and they also needed several devices mounted on them.

Because of those constructions, the total price of the turbines became rather expensive. According to

Ginting (1993), the velocity of the wind in East Lombok reached 5.4 m/s at 14 m of tower height. With

that wind velocity, Ginting predicted that the wind was able to produce 73.21 kWh/m2 of energy.

Wind Turbines

There have been many opinions about wind turbines and there have been many researchers who

conducted research on wind turbines. However, several things must be concerned in utilizing of wind

turbines. According to Ginting (1993) there are at least 3 things that must be considered on wind

turbines. Those are wind turbine characteristics, wind potency and efficiency of the system. With good

wind turbine characteristic, enough wind potency and good system, wind turbine can work optimally.

Several blade shapes of vertical axis wind turbines were also investigated. The blades shapes

were a half globe shape, cone shape and closed curve shape. Four a half globe blade wind turbine with

wind velocity of 5.2 m/s had 4.34% of efficiency, whereas other blade wind turbine had a lower

efficiency.

The characteristics of wind turbine, according to Ginting (1993), can be revealed as equation

below:

2

3AVCP tp

1)

Where P is power (Watt), Cp is power rotor coefficient, t is efficiency, is density of air (kg/m3),

A is frontal rotor area (m2), V is wind velocity (m/s). Whereas the wind power can be predicted by

using the equation below:

2

3AVPangin

2)

Where Pwind is wind power (Watt), is air density (kg/m3), A is frontal rotor area (m2), V is wind

velocity (m/s).

Impulse wind turbine is a simple rotor-dynamic machine and it has almost the same work

principle as Savonius model. Both models, basically, use wind power captured by their face blade that

have shape of a half of globe. Power rotor coefficient can be calculated by using equation 3 as follows:


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tPC

1

3)

Soeripno (1992) ever conducted an experiment on utilizing SKEA that generates an electrical

power for small household in remote area that is far from conventional electricity connection. The

result of the research shows that the turbine has four blades and rotor with 2.8 m in diameters produces

500 Watts. This power is sufficient for household demand. The device that is used for measuring wind

energy in this research is electric generator. It generates current and voltage that can be measured by

using of multi tester. From output of multi-tester, it can be predicted the energy related to each wind

velocities that cross over frontal turbine area.

OBJECTIVES

The specific aims of this research are: To know the wind potency in Sandik, Batu Layar,

Mataram, To know the influences of vertical wind turbine’s blade shape and the number of blades, To

know the efficiency and the power of wind turbine, To give an alternative energy information.

Output of this research is a small-scale vertical wind turbine that can be used for generating

electrical power for small household. Electrical energy from this wind turbine can be used for turning a

centrifugal pump. Water pumped by that pump is used for watering rice fields and supplying water

consumption in Sandik. In addition, the research report can also be utilized as a reverence for further

SKEA research in this area.

EXPERIMENT SET UP AND PROCEDURE

A research method that is used in this research is literature study (collecting relevant data from

some reverences and from BMG) and an experiment that was done on beach as well as on dray rice

fields. Then all data collected in this research are analyzed for making conclusion.

1. Material used

1. Iron shaft

2. Concrete iron

3. Pulley and Belt

4. Bearing

5. Nut and bolt

6. Aluminum plat


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2. Devices used

a. Generator

b. Anemometer

c. Tachometer

d. Ampere meter

e. Manometer

f. Thermometer

g. Volt meter

3. Experiment procedure

In this research, there are 4 types of rotor in which each rotor has 2, 4, and 6 blades. Diameter

of each rotor is 1.5 m. Blade shapes are parabolic, cube, beam and ellipse. The Blades are then

assembled with holder and shaft. The end of shaft is jointed with gear that is coupled with generator.

The wind turbine is mounted on tower that has height of 2 and 3 meters.

c62.5 cm

Ø56.4 cm

40 c

m

a

50 c

m

50 cmb

63.7 cmd

0.5

cm

a. Circle, b. Square, c. Rectangular, d. EllipticalFigure 1. The shapes of frontal area of blades


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Figure 2. Schematic of experiment apparatus

Testing on the wind turbine is conducted in several places; both are on the beach and in rice

field. Variables tested were wind velocity, RPM of rotor, current and voltage resulted by generator.

Based on those variable data, the efficiency of turbine or characteristic of turbine performance can be

obtained. Testing was done on various blade shapes and on the number of blades. Data were taken 10

times of each measurement.

Procedures:

1. Install rotor that has certain blades shapes and the number of blades.

2. Release the brake in order that rotor can turn around.

3. Note wind velocity, rpm, current and voltage resulted by generator and environment

temperature.

4. Repeat point 1 to 3 ten times.

5. Repeat procedures 1 to 4 with deferent blades model and deferent number of blades.

Data from each testing then are analyzed in order to know significance of blades shapes and the

number of blades affecting to the wind turbine performances.

100 cm

75 cm 75 cm

blade

BearingBlade support

Frame

Transmission

Generator

600 cm


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RESULTS AND DISCUSSION

Electrical power variable could not be obtained because the wind turbine did not result the rpm

requirement of generator. Therefore, this paper only provides data of wind velocity (m/s), shaft rpm,

wind power (watt) and shaft power (watt). All of those data are shown graphically below.

From the graph, it is clear enough that the influence of the number of blades is not significant

so that data of wind turbine performances are very close together. What causes this phenomenon is due

to all blades almost have the same resistance for turning them self. One blade that has frontal area

perpendicular to the wind direction tends to turn the rotor but the other blades that do not face to the

wind direction tend to resist the rotor to turn. Therefore, the rotor that has 2 blades or more and that has

whatever blade shape almost has the same rpm although the wind that blows over it has the same

velocity. However, there is a possibility for the number of the blades to have significant deference of

characteristics when the rotor has big difference of blades number.

Average wind velocity is from 1.2 m/s to 1.33 m/s while average of rotation (RPM) is from

15.08 to 16.35 RPM. Maximum power resulted in the research is between 22.343 Watt and 6.7 Watt,

while wind velocity, according to Meteorology and Geophysics Bureau, is 3 m/s in average. This

difference value is caused by location where the measurement is taken.

Vertical axis wind turbine that has little number of blades is not suitable to be placed or used in

the area, which has low wind velocity because it cannot have high efficiency. In order to make it be

useful, it should be placed in the area that has high velocity wind flowing. Another graph shows

information of research data for turbine that has rotor with different blade shape. The influence of

blade shape is also not significant because all rotors have the same length of blade arms. Thus, all

rotors have the same torque.


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Figure 3. Research data for square blade shape

Figure 4. Research data for rectangular blade shape

Rectangular blades

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

0.00 0.50 1.00 1.50 2.00 2.50 3.00

Wind velocity (m/s)

RPM for 4 bladesWind power (watt) 4 bladesShaft power (watt) 4 bladesRPM for 3 bladesWind power (watt) 3 bladesShaft power (watt) 3 bladesRPM for 2 bladesWind power (watt) 2 bladesShaft power (watt) 2 blades

Square blades

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

0.00 0.50 1.00 1.50 2.00 2.50 3.00

Wind velocity (m/s)

RPM for 4 bladesWind power (watt) 4 bladesShaft power (watt) 4 bladesRPM for 3 bladesWind power (watt) 3 bladesShaft power (watt) 3 bladesRPM for 2 bladesWind power (watt) 2 bladesShaft power (watt) 2 blades


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Figure 5. Research data for circle blade shape.

Figure 6. Research data for elliptical blade shape.

Elliptical blades

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

0.00 0.50 1.00 1.50 2.00 2.50 3.00

Wind velocity (m/s)

RPM for 4 bladesWind power (watt) 4 bladesShaft power (watt) 4 bladesRPM for 3 bladesWind power (watt) 3 bladesShaft power (watt) 3 bladesRPM for 2 bladesWind Power (watt) 2 bladesShaft power (watt) 2 blades

Circle blades

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

0.00 0.50 1.00 1.50 2.00 2.50 3.00

Wind velocity (m/s)

RPM for 4 blades

Wind power (watt) 4 blades

Shaft power (watt) 4 bladesRPM for 3 blades

Wind power (watt) 3 blades

Shaft power (watt) 3 blades

RPM for 2 blades

Wind power (watt) 2 bladesShaft power (watt) 2 blades


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Figure 7. Research data for several blade shapes

CONCLUSION AND SUGGESTION

CONCLUSION

After conducting an experiment with real condition in the field and analyzing research data,

conclusion can be made as follows:

1. Research does not result data that are in accordance with the desire yet.

2. Research is only able to collect data such as wind velocity, RPM, wind power and shaft power

while electrical power data cannot be obtained yet.

3. Wind velocity available is too low.

4. Average wind velocity is 6 Knot (data from Meteorology and Geophysics Bureau) and the real

average wind velocity in the field is from 1.2 m/s to 1.33 m/s.

5. Average RPM is between 15.08 RPM and 16.35 RPM.

6. Maximum wind power is 22.343 Watt.

7. Maximum shaft power is 6.7 Watt.

8. Shape and the number of blades do not influence significantly to the characteristics of wind

turbine.

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

0.00 0.50 1.00 1.50 2.00 2.50 3.00

Wind velocity (m/s)

RPM for square blade shape

Wind power (watt) square blades

Shaft power (watt) square blades

RPM for rectangular blades

Wind power (Watt) rectangular blades

Shaft power (watt) rectangular blades

RPM for circle blades

Wind power (watt) circle blades

Shaft power (Watt) circle blades

RPM for elliptical blades

Wind power (Watt) elliptical blades

Shaft power (Watt) elliptical blades


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SUGGESTION

After collecting research data, facing problems appeared and analyzing research data,

suggestion may come out as follows:

1. It is recommended that this model of wind turbine not be placed in the area that is surrounded

by any building but be placed on the beach/in the area that is full of high velocity wind

blowing.

2. Low speed wind turbine is only suitable for some purposes but not for electrical power

generating.

REVERENCES

Anonimus, 2002, Nusa Tenggara Barat Dalam Angka, BPS, Nusa Tenggara Barat.

Cengel, 1994, Thermodynamic an engineering approach, McGraw Hill, New York.

Gintings D, 1993, Pengembangan Instalasi Pembangkit Listrik Tenaga Angin di dusun Selayar, Lombok Timur, Nusa Tenggara Barat, Warta Lapan no. 45, Jakarta.

Ginting, Soeripno, 1993, Pemasangan dan Uji Coba Pemanfaatan SKEA Listrik 500 Watt Untuk Penerangan, Warta LAPAN no. 28,29, Jakarta.

Kadarwati, S., 2001, Studi Pembuatan Biogas dari Kotoran Kuda dan SampahOrganik Skala Laboratoriu,.http://www.litbang.esdm.go.id/litbang/biogas.doc+nilai+kalor%2Bsampah&hl=id.

Soeripno, 1992, Uji Coba Pemanfaatan SKEA Untuk Pengairan Sawah Serang Jawa Barat, Warta LAPAN No. 60/61, Jakarta.

Suryantini, 2003, Potensi energi angin di NTB, Skripsi S1, Jurusan Teknik Mesin, Fakultas Teknik, Universitas Mataram.

Tjokrowisastro dkk, 1990, Teknik Pembakaran Dasar dan Bahan Bakar, Diktat Kuliah, ITS, Surabaya.

APPENDIX

WIND TURBINE PHOTOGRAPH


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